Huang WL, Liang KM, Cui SH, Gu SR
Department of Materials Science and Engineering, Tsinghua University, Beijing, 100084, People's Republic of China
J Colloid Interface Sci. 2000 Nov 1;231(1):152-157. doi: 10.1006/jcis.2000.7105.
Silica xerogels were prepared under three different solvent evaporation conditions before gelation and two calcination procedures after aging and drying, using a hydrochloric acid-catalyzed tetraethyl orthosilicate system with acetone as the solvent. The influence of calcination procedures on the percentage porosity and surface fractal dimensions of the resultant xerogels is investigated. The evaluation of percentage porosity and surface fractal dimensions based on field emission gun-scanning electron microscopy indicates that calcination generally causes an increase in percentage porosity and surface fractal dimensions. Calcination at 700 degrees C without an intermediate stay at 600 degrees C leads to larger extent of further condensation that hinders the increase of porosity and surface fractal dimensions, in comparison with calcination with an intermediate stay. The difference in porosity and surface fractal dimensions derived from calcination procedures is also influenced by the solvent evaporation conditions before gelation in preparation of the samples. When the solvent evaporation rate is slower, the difference is slight because further condensation in the resultant finer gel textures proceeds more efficiently. Copyright 2000 Academic Press.
在凝胶化之前，在三种不同的溶剂蒸发条件下制备二氧化硅干凝胶，并在老化和干燥后采用两种煅烧程序，使用盐酸催化的正硅酸乙酯体系，以丙酮为溶剂。研究了煅烧程序对所得干凝胶的孔隙率百分比和表面分形维数的影响。基于场发射枪扫描电子显微镜对孔隙率百分比和表面分形维数的评估表明，煅烧通常会导致孔隙率百分比和表面分形维数增加。与有中间停留的煅烧相比，在700℃煅烧且没有在600℃中间停留会导致更大程度的进一步缩合，这阻碍了孔隙率和表面分形维数的增加。煅烧程序导致的孔隙率和表面分形维数的差异也受到样品制备过程中凝胶化前溶剂蒸发条件的影响。当溶剂蒸发速率较慢时，差异较小，因为在所得更细的凝胶结构中进一步缩合进行得更有效。版权所有2000年学术出版社。
