Development of characterization method for sub-nano scale small voids of amorphous materials by multi probe gas diffusion technique.

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A novel equipment and technique for characterization of small void volume of microporous powder sample were developed based on the volumetric method by using various gas molecules as a probe molecule. As microporous materials, the porous powder sample of amorphous silica and BTESE(bis-triethoxysilyl ethane) silica was prepared, and the detailed void structure was evaluated using the multi-probe gas molecular diffusion method. This technique enables us to estimate the difference in the sub-nano scale void structure of these amorphous materials. The validity of this technique verified by evaluating the void volume of Y type zeolite whose micro structure is well known, and the theoretical pore volume was successfully obtained. The difference in the structure of amorphous silica and BTESE silica was examined also by the molecular simulation. The simulated molecular size dependence of gas diffusivity in these small void structures showed good correlation with the void volume distribution measured with the multi-probe gas molecular diffusion method.