球形纳米氧化镁团聚粉末的制备研究

发布时间：2018-05-20 13:22

本文选题：纳米氧化镁粉末 + 均匀沉淀法　；参考：《湖北工业大学》2015年硕士论文

【摘要】：氧化镁是一种典型的碱土金属氧化物,它广泛应用于耐火材料、医疗、食品等领域。纳米氧化镁具有表面效应、体积效应等,它的性能比普通氧化镁更加优越,可应用于纳米陶瓷、催化剂等新领域。然而,纳米氧化镁容易团聚,而且形貌难以控制,导致它的应用受到限制。球形纳米氧化镁团聚粉末具有比表面积大、粒径分布均匀等优点,因此它的反应活性较高、化学稳定性强、与基体结合能力强,可广泛应用于电池、催化剂、杀菌剂、纳米陶瓷涂层等领域。本文采用乳液法结合均匀沉淀法来制备球形纳米氧化镁团聚粉末,以解决纳米氧化镁应用受限的问题。本文的主要内容如下:1、以尿素为均匀沉淀剂、硝酸镁为盐溶液,在高温密闭的环境下制备了纳米氧化镁粉末。研究了硝酸镁的浓度、尿素与硝酸镁的摩尔比、反应时间、反应温度对纳米氧化镁粉末的平均粒径和粒度分布的影响。对前驱体粉末和纳米氧化镁粉末采用TG-DTA、BET、XRD、激光粒度测试仪、SEM进行表征。结果表明,制备的氧化镁粉末粒径大约为30nm且粒度分布均匀。最后,对均匀沉淀法制备纳米氧化镁的机理进行了简单的探讨,结果表明尿素水解反应控制着整个反应的进程,选择合适的反应时间和温度将决定纳米氧化镁的性能。2、为了达到控制团聚颗粒形貌的目的,研究了乳液黏度与乳液中水相和乳化剂含量之间的关系以及电导率与水相含量之间的关系。此外,还研究了乳化方式和复合乳化剂的HLB值对乳液稳定性的影响。结果表明,采用数显均质乳化机和HLB=5.5的复合乳化剂配制的乳液稳定性较好。最后,绘制了W/O型乳液的三元系统相图,发现稳定乳液存在乳白色区域和透明区域,并对乳液的形貌进行了观察。结果发现,乳液的球形度良好、分散均匀且为微米级别,可用作球形团聚粉末制备的软模板。3、采用乳液法结合均匀沉淀法制备了球形度良好、粒径分布窄的纳米氧化镁团聚粉末,并研究了各实验因素对粉末性能的影响。结果显示,在乳液体系稳定的情况下,氧化镁团聚粉末的形貌和粒度分布受镁盐的浓度、反应时间、尿素与镁盐溶液的摩尔比、反应温度的影响较小;但是受M值(乳化剂体积分数)、N值(水相体积分数)、乳化搅拌转速、煅烧升温速率的影响较大。4、为了使团聚粉末在保持球形度的同时比表面积最大化,设计了L9(34)的正交实验,以团聚粉末的比表面积值作为指标,得出最佳工艺条件。并在此条件下制备了氧化镁团聚粉末,用XRD、BET、SEM对粉末进行表征。结果表明,制得的团聚粉末的球形度良好、分散性能优异,粒度分布范围:2μm~50μm,平均粒径大约为30μm,BET的值为54.65m2/g。最后,还对均匀沉淀法与乳液法相结合制备球形纳米氧化镁团聚粉末的机理进行了简单的探讨,结果表明稳定的乳液和乳化搅拌转数、煅烧升温速率将决定氧化镁球形团聚粉末的性能。
[Abstract]:Magnesium oxide is a typical alkali earth metal oxide, it is widely used in refractory, medical, food and other fields. Nanometer magnesium oxide has surface effect, volume effect and so on. Its performance is superior to that of ordinary magnesium oxide. It can be used in new fields such as nano-ceramics, catalysts and so on. However, nano-MgO is easy to agglomerate and its morphology is difficult to control, so its application is limited. The spherical nano-magnesium oxide agglomerate powder has the advantages of large specific surface area and uniform particle size distribution, so it has high reaction activity, strong chemical stability, strong binding ability with matrix, and can be widely used in batteries, catalysts and fungicides. Nano ceramic coating and other fields. In order to solve the problem of limited application of nano-MgO, spherical nano-MgO agglomerated powder was prepared by emulsion method combined with homogeneous precipitation method in this paper. The main contents of this paper are as follows: 1. The nanometer magnesium oxide powder was prepared by using urea as homogeneous precipitating agent and magnesium nitrate as salt solution in a closed environment at high temperature. The effects of concentration of magnesium nitrate, molar ratio of urea to magnesium nitrate, reaction time and reaction temperature on the average particle size and particle size distribution of nanometer magnesium oxide powder were studied. The precursor powder and nano-MgO powder were characterized by TG-DTA-BET-XRDand laser particle size tester (SEM). The results show that the particle size of the prepared MgO powder is about 30nm and the particle size distribution is uniform. Finally, the mechanism of preparation of nano-MgO by homogeneous precipitation method was discussed. The results showed that the hydrolysis of urea controlled the whole process of the reaction. Choosing the appropriate reaction time and temperature will determine the properties of nano-MgO _ 2. In order to control the morphology of agglomeration particles, The relationship between the viscosity of emulsion and the content of water phase and emulsifier and the relation between conductivity and content of water phase were studied. In addition, the effects of emulsification mode and HLB value of composite emulsifier on emulsion stability were also studied. The results showed that the stability of emulsion prepared by using digital display homogenizing emulsifier and HLB=5.5 composite emulsifier was better. Finally, the ternary system phase diagram of the W / O emulsion was drawn. It was found that the stable emulsion had a milky white region and a transparent region, and the morphology of the emulsion was observed. The results showed that the emulsion had a good spherical degree, uniform dispersion and micron size, and could be used as a soft template for the preparation of spherical agglomeration powder. The spherical degree was obtained by emulsion method combined with homogeneous precipitation method. The effect of various experimental factors on the properties of nano-magnesium oxide agglomerated powder with narrow particle size distribution was studied. The results showed that under the condition of stable emulsion system, the morphology and particle size distribution of magnesium oxide agglomerate powder were less affected by the concentration of magnesium salt, reaction time, the molar ratio of urea to magnesium salt solution, and the reaction temperature. However, the orthogonal experiment of M value (emulsifier volume fraction and N value (water phase volume fraction, emulsifying stirring speed, calcining heating rate) is more important. In order to keep the globality of the agglomerated powder and maximize the specific surface area, the orthogonal experiment was designed. Taking the specific surface area value of agglomerated powder as the index, the optimum process conditions were obtained. Under these conditions, magnesium oxide agglomerated powder was prepared and characterized by XRDX BET-SEM. The results show that the agglomeration powder has good sphericity, excellent dispersion property, particle size distribution range of 50 渭 m ~ 2 渭 m and average particle size of about 30 渭 m BET of 54.65 m ~ 2 / g. Finally, the mechanism of preparation of spherical nano-MgO agglomerated powder by homogeneous precipitation method and emulsion method was simply discussed. The results showed that stable emulsion and emulsified agitating speed were obtained. The calcination rate will determine the properties of MgO spherical agglomerates.
【学位授予单位】：湖北工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ132.2;TB383.1

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