反应温度和反应时间对三水碳酸镁晶须长径比的影响

为了扩大其作为增强补韧剂和阻燃剂的应用，以氯化镁和碳酸氢铵为原料，通过水热法成功合成了不同长径比的三水碳酸镁晶须. 采用X射线衍射、扫描电子显微镜、透射电子显微镜对所得三水碳酸镁晶须的物相和形貌进行分析. 结果表明:当反应时间为5 h时，随着反应温度（50 ℃~80 ℃）的升高，三水碳酸镁晶须长径比减小. 当温度为50 ℃，反应时间在4 h~5 h内时，晶须处于生长阶段，长径比增大；反应时间延长至7 h，由于发生相转变，晶须开始溶解，导致长径比减小. 通过对晶须尖端的分析，证实晶须属于台阶生长机制.

Influence of Temperature and Time on Aspect Ratios of Magnesium Carbonate Trihydrate Whiskers

To expand the application as enhanced toughening agent and flame retardant agent，the magnesium carbonate trihydrate whiskers with different aspect ratios were synthesized by hydrothermal method，using magnesium chloride and ammonium bicarbonate as raw materials.The phase and morphology of the magnesium carbonate trihydrate whiskers were characterized by X-ray Diffraction，Scanning Electron Microscopy and Transmission Electron Microscopy.The results show that the aspect ratios of magnesium carbonate trihydrate whiskers decrease with the reaction temperature rising from 50 ℃ to 80 ℃ at reaction time of 5 h，but they increase with whiskers further growth at reaction time of 4 h-5 h and reaction temperature of 50 ℃. The whisker dissolves with phase transition at reaction time of 7 h，which reduces the aspect ratios.Finally，we find that the growth mechanism of magnesium carbonate trihydrate whiskers belongs to the step growth mechanism through the further analysis of whiskers head.