Ceramic biomaterials have been used clinically for repairing bony defects due to their biological affinity to living bone. Among ceramic biomaterials, bioactive ceramics directly bond to living bone. The bonding mechanism of bioactive ceramics to living bone provides a unique strategy in the development of novel biomaterials with high functionality. The mechanism of bone-bonding has been clarified through observation of interfaces between artificial materials and living bones as well as investigation of structural changes of the materials in solutions mimicking in vivo conditions. A simulated body fluid (SBF) that has similar concentrations of inorganic ions has been used to estimate surface structural changes of implanted materials in bony defects. Bone-like apatite deposition on the surface of implants is an important event to achieve bone-bonding with bioactive ceramics. Thus, it is important to control the reaction of such materials with body fluid during the development of novel biomaterials. Based on a fundamental understanding of the reactions of ceramic materials in SBF, novel types of biomaterials have been designed, such as surface-modified titanium metal, organic–inorganic hybrids, biomimetic composites, bioabsorbable materials, and calcium phosphates with designed morphology. In this review, the development of bioactive materials is described through a fundamental understanding of the calcification mechanisms of bioactive ceramics in SBF.

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A variety of new inorganic compounds have been prepared by hydrothermal reaction and their crystal structures were determined by single crystal X-ray diffraction or powder neutron diffraction data. They are divided into three groups; i) transition metal oxides, ii) zirconium phosphates and iii) bismuth oxides. Most of new compounds can not be synthesized by high temperature solid state reaction. Particularly some of bismuth oxides prepared by using NaBiO₃·nH₂O as a starting compound exhibited interesting properties such as superconductivity or photocatalysis under visible light. Synthesis, crystal structure and some properties of these new compounds were reviewed briefly.

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Novel metal oxynitrtides have been prepared by nitridation of amorphous metal oxide precursors obtained through citrate route. Their crystal structure, especially in O/N distribution and local bonding characteristics has been analyzed by using neutron diffraction, X-ray absorption and transmission electron microscopy, to investigate their electric and optical properties. In dielectric SrTaO₂N, crystal structure refinement suggested the short range O/N ordering and local tilting of cis-TaO₄N₂ octahedra, resulting in its unusual large permittivity. Its dense ceramics were sintered with SrCO₃ additive and exhibited superior dielectric constant above 1 × 10⁴ at room temperature. New biphasic wurtzite and zinc-blende structure of gallium oxynitride nanowire was observed by using transmission electron microscopy. As-grown long gallium oxynitride nanowire exhibited a characteristic broad UV emission at 4.3 eV in its cathodoluminescene spectrum. New oxynitride phosphor having magnetoplumbite structure, LaAl₁₂(O,N)₁₉:Eu showed photoluminescence emission peak splitting due to Eu²⁺ site splitting to two crystallographic sites induced by the two kinds of anions in its crystal structure.

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Light emission in rare earth (RE)-free SnO–ZnO–P₂O₅ glasses is demonstrated. The RE-free transparent phosphate glasses show light emission with high quantum efficiency (QE) values, comparable to conventional crystalline phosphors, by excitation with deep-UV light. The broad emissions of the RE-free transparent glasses can be continuously tuned by both the amount of activator and the composition of the glasses, without reduction of the QE values. For future emitting devices, we believe that the low-melting glasses will constitute one of the most industrially favorable inorganic materials possessing transparency and emitting properties.

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The size effect of ferroelectric materials is one of the most important issues to develop next-generation dielectric devices. In this paper, we reviewed our studies on the size effects of barium titante (BaTiO₃) fine particles and ceramics. In the size effect of BaTiO₃ fine particles, the maximum of dielectric permittivity was observed at a particle size of around 140 nm, and was explained by the composite structure model including a gradient lattice strain layer (GLSL) having a very high permittivity. In contrast, the grain size effect of BaTiO₃ ceramics, where the permittivity showed a maximum at a grain size of about 1.1 µm, was interpreted as the superposition effect of domain-wall contributions and grain boundary effect.

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Wide range of porosity in 30–90 vol % could be created into silicon carbide by employing carefully selected manufacturing methods. Two fabrication methods have been proposed and reviewed in the present paper: (1) partial sintering of submicrometer-sized silicon carbide particle with a suitable amount of sintering additive, acting as an inhibition of grain growth during sintering; (2) the use of ice crystals, as sacrificial pore formers, formed by freezing a silicon carbide particle dispersed gel body, leading to highly porous silicon carbide after sublimating ice crystals by vacuum drying and subsequently sintering. Depending on the processing route adopted, average pore size could be modulated in the range from 0.03 to 0.70 µm and 30 to 150 µm by partial sintering and gelation freezing, respectively. All fabrication methods proposed are simple, economical and versatile to produce macroporous body with tailored pore architecture and engineering porosity.

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Apatite-type ALa₉Si₆O₂₆ (A = Li, Na, K) were prepared by solid state reaction method. The hexagonal unit cell volumes of ALa₉Si₆O₂₆ increased with increasing ionic radii of alkali metal ions, indicating that the alkali metal ions were incorporated into the apatite-type lattice. The specific surface areas of ALa₉Si₆O₂₆ were less than 1 m²/g. X-ray photoelectron spectroscopy measurement showed that Pt species on as-prepared catalysts were highly oxidized. Reduction temperature of Pt oxides on the catalyst for temperature-programmed reduction by H₂ was decreased by substitution of alkali metal ion at La site in the apatite-type silicate. For C₃H₆–NO–O₂ reaction, Pt/NaLa₉Si₆O₂₆ catalyst exhibited a maximum NO conversion of 42%, the highest among Pt/ALa₉Si₆O₂₆ catalysts. The temperature for maximum NO conversion over Pt/NaLa₉Si₆O₂₆ catalyst was lower than that over Pt/γ-Al₂O₃ catalyst under the same reaction condition. The temperature of 50% C₃H₆ conversion for C₃H₆–O₂ reaction over Pt/ALa₉Si₆O₂₆ catalysts increased in the sequence of A = K < A = Na < A = Li. In addition, C₃H₆ oxidation activity was suppressed by presence of CO₂ and NO on the catalyst. These results suggest that the basic sites on the apatite-type support affect the catalytic activities of Pt/ALa₉Si₆O₂₆ catalysts for C₃H₆–NO–O₂ and C₃H₆–O₂ reaction.

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Fictive temperature dependence of refractive index, density, and Raman spectra of commercial dense crown optical glass widely used for lens production is investigated. It is found that the main peak in Raman spectra shifts higher with increasing the fictive temperature. As well as density and refractive index, this peak position has linear relationship with the fictive temperature. Relaxation of Raman spectra is similar with that of refractive index, and they are different from that of density.
For the comparison, one commercial soda-lime-silicate glass is investigated as well as dense crown optical glass. Raman spectrum of this glass shifts lower as the fictive temperature. The difference between each relaxation time is less than that of dense crown optical glass.

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In this paper, the dispersion stability of zirconium diboride (ZrB₂) slurries and their anti-oxidation behavior to prevent re-oxidation in the ZrB₂ slurries were studied.
SPEX-milled ZrB₂ powder was used to improve the dispersion stability, and the viscosity and zeta potential as a function of pH were measured in order to confirm the dispersion behavior in aqueous ZrB₂ slurries using various additives [polyethylenimine (PEI), polyacrylicacid (PAA), polyvinyl pyrrolidone (PVP), and polyvinyl alcohol (PVA)]. In addition, the oxygen contents were measured before and after processing to evaluate the oxidation behavior in the ZrB₂ slurries.
By using 2 wt % PEI, the isoelectric point (IEP) of the ZrB₂ slurry increased from a pH of 5.8 to above a pH of 12. Also, the viscosity was below 6.27 mPa·s in the 20 vol % ZrB₂ slurry at pH values of 2–12. The oxygen content of the ZrB₂ powders increased from 2.42 to 3.79 wt % after preparing an aqueous slurry, but by using 2 wt % PVP and 2 wt % PEI, the oxygen contents of the 20 vol % ZrB₂ slurry could be reduced from 3.79 to 2.6 and 2.8 wt %, respectively. Consequently, a 50 vol % ZrB₂ slurry with an oxygen content was 2.92 wt % could be prepared in the pH range of 6–9 using 2 wt % PEI.

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Diamond film and ultrananocrystalline diamond (UNCD) film were synthesized on BeCu alloy substrate by using hot filament CVD apparatus. We succeed in the synthesis of diamond film and Boron-doped electrically conductive diamond film on the substrate. Moreover, UNCD film was successfully synthesized by the CVD apparatus, although this film was not electrically conductive electrically conductive. At the first stage of the CVD process for UNCD, needle-shape deposits appeared. A two-step process, that is, the synthesis of UNCD and then boron-doped diamond, was effective for the synthesis of the electrically conductive diamond film having smooth surface.

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Local distribution of oxide ionic flows was visualized at the cathode/interlayer/electrolyte interfaces in real flat tube Solid Oxide Fuel Cells (SOFCs) stacks under operating condition. Isotope labeling (¹⁸O labeling) technique and secondary ion mass spectrometry (SIMS) analysis enabled us to visualize the trace of ¹⁸O diffusion through the (La,Sr)FeO₃ cathode/CeO₂ interlayer/YSZ electrolyte interfaces in a “frozen state”. The difference of ¹⁸O intensity was observed at (La,Sr)FeO₃ cathode as well as CeO₂ interlayer among different cells. This difference can come from the surface ¹⁶O/¹⁸O exchange rates of (La,Sr)FeO₃ cathode and the amounts of ¹⁸O₂ supplied to cells. Local difference of ¹⁸O intensity suggested the local distribution of oxide ionic currents at different cells in the stack.

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The purpose of this study is to develop lightweight pottery using organic hollow microsphere and to evaluate the mechanical properties of lightweight pottery. Spherical pores about 100 µm were formed in body, and total porosity increased proportionally with the addition of organic hollow microspheres. Many pores were isolated so that open porosity is extremely smaller than total porosity. A small amount addition of microspheres drastically degraded bending strength of pottery with slight decrease in density, indicating pores act as fracture flaws. On the other hand, a decrease in bulk density degraded fracture toughness moderately. In a wide range of porosity, a bending strength σ and a fracture toughness K_IC of lightweight pottery could be expressed in σ = 70.4d^1.57, and K_IC = 1.27d^1.54, respectively. Here, d equals to relative density.

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Crystal structures of the Ln₂Zr₂O₇ (Ln = Nd and La) were refined by the Rietveld analysis of powder neutron diffraction (ND) data at room temperature. La₂Zr₂O₇ had a pyrochlore (P)-type structure of almost completely ordered for oxygen vacancy. On the other hand, Nd₂Zr₂O₇ had the P-type structure for the oxygen vacancy distributed between the O2 (8b) and O3 (48f) sites. The Rietveld refinement results of powder X-ray diffraction (XRD) data of Ln₂Zr₂O₇ (Ln = Eu, Nd and La) indicated that the Ln³⁺ and Zr⁴⁺ ions exist in ordered states in 16c and 16d sites, respectively. The refined lattice parameters (a), occupancies (g) for oxygen sites (O1, O2 and O3) and x-positional parameters for O3 (48f) site of La₂Zr₂O₇ and Nd₂Zr₂O₇ by using powder XRD data were in almost agreement with those by using powder ND data. The refined ND and XRD data of Ln₂Zr₂O₇ (Ln = Eu, Nd and La) system revealed that the O3 (48f) site occupancy (g_48f) decreases with increasing O2 (8b) site occupancy, while O1 (8a) site occupancy keeping 1.0. The change in oxide-ion conductivity (σ) in Ln₂Zr₂O₇ (Ln = Eu, Nd and La) system can be related to a change in the product of site occupancy (g_48f) and the oxygen vacancy rate (1-g_48f) in the O3 (48f) site, g_48f(1-g_48f).

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One-dimensional (1D) β-SiC/SiO₂ nanochains, β-SiC nanowires and rod-like β-SiC were directly obtained from the vapor deposited products that formed on graphite by pyrolysis of rice husks (RHs) in argon atmosphere. 1D β-SiC/SiO₂ nanochains composed of β-SiC stems and amorphous SiO₂ beads were synthesized at 1500°C for 2 h. Pure 1D β-SiC nanowires having diameter of around 160 nm and tens of micrometers in length were obtained at 1500°C for 4 and 6 h. As pyrolysis temperature was increased to 1600 and 1700°C, β-SiC nanowires and rod-like β-SiC with larger diameters and shorter lengths were received, respectively. The possible growth processes based on vapor–solid (VS) mechanism were proposed to explain the formation of the 1D β-SiC nanostructures.

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Gas barrier silica coatings were prepared from perhydropolysilazane (PHPS) by vacuum ultraviolet (VUV) irradiation under several irradiation conditions to investigate the relationship between their water vapor transmission rate (WVTR) and the irradiation conditions. PET substrates were coated with PHPS using its xylene solution, and the coatings were irradiated with VUV light (172 nm). The oxygen concentrations and irradiation distances were varied. The sample irradiated under conditions of lower oxygen concentration (less than 5%) and shorter irradiation distance (2.6 mm) showed the lowest WVTR (0.721 g m² d⁻¹). The sample irradiated under conditions of higher oxygen concentration (19%) and longer irradiation distance (13.4 mm), on the other hand, showed the highest WVTR (2.738 g m² d⁻¹). These results suggest that VUV irradiation improves the gas barrier properties by Si–N bond cleavage rather than by oxidative reactions caused by O(¹D) and O₃.

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Octacalcium phosphate (OCP) has a layered structure composed of apatitic and hydrated layers. HPO₄²⁻ in the hydrated layer can be substituted by dicarboxylate ions. We investigated formation of OCP with incorporated dicarboxylate ions, namely octacalcium phosphate carboxylate (OCPC), under synthetic conditions with various concentrations of benzenedicarboxylic acids (BDCAs) such as 1,2-benzenedicarboxylic acid (1,2BDCA, phthalic acid), 1,3-benzenedicarboxylic acid (1,3BDCA, isophthalic acid), and 1,4-benzenedicarboxylic acid (1,4BDCA, terephthalic acid). 1,3BDCA or a small amount of 1,2BDCA could be incorporated into OCP, but 1,4BDCA could not be incorporated into OCP. When the added amount of 1,3BDCA was larger than 2 mmol, OCPC with 1,3BDCA (1,3BDCA-OCPC) was formed with dicarboxylate-free OCP (Pure-OCP). The fractions of 1,3BDCA-OCPC with respect to Pure-OCP increased with increasing amounts of 1,3BDCA. When excessive amounts of 1,3BDCA, namely 25 times with respect to the stoichiometric composition of OCPC, were used for formation of OCPC, 1,3BDCA-OCPC was formed as a single phase. Addition of excessive amounts of 1,3BDCA prevented formation of Pure-OCP and had an advantage in formation of 1,3BDCA-OCPC.

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Ni nanoparticles were precipitated on Al₂O₃ support powder by rotary chemical vapor deposition (RCVD). The Ni nanoparticle size increased from 8 to 62 nm in diameter and the content of Ni decreased from 6.6 to 2.4 mass % with increasing Al₂O₃ powder diameter (D_Al2O3) from 80 nm to 150 µm. The catalytic activity of Ni precipitated Al₂O₃ (Ni/Al₂O₃) powder was evaluated by the hydrogen production rate (R_H2) in a methanol-steam flow. The R_H2 decreased with increasing D_Al2O3 and increased with increasing specific surface area of Ni/Al₂O₃ powder. The highest R_H2 of Ni/Al₂O₃ powder was 709 × 10⁻³ mol kg⁻¹ s⁻¹ at 633 K, D_Ni = 8 nm and D_Al2O3 = 80 nm.

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Ferroelastic β′-Gd₂(MoO₄)₃ and β′-Eu₂(MoO₄)₃ crystals were synthesized through the crystallization of 21.25Gd₂O₃–63.75MoO₃–15B₂O₃ glass and 22.5Eu₂O₃–47.5MoO₃–30B₂O₃ glass, respectivelty, and their magnetism and photoluminescence properties were examined. It was demonstrated from the temperature dependence of the magnetic susceptibility and specific heat down to T = 1.8 K that the magnetic state of Gd³⁺ ions in the crystallized samples, i.e., in the β′-Gd₂(MoO₄)₃ crystals and the residual glasses, is paramagnetic and any magnetic interaction is not formed among Gd³⁺ ions down to T = 1.8 K, i.e., the effective magnetic moment of µ_eff = 7.94 µ_B and Weiss constant of θ = –0.3 K. Photoluminescence (PL) of Eu³⁺ ions was clearly observed in the crystallized samples, although the melt-quenched glass did not show any photoluminescence. The present study proposes that the concentration quenching among Eu³⁺ ions in β′-Eu₂(MoO₄)₃ crystals is small and β′-RE₂(MoO₄)₃ crystals would be good hosts for PL emissions of RE³⁺.

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This study examined improvement of the crystallinity and the decomposition mechanism for the Pb(Mg_1/3Nb_2/3)O₃ (PMN) thin films using chemical solution deposition (CSD) technique with a metallo-organic decomposition (MOD) solution. The PMN thin film crystallinity increases with higher annealing temperature, but improvement is slight at temperatures higher than 700°C. The facing annealing has a distinct effect on the crystallinity of PMN thin film at 650°C, which is the lowest annealing temperature examined in this study. The ratio of the pyrochlore phase has a peak at 750°C with or without the facing annealing. The facing annealing also has a distinct effect on PMN thin film decomposition at 800°C. Improvement of the crystallinity and of the homogeneity of the morphology of PMN thin films deposited at 650°C was possible under the facing condition. The decomposition occurs locally, and the residual PMN region has high crystallinity and stoichiometry. The atomic structure of the PMN lattice has a fluctuation that is characteristic in the relaxor, which is related to the polar-nano region (PNR). The chemically ordered region (COR) also appears in PMN even at a lower annealing temperature than that of bulk relaxor materials.

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Silicon oxynitride particles intended for use as radiative cooling materials were synthesized via the nitridation of mixtures of Si and SiO₂ powders. The optimal heat-treatment conditions for the formation of silicon oxynitride were determined to consist of a temperature of 1450°C applied for one hour. Specimens formed in this manner from mixtures of Si and SiO₂ in 2:1 or 3:1 molar ratios under a nitrogen atmosphere were composed almost exclusively of a single Si₂N₂O phase. The resulting Si₂N₂O powders exhibited significant absorption in the so-called atmospheric window IR region between 8–13 µm and had only limited absorption outside of that range.

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Perovskite-type SmFeO₃ fine powder was synthesized by the polymer precursor method using carbonate powder as an anti-sintering agent. SmFeO₃ particles synthesized at 550°C were smaller than 100 nm and had a specific surface are of 36 m²/g. Also, the addition of carbonate in the calcinations process enabled the synthesis temperature for crystal formation of SmFeO₃ to be reduced by 100°C. Results of thermal analysis suggested that carbonate stimulates a combustion reaction required for the formation of SmFeO₃.

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A nano-composite powder composed of silica and carbon with a unique property could be prepared from a mixture of a silicate compound and an epoxy compound, in which the silica within the nano-composite powder has a BET surface area of as high as greater than 800 m²/g although the nano-composite powder has a BET surface area of less than 10 m²/g. It was estimated that the silica and the carbon are in a very finely and uniformly mixed state within the nano-composite powder and that the silica and the carbon form particles having a diameter of several tens nm and a number of silica particles having a diameter of several nm exist within the every particle of the nano-composite powder. It was demonstrated that the nano-composite powder exhibits characteristic behaviors under calcination at a temperature of 1450°C such that an amorphous state of the nano-composite powder is maintained, a large amount of gaseous reactant generates from the nano-composite powder, and a reaction product of SiC is synthesized in the presence of another ingredient.

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Although photocatalytic activity of TiO₂ is mainly discussed in terms of the band gap energy, the importance of surface oxygen for the decomposition of chemicals on the photocatalyst is emphasized in several reports. The availability and stability conditions of the surface oxygen atoms on TiO₂ crystals depend on the surface orientation of the crystals. In this study, rutile TiO₂ single crystals with different orientations are used and we evaluate the progress of photocatalytic decomposition reactions by the weight loss of the salad oil and linoleic acid due to formation of gaseous species. If the surface of rutile TiO₂ single crystals is not reconstructed and surface oxygen is involved, the orientation of the surface affects the photocatalytic activity of TiO₂; the photocatalytic activity increases in the order of (114) < (100) < (101) < (001).

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Tensile and fracture tests for dried nacre were carried out. Dried nacre fractured in a brittle fashion, but its toughness perpendicular to the plane of the plate was 10 times greater than that of natural CaCO₃. A simple model in which plates interlock was proposed based on the observations of fracture behavior and the fractured surface. The contribution of interlocking to toughness was estimated; it was confirmed that the interlocking of the plates is the main factor in the toughening of dried nacre.

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A double oxide containing Pt and Li, Li₂PtO₃, was prepared to search for an environment-friendly route to dissolve Pt in hydrochloric acid (HCl). Li₂PtO₃ powder was obtained by calcination of a mixture of Pt black and Li₂CO₃ powder at 600, 700 and 800°C. The resulting Li₂PtO₃ powder was soluble in HCl which has no oxidizing power at ambient temperatures. The Pt solubility of Li₂PtO₃ obtained at 600°C increased from 39.2 to 99.9% as the temperature of 12 M HCl increased from 40 to 80°C. From ultraviolet–visible absorption spectra, it was found that, a complex ion [PtCl₆]²⁻ formed as a result of a reaction of Li₂PtO₃ with HCl. The dissolution process by way of this compound is expected to benefit the establishment of environment-friendly recovery process of Pt.

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