Phase equilibria and reactive chemical vapor deposition (RCVD) of Ti3SiC2

The present article addresses the issue of properly modelling the thermodynamic aspect of chemical reactions proceeding at the solid/gas interface in a multi-component system. Attention is more especially paid to the formation of Ti(3)SiC(2) by reactive chemical vapor deposition (RCVD) on a silicon carbide substrate heated at 1100 degrees C. A deposition diagram has been calculated by Gibbs free energy minimization in the C-Cl-H-Si-Ti quinary system. It is shown that this deposition diagram can account for experimental results obtained by RCVD only for the short period of time during which the reaction layer is thin and discontinuous. For thick, dense and continuous reaction layers, the deposition diagram is no longer appropriate and reaction-diffusion models developed for solid-state diffusion couples have to be used in place of it.