３パラメター吸着式の誘導とその適応性 ＩＶ 微小表面積粉体へのＮ２吸着等温線に対する３パラメター吸着式の適応性

Abstract

Nitrogen adsorption isotherms at 77K on non-porous powders, such as γ-Fe2O3, A1100 and SM and silicon carbide, SiC(P) have been measured. The application of experimental isotherms to the 3-parametric adsorption equation was compared with that of the BET equation. The applicable relative pressure range of the 3-parametric adsorption equation was compared with that of the BET equation. The applicable relative pressure range of the 3-parametric adsorption equation was wider, from 0.05 to 0.65, than that of the BET equation which was in the range from 0.05 to 0.35. The surface areas, ∑T obtained from the 3-parametric adsorption equation showed an agreement within 10% with that from the BET equation, ∑B. Since the straight line in αs-plots of N2 adsorption isotherms were found to pass through the origin of the coordinate, the powders were confirmed to have no micropore. The outer plane surface areas, ∑Tαs and ∑Bαs, were determined from the slope of the straight line in αs-plots of the standard isotherm of N2 on non-porous hydroxylated silica, on the basis of the surface areas by application of the standard isotherm to the 3-parametric adsorption equation and BET equation, respectively. There is a reasonable agreement of ∑T and ∑B with ∑Tαs, and ∑Bαs, respectively, and therefore it will be difficult to determine which surface areas were the most reasonable. However, the surface areas obtained from the measurement of the particle diameter in use of a photograph of a scanning electron microscope showed better and reasonable agreement with the surface areas from the 3-parametric adsorption equation than that from BET equation. Therefore, the 3-parametric adsorption equation seemed to be more reasonable than the BET equation.