高长径比硼酸镁晶须的制备及生长机理研究

以六水氯化镁和硼砂为原料, 以氯化钠、氯化钾作为助熔剂, 通过熔盐法制备出长为200~800μm, 最大长径比为250, 品质均匀的硼酸镁晶须. 采用XRD分析、光学显微和SEM观察, 研究产物的结构和形貌, 并研究不同n(B)/n(Mg)、反应温度和时间对硼酸镁晶须生长过程及质量的影响, 结果表明, 反应的最佳条件是n(B)/n(Mg)=3:1、反应温度为900℃、恒温时间为6h. 根据XRD分析, 表明Mg₂B₂O₅晶须的生成经过中间产物方硼石Mg₃B₇O₁₃Cl的转化过程, 晶须生长需要一个富硼的环境. 晶须的生长机理符合L-S机理.

Preparation and Growth Mechanism of Magnesium Borate Whiskers with High Aspect Ratio

Magnesium borate whiskers were prepared by molten salt method using MgCl₂ · 6H₂O and Na₂B₄O₇ · 10H₂O as raw materials, KCl and NaCl as fluxes. The lengths of the above whiskers varied from 200μm to 800 μm, and the maximum aspect ratio reached 250. The produced samples were characterized by X-ray diffraction (XRD), microscope and scanning electron microscope (SEM). The effects of n(Mg)/n(B), reaction temperature and reaction time on the whisker growth process and product quality were explored. It was found that the best operating parameters of n(Mg)/n(B), reaction temperature and reaction time were 3.0, 900 ℃ and 6h, respectively. According to the XRD analysis, Mg₃B₇O₁₃Cl is the intermediate product, and the growth of Mg₂B₂O₅ whiskers needs a boron- enriched environment. The whisker growth process agrees to the liquid-solid (L-S) mechanism.