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以正硅酸乙酯(TEOS)为前驱体,采用溶胶-凝胶法制备SiO2气凝胶薄膜,并以不同体积分数的六甲基二硅胺烷(HMDZ)对SiO2气凝胶薄膜进行了疏水改性研究,采用椭偏仪、FITR、接触角测试仪、SEM和光谱仪等对薄膜的疏水性、微观结构及透光性进行了表征,研究了HMDZ疏水改性对SiO2气凝胶薄膜性能与结构的影响。结果表明,疏水改性后,SiO2胶粒表面的大部分亲水性-OH被疏水基团-CH3所取代,其与水的接触角达159°,疏水性好;SiO2气凝胶薄膜在可见光范围内透光率接近90%,透光性高;其孔隙率为78.8%,密度为0.464g/cm3,骨架颗粒尺寸小于40nm,具有纳米多孔网络结构特性。 相似文献
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本文以正硅酸乙酯(TEOS)为前驱体,通过酸碱两步溶胶-凝胶法,常压干燥制备疏水性SiO2气凝胶。研究了两种改性剂(三甲基氯硅烷、六甲基二硅氮烷)对二氧化硅气凝胶结构和性能的影响。对制备的气凝胶样品进行表面微观形态分析、热重差热分析、傅里叶红外分析以及比表面积分析。结果表明,通过改性制备的样品具有较好的性能,使用六甲基二硅氮烷改性得到的SiO2气凝胶密度为0.204g/cm3,接触角为128°,BET比表面积为973m2/g,平均孔径7.57nm;使用三甲基氯硅烷改性得到的SiO2气凝胶密度为0.115g/cm3,疏水性优良,接触角为158°,BET比表面积为1067m2/g,平均孔径13.40nm。综合考虑各种因素,采用TMCS进行改性制备得到的SiO2气凝胶综合性能更加优异。 相似文献
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采用溶胶-凝胶法制备SiO2气凝胶,以三甲基氯硅烷/环己烷、二甲基二氯硅烷/环己烷体系为化学表面修饰剂,通过衍生法制备了疏水性SiO2气凝胶.利用气质联用对表面改性过程中发生的反应进行了剖析;并利用扫描电镜、红外光谱、比表面测定等测试方法对2种改性方法所获得的SiO2气凝胶的结构、形貌及性能组成进行了比较.研究表明,2种改性方法均可获得连续网络结构、多孔纳米材料.所得SiO2气凝胶的比袁面积分别为652m2/g和656m2/g,主要孔径尺寸为2~10nm.样品表面连有疏水基团,呈现明显的疏水性. 相似文献
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以正硅酸四乙酯(TEOS)为硅源,在溶胶-凝胶过程中添加六钛酸钾晶须制备SiO2复合凝胶,通过表面改性和超临界CO2干燥技术获得了大块无裂纹的SiO2气凝胶复合材料。由分析可知,SiO2溶胶的凝胶时间与溶胶体系酸碱性有密切关系,而掺杂不同含量的六钛酸钾晶须对凝胶时间无显著影响;用红外光谱(FT-IR)、BET技术等进一步对其表征,结果表明,制备的样品密度范围为0.20g/cm3~0.29g/cm3,经过疏水改性后,气凝胶表面存在大量憎水基团。BET检测显示,SiO2气凝胶复合材料比表面积达到700m2/g以上,平均孔径为18nm左右,是一种轻质纳米多孔材料。 相似文献
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以TEOS为硅源,TMCS/HMDSO为混合表面改性剂,采用酸碱两步催化溶胶-凝胶法和常压干燥法制备疏水性SiO2气凝胶,并借助BET、SEM、FT-IR等测试手段对样品进行表征。结果表明:TMCS/HMDSO混合改性剂的改性效果优于单一改性剂,当TMCS体积分数为混合表面改性剂的60%,改性温度为60℃时,制备的SiO2气凝胶具有较佳的综合性能,密度为0.1213g·cm-3,比表面积高达899.8m2·g-1,孔容为2.856cm3·g-1。 相似文献
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SiO_2气凝胶是具有优异性能的新型多孔纳米材料,是国内外热学、光学、声学及电学等学科的研究和发展热点。SiO_2气凝胶的制备包括凝胶形成、凝胶老化及后处理3个阶段,其结构和性能与制备参数有关。对3个阶段制备参数的影响规律进行了综述。针对凝胶形成阶段,从硅源种类、化学配比、pH值、反应温度及水解时间5个参数进行概述;针对凝胶老化阶段,从老化温度与时间两个参数进行概述;针对后处理阶段,从干燥剂种类、改性剂种类和浓度及改性温度与时间5个参数进行概述。通过进一步探索制备参数对SiO_2气凝胶结构与性能影响的规律,不断优化生产制备工艺,对推动SiO_2气凝胶规模化生产及推广应用有指导意义。 相似文献
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常压干燥制备疏水SiO2气凝胶的影响因素分析 总被引:1,自引:0,他引:1
常压干燥制备SiO2气凝胶是近年来该领域的研究重点,工艺条件的优化是提高气凝胶性能的关键。以正硅酸乙酯为硅源,甲基三乙氧基硅烷为共前驱体,采用溶胶-凝胶法,结合老化和三甲基氯硅烷-正己烷-无水乙醇混合溶液的二次表面改性,通过常压干燥工艺制备疏水SiO2气凝胶。利用BET,FT-IR,SEM,TEM和接触角测试等手段对气凝胶进行表征,系统研究水解时间、老化时间、老化温度和改性剂用量对气凝胶性质的影响。结果表明:水解16h,凝胶于55℃下老化48h后,在三甲基氯硅烷与正硅酸乙酯的摩尔比为1.56的混合液下改性48h制备的SiO2气凝胶的性能最好,其孔隙率92%,比表面积969m2/g,接触角达157°。 相似文献
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《材料与设计》2015
Highly porous carbon aerogels were prepared by pyrolyzing the novolac–silica aerogels. The silica phase was extracted from rice husk ash (RHA). The polymer aerogel was synthesized via the novel method of sol–gel polymerization in solvent vapor-saturated atmosphere. This method removes the need for supercritical drying and reduces the shrinkage of aerogels during drying stage and also has much lower process time compared to the conventional sol–gel method. In the next step, polymer composite aerogels become carbon/silica and carbon/silica/silicon carbide composites in pyrolysis (800 °C) and carbothermal reduction (1500 °C) stages, respectively. The characterization of the prepared composite aerogels was performed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses, respectively. Thermal and mechanical properties of the samples were investigated by differential scanning calorimetry (DSC) and compressive strength analysis. The resultant composite aerogels show a nanostructure with high porosity (above 82%) and low density (below 0.3 g cm− 3). Si mapping images showed the good distribution of silica phase throughout the carbon matrix. Also the rate of oxidation for carbon composites decreased by silica incorporation and oxidation temperature increased about 20% by adding RHA silica. Compressive strength of composite samples increased about 25% by increasing RHA silica phase content. 相似文献
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Silica aerogels are highly porous solid materials consisting of three-dimensional networks of silica particles and are typically obtained by removing the liquid in silica gels under supercritical conditions. Several unique attributes such as extremely low thermal conductivity and low density make silica aerogels excellent candidates in the quest for thermal insulation materials used in space missions. However, native silica aerogels are fragile at relatively low stresses. More durable aerogels with higher strength and stiffness are obtained by proper selection of silane precursors and by reinforcement with polymers. This paper first presents a brief review of the literature on methods of silica aerogel reinforcement and then discusses our recent activities in improving not only the strength but also the elastic response of polymer-reinforced silica aerogels. Several alkyl-linked bis-silanes were used in promoting flexibility of the silica networks in conjunction with polymer reinforcement by epoxy. 相似文献
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CdS coatings are deposited on the external and inner surfaces of silica aerogels with a single-source metal-organic chemical vapor deposition method at atmospheric pressure. Thermogravimetry analysis and differential scanning calorimetry experiments are used to investigate the thermal behavior of silica aerogels, and the sample treated at 500 °C for 120 min has been found to possess the lowest density. The densities and morphologies of the silica aerogels under the different treatment temperatures are also studied. The CdS coatings are deposited on the inner surface of the silica aerogels with a 4 l/min flow of Ar gas. The procedure for the preparation of the CdS coatings on the inner surface is reported in details. The surface morphologies of the CdS-coated silica aerogels are analyzed by scanning electron microscopy. The results of the energy dispersive X-ray spectroscopy and X-ray diffraction analysis demonstrate that the CdS coatings are composed of cadmium and sulphur with an approximately atomic ratio of 1:1, and they are hexagonal structures. 相似文献
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Polyimide aerogels cross-linked through amine functionalized polyoligomeric silsesquioxane 总被引:1,自引:0,他引:1
Guo H Meador MA McCorkle L Quade DJ Guo J Hamilton B Cakmak M Sprowl G 《ACS applied materials & interfaces》2011,3(2):546-552
We report the first synthesis of polyimide aerogels cross-linked through a polyhedral oligomeric silsesquioxane, octa(aminophenyl)silsesquioxane (OAPS). Gels formed from polyamic acid solutions of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), bisaniline-p-xylidene (BAX) and OAPS were chemically imidized and dried using supercritical CO(2) extraction to give aerogels having density around 0.1 g/cm(3). The aerogels are greater than 90 % porous, have high surface areas (230 to 280 m(2)/g) and low thermal conductivity (14 mW/m-K at room temperature). Notably, the polyimide aerogels cross-linked with OAPS have higher modulus than polymer reinforced silica aerogels of similar density and can be fabricated as both monoliths and thin films. Thin films of the aerogel are flexible and foldable making them an ideal insulation for space suits, and inflatable structures for habitats or decelerators for planetary re-entry, as well as more down to earth applications. 相似文献
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Dylan J. Boday Robert J. Stover Beatrice Muriithi Douglas A. Loy 《Journal of Materials Science》2011,46(19):6371-6377
Nanocomposite aerogels were prepared by chemical vapor deposition and polymerization of cyanoacrylate on the surface of bridged
polysilsesquioxane aerogels. Phenylene- and hexylene-bridged aerogels were prepared by sol–gel polymerizations and supercritical
carbon dioxide drying. Hydrophobic organic bridging groups in the polysilsesquioxane aerogels reduced the amount of adsorbed
water available for initiating polymerizations and led to higher molecular weight polycyanoacrylate than was observed with
silica aerogels. Densities increased as much as 65% due to the addition of the organic polymer, but the nanocomposite aerogels
remained highly porous with surface areas between 440 and 750 m2/g. Polycyanoacrylate–phenylene-bridged aerogel composites were the strongest with flexural strengths up to 780 kPa or 16-fold
stronger than the untreated phenylene-bridged aerogels and fivefold stronger than a silica aerogel of the same density. The
strongest polycyanoacrylate–hexylene-bridged aerogel composites had flexural strength of 285 kPa or ninefold stronger than
the untreated hexylene-bridged aerogels and twice as strong as a silica aerogel of comparable density. The greater strength
of the new composites is, in part, due to the greater strength of the bridged aerogels. However, higher molecular weight polycyanoacrylate,
due to less surface water on the hydrophobic bridged aerogels, also contributes to the greater nanocomposite strengths. 相似文献