The green bodies of the oxide cermets containing NiO or Fe₂O₃ were sintered in a hydrogen furnace in which these metal oxide components were reduced to their respective metals.
The particle size of these reduced metals at the lower temperature stage of sintering was expremely small, therefore the strength of the cermets obtained was high. The shrinkage in sintering was, however, a little higher than that of the ordinary cermets in which metal components are added.
The sintering temperature for oxide cermets containing nickel was always around 1670°C for various contents of metal, while that for those containing iron decreased as the content of iron was increased, namely, 1550°C for 30% iron content. Also similar results were obtained in the cases of the other oxide cermets studied, and it is suggested that the properties of the boundary of oxide-to-metal in the oxide cermet are very different between the respective cermets containing nickel and iron metal.
The microstructures of oxide cermets containing 0-70 percent metals revealed that the oxide phase was continuous while the metal phase was discontinuous. Therefore, the properties of cermets are thought to be determined chiefly by the properties of their oxide phase. Thus the superiority of the cermets of alumina series among the oxide cermets studied for the mechanical strength as well as the thermal shock resistance was explained.
Althongh the crystal size in oxide phase of the cermet is much smaller than that of pure oxide body, the size of metal particles in the 30% metal-containing cermet is about 10μ, and in the case of 70% metal-containing cermet, larger grogs of metal are present in nickel cermet, and metal particles gathered into long strings are found in iron cermet. Investigations on the broken samples of cermets showed that the breaks took place at these boundaries, and that for nickel cermet, these boundaries were especially weak.

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In order to study some of the fundamental properties of porous body hydration products of plaster of Paris whose porosities were ranging from 45 to 88%, were prepared, and their properties were measured.
The results obtained were summarized as follows:
(1) The modulus of rupture of porous bodies was decreased exponentially with increase of porosity, but in the range of porosity higher than 70%, this was decreased more markedly (Figs. 3 and 4).
(2) Dielectric constants in the direction of c axis, (100), and (010) of crystal from Yamagata district were measured at 20 Mc and found to be 8.7, 5.1 and 4.9, respectively.
(3) Dielectric constants of the porous bodies were decreased directly with increase of their porosities (Fig. 6), and these relationship was formulated as follows:
K′=K₀(1-x)+K_p(x)
where, K′: apparent dielectric constant of the porous body, K₀: mean dielectric constant of solid phases composed of the body, K_p; dielectric constant of gas, mostly air, included in the pores, and x: volume ratio of pore in the body.
(4) Permeability of the body was decreased with increase of the porosity. When the square root of permeability and the cubic root of porosity are chosen as ordinate and abscissa, the relationship can be represented by a set of straight lines knicking at a point corresponding to the porosity of 70% (Fig. 9).
(5) From the relationship between the size of deposited crystals and stirring time (Fig. 11), process of the crystal growth was inferred as follows: the crystals formed in the earlier stage of mixing the solution of plaster of Paris and water, grew markedley in the direction of c axis, but after the stirring of 4 or 5 minutes, growth in this direction was distinguishedly diminished, while growth in the direction of a and b axes, especially in a axis, was gradually increased. This change of directional predominance of crystal growth affected the structure of cast bodies, and consequently, on their physical properties, e.g., the modulus of rupture or the permeability, as described above.

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The ν-value of the glass containing TiO₂, for example TiO₂-KF-SiO₂ and TiO₂-K₂O-SiO₂ glasses, was found to be decreased by annealing, while the ν-values of other glasses are generally constant or increased. The absorption in the ultra-violet region of this glass tends to shift towards the longer wave-length side and become broader by annealing, as expected from the Drude-Voigt dispersion formula. Abnormal change of the ν-value of the glass containing TiO₂ by annealing is probably attributed to the shift of the absorption towards the longer wave-length side in the ultra-violet region. The displacement of the absorption in the ultra-violet region towards the longer wave-length side is seemed to be due to the loosening of the electron around the anion which comes from the stronger interaction between cation and anion by annealing. This explanation is supported by the fact that the molecular refraction of this glass is increased by annealing.

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