【作者】 夏涛；

【导师】 王玺堂；

【作者基本信息】 武汉科技大学 ， 材料学， 2010， 硕士

【摘要】 本研究开展了以氯化镁和碳酸钙(氧化钙、白云石)为原料制备氧化镁粉体的新工艺研究,为利用我国丰富的卤水资源制备高纯氧化镁奠定基础。实验以无水氯化镁、六水氯化镁和碳酸钙、氧化钙、白云石为原料,氯化锂为辅助熔盐,采用固相法和熔盐法制备出了不同形貌的氧化镁。使用热重/差热仪(TG/DSC)和高温XRD对原料热分解过程以及合成氧化镁的反应机理行了分析。通过X衍射分析仪、场发射扫描电镜等对产物进行了表征,并对原料种类、合成温度、保温时间、熔盐含量对氧化镁产物性能的影响进行了研究。研究结果表明,分别采用固相法和熔盐法以MgCl2和CaCO3,CaMg(CO3)2为原料制备的氧化镁粉体形貌不一,大小分布不均匀;以MgCl2和CaO为原料制备的氧化镁粉体大小分布较均匀,主要由近似八面体形貌和球状的颗粒组成;以MgCl2·6H2O和CaCO3、CaO、CaMg(CO3)2为原料制备的氧化镁粉体形貌不一,大小分布不均匀;在浸泡与洗涤的过程中加入表面活性剂聚乙二醇(PEG)、十六烷基三甲基溴化铵(CTAB)、十二烷基苯磺酸钠(SDBS)后制备的氢氧化镁前躯体形态各异,其中加入PEG的氢氧化镁形貌为片状;加入CTAB后的氢氧化镁形貌为三角形堆积体;加入SDBS后的氢氧化镁形貌为球状聚集体。所有原料体系中以MgCl2·6H2O和CaCO3原料制备的氧化镁活性相对较好,同时粉末的合成温度越低,其烧结活性越高,氧化镁粉体越易于烧结致密化;热处理温度的升高和保温时间的延长以及增大LiCl的加入量均有利于氧化镁晶体的生长,而氧化镁晶体的结晶度增大,其活性降低。采用熔盐法对氧化镁粉体进行提纯可以除去其中的氧化硼杂质和少量的氧化硅、氧化铝杂质。更多还原

【Abstract】 This paper is about the new technics to prepare the MgO powders using the materials of magnesium chloride and calcium carbonate(calcium oxide,dolomite). This research has laid a solid foundation for using our abundant brine resources to prepare high purity MgO powders. MgO was synthesized via solid state reaction and molten salt methods by using MgCl2,MgCl2·6H2O and CaCO3, CaO, CaMg(CO3)2 as starting materials, and LiCl as flux. Thermo-decomposing process of starting materials, synthetic reaction of MgO was studied by using TG/DSC and high temperature XRD analysis. The product powders were characterized with XRD and SEM. The influenc of different raw materials, synthesis temperature, holding time and the relative content of molten salt on the performances of the products have been studied.The results show that using MgCl2 and CaCO3, MgCl2 and CaMg(CO3)2 as raw materials respectively, the prepared magnesium oxides had the mixed morphologies and uneven size distributions. Using MgCl2 and CaO as raw materials, the prepared magnesium oxides were characterized with a uniform size distribution and a near sphere-like and octahedron morphology. Whereas using MgCl2·6H2O and CaCO3, MgCl2·6H2O and CaO, MgCl2·6H2O and MgCa(CO3)2 as raw materials, all of products had the mixed morphologies and uneven size distributions, in which the product has a relatively better reactive activity when MgCl2·6H2O and CaCO3 has been used as raw materials. Using PEG, SDBS and CTAB as surfactant in experiment, the prepared Mg(OH)2 precursor have different morphologies. The prepared Mg(OH)2 precursor have flake morphologies when PEG has been used as surfactant. Whereas using SDBS and CTAB as surfactant respectively, the prepared Mg(OH)2 precursor have globular aggregates morphologies and triangle aggregates morphologies. Lower synthesis temperature of MgO powders not only has better sintering activity, but also could improve the sintering densification of MgO powders. A higher heat treatment temperature, longer holding time and the increase of LiCl addition content were favorable for the growth of magnesium oxide crystals, resulting in the decrease of crystal cell volume and reactive activity.The B2O3 impurities and a small amount of SiO2, Al2O3 impurities could be removed by molten salt method to purify MgO powders.更多还原