Calcium phosphate bioceramics, especially those in hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP), are leading candidates for scaffolds used in regenerative medicine for bone tissue. The precise control of chemical composition, pore structure, and crystal faces is important for both the tissue regeneration and bioresorption of the materials. The excellent characteristics of HA and β-TCP for cell activity could be shown by using transparent ceramics of HA and β-TCP. Both calcium phosphates prepared through hydrothermal processing composed of rod-shaped particles were compared to conventional materials prepared by sintering methods, and their superior properties for bone regeneration were demonstrated. The in vivo behavior of HA and β-TCP is discussed from the viewpoint of chemical dissolubility.

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The effect of mixing ratio, firing temperature and matrix glass composition on afterglow luminance property of SrAl₂O₄:Eu²⁺,Dy³⁺-glass composites were investigated. As a result, the brightness showed a maximum at 35 mass % of the mixing ratio of the phosphor for the glass and 780°C of the firing temperature. And it was increased with decreasing the Na₂O content of the matrix glass. From the backscattered electron and the EDX analysis, it is thought that the intermediate layers generated between the phosphors and the Na₂O-poor matrix glass work as antireflective and the phosphor particles in the composite emit phosphorescent light more efficiently. As higher the basicity parameter, B, the intermediate layer was clearer, which means that the reactivity at the phosphor/glass boundaries was lower, and the narrow reaction layers was formed.

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An excimer laser assisted metal organic deposition process for the preparation of vanadium dioxide (VO₂) films is described. When a precursor film grown on a silica glass substrate by preheating at 300°C was irradiated with a KrF laser at room temperature in air, the film was crystallized into polycrystalline VO₂ phases. Generally, the preparation of VO₂ films requires strict atmosphere control, but in this process, the polycrystalline VO₂ films were successfully prepared without it. Moreover, it was revealed that crystallization into the VO₂ phases was promoted by a TiO₂ buffer layer placed on the glass substrate. This means that the photochemical reaction induced by the TiO₂ absorbing the laser participates in the crystallization. The electrical resistivity of the film grown on the TiO₂/glass substrate was lowered compared to that of the film grown on the glass substrate due to improvement of the film uniformity. The crystallinity of the obtained film was dependent on the irradiation time. With the improved crystallinity of the film, the resistivity drop through the metal-insulator transition became large.

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Effect of B₂O₃ content on crack resistance was investigated by indentation tests of glass samples with various compositions of B₂O₃. The ternary SiO₂–B₂O₃–Na₂O glass system (SBN series) and non-alkaline aluminoborosilicate glass system (SAB series). When B₂O₃ is substituted with SiO₂ in the SBN system (“SBN1” series), crack resistance has a relationship with density. In a series of the SBN system where density did not change with B₂O₃ content (“SBN2” series), crack resistance decreased with increasing B₂O₃ content. On the other hand, crack resistance increased with increasing B₂O₃ content in the SAB series, where density did not change. According to the results of NMR measurement, boron in 4-cordination state (^[4]B) increased in the SBN2 series while boron in 3-cordination state (^[3]B) increased in the SAB series with increasing B₂O₃ content. Therefore, crack resistance increases with increasing ^[3]B and decreases with increasing ^[4]B. The difference in structure between ^[3]B and ^[4]B containing glasses leads to different effect on residual stress around the indentation, resulting in difference in crack resistance.

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Powder- and tape-like joining materials composed of SiC with Al–B–C (ABC) or Al–B₄C–C (ABCC) sintering additives were used for the joining of SiC. The effect of interlayer composition, joining temperature and particle size of SiC on the microstructure and mechanical properties of SiC joints was studied. The results indicated that the tape-like adhesive introduces denser microstructure of interlayer relative to the powder-like one under the same conditions. It was demonstrated that using fine starting SiC powder instead of coarse one enhances the densification process of SiC joints. As joined at 1650°C, the microstructure of interlayer is improved gradually with the increasing Al content from 1 to 6 wt % in composition while slightly affected by the forms of additives, i.e. ABCC additive having the equal action to ABC one on the densification of joints. At higher joining temperature of 1750°C, the microstructure of interlayer containing 3 wt % Al almost does not change while that containing 6 wt % degrades. SiC joints with strength higher than 344 MPa have been produced by using optimized joining variables, where the fracture of bonded SiC generally occurs within the SiC substrate.

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The effect of the CTAC/Al ratio and the Al precursor type on the texture properties of alumina prepared by the evaporation-induced self-assembly (EISA) of aerosols was studied using N₂ adsorption isotherms, small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). For the CTAC/Al ratio range 0.05 < CTAC/Al < 0.5 the prepared alumina particles had worm-like pore structure with a BET surface area of 170–365 m²/g and pore size of 2.7–3.4 nm. At CTAC/Al = 0.3, the largest surface area was achieved. The chloride precursor was most profitable to obtain the largest surface area (∼365 m²/g). However, the nitrate precursor was better for preparing non-hollow and mesoporous alumina, maintaining high surface area (∼320 m²/g) and pore regularity.

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The effect of additive incorporation in porous self-bonded SiC (SBSC) ceramics fabricated from a mixture of coarse SiC powder (∼65 µm), Si and C is investigated here. Generally, it was found that the additive reduced the porosity and increased the flexural strength of the SBSC ceramic material. This was consistent with the presence of necking in the ceramic microstructure. The flexural strength of the material without additive (control sample) was ∼16–17 MPa and this was found to be enhanced up to ∼33 MPa using 2 wt % B and ∼38 MPa, using a mixture of 1 wt % Al + 1 wt % B. Thus, the porous SiC ceramic with Al–B additive (typical flexural strength ∼38 MPa at 42% porosity) is very promising, contrasting its mechanical properties with the cost-effectiveness of the raw materials.

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In situ observations of inelastic light scattering of Raman and Boson regions were performed in nanocrystallized 15K₂O–15Nb₂O₅–70TeO₂ glass to investigate nanocrystallization dynamics during the heating process. These in situ observations revealed a drastic structural rearrangement during the evolution of metastable K[Nb_1/3Te_2/3]₂O_4.8 nanocrystals. It is suggested that the distortion of the octahedral NbO₆ unit being released in the glassy phase is the key to nanocrystallization.

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Porous ceramics based on refractory double oxides are promising for the next-generation diesel particulate filter (DPF) materials. Similarly to aluminum titanate (Al₂TiO₅), MgTi₂O₅ has a pseudobrookite-type crystal structure with low thermal expansion coefficients among oxides. Since MgTi₂O₅ has higher stability of pseudobrookite phase than Al₂TiO₅, it is expected that MgTi₂O₅-based materials are suitable for the next-generation DPF materials. In this study, porous MgTi₂O₅/MgTiO₃ composites have been prepared by in situ processing (viz. reactive sintering) at 1000–1200°C. Porous MgTi₂O₅/MgTiO₃ composites with very narrow pore-size distribution at the diameter of ∼1 µm were obtained by the pyrolytic reactive sintering at 1000–1100°C. Internal pore-structure was characterized by mercury intrusion–extrusion porosimetry.

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Composites consisting of Ce-TZP matrix and in situ-grown particles of barium ferrite (BaM) were prepared using various starting materials. For the starting material for the second phase, an amorphous precursor powder of BaM was prepared by coprecipitation and calcination. Uniform hematite particles were also prepared using liquid-phase synthesis under hydrothermal conditions. The Ce-TZP/20 wt % BaM composites were prepared by sintering the mixed powders of Ce-TZP, barium carbonate, hematite, and amorphous precursor of BaM. The aspect ratio of the in situ-grown BaM particles increased concomitantly with an increase in the mixing ratio of the amorphous precursor powder. The exaggerated grain growth of the BaM in the Ce-TZP matrix was efficiently suppressed by the addition of a small amount of barium carbonate and hematite to the amorphous precursor of BaM.

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Ca-α SiAlON powders were prepared at different starting compositions and carbon contents at 1450°C for 2 h in N₂ from mixtures of SiO₂, Al₂O₃, CaCO₃ and carbon powders by carbothermal reduction–nitridation. Crystalline phases and particle morphology of the products were investigated. With increasing the x value in nominal Ca-α SiAlON compositions Ca_xSi_12−3xAl_3xO_xN_16−x, the number of small hollow spheres decreased and the size of primary grains consisting of the hollow spheres increased. The addition of carbon powder to more than 1.2 times of the necessary stoichiometric value was required to form Ca-α SiAlON hollow spheres composed of ultrafine grains.

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La-doped YBCO (Y_0.9La_0.2Ba_1.9Cu₃O_y) superconducting films were deposited by an off-axis DC magnetron sputtering method. We investigated the relationship between the film characteristics and the deposition conditions, and drew systematical maps in terms of composition, surface morphology, crystal structure and superconducting properties for the films deposited at various spatial geometries of a substrate and a target. Correspondence between the Cu content and the surface morphology was clearly observed. Cu-rich films had precipitates on the surface. Slightly Cu-poor films exhibited c-axis orientation and a high T_c of 87 K. Among them, the film deposited at a rather fast deposition rate exhibited a flat surface with an average surface roughness R_a less than 1 nm for an area of 10 micron square. Considerably Cu-poor films contained a-axis oriented grains or exhibited very rough surfaces. The cationic ratio of Y:La:Ba did not change significantly.

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The effect of sintering temperature and sintering additives on the ionic conductivity of LiSi₂N₃ was studied by performing complex impedance measurements. LiSi₂N₃ materials were fabricated by the reaction of Li₃N, Si₃N₄, and sintering additives at temperatures of 1873–2073 K. Dense hot-pressed bodies were obtained at 1973–2073 K in the case of undoped LiSi₂N₃ and at 1873 K in the case of Y₂O₃, CaF₂, and B₂O₃ addition. The ionic conductivity increased greatly with increasing sintering temperature and exhibited a strong dependence on the type of sintering additive. When the sintering temperature was constant at 1873 K, although the conductivities of Y₂O₃-doped LiSi₂N₃ and CaF₂-doped LiSi₂N₃ were lower than that of undoped LiSi₂N₃, the conductivity of B₂O₃-doped LiSi₂N₃ was higher than that of undoped LiSi₂N₃. The enhanced conductivity of B₂O₃-doped LiSi₂N₃ can be attributed to the increase in the density of the sintered material without the formation of a phase of significant resistance at the grain boundaries.

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The high frequency (∼100 kHz) dependence of Pb_1.1(Zr_0.53,Ti_0.47)O₃ (PZT) piezoelectric characteristics was investigated. PZT films were prepared onto Pt/Ti/SiO₂/Si substrates using a chemical solution deposition process. A twin-beam laser doppler equipment system was developed for determining the piezoelectric characteristics of a PZT film and simultaneously evaluating its polarization and displacement characteristics. Moreover, the sample temperature was changed from −190°C to room temperature (RT). As the measurement frequency increased and the measurement temperature decreased, the remanent polarization (2P_r) and coercive field (2E_C) were observed to increase and the effective longitudinal piezoelectric constant (d_33,Eff.) was observed to decrease.

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High-dispersion-treated carbon nanofibers (CNFs) were used to fabricate uniformly-dispersed CNFs-alumina composites with enhanced mechanical properties. The treatment was effective in obtaining dense and uniform composites. The composites containing 0.4–0.8 wt % CNFs were densified to a relative density of more than 99% by vacuum sintering and subsequent hot isostatic pressing, and those containing 1.6–2.5 wt % CNFs were densified to full density by plasma activated sintering. The maximum bending strength of the composites (1050 MPa) was approximately the same as the bending strength of monolithic alumina (1079 MPa). The maximum fracture toughness of the composites was 5.9 MPa·m^0.5, which was a 69% increase compared with the fracture toughness of monolithic alumina (3.5 MPa·m^0.5). Fracture toughness (K_IC) increased rapidly with a decrease in alumina grain size (G), and we found that the relationship could be expressed by the following equation: K_IC = (k₁/G²) + k₂ (where k₁ and k₂ are constants).

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