Cold-wall reactors, chemical vapor

Another candidate material for high temperature fiber is titanium diboride. It has a melting point of around 3000°C. Diefendorf and Mazlout (1994) used a gas mixture of titanium tetrachloride boron trichloride, hydrogen, and hydrochloride to make titanium diboride fibers by chemical vapor deposition (CVD) in a cold wall reactor at atmospheric pressure. 

Chemical vapor deposition of polynapthalene differs from the parylene and polyimide systems in terms of the deposition process. As mentioned in earlier sections deposition of parylenes and polyimides occurs on cold surfaces, and the deposition rate decreases with increasing substrate temperature. In other words, deposition is done in a "hot wall" reactor. In contrast, CVD of polynapthalenes is performed in a "cold wall" reactor, meaning that the substrate is maintained at a high temperature ( 350°C) while the surrounding wall temperature is kept at near room temperature. A schematic of the CVD reactor setup employed by Lang et al. can be found in Ref. 28. 

A review article on the CVD processes used to form SiC and Si3N4 by one of the pioneers in this area, Erich Fitzer [Fitzer, E., and D. Hegen, Chemical vapor deposition of silicon carbide and silicon nitride—Chemistry s contribution to modem silicon ceramics, Angew. Chem. Int. Ed. Engl, 18, 295 (1979)], describes the reaction kinetics of the gas-phase formation of these two technical ceramics in various reactor arrangements (hot wall, cold... 

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