The bone-bonding ability of a glass ceramic can be evaluated by using simulated body fluid (SBF). Furthermore, rat primary osteoblast cell culture is effective in collecting preliminary information for potential application of any material of organic or inorganic origin. In this study, the effect of CeO₂ addition on crystallization behavior and bioactivity of potassium mica and fluorapatite based glass ceramics was investigated. Also an osteoblast cell culture model was utilized to investigate the effect of CeO₂ addition on biocompatibility of potassium mica and fluorapatite based glass ceramics by using biological criteria such as cell viability, metabolic activity and nitric oxide production.

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Magnesia-graphite composite ceramics were fabricated by hot pressing in Ar atmosphere, and their electrical properties were measured. The electrical resistivity increases as the graphite volume fraction x decreases, following well-accepted power law model based on the percolation theory. Renormalized pressure coefficient of resistance, d(ln R)/dP, decreases as x decreases. This behavior can be explained by the strong enhancement of d(ln ρ)/dx toward the percolation threshold. By fitting the x dependence of d(ln R)/dP with a theoretical equation, the Young's modulus of the composites was estimated.

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Lead-free piezoelectric (100-x)Na_1/2Bi_1/2TiO₃-xBaTiO₃ solid solution ceramics are investigated by Raman spectroscopy and X-ray diffraction over a composition range of 0 ≤ x ≤ 10. Distinct changes in the Raman spectra and X-ray diffraction patterns were discussed in the light of a rhombohedral to tetragonal phase transition. The dominant bands in the Raman spectra were analyzed by observing the changes in their respective peak positions, widths and intensities as the composition increased. Based on these results, it is suggested that the morphotropic phase boundary in the studied system lies at the composition of x ≈ 5.5. This is further evidenced by the X-ray diffraction analysis.

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Dielectric approaches for estimating microwave heating of ceramics and polymers assuming that resistive effects are small enough to be neglected have been applied quite often. However, these approaches are not valid for semiconductors. Permittivity and resistivity are very sensitive to chemical composition; therefore it is difficult to extrapolate properties from similar materials as can be done with thermal properties. The objective of this work is to estimate the dielectric and resistive contributions during microwave heating, solving the electromagnetic and heat transfer equations by means of Finite Element Method (FEM) using the software ANSYS^TM. The experiments were performed over a parallelepiped made of compacted and sintered powders of the manganite, which is a negative thermal coefficient thermistor, placed inside a waveguide and exposed to 2.45 GHz microwaves at different powers. Temperature was taken with sheathed thermocouples that also served as electrodes for monitoring electric resistance. Matching experimental data and simulation results provided values for the properties within acceptable range. An operative model for simulating heating of a sample placed in a waveguide was built, considering either resistive or dielectric effects, which in turn helps to estimate these properties applying it jointly with the experimental technique shown.

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Titanium dioxide (TiO₂) has been one of the most attractive materials in the experimental investigation during the last decades due to its scientific and technological importance. The electrochemical photolysis of water with TiO₂ was intensively studied as a candidate for a new energy source. Sterilization and sewage disposal using TiO₂ as an electrochemical catalyst were also investigated. We fabricate the photocatalytic multi layer membrane with TiO₂ thin film by aerosol deposition method at room temperature. To fabricate the TiO₂ thin film, the aerosol bath pressure and chamber pressure were 500 torr and 0.4 torr, respectively. The difference of aerosol bath pressure and chamber pressure accelerated the TiO₂ nano powder to ultrasonic velocity through the nozzle of 0.4 mm × 10 mm. Multi layer SUS membrane with diameter of 50 mm was used as a substrate to apply the TiO₂ thin film to water quality purification. The anatase phase of TiO₂ thin film was observed by X-ray diffraction. The multi layer membrane with TiO₂ thin film had the good photocatalytic activity for organics removal.

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The influence of glass composition on mechanical property of BaTiO₃ ceramics was investigated with nanoindentation technique and also its effect on densification and dielectric property was analyzed. Two different glasses of BaO-CaO-SiO₂ and BaO-ZrO₂-SiO₂ system were used as the sintering aid of BaTiO₃ powder. It was found that the addition of BaO-ZrO₂-SiO₂ glass to BaTiO₃ was beneficial for the densification compared to that of BaO-CaO-SiO₂ glass, resulting in high dielectric constant over 2500, the hardness vale of 13.6 GPa and the elastic modulus of 167.9 GPa after sintering at 1240°C.

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To encourage the recycling of spent SiC abrasive powders, we investigated the synthesis of CNTs from several types of powders. The surface decomposition method was applied to as-received powders, and graphite was observed on the SiC surface but CNTs were not. This could be caused by the turbulence of the crystal structure and Fe contaminants on the SiC surface. On the other hand, from TEM observations we found that particle covered of CNTs could be synthesized by applying the surface decomposition method to powders pretreated by acid and heat, because the turbulence of the crystal structure on the surface could be improved and Fe contaminants could be removed. Consequently, the spent SiC abrasive powders pretreated by acid and heat could be used as a resource for synthesizing CNT particles.

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Rutile TiO₂ with high specific surface area was synthesized by self-hydrolysis of TiOCl₂ in the presence of sodium dodecyl sulfate (SDS). The aggregates of rutile acicular particles formed from 0.5 M TiOCl₂ at 50°C. In order to synthesize rutile with high specific surface area, the effect of surfactant was investigated. Three kinds of surfactants were used in this study, such as stearyltrimethylammmonium chloride (C₁₈TAC) as cationic surfactant, polyoxyethylene lauryl ether (Brij35) as nonionic surfactant, and SDS as anionic surfactant. Neither C₁₈TAC nor Brij35 was influenced on the morphology of rutile particles. On the other hand, the addition of SDS was effective for the formation of mesopore, which led to specific surface area of 210 m²/g in product.

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ZnO films used as photoanodes for dye-sensitized solar cells were fabricated by a facile doctor-blade printing method. Pastes containing nanocrystalline ZnO powders and polyethylene glycol (PEG) were coated on conducting glass sheets and heated at 450°C for 10 min in air. It was shown that the microstructure of the resultant films was largely dependent on the amount of PEG in the pastes. The film without PEG had large interconnected voids, which were decreased by increasing the PEG amount. The films were dyed with a ruthenium complex dye (N-719) and their photoelectrochemical performance was investigated in terms of film properties such as thickness, specific surface area, density, and roughness factor. By optimizing the film thickness and introducing the light scattering layer, a light-to-electricity conversion efficiency of a cell using our ZnO/N-719 photoanode reached 4.3% under the AM 1.5 illumination at 100 mW/cm² (1 sun).

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Sr and Ce co-doped BaTiO₃ ceramics prepared by the cold-pressing ceramic process exhibited a worse solid solution. The influence of slight La doping on solid solution and dielectric properties of (Ba,Sr)(Ti,Ce)O₃ ceramics (BSTC) was investigated by XRD, SEM, and dielectric measurements. The results indicated that La addition to BSTC may form a single-phase solid solution up to 15% Sr and result in a grain-size refinement (< 1 μm). The most marked effect is strong broadening and rise of Curie peak around room temperature and a dramatic dielectric-peak shift rate of -56°C/at.% La for dense (Ba_1-x-zSr_xLa_z) (Ti_1-z/4-yCe_y)O₃ (x = 0.10, y = 0.03, z = 0.01) ceramic with higher room-temperature dielectric permittivity (∼3500) and lower dielectric loss (< 0.02).

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Ni-doped γ-Al₂O₃ with different molar compositions has been synthesized on α-Al₂O₃ porous supports by the sol-gel method using nitrate-alkoxide precursors. The increasing of lattice constants by Ni doping showed the formation of uniform solid solution. When the Ni content increased up to 10 mol%, NiO phase was formed. The relationship between molar compositions and hydrothermal stability under atmosphere of steam/N₂ = 3 at 773 K for 0-50 h was compared. The pore size distribution of 5 mol% Ni-doped γ-Al₂O₃ on α-Al₂O₃ porous support was stable even after hydrothermal exposure at 773 K for 50 h.

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We previously proposed the toughening and strengthening mechanisms of alumina-based nanocomposites on the basis of dislocation activities, assuming that nano-sized particles were embedded within the alumina grains. In this research, we fabricated both intragranular dominant and intergranular dominant nanocomposites of alumina/nickel(Ni) system. In order to fabricate intragranular dominant nanocomposites, γ-alumina powder with many nanopores was used as a starting material through a soaking method. Intergranular dominant nanocomposites were prepared using α-alumina powder as a starting material. Monolithic alumina samples were also sintered for comparison. Mechanical, thermal, and electrical properties were estimated for those specimens. The results showed that the intragranular nanocomposites had a higher mechanical strength and fracture toughness than the intergranular nanocomposites. The values of thermal expansion and thermal conductivity were slightly high in the intragranular nanocomposites compared to the intergranular one. The intergranular nanocomposites indicated a low dielectric breakdown voltage. Relations between the functional properties of the nanocomposites and the location of the dispersed Ni particles were discussed based on dislocation activities and the percolation model.

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We have developed organic-inorganic silicophosphate and silicophenylphosphite hybrid materials by means of alcohol condensation between organically modified alkoxysilane and anhydrous phosphoric or phosphonic acid under a solventless, catalyst-free, low-temperature, one-pot condition. The hybrid exhibits a low-melting property and is chemically more durable than that prepared by using a nonaqueous acid-base reaction between anhydrous phosphoric acid and organically modified chlorosilane. ²⁹Si and ³¹P NMR analyses have shown that the alcohol condensation yield was around 80%. Quantum chemical calculations have also performed in order to clarify the chemical durability improvement of the hybrids.

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The behavior of protein adsorption on needle-shaped hydroxyapatite (HAp) crystals was investigated and compared with that on irregularly shaped HAp crystals in phosphate buffer solutions. The proteins used were bovine serum albumin (BSA) and lysozyme chloride (LSZ). The effect of phosphate ions in the buffered solutions was evaluated at concentrations in the range 2-200 mol·m^-3. In 50 mol·m^-3 or lower buffer concentrations, the saturated amount of BSA adsorbed on needle-shaped HAp was greater than that on irregularly shaped HAp. The saturated amount of BSA adsorbed on needle-shaped HAp decreased with increasing phosphate buffer concentration. This resulted in little difference in BSA adsorption between the needle-shaped HAp and the irregularly shaped HAp at phosphate concentrations of 100 mol·m^-3 or higher. In contrast, the saturated amount of adsorbed LSZ increased with increasing phosphate buffer concentrations up to 10 mol·m^-3 and subsequently decreased with increasing phosphate concentrations between 10 and 200 mol·m^-3. There were no differences in the protein adsorption behaviors between the needle-shaped HAp and irregularly shaped HAp at a phosphate concentration of 200 mol·m^-3. A specific adsorption, useful for the separation of BSA and LSZ proteins was observed for the needle-shaped HAp at a low phosphate buffer concentration. This separation was caused by the large a-face surface area of the needle-shaped HAp by comparison with that of the irregularly shaped HAp.

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SnO₂-based varistor material was fabricated by doping of CoO, Nb₂O₅, Cr₂O₃, and Y₂O₃ or Ho₂O₃. The microstructure, nonlinear I-V characteristic and surge current performances have been investigated. The average grain boundary voltage of the obtained materials is close to that of ZnO varistors. Similar to Cr³⁺, Y³⁺ or Ho³⁺ acts as the acceptor in the grain boundaries and the depletion layers. Moderate co-doping Y₂O₃ or Ho₂O₃ with Cr₂O₃ is helpful to improve the electrical performances and to prevent poor densification. The obtained optimal samples with a diameter of about 14 mm have a nonlinear coefficient (α) of about 60, threshold electric field (E_b) of about 380 V/mm, and the withstanding peak current of 8/20 μs wave is about 2400 A. Higher surge current will cause failure but no visual damage happen. This kind of failure mode is helpful for safety use of varistors.

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