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[in Japanese]

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In order to produce the slaking resistant calcia clinker, the additives of FeO-TiO₂ system as a preventing agent against slaking have been studied. The results obtained are summarized as follows. It was recognized that optimum composition of the additives of FeO-TiO₂ system effective for preventing against slaking had a tendency to remove to the TiO₂ rich side in relation to increase of SiO₂ content in the limestone as a raw material of calcia clinker.
Moreover, it was observed that SiO₂, contained as an impurity in the limestone and the preventing agent against slaking, formed a high melting crystal matrix consisting with 2 CaO⋅SiO₂, 3 CaO⋅SiO₂ and prevented the grain growth of CaO crystals when these mixtures were burnt.
As a result, the increase of SiO₂ content in the calcia clinker showed a deterious effect against slaking resistance.
Best slaking resistant clinker in this study was obtained by adding about 5% iron oxide to the limestone containing 0.3-0.4% SiO₂.

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The vaporization behavior of multicomponent commercial refractories composed mainly of the system MgO-Al₂O₃-Cr₂O₃ was studied at 1600°C in vacuum It is found that the least volatile component in refractories, i.e., Al₂O₃, CaTiO₃ or Mg (Al_1-xCr_x) ₂O₄, remained on the surface and made a non-volatile stable surface layer which disturbed diffusion of the more volatile components.
The vaporization rate of MgAlCrO₄ spinel increased with increasing amount of additives, most pronounced with CaO followed by Fe₂O₃ and SiO₂. Effect of CaO was explained by the formation of a volatile compound 8CaO⋅6Al₂O₃⋅2CrO₃.

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Monolithic non-crystalline silica was produced by heating the gelled mass of Si (OC₂H₅)₄ hydrolyzed with H₂O. The Structure and properties of obtained material were compared with those of fused silica. A broad absorption band ranging from 3700 to 2700cm^-1 was observed in the infrared spectrum of the sample heated at a temperature below 500°C. This broad band was resolved into four absorption bands with peaks at 3650, 3600, 3400 and 3200cm^-1, respectively, which were all related to Si-OH bonds. The intensity of these absorption bands decreased with the heating temperature. The bands with peaks at 3400 and 3200cm^-1 which were ascribed to surface hydroxyl groups were especially sensitive to the temperature and disappeared in the range 600°-800°C. The gelled mass abruptly decreased its surface area at the temperature corresponding to disappearance of absorption bands at 3400 and 3200cm^-1 and transferred to the pore free material. Vickers hardness also increased abruptly at the similar temperature approaching nearly the same value as that of fused silica with heating temperature.
In the obtained material by the heat treatment above 600°-800°C, the intensity of small angle X-ray scattering was not pronounced and the positions of absorption bands due to OH bonds agreed with those of fused silica. Density and refractive index were comparable with those of fused silica, though water content was a little more than in fused silica.

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Na-β-alumina is important for industrial uses as refractories for grass tank furnace and as solid electrolyte, and is also very interesting material with anisotropic properties caused from its characteristic layer crystal structure. In this report Na-K ion exchange rates of sintered polycrystalline body (12mmφ and 97% density) of β-alumina solid solution (Na₂O⋅9.23 Al₂O₃) in NaNO₃-KNO₃ melts were measured at 280°-440°C by determining weight changes. The exchange rate obtained in all experiments was proportional to (time) ^1/2 indicating a process controlled by counter diffusion of Na or K ion in the body, and its rate constant is proportional to the diffusion constant.
For the exchange of Na-β or K-β in the NaNO₃-KNO₃ melt, the diffusion coefficients decreased with increasing contents of Na or K from 10^-6-10^-7 to 10^-7-10^-8cm²/s and its activation energy increased to 10-13kcal/mol from 4-5kcal/mol for single crystals. This situation corresponds to the so called mixed alkali-effect. In the case of exchange of mixed Na-K β-alumina in the NaNO₃ or KNO₃ melt, the preceding effect was also found indicating the minimum diffusion at intermediate compositions. In the exchange of Na-β in the NaNO₃-KNO₃ melt with compositions larger than 50 at% of K and also in the exchange of Na-K-β containing less than 50 at% of K in the pure KNO₃ melt, the sintered bodies disintegrated because of an expansion effect of diffused K.
The concentration profiles of Na or K in the exchanged bodies were measured by EPMA, from which the diffusion coefficients by Matano were obtained for the various compositions of Na-K-β alumina. For example, diffusion layers of 100-1000μm were observed in the exchange of 300°-400°C for 10-13min.

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Single crystals of γ_II-Li₂ZnSiO₄ were grown from Li₂MoO₄ and Li₂WO₄ solvents by the slow cooling flux method. The growth experiments were accomplished at the soaking temperatures of 1270°-1420°C and the cooling rates of 3.3°-7.0°C/h. Zn₂SiO₄ was more suitable as a starting material for the crystal growth than Li₂ZnSiO₄ and a mixture of Zn₂SiO₄ and SiO₂. During soaking period, crystals of the composition, Li₂ZnSiO₄, were produced by reaction of Zn₂SiO₄ and the flux of Li₂MoO₄ as follows:
Zn₂SiO₄+Li₂MoO₄→Li₂ZnSiO₄+ZnO+MnO₃
The grown crystals up to 3mm across were obtained generally as mixtures of transparent and translucent ones. Many transparent γ_II-Li₂ZnSiO₄ crystals, which were stable above 961°C, were obtained when the soaking temperature was below 1368°C. The translucent crystals were found to contain imperfections of many fine cracks which were induced by volume shrinkage of 1.9% due to transformation of small or large part of primarily-grown γ_II-Li₂ZnSiO₄ crystals to β_II-phase below 961°C during slow cooling. The platy and granular γ_II-Li₂ZnSiO₄ crystals were sometimes well-faceted and surrounded by (010), (120) and (101) faces.
Space group P2₁/n, Z=4 and density 3.41 for γ_II-Li₂ZnSiO₄ crystal were determined. Its monoclinic lattice constants are a₀=6.2823, b₀=10.626, c₀=5.0327(Å) and β=90.49°. The orthorhombic lattice constants for β_II-Li₂ZnSiO₄ are a₀=6.2592, b₀=10.626 and c₀=4.9529(Å).

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The chemical corrosion of a glass by alkaline solutions has been studied using a 15.5Na₂O-12.5CaO-72.0 SiO₂ (wt%) glass. LiOH, NaOH, RbOH, NH₄OH and N(CH₃)₄OH were employed as alkaline solutions of univalent cations and Ca(OH)₂, Sr(OH)₂ and Ba(OH)₂, as alkaline solutions of divalent cations and the corrosion was examined not only by single alkaline solutions but also by mixed two alkaline solutions. All the alkaline solutions were adjusted to the same pH value by a pH meter. A half surface of each glass plate was coated with an organic paint (vinylose) and then the plates were immersed in each alkaline solution at a constant temperature. After a definite time of corrosion the corroded depth in the uncoated surface was determined by multiple-beam interferometry.
In the corrosion by single alkaline solutions the corroded depth was found to be different depending upon the kind of cation in alkaline solution despite the same pH value of all the alkaline solutions, suggesting that the concentration of OH^- ion alone is not a corrosion-governing factor. The corroded depth decreases in the order Ba(OH)₂, Sr(OH)₂, NH₄OH, RbOH, NaOH, LiOH, N(CH₃)₄OH and Ca(OH)₂. The magnitude that cations enhance corrosion reactions was found to be closely related to the ability of adsorption on glass surface, the activity coefficient and the hydration number of a cation.
The process of corrosion reaction by alkaline solutions is deduced to proceed by the following three steps: (1) Cations in the alkaline solutions are adsorbed by glass surface, (2) OH^- ions are brought on the glass surface together with the cations and attack the silica net work, producing silicate ions and (3) the silicate ions react the cations adsorbed on the glass surface to produce the corresponding salts and then the salts dissolve in the alkaline solutions. The small magnitude of corrosion by a Ca(OH)₂ solution may be attributed to a small solubility of calcium silicates produced on glass surface in step (3) because the calcium silicates act as a protective film against corrosion.
In the corrosion by mixed two alkaline solutions the relative difference in the ability of adsorption between the two cations may be regarded as a dominant factor determining the characteristic of corrosion.

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