A new class of glass composite membranes of various compositions was prepared via a sol-gel technique. The membranes, consisting of (phophotungsticacid/phosphomolybdicacid) PWA/PMA-P₂O₅-SiO₂ mixed with either ZrO₂ or TiO₂ displayed varying properties depending on their composition and mode of fabrication. The structure and property of the obtained glass ceramic composite membranes were investigated by FTIR, TG/DTA and textural analysis. The results included good mechanical, textural and thermal properties and the materials were deemed to be suitable electrolytes for fuel cell applications.

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Composite TiBC-SiC film coatings with various contents of SiC were deposited on Si wafer at 800°C from a mixed solution of titanium tetra-ethoxide, boron tri-ethoxide and/or hexa-methyl-disiloxane by an Ar/H₂ thermal plasma CVD. The crystalline phases (TiB₂, TiC, SiC) in the coatings are identified by thin film grazing incidence X-ray diffraction. The surfaces and cross-sections of the monolithic TiBC and SiC and composite TiBC-SiC coatings are observed by scanning electron microscopy. The microstructure of a cross-section of composite TiBC-55 mol% SiC film is observed by transmission electron microscopy with EDX analysis. The wear rates of the composite TiBC-SiC film are evaluated from cross-sectional profiles of the residual wear tracks formed by ball-on-disk wear tests using SUS and alumina balls with their results correlated with the SiC content and film hardness.

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Mullite-silicon carbide composites were fabricated via a reaction sintering using SiC and alumina (Al₂O₃) powders. The mullite phase was in situ synthesized from the reaction between the oxidation-derived SiO₂ and alumina. The effects of incorporating submicron (∼0.5 μm) SiC powder (in addition to the coarser (∼65 μm) SiC powder) on the microstructures, densities, and flexural strengths of the composites were investigated. The addition of submicron SiC powder was found to increase the mullite content, relative density, and flexural strength of the composite. The 6-h-sintered composite containing 40 mass% submicron SiC powder had the highest flexural strength. A slightly lower strength was observed for the composite containing 50 mass% submicron SiC powder. This was attributed to there being insufficient alumina in the starting powder for synthesizing the mullite. The composites sintered for 6 h typically had flexural strengths of ∼90 MPa at 25% porosity.

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Epitaxial BaRuO₃ (BRO) thin films were prepared on (001) and (111) MgO substrates by laser ablation, and the relationship of lattice matching, morphology and electrical conductivity was investigated. (205)- and (001)-oriented rhombohedral BRO thin films were epitaxially grown on (001) and (111) MgO substrates, respectively. The (205) BRO thin films showed an orthogonal texture with faceted island grains, whereas the (001) BRO thin films had a hexagonal columnar structure with a flat terrace. Epitaxial BRO thin films showed metallic conduction, and the (205) BRO thin films exhibited the highest electrical conductivity, i.e., 1.0 × 10⁵ S·m^-1, at room temperature. A higher lattice matching between epitaxial thin film and the substrate yielded a higher electrical conductivity.

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The two dissimilar dopants, Li₂Si₂O₅ with small ionic sizes and inert Ag with a large atomic size were selected to understand the effects of activators on non-stoichiometrically activated sintering of Ca_0.8Sr_0.2TiO₃ by doping with Ag, or co-doping with Ag and Li₂Si₂O₅. The solubility limit of Ag⁺ in Ca_0.8Sr_0.2TiO₃ was ca. 7.0 mass%. The optimum sintering temperature was as low as 1353 K by co-doping of 5.0 mass% Ag and 0.5 mass% Li₂Si₂O₅. This firing temperature was lower than that of 1623 K using 5.0 mass% Ag, and 1473 K for 0.5 mass% Li₂Si₂O₅, respectively. The fracture strength of 363 MPa attained by co-doping was much high than the values of 291 and 292 MPa using 5.0 mass% Ag and 0.5 mass% Li₂Si₂O₅, respectively.

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CaO and ZrO₂ co-substituted polycrystalline BaTi₂O₅, (Ba_1-xCa_x)(Ti_0.995Zr_0.005)₂O₅, (BCT₂Z), was prepared by arc melting and the dielectric properties were investigated by AC impedance spectroscopy. b-direction orientation was obtained at any composition. The lattice parameters of a-, b- and c-axes first increased until x = 0.003 and then slightly decreased with increasing CaO content up to x = 0.020. The maximum permittivity of polycrystalline BaTi₂O₅ showed the highest value of 6230 at x = 0.020. The T_c of polycrystalline BaTi₂O₅ slightly decreased from 750 to 716 K when CaO content was increased up to 0.020.

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High-yield SiC/SiO₂ core-shell nanowires were synthesized without adding metal catalysts from outside through a simple thermal evaporation of silicon powders during decomposition of methane gas. The influence of three parameters, size of Si raw powder (50 nm and 5 μm), reaction temperature (1573, 1623 and 1673 K), and soaking time (1, 3 and 6 h), was investigated. The typical synthesized nanowires from different conditions possess the diameter of no thicker than 100 nm with several tens micrometers in length. It was addressed that the condition using the smaller size Si powder, which contained the highest amount of oxygen, at higher temperature lead to more complete reaction to obtain a large quantity of nanowires. The synthesized nanowires at higher reaction temperature and longer soaking time possessed larger core than those nanowires prepared at lower reaction temperature and shorter soaking time. Oxidation of larger size Si powder improved yield of nanowires. Based on these results, it was suggested that the typical nanowires should be grown via the oxide-assisted growth mechanism.

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The preparation of pore gradient silicon nitride (Si₃N₄) ceramics was investigated by thermally spraying dense Si₃N₄ coatings onto the porous Si₃N₄ ceramic substrates via a high-velocity oxyfuel (HVOF) spraying method. Spray powders with excellent processability were developed and produced by spray drying and sintering in a nitrogen atmosphere. After sieving, the powders with average particle size of 45-75 μm were selected. Optimization of spray parameters such as spray distance and hydrogen flow rate was carried out in order to find the most decisive factor necessary for the production of dense and well-adhering coatings and pore gradient stuctures. Zirconium phosphate bonded Si₃N₄ porous ceramics were used as the substrate and coatings were obtained only when spray distance was 200 mm. A pore gradient structure was obtained at lower H₂ flow rate, while poor-adhering coatings were obtained at higher H₂ flow rate due to the etching. The hardness is significantly improved after Si₃N₄ coatings were successfully applied.

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Dense calcia-stabilized zirconia (CSZ) ceramics were prepared by using a small amount of boric acid (H₃BO₃) as the sintering additive at the sintering temperature of 1700°C. The effect of H₃BO₃ content on the sintering behavior, the change of phase composition and mechanical properties of the CSZ ceramics were mainly investigated. The results showed that, due to the reaction between B₂O₃ and CaO, borate liquid was formed during the sintering, which promoted the the densification of CSZ ceramics. Meanwhile, the depletion of the CaO from the lattice of CSZ ceramics resulted in the phase transformation of ZrO₂. The content of tetragonal ZrO₂ phase increased with increasing the H₃BO₃ content. So the phase composition of CSZ ceramics could be well controlled by adjusting the amount of H₃BO₃. The bending strength and fracture toughness of the sintered CSZ ceramics also increased with increasing the H₃BO₃ content, namely the content of tetragonal ZrO₂ phase, which had better mechanical properties, and the highest value reached 267 MPa and 3.35 MPa·m^1/2, respectively.

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The mullite composite powders with embedded Fe and Ge nanoparticles were individually prepared through the reduction of Al_5.4Fe_0.6Si₂O₁₃ and Al₁₂Si_3.75Ge_0.25O₂₆ solid solution. The complete reduction of Fe³⁺ cation in solid solution is realized by hydrogen at 1200°C for 1 h. The magnetic properties of composite powders such as hysteresis loops and magnetization versus temperature were measured using SQUID. The Fe nanoparticles with the particle size around 10 nm embedded in mullite grain show the superparamagnetic behavior with the blocking temperature around 50 K. The mullite composite powders with Ge nanoparticles have strong room temperature photoluminescence (PL) at 561, 610, 676, 713 and 787 nm, respectively. The highest photoluminescence intensity was observed in the sample reduced at 500°C for 3 h. Based on the analysis of XPS and Raman spectra, it is clear that the PL phenomenon is derived from the formation of embedded Ge clusters with the average size of around 1-2 nm in mullite composite powders. It is proved that the multi-functional mullite nanocomposites with functional metal nanoparticles can be prepared through the selective reduction of designed solid solutions.

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LiBH₄ with high hydrogen density has been attracting great interest as one of potential candidates of advanced hydrogen storage materials. A feasible way to overcome problematic issues on dehydrogenation of LiBH₄, such as formation of fine powders and overflow by melting, is expected to synthesize bulk LiBH₄ by applying the "impregnation method". In the present study, LiBH₄ on a Ni foam with porosity of 98% homogeneously impregnated the foam at 573 K without changing the original bulk morphology of the foam. The morphology of the impregnated LiBH₄ was also well retained, even after a partial dehydrogenation at 873 K. Some Ni borides were found to be newly formed depending on the heating (dehydrogenation) conditions, and the formation probably dominates the microstructure and dehydrogenation property of the impregnated LiBH₄.

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Calcium titanate (CaTiO₃), α-tricalcium phosphate (α-TCP) and hydroxyapatite (HAp) films were prepared by metal-organic chemical vapor deposition (MOCVD) using Ca(dpm)₂, Ti(O-i-Pr)₂(dpm)₂ and (C₆H₅O)₃PO precursors. The phases, composition and surface morphology of these films changed depending on substrate temperature (T_sub), total pressure (P_tot) and molar ratio of each precursors (R_Ca/Ti, R_Ca/P). The surface morphology of CaTiO₃ films changed from granular structure to cauliflower-like texture, and its cross-sectional morphology changed from dense to columnar structure with increasing T_sub. α-TCP and HAp films had granular surface and dense cross-sectional morphology. CaTiO₃, α-TCP and HAp films were immersed in a Hanks' solution for 28 d. Apatite formation rate strongly depended on the surface morphology of CaTiO₃ film, and apatite covered CaTiO₃ film having a granular surface after 4 w while CaTiO₃ film having a cauliflower-like texture after 3 d. Apatite covered α-TCP films after 14 d and HAp films after 6 h, respectively. HAp films prepared by MOCVD were promising as bone conductive materials.

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Polycrystalline bulk CaIrO₃ as a main phase with minor phases of IrO₂ and/or Ca₂IrO₄ was prepared by spark plasma sintering (SPS) at 1273 K. Metastable CaIrO₃ with a perovskite-type structure (pv-CaIrO₃) formed by heat-treatment at 1273 K for 43.2 ks and transformed into a post-perovskite structure (ppv-CaIrO₃) by heat-treatment at 1273 K for 259.2 ks. The electrical conductivity (σ) of the pv-CaIrO₃ specimen decreased from 1.74 × 10⁴ to 1.45 × 10⁴ Sm^-1, while the σ of the ppv-CaIrO₃ specimen increased from 5.0 × 10¹ to 9.8 × 10² Sm^-1 with increasing temperature from 298 to 1023 K. The Seebeck coefficient (S) of the pv-CaIrO₃ specimen was around -44 μVK^-1 at room temperature and increase to the highest value of 40 μVK^-1 at 1023 K. The S of the ppv-CaIrO₃ specimen decreased with increasing temperature and had an almost constant value of about 60 μVK^-1 above 600 K. The thermal conductivity (κ) of the ppv-CaIrO₃ specimen decreased from 2.7 to 1.2 Wm^-1K^-1 and that of the pv-CaIrO₃ specimen decreased from 1.5 to 1.2 Wm^-1K^-1 with increasing temperature from 298 to 1023 K. The highest dimensionless figure of merit values (ZT) of the pv-CaIrO₃ and the ppv-CaIrO₃ specimens were 0.02 and 0.003 at 1023 K, respectively.

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The advantages of a good colloidal processing of tetragonal zirconia for achieving a full densification and a small grain size were determined in this study. The optimization of slurry preparation was studied to obtain well-dispersed suspensions. A deagglomeration technique was applied by bead-milling using grinding media of 50 μm diameter and initial particle size and green density were improved. Colloidal processing was considered responsible for the improvements of particle packing that increase the green density. A conventional sintering at low temperatures and two-step sintering were observed to be more effective with the final bead-milling treatment.

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Gallium nitride (GaN) films were grown with and without lattice-matched (In,Ga)N buffer layers on the c(+) and c(-) faces of ZnO single-crystal substrates using molecular beam epitaxy, and their interface structures, including the relationship between the crystallinity of the GaN film and the polarity of the ZnO substrate, were investigated. Growth at a high temperature (e.g., 800°C) was made possible by using an (In,Ga)N buffer layer, which improved the crystallinity of the GaN films compared with that of GaN films grown directly on a ZnO substrate. Ion scattering, i.e., coaxial impact-collision ion scattering spectroscopy, and electron beam channeling, i.e., convergent beam electron diffraction, profiles revealed that the GaN films grown on c(+)- and c(-)-ZnO substrates with an (In,Ga)N buffer layer had a (0001) surface (i.e., c(+) polarity). That is, polarity inversion occurs when GaN film is grown with an (In,Ga)N buffer layer on a c(-)-ZnO substrate.

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The corrosion resistance of β-SiAlON based advanced ceramic materials in molten aluminum, equimolar NaCl-KCl melt and also in the melted mixture of NaF and AlF₃ (molar ratio 1 : 1.163) were investigated. Two kinds of β-SiAlONs were tested; β-SiAlON prepared from powder precursors produced by carbothermal reduction and nitridation (CRN) of pyrophyllite and β-SiAlON made from commercial powders (AlN, Al₂O₃ and Si₃N₄). Corrosion tests were realized at 760°C for 7, 36 and 72 h under nitrogen atmosphere by dip-finger test method. All types of β-SiAlONs have great corrosion resistance against molten aluminum and NaCl-KCl melt at these conditions. The results of corrosion test were different for the β-SiAlONs in molten fluorides. While the corroded zone was only about 100 μm deep after 72 h corrosion test in reference β-SiAlON prepared from synthetic powders (SiAlON-R), in sample prepared from CRN pyrophyllite (SiAlON-P) it was almost 230 μm thick. Additionally, the oxidation resistance of β-SiAlONs was tested. The results showed that both SiAlON-P and reference SiAlON-R have comparable good oxidation resistance.

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Single crystals of a magnesium niobium oxide Mg₅Nb₄O₁₅ were prepared at 1673 K. This compound has an orthorhombic pseudobrookite-type structure (space group Cmcm). The single-crystal structure refinement was carried out in the temperature range from 293 to 1173 K. The final R-factors were R = 0.025-0.038 and R_w = 0.031-0.044. The lattice parameters were a = 3.806(3), b = 10.057(3) and c = 10.260(4) Å at 293 K and a = 3.810(6), b = 10.188(5) and c = 10.398(5) Å at 1117 K. The linear thermal expansion coefficients were α_a = 1.28 × 10^-6, α_b = 15.8 × 10^-6 and α_c = 16.3 × 10^-6 K^-1. Thermal expansion anisotropy in the bond distances and angles is consistent with the thermal expansion anisotropy in the lattice parameters.

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The subsolidus phase relations in the Bi₄Ti₃O₁₂-Ag/Ag₂O-TiO₂ system were determined by means of solid-state reaction, X-ray diffraction and scanning electron microscopy. The rutile and anatase phases showed different chemistries when reacting with the Ag/Ag₂O-Bi₂O₃, and the Ag_0.5Bi_8.5Ti₇O₂₇ phase can be obtained from the anatase form but not from the rutile form. In the present study the phase relations in the Bi-Ag-Ti-O system were established for the rutile form. The solid solutions TiO_2SS, Bi₄Ti₃O_12SS and Bi₂Ti₂O_7SS were identified in the Bi₄Ti₃O₁₂-Ag/Ag₂O-TiO₂ system and silver was found to be compatible with all three. There was no compatibility between the silver and the Bi₂Ti₄O₁₁. A single-phase compound was obtained for the pyrochlore phase Bi_1.55Ag_0.1Ti₂O_6.375.

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Porous lanthanum doped alumina ceramic composite was prepared by self-organization and solid-state reaction between Al₂O₃ and La₂O₃. Crystal phases, microstructure and density of ceramics were examined to characterize novel composites in the system of Al₂O₃ and La₂O₃. After heat treatment at 1300°C and 1400°C, LaAl₁₁O₁₈ plate-like crystals were formed through the solid-state reaction of LaAlO₃ with Al₂O₃. The addition of large amounts of La contributed to the increase of LaAl₁₁O₁₈ plate-like crystals and their cross-linking microstructure. The porous alumina composites maintained high surface areas of 20 m²/g after heating at 1300°C, and 11 m²/g at 1400°C. The bending strength of La added alumina composite was 57 MPa after heating at 1400°C.

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Oriented hexagonal BCN films were synthesized on Si (1 0 0) substrate by radiofrequency plasma enhanced chemical vapor deposition using tris-(dimethylamino)borane as a precursor. The formation of the crystalline hexagonal BCN hybrids was confirmed by FT-IR and XRD. CH₄ + H₂ carrier gas increased the C content in the films in comparison with N₂ carrier gas. XPS measurement showed that the films were composed of a variety of B-N, B-C, C-N bonds to form the BCN atomic hybrids. The π* resonance peak in the B K-edge NEXAFS spectra also indicated the presence of the sp² hybrid configuration of B-C-N bonds like BN₃ in h-BN. The σ* resonance peaks suggested the diversity in the σ bonds in the films. Orientation of the h-BCN hybrids was suggested on the basis of the polarization dependence of NEXAFS.

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Ga:ZnO whiskers were grown by atmospheric chemical vapor deposition on single crystalline silicon (100). By adjusting the concentration of the gallium dopant, the crystallite density and radius of curvature could be varied. The c-axis orientation of the Ga:ZnO crystallite was less than that of the Al:ZnO crystallite. The field emission characteristics of Ga:ZnO whisker emitters were investigated by varying the crystallite density and radius of curvature. Moreover, when the crystallite density was in the range 0.8 × 10⁴-1.6 × 10⁴/mm² and the crystallite radii of curvature were in the range 46-106 nm, the electric field, E, necessary to obtain a current density, J, of 100 μA/cm² was in the range 5.3-5.7 V/μm.

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We report on the effect of using a spatial gap on heterogeneous nucleation on the surface of thermally oxidized titanium substrates. Induction of heterogeneous nucleation of bone-like hydroxyapatite (BHAp) was evaluated in the spatial gaps between substrates that were thermally oxidized at temperatures of 100-800°C on exposure to a simulated body fluid (SBF). After soaking in a SBF for 7 d, BHAp spontaneously deposited inside the gap on the surface of samples that were thermally oxidized at temperatures above 400°C, but not on samples that were thermally oxidized at temperatures of 300°C or less. Among the substrates studied, BHAp particles were most readily deposited inside the gap on the surface of the samples that were thermally oxidized at 400°C after soaking in an SBF. A smaller gap led to a higher number of BHAp particles being deposited on the surface of the samples that were thermally oxidized at 400 or 500°C. Our results suggest that the formation of BHAp in a SBF is dependent on the temperature during thermal oxidization, and also on the spatial gap between the samples. The ease of formation of BHAp on thermally oxidized titanium increases with increasing thickness of the rutile phase and the number of Ti-OH groups, which are produced during the thermal oxidization process. In addition to the surface structure of the substrates, the spatial gap is regarded as an important parameter for enhancing the deposition of BHAp. Since the formation of BHAp allows osteoconduction to occur after implantation in a bony defect, it is possible to design titanium-based implants with a high biological affinity to bone by processing using an appropriate spatial design of the substrate.

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Three-dimensional, periodic macroporous frame of hydroxyapatite(HA) has been fabricated via a template-assisted colloidal processing technique. In the present method, colloidal template was firstly prepared with SiO₂ spheres by gravitational sedimentation, which was then infiltrated with HA precursor prepared by sol-gel process. The resulting HA therefore replicated the three-dimensionally ordered macroporous structure of SiO₂ template. After removal of the template by immersing in NaOH solution, the periodic macroporous frame made from HA was obtained. The arrangement of the pore structure was hexagonal close-packed and pores were connected with each other. The resulting highly ordered macroporous frame of HA could have potential applications in bio-medical field.

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In this study, self-propagating high-temperature synthesis (SHS) of the powder compact consisting of titanium and graphite was used to synthesize titanium carbide (TiC_x). The relationship between the C/Ti ratio in the reactants and the stoichiometry of the resultant TiC_x phase was investigated. The result showed that when the molar ratio of C to Ti in the reactants increased from 0.6 to 1.2, the stoichiometry of the resultant TiC_x phase first increased and then decreased with the maximum value appearing at C/Ti = 1.0, so did the change in the maximum combustion temperature; Furthermore, with an increase in the particle size of graphite, the maximum combustion temperature and the stoichiometry of the resultant TiC_x phase decreased. Consequently, the maximum combustion temperature might play a dominating role in determining the final composition of the TiC_x phase.

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We have investigated the crystal phase and oxide ion conductivity of (Ba_0.3Sr_0.2La_0.5)(In_1-xM_x)O_2.75 (M = Sc and Yb) systems as a function of dopant content and unit cell free volume. All peaks in the XRD diffraction patterns of these systems (x = 0.0 - 0.4) were found to be assignable to pure cubic symmetry. The lattice parameter of the Sc-doped system decreased monotonically with rising dopant content, while the Yb-doped one showed a monotonic increase. The oxide ion conductivity of these systems increased with a unit cell free volume. Above a volume of 2.43 × 10^-2 nm³, the oxide ion conductivity decreased. The oxygen vacancy content of the systems was controlled to be constant over the whole compositional range, which suggests that the mobile oxygen content should also be constant over the whole range. Above a free volume of 2.43 × 10^-2 nm³, a broad Raman mode emerged from 350 cm^-1 to 400 cm^-1, which might relate to the local distortion of oxygen octahedra. We conclude that the oxide ion mobility grows with increasing unit cell free volume up to a critical volume, and then the mobility is degraded by the local distortion of the oxygen octahedra.

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Nanoimprint lithography (NIL), is recognized as one of the candidates for next generation nanolithography. Usually nanoimprint equipment is highly expensive because the nano-scale mold needs to be hardened with thermal and photonic treatment after casting. In this study, we attempted to fabricate finestructured alumina materials without using highly expensive equipment. This method is based on the idea that poly vinyl alcohol (PVA) is simply detached from silicon mold by peeling. The experiment process used PVA and alumina nano-size particle, mixed in water solution. The mixed solution was then put into a micro-scale Si-mold and hardened at room temperature. After hardening the PVA and alumina nano-size particle mixed solution was detached from the micro-scale Si-mold. Throughout burn-out and low-temperature sintering, we confirmed the fabrication of finestructured micrometer-size alumina with nano-size pores.

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Amino-modified TiO₂ particles were derived from precursor mixtures of tetraethylorthotitanate and aminopropyltriethoxysilane (APTES) that both were dissolved in ethanol/water solution. Size, morphology, crystalline structures, and formation mechanism of the particles were discussed in terms of the APTES amount and the pH value in the solution. The addition of APTES resulted in amorphous amino-modified TiO₂ particles. The low crystallinity in the final particles was attributed to the polar amino groups.

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