Glass of 3CoO⋅Al₂O₃⋅3SiO₂ composition was treated at temperatures ranging from 600° to 1900°C at pressures of 20 to 40kb using a girdle type high pressure apparatus. The glass specimen was placed in a platinum tube heater 3.0mm in diameter and 9.0mm long. The heat treatment temperature was measured by a platinum-alumel thermocouple inserted in the specimen chamber or was estimated from the temperature-heating power input relations at several pressures. The temperature distribution and the pressure gradient in the specimen chamber were measured. Minerals in the treated specimens were identified by the X-ray diffraction method and the microscopic observations. Specimens used for the identification were taken from a layer of 0.5mm thick at the central part of the specimen chamber, in order to minimize the variation of temperature and pressure of the treatment. The maximum deviation of the measured temperatures was ±40°C at 1700°C at 40kb. It decreased with decreases in temperature and pressure to ±20°C at temperatures lower than 1300°C at 20kb. The error in the pressure measurement was estimated to be ±2kb at the maximum.
Cobalt garnet is stable at pressures above 23kb at 1200°C and above 24kb at 1500°C. Below these pressures at the respective temperatures, mixtures of cobalt spinel (CoO⋅Al₂O₃), cobalt olivine (2CoO⋅SiO₂) and quartz were obtained from the glass. Garnet produced at 1400°C at 25kb broke down to spinel, olivine and quartz when it was held at 18 kb at the same temperature. Cobalt garnet melts congruently at 1670°C and 25kb. It seems that the garnet melts incongruently to spinel and liquid at temperatures from 1500°C to 1670°C at pressures lower than 23kb. The slope of melting curve of the garnet is 12°C/kb. At 900°C the glass devitrifies to a mixture of spinet, olivine and quartz even at 25kb, and at 800°C the same mixture was obtained at 30kb.
The lattice constant a₀ of the cobalt garnet (Co₃Al₂Si₃O₁₂) is 14.473±0.008 Å and the refractive index n_D is 1.82±0.01 (25°C). The color of the garnet is bright pink.

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It has been reported that wear of a sapphire single crystal along a plane close to the basal plane is progressed by basal slip and that the wear is obstructed by prismatic dislocations which disturb the basal dislocation motion. Since it appears that dissolved Cr₂O₃ in a α-Al₂O₃ crystal disturbs the dislocation motion, influence of dissolved Cr₂O₃ on wear of α-Al₂O₃ crystals along a plane leant by 5° to the basal plane was experimentally investigated using ruby single crystals dissolving 0-0.9mole% of Cr₂O₃.
The crystals were worn on a rotating mild steel disk at a speed of 0.60m/sec and a load of 0.95kg under water lubrication.
Influences of annealing of the crystals at 1900°C for 6hrs. and of prismatic dislocation density on wear were also investigated. It was found that only the prismatic dislocation density was significant to wear. Lower wear rate was observed on the crystals of higher dislocation density.

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Differing from the previous studies by various investigators, the present research concerns with the formation of hydrated sodium aluminosilicates by the water vapor-solid reactions. Sodium aluminosilicate phases, amorphous or crystalline with nepheline-carnegieite compositions, which were obtained by heating the mixtures, Al₂O₃⋅2SiO₂⋅2H₂O(kaolinite)+aNa₂⋅CO₃(a=1.00-2.00), up to various temperatures below 1300°C, were used as the starting solids. A silver capsule was filled with the starting solid and suspended above the liquid water in a Moley-type autoclave (Fig. 1). The bottom of the capsule was not sealed to allow the water vapor to penetrate into the capsule. The saturated water vapor pressure within the autoclave at 310°C is 100kg/cm². This condition was used throughout the present experiments. Under this condition, the reaction may well be called a hydrothermal metamorphosis.
As compared with the previous studies in which the thermodynamic equilibria are attained in the given homogeneous systems, the reactions in the present experiments start at the interfaces between the water vapor and the solid with a consequence that the reaction products are not necessarily equilibrated under the given experimental conditions. As the result, three sorts of hydrated phases, hydroxy-sodalite, nepheline hydrate I, and species Y (a new phase of the composition, Na₂O⋅Al₂O₃⋅2SiO₂ 1.33-1.5 H₂O, which has not been found in the previous hydrothermal studies), were formed during 1-7 days' run according to the nature of the starting solid phases. Correlations among the starting solids and the resulting hydrates are summarized in Table 2 and Fig. 2. In the table the first three columns stand for the preparation of starting solids and the forth the duration of metamorphosis, the fifth the products under the respective experimental conditions.
During the hydrothermal treatment, grains of the original solids as shown in the electron microphotographs of Figs. 3 (a)-(c), changed to well-shaped crystallites of the hydrates, nepheline hydrate I and species Y, as shown in Figs. 4(a)-(c), except hydroxysodalite which was formed only in massive grains. Considerable amount of water molecules may have been adsorbed on the surface of solid to gelatinize the surface and eventually to recrystallize the solid into the hydrate crystallites. The original structural framework may still be retained to some extent under these conditions. The metastable phase formation in this experiment will be treated from this point of view in a following paper.

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[in Japanese]

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Calculating methods of viscosity for porcelain enamels from the fusion flow test which had been already presented by P. Decker is rather complicated, because those include the inherent value for each frit, i.e., flow point or the maximum flow point which were somewhat hard to preestimate.
Therefore, in order to derive the more convenient experimental formula, the following experiments were carried out.
Several kinds of silicone oils of known viscosity, 3, 000 c. s., 6, 000 c. s., 10, 000 c. s., 30, 000 c. s. and 100, 000 c. s., were fusion flow tested on the glazed wall tile which was kept in 45′ inclination, and the relationship between flow length F, flow time t, and viscosity η was investigated.
As the results of above experiments, exponential function between both F and t, or F and η was obtained, and thus, F=A⋅t^K was derived where A is the mean flow ratio and K is the exponential constant for time.
K was estimated to be 0.453, while A was a function of η, i.e., A=Bη^K′, where B was 310 and K′ was -0.429.
However, after the various flow resistances in fusion flow test was considered, K′ must be corrected to be -0.386, and then
F=310η^-0.386t^0.453
was derived as the calculating formula from the fusion flow test of various kinds of frits.
In order to check the above experimental formula, the fusion flow tests of various frits were run, and the obtained viscosity value from F and t were fairly well coincided with one estimated by the pulling up-sphere type viscometer.

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The granulation and the Forming are very important processes in the fabrication of the ceramic dielectrics. Generally, in the case of dry pressing, the raw powder is mixed with an organic binder and water and then the second particle (i.e. granule) is prepared by a method such as screening or spray drying in order to flow quickly from the hopper into the die cavity. The authors carried out systematic experiments on the effects of the binder influencing upon the electrical and physical properties of the final products and on some factors affecting to the properties of granules.
The results obtained are summarized as follows.
(1) The mechanical strength (S) of the pressed body was measured as a function of the heating temperature (T) from room temperature to the sintering temperature. As a result, it was found that the S-T curve has a minimum point at about 400°C, which corresponds just to the decomposing temperature of the binder and this characteristic is fairly influenced by the quantity of the binder.
(2) By the same method as above, electrical resistivity (ρ) at 150°C versus heating temperature (T) curve was measured with the results that the ρ-T curve has a minimum point at about 1000°C.
It can be interpreted as a resultant curve of two effect, that with highter heating temperature, the contact area between particles is increased and the concentration of the non-reacted ion is decreased accompanying with the soild reaction.
(3) It was clarified that the void remaining inside ceramics was increased by increasing the quantity of the binder and this affected to the breakdown characteristics of the dielectric ceremics.
(4) The experiments on the PZT ceramics containing PbO under a hot-pressing condition were carried out with the results that the organic binder has a considerable reducing action such as separating of metalic Pb.
(5) The fluidity of the granules was correlative to the bulk density for any granules prepared by various conditions. It was concluded that the most important charactor of a well-granulated body is to have a high bulk density, with an exception of the case of dry pressing for a very thin body.

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