中孔纯硅分子筛的表面分形结构表征

Fractal Structure Characteration of the Mesoporous Molecular Sieve

采用计盒维数方法对中孔纯硅分子筛的结构进行了分形研究。结果表明:所研究的多孔分子筛结构存在分形现象。根据计算,室温晶化(25℃)和水热晶化(125℃)工艺所得到的产物分形维数分别为2.56和2.61,高于典型活性炭的分形维数2.21;而且3个样品的分形维数与其BET低温氮吸附法测试的比表面积变化趋势一致。因此,对多孔材料表面进行分形表征可与其表面性质相联系。

The fractal dimension of the surface structure of pure silica mesoporous molecular sieve was investigated by the box-counting algorithm and compared with that of the active carbon. It is found that molecular sieve structure is fractal. According to calculation, the fractal dimension of the sample from crystallization at 25℃ and from hydrothermal crystallization at 125℃ is 2. 56 and 2. 61, respectively, which are higher than that of active carbon (2. 21 or so). Moreover, the fractal dimension of three samples increases with increasing specific area measured by BET low-tem- perature N_2 adsorption method, i. e. the change of fractal dimension is identical with that of surface nature. Thus it is supposed to build up the connection between the fractal dimension and the surface nature of porous structure.