Abstract

Titanium silicides are well known as intermetallic compounds having excellent heat resistance and high hardness. However, it is difficult to fabricate the compounds using the powder sintering method to produce the strong bonding force between atoms characteristic of the compounds. Chemical vapour deposition (CVD) has been a useful method of fabricating a series of intermetallic compounds. In many CVD processes, thermal CVD without plasma is known as a thermally equilibrated process. Therefore, it is possible to predict the deposited phases by means of previous thermodynamic calculations. Many studies have been reported on titanium silicides. Wahl et al. reported the deposition of Ti-Si compounds from the Ti -S i -H-C1 system [1]. Other studies have considered the T i S i C H C 1 system. Most of these have reported both the synthesis and the thermodynamic calculations for a variety of composites consisting of Ti-Si-C, and compared the experimental results with the calculations [2-8]. These reports mention the rare case in which non-equilibrium phases deposit, even in the thermal CVD process. The fabrication of TiC-SiC composites performed by Stinton et al. [2] included the deposition of TiSi2 phase, which was not predicted by the thermodynamic calculation. Similarly, Goto and Hirai [3, 4] suggested that the difference in the deposited phase between the experiments and the calculations might be caused by kinetic restriction. However, detailed kinetic studies, such as deposition rate, have not been reported. In the research reported here, we found a high rate deposition of titanium silicides, which were non-equilibrium phases in a CVD system, under high gas flow rate. Fig. 1 shows the CVD apparatus. TiCI4, SiC14, CH 4 and H2 were used as source materials. The L

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