【作者】 吴敬元；

【导师】 薛冬峰；

【作者基本信息】 大连理工大学 ， 无机化学， 2009， 硕士

【摘要】 高品质镁质功能材料是材料领域的研究热点之一,在环保、阻燃、医药、催化等领域都有着重要应用,镁质功能材料的性能与其粒径大小、形貌等因素密切相关,因此镁质功能材料的形貌、尺寸调控一直是材料制备领域中的重要研究课题。本论文选取碱式硫酸镁、氢氧化镁和氧化镁作为研究对象,开发了一系列新型制备工艺,成功地调控了这几种材料的形貌和尺寸。本文设计了一个包含Mg²⁺、SO₄^2-、NH₄⁺和二乙醇胺的新碱性缓冲溶液体系,在水热条件下,氢氧化镁纳米粒子可以从该体系中均匀沉淀出来,在溶液中SO₄^2-的引导下,这些氢氧化镁纳米粒子可以转化为长径比大于100、具有均一形貌和尺寸的512型碱式硫酸镁晶须。在保持其他条件不变的情况下,简单地增大反应物浓度,晶须的平均直径从4μm至50 mn之间可调可控,能够适应各种具体应用的要求。在对实验结果进行深入分析的基础上,对该体系下碱式硫酸镁晶须的生长机理进行了初步探讨,有助于人们对碱式硫酸镁晶须结晶习性的理解。为了提高晶须材料与聚合物的相容性,使用硬脂酸钠对晶须进行了表面疏水改性处理。以制备出的碱式硫酸镁晶须为原料,设计了一个包含丙三醇和氢氧化钠的可控阴离子交换反应体系,来控制碱式硫酸镁晶须中SO₄^2-和溶液中OH^-的交换反应,在常压80℃水浴条件下转化,得到的氢氧化镁晶须几乎能够完美保持前驱物的形貌,对于这样一个可控的阴离子交换体系,少量丙三醇的添加对于形貌保持和转化效率来说都是至关重要的。基于理论和实验的分析,这种可控的离子交换机理被简单讨论。以直接沉淀的氢氧化镁为前驱物,利用添加柠檬酸盐的氢氧化钠溶液这一复合水热改性剂水热改性,合成了结晶度高、粒径均一、分散性好的完美六方片状氢氧化镁功能粉体产品,并对该粉体产品的表面进行了疏水性处理,同时对氢氧化镁在水热条件下的结晶生长机理进行了简单讨论。以六方片状氢氧化镁为前驱物,通过热处理制备了具有相同形貌的氧化镁功能粉体,明显增加了具有高催化活性晶面的暴露。本文制备的具有可控直径的碱式硫酸镁和氢氧化镁晶须产品兼具阻燃和补强双重功能,是高聚物理想的环保型添加剂;制备的氢氧化镁功能粉体产品除可作为高品质阻燃剂使用外,还可以被应用于催化、医药、环保等诸多领域;具有高活性面的氧化镁功能粉体将是性能优良的催化材料。另外,本文所设计一些材料制备的新工艺以及所提出的生长机理也为其他微纳米材料的合成提供了有益的参考。更多还原

【Abstract】 The study of high-quality magnesium functional materials is one of the most interesting topics in the field of materials due to their important applications in environmental protection, flame retarding,medicine and catalysts The performance of these materials is closely related to their size and morphology.Accordingly,the morphology and size control of magnesium functional materials is one of the most important research subjects.We developed some new preparation technologies for magnesium hydroxide sulfate hydrate,magnesium hydroxide and magnesium oxide,and their morphologies and sizes were successfully controlled.A new alkaline buffer solution system including Mg²⁺、SO₄^2-、NH₄⁺ and diethanolamine was designed,in which Mg（OH）₂ nanoparticles can be homogeneously precipitated under a hydrothermal condition.These Mg（OH）₂ nanoparticles can be converted into 5Mg（OH）₂·MgSO₄·2H₂O（512MHSH） whiskers with uniform size and shape,an aspect ratio no less than 100 by the direction of SO₄^2- ions.The average diameter of whiskers can be facilely controlled from 4μm to 50 nm only by adjusting the concentration of reactants and without varying any other experimental parameters.The growth mechanism of 512MHSH was discussed by analyzing the experimental results,which contributes to more profound understanding of 512MHSH growth habit.In order to improve the compatibility between inorganic materials and polymer,the surface of as-prepared whiskers was modified by using sodium stearate.A controllable system of anion exchange between SO₄^2- and OH^- ions,which includes glycerol and NaOH,was designed to fabricate Mg（OH）₂ whiskers in a normal atmosphere at 80℃using 512MHSH obtained above as precursors.The morphology of as-synthesized Mg（OH）₂ whiskers is similar to that of precursors.The addition of a little glycerol is vital not only to perfectly maintain the morphology of precursors but also to ensure conversion efficiency in this system.The controllable anion exchange mechanism was discussed on the basis of the theoretical and experimental analysis.The functional Mg（OH）₂ powder with high crystallinity,good dispersibility, homogeneous granularity and hexagonal shape was successfully synthesized by using a new compound hydrothermal modifying agent including citrate and NaOH.The Mg（OH）₂ powder was modified by using sodium stearate,and its surface became hydrophobic.The growth mechanism of Mg（OH）₂ crystal in hydrothermal condition was also discussed.The functional MgO powder with the same morphology was prepared by hot-treatment of Mg（OH）₂ powder. The exposure of crystal surface with high catalysis activity is distinctly enhanced.The as-prepared 512MHSH and Mg（OH）₂ whiskers with controllable diameter,which have dual functions as flame retardant and reinforcing materials,are the perfect additive for polymer.The functional Mg（OH）₂ powder is a kind of high-quality flame retardant,which can also find application in catalysis,medicament,environmental protection,etc.The functional MgO powder with high activity crystal plane may be an excellent catalytic material. In addition,both new preparation technologies and growth mechanisms mentioned in this paper can provide useful references for fabrication of other micro/nano-materials.更多还原