热重分析法研究氢氧化镁纳米粉体的非等温分解动力学

以白云石为原料，盐酸酸溶后得到CaCl₂-MgCl₂滤液，采用氨水直接沉淀法制备出符合HG/T 3607-2000Ⅰ型标准的六方片状的纳米氢氧化镁。六方片厚度为25～30 nm，直径为0.3～0.4 mm。利用热重分析法对纳米氢氧化镁在不同升温速率下的热分解动力学进行研究，以期深入了解纳米氢氧化镁热分解制备纳米氧化镁粉体过程的物理化学本质。采用Kissinger法和Ozawa法计算出氢氧化镁热分解反应活化能分别为115.47 kJ·mol^-1和126.04 kJ·mol^-1。对热重分析数据进行处理和拟合，判断纳米氢氧化镁粉体热分解反应机理函数为Avrami-Erofeev（n=1.5）的随机成核和随后生长机理。指前因子为3.077×10¹⁰ s^-1。纳米氢氧化镁经煅烧制备得到的氧化镁纳米球的直径为80～100 nm。

Non-isothermal decomposition kinetics of nano-Mg(OH)2 using thermal gravimetric analysis

Hexagonal nano-magnesium hydroxide with thickness of 25—30 nm and diameter of 0.3—0.4 μm was synthesized via acid immersion and ammonia precipitation from dolomites. Its quality met the standards of typeⅠ in HG/ T 3607—2000. The thermal decomposition kinetics of Mg(OH)₂ was investigated by using thermal gravimetric analysis at different heating rates for deep understanding of physical chemistry in this process. The activation energies of decomposition estimated by the Kissinger and Ozawa methods were 115.47 kJ·mol^-1 and 126.04 kJ·mol^-1 respectively. Decomposition reaction of magnesium hydroxide was controlled by Avrami-Erofeev function (n=1.5). Pre-exponential was 3.077×10¹⁰ s^-1. Nano-magnesium oxide with average diameter of 80—100 nm was prepared after calcination of magnesium hydroxide.