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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Zirconia aerogels: effect of acid-to-alkoxide ratio, alcoholic solvent and supercritical drying method on structural properties
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Zirconia aerogels: effect of acid-to-alkoxide ratio, alcoholic solvent and supercritical drying method on structural properties

机译：氧化锆气凝胶：酸与醇盐比，酒精溶剂和超临界干燥方法对结构性能的影响

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Zirconia aerogels have been prepared by the sol-gel method using tetra-n-butoxy zirconium(IV) and acid catalysis. The nitric acid-to-alkoxide ratio and the alcoholic solvent, as important sol-gel parameters, were varied. After aging, the solvent entrapped in the sol-gel products was removed applying two different methods: supercritical drying at high-temperature and low-temperature extraction with supercritical CO2. Finally, for gel stabilization and removing of organic residues the aerogels were calcined at 573 and 773 K, respectively. The effects of the varied sol-gel parameters, different supercritical drying methods, and calcination temperature on the structural and textural properties were investigated. The aerogels were characterized by means of N-2 physisorption, X-ray diffraction, thermal analysis, scanning and transmission electron microscopy. Depending on the kind of alcoholic solvent, nitric acid-to-alkoxide ratio and drying method, the specific surface areas of the mesoporous aerogels varied from 55 to 205 m(2) g(-1) after calcination in air at 773 K. The aerogels supercritically dried at high-temperature possessed larger pores (17-65 nm) and BET surface areas (143-205 m(2) g(-1)) compared to the aerogels dried by low temperature extraction (< 20 nm and 55-112 m(2) g(-1), respectively). The width of the pore size distribution of all high-temperature supercritically dried gels became smaller with increasing amount of acid. All aerogels dried by low temperature extraction with supercritical CO2 were X-ray amorphous. Upon calcination in air at 773 K, the amorphous aerogels crystallized to tetragonal zirconia. The high-temperature supercritically dried aerogels contained predominantly tetragonal zirconia. The fraction of monoclinic ZrO2 shares increased with increasing nitric acid-to-alkoxide ratio, the use of a long-chained branched alcoholic solvent, such as t-butanol, and increasing calcination temperature. (C) 1998 Elsevier Science B.V. [References: 24]
机译：氧化锆气凝胶已经通过使用四正丁氧基锆（IV）和酸催化的溶胶-凝胶法制备。作为重要的溶胶-凝胶参数，硝酸与醇盐的比例和醇溶剂是变化的。老化后，采用两种不同的方法去除残留在溶胶-凝胶产品中的溶剂：高温下的超临界干燥和超临界CO2的低温萃取。最后，为了使凝胶稳定并去除有机残留物，将气凝胶分别在573 K和773 K下煅烧。研究了变化的溶胶-凝胶参数，不同的超临界干燥方法和煅烧温度对结构和织构性质的影响。通过N-2物理吸附，X射线衍射，热分析，扫描和透射电子显微镜对气凝胶进行表征。根据酒精溶剂的种类，硝酸与醇盐的比例和干燥方法的不同，介孔气凝胶的比表面积在773 K的空气中煅烧后从55到205 m（2）g（-1）不等。与通过低温萃取干燥的气凝胶（<20 nm和55-）相比，在高温下超临界干燥的气凝胶具有更大的孔（17-65 nm）和BET表面积（143-205 m（2）g（-1））。分别为112 m（2）g（-1））。随着酸的增加，所有高温超临界干燥凝胶的孔径分布宽度变小。通过超临界CO2低温萃取干燥的所有气凝胶均为X射线无定形的。在773 K的空气中煅烧后，无定形气凝胶结晶为四方氧化锆。高温超临界干燥气凝胶主要含有四方氧化锆。单斜晶体ZrO2的份额随硝酸与醇盐比率的增加，使用长链支链醇溶剂（例如叔丁醇）的增加以及煅烧温度的升高而增加。 （C）1998 Elsevier Science B.V. [参考：24]

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