Formation of SiC-AlN solid solution by combustion nitridation of Al with SiC

Self-propagating high temperature synthesis (SHS) of SiC-AlN solid solution formation from aluminum and silicon carbide powders and nitrogen gas was investigated in the present study. The dependencies of combustion temperatures and wave propagation velocities on green mixture densities and nitrogen pressure were obtained. A nitrogen pressure of 6 MPa is found to be sufficient for self-sustained regime of solid solution formation, while a pressure of 0.1 Mpa was not. The combustion temperatures for 6 MPa do not strongly depend on the density of the green mixture and ranged about 2500 degreesC, but for 0.1 MPa SHS did not occur for the densities above 40 %. The combustion wave velocity for p(N2)=0.1 MPa decreases from 0.3 cm/sec for green mixture density 23 % to 0 for the density 40 %. For 6 MPa non-monotonous dependence is observed with a maximum 1 cm/sec for 45 %. The results of X-ray diffraction analyses and scanning electron microscopy studies are presented. The conditions of homogeneous solid solution formation are revealed. The dissolution of silicon carbide during the reaction is established and the formation mechanism is proposed.