基于诱导结晶的碱式氯化镁晶须高效水热制备技术及机理研究

The present use of the salt lakeresources in our country isfocused mainly on the fabrication of K/Na-bearing products and thecontinuousaccumulation of Mg-bearing resources inhibited the further development of the relatedindustries..China is rich in salt lakes magnesium , especially in western. However, accumulation of magnesium salts elicited by long-term unbalanced mining lead to wastes of resources and seriously inhibited the sustainable development. As a material with advanced performance, high value and large market capacity, magnesium hydroxide chloride hydate whiskers can turn waste into treasure, providing a new way for large-scale and value-added utilization of salt lake magnesium resources. However, its application has been limited by the time-consuming inefficient preparation process and structural instability. Therefore, it’s beneficial to promote the high value-added utilization of magnesium hydroxide chloride hydate whiskers by introducing surfactant-induced high-efficiency hydrothermal whisker preparation technology and the transformation of metastable whisker dehydration phase into stable structure in the field of composite materials. MgCl2 and activated MgO will be used as raw materials to promote whisker growth by surfactant-inducing effect, and high aspect ratio basic magnesium chloride whiskers will be prepared to reveal the selective growth mechanism. Then the heating decomposition characteristics, phase change and morphology change of whiskers will be studied by means of knowledges of the crystallization, structure,solution,interphase and molecular simulation,etc, and its dehydration conversion mechanism will be explored, and structurally stable anhydrous magnesium hydroxide chloride hydate whiskers were obtained. Finally, the surface of the wiskers will be modified, dispersed and composited.A new technology for preparing reinforced polymer composites from whiskers will be established..

我国盐湖镁丰富，西部资源尤其丰富，但长期的不平衡开采使得镁盐大量富集，既浪费资源又严重制约可持续发展。碱式氯化镁晶须作为一种性能先进、附加值高、市场容量大的材料，可望变废为宝，为盐湖镁资源的规模化高附加值利用提供一条新途径。但其长时低效制备过程和结构不稳定性限制了其应用。因此，引入表面活性剂诱导的高效水热晶须制备技术以及介稳态晶须脱水相转化为稳定结构等思路，有利于促进碱式氯化镁晶须的在复合材料领域的高附加值利用。本项目拟以氯化镁和活性氧化镁为原料，通过表面活性剂诱导效应促进晶须生长，制备高长径比碱式氯化镁晶须，揭示其选择性生长机理。然后利用结晶/结构/溶液/界面理论和分子模拟技术对晶须加热分解特性、物相变化、形貌变化进行研究，探索其脱水转化机制，制得结构稳定的无水碱式氯化镁晶须；最后进行晶须表面改性、分散及复合，建立由晶须制备增强高分子复合材料的新技术。

围绕当下我国镁资源急需利用现状，针对镁盐晶须研究过程中出现的工艺复杂、生长规律机理不清楚、热分解行为研究较少、缺少基础数据等情况，本研究探讨了镁盐晶须形成规律，选择性生长机制，脱水转化规律，以及在环境领域中磷酸盐的去除，在阻燃领域中以改性晶须制备复合阻燃材料。(1)首先采用液体法合成了超高长径比的3Mg(OH)2·MgCl2·8H2O (318MHCH)纳米线，研究了十六烷基三甲基溴化铵(CTAB)在高浓盐溶液中的作用。对合成的318MHCH纳米线的结构和形貌进行了表征。所制备的318MHCH纳米线具有典型的三斜结构和相对较好的单晶性能。通过引入CTAB，318MHCH纳米线的长径比将显著提高，从500提高到4000。318MHCH纳米线的高长径比是由于溶液粘度的增加和CTAB分子在晶体表面的选择性吸附所致。FTIR和拉曼光谱证实了CTAB分子的带正电荷的含氮头与318MHCH晶体的表面相互作用。此外，由于(-1 0 1)平面具有较低的静电势，具有高电势的CTAB含氮端更容易被吸附，分子动力学模拟证实了这一点。因此，CTAB被选择性地吸附在318MHCH纳米线的一侧，阻碍了318MHCH纳米线的横向生长，促进了长径比。此外，其他阳离子表面活性剂已被证明对纳米线的选择性生长有类似的影响。(2)本研究采用简单的水热转化方法以碱式氯化镁晶须（MHCH）为前驱体，在氢氧化钠-乙醇-水溶液中脱去了碱式氯化镁晶须中的结晶水制备多孔Mg(OH)2纳米线，采用静态吸附法研究了其对废水中磷酸盐的吸附能力。通过一系列表征探讨了脱水机制，OH-进入晶格，与Mg2+、水和Cl-从晶格中逃逸，从而形成多孔的Mg(OH)2纳米线，乙醇保护这些孔洞不坍塌。通过分析吸附数据，磷酸盐在多孔Mg(OH)2纳米线上的吸附过程符合伪二阶动力学，是自发的、吸热的和熵增加的。它被证实是Mg2+和HPO42-和H2PO4-的络合过程。在313K时的最大吸附量为162.15mg·g-1，受共存离子的影响较小，具有良好的回收性能。研究表明，Mg(OH)2纳米线是一种实用且有前途的磷酸盐吸附剂。(3)以γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH-570)为改性剂对碱式碳酸镁进行表面改性，并研究了其对聚乙烯的阻燃和机械性能的影响。