The effect of trivalent cation on the properties and structure of the glasses in the system Na₂O-M₂O₃-SiO₂ (M: B, Al, Sc, Cr, Fe, Ga, As, Y, In, Sb, La, Bi) was investigated. Three series of glasses, 30Na₂O⋅5M₂O₃⋅60SiO₂, 30Na₂O⋅10M₂O₃⋅60SiO₂ and 21Na₂O⋅9M₂O₃⋅60SiO₂ were prepared, and their properties such as density, refractive index, thermal expansion, DTA, TG, infrared spectrum and Vickers microhardness were measured. The glasses containing Cr₂O₃ or As₂O₃ couldn't be prepared owing to the phase separation of the components or the volatilization of As₂O₃, respectively.
Thermal expansion coefficient factor, α_M, is calculated from the observed values by Takahashi's equation, α=∑p_Mα_M, where α is the expansion coefficient, α_M is the expansion coefficient factor for MO_x, and p_M is the molar fraction of MO_x. From the curve plotting α_M against the field strength of trivalent cation, it is shown that these cations can be classified into two groups, the first group containing B³⁺, Al³⁺, Ga³⁺ and Fe³⁺ ions, and the second containing Sc³⁺, Y³⁺, In³⁺ and La³⁺ ions. The expansion coefficient of the glass decreases by addition of the second-group-cation, because its α_M is negative or positively small in value owing to the high field strength of the cation.
Vickers microhardness of the glass containing the second-group-cation is larger than that containing the first-group-one.
The above results clearly indicate that the first-group-cations are NWF, and the second-group-ones NWM. The introduction of the second-group-cation, however, tends to strengthen the glass structure because of its high field strength in spite of producing nonbridging oxygens in the network. Sb³⁺ and Bi³⁺ ions belong to neither the first group nor the second one owing to its intermediate effect on the glass properties.

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Cubic polycrystalline ferrites in which {111} planes of the grains preferably orientated to the perpendicular direction to the axis of hot-pressing load were obtained. The plate-like iron oxide powder (Teikoku-kako Co., Ltd., MIO) of which the flat surfaces are made of c-plane were mixed with nickel oxide, manganese oxide and zinc oxide of ordinary powder shape. The slurry of these raw materials was pressed in a mold with many drilled holes in the pistons permitting permeable pressing. In the pressed body, the plate-like iron oxide powder orientated fairly well to the perpendicular direction to the pressing axis. After the green body was hot-pressed at 1200°-1300°C and 300kg/cm² for 30 minutes, the orientation degree f of the grains in the hot-pressed ferrite polycrystal was determined by using (hhh) and (hkl) reflection intensities of X-ray from the outer surface perpendicular to the hot-pressing direction. The orientation degree f of the hot-pressed pellet in both Ni-Zn and Mn-Zn ferrite was only 0.05-0.3, in spite of the fact that the grains in the pellet kept the plate-like shape and the orientation of the iron oxide. After the annealing of the hot-pressed body at a higher temperature than the hot-pressing temperature, f of the grains was remarkably increased. Especially, Mn-Zn ferrite with f higher than 0.8 was easily obtained, probably as the result of the recrystallization grain growth from the stressed grains of plate-like shape in the hot-pressed body to the stress-free ones of equiaxial shape.

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In order to make clear the relation between the stress concentration around a pore and the fracture mechanics, the method of the finite element analysis has been applied to elastic-plastic plain strain problems and calculated the effect of the shape of pores on the stress distribution in hardened cement paste in case of three kinds of pore models.
The stress concentration factor is strongly affected by the shape of pore-tip. The stress concentration factors have been calculated to be approximately three, four and six to the corresponding ellipsoidal pore having one, two and five of long to short radius ratio.
From the results of the calculation after unloading, the residual strain in yielding region around flat ellipsoidal pores having five of long to short radius ratio is about ten times larger than that around spherical pores.
Stress distribution in concrete is also strongly affected by both bonding strength between cement paste and aggregate, and shape of aggregate. Stress distribution is also influenced by the radius of curvature of aggregate normal to the direction of loading, that is, the more the shape of aggregate is flat, the less stress concentration factor becomes. Therefore, it may be effective to set flat ellipsoidal aggregate in array normal to loading in order to obtain high strength concrete.

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The graphitization of furfuryl alchohol condensate mixed with 4.0vol% of carbon fibre was investigated as a function of heat treatment temperature with an aid of optical microscope in polarized light and X-ray diffraction technique.
Lamellar structure considered as graphite has evolved microscopically arranging perpendicular to the direction of compressive stress in optically anisotropic matrix heat treated above 2200°C. The X-ray diffraction profile corresponding to the (004) diffraction of graphite was separated into two components with 2d₍₀₀₄₎≅3.42 and 3.36 Å. Although the first component showed no remarkable change irrespective of the heat treatment temperature, the second component increased its intensity and decreased its spacing nearly to that of graphite, as the heat treatment temperature was raised. The high angle second component corresponded to the lamellar structure. The stress induced in the matrix near the fibre was roughly estimated as below 5kbar by a calculation based on an assumption that the contraction of the condensate was restrained by the presence of the fibre. This value agreed with the pressure graphitizing glassy carbon, as reported. It was then supposed that the activated stage formed by the stress induced on the carbonization would act as a source for the graphitization of the composite at high temperature.

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The optical properties of Eu³⁺ in the system of Na₂O⋅xAl₂O₃⋅2SiO₂ glasses were investigated for x values from 0.0 to 1.2.
The variation of the oscillator strength, intensity ratio, S(⁵D₀-⁷F₂)/S(⁵D₀-⁷F₁), and the broadening of emission line with composition showed a maximum at arround Al/Na=1.0, while the transition energy of the CTB and the decay time constant of the ⁵D₀ state showed a minimum at the same ratio. These results suggest that the Eu-O interaction, the assymetry and the variety of sites associated with Eu³⁺ are the greatest in the vicinity of 1.0.
The discontinuous changes of the structure-sensitive parameters were discussed with respect to the change of glass structure in terms of the increase of AlO₄ tetrahedra and the formation of tri-cluster groups.
The decay time constant showed pronounced decreasing with the increase of Al/Na ratio in the composition range Al/Na≤1.0. It may be regarded from the view point of the estimation of the quantum efficiency of emission from the ⁵D₀ state that the decrease of the constant are largely attributed to the increase of the radiative transition probability due to the increase of coupling of Eu³⁺ with the surrounding.

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The solid solubility of calcium hydroxide in magnesium hydroxide was studied. The samples were prepared by the reaction MgCl₂+Ca(OH)₂→Mg(OH)₂↓+CaCl₂. Milk of calcium hydroxide of 1mol/l was added with vigorous stirring into magnesium chloride aqueous solution of 0.05mol/l. Samples were composed under 0.95, 1.05 and 1.10 of molar ratio of calcium hydroxide to magnesium chloride.
The lattice parameter of magnesium hydroxide measured by X-ray increased with the excess of calcium hydroxide.
It is estimated from the values of lattice parameter that approximately 1mol% of calcium hydroxide is soluble in magnesium hydroxide.

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Initial sintering of alumina was investigated by measuring the isothermal shrinkage of the compacts of spherical alumina particles with the diameter from 3μ to 30μ in the range 1300°C to 1500°C. The data were discussed to compare with the kinetic equations of initial-stage sintering model. The results obtained were summarized as follows:
1) Grain boundary diffusion mechanism was predominantly operative during initial-stage sintering of alumina in the region of the examined temperature.
2) Equation of grain boundary diffusion model could be applied for the shrinkage smaller then 1-1.5%, but could not for the larger one. Furthermore the equation could not be applied to the shrinkage of too long soaking periods, although the shrinkage was smaller than 1-1.5%.
3) Assuming that the grain boundary diffusion was the only mechanism for the sintering of the compacts of spherical alumina, following relation was obtained
b⋅D_gb=10exp[-(130000±15000)/RT]
where b is the width of grain boundary, D_gb, the grain boundary diffusion coefficient, R, the gas constant and T, the absolute temperature.

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This study was concerned with the formation and color development of the spinel solid solution in CoO-MgO-Al₂O₃-Cr₂O₃-Fe₂O₃ system, and its application to colored glazes.
Specimens were prepared by calcining the oxide and hydroxide mixtures at 1400°C for 1hr. The formation of spinel solid solution was examined by X-ray diffraction, the color was discussed by measuring the spectral reflectance and the stability of the spinel in glazes was tested. The results were summarized as follows.
1) Formation of a continuous solid solution was confirmed by X-ray analysis.
2) As the amount of Cr³⁺ increased in MgO-Al₂O₃-Cr₂O₃ system, the color changed from white through pale pinkish beige and grayish yellow to grayish leaf, and the absorption of Cr³⁺ shifted towards red region.
3) An increase of Fe³⁺ in MgO-Al₂O₃Fe₂O₃ system, caused the color to change from white through dull orange yellow to grayish brown.
4) As the amount of Fe³⁺ increased in MgO-Cr₂O₃Fe₂O₃ system, the color changed from grayish leaf through dark grayish red to grayish brown, and when Cr³⁺ and Fe³⁺ coexisted, an additional absorption was observed within a range of 600-700mμ
5) Colors obtained in MgO-Al₂O₃-Cr₂O₃-Fe₂O₃ system, ranged from yellowish brown through brown to dark grayish red.
6) Brilliant hue, so-called cobalt-blue, developed in CoO-MgO-Al₂O₃ system. An increase of Cr³⁺ in CoO-MgO-Al₂O₃-Cr₂O₃ system, yielded the colors ranging greenish blue to blue green so-called peacock.
7) In CoO-MgO-Al₂O₃-Cr₂O₃-Fe₂O₃ system, colors ranging from grayish olive green to dark gray developed, as the amount of Fe³⁺ increased.
8) An increase of Fe³⁺ in CoO-MgO-Cr₂O₃-Fe₂O₃ system, yielded the colors ranging from turquoise through reddish gray to dark gray.
9) Colors ranging from grayish olive to dark purplish gray developed in CoO-MgO-Al₂O₃-Cr₂O₃-Fe₂O₃ system.
10) According to the result of the colored glaze test, these MgO-containing spinels with the composition in Cr³⁺ rich region were stable as a glaze stain.

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