Angstrom Porosimety with quantum Herium

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A He atom is the smallest spherical monoatomic molecule and interacts nonspecifically with any solid surface. He adsorption at 4.2 K is an effective method for determination of Angstrom pore structures. The He adsorption at 4.2 K was applied to activiated carbon system. The adsorption isotherms were compared with N_2 adsorption isotherms using the theoretical adsorbed He density (0.202gml^<-1>) on the flat surface and the liquid N_2 density (0.807gml^<-1>) , respectively. The amount of He adsorption was much greater than that of N_2 in the low relative pressure region. This suggests better accessibility and accelerated bilayr adsorption of He. The He adsorption isotherm was analyzed by the Dubinin-Radushukevich plot and we developed the determination method of the Angstrom pore size distribution from the He adsorption isotherm using the Gaussian distribution function and the Dubinin-Stoeckli relation. This analysis was quite effective for determination of the Angstrom pore size distrib … More ution for activated carbon. It can show presence of the Angstrom pores which cannot be evaluated by N_2 adsorption method. However, the application of this approach is limited to activated carbon system. We developed a more general analysis using the potential profile and distribution of a He atom in the pore. We applied the Steele approach to He adsorption on the flat surface to the Angstrom pore analysis. The potential profile of a He atom with the pore was determined by calculation using the Lennard-Jones potential as a function of the pore width. This potential profile and statistical considerations lead to a possible population of He atoms in the pore. Hence, we can determine the micropore size distribution by the best fit procedure to the observed adsorption isotherm. It was shown that this molecular potential approach for He adsorption having a general applicability is a hopeful method for Angstrom pore characterization. Also the Grand Canonical Monte Calro (GCMC) computer simulation was applied to analyze the He adsorption isotherm. However, it will take more time to establish the development of the Angstrom pore size distribution-determination with the GCMC method. Less