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The microstructure just below the fracture surface in hydrogen-charged stable austenitic SUS 316L stainless steel, which was subjected to a low strain rate tensile test at −70°C, was studied by a combination of the focused-ion-beam method and transmission electron microscopy. An amorphous region with a chemical composition almost identical to that of the polycrystalline region was found under the lath-like structure on the fracture surface, although no deterioration of tensile properties by hydrogen appeared. In the amorphous region, band-like regions with wavy contrasts were observed, which were often accompanied by cracks at the boundaries. The presence of the amorphous region with band-like regions implies that amorphization occurred due to high-density vacancies accompanied by agglomerations of excess vacancies in the hydrogen-charged SUS 316L stainless steel that was tensile-tested at low temperatures.

The aqueous oxidation of pulverised pyrite by ferric ion was investigated in a concentrated, acidic chloride solution. The ratio of the concentration of sulphate ion to elemental sulphur produced during the reaction was approximately 1.3, regardless of the leaching conditions such as temperature and acid concentration. The oxidation rate increased with decreasing acid concentration and increasing initial ferric chloride concentration and was retarded by an addition of ferrous ion. It was found that the oxidation rate was not linearly related to the pyrite loading and the reciprocal of the particle diamter. A kinetic model was proposed assuming that fine mineral powder and irregular pits on the outer surface of the crushed pyrite are responsible for the high initial reaction rates., The aqueous oxidation of pulverised pyrite by ferric ion was investigated in a concentrated, acidic chloride solution. The ratio of the concentration of sulphate ion to elemental sulphur produced during the reaction was approximately 1.3, regardless of the leaching conditions such as temperature and acid concentration. The oxidation rate increased with decreasing acid concentration and increasing initial ferric chloride concentration and was retarded by an addition of ferrous ion. It was found that the oxidation rate was not linearly related to the pyrite loading and the reciprocal of the particle diamter. A kinetic model was proposed assuming that fine mineral powder and irregular pits on the outer surface of the crushed pyrite are responsible for the high initial reaction rates.