Synthesis of spherical Al2O3 and AlN powder from C@Al2O3 composite powder

A novel approach has been taken to produce (1) spherical Al2O3 particles by decarbonisation and (2) spherical AlN particles by nitridation and subsequent decarbonisation of C@Al2O3 composite particles. C@Al2O3 composite particles have been prepared by heterogeneous nucleation and crystallisation of Al(NO3)3 on surfactant encapsulated carbon nano particles followed by evaporative decomposition of the nitrate. Overpressure (0.4 MPa) of nitrogen and a temperature range (1723– 1873 K) have been used for nitridation. Whiskers as well as spherical particles of AlN have been observed in the final product. The final product has been characterised by X-Ray Diffraction, Scanning Electron Microscope and Carbon– Hydrogen–Nitrogen content analysis by Elemental Analyser and the mechanism of the nitridation reaction has been analysed. The average size of the spherical AlN particles consisting of crystallites in nano-dimensions (30–50 nm) could be varied from 100 nm to 8 lm by changing the composition of the sol.