Synthesis and Characterization of Silicon Nitride-Aluminium Nitride Nanocomposite Through Sol-gel Route

Nanostructured Si₃N₁/AIN has been prepared by carbothermal reduction followed by nitridation of silica -alumina gel over a temperature range of 1200 -- 1350°C and time period of 30 minutes to 3 hours in nitrogen atmosphere. Before heat treatment the gel is repeatedly evacuated and purged with ammonia. The nanopores of the gel are filled with ammonia which acts as a source of in situ nitrogen at heat treatment temperature. Dextrose also decomposes during reduction and generates ultra fine carbon. This carbon as well as hydrogen from the cracking of ammonia is not sufficient to create the extremely low partial pressure of oxygen required for the stabilization of Si₃N₁ and AIN. So the sample is heat treated in charcoal boat in nitrogen atmosphere to achieve that extremely low partial pressure of oxygen. The material has been characterized through XRD, SEM and EDX, Si₃N₁, nanowires formed by this process areof 135nm-175nm in diameter and several micron meters in length. On the other hand, the obtained particle size of AIN is in the range of 12nm to 28nm.