Silicon carbide was chemically deposited on the (111) surface of silicon single crystal and isotropic pyrolytic graphite by using methyltrichlorosilane as source gas. The deposits were examined by X-ray diffractometry and electron scanning microscopy (SEM) and found to be composed of β-SiC, free Si and a trace of 2H-SiC. The coatings yielded the less free silicon in it using graphite as substrate and at a higher argon flow rate. X-ray analysis indicated that the degree of preferred orientation varied with the kinds of substrate materials and the amount of argon added. A film with ‹111› preferred orientation was obtained on silicon substrate comparing to the ‹220› orientation on the graphite substrate. Increasing the flow rate of argon led to decrease probability of the ‹111› orientation but enhance the ‹220› one on graphite substrate, whereas the deposition rate was greatly lowered by adding argon. The morphologies of deposits obtained by the CVD process was dependent on the input fraction of argon at 1400°C.

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Effects of the addition of B, Al, Fe, and C on the annihilation of stacking faults (S. F.) in β-SiC powder compacts were investigated. The separability of the X-ray diffraction lines, Kα₁ and Kα₂, was applied to the qualitative evaluation of the lattice strain to elucidate the annihilation phenomena. Dissolution of B or Al (rapid heating condition) into SiC grains enhanced the lattice strain suppressing both grain growth and S. F. annihilation. The second phases formed in Al (slow heating condition) and Fe addition to β-SiC promoted both grain growth and S. F. annihilation, while the residual free carbon in C- added β-SiC impeded the grain boundary movement and hence suppressed grain growth and S. F. annihilation.

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Bi-Pb-Sr-Ca-Cu-O superconducting thin films with various Ca contents were prepared by rf-magnetron sputtering method using multi targets. The influence of the annealing on the obtained films was investigated. Ca-rich films compared to the high T_c phase did not show zero resistivity after the annealing. The c-axis length of the high T_c phase in these films was in a range of 3.710-3.720nm. Moreover, as the annealing time was increased, the orientation of the grains was improved and the film was composed of the stacking layer structure of the thin and plate like crystals. These results suggest that the liquid phase between plate like crystals produced by the annealing had the bad influence on the superconductive properties of the annealed films because the grain was isolated and grainboundary works as insulator.

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In order to achieve high green density of alumina powder compacts of particles with bimodal size distribution, stearic acid and polyethleneglycol were used as forming aids. Burn-out of binder and sintering behavior of these powder compacts were investigated. The forming aids melted at 50°C and concentrated on contact points of particles where large capillary force acts and became difficult to burn out. Therefore, the forming aids in compacts containing a large amount of fine particles tended to burn out at higher temperature. Powder compacts containing 40-100% fine particles expanded prior to burn-out of forming aids and began to contract simultaneously with burn-out of forming aids at 170°C. Powder compacts containing 0-30% fine particles did not expand but began to contract at 300°C. As forming aids burn-out, small pores in compacts shrank, whereas large pores grew. The sintered densities of compacts that were high green density with forming aids were also higher than those of compacts that were low green density without forming aids, until the relative density reached 95%. However, the effect of green density on the densification decreased when the relative density exceeded 95% due to remarkable grain growth.

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The composite materials consisting of crystals and glasses were prepared by heat-treating the mixtures of Li₂O-SiO₂ (LS) and Na₂O-CaO-SiO₂ (NCS) glass powders. In the specimens in which the proportion of Li₂O-SiO₂ glass is high, the main crystalline phase was Li₂O⋅2SiO₂, and as the Li₂O-SiO₂ glass content decreases, other crystals such as α-quartz, β-cristobalite, and wollastonite were detected. The differential thermal analysis, thermal expansion coefficient, softening temperature, apparent density, porosity, compressive strength and bending strength were measured. The relations between the strengths and the mixing ratio of LS and NCS glass were analyzed based on the crystal content and the porosity. The crystallization behavior and the composite reaction process were also discussed.

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Electrical resistivity of diamond films grown by a thermal plasma chemical vapor deposition technique was measured from room temperature to 870°C at 3×10^-5-1×10^-6 Torr. The surface-treatments of the films were carried out in the following ways, i.e., (1) immersing in an aqua regia at 75°C for a week, (2) immersing in a solution of CrO₃ in H₂SO₄ for a day, (3), (4) heat treating at 400° and 550°C respectively in air for two hours. Electrical contacts on the resultant films were made by gold electrodes deposited by an ion sputtering technique in air at 0.2 Torr and argon gas at 0.2 Torr, respectively. The films with gold electrodes deposited in air had peaks in electrical resistivity at temperature of 400°-530°C, but the peaks did not appear with the gold electrodes deposited in argon gas and without gold electrode. It can be explained that this phenomenon was caused by the desorption of oxygen molecules, which were adsorbed from an air plasma generated by the ion sputtering, from the diamond surface and the diamond/electrode interface, further by subsequent reconstructions of the diamond surfaces.

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The effects of CVD conditions, thickness and composition of CVD-C, SiC coating on the mechanical properties, microstructure and thermal stability of Nicalon-SiC fibers were studied. Tensile strength of fibers coated at 1300°C was lower than that of as-received fiber, because large flaws were formed on the fiber surface during the heating stage of the CVD process. When a fiber was treated at elevated temperatures, the coating layer acted as an effective fiber-coating interfacial diffusion barrier, and resisted the gas (CO, SiO) evolution from the fiber surface, which improved thermal stability of coated fibers. Thicker coating layer was more effective to prevent decomposition of Nicalon fiber at higher temperatures. The fibers coated at 1200°C possessed high values of strength, though it decreased due to the interface reaction in the heat treatment process.

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Series of Ga- and Al-Substituted Na-fluorine micas NaMg_2+xLi_1-x(T_xSi_4-x-yGe_yO₁₀)F₂ and NaMg_2+xLi_1-x(T_xGe_4-x-ySi_yO₁₀)F₂; x=0.0-1.0, T=Ga, Al, y=0, 1, 2, 3, were synthesized. Variations of infrared spectra, lattice constants and swelling properties were studied, and compared with those of corresponding K-series micas. Continuous changes in basal spacing (c·sinβ) with increasing Ga- and Al-contents proved that there were complete series of solid solutions between the end member micas with an exception of NaMg₃(AlSi₃O₁₀)F₂. Linear relations between c·sinβ or b-axis values and mean radius of tetrahedral cation were obtained for Ga- and Al-substituted Na-micas having x-value of 1.0. However, the b-axis values of Na-micas are far smaller than those of corresponding K-analogues, demonstrating that the degree of distortion in tetrahedral rotation angle α and octahedral flattening angle ψ is determined by the size of interlayer cation as well as that of tetrahedral cation. The values of α for Na-micas increased with the amounts of Ga- and Al-substitution. Na-micas lose also their swelling ability with increasing Ga- and Al-substitution. The loss of hydration property of interlayer cation results from the increase of α and the change of charge balancing, which increase the stability of interlayer structure.

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In an attempt to develop a new method for decorating porcelain, TiN films were deposited onto the glaze of porcelain by reactive DC magnetron sputtering of Ti in NH₃ discharge gas. For comparison with the glaze, effects of other substrates such as Si, Ti, Al₂O₃, ZrO₂, and MgO on the formation of TiN films were examined. A pleasing gold-like appearance was obtained under the following sputtering conditions; pressure of 0.007 Torr, discharge power below 40W and substrate temperature above 300°C. At higher pressures, higher discharge powers, or lower substrate temperatures, the hue of TiN films changed gradually to reddish gold and then dark red. The degradation in color is ascribed to the increasing oxygen contamination as well as the deviation of the nitrogen content from the stoichiometry. XPS analysis revealed the existence of a considerable amount of O-H bonds in the film when the substrate temperature was below 200°C. In the case of oxide substrates such as glaze, gray diffusion layers with a thickness less than 100nm were formed between TiN films and the substrates. The layers contained more Ti-O bonds and less nitrogen than those on Si or Ti substrate. TiN films with a similar hue and reflection to gold over-glaze were obtained on the glaze with surface roughness of 0.25μm.

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Fine CaSiO₃ powders were prepared by the coprecipitation method using an ethanol solution of calcium nitrate and tetraethyl orthosilicate. The powder composed of only β-CaSiO₃ was synthesized by adding NH₄OH to the solution and firing the precipitates at 1000°C for 2h. Addition of oxalic acid in this preparation process suppressed the formation of β-CaSiO₃, and the powders composed mainly of α-CaSiO₃ were prepared. The primary particle sizes were under 1μm, but particles agglomerated to several microns in diameter. These powders were sintered to around 90% theoretical density by firing at 1400°C for 1h without sintering additives. The sintered bodies did not absorb water.

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Influence of powder characteristics on mullitization, sinterability and mechanical properties was investigated for silica-alumina powders with 74wt% Al₂O₃ composition synthesized by various methods. Mullitization of the synthesized powders showed a different depending on the degree of homogeneity of the starting powders. However, all the calcined powders, except for the specimen of oxide mixtures, showed a similar result for the sinterability and microstructure of the sintered bodies. The sinterability of the oxide mixed specimen, which contains unreacted corundum and cristobalite besides mullite, was poorer than those of the other specimens. It can be attributed to the co-existence of corundum, which inhibits sintering of mullite in a similar manner as observed in a solid phase sintering of various particulate composites. The powder processing routes for mullite synthesis do not affect their high temperature mechanical properties, when mullitization occurred fully prior to densification.

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This research was undertaken to determine the reason for the occurrence of metastable tetragonal zirconia (ZrO₂). Metastable tetragnal ZrO₂ was prepared by low temperature calcunation of zirconium oxychloride octahydrate ZrOCl₂⋅8H₂O. The tetragonal-to-monoclinic (t-m) transformation in pure metastable tetragonal ZrO₂ powder was investigated with special reference to the isothermal annealing temperature, the variation of crystallite size and the annealing environment. The results indicate that the metastable tetragonal ZrO₂ is stabilized thermodynamically by surface free energy and there is a so-called “critical diameter (crystallite size)”. Moreover, thermodynamic calculation showed that the t-m transformation temperature depends on the critical crystallite size.

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The hollow glass microspheres named “Shirasuballoons” can be produced from Shirasu, a kind of acidic volcanic ejecta. Weathered surface layers of the Shirasu particles have several good properties, keeping the shape of the Shirasuballoons and preventing sticking each other during heat treatment. However, they can not be produced from the particles milled under 10μm, because of the insufficient amount of water for foaming; ground particles have no weathered surface layer. This paper describes the hydrothermal treatment of milled particles to form the surface layer having the same properties as weathered one and to increase structural water. The results obtained are as follows: (1) The weathered surface layer of the Shirasu particles milled under 10μm is destroyed almost completely by milling process. (2) Sodium and potassium ions are replaced with H⁺ by the treatment in 2wt% HCl solution at 200°C and about 15atm. The structural water increased with increasing volume of the solution, pressure, and time. Other ions such as Ca⁺⁺ and Fe⁺⁺ were removed also. (3) The highest yield of the micro-Shirasuballoons obtained by hydrothermal treatment in HCl solution was 10 times than without treatment. Even if heat treatment is performed in oxidizing atmospheres, whiteness of the micro-Shirasuballoons was more than 85.

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A nano-structure composite consisting of PZT-PMN-MnO₂-NiO ceramics and Alumina has been investigated. SEM observations of the composite revealed that particles of the dispersing phases were enclosed in the grain of matrix. The composition of one of disperse phases was analyzed by the X-ray method to be. PbAl₁₂O₁₉. The composition of the other phase was analyzed by the TEM method and estimated to be a mixture of spinel structure compounds, such as MgAl₂O₄, NiAl₂O₄ and MnAl₂O₄. It was found that the bending strength, mechanical Q and electromechanical coupling factor (kr) were increased by 30-40%, 20% and 10%, respectively. As a result, properties of this composite have been improved.

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β-sialon sintered body was fabricated from a spray dried mixture of α-Si₃N₄ and Al(Oi-Pr)₃ solution by hot-pressing. The bending specimens with the size of 3mm×3mm×30mm were ground using a #600 diamond wheel. Change of grinding flaws by oxidation at 1400°C for 100h was observed by an optical microscope. Change of bending strength with oxidation and polishing after oxidation was examined. Grinding flaws consisted of surface flaws with depth of 5μm and cracks with depth of more than 20μm following the flaws. The surface flaws changed to a smooth and dense oxide layer by oxidation. However, the cracks were supposed to remain with the original size even after oxidation, though they were filled with the oxide. The strength of sample after oxidation was about 1000MNm^-2, that of sample after removing the oxide layer by polishing was about 1200MNm^-2, and that of sample heat treated at 1200°C 2h in air after polishing was about 1400MNm^-2, all increased comparing with as-ground sample. These increase of strength was supposed to be a result from the decrease of depth of the cracks as fracture origins. To evaluate essential strength of β-sialon, it is necessary to remove the cracks by polishing or milder machining at least more than 25μm.

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Tetrapropylammonium (TPA)-Na type, Na type, and H type of ZSM-5 zeolites were synthesized hydrothermally from natural siliceous stone containing Al₂O₃ of 1.40wt% (produced in Ioh island, Kagoshima), TPABr, and NaOH solution, and their physicochemical properties (thermal stability, ion exchange, specific surface area, methanol to gasoline (MTG) test) were investigated. Thermal decomposition temperature of TPA ions in TPA-Na type ZSM-5 and that of Na type ZSM-5 increased with increasing amount of Alions substituted for Si ions in the zeolite. H type ZSM-5 showed a higher thermal stability than Na type and was stable against heating at 1100°C for 3h. More than 90% Na ions in ZSM-5 was replaced with proton in HCl solution through diffusion-controlled ion exchange at 45°-85°C for 24h. H type ZSM-5 with specific surface areas of 360 to 420m²/g converted methanol into gasoline completely at 370°C with no degradation of conversion ratio until 5h (the longest experimental time).

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Corrosion test of gas-pressure sintered silicon nitride with the additions of yittria and alumina was carried out under various testing conditions. As a result compared with specimens sustained in 6N-H₂SO₄ and those placed at the bottom of glass containers, no significant differences were observed in weight and bending strength. Also, there was no distinctive observation in the test at 90°C and boiling sulfuric acid. Silicon nitride was found to be corroded more severely in H₂SO₄ and H₃PO₄ than NaOH and H₂O. In addition, the test in boiling water resulted in strength degradation of the specimens, while weight change was not detected through corrosion. Relationship between bending strength and weight loss indicated that the rapid decrease of the strength has taken place at below 0.1mg/cm² of weight loss.

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Thermal and mechanical properties of SiC-particle/Al₂O₃ composite produced by direct metal oxidation process were investigated. The composite shows similar level of bending strength (537MPa) and fracture toughness (4.8MPa√m) comparing to monolith alumina and SiC. On the other hand heat absorption at 578°C caused by Al-Si eutectic and exothermal peak at 960°-1140°C resulted from AlN formation were detected by PTA in N₂. Therefore, residual metallic phase from starting metal alloy influences the microstructure and properties of composite at elevated temperature.

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Bioactive β-tricalcium phosphate (β-TCP) coating onto titanium was studied. It is shown that the β-TCP adhered to the surface of a titanium plate by the use of a frit, which was composed of CaO, TiO₂, P₂O₅ and a few mol% Na₂O. The frit as a coated layer resulted in the formation of β-TCP and CaTi₄(PO₄)₆ phases by a thermal treatment at 800°C for 24h.

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The composite porous glass membrane was prepared by coating on porous alumina tubing by sol-gel method. The porous glass layer of the membrane contains 30mol% of ZrO₂. The permeation rate of hydrogen of this membrane is ca. 50 times higher than that of a symmetric porous glass membrane with a reasonable separation factor for H₂/N₂ mixture and this membrane shows no degradation by heating at 500°C. This membrane is also proved to be stable by water vapor exposuring test at 350°C in an autoclave.

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Pollucite (Cs_1-xLi_xAlSi₂O₆) powders of single phase have been synthesized by isomorphous replacement of part of the Cs⁺ ion by Li⁺ ion in the pollucite structure using sol-gel processing. Thermal expansion of the synthesized powders has also been investigated with a high-temperature XRD. The pollucite powders of single phase were synthesized in the case of the composition (Cs₂O:Li₂O: SiO₂:Al₂O₃ (molar ratio)=0.95-0.90: 0.05-0.10: 4.5:1). Thermal expansion was less than 0.2% (room temperature to 1200°C). In particular, the powders showed almost zero thermal expansion in the range of room temperature to 500°C.

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