The formation of Si-impregnated surface layer on reaction sintered silicon nitride and oxidation behavior of these impregnated samples were studied with wetting between silicon nitride and liquid silicon. Stable impregnated layers 40-100μm thick were formed by heating silicon blocks on porous silicon nitride sintered disks for 10-15 minutes at 1430-1450°C under 1atm of nitrogen. It was found that these layers were air tight and behaved as excellent protective layers against oxidation in moist air up to 1400°C. Wetting of silicon nitride with liquid silicon was briefly discussed in connection with oxygen partial pressure.

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The distribution of boron contained in small quantities in sea-water and natural magnesia clinkers was determined by α-particle tracks that resulted from ¹⁰B(n, α)⁷Li reaction. Cellulose nitrate film was pressed onto the polished surface of specimens which had been moistened with amyl acetate, then the specimens were irradiated in thermal neutron flux to 10¹⁴n/cm². After the irradiation, the α-track image was developed in the film by etching the film surface. Comparing with α-track analysis, electron probe microanalysis was made on the same position of the same specimen.
As for the sea-water magnesia containing 0.26wt% B₂O₃ and having the CaO/SiO₂ ratio of 0.46, it was found that boron existed around periclase grains together with calcium in a form of matrix. As for the specimens having the C/S ratio of more than 2.5, boron was also distributed at grain boundary, but it was not confirmed owing to background whether boron existed in periclase grain.

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An apparent activation energy for the rearrangement process in the initial stage of sintering was determined in the temperature range from 1400° to 1600°C on vapor phase decomposed alumina.
The slopes of log-log plots for the shrinkage of this alumina were unity. From this result it was concluded that the rearrangement process occurred in the early stage of sintering. The apparent activation energy for the process was 45kcal/mol. This value was far lower than that obtained for various diffusion processes.

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In the temperature range of 1500-1600°C, polycrystalline β-alumina showed brittle fracture in appearance. However, the slip bands in some grains and the cavity-type fracture of the grain boundary showed that plastic deformation occurred even in the temperature range. At 1600-1700°C, the number of the grain disclosing slip band increased, and the deformation of the grains themselves in the polycrystal was also observed. Above 1700°C, especially 1800°C, the ductile deformation of polycrystalline β-alumina was possible without grain boundary fracture. The grains, in the temperature range, deformed easily by the slip resulting from the dislocation movement on c-plane accompanying the grain boundary slip, and the grain-shape changed to the elongated one. This deformation gave a possibility making the polycrystalline β-alumina in which c-plane of the grains orientated perpendicularly to the press forging direction.

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The thermal conductivity of refractory bricks with a high thermal conductivity was measured by the hot wire method. So far a sufficiently large specimen was used, a linear relation was obtained between the heat source temperature (θ) and the logarithm of time (logt) for high conductive materials such as a dense magnesia brick. The thermal conductivity values which were obtained from the linear relation were accurate within ±4% from the mean value.
However, the length of the linear portion in θ-logt plot decreased with decreasing specimen size, and it gave a large error in the result. That is, it became more than ±17% when a cylindrical specimen of a diameter about 70mm was used.
By adjusting the nonlinear portion in θ-logt at the beginning of the measurement with the time t₀ which was obtained by ∂t/∂θ-t plot, the length of the linear portion could be made longer and the error was decreased below the permitted limit in the practical measurement.
With application of this adjustment, thermal conductivities of magnesia, carbon and silicon carbide bricks were measured up to 1200°C. The thermal conductivities of these bricks decreased as the temperature rises.

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The preparation of finely-divided alumina by vapor phase reaction between aluminum tribromide and oxygen was investigated at 950° to 1200°C, with an emphasis on the effects of the reaction conditions on the particle size distribution of the products. The results were as follows:
1) The reaction products were amorphous at 950°C and were δ- or γ-Al₂O₃ at 1100° and 1200°C. Products were spherical and non-porous particles with the diameter of 350 to 3000Å. The particle size decreased with the increase in temperature and with the decrease of [AlBr₃]. When [AlBr₃]≅4.5%, the particle size increased with the increase of [O₂]. When [AlBr₃]≅1%, the particle size was minimum at about [O₂]=32%. By controlling these three factors, ultrafine alumina powders with a controlled particle-size distribution were prepared by the vapor phase oxygenolysis of aluminum trihalides.
2) In contrast with AlCl₃-O₂ system, alumina powders obtained from AlBr₃-O₂ system. The concentration of oxygen influenced Predominantly on the bromine content which was 7-16wt% at [O₂]≥32% and was less than 2.5wt% at [O₂]<8%. A heat treatment above 1100°C was required to remove bromine.

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[in Japanese]

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The effect of V₂O₅ additive on the sintering of SnO₂ was studied by measuring relative density and isothermal shrinkage in the temperature range 800 to 1400°C. The optimum amount of V₂O₅ added was 10wt%, which might be the solid solubility limit of vanadium ion into SnO₂ lattice. With this amount of V₂O₅, the shrinkage behavior agreed with a model based on liquid-phase sintering at lower temperature. At higher temperature above 1250°C, the major parts of the densification occurred very rapidly and was followed by a much slower sintering process typical of volume diffussion. The fast early shrinkage might be caused by the capillary forces of liquid and the rapid formation of solid solution.
Grain growth followed the expression G³-G₀³=At with an apparent activation energy of 104kcal/mol. The volume diffusion of oxygen ion was rate determining step for grain growth in this experiment.

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Some compounds in the ternary system Li₂O-B₂O₃-H₂O were synthesized, e.g. LBH₁₆ (L: Li₂O, B: B₂O₃, H: H₂O), LBH₄, LB₂H₃, LB₅H₁₀ etc. Each compound was confirmed to be single phase by means of chemical analysis, DTA, TGA and X-ray diffraction.
The compound LBH₁₆ is hexagonal with the lattice parameter a₀=5.70 and c₀=6.20Å. The diffraction data of “LBH₁₆” (Powder Diffraction File No. 16-286) did not coincide with those of the synthesized LBH₁₆, and should be attributed to LBH₄ contaminated with a small amounts of LB₂H₃. The diffraction data of synthesized LBH₄ were not consistent with those of “LBH₄” (File No. 16-312), and practically agreed with those of LBH₄ reported by Sastry and Hummel [J. Am. Ceram. Soc. 41, 7 (1958)].
Instead of “LBH” (File No. 16-198), LBH_x with variable x smaller than 1 was obtained through dehydration of LBH₄. The crystal structure of this compound is considered to remain unchanged within a certain range of water content.
The diffraction data of the synthesized LB₂H₃ agreed approximately with those of “LB₂H₄” (File No. 16-313) and “LB₂H₅” (File No. 1-0112), and those of LB₂H₃ reported Bouaziz [Bull. Soc. Chem. (France) 2, 1451 (1962)] were in rough agreement with the data of LB₂H_x which was obtained in the course of dehydration process of the synthesized LB₂H₃.

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