Synthesis of nano-sized TiC powders by designing chemical vapor deposition system in a fluidized bed reactor

Abstract

Chemical vapor deposition (CVD) process is an effective way to fabricate highly pure ultra-fine powders; however commercial fabrication of high quality TiC powders through conventional CVD (TiCl4–H2–CH4) system remains a great challenge. The main obstacle is that the conversion of chemically stable TiCl4 to TiC is too low (theoretically 13.3% at 1000 °C) to provide sufficient supersaturation to form powders but only coating. To tackle this problem, relatively unstable TiCl3 was proposed as a novel precursor, which is easier to achieve homogeneous nucleation due to the higher conversion of TiCl3 to TiC in the TiCl3–CH4–H2 system (theoretically 37.7% at 1000 °C). In addition, a fluidized bed reactor (FBR) with fluidized TiC seeds providing local turbulence was employed to boost the homogeneous nucleation. Based on the novel idea, for the first time, high purity nano-sized TiC powders (about 77.1 nm, purity 99.46 at.%) were successfully fabricated by a fluidized bed chemical vapor deposition (FBCVD) process. More importantly, an advanced simple and effective process was successfully developed to activate the common TiCl4 raw material to synthesize nano-sized TiC powders by designing the reactor.