The powder magnetic core having a spinel ferrite insulating layer has enabled high magnetic flux density and high electrical resistivity, because spinel ferrite exhibits magnetic insulating properties. However, the electrical resistivity of the powder magnetic core was decreased after annealing at 873 K, since FeO was formed in the spinel ferrite insulating layer. Based on the eutectoid transformation of FeO, which decompose into Fe₃O₄ and α-Fe at the temperature range below 833 K, we verified the possibility of eutectoid transformation of FeO in the insulating layer by 2 steps heat treatment at 873 K and 773 K. The results showed that electrical resistivity was increased due to the disappearance of FeO by eutectoid transformation even in the insulating layer.

The long afterglow phosphor SrAl₂O₄:Eu²⁺, Dy³⁺ with various particle size and shape were prepared by solid state reaction at 1200~1500°C for 3 h. In the synthesis, five kinds of α-Al₂O₃ were used as the starting materials, whose particle size ranged between submicron and a hundred micron orders. The peak intensity of excitation and emission spectra and the afterglow life time depended on the size of calcined particle, showing the higher performance with the larger particle size. SrAl₂O₄:Eu²⁺, Dy³⁺ synthesized using the alumina with a few micron size of primary particle but forming 50 μm of secondary particles showed high particle growth rate even at the low calcination temperature of 1200°C, giving almost the similar particle size until at 1500°C. Accordingly, the phosphorescence property was also independent on the calcined temperature. On the other hand, SrAl₂O₄:Eu²⁺, Dy³⁺ prepared from the alumina with 0.1~0.5 μm of dispersed particles depended largely on the calcined temperature, showing the highest performance for the samples prepared at 1400~1500°C. The large particles with smooth surface were effective for the high emission and afterglow properties.

CeO₂ and CeO₂-ZrO₂ (CZ) nanoparticle catalysts were prepared by hydrothermal method and their catalytic soot combustion activities were studied. Nanoparticles were characterized by X-ray diffraction (XRD), Raman scattering, N₂-physisorption, transmission electron microscope (TEM) and thermogravimetric (TG) analysis. It was observed that both of CeO₂-based particles were pseudocubic nanometer-sized crystals with less than 10 nm in diameter. TG measurement of mixture between soot and catalysts showed the excellent catalytic effect on soot combustion. CeO₂ accelerated soot combustion in which peak temperatures were shifted to 381°C from ordinary soot combustion temperature of 657°C. In this work, soot combustion catalysis was demonstrated by synthesized nanoparticles.

The solid state reaction at the interface between ZrO₂ electrolyte and CeO₂ interlayer in a model solid oxide fuel cell (SOFC) was examined. At the interface, both Y₂O₃-stabilized ZrO₂ electrolyte and CeO₂ diffuse each other and form the ZrO₂-CeO₂ solid solution. Cation diffusion coefficient and enthalpy were derived by using the Y₂O₃-doped ZrO₂/CeO₂ diffusion couples at 1400-1600°C. The data of inter-diffusion enthalpy of Zr and Ce was 510 kJ mol⁻¹ which should enable to predict how much the interface solid state reaction occurs for simulating the long time cell operation.

Metal-dispersed composites were derived from Zr₆₀Ce₅Pd₃₀Pt₅ amorphous alloy and their catalytic behavior for diesel soot combustion was studied. X-ray diffractograms and scanning electron micrographs indicated that mixtures of ZrO₂ phase and the dispersed metallic phase were formed in the resulting material after heat treatment at 800°C in air. The oxidized alloy resulted in the enhanced soot combustion activity. The removal property of catalyst, evaluated as temperature, is almost 100°C better than that in the non-catalyzed reaction. The results indicated the importance of the composite structure for the fabrication of a new type of catalytic material prepared from amorphous alloys.

Octacalcium phosphate (OCP) is known as a precursor of hydroxyapatite (HA), and is reported to show high bone-regeneration ability. Porous OCP granules are expected to be drug carriers to treat the bone tumor when anticancer drugs are loaded. When OCP granules loaded with drugs are implanted into a bone defect site, it is expected that drugs are released during the transformation of OCP to HA due to the dissolution of OCP and the difference in the adsorption properties. We investigated the transformation behavior of OCP to HA in vitro, and revealed that the nucleation of HA is the rate-determining step in the transformation of OCP to HA. Based on this knowledge, spherical porous granules composed of OCP and HA (OCP/HA granules) were prepared, expecting that the transformation of OCP to HA is accelerated. When human osteosarcoma cells were cultured in the medium in which the methotrexate-loaded OCP/HA granules were immersed, the cell proliferation was significantly inhibited. The granules released the drug continuously. We successfully prepared spherical porous OCP/HA granules and revealed the potential of the granules as drug carriers for the bone tumor treatment.

CaF₂ nanocrystals with a clear cubic shape were synthesized using both simple mixing and a hydrothermal method that neither of which required the use of surfactants or dispersants. The concentration and pH of the reaction medium, which in this case was an aqueous HNO₃ solution, was found to be very important for determining the morphology of the CaF₂ particles.

We soaked porous ultrahigh molecular weight polyethylene (UHMWPE) treated with oxygen plasma in simulated body fluid (SBF) with higher pH in comparison with that of conventional SBF, and precipitated calcium phosphate in the pores of the porous UHMWPE by raising temperature of the SBF. By soaking in physiological SBF, apatite formation was induced and the apatite covered the whole surface of the above-mentioned composite. High adhesive strength between the formed apatite and the composite was obtained by conducting the oxygen plasma treatment as a pre-treatment.

Roughened surface was formed on the surface of cobalt-chromium-molybdenum (Co-Cr-Mo) alloy substrate by sandblasting method using silicon carbide grinding particles with 3 μm in average diameter. In order to impart apatite formation ability to the Co-Cr-Mo alloy, the substrate was immersed in simulated body fluid (SBF) adjusted at higher pH in comparison with that of conventional SBF and subsequently the SBF was heated. When thus-treated substrate was immersed in physiological SBF, apatite formation was induced by the calcium phosphate film and the apatite covered the whole surface of the substrate within 1 day. The formed apatite layer adhered to the Co-Cr-Mo alloy substrate by mechanical anchoring effect.