草酸盐法制备硼酸镁晶须及其生长机理

摘要

With MgCl2 · 6H2O,H3BO3 and H2C2O4 · 2H2O as raw materials,magnesium borate whiskers were synthesized by oxalate method.The lengths of the whiskers varied from 4.0 μm to 8.0 μm,the diameters varied from 0.6μm to 1.5 μm,and the aspect ratio was about 10.The produced samples were characterized by XRD,SEM,and TG-DTA.The effects of reaction temperature,reaction time,n(B)(Mg),and n(H2C2O4)(Mg) on the whisker growth process and product quality were explored.The best preparation conditions were obtained.It was found that the best prepared parameters of reaction temperature,reaction time,n (B) (Mg),and n (H2 C2 O4)/ n(Mg) were 800 ℃,4.0 h,1.2 and 1.2,respectively.According to the XRD and TG-DTA analysis,MgC2O4 precursor greatly promotes the formation and growth of Mg2 B2 O5 whiskers,its decomposition products do not introduce impurities,making the whiskers more purity.The whisker growth process is solid-liquid-solid (S-L-S) mechanism.%以MgCl2·6H2O、H3BO3和H2GO4·2H2O为原料,利用草酸盐法制备出长度为4.0～8.0μm,直径为0.6～1.5 μm,长径比约为10,形貌良好的硼酸镁晶须.采用XRD、SEM及TG-DTA等分析手段,研究了烧结温度、烧结时间、n(B)(Mg)、n(H2C2O4)(Mg)对硼酸镁晶须的生长过程和质量的影响,探讨了其最佳制备条件.结果显示,硼酸镁晶须的最佳制备条件为:烧结温度为800℃,烧结时间为4.0h,n(B)(Mg) =1.2,n(H2C2O4)(Mg)=1.2.根据XRD和TG-DTA分析,MgC2O4前驱体对硼酸镁晶须的形成和生长有较大的促进作用,分解产物不引入其它杂质,使得制备的晶须纯度较高.晶须的生长机理为S-L-S机理.