Pure anorthite was prepared by calcination of a gel formed by mixing boehmite, silica sols with Ca(NO₃)2⋅4H₂O solution at 1050°C. Doping of this sol with B₂O₃ lowered the crystallization temperature of anorthite to less than 950°C depending on the dopant content. B₂O₃-doped anorthite powders were sintered at temperatures below 1000°C. The sintering was promoted by the formation of a B₂O₃-rich glassy phase around the grains. The dielectric constant of pure anorthite was 8.5 and decreased to 7.2 with the addition of 2.8wt% B₂O₃. Doping of B₂O₃ decreased the thermal expansion coefficient, whereas the mechanical properties were only little affected.

抄録全体を表示

Vanadium oxide thin films were prepared by the r.f. magnetron sputtering using vanadium metal powder as the target. The results are summarized as follows;
(1) The deposition rate depended largely on the deposition parameters, such as sputtering power, gas pressure and oxygen concentration in the Ar-O₂ gas atmosphere.
(2) The films deposited at room temperature were amorphous. When the substrate temperatures were above 200°C, crystalline films were obtained.
(3) With the increase of oxygen concentration in sputtering gas, the composition of thin films was transformed as follows: V→VO₂→V₄O₉→V₂O₅.

抄録全体を表示

The usage of mixed N₂/O₂ gas in the preparation of tin oxide thin films by sputtering was examined in order to clarify the relationship between the resulting crystal structure and the H₂ gas sensing properties. The formation of single-phase SnO₂ and the degree of preferential orientation of the (110) plane were improved by increasing the oxygen concentration in the sputtering gas. A higher gas sensitivity was observed in films having higher degrees of the orientation of the (110) plane, and the maximum sensitivity was increased by about 1.5 times of that for the film prepared in Ar/O₂ atmosphere.

抄録全体を表示

Sb₂O₃-SrO-V₂O₅ glasses were prepared by a castquenching method and their electrical conductivity was investigated, together with that of crystallized ones from these glasses. The glass forming region was V₂O₅ 65-95, SrO 5-35, Sb₂O₃ 0-15 (mol%) with T_g=280°-282°C. The electrical conductivity was in the range from 7×10^-7S⋅cm^-1 to 10^-5S⋅cm^-1 at 300K exhibiting small polaron hopping conduction of electrons. At temperatures lower than room temperature, another mechanism of conduction superposed on that hopping conduction. These glasses and crystallized ones were confirmed to be n-type semiconductors by Seebeck constant measurements. The crystallized glasses gave higher conductivities from 3.3×10^-4S⋅cm^-1 to 1.8×10^-2S⋅cm^-1 at 300K. The relationships between conductivity and temperature showed that the conduction was due to variable range hopping in a temperature range from 100K to 300K. Mott's parameter for variable range hopping for these crystallized glasses were evaluated, their disorder energy at low temperature was estimated to be of the order of 0.09-0.11eV. Discussions led to the conclusion that the conduction of these crystallized glasses was interpreted to be a mixed conduction of small polaron hopping and variable range hopping at temperature between 100K and 300K.

抄録全体を表示

Al₂O₃/Al composites containing a small amount of tin were prepared by the oxidation of the powder compacts of aluminum and tin coated with MgO powder at 1200° and 1250°C. The composite phase grew mainly on the MgO-coated face of the compacts. The thickness of the composite phase varied with the amounts of coated MgO and tin. The effects of the amount and particle size of the MgO powder on the thickness of the composite phase were explained on the basis of the concentration of magnesium produced by the reaction between MgO and molten aluminum. The volume fraction of aluminum in the composite phase decreased with increasing amount of MgO and increased by the addition of tin. The volume fraction of pore in the composite was less than 3vol% under usual conditions.

抄録全体を表示

Mechanical strength and thermal resistance of porous glass membranes prepared by phase separation of calcium alumino borosilicate glass were studied to obtain basic information for application to membrane technology. The porous glass showed relatively high strength due to uniformly controlled pores and interconnected glass skeleton in spite of the high porosity. The reliability of its mechanical strength was superior to that of commercial glass articles in that Weibull modulus obtained from compressive strength of porous glass was 23.8. Pore structure of the glass membrane played a very important role in order to ease the thermal shock and maintain high thermal shock resistance.

抄録全体を表示

The present investigation reveals that grain boundaries of β-SIALON are corroded selectively by molten copper oxide. β-SIALON ceramics become more vulnerable as the amount of grain boundary phase, mainly glass, increases. High density β-SIALON ceramics (fraction to the theoretical density from 0.9 to 1) were heated with CuO powder at 1200°C for 1h in air. The HIPped sample which had the highest density was corroded most severely, in contradiction to the general relationship between density and corrosion of refractories. Cryogenic specific heat measurements showed that the HIPped sample contained the largest amount of grain boundary phases. Among the normally sintered samples, one with larger amount of grain boundary phases was corroded most severely. The difference of the amount of grain boundary phases may have been attributed to the thermal treatment conditions, especially to the cooling rate and the highest temperature attained. The corrosion behavior of β-SIALON ceramics in molten copper oxide coincided well with the results of SEM observations and the data of phase diagrams. Also, the cryogenic specific heat is a sensitive property, with which slight differences of the amount of grain boundary phases can be detected. These small differences can not be distinguished by means of SEM observations or XRD analysis.

抄録全体を表示

The component region for the growth of long rodshaped β-LiAlO₂ crystal was systematically examined in the LiOH-Al₂O₃-NaOH system. The formation of rod-shaped β-LiAlO₂ could be observed within the region, where the molar ratio of LiOH/Al₂O₃ is greater than 1.5 and the molar percentage of NaOH is less than 70. It was revealed that long rod-shaped β-LiAlO₂ crystals could be obtained in the component region; LiOH 40-60mol%, NaOH 30-50mol%, and Al₂O₃ 10mol%.

抄録全体を表示

The effect of Na₂O, K₂O, Li₂O, F and B₂O₃ contents on the crystallization and relative opacity of low temperature melting TiO₂-opacified porcelain enamels was investigated by means of DTA, XRD, SEM observations and a Hunter color difference meter. An increase in Na₂O, K₂O and Li₂O content in frit raised the temperature of crystallization peak of DTA, while the increase in B₂O₃ and F content lowered the temperature of the peak. The opacity of the enamel fired at 690°C showed a maximum value with the change in the Na₂O, K₂O, Li₂O, F and B₂O₃ contents. The developed TiO₂-opacified porcelain enamel frit was capable of firing at temperatures lower than 690°C, which is 110°C lower than commercial frits.

抄録全体を表示

CFGFRP (carbon fiber-glass fiber reinforced plastics) composites are found to be promising materials for self-diagnosis of fracture in the present paper. When the carbon fiber tows fractured, the electrical resistance of CFGFRP composites increased largely, and afterwards CFGFRP composites were able to resist the load due to the presence of the glass fiber tows. Large changes in the electrical resistance of CFGFRP composites during and after loadings are very useful phenomena for foreseeing the fracture by self-diagnosis. The property of self-diagnosis of the fracture of CFGFRP composites was controllable by selecting the type of the carbon fibers with different ultimate elongations. In the application of this method, changes in the electrical resistance of CFGFRP-reinforced concrete were measured during and after loadings. Also, the information on the position of fracture by the self-diagnosis was attainable by the arrangement of CFGFRP composites. A method based on monitoring the changes in the electrical resistance is a promising method for foreseeing the fracture of the CFGFRP-reinforced concrete by self-diagnosis.

抄録全体を表示

Effects of CaO and SiO₂ addition on microstructure and intrinsic coercivity (iHc) of sintered Sr-ferrite were investigated. The amount of CaO and SiO₂ additives had direct effects upon microstructure and iHc. In CaO addition, remarkable grain growth parallel to the c-plane of Sr-ferrite crystals was observed, resulting in a decrease in iHc below 80kA⋅m^-1. On the other hand, simultaneous addition of CaO and SiO₂ suppressed the grain growth of Sr-ferrite crystals and shifted the grain size distribution to smaller values. As the amount of SiO₂ additive increased, iHc increased up to 250kA⋅m^-1 in spite of the further densification with raising sintering temperature. In this case, sintered Sr-ferrite had a homogeneous microstructure consisting of nearly isodimensional crystals in the directions parallel to the c-plane and c-axis. Therefore, the increase in iHc of sintered Sr-ferrite with suitable amounts of CaO and SiO₂ can be attributed to the decrease in average size of crystals having nearly spherical geometry, which enhances shape magnetoanisotropy of Sr-ferrite crystals.

抄録全体を表示

In order to study the detailed propagation of fast growing cracks in tempered glass, we used high-speed photography together with holographic interferometry. Tempered soda-lime-silica oval glass plate was used as the specimen, in which the thickness was 8mm, the major axis was 150mm, and minor axis was 105mm. Shock wave propagation and crack generation were photographically observed simultaneously. Also, two kinds of cracks which had different velocities were observed.

抄録全体を表示

Silica-gel particles were synthesized by the sol-gel method in W/O emulsion. Preparation conditions were studied for controlling the particle diameter of the silica-gel, i.e., reaction temperature, agitation speed, the value of hydrophile-lipophile-balance of surfactants, and the nature of reaction vessel. Properties of the silica-gel were determined by the scanning electron microscopic method, particle diameter distribution, specific surface area, and pore size distribution. The particle diameter of the silica-gel was about 5-15μm. The silica-gel was applied to packing materials for high-performance liquid chromatography (HPLC) after modifying the surface of the silica-gel with octadecyl group. The amino acids and aromatic compounds were successfully separated and the quantitative analysis of phenylalanine could thoroughly be performed.

抄録全体を表示

The effect of additives on the vitrification temperature was investigated using the isothermal method. Lime, talc and materials containing alkaline earth metals were added to porcelain bodies in the quartz-feldsparkaolinite system which were the representative ceramic composition for building construction. The alkaline earth metals of about 3% lowered the vitrification temperature of the body without affecting temperature sensitivity. The decrease in the vitrification temperature depended on the molar concentration of the alkaline earth metals irrespective of their kinds. In addition, the apparent viscosity of the body was evaluated from the pressure softening displacement, and the decrease in the vitrification temperature has been ascribed to the decrease in the apparent viscosity.

抄録全体を表示

Effect of heat treatment conditions on properties of aqueous alumina green sheets was investigated. A suspension was prepared by mixing alumina, water and binder using a ball mill. The binder was acrylic ester and acrylic acid copolymer stabilized at pH 8.5 with a dilute ammonium solution. Green sheets were fabricated with a doctor blade. The suspension was cast on a PET film and dried at 70°C 1h. The green sheets were heated at 80°, 100°, 120°, 150°, and 200°C for 1h. The properties of green sheets, such as strength, extension, solubility in a dilute ammonium solution and adsorption behavior of moisture changed remarkably at the temperature of treatment from 120° to 150°C. FTIR analysis revealed that changes in the properties of green sheets were caused by self-crosslinking of carboxylic groups of the binder. A small amount of water in a green sheet was found to be a kind of plasticizer.

抄録全体を表示

To investigate the shaft seal for NH₃-H₂O binary vapor turbines, first of all, immersion tests of several sliding materials were carried out in a static NH₃-H₂O mixture (NH₃ concentration: 30wt%) for 100h under the condition of maximum temperature at 450°C. The test materials were selected from the sliding materials commonly used as mechanical seal rings, such as SiC ceramics, Al₂O₃ ceramics, hard metals and carbon materials. (1) SiC specimens prepared with B (boron) and C (carbon) as sintering additives under the pressureless sintering process were confirmed to be most preferable. On the other hand, pressureless sintered SiC with Al₂O₃ additive and reaction bonded SiC indicated worse anti-corrosive resistivity. The Al₂O₃ additive in the pressureless sintered SiC and the excess metallic Si in the reaction bonded SiC were the most corrosive parts in the structure of SiC ceramics. (2) Al₂O₃ were recognized as anti-corrosive materials. (3) Hard metals were corroded easily. (4) The resin was corroded selectively in resin impregnated carbon material. Non-impregnated carbon material was hardly corroded. (5) These materials, with better anti-corrosive properties, can be used for the mechanical seal of NH₃-H₂O binary vapor turbines, although the increase in the surface roughness and the reduction of the bending strength were observed slightly.

抄録全体を表示

The effect of starting materials and addition of additives on sinterability of Ba(Mg_1/3Ta_2/3)O₃ (BMT) powder was investigated. Sinterability depended on starting materials and additives. The BMT-powder synthesized by calcining powder mixtures of BaCO₃ and MgTa₂ O₆ showed better sinterability than the BMT-powder synthesized by calcining those of BaCO₃, MgO and Ta₂ O₅. The sinterability of the BMT-powder prepared by BaCO₃ and MgTa₂ O₆ was enhanced by BaTa₂ O₆ and suppressed by BaCO₃. A BMT ceramic with a 98% theoretical density was obtained by the addition of 1mol% BaTa₂ O₆, followed by firing at 1600°C for 2h in air. Sinterability of a BMT-powder was improved by starting materials and addition of BaTa₂ O₆.

抄録全体を表示

Joining strength of Si₃N₄ with a 80wt%Ni-20wt%Cr alloy interlayer was evaluated by a four point bending test at elevated temperatures in air. After holding at 1273K for 3.6ks, the average joining strength was 220MPa, which was almost the same as room temperature strength. Furthermore, after annealing for 75ks at 973K in air, the strength of the joints at room temperature did not decrease.

抄録全体を表示

Mullite/20vol% SiC whisker composites were prepared using SiO₂-Al₂O₃ powders with various Al₂O₃ contents (63.7, 69.1, 71.8, 73.9wt% Al₂O₃). They were subjected to oxidation in dry air at 1300°C for 10 to 360h, and the oxidation behavior and the flexural strength after oxidation were examined. (1) Oxidation was accelerated after 200h exposure. (2) The composites showed almost the same oxidation behavior, but the weight gain decreased with increasing Al₂O₃ content of matrix. (3) The strength of dense composites degraded about 10% after 360h exposure, however, that of the composites with low density decreased sharply after 200h exposure.

抄録全体を表示

The crystal structure of Ti_0.85Sn_0.15O₂, synthesized by chemical vapor deposition, was studied by the Rietveld analysis of an X-ray powder diffraction pattern. The structure was explained by the anatase-type structure in which 15 at% of Ti was substituted by Sn. The cell parameters were a=3.8065 (2) and c=9.6733 (8) Å.

抄録全体を表示