多层次结构硅酸盐复合材料的制备及其在水处理和锂离子电池中的应用

发布时间：2018-07-14 16:32

【摘要】：硅酸盐是固体地球的主要组成成分,大自然中的硅酸盐主要以岛状、链状、网状和层状的形式存在,其中层状硅酸盐以其独有的层状孔道结构而吸引了广泛的研究。硅酸盐材料由于其制备简单、来源丰富、价格便宜、及独特的多孔结构在吸附、催化、药物等领域得到了广泛应用。但其固有的一些性能缺陷如导电性较差等又限制了实际的应用。纳米颗粒合成技术的发展使得各种形貌的硅酸盐制备得以实现,也便于将硅酸盐和其他材料进行复合以克服其缺点,进而发挥协同效应。因此,本论文设计合成了一系列具有多层次结构的层状硅酸盐纳米复合材料,从组分和结构上对硅酸盐进行优化,提高其在水处理和锂离子电池中的性能。例如,一维的碳纳米管／层状硅酸镍的同轴结构,二维的硅酸镁／氧化石墨烯三明治结构,三维的氧化镁／介孔二氧化硅纳米球核壳结构。本课题的创新点主要在于：1)首次研究了同轴结构的硅酸镍／碳纳米管在锂离子电池负极当中的应用。通过引入碳纳米管,克服了硅酸镍导电性能差的缺点,提高了复合材料的电化学性能。2)首次合成了三明治结构的硅酸镁／石墨烯,并对其重金属离子和染料的吸附能力进行了研究。3)首次合成了硅酸银／氧化石墨烯和硅酸银／碳纳米管,并对其光催化性能进行了比较和研究。1、使用碳纳米管为物理模板和导电剂,合成了一维同轴结构的硅酸镍@碳纳米管复合材料。层状硅酸镍纳米片的层间距约为0.74纳米,不仅有利于锂离子的嵌入脱嵌,而且可以实现钠离子嵌入脱嵌。碳纳米管使复合材料的导电性能得以提升,有助于电子和锂离子的传输；其空心管状结构也为循环充放电过程中锂离子嵌入和脱嵌提供了缓冲空间,有利于循环稳定性能的提高。作为锂离子电池负极,硅酸镍@碳纳米管在电流密度为50 mA/g的条件下,50圈的循环充放电之后,仍能维持489 mA h/g的可逆容量,远高于纯硅酸镍纳米管的107mAh/g,亦高于文献报道的其他纯硅酸盐材料的可逆容量。2、通过水热法制备二维三明治结构的硅酸镁/石墨烯复合材料,研究其对有机染料和重金属离子的吸附性能。BET比表面积达到450m2/g。复合材料对亚甲基蓝染料和铅离子的吸附符合Langmuir吸附模型,对亚甲基蓝和铅离子的最大吸附量分别为424 mg/g和416mg/g,是纯硅酸镁材料的271%和126%。石墨烯不仅作为负载基体有效地分散硅酸镁纳米片结构,提高了复合材料的比表面积；其自身具有的大量含氧官能团也为复合材料提供了更多的吸附位点,微米尺寸片层结构也使吸附剂可以在重力作用下进行有效分离。除了保留各组分优异物理化学特性,复合材料还表现出良好的协同作用,使机械稳定性和吸附性能得以提高。该复合材料在水污染处理领域有较好的应用潜力。3、合成了三维核壳结构的氧化镁@介孔二氧化硅复合材料。在由氧化镁纳米颗粒组装形成的多孔微球外包覆一层介孔二氧化硅的外壳,不仅提高了氧化镁的机械稳定性,以防止在机械搅拌过程中结构被破坏；同时还为溶液中污染物质的扩散提供了浓度梯度和更好的传质效果。合成的核壳结构复合材料对铅离子和亚甲基蓝分别达到了3155毫克/克和420毫克/克的吸附容量,远高于纯氧化镁对铅离子和亚甲基蓝的2454毫克/克和61毫克/克的吸附容量。4、首次制备硅酸银/碳纳米管以及硅酸银/氧化石墨烯复合材料,并对这两种材料对有机染料的可见光催化降解性能进行了比较。不同碳材料添加含量使复合材料的形貌和性能发生较大变化。对碳纳米管而言,少量加入碳纳米管即可明显提高光催化效率,但进一步增加碳纳米管添加量反而会使光催化效率有所降低;对氧化石墨烯而言,亚甲基蓝去除率随着氧化石墨烯含量的增加而增加。
[Abstract]:Silicate is the main component of solid earth. The silicates in nature are mainly in the form of island, chain, reticulate, and stratified forms, in which the layered silicate attracts extensive research with its unique layered pore structure. Silicate materials are simple, rich, cheap, and unique porous structure. It has been widely used in the fields such as catalysis and medicine, but some of its inherent performance defects, such as poor conductivity, have restricted practical applications. The development of nano particle synthesis technology makes the preparation of various forms of silicate can be realized, and the silicate and other materials are compounded to overcome their shortcomings and thus play synergy. Therefore, a series of layered silicate nanocomposites have been designed and synthesized in this paper. The composition and structure of silicates are optimized to improve their performance in water treatment and lithium ion batteries. For example, the coaxial structure of one dimensional carbon nanotubes / layered nickel silicate, two dimensional magnesium silicate / graphite oxide The structure of the sandwich, three dimensional Magnesium Oxide / mesoporous silica nanospheres structure. The main innovation of this topic lies in: 1) the application of the coaxial structure of nickel silicate / carbon nanotubes in the anode of lithium ion battery for the first time. By introducing the carbon nanotube, the defects of poor conductivity of nickel silicate were overcome and the composite material was improved. The electrochemical properties of the material.2) the sandwich structure of magnesium silicate / graphene was synthesized for the first time. The adsorption capacity of heavy metal ions and dyes was studied for the first time..3) silver / graphene oxide and silver / carbon nanotubes were synthesized for the first time. The photocatalytic properties of them were compared and studied by.1, and the carbon nanotubes were used as the physical template. The interlayer spacing of the layered nickel silicate nanoplates is about 0.74 nanometers, which is not only conducive to the insertion of lithium ions, but also to embed and embed with sodium ions. The conductivity of the nanotube can be enhanced and the transmission of the electrons and lithium ions is helpful. The hollow tubular structure also provides a buffer space for the insertion and removal of lithium ion in the cycle charge and discharge process, which is beneficial to the improvement of the cyclic stability. As a negative electrode of lithium ion battery, under the condition of the current density of 50 mA/g, the nickel dioxide @ carbon nanotube can still maintain the reversible capacity of 489 mA h/g after the cycle of charging and discharging. 107mAh/g, which is higher than pure nickel silicate nanotube, is also higher than the reversible capacity.2 of other pure silicate materials reported in the literature. The two-dimension sandwich structure of magnesium silicate / graphene composite was prepared by hydrothermal method. The adsorption properties of the organic dyes and heavy metal ions were studied by the.BET specific surface area of the composite material for methylene blue dyeing. The adsorption of material and lead ions conforms to the Langmuir adsorption model. The maximum adsorption capacity for methylene blue and lead ions is 424 mg/g and 416mg/g respectively. It is 271% and 126%. graphene, which is a pure magnesium silicate material, not only effectively disperses magnesium silicate nanostructure as the load matrix, but also improves the specific surface area of the composite. The oxygen functional groups also provide more adsorption sites for the composites, and the micrometer layer structure also enables the adsorbents to be effectively separated under the action of gravity. In addition to retaining the excellent physical and chemical properties of each component, the composite also exhibits good synergy, which makes the mechanical stability and adsorption properties improved. The field of water pollution treatment has a good application potential.3, which has synthesized a three dimensional nuclear shell structure of Magnesium Oxide @ mesoporous silica composite. The outer shell of a porous silica coated with a porous microsphere assembled by Magnesium Oxide nanoparticles not only improves the mechanical stability of Magnesium Oxide, so as to prevent the structure of the mechanical agitation in the process of mechanical agitation. It also provides a concentration gradient and a better mass transfer effect for the diffusion of contaminants in the solution. The synthetic nuclear shell structure composite has a capacity of 3155 mg / g and 420 mg / g respectively for lead and methylene blue, which is far higher than that of pure Magnesium Oxide for 2454 mg / g and 61 mg of the lead and methylene blue. The adsorption capacity of.4, silver / carbon nanotubes and silver / graphene silicate composites were prepared for the first time. The visible photocatalytic degradation performance of these two materials for organic dyes was compared. The morphology and properties of the composites changed greatly with the addition of different carbon materials. Nanotube can obviously improve the photocatalytic efficiency, but the addition of carbon nanotubes will reduce the photocatalytic efficiency. For graphene oxide, the removal rate of methylene blue increases with the increase of the content of graphene oxide.
【学位授予单位】：北京化工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TB332;TQ170.1

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