Oxide ion conductivity in defect perovskite, mainly Pr₂NiO₄ with K₂NiF₄ structure, was studied in details. Defect perovskite oxide consists of perovskite block connected series to oxygen deficient block and although it is known that oxygen deficient block traps mobile oxide ion in lattice, interstitial oxygen introduced at rock salt block in Pr₂NiO₄ shows high mobility resulting in the high oxide ion conductivity. Oxide ion conductivity is much increased by doping Cu and Ga for Ni site and Pr deficient. The observed oxide ion conductivity was high like log (σ/Scm⁻¹) = −0.25 at 1173 K. Conducting property of Pr_1.91Ni_0.75Cu_0.21Ga_0.05O₄(PNCG)/Ce_0.8Sm_0.2O₂(SDC) nano laminated film was further studied and the conductivity was much increased by formation of residual strain and the ion blocking method shows the transport number of the laminated film is almost unity and so high conductivity of PNCG/SDC laminated film could be assigned to pure oxide ion. Application of PNCG for anode of SOFC was further studied and it was found that surface activity of Pr₂NiO₄ doped with Cu and Ni shows high and so superior cathodic property was achieved at low temperature by mixing Pr₂NiO₄ with SDC. The maximum power density of the cell using LaGaO₃ thin film electrolyte was achieved at 0.12 W/cm² at 673 K.

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Almost monodisperse Fe₃O₄ nanoparticles (NPs) with four distinct mean sizes prepared by thermal decomposition were self-assembled onto a silicon substrate in the form of multi-layers using a simple drop-drying method. These multilayered Fe₃O₄ NPs were used as the catalysts to grow vertically-aligned carbon nanotube arrays (VACNTAs) by chemical vapor deposition (CVD). The correlation between the CNT diameter and the NP size was determined. Catalysts with different sizes play a vital role in influencing the diameters and structures of CVD-grown CNTs. In addition, the size of the catalyst NPs is a critical factor for obtaining dense arrays of VACNTs. This method is a relatively simple and environmental friendly process compared to previous methods, and has the potential for the mass production of VACNTAs.

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Single crystals of cerium tetra-boride, CeB₄, were prepared in 0.4 MPa of argon ambient gas by the RF-heated floating zone method. The feed rod was prepared according to the following reaction formula: CeB₆ + 1/2 (CeO₂ + 2C) → 3/2 CeB₄ + CO↑. The growth rate was 0.3 cm/h. The obtained crystal rods were 4 cm long and 1.2 cm in diameter. The lattice constants were a = 0.72052 nm and c = 0.40898 nm of a tetragonal lattice. The micro Vickers hardness, H_v, values on the (100), (110), and (001) planes were 1403, 1440, and 1099, respectively.

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We studied a means of synthesizing colloidal nanocrystals (NCs) of β-LiGaO₂, a wide-band gap semiconductor oxide, by reacting lithium hydroxide (LiOH) with gallium tri-iso-propoxide [Ga(OiPr)₃] in benzylamine. This reaction yielded near-stoichiometric β-LiGaO₂ NCs, 4–5 nm in diameter and capped with n-octylamine, which were highly dispersible in an organic solvent. We proposed that the LiOH and Ga(OiPr)₃ reacted via electrophilic attack of Li⁺ on the bridging oxygen of Ga(OiPr)₃ and/or nucleophilic attack of OH⁻ on the α-carbon of Ga(OiPr)₃. This reaction formed Li–O–Ga bonds and contributed to the near-stoichiometry of the resultant β-LiGaO₂ NCs.

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Among ultra-high temperature ceramics (UHTCs), zirconium diboride (ZrB₂) ceramics have high electrical/thermal conductivity, excellent corrosion resistance, and a chemically stable crystal structure. These properties make ZrB₂ suitable for extreme chemical and thermal environments, such as atmospheric re-entry and hypersonic aircrafts. ZrB₂ has low intrinsic sinterability due to its strong covalent bonds and low self-diffusion coefficients. In the ZrB₂ sintering process, decreased ZrB₂ particle size is an important factor for increasing the driving force of densification. SPEX mill, a type of high energy milling, was employed to decrease particle size. Co-bonded WC was used by jar and media in SPEX mill because Co–WC is hard enough to pulverize ZrB₂ particles. During SPEX milling, ZrB₂ powders were contaminated by Co–WC. Co–WC contaminant could be also used by sintering additives. This study investigated the effects of Co, WC, and Co–WC for the densification of ZrB_2. The ZrB₂ composites were sintered by spark plasma sintering (SPS). Microstructures were observed using scanning electron microscopy (SEM) and phases of sintered samples were characterized by X-ray diffraction (XRD).

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The purpose of this study is to develop lightweight porcelain using pore-forming additives, such as organic microspheres, organic hollow microspheres and inorganic hollow microspheres, and to evaluate the effect of pores on the mechanical properties. Spherical pores below 100 µm were created in the fired body having porosity up to 45% depending on the amount and type of additives. When a large amount of organic spheres were added, many pores connected each other and open porosity increased. On the other hand, inorganic hollow microsphere were isolated in the fired body so that an open porosity was extremely smaller than a total porosity. Effects of a porosity P on the relative Young’s modulus E/E₀ and relative fracture toughness K_IC/K_IC0 were evaluated and the correlations were in good agreement with the equations E/E₀ = (1 − P)^1.88, K_IC/K_IC0 = (1 − P)^0.94(1 − P^2/3)^0.5, respectively.

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The water resistance of AlN particles was improved by surface coating with hybrid α-Al₂O₃/organic layers. To maintain thermal conductivity, the higher-thermal-conductivity α-Al₂O₃ layer was designed to cover most of the AlN surface, and the lower-thermal-conductivity organic layer was formed on the remaining area. Scanning electron microscopy, energy dispersive X-ray spectrometry and thermogravimetric analyses of the particles revealed that the small amount of organic layer was filling the cracks in the α-Al₂O₃ layer. The water resistant property was evaluated by a water immersion test. The pH of water dispersing the particles with hybrid layers was less than that of water dispersing the particles coated only with α-Al₂O₃ or organic layers, which indicated that the particles with hybrid layers had improved water resistance. The particles have applications in polymer composites for insulation in electronic devices which require improved reliability.

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In this study, we prepared two types of europium (Eu)-doped nanoparticle, yttoria and titania and investigated their photophysical properties and biocompatibilities. These particles do not inhibit cell culture, even at higher concentrations. The obtained nanoparticles had a strong and narrow red photo-luminescent peak. The narrow emission was observed even when the particles were uniformly doped into a polymer film. These results suggest that they can be used for applications not only in optoelectronic devices but also in biomedical devices for bioimaging and luminescent biomedical materials.

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Laminated Ti/Al₂O₃ composite was fabricated by tape casting with close control of thickness (about 200 µm) of Al₂O₃ and titanium layers. The green tapes of titanium and Al₂O₃ were prepared at room temperature due to high flexibility and strength. In order to improve the density of green layers, the binder removal temperature range of titanium and Al₂O₃ layers was investigated by differential scanning calorimeter (DSC/TG). The compact laminated Ti/Al₂O₃ composite sintered by vacuum hot-pressing at 1450°C for 60 min under pressure of 25 MPa was researched by X-ray diffraction and scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX). The results showed an obvious diffusion region between Al and Ti layers, and the interfacial phases were composed mostly of Ti and Al₂O₃, together with a little amount of Ti₃Al, TiAl and AlTi₂, and solid solution of O (AlTiO₂). Diffusion line of EDX spectrum indicated that the diffusion distance of dissociated Al³⁺ in Ti layers was about 5 µm.

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The electric power produced by a Ni/Gd-doped ceria (GDC) anode-supported solid oxide fuel cell with a GDC electrolyte (40 µm thick) and a (La_0.8Sr_0.2)(Co_0.8Fe_0.2)O₃ (LSCF) cathode using a 3 vol % H₂O-containing H₂ fuel was measured. The addition of 10 or 50 mass % GDC powder (Ce_0.8Gd_0.2O_1.9) to the LSCF cathode reduced the power density from 320 mW/cm² in the case of no GDC to 137 or 122 mW/cm², respectively. The added GDC particles blocked the conduction path between LSFC particles. The as-prepared LSCF powder was ball-milled using α-Al₂O₃ balls. The milling decreased the charge transfer resistance at the cathode and increased the power density of the fuel cell.

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