含镍硅酸乙酯的Sol-Gel过程制备金属/SiO2复合气凝胶

首次采用含镍硅酸乙酯（NiTEOS）进行溶胶-凝胶反应来制备高镍含量的Ni／SiO2复合气凝胶，且Ni含量可在＜60wt％的范围内任意调节．并系统研究了水浓度、催化剂浓度、溶剂用量及合镍硅酸乙酯的组成对溶胶-凝胶过程的影响．所制备的Ni／SiO2复合气凝胶的比表面积高达420～650m2／g.     

Flexible shielding layers for solar cells in space applications

The development of flexible, thin‐film, and high‐efficiency III–V solar cells enables the design of new flexible, lightweight solar arrays for space applications. A requirement for these solar panels is the replacement of the rigid coverglasses by a flexible shielding layer. In this work, three candidate materials based on commercially available polyimides and synthesized polysiloxanes for such a shielding layer are compared with respect to their ease of synthesis, transparency. Polysiloxanes based on methyltrimethoxysilane (MTMS) based siloxane (MBS) showed the best reproducibility in synthesis of layers of the required thickness of about 300 µm with sufficient transparency and was therefore selected for further analysis. It was demonstrated that the MBS material could be doped with Ce to increase the radiation hardness. Showing virtually no loss of volatile condensable components in outgassing tests it can be concluded that the properties MBS are found suitable for further space qualification testing. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43661.     

Interaction of TEOS with cementitious materials: Chemical and physical effects

This study explored the effectiveness of tetraethyl orthosilicate (TEOS) as a Portland cement mortar consolidant to verify whether it meets the requirements for use in cultural assets. TEOS was found to raise cement mortar strength, lower its porosity and permeability and occasion minimal alteration in its appearance, an indication of its suitability to conserve heritage mortar works.FTIR and ²⁹Si MAS NMR studies supported the notion that TEOS interacts with the hydrated phases of the cement, portlandite and C–S–H gel. The reaction product between portlandite and TEOS was C–S–H gel and between TEOS and C–S–H gel was a gel with longer chain.     

The development of PTFE/Nafion/TEOS membranes for application in moderate and high temperature proton exchange membrane fuel cells

PTFE/Nafion (PN) and PTFE/Nafion/TEOS (PNS) membranes were fabricated for the application of moderate and high temperature proton exchange membrane fuel cells (PEMFCs), respectively. Membrane electrode assemblies (MEAs) were fabricated by PTFE/Nafion (and PTFE/Nafion/TEOS) membranes with commercially available low and high temperature gas diffusion electrodes (GDEs). The effects of relative humidity, operation temperature, and back pressure on the performance and durability test of the as-prepared MEAs were investigated. Incorporating TEOS into a PNS membrane and adding another layer of carbon onto a GDE would result in low membrane conductivity and low fuel cell performance respectively. However, in this work it is shown that HT-PNS MEAs demonstrate a higher performance than LT-PN MEAs in severe conditions - high temperature (118 °C) and low humidity (25% RH). The TEOS and additional carbon layer function as water retaining agents which are especially important for high temperature and low humidity conditions. The HT-PNS MEA showed good stability in a 50 h fuel cell test at high temperature, moderate relative humidity (50% RH) and back pressure of 14.7 psi.     

Design of Nanostructured Tamarind Seed Kernel Polysaccharide-Silica Hybrids for Mercury (II) Removal

Tamarind (Tamarindus indica L.) seed kernel polysaccharide-silica (TKP-Si) nanohybrids have been fabricated in a base catalyzed sol-gel reaction where tetraethylorthosilicate (TEOS) and tamarind kernel polysaccharide were used as silica precursor and template respectively. The nanohybrids were found to be photoluminescent and efficient in Hg(II) removal from the synthetic aqueous solution. The synthesized nanohybrids were characterized using Fourier Transform Infra-red spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA), and Photoluminescence (PL) analysis. For obtaining the most efficient sample in terms of mercury (II) binding, various ratios of reactants (Polysaccharide: TEOS: H₂O: EtOH) were used and the optimum sample thus obtained was calcined at 200°C (in air) to further enhance its binding performance. A mechanism for the sorption of Hg(II) by the optimum hybrid sample (TH₁) has been proposed and to understand its sorption behavior, kinetics and isotherm studies have also been performed. Regeneration studies indicated that the loaded Hg(II) from the used hybrid can be easily desorbed and can be successfully reused for eight consecutive adsorption-desorption cycles.     

高温自生压力法制备基于天然产物的碳及其复合材料

高温自生压力法(RAPET)是一种新型、简单而又高效的无机材料制备方法。以含水天然产物如甘薯、香菜和野藤等为前驱物,经冷冻干燥其骨架结构得以维持,然后通过RAPET法在700℃碳化,制得了保持天然物原有微观骨架结构的碳材料;以液态油脂花生油为原料,经RAPET法直接制得微米碳球;粘胶纤维和脱脂棉经RAPET碳化后能维持其原有纤维形貌;用钛酸丁酯(TBOT)和正硅酸四乙酯(TEOS)浸渍的脱脂棉和粘胶纤维,经RAPET法一步合成了C/TiO2和C/SiO2复合材料。利用扫描电子显微镜(SEM)观察了产物的形貌,以比表面积及孔径分布测试仪对产物的比表面积和孔结构进行了表征,通过X射线衍射(XRD)研究了所得C/TiO2和C/SiO2复合材料的晶相特征。结果显示,所得产物比表面积从4m2/g到405m2/g不等,C/TiO2中TiO2晶相为锐钛矿型。     

水泥表面硬化剂的制备

以正硅酸乙酯(TEOS)、甲基三甲氧基硅烷(MTMS)、硅溶胶为主要原料制备了水泥表面硬化剂,研究TEOS/MTMS比例、硅溶胶用量、硅溶胶粒径等因素对涂层硬度、附着力的影响,研究了反应程度、体系的pH值等对储存稳定性的影响.结果表明,TEOS/MTMS比例对涂层硬度有显著影响,涂层硬度随着TEOS用量的增加而增大,但TEOS/MTMS比例过大会造成涂层脆性增大；随着MTMS用量增加,涂层的附着力增大,但涂层硬度会显著降低；加入适量的硅溶胶可提高涂层的硬度,但硅溶胶的用量不能过大,且硅溶胶的粒径越小,涂层硬度越高.     

Fabrication of transparent Nd:YAG ceramics by vacuum sintering with CaF2 and tetraethoxysilane additives

Abstract

Nd:YAG ceramics with CaF₂ and tetraethoxysilane (TEOS) as sintering additives were fabricated by vacuum sintering at 1750°C for 5 h and the microstructures were characterised using X-ray diffraction and scanning electron microscopy. Scanning electron microscopy result shows that the sintered bulk doped with TEOS contains many pores in the grains. The bulk doped with CaF₂ displays uniform microstructure. The average size of the grains is 10 mm and few pores can be detected in this sintered bulk. The maximum transmittance of the sintered Nd:YAG ceramics were 44% doped with CaF₂ and 14% doped with TEOS.     

硅钛柱撑蒙脱土微孔材料的制备与表征

合成了一种硅钛柱撑蒙脱土微孔材料.用十六烷基三甲基溴化铵改性蒙脱土,制得有机蒙脱土,再以正硅酸乙酯为硅源,采用溶胶-凝胶法,在正硅酸乙酯-蒙脱土水溶液中加入四氯化钛,以四氯化钛作为硅柱前驱体进入粘土片层间反应的驱动力,在钛阳离子的驱动下,使正硅酸乙酯在蒙脱土的片层之间发生水解缩合反应,制备了硅钛柱撑蒙脱土微孔复合材料.用XRD、DTA以及N2吸附脱附测试,分别对材料进行了表征.XRD测试结果表明:复合材料的最大层间可达到17.7 A.;DTA测试结果表明:改性后蒙脱土复合材料的热稳定性明显提高了;N2吸附脱附曲线以及孔径分布曲线说明合成的多孔材料中多为微孔分布,平均单孔体积为0.14 cc/g,平均孔径达到17.5 A.,SBET表面积由30.2 m2/g增加到242.0 m2/g.这种材料以其柱撑多孔结构,作为环保材料如:吸收剂、催化剂应用,具有广阔的发展前景.     

W/O微乳体系酸催化水解硅酸乙酯合成单分散酸性超微二氧化硅

研究不同亲水亲油平衡值 (HLB)的Span80 Tween60表面活性剂复配体系对酸性水溶液微乳化增溶力的影响 ,最佳HLB值在 1 3左右 ,该体系用作超微或纳米粒子的微乳法合成体系。在水 (HNO3) /Span80 Tween60 /环己烷体系中水解硅酸乙酯(TEOS)合成了 1 1 0～ 550nm的单分散酸性超微二氧化硅粒子 ,研究了R(n水/n表)和H(n水/nTEOS)对粒径的影响 ,随着R的增大 ,粒径越小 ,达到最小值再增大 ;H越高 ,粒径越大。提出了W/O微乳体系酸催化水解TEOS合成二氧化硅粒子的过程模型 ,指出酸催化过程中缩聚凝结是晶核长大的重要方式