Formation of titanium carbide on graphite via powder immersion reaction assisted coating

The surface of graphite was modified employing powder immersion reaction assisted coating (PIRAC) method. Graphite plates were immersed into Ti powder and annealed at 800-1000 °C. Crystalline iodine was admixed to Ti powder in order to accelerate the transfer of Ti atoms onto the graphite surface. As a result of interaction between Ti and graphite, continuous Ti carbide coatings were formed with a thin layer of stiochiometric TiC on the graphite substrate/coating interface and Ti-rich TiC1−x in the outer part of the coating with concentration of carbon decreasing towards the surface of the coating. The coating was found to grow by a parabolic law with the kinetic constant, k = 3.7 × 10−8 exp(−160,000/RT) m2/s, the process being controlled by diffusion along fast diffusion paths. At low iodine concentrations and short exposures the amount of admixed iodine affected the rate of titanium carbide coating growth. A kinetic model of the process of coating growth is proposed.