SnO_2凝胶干燥及固化过程中的结构变化

Structural Evolution During Drying and Solidification of SnO_2 Gels

通过ＴＧ－ＤＴＡ、ＢＥＴ－Ｎ２吸附和Ｘ衍射分析，详细研究了ＳｎＯ２凝胶在２０～７００℃区间干燥固化过程中的收缩、失重机理、凝胶骨架纳米结构的变化规律，研究了掺杂元素Ｓｂ、溶胶阶段加入的催化剂和溶剂种类对干燥过程和固化过程中结构演变的影响．研究发现：ＳｎＯ２凝胶为１～１０ｎｍ尺寸的纳米多孔结构，符合圆柱通孔模型．在干燥固化过程分别为２０～２００℃、２００～５５０℃和＞５５０℃三个不同阶段，分别发生骨架吸附溶剂解附、－ａｃａｃ 螯环分解氧化、网链结构驰豫和无定型→晶态转变等四个过程，它们是支配凝胶失重、收缩、固化的主要机理．随团化温度增加；纳米骨架粗化长大但其径长比保持不变，同时Ｓｂ加入有细化骨架作用，而催化剂对凝胶结构无明显影响．

This paper dealt with in detail the drying-solidification process, contraction and weight-loss: mechanisms, skeleton nanostructures and its evolution trends with temperature increasing for SnO2 gel system within 20 similar to 700 degreesC heat-treatment interval by TG-DTA, BET-N-2 adsorption, and X-ray diffraction three measuring methods, and further covered with the influences of doping Sb addition amounts, catalysts and solvents needed in sol stage on drying process and nanostructure of SnO2 gels. Based on the measurements and analysis, it is shown that SnO2 gels are of porous nanostructure of size 1 similar to 15nm, in good agreement with Sherer's Cylinder Skeleton Model, and drying solidification includes three evolution stages: 20 similar to 200 degreesC, 200 similar to 550 degreesC and >550 degreesC, in which the desorption of solvents on the surfaces of gel skeleton, break-up and oxidation of -acac ring chelated on Sn atom, structural relaxion of gel chain net and gel skeleton crystallization are responsible for the weight-loss, contraction and solidification of gels, as temperature increases, the nano-skeleton coarsens and enlarges but keeps its radium-length ratio unchanged, on the other hand, doping Sb addition makes gel skeleton more slender but catalysts do not influence gel structure considerably.