The chemical strengthening of Li₂O•2SiO₂ transparent glass-ceramics was investigated. The fracture strength of glass and glass-ceramics increased first and then decreased, and the crack formation and peeling of ion exchanged layer were observed for both Li⁺↔Na⁺ and Li⁺↔K⁺ ion exchange. This suggests that the submicroscopic crack generates perpendicular to the surface when the ion exchanged layer peels off from the surface. The volume change by Li⁺↔Na⁺ and Li⁺↔K⁺ ion exchange is very large, over 10%, this large volume change causes the peeing and crack formation of ion exchanged layer despite in which the compressive stress arise. In the early stage of ion exchange, the compressive stress arisen affects effectively on the increase in strength. However, as increase in the thickness of ion exchanged layer, the volume change of ion exchanged layer can not be neglected, and crack and peeling may generate in that layer. Finally, the fracture strength decreases.

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The microstructure in 2.9 mol% Y₂O₃-stabilized tetragonal zirconia polycrystal (Y-TZP) sintered at 1100°-1650°C was examined to clarify the role of Y³⁺ ions on the cubic-formation and grain growth processes. The cubic phase in Y-TZP stared to appear at 1300°C and the fraction of the cubic phase increased with the increasing sintering temperature. Scanning transmission electron microscopy and nanoprobe X-ray energy dispersive spectroscopy (EDS) measurements revealed that the Y³⁺ ion distribution in the grain interiors in Y-TZP was nearly homogeneous up to 1300°C and cubic phase regions in the grain interiors were formed clearly over 1300°C. The cubic phase region in the grain interior was extended as the sintering temperature increased. High-resolution electron microscopy and nanoprobe EDS measurements revealed that no amorphous layer existed along the grain-boundary faces in Y-TZP, and Y³⁺ ions segregated at their grain boundaries over a width of ~10 nm. The segregation peak of Y³⁺ ions was clearly seen at 1300°C, and above this temperature, Y³⁺ ions segregated at the grain boundaries not only between tetragonal grains but also between tetragonal and cubic grains. These results show that cubic phase regions started to be transformed from the grain boundaries and/or the triple junctions in which Y³⁺ ions segregated. The cubic-formation mechanism in Y-TZP can be reasonably explained from the viewpoint of the Grain Boundary Segregation-Induced Phase Transformation model, and the grain-growth behavior is probably controlled by the solute drag effect of Y³⁺ ions segregating along the grain boundary.

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TiO₂ gel films were prepared from titanium tetra-n-butoxide modified with 1-(2-hydroxyphenyl)-3-phenyl-2-propen-1-one in 1-butanol by the sol-gel method. The obtained gel film showed an absorption band, characteristic of the chelate ring, at 425 nm. The absorption band was shifted to the longest wavelength region in the photosensitive gel films which we have examined. The band gradually decreased in intensity by UV-irradiation using a high pressure mercury lamp. This indicates that the gel film is photosensitive. Using the photosensitivity, fine patterns (about 3 μm) could be fabricated by the UV-irradiation through a mask and leaching.

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The morphotropic phase boundary (MPB) for the PMNZT series of high-density ceramics (xPb(Mg_1/3Nb_2/3)O₃-yPbZrO₃-zPbTiO₃; x=0.1-0.2, y=0.400-0.486, z=0.395-0.477) is relocated based on analyses of the dielectric, piezoelectric and ferroelectric properties of incremental compositions. The PMNZT ceramics, fabricated by the columbite route, exhibit a single-phase perovskite structure. The refined MPB line is shifted toward the PbTiO₃ (PT) side in the ternary field by approximately 2.4 mol% from the position reported in the literature and the pinpoint composition for piezoelectric applications is further shifted toward the PT side by approximately 1.2 mol% from the obtained MPB line. The PMNZT 14.2/41.6/44.2 (100x/100y/100z) composition near the MPB line is shown to have properties suitable for practical applications.

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A SiC powder of median size 0.8 μm was mixed with polyacrylic acid (PAA, dispersant) in a 0.3 mol/l-R(NO₃)₃ solution (R=Yb, Y, Gd, Sm, Nd and La) at pH 5 to adsorb uniformly the sintering additive (R³⁺ ion) on the SiC surface. The aqueous 30 vol% SiC suspension with 0.52 mass% PAA and 1.50 mass% R₂O₃ (as R(NO₃)₃), relative to SiC, was consolidated by filtration through a gypsum mold to form green compacts of 50-52% of theoretical density. The consolidated green compacts were densified with grain growth to 76-99% relative density by hot-pressing under a pressure of 39 MPa at 1950°C for 2 h in an Ar flow. The addition of R₂O₃ of smaller R³⁺ ion was effective to enhance the sinterability of SiC and also to achieve smaller grain size of SiC. This result was discussed based on the additional experiment result on the chemical interaction between SiC compact and the SiO₂-R₂O₃ liquid. The average flexural strength and Weibull modulus of dense SiC were 612 MPa and 5.1, 719 MPa and 6.7, and 731 MPa and 9.8 for Gd₂O₃, Y₂O₃ and Yb₂O₃ addition, respectively.

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Titania layers were deposited on titanium substrates in titanylsulfate solutions under varied concentration (0.01 and 0.03M), pH (0.67-1.27) and temperature (60 and 80°C). They were rinsed and subsequently aged in water at 80°C for 3d. The layers consisted of only rutile or rutile with trace anatase, depending on the conditions. The X-ray diffraction intensity indicates that the rutile particles grew preferably in (101) plane, regardless of being aged or not. When aged, the anatase diffraction intensity increased, and anatase newly grew in the layer consisting only of rutile. When soaked in a simulated body fluid (SBF) of the Kokubo recipe, the rinsed layer with only rutile was weakly active to deposit apatite within 5 d, while the other two exhibited no deposition. The aging improved activity. Although anatase is reported in the literature to be more active than rutile, the present study indicates that the rutile layer is more active. Thus, it is concluded that topotaxy or epitaxy would not work well but other issues like the presence of Ti-OH affect apatite deposition.

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The applied pressure and suspension height during consolidation of an aqueous suspension with 800 or 30 nm SiC particles were continuously recorded using a developed pressure filtration apparatus. The suspension of 5-30 vol% solid was filtered through three sheets of a 0.1 μm pore diameter membrane filter attached to the bottom of the piston displaced at 0.05-0.5 mm/min. The dehydrated solution flowed into the pore channels in the piston in the Teflon cylinder. The final packing density of 800 nm particles reached 55-62%, depending on the surface charge of particles. On the other hand, the final packing density (41% density) of 30 nm SiC particles was not influenced by the surface charge, and was lower than that of 800 nm SiC particles. The consolidation energy for 1 cm³ SiC was 1.1-5.5 J/cm³ for 800 nm SiC particles and 17.2 J/cm³ for 30 nm SiC particles. Decrease of the pore size of the consolidated SiC compact increased the consolidation energy. The ratio of energy applied between two particles during consolidation to the interaction energy between two particles in a suspension was correlated to the packing density of the consolidated SiC cake.

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Zirconia balloon with pores through the crust was synthesized by dispersing polystyrene added Zr(OC₄H₉ⁿ)₄ benzene solution to formamide. Zirconia balloon precursor was formed in F/B/F (formamide/benzene/formamide) emulsion. As benzene was extracted to formamide from the F/B/F droplets, polystyrene and Zr(OC₄H₉ⁿ)₄ phase separation occurred, and the F/B/F droplets solidified. In the balloon precursor crust polystyrene spheres dispersed in a Zr(OC₄H₉ⁿ)₄ matrix. The crust thickness was about 2 μm. The diameter of the polystyrene spheres was almost the same as the crust thickness. The spheres were removed with extraction by benzene. Spherical pores which were left in the crust opened only to the inner surface of the crust. The spherical pores were opened to the outer surface of the crust by etching the precursor balloons with hydrochloric acid. On heat-treatment at 1300°C the precursor balloons after hydrochloric acid treatment were transformed to zirconia balloons with pores through the crust. The size distribution of heat-treated balloons was in the range between 1 μm and 35 μm with a mean value of about 10 μm in diameter.

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Dense yttrium oxide film was prepared by aerosol deposition process at room temperature. The deposition rate was very high ~60 μm/h. The thickness of the films were 25 μm and 10 μm on aluminum alloy and quartz substrates, respectively. Transmission electron microscopy showed that the film was highly dense without voids and had a homogeneous interface between the layer and the quartz substrate used. The film was composed of randomly oriented Y₂O₃ crystallites of size less than 20 nm. The film (2 μm thick) had a 55-85% transmittance in the region 250-800 nm. Electrical and mechanical properties of the film were examined. The volume resistivity of the film was 10¹⁴ Ω•cm. The adhesion force of the interface between the Y₂O₃ layer and the substrate was 59 MPa.

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The objective of this study was to form a polycrystalline oxide film on a Zr substrate using micro-arc-technology, and to identify the mechanism by which micro-arc occurs with valve metal. Polycrystalline oxide film was able to form on the Zr substrate. The polycrystalline oxide film generated on the Zr substrate had a mixed phase with tetragonal ZrO₂, of which monoclinic ZrO₂ was the main constituent. The choice of electrolytic aqueous solution for making micro-arc occur with Zr is wide in comparison with that in Al or Ti. The reason for this can be explained as follows: Among oxide films that consist of a two-layer structure, in Al and Ti, micro-arc occurs in the second layer due to the large resistance caused by anions mixed in the electrolytic aqueous solution. In Zr, micro-arc occurs in the first layer because the resistance of the first layer becomes large due to film thickness. Whether micro-arc occurs in the first layer or in the second layer of the valve metal depends on the value of the transport number of cation in the oxide film for the substrate metal.

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Production method of spherical silica beads with macropores was investigated from water glass. Spherical beads with continuous macropores were obtained by inducing phase separation in sol droplets in an organic solvent, and the diameter of beads was controlled between 0.7 and 2.8 mm by changing volume of droplets. The macroporous silica beads have dense external surface layer with thickness of ca. 2 μm. The surface layer was removed by soaking the wet gel in 1 mol dm^-3 HF solution for 10 s before drying.

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Commercial sub-micron high purity α-Al₂O₃ powders ground and not ground in the manufacturing process, produced by three different processes; in-situ chemical vapor deposition (A1, A2 and A3), hydrolysis of aluminum alkoxide (B1, B2 and B2) and thermal decomposition of ammonium alum (C1 and C2) methods, were thermally hydrated and the effects evaluated by DRIFT spectroscopy in dry air atmosphere. The hydration process was conducted by placing all powders, without contact with water, in a modified pressure cooker heated inside an oven at 100°C under water saturated pressure. The surface of powders ground in the manufacturing process was easily hydrated by the hydrothermal treatment and aluminum trihydroxide peaks were observed on the DRIFT spectra. The results demonstrate that grinding in the manufacturing process affects the hydration ability of high purity α-Al₂O₃ powder surfaces.

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Spherical alumina particle compacts were prepared by drying alumina slurry in high magnetic field (0-10 T) and cold isostatic pressing (CIP). Anisotropy of shrinkage during sintering was examined for the alumina compacts in detail. The spherical alumina particle compact prepared in 10 T showed sintering shrinkage anisotropy. The sintering shrinkage was larger in the direction parallel to magnetic field direction (i.e., the c-axis direction of alumina crystal) than that in its perpendicular direction. On the other hand, isotropic sintering shrinkage occurred in the compacts prepared in 0 T. The experimental results indicate that the sintering shrinkage of spherical alumina particle compact depends on alumina crystal axis direction. Origin of the sintering shrinkage anisotropy for the spherical alumina particle compacts can be attributed to the particle orientation caused by high magnetic field.

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We report on a novel technique for formation of nano-particle structures in KNbO₃-TeO₂ glasses induced by ultraviolet (UV) XeCl excimer laser irradiations operating at 308 nm wavelength. The glasses with a composition of 0.5Er₂O₃-15K₂O-15Nb₂O₅-70TeO₂ (mol%), which are known to exhibit a nano-crystallization behavior by heat treatments, have been used in this experiment. It has been found that the morphological properties of nano-particles, such as diameter, height, and distribution density of nano-particles, can be tailored by the pulsed UV laser conditions. The nature of these nano-structures on glass surface induced by laser processing has been clarified that laser-induced nano-particles are consisting of the same composition as that in glass substrate.

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Highly c-axis-oriented aluminum nitride (AlN) thin film sensor elements were prepared on Inconel substrates by rf magnetron sputtering technique. The sensor characteristics were evaluated under pressures of 1.0 to 30.0 MPa and frequencies of 0.1 to 100 Hz at room temperature. The deviation from the linearity of charges with pressures for the AlN sensor was within 0.13% of a full scale at 30.0 MPa, which indicates a good linearity between 1.0 and 30.0 MPa. Furthermore the sensor characteristics were evaluated under pressures of 0.4 to 6.4 MPa and a frequency of 1 Hz at 500°C. The deviation from the linearity of charges with pressures for the AlN sensor was within 2.50% of a full scale at 6.4 MPa, which indicates a good linearity between 0.4 and 6.4 MPa. The temperature dependence of charge for the AlN sensor was small under pressure of ±1.6 MPa in the temperature range from 25 to 500°C. It is confirmed that the AlN thin films have a good possibility for a pressure sensor under high temperatures and high pressures.

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