Influence of ball milling parameters on the structure of the mechanically alloyed SiBCN powder

SiBCN powders were prepared by an improved mechanical alloying technique, using cubic silicon, graphite and hexagonal boron nitride powders as raw materials. The influences of ball milling parameters on the structures and the particle size distribution of the prepared powders were carefully studied by XRD, HRTEM, EFTEM and particle-size analysis. Results show that well amorphized SiBCN powder can be prepared when the rotation speed of the vials is between 600 and 800 rpm, the ball-to-powder mass ratio is larger than 20:1, and the milling time is longer than 20 h. A higher rotation speed and a larger ball-to-powder mass ratio may enhance the power input into the powder, and hence facilitate the formation of SiC crystallites. While a longer milling time has little influence on the powder microstructure, it promotes the reaction between silicon and carbon atoms. The optimized ball milling parameters are 600 rpm, 20:1, 30 or 40 h, respectively. The prepared SiBCN powders mainly consist of near-spherical agglomerates, 4.6-5.3 μm in the average particle size. The particle size distribution of these powders is slightly affected by the variation of ball milling parameters.