【作者】 王卓鹏；

【导师】 于吉红； 徐如人；

【作者基本信息】 吉林大学 ， 无机化学， 2010， 博士

【摘要】 分子筛在石油化工、精细化工及日用化工等领域具有极其广泛的应用。其晶化机理及应用研究一直是分子筛领域的重要研究内容。本论文主要围绕这两个方面展开了研究。应用小角X-射线散射(SAXS)和冷冻透射电子显微镜(cryo-TEM)技术对MFI型分子筛清液合成体系的室温晶化过程进行了近300天的跟踪监测。首次发现了在MFI型分子筛晶体出现之前存在的一种较大的无定形聚集状纳米粒子,这种粒子会在较短时间内转变为MFI型分子筛晶体。对于NaX分子筛的清液合成体系,综合应用小角X-射线散射(SAXS)、冷冻透射电子显微镜(cryo-TEM)、紫外拉曼光谱(UV Raman Spectroscopy)、红外光谱(IR Spectroscopy)、核磁共振(NMR)等表征技术对其在室温下的晶化机制进行了研究。研究结果发现体系中也存在极小的纳米粒子,这些粒子随着时间的演化在结构和组成上越来越接近NaX分子筛,我们推测铝在固相中的富集对成核起了重要作用。此外,首次在钛合金表面制备了含银分子筛抗菌薄膜涂层,并进行了体外抗菌和细胞毒性检测。结果表明该薄膜涂层不仅显示出很强的抗菌能力,而且具有良好的生物相容性,因此该涂层可用于骨科内外固定板和人工假体表面,在临床上具有潜在的应用价值。首次以单分散的GeO2晶体为模板,使用温和的方法制备了具有较好形貌和稳定性的立方SiO2空心壳纳米粒子,通过使用“手动组装”(manual assembly)和挥发溶剂组装等技术,将这种SiO2空心立方壳及GeO2-SiO2核-壳粒子组装成了单层薄膜涂层。更多还原

【Abstract】 In the past half century, zeolites have played increasingly important roles as catalysts in petroleum refining, petrochemical and other chemical industries. Currently, there are 194 known zeolite frameworks, however, only a few of them have been widely used in industry. More and more zeolites with novel structures and compositions were highly desired not only in the traditional fields of catalysis, adsorption and ion-exchange, but also in the newly developed fields such as petroleum refining and intermediacy chemistry process. However, the elusive formation mechanism of zeolite limits the discovery of novel zeolites. Studies on the crystallization process and formation mechanism of zeolites are very important not only because of their theoretical significance but also due to practical values. Extensive efforts have been made to elucidate the crystallization mechanism of zeolites since 1950s. Several mechanisms were proposed based on the observations from specific synthesis conditions. However, no general mechanism was obtained to describe the formation of zeolites due to the complexity of hydrothermal chemical reactions. In this dissertation, zeolites MFI and FAU were selected as models to study the crystallization mechanism of zeolites.Room-temperature aging of zeolite precursor silica sol (with and without Al) was followed by SAXS and cryo-TEM. The results from all-silica system provide evidences supporting the recently proposed mechanism of evolution of nanoparticles followed by aggregative crystal growth while adding a new element. The new element, not included in the previously proposed model, is the formation of predominantly amorphous aggregates before MFI crystallization and points to the importance of intra-aggregate rearrangements in nucleation and growth. For the aluminosilicate clear sol, smaller nanoparticles were found in the initial clear sol. The particle size was slightly increasing with time but no larger particle was indentified throughout nearly 300-day aging process. The aluminosilicate nanoparticles have better colloidal stability compared with all-silica ones.The early stage of nucleation and crystal growth of FAU was investigated by using combined in situ/ex situ techniques such as Small Angle X-ray Scattering (SAXS), Nuclear Magnetic Resonance (NMR) and UV Raman Spectroscopy. The results show that ca. 2 nm particles exist in the clear solution and the composition and structure of those nanoparticles were evolved with time during the room-temperature aging. The crystal growth curve indicates that a large amount of nuclei exist in the 24-hour aged clear sol, while no change of the particle size was observed during the early 30-hour-aging period. In situ UV Raman and liquid 29Si NMR spectra show that only low-polymerized species exist in the liquid phase and those species do not change within the 4-day-aging process. From the FTIR spectra, we found that broaden bands at the characteristic regions do not show much structural changes with various aging times. All the aluminium atoms in the solid phase are 4-coordinated. The increasing fraction of Si(4Al) in the solid 29Si NMR spectra indicates that the solid phase was getting ordered and there was a chemical composition change during the aging period. The changes of the Si/Al ratio were confirmed by ICP elemental analysis. Based on the studies on both liquid phase and solid phase, we can conclude that i) nucleation happens in solid phase or solid-liquid interface; ii) the chemical evolution catalyzed by OH– anion makes the composition and structure of solid phase similar to that of zeolite; iii) aluminium is enriched onto the nanoparticles and the stability of nanoparticles decreases with time; iv) the aluminium enriched spots in the solid phase might be the starting points of nucleation.Besides the research on the fundamental formation mechanism, studies on preparation and applications of porous coatings are also main objects of this dissertation. Porous coatings have attracted much attention due to their usefulness as supporting media in tissue engineering, membranes in separation process, templates for inorganic growth, dielectric materials for electronic devices, and optical materials.A silver-ions exchanged zeolite (type LTA) coating on Ti alloy surface was successfully prepared for the first time. In vitro antimicrobial assessments indicates that the Ag-zeolite coating provides efficient antibacterial effect to inhibit the proliferation of bacteria both in suspension surrounding the materials and on the surfaces of the materials. Zeolite exhibits many advantages such as good biocompatibility, mechanical stability, easy manufacture and low cost when used as a Ag+-host surface coating material. Since Ag+ ions can be stoichiometrically exchanged into zeolite, the antibacterial activity and cytotoxicity can be finely tuned by optimizing the loading amount of Ag+ ions. These advantages may potentially benefit the application of this antibacterial coating in orthopedic implants.A benign and facile process for forming monodisperse, hollow porous silica shells of a novel cubic morphology is identified. Templated on monodisperse crystalline germania cores that can be removed via aqueous dissolution. The hollow shells and their core–shell precursors are amenable to assembly into highly porous, gap-free near-monolayer films through manual and evaporative assembly techniques.更多还原