Glasses in the system Li₂O-MoO₃-WO₃ were prepared by rapid quenching with a twin-roller apparatus. Since the compositions changed during the preparation due to high vapor pressure of MoO₃ and Li₂O, all the specimens were chemically analyzed. Thermal stability of the specimens was evaluated by DTA in terms of glass transition and crystallization temperatures. Electrical conductivities were obtained from impedance measurement between 10Hz and 500kHz. Glasses were produced in the region where the Li₂O content was about 20-40mol%, with slight dependence on MoO₃ and WO₃ contents. Uniform glasses were obtained in the two regions, one in the WO₃-rich side and the other in the MoO₃-rich side. Glass formation with 5-25mol% Al₂O₃ added was also examined. The glass-forming region of these compositions was enlarged in great extent and covered almost all the area comprising less than 45mol% Li₂O. The composition drift due to vaporization was not so serious as far as the composition was within the glass forming region. The glass transition temperature was between 200°C and 350°C and crystallization temperature between 270°C and 390°C, both depending on the composition. An increase in the WO₃ content raised these characteristic temperatures. Glasses were thermally stabilized by the addition of Al₂O₃, as judged from hgiher glass transition and crystallization temperatures. The electrical conductivity in the system Li₂O-MoO₃ WO₃ did not differ too much from that in the binary component systems Li₂O-MoO₃ and Li₂O-WO₃. On the other hand, the addition of Al₂O₃ lowered the conductivity. A possible glass structure of these glasses was also discussed.

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It has been believed for a long time that in the early stage of sintering the shrinkage of the compacts of viscous spherical bodies is directly proportional to the sintering time as first proposed by Frenkel in 1945. A treatment of sintering geometry reveals that the assumption that the length of the shrinkage of each body equals to the radius of the curvature of the “neck” formed at the contact point of two bodies is not correct even in the initial stage of sintering. Therefore, it is concluded that the linear relation between shrinkage and time is not valid.

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The effect of non-stoichiometry on sintering and mechanical properties of titanium carbide TiC_x (x=0.5-0.9) was studied between 773°C and 1396°C. The sintering rate increased markedly with increasing temperature and with decreasing carbon content, x. Sintered specimens with high densities were obtained at 1396°C for 16h for all compositions. The apparent density ranged from 95.6 to 93.3% and decreased with increasing carbon content. Vickers micro-hardness was from 1430 to 2120kg/mm² and increased with increasing carbon content. Bending strength showed a minimum of 31kg/mm² at x=0.7 and increased with both increasing and decreasing carbon contents. The maximum strength of 55.8kg/mm² was obtained at x=0.5. The initial sintering was analyzed to obtain the diffusion coefficients of rate limiting species in sintering. The sintering of titanium carbide was limited by the bulk duffusion of carbon.

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A ceramic composite of silicon nitride reinforced with silicon carbide whisker was fabricated by hot-pressing at 1800°C under 34.3-39.2MPa and its mechanical properties were evaluated. Two dimensional allignment of the whisker perpendicular to the pressing direction was facilitated in the sintering process. The composite had a bending strength of 590-680MPa at a room temperature up to 1300°C, showing that it was degraded only little at 1300°C. The addition of the whisker over 40wt% made it difficult to density the composite, resulting in an decreased porosity of over 10%, which, nevertheless, did not cause a decrease in the strength of the composite. This suggests that the addition of the whisker introduce the controlled defects finely in the composite to prevent the stress-concentration and make the composite insensible to the inner defects or cracks. Statistical analysis gave a Weibull's modulus of 25 for the room temperature strength of the composite, which indicate that the mechanical reliability of the composite was much higher than that of ordinary Si₃N₄ ceramic.

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Synthesized γ-C₂S samples were heated at 800°-1500°C for 10min-48h, and cooled rapidly, in order to study the effect of thermal history on β→γ transformation of pure C₂S. The results obtained were as follows:
(1) β-C₂S/γ-C₂S ratio varies in a complicated way depending on the heating temperature and time.
(2) When samples are heated below 1000°C, β/γ ratio increases with heating time. β/γ ratio should depend on the amount of α' phase produced by γ→α' transformation.
(3) When temperatures are heated between 1000°-1400°C, β/γ ratio is supposed to be determined by the particle size of β-C₂S. The nucleation of γ-C₂S must take place on the surface of β-C₂S, and the amount of γ-C₂S is largest when particle diameter is about several micrometers. The particle growth causes the decrease in β/γ ratio at first, and the increase later.
(4) High β/γ ratios are obtained by heating at 1500°C. Heating time or particle size does not play an important role in this case.

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Silicon carbide (SiC; β-type) plates were prepared by a chemical vapor deposition technique using SiCl₄, C₃H₈ and H₂ as source gases under the following conditions: deposition temperature (T_dep); 1300°-1800°C, total gas pressure (P_tot); 30-760Torr and C₃H₈ gas flow rate [FR(C₃H₈)]; 10-90cm³/min, and the effects of FR(C₃H₈) on the carbon content, density, crystal structure, surface morphology and deposition rate of the deposits were investigated. β-SiC plates were obtained at FR(C₃H₈) between 10 and 40cm³/min under the above given T_dep-P_tot conditions. The density and carbon content of the β-SiC plates were about 3.2g/cm³ and 30wt%, respectively in agreement with the theoretical values. The surface morphology of the β-SiC plates was faceted pyramid-like at low Ptot and cone-like at high Ptot. The deposition rate of β-SiC increased with increasing FR(C₃H₈) and the maximum deposition rate was 1.4mm/h at T_dep=1600°C, P_tot=30Torr and FR(C₃H₈)=25cm³/min. The activation energy for the β-SiC formation were 12-26 and 10-12kcal/mol at P_tot=30 and 760Torr, respectively. Free carbon deposited together with β-SiC when FR(C₃H₈) exceeded the value between 55 and 70cm³/min. The density of the mixture of β-SiC and C decreased from 3.2 to 2.4g/cm³ as the carbon content increased from 30 to 50wt%, implying that the mixture contained closed-pores.

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The immiscible region in RO-GeO₂ (R=Ba, Sr, Ca, Mg), Bi₂O₃-GeO₂, PbO-GeO₂ and ZnO-GeO₂ bianry germanate systems has been determined by observing the molten state with a microscope by the hot-thermocouple technique, which is capable of heating the sample and measuring the temperature simultaneously. Three typical immiscibilities were observed in these systems. The type (I) is the liquid-liquid separation observed in the systems MgO-GeO₂, ZnO-GeO₂ and CaO-GeO₂. The type (II) is the metastable immiscibility observed in the systems in Bi₂O₃-GeO₂ and PbO-GeO₂, which a binodal curve exists at low temperatures. The type (III), observed in BaO-GeO₂, SrO-GeO₂ and a part of CaO-GeO₂ systems, is the metastable immiscibility which has a binodal curve between liquidus and crystallization temperatures. All binodal curves are represented by the Rowlinson empirical equation reported for silicates and borates. So called non-glass forming range in binary germanate systems corresponded to the phase-separated glass forming range.

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Thermochemical quantities such as the heats of formation and solution of alkali borate cry-stals are assumed to be the sum of the partial molar quantities of the component borate units such as BO₃, RBO₄ and ROBO₂. According to examination of composition dependence of the heats of solution of the alkali borate crystals reported previously (Yogyo-Kyokai-Shi, 84, 62-70 (1976)), the ΔH_f data of the crystals are calculated. The stabilization energy H_stab of an RBO₄ unit relative to an ROBO₂ unit, defined as the heat of decomposition RBO_4/2→ROBO_2/2+H_stab, has been evaluated for several crystals based on roported and calculated heats of formation data. The composition dependence of the fraction N₄ of the four-coordinated boron atoms has been interpreted in terms of H_stab. The B-O bond energies of the RBO₄ units in some crystals have also been calculated, ranging from 130 to 135kcal/mol.

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