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Title: Cast Forming of Carbon Nanotube Networks Using Paraffin.
Creator: Veliky, Kenneth, Department of Industrial and Manufacturing Engineering
Abstract/Description: Carbon nanotube thin film, or buckypaper, is one of the most revolutionary materials in the 21st century. Mechanical, electrical, and thermodynamic properties that can only be dreamed of in science fiction novels are now within reach in the science and technology field. As amazing as this material is, there exist problems within the manufacturability of buckypaper. Problems such as process time, scalability, and cost effectiveness to produce a sample hinder the ability to produce buckypaper...
Show moreCarbon nanotube thin film, or buckypaper, is one of the most revolutionary materials in the 21st century. Mechanical, electrical, and thermodynamic properties that can only be dreamed of in science fiction novels are now within reach in the science and technology field. As amazing as this material is, there exist problems within the manufacturability of buckypaper. Problems such as process time, scalability, and cost effectiveness to produce a sample hinder the ability to produce buckypaper to the commercial market. This research effort is to study, through experimentation, a new approach to create buckypaper using cast formation of a carbon nanotube network while in a paraffin suspension. Because current nanotube dispersion and filtration methods, such as sonication can produce high costs and slow processing times, the need for new buckypaper manufacturing method is evident. During this experiment, buckypaper was created using two methods for dispersion, the first was a mechanic mixing method and the second was the traditional method of sonication. The study proves that the use of paraffin as the dispersion and flow medium does not provide ideal results to eliminate steps such as sonication and filtration. The resultant buckypaper through mixing did not yield good results due to the nature of carbon nanotube's tendency to agglomerate while heat is applied during the dispersion process. Poor dispersion leads to a decrease in functional properties such as mechanical, electrical or thermodynamic. It is conclusive that further investigation into this method is necessary.
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Date Issued: 2014
Identifier: FSU_migr_uhm-0361
Format: Thesis

Title: Biocompatible Poly (Lactic Acid)/Thermoplastic Polyurethane Blends.
Creator: Burkett, Mary K., Department of Industrial and Manufacturing Engineering
Abstract/Description: In order to create a polymer that has the morphology and structure to be used for industrial applications, the foamability of the PLA must be improved by blending. Blends were made in specific ratios of 80/20, 50/50, and 20/80. Next, the blends were extruded and injected into molds for testing. The mechanical and thermal properties of the blends were tested using the tensile test and the DSC. The morphology was also observed using the SEM. Finally, a series of stock materials were created to...
Show moreIn order to create a polymer that has the morphology and structure to be used for industrial applications, the foamability of the PLA must be improved by blending. Blends were made in specific ratios of 80/20, 50/50, and 20/80. Next, the blends were extruded and injected into molds for testing. The mechanical and thermal properties of the blends were tested using the tensile test and the DSC. The morphology was also observed using the SEM. Finally, a series of stock materials were created to be used for melt-electrospinning or 3D printing.
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Date Issued: 2015
Identifier: FSU_migr_uhm-0526
Format: Thesis

Title: A Study on Sonication Dispersion Parameters for Batchproduction of Carbon Nanotube Buckypaper.
Creator: Vargas, Emily Anne, Department of Industrial and Manufacturing Engineering
Abstract/Description: Buckypaper (BP) is a macroscopic aggregate of carbon nanotubes. More specifically, it is an easy-to-handle thin film formed from carbon nanotube networks. Buckypaper contains valuable high mechanical strength, electrical, and thermal conductivity due to their nanoscale dimension and unique structural network. Application examples of buckypaper include for fire and lightning protection, aerospace structures, armor plating, artificial muscles, miniaturization of electrical connections, and etc....
Show moreBuckypaper (BP) is a macroscopic aggregate of carbon nanotubes. More specifically, it is an easy-to-handle thin film formed from carbon nanotube networks. Buckypaper contains valuable high mechanical strength, electrical, and thermal conductivity due to their nanoscale dimension and unique structural network. Application examples of buckypaper include for fire and lightning protection, aerospace structures, armor plating, artificial muscles, miniaturization of electrical connections, and etc. The current batch-production method has its own associated limitations and problems, including long process time, cost effectiveness, as well as spilling and improper sonication operation. This research will focus on the analysis of sonication time, examining an effective filtration model that will produce buckypaper at effective rates, and the effect of oven drying on the buckypaper, without sacrificing its conducive, electric, and strength properties. The technical approach used in this work is to study the effect of varying the sonication process time on the quality and properties of the resultant buckypaper samples. During this experiment, buckypaper was created using high, medium, and low sonication times, as well as samples were placed in the oven and compared to those that were not. The study proves that lower sonication time does not prove to be ideal in the maintaining the properties of the buckypaper. The resultant buckypaper did not yield good results due to the tendency of carbon nanotubes to agglomerate with short sonication dispersion time. Additionally, samples that were not placed in the oven after water and methanol baths still proved to have large amounts of surfactant left over, affecting the density and properties of the buckypaper. Poor dispersion and high residual surfactant lead to a decrease in functional properties such as mechanical, electrical, and thermodynamic of the buckypaper. Further investigation into applying those batch-production parameters to the continuous manufacturing process is necessary.
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Date Issued: 2015
Identifier: FSU_migr_uhm-0585
Format: Thesis

Title: Stretchable Polymer Light-emitting Diodes for Healthcare Applications.
Creator: Smith, Rachel
Date Issued: 2018-04-23
Identifier: FSU_libsubv1_scholarship_submission_1524513142_9db7079d
Format: Thesis

Title: Multistage Process Monitoring Using Group Exponential Weighted Moving Average Control Chart.
Creator: Symum, Hasan, Vanli, Omer Arda, Awoniyi, Samuel A. (Samuel Ayodele), Wang, Hui, Florida State University, FAMU-FSU College of Engineering, Department of Industrial and...
Show moreSymum, Hasan, Vanli, Omer Arda, Awoniyi, Samuel A. (Samuel Ayodele), Wang, Hui, Florida State University, FAMU-FSU College of Engineering, Department of Industrial and Manufacturing Engineering Department of Industrial and Manufacturing Engineering
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Abstract/Description: This thesis proposes a new variation propagation modeling and group EWMA control chart method for quality improvement in multistage process that aims to detect and isolate the largest variation propagation and faulty stages in a multistage process. Since, it is computationally difficult to estimate the variation propagation, this model can provide important estimation for quantifying the variation in each stage. Also it is crucial to develop a control chart that enables to detect the faulty...
Show moreThis thesis proposes a new variation propagation modeling and group EWMA control chart method for quality improvement in multistage process that aims to detect and isolate the largest variation propagation and faulty stages in a multistage process. Since, it is computationally difficult to estimate the variation propagation, this model can provide important estimation for quantifying the variation in each stage. Also it is crucial to develop a control chart that enables to detect the faulty product quickly and isolate the faulty stage effectively in sequential process. A test statics of control chart is proposed. Two different case studies are used to illustrate the proposed approach. Error are estimated using linear and logistic regression equation and EWMA parameters are calculated for in control dataset. The result of the case study from automotive hood assembly and Healthcare Performance Monitoring shows that, group EWMA can achieve quicker detection than traditional EWMA in later stages of multistage process
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Date Issued: 2015
Identifier: FSU_migr_etd-9467
Format: Thesis

Title: Extraction of Nanorod Projections from Scanning Electron Micrographs.
Creator: Das, Tanmoy, Shrivastava, Abhishek Kumar, Park, Chiwoo, Vanli, Omer Arda, Florida State University, College of Engineering, Department of Industrial and Manufacturing...
Show moreDas, Tanmoy, Shrivastava, Abhishek Kumar, Park, Chiwoo, Vanli, Omer Arda, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering Department of Industrial and Manufacturing Engineering
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Abstract/Description: The dimensions of nanoobjects are important because the properties of nanoobjects are related to dimension and automatic manufacturing inspection of nanoobject requires dimensional information. The current approaches to estimate the projection lengths (one of the important dimensions of nanorods) are manual, error leading and time consuming. So, an automated approach is essential to determine the projection lengths . We propose an innovative approach to estimate projection lengths of nanorods...
Show moreThe dimensions of nanoobjects are important because the properties of nanoobjects are related to dimension and automatic manufacturing inspection of nanoobject requires dimensional information. The current approaches to estimate the projection lengths (one of the important dimensions of nanorods) are manual, error leading and time consuming. So, an automated approach is essential to determine the projection lengths . We propose an innovative approach to estimate projection lengths of nanorods from scanning electron micrographs. Extracting projection length is very crucial to dimensional quality engineering because once we have projection length, we can determine actual length of each nanorod and establish a proper measurement system. The large volume of production of nanorods depends on proper manufacturing process of nanorod which is challenging until there is any proper measurement process exists to understand the manufacturing process of nanorod. Our proposed automated algorithm can extract nanorods by following steps: consider an image of nanorod, determine top edges and side edges of each nanorod separately, associate edges to corresponding nanorods, extract correct nanorods. Then we estimate the projection lengths. Low signal to noise ratio and high degree of overlaps of nanorods in scanning electron micrographs are the major challenges in this research task. Currently there is no image processing algorithm that can measure the dimensions of nanorods from scanning electron micrograph. Hence our research work will contribute to this area. We calculate the total number of true and false detection of nanorods obtained by our automated algorithm. We compare the algorithm with other relevant algorithms (e.g. Normalized cut, Snake and simagis). This research work is promising to dimensional quality control as it can contribute to establish a proper measurement system of nanomanufacturing.
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Date Issued: 2015
Identifier: FSU_migr_etd-9588
Format: Thesis

Title: Fabrication of Micro/Nano-Structured Wrinkles Through Surface Modifcation of Poly(dimethylsiloxane).
Creator: Daramola, Ebunoluwa, Okoli, Okenwa, Dickens, Tarik J., Yu, Zhibin, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering...
Show moreDaramola, Ebunoluwa, Okoli, Okenwa, Dickens, Tarik J., Yu, Zhibin, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering Department of Industrial and Manufacturing Engineering
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Abstract/Description: There is a plethora of interesting science and many applications that rely on wrinkling in thin sheets. Though wrinkling may not be appreciated in some instances, in many other situations wrinkles can help to comprehend various physical phenomena. This work reports on the development of materials that can induce surface roughness through the creation of wrinkled surfaces. The textured surfaces are engineered through a bilayer system consisting of poly(dimethylsiloxane) and a modified surface...
Show moreThere is a plethora of interesting science and many applications that rely on wrinkling in thin sheets. Though wrinkling may not be appreciated in some instances, in many other situations wrinkles can help to comprehend various physical phenomena. This work reports on the development of materials that can induce surface roughness through the creation of wrinkled surfaces. The textured surfaces are engineered through a bilayer system consisting of poly(dimethylsiloxane) and a modified surface layer. This research sought to study and understand methodologies for the controlled formation of wrinkles on surfaces of structures. The creation of wrinkled surfaces was explored in metal deposited thin films atop PDMS. A series of experiments were designed to investigate the significant material parameters that effect low deformation wrinkling mechanics. In doing so, the experimental bilayer system successfully validated an empirical model. Building upon the understanding of key material parameters that affect low deformation wrinkling, oxidized PDMS was used to extend this knowledge in mechanically perturbed-induced wrinkling. A model was constructed that describes the wrinkle profile in terms of the paramount process parameters of plasma treatment. This feature enables integration of micro/nano-wrinkle manufacturing on large-scales. Finally, wrinkle morphology was controlled in a series of wrinkle patterning experiments. Transformations of various wrinkle patterns was achieved by coordinating the amount/direction of strain exerted on the system and exploiting the strain release process, and also by manipulating the geometric properties. The versatility of wrinkle patterning techniques demonstrates further advances in surface roughness engineering. The impact of this work is aimed at enhancing aerodynamic technologies and capabilities. This study demonstrated that by modifying the PDMS surface to create bilayer systems, the wavelength, amplitude, and surface roughness of the wrinkled films can be effectively controlled.
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Date Issued: 2015
Identifier: FSU_migr_etd-9586
Format: Thesis

Title: Additive Technology of Soluble Mold Tooling for Embedded Devices in Composite Structures: A Study on Manufactured Tolerances.
Creator: Roy, Madhuparna, Dickens, Tarik J., Liang, Zhiyong Richard, Vanli, Omer Arda, Florida State University, FAMU-FSU College of Engineering, Department of Industrial and...
Show moreRoy, Madhuparna, Dickens, Tarik J., Liang, Zhiyong Richard, Vanli, Omer Arda, Florida State University, FAMU-FSU College of Engineering, Department of Industrial and Manufacturing Engineering Department of Industrial and Manufacturing Engineering
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Abstract/Description: Composite textiles have found widespread use and advantages in various industries and applications. The constant demand for high quality products and services requires companies to minimize their manufacturing costs, and delivery time in order to compete in general and niche marketplaces. Advanced manufacturing methods aim to provide economical methods of mold production. Creation of molding and tooling options for advanced composites encompasses a large portion of the fabrication time,...
Show moreComposite textiles have found widespread use and advantages in various industries and applications. The constant demand for high quality products and services requires companies to minimize their manufacturing costs, and delivery time in order to compete in general and niche marketplaces. Advanced manufacturing methods aim to provide economical methods of mold production. Creation of molding and tooling options for advanced composites encompasses a large portion of the fabrication time, making it a costly process and restraining factor. This research discusses a preliminary investigation into the use of soluble polymer compounds and additive manufacturing to fabricate soluble molds. These molds suffer from dimensional errors due to several factors, which have also been characterized. The basic soluble mold of a composite is 3D printed to meet the desired dimensions and geometry of holistic structures or spliced components. The time taken to dissolve the mold depends on the rate of agitation of the solvent. This process is steered towards enabling the implantation of optoelectronic devices within the composite to provide sensing capability for structural health monitoring. The shape deviation of the 3D printed mold is also studied and compared to its original dimensions to optimize the dimensional quality to produce dimensionally accurate parts. Mechanical tests were performed on compact tension (CT) resin samples prepared from these 3D printed molds and revealed crack propagation towards an embedded intact optical fiber.
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Date Issued: 2015
Identifier: FSU_migr_etd-9674
Format: Thesis

Title: Topological and Electrical Properites of Carbon Nanotube Networks.
Creator: Li, Min-Yang, Liang, Zhiyong Richard, Park, Chiwoo, Andrei, Petru, Zhang, Mei, Florida State University, College of Engineering, Department of Industrial and Manufacturing...
Show moreLi, Min-Yang, Liang, Zhiyong Richard, Park, Chiwoo, Andrei, Petru, Zhang, Mei, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: A major challenge to the study of the structure-property relationship of carbon nanotube (CNT) networks is to characterize the complex nanostructure with complicated nanoscale contacts and pore structures. An image-based characterization methodology was proposed to extract CNT network information directly from scanning electron microscope (SEM) images of various CNT thin films to characterize critical topological factors including bundle size, diameter, and orientation from the CNT networks....
Show moreA major challenge to the study of the structure-property relationship of carbon nanotube (CNT) networks is to characterize the complex nanostructure with complicated nanoscale contacts and pore structures. An image-based characterization methodology was proposed to extract CNT network information directly from scanning electron microscope (SEM) images of various CNT thin films to characterize critical topological factors including bundle size, diameter, and orientation from the CNT networks. This approach provided high-fidelity and fast analysis of CNT network structures with low false positive rate (FPR) of ~3% and ~90% accuracy in most of our case studies. We applied the new approach to study different networks of multi-walled carbon nanotube (MWNT), single-walled carbon nanotube (SWNT), MWNT-SWNT mixed, and stretched MWNTs with different CNT alignments, which revealed the electrical conductivity-structure relationships of MWNT networks. On the other hand, controlling the transfer of electrical and mechanical properties of nanotubes into nanocomposites remains one of the major challenges due to the lack of adequate measurement systems to quantify the variations in bulk properties while the nanotubes were used as the reinforcement material. One-way analysis of variance (ANOVA) on thickness and conductivity measurements were conducted. By analyzing the data collected from both experienced and inexperienced operators, we found some operation details users might overlook that resulted in variations, since conductivity measurements of CNT thin films are very sensitive to thickness measurements. In addition, we demonstrated how issues in measurements damaged samples and limited the number of replications resulting in large variations in the electrical conductivity measurement results. Based on this study, we proposed a faster, more reliable approach to measure the thickness of CNT thin films that operators can follow to make these measurement processes less dependent on operator skills.
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Date Issued: 2015
Identifier: FSU_2016SU_Li_fsu_0071E_13311
Format: Thesis

Title: Nanocarbon Foam/Polymer Composite.
Creator: Jamal, Muhamad Shahrizan, Zhang, Mei, Okoli, Okenwa, Shrivastava, Abhishek Kumar, Florida State University, College of Engineering, Department of Industrial and Manufacturing...
Show moreJamal, Muhamad Shahrizan, Zhang, Mei, Okoli, Okenwa, Shrivastava, Abhishek Kumar, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: Weight of a material and the system formed by such material is a critical factor for many applications. Traditionally, engineering designed porous structures, typically honeycomb structures, have been utilized for weight critical applications. The goal of this thesis work is to utilize the material with the lightest weight to fabricate a new type of foam that is not only lightweight and strong, but also electrically as well as thermally conductive and with tunable elasticity. A carbon...
Show moreWeight of a material and the system formed by such material is a critical factor for many applications. Traditionally, engineering designed porous structures, typically honeycomb structures, have been utilized for weight critical applications. The goal of this thesis work is to utilize the material with the lightest weight to fabricate a new type of foam that is not only lightweight and strong, but also electrically as well as thermally conductive and with tunable elasticity. A carbon nanotube (CNT) based nanocarbon foam was fabricated by using poly (methyl methacrylate) spheres as a template to create engineered pores. The junctions between the CNTs are secured using nanocarbon via the oxidation and carbonization of polyacrylonitrile. The resulting low density foam exhibits robustness in structure, high elasticity, thermal stability, corrosion resistance and is also electrically as well as thermally conductive. The strength of the foam is further boosted with the infiltration of PMMA polymer. The resulting composite foam is still porous and has higher mechanical strength. The electrical conductivity of the composite foam is not affected despite the presence of PMMA.
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Date Issued: 2016
Identifier: FSU_2016SU_Jamal_fsu_0071N_13228
Format: Thesis

Title: Laser Heat Treatment Processing for Pan Based Carbon Fiber Structure Modification.
Creator: Daniels, Esther Osemudiamen, Zhang, Mei, Zeng, Changchun (Chad), Dickens, Tarik J., Florida State University, College of Engineering, Department of Industrial and Manufacturing...
Show moreDaniels, Esther Osemudiamen, Zhang, Mei, Zeng, Changchun (Chad), Dickens, Tarik J., Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: Carbon fiber is one of the most successful fibers in over 30 years as a result of its high specific strength and modulus, good coefficient of thermal expansion, and its excellent fatigue, and corrosion resistance. From its early use in the military and aerospace applications, carbon fiber composites have become a good light weight replacement material in place of heavier materials like metals (such as steel and aluminum) without compromise on the required mechanical properties....
Show moreCarbon fiber is one of the most successful fibers in over 30 years as a result of its high specific strength and modulus, good coefficient of thermal expansion, and its excellent fatigue, and corrosion resistance. From its early use in the military and aerospace applications, carbon fiber composites have become a good light weight replacement material in place of heavier materials like metals (such as steel and aluminum) without compromise on the required mechanical properties. Polyacrylonitrile (PAN) -based carbon fiber accounts for over 90% of the global demand today as a result of its superior tensile strength and light weight properties. As a good structural reinforcement material, the demand for this fiber continues to grow in high-end applications but is largely limited in industrial and commercial applications by its high cost; accrued from the procurement of the PAN precursor and its manufacturing costs (which involves pyrolysis at temperatures up to 3000° C supplied by a furnace based heating system). This current manufacturing system is characterized by energy losses and slow processing rates which make it inefficient. Also, the large facility requirement and high production costs contribute to the high cost of the fiber. Hence, more cost effective processing systems are desired in meeting the growing demand of this fiber. This research demonstrates the use of the laser as an alternative heat treatment source based on its fast and high energy generation capabilities. In this study, the CO2 continuous pulsed wave laser was employed due to its higher energy generation capabilities. As the laser beam radiated on the surface of the fiber, the energy produced from the laser beam caused the fiber's atoms to vibrate and restructure themselves along the direction of the laser scan. By varying the laser scan settings, changes in the structure of the laser treated low-grade carbon fibers were investigated with the aim of increasing the fibrilla orientation during the graphitization process. The laser treated fibers tested exhibited internal structural changes indicative of plausible structural alignment in the fiber. Lasers provide highly concentrated and localized energy at a high speed of operation. In understanding the process conditions, preliminary understudy of the interrelationship between the lasing parameters and structure of the treated fibers formed in this research were reported. This novel study provided more insight in the microstructure enhancement of carbon fiber possible with use of the laser during the carbon fiber manufacturing process.
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Date Issued: 2017
Identifier: FSU_2017SP_Daniels_fsu_0071N_13645
Format: Thesis

Title: Hierarchy Generation for Designing Assembly System for Product with Complex Liaison and Sub-Assembly Branches.
Creator: Jiang, Zhengqian, Wang, Hui, Okoli, Okenwa, Vanli, Omer Arda, Florida State University, FAMU-FSU College of Engineering, Department of Industrial and Manufacturing Engineering
Abstract/Description: Manufacturers need to deploy their assembly systems in a timely manner to cope with expedited product development. Design of such responsive assembly systems consists of generation of assembly/subassembly operations and their hierarchies, operation-machine assignment, selections of machine types and quantities, and the material flow among machines. Exploration of all the feasible solutions to the assembly operations and their hierarchical relationships is vital to optimization of system...
Show moreManufacturers need to deploy their assembly systems in a timely manner to cope with expedited product development. Design of such responsive assembly systems consists of generation of assembly/subassembly operations and their hierarchies, operation-machine assignment, selections of machine types and quantities, and the material flow among machines. Exploration of all the feasible solutions to the assembly operations and their hierarchical relationships is vital to optimization of system designs. This research developed a theoretical framework based on a recursive algorithm to automatically generate all feasible and non-redundant assembly hierarchies efficiently, thereby investigating its impact on assembly system designs. Then this research further discussed the potential applications of the recursive framework in system optimization including joint determination of optimal assembly operations, operation-machine assignment, machine types and quantities, and the material flows among machines. The work was also extended to the optimization of assembly systems for the products with complex liaison relations and product families.
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Date Issued: 2015
Identifier: FSU_2015fall_Jiang_fsu_0071N_12971
Format: Thesis

Title: Fully Printable Single Layer Halide Perovskite/Peo Composite Thin Film LEDs.
Creator: Bade, Sri Ganesh Rohit, Yu, Zhibin, Liang, Zhiyong Richard, Wang, Hui, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
Abstract/Description: Traditional light emitting diodes (LEDs) involve a complicated device structure with multiple layers stacked over one another. Such a complex, multilayered architecture restricts the application of diverse fabrication techniques. Earth-abundant organometal halide perovskites (Pero) have been well astounded for their appealing optoelectronic properties, low cost and solution processability which make them ideal candidates for large size photovoltaic and LED applications. The objective of this...
Show moreTraditional light emitting diodes (LEDs) involve a complicated device structure with multiple layers stacked over one another. Such a complex, multilayered architecture restricts the application of diverse fabrication techniques. Earth-abundant organometal halide perovskites (Pero) have been well astounded for their appealing optoelectronic properties, low cost and solution processability which make them ideal candidates for large size photovoltaic and LED applications. The objective of this thesis work is to fabricate Pero LED with uniform surface morphology, eliminating the multilayers with the help of Pero/Polyethylene oxide (PEO) composite thin film. Because of the simplicity in device architecture, this novel approach has the potential to surpass all the conceivable troubles involved in the fabrication of Pero LEDs. Preliminary results show a working device achieved by spin coating a thin film of Pero/PEO composite on ITO/glass serving as a bottom electrode and with In/Ga as the top electrode. Furthermore, fully printable and flexible Pero LEDs can be developed from this approach which can be scaled to large commercial roll to roll manufacturing.
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Date Issued: 2016
Identifier: FSU_2016SU_Bade_fsu_0071N_13351
Format: Thesis

Title: Iterative Multi-Task Learning on Spatial Time Series Data with Applications to Improvement of Performance Prediction and Monitoring for Solar Panels.
Creator: Shireen, Tahasin, Wang, Hui, Zhang, Mei, Shrivastava, Abhishek Kumar, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
Abstract/Description: Health condition monitoring and failure detection play a crucial role in estimating the performance of solar panels such as degradation trend over time and occurrence of failures. Monitoring and detecting significant degradation can help solar panel owners establish as-needed maintenance strategies on a timely manner. But in some occasions, degradation trend estimation becomes challenging due to limited availability of training data such as many missing observations in time series over a...
Show moreHealth condition monitoring and failure detection play a crucial role in estimating the performance of solar panels such as degradation trend over time and occurrence of failures. Monitoring and detecting significant degradation can help solar panel owners establish as-needed maintenance strategies on a timely manner. But in some occasions, degradation trend estimation becomes challenging due to limited availability of training data such as many missing observations in time series over a large time span and a lack of history of failure records that are sufficient to establish statistical models. To fill the gap, this thesis proposes a new approach of iterative multi-task learning of Gaussian process in time series data (MTL-GP-TS) by sharing information among similar-but-not-identical datasets from multiple solar panel locations. The proposed MTL-GP-TS model learns unobserved or missing values in a particular time series dataset to forecast the future trend with autoregressive integrated moving average (ARIMA) model, resulting in substantial improvement of forecast over conventional time series modeling approaches. Moreover, the estimated degradation trend with proposed MTL-GP-TS method has the potential to improve the monitoring of significant performance degradation compared with the conventional time series model. This thesis also studies the effect of temporal dependent weather factors on the solar panel performance by integrating a covariate with the MTL-GP-TS algorithm. A case study has demonstrated that inclusion of weather factors into the monitoring of degradation with PV-Weather data integration model can significantly improve the solar panel performance prediction.
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Date Issued: 2016
Identifier: FSU_2016SP_Shireen_fsu_0071N_13167
Format: Thesis

Title: Partial Gauss-Seidel Approach to Solve Large Scale Linear Systems.
Creator: Ghadiyali, Huzefa Shabbir, Park, Chiwoo, Shrivastava, Abhishek Kumar, Vanli, Omer Arda, Florida State University, College of Engineering, Department of Industrial and...
Show moreGhadiyali, Huzefa Shabbir, Park, Chiwoo, Shrivastava, Abhishek Kumar, Vanli, Omer Arda, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: With the advancement in technology and the constant need for optimization, a lot of resources are directed towards analyzing information collected. This information is in the form of large amounts of data that is gathered at every instant. The analysis of this data is often expressed in the form of linear system equations, where the size of the equations increases proportionally to the size of the data. Many methods have been developed to solve these systems. The main challenge in solving...
Show moreWith the advancement in technology and the constant need for optimization, a lot of resources are directed towards analyzing information collected. This information is in the form of large amounts of data that is gathered at every instant. The analysis of this data is often expressed in the form of linear system equations, where the size of the equations increases proportionally to the size of the data. Many methods have been developed to solve these systems. The main challenge in solving such large systems is to get an accurate solution along with computational eciency. The goal of this thesis is to develop a method which addresses both accuracy and computational eciency in solving large-scale linear systems. Our method will improve existing iterative techniques particularly for a linear equation system i.e. Ax = b where A is a positive denite and sparse full rank matrix. Linear systems of such kinds are commonly found in applications of Spatial regression. Hence, we will be using spatial data available publicly to test our method and present results of our method in this thesis.
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Date Issued: 2016
Identifier: FSU_2016SP_Ghadiyali_fsu_0071N_13280
Format: Thesis

Title: Model Characteristics and Properties of Nanorobots in the Bloodstream.
Creator: Zimmer, Michael Makoto, Owusu, Yaw A., Roberts, Rodney G., Parker, Reginald, Zhang, Chun, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Many researchers have various visions and concepts about what the nanorobot will be like and what they will do. Most people see nanorobots doing a lot of functions in the medical field, having ideas of them doing cell repair, seek-and-destroy harmful diseases, clean arteries of cholesterol buildup, and much more. There are many questions that need to be answered as to what exactly is needed for the nanorobot to perform these medical functions. This project is not interested in the design of...
Show moreMany researchers have various visions and concepts about what the nanorobot will be like and what they will do. Most people see nanorobots doing a lot of functions in the medical field, having ideas of them doing cell repair, seek-and-destroy harmful diseases, clean arteries of cholesterol buildup, and much more. There are many questions that need to be answered as to what exactly is needed for the nanorobot to perform these medical functions. This project is not interested in the design of the nanorobot, but focuses on the characteristics and parameters that should be considered for a nanorobot to function through the bloodstream of a human body, specifically. To do this, a mobile robot was being used to traverse through a scaled model of the bloodstream. The scale model consisted of clear tubing or piping enclosed in a loop filled with liquid to nearly the exact viscosity of blood. The liquid had particles to emulate the various obstacles that a nanorobot would encounter like red blood cells and other molecules. The simulation had a continuous flow at the appropriate rate and pressure expected in the bloodstream. The pipe size was calculated setting the ratio of the diameter of a particular blood vessel over the diameter face of the assumed size of a nanorobot (DBV / DNR) equaling the diameter of the pipe (unknown variable) to the diameter face of the mobile robot (DPipe / Dsub). The pipe size came to be 6.66 inches, however pipe sizes come in increments of 2 inches larger than 4 inch pipes. It was settled to use 6 inch pipes. With this variable, the Reynolds number is the diameter of pipe times the velocity of the fluid over the kinematic viscosity of the fluid (R = (DPipe * ν) / υ). Setting the Reynolds value of the bloodstream equal to the Reynolds value of the model, the velocity of the pipe could be isolated. With that the flow rate was evaluated by multiplying the velocity to the cross-sectional area of the pipe (Flow Rate was equal to 0.2021392 gallon/minute). With all conditions met for an accurate model of the bloodstream, the physical model was designed and constructed then testing with the mobile robot was done to determine how the robot functions in the simulated environment. The results of the experiment showed that the mobile robot is influenced by the environment. The speed it travels decreases as viscosity of the fluid increases. The particles in the fluid also affect the speed along with the flow of the fluid. Mobility and control of the mobile robot were hindered with the increase of viscosity and the presence of particles. When traveling against the flow of the fluid it was further hindered. Stability of the craft increased along with viscosity but was chaotic traveling with particles. The performance of the mobile robot was affected by the conditions and parameters involved in the bloodstream.
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Date Issued: 2005
Identifier: FSU_migr_etd-0496
Format: Thesis

Title: Investigation of Vartm Processing of High Temperature RP-46 Resin System.
Creator: Prasad, Thammiah M., Zhang, Chuck, Okoli, Okenwa, Liang, Zhiyong, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: The advantages of using polymer matrix composites in various applications are very well known throughout many industries. Their introduction and subsequent development since the 1940's has led to major cost savings due to their lightweight and excellent mechanical properties. Off late, product designers have been taking advantage of improved thermal properties (CTE, thermo-oxidative stability) that these composite materials have to offer. This began with the development of PMR-15, a high...
Show moreThe advantages of using polymer matrix composites in various applications are very well known throughout many industries. Their introduction and subsequent development since the 1940's has led to major cost savings due to their lightweight and excellent mechanical properties. Off late, product designers have been taking advantage of improved thermal properties (CTE, thermo-oxidative stability) that these composite materials have to offer. This began with the development of PMR-15, a high temperature polyimide resin back in the 1970's. The aerospace industry has increasingly turned towards high temperature polymer matrix composites (HTPMC) to replace other heavier materials in engine components thus improving the thrust to weight of the engine. But, PMR-15 has a major drawback related to high safety standards that are needed during processing. The implementation of these controls during processing resulted in huge costs to the industry. This led to the development of a new polyimide high temperature resin system called RP-46 at NASA Langley research center. RP-46 has excellent thermal and mechanical properties comparable to PMR-15 and is safer to handle due to the absence of the lethal MDA monomer, a carcinogen. This research investigates the issues related to processing of RP-46 resin system using the Vacuum Assisted Resin Transfer Molding (VARTM) process, a cost effective method for manufacturing composite materials. The entire process is setup keeping in consideration the requirement of high temperature environments for processing of RP-46. A number of initial trials helped understand the dynamics of the process and identify critical factors and key parameters. The various laminates that were made were tested for mechanical properties (ASTM D3039 - Tensile strength and modulus) and thermal properties (Dynamic Mechanical Analysis, Thermal Mechanical Analysis, Thermal Gravimetric Analysis) were performed and the results were compared with RP-46 samples made using autoclave processing. Although the VARTM laminates had issues related to void contents and the release of volatiles during the infusion stage of the process, the VARTM process was found to be feasible to make composites with RP-46.
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Date Issued: 2004
Identifier: FSU_migr_etd-0441
Format: Thesis

Title: Performance of Control Charts for Weibull Processes.
Creator: Zhang, Mang, Pignatiello, Joseph J., Awoniyi, Samuel A., Vanli, Arda, Okoli, Okenwa, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Statistical Process Control (SPC) is a statistical method for monitoring variability of processes. Process variation can be categorized as common cause and special cause. Common causes are the natural or expected variation of some change in the process. The presence of a special cause indicates that the process is not in a state of statistical control. The SPC methodology dictates that a search should be initiated when a special cause is detected. This thesis is about the set-up of magnitude...
Show moreStatistical Process Control (SPC) is a statistical method for monitoring variability of processes. Process variation can be categorized as common cause and special cause. Common causes are the natural or expected variation of some change in the process. The presence of a special cause indicates that the process is not in a state of statistical control. The SPC methodology dictates that a search should be initiated when a special cause is detected. This thesis is about the set-up of magnitude robust control chart and CUSUM charts for detecting changes in Weibull processes. The research includes the comparison of the ARL performance of the control charts.
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Date Issued: 2009
Identifier: FSU_migr_etd-0537
Format: Thesis

Title: Dimension Variation Prediction and Control for Composites.
Creator: Dong, Chensong, Zhang, Chuck, Buzyna, George, Liang, Zhiyong, Okoli, Okenwa, Wang, Ben, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: This dissertation presents a systematic study on the dimension variation prediction and control for polymer matrix fiber reinforced composites. A dimension variation model was developed for process simulation based on thermal stress analysis and finite element analysis (FEA). This model was validated against the experimental data, the analytical solutions and the data from literature. Using the FEA-based dimension variation model, the deformations of typical composite structures were studied...
Show moreThis dissertation presents a systematic study on the dimension variation prediction and control for polymer matrix fiber reinforced composites. A dimension variation model was developed for process simulation based on thermal stress analysis and finite element analysis (FEA). This model was validated against the experimental data, the analytical solutions and the data from literature. Using the FEA-based dimension variation model, the deformations of typical composite structures were studied and the regression-based dimension variation model was developed. The regression-based dimension variation model can significantly reduce computation time and provide a quick design guide for composite products with reduced dimension variations. By introducing the material modification coefficient, this comprehensive model can handle various fiber/resin types and stacking sequences. It eliminates the complicated, time-consuming finite element meshing and material parameter defining process. The deformation compensation through tooling design was investigated using the FEA-based and the regression-based dimension variation models. The structural tree method (STM) was developed to compute the assembly deformation from the deformations of individual components, as well as the deformation of general shape composite components. The STM enables rapid dimension variation analysis/synthesis for complex composite assemblies with the regression-based dimension variation model. Using the STM and the regression-based dimension variation model, design optimization and tolerance analysis/synthesis were conducted. The exploring work presented in this research provides a foundation to develop practical and proactive dimension control techniques for composite products.
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Date Issued: 2003
Identifier: FSU_migr_etd-0711
Format: Thesis

Title: Assessment of Triboluminescent Materials for In-Situ Health Monitoring.
Creator: Dickens, Tarik Jamel, Okoli, Okenwa, Liang, Zhiyong, Simpson, James, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Advanced composites which offer robust mechanical properties are being increasingly used for structural applications in the aerospace, marine, defense and transportation industries. However, the anisotropic nature of composite materials leaves it susceptible to problematic failure; the development of means for detecting failure is imperative. As design and functionality requirements of engineering structures such as spacecraft, aircraft, naval vessels, buildings, dams, bridges and ground...
Show moreAdvanced composites which offer robust mechanical properties are being increasingly used for structural applications in the aerospace, marine, defense and transportation industries. However, the anisotropic nature of composite materials leaves it susceptible to problematic failure; the development of means for detecting failure is imperative. As design and functionality requirements of engineering structures such as spacecraft, aircraft, naval vessels, buildings, dams, bridges and ground-based vehicles become more complex; structural health monitoring (SHM) and damage assessment is becoming more rigorous. Though structures involved have regular costly inspections, the damage associated with composites in SHM systems can lead to catastrophic and expensive failures. Industry and research have no single technique used on its own to provide reliable results. Integrating several nondestructive evaluation (NDE) techniques could provide a solution for real-time health monitoring. Such studies, utilizing acoustic emission (AE), A-scans, C-scans, and laser shearography have reported considerable success. Nevertheless, damage detection has to be reliable and cost effective. The answer may lie with the development of SHM systems by the use of triboluminescent crystals, as well as optical fibers embedded in the composite matrix. These crystals react to straining or fracture by emitting light of varied luminous intensity. Thus, a fiber-reinforced plastic (FRP) laminate doped with Triboluminescent (TL) or Mechanoluminescent (ML) crystals, acting as health sensors to its host material, will give an indication of crack initiation well ahead of catastrophic failure(s). The development of an in-situ health monitoring system for safety critical structures is a viable route through 'Triboluminescence'. Assessing the viability of a proposed structural sensor system requires cross-linking between key areas in science and engineering. Initial testing has shown that light can propagate through doped resins alone, as well as doped FRP laminates. The luminous intensities relation to impact velocity adds credence to a monitoring system that can characterize impact activity. However, Triboluminescent crystals have high material density. In response, a two-dimensional rotational mold was built to counteract massive settling under normal vacuum molding processes. Micro-structural evaluations using scanning electron microscopy (SEM) and EDAX imaging have aided in demystifying particulate dispersion of TL fillers through use of image processing.
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Date Issued: 2007
Identifier: FSU_migr_etd-0734
Format: Thesis

Title: Comparative Analysis of the Power Output of Crystalline Photovoltaic (PV) Modules Using Solar Tracking System.
Creator: Anthony, Thomas P., Owusu, Yaw A., Simpson, James, Moore, Carl A., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: The focus of this thesis was to employ the use of two widely used types of photovoltaic (PV) modules namely monocrystalline and polycrystalline in a tracking system to determine which produces the greater output and compare these results to those reached by my predecessor, Michael O. Case[Case, 2003]. Several factors affect the overall productivity of a solar system. These include but are not limited to, time of day, time of year, latitude and atmospheric conditions, all of which were dealt...
Show moreThe focus of this thesis was to employ the use of two widely used types of photovoltaic (PV) modules namely monocrystalline and polycrystalline in a tracking system to determine which produces the greater output and compare these results to those reached by my predecessor, Michael O. Case[Case, 2003]. Several factors affect the overall productivity of a solar system. These include but are not limited to, time of day, time of year, latitude and atmospheric conditions, all of which were dealt with throughout this thesis. The thesis began with the design and assembly of a solar tracking system. This system was used to collect data using monocrystalline and polycrystalline modules in various configurations. The configurations were stationary zero degrees, stationary forty degrees and solar tracking at forty degrees. Once data was acquired, it was entered in to the statistical software "Design Expert V6.0". Statistical analysis was then performed to determine the effect the chosen factors had on the power output of the two types of modules in terms of which type provides greater output and in what configuration. It was determined that the monocrystalline module produces greater power output than its polycrystalline counterpart. A final experiment was set up to determine the mode that produces the greatest power output. The results from the experiment revealed that monocrystalline modules deliver greater power in a tracking configuration. However, it may be necessary to consider the effects of temperature depending on application of these modules.
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Date Issued: 2006
Identifier: FSU_migr_etd-0222
Format: Thesis

Title: Application of Experimental Design for Efficient Wind Tunnel Testing: The Tandem Wing Mav Case.
Creator: English, Teresa Gail, Simpson, James R., Landman, Drew, Okoli, Okenwa I., Pignatiello, Joseph J., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Micro air vehicles (MAVs) are small scale unmanned aerial vehicles (UAVs) that are used for reconnaissance, intelligence gathering and battle damage assessment. The U.S. Air Force Research Lab Munitions Directorate develops MAVs for various defense missions. The case involves a tandem wing MAV that is designed to have retractable wings for transport, control surfaces on the aft wing, and two different vertical tail configurations. Wind tunnel testing is one of the vital steps in MAV...
Show moreMicro air vehicles (MAVs) are small scale unmanned aerial vehicles (UAVs) that are used for reconnaissance, intelligence gathering and battle damage assessment. The U.S. Air Force Research Lab Munitions Directorate develops MAVs for various defense missions. The case involves a tandem wing MAV that is designed to have retractable wings for transport, control surfaces on the aft wing, and two different vertical tail configurations. Wind tunnel testing is one of the vital steps in MAV development for evaluating and ensuring that stability and control requirements are met for sustained flight. Traditionally, wind tunnel tests have been performed using a one factor at a time (OFAT) approach. Wind tunnel OFAT involves testing at many levels of one particular factor, usually angle of attack (AoA), while holding all other input factors constant; this technique is then repeated for various input factor configurations. This classic approach can be useful in determining the effect that each input alone has on the desired response. However, OFAT is not capable of identifying the influence that inputs interacting with one another have on the response, which commonly affect aircraft performance. Furthermore, OFAT is not capable of characterizing uncertainty that is present in experimentation. The research objective is to develop a testing strategy that provides an efficient number of test points to run in the wind tunnel effectively characterizing the aerodynamic behavior of MAVs as a function of design changes, changes in attitude and control inputs, while reducing costs and resources using design of experiments (DOE) and response surface methods (RSM). The research involves one of the first applications of second-order split plot designs, as well as the traditional completely randomized design. The DOE/RSM approach will be directly compared to the traditional OFAT wind tunnel testing that is performed during the same test period. The analyses resulting from the DOE/RSM approach will highlight its capabilities in identifying factor interactions, characterizing system uncertainty, and providing stability and control analyses – the common objectives of wind tunnel testing. The outcome of the study will demonstrate the effectiveness of DOE/RSM techniques when tailored to meet the specifications of wind tunnel testing. Some characteristics involved with the wind tunnel environment are low noise, qualitative factors, hard-to-change factors, and second-order models. The collaboration of experimental design techniques adapted to traditional wind tunnel testing techniques will provide a powerful approach to characterizing and optimizing aerodynamic systems.
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Date Issued: 2007
Identifier: FSU_migr_etd-0559
Format: Thesis

Title: Fault Diagnosis in Multivariate Manufacturing Processes.
Creator: Ding, Yi, Vanli, Arda, Wang, Ben, Zhang, Chuck, Pignatiello, Joseph J., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: As manufacturing systems are becoming more complex, the use of multivariate fault detection and diagnosis methods are increasingly important. Effective fault detection and diagnosis methods can minimize cost of rework, plant down time and maintenance time and improve reliability and safety. This thesis proposes Principal Components Analysis (PCA) based root cause identification approach for quality improvement in complex manufacturing processes. Simulation studies are presented to demonstrate...
Show moreAs manufacturing systems are becoming more complex, the use of multivariate fault detection and diagnosis methods are increasingly important. Effective fault detection and diagnosis methods can minimize cost of rework, plant down time and maintenance time and improve reliability and safety. This thesis proposes Principal Components Analysis (PCA) based root cause identification approach for quality improvement in complex manufacturing processes. Simulation studies are presented to demonstrate the improved diagnosability of the proposed approach compared to existing methods.
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Date Issued: 2010
Identifier: FSU_migr_etd-0729
Format: Thesis

Title: Optimization of Ultraviolet Lamp Placement for the Curing of Composite Manufactured by the Ridft Process.
Creator: Adewuyi, Olalekan Sunday, Okoli, Okenwa I., Awoniyi, Samuel A., Jack, David A., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: The ultraviolet curing technique, when applied to composite manufacturing processes, allows UV rays to radiate the component reducing the curing time of composite materials from hours to minutes. This technique has been demonstrated with the Resin Infusion between Double Flexible Tooling (RIDFT) process for flat components. However, the curing of composites other than flat components remains a challenge. Applying UV curing to three-dimensional geometries mostly requires utilization of several...
Show moreThe ultraviolet curing technique, when applied to composite manufacturing processes, allows UV rays to radiate the component reducing the curing time of composite materials from hours to minutes. This technique has been demonstrated with the Resin Infusion between Double Flexible Tooling (RIDFT) process for flat components. However, the curing of composites other than flat components remains a challenge. Applying UV curing to three-dimensional geometries mostly requires utilization of several lamps positioned around the component. Not only is this expensive, but it may allow for UV exposure overlap resulting in excessive curing of some areas on the component. Trial-and-error positioning, utilization of large arrays of UV lamps with components moving on a conveyor, and robotically actuated UV lamps have been employed in some quarters. These methods are too expensive, time consuming, and complex, thus negating the idea of simplicity that composite manufacturing processes tend to portray. To tackle this problem, a general-purpose model was proposed. Solving this model involves two stages: numerical integration using Gauss quadrature method, and optimization problem using Davidon-Fletcher Powell (DFP) algorithm. The model predicts the UV lamps' optimum positions and generates the UV intensity on the predefined sections on the composite substrates. Furthermore, three-dimensional composite materials were manufactured using different manufacturing parameters. Mechanical and rheological tests were carried out to determine uniformity of curing; the results of these tests were compared with three-dimensional catalytic cured composite components. The UV cured composites have mechanical properties that are comparable with the catalytic cured composite.
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Date Issued: 2009
Identifier: FSU_migr_etd-0120
Format: Thesis

Title: Continuous Buckypaper Manufacturing Process: Process Investigation and Improvement.
Creator: Young, Jasmine, Liang, Zhiyong, Wang, Ben, Zhang, Chuck, Vanli, Arda, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes have excellent electrical, thermal, and mechanical properties as determined theoretically and experimentally. Their properties make them great candidates for use in a number of applications ranging from lightning strike protection for airplanes to computer heat sink. However, carbon nanotubes are incredibly small, with diameters as small as 1nm and just a few micrometers long. The nanoscale size makes carbon nanotubes impractical to be used individually for many industrial...
Show moreCarbon nanotubes have excellent electrical, thermal, and mechanical properties as determined theoretically and experimentally. Their properties make them great candidates for use in a number of applications ranging from lightning strike protection for airplanes to computer heat sink. However, carbon nanotubes are incredibly small, with diameters as small as 1nm and just a few micrometers long. The nanoscale size makes carbon nanotubes impractical to be used individually for many industrial purposes, thus methods have been developed to fabricate macroscale networks of carbon nanotubes. The carbon nanotube networks, also called Buckypaper, have showed mechanical, thermal and electrical properties inferior to those of individual nanotubes. Extensive work has been conducted to develop and optimize suitable production methods of producing high quality Buckypaper and enhance their properties. Many approaches are capable of producing a carbon nanotube network, but most are not able to scale up for industrial applications due to size and production rate limitations. This research focuses on two aspects of Buckypaper manufacturing improvements. The first is to test 90 mm samples of Buckypaper disks to determine the impact of each processing parameter on the quality and properties. Statistic analysis was used to reveal the effect of processing parameters. Utilizing these results, a long sample of Buckypaper was produced and examined for property and quality consistency along the sample length, using modified customer-made continuous filter devices. Additionally, long samples with larger width were produced to demonstrate production rate of continuous Buckypaper manufacturing. Through this research it was found that the electrical conductivity of the Buckypaper was affected positively by an increase in sonication pressure. Additionally, increases in pressure and increase in power of sonication led to an increase of Buckypaper strength. Strength and electrical properties of the continuous Buckypaper were considered consistent throughout the length. These results provide essential understanding of the continuous Buckypaper manufacturing process.
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Date Issued: 2009
Identifier: FSU_migr_etd-0872
Format: Thesis

Title: Polypyrrole as a Smart Material for Phosphate Contaminate Detection in Water.
Creator: Woodard, Yoshino N., Owusu, Yaw A., Parker, Reginald, Kalu, Peter N., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Polypyrrole is a conductive polymer that has the potential to be used in many systems where conductivity can be studied. Polypyrrole when combined with a catalyst such as calcium acetate maybe able to provide a method of detecting phosphate in water systems. The hypothesis of this research explores the concept that a polypyrrole sensor could be manufactured via a casting method to produce a sensor that detects phosphates in water. Varying three primary factors produced a designed experiment...
Show morePolypyrrole is a conductive polymer that has the potential to be used in many systems where conductivity can be studied. Polypyrrole when combined with a catalyst such as calcium acetate maybe able to provide a method of detecting phosphate in water systems. The hypothesis of this research explores the concept that a polypyrrole sensor could be manufactured via a casting method to produce a sensor that detects phosphates in water. Varying three primary factors produced a designed experiment and ANOVA analysis and comparison of means for three response variables: voltage, resistance and conductivity (calculated). Careful attention was paid to the values of the response variables across the geometry of the sensor prototypes. The sensor was evaluated for accuracy, sensitivity after multiple uses, and selectivity. After examining all of the data, the information obtained did not disprove the hypothesis, however it pointed to calcium acetate as the most powerful factor in the polypyrrole sensor in the accuracy test. Sensitivity and Selectivity tests had mixed findings. The samples not containing calcium acetate near the surface did not produce great changes in the response variables. The work presented in this thesis is an analysis of the raw data and materials used for generating the polypyrrole sensor prototype in order to introduce a new concept for manufacturing sensors using advanced materials; namely smart structures as sensors.
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Date Issued: 2006
Identifier: FSU_migr_etd-0787
Format: Thesis

Title: Carbon Nanotube Buckypaper Permeability and Prepreg Process Study.
Creator: Click, Bryant Marshall, Liang, Richard, Wang, Ben, Okoli, Okenwa, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes (CNTs) possess great potential for developing high-performance and multifunctional nanocomposites for a wide variety of applications. As the cost of producing CNT buckypaper, a thin film of CNT networks, continues to decrease while the quality increases, more users and companies are becoming interested in buckypaper for potential applications. Many of these applications, such as electromagnetic interference (EMI) shielding and fire retardant surface skins for fiber-reinforced...
Show moreCarbon nanotubes (CNTs) possess great potential for developing high-performance and multifunctional nanocomposites for a wide variety of applications. As the cost of producing CNT buckypaper, a thin film of CNT networks, continues to decrease while the quality increases, more users and companies are becoming interested in buckypaper for potential applications. Many of these applications, such as electromagnetic interference (EMI) shielding and fire retardant surface skins for fiber-reinforced composites or plastics, may not require buckypaper-based composites to be much stronger compared to fiber-reinforced composites. This means that there is a market for buckypaper even without its theoretical super strength, but desired functionality. There is however a number of challenges with the potential scale-up production of composite parts with affordable buckypaper materials usually made of low cost CNTs, such as multi-walled carbon nanotubes (MWNTs). Such buckypaper is usually very lightweight (10-25 g/m2), thin (10-20 microns), and fragile, hence even small variations and damage in the wet lay-up process can result in large quality variations in the final buckypaper composite. These variations include buckypaper volume fraction, resin rich areas, and contact between BP and other reinforcement materials etc. Thus, keeping the consistency of the resulting microstructure and quality of buckypaper composites is a very challenging issue. The objective of this project is to study nanostructure-permeability relationships of different types of buckypaper materials, and explore effective prepreg processes to make buckypaper composites with greatly increased consistency, quality, CNT weight fraction and uniformity in the resulting products. The experimental results show that buckypapers have very low permeability, about 8-12 orders lower than those of carbon fiber preform cases, and also sensitive to liquid polarity due to their nanoscale porosity and large surface area. Both solution and resin film transfer prepregging processes were studied to pre-impregnate buckypaper to achieve 50 wt. % CNT concentration. The late one showed better quality in the resultant nanocomposites, but difficult for high viscosity resins. Three case studies were also conducted to demonstrate quality and property consistency of buckypaper composites.
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Date Issued: 2010
Identifier: FSU_migr_etd-3581
Format: Thesis

Title: Preparation and Characterization of Magnetically Aligned Carbon Nanotube Buckypaper and Composite.
Creator: Shankar, Kadambala Ravi, Liang, Zhiyong, Wang, Ben, Zhang, Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes are theoretically one of the strongest and stiffest materials with a calculated tensile strength of ~200 giga Pascal and modulus of more than 1-4 tera Pascal for a single walled nanotube (SWNT). If the mechanical properties of SWNT could be effectively incorporated into a polymer matrix, composites with lightweight, exceptional strength and stiffness can be achieved. The effective utilization of nanotubes in composites for applications depends on the ability to disperse the...
Show moreCarbon nanotubes are theoretically one of the strongest and stiffest materials with a calculated tensile strength of ~200 giga Pascal and modulus of more than 1-4 tera Pascal for a single walled nanotube (SWNT). If the mechanical properties of SWNT could be effectively incorporated into a polymer matrix, composites with lightweight, exceptional strength and stiffness can be achieved. The effective utilization of nanotubes in composites for applications depends on the ability to disperse the nanotubes uniformly throughout the matrix. Carbon nanotubes are anisotropic in nature. Therefore to take advantage of the nanotubes in the axial direction, controlled tube orientation or degree of alignment of nanotubes in the polymer matrix is very important to realize their high mechanical and functional properties. The nanocomposites produced by current conventional methods using direct mixing, melt blending or solution casting have failed to yield significant improvements in composite modulus. Although tremendous progress has been made towards understanding the properties of individual carbon nanotubes, but attaining the true potential of the bulk polymeric nanocomposites have been hindered by the lack of uniform SWNT dispersion, poor interfacial bonding, inadequate tube loading and uncontrollable tube orientation or degree of alignment. This thesis work developed an innovative approach for producing nanocomposites that has uniform SWNT dispersion, high tube loading and most importantly controlled tube orientation. In this research, these properties in composites were achieved by using magnetically aligned buckypapers and resin infusion system. The aligned nanotube buckypaper and composite were characterized using AFM and SEM. The mechanical properties of these materials were experimentally determined using DMA and were theoretically verified. The electrical properties of these materials were also experimentally determined using 4-probe resistivity measurements. Significant tube alignment has been achieved in the resultant buckypaper and nanocomposites. It is shown that the developed method is an effective way for producing nanocomposites with uniform SWNT dispersion desired tube alignment and high tube loading.
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Date Issued: 2003
Identifier: FSU_migr_etd-3403
Format: Thesis

Title: Nanowire Alignment and Patterning via Evaporation-Induced Directed Assembly.
Creator: Abdelsalam, Farag, Zhang, Mei, Okoli, Okenwa, Liang, Zhiyong Richard, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: The post synthetic assembly of nanowires into desired configurations presents a unique challenge. The inherent size of nanowires does not lend it self to a method or process capable of easily arranging or manipulating these materials. The recent understanding of how contact-line deposition, or the "coffee-ring effect", influences isotropic particles has lead to interest in investigating its influence over nanowires. Research has shown that nanowires can be aligned and selectively deposited at...
Show moreThe post synthetic assembly of nanowires into desired configurations presents a unique challenge. The inherent size of nanowires does not lend it self to a method or process capable of easily arranging or manipulating these materials. The recent understanding of how contact-line deposition, or the "coffee-ring effect", influences isotropic particles has lead to interest in investigating its influence over nanowires. Research has shown that nanowires can be aligned and selectively deposited at the edge of a drying droplet as a result of evaporation-induced capillary flow. From this basic understanding several methods have developed with the intent of producing a facile, robust, and scalable nanowire assembly process. This work provides insight into the coffee-ring effect and the mechanisms that draw from it to align, assemble, and pattern nanowire structures prior to introducing and providing the results of a new contact line deposition method.
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Date Issued: 2011
Identifier: FSU_migr_etd-4679
Format: Thesis

Title: Design, Manufacture and Performance of Solar Powered Floating Fountaing.
Creator: Gomez, Eduardo J., Owusu, Yaw A., Roberts, Rodney, Simpson, James, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Photovoltaic (PV) systems behave in an extraordinary and useful way: they react to light by transforming part of the incoming photons into electricity. Since PV installations require no fuel to operate, produce no pollution while producing electricity, they require little maintenance and are modular. These unique properties make the technology a cost and energy-effective means of permitting a wide range of solar- electric applications. Thus, innovative design and manufacture of PV devices and...
Show morePhotovoltaic (PV) systems behave in an extraordinary and useful way: they react to light by transforming part of the incoming photons into electricity. Since PV installations require no fuel to operate, produce no pollution while producing electricity, they require little maintenance and are modular. These unique properties make the technology a cost and energy-effective means of permitting a wide range of solar- electric applications. Thus, innovative design and manufacture of PV devices and equipment, offers a new vision for consumers and business as to how power can be provided. One such application involves the design and manufacture of a Solar-Powered Floating Fountain, including a robust design of experiment, performance, cost and safety analyses, is presented in this thesis. The uniqueness of the fountain manufactured for this research is the capability for aeration of stagnant water bodies, such as lakes and ponds. Aeration of these water bodies by using solar power is not only a new application of the renewable energy, but also, it provides an affordable method to promote biodiversity in stagnant ponds and lakes. The fountain was built by the Research Center for Cutting-Edge Technologies (RECCET) and installed on a pond at Innovation Park, Tallahassee. The system is composed of two pumps, an air compressor, six solar panels, kit of batteries, a linear current booster, pressurized water tank and the float. Aeration was by exposing the water to air through the nozzles on the tank. By using this technique, the lake gained dissolved oxygen in the lowest layer, accomplishing the main objective of this project. Statistical analysis using a Split Plot design showed a significant uptake of both dissolved oxygen and destratification.
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Date Issued: 2006
Identifier: FSU_migr_etd-4152
Format: Thesis

Title: Study of a New Manufacturing Technology for Multi-Functional Composite Structures with Aerosol-Jet Printing.
Creator: Zhao, Da (Daniel), Wang, Ben, Zhang, Mei, Liu, Tao, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Traditional multifunctional composite structures are produced by embedding parasitic parts, such as foil sensors, optical fibers and bulky connectors. As a result, the mechanical properties of the composites, especially the interlaminar shear strength (ILSS), could be largely undermined. In the present study, we demonstrated an innovative aerosol-jet printing technology for printing electronics inside composite structures without degrading the mechanical properties. Using the maskless fine...
Show moreTraditional multifunctional composite structures are produced by embedding parasitic parts, such as foil sensors, optical fibers and bulky connectors. As a result, the mechanical properties of the composites, especially the interlaminar shear strength (ILSS), could be largely undermined. In the present study, we demonstrated an innovative aerosol-jet printing technology for printing electronics inside composite structures without degrading the mechanical properties. Using the maskless fine feature deposition (below 10µm) characteristics of this printing technology and a pre-cure protocol, strain sensors were successfully printed onto carbon fiber prepregs to enable fabricating composites with intrinsic sensing capabilities. The degree of pre-cure of the carbon fiber prepreg on which strain sensors were printed was demonstrated to be critical. Without pre-curing, the printed strain sensors were unable to remain intact due to the resin flow during curing. The resin flow-induced sensor deformation can be overcome by introducing 10% degree of cure of the prepreg. In this condition, the fabricated composites with printed strain sensors showed almost no mechanical degradation (short beam shearing ILSS) as compared to the control samples. Also, the failure modes examined by optical microscopy showed no difference. The resistance change of the printed strain sensors in the composite structures were measured under a cyclic loading and proved to be a reliable mean strain gauge factor of 2.2±0.06 which is comparable to commercial foiled metal strain gauge.
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Date Issued: 2011
Identifier: FSU_migr_etd-6092
Format: Thesis

Title: Electrical Properties of Carbon Nanotube Networks: Characterization, Modeling and Sensor Applications.
Creator: Li, Shu, Liang, Richard, Andrei, Petru, Vanli, Arda, Zhang, Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes (CNTs) possess extraordinary electrical properties including conductivity that is comparable to metals and breakdown current density that is orders of magnitude higher than copper. In order to take advantage of the electrical performance of CNTs in engineering applications, macroscopic carbon nanotube networks (NTN) are fabricated by entangling large amounts of CNTs into thin sheets. However, the electrical properties of these networks are much lower than those of individual...
Show moreCarbon nanotubes (CNTs) possess extraordinary electrical properties including conductivity that is comparable to metals and breakdown current density that is orders of magnitude higher than copper. In order to take advantage of the electrical performance of CNTs in engineering applications, macroscopic carbon nanotube networks (NTN) are fabricated by entangling large amounts of CNTs into thin sheets. However, the electrical properties of these networks are much lower than those of individual nanotubes. Stretch-induced alignment of CNTs is an effective approach to enhance the electrical conductivity of the NTNs. However, the alignment mechanism of NTNs during the stretching process has not been fully investigated. This study employed in-situ X-ray and Raman scattering techniques to characterize the NTN structural evolution during stretch-induced alignment. The observed inhomogeneous alignment of NTNs prompts the need for a method that accurately determines the degree of nanotube alignment in bulk materials. A method that combines X-ray scattering and electrical anisotropy measurement was explored and proposed to determine the aligned fractions of nanotubes. Based on the characterization results, the structure-property relationship of NTNs and their electrical conductivity was studied through a 3D physics-based electrical model. The model was built in two stages. First, the structural model of NTNs was built using coarse-grained molecular dynamics, which provides high fidelity representation of the waviness, contacts and self-assembly of constituent nanotubes and ropes that originated from the van der Waals interactions. By applying tensile strains, the dynamics model also enabled the direct simulation of the dynamics of networks aligned through stretching. After the network structure was established, the simulated NTNs were translated into equivalent electrical circuits. The electrical model was developed based on the Simulation Program with Integrated Circuit Emphasis, which allows us to directly conduct device design and analysis using NTNs. This model is able to capture the effects of alignment and contact changes on the electrical properties of NTNs. Based on the understanding of the unique contact resistance dominated transport mechanism of NTNs, sensor applications of the novel materials were explored. By manipulating the tunneling barrier through either polymer molecule insertion or increasing the tunneling distances, NTNs were studied for potential applications in detecting organic solvent leakage and sensing tensile strains. Scaling-up of sensor fabrication using aligned NTNs and advanced printing technology was also explored and demonstrated.
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Date Issued: 2012
Identifier: FSU_migr_etd-6957
Format: Thesis

Title: Composites Electronic Enclosure Using Integrated Design & Manufacturing Approach and Carbon Nanotube Buckypaper Materials.
Creator: Young, Charles “Chip”, Liang, Richard, Okoli, Okenwa, Vanli, Arda, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Due to both the advantageous mechanical and unique functionality properties of advanced composite materials, it has become common practice to replace traditionally metal alloy vehicle components, with components comprised of composite materials. Though the primary functionality is that of structure, composites can be custom-tailored to possess application-specific functionalities of their alloy counterparts, such as electromagnetic interference (EMI) shielding, or high thermal and electrical...
Show moreDue to both the advantageous mechanical and unique functionality properties of advanced composite materials, it has become common practice to replace traditionally metal alloy vehicle components, with components comprised of composite materials. Though the primary functionality is that of structure, composites can be custom-tailored to possess application-specific functionalities of their alloy counterparts, such as electromagnetic interference (EMI) shielding, or high thermal and electrical conductivities. In this study, a comprehensive software environment was selected and implemented for a case study involving the design, analysis, and manufacturing of a composite electronics enclosure, with particular emphasis on the integrated design and fabrication of composite products. Additionally, the multifunctional, hybrid composite materials for such an enclosure were investigated, using carbon fiber fabric and multiple-walled carbon nanotube (CNT) buckypaper thin film as the functional materials with a bismaleimide (BMI) thermoset matrix. A study of fabricating carbon fiber-buckypaper composites was performed along with the subsequent mechanical property testing of this hybrid composite material. While developing the hybrid material, the process for manufacturing of a resin-impregnated buckypaper thin film, or buckypaper prepreg," was also achieved. The advantages of a prepreg material over dry, thin-film buckypaper are substantially improved handleability and processability, and overcoming the challenge faced with the low permeability issues encountered when utilizing buckypaper in composite fabrication.
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Date Issued: 2012
Identifier: FSU_migr_etd-6872
Format: Thesis

Title: Damage Detection in Carbon Fiber Composites Using Electrical Resistance Measurements.
Creator: Gory, Ryan, Vanli, Arda, Okoli, Okenwa, Liang, Richard, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: This thesis proposes a methodology for structural health monitoring that incorporates the inherent multi-functionality of carbon fibers. The hypothesis of the thesis is that by monitoring the electrical resistance of composite panels it is possible to detect impacts and statistically model their effects on the remaining useful service life of structures. The proposed research investigates the application of statistics-based analysis to the measured electrical resistance signals during loading...
Show moreThis thesis proposes a methodology for structural health monitoring that incorporates the inherent multi-functionality of carbon fibers. The hypothesis of the thesis is that by monitoring the electrical resistance of composite panels it is possible to detect impacts and statistically model their effects on the remaining useful service life of structures. The proposed research investigates the application of statistics-based analysis to the measured electrical resistance signals during loading. The research also investigates the use of electrical resistance as a stress sensor by monitoring the resistance of test samples under tensile loading.
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Date Issued: 2012
Identifier: FSU_migr_etd-4872
Format: Thesis

Title: Short Carbon Nanotubes and Carbon Nanofibers Composites: Fabrication and Property Study.
Creator: Koo, Ana, Liang, Zhiyong Richard, Liu, Tao, Zhang, Chun Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes (CNTs) have drawn interest for many applications since their discovery. While they provide exceptional mechanical, physical and chemical properties, several technical barriers must be overcome before these properties can be fully used. Some of such drawbacks concern length control, lack of good dispersion and poor interfacial bonding. Currently, CNTs such as single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs) and carbon nanofibers (CNFs) are...
Show moreCarbon nanotubes (CNTs) have drawn interest for many applications since their discovery. While they provide exceptional mechanical, physical and chemical properties, several technical barriers must be overcome before these properties can be fully used. Some of such drawbacks concern length control, lack of good dispersion and poor interfacial bonding. Currently, CNTs such as single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs) and carbon nanofibers (CNFs) are produced in lengths ranging between several to hundreds micrometers and are usually bounded into macroscopically entangled networks. This contradicts with the requirements of some applications, which in the end will benefit with short and highly dispersed CNTs in lengths of a few hundred nanometers or less, such as drug delivering and energy storage carriers. Short CNTs (s-CNTs) and CNFs (s-CNFs) can enhance the mechanical properties of a composite due to the increased interaction with the polymer matrix, through the improvement of the interfacial bonding and resin encapsulation, which is possible with existing open ends of nanotubes. Ultimately this influences the matrix's properties by affecting its chain entanglements, morphology, and crystallinity in the nanocomposite. This research is a continuous effort on nanoscale cutting and characterization of s-CNTs and s-CNFs. Moreover, this research used s-MWNTs and s-CNFs in the lengths of 200 and 500 nm to manufacture the nanocomposites. The mechanical properties of the resultant nanocomposties were characterized. The interactions of the s-MWNT and s-CNTs with epoxy resin matrix were observed using high-resolution SEM and atomic-resolution TEM. The results were compared to nanocomposites with pristine MWNTs and CNFs. In the study, four case studies were explored: 1) 200 nm s-MWNT/epoxy composites; 2) 500 nm s-MWNTs/epoxy composites; 3) 200 nm s-CNF/epoxy composites; 4) 500 nm s-CNF/epoxy composites. For all four cases the MWNT and CNF concentrations were 0.05 wt%, 0.10 wt%, and 1.00 wt%, respectively. Significant mechanical improvements were observed. The strength of the s-MWNT nanocomposite at 1.00 wt% gave a 64% improvement compared to the control sample. The highest young's modulus was also obtained in the 1.00 wt% s-MWNT (200 nm) nanocomposite, and it showed an increase of 44%. In general, the most significant improvements were seen with the s-MWNTs (200 nm) nanocomposites due to their smaller diameters and shorter length. Glass transition temperature was also studied. Finally, the interfacial bonding and interactions of the nanotube's opened ends with the resin matrix were observed through HR-SEM and atomic-resolution TEM analysis, which validated the creation of MWNT and CNF opened ends and the actual resin encapsulation inside the nanotubes' hollow structures.
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Date Issued: 2011
Identifier: FSU_migr_etd-2841
Format: Thesis

Title: In-Situ Triboluminescent Optical Fiber Sensor for Real-Time Damage Monitoring in Cementitious Composites.
Creator: Olawale, David Oluseun, Okoli, Okenwa I., Sobanjo, John O., Liu, Tao, Liang, Zhiyong, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Triboluminescent-based sensor systems have the potential to enable in-situ and distributed structural health monitoring of composite structures. Inability to effectively capture and transmit optical signals generated within opaque composites like concrete and carbon fiber reinforced polymers have however greatly limited their use. This problem has been solved by developing the bio-inspired in-situ triboluminescent optical fiber (ITOF) sensor. This sensor has the potential for wireless, in...
Show moreTriboluminescent-based sensor systems have the potential to enable in-situ and distributed structural health monitoring of composite structures. Inability to effectively capture and transmit optical signals generated within opaque composites like concrete and carbon fiber reinforced polymers have however greatly limited their use. This problem has been solved by developing the bio-inspired in-situ triboluminescent optical fiber (ITOF) sensor. This sensor has the potential for wireless, in-situ, real-time and distributed (WIRD) damage monitoring. Its integrated sensing (triboluminescent thin film) and transmission (polymer optical fiber) components convert the energy from damage events like impacts and crack propagation into optical signals that are indicative of the magnitude of damage in composites. Utilizing the triboluminescent (TL) property of ZnS-Mn, the ITOF sensor has been successfully fabricated. Key design parameters were evaluated to develop a sensor with enhanced damage sensing capability. Sensor's performance was then characterized with Raman spectroscopy, field emission scanning electron microscopy (FESEM) and dynamic mechanical analysis (DMA). Flexural tests were also carried out to evaluate the damage sensing performance of the sensor before integrating into unreinforced concrete beams to create triboluminescent multifunctional cementitious composites (TMCC) with in-situ damage monitoring capabilities like biological systems. Results show that the ZnS-Mn in the epoxy coating of the ITOF sensor does not degrade the thermo-mechanical properties of the composite system. Raman spectroscopy indicates that the ZnS-Mn crystals retained their physical and chemical properties after undergoing the sensor fabrication process. Enhanced side-coupling of TL signals from the ITOF coating into the polymer optical fiber (POF) was achieved with TL thin film coating on POF. This makes distributed sensing possible when the length of the POF is coated with TL thin film. A new approach to damage characterization using TL emission profiles was employed with the TMCC. Three modes of sensor excitation in the TMCC were identified indicative of sensor's ability to sense crack propagation through the beam even when not in contact with the crack. FESEM analysis indicated that fracto-triboluminescence was responsible for the TL signals observed at beam failure. The TL profile analysis promises to facilitate better understanding of crack propagation in composite structural materials.
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Date Issued: 2013
Identifier: FSU_migr_etd-7954
Format: Thesis

Title: Nanostructure-Based Modeling and Experimental Characterization of Electrical Conductivity of Carbon Nanotube Networks.
Creator: Li, Shu, Liang, Richard, Andrei, Petru, Wang, Ben, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes (CNTs) possess exceptional electrical properties. Networks of densely packed nanotubes that are formed by intercontacted or interconnected nanotubes and bundles were observed to form electrically conducting pathways over macroscopic dimensions and can be used for fabricating electronic devices and multifunctional composites. However, the electrical conductivity of these macroscopic networks is much less than the individual CNT's performance, primarily due to the large contact...
Show moreCarbon nanotubes (CNTs) possess exceptional electrical properties. Networks of densely packed nanotubes that are formed by intercontacted or interconnected nanotubes and bundles were observed to form electrically conducting pathways over macroscopic dimensions and can be used for fabricating electronic devices and multifunctional composites. However, the electrical conductivity of these macroscopic networks is much less than the individual CNT's performance, primarily due to the large contact resistance between nanotubes. Many factors contribute to the contact resistance, and the majority of these factors are difficult to directly measure and control due to nanoscale dimensions. The approach of physics-based simulation would help to understand the dominating factors of carbon nanotube networks (CNNs) conductivity. In this thesis work, experimental characterization of the nanostructures and electrical properties of CNNs were carried out, and an equivalent electrical circuit model of CNNs was improved to study the electrical conduction mechanism and properties. To systematically investigate the structure-property relationship between the conductivity of CNNs and their nanostructures, microscopic images of CNNs were characterized with image analysis software to obtain the CNT rope length and diameter distributions. Volume fractions of CNTs in these CNNs were also determined by experimental measurements and literature reported density of CNTs. Raman spectroscopy results were used to characterize the alignment degree of magnetically aligned CNNs. The electrical properties of CNNs, including electrical conductivity and current-carrying capacity tests, were carried out. The conductivities of various types of CNNs were obtained, including single-walled nanotubes (SWNTs), multi-walled nanotubes (MWNTs), and carbon nanofibers (CNF). CNNs of pure SWNTs possess the highest conductivity among all the networks studied. Another important electrical property, the current-carrying capacity, was also studied to understand the breakdown mechanism of CNNs. The tests were conducted to characterize the breakdown temperature and current density of the CNNs. It was determined that the breakdown of CNNs under high current stimuli was due to Joule heating. The modified electrical conductivity model is an electrical circuit simulation approach that reflects multiscale electrical conduction mechanisms and statistical nature of the CNNs. The model begins with nanoscale factors such as nanotube chirality and contact type, and then incorporates microscale factors such as dispersion and nanotube orientation, and further uses circuit computation simulation to calculate the bulk conductivity of the CNNs. Case studies were conducted to first validate the model and then reveal the structure-property relationships of different types of CNNs, including the effects of CNT orientation and chirality on the conductivity of the CNNs. The experimental results and developed model can be used to design and optimize CNNs for electrical applications.
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Date Issued: 2009
Identifier: FSU_migr_etd-7182
Format: Thesis

Title: Assessment of Triboluminescent Materials for Intrinsic Health Monitoring of Composite Damage.
Creator: Dickens, Tarik J., Okoli, Okenwa, Dalal, Naresh, Liu, Ted, Liang, Richard, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Advanced composites offer robust mechanical properties and are widely used for structural applications in the aerospace, marine, defense and transportation industries. However, the inhomogenous nature of composite materials leaves them susceptible to problematic failure; thus the development of a means for detecting failure is imperative. Damage occurs when a load is applied and a distortion of the solid material results in deformation. This process also results in straining of the material....
Show moreAdvanced composites offer robust mechanical properties and are widely used for structural applications in the aerospace, marine, defense and transportation industries. However, the inhomogenous nature of composite materials leaves them susceptible to problematic failure; thus the development of a means for detecting failure is imperative. Damage occurs when a load is applied and a distortion of the solid material results in deformation. This process also results in straining of the material. Strain, however, is a physical result of work being performed on a solid material making energy the commonality among all failure mechanisms. This study investigated the feasibility of using Triboluminescent zinc-sulphide manganese (ZnS:Mn) phosphors concentrated in vinyl ester resin for damage monitoring of polymer composites under flexural loading. These particulates react to straining or fracturing by emitting light of varied luminous intensity and detecting the crack initiation presently leading to catastrophic failure(s). Unreinforced vinyl ester resins and fiber-reinforced composite beams incorporated 5 - 50 % wt. concentrations of TL fillers, and were subjected to three-point bend tests. The intent of flexural testing was to observe the transient response of triboluminescence (TL) in both two- and three-phase composite systems throughout the failure cycle of notched beams, while changing the geometric constraints. Results indicate TL crystals emit light at various intensities corresponding to crystal concentration, the notch-length and imminent matrix fracture. The fracturing or deformation energy was estimated by the method of J-integral with varied notch-lengths, where a lower threshold for excitation was found to be approximately <2 J/m^2, far below its critical fracture energy (~ 3 & 7 J/m^2). Consequently, concentrated samples showed nearly 50 % reductions of mechanical moduli due to high loading levels, which subsequently affected the Triboluminescent response. As a result, an optimal 6 % vol. of TL particulates was chosen for further study and exhibited significant signal-to-noise response. Scanning electron microscopy (SEM) revealed particulate inclusions with shearing bands and semblance of particle to resin adhesion, as well as, cases of micro-cracking in reinforced samples. Despite significant parasitic affect to mechanical properties, the luminescent properties of TL occur at rupture for unreinforced composites. The cases of TL concentrated reinforced composites show detection of localized matrix phenomenon which are related to the material response and incurring internal strain-energy prior to any catastrophic failure. This indicates that TL in composite systems has the potential to detect micro-failures (micro-cracks) related to the weak matrix component. The triboluminescent signal was simulated as a rate-dependent model considering the load profile of the composite beam is known.
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Date Issued: 2013
Identifier: FSU_migr_etd-7772
Format: Thesis

Title: Auxetic Polyurethane Foam: Manufacturing and Processing Analysis.
Creator: Jahan, Md. Deloyer, Zeng, Changchun, Liang, Zhiyong, Vanli, Arda, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Materials with negative Poisson's ratio are referred to as auxetic materials. They are different from conventional materials in their deformation behavior when responding to external stresses. The cross-section of the materials widens in the lateral direction when being stretched in the longitudinal direction and becomes narrower when being compressed longitudinally. While a number of natural auxetic materials exist, most auxetic materials are synthetic. They show interesting properties and...
Show moreMaterials with negative Poisson's ratio are referred to as auxetic materials. They are different from conventional materials in their deformation behavior when responding to external stresses. The cross-section of the materials widens in the lateral direction when being stretched in the longitudinal direction and becomes narrower when being compressed longitudinally. While a number of natural auxetic materials exist, most auxetic materials are synthetic. They show interesting properties and have potential in several important applications. Auxetic materials exhibit better mechanical properties than conventional materials such as enhanced indentation resistance, shear resistance, toughness, damping and energy absorption capacity, sound absorption, variable permeability and capability of producing complex curvature. These properties are beneficial in a wide range of applications including personal protective equipments, sound absorbers, packaging, smart filtration, drug delivery, tissue scaffolding, seat cushioning, etc. A wide range of auxetic materials has been synthesized. They include different polymers, metals, composites and ceramics. Among these, auxetic polyurethane (PU) foam is one of the most widely studied types of auxetic materials. Auxetic PU foams are usually fabricated by altering the microstructure of conventional foams and the unusual mechanical properties originate from the deformation characteristics of the microstructures. Three most important processing parameters in fabricating auxetic PU foam that dictate auxetic behavior are processing temperature, heating time and volumetric compression ratio. This study addresses several important issues in the manufacturing and characterization of auxetic PU foam. First, an improved automatic measuring technique has been developed to determine Poisson's ratio of auxetic PU foam. The technique involves development of a Matlab based image processing program. The second part of the study includes an experimental design approach to identify significant processing parameters followed by optimization of those processing parameters in fabrication of auxetic PU foam. A split-plot factorial design has been selected for screening purpose. Response Surface Methodology (RSM) has been utilized to optimize the processing parameters in fabrication of auxetic PU foam. Two different designs named Box-Behnken and I-optimal designs have been employed for this analysis. The results obtained by those designs exhibit that I-optimal design provides more accurate and realistic results than Box-Behnken design when experiments are performed in split-plot manner. Finally, a near stationary ridge system is obtained by optimization analysis. As a result a set of operating conditions are obtained that produces similar minimum Poisson's ratio in auxetic PU foam.
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Date Issued: 2014
Identifier: FSU_migr_etd-9011
Format: Thesis

Title: The High Current-Carrying Capacity of Various CNT Enhanced Composites.
Creator: Azamian, Pegah, Liang, Richard Zhiyong, Zhang, Chuck, Zheng, Chad, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon fiber reinforced composites (CFRPs) are light weight, have high strength and modulus, which make them qualified candidates for numerous automotive and aerospace industries. However one of the major technical challenges for these materials in airplanes bodies, in terms of aircraft safety and durability, is lightning strike protection (LSP). This is due to the inadequate electrical properties of normal CFRPs. Although, CFRPs have relatively good in-plane electrical conductivity compared...
Show moreCarbon fiber reinforced composites (CFRPs) are light weight, have high strength and modulus, which make them qualified candidates for numerous automotive and aerospace industries. However one of the major technical challenges for these materials in airplanes bodies, in terms of aircraft safety and durability, is lightning strike protection (LSP). This is due to the inadequate electrical properties of normal CFRPs. Although, CFRPs have relatively good in-plane electrical conductivity compared to neat epoxy resin, they lack metal-like high conductivity for LSP applications. To solve this issue, metal materials such as copper or aluminum mesh are attached to carbon fiber composites in the aircraft's body. This solution is not satisfactory due to heavy weight of metals and the occurrence of galvanic corrosion between metals and CFRPs. On other hand carbon nanotubes (CNTs) possess great potential for enhancing high-performance and multifunctional nanocomposites and exhibit incredible mechanical, electrical and thermal properties, which can replace the metal mesh materials. This study investigates the use of carbon nanotubes to enhance composite conductivity for potential metal material replacement and their basic current- carrying capacity. During testing, the samples were exposed to high temperatures with electrical current-induced thermal heating in atmosphere condition. High electrical currents generated Joule heating causing thermal degradation at over 600 °C (main failure mechanism). Micro-structural changes of the samples after electrical current heating were observed using SEM and EDS analyses. The result show resin evaporation at the notch and nucleation of Fe and Ti particles. CNTs enhance the current carrying capability of the CFRP and Buckypaper (preformed thin CNT film) composites. However, the performance improvement differs upon on the epoxy used as well as the manufacturing method and nantubes types. In addition higher conductivity of the samples contributed to higher current-carrying density at the breakdown point. These results provide a preliminary understanding of the effect of the CNTs on the current carrying capability and the electrical properties of CNT enhanced CFRPs and BP composites.
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Date Issued: 2010
Identifier: FSU_migr_etd-0268
Format: Thesis

Title: Dielectric and Mechanical Properties of PMMA/BTA Nanocomposites for HTS Applications.
Creator: Ingrole, Aniket, Liang, Zhiyong Richard, Rodrigo, Horatio, Okoli, Okenwa, Zhang, Mei, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: To prepare dielectric materials for High Temperature Superconductor (HTS) cables, nanocomposites consisting of Polymethylmethacrylate (PMMA) and Barium Titanate (BTA) nanoparticles have been manufactured and evaluated. The main objective of this research is to enhance the dielectric breakdown strength and reduce the dielectric losses of the nanocomposites. Polymethylmethacrylate (PMMA) with the addition of BTA (5wt.% and 10wt.% ) nanocomposites were fabricated by using two different methods....
Show moreTo prepare dielectric materials for High Temperature Superconductor (HTS) cables, nanocomposites consisting of Polymethylmethacrylate (PMMA) and Barium Titanate (BTA) nanoparticles have been manufactured and evaluated. The main objective of this research is to enhance the dielectric breakdown strength and reduce the dielectric losses of the nanocomposites. Polymethylmethacrylate (PMMA) with the addition of BTA (5wt.% and 10wt.% ) nanocomposites were fabricated by using two different methods. The breakdown voltage measurements have been conducted under AC, DC and lightning impulse high voltage. The measurements were conducted at both room temperature (293 K) and liquid nitrogen temperature (77 K). The results of the electrical breakdown field measurements of the nanocomposites are compared with those of the base polymer. Fracture surface analysis was carried out with SEM analysis. The difference in the breakdown area due to different modes of voltages applied and effect of the nanoparticles was studied. Mechanical characterization of the resultant nanocomposites was also carried out at both the room temperature (293K) and at cryogenic temperature (77K). The effects of nanoparticles on the electrical and mechanical properties were observed. A marginal increase in the dielectric strength of the nanocomposites was observed for AC conditions at both the temperatures. There was a decrease in the values of nanocomposites for impulse conditions. At cryogenic temperature nanocomposites showed higher dielectric strength when DC voltage was applied. For both the temperatures, dielectric losses increased as the voltage was increased for all the materials studied, except for PMMA/10wt.%BTA nanocomposites at cryogenic temperature, which showed decrease of losses by ~ 70%. An increase of ~12% in Young's modulus and ~ 65% increase in tensile strength of the nanocomposites were observed at cryogenic temperature. It also shows that more material damage was observed under AC breakdown voltage compared to the impulse and DC voltage breakdown cases. Also the material damage was more pronounced at 77 K than that at 293 K.
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Date Issued: 2010
Identifier: FSU_migr_etd-3865
Format: Thesis

Title: Elastic Property Prediction and Variation Quantification for Buckypaper-Polymer Nanocomposites: Modeling and Experimental Validation.
Creator: Tsai, Chao-hsi, Zhang, Chuck, Oates, William, Wang, Ben, Vanli, O. Arda, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: A practical method to utilize carbon nanotubes (CNTs) in structural applications is to fabricate them into buckypapers (BPs), a thin film containing two-dimensional CNT networks, and combine them with a polymer matrix to make BP-polymer (BPP) composites. It has been demonstrated that BPP composites have very good mechanical properties with multi-functional capabilities. However, due to the uncertainties involved in different manufacturing stages, the resulting BPP composites exhibit larger...
Show moreA practical method to utilize carbon nanotubes (CNTs) in structural applications is to fabricate them into buckypapers (BPs), a thin film containing two-dimensional CNT networks, and combine them with a polymer matrix to make BP-polymer (BPP) composites. It has been demonstrated that BPP composites have very good mechanical properties with multi-functional capabilities. However, due to the uncertainties involved in different manufacturing stages, the resulting BPP composites exhibit larger property variations when compared with traditional metal or ceramic materials. As such, there is need for an improved modeling strategy that can provide rapid property predictions and variation quantifications for BPP composites through measurable buckypaper nanostructures and processing conditions. Due to high material costs and long production cycle times, it is nearly impossible to construct a statistical-based model for BPP composites purely from physical experiments. Theoretical (micromechanical) models are more cost effective, but they also have some drawbacks. Namely, they are computationally intensive, deterministic in nature, and have questionable accuracy due to underlying simplified assumptions. Different sources of variations in BPP composite manufacturing also build on the inadequacy of these micromechanical models for providing reasonable predictions without further adjustments. Therefore, the main objective of this study is to provide a better modeling strategy for the prediction of BPP composite stiffness. By integrating a series of statistical methods with traditional micromechanical models, the variations observed in different stages were quantified, and a better predictive surrogate modeling strategy was constructed as a result. The statistical dispersions of buckypaper nanostructures (nanotube bundle length, diameter, orientation and waviness) were first analyzed and characterized by applying image analysis to microscopic images of buckypaper surface. It was found that the distribution of bundle length and diameter can be reasonably described by a two-parameter Weibull distribution, and the orientation of nanotubes can be represented by a periodic Fourier series. A stochastic based model was then constructed to predict the theoretical dispersions of BPP composite stiffness through experimentally measured nanostructure distributions by combining micromechanics with a Monte-Carlo simulation. It was found that the distribution of BP nanostructures would bias the resultant BPP composite modulus if a non-symmetric nanostructure distribution was present. The degree of nanostructure effects and interactions was analyzed using polynomial modeling and sensitivity analysis. The diameter and waviness of nanotube bundles were found to be the most influential factors for BPP composite modulus in most cases. The intra/inter buckypaper variations were studied using an Analysis of Variance (ANOVA) test. Both variations were tested as insignificant and can thus be statistically combined using the "mean nanostructure distribution" with pooled mean and variance. Lastly, two different sets of BPP composite experiments were used to validate the predictive capability of the constructed model. Preliminary results exhibited a noticeable discrepancy between theoretical predictions and physical observations due to the imperfections of the CNT-polymer interface. Therefore, statistical two-stage sequential modeling was applied to calibrate the original micromechanical model, and the resultant surrogate model was demonstrated to possess improved predictive capabilities. Recently functionalized BPP composite data also showed a very good correspondence to the theoretical predictions after the CNT-polymer interface was improved.
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Date Issued: 2010
Identifier: FSU_migr_etd-1500
Format: Thesis

Title: Experimental Study and Modeling of Nanotube Buckypaper Composite Actuator for Morphing Structure Applications.
Creator: Tsai, Szu-Yuan, Liang, Zhiyong, Oates, William, Wang, Ben, Zhang, Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: The objectives of this research are to develop lightweight high-performance nanotube composite actuators that can be operated in open air and to study their actuation mechanisms. We successfully demonstrated solid electrolyte-based buckypaepr actuators. Long MWNT and dopped SWNT BP actuators showed significant improvement of actuation performance. A constitutive structure-stimulation-performance model has been developed to analyze and predict actuation performance. The modeling results can be...
Show moreThe objectives of this research are to develop lightweight high-performance nanotube composite actuators that can be operated in open air and to study their actuation mechanisms. We successfully demonstrated solid electrolyte-based buckypaepr actuators. Long MWNT and dopped SWNT BP actuators showed significant improvement of actuation performance. A constitutive structure-stimulation-performance model has been developed to analyze and predict actuation performance. The modeling results can be further used to improve the actuation performance through parameter studies. Lightweight all-solid-state nanotube composite actuators developed in this research were a bimorph configuration with a high conductive solid electrolyte layer sandwiched by two nanotube buckypaper electrode layers. The effects of driving voltages and frequencies were studied. The nanotube buckypaper composite actuators demonstrated consistent responses to electrical stimulation frequencies up to 40 Hz. Different types of nanotube buckypapers were tested to determine their actuation performance, including randomly dispersed single-walled carbon nanotubes (SWNT), aligned SWNT, randomly dispersed multi-walled carbon nanotubes (MWNT), randomly dispersed long MWNT and SWNT-MWNT mixed nanotube buckypapers. Dynamic mechanical analysis (DMA) and tensile tests were conducted to determine actuator mechanical properties. A Young's modulus of 2.17 GPa from long MWNT buckypaper composite actuator was one of the highest reported values among electro-active polymer composite actuators. The research also realized significant performance improvements by using long MWNT nanotube buckypapers and lithium ion doped SWNT buckypapers as electrode layers. The resultant actuators can achieve more than 20 mm displacements, which is about 10 times greater than untreated SWNT buckypaper composite actuators. Ionic doped SWNT buckypaper actuators are especially promising because they consume 70% less power to perform the same amount of actuation compared to long MWNT buckypaper actuators. The maximum strain and blocking force of the long MWNT BP composite actuators were 0.77% and 8.7 mN, respectively. The research indicated two actuation mechanisms of nanotube buckypaper actuators co-exist: 1) carbon-carbon (C-C) bond extensions when an electrical charge applied, as previously reported in the literature, and 2) an ionic current flow effect in the solid electrolytes. The developed structure-stimulation-performance model was able to predict the displacement of nanotube buckypaper actuators based on both mechanisms. Modeling results indicate that ionic current flow effect was the dominant effect in the devices. By conducting parameter studies, we can reveal the influential factors for actuation performance. The modeling results for the SWNT BP/Nafion actuator were in good agreement with experimental data. The resultant actuators are promising for lightweight morphing structure applications.
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Date Issued: 2010
Identifier: FSU_migr_etd-1504
Format: Thesis

Title: Interfacial Bonding Property Study of Functionalized Cnt Nanocomposites Based on a Modified Cox's Model.
Creator: Wang, Xianping, Liang, Richard, Wang, Ben, Okoli, Okenwa, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Many researchers have studied the interfacial shear stress (ISS) in nanocomposites through theoretical calculation, computational simulation or sophisticated nanomanipulation experiment measurement. In this research, we attempt to directly calculate ISS values in actual nanocomposites based on a modified Cox's model using tensile test results of various macroscopic carbon nanotube (CNT) nanocomposites. Young's modulus, tensile strength and strain of CNT ropes rather than individual CNT...
Show moreMany researchers have studied the interfacial shear stress (ISS) in nanocomposites through theoretical calculation, computational simulation or sophisticated nanomanipulation experiment measurement. In this research, we attempt to directly calculate ISS values in actual nanocomposites based on a modified Cox's model using tensile test results of various macroscopic carbon nanotube (CNT) nanocomposites. Young's modulus, tensile strength and strain of CNT ropes rather than individual CNT properties were applied into the model. The effects of functionalization, CNT rope length, volume fraction and CNT type (SWNT, DWNT, MWNT) on interfacial shear stress were studied. It was found that the functionalization increased the mechanical properties of both interfacial bonding and DWNT and MWNT rope themselves; however, it decreased the mechanical properties of SWNT ropes. The major failure mode of the CNT nanocomposites was identified to be CNT rope rupture. The calculation results revealed that the ISS values in the nanocomposites are comparable with the ones reported in literature.
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Date Issued: 2010
Identifier: FSU_migr_etd-1252
Format: Thesis

Title: High Temperature Polyimide/Carbon Fiber/Carbon Nanotubes Multiscale Composites: Processing, Cure Kinetics and Multifunctionality.
Creator: Fu, Xiang, Zhang, Chuck, Liu, Tao, Shanbhag, Sachin, Liang, Zhiyong, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: The discovery of carbon nanotubes (CNTs) by Iijima in 1991 has initiated a great deal of scientific research on exploring their unique properties and potential applications. One of the promising applications is integrating CNTs into polymer or polymer/fiber composites to form nanocomposite or multi-scale composites. High temperature polymer composites are required for use in structural components in advanced high speed aircraft, weapon systems and space vehicles. Motivated by the potential of...
Show moreThe discovery of carbon nanotubes (CNTs) by Iijima in 1991 has initiated a great deal of scientific research on exploring their unique properties and potential applications. One of the promising applications is integrating CNTs into polymer or polymer/fiber composites to form nanocomposite or multi-scale composites. High temperature polymer composites are required for use in structural components in advanced high speed aircraft, weapon systems and space vehicles. Motivated by the potential of significantly improving thermal, electrical, mechanical and properties and fire retardancy of polymer matrix composites at relatively low concentration, this research focuses on integrating CNTs into high temperature fiber-reinforced composites aiming at matrix enhancement at the inter-fiber level, z-direction reinforcement and multi-functionality such as thermal and electrical conductivity, fire retardancy or resistance. High temperature vacuum-assisted resin transfer molding was designed and successfully demonstrated with in-plane and through-thickness resin flow methods. Polyimide based PETI-330/carbon fabric T650-35 laminates were manufactured with fiber volume fraction of ~60% and void contents of 3-4%. The tensile strengths of PETI-330/T650-35 laminates fabricated by in-plane and through-thickness processes are 834 and 799 MPa, respectively. Short beam strengths of the laminates via both processes are 43 and 52 MPa, which are ~77% and ~93% of that processed via RTM using an injection pressure of 2.75 MPa. CNT/carbon fiber/PETI-330 multi-scale composites were fabricated using prepreg-assisted RTM process. Homogeneous dispersion of CNTs in the PETI-330 matrix were achieved using the solution processing method. Using this method, multi-scale composite laminates with various concentrations of CNTs were manufactured. Comprehensive characterizations were carried out to investigate the thermal stability, thermal mechanical properties, micro-structure and morphologies of the CNT/PETI-330/T650 multi-scale composite laminates. As a result, we found that: (1) the incorporation of small amounts of CNTs can significantly improve the high-temperature thermal mechanical properties of the PETI-330 resin; (2) after postcuring the room temperature storage modulus of 1 wt% CNT/PETI-330/T650 composite increased from ~60 GPa to ~71GPa, the glass transition temperature increased from 331°C to 350°C; (3) the existence of CNT induces hindered cure kinetics of PETI-330. Multiscale composites were also fabricated using buckypapers made of mixed SWNTs/MWNTs integrated onto polyimide/carbon fibre composite surface and their fire retardancy was characterized. Compared to the control sample (CP), buckypaper incorporated sample produced further delayed ignition, 40% lower peak heat release rate, 26% lower heat release, 82% less smoke release and 33% less mass loss. Further, buckypaper effectively increases the thermal conductivity of PETI-330/carbon fiber composite; the thermal conductivity improves 13% at 25°C and 27% at 300°C. The buckypaper is more efficient as fire retardant in polyimide/carbon fiber composites than direct mixing CNTs into polymer matrix. The effect of CNTs on the cure kinetics of imide oligomer was studied using differential scanning calorimetry. During isothermal cure, the neat resin begins to cure first. As the reaction proceeds, the enthalpy of reaction decreases for the nanocomposites. As the samples vitrify and the reaction is completed, the neat PETI-330 vitrifies faster than the 1% CNT/PETI-330 nanocomposite sample. The adding of 1 wt% CNTs caused lower enthalpy, slightly lower activation energy. The cure kinetics of neat PETI-330 and the PETI-330/CNT systems can be modeled as first-order reactions, meaning the reactions are mainly ethynyl-ethynyl addition polymerization to form carbon-carbon double bonds. Comparison of the activation energies, rate constant and cure times suggests that the cure mechanisms of the neat PETI-330 resin and CNTs embedded nanocomposites are similar. Last but not least, the molecular models of the PETI-330 imide oligomer and CNTs were constructed. Molecular dynamics simulations showed that molecular interaction energy of imide/ CNT system is -37.5 kcal/mol. The major contributor of the interactions between CNT and the imide oligomer is van de Waals energy which is due to the ÆÃ -stacking effect between similar molecular structure of CNT surface and the phenyl rings in the backbone and side-groups. The attractive energy between CNT and imide oligomer can explain why the glass transition temperature shifts toward higher temperature in multi-scale composites manufactured in this study.
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Date Issued: 2010
Identifier: FSU_migr_etd-4388
Format: Thesis

Title: Experimental Study of Electrical Conductivity of Carbon Nanotube, Nanofiber Buckypapers and Their Composites.
Creator: Xue, Yuan, Liang, Zhiyong, Andrei, Petru, Wang, Ben, Zhang, Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: The discovery of carbon nanotubes brought on a whole new world of nanotechnology. Various forms of carbon materials were developed, including single-walled carbon nanotube (SWNT), multi-walled carbon nanotube (MWNT), and carbon nanofiber (CNF). These carbon nanomaterials attract academic and industrial interests because of their exceptional mechanical, thermal and electrical properties. For electrical conductivity in particular, it is widely recognized that SWNTs have considerable potential...
Show moreThe discovery of carbon nanotubes brought on a whole new world of nanotechnology. Various forms of carbon materials were developed, including single-walled carbon nanotube (SWNT), multi-walled carbon nanotube (MWNT), and carbon nanofiber (CNF). These carbon nanomaterials attract academic and industrial interests because of their exceptional mechanical, thermal and electrical properties. For electrical conductivity in particular, it is widely recognized that SWNTs have considerable potential as building blocks for future nanoscale electronics and conducting composites. The first objective of this thesis is to develop a comprehensive electrical resistivity measurement system which can measure the electrical resistivity of nanotube-based materials ranging from 1.0E-6 ''cm to 1.0E+17 ''cm. The test setup performance was examined using Gage R and R (Repeatability and reproducibility) analysis. The second objective is to characterize and analyze electrical conductive properties of different Buckypapers (thin film of nanotube network) and nanocomposites to demonstrate their performance and establish a database for future applications. Detailed characterizations of the electrical conductivities of SWNT, MWNT, and carbon fiber Buckypapers and their composites were conducted. The influential factors of resistivity of Buckypapers were discussed, including the effects of nanotube batches, processing methods, and surfactant types. In this study, the electrical resistivity properties of the mixed Buckypapers of SWNT/MWNT and SWNT/CNF were also investigated. The effects of nanoparticle types (SWNT, MWNT, and CNF) were examined. The results show that the low cost MWNT and nanofiber materials can still retain good electrical conductivity of the resultant mixed Buckypapers, creating excellent application potentials for developing cost effective multifunctional composites. The thesis also studied the electrical conductivity of functionalized SWNT Buckypapers. Functionalization of nanotubes was suggested to be an effective way to tune the electrical conductivity of CNTs. The functionalization methods included electron-beam irradiation and fluorinated grafting. The resistivities of the functionalized SWNT Buckypapers were experimentally investigated.
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Date Issued: 2007
Identifier: FSU_migr_etd-7081
Format: Thesis

Title: Characterizing the Single-Walled Carbon Nanotube Dispersions: Novel Methods Development and Their Applications.
Creator: Xiao, Zhiwei, Liu, Tao, Ramakrishnan, Subramanian, Liang, Zhiyong, Guan, Jingjiao, Zhang, Mei, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Single-walled carbon nanotubes (SWCNTs) thin films exhibit great potential in various applications thanks to their extraordinary physical and mechanical properties. However, to fully take advantage of their superior properties there are still several barriers to be overcome. On one hand, SWCNTs are rarely found as isolated individual tubes, which makes them very difficult to exfoliate and disperse. On the other hand, SWCNTs are not with perfect defect-free chemical structure, which can...
Show moreSingle-walled carbon nanotubes (SWCNTs) thin films exhibit great potential in various applications thanks to their extraordinary physical and mechanical properties. However, to fully take advantage of their superior properties there are still several barriers to be overcome. On one hand, SWCNTs are rarely found as isolated individual tubes, which makes them very difficult to exfoliate and disperse. On the other hand, SWCNTs are not with perfect defect-free chemical structure, which can severely degrade the intrinsic properties of the pristine SWCNTs and thus deteriorate the various SWCNT based applications. In many cases, when people perform chemical functionalization to SWCNTs, they have to find a balance between the improvement of the dispersability and compatibility of SWCNTs and the degradation of the intrinsic properties of SWCNTs. Therefore, it is crucial to have an easy-to-use and reliable way to characterize and quantify the corresponding structural information of SWCNT in dispersion such as bundle size, bundling state, defect density, etc. Two different techniques for in-situ structural characterization of SWCNTs in dispersion have been developed. The Preparative Ultracentrifuge Method (PUM) combined with dynamic light scattering (DLS) technique provides us an approach to investigate the bulk averaged SWCNT bundle size in dispersion. The Simultaneous Raman Scattering and Photoluminescence (SRSPL) technique allows us to study the bundling state/degree of exfoliation of SWCNT in dispersion. Based on the 1D exciton diffusion model, we can also use the SRSPL technique to estimate the defect density of SWCNTs in dispersion. The application of PUM and SRSPL has been demonstrated in studying the structural changes of SWCNT dispersion under different processing (sonication and ultracetrifugation) conditions. It revealed the exfoliation mechanism of SWCNT under sonication technique. Moreover, the developed PUM characterization techniques were further applied to study the interactions between SWCNT and polyacrylonitrile (PAN) homo- and copolymers. On the basis of the established PUM and SRSPL characterization methods, my proposed work focuses on an in-depth understanding of the effects of bundling states and defect density on the electrical and mechanical properties of SWCNT thin films. The detailed proposed tasks include: 1) improve the current physical model for quantifying defect density; 2) prepare and characterize the SWCNT dispersions with controlled bundle size and defect density; 3) fabricate and characterize the electrical and mechanical properties of SWCNT thin films to elucidate the effects of bundling state and defect density of SWCNTs in the dispersion.
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Date Issued: 2013
Identifier: FSU_migr_etd-7670
Format: Thesis

Title: Recycling High-Performance Carbon Fiber Reinforced Polymer Composites Using Sub-Critical and Supercritical Water.
Creator: Knight, Chase C., Zeng, Changchun, Zhang, Chuck, Chella, Ravindran, Liang, Richard, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon fiber reinforced plastics (CFRP) are composite materials that consist of carbon fibers embedded in a polymer matrix, a combination that yields materials with properties exceeding the individual properties of each component. CFRP have several advantages over metals: they offer superior strength to weight ratios and superior resistance to corrosion and chemical attack. These advantages, along with continuing improvement in manufacturing processes, have resulted in rapid growth in the...
Show moreCarbon fiber reinforced plastics (CFRP) are composite materials that consist of carbon fibers embedded in a polymer matrix, a combination that yields materials with properties exceeding the individual properties of each component. CFRP have several advantages over metals: they offer superior strength to weight ratios and superior resistance to corrosion and chemical attack. These advantages, along with continuing improvement in manufacturing processes, have resulted in rapid growth in the number of CFRP products and applications especially in the aerospace/aviation, wind energy, automotive, and sporting goods industries. Due to theses well-documented benefits and advancements in manufacturing capabilities, CFRP will continue to replace traditional materials of construction throughout several industries. However, some of the same properties that make CFRP outstanding materials also pose a major problem once these materials reach the end of service life. They become difficult to recycle. With composite consumption in North America growing by almost 5 times the rate of the US GDP in 2012, this lack of recyclability is a growing concern. As consumption increases, more waste will inevitably be generated. Current composite recycling technologies include mechanical recycling, thermal processing, and chemical processing. The major challenge of CFRP recycling is the ability to recover materials of high-value and preserve their properties. To this end, the most suitable technology is chemical processing, where the polymer matrix can be broken down and removed from the fiber, with limited damage to the fibers. This can be achieved using high concentration acids, but such a process is undesirable due to the toxicity of such materials. A viable alternative to acid is water in the sub-critical and supercritical region. Under these conditions, the behavior of this abundant and most environmentally friendly solvent resembles that of an organic compound, facilitating the breakdown of the polymer matrix. To date, very few studies have been reported in this area and the studies thus far have only focused on small scale feasibility and have only shown the recovery of random fibers. The goal of this research is to advance the knowledge in the field of sub-critical and supercritical fluid recycling by providing fundamental information that will be necessary to move this process forward to an industrial scale. This dissertation work consists of several phases of studies. In the first phase of this research, the feasibility of recycling woven CFRP was established on a scale approximately 30 times larger than previously reported. The industrial relevance was also conveyed, as the process was shown to remove up 99% of a highly cross-linked resin from an aerospace grade composite system with 100% retention of the single filament tensile strength and modulus whilst also retaining the highly valuable woven fiber structure. The second phase of research demonstrated the power of this technology to recycle multi-layer composites and provide the ability to reuse the highly valuable materials. Up to 99% resin elimination was achieved for a woven 12-layer aerospace grade composite. The recycled woven fabric layers, with excellent retention of the fiber architecture, were directly reused to fabricate reclaimed fiber composites (RFC). Manufacturing issues associated with the use of the recycled fiber were investigated. Several fabrication technologies were used to fabricate the composite, and the composites show moderate short beam shear strength and may be suitable for certain industrial applications. Moreover, fresh composites were also recycled, recovered, and reused to investigate the retention of flexural properties of the fibers after recycling. Up to 95% of the flexural strength and 98% of the flexural modulus was retained in the reclaimed fiber composites. The recycled resin residual can be incorporated into fresh resin and cured, demonstrating a near complete recycling loop. After showing the feasibility and power of this technology, the third phase of the study was focused on the fundamentals on the degradation of highly cross-linked polymer network by sub- and near-critical water. A methodology framework was established to study the apparent kinetics of the degradation of epoxy in sub-critical water. The reaction rate was modeled by a phenomenological rate model of nth order, and the rate constant was modeled by taking into account of the contributions of important physical parameters, e.g., pressure, temperature and dielectric constants. The applicability of the established model to describe the degradation kinetics was confirmed by the validation runs. This model is a suitable starting point to gain the knowledge required for eventual industrial process design. The final phase of this research consisted of a preliminary foray into investigating the economic feasibility of this technology. A process model was designed around a reactor which was sized according to considerations of industrial relevancy. The simulation of the process was done using Aspen Plus, powerful and comprehensive process simulation software. Economic analysis of this pseudo-realistic process suggested that such technology was economically viable and competitive comparing to other recycling technologies. In summary, this dissertation work represents the first comprehensive investigation on recycling aerospace-grade, multilayer woven fabric composites using supercritical and sub-critical water. The fundamental knowledge gained and process technology developed during this research is anticipated to play an important role in advancing this recycling technology toward potential adoption and implementation by the recycling and composite industry.
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Date Issued: 2013
Identifier: FSU_migr_etd-7450
Format: Thesis

Title: Processing-Structure-Property Relationships of Carbon Nanotube and Nanoplatelet Enabled Piezoresistive Sensors.
Creator: Luo, Sida, Liu, Tao, Brooks, James, Zhang, Chuck, Zhang, Mei, Shanbhag, Sachin, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Individual carbon nanotubes (CNTs) possess excellent piezoresistive performance, which is manifested by the significant electrical resistance change when subject to mechanical deformation. In comparison to individual CNTs, the CNT thin films, formed by a random assembly of individual tubes or bundles, show much lower piezoresistive sensitivity. Given the progress made to date in developing CNT ensemble based-piezoresistive sensors, the related piezoresistive mechanism(s) are still not well...
Show moreIndividual carbon nanotubes (CNTs) possess excellent piezoresistive performance, which is manifested by the significant electrical resistance change when subject to mechanical deformation. In comparison to individual CNTs, the CNT thin films, formed by a random assembly of individual tubes or bundles, show much lower piezoresistive sensitivity. Given the progress made to date in developing CNT ensemble based-piezoresistive sensors, the related piezoresistive mechanism(s) are still not well understood. The crucial step to obtain a better understanding of this issue is to study the effects of CNT structure in the dispersion on the piezoresistivity of CNT ensemble based-piezoresistive sensors. To reach this goal, my Ph.D. research first focuses on establishing the processing-structure-property relationship of SWCNT thin film piezoresistive sensors. The key accomplishment contains: 1) developing the combined preparative ultracentrifuge method (PUM) and dynamic light scattering (DLS) method to quantitatively characterized SWCNT particle size in dispersions under various sonication conditions; 2) designing combined ultrasonication and microfluidization processing protocol for high throughput and large-scale production of high quality SWCNT dispersions; 3) fabricating varied SWCNT thin film piezoresistive sensors through spray coating technique and immersion-drying post-treatment; and 4) investigating the effect of microstructures of SWCNTs on piezoresistivity of SWCNT thin film sensors. This experimental methodology for quantitative and systematic investigation of the processing-structure-property relationships provides a means for the performance optimization of CNT ensemble based piezoresistive sensors. As a start to understand the piezoresistive mechanism, the second focus of my Ph.D. research is studying charge transport behaviors in SWCNT thin films. It was found that the temperature-dependent sheet resistance of SWCNT thin films could be explained by a 3D variable range hopping (3D-VRH) model. More importantly, a strong correlation between the length of SWCNTs and the VRH parameter T0, indicating the degree of disorder of the electronic system, has been identified. With the structure dependent transport mechanism study, a very interesting topic - how T0 changes when SWCNT thin film is under a mechanical deformation, would be helpful for better understanding the piezoresistive mechanism of SWCNT thin film sensors. As demonstrated in transport mechanism study, SWCNT thin film exhibits a negative temperature coefficient (NTC) of resistance. In contrast, another family of carbon nanomaterials, graphite nanoplatelets (GNPs), shows positive temperature coefficient (PTC) of resistance, attributed to their metallic nature. Therefore, upon a wise selection of mass ratio of SWCNTs to GNPs for fabrication of hybrid SWCNT/GNP thin film piezoresistive sensors, a near zero temperature coefficients of resistance in a broad temperature range has been achieved. This unique self-temperature compensation feature along with the high sensitivity of SWCNT/GNP hybrid sensors provides them a vantage for readily and accurately measuring the strain/stress levels in different conditions. With the unique features of SWCNT/GNP hybrid thin film sensors, my future work will focus on application exploration on SWCNT/GNP thin film sensor based devices. For example, we have demonstrated that it is potential for man-machine interaction and body monitoring when coating the hybrid sensor on highly stretchable nitrile glove. The structure health monitoring (SHM) of composite materials could also be realized by coating the thin film sensor on a glass fiber surface and then embedding the fiber sensor in composite structure.
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Date Issued: 2013
Identifier: FSU_migr_etd-7478
Format: Thesis

Title: Supercritical Fluid Deposition of Vanadium Pentoxide within Carbon Nanotube Buckypaper for Electrochemical Capacitor.
Creator: Do, Quyet Huu, Zeng, Changchun, Zhang, Chuck, Zheng, Jim P., Zhang, Mei, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: There is a pressing need from a broad range of industries for high-performance energy storage devices with high power, high energy capacity, light weight, long lifetime, high efficiency, and low cost. A typical energy storage device, current electrochemical capacitors do not possess sufficient energy density to meet the needs. Recently utilization of oxide materials as pseudocapacitance materials has attracted a great deal of interest. However obtaining a high pseudocapacitance using an...
Show moreThere is a pressing need from a broad range of industries for high-performance energy storage devices with high power, high energy capacity, light weight, long lifetime, high efficiency, and low cost. A typical energy storage device, current electrochemical capacitors do not possess sufficient energy density to meet the needs. Recently utilization of oxide materials as pseudocapacitance materials has attracted a great deal of interest. However obtaining a high pseudocapacitance using an affordable oxide, while maintaining the high rate performance, remains elusive. This dissertation work aims to develop high-performance carbon nanotube (CNT) vanadium oxide hybrid nanostructured electrode materials for electrochemical capacitors. The CNT was in a form of freestanding thin film buckypaper (BP), which served as the current collector whilst providing double-layer capacitance, and vanadium oxide, coated on the CNT, was the pseudocapacitance material. Using a novel supercritical fluid deposition process, ultrathin vanadium oxide were uniformly deposited throughout the buckypaper with exceptional conformity at relatively low temperature, enabled by the unique properties of the supercritical fluids such as high solvation power, high diffusivity and zero surface tension. This overcame many of the transport limitations associated with the vanadium oxide material and indeed excellent electrode performance, particularly high rate performance, was achieved. The deposition process, the morphology and structure, and the capacitance behaviors of the composites were studied in detail, and the processing-morphology-electrochemical properties of the composites were elucidated. A high-pressure deposition system was constructed first for this dissertation research. Thereafter several deposition processes were investigated: physical adsorption - annealing, and in-situ reactive deposition. In the physical adsorption approach, the V2O5-buckypaper composite electrodes were fabricated by firstly physical adsorption of vanadium precursor in supercritical carbon dioxide (scCO2), followed by oxidation in air under elevated temperature. This approach resulted in the conformal deposition of V2O5 of molecular thickness onto the CNT and uniformly distributed throughout the BP. The V2O5 specificpseudo-capacitance of more than 1000 F/g were realized, even at high working power. To improve the active materials loading in the composite electrodes, two strategies were explored. In the first strategy, based on the qualitative fundamental understanding of the adsorption process, important physical parameters were identified, and the adsorption process was optimized by synergic use of physical understanding and statistical experiment design methods. The study resulted in an estimated second order model, which facilitated the search for adsorption conditions for higher precursor loading and higher total capacitance. The second strategy aimed to increase the available surface area for adsorption by the use of high specific surface area substrate material. Thus binder-free single-walled carbon nanotube (SWCNT)-activated carbon (AC) composite substrate was studied in comparison with the traditional activated carbon electrode. Based on thermogravimetric investigation of the precursor oxidation behavior, a conversion process was designed to maximize oxide materials conversion whilst minimizing substrate perturbation and degradation. The loading in the SWCNT-AC was increased by several times, and the composite electrodes showed excellent capacitance. In-situ reactive deposition was explored to further increase the oxide materials loading whiling maintaining the conformity and uniformity. Oxygen was used as the oxidizer and oxidation took place within the reactor. Conformal thin film of V2O5 layer with thickness varying from a few atomic layers to a few nm, with weight loading ~60%, was achieved. Together with the high V2O5 loading and high specific pseudo-capacitance enabled by the ultrathin film structure, excellent high-rate total capacitance was achieved. For example, the composite electrode with a 40% V2O5 showed a total capacitance ~130 F/g at a scan rate of 100 mV/s.
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Date Issued: 2013
Identifier: FSU_migr_etd-8678
Format: Thesis

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