有机铜催化剂催化合成三乙氧基硅烷

传统的直接法合成三乙氧基硅烷多以卤化铜为催化剂,存在产品卤素含量高,反应过程中产物易水解的问题.本文以乙酸铜和自制双二乙基磷酸铜为催化剂,对硅粉与催化剂的混合体(触体)进行微波活化处理,研究了活性触体和乙醇进行反应合成三乙氧基硅烷的工艺影响因素,主要考察了微波功率、微波处理时间、反应温度、促进剂及搅拌速度等因素对三乙氧基硅烷的选择性和硅粉转化率的影响.通过对两种有机铜催化剂的对比研究发现,双二乙基磷酸铜的催化效果较好.微波处理触体[m(Si):m(双二乙基磷酸铜)=10∶1],以氟化铵和噻吩为双重促进剂,得到三乙氧基硅烷的选择性达到99.3%,硅粉转化率为41%.     

酞菁类有机光导体的研究进展

综述了酞菁类有机光导体的发展历程、结构性能,讨论了其性能的主要影响因素,归纳了酞菁类有机光导体主要类型的合成过程,对酞菁类有机光导体的发展前景作出了展望.     

仿生制备非担载SiO2无机膜的实验研究

以正硅酸乙酯(TEOS)为硅源,十六烷基三甲基溴化铵(CTAB)为有机模板,利用仿生合成技术于气-液界面制备出非担载的SiO2无机膜.考察了仿生制备SiO2膜过程中TEOS和CTAB的初始浓度及溶液pH值对膜质量的影响,并在优化所得物料条件下考察了干燥添加剂丙三醇和灼烧条件对膜质量的影响.各种分析和表征结果说明制备出的SiO2仿生膜具有1.8nm的最可几孔径,且上表面光滑平整.     

氮化碳晶体的研究进展

介绍了氮化碳晶体的合成与表征研究进展，分析了氮化碳晶体合成中存在的主要困难。分析表明：现有的研究结果还没有给出氮化碳晶体合成的确信证据。高温高压法的主要困难在于反应前驱体的选择与制备以及在高压过程中对热力学参数进行有效地控制；等离子体化学气相沉积中，基体原子，主要是硅原子对氮化碳晶体的合成有很大的影响，但目前缺少这方面的系统研究。反应溅射合成时需要解决的困难是在保持较低基片温度的同时如何提高反应气氛中的N原子含量，寻求高比例的sp^3c-N单键的合成条件。电化学方法利用了前驱体中的碳氮单键，能够有效地降低反应能垒和沉积温度，需要解决的问题是如何促进合成产物的晶化和减少副产物。综合运用多种合成技术如在较低的基片温度下，在氮等离子体中通过溅射含有碳氮单键的有机前驱体而引入大量的碳氮单键，控制硅原子在氮化碳晶体生长中的影响程度将是今后氮化碳晶体合成研究的有效途径。     

气-液界面非担载SiO2无机膜的仿生制备

利用有机大分子CTAB的自组装体为模板来调制正硅酸乙酯（TEOS）的水解缩聚，于气－液界面上制备出非担载SiO2无机膜，对了膜时间进行了选择，考察了仿生制备SiO2膜过程中物料配比对成膜质量的影响，对其进行了优化，由CTAB极性头基排列而成的六边形区域聚集于溶液表面，TEOS在其内部的水解缩聚及随后的层层复制过程形成了仿生合成膜的空间网络结构。     

耐高低温环氧有机硅胶黏剂的力学性能研究

介绍了一种研制的室温固化、耐高温、耐低温环氧有机硅胶黏剂.通过对胶黏剂的剪切强度分析,探讨了原料配比,偶联剂等因素对环氧有机硅胶黏剂力学性能的影响.研究表明:增韧剂在胶黏剂中含量适当时(质量比25%),能与固化剂充分反应,有机硅与环氧树脂也能获得较好的相溶性,制备的环氧有机硅胶黏剂的综合性能较优;硅烷偶联剂能改善胶膜界面层的胶接强度,提高环氧有机硅胶黏剂的剪切强度.     

丁苯锂系阴离子聚合物中大分子的成因研究

以正丁基锂为引发荆,合成丁苯阴离子聚合物,通过对不同的反应温度、活性聚合物停留时阃、极性添加荆及单体浓度的试验．分析其中大分子的含量。结果表明,反应温度、活性聚合物停留时阃是形成大分子的主要因素。通过反应机理分析,大分子主要是由于活性聚合物热分解产生共轭双键的聚合物继续与未终止的活性物反应而成。     

碱金属化合物在水热法合成纳米ZrO2粉料中的作用研究

研究了各种碱金属化合物作为水热溶液在水热合成纳米ZrO2晶体中的作用以及过程动力学的特征.加入碱金属氟化物和KI对ZrO2的结构影响最大,它们能诱导快速形成单斜ZrO2晶体.揭示了碱金属氢氧化物和氟化物添加剂在纳米ZrO2晶体形成中的作用机理.     

以AC发泡剂为添加剂燃烧合成α-Si3N4粉体

以硅粉和Si3N4粉体为反应剂,偶氮二甲酰胺(AC发泡剂)为添加剂,利用燃烧合成技术在较低氮气压力下制备了高α相含量的Si3N4粉体.采用X射线衍射和扫描电镜分别对产物的物相组成及显微结构进行了表征,研究了AC发泡剂对α相Si3N4粉体的形成和产物颗粒形貌的影响.结果表明,AC发泡剂能促进硅粉快速氮化,产物中α-Si3N4的含量随着AC发泡剂添加量的增加而增加.当AC发泡剂的添加量为24wt%时,产物中α-Si3N4的含量高达85.2wt%.对AC发泡剂作用下的燃烧合成Si3N4的反应机理做了初步探讨,研究表明:AC发泡剂的分解产物N2、CO、NH3不仅增加了坯体的透气性,而且改变了燃烧反应的传热和传质路线,从而促进了硅粉快速氮化和α-Si3N4粉体的生成.     

软模板法合成纳米材料的研究进展

介绍了近年来合成高分子模板法、生物高分子模板法、表面活性剂模板法、有机小分子添加剂模板法制备纳米材料的研究进展,重点介绍了模板剂诱导不同形貌和结构的纳米材料形成的作用机理。因合成高分子模板制备简单,结构设计灵活,生物高分子模板绿色环保,能更精确调控纳米材料结构,故详细综述了这2种方法。     

自组装制备有机/无机层状复合材料

自然界中形成的生物材料在结构和性能上具有优异的配备性。模仿生物矿化的形成机制,利用自组装原理能够仿生合成出性能优良和具有多级结构特点的有机/无机界面层状复合材料。本文在总结近年来最新研究的成果上,简要介绍了自组装和生物矿化的机理,重点阐述了基于无机相层的自组装和以有机大分子为模板自组装制备有机／无机层状复合材料两种合成连径,并对未来的发展趋势做了展望。     

Silica Glass from Aerosil by Sol-Gel Process: Densification and Textural Properties

Sol-gel processes allow the synthesis of inorganic materials from solutions of molecular precursors. These precursors can be either organic, inorganic, or a mixture of the two. The aim of this work is the preparation of aqueous solutions consisting of Aerosil OX 50 (fumed silica) using small amount of additives like ammonium fluoride NH₄F (less than 2%), which are dried at room temperature in order to obtain monolithic gels. These are then densified at temperatures below 1200°C and sintered at 1300°C in order to obtain pure silica glass. The textural properties evolution of these gels is investigated as a function of temperature by thermal analysis (mass loss, shrinkage, and density) and scanning electron microscopy.     

利用四氯化硅制备二氧化硅粉体的研究

以多晶硅副产物四氯化硅和硅酸钠为硅源,以低浓度的非离子表面活性剂聚乙二醇和无水乙醇为添加剂成功合成了二氧化硅粉体。讨论了硅酸钠浓度、反应温度和表面活性剂的加入对二氧化硅颗粒粒径和形貌的影响。利用透射电子显微镜、扫描电子显微镜、Fourier红外光谱仪、X射线粉末衍射仪、激光粒度分析仪等测试工具对所制备的二氧化硅的结构、粒径、表观形貌进行了测试与表征。结果表明：在最佳试验条件下,可制得平均粒径为150nm的二氧化硅粉体;非离子表面活性剂的加入可使二氧化硅颗粒分散均匀;二氧化硅颗粒粒径随硅酸钠浓度的增大而增大,故控制硅酸钠的浓度是本实验的关键。     

Influence of matrix properties on alkali silica reaction rates

Matrices with different cracking and confinement characteristics are utilized to isolate the important parameters that influence gel initiation and alkali silica reaction rate. The paper is divided into two parts. In Part I, the matrix exhibits crack growth resistance behavior which induces compressive stresses on the alkali silica gel and in addition prevents the alkali silica gel from leaving the reaction site, which slows down the alkali silica reaction rate and modifies the gel composition. In Part II the matrices are designed to provide little confinement and hence allow the alkali silica gel to expand almost freely. However, the matrices in Part II differ in their ability to allow the alkali silica gel to escape the reaction site. The results reveal that lack of confinement accelerates early gel formation whereas the lack of escape of alkali silica gel products away from the reaction site reduces the alkali silica reaction rate.     

Silicon carbide formation from pretreated rice husks

The differences in nature of organic matter in raw rice husks (RRH) and coked rice husks (CRH), and their effect on silicon carbide synthesis have been studied by means of infrared spectroscopy and X-ray diffractometry, so that the benefit of RH structure is fully exploited. Both RRH and CRH can be used as precursors for SiC synthesis, although different reaction kinetics and thus different control parameters are required. It is proposed that kinetics of silicon carbide synthesis from rice husks can be divided into 3 stages: organic decomposition, transformation of silica and condensed organic/graphite, and silicon carbide formation.     

Biotemplated Synthesis of Hollow Double‐Layered Core/Shell Titania/Silica Nanotubes under Ambient Conditions

Bacterial flagella, protein nanotubes (～15 nm wide) detached from Salmonella typhimurium bacteria, are used to template the formation of titania/silica core/shell double‐layered nanotubes in aqueous solution under ambient conditions through a sol–gel process. The thickness of each layer is tunable by varying the concentration of precursor solutions or reaction times. Upon heating, the flagella can be removed and the inner titania layer can be transformed into a nanocrystalline layer supported by the outer silica sheath. Nanotubes with different inner pore diameters and morphologies could be templated by other bionanofibers such as M13 phage and bacterial pili. This work shows that bionanofibers can be used as a universal biotemplate for the green synthesis of nanotubes with tunable wall thicknesses.     

The formation of zircon from amorphous ZrO2 · SiO2 powders

The different factors affecting the mechanism of zircon formation from amorphous ZrO₂ · SiO₂ powders have been studied. It was shown that zircon was formed by solid state reaction between tetragonal zirconia and silica (amorphous and cristobalite). The previously suggested Hedvall effect associated with the crystallization of amorphous silica into cristobalite did not play any role in this reaction. A high degree of Si-Zr mixing in the starting amorphous powders did not affect the mechanism of zircon formation, but speeded up the reaction rate due to the small particle size of the zirconia and silica particles segregated previously to zircon formation. It was also found that the formation reaction was retarded by the presence of carbonaceous species coming from the alkoxide precursors, which were probably retained at grain boundaries after calcination, acting as a diffusion barrier. These factors can explain the observed differences in the temperatures of zircon formation previously reported.     

Aligned bioactive mesoporous silica coatings for implants

Ongoing research is reported aimed at preparing mesoporous silica coatings on various substrates for medical applications by a biomimetic approach (self-assembling of organic/inorganic sol-gel systems into ordered structures). Tetraethylorthosilicate (TEOS) was selected as the silica precursor, and amphiphilic triblock copolymers poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), and the cationic surfactant cetyltrimethyl ammonium chloride (CTAC), as structure-directing agents. The mesochannels diameter could be adjusted by changing the directing agent, and a preferred alignment of the mesostructure was observed independently of the used substrate (glass, silicon, Ti or Ti6Al4V). Three different treatments (thermocalcination, photocalcination, and solvent extraction) have been also studied to remove the organic templates, of which photocalcination showed to be the most versatile. When soaked in a simulated body fluid, mesoporous silica coatings induced apatite formation after seven days.     

影响多孔SiO_2聚集体颗粒粒径的因素

在不考虑交互作用情况下,设计了五因素四水平正交实验以考察诸因素对硅灰石制多孔SiO2聚集体颗粒粒径的影响。实验结果表明,当反应时间统一为80min,陈化时间20min,反应温度50～55℃,HCl浓度为12mol/L,硅灰石用量为80g时,表面活性剂种类的选用对多孔SiO2聚集体颗粒粒径的影响最大,表面活性剂加入时间影响最小。