Low temperature formation of ultra high temperature transition metal carbides from salt-polymer precursors
Refractory transition metal carbides were produced via carbothermal reduction of transition metal halides in a polymer precursor at low temperatures (o12001C). This approach was used to generate TaC (Tm = 3883oC), NbC (Tm = 3610oC), and WC (Tm = 2870oC) from TaBr5, NbBr5, and WCl4/WCl6, respectively. Solubility of transition metal halides and polymers in the same organic solvents allows for intimate mixing on the molecular level, which reduces the synthesis temperature. Greater than 90% TaC conversion was achieved by exposing a 50:50 weight ratio mixture of TaBr5 and polyimide (or polystyrene) to 12001C for 1 h. Even at temperatures as low as 10001C, the major product remains TaC. The ability to process these high-temperature materials so simply, and at relatively low temperatures, makes them accessible for different applications requiring thermal protection such as coatings for metallic components of hypersonic aircraft, rocket engine components, fibers, or refractory containers.
Adamczak, AD; Spriggs, AA; Fitch, DM; Radovic, M; Grunlan, JC; J. Am. Ceram. Soc., 2010, 93 (8), 2222-2228.