Influence of HF treatment of fly ash on the strength of hardened bodies was investigated in order to evaluate the contribution of the pozzolanic reaction of glass phase in the fly ash surface to the compressive strength of the hardened bodies. X-ray diffraction and SEM have been used to characterize the hardened bodies as well as the fly ash used. These results indicated that the pozzolanic reaction of glass in the fly ash is important to enhance the strength of the hardened bodies.
The dissolution of calcium ion from coal fly ash and flow behavior of the slurry in supersonic flow field were investigated. It was found that the maximum concentration of the coal fly ash showing slurry in supersonic flow field was 55 mass%, but the flow behavior of the slurry was quite different on the boundary of 25 mass%. The solubility of Ca2+ ion dissolved from the coal fly ash was measured after operation of membrane process combined with supersonic washing. Consequently, it was found that the concentration of Ca2+ ion increased with increasing time, and the value reached the maximum at 60 minuts. The permeation flux of ceramic membrane in supersonic flow field decreased with increasing time because of the pore narrowing.
Morphology of boehmite crystals hydrothermally synthesized from gibbsite in metal acetate solutions at 200°C were studied in connection with the chemical species in the hot solutions. In acetate (MAc2) solutions where cations were large-sized, plate-like boehmite crystals were formed (M = Ba, Sr, Ca). On the other hand, columnar crystals were produced in MAc2 solutions where M were comparatively small-sized cations (M = Mg, Mn, Co). It was assumed that when highly stable cationic complexes between metal and acetate ions were absorbed on growing boehmite crystals, they blocked the access of AlO2- and eventually regulated the crystal morphology to from columnar crystals. Formation of not columnar but plate-like boehmite crystals observed in the cases of synthesis in rare-earth acetate (REAc3) solutions was explained in terms of the low blocking ability of electrically neutral REAc3 species resulting from its weak absorption on the crystal surfaces.
Halons (bromo-fluoro-carbons) are known as the material showing both large Ozone Depleting Potential (ODP) and Global Warming Potential (GWP). Appropriate decomposition treatments of waste halons are important for global environment. A dry process to decompose halon is developed. Halon and burnt lime and burnt dolomite (reactants) are heated in electric furnace over the temperature of 800°C. Halon is decomposed and simultaneously reacted with the reactants to generate fluorides and bromides. The reaction mechanism of reactants with halon was invesitigated by means of SEM, XRD, IC, and by measuring specific surface area of the reactants. Burnt dolomite showed higher recovery and conversion effect than that of burnt lime for halon decomposition. Magnesium oxide in burnt dolomite is found to have an important role for effective decomposition of halon.