High chemically durable porous glasses containing Na₂O, Al₂O₃, ZrO₂ and SnO₂ up to about 10wt% were obtained by using immiscible SiO₂-B₂O₃-RO glass systems as the base glass. It was found that the amounts of Al₂O₃, ZrO₂ and SnO₂ in porous glasses increased with increasing heating temperature. Alkali resistance of these porous glasses was 6-20 times higher than that of usual Vycor type porous glass.

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Titanium nitride powders were synthesized using the spark discharge between titanium electrodes in a liquid nitrogen. The powders were presumed to be the nitrogen defective titanium nitrides by X-ray diffraction and nitrogen analysis. There were irregular shape particles beyond 100μm, spherical particles below 40μm and ultra fine particles below 40nm in the powders. It was suggested that irregular shape and spherical particles were formed of solidified titanium nitride of electrode couples and molten titanium containing nitrogen in discharge point respectively, and that ultra fine particles were formed by gas phase reaction of titanium with nitrogen particularly.

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The Raman spectra of hydrous zirconia particles prepared by hydrolysis of ZrOCl₂ were measured. The number of Roman bands and the Roman shift observed for as-prepared hydrous zirconia particles are similar to those observed for the monoclinic crystalline ZrO₂ except the width of measured Raman bands are broad. Using high resolution TEM, it was observed that hydrous zirconia particles consist of highly crystallized primary particles of 30Å in diameter. These experimental facts indicated that the broadness of Raman bands were resulted from breakdown in K-momentum conservation in small size particles. The Raman bands of hydrous zirconia particles heated up to 900°C became narrower with increasing temperature. TEM observations also showed that the size of heat-treated particles increased with increasing temperature. Therefore, the narrowing in Raman bands is considered as a result of increase in particle size as observed in small particle size crystalline silicon. The relationship between the width of Roman band and the particle size in hydrous zirconia particles was experimentally established.

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Mullite ceramics are stable at high temperature, and expected for structural applications at high temperature. But the mullite ceramics have low fracture toughness. In this study, method to optimize the microstructure for high toughness in Si₃N₄ system was used as a reference, and microstructure of mullite ceramics were controlled to have needle-shaped grains with narrow size distribution. As a result, fracture toughness of the mullite ceramics was improved. At first, we synthesized an amorphous mullite powder containing Y₂O₃ by the coprecipitation method. The powder mixture of amorphous mullite and crystallized mullite was sintered at 1600°-1700°C. It was found that mullite whiskers and crystallized Y₂Si₂O₇ precipitated in the sintered body containing Y₂O₃. Its fracture toughness increased and the bending strength showed no degradation at high temperature.

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The hydration behavior of CaAl₂O₄ in the presence of CO₂ was studied. The hydration was conducted by suspending CaAl₂O₄ in water into which CO₂ gas was bubbled. In 100% CO₂, an almost insoluble coating, a reaction product of carbonic acid and CaAl₂O₄, was formed on CaAl₂O₄ surface. Therefore, the hydration of CaAl₂O₄ did not proceed. In this system, the solubility product which was determined from the concentrations of Ca²⁺ and CO₃^2- agreeded with that of CaCO₃. When the hydration was carried out at pH 9.5 or above in a buffer solution, this coating was broken by the dissolution of aluminum and thus the hydration proceeded. The reaction of CO₂ with calcium aluminate solution yielded the amorphous products containing amorphous CaCO₃. Their composition (by molar ratio) was as follows; CaO:Al₂O₃:CO₂:H₂O=1.0:2.4:1.1:17.1.

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TiO₂ coating films prepared by dip-coating of various substrates with Ti(OC₃H₇ⁱ)₄/cyclohexane solution were heated in a flow of N₂ gas below 1080°C for one hour. After this heat treatment, TiN coating obtained from TiO₂ was investigated by XRD, ESCA, TEM, EDS and UTW-EDS. TiN formed on carbon steel substrates (C content; 0.04-1.0wt%). On the carbon steel substrate (C content; 0.48wt%), MnTiO₃ and Ti₂O₃ formed by the reaction of TiO₂ with a small amount of Mn contained in substrates above -580°C, and then changed to TiN in a flow of N₂ at >780°C. However, MnTiO₃ or Ti₂O₃ on the decarburized carbon steel (C content; 0.005wt%) was not converted to TiN. TiN was not observed on other substrates such as silica glass, Si wafer, SUS 444, Ni, Mo and Pt.

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The mechanism of pyrolysis of amorphous silicon carbide fibre has been investigated. Using two types of fibres (Nicalon NL400 and NL200), the rate of pyrolysis has been measured with a thermobalance in an argon atmosphere at temperatures from 1673K to 1973K. X-ray diffraction patterns showed that the atomic arrangement in NL400 was disordered in comparison with that in NL200. The amorphous fibre NL400 decomposed to β-SiC rapidly. TEM observation showed that the crystallites of SiC grew three-demensionally during pyrolysis. At the same fractional decomposition of fibre, the size of the crystallites of NL400 was smaller than that of NL200. The pyrolytic rate was analyzed by means of an Avrami-Erofeev's equation. The mean value of the exponent m in the rate equation was 1.3 for both fibres. Because large amounts of stable nuclei were generated immediately after the onset of pyrolysis of NL400, its rate constant was about 3 times larger than that of NL200. The activation energies were 487kJ/mol for NL400 and 484kJ/mol for NL200. The rate of pyrolysis of amorphous silicon carbide fibre was controlled by the nucleation and growth of SiC crystallites.

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AlC₄B₂₄ and Al₃C₂B₄₈ crystals were prepared by the reaction between carbon and boron powders using a molten aluminium flux in an argon atmosphere. The conditions for obtaining these crystals with a relatively large size were established. As-grown AlC₄B₂₄ and Al₃C₂B₄₈ crystals were used for the study of oxidation in air at high temperatures, and also measurements of density, unit cell dimensions and Vickers microhardness. AlC₄B₂₄ crystals were obtained together with crystals of Al₃C₂B₄₈ or Al₄C₃. Al₃C₂B₄₈ were prepared as twinned crystals of A and B phases, without accompanying α-AlB₁₂, β-AlB₁₂ type, γ-AlB₁₂, AlC₄B₂₄ or Al₄C₃ crystals. The optimum conditions for growing AlC₄B₂₄ single crystals and Al₃C₂B₄₈ crystals are the following atomic ratios of starting materials (C/B, Al/B), soaking temperature and soaking time; C/B=9.60/24, Al/B=144.24/24, 1500°C and 5h for AlC₄B₂₄ and C/B=0.24/24-0.48/24, Al/B=144.24/24, 1300°C and 5h for Al₃C₂B₄₈, respectively. Under these conditions, AlC₄B₂₄ single crystals, having a black color and metallic luster, were generally obtained in the form of a bipyramidal shape. On the other hand, the twinned crystals of Al₃C₂B₄₈ were yellowish brown and semitransparent, having a nearly spherical polyhedral shape with smooth planes. The largest crystals prepared have the maximum dimensions of about 2.1mm×2.1mm×2.2mm (for Al₃C₂B₂₄) and 1.1mm×1.1mm×1.2mm (for AlC₄B₂₄). Unit cell dimensions, Vickers microhardness (H_v) and densities (d_m) are as follows:
AlC₄B₂₄; a=8.892(2), b=9.112(1), c=5.692(2) (Å), V=461.1(3) (ų). H_v=2500-2690kgf/mm², d_m=2.55(1)g/cm³ Al₃C₂B₄₈; for A phase, a=12.377(2), b=12.627(1), c=5.079(1) (Å), V=793.8(1) (ų)-a=12.363(2), b=12.616(1), c=5.102(1) (Å), V=795.8(2) (ų) for B phase, a=6.166(2), b=12.635(2), c=10.156(2) (Å), V=791.2(2) (ų)-a=6.181(2), b=12.622(1), c=10.161(1) (Å), V=792.7(2) (ų). H_v=2570-3050kgf/mm², d_m=2.59(2)g/cm³
The oxidation reaction in air of AlC₄B₂₄ and Al₃C₂B₄₈ crystals began to proceed at about 760°C and 710°C, respectively, and their oxidation products were found to be 9Al₂O₃⋅2B₂O₃ (orthorhombic system) and B₂O₃ (hexagonal system) phases.

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Hydroxyapatite (HAp) powders with Si₃N₄ whiskers dispersion were synthesized hydrothermally at 200°C under 2MPa for 10h. The transmission electron microscopy (TEM) demonstrated that the homogeneous mixture of ultra-fine HAp single crystals and Si₃N₄ whiskers was obtained by this technique. The mixture was hot-pressed at 1000°C under 30MPa for 1h in Ar, and then post-sintered by HIP at the same temperature under 200MPa of Ar for 1h. The product had almost pore free microstructures consisting of HAp and TCP matrix and Si₃N₄ whiskers. The value of K_IC was 3.1MPa⋅m^1/2, and was 3 times as high as that of the transparent HAp ceramics.

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High-frequency cyclic fatigue properties of lead titanate (PT) and lead zirconate titanate (PZT) were investigated experimentally. No obvious effect of cyclic load was observed on the crack propagation in PT, whereas the stress ratio (R) resulted in different crack propagation behavior in PZT (i.e., R-curve behavior or accelerative effect). In order to express the phenomenon quantitatively, the constants (A and n) in the crack propagation rate equation V=A(K_I/K_IC)ⁿ were determined. When the relation was plotted, ΔA((A_C/A_S): ratio of constant A under respective static fatigue to cyclic fatigue conditions) proved to be a very effective parameter to express the crack propagation characteristics.

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Utilization of mining wastes of Kuroko-type ore deposit has been attempted to prepare novel porous materials called KGL (Kuroko-Gypsum-Lime) by steam caring. Gypsum and slaked lime were added as reaction agents. The wastes comprise chlorite, sericite and quartz all associated with a small amount of barite. The mining wastes were calcined beforehand at various temperatures below 1000°C. Processing above 500°C yielded very reactive pozzolana. III-anhydrite converted from desulfuration gypsum or commercial hemihydrate was used as gypsum source in order to obtain consolidated precursors from slurry mixtures of the three raw materials in a short period of time. The precursors were steam-cured for 24h under the conditions of 80°C and 90% R. H. Thus, water resistant porous materials with the lowest bulk density of 0.62g/cm³ were prepared, depending on the W/S (weight ratio of water to solid). The resulting hydrates are gypsum and C-S-H. The gypsum showed acicular to lath-like morphology, when the wastes processed above 500°C were used, whereas it showed irregular platy morphology, when the wastes processed below 400°C were used. The elongated form of gypsum may be useful to strengthen the porous materials. The thermal conductivity values are dependent on the W/S, their lowest value being 0.14kcal/m⋅h⋅°C. Consequently, KGL has a potential of practical use as heat and sound insulating materials, judging from the resulting thermal conductivity and bulk density.

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Using the isothermal method and press softening measurements, the densification process of clays from the Westerwald deposits in West Germany was compared with that of a feldspathic body prepared from Japanese raw materials. The clays from the Westerwald deposits completed the densification at around 120°C lower than that of the feldspathic body and showed high deformation resistance as well, the softening deformation being 1/3 that of the feldspathic body. This is closely related to the fact that 90% of the illite which is flux component and 22% of the quartz particles are concentrated in the range lower than 2μm. In addition, it is believed that the composition of mullite is different, as judged by the marked difference in the shape of the crystallized mullite.

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Resistivity of a sintered YBa₂Cu₃O_7-x oxide superconductor was measured at large current densities (j=-100A/cm²) above liquid nitrogen temperature to clarify the poor critical current property of a sintered specimen. Three steps of resistivity transition were observed as the temperature lowered; (1) A sharp drop was found at T=93K, which corresponds to the superconducting transition of the material. (2) A broad shoulder appeared at T=92K to 82K. A gradual decrease in resistivity may be due to the weak intergranular coupling at grain boundaries. (3) The resitivity became almost constant and a finite value was detected even at 77K, suggesting that extremely weakly-coupled grain boundaries are present in a sintered specimen.

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Hydrated vanadium oxides containing alkali ions were prepared by the hydrothermal treatment of VOSO₄ aqueous solutions. The products adopted layered structures with a general composition of A_0.3V₂O₅⋅nH₂O (A=Na, K, Rb, Cs and NH₄; n=0.6-1.2). The layer spacings were around 11Å. They were almost unchanged for the compounds of different alkali ions. The layered structures are considered to be composed of the V₂O₅ layers intercalated with water molecules and alkali ions. Dehydration by heating or evacuation caused transitions into the phases where the layer spacings contracted by 1 to 2Å leading to the values proportional to the size of alkali ions.

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Varying the frequency of the pressure change, alumina powders were formed by Cyclic-CIP. The following results were obtained;
(1) The bulk density of alumina compacts increased remarkably as the number of cycles increased in each frequency.
(2) The frequency did not affect the bulk density in the range 0.02Hz to 3Hz.
(3) The rate of loading and unloading did not influence the densification.

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