【作者】 杜春芳；

【导师】 杨华明；

【作者基本信息】 中南大学 ， 材料学， 2010， 博士

【摘要】 利用天然矿物的组成、结构及物理化学特性制备新型功能材料,探索矿物资源制备先进功能材料的新方法,建立天然矿物结构与先进功能材料结构、性能之间的基本联系并开发其应用领域,是材料学科发展的一个重要方向。多孔材料的发展经历了从天然沸石到近十年兴起的介孔与大孔材料,其骨架组成元素多为硅和铝,在传统合成方法中涉及到的硅铝源多为化学试剂,这使得合成成本高,难以实现工业化生产。储量丰富的层状硅酸盐矿物由于其独特的层状结构和丰富的硅铝成分,有望成为天然矿物制备多孔材料新方法中的首选原料。本论文利用层状硅酸盐矿物独特的层状结构制备孔径双峰分布的多孔材料；以其丰富的硅铝成分为原料制备沸石分子筛及有序介孔材料。采用X-射线衍射分析(X-ray diffraction, XRD)、扫描电镜(scanning electron microscope, SEM)、高分辨透射电镜(high-resolution transmission electron microscopy, HRTEM)、热重-差示扫描(thermogravimetric-differential scanning calorimeters, TG-DSC)、核磁共振(nuclear magnetic resonance)、红外光谱(fourier transform infrared spectroscopy, FT-IR)、荧光光谱(Photoluminescence, PL)、粒度分析、以及N2吸附-脱附测试、抗压强度和静态水吸附量测试对所制备样品进行了结构和性能表征。以层状硅酸盐矿物为原料,采用机械活化浸出法制备了孔径在微孔区域(0.36nm)和介孔区域(3.80nm)双峰分布、比表面积可达400m2·g-1、孔容为0.80ml·g-1的多孔材料。重点讨论了球磨时间和酸浸时间对所制备多孔材料孔性能的影响。研究结果表明球磨过程促使层状硅酸盐矿物晶体结构趋向无定形化,此举有利于后续酸浸过程的进行。H+离子通过离子交换浸出层状硅酸盐矿物中的八面体层离子,所留空位即为微孔区域；硅氧四面体层通过结构重排、缩聚形成介孔。相比于酸浸时间,球磨时间对多孔材料孔性能的影响更显著。层状硅酸盐矿物本身化学成分及层状类型(1：1型和2：1型)的不同导致其在制备过程中结构及孔性能变化行为有所区别,最终导致所制备多孔材料孔性能上的差异。以层状硅酸盐矿物为原料采用水热法成功制备了有序介孔材料MCM-4l,其比表面积可达1100m2·g-1、孔容为1.00ml·g-1、孔径在2.80nm处集中分布。所制备的MCM-41具有良好的热稳定性,承受温度可达940℃。电荷匹配和硅酸盐物种的缩聚程度决定了产物的最终结构,本技术依据电荷匹配原则,以协同作用方式实现了低表面活性剂浓度(2wt%)下有序介孔材料MCM-41的合成。在选定pH值下,H3SiO4-和H4Si04是硅酸物种存在的两种主要形式,它们之间通过缩聚组合使最终产物MCM-41主要含有Q3(Si(SiO)3OH)结构和Q4(Si(SiO)4)结构。以不同层状硅酸盐矿物为原料合成的有序介孔材料孔壁都为无定形的Si02；层状硅酸盐矿物的层状类型对最终合成的有序介孔材料的结构没有直接影响；层状硅酸盐矿物中所含的硅氧四面体是合成有序介孔材料的必备条件。以层状硅酸盐矿物为原料制备有序介孔材料,其结构经历了从层状硅酸盐晶体结构→无序多孔结构→有序介孔结构的转变。采用有序介孔材料为主体,把不同功能客体分子组装到主体介孔材料的孔道中,可以制备不同种类的复合功能材料,其性能都将优于单个主体或客体的性能。以SnO2纳米颗粒为代表,以所制备的MCM-41为主体采用水热法成功制备了SnO2/MCM-41复合材料。研究表明除极少部分Sn原子进入到有序介孔材料的孔壁中以外,大部分SnO2纳米颗粒存在于有序介孔材料的孔道中,且纳米颗粒的存在并没有破坏有序介孔材料的孔道结构。以主体介孔材料的孔道为“微反应器”,通过调节Sn/Si摩尔比可实现对Sn02／MCM-41复合材料荧光性能的调控,所制备复合材料的荧光强度比纯SnO2纳米颗粒荧光强度提高了近七倍。以层状硅酸盐矿物(高岭土为例)为原料采用低温水热合成法成功制备了4A沸石分子筛,分子筛颗粒呈立方体相,尺寸在4μm左右。所制备的4A分子筛干燥剂的静态水吸附量为21.0wt%,抗压强度为51.ON／颗,达到化学工业部标准HG／T 2524-93(静态水吸附量≥20wt%,抗压强度≥50N／颗)。成功进行扩大试验后,4A分子筛干燥剂各项性能指标都达到干燥剂应用标准。合成采用低温水热合成,操作简单,无需额外添加硅源或铝源。实验过程中通过调节工艺参数实现对4A分子筛粉体纯度及形貌的控制；通过调节样品的结晶度,从而获得性能良好的4A沸石分子筛干燥剂产品。本论文基于层状硅酸盐矿物独特的层状结构和化学成分,围绕功能材料的结构-性能关系,通过机械活化浸出及水热等物理化学方法制备了结构独特、性能良好的多孔及复合功能材料,开发了所制备功能材料在干燥剂领域中的潜在应用；探索矿物资源制备先进功能材料的新方法,弄清制备过程中的物理化学变化,初步建立矿物与先进功能材料结构、性能之间的基本联系并开发其应用领域,为资源-材料一体化提供基础理论和技术保障。更多还原

【Abstract】 It has been an attractive trend for the materials science to pursue new technologies for preparing novel functional materials by means of the chemical compositions, special structures and physical-chemical characteristics of natural minerals.The structure-property relationship between the natural minerals and the as-synthesized advanced functional materials is especially emphasized, and the potential application of the obtained functional materials is a key research focus. The development of porous materials experienced from natural zeolites to mesoporous materials and macroporous materials.For porous materials, Si and Al act as the basic compositions in the framework. With regard to the traditional approaches, Si and Al sources in the preparation of porous materials are mainly chemical reagents, which are of high cost and baffle the industrial production of porous materials.On the basis of their special structures and compositions,layered silicate minerals usually act as a preferred candidate for the preparation of novel porous materials.In this thesis, based on a comprehensive review of the research and current issues of porous materials,we have conducted a detailed study of porous material with bimodal pore size distribution, ordered mesoporous material and zeolite by means of the special layered structure and the rich Si, Al contents of the natural minerals.The structures and properties of the obtained products are characterized by X-ray diffraction(XRD), scanning electron microscope(SEM),high-resolution transmission electron microscopy(HRTEM),thermogravimetric-differential scanning calorimeters(TG-DSC), solid-state nuclear magnetic resonance(NMR), fourier transform infrared spectroscopy(FT-IR), Photoluminescence(PL), N2 adsorption-desorption measurement, water adsorption capacity and compression strength techniques.Porous materials with bimodal pore size distribution of micropores (0.36nm) and mesopores(3.8nm),specific surface area of 400m2·g-1 and pore volume of 0.80ml·g-1 are synthesized through mechanochemically activating and acid-leaching of layered silicate minerals.The effect of grinding time and leaching time on porous properties of the synthesized materials are mainly investigated. The results show that the grinding process induces the crystal structure of layered silicates becoming amorphous, which is beneficial to the following leaching process.The octahedral metal ions are leached out by H+ions through ion exchange. Consequently, the residual voids after leaching form micropores and the SiO4 tetrahedrons layers form mesopores through structure rearrange and condensation. Compared with the leaching time, the grinding time shows more significant effect on the porous properties of the resulting porous materials.The difference of layered silicate minerals in chemical compositions and layer types (type 1:1 and type 2:1)result in the various change behaviors of structure and porous properties of the layered silicates, and finally result in discrepancy of porous properties for the resulting porous materials.Ordered mosoporous material MCM-41,with huge specific surface area of 1100m2·g-1, pore volume of 1.00ml·g-1 and pore size of 2.80nm, is successfully synthesized via hydrothermally heating acid-leached layered silicates.The obtained MCM-41 has fine thermal stability and the endurable temperature is up to 940℃.Charge density matching and polymerization of silicate species determine the final structure of the resulting product.This technique realizes the synthesis of ordered mesoporous material MCM-41 in low surfactant concentration through cooperative formation mechanism according to the charge density matching rule. H3SiO4- and H4SiO4 are main species existed in the alkaline solution. The polymerization and assembly of these species result in the formation of the final product MCM-41 which mainly contains Q3(Si(SiO)3OH) and Q4(Si(SiO)4) structures.The component of pore wall of MCM-41 synthesized from different layered silicates is amorphous SiO2.The layer type of silicates shows little influence on the final structure of ordered mosoporous materials.It should be emphaseized that the SiO4 tetrahedrons contained in layered silicates are regarded as the essential ingredient for the preparation of ordered mesoporous materials. The structural evolution from layered silicates to ordered mesoporous materials involves the transformation from layered crystal structure to disordered porous structure, and finally to ordered mesoporous structure. Taking ordered mesoporous materials as host matrix, various kinds of functional composites have been succussfully synthesized by incorporating various guest molecules into the channels of the host matrix. The properties of the obtained composites were superior to that of the host matrix or the guest molecules.SnO2/MCM-41 composite is synthesized by hydrothermal method taking SnO2 nanoparticles as guest and as-prepared MCM-41 as host matrix. The result shows that most SnO2 nanoparticles exist in the channels of the host matrix without damaging the mesoporous structure of the host matrix, except that little amount of Sn atoms is incorporated into the framework of the host matrix. Taking the channels of the host matrix as "micro-reactor",the PL property of SnO2/MCM-41 composite could be modulated by varying the Sn/Si molar ratios.The PL intensity of SnO2/MCM-41 composite is nearly 8 times as that of the pure SnO2 nanoparticles.Zeolite 4A molecular sieve powder is synthesized using layered silicates (taking kaolin as an example) as raw material via hydrothermal method. The obtained 4A molecular sieve particles show cubic morphology with the particle size of about 4μm. The water adsorption capacity and compression strength of the final desiccant are 21.0wt% and 51.0N/particle, respectively, which meet the standard of HG/T 2524-93 (water adsorption capacity≥20 wt% and compression strength≥50N/particle).4A molecular sieve powder and desiccant also can be successfully prepared in the pilot test, and the properties of the desiccant meet the application standard. The preparation is processed in low hydrothermal condition without any additional silica and alumina sources. The purity and morphology of the 4A molecular sieve powder could be modulated by adjusting the involved parameters, and the excellent properties of the desiccant product could be obtained through optimizing the crystalline degree of the 4A molecular sieves.Based on the special layered structure and chemical compositions of layered silicates, the aim of this thesis is to synthesize porous materials and functional composites with unique structures and excellent properties through mechanochemical activation and leaching method as well as hydrothermal treatment.Moreover, the potential application of the prepared products in desiccant field is exploited. The standpoint of this thesis is to develop a new method for the preparation of functional materials from natural minerals, investigate the physical and chemical behaviors during the preparation process, establish a structure-property relationship between the natural minerals and the obtained functional materials, and finally expand the unprecedented applications of the functional materials.All of these will provide basic fundamental and technical support for the integration of resources and materials.更多还原