In guided bone regeneration (GBR) technique, a barrier membrane is placed over the alveolar bone defect to prevent the down-growth of cells. However, the conventional membrane has no adhesive property for the tissue. This study challenged to develop a GBR membrane that has easily well adhesion to periodontal tissue with biocompatibility.

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Transparent MgAl₂O₄ spinel ceramics were fabricated by hot isostatic pressing of the sintered materials composed of fine grains. Since the fine-grained sintered materials were difficult to obtain from pure powders at low temperatures, the additives reducing sintering temperatures were examined. As a result, a small addition of boron oxides (0.05-0.5 mass%-B₂O₃) was found to be very effective. The influence of boron oxides on the microstructure was investigated. The restriction of anomalous grain growth was important for transparency. The samples added with 0.15 mass%-B₂O₃ showed high optical transmittance (80% with 1 mm thick).

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Complexes between TiO₂ and sugar alcohol molecules or polyol molecules were prepared by heating the mixture of titanium isopropoxide (TIP) and ethylene glycol, glycerin, meso-erythritol, or D-mannitol aqueous solution at 368 K for 24 h. The degree of crystallization of TiO₂ in the obtained TiO₂-sugar alcohol or polyol complex depended on the concentration of the polyol and sugar alcohol aqueous solution. When the TiO₂-sugar alcohol or polyol complex was prepared by using the same concentration of the sugar alcohol or polyol aqueous solution, the degree of crystallization of the TiO₂ in the complex decreased with increase in the number of OH groups per molecule. According to the results of the DTA measurements and the element analysis, the strength of the interaction between Ti⁴⁺ ions and polyol or sugar alcohol molecules increased with increases in the number of OH groups in the molecules. The heat treatment of TiO₂-D-mannitol complex in 0.5 mol/l HNO₃ aqueous solution at more than 318 K enabled to obtain TiO₂-D-mannitol complex nanoparticles by breaking the bonds between the D-mannitol molecules and Ti⁴⁺ ions. The obtained TiO₂-D-mannitol complex nanoparticles had large surface area which was more than 300 m²/g and showed photocatalytic activity. Furthermore, the complex nanoparticles can be dispersed into the distilled water with high stability.

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TiO₂ nanoparticles were synthesized by self-hydrolysis of TiOCl₂ using conventional and microwave heating methods. By XRD analysis, rutile and anatase phases were detected at the early stage of reaction. In conventional heating method, the XRD peaks of rutile became stronger with time and the roundish agglomerates surrounded by acicular particles were observed by SEM. The initial product was confirmed by TEM to consist of small acicular particles assigned to rutile and fine nanoparticles assigned to hydrous TiO₂ sol having anatase-like structure. As the reaction time was longer, the amount of acicular particles increased. These results suggest that TiO₂ sol formed at the early stage by hydrolysis of TiOCl₂ and the crystal growth of rutile progressed by dissolution-reprecipitation of TiO₂ sol. In order to synthesize TiO₂ nanoparticles, microwave was applied to this system. The microwave irradiation shortened the period of the precipitation because microwave can quickly heat up the aqueous solution, but retarded the crystal growth of rutile, leading to size reduction of TiO₂ particles identified a hydrous TiO₂ phase.

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A novel ordered siloxane-organic hybrid material has been prepared by hydrolysis and polycondensation of a well-defined alkoxysilane precursor consisting of a tetrasiloxane unit and a 4-phenylbutyl group (1). Evaporation-induced self-assembly during hydrolysis and polycondensation of 1 led to the formation of a two-dimensional (2D) hexagonal mesostructure, which was revealed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Solid-state ¹³C CP/MAS NMR and ²⁹Si MAS NMR confirmed that the product consisted of 4-phenylbutyl groups and siloxane networks, both of which are linked via Si-C bonds. These results will allow us to produce functional hybrid materials by chemical modification of phenyl groups, and also by incorporating other organic groups. Furthermore, calcination of this hybrid to remove organic groups led to the creation of an ordered microporous silica with the Brunauer-Emmett-Teller (BET) surface area of 570 m² g^-1 and the average pore diameter of 1.2 nm.

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The slurries studied were characterized by a conventional apparent viscosity measurement, a constant rate filtration and a stress relaxation test proposed in this study in order to identify the most affective property of a slurry on the crack formation of a green sheet during drying. We evaluated the packing ability of the slurry from the constant rate filtration and stress relaxation rate of a cake form by the stress relaxation test. Slurries were also tape cast, dried at room temperature and then cracks formed in green sheets were observed. Slurry properties were controlled by changing the pH value of the slurry or the additive amount of the binder. It was shown that there is not a good correlation between the apparent viscosity, packing ability of slurry and crack formation in the green sheet, while the number of cracks decreased with an increase in the stress relaxation rate of the cake. The stress relaxation test can be useful to predict crack formation during drying regardless of the slurry preparation method such as the pH adjusted or binder containing slurries.

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The design and reliability of NGK type clay hardness tester, which has been used for measuring the hardness of plastic clay body in order to control and/or check the consistency of the ceramic clay dough in the ceramic production, were investigated. It was found that the hardness values were depended on the design of the hardness tester, and to a larger extent on the human error. The factors affecting the reliability of the hardness values were also discussed.

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We already reported a new single-phase ceramic material (Al_2x(HfMg)_1-x)(WO₄)₃ which shows a low thermal expansion of less than ±2 ppm/°C for the mixing ratio x between room temperature and 800°C. If we control the thermal expansion coefficient in a wide range, it is easy to adjust the thermal expansion coefficient to those of other materials. It also becomes possible to apply thermal-expansion-controlled material in various fields, such as electronic, optical and nanoscale devices. In this report, the authors tried to control more widely the thermal expansion coefficient for the ceramic system of the cofired HfW₂O₈ (negative thermal expansion)-MgWO₄ (positive thermal expansion). For all the compositions in this system, (HfMg)(WO₄)₃ was synthesized from HfW₂O₈ and MgWO₄. It was clarified that the HfW₂O₈-MgWO₄ cofired system was divided into the (HfMg)(WO₄)₃-MgWO₄ binary ceramic and the (HfMg)(WO₄)₃-HfW₂O₈ binary ceramic. Finally, those thermal expansion coefficients can be adjusted from -6 to +9 ppm/°C by changing the compositional ratio of HfW₂O₈ and MgWO₄.

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An acid resistant fluoroapatite (FAp) coated titanium dioxide (TiO₂) was synthesized by adding a fluoride ion (F^-) to hydroxyapatite (HAp), in order to avoid dissolution of the HAp at an acidic atmosphere. In this study, different methods of adding F^- to the apatite in a simulated body fluid were tested; one was synthesized by coating a simulated body fluid including Ca²⁺, PO₄ ^3- and F^- to the TiO₂ (method 1), and another method was by mixing the F^- after coating a simulated body fluid without the F^- to the TiO₂ (method 2). The apatite crystalline phase of the coated TiO₂ was found to increase with F^-, by using a XRD and a FT-IR. The size of crystalline apatite was strongly affected by the method of adding F^-. The size of the crystalline synthesized by method 1 was larger than that by method 2. The photocatalytic activities of the apatite coated photocatalysts to organic substrates such as propionic acid were evaluated using an ion chromatography. The deterioration of FAp coating during photooxidation of the propionic acid with an UV-irradiation was largely suppressed compared with that of the HAp coating.

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Mixtures of chrysotile (Mg₆Si₄O₁₀(OH)₈) and CaCO₃ were burned at temperatures ranging from 500°C to 1000°C; the decomposition temperature of chrysotile was lowered by adding CaCl₂. Thermal analysis and succeeding SEM observation confirmed the formation of melts, which was supposed to be responsible for the effect of the added CaCl₂. The melts were detected even when the added CaCl₂ was as little as 1-5 mass% of the CaCO₃; the quantity of the CaCl₂ was smaller than that predicted from the phase diagram. Thermodynamic calculations of chemical equilibrium showed that forsterite (Mg₂SiO₄), which was a thermal decomposition product of chrysotile and had a fibrous shape, destructed at about 500°C. In the common decomposition methods to convert asbestos-cement composites to oxides of Ca-Si system, the decomposition reaction occurs via a solid-solid reaction and reacts slowly. So to increase the reaction rate, a reaction temperature above 1000°C is required. The present study has experimentally evidenced that the formation of melts enlarges the reaction interface between the chrysotile and the CaCO₃ so that the decomposition reaction can proceed even at lower temperatures.

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We synthesized the LiMn_1-xM_xO₂ (M=Mn, Co, Ni) and investigated the electron density map by X-ray diffraction using the Maximum Entropy Method(MEM)/Rietveld Analysis and first principles calculation. The electron density map shows that the covalent bonding of (Mn, M)-O of o-LiMn_1-xM_xO₂ is stronger than that of o-LiMnO₂. Next, we calculated the electron density of o-LiMn_1-xM_xO₂ (M=Mn, Co, Ni, Zn) using the first principles calculation by FLAPW method. The covalent bonding of Mn-O and M-O of each o-LiMn_1-xM_xO₂ is stronger than that of o-LiMnO₂ by substitution of Mn with M.

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Thermoelectric hydrogen sensor (THS) is a promising candidate for a hydrogen leak alarm system because of its unique, reliable working principle and its performance has been improved by fabricating it as a micro-device. In this study, we have investigated the performance of a micro-THS with new design of 4×4 mm² chip. The integration of a thermoelectric thin film of B-dope SiGe and a ceramic catalyst of Pt 40 mass% loaded alumina into a micro hot-plate on a thin membrane, has improved its performance. We have demonstrated that the micro-THS detected the wide range of H₂ concentration in air from low as 0.5 ppm to high as 5 vol%.

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Lead-free piezoelectric ceramics (1-x)(Bi_0.5Na_0.5)TiO_3-xBa(Zr_0.04Ti_0.96)O₃ (abbreviated as BNT-BZT100x, with x ranged from 2 to 10 mol%) have been investigated. The samples were prepared by a conventional sintering technique. Effect of amount of BZT on the electrical properties and microstructures of BNT-BZT lead-free piezoelectric ceramic were examined. The X-ray diffraction (XRD) patterns shows that incorporated BZT diffuses into the BNT lattice to form a solid solution during sintering, but changes the crystal structure from rhombohedral to tetragonal symmetry at higher BZT amounts. The measurements of piezoelectric properties reveal that BNT-BZT6 ceramics has highest piezoelectric performance: the piezoelectric constant d₃₃ reached to 168pC/N and planar electromechanical coupling factor k_p enhanced to 0.27. The morphotropic phase boundary (MPB) between BNT(rhombohedral) and Ba(Zr_0.04Ti_0.96)O₃ (tetragonal) should be near the BNT-BZT6 composition.

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We prepared low temperature phase of triple layered perovksite KCa₂Nb₃O₁₀ by an ion-exchange reaction. Li-intercalated low temperature phase, Li_0.79KCa₂Nb₃O₁₀, shows strong diamagnetic signal around at 7.8 K. The magnetic phase transition temperature of Li-intercalated low temperature phase is higher than that of Li-intercalated high temperature phase.

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