Ohuchi, Fumio SYANG, YI HSUN2018-07-312018-07-312018YANG_washington_0250E_18941.pdfhttp://hdl.handle.net/1773/42449Thesis (Ph.D.)--University of Washington, 2018In the presented SiC/C system, a thorough characterization has been done including analyzing structural, morphological, elemental and surface electronic data. X-ray diffraction (XRD) was used for structure analysis; scanning electron microscope (SEM) was for morphologic analysis; X-ray photoelectron spectroscopy (XPS) and glow discharge optical emission spectroscopy (GDOES) was used for elemental analysis; 29Si NMR provided bulk silicon chemical state; Raman spectra provided further information on carbon species. There are a few custom designed experimental apparatuses, including electrical resistivity measurement at elevated temperature to ensure suitability for electrode applications, in-situ Auger electron spectroscopy (AES) for high temperature surface property analysis, and thermionic emission energy distribution (TEED) developed to decipher the material’s work function at desired temperature. We utilized two methods relating to thermionic emission to measure the material’s work function. The first method takes advantage of the Richardson Dushman equation; it describes a relationship between total emission current density and work function for certain temperature range. Alternatively, the work function at certain temperature can be evaluated using the TEED technique by comparing the on-set energy with a tungsten reference sample. In our investigation, specimens from the HP process are mostly 6H polytype, whereas specimens from PIP process created 3C polytype. The chemical compositions can be adjusted through changing the portion of the additives in the process. The electrical resistivity in the measured temperature range shows semiconductor behavior. Using in-situ AES coupled with thermionic emission experiments, spontaneous graphitization occurred at elevated temperature for all the specimens. The work function acquired from the two thermionic related methods did not agree with each other. However, the TEED method would be better for work function measurement at elevated temperature. A successful outcome of this research will result not only in the emergence of reliable and affordable designed materials for direct energy extraction applications but also suitable for other future material exploratoration.application/pdfen-USCC BY-NCMaterials ScienceMaterials science and engineeringThesis