Molybdenum disilicide has recently been developed as an excellent heating element of high refractoriness and of high oxidation resistivity. The binary system of MoSi₂-ZrO₂ was studied for the purpose of improving the too low electrical resistivity of MoSi₂ without changing the other favorable characteristics.
ZrO₂ used was previously stabilized by dissolving 10 mol % of Y₂O₃ at 1600°C. Samples of six different chemical compositions differing from each other by 20% in ZrO₂ content, were formed under the pressure of 6ton/cm² and sintered at five different temperatures between 1300° and 1650°C in H₂ gas.
The electrical resistivity, density and modulus of rupture were measured on sintered specimens and expressed as functions of sintering temperature, chemical composition and sintering time.
The density becomes minimum at about 60% of ZrO₂ content and the modulus of rupture varies approximately with the density.
The electrical resistivity at a room temperature increases rapidly with the amount of ZrO₂ above 60%. The change of the electrical resistivity was also investigated up to the surface temperature of 1700°C. The resistivity increases with temperature on the MoSi₂ side, while decreases on the ZrO₂ side.
The thermal shock test by repeated rapid heating and cooling between a room temperature and 1400°C, showed that the samples of the medium composition had the least thermal shock resistance.

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As part of the investigation of the system SiO₂-Al₂O₃-P₂O₅, solid solution of SiO₂ and AlPO₄, both of cristobalite structure, was studied.
At first it was confirmed that AlPO₄ can be formed from Al(OH)₃ and H₃PO₄ by mixing and drying at 110°C. Specimens of the SiO₂-AlPO₄ system were prepared from mixtures of various mole ratios of Al(OH)₃, SiO₂ gel and H₃PO₄, dried and stored overnight at 110°C. After formed into tablets, the mixtures were heated at 1450°C for 2 hours.
Crystals of tetragonal cristobalite structure were obtained which were determined to be of homogeneous phase by X-ray diffraction, D. T. A., microscopic observation and chemical analysis, and it was confirmed that AlPO₄ and SiO₂ were solid-soluble in any proportions at a high temperature.
When increasing the amount of the substitution, the crystal structure became so disturbed that only the diffraction from (101) plane was able to be observed and the others diminished. D. T. A. peaks of α-β inversion (tetragonal-cubic inversion) which appeared sharp at the end members, became also feeble and broad and shifted toward low temperature.
Refractive indices by microscopic observation changed gradually with the composition of solid solutions, and at the same composition the value varied place to place in some small range, showing that the solid reaction did not proceed perfectly homogeneously.

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Properties of glasses in the system Li₂O-PbO-B₂O₃ have been investigated for the application as radiation shielding material. This system is selected because of large cross section of boron for neutron, high absorption property of lead for gamma ray and favorable property of lithium in respect of secondary gamma ray.
The glass formation range determined in this system was fairly wide and twelve samples were prepared in this region. Measurements were made on thermal expansion coefficients, incipient softening points and densities, which gave the values of 6-15×10^-6cm/cm°C, 300-500°C and 2-7.5g/cm³ respectively. Differential thermal analysis indicated very strong exothermal peaks owing to crystallization of glasses, which was proved by X-ray diffractions.
Radiation shielding characteristics were showed by linear absorption coefficients for gamma ray and macroscopic total cross sections for thermal neutrons (2200m/sec) calculated from known nuclear data, compositions and densities which were determined in the experiment, and were compared with those of commercial X-ray absorbing glass and neutron absorbing glass. As a result, glasses of this system were confirmed to have considerable radiation shielding abilities for gamma ray and neutrons. A defect of glasses in this system is low chemical durability, therefore improvement by addition of the forth component or surface coating is necessary for practical use.

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The effect of pores on the grain growth rate of alumina was investigated using specimens of various green densities in the range from 20 to 94% of theoretical one, which were prepared in four different methods in graphite molds, a) hot-pressing at 1600°C, b) hot-pressing at 1200°C, c) pressing at a room temperature and d) filling at a room temperature. After the forming pressure was removed graphite molds were heated inductively up to 1800°, 1850° or 1900°C and kept at the temperatures for 5, 10 or 60 min. The forming and heating atmosphere was a mixture of nitrogen and carbon monooxide gas.
By these experiments the rate of grain growth: dD/dt, the average grain diameter: D, and the volume fraction of pores: f and the average diameter of pores: d, were determined. Among them next relationship was found to exist:
dD/dt=K(1/D-2f/d)
The same experiments as above were carried out with 0.16% addition of magnesia, and the significant retarding effect of magnesia on the grain growth of alumina was observed. In this case next relationship was found to exist:
dD/dt=K(1/D-2f/d-K′)
K′ represents the retarding effect of magnesia, the value of which was found to be constant among specimens of the same heating temperature and time, and larger than the value of 2f/d corresponding to 16 vol.% of pores.
The exponent of time, m, in the equation D²-D₀²=kt^m was found to increase with decreasing green density of specimens.
The growth of pores in specimens was observed and added magnesia was found also to have an effect on the pore growth.

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