Chemical Vapor Deposition of Tantalum Carbide from TaCl5-C3H6-Ar-H2 System

Tantalum carbide, which is one of the ultra-high temperature ceramics, was deposited on graphite by low pressure chemical vapor deposition from a TaCl5-C3H6- Ar-H2 mixture. To maintain a constant TaCl5/C3H6 ratio during the deposition process, TaCl5 powders were continuously fed into the sublimation chamber using a screw-driven feeder. Sublimation behavior of TaCl5 powder was measured by thermogravimetric analysis. TaC coatings have various phases such as Ta+α-Ta2C, α-Ta2C+TaC1-x, and TaC1-x depending on the powder feeding methods, the C3H6/TaCl5 ratio, and the deposition temperatures. Near-stoichiometric TaC was obtained by optimizing the deposition parameters. Phase compositions were analyzed by XRD, XPS, and Raman analysis. Key words: Tantalum carbide, Chemical vapor deposition, Chloride process, UHTC