A new granulation method was proposed for modifying microcrystalline inorganic ion-exchangers into granular shape suitable for practical applications. By this method the ion-exchanger can be supported in porous ceramics having large particle size for column operations. Spherical composite materials of λ-MnO₂ and porous ceramics, for example, were examined by X-ray powder diffraction (XRD), chemical analysis, specific surface area determination and electron probe microanalysis. The composites were produced by impregnating the pores in ceramics with lithium and manganese nitrates (Li/Mn molar ratio=0.5) and transforming the nitrates to LiMn₂O₄ by heating and then to λ-MnO₂ by acid-treatment. The optimum heating temperature was about 600°C at which almost all the nitrates crystallized to form LiMn₂O₄ and little amounts of impurities such as α-Mn₂O₃, β-MnO₂, Mn₃O₄, etc., were present. After acid-treatment λ-MnO₂ was confirmed to be distributed uniformly in the ceramics particles. These composites had large specific surface areas up to 250m²⋅g^-1 and adsorbed Li⁺ ion selectively from a mixed alkali metal ions solution.

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Relationship between fracture strength of ground ceramics and maximum grain depth of cut, g, has been formulated. The strength was expressed by an exponential function of g. This expression is based on the assumption that the crack depth of the ground specimen is represented in terms of normal grinding force applied with a single abrasive grain of a wheel, as median crack length in indentation fracture is the function of indenting load. The four-point bending strength of sintered silicon carbide ceramics ground with 4 kinds of grit diamond wheels under various conditions showed good agreement with the approximation by the function of g. In particular, the strength decreased steeply from the inherent level with a slight increase in g.

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Donor density (N_d=9.5×10²⁴/m³) and energy depth of interfacial state (ΔE_i=0.86eV) at vicinities of SrTiO₃ ceramics grain boundaries were estimated using Hall coefficient and ICTS, respectively. The voltage of SrTiO₃ ceramic grain boundary was analysed by C-V characteristics, N_d and ΔE_i on the basis of the structure and composition of the grain boundaries, which were investigated by TEM, μAES and SIMS. The electrical conduction mechanism of SrTiO₃ ceramics grain boundary was proposed.

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Four whiskers; β-SiC, β-Si₃N₄, α-Si₃N₄ and 9Al₂O₃⋅2B₂O₃, were tested as a reinforcement material of the cordierite glass ceramics. The composites containing of 10 or 30vol% whisker and the monolithic glass ceramics were sintered by hot-pressing at 1000°C in Ar under 30MPa for 60min. Their sinterability and mechanical properties were investigated. Fully dense composites containing up to 30vol% whisker were obtained, and no reaction products were observed between cordierite glass ceramics and each whisker. Bending strength, fracture toughness, elastic modulus ans Vickers hardness increased with increasing whisker content. A maximum strength of approximately 400MPa and a fracture toughness of nearly 4.5MPa⋅m^1/2 were obtained for both 30vol% β-SiC and 30vol% β-Si₃N₄ whisker, respectively. The strength was more than twice as large and the fracture toughness was roughly 2.7 times larger than that of monolithic cordierite glass ceramics. Fracture surfaces and crack propagation behavior in these composites suggested that the main toughening and strenghening mechanisms were based on the whisker Debond-bridging and load transfer model, respectively.

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The ramsdellite phase (R), Li₂Ti₃O₇, was synthesized by the melt-quenching method and its phase changes were investigated by thermal analyses (TG-DTA, TMA), powder X-ray diffractometry, and scanning electron microscopy. In the heating process, the R phase transformed into a hexagonal phase (H) followed by decomposition into Li₄Ti₅O₁₂ (spinel phase=S) and TiO₂ (rutile phase=r), and finally, the R phase was reproduced. This reaction path agreed well with that reported by Mikkelsen, but each reaction temperature differed from that, and the single phase region for the H phase was not detected. The rate-determining step for the R→H transformation was the nucleation of the H phase. An abnormal change of the order of 10^-3K^-1 in the thermal expansion coefficient was observed at -630°C, which is attributed mainly to the formation of cracks accompanied by the transformation from R to H phase. In the cooling process, the R phase transformed into an H phase followed by the successive decomposition into the S and r phases, taking the same phase change path as in the heating process.

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The influence of grain size and secondary phase on the fracture toughness K_IC of sintered MgO bodies was investigated. Sintered MgO bodies doped with 1-10wt% Al₂O₃ were made by hot-pressing. The grain size was changed by annealing. The fracture toughness K_IC was measured by a chevron-notched beam method. The fracture toughness of sintered MgO bodies doped with Al₂O₃ was independent of the grain size and the amount of Al₂O₃, and indicated a constant value of 2.2MPa√m, 20% larger than that of pure MgO. The fractography revealed that the toughening of Al₂O₃-doped MgO bodies corresponded to the increase in the fraction of stepwise transgranular fracture on the fracture surfaces. It was considered that the change in fracture mode resulted from residual thermal stresses generated near secondary phase particles (MgAl₂O₄).

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The effective strength of nipple in the joint part constructed by two poles and one nipple as artificial graphite electrodes was investigated in the uniaxial tension loading. The theoretical stress distribution of nipple was analyzed using the finite element method in the several types of distributed loads on the surface of each thread which was contacted with the thread of pole. It became clear that stresses were concentrated to the area around the maximum diameter in the case of JIS nipple and the decrease of height of thread near the maximum diameter caused higher effective strength of nipple. These results of the analysis suggested a certain shape of nipple, in which the height of threads were decreased by a cutting line with the origin on the top of thread at the minimum diameter and smaller taper than that of JIS. According to these analytical results, this nipple was machined, jointed to poles and fractured by bending moment, and it showed higher effective strength (bending moment) than that of JIS nipple. These results agreed with the data of theoretical analysis by a finite element method. This nipple is expected to have high strength for use in electric arc furnace.

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The kinetics and the mechanism of the reaction of Si₃N₄ with Ni have been investigated. Using a powdered Si₃N₄-Ni mixture, the reaction rates were measured by means of a thermo-balance in Ar or N₂ gas stream. Reaction products were examined by X-ray diffraction. The reaction of Si₃N₄ with Ni initiated after heating to about 800K. The reaction product layer was a Ni-Si solid solution below 1073K and nickel silicides above 1123K. The reaction rates and the reaction products were independent of the atmosphere. The initial rate was described by the linear rate law. The activation energy was 118kJ/mol. A chemical reaction may be considered as the rate-determining step. When the Ni particles were covered with the reaction product layer, the kinetics obeyed by the parabolic rate law. The formation of nickel silicide increased the rate constant abruptly. The activation energy changed from 171kJ/mol in a regeon of the Ni-Si solid solution to 214kJ/mol in the regeon of nickel silicide. The reaction rates of Si₃N₄ with Ni are probably controlled by the diffusion through the reaction layer.

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Na_1-XTi_2+XAl_5-XO₁₂ system continuous fibers were prepared by firing precursor fibers which were spun from aqueous solution of Al(NO₃)₃-Al(OPrⁱ)₃-Ti(OPrⁱ)₄-Na₂CO₃-Citric acid (and Oxalic acid) system (Method A-a and A-b) and AlCl₃-Al(OPrⁱ)₃-Ti(OPrⁱ)₄-Na₂CO₃-Citric acid (and Oxalic acid) system (Method B-a and B-b). Spinnable composition range of the solution enclosed with index of Al(OPrⁱ)₃mol/(Al(NO₃)₃mol or AlCl₃mol) and Citric acid mol/(Al+Ti)mol became broader as oxalic acid content increases. When the precursor fiber in method A was fired, freudenbergit and Na-β″-alumina appeared at 800°C, and in addition to these, α-alumina and rutile appeared at 1000°C. On the other hand, in method B, sodium oxide appeared at 400°C, and anatase, rutile, freudenbergit and Na-β″-alumina at 800°C. It is considered that the reaction rate in method A may be faster than that in method B interpreting from the grown phase. When the precursor fiber obtained from method A-b was fired at 1100°C for 5h, NTAO phase became dominant, and grown phase reached equilibrium at 1300°C, although unreacted phase still remained. It was found that preparation at a low temperature compared to usual solid phase reaction was possible. The fiber heat treated at 1000°C had dense surface. As the heat treating temperature was raised, the fiber appearance changed to aggregation of deep grooves and slender particles, then to porous surface. When the fiber was fired at 1350°C, its morphorogy turned to aggregation of spherical particles having diameter of several μm. This may be considered to be the result that NTAO phase grown as nucleation point which was deposited intermediate by heteronucleation occured at lower heat treatment.

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Large transparent ZnO polycrystals with high degrees of c-axis orientation were obtained by the vapor transport method. Homogeneous junctions were made by forming another polycrystal on the (001) surface so that they were aligned as either (001)//(001) or (001)⊥(001). The electrical conductivity of the oriented polycrystal was higher in the direction perpendicular to c-axis (‹001›) than that parallel to c-axis. The (001)//(001) junction had a high resistivity and it acted as the conduction barrier at low temperatures.

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Y₂O₃-Nd₂O₃-doped β-Si₃N₄ was sintered at 1700° to 1900°C for 4h in 10MPa N₂, and the effect of the amount of the additives and sintering temperatures on stength, fracture toughness and the microstructure was investigated. A dense material (>98% of the theoretical) was obtained by firing at 1900°C with addition of 1 to 10mol% of oxides. Rod-like β-Si₃N₄ grains developed by firing at 1900°C increased the fracture toughness up to 7.8MPa√m because of the pull-out and the crack-deflection mechanism. The material made from β-Si₃N₄ powder had a high Weibull modules than that from α-Si₃N₄ powder.

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Diamond-like carbon films have been deposited by hybrid plasma decomposition of CH₄ diluted with H₂ gas. A hybrid plasma was generated by microwave and RF discharges, and an ion beam was produced by applying do voltage between these two plasmas. The ion beam energy was controllable by adjusting the bias voltage. The property of the films strongly depended on the bias voltage corresponding to ion beam injection energy for deposition. The infrared bands had a main peak at 2955cm^-1 and a broad band around 2860cm^-1, corresponding to tetrahedral (sp³) bonding structure. The deposition rate was decreased from 50Å/min to 25Å/min by increasing the bias voltage. The optical gap was measured with a UV-BIS absorption spectrometer for the films deposited on a quartz plate, and estimated to be 2.15-2.45eV; its value declined with increased bias voltage during deposition. The microvickers hardness of the films was increased from 200kg/mm² to 600kg/mm² by increasing the bias voltage during deposition. Raman spectra showed two broad peaks at approximately 1300cm^-1 and 1600cm^-1 at a bias voltage of 100V, identified with the peaks of microcrystalline glass-like carbon.

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Fracture toughness (K_IC) of CVD⋅TiC-SiC composites with columnar structure was measured by the indentation microfracture method. In order to explain the resulting high fracture toughness, residual stress in the composites was measured by the X-ray diffraction method (2θ-sin²Ψ method). Crack deflection was observed in both surfaces perpendicular and parallel to columnar structure of TiC-SiC composites, more pronounced with the latter. The K_IC values were about three to four times as large as that of monolithic SiC or TiC, and were about twice as large as sinterd TiC-SiC composites with TiC-dispersed type of structure. It was presumed that the residual stress in the CVD⋅TiC-SiC composites was much larger than that in monolithic SiC or TiC, and the values parallel to the columnar structure of the composites was larger than that perpendicular. From above result, it was considerd that the high fracture toughness of CVD⋅TiC-SiC composites was achieved by crack deflection, the effect of which depended on the residual stress in the composites.

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Using oxide glasses of compositions xNa₂O⋅(100-x)SiO₂ (x=20-50 in mol) and 40Na₂O⋅(60-y)SiO₂⋅yAl₂O₃ (y=5, 10 in mol) as base glass, Na-Si-O-N and Na-Al-Si-O-N oxynitride glasses were prepared by melting powder mixture of oxide glass and Si₃N₄ or AlN, and the effects of the base oxide glass composition on the glass forming ability, the amount of incorporated nitrogen and the chemical durability of oxynitride glasses were studied. It was found in Na-Si-O-N glasses that the lower Na₂O content is favorable for the formation of nitrided glass, giving larger glass forming regions. Retained nitrogen content decreased with increasing Na₂O content in Na-Si-O-N glasses and with increasing Al₂O₃ content in Na-Al-Si-O-N glasses. Chemical durabilily of Na-Si-O-N glass increased with increasing of nitrogen content for any Na₂O content of the base glass. For Na-Al-Si-O-N system, however, nitrogen incorporation increased or decreased chemical durability, depending on the Al₂O₃ content and nitrogen content in the glasses or had no appreciable effect.

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Tape casting and co-firing technique was applied to the fabrication of a planar solid oxide fuel cell. Yttria stabilized zirconia (YSZ), (La, Sr) MnO₃, Ni-YSZ cermet and (La, Ca) CrO₃ were used as an electrolyte, a cathode, an anode, and a separator, respectively. Sheets of those materials were tape-cast with organic binder, laminated, and fired. A highly porous structure of the gas-distributor layer was formed using urethane-foam as a skeleton which can be burnt out during the firing process. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) revealed that (1) Mn in the cathode material diffused and dissolved into YSZ and (2) Ca migrated from the (La, Ca) CrO₃ separator to the other parts of the cell. The densification of the (La, Ca) CrO₃ was impeded by the Ca migration.

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By the condition of system free energy minimization, it is theoretically proven that the dihedral angle of a closed pore on grain boundaries does not depend on the internal gas pressure of closed pores, and that it would satisfy the Young-Dupré equation at equilibrium state. In the measurement of dihedral angle, it is pointed out that the equilibrium state would be changed with transformation from closed pores to open pores. Moreover, the distribution of measured dihedral angle caused by sectioning and the change in the measured value of dihedral angle at high temperature are discussed.

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Dense polycrystals of boron carbide with various compositions were synthesized by a thermal CVD method using a reaction in the BCl₃-CH₄-H₂ system. Results of electrical conductivity and thermoelectric power measurements indicated that the thermoelectric power-factor increased with increasing boron content from B₄C to B₁₃C₂ and stayed practically unchanged for further boron-rich compositions within the single-phase region. This result was slightly different from those in the previous reports in which hot-pressed samples were employed for measurements. Thermally activated hopping of small polarons was confirmed to be a dominant conduction mechanism at high temperatures, but it was pointed out that more detailed investigation would be needed to specify their hopping sites. A strong effect of microstructure on the thermoelectric properties, especially Seebeck coefficient, of B₄C was also found.

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Damage of several commercial cement boards and laboratory-made samples by ASTM (C-666 A) test and unidirectional freeze-thaw (named as “N-method”) test methods was compared, and factors which enhance the frost durability of non-asbestos fiber reinforced cement boards were identified. They are (1) suppression of water absorption, (2) reduction of intravoid in a fiber bandle, (3) elimination of structural defects such as lamination coming from the board-forming processing, and (4) addition of proper amount of silicious fine aggregates. Several technological advantages of the “N-method” coupled with measurement of residual linear expansion as the frost evaluation factor were presented from the comparison of freeze-thaw test results between above two methods.

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Silica-supported maghemite was prepared by the pyrolysis of a ternary composite of poly (vinyl alcohol) (PVA), iron (III) hydroxide and silica gel, and was characterized by X-ray diffraction, infrared spectroscopic and BET surface area measurements. Particles of maghemite in silica were of <10nm in diameter and stable up to 800°C. The formation mechanism of maghemite in silica was proposed as follows: Iron oxide formed by the dehydration of iron (III) hydroxide was reduced at elevated temperature to magnetite by either PVA itself or its degraded residue, and then the magnetite was oxidized gradually to maghemite.

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The microstructures and electrical properties for the LiXSiO₄ (X=Al, Y, La, Nd, Sm, Gd, Dy, Ho, Er, Yb) ceramics were investigated. The XRD patterns of LiX SiO₄ were classified into three groups. The crystal system of the first group, LiXSiO₄ (X=La, Nd, Sm, Gd, Dy), was hexagonal. That of the second group, LiXSiO₄ (X=Y, Ho, Er, Yb), was orthorhombic. That of the third group, LiAlSiO₄, was hexagonal. The particle sizes of LiNdSiO₄, LiSmSiO₄ and LiGdSiO₄ were 1-2μm. The relative densities of LiLaSiO₄, LiNdSiO₄ and LiSrSiO₄ were higher than 97%. The conductivities of LiXSiO₄ measured in the temperature region of 200° to 500°C. The conductivities for LiXSiO₄ (X=Al, La, Nd, Sm, Gd, Dy) of the hexagonal system were higher than those for LiXSiO₄ (X=Y, Ho, Er, Yb) of the orthorhombic system in the whole region. For LiSrSiO₄, the highest conductivity was obtained and that was 8.9×10^-6S⋅cm^-1 at 300°C.

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Synthetic magadiite was obtained as spherically-aggregated particles with a dimension between 10μm and 30μm, which consisted of loosely-packed platy crystals. Transformations of magadiite to H-form by HCl treatment and to the original magadiite by NaOH treatment took place reversibly without any morphological changes. However, it was found by SEM observation that the aggregates of H-magadiite particles were dispersed into pieces of platy crystals by treatment with KOH, LiOH and NH₄OH solutions. The extent of the dispersion was in the following order: LiOH>KOH>NH₄OH. According to the measurement of relative acoustophoretic mobility, this phenomenon was considered to reflect an interaction between crystals and alkali ions at the interface.

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