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利用溶胶-凝胶技术和超临界干燥技术,制备了PMMA/SiO2复合气凝胶,并对气凝胶样品进行了表征。 相似文献
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亚临界干燥制备疏水SiO2气凝胶 总被引:12,自引:0,他引:12
以E-40(多聚硅氧烷)为硅源,三甲基氯硅烷的异丁醇溶液为干燥介质,用溶胶凝胶法,在亚临界条件下制备出疏水的SiO2气凝胶,通过SEM,孔径分布,比表面积,接触角以及红外光谱的测试对其物性进行了研究,结果表明,所制备的SiO2气凝胶具有典型的纳米网络结构,比表面大具具有疏水性能,亚临界干燥使得制备压力从6.4MPa降低到2.3MPa,降低了制备成本和风险,同时疏水性能提高了SiO2气凝胶环境适应性,从而十分有利于气凝胶的商业应用。 相似文献
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以廉价的工业水玻璃为凝胶前躯体,柠檬酸为凝胶促进剂,使用溶胶-凝胶与CO2超临界干燥工艺制备了块状的SiO2气凝胶,并探讨了酸性和碱性条件对所制备SiO2气凝胶结构与性能的影响.实验结果表明:水玻璃在酸性条件(pH≈4)和碱性条件(pH≈10)下均可以制备出完整、无开裂的二氧化硅气凝胶块体样品,酸性和碱性环境对水凝胶和最终SiO2气凝胶结构和性能的影响较大.酸性条件下获得的水凝胶呈透明块体,而碱性条件下所得水凝胶为白色不透明体.与碱性条件下制备的SiO2气凝胶相比,酸性条件下所得气凝胶具有更高的比表面积、较大的密度以及尺寸较小的胶体粒子. 相似文献
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SiO2-TiO2两元气凝胶的制备及其结构表征 总被引:5,自引:0,他引:5
SiO2-TiO2两元气凝胶是一种新型纳米光催化氧化剂。本文以正硅酸乙酯(TEOS)、钛酸丁酯为原料,以乙醇为溶剂,分别以HNO3、醋酸为催化剂用溶胶-凝胶法经超临界干燥制备出了SiO2-TiO2两元气凝胶。研究了不同催化剂以及SiO2:TiO2不同配比等制备因素对溶胶-凝胶过程的影响。用BET、XRD、SEM等测试方法对其结构进行了研究,结果表明:所制备的SiO2-TiO2两元气凝胶具有大比表面积(600m^2g^-1),纳米多孔结构(骨架颗料约为30-50nm, 孔洞尺寸为几十nm);经乙醇超临界干燥所得的TiO2为锐钛矿型;所制备的SiO2-TiO2两元气凝胶比纯TiO2气凝胶骨架结构强度得到明显增强。 相似文献
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采用常压干燥法制备了SiO2气凝胶,所得气凝胶为介孔结构,比表面积618.8m2/g,孔径分布5~20nm.以SiO2气凝胶为原料,通过静电吸附法制备了SiO2气凝胶/壳聚糖复合药物载体材料,采用扫描电镜(SEM)、红外光谱(FTIR)等对复合材料的结构形貌进行了分析,研究了复合材料对硫酸庆大霉素药物的担载和释放性能.结果表明,所得SiO2气凝胶/壳聚糖复合材料为多孔网络结构,其中,由450℃处理的SiO2气凝胶制得的气凝胶/壳聚糖复合材料对硫酸庆大霉素具有较好的药物担载和缓释性能. 相似文献
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本文通过搭建低温低压热泵干燥装置,研究了工业铁粉在不同低压下的干燥效果并分析了低温低压干燥过程中的传热与传质。结果表明:降低干燥环境压力会增大湿铁粉的除湿量,当环境压力从101 kPa降至10 kPa,除湿量增加2.5倍,且在10 kPa压力下铁粉含湿量能降至1%以下。当干燥空气为50℃,风速为0.5 m/s时,随着压力从101 kPa逐渐降至10 kPa,传质系数降低28.1%,传热系数降低68.4%,因此表征传热传质相对强度的刘易斯因子LF随着环境压力的降低而降低。当环境压力为10 kPa、风温为50℃时,流速从0.2 m/s增至2.0 m/s时,传质系数增加32.9%,传热系数增加67.8%,表明低压环境抑制了风速对传质系数的强化作用,因此LF随着风速的增加而增加。在10 kPa环境压力下,LF低至0.5~0.6,表明低压环境中质量扩散与热量扩散存在明显区别。 相似文献
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Rashmi Singh R.K. Khardekar D.K. Kohli M.K. Singh Himanshu Srivastava P. K Gupta 《Materials Letters》2010,64(7):843-845
Platinum nanoparticles were successfully synthesized on porous carbon aerogel with narrow pore size distribution by ambient pressure drying method. Platinum doped carbon aerogels were synthesized by sol-gel polymerization of resorcinol with furfural in non aqueous medium followed by ambient pressure drying and pyrolysis of organic gel. These samples were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD) and Flow Chemisorption. TEM and XRD results showed that size of platinum nanoparticle varies between 2 and 5 nm depending on platinum loading and pyrolysis temperature. Hydrogen pulsed chemisorption showed 26.5% dispersion of platinum nanoparticles in carbon aerogel. 相似文献
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Gui-Mei Gao Li-Na Miao Gui-Juan Ji Hai-Feng Zou Shu-Cai Gan 《Materials Letters》2009,63(30):2721-2724
The silica aerogels were successfully synthesized using oil shale ash which is a by-product of oil shale processing via ambient pressure drying. The physical and textural properties of the silica aerogels have been investigated and discussed. The results showed that the organic modification of hydrogels was a crucial step during the processing which preserved mesopores in ambient pressure drying. The unmodified hydrogel underwent tremendous shrinkage during the drying and yielded microporous silica aerogel. Using this novel route, it could produce silica aerogel with low tapping density of 0.074 g/cm3, high specific surface (909 m2/g) and cumulative pore volume of 2.54 cm3/g. From the industrial point of view, the present process is quite suitable for a large scale production of powdered silica aerogel. Furthermore, it provides a new way to solve the problem of oil shale ash pollution. 相似文献
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SiO_2气凝胶复合材料具有低密度、低热导、高强度等优异性能,已在航空航天、石油化工、建筑保温等领域获得较好应用。然而现有成熟的超临界干燥制备SiO_2气凝胶复合材料工艺需要维持高温、高压条件,能耗高、危险性大且设备复杂,常压干燥制备工艺由于所需条件温和、设备简单,有望实现连续性规模化生产。本文结合国内外关于常压干燥制备SiO_2气凝胶复合材料的研究进展,按照颗粒、纤维等增强相的不同,对常压干燥制备SiO_2气凝胶复合材料进行综述并对其未来发展方向进行了展望。 相似文献
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Low-dielectric silica aerogel films could be synthesized via solvent exchange-ambient drying of wet gel films that were obtained by spin-coating the isopropanol based silica sol on a p-Si (100) wafer. Using isopropanol as a drying solvent, the thickness and the dielectric constant of silica films significantly changed from 1100 nm to 350 nm and from 2.1 to 3.6, respectively, with the drying pressure of [8 MPa (270 °C)→2.6 MPa (200 °C)]. However, when isopropanol in pores was exchanged with n-heptane followed by ambient drying technique, the aerogel films had 1350 nm thickness, 80% porosity, and 2.0 dielectric constant, regardless of the drying pressure. The degree of planarization and the gap filling capability on 0.7 μm tungsten patterning wafer were excellent. It was proven that the ambient-dried aerogel films have a possibility of an application to IMD (inter-metal dielectrics) materials in the next generation of semiconductor devices beyond the giga level. 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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Xiao Han Khalil T. Hassan Alan Harvey Dejan Kulijer Adrian Oila Michael R. C. Hunt Lidija Šiller 《Advanced materials (Deerfield Beach, Fla.)》2018,30(23)
Aerogels are the least dense and most porous materials known to man, with potential applications from lightweight superinsulators to smart energy materials. To date their use has been seriously hampered by their synthesis methods, which are laborious and expensive. Taking inspiration from the life cycle of the damselfly, a novel ambient pressure‐drying approach is demonstrated in which instead of employing low‐surface‐tension organic solvents to prevent pore collapse during drying, sodium bicarbonate solution is used to generate pore‐supporting carbon dioxide in situ, significantly reducing energy, time, and cost in aerogel production. The generic applicability of this readily scalable new approach is demonstrated through the production of granules, monoliths, and layered solids with a number of precursor materials. 相似文献