【作者】 霍成立；

【导师】 杨华明；

【作者基本信息】 中南大学 ， 材料科学与工程， 2014， 博士

【摘要】 摘要：硅酸盐矿物具有比表面积大、吸附能力强、表面活性位点多等优点,基于其结构与形貌特性建立矿物资源-材料一体化的体系,已成为硅酸盐矿物近年来开发利用的研究热点。我国硅酸盐矿物资源丰富,但是综合利用水平较低,因此开发高性能矿物基复合功能材料并实现低成本制备,对优化硅酸盐矿物资源综合利用和促进经济发展具有重要的现实意义。本论文以纤维状形貌的凹凸棒石粘土矿物为研究对象,通过表面活化与纳米化修饰实现功能改性,制备了矿物基复合功能材料并实现性能强化；基于硅酸盐矿物与多孔氧化硅具有相同的硅氧骨架,提出了一种由凹凸棒石粘土矿物制备有序介孔材料并原位组装功能纳米粒子的合成方法；构建了基于介孔材料自组装形成的新型微胶囊结构,为设计硅酸盐矿物微反应器提供技术指导。本论文主要的研究内容和结果如下：利用凹凸棒石的表面特性,在保持其纤维状形貌的基础上对其进行功能纳米粒子改性,制备凹凸棒石基复合功能材料。首先对凹凸棒石进行活化处理,增加其比表面积和表面硅羟基,以提高其对金属阳离子的吸附能力,进而以活化凹凸棒石为载体,利用原位沉淀法负载ZnO、NiO、CuO纳米粒子制备凹凸棒石基复合功能材料。通过X-射线衍射、透射电子显微镜等测试分析表明利用矿物负载,不仅可以解决纳米光催化剂颗粒的团聚问题,而且能有效的抑制颗粒尺寸长大。制备的ZnO/凹凸棒石复合材料具有较强的抗菌活性,对大肠杆菌的最小抑菌浓度可达0.1g/L,其值要低于纯ZnO的0.25g/L,复合材料增强的抗菌性能要归因于纳米粒子与矿物基体间的协同增强效应。对CuO/凹凸棒石复合材料进行Pd活化修饰获得了Pd-CuO/凹凸棒石复合光催化材料,测试结果表明CuO纳米颗粒均匀的负载于凹凸棒石表面且矿物的晶体结构得到有效保持。Pd-CuO/凹凸棒石复合材料对甲基橙表现出优异的光降解能力,在20min内对甲基橙的降解效率可达98%,增强的光催化降解性能可归功于凹凸棒石粘土的高吸附活性和贵金属Pd有效阻止光生电子-空穴结合的协同效应。基于凹凸棒石的层状结构特性,对其进行结构改型制备了有序介孔材料。通过对凹凸棒石不同前处理方法优化,筛选出对凹凸棒石进行煅烧碱浸前处理为硅、铝源,十六烷基三甲基溴化铵(CTAB)为模板,通过水热法制备了有序介孔材料Al-MCM-41,其比表面积高达1044m2/g。在此基础上,提出了有序介孔材料原位组装功能粒子制备介孔复合材料的合成方法,该方法可以克服在后组装过程中纳米颗粒易团聚、堵塞孔道等缺点。以CuO纳米颗粒为客体,通过原位组装制备了CuO/Al-MCM-41复合材料,考查了铜源和铜负载量对复合材料微结构的影响,通过小角x-射线衍射、透射电子显微镜、氮气吸附-脱附等测试分析表明所得复合材料均具有较高的孔道有序度和比表面积,且大部分CuO纳米颗粒存在于有序介孔材料的孔道中。利用氢气程序控温还原测试证明了原位组装比后组装样品具有更低的还原温度,说明原位组装样品中CuO纳米颗粒较易还原,意味着原位组装样品具有更好的氧化还原特性。通过原位组装Au纳米颗粒制备了Au/Al-MCM-41介孔复合材料,结果证明该方法可以有效的控制Au尺寸为3nm左右,且保证Au纳米颗粒在介孔孔道中的均匀负载。对原位组装纳米Au颗粒的合成机理研究认为CTAB包裹AuC14-形成棒状胶束是实现原位组装的关键。提出的原位组装方法可以确保纳米颗粒在介孔孔道中的均匀组装,从而实现复合材料的性能强化,拓展其应用范围。为研究介孔材料的组装效应及界面特性,利用正硅酸乙酯(TEOS)为硅源、CTAB和Brij56为模板剂合成了尺寸为60nm左右的介孔氧化硅球,该纳米球呈单分散特性,具有类MCM-41的介孔结构。基于此介孔硅球在Pickering乳液体系中的自组装行为构建了一种新型的具有介孔膜层的微胶囊(colloidosomes),该粒子稳定的乳液克服了由表面活性剂稳定的乳液存在有毒性等不足。光学显微镜测试结果表明有模板剂的介孔硅球可稳定水包油(O/W)和油包水(W/O)两种类型的微乳体系,而除模板剂的介孔硅球只能稳定水包油(O/W)微乳体系从而形成微胶囊结构。通过调节介孔硅球表面的亲/疏水程度,可以实现对微乳液体系类型的调控,相对亲水的介孔硅球易于稳定水包油(O/W)体系的微乳液,而相对疏水的介孔硅球则更倾向于稳定油包水(W/O)类型的微乳液。固定油包水乳液体系中的油水比例,调节表面修饰改性介孔硅球的加入量,可以有效实现微胶囊的尺寸在300～120μm之间调控,且微胶囊均能保持规则稳定的球形。通过荧光染料在微乳液体系中水油相的扩散行为证明了微胶囊的半透性和膜层的吸附释放特性。利用后合成法制备了Au/介孔氧化硅复合材料,基于此复合材料在油包水微乳液中的自组装设计了一种新型的界面催化反应体系。该界面催化体系有助于克服单一相催化体系中由于反应物的溶解性不同导致的催化反应效率低的问题,同时有利于解决催化反应过程中催化剂颗粒易团聚以及反应物与产物难分离等问题,可以为基于硅酸盐矿物微反应器的构建提供理论和技术借鉴。本论文旨在研究凹凸棒石粘土矿物的精细化加工及高值化利用。详细研究了通过表面纳米化修饰负载功能纳米粒子制备凹凸棒石基复合功能材料的制备方法与机理,设计的合成方法可为相关的硅酸盐矿物制备复合功能材料提供新的思路与技术参考。开发了由凹凸棒石粘土矿物制备有序介孔材料并原位组装纳米颗粒的合成方法,理清了硅酸盐矿物在制备介孔材料过程中的结构演变,确立了有序介孔材料原位组装纳米粒子的反应模型,建立了复合材料的微结构与性能之间的关系,初步探索了复合介孔材料作为催化材料的潜在应用,提出的矿物为原料制备有序介孔材料原位组装纳米颗粒可为其他矿物制备介孔复合材料提供理论基础。设计了基于介孔硅球自组装形成的新型微胶囊结构,可为多相界面催化反应体系提供新的思路,同时也可为基于硅酸盐矿物的微反应器提供技术参考。更多还原

【Abstract】 Abstract:The silicate minerals have many extraordinary properties, such as huge specific surface area, high adsorption capacity, and abundant surface active sites and so on; therefore, it has been an important research focus for the development and utilization of silicate minerals that constructs the system of the integration of resources and materials. Our country is abundant in silicate minerals; however, the level of comprehensive utilization is too lower. Consequently, it is meaningful to optimize the silicate mineral resources utilization and promote the economic development that prepares minerals-based functional composites with high-performance at a low cost. This thesis focuses on the palygorskite clay mineral with a fibrous microstructure. Firstly, the palygorskite-based functional composites are prepared and the enhanced properties are realized by means of the surface activation and nanocrystallization modification. Secondly, a route that synthesize of ordered mesoporous materials and in-situ encapsulation nanoparticles using palygorskite as silicon and aluminum resources is proposed due to the silicate minerals has the same silicon-oxide skeleton with porous silica material. Finally, a novel microcapsules based on the self-assembly of mesoporous silica nanospheres in the emulsion phase is constructed, which will provide technical reference for the designing of silicate minerals-based microreactors. The main research contents and results of this thesis are as follows:In order to make better use of the unique surface properties of palygorskite, the palygorskite-based functional composites are prepared by surface functionalization of palygorskite with functional nanoparticles under the preservation of its fibrous morphology. The palygorskite is activated to increase its specific surface area and silicon hydroxyl to improve the adsorption capacity for metal cations, the palygorskite-based functional composites are successfully prepared via in-situ precipitation of loading ZnO、NiO、CuO nanoparticles onto activated palygorskite being as carrier. These samples are characterized by X-ray diffraction (XRD) and transmission electronic microscope (HRTEM) and the results show that the drawbacks of agglomeration of photocatalyst can be avoided and the size of nanoparticles can be restrained by loading photocatalyst nanoparticles onto the surface of palygorskite nanofibers. The ZnO/palygorskite composites demonstrate enhanced antibacterial activity with a minimum inhibitory concentration against E. coli of0.1g/L, which is lower than that of pure ZnO of0.25g/L. The enhanced antibacterial activity of ZnO/palygorskite composites can be ascribed to the synergistic effect between the high adsorption capacity of palygorskite clay carriers and the antibacterial property of ZnO nanoparticles. The Pd-CuO/palygorskite composites are obtained after the CuO/palygorskite composites modified with PVP-Pd solution. The results show that CuO nanoparticles are successfully anchored onto the surface of palygorskite fibers and uniformly dispersed, and the structure of palygorskite is well maintained after loading. The Pd-CuO/palygorksite composites display significantly high degradation ability for MO under UV irradiation, up to98%in20minutes; the enhanced photocatalytic activity of Pd-CuO/ATP composites can be interpreted by the fact that synergetic effect between the high adsorption capacity and active sites of palygorskite and the efficient electron-hole separation at the coupled Pd-CuO/ATP photocatalyst interface due to the introduction of Pd.The ordered mesoporous material is successfully synthesized from structure modulation of palygorskite based on its layered structure. Through the optimization of different pretreatment to palygorskite, the highly ordered Al-MCM-41mesoporous material can be obtained with alkaline leached palygorskite as source and cetyltrimethylammonium bromide (CTAB) as template via hydrothermal reaction, and the obtained Al-MCM-41mesoporous material has a high specific surface area of1044m2/g. The in-situ encapsulation route is proposed on the base of mesoporous materials incorporation of nanoparticles, which may avoid the problems of aggregation and blocked pores during the post-synthesis process. Taking CuO nanoparticles as guest, the CuO/Al-MCM-41composites are prepared by in-situ incorporation of CuO nanoparticles into the Al-MCM-41matrix. The effect of different copper sources and copper loading amount on the microstructure of mesoporous materials are investigated, the SAXRD, TEM and N2adsorption-desorption results manifest that the CuO/Al-MCM-41composites have high degree of channel order and specific surface area and the majority of CuO nanoparticles are incorporated into the pores of Al-MCM-41. H2temperature programmed reduction (H2-TPR) measurement results demonstrate that the in-situ synthesized sample has a lower reduction temperature than that of post-synthesized sample, confirming that the CuO nanoparticles in the in-situ synthesized sample can be reduced easier, meaning that the in-situ synthesized sample has a better redox property. Taking Au nanoparticles as another guest, the Au/Al-MCM-41composites are prepared by in-situ encapsulation of Au nanoparticles into the Al-MCM-41, Using this in-situ encapsulation route, the size of gold nanoparticles can be well controlled close to3nm, and ensure that the gold nanoparticles can be well confined in the pores of Al-MCM-41. The mechanism of the in-situ assembling gold nanoparticles into mesoporous materials reveals that the formation of the rod-like micelles by CTAB stabilized AuCl4" is the key for in-situ encapsulation. The proposed in-situ encapsulation technique guarantee that the nanoparticles can be well embedded in the mesopores, and ensure that the composites have an enhanced performance and expanded application.In order to study the behavior of self-assembly and property of interface of mesporoues materials, the mesoporous silica nanospheres with a size of60nm and MCM-41-like hexagonal structure are prepared with TEOS as silicon source, CTAB and Brij56as templates. A novel colloidosome microcapsules with mesoporous membrane is constructed by the self-assembly of various mesoporous silica in the emulsion phase, the particles-stabilized emulsion overcome the drawback of toxicity in the surfactant-stabilized emulsion. The optical microscope test results demonstrate that the mesoporous silica nanoparticles with template can stabilize the water-in-oil (W/O) and oil-in-water (O/W) emulsions, while the mesoporous silica nanoparticles with template removal can only stabilize the oil-in-water (O/W) emulsion to form the colloidosome microcapsules. The type of colloidosomes of water-in-oil or oil-in-water can be switched by the degree of the hydrophilic or hydrophobic surface properties of the mesoporous silica nanoparticles, the relative hydrophilic nanoparticles are willing to stabilize the oil-in-water emulsion, while the hydrophobic nanoparticles are inclined to stabilize the water-in-oil emulsion. By fixing the ratio of water and oil in the water-in-oil emulsion, and changing the amount of modified mesoporous silica nanoparticles, the size of colloidosomes can be effectively controlled from about300micrometers to120micrometers, and all the colloidosome microcapsules can maintain the regular and stable spherical shape. Meanwhile, the semipermeability and adsorbability of the mesoporous colloidosomes are demonstrated by the diffusion of fluorescent dye in the oil and water phase. Au/meso-SiO2composites are synthesized via post-synthesis route, and the composites are applied as emulsifiers to stabilize the water-in-oil emulsion to construct the interfacial catalytic reaction system. The Pickering emulsion-based interfacial catalytic system can overcome the drawback of the low efficiency in the single phase catalytic system due to the different solubility of substrate, and as well solve the problems of aggregation and difficult separation of substrate and product, and also provide theoretical and technical reference for the construction of microreactors based on silicate minerals.This thesis aims to study the fine processing and high-value utilization of palygorskite clay. It detailedly studies the mechanism and routes of preparation palygorskite-based functional composites via surface nanocrystallization modification to decorate functional nanoparticles, the designed synthetic method will provide the new concept and technical reference for the synthesis of functional composites using others relevant silicate minerals. Furthermore, this thesis develops a new synthetic route of preparation ordered mesoporous material and in-situ encapsulation nanoparticles using palygorskite caly mineral, clarifies the structure evolution of silicate mineral during the process of fabrication mesoporous material, establishes the reaction model of the ordered mesoporous material in-situ encapsulation nanoparticles, constructs the relation between the microstructure and property of the composite, explores the potential application of the composite being as catalyst, the proposed technique that produce the ordered mesoporous material and in-situ assemble nanoparticles using clay minerals can provide fundamental basis for the synthesis mesoporous composites using others minerals. Finally, this thesis creates a novel microcapsule structure based on the self-assembly of mesoporous silica spheres in the emulsion phase, it can not only offers new idea for the system of multi-phase interfacial catalytic reaction, but also supplies technical reference for the microreactor based on silicate minerals.更多还原