熔盐法制备氧化镁粉体及其反应机理研究

Study on Synthesis of MgO Powder by Molten Salt Method and the Reaction Mechanism

以MgCl2、CaCO3、NaNO3和KNO3为原料，采用熔盐法制备了MgO粉体。通过x射线衍射仪（XRD）、场发射扫描电子显微镜（SEM）对产物的组成与形貌进行了表征，借助热重-差示扫描热量计（TG-DSC）、X射线衍射仪（XRD）对制备氧化镁粉体的反应机理进行了探讨。结果表明，在熔盐反应过程中，Mg^2＋与Ca^2＋发生置换反应，生成白云石和碳酸镁等中间产物，随着反应的不断进行，白云石最终转变为碳酸镁；550℃热处理碳酸镁分解为氧化镁，经水浸泡后氧化镁水解生成氢氧化镁，氢氧化镁前驱物为不规整的层状形貌，厚度介于0．03—0．05μm，直径介于0．2—1．0μm之间；600℃热处理氢氧化镁分解为氧化镁，产品氧化镁为颗粒状形貌，粒径介于0．2—0．5μm之间。

MgO powder was prepared through molten salt synthesis with MgCl2, CaCO3, NaNO3 and KNO3 as raw materials. The composition and morphology of the product were studied by XRD and SEM, and the reaction mechanism of preparing MgO powder was investigated by TG-DSC and XRD. The results indicated that Ca^2＋ was replaced by Mg^2＋ to form intermediate products such as dolomites and magnesium carbonates in the course of molten salt synthesis. Dolomites were finally turned into magnesium carbonates with the reaction＇s continuing. Calcined at 550 ℃, MgCO3 was decomposed to MgO, which was hydrolyzed into Mg（ OH）2 after soaked in water. The precursor Mg（ OH）2 powder was in irregular layer shape with thickness of 0.03 - 0.05 μm and diameter of 0.2 - 1.0μm. The heat treatment of Mg （OH） 2 at 600 ℃ resulted in MgO, which was in granular shape with diameter of 0.2 - 0.5 μm.