The effect of functionalities of acrylic binders on rheological behavior of aqueous alumina suspensions and properties of green sheets was investigated to find optimal conditions for the tape casting process. The functionalities of binders were 35, 20 and 10mg KOH/g. These binders had almost the same glass transition points (T_g) and molecular weights (M_w). Suspensions containing binders with low functionalities showed high shear-thinning flow behavior and high yield stresses. The resultant green sheets had low packing densities, low strengths and small elongations. In contrast, suspensions containing binders with high functionalities showed low shear-thinning flow behavior and low yield stresses. Suspensions gave green sheets with high packing densities, high strengths and large elongations in this case. As functionalities of binders increased, the amounts of adsorbed binders on alumina particles decreased and solubilities of binder sheets in aqueous solutions increased. It is found that the dispersibility of suspension is controlled by adsorption of binder on alumina particles and binder solubility in aqueous solution. It is also found that the strength of green sheet is determined by that of binder sheet. The results are interpreted as follows; increase in functionality enhances the cross-linking of chain molecules in the binder by forming hydrogen bonds between carboxylic acid sites.

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CdS-microcrystallites were prepared in porous Vycor glass (PVG) by impregnation of PVG with an aqueous solution of Cd(NO₃)₂⋅4H₂O and subsequent reaction with H₂S gas. The optical absorption edge of the CdS/PVG containing 1.0wt% cadmium exhibited a blue shift by 0.37eV compared to bulk CdS, indicating the quantum size effect. The blue shift decreased with increasing diameter of CdS-microcrystallites in PVG. In the photoluminescence spectra of the CdS/PVG, the band-edge emission and the deep-level emission were observed. In accordance with the optical absorption spectra, the blue-shifted band-edge emission was also observed. The deep-level emission was effectively quenched by heating the CdS/PVG up to 300°C in air or by addition of methyl viologen (MV²⁺) as an electron acceptor, suggesting that the emission arose from electron-hole pair recombination on the surface of CdS-microcrystallites.

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Corrosion behavior of powdered, hot-pressed, and pyrolytic boron nitride was investigated under hydrothermal conditions at 120°C to 300°C and saturated vapor pressure of water for 1 to 11 days. The reaction kinetics of the corrosion of hexagonal boron nitride (BN) were found to obey linear rate law. Scanning electron microscopic (SEM) observations of the BN powder after hydrothermal corrosion showed that the rate of hydrothermal attack by H₂O was determined by anisotropy due to crystallographic orientation. The weight loss of hot-pressed BN specimens was greater than that of pyrolytic BN specimens at each temperature. This result may be explained by the difference in the B₂O₃ content and the microstructure due to the processing of materials. The corrosion rate of hexagonal BN in hydrothermal corrosion could be expressed by the chemical reaction controlled kinetics with the apparent activation energy around 60kJ/mol.

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Concrete reinforced by CFGFRP (carbon fiber-glass fiber-reinforced plastics) composites containing carbon and glass fiber tows with small and large values of ultimate elongation respectively was found to be an intelligent material with a self-diagnosing function for preventing fatal fractures. The electric resistance of the CFGFRP composites increased with increasing load, strain and deflection in the CFGFRP-reinforced concrete. A large change in electric resistance occurred at the point where carbon fiber tows fractured, and the point was controllable by a suitable selection of the type of carbon fibers with different ultimate elongations. Permanent, residual electrical resistance of the CFGFRP composites was observed even after the removal of load, and the changes in the electric resistance was dependent on the maximum load applied. In the application of this method, information on the position of fracture by the self-diagnosis was obtained by the arrangement of the CFGFRP composites in a reinforced concrete. A method based on monitoring changes in electric resistance of the CFGFRP composites during loading and after unloading is a promising method for foreseeing the fracture of the CFGFRP-reinforced concrete by self-diagnosis.

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A microstructure of a barrier-layer capacitor with Bi₂O₃ diffused SrTiO₃ has been studied by means of SEM, TEM, and XPS. Samples for SEM observations were prepared by electrolytic etching, which allowed a visual characterization of insulating boundary layers. They were O₂-diffused layers wider than Bi-diffused layers, which observed as lattice-disorder region by TEM. Metal Bi was observed in addition to Bi₂O₃ by XPS. Barrier-layer model unique in case of Bi₂O₃ was investigated for oxygen supplyment from Bi. And we revealed it's propriety using standard free energy of metal oxide.

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The tetragonal (t)→←monoclinic (m) phase transition temperature of compositionally homogeneous arc-melted ZrO₂-RO_1.5 solid solutions (R=Nd, Rm, Er, Yb and Sc) was investigated by TMA (thermomechanical analysis; dilatometer) and high-temperature X-ray diffraction. The t→←m transition was observed in ZrO_2-x mol% RO_1.5 (x=0, 2 and 4 for R=Nd, Sm, Er and Yb, and x=2, 4, 6 for R=Sc), but not in specimens with higher dopant content. The equilibrium temperature T_0t-m between t-and m-phases decreased linearly with an increase of dopant content x, the degree of which |dT₀/dx| was larger for dopants with larger ionic radii.

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AlN/Al composites were prepared by the nitridation of Al-MgO (0-7.5wt%) powder compacts at 1100-1400°C. The dense composite layer grew outward from the bottom surface of the powder compact at 1250-1400°C. The conversion of Al to AlN and the thickness of the composite increased with increasing content of MgO, reaction temperature and time. The nitridation of the powder compact proceeded in the following four steps: (i) nitridation of the surface of Al particle, (ii) destruction of the surface AlN film and the eruption of molten Al by thermal mismatch between Al and AlN, (iii) dissolution of MgO into erupted Al, (iv) growth of AlN/Al composite by the nitridation of MgO-dissolved Al. The microstructure of the resulting composite from which Al metal was removed by etching shows the channels which molten Al might wick through during nitridation. According to the outward growth and the microstructure of the composite, the growth mechanism of AlN/Al composite may be the same as that of so-called Lanxide^TM process.

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The influence of small addition of selected oxide additives and brittle SiC-phases of various morphologies on the mechanical behavior of high-purity Si₃N₄ has been investigated. Dense monolithic (doped with SiO₂, Y₂O₃ or Yb₂O₃) and composite bodies (containing SiC whiskers or platelets) were obtained by hot-isostatic-press (HIP) sintering via glass-encapsulation and tested from room-temperature to 1400°C in comparison with the additive-free Si₃N₄. A remarkable increase in toughness was obtained only by doping with 1.7vol% Y₂O₃ or Yb₂O₃ (the largest amount added in the present investigation), or by dispersing 25vol% of SiC platelets. The mechanical performance at 1400°C was evaluated with emphasis on the time-dependent strength and deformation behavior. Two different trends were recognized: (1) the materials containing only SiO₂ at grain boundaries including composites showed linear strength behaviors and the critical phenomenon for strength degradation at 1400°C was the subcritical crack growth from pre-existing defects. (2) doping with oxide additives led to significant reduction of flaw sensitivity due to crack-tip blunting/healing mechanism concurrently, however, with marked degradation of the deformation resistance. Among the tested materials, the one containing 25vol% SiC platelets showed a combination of properties convenient for long-term high-temperature applications: a fracture resistance comparable with that of materials containing additives as well as a superior time-dependent strength and deformation behaviors up to 1400°C.

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Alumina with SiC or TiC particles was hot-pressed at 1500°C for 2h in N₂ under a pressure of 40MPa, and the effect of the size and volume fraction of dispersed particles on mechanical properties of the composites was investigated. Compared with monolithic alumina, the flexural strength of both composites increased when the dispersed particle size was small. The fracture toughness of Al₂O₃/SiC composites increased with a decrease in particle size. However, a maximum fracture toughness was observed for Al₂O₃/TiC composites when the particle size was 4-6μm. These results are explained as follows. The increase in fracture toughness is caused by microcracks originated by thermal expansion mismatch between the matrix and the dispersed particle. In the case where the thermal expansion mismatch and the size of dispersion particles are both large, cracks develop spontaneously during cooling, releasing thermal stress, and thus hindering the operation of the microcracking mechanism that would increase the fracture toughness of the composites. It is concluded that each system has a suitable size of dispersed particles. On the other hand, the increase in strength is caused by the increase in fracture toughness and by the decrease in the length of pre-existing flaws due to suppression of abnormal grain growth of the matrix.

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Pyrolysis of basic calcium carbonate (BCC) in inert gas flow was studied. Three endothermic peaks in the DTA curve and three weight losses corresponding to the DTA peaks in the TG curve were observed. The evolved gas was analyzed and the thermal decomposition process was investigated by high temperature X-ray diifractometry. The first endothermic process was found to correspond to the formation of BCC anhydride by dehydration of BCC crystals. The second one corresponded to the formation of calcite and Ca(OH)₂ by decomposition of BCC anhydride, and dehydration of the resulting Ca(OH)₂ into CaO. The third one was related to decarbonation of the calcite into CaO. Infrared absorption spectra of intermediate products support these results. Electron microscopic studies showed that, after the decomposition of plate-like BCC anhydride, calcite particles were produced inside the plate-like condensates. After decarbonation, single crystals of CaO were formed by disintegration of the condensates.

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A TiO₂ powder compact was exposed to 2.45GHz microwave (0.1-0.8kW) for 0.5-60min and the response of TiO₂ was examined by measuring the surface temperature of the specimen. Anatase-type TiO₂ was heated up to 950°C but rutile-type TiO₂ was not heated. At a constant power output the temperature of anatase-type TiO₂ was higher for larger specimens, and at a constant specimen weight the temperature of the specimen was higher at higher power output. The grain size was larger in the bulk than near the compact surface. The transformation of anatase-type TiO₂ to rutile-type TiO₂ also proceeded more extensively in the bulk than near the surface. These differences were ascribed to the temperature difference caused by the small penetration depth of microwave in this oxide.

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Effects of milling conditions and particle size of Sr-ferrite powder on microstructure and magnetic properties of sintered Sr-ferrite have been investigated. Processes for obtaining a fine Sr-ferrite powder have direct effects upon the crystallite size and its distribution of sintered Sr-ferrite specimens. As a result of new improved processing for obtaining fine powders having a narrow particle size distribution, both Br and iHc of sintered Sr-ferrite specimens increased. Probably, these phenomena are related to the increase in the amount of crystals having magnetic single domain. To improve the particle size distribution of Sr-ferrite powder in the milling process, a new process consisting of three steps, i.e., primary milling, annealing and remilling, has been studied. In this process, annealing makes submicron particles grow into spherical particles of about 1μm. In the subsequent remilling process, residual coarse particles of more than 2μm can be milled selectively into fine particles. Consequently, the new annealing-remilling process gives Sr-ferrite powders with more uniform particle size distributions than the conventional milling process, resulting in success of fabricating high-performance sintered Sr-ferrite magnets having Br≥0.44T, iHc≥287kA/m, (BH)max≥37.4kJ/m³ or Br≥0.42T, iHc≥334kA/m, (BH)max≥34.2kJ/m³.

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Improvement of output-voltage of IR (infrared ray) sensor using semiconductive ceramic-fiber is to use fiber with higher electric resistivity decreased the electric resistance by the partial treatment of high-voltage pulse. The apparatus of high-voltage pulse was made, and the method is simple in technique and low in cost. The method cutting surface of semiconductive carbonfiber near both electrodes had a little effect for improvement of output voltage. The electric resistance of the semiconductive carbon-fiber decreased by the application of high-voltage pulse, and the band with a low electrical resistance was easily made by this technique. The method treating partially by the application of high-voltage pulse decreased the electric resistance, and the part without application of high-voltage pulse remained of state of high temperature dependence. The fibers thus treated can show small electric resistance with high thermistor constant. IR sensor using such fiber showed higher output-voltage for IR source. The treatment of high-voltage pulse was found to be an effective method for improvement of the output-voltage in IR sensor using semiconductive carbon-fibers.

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BaTi₅O₁₁ coating films were prepared by the sol-gel method using metal alkoxides. Effects of organic sol-vents and hydrolysis-inhibiting additives on structure and sinterability of gel films were examined. Transparent coating films were obtained in air by partial hydrolysis of Ba/Ti alkoxides using 2-ethoxyethanol as a sol-vent, and addition of ethyl acetoacetate was also attractive. After firing at 900°C to 1000°C, single-phased and dense BaTi₅O₁₁ films were prepared on YSZ. However, these films had different gel structures and sintering behavior; thus, organic additives such as ethyl acetoacetate affect the sinterability of the gel films and microstructure of resultant films.

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Hydroxyapatite (HAp) powders with spherical Al₂O₃ particles dispersion were synthesized by a wet process or hydrothermal process. The transmission electron microscopic observations of Al₂O₃-HAp powder mixtures showed that the Al₂O₃ particles were uniformly dispersed in and surrounded by fine HAp crystals. Al₂O₃-HAp composite ceramics were prepared by hot pressing at 1000°C under 50MPa for 1h. The fracture toughness of the ceramics with Al₂O₃ dispersion increased up to 1.80 times that of pure HAp ceramics.

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Physical properties of advanced ceramics are influenced by defects produced in the forming process, and large defects can not be removed even by hot isostatic pressing process. The slip casting, which has been used in the forming process of traditional ceramics, enables one to make large and dense green bodies with complicated shapes. Wear and dissolution of gypsum molds contaminates the green bodies with calcium and sulfur. Porous alumina ceramics as casting molds were examined in comparson with gypsum from view points of wettability with water and rate of filter cake buildup. Porous alumina ceramics produced by a firing showed very high wettability values as compared with those for gypsum. Therefore, porous alumina ceramic mold with small pores provided larger penetration pressure and higher rate of filter cake buildup than gypsum mold.

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Two methods of thermal stress calcutation by Timoshenko's method and Poritsky's method for circular cylinders and disks were discussed, and the results of calculation were compared. The first method was given by Timoshenko based on the integration of a temperature×distance from central axis function, and the other was that given by Poritsky based on multivariant simultaneous equations which represent elastical balances of principal stresses and strains in a cylinder and a disk. Calculations were carried out for the following four cases: a solid cylinder, a cylinder with a concentric hole, a solid disk and a disk with a concentric hole. The results obtained by the two methods were identical for the four cases. It was proved that the two methods were mathematically equivalent.

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The effect of preparation conditions of alumina ceramics to the properties of green and sintered bodies was investigated. In this experiment, both ball milling and attrition milling techniques were applied to prepare the suspensions, and the effects of the content of an organic binder, the temperature of spray drying, and the pressure of uniaxial mold pressing and CIPing were studied to the properties of green and sintered samples. Results indicated that the density and the pore size distribution of the green compact depended upon the content of a binder, showing the densities of compacts before dewaxing were higher in the case of more amount of an added binder probably due to the effects of improved plasticity and lubricity of granules. After dewaxing, however, the addition of lower amount of a binder contributed to the increase of green densities with the formation of small pores in the matrix. Decrease of an added binder was also effective to obtain the increased density and the improved bending strength after sintering.

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The effects of compositions of Al₂O₃-Y₂O₃ sintering additives and sintering conditions on the mechanical properties were studied to determine the fabrication conditions of silicon nitride via slip casting. Slurries containing 67wt% solids (92wt%Si₃N₄ and 8wt%Al₂O₃-Y₂O₃), 33wt% distilled water and 0.01wt% deflocculant (polyacrylic ammonium) were prepared. After the forming by vacuum filtration using a porous polymer resin mold, samples were adequately dried and sintered in the temperature range from 1775 to 1825°C at 0.9MPa of N₂ pressure. High-density sintered bodies (3.16-3.25g/cm³) were obtained. The density tended to increase with raising temperature for a short sintering period (4h), while, decrease with raising temperature for a long sintering period (10h). Under the present preparation conditions, flexural strength maxima were observed at 3wt%Al₂O₃-5wt%Y₂O₃. A sample sintered at 1775°C for 10h showed an average flexural strength of 1138MPa and a Weibull modulus of 17.3. A composition of 3wt%Al₂O₃-5wt%Y₂O₃, that ratio corresponds to the liquid phase compositions at the lowest temperature in the system Al₂O₃-Y₂O₃-SiO₂, was favorable to obtain silicon nitride ceramics with high-strength at room temperature.

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Research has been conducted toward developing a compressive testing method more suitable than present procedures for use on advanced ceramics with extremely high compressive strength. A dumbbell-shaped specimen is proposed as an edge-effect-free shape, and testing equipment with a self-aligned system is suggested to estimate accurately the compressive strength. Experimental results for some structural ceramics indicate that the columnar specimen prescribed in JIS has edge effects, whereas a dumbbell-shaped specimen has no edge effect and shows higher strength than the columnar specimen.

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Influence of the substrate temperature on the formation of carbon films by hybrid plasma CVD is discussed. The carbon film deposited on a molybdenum substrate at 120-570°C was amorphous and showed appreciable sp³ bonds in the infrared absorption spectra. Typical Raman spectra of films deposited on Mo substrate at three different substrate temperatures were studied. The Raman spectra exhibit three (substrate temperature dependent) features: (1) two broad peaks at 1300 and 1600cm^-1 at 120°C, (2) two broad peaks at 1339 and 1580cm^-1 at 430°C, and (3) two sharp peaks at 1351cm^-1 and 1585-1581cm^-1 at above 600°C. By heating the substrate to 600°C, the films had higher mechanical and electrical characteristics (dynamic-hardness: 400, sheet resistance: 10⁷Ω/cm²). The deposition rate of the films increased with increase in substrate temperature above 430°C.

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The influence of Sb doping on the grain growth in BaTiO₃ is examined. After equilibrating below the eutectic temperature of small amount of liquid phase, samples were heated up to a sintering temperature above the eutectic point. The nucleation at lower sintering temperature in Sb-doped samples started earlier than in non doped samples. The nucleation rate increased with increasing sintering temperature. Sb doping and increasing sintering temperature lead to uniform microstructure and smaller average grain size. Due to the higher nucleation rate, increasing sintering temperature also leads to narrower grain size distributions.

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H-R, a strongly acidic ion exchange resin, is an effective dissolution agent for water-insoluble inorganic materials. This paper deals with the calorimetric measurement of dissolution of commercially produced portland cement, cement minerals and their hydrated products in an H-R aqueous suspension at 25°C in comparison with the HF-HNO₃ method. Examples illustrating the results of calorimetric measurement during the dissolution process of RHC, rapidly hardening cement, and hydrogarnet (C₃AH₆) are shown.

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Compounds in the (PrGd_0.8A_0.2)CuO_z (A=Ca, Sr) systems were prepared by the solid-state reaction. The PrGd_0.8Sr_0.2CuO_z was crystallized to the T-type structure whereas the PrGd_0.8Ca_0.2CuO_z was crystallized to the T′-type one. The electrical conductivity and the magnetic susceptibility measurements showed that the compounds containing Sr were bulk superconductors with T_c=50-60K after the treatment in oxygen atomspheres at pressures of 7-10MPa at 300°C. The oxidizing treatment converted Cu ions to the high valence state, but did not change the valence state of Pr ions. It became clear that the preferential oxidation of Cu ions in the T-type compounds containing Sr genarates the superconductivity.

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Pyrochlore type Na_0.39Bi_3.47O₇ containing Bi⁵⁺ was prepared by low temperature hydrothermal reaction using hydrated sodium bismuth oxide, NaBiO₃⋅nH₂O, as a starting material. The mean valence of Bi in the pyrochlore is 3.94. The X-ray powder pattern for the pyrochlore was indexed in the cubic system with a=10.943(8)Å. The crystal structure was refined with the X-ray powder Rietveld method. The final R-factors, R_WP, R_P and R_B were 13.3, 9.5 and 12.8%, respectively. The pyrochlore decomposes above 380°C with two steps of weight losses caused by complete reduction from Bi⁵⁺ to Bi³⁺. The Na-pyrochlore exhibited high electric resistivity (-10⁷Ω⋅cm) at room temperature.

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