Preferred orientation and microstructure of MgO films prepared by ion beam sputtering were investigated. The crystallographic orientation of MgO films was a function of the substrate angle (δ), O₂ gas partial pressure (P_O2) and the substrate temperature (T_s). As δ changed from 90° to 0°, the transmission electron diffraction (TED) pattern of the films deposited in P_O2 of 1×10^-4 Torr at T_s=R. T. changed from a random orientation to the (111) preferred orientation in which the crystallographic (111) plane was parallel to the substrate surface. An increase in P_O2 from 0.1×10^-4 to 10×10^-4 Torr caused the (111) preferred orientation. At T_s>100°C, the TED pattern of the films on NaCl (200) deposited with δ=90° showed epitaxial growth in contrast with a random orientation at T_s<100°C. Annealing below 500°C did not change the orientation and size of the crystallite. Annealing above 1000°C for 30min, however, caused crystallite growth from 5nm to 20nm without any change in orientation. This size is still smaller than that of the crystallites deposited on a heated substrate. The origin of the crystallographic preferred orientation of the MgO thin film deposited by ion beam sputtering was explained in terms of the growth competition. The (111) preferred orientation becomes predominant in the growth competition over others with decreasing the arrival ratio of Mg/O.

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Crack initiation and propagation behavior in alumina pellets subjected to thermal shock with various temperature differences (ΔT) were investigated. Change in specimen surface area, i.e., in crack surface area, resulting from the thermal shock was measured non-destructively by a BET surface area measurement technique. The extent of crack propagation at a certain ΔT was compared on the specimens subjected to only a single thermal shock and specimens repeated thermal shock with a gradual increase in the temperature difference up to the ΔT. The single thermal-shocked specimens sustained severer damage than the repeatedly thermal-shocked specimens. Good coincidence was obtained between calculated and measured crack surface areas, demonstrating the validity of the BET technique as a non-destructive method for evaluating the thermal shock damage.

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A sintered composite, which was made of MoSi₂ and granulated Al₂O₃ by a new technique, realized high electric conductivity even in the range of much Al₂O₃ and was used as a material for heating element. It was already reported. This study shows the material was not appropriate for high temperature thermistor, however was attained by obtaining a superior material in high temperature stability as a result of improving its surface from forming aluminosilicate glass layer. Moreover it was found to be a peculiar material to positive temperature characteristics of electric resistance and to stabilize B constant at a small number, compared with properties of the other present materials for high temperature thermistors.

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Molds were estimated by using 4 kinds of molds and 4 kinds of pure metals for soda-lime-silica glasses (colorless and amber container glasses) below 900°C in reducing atmosphere. The estimation was based on sessile drop measurement and observation of metal surfaces. The sessile drop measurement showed wettability by measuring the contact angle and interfacial diameter between glass and metal. Copper and copper alloy showed poor wettability, and their surface roughness increased. Iron showed good wettability and roughening of its surface. In metals except copper, grain boundary development and surface film formation were observed after heating. The contact angle on nickel was determined as a function of roughness, and the following empirical formula was obtained. θ_r=26.4r²+18.6r+77.1 θ_r: contact angle (degree) r: surface roughness (μm) These results suggested that the wettability and the surface roughness, owing to the reacted materials, crystal growth and kind of metals, are the essential factors for glass shaping molds.

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Flexural strength, Young's modulus, Vickers hardness and fracture toughness of SiC whisker reinforced glass ceramics (diopside, anorthite and cordierite) were measured. Maximum strengths of these composites were 550MPa for 30vol% whisker-diopside, 427MPa for 25vol% whisker-anorthite and 391MPa for 30vol% whisker-cordierite. Young's modulus and Vickers hardness of the composites increased with increasing whisker contents, exhibiting maximum at 25-30vol% whisker. While they decreased with more whisker contents. Apparent fracture toughness of SiC whisker-glass ceramic composites obtained by the indentation fracture technique was dependent on the indenter load. The maximum values of fracture toughness at indenter load of 10kg were 4.53MPa·m^1/2 for 40vol% whisker-diopside, 4.37MPa·m^1/2 for 30vol% whisker-cordierite and 4.13MPa·m^1/2 for 25vol% whisker-anorthite. It was assumed that the strengthening mechanism of SiC whisker-glass ceramic composites was load transfer. While, it was suggested that the toughening mechanisms of these composites were whisker pullout, crack deflection and load transfer to whisker for diopside glass ceramics, and crack deflection and load transfer for anorthite glass ceramics, and load transfer to cordierite glass ceramics.

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Bending strengths of porous Al₂O₃ ceramics with relative densities of 97, 74 and 60-65% were measured before and after the thermal shock by water quenching. An instantaneous decrease in strength was observed when the ceramics with relative densities of 97 and 74% were thermally shocked through the temperature difference of larger than 200°C. On the other hand, the strength of the ceramics with relative densities of 60-65% did not show the instantaneous decrease, but gradually decreased with an increase in quenching temperature. The width of the cracks caused by the thermal stress fracture was 2-3μm when the temperature difference in quenching was 585°C. Thermal shock fracture resistance parameter (R′) and thermal shock damage resistance parameter (R″) were calculated for each ceramics, which resulted that the high density ceramics showed higherest R′ and the lowest R″ values.

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The effect of a second phase (ZrO₂ particles) on the thermal shock resistance of MgO was investigated. MgO doped with 1mol% LiF and MgO dispersed with 10mol% ZrO₂ (t-ZrO₂ or c-ZrO₂) were fabricated by sintering. Sintered specimens were heated to various temperatures, quenched into water or lubricating oil, and then examined by the 4-point bending test to investigate the severity of the thermal shock. The critical temperature difference ΔT_c at which the fracture stress of specimens considerably decreased was higher in MgO dispersed with c-ZrO₂ (200K in water and 650K in lubricating oil) or t-ZrO₂ (250K and 620K) than that in MgO doped with LiF (115K and 300K). These results have been attributed partially to the increase in fracture stress of MgO due to the existence of dispersed ZrO₂. The strength of MgO dispersed with t-ZrO₂ did not instantaneously decrease at the temperature difference in excess of ΔT_c. This behavior was not observed in other specimens. It was thought to be caused by the microcracks created by m-ZrO₂ which was also present in the specimen. The critical temperature difference ΔT_c of specimens quenched in lubricating oil was higher than ΔT_c quenched in water. It was qualitatively in accordance with the prediction of the calculation of heat transfer coefficient.

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Quartz in Amakusa pottery stones was characterized by various methods. Two specimens were collected from Tsurugasako-ko in Sarayama-vein and Kadonosako in Kaigan-vein among the Amakusa pottery stone deposits. They were crushed and classified into six fractions. Quartz was extracted from the classified pottery stones by chemical treatment using phosphoric acid and fluoric acid. The following anomalies were observed for quartz in the pottery stones. (1) Lattice constants of quartz in Tsurugasako-ko were larger than those in synthetic rock crystal up to 0.0029Å in a-axis and 0.0051Å in c-axis, and those in Kadonosako were up to 0.0038Å in a-axis and 0.0026Å in c-axis. (2) Lattice strains were 2-17×10^-4 in Tsurugasako-ko and 7-24×10^-4 in Kadonosako, and increased with decreasing grain size. (3) The temperature of the endothermic peak due to α-β phase inversion was a little lower than 573°C, the inversion temperature of normal quartz. The peak was broader than that for normal quartz, and asymmetric in large grains. Double peaks were observed in smallgrained specimens. (4) The content of Al₂O₃ analysed was from 0.5 to 0.9wt% and increased with decreasing grain size. These anomalies can be understood assuming substitution of Al ions into quartz. The transition temperature from quartz to cristobalite in pottery stones was lower than that in synthetic rock crystal, and was dependent on the localities.

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Thermally induced coloring and bleaching in reduced phosphate glasses were investigated by means of DTA. As-quenched glasses prepared under reducing conditions are transparent and colorless. On reheating at around the softening temperature of the glasses, they turn red (“striking”). The struck glasses become almost transparent and colorless (“bleaching”) when they are heated above 580°C and quenched subsequently. The resultant glasses (PTC-RP glass) exhibit red-coloring by reheating above 200°C and/or light irradiation. It was explained in terms of transformation of colloidal phosphorus in the PTC-RP glasses that the endotherms at about 60° and 580°C in the DTA curves are due to melting of white and red phosphorus, respectively, and that the exotherm at about 270°C is due to transformation of liquid phosphorus to amorphous red phosphorus, i.e., to ring opening polymerization of P₄ molecules.

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Silicon carbide containing 5-15wt% graphite was fabricated by hot-pressing at 2000°-2300°C using carbon black as a starting carbon material. B₄C of 1wt% was doped in SiC as a sintering aid before mixing with carbon black. X-ray diffractometry and SEM revealed that the grain growth of SiC was suppressed by the carbon addition, and that carbon black changed to graphite microcrystals. Carbon addition increased the flexural strength of the composite appreciably. The composite with 10% graphite had the average strength of 820MPa and the maximum value of 1000MPa. The fracture toughness of 4.5MPa √m for the 10% graphite composite was obtained, as compared with 3.3MPa √m for monolithic SiC.

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V₂O₅-P₂O₅ glasses containing large amounts of V₂O₅ are known to have relatively low transformation and deformation temperatures, in spite of their low thermal expansion coefficients. However, poor water durability and strong devitrifying tendency prevent these glasses from being used as bonding glass. To improve these properties, the effects of composition and additives on the glass properties were studied, and the following results were obtained.
(1) An increase in P₂O₅ content improved the water durability and restrained the tendency of devitrification, while the transformation and deformation temperatures increased.
(2) On the other hand, addition of a small amount of Sb₂O₃ or PbO improved the water durability without affecting other properties of glasses.
(3) Infrared spectrum analysis confirmed that the glass was transformed from layered into network structures with increasing P₂O₅ content or by addition of Sb₂O₃ or PbO. The improved water durability was explained by the network structure which prohibits the water penetration into glasses.

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Dry rice hull contains 13-29wt% inorganic matter depending on the species, climate and geographic location. The inorganic matter is composed of silica (87-97wt%) with small amounts of alkali and other trace elements. Properties of ash obtained by combustion of between 400° and 1500°C were investigated. The SiO₂ in the rice hull was localized in the outer and inner epidermis of rice hull. The SiO₂ in rice hull ash formed by combustion below 800°C of rice hull powder with a particle size below 152μm was amorphous. Particles of the ash having an average diameter of 20μm were aggregates of small particles with a diameter of 2-5μm. At combustion temperatures above 900°C, the SiO₂ in rice hull ash consisted of cristobalite and a small amount of tridymite. The surface of ash particles melted and the particles bonded to each other. The particle size was 40-60μm. It was found that potassium contained in the rice hull ash caused surface melting of SiO₂ particles and accelerated the crystallization of amorphous SiO₂ to cristobalite.

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Two kinds of silicon carbide powders prepared from different synthesizing process were classified and decarbonated to investigate the particle size dependence of powder properties. Influence of the particle size on the sintering behavior was studied by dilatometry and microstructural observations. A powder synthesized from metallic silicon and carbon in solid state has a broad primary particle size distribution. This powder was also characteristic in having large amounts of unreacted carbon and impurity oxygen in the fine fraction of classified powder. The densification with boron and carbon additives progressed initially with equiaxial grain growth, and then, with formation of plate-like grains at high temperatures. The free carbon contained in the fine fraction promoted the densification remarkably at the initial stage sintering, while the coarse fraction reduced the densification rates. Inhomogeous sintered bodies were obtained from the powder consisted of the fine fraction with the large amount of free carbon and poorly sinterable coarse fraction. On the contrary, the other powder synthesized from tetrachlorosilane and heavy oil in gas phase had a narrow size distribution. In this case, the classified and decarbonated fractions showed almost the same densification behavior producing sintered bodies with homogeneous microstructure. The starting powder have to be homogeneous in chemical composition especially in fine fractions in addition to the reduced fraction of coarse particles.

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Crystal growth of MgO doped with AlF₃ and MgF₂ has been studied by BET method and X-ray powder diffractometry. The fluorides were hydrolyzed by the water contained in MgO powder above 500°C and generated HF gas, which was adsorbed on the surface of MgO. Fluorides inhibited crystal growth of MgO below 900°C, but accelerated the growth above 1000°C, because of evaporation of adsorbed HF. Departure of HF from the surface increases the surface energy of MgO and/or forms active points on the surface, and then migration of MgO between grains, mainly through evaporation and condensation, is promoted and would result in rapid crystal growth. MgF₂ crystallized again at 1000°C for MgO doped with MgF₂ in dry air. The HF coverage of MgO grains in a specimen containing 2mol% MgF₂ (evaluated as monolayer) was constant up to 1000°C and decreased above 1100°C. It was inferred that crystal growth of MgO proceeded so as to maintain the balance of surface energy for the evaporation of HF from the surface at 1000°C and that the crystal growth couldn't follow because of the rapid evaporation of HF above 1100°C.

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AlN powders were prepared by vapor phase reaction of AlCl₃⋅NH₃-NH₃-N₂ system. AlCl₃⋅NH₃ was prepared by the evaporation and decomposition of AlCl₃⋅nNH₃ (n=1.7-1.8) at 430°C. The shape of AlN particles varied with the molar ratio [NH₃]/[AlCl₃⋅NH₃] (X) or the synthesis temperature (T_R). At T_R=1400°C, AlN particles had columnar crystals at X≤7, but had smooth surface at X≥9. However, at T_R=1000°C, AlN particles had smooth surface even at X=4.2.

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Polycrystalline ruby was prepared using high purity oxides synthesized from metal salts. Polycrystalline ruby, which is equivalent to single crystal ruby in various properties, was developed. Detailed method of production and result of analyses will be reported later on.

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Si₃N₄ ceramics composed of fine-grained α′-Si₃N₄ and β′-Si₃N₄ were fabricated by hot-pressing mixtures of Si₃N₄, Y₂O₃ and AlN powders. The Si₃N₄ ceramics showed a very high strength (about 1.3GPa at room temperature and 1.0GPa at 1400°C) and a high fracture toughness (about 7.0MPa·m^1/2).

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Infrared reflection and Raman spectra of the complex perovskite-type compounds, Ba (Mn_1/3Ta_2(1-x)/3Nb_2x/3)O₃ have been measured at x=0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0. Two mode behavior was observed for both end-members and all the solid-solution in the vibration of BO₆-type octahedrons, where B indicates Mn, Ta and Nb ions. The coexistence of TaO₆ and MnO₆ octahedrons in solid solutions, however, resulted in the one-mode behavior, instead of the two-mode one. That is, these two octahedrons represent one-mode behavior.

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Whiskers of 2H-SiC were synthesized by the decomposition of silicon nitride in a graphite reaction vessel at 1900°C under the nitrogen pressure of 1MPa. The obtained long whiskers were typically -10mm long and 0.05-0.1mm in diameter and short whiskers were -0.1mm long and -10μm in diameter. Morphology observations suggested that they had grown by the spiral growth mechanism.

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