Synthesis of composite filmsfor graphite protection using chemical vapor deposition technique

• Main Authors: Chen Shih-Ping, 陳詩平
• Other Authors: Hong Lu-Sheng
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/23213778464511869860

碩士 === 國立臺灣科技大學 === 化學工程系 === 93 === The purpose of this research is to grow silicon carbide/silicon nitride composite films using TMS (tetramethylsilane), ammonia and hydrogen as the reactant gases by chemical vapor deposition. The reactant feed ratio of TMS/NH3 were varied from 0.75 to 24,the composition ratio of Si-C/S-N in the films were increasing from 0.9 to 6, the corresponding theoretical thermal expansion coefficient of films were varied from 4.6 to 4.75. It was found that this first gradient layer was familiar with graphite substrate at 1000℃ and PTMSNH3 = 3. When temperature in the range of 1000 to 1165℃ to fabricate other serial gradient layers. Then, the substrate treated with the CVI process at 700℃, TMS partial pressure of 14.6 × 10-2 Torr NH3 = 0.5sccm and reaction time = 55min. The gardinet layer (2.8μm) is grow on graphite. Finally, grow thickness 5μm on top layer. This process makes the weight loss of sample below 3% under the 16 cycles of thermal shock test in air atmosphere (1000℃). After 220 cycles of thermal shock test in ammonia atmosphere (1200℃), there were a few cracks in SiC coating film observed by optical microscope and the weight loss was unapparent.