Effect of carbon fibers crystallinity on the formation and growth of TiC coating in molten salt

Abstract

To improve the application of molten salt method in carbon fibers (CFs) surface modification, the work explores the effect of the CFs-itself crystallinity on the formation and growth mechanism of TiC coating in the molten salt reaction. Three different types of CFs were used to prepare TiC coatings at 850°C, and the formation and growth mechanisms were studied. The results showed that CFs surface defects could preferentially initiate nucleation and cause inhomogeneity of TiC particles in the initial stage of TiC coating formation. The CFs surface with high crystallinity could obtain a finer and more uniform TiC coating because the growth rate of TiC particles is slower and the particles do not accumulate with each other during the coating growth. At the same time, the growth rate of TiC coating decreased with increasing CFs crystallinity during the TiC coating growth, which reason is that CFs with higher crystallinity require more activation energies of carbon atom counter diffusion. Therefore, the surface of CFs with higher crystallinity and fewer surface defects is easier to obtain a uniform and particle size TiC coating during the molten salt reaction.