水热法制备碱式硫酸镁晶须的过程机制

Hydrothermal Synthesis Process of Magnesium Oxysulfate Whiskers

以MgSO4和NaOH为原料,采用常温合成-水热反应方式制备出直径0.5-1.0μm、长30-50μm的碱式硫酸镁(5Mg(OH)2·MgSO4·3H2O)晶须。电导率实验表明:添加氢氧化镁可显著提高硫酸镁水热溶液的电导率,由此初步推测晶须的水热合成属溶解-结晶机制:氢氧化镁首先溶解,然后溶液中Mg2+、SO42-和OH-发生反应生成碱式硫酸镁晶须。晶须的水热合成过程受晶体生长控制,宏观动力学方程为:-dc/dt=0.438(c-0.417)

Magnesium oxysulfate whiskers (5Mg(OH)(2)(.)MgSO(4)(.)3H(2)O) with a diameter of 0.5similar to1.0 mum and a length of 30similar to50mum were synthesized via precipitation in room temperature followed with the hydrothermal reaction, using MgSO4 and NaOH as the raw materials. The experimental results indicate that the addition of magnesium hydroxide increases the specific conductance of the magnesium sulfate hydrothermal solution obviously, implying that magnesium oxysulfate whiskers may be formed via the dissolution of Mg(OH)(2) followed with the interaction of Mg2+, SO42- and OH- ions. The hydrothermal process of the whiskers is controlled by the crystal growth step and the corresponding kinetic model is as follows: -dc/dt = 0.438 (c - 0.417)(4).