A new process by which fibers as good as hydrothermal or flux growth fibers are easily formed with lower cost than the other methods. The new method is called kneading-drying-calcination process (KDC process). Two new potassium fiber phases, non-crystalline “Fur-fiber” and hydrous potassium titanate (X-phase), were formed through the method in addition to the three phases known as an established fact.
An interesting phenomenon was observed, that is, non-crystalline potassium titanate “Fur-fibers” grew on the surface of pellets. The length of the “Fur-fiber” was around 7mm after 3h reaction. The “Fur-fibers” were non-crystalline by X-ray powder diffraction analysis, but were crystallized into potassium tetratitanate by heating 800°C for 1h.
Potassium tetratitanate was attacked by water and changed into a new phase (X-phase) which was a hydrous potassium titanate. The X-phase was changed into potassium hexatitanate by heating 800°C for 1h.

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On the vitreous china bodies which were prepared using quartz powder of various fineness, stress in the glaze and the crystal content in the bodies were measured by the method previously reported. The quartz powder fractions classified by an elutriation were <1μm, 1-3μm, 3-6μm, 6-10μm, 10-15μm, 15-20μm and >20μm; the body A (standard body) was composed of 40% quartz, 15% feldspar, 25% kaolin and 20% ball clay; biscuit firing was done in a tunnel kiln at SK 12RF for 42h; glost firing was done at 1130°C.
The compressive stress in the glaze was -500--800kg/cm² with the particle fractions from >20μm to 3-6μm, regardless of the difference in the particle size, but the stress increased to about -1200kg/cm² with the fractions of 1-3μm and <1μm. The rather uniform stress in the glaze concerning the bodies with the coarser quartz particle fractions from >20μm to 3-6μm may be due to the adequate cristobalite formation compensating the decrease in the amount of residual quartz. Great stress occurred in the bodies with the fine fractions of 1-3μm and <1μm on account of the copious formation of cristobalite.
With body K′-3, which was prepared by adding 3% kaolin to body A, the compressive stress in the glaze decreased with the decrease in the particle size of quartz in the body when the bodies were biscuit-fired in a tunnel kiln to SK 12RF for 42h (12S). On the other hand, the compressive stress in the glaze increased with the decrease in the particle size of quartz when the bodies were biscuit-fired in a tunnel kiln to SK 13RF for 126h (13L).
This tendency can be explained by the fact that the formation of cristobalite increased remarkably with the increase of fineness of the quartz. Generally, the compressive stress in body A was much larger than that in body K′-3 regardless of the fineness of the quartz, because the cristobalite formation was more active in body A than in body K′-3.
Although the effect of the particle size of the quartz in the body on the crazing resistance of vitreous china is very complicated, it is understood accurately by the measurement of the stress in glazes and that of the quartz and the cristobalite content in bodies.

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The effects of applied pressure on the densification during hot-pressing and the hardness of zirconium diboride, ZrB₂, compacts were investigated. Hot-pressing experiments were carried out in graphite dies at the temperatures of 1600° to 2250°C and at the pressures up to 1200kg/cm². High strength carbon was used as the die materials for the hot-pressing at above 400kg/cm².
The densification of ZrB₂ compacts was accelerated by increasing pressure, and this pressure effect was especially clear in hot-pressing at around 2000°C. The finer the raw powder was, the quicker the densification took place, but the pressure effect appeared more remarkably in hot-pressing of coarse powder. Empirical equations were deduced of the pressure effect on realizing 95% density.
Generally, the compacts prepared at high temperatures and pressures, namely having high densities, showed high Rockwell hardness. However, it was observed that the compacts hot-pressed at high temperatures but low pressures gave higher hardness than those at low temperatures but high pressures having the same density. The compacts of the relative densities over 0.9 pepared at 2050°C or above showed the Rockwell hardness of 85 to 88. Rockwell hardness is thought to be macroscopic and to reflect the bonding strength of the particles constituting the compacts. Observation of the microstructures revealed the pores or the voids in the compacts became round at about 2000°C, therefore, at these high temperatures the bonding between the particles was thought to become firmly. These facts mean that the pressure is mainly effective on accelerating the densification and the temperature is effective on increasing the hardness. Therefore, in order to prepare well sintered ZrB₂ compacts with high hardness hot-pressing should be done at above 2000°C as well as higher pressure.

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In the phase diagrams studies on the Al₂O₃-Ln₂O₃ systems, liquidus temperatures of the Al₂O₃-Dy₂O₃ system were measured from the cooling curves of specimens by the specular reflection method with a heliostat-type solar furnace. Quenched specimens from the melt were examined by X-ray diffractometry and chemical analysis.
The single phases of 3Dy₂O₃⋅5Al₂O₃ of garnet structure, DyAlO₃ of perovskite structure, and 2Dy₂O₃⋅Al₂O₃ of monoclinic structure were observed when the mixtures of the respective stoichiometric composition were heated at 1600°C in an electric resitance furnace, and also when the specimen were cooled after fusion in the solar furnace.
Lattice parameters of these three compounds quenched from the melt were as follows:
3Dy₂O₃⋅5Al₂O₃: a₀=12.034Å DyAlO₃: a₀=5.204Å, b₀=5.308Å, c₀=7.413Å 2Dy₂O₃⋅Al₂O₃: a₀=7.403Å, b₀=10.487Å, c₀=11.143Å, β=108.68°
All of the above compounds appeared to be stable phases, because they showed no phase transition in the repeated heating and cooling cycles.
The freezing points of 3Dy₂O₃⋅5Al₂O₃, DyAlO₃ and 2Dy₂O₃⋅Al₂O₃ were measured as 1920±20°C, 2000±20°C and 1954±20°C, respectively.
The phase diagram shows four eutectic points at 1760°C, 1890°C, 1920°C and 1830°C with 18, 42, 60 and 79mol% of Dy₂O₃ composition.
The cooling curve of Dy₂O₃ showed four exothermic peaks related to the solidification as well as the solid state phase transformations below the solidification point.
A high temperature phase diagram for the Al₂O₃-Dy₂O₃ system was presented tentatively.

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The phase relations appeared at 1400°C in a system of Si₂ON₂-Y₂O₃-Al₂O₃ were studied. The samples were hot-pressed at 1740°C for 10min and annealed at 1400°C for 5h under nitrogen atmosphere. The compounds formed were identified by X-ray diffraction method.
The stable phases appeared near N (Y₃AlSi₂O₇N₂) composition were N, N_ss (N-YSiO₂N solid solution), J (4Y₂O₃⋅SiO₂⋅Si₃N₄), J_ss (J-2Y₂O₃⋅Al₂O₃ solid solution), G (3Y₂O₃⋅5Al₂O₃), Ap (10Y₂O₃⋅9SiO₂⋅Si₃N₄), YAM (2Y₂O₃⋅Al₂O₃), Y2S (Y₂O₃⋅2SiO₂) and β-SN (Si₃N₄). G-N-YAM, N-G-Ap-β-SN and G-Ap-β-SN-Y2S are expected to be in equilibrium at 1400°C in the studied phase system. The solid solutions were found between N and YSiO₂N together with J and YAM. N is considered to be a solubility limit of YSiO₂N to yttrium silicate.

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A Li₂O⋅2SiO₂ (mole ratio) melt was unidirectionally solidified at rates of 0.7, 1.3, 3.3, 6.7 and 13mm/h in a clay crucible from its bottom, and effects of the solidification rate on the porosity of ingots was investigated. In all cases, the inner bottom surface of the crucible was previously covered with a thin Li₂O⋅2SiO₂ glass-ceramic layer which acted as seed crystals. The temperature gradient imposed in the melt at the start of solidification was 80°C/cm.
The ingots solidified at rates higher than 3.3mm/h had many cylindrical pores arrayed parallel to the direction of solidification. These pores were considered to be formed by a big difference in solubility of gases between the Li₂O⋅2SiO₂ melt and its crystal. The porosities of these ingots were all larger than 4% and increased with increasing solidification rate. The porosities of the ingots solidified at rates lower than 1.3mm/h were all nearly constant of 3%. In these ingots no cylindrical pore was observed but many microcracks were found present at the boundary of columnar Li₂O⋅2SiO₂ crystals well oriented with their c axis parallel to their elongation direction. The formation of the microcracks was attributed to mechanical stresses induced by a big difference in thermal shrinkage between the a and b crystallographic axes of the constituent columnar grains of Li₂O⋅2SiO₂ crystal.

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Photochromic glasses exposed to certain amount of gamma rays in advance of heat treatment show much higher photosensitivity than non-irradiated glasses. It was clarified that the crystal size of AgCl formed in the glass during the heat treatment shifted smaller, and that the number of the crystals in unit volume increased with increasing gamma irradiation dose.
Size and number density of the AgCl crystals in the sample glasses are observed by electron microscope and X-ray diffraction method.
The effects of gamma ray irradiation are possibly explained that gamma ray produces nuclei, each of which grows into AgCl crystal during the subsequent heat treatment.
Photoabsorption spectrum of each photochromic glass sample exposed to visible light was observed, and it shows that the wavelength of absorption peak depends on gamma ray irradiation dose.

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