Mechanical Activation Assisted Synthesis Of ¦Â-sialon Powder

In this study,a powder mixture of gibbsite,Al and Si for synthesis ofβ-Sialon was ground in a vibration ball mill in air atmosphere for varying periods,and then heated in nitrogen atmosphere in MoSi₂ furnace and microwave furnace respectively.The results revealed that mechanical activation at ambient temperature resulted in an enhanced nitridation reactivity of mixed powders at high temperatures.After heating in MoSi₂ furnace,monolithicβ-Sialon was formed at 1300℃from the powders milled for 10 h whereas the synthesis ofβ-Sialon from unmilled mixture completed at 1400℃.For samples treated in microwave furnace,the nitridation reaction was also accelerated by mechanical activation.In comparison with powder mixtures without milling,the onset formation temperature ofβ-Sialon was decreased by 100℃and the complete formation temperature by 200℃.For samples milled more than 6 h,β-Sialon began to form at 900℃.For samples milled 20 h,β-Sialon was mainly produced at 1000℃.According to the experimental results,mechanical activation turned gibbsite from crystalline to amorphous,reduced the decomposition temperature of gibbsite,increased the surface area which associated with particle-size reduction and raised uniform distribution of Al,O,Si elements in sub-micron range,which contribute to the enhanced reactivity of reactants.