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Laser Processing for Manufacturing Nanocarbon Materials

Title: Laser Processing for Manufacturing Nanocarbon Materials.
Name(s): Van, Hai Hoang, author
Zhang, Mei, professor directing dissertation
Li, Hui, university representative
Okoli, Okenwa, committee member
Liang, Zhiyong Richard, committee member
Liu, Tao, committee member
Florida State University, degree granting institution
FAMU-FSU College of Engineering, degree granting college
Department of Industrial and Manufacturing Engineering, degree granting department
Type of Resource: text
Genre: Text
Issuance: monographic
Date Issued: 2015
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
online resource
Extent: 1 online resource (123 pages)
Language(s): English
Abstract/Description: CNTs have been considered as the excellent candidate to revolutionize a broad range of applications. There have been many method developed to manipulate the chemistry and the structure of CNTs. Laser with non-contact treatment capability exhibits many processing advantages, including solid-state treatment, extremely fast processing rate, and high processing resolution. In addition, the outstanding monochromatic, coherent, and directional beam generates the powerful energy absorption and the resultant extreme processing conditions. In my research, a unique laser scanning method was developed to process CNTs, controlling the oxidation and the graphitization. The achieved controllability of this method was applied to address the important issues of the current CNT processing methods for three applications. The controllable oxidation of CNTs by laser scanning method was applied to cut CNT films to produce high-performance cathodes for FE devices. The production method includes two important self-developed techniques to produce the cold cathodes: the production of highly oriented and uniformly distributed CNT sheets and the precise laser trimming process. Laser cutting is the unique method to produce the cathodes with remarkable features, including ultrathin freestanding structure (~200 nm), greatly high aspect ratio, hybrid CNT-GNR emitter arrays, even emitter separation, and directional emitter alignment. This unique cathode structure was unachievable by other methods. The developed FE devices successfully solved the screening effect issue encounter by current FE devices. The laser-control oxidation method was further developed to sequentially remove graphitic walls of CNTs. The laser oxidation process was directed to occur along the CNT axes by the laser scanning direction. Additionally, the oxidation was further assisted by the curvature stress and the thermal expansion of the graphitic nanotubes, ultimately opening (namely unzipping) the tubular structure to produce GNRs. Therefore the developed laser scanning method optimally exploited the thermal laser-CNT interaction, successfully transforming CNTs into 2D GNRs. The solid-state laser unzipping process effectively addressed the issues of contamination and scalability encountered by the current unzipping methods. Additionally, the produced GNRs were uniquely featured with the freestanding structure and the smooth surfaces. If the scanning process was performed in an inert environment without the appearance of oxygen, the oxidation of CNTs would not happen. Instead, the greatly mobile carbon atoms of the heated CNTs would reorganize the crystal structure, inducing the graphitization process to improve the crystallinity. Many observations showing the structural improvement of CNTs under laser irradiation has been reported, confirming the capability of laser to heal graphitic defects. Laser methods were more time-efficient and energy-efficient than other annealing methods because laser can quickly heat CNTs to generate graphitization in less than one second. This subsecond heating process of laser irradiation was more effective than other heating methods because it avoided the undesired coalescence of CNTs. In my research, the laser scanning method was applied to generate the graphitization, healing the structural defects of CNTs. Different from the reported laser methods, the laser scanning directed the locally annealed areas to move along the CNT axes, migrating and coalescencing the graphitic defects to achieve better healing results. The critical information describing the CNT structural transformation caused by the moving laser irradiation was explored from the successful applications of the developed laser method. This knowledge inspires an important method to modify the general graphitic structure for important applications, such as carbon fiber production, CNT self-assembly process and CNT welding. This method will be effective, facile, versatile, and adaptable for laboratory and industrial facilities.
Identifier: FSU_2016SP_Van_fsu_0071E_12881 (IID)
Submitted Note: A Dissertation submitted to the Department of Industrial and Manufacturing Engineering in partial fulfillment of the Doctor of Philosophy.
Degree Awarded: Fall Semester 2015.
Date of Defense: December 11, 2015.
Keywords: Carbon Nanotube, Graphene, Laser, Manufacturing, Oxidation, Thermal Treatment
Bibliography Note: Includes bibliographical references.
Advisory Committee: Mei Zhang, Professor Directing Dissertation; Hui Li, University Representative; Okenwa Okoli, Committee Member; Richard Liang, Committee Member; Tao Liu, Committee Member.
Subject(s): Industrial engineering
Materials science
Persistent Link to This Record:
Owner Institution: FSU

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Van, H. H. (2015). Laser Processing for Manufacturing Nanocarbon Materials. Retrieved from