【作者】 路绍琰；

【导师】 李先国；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2010， 硕士

【摘要】 纳米结构的硼酸镁和氢氧化镁具有优异的力学性能、耐高温耐腐蚀性、独特的增强、阻燃性能,它们在改善金属、塑料及陶瓷等复合材料性能方面都有重要的应用价值。硼酸镁和氢氧化镁是重要镁盐功能材料,应用前景广阔。本文研究了硼酸镁晶须和六方片状氢氧化镁的制备工艺；考察了反应温度、反应时间、反应物浓度、表面活性剂等因素对产品性能的影响；利用X射线衍射(XRD)、扫描电子显微镜(SEM)、红外光谱(FT-IR)及热重分析(TG)等测试手段对产品性能进行了表征；获得了水热制备硼酸镁晶须和氢氧化镁的优化工艺条件,并初步探讨了他们的生长过程。以MgCl2·6H2O, Na2B4O7·10H2O, NH3·H2O为原料,向反应体系中加入聚乙二醇,经水热法制得了碱式硼酸镁晶须,其化学组成为MgBO2(OH)。对碱式硼酸镁晶须的制备条件进行了研究,考察了反应物浓度、氯化镁与四硼酸钠浓度比、反应温度、反应时间、表面活性剂对产品形貌的影响。获得制备碱式硼酸镁晶须最佳的反应条件为：氯化镁浓度为1.67mol/L,四硼酸钠浓度为0.31mol/L,氨水浓度为6.3mol/L,反应温度190℃,反应时间10小时。得到了直径约为60-90纳米,长度为3-7微米,长径比为30-90,分散性良好的碱式硼酸镁晶须。碱式硼酸镁晶须经700℃高温焙烧3h以上,因脱水发生物相转化,得到硼酸镁(Mg2B2O5)晶须,制得的硼酸镁晶须长径比为50-80,晶须尺寸均匀。根据水热反应中溶解—再结晶机制对硼酸镁晶须的生长过程进行了研究。碱式硼酸镁晶须是多步离子反应经特定晶面选择生长的结果,再通过焙烧脱水得到硼酸镁晶须。以MgCl2·6H2O, NH3·H2O为原料,向反应体系中加入聚乙二醇,经水热制备法制得规则六方片状氢氧化镁。对氢氧化镁的制备条件进行了研究,考察了反应温度、反应时间、氨水浓度、表面活性剂对产品形貌的影响。氯化镁溶液浓度为1.67mol/L,氨水浓度为0.25mol/L190℃反应6h是其制备六方片状氢氧化镁的最佳条件,其直径为200-300nm,厚度为20-50nm。六方片状氢氧化镁的生长也是溶解—再结晶过程。随水热反应温度的升高氢氧化镁逐渐溶解,于是Mg2+和OH-不断聚集成晶胚,晶胚形成一定大小的晶核,晶核继续长大生成氢氧化镁。更多还原

【Abstract】 Nanostructured Magnesium borate and Magnesium hydroxide has excellent mechanical properties, high temperature, corrosion resistance, unique strengthen’ property and flame-retardant property and they have important application value on improveing performance of the metal, plastic and ceramic composites. Magnesium borate and Magnesium hydroxide are important functional materials with wide application prospect.In this paper, the preparation technology of Nanostructured Magnesium borate and Magnesium hydroxide was researched; The influence of reaction temperature, reaction time, concentration and surfactant conditions on performance of the products were investigated; XRD, SEM, FT-IR, TG were employed to characterize the structural feature, morphology, chemical composition and thermal behavior of the products. The optimized hydrothermal synthesis process conditions of them were obtained and also their growth processes were discussed.Magnesium borate hydroxide whiskers was prepared by using a hydrothermal method with MgCl2·6H2O, Na2B4O7·10H2O, NH3·H2O and adding dispersant into the reaction system. The experiment results showed that it was MgBO2(OH).The effect of operational parameters such as concentration, material ratio, reaction temperature, reaction time, surfactant on the composition and morphology of the products were studied. The optimum condition were:the concentration of MgCl2·6H2O:1.67 mol/L, Na2B4O7·10H2O:0.31mol/L, NH3:6.3mol/L, reaction temperature:190℃, reaction time:10h. MgBO2(OH) has a aspect ratio of 30-90, a diameter of 60-90, length 3-7μm and good dispersibility. Magnesium borate whiskers (Mg2B2O5) with aspect ratio of 50-80 were then obtained by calcining of the precursor at 700℃for 3h due to water loss.Magnesium borate hydroxide whiskers growth process was studied under dissolution recrystallization mechanism of hydrothermal method. Magnesium borate whisker growth is a multi-step reaction by ions selective on specific crystal face, it was then sintered to achieve Magnesium borate whiskers.Magnesium hydroxide nano-plates was prepared by using a hydrothermal method with MgCl2·6H2O and adding dispersant into the reaction system.The effect of operational parameters such as reaction temperature, reaction time, surfactant on composition and morphology of the products were studied. Magnesium hydroxide hexagonal plate with a thickness of 20-50nm and a diameter of 200-300nm was prepared when the concentration of MgCl2·6H2O:1.67 mol-L, NH3·H2O: 6.3mol/L.Magnesium hydroxide hexagonal plate growth is dissolution recrystallization mechanism too. Magnesium hydroxide gradually dissolved as the temperature increasing. Mg2+ and OH- continued to gather into embryos, embryos formed a certain size nuclei, thus Magnesium hydroxide nano-plates was generated finally.更多还原