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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 >A SAXS study of the nanostructural characteristics of TEOS-derived sonogels upon heat treatment up to 1100 degrees C
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A SAXS study of the nanostructural characteristics of TEOS-derived sonogels upon heat treatment up to 1100 degrees C

机译：SAXS研究TEOS衍生的声波凝胶在1100摄氏度以下热处理时的纳米结构特征

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摘要

Xerogels obtained from the acid-catalyzed and ultrasound stimulated hydrolysis of TEOS were submitted to heat treatment at temperatures ranging from 60 to 1100 degreesC and studied by small-angle X-ray scattering (SAXS). The SAXS intensity as a function of the modulus of the scattering vector q was obtained in the range from q(0) = 0.19 to q(m) = 4.4 nm(-1). At 60 degreesC the xerogels exhibit an apparent surface fractal structure with a fractal dimension D-s similar to 2.5 in a length scale ranging from 1/q(1) similar to 1 to 1/q(m) similar to 0.22 nm. This structure becomes extremely rough at 120 degreesC (D-s similar to 3) and at 150 degreesC, it apparently converts to a mass fractal with a fractal dimension D similar to 2.4. This may mean an emptying of the pores with preservation of a share of the original mass fractal structure of the wet aged gel, for it had presented a mass fractal dimension D similar to 2.2. A well characterized porous structure formed by 2.0 nm mean size pores with smooth surface of about 380 m(2)/g is formed at 300 degreesC and remains stable until approximately 800 degreesC. At 900 degreesC the SAXS intensity vanishes indicating the disappearance of the pores in the probed length scale. The elimination of the nanopores occurs by a mechanism in which the number of pores diminishes keeping constant their mean size. The xerogels exhibit a foaming phenomenon above 900 degreesC and scatter following Porod's law as does a surface formed by a coarse structure. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 11]
机译：通过酸催化和超声刺激的TEOS水解获得的干凝胶在60至1100℃的温度范围内进行热处理，并通过小角X射线散射（SAXS）研究。在从q（0）= 0.19到q（m）= 4.4 nm（-1）的范围内，获得了SAXS强度与散射矢量q的模量的关系。在60摄氏度时，干凝胶表现出明显的表面分形结构，其分形维数D-s类似于2.5，其长度范围为1 / q（1）类似于1 / q（m）类似于0.22 nm。该结构在120摄氏度（D-s与3相似）和150摄氏度下变得极为粗糙，显然转变为分形维数D与2.4类似的质量分形。这可能意味着排空孔，保留湿老化凝胶的原始质量分形结构的一部分，因为它的质量分形维数D类似于2.2。一个良好表征的多孔结构是在300摄氏度下形成的，平均孔径为2.0 nm，表面光滑度约为380 m（2）/ g，并保持稳定，直到大约800摄氏度。在900摄氏度时，SAXS强度消失，表明所探测的长度尺度中的孔消失了。纳米孔的消除是通过一种机制来实现的，在这种机制中，孔的数量减少，保持其平均大小不变。所述干凝胶在900℃以上表现出起泡现象，并且根据粗糙的结构形成的表面也遵循Porod定律散射。 （C）2002 Elsevier Science B.V.保留所有权利。 [参考：11]

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