利用水镁石水热法制备定形氢氧化镁晶体的研究

发布时间：2018-06-02 11:09

本文选题：水镁石 + 氢氧化镁　；参考：《东北大学》2010年博士论文

【摘要】：水镁石是迄今为止发现的含镁量最高的一种矿物,在世界上分布不广,产出比较稀少,我国具有丰富的水镁石资源。作为一种工业矿物,水镁石在耐火材料、环境保护、建材、陶瓷和核工业等领域得到了广泛应用。但是,由于技术比较落后,目前我国的水镁石的开发利用还处于原矿的出口及生产耐火材料等低附加值产品的初级阶段,这对水镁石资源造成了极大的浪费并限制了水镁石的高效利用。为了避免这种浪费,应将其用于高附加值、具有高技术含量的功能材料的生产与加工上。用水镁石制备环境友好型的氢氧化镁无机阻燃剂受到了广泛的关注,近年来,随着人们环保意识的日益增强,氢氧化镁作为环境友好型的无机阻燃剂,由于其阻燃、抑烟、无毒、热稳定性高等特点,在聚合物、电缆、建筑和装饰材料等领域得到了广泛的应用。氢氧化镁的晶形和粒度对其性能有十分显著的影响,具有优良阻燃性能的氢氧化镁应为纤维状和片状,纯度大于97%,厚度大于80nm,颗粒的平均尺寸为0.5-1μm,(101)极性面的微观应变小于3.0×10-3。但是,以水镁石为原料采用物理法所制得产品的纯度不高、晶形难以控制,严重影响了其阻燃性能。目前,优质氢氧化镁主要是以金属镁和镁盐为原料,采用化学法制备所得,成本较高。因此,利用水镁石资源制备高纯、超细的氢氧化镁对提高我国优势镁资源的市场竞争力具有十分重要的意义。本文以水镁石为原料,通过水热合成和水热处理法制备出了超细、高纯、颗粒均一、分散均匀的具有不同形貌的氢氧化镁颗粒,利用X-射线衍射仪(XRD)和扫描电子显微镜(SEM)对所制得氢氧化镁颗粒的晶相、形貌和颗粒尺寸进行了表征,结合实验结果,对水热条件下晶粒的形成机理进行了研究。本文取得了以下研究成果： (1)通过现场调研和大量的资料分析,研究了辽宁省水镁石矿床形成的地质条件、不同形态水镁石的形成及其矿物学性质,为水镁石的开发利用提供了地质依据。同时,结合辽宁省水镁石资源特点,提出制备定形氢氧化镁晶体的技术方法。 (2)采用水热合成法和水热处理法分别制备出了高纯、分散均匀、厚度为80-100nm、直径为200-400nm的六方片状和直径为100-500nm、长度为1-20μm纤维状氢氧化镁。所得产物的特征峰值与氢氧化镁的标准峰值完全一致,没有杂峰出现,(101)晶面的微形变小于3.0×10-3,这表明,所得产物为高端无机阻燃剂。 (3)系统研究了搅拌速度、填充度、前驱物浓度、反应温度、反应时间、pH值、氢氧化钾、硫酸根离子、溶剂和表面活性剂等对氢氧化镁晶形的影响。通过计算(001)晶面和(101)晶面的衍射强度比值I001/I101,对比了不同晶面的优先生长方向。 (4)研究了晶体的晶形和结晶度与过滤性能的关系,发现六方片状晶体与纤维状晶体相比,具有较好的过滤性能,通过控制晶体的晶形和结晶度可以显著改善其过滤性能。 (5)根据大量的实验数据,结合现代物理学、溶液化学和结晶学知识,以“负离子配位多面体模型”为基础,发现晶体的形貌和尺寸由其内部结构和外在生长条件共同决定,晶体生长过程是生长基元在其界面叠加的过程。生长基元在晶体晶面的叠加过程受晶面结构和外在生长条件的共同影响。 Mg(OH)64为氢氧化镁晶体的生长基元,根据键价理论模型计算表明,氢氧化镁的理想生长形态为正六边形。Mg(OH)64生长基元在不同晶面的叠加过程受晶面上Mg-O-Mg键桥和位于“三配位”位置OH基团数目的影响。外在生长条件通过影响生长基元的形成和生长基元在晶面的叠加过程来影响晶体的形成。通过理论分析得到了和实验结果相一致的结论。通过本文的工作,可以看出,生长基元模型把晶体生长过程中晶体的结构、外在生长条件和晶体的生长形态紧密的联系起来,具有很强的生命力。本文研究为水镁石制备定形氢氧化镁晶体提供了理论基础和技术方法。
[Abstract]:As an industrial mineral , brucite has been widely used in refractory , environmental protection , building materials , ceramics and nuclear industry .

Magnesium hydroxide is widely used in the fields of polymer , cable , building and decorative materials . The crystal form and particle size of magnesium hydroxide have been widely used in the fields of polymer , cable , building and decorative material .

The crystal phase , morphology and particle size of the prepared magnesium hydroxide particles were characterized by hydrothermal synthesis and hydrothermal treatment by using brucite as the raw material . The crystal phase , morphology and particle size of the magnesium hydroxide particles were characterized by X - ray diffraction ( XRD ) and scanning electron microscopy ( SEM ) .

( 1 ) Through field investigation and abundant data analysis , the formation of brucite deposit in Liaoning province is studied , the formation of brucite in different forms and its mineral properties are studied , and the geological basis is provided for the development and utilization of brucite .

( 2 ) High purity , uniform dispersion , thickness of 80 - 100 nm , diameter of 200 - 400 nm and fibrous magnesium hydroxide of 100 - 500 nm and length of 1 - 20 渭m were prepared by hydrothermal synthesis and hydrothermal treatment respectively . The peak value of the product was 100 - 500 nm and the length was 1 - 20 渭m . The peak value of the product was identical with the standard peak value of magnesium hydroxide . The microdeformation of ( 101 ) crystal plane was less than 3.0 脳 10 - 3 , which showed that the product was high - end inorganic fire retardant .

( 3 ) The effects of stirring speed , filling degree , precursor concentration , reaction temperature , reaction time , pH value , potassium hydroxide , sulfate ion , solvent and surfactant on the crystal form of magnesium hydroxide were studied .

( 4 ) The relationship between crystal form and crystallinity and filtration performance was studied . It was found that the hexagonal flake crystals had better filtration performance than the fibrous crystals , and the filtration performance of the crystals could be improved by controlling the crystal form and crystallinity of the crystals .

( 5 ) Based on a large number of experimental data , based on the knowledge of modern physics , solution chemistry and crystallization , the morphology and size of crystals are determined by their internal structure and external growth conditions .

Mg ( OH ) 64 is a growth element of magnesium hydroxide crystal . According to the theoretical model of bond valence , it is shown that the ideal growth form of Mg ( OH ) 64 is regular hexagon . Mg ( OH ) 64 growth element is influenced by Mg - O - Mg bond bridge on the crystal plane and the number of OH groups in the " three coordination " position .

The external growth conditions affect the formation of the crystal by influencing the formation of growth elements and the stacking process of the growth elements on the crystal planes .

Through the work of this paper , it can be seen that the growth primitive model links the structure of the crystal to the growth condition and the growth form of the crystal in the process of crystal growth , and has strong vitality .

A theoretical basis and a technical method for preparing shaped magnesium hydroxide crystals from brucite are studied in this paper .
【学位授予单位】：东北大学
【学位级别】：博士
【学位授予年份】：2010
【分类号】：O614.22

【引证文献】