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POLYMER-DERIVED CERAMICS: ELECTRONIC PROPERTIES AND APPLICATION
Title
POLYMER-DERIVED CERAMICS: ELECTRONIC PROPERTIES AND APPLICATION.
Creator
xu, weixing, An, Linan, University of Central Florida
Abstract / Description
In this work, we studied the electronic behavior of polymer-derived ceramics (PDCs) and applied them for the synthesis of carbon nanotube reinforced ceramic nanocomposites and ceramic MEMS (Micro-Electro-Mechanical Systems) structures. Polymer-derived SiCN ceramics were synthesized by pyrolysis of a liquid polyureasilazane with dicumyl peroxide as thermal initiator. The structural evolution during pyrolysis and post-annealing was studied using FTIR, solid state NMR and Raman. The results...
Show moreIn this work, we studied the electronic behavior of polymer-derived ceramics (PDCs) and applied them for the synthesis of carbon nanotube reinforced ceramic nanocomposites and ceramic MEMS (Micro-Electro-Mechanical Systems) structures. Polymer-derived SiCN ceramics were synthesized by pyrolysis of a liquid polyureasilazane with dicumyl peroxide as thermal initiator. The structural evolution during pyrolysis and post-annealing was studied using FTIR, solid state NMR and Raman. The results revealed that the resultant ceramics consisted of SiCxNx-4 as major building units. These units were connected with each other through C-C/C=C bonds or by shearing N/C. The amount of sp2 free carbon strongly depends on composition and processing condition. Electron paramagnetic resonance (EPR) was used to investigate electronic structure of PDCs; the results revealed that the materials contain unpaired electron centers associated with carbons. Electronic behavior of the SiCN ceramics was studied by measuring their I-V curves, temperature dependence of d.c.-conductivities and impendence. The results revealed that the SiCN ceramics exhibited typical amorphous semiconductor behavior, and their conductivity varied in a large range. The results also revealed that the materials contain more than one phase, which have the different electronic behavior. We explored possibility of using polymer-derived ceramics to make ceramic MEMS for harsh environmental applications with a lithography technique. The cure depth of the polymer precursor was measured as a function of UV intensity and exposure time. The experimental data was compared with the available theoretical model. A few typical SiCN parts were fabricated by lithography technique. We also prepared carbon nanotube reinforced ceramic nanocomposites by using PDC processing. The microstructures of the composites were characterized using SEM and TEM; the mechanical properties were studied characterized using nanoindentation. The significant improvement in mechanical properties was observed for the nanocomposites.
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Date Issued
2006
Identifier
CFE0001228, ucf:46885
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001228
Textbook Cost-Lowering Initiatives: An Exploration of Community College Faculty Experiences
Title
Textbook Cost-Lowering Initiatives: An Exploration of Community College Faculty Experiences.
Creator
Dunn, Susan, Cintron Delgado, Rosa, Owens, James, Boyd, Tammy, Mcardle, Michele, University of Central Florida
Abstract / Description
Faculty have been identified as critical players in the implementation of textbook affordability efforts at community colleges. Furthermore, emerging lower-cost alternatives to traditional textbooks present a wide and growing range of options that may help further efforts. This study sought to examine more closely the role of faculty with respect to textbook cost-lowering initiatives. The researcher utilized in-depth interviews to gain a rich picture of the experiences, attitudes, beliefs,...
Show moreFaculty have been identified as critical players in the implementation of textbook affordability efforts at community colleges. Furthermore, emerging lower-cost alternatives to traditional textbooks present a wide and growing range of options that may help further efforts. This study sought to examine more closely the role of faculty with respect to textbook cost-lowering initiatives. The researcher utilized in-depth interviews to gain a rich picture of the experiences, attitudes, beliefs, and behaviors of nine full-time community college faculty as they confronted textbook affordability efforts and textbook alternatives. The interview data were analyzed using a thematic analysis process. Five major themes and three minor themes were identified. The five major themes were: (a) campus administrators support, but do not mandate, efforts; (b) frequent edition revisions frustrate faculty; (c) departmental approaches to textbook selection vary; (d) content, then affordability, drive selection choices; and (e) faculty have mixed feelings about textbook alternatives. The three minor themes were: (a) faculty efforts to save students money are thwarted by campus bookstores and financial aid policies; (b) English faculty benefit from public domain readings; and (c) more faculty participating in textbook selection means more difficulty deciding on a text. Implications and recommendations were offered for community college leaders, campus bookstores, publishers, and future researchers.
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Date Issued
2014
Identifier
CFE0005159, ucf:50715
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005159