机械合金化制备Al_2O_3-AlB_(12)陶瓷粉体的热力学分析

Thermodynamic Analysis of Al_2O_3-AlB_(12) Ceramic Powder Prepared by Mechanical Alloying

以Al-B_2O_3粉末为原料,在氩气的保护下进行球磨,制备了Al_2O_3-Al B_(12)复合陶瓷粉体。对球磨不同时间的粉末进行X射线衍射(XRD)、差示扫描量热仪(DSC)和扫描电镜(SEM)检测,分析了混合粉末的物相变化、燃烧反应的临界温度变化以及混合粉末的结构变化,通过热力学计算,分析了球磨过程中化学反应发生的规律以及球磨对化学反应的影响及作用。研究结果表明:物相在球磨8 h内物相没有变化,球磨10 h时出现Al_2O_3和Al B12物相;球磨不同时间的粉末,其燃烧反应的临界温度随球磨时间的延长而下降;球磨8 h内粉末经历了塑性变形-冷焊-加工硬化-微断-破碎过程,球磨至10 h发生化学反应生成α-Al_2O_3-Al B12微米级复合粉体;由热力学计算,球磨过程中首先发生2Al+B_2O_3=Al_2O_3+2[B]的自蔓延反应,其放出的热量驱动Al+12B=Al B12的反应。球磨至4 h,反应的临界温度由1010.80℃下降到650.58℃,球磨至8 h临界温度下降到641.84℃,球磨能够促进反应进行。

Al2O3-Al B12 powder was prepared by ball milling under the protection of argon with Al-B2O3 powder as raw material. The phase change,combustion reaction critical temperature change and powder mixing structure change of the mixed powder with different milling time was analyzed by X-ray diffraction（ XRD）,differential scanning calorimeter（ DSC）,and scanning electron microscopy（ SEM） detection. Through thermodynamic calculation,the regularity of chemical reaction and the effect of ball milling on chemical reaction were analyzed. The results showed that the phase constitution did not change in the milling time of 8 h,but after milling for 10 h Al2O3 and Al B12 phases appeared; the critical temperature of combustion reaction decreased with the increase of milling time for the powder with different milling time; during the 8 h ball milling,the powder experienced plastic deformation-cold welding-hardening-micro fracture crushing process; chemical reaction occurred and α-Al2O3-Al B12 micron composite powder was obtained after ball milling to10 h; according to thermodynamic calculation,2Al ＋ B2O3= Al2O3＋ 2[B] first occurred in the ball milling process,and the heat released initiated the reaction of Al ＋ 12 B = Al B12. After ball milling to 4 h,the critical reaction temperature decreased from 1010. 80 to650. 58 ℃,and the critical temperature decreased to 641. 84 ℃ after ball milling to 8 h,which could promote the reaction.