多孔質物質のEPMA定量分析における細孔構造のX線強度への影響

抄録

The quantitative determination method of the chemical composition of a solid matter by using an Electron Probe Micro Analyzer has been widely applied in the analysis of metals and minerals. However, this method has not been used for catalysts, synthetic minerals and composite materials which are porous matters. It comes from several reasons: (1) surface roughness of porous matter, (2) increase in electron beam penetration depth, and (3) electric charge up in an insulator such as oxides and organic substances. In the conventional quantitative analysis of EPMA, nonporous matter is preferred not only as the measuring samples, but also as the standard samples. The main purpose of this study is to find out a method to calculate the true composition of a porous matter referrable to the data of nonporous samples. The present report describes the influences of the pore structure of analyzing samples on the X-ray intensity observed and on the composition corrected by the conventional Bence and Albee calculation method. Three series of samples known as industrial catalysts, i. e., SiO₂ gel, SiO₂Al₂O₃ (W) and SiO₂MgO (SM) were used, and each series consisted of several samples controlled to various porosities by calcination. The pore structure was measured by a mercury porosimeter. The results obtained were as follows.
(1) The X-ray intensity was found to be greatly influenced by the porosity and the pore structure of the samples.
(2) The experiments of SM calcined at lower temperatures and of porous metal (Pb) plate show that the data are meaningless unless a proper linear relation between the incident beam current and the absorbed one exists, since the sample can be charged up electrically.
(3) The sum of the mass fraction corrected by the Bence and Albee method approached to 1.0 with decreasing porosity of samples W and SM.