【作者】 姜艳秋；

【导师】 王子忱；

【作者基本信息】 吉林大学 ， 物理化学， 2005， 博士

【摘要】 本论文致力于复合氧化物中空球的制备与表征,研究了影响复合氧化物中空球壳壁上的介孔以及球形粒子尺寸的因素,并在此基础上合成了壳壁上具有有序介孔排列的二氧化硅中空球。第一章为前言,介绍了多孔材料的分类,性质,应用及发展前景;球形材料的发展,应用背景,中空球的制备方法及球的内部修饰;在第二章中,把O/W/O 乳液同溶胶-凝胶过程有机的结合起来,合成了SiO2/Al2O3中空微球,并发现球壳上具有大量均一无序的介孔,且孔尺寸随着加入到体系中的PEG 的分子量的增加而增加;第三章在前面工作的基础上,采用沸水处理的方法,得到了SiO2/Al2O3,SiO2/TiO2 中空球,并发现这种方法避免了由于高温焙烧可能引起的烧结以及表面硅羟基的损失;在第四章中合成了SiO2/ZrO2 中空球,并把它用于大分子的催化反应,发现由于球壳上大量介孔的存在,使得SiO2/ZrO2 中空球在大分子的催化反应中表现出很好的活性,同时把这种方法推广到了三元复合氧化物的合成中;在第五章中,把乳液技术,溶胶-凝胶过程,水热反应结合在一起,合成了壳壁上具有三维Ia3d 结构的介孔结构的SiO2 中空球,这是中空球合成中的一个突破。本论文详细的阐述了上述化合物的合成条件和方法、表面形貌和物理化学性质,并考察了影响产物形貌的因素,为材料在理论和实践中的应用提供了有利的依据。更多还原

【Abstract】 In recent years, there has been intense interest in the fabrication ofinorganic materials with hollow spherical structures for technologicalapplication and fundamental studies in chemistry, biotechnology, andmaterials science due to their advantages of good surface permeability, largespecific area, low density, and high mechanical stability. Inorganic materialswith hollow spherical structures have been widely used in many fields, suchas drugs delivery, protection of biologically active agents (e.g. proteins,enzymes, or DNAs), and controlled release capsules of various substances.Additionally, mesoporous materials have attracted much attention becauseof their possible uses in acting as molds for new materials syntheses, catalysts,low-dielectric coatings, and optical materials. They are proved to be animportant class of functional materials for their super performance comparedwith other porous materials. The question how to combine the advantages ofinorganic hollow spheres, mesoporous materials and binary composite oxidesis therefore very important in the research of material chemistry.There have been a number of methods for the synthesis of hollow spheres,such as nozzle-reaction system, sacrificial cores, emulsion/water extraction,and layer-by-layer self-assembly techniques. Though inorganic hollowspheres have shown many good potential properties, most of them prepared bythese methods lack thermal stability, and few of them are focuse on compositeoxides. Here we present a facile route for preparing hollow SiO2/Al2O3spheres by using TEOS and aluminum nitrate as silica and alumina sources, inwhich we combine a sol-gel process with an O/W/O microemulsion. PEGmolecules acts as an additive in this study. When the self-assembly process isgoing, PEG molecules uniformly disperse in the shell wall, thus a large amoutof uniform mesopores are formed in the shell wall after remove of PEG bycalcination at 550 °C. The mesopores in the shell wall make the hollowSiO2/Al2O3 spheres maintain their hollow structures after calcination,indicating the hollow SiO2/Al2O3 spheres have highly thermal stability basedon this approach. Characterizaion results show that the particle size of thehollow spheres and pore size of mesopores in the shell wall can be controlledby many factors, such as emulsion temperature, stirring speed, averagemoecular weight of PEG, the amounts of HNO3 and Al(NO3)3 in theprecursors, and the oil phase. The particle size of hollow spheres increasealong with the increase of stirring speed and the pore size of mesopores in theshell wall increase along with the increase of average molecular weight ofPEG. The sol viscosity is found to have a significant influence on theformation of hollow spheres. More recently, inorganic materials with hollow structures have attractedmore attention on controlled release of drugs. In application of controlledrelease of drugs the modification of inorganic materilals with organic reagentsis needed to realize the better controllable property. It is well known that thepresence of a large amount of silanol groups is an important factor that theinorganic materials can be further modified with organic reagents. However,most of inorganic spheres with hollow structures have less silanol groups afterremove of the templates or organic components by calcination becaue of thecondensation of silanols groups at high temperature. We prepare hollowSiO2/Al2O3 spheres with uniform mesopores in the shell wall and a largeamount of silanol groups base on the above-mentioned approach. It is the onlydifference that we wash the spheres with acetone, ethanol and boiling water toremove the organic componets in place of calcination. Characterization resultsindicate that although the hollow spheres show somewhat distorted shape theintact hollow structure and mesopores in the shell wall are still obvious. Moreimportantly, a large amount of silanol groups are retained for the absence ofcalcination. Additionally, we also prepare hollow SiO2/TiO2 spheres withuniform mesopores in the shell wall and a large amount of silanol groups bythe same method. Characterizaion results are very similar to those of hollowSiO2/Al2O3 spheres. Acetyl acetone is used as chelated reagent to control thehydrolysis of titanium source (TBOT). UV-vis spectra indicate thatfour-coordinated environment of titanium species similar to TS-1 can beobtained by controlling the hydrolysis of TBOT. Thus, the hollow SiO2/TiO2spheres we prepare by washing with boiling water have these advantages ofuniform mesopores in the shell wall, a large amount of silanol groups andfour-coordinated environment of titanium species. To realize the application of hollow spheres in catalysis, we synthesizestable hollow ZrO2/SiO2 spheres with mesopores in the shell wall by a sol-gelprocess in an oil/water/oil microemulsion. Here, zirconium nitrate and octaneare used as zirconium source and oil phase, respectively. The samples arecharacterized by transmission polarized light microscopy, SEM, TEM, and N2adsorption-desorption isotherms. The characterization results indicate that alarge number of mesopores are also present in the shell wall of the calcinedhollow ZrO2/SiO2 spheres, and that the diameter and shell thickness are ca.50and 15 μm, respectively. The hollow spheres exhibit high thermal stability andremain intact spherical structures even after calcination at 550 °C for 8 h,which is similar to hollow SiO2/Al2O3 spheres. In the cracking reactions ofcumene and 1,3,5-triisopropylbenzene the sulfated hollow ZrO2/SiO2 spheresshow very high catalytic activities. Especially, the higher catalytic activity of1,3,5-triisopropylbenzene cracking suggests the potential application incracking of bulky molecules for the presence of mesopores. A possibleformation mechanism of hollow spheres of binary composite oxide is alsoproposed. Additionally, it is proved that this approach for preparing hollow spheresof composite oxides by combining a sol-gel process with an O/W/Omicroemulsion is appropriate for the synthesis of Si-Al-Zr, Si-Al-Ti 和Si-Zr-Ti composite oxides. The characterization results are very similar tothose of hollow spheres of binary composite oxides. Although there are uniform mesopores in the shell wall of hollow spheresprepared by our approach, the mesopores are disordered. It is well known tous that mesoporous materials with ordered mesopores are proved to be animportant class of functional materials for their super performance comparedwith other porous materials. To obtain hollow spheres with ordered mesoporesin the shell wall, we present a novel route for combining sol-gel process andO/W microemulsion with hydrothermal technique. We successfully synthesizehollow SiO2 spheres with ordered mesopores in the shell wall by using CTABas template. Characterization results indicate the sample has cubic symmetry更多还原