The optical absorption spectra of VO²⁺ ions dissolved in K₂O-MO-B₂O₃ glasses (M=Ca, Sr and Ba) have been measured in order to examine the behavior of π-electrons in the glass network. By using the spectral results, the behavior of Ca, Sr and Ba in the glasses has been discussed. Judging from the dependence of the peak position for B₂*-E_π* transition on the glass composition, it has been suggested that although Ca, Sr and Ba behave as network modifiers in the glasses, a part of each element contributes to the formation of glass network. It has been also suggested that, in going from Ca to Ba, the ability of these elements as network former becomes weak.

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Diffusion behavior and electrolytic reduction of Ni²⁺ ions were investigated by constant current voltammetry (chronopotentiometry) in three series of molten alkaline earth borate glasses, CaO-B₂O₃, SrO-B₂O₃ and BaO-B₂O₃ in the temperature range 880° to 1350°C.
Ni₂₊ ions were reduced reversibly to metallic states with 2-electrons process in the respective alkaline earth borate glasses by using platinum electrodes. It was shown that the transport by diffusion of Ni₂₊ ions toward the electrode surface was the rate determining step in the overall electrode reaction.
The isothermal diffusion coefficient of Ni₂₊ ions increased with increasing concentration of alkaline earth oxide. In each case of Arrhenius plots of the diffusion coefficients, there was apparent curvature indicating departure from Arrhenius behavior. This curvature, however, could be divided approximately into two linear parts.
It was shown that the diffusion coefficient of Ni₂₊ ions did not apparently correlate with the pre-exponential term in Arrhenius equation, but depended upon the activation energy.
The activation energy for diffusion of Ni₂₊ ions decreased with the order BaO>SrO>CaO at corresponding concentration of alkaline earth oxide. This fact may be explained as follows: The interaction between Ni₂₊ and oxygen ions becomes relatively weaker with increasing the ion-oxygen attraction of alkaline earth ions.
The activation energy for electric conduction in BaO-B₂O₃ measured by Shartsis et al. was somewhat smaller than the value for diffusion of Ni₂₊ ions, and the composition dependence of both cases had same inclination. However, the activation energy for viscous flow showed opposite composition dependence to the previous two cases.
The diffusion coefficient of alkaline earth ions calculated by Nernst-Einstein equation by assuming correlation factor to be 0.6 was in almost same order as the value of Ni₂₊ ions in the respective alkaline earth borate glasses. It may be concluded that Ni₂₊ ions play the almost same roles as alkaline earth ions in the molten glasses.
The diffusion coefficient of Ni₂₊ ions decreased with increasing the total number of oxygen ions per unit volume in the base glasses.

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The formation mechanism and kinetics of zirconium nitride were studied by reducing ZrO₂ with C in flowing N₂ gas at temperatures between 1300° and 1600°C for 0 to 16h.
Increase in the ratio C/ZrO₂ promoted the formation of zirconium nitride. Nitridation of ZrO₂ began at 1350°C. As the intermediate phases, stable tetragonal ZrO₂ and cubic ZrC_1-xN_x were obtained.
The rate of formation of Zirconium nitride followed the first-order rate equation and the apparent activation energy was 64.7kcal/mol.
As the intermediate phases, zirconium carbide and zirconium oxynitrides (β-Zr₇O₁₁N₂, β-Zr₇O₈N₄ and γ-Zr₂ON₂) were not identified.
It is difficult to synthesis pure zirconium nitride in the temperature range of this work.

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The peresent study was performed in order to clarify deformation-fracture behavior for several kinds of refractories in relation to acoustic emission characteristics under three-point bending. Effects of microstructural changes of refractories on acoustic emission characteristics were also studied.
For normal refractories, elastic waves were detected at lower stress level and the rate of acoustic emission increased with increasing stress and it increased exponentially at the stress level above 70-80% of fracture stress. On the other hand, for relatively dense materials, only small number of acoustic emission were detected up to the point of fracture stress. Although each refractory material exhibited different acoustic emission chracteristics or different microfracture behavior corresponding to the difference in microstructure, the deformation process to fracture of each refractory consisted of four common stages macroscopically.
For most refractories, Kaiser effect was clearly recognized at lower stress level, but it was not valid at higher stress level and for specimens containing unstable cracks in them.
The existence of surface flaw and lamination in refractories could be detected as the changes of acoustic emission characteristics during three-point bending. This indicates that it may be possible to detect cracks in refractory materials nondestructively by using acoustic emission technique.

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Isothermal shrinkage of β-SiC compacts with 1 wt% of B and of C was measured with a high-temperature dilatometer at a given temperature of 1700° to 1900°C in pure helium. And also, compacts of pure, 1 wt% C-doped and 1 wt% B+1 wt% C-doped β-SiC were fired and then the microstructures of the fired compacts were observed with a scanning electron microscope, in order to study the influence of additives on coarsening of β-SiC particles.
The results obtained were as follows:
(1) Coarsening of β-SiC particles was inhibited in the case of carbon addition only, but no densification took place unless boron was added.
(2) This fact suggested that densification of the β-SiC compact could not be led unless additives contributed directly to material transport, no matter how great a driving force was held at high temperature.
(3) Initial sintering of β-SiC with concurrent B and C additions proceeded by a mechanism that shrinkage was proportional to 1/3 power of time. Activation energy for the mechanism was obtained as 200±29 kcal/mol.
(4) Results obtained were reasonably interpreted by considering the following densification model: additives existed as the boundary phase at the grain boundary between β-SiC particles, and so densification was initially rate-controlled by diffusion of Si (or C) atom through the boundary phase from the grain boundary to the neck surface, resulting from the difference between the solid solubility of β-SiC into the boundary phase at the grain boundary and that into the additives at the neck surface.

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The vapor phase growth of β-SiC whiskers from gaseous species evolved by the reaction of fluorosilicate melts with carbon has been studied at elevated temperature. NaF, Na₂SiF₆ and Na₃AlF₆ were used as fluoride. The fibrous crystals produced were identified as β-SiC by X-ray diffraction method and also as single crystals, whiskers, by electron diffraction method and electron microscopic observation. The whiskers grew in length of 3-5mm with good yield under the following conditions: the molar ratio of SiO₂ to NaF component in the melts was about unity, the temperature range was from 1350°C to 1400°C, and the period of the reaction was ranging 1 to 4h in these experimental runs.
As previously suggested, SiO was thought as an intermediate species on the reaction in the present work. The evolution of SiO gas might be promoted with that of SiF₄ gas. The SiF₄ gas should have evolved above atmospheric pressure from inside of the melt under the condition, in which molar ratio of SiO₂/NaF was about unity. The whiskers, on which small spheres of silicate attached like beads, often appeared. The beads-like whiskers could be formed by the reaction, 3SiO+CO=SiC+SiO₂. On the other hand, it was deduced that normal whiskers grew with the reaction, SiO+3CO=SiC+2CO₂. The results obtained have been discussed in detail from thermochemical data.

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The structure of Li₂O⋅SiO₂ glass has been determined by the pair-function analysis of the radial distribution function (RDF). The glass sample was prepared by quenching the melt on a platinum ring with ice-water. X-ray scattering intensity of the glass was measured by use of an instrument with a rotating target of the capacity of 50kV-100mA. MoKα radiation was monochromatized with a graphite monochromator and balanced filters. The RDF was calculated after the correction (Fig. 3). The structure of this glass has been studied and several structural models have been proposed by investigators. In this study many structural models with single chain, branched chain and 3-6 membered ring structures were constructed. First, adequacy of each model was evaluated from the fitness of calculated and observed densities, and from the principle of parsimony proposed by L. Pauling. After this selection, RDFs were calculated for the models remained. As a result, it was proved that the structural model was most suitable, which consisted of the single chains of the SiO₄ tetrahedra, as in the case of the crystal (Fig. 4). The RDFs, the summation of the pair-functions of the model, were compared with the observed RDF with varying the structural parameters (Fig. 7). It was proved from this that the chain bended in 0-8° in zigzag in the same direction as in the crystal or in the direction perpendicular to the former (Fig. 6). This bending angle was much less than the one of the crystal (24.8°). It was found that the Li⁺ ion could not be surrounded by two non-bridging oxygen atoms but by a non-bridging and a bridging ones of the same chain and two non-bridging ones of other chains, which is different from the case of K⁺ ion in the K₂O⋅SiO₂ glass. The introduction of the disorders based on the statistical distribution and the structural characteristics, e.g., flexibility of the chains or changeability of the relative positions of the chains, improved the agreement of the calculated RDF with the observed one satisfactorily (Figs. 10 and 11).

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The corrosion of soda-lime-silica glass bottle by alcoholic solution and the formation of solid reaction products in the solution have been studied.
Neutral or slightly alkaline water and 33 per cent ethyl alcohol solution were heated in the glass bottle keeping the temperatre below the boiling point of ethyl alcohol. Na, Ca and Si ions dissolved from the glass were determined and the process of the formation of the solid products was discussed.
The following conclusions were drawn:
(1) The amounts of the ions extracted from the glass by alcoholic solution are less than those by water. The extent of corrosion of glass by water can be reduced by the addition of alcohol.
(2) Alcoholic solution has a marked tendency to form the solid products such as a precipitate or turbidity consisting of fine and white amorphous particles. This can be accounted for by the poor solubility of calcium silicate compounds, formed in the reaction of the glass with water in alcoholic solution.
(3) It dose not appear that the flakes (spicules) is more easily formed in alcoholic solution than in water.

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The phase transitions of Ca₂SiO₄ have been investigated by the precession camera with a high temperature apparatus. The topotaxial relations are maintained through the phase transitions among the modifications of Ca₂SiO₄. The results obtained are summarized as follows:
(1) For γ→α′_L transition, a_γ//a_α′L, b_γ//b_α′L, c_γ//c_α′L.
(2) For α′_L→α′_H transition, a_α′L//a_α′H, b_α′L//b_α′H, c_α′L//c_α′H. The intensities of the superstructure reflections of α′_L-phase decrease with increasing temperature during the α′_L→α′_H transition.
(3) For α′_L→β transition, a_α′L//a*_β, b_α′L//c_β, c_α′L//b_β. (100) twin is often observed in the β-phase crystal formed by the α′_L→β transition.
(4) For β→γ transition, a*_β//a_γ, b_β//c_γ, c_β//b_γ.
On the basis of the topotaxial relations through the phase transitions and the crystal structures of the modifications of Ca₂SiO₄, the mechanisms of the phase transitions of Ca₂SiO₄ have been discussed in terms of the movements of atoms during the transitions.

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Hot-pressed Si₃N₄ were prepared from two kinds of commercial Si₃N₄ with addition of Y₂O₃ and Al₂O₃. Oxidation behavior of hot-pressed Si₃N₄ bodies were investigated in pure dry oxygen at 1200° and 1300°C, at several steps up to 30 days.
Results of the weight gain, X-ray diffraction analysis, EPMA analysis and SEM observations on the oxidized layer are discussed in relation to the mechanism of oxidation.

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To investigate the influence of the intergranular phase on high temperature strength, two kinds of β-sialon were hot-pressed, (i) “balanced” β-sialon (B-sialon) for which starting powders were mixed so as to adjust the composition into Si₄Al₂O₂N₆ by considering the amount of oxides on nitrides and alumina contamination during ball milling, and (ii) “as-mixed” β-sialon (A-sialon) for which the powders were mixed without the consideration.
The bending strength of A- and B-sialon was measured at room temperature and high temperature up to 1400°C. The strength of A-sialon at room temperature was 48kg/mm² and decreased with temperature to 37kg/mm² at 1400°C. On the other hand, the strength of B-sialon was 44kg/mm² at room temperature and retained up to 1300°C. The strength was slightly decreased to 41kg/mm² at 1400°C.
The presence of intergranular X-phase in A-sialon was detected by means of transmission electron microscopy and thermal expansion measurements. The amount of X-phase in A-sialon and B-sialon was about 3vol% and negligibly small, respectively. The strength degradation of A-sialon at high temperatures was attributed to the presence of larger amount of intergranular phase than B-sialon.
The observation of fractured surfaces revealed that fractures initiated at surface flaws and large particles which are related to the inhomogeneity in sintered materials. The fracture propagated transgranular at room temperature, and both transgranular and intergranular at high temperatures.
The results showed that “balancing” the composition was useful to improve high temperature strength.

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