机械活化辅助合成β-Sialon粉体

【作者】 张东睿；

【导师】 叶国田；

【作者基本信息】 郑州大学 ， 材料学， 2009， 硕士

【摘要】 本论文以铝粉、硅粉、三水铝石粉为原料,通过高能球磨对混合原料进行不同时间的机械活化,再分别采用普通氮化和微波氮化两种方法合成β-Sialon粉体,降低了β-Sialon的合成温度。机械活化辅助普通氮化合成β-Sialon,机械活化≥10h的试样在1300℃保温5h后反应完毕合成β-Sialon,而未经机械活化的试样在1400℃保温5h后才完全生成β-Sialon,即机械活化辅助普通氮化将β-Sialon的合成温度降低了100℃。机械活化辅助微波氮化合成β-Sialon,机械活化≥6h的试样在900℃保温2h后有部分β-Sialon生成;1000℃保温2h后,机械活化20h的试样合成较纯的β-Sialon;未经机械活化的试样于1200℃保温2h后合成β-Sialon反应完毕。和未经机械活化的试样相比,经过机械活化的试样开始生成β-Sialon的温度降低了100℃,完全生成β-Sialon的温度降低了200℃。XRD研究表明,机械活化造成混合原料中三水铝石从晶态向无定形态转变,机械活化20h后,混合原料中的三水铝石完全变为无定形态。BET比表面积研究表明,机械活化增加了混合原料的比表面积,机械活化20h后,混合原料的比表面积由最初的2.74m~2/g增至9.56m~2/g。SEM、EDS研究表明,机械细化了混合原料,使铝、硅、三水铝石在亚微米级别上混合均匀。TG-DSC研究表明,机械活化降低了三水铝石的分解温度,加快了混合原料的反应速率;机械活化20h后,混合原料中三水铝石在290℃脱水吸热谷完全消失,从30℃便开始脱水失重;相同的升温速率下,未经机械活化试样的最终增重率为-7.35%,机械活化20h试样的最终增重率为4.35%。这些现象共同作用提高了混合原料的反应活性,加快了氮化速率,使其在较低温度下就开始氮化反应,从而降低了β-Sialon的合成温度。更多还原

【Abstract】 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.更多还原