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To produce insulating construction materials using hydrothermal reaction from blast furnace slag (BF slag) such as air-cooled, air granulated, and water-cooled slags, we investigated the fabrication of porous solidified materials from BF slag by a hydrothermal hot-pressing method. The thermal conductivity of the solidified materials was also investigated. The experimental conditions were; hydrothermal holding time from 0 to 120 min, hydrothermal temperature from 250 to 350°C, hydrothermal pressure from 20 to 80 MPa, and slag powder sizes less than 15 μm, 39±24 μm, 84±21 μm, 178±72 μm, 375±125 μm and more than 500 μm. It was found that growth of the hydrothermally reacted phase led to a higher density and higher thermal conductivity of the solidified materials. It was noteworthy that the thermal conductivity of the hydrothermal solidified materials became smaller when the size of the slag powder was larger. This was because the more porous structure introduced into the solidified materials resulted in a lower density of the solidified materials. It was also found that glassy slag such as water-cooled and air granulated slags can be solidified even if the size of the slag powder was more than 500 μm.

PbO2 powder, which is active positive-electrode material in the lead-acid battery, was mechanically milled with Sb2O3 powder. It is well known that Sb contained in the grid of the lead-acid battery is useful for the protection of the premature capacity loss. The results of the X-ray diffraction and EPMA (Electron Probe Micro Analyzer) showed that the alloying between PbO2 and Sb2O3 proceeded during the milling process. The position of the reduction peak in the CV (Cyclic Voltammetry) curve shifted to the lower potential and the intensity of the reduction peak increased with an increase of the scanning speed of the potential. The intensity of the reduction peak in the CV curve for the electrode constructed from PbO2 powder added with Sb2O3 was much reduced compared to that for the electrode constructed from PbO2 powder. The result of EPMA showed that the reduction reaction from PbO2 to PbSO4 proceeded more rapidly in the electrode constructed from PbO2 powder added with Sb2O3, and that Sb was not detected in PbSO4 particles. The above phenomena observed in the electrode constructed from PbO2 powder added with Sb2O3 seem to be concerned with the protection of the premature capacity loss of the lead-acid battery.

中嶋英雄監修『マクロおよびナノポーラス金属の開発最前線』