TiO₂ fine particles were anchored on a porous alumina ceramic support by the alkoxide method under various hydrolysis conditions. The photocatalytic property of the obtained TiO₂ precipitates, such as the photo-oxidation of ethanol, has been investigated. The amount, the dispersibility and the morphology of TiO₂ precipitates on the ceramic support were closely related to the efficiency of the photo-oxidation of ethanol.

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Creep behavior of MgO single crystals with ‹100› loading axis was investigated over temperature range from 1575° to 1725°C and under compression stresses from 3 to 10MPa. It was found that MgO single crystals had a sigmoidal creep behavior which can be described by Haasen's theory. Dislocation multiplication in which a few dislocation interactions were involved was responsible for the increase in creep rate at the initial stage of deformation. The stress exponents were measured to be about 3.4 at inflection point in sigmoidal creep curve and near 2.2 at steady state. The creep behavior at steady state mainly related to dislocation movement on two orthogonal conjugate {110} ‹110› slip systems. The main barriers to slip were caused by dislocation intersections occurring between two orthogonal {110} planes. The deformation at steady state was caused by dislocation gliding which depends on the climb motion. The dislocation substructure formed during creep was examined and the deformation mechanism was discussed.

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Fine Al-rich spinel MgO⋅1.5Al₂O₃ powder was synthesized by hydrolysis of mixed alkoxides. High sinterability of powder allowed to obtain relative density higher than 95% at temperature as low as 1300°C by pressureless sintering in air. Samples sintered at temperature of 1100°-1500°C had quite heterogeneous microstructure owing to precipitation of large corundum particles (<1400°C) and discontinuous grain growth of spinel matrix (>1400°C). However, homogeneous microstructure with fine grains could be obtained by a two step sintering process in which spinel grain growth at high temperature was inhibited by corundum particles momentarily retained above solvus temperature. Precipitation behavior during sintering was compared with that during annealing, and the precipitation mechanism was discussed.

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Based on the fractal nature of pulverized solid particles described in previous reports by the authors, the reaction mechanism which defines the reaction rate of a heterogeneous system is reconsidered. The 9 functions given in a commonly used classification by Sharp et al. are shown collectively in 3 functions. The introduction of diffusion in a non-integer dimension results in functions deviating from the known ones, particularly in a diffusion-controlled reaction. Though the models referred here are too simple to be directly applied to a system consisting of many particles, this paper shows that it is meaningless to discuss a particular reaction by fitting it to a classical 1-, 2-, and 3-dimensional reaction mechanism.

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Dense β, β″-alumina ceramics were fabricated by the reaction sintering in the Na₂O-MgO-Al₂O₃ system using α-alumina compacts infiltrated with Na₂O and MgO. High-density β, β″-alumina ceramics with uniform texture were prepared at 1600°C by liquid phase sintering through controlling the pore volume of α-alumina compacts and the amount of infiltrated Na₂O and MgO. High-porosity α-alumina compacts were superior to low-porosity ones in introducing a large amount of Na₂O in pores, and enhanced the densication rate through the formation of liquid phase of Na₂O-Al₂O₃ system. The effects of MgO content on the densification and phase composition of β- and β″-phases were also discussed.

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The crystallization process of BaFe₁₂O₁₉ from barium iron borate glass of 35.7BaO⋅34.3Fe₂O₃⋅30.0B₂O₃ composition has been investigated by using electron spin resonance (ESR) and Mössbauer spectroscopies. The linewith of ESR spectra of the specimens heat-treated at 500°C to 560°C is narrow because of superparamanetism of small BaFe₁₂O₁₉ particles precipitated. The ESR spectrum of specimen heat-treated at 580°C manifested an asymmetrical line. Also, in the Mössbauer spectrum of this specimen, the hyperfine structure was observed in addition to paramagnetic quadrupole doublet. These facts indicate that both ferrimanetic and superparamagnetic BaFe₁₂O₁₉ particles are present in this specimen. From the broad linewidth of ESR spectra and intense peaks due to internal fields in the Mössbauer spectra for the specimens heat-treated above 600°C, it is shown that most of BaFe₁₂O₁₉ particles in these specimens are ferrimanetic at room temperature as a result of crystal growth.

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The effect of additives on the densification and strengthening of titanium nitride (TiN) ceramics has been described. The additives studied were oxides (Al₂O₃, Y₂O₃ and MgO), nitrides (BN, AIN and Si₃N₄) and carbides (SiC and B₄C). The TiN compacts containing 5 and 10wt% additives were hot-pressed at 1950°C for 60min (except for Si₃N₄) in the ambient Ar gas of normal pressure. Additions of 10wt% Al₂O₃, 10wt% Y₂O₃ and 10wt% B₄C gave the relative densities of 97.4, 96.2 and 97.7%, respectively. The mechanical and electrical properties are as follows: 10wt% B₄C increased the hardness; 5wt% BN the flexural strength; 10wt% B₄C or 10wt% Y₂O₃ the values of fracture toughness (K_IC); 10wt% Al₂O₃ or 10wt% B₄C the Young's modulus and the rigidity; 10wt% B₄C the electrical conductivity. As a whole, 10wt% Al₂O₃, 10wt% Y₂O₃ and 10wt% B₄C additives contributed to both densification and strengthening. The most promising additive is 10wt% B₄C for TiN ceramics from the view point of relative density, mechanical and electrical properties, and prevention of grain growth.

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Powder properties of raw materials have a great influence on the dispersion of sintering aids, and green microstructure and sintering behavior on the preparation of Si₃N₄ ceramics. The mixing time required for sufficient dispersion of the raw material powders in a suspension increased with decreasing particle size of Si₃N₄. For sintering below 1700°C, the relative density of sintered bodies was quantitatively related with specific surface area of Si₃N₄ powders and the mode pyre size in green compacts. Decrease of pore diameter in green compacts and particle diameter of Si₃N₄ powders improved the densification of Si₃N₄ ceramics at relatively low temperatures.

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Films in the system ZrO₂-Y₂O₃ were prepared at 600°to 1000°C by chemical vapor deposition using β-diketone chelates of Zr and Y and O₂. The films having Y₂O₃ contents from 2 to 12% were obtained at various evaporatiorn temperatures of the sources. The films containing less than 3mol% Y₂O₃ were composed of cubic and tetragonal phases. The films containing more than 3mol% Y₂O₃ had a cubic crystal structure. The lattice parameter of the cubic phase increased. from 5.11 to 5.16Å with increasing Y₂O₃ content. The deposition rates of the cubic-phase films at 620° and 660°C were 1.8 and 9.0μm/h, respectively. The film deposited at 660°C was composed of randomly oriented fine grains. Dendritic structures were observed for the films deposited above 660°C. The films exhibited a crystallographic orientation of (100) parallel to the substrate plane.

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The pyrolysis of Si-C-O fiber (Nicalon) coated with an oxide film has been investigated. Nicalon fiber was heated in an O₂ stream, and was subsequently heated in an Ar stream at temperatures from 1573 to 1773K. The mass change of the fiber was determined with a thermobalance. The reaction products were examined by X-ray diffraction, SEM and TEM observations. During formation of the oxide film, the amorphous fiber core grew to the microcrystalline β-SiC. The mass of Nicalon coated with the oxide film did not change, when heated in an Ar stream, indicating the suppression of the pyrolysis of the fiber core. Because of the suppression, the high temperature strength of the core was appreciably retained. The oxide film was smooth, and crystallized from amorphous silica to cristobalite only partially during the heat treatment in Ar. Hence, it is considered that the SiO₂ layer retards the pyrolysis of the fiber core by restricting the outward transport of the gaseous products, SiO and CO.

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Two kinds of carbon layers comprised of graphite, were deposited on silica optical fibers by CVD. C-axis orientation of graphite structure has been found in one of the layers. Microstructure of carbon layers and hydrogen diffusion in the layers were studied. (1) Both layers were found to be uniform microstructure by transmission electron microscope. (2) Diffusion constant of hydrogen in one carbon layer which had c-axis oriented graphite structure, was one order of magnitude smaller than that in other carbon layer.

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Control factors of thermal expansion of feldspathic porcelain body for building materials and their control methods are discussed. The additivity can be established between the thermal expansion of feldspathic body consisting of quartz, mullite and glass phase and its amount of constituent phase irrespective of firing time and temperature within an ordinary range of the particle size distribution. However, the actual thermal expansion becomes lower than the value calculated by the method of additivity because of generation of cracks on and vicinity of quartz when its diameter becomes bigger than a certain range of the size. A progress of internal cracks of the porcelain body and its consequent release of stress were clarified in view of changes of the d-spacing of quartz, a decrease of bending strength and an observation of polarizer microscope.

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Densification conditions of alumina, MgO stabilized zirconia (MSZ) and zircon composite were studied, and sintered bodies were evaluated as cutting tool by the temperature dependence of three-point bending strength. The Mg-spinel formed from Al₂O₃ and MgO, stabilizer of zirconia, prevented the densification Al₂O₃-MSZ composite. Thus, the zircon was added to the Al₂O₃-MSZ composite and then the powder mixture was sintered after molding. The addition of zircon prevented the Mg-spinel formation, and the composite was densified by controlling the cooling rate. Pre-sintering and HIP treatment of the composite which contained 60wt% Al₂O₃, 25wt% MSZ and 15wt% zircon were performed. The bending strength of the composite did not decrease to 1200°C, and increased with increase in the content of zircon. On the other hand, high temperature bending strength decreased with increase in the content of zircon. In order to evaluate the composite as a cutting tool, the resistance to fracture was investigated. It was found that the sample, which had a high temperature bending strength, had good resistance to fracture.

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Monodispersed, spherical metal oxide (ZrO₂, TiO₂, Al₂O₃, Nb₂O₅ and Ta₂O₅) particles with submicrometer size have been prepared via an alkoxide route using an emulsion technique. The effects of experimental factors (reactants concentration, organic solvent, reaction temperature and time and HPC concentration) on average particle size, size distribution, morphology and aggregation were investigated. The addition of 40vol% acetonitrile to an alkoxide-octanol solution led to the formation of alkoxide emulsion droplets with narrow size distribution. Monodispersed particles were obtained under carefully selected reaction conditions. The formation mechanism of monodispersed particles in octanol/acetonitrile solvent was different from the homogeneous nucleation and diffusion growth of particles observed for the hydrolysis of alkoxide in ethanol.

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Grinding forces on ceramics have been expressed by quadratic functions of the maximum grain depth of cut g, a function of a grinding condition including various kinds of setting parameters. The variation of g was very small in comparison with the grain size. Thus, the expressions are based on the assumption that the number of abrasive grains is dependent only on the specification of a grinding wheel such as the grain size classification and the volume fraction of the grain. Grinding forces on B, C-doped silicon carbide ceramics showed good agreement with the estimation by the expressions. The coefficients in the expressions were obtained as a function of the number of gains on unit width of the wheel, which was calculated from the grain size classification and the volume fraction of the grain. It is suggested that change in grinding force is easily predicted from the specification of the wheel and the grinding condition.

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A TEM observation and an EDX analysis were carried out on interfaces between Ag-Cu-2wt% Ti alloy and three types of SiC containing B and C, BeO or Al₂O₃ as additives. They were brazed at temperatures of 850° or 950°C for 30 min. Interfacial structures of the specimens joined at 850°C were SiC (containing B+C)/TiC/Ti₅Si₃/brazing metal, SiC (containing Al₂O₃)/amorphous oxide/TiC/Ti₅Si₃/brazing metal and SiC (containing BeO)/brazing metal/TiC/Ti₅Si₃/brazing metal. The amorphous oxide disappeared in the specimen brazed at 950°C using the SiC containing Al₂O₃. The bonding strength of SiC containing Al₂O₃ with itself using the same brazing alloy was nearly the same with that of the SiC containing B and C, but interfacial strength between SiC containing BeO and the reaction layer was much lower. The difference in interfacial structure was discussed in terms of excess C in the SiC ceramics and changes in the diffusion coefficients of Si and C in SiC ceramics, those are influenced by the sintering additives.

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The phenomena in the sintering process of Y₂O₃-added mullite ceramics and the crystallization behavior of liquid phase in sintered bodies were studied using differential thermal analysis, X-ray powder diffractometry, scanning and transmission electron microscopies. The mullite powder compacts containing 2-10wt% Y₂O₃ were sintered at 1500°C for 2h, and were then cooled in furnace or quenched in order to study the crystallization phenomena. During the firing process, a liquid phase containing Y, Al, Si and O components was formed in the sintered body. When the specimen was cooled in furnace, the liquid phase solidified into glassy state or crystallized depending on the amount of Y₂O₃. The glass phase in the furnace-cooled specimen could also crystallize on annealing. Some crystallization phenomena of the liquid phase were observed. A small α-Al₂O₃ grain, which was formed by the solid state reaction between mullite and Y₂O₃ during the firing process, was observed inside a mullite grain. Larger α-Al₂O₃ grains, which were formed from the solution-reprecipitation process of liquid phase, were observed in the sintered body.

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The acid catalyzed hydrolysis of bis (ethyl acetoacetato) zirconium diisopropoxide [(etac)₂Zr(OPrⁱ)₂; EZP] in methanol followed by concentration of the reaction mixture gave a polyzirconoxane (PZO) solution which showed excellent spinnability and very remarkable stability to self-condensation as not to gel for more than one year. A 3.0mol% Y₂O₃-containing solution (Y-PZO) was prepared by addition of tris (acethyl acetonato) yttrium [Y(acac)₃] to PZO solution without changing spinnability and stability. Dry spinning of the Y-PZO solution provided continuous pale yellow precursor fibers of 10-30μm diameter with circular or ellipsoidal cross sections, Continuous ZrO₂-Y₂O₃ fibers of 10-13μm diameter with a tensile strength of about 1 GPa were obtained by sintering precursor fibers at 1200°C (2°C/min) for 1h after steam treatment.

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The preparation conditions and formation process of HfC fine powders from HfO₂ by Mg-thermite method were examined under a CH₄ flow. HfC fine powders of single phase were successfully prepared by heating powder mixtures of Mg and HfO₂ with molar ratio of 4 and 5 at 800°-950°C for 1h in a 25-100vol% CH₄ flow. The formation process of HfC powders was as follows: (1) HfO₂+2Mg→α-Hf+2MgO, (2) 3CH₄+2Mg→Mg₂C₃+6H₂, (3) Mg₂C₃→2Mg+3C, (4) α-Hf+xC+y/2H₂→HfC_xH_y and (5) HfC_xH_y+(1-x)C→HfC+y/2H₂. Where, the above reactions took place above 650°C in parallel. It was found that hydrogen and carbon for HfC_xH_y were supplied by the reaction of CH₄ with Mg and by thermal decomposition of Mg₂C₃, and carbon of HfC was also supplied by the thermal decomposition of Mg₂C₃. The supply of hydrogen and carbon continued according to a recycle of Mg (Mg→Mg₂C₃→Mg) which exists in the reaction system.

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The dc conductivity of V₂O₅-Bi₂O₃-TeO₂ glasses prepared by press-quenching was studied at temperatures from RT to 473K and the mechanism of conduction was discussed. The glasses were found to be n-type semiconductors and gave the conductivities of 6.6×10^-6-3.0×10^-4S⋅cm^-1 at 473K, activation energies of 0.42-0.53eV for V₂O₅=30-69mol%. The conduction was confirmed to be due to small polaron hopping and was adiabatic for V₂O₅>50mol% and non-adiabatic for V₂O₅<50mol%. The polaron band width ranged from J=0.02 to 0.11eV, depending highly upon the V-V spacing. The carrier mobility was evaluated to be 10^-7-10^-5cm²V^-1s^-1 which varied extensively with V₂O₅ concentration. The estimated carrier density was 0.8-1.3×10²⁰cm^-3, almost independent of V₂O₅ content in the glasses.

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Formation mechanism of the oxygen deficient regions in electrochemically reduced 4.5mol% Y₂O₃-ZrO₂ crystals was examined by electric measurement and X-ray photoelectron spectroscopy (XPS) techniques. Reduced samples were composed of two regions; severely reduced region near the cathode and weakly reduced region near the anode. During passage of d. c. current with a constant current density, the voltage across the sample decreased linearly with time. The severely reduced region progressed through the sample toward the anode linearly with time. These results showed that the resistivity of the severely reduced region was lower than that of the weakly reduced region, and the total resistivity of the sample decreased with increasing volume fraction of the severely reduced region and that the rate limiting process of formation of the severely reduced region was considered to be mainly surface reaction at the boundary of severely and weakly reduced regions. The measurement of oxidation state of zirconium by the XPS showed that both severely and weakly reduced regions were uniformly reduced and that degree of reduction was independent of the reduction time. This was a direct evidence that during electrochemical reduction, the degree of reduction of both severely and weakly reduced regions was constant and that total reduction progressed with increasing volume fraction of the severely reduced region. On the other hand, there was no clear difference of oxidation states of yttrium between as-grown and reduced samples.

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X-ray photoelectron spectroscopy (XPS) was applied to determine relative quantities of lead (Pb), zirconium (Zr), and titanium (Ti) in lead zirconate titanate (PZT) systems. Standard samples were PZT's with several Zr/Ti ratios prepared by solid state reaction from metal oxide mixtures, and analyzed peaks in the XPS spectra were Pb_4f7/2, Zr_3d5/2, and Ti_2p3/2 corresponding to Pb, Zr, and Ti, respectively. The ratio of their relative detectability was calculated from their peak intensities, that is, Pb_4f7/2:Zr_3d5/2:Ti_2p3/2=4.30:1.50:1.00. This value was considerably different from that theoretically induced based on the reported parameters such as the cross section of photoionization, the mean free path of electron, and the instrumental detection efficiency. Empirical formulae expressing the relationships between relative quantities of elements and relative intensities of corresponding peaks were obtained based on the above results. The reliability for analyzed compositions by means of these formulae was within ±2% for a single analysis, however, it was within ±1% when the number of analyses was 3 to 5.

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In a whisker containing slurry, the correlation between pH and the viscosity of the slurry was effectively utilized to achieve a homogeneous distribution of whiskers in a matrix. The process consists of two-step adjustment of the slurry pH. The application of the process to the Si₃N₄-SiC whisker-TiN particulate ternary system achieved the room temperature strength higher than 900MPa. The strength degradation due to incorporation of whisker was minimized by this process. The high temperature flexural strength for the Si₃N₄-SiC whisker-TiN ternary system composite was as high as 600MPa at 1400°C, which was higher than that of Si₃N₄-TiN composites. The fracture toughness was also improved by the ternary system composite comparing to the matrix Si₃N₄.

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Zircon composites reinforced with 20vol% silicon carbide whiskers were prepared by hot-pressing. Three kinds of silicon carbide whiskers with different diameters were used as a reinforcement agent. The mechanical properties of the hot-pressed bodies, such as bending strength, elastic modulus, hardness, and fracture toughness, were measured. Dense composites were obtained at the sintering temperatures of 1600° and 1650°C. At these sintering temperatures, a few percent of zircon decomposed. The room temperature bending strength was improved largely by an addition of whiskers with small and middle diameters. In all composites, the high temperature strength measured at 1200°C was 1.8 times larger than monolithic zircon. Although elastic modulus and hardness of dense bodies increased with the addition of whiskers, the composite containing whiskers with large diameter had lower values compared to the other composites. Fracture toughness was improved by the addition of whiskers. Notable crack deflection by whiskers was not observed, but some pull-out of whiskers occurred in the composites.

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A package of programs for obtaining unit-cell constants and possible space groups from X-ray powder diffraction data is presented. The major programs included in the package are: CELL, CELL-Q, CELL-2, CELL-S, LS and HKL series. CELL series are programs for finding unit-cell constants and possible space groups from the first 20 observed lines. CELL-Q series are programs for finding unit-cell constants and lattice types from the first 25 lines containing impurities or lines from other phases. CELL-2 series are programs for finding space groups from all observed lines for given unit-cell constants. CELL-S series are programs for finding reliable unit-cell constants when approximate unit-cell constants and space group (or lattice type) are known. LS series are least-squares programs for obtaining precise unit-cell constants. HKL series are programs for calculating hkl, 2θ and d for given unit-cell constants and space group (or lattice type). Creation and correction of diffraction data files and execution of programs are controlled by a main program CELL. The programs are written in QuickBASIC (Microsoft).

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