CaO-MgCl_2H_2O体系中一维碱式氯化镁的水热合成与表征

Hydrothermal Synthesis and Characterization of One-dimensional Magnesium Hydroxide Chloride Hydrate in CaO-MgCl_2-H_2O System

通过水热反应在CaO-MgCl2-H2O体系中合成了不同结构与形态特征的一维碱式氯化镁(MHCH),分析了MgCl2浓度、CaO与MgCl2的摩尔比R及水热条件对产物的影响.结果表明,当MgCl2浓度>3mol/L,且R<0.5时才能得到MHCH;MHCH的直径和径长比随MgCl2浓度和R的增加而增大.MHCH的最佳制备条件为[MgCl2]=4mol/L,R=0.05.MHCH的结构相与反应温度密切相关,温度低于150℃时,体系中的产物为相3(Mg2(OH)3Cl.4H2O);温度高于150℃时的产物为相9(Mg10(OH)18Cl2.5H2O).常温下体系中首先出现Mg3(OH)5Cl.3H2O和相5(Mg3(OH)5Cl.4H2O),经陈化后两者均转化为相3,经160℃水热反应后相3转化为相9.

One-dimensional magnesium hydroxide chloride hydrate（MHCH） with different structures and morphologies was prepared in CaO-MgCl2-H2O system via a hydrothermal method.The effects of MgCl2 concentration,molar ratio of CaO to MgCl2（R）,and hydrothermal conditions on the structure and morphology of MHCH were investigated.It was found that MHCH could be prepared when the concentration of MgCl2 was greater than 3mol/L and R was less than 0.5.Both the diameter and radius-length ratio of MHCH increased with the MgCl2 concentration and R,and the optimum conditions of preparing MHCH were =4mol/L and R=0.05.The phases of MHCH was strongly depended on the reaction temperature,where phase 3（Mg2（OH）3Cl·4H2O） was stable below 150℃ and phase 9（Mg10（OH）18Cl2·5H2O） was formed above 150℃.In this reaction system at room temperature,Mg3（OH）5Cl·3H2O and phase 5（Mg3（OH）5Cl·4H2O） appeared firstly,they were both transformed to phase 3 after aged for 1 d.Phase 3 could be converted to phase 9 during hydrothermal treatment at 160℃.