Lattice parameters and the crystal structure of NH₄-dawsonite were determined from X-ray powder diffraction data. Crystal system is orthorhombic and lattice parameters, a, b and c, are 6.618±0.003, 11.944±0.004 and 5.724±0.002Å, respectively.
The structure of NH₄-dawsonite differs from that of dewsonite in symmetry, i.e., the former is base-centered and the latter body-centered, though both of them are composed of the same chain structures with Al-O(OH) octahedra.
System of K-dawsonite was also determined to be the base-centered orthorhombic which was the same with NH₄-dawsonite.

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A Li₂O⋅2SiO₂ melt was unidirectionally solidified in a clay crucible from its bottom with a constant temperature gradient of 80°C/cm. When the solidification rate was higher than 3mm/h, many bubbles developed in the melt near the solid-melt interface. Mass spectroscopic analysis of the gas extracted from the bubbles showed that the main component of the gas was H₂O. Infrared spectroscopic analyses of the quenched melt (glass) and the solidified ingot (crystals) showed that the H₂O contents of the melt before and after solidification were 0.025 and 0.003mol/l, respectively. The developement of bubbles was thus attributed to the big difference in solubility of H₂O between the melts before and after solidification; the H₂O gas expelled from the melt on its solidification was concentrated in the melt near the solid-melt interface, supersaturated and finally developed as the bubbles. When the solidification rate was less than 1mm/h, no bubble was observed in the melt throughout the solidification process. In this case the H₂O gas expelled from the solidified melt would not have been concentrated heavily enough to form the bubbles but moved away from the interface by diffusion upward through the melt. Mathematical analysis of the H₂O distribution in the solidifying melt indicated that an upper limit of supersaturation of H₂O in the melt, over which the H₂O gas formed bubbles in the melt, was about 15 times the equilibrium saturated H₂O concentration of the melt.

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The formation of fine titanium carbide powders by the vapor-phase reaction of the titanium halides-carburizing gases-hydrogen systems was studied between 1000°C and 1500°C with emphasis on the formation conditions and properties of TiC powders.
(1) For the formation of TiC powders, the titanium halides were effective as Ti-source in the sequence of TiCl₄<TiBr₄<TiI₄ and the carburizing gases as C-source in the sequence of CCl₄<<C₂H₄<CH₄. The powder produced consisted of TiC_x and free carbon.
(2) In the system of TiI₄-CH₄ or TiI₄-C₂H₄, the yield and content of TiC powder in the product were high when the mixing temperature of halide and hydrocarbon was 1200°C-1300°C. The increase in the concentrations of TiI₄ and CH₄ accelerated TiC powder formation, but the high [CH₄]/[TiI₄] mole ratio suppressed it and increased the amount of free carbon as by-product.
(3) TiC_x powders produced consisted of single-crystalline particles of 0.01μm to 0.2μm. The lattice constant of TiC_x was 4.307Å to 4.331Å which corresponds to C/Ti ratio (x) of 0.57 to 1.00.
(4) The formation of TiC particles was concluded to occur by the homogeneous nucleation of TiC and its growth process. This process could explain the experimental results satisfactorily.

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(1) “Balanced” powder mixture of Si₃N₄, AlN and Al₂O₃ for sialon (Si_6-zAl_zO_zN_8-z with z=1, 2, 3 or 4) was hot pressed at 1750°C for 1h under 200kg/cm². The densification was incomplete in a sialon with z=1. Other sialons were pore free.
(2) The reactions included in the process of β-sialon formation were inferred to be, (a) the formation of 15 R-sialon, x-phase and β-sialon with z=2.3-2.5 at low temperature (equations (2) and (3)),
(b) steep densification at higher temperature than 1600°C by “transient liquid phase sintering” with x-phase as a liquid, (c) the final step to approach z value of β-sialon into predicted one (equations (5) and (6)).
(3) Density measurement and chemical etching with diluted HF+HNO₃ of fracture surface of sialon revealed that there was unreacted materials in sialons with z=3 and 4. A single phase and fully dense sialon was obtained in the composition z=2 with very small amount of grain boundary phase, if any.
(4) Small amount of excess oxide (about 3 wt%) in a sialon with z=2, which existed as grain boundary phase, was detected by chemical etching.

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The atomic absorption spectrometric determination of trace amount of copper, manganese, lead and chromium in cements by direct atomization in a carbon furnace from solid state was developed. Cement powder samples were introduced in the carbon furnace, and then dried, asked and atomized. The peak height of atomic absorption signal was taken as a measure of the intensity of absorption. Calibration curves were linear concerning Cu (5.0-16.0ng), Mn (6.0-25.9ng), Pb (3.6-16.8ng), and Cr (4.1-17.1ng). The coefficients of variation of this method were as follows: Cu 3.2%, Mn 3.7%, Pb 2.8% and Cr 3.4%. When this method was applied to the determination of Cu, Mn, Pb and Cr in ordinary portland cement, the values obtained were in fair agreement with those obtained by the Cement Association of Japan Standard method. The developed method was practically free from matrix effects, and no tedious pretreatment of sample was necessary. It took only about 5 minutes, whereas several hours were required to determine Cu, Mn, Pb, Cr by other atomic absorption methods. As the contamination of heavy metal elements and poisonous reagents was avoidable during the pretreatment, this method was recognized to be satisfactory as one of clean analyses.

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On the basis of optical absorption spectra of VO²⁺ ions dissolved in Na₂O-SiO₂-B₂O₃ glasses, the structure of matrix glasses has been studied in order to clarify the process of phase-separation in alkali borosilicate glasses. It has been indicated from the spectra that the Si-O-B bond is not formed in the glasses in the range of Na₂O/B₂O₃<1, in which the Na₂O/B₂O₃ is the molar ratio of Na₂O to B₂O₃, and the glasses are separated into Na₂O-B₂O₃ and SiO₂ phases. This has been interpreted as suggesting that the “phase-separation” of these Na₂O-SiO₂-B₂O₃ glasses due to heat treatment is the development of the separated phases originally existing in the glasses. On the other hand, the spectral information on the structure of glasses in the range of Na₂O/B₂O₃>1 has not been sufficient for discussing phase-separation in the glasses.

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Submicron powders of β-SiC were prepared by reactions of carbon black with silicon, silicon monoxide, or silicon dioxide at temperatures from 1340° to 1570°C. Physical and chemical properties of the powders showed that they were active and their properties were different from those of the common β-SiC powder.
Submicron powders of β-SiC had carbon-rich nonstoichiometric composition, and their lattice parameters were significantly smaller than that of β-SiC single crystal. Powders were vigorously corroded by the mixture of fluoric and nitric acids. The acid treatment on the powders caused the increases of the deviation from stoichiometry, specific surface area and lattice parameter, and the change of infrared absorption spectra.
Powder derived from SiO had the highest specific surface area among the powders prepared in this experiment and also the lowest beginning temperature of oxidation. The weight gain of typical acid-treated powder began to take place at about 270°C in air.

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Three different surface treatments were carried out on the surface of the bending specimens, in order to know the effect of surface roughness on the high temperature strength of high purity and high density graphite and alumina. In the graphite specimens, which were fractured in brittle, higher bending strength was obtained as the surface roughness became smaller throughout the temperature range of room temperature to 1500°C. Alumina which had smoother surface had higher strength up to 1000°C, but the effect was reduced above 1200°C where material transport becomes enhanced and the effect disappeared at 1400°C.
Calculated crack size which was obtained using fracture mechanics agreed with the combination of the surface roughness and the observation of fractured surface of graphite, while the calculated crack size of alumina was found to be significantly different from the observed roughness and only in the same order of magnitude.

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Possibility of preparing silica glass fibers and pieces by hydrolyzing silicon tetraethoxide Si(OC₂H₅)₄ and heating at temperatures not higher than 1000°C has been examined. Mixtures of Si(OC₂H₅)₄, H₂O, HCl and C₂H₅OH with varying [H₂O]/[Si(OC₂H₅)₄] ratio from 1 to 29, [HCl]/[Si(OC₂H₅)₄] ratio from 0.003 to 0.3 were digested into homogeneous solutions by heating at 80°C, hydrolyzed and polymerized to gel by keeping at 30°C, and converted to silica glass by heating up to 1000°C. The mixtures with the [H₂O]/[Si(OC₂H₅)₄] ratios less than about 2 exhibited a marked spinnability just before gelling in the course of hydrolysis, which made fiber drawing from the solution possible. The drawn fibers were converted to silica glass fibers by the subsequent heating. On the other hand, the mixtures with the larger [H₂O]/[Si(OC₂H₅)₄] ratios of 15-29 gave a piece of transparent silica glass of the size 0.8mm×7mm×7mm, for example, with the density of 2.20g/cm³ when, after gelling, they were heated up to 1000°C with the appropriate heating schedule.

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The possibility of producing glass-ceramics from the inorganic waste materials with no additives was examined. Blast furnace slag, waste enamel, aluminum slugde, waste clay and waste silica sand were used as raw materials to prepare the glasses which were subjected to the heat treatment for crystallization. Chemical composition of the glasses was located in the range SiO₂ 29.2-47.6, Al₂O₃ 18.6-26.7, CaO 21.6-29.2, MgO 4.2-6.1 and total of others (Na₂O, TiO₂ B₂O₃, MnO₂, SO₃, etc.) 7.6-12.8 (wt%). Melilite and/or anorthite, always with small amount of diopside, were identified in the heat treated glasses. However only the glasses that precipitated melilite as a major crystalline phase were converted into glass-ceramics, of which bending strength was over 1000kg/cm². It was found that the amount of Cd, Cr and Pb leached out in HCl solution was lower in the glass-ceramics than in the original glass.

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An automatic differential dilatometer for glass was improved by introducing solid state circuits for controlling the operations. Expansion of a sample was transformed by an optical lever into the motion of light image, which was followed by an automatic light tracing mechanism to provide the chart drive of a recorder in proportion to the expansion; temperature vs. differential expansion curve was thus obtained. By complemental application of JIS-type dilatometer, measurement and quality control on glasses are now carried out with high precision and efficiency.

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