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You searched for +publisher:"Clemson University" +contributor:("Dr. David P. Anderson"). Showing records 1 – 2 of 2 total matches.

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Clemson University

1. Morales Sandoval, Marlon Salvador. UV-Assisted Stabilization of Polyacrylonitrile-Based Carbon Fiber Precursors.

Degree: PhD, Chemical Engineering, 2013, Clemson University

Due to their high strength and stiffness coupled with low density, carbon fibers are the preferred reinforcing fibers used in high-performance polymer matrix composites. Consequently, the demand for carbon fibers is expected to grow from 40,000 metric tons to about 150,000 metric tons over the next decade. A large fraction of the increase is anticipated in the industrial sector that is cost-sensitive. Therefore, there is a need for the development of novel processes and precursors to reduce the carbon fiber production cost and expand the use of carbon fibers. This research focuses on the development of an alternative, rapid stabilization route for polyacrylonitrile (PAN) precursor-based carbon fibers. The main goal was to investigate the stabilization reactions induced by the addition of photo-initiators and UV-treatment of polyacrylonitrile (PAN) based precursors. Also, the role of this external photoinitiator on the fiber spinnability, properties of the spun precursor fibers, and the properties of the resulting thermal stabilized and carbonized PAN-based fibers were systematically studied. Two mechanisms of photo-initiation were investigated: homolytic cleavage and hydrogen abstraction. Solution-cast PAN copolymer samples containing both types of photo-initiators were irradiated for different durations (100 - 600 s) and temperatures (65 - 100°C, i.e., below and above glass transition temperature). FTIR spectra show the formation of carbon-oxygen, carbon-nitrogen, and carbon-carbon double bonds attributed to the development of cyclized structure. Samples containing hydrogen abstraction photoinitiator show higher extents of cyclization among the different set of samples. This observation was also confirmed by higher gel contents. FTIR conversion indices of samples UV treated above glass transition temperature were higher compared with that for the same specimens UV treated below glass transition temperature, as expected. DSC results show that samples containing hydrogen abstraction photoinitiator enable a higher extent of post-UV thermal stabilization. FTIR spectra of the UV treated samples, when compared with only thermally stabilized specimens, confirm that the addition of 1 wt% photoinitiator to PAN followed by 5 minutes of UV treatment increases the rate of the cyclization reaction and reduces the thermal oxidation time by over an hour, which could significantly reduce the conventional stabilization time by half. Rheology measurements show no adverse effect on the viscosity of solutions by the addition of the photoinitiator. Fibers containing photoinitiator were successfully wet-spun from PAN-DMSO solution. SEM micrographs show no deterioration of the post-stretched fiber microstructure due to the presence of photoinitiator. After UV treatment, fibers that contained 4,4’-bis(diethylamino)benzophenone display a higher tensile modulus as compared with that of other sets. Wide-angle X-ray diffraction results show no significant decrease in interplanar spacing and size of the crystals within the… Advisors/Committee Members: Dr. Amod A. Ogale, Dr. Douglas E. Hirt, Dr. Christopher L. Kitchens, Dr. David P. Anderson.

Subjects/Keywords: Chemical Engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Morales Sandoval, M. S. (2013). UV-Assisted Stabilization of Polyacrylonitrile-Based Carbon Fiber Precursors. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/1611

Chicago Manual of Style (16th Edition):

Morales Sandoval, Marlon Salvador. “UV-Assisted Stabilization of Polyacrylonitrile-Based Carbon Fiber Precursors.” 2013. Doctoral Dissertation, Clemson University. Accessed December 04, 2020. https://tigerprints.clemson.edu/all_dissertations/1611.

MLA Handbook (7th Edition):

Morales Sandoval, Marlon Salvador. “UV-Assisted Stabilization of Polyacrylonitrile-Based Carbon Fiber Precursors.” 2013. Web. 04 Dec 2020.

Vancouver:

Morales Sandoval MS. UV-Assisted Stabilization of Polyacrylonitrile-Based Carbon Fiber Precursors. [Internet] [Doctoral dissertation]. Clemson University; 2013. [cited 2020 Dec 04]. Available from: https://tigerprints.clemson.edu/all_dissertations/1611.

Council of Science Editors:

Morales Sandoval MS. UV-Assisted Stabilization of Polyacrylonitrile-Based Carbon Fiber Precursors. [Doctoral Dissertation]. Clemson University; 2013. Available from: https://tigerprints.clemson.edu/all_dissertations/1611

2. Alway Cooper, Rebecca Marie. Structure-Property Relationship of Nanomodified Mesophase Pitch-Based Carbon Fibers.

Degree: PhD, Chemical Engineering, 2014, Clemson University

Mesophase pitch-based carbon fibers are known for their excellent thermal and electrical conductivity, high tensile modulus, moderate tensile strength, but poor compressive strength. This collection of properties results from the texture and crystalline structure (together known as microstructure) of the fibers. Fiber microstructure, in turn, develops during processing due to the discotic nature of the mesophase pitch precursor. In prior studies, such important parameters as the size and shape of capillaries in the spinneret, spinning temperature and carbonization temperature have been varied to produce fibers with different microstructures and properties. In this dissertation, the primary research goal was to investigate how the microstructure and resulting transport properties of carbon fibers would be influenced by the incorporation of short aspect ratio multiwalled carbon nanotubes (MWCNTs) or, as a low-cost alternative, carbon black (CB) at ultra-dilute concentrations. Thus, MWCNTs and CB were dispersed into the mesophase pitch precursor at only 0.3 wt%. At this extremely low concentration, rather than acting as traditional fillers, these nanomodifiers served as surface-anchoring agents, which led to changes in the microstructure of the precursor and resulting carbon fibers. These microstructural modifications then impacted fiber and composite properties. In the first part of this study, the effect of nanomodification on fiber microstructure was evaluated. Using light and scanning electron microscopy, it was observed that the cross-section of unmodified (0 wt%) fibers had a well-defined radial texture, with minimal folding of the graphitic layers (average pleat length ~40 nm), especially for the large fraction (~83%) of fibers that exhibited “pac-man” type splitting. The cross-section of fibers modified with CB had a line-centered texture that exhibited increased folding of the graphitic planes (average pleat length ~30 nm) toward the outer surface of the fiber, resulting in ~45% of CB-modified fibers displaying “pac-man” splitting. Fibers modified with MWCNTs were found to have a largely random cross-sectional texture with significant folding of the graphitic planes (average pleat length ~30 nm) across the entire surface, and only ~3% of MWCNT-modified fibers showed “pac-man” splitting. Finally, via x-ray diffraction, it was determined that nanomodification had no adverse impact on crystallite size (Lc ~40 nm and La ~80 nm), orientation (FWHM ~2°), or graphitic perfection (d002 ~0.338 nm). This indicates that nanomodification could be a possible route for producing highly graphitic fibers, which are mechanically toughened by increased folding of the graphitic pleats. The second major component of this work focused on quantifying the density, electrical resistivity, thermal conductivity and mechanical properties of individual carbon fibers (i.e., single filaments). Using a set of calibrated cesium formate aqueous solutions, fiber densities were accurately measured to be 2.20 ≤ ρ0wt% < 2.25 g/cm3, 2.15 ≤… Advisors/Committee Members: Dr. Amod A. Ogale, Committee Chair, Dr. David P. Anderson, Dr. Christopher L. Cox, Dr. Christopher L. Kitchens, Dr. Mark C. Thies.

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Alway Cooper, R. M. (2014). Structure-Property Relationship of Nanomodified Mesophase Pitch-Based Carbon Fibers. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/1799

Chicago Manual of Style (16th Edition):

Alway Cooper, Rebecca Marie. “Structure-Property Relationship of Nanomodified Mesophase Pitch-Based Carbon Fibers.” 2014. Doctoral Dissertation, Clemson University. Accessed December 04, 2020. https://tigerprints.clemson.edu/all_dissertations/1799.

MLA Handbook (7th Edition):

Alway Cooper, Rebecca Marie. “Structure-Property Relationship of Nanomodified Mesophase Pitch-Based Carbon Fibers.” 2014. Web. 04 Dec 2020.

Vancouver:

Alway Cooper RM. Structure-Property Relationship of Nanomodified Mesophase Pitch-Based Carbon Fibers. [Internet] [Doctoral dissertation]. Clemson University; 2014. [cited 2020 Dec 04]. Available from: https://tigerprints.clemson.edu/all_dissertations/1799.

Council of Science Editors:

Alway Cooper RM. Structure-Property Relationship of Nanomodified Mesophase Pitch-Based Carbon Fibers. [Doctoral Dissertation]. Clemson University; 2014. Available from: https://tigerprints.clemson.edu/all_dissertations/1799

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