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| 1.
論文 |
論文
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土成, 昭弘 ; 保木井, 利之 ; 下林, 修 ; 金岡, 千嘉男
概要:
Changes in the structure and permeability of porous magnesia ceramic with a TiO_2-Al_2O_3 matrix with a TiO_21Al_2O_3 molar ratio of 0.96 were studied at different matrix contents. The shape of pores became complicated and pores
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tended to have fractal nature as the matrix content increased. It was proposed that the change of pore shape was caused by the increase in the amount of the matrix and its reaction with MgO grains. Both mean pore diameter and permeability showed a maximum at a matrix content, 10 wt% and 15%, respectively. On the other hand, the fractal dimension of pore shape changed from 1.39 at 5 wt% to 1.65 at 20 wt% of matrix. The fractal dimension changed sharply between 10-15 wt%. The permeability was found to agree well with that of a nonspherical particle system by using pore size modified by the its fractal dimension.
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| 2.
論文 |
論文
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土成, 昭弘 ; 保木井, 利之 ; 平木, 外二 ; 金岡, 千嘉男
概要:
Properties of permeable magnesia refractory containing titania and alumina powder in the matrix were investigated in order to produce permeable refractory with high thermal shock resistance, corrosion resistance and low penetration of
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molten steel. By adding titania and alumina powder in the matrix, bright glossy portion and dark glossy portion were observed in the matrix and in the grain boundary of magnesia. Bright glossy portion was CaTiO_3 (Perovskite) from X-ray diffraction and EPMA analyses. Dark glossy portion was suspected to be Al_2TiO_5 (Aluminum Titanate) from EPMA analyses although Al_2TiO_5 was not detected by X-ray diffraction. The collapse of magnesia grains was caused by the generation of CaTiO_3 and Al_2TiO_5 in the magnesia grain boundary. Apparent porosity, mean; pore diameter and permeability became high and large as TiO_2/Al_2O_3 molar ratio decreased, and reached the maximum value at the equivalent molar ratio. However, above the equivalent molar ratio the values became low and small. Permeability was proportional to the product of apparent porosity and the square of average pore diameter. Thermal shock resistance increased twice compared with no addition of TiO_2/Al_2O_3. Although corrosion resistance deteriorated by adding TiO_2/Al_2O_3, it was superior to the conventional porous alumina refractory. Penetration thickness of molten steel was not dependent on TiO_2/Al_2O_3 addition, and was very small compared with conventional one. This permeable magnesia refractory will have a good possibility of being used on actual operation.
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