Papers by Author: Junichi Matsushita

Abstract: Titanium carbide has been attractive for years an engineering ceramics due to its high hardness, high melting point, and good chemical stability. Similarly, titanium dioxide has excellent anti-microbial ceramic material by photon energy. In this study, the anatase type titanium dioxide layer prepared by oxidation of the titanium carbide powder by high temperature oxidation in air atmosphere was investigated in order to determine the possibility of its photocatalyst materials by radiant energy. TiC powder samples of different grain size were gained by ball mill. These samples were oxidized at room temperature to high temperature. The samples exhibited a steady mass gain with increasing oxidation temperature. Based on the results of the X-ray diffraction analysis, anatase type TiO₂ was detected on the titanium carbide samples. It is considered, the titanium carbide showed convension anatase type titanium dioxide layer produced by oxidation.

Abstract: The material study on bioactivitying artificial bone is lacking results for improve the quality of life (QOL) for individuals to fulfill their happy life in the society, which requires artificial bone to be replaced with neonatal bone by absorbing, regenerating the bone, which is not possible. Hydroxyapatite Ca₁₀(PO₄)₆(OH)₂, (HAp) has excellent biomaterial for biomedical and dental applications because of its superior properties. However, HAp had poor mechanical properties such as low hardness and fracture toughness. In this study, HAp containing titanium and titanium hydride (TiH₂) sintered bodies were studied in order to investigate the possibility of its advanced biomaterials application. The nano particle size starting powders were milled by using mortar and muddler equipment. The sintered bodies were prepared by pressureless sintering at argon-hydrogen gas atmosphere. The samples were evaluated for bioactive performance by using simulated body fluid (SBF) solution for. The HAp-Ti, the HAp-TiH₂ composite material is attractive as a bioceramics compared with HAp ceramics.

Abstract: Tantalum (Ta) can be use a suture for operation and implant material in order not to react with body fluid and stimulate a human body. In this study, the stable oxide of a tantalum, tantalum oxide layer produced by oxidation of the tantalum nitride, TaN powders by high temperature oxidation were investigated in order to determine the possibility of its a distributed aid for biomaterial composite such as an artificial root etc. The sample, TaN powder oxidized at high temperature exhibited a steady mass gain with increasing oxidation temperature. Based on the results of the XRD, tantalum oxide, Ta2O5 was detected on the samples. It is considered, the TaN showed a good oxidation film produced by high temperature oxidation.

Abstract: The Na-bentonite compact with absorbent polymer was fabricated in order to observe their absorption and preservation about water. Absorption of fabricated specimens in the water and preservation of absorbed samples in the drying machine at 323 K was measured. It was obtained that the absorption had been increasing with inhancing absorbent polymer. Absorption of As-received Na-bentonite was lower than absorption of As-received absorbent polymer. The preservation had been also increased with absorbent polymer was obtained. Na-bentonite compact with absorbent polymer ware investigated the good absorption and preservation when the Na-bentonite compact with absorbent polymer 40 mass %.

Abstract: The Na-bentonite with contained smectite was fabricated in order to observe their absorption and preservation about water. Absorption of fabricated specimens in the water and preservation of absorbed samples in the drying machine at 323 K was measured. It was obtained that absorption had been decreasing with increasing smectite. Absorption of As-received Na-bentonite was higher than absorption of As-received smectite. The preservation has been also decreased with increasing smectite was obtained. Na-bentonite with contained smectite were investigated the good absorption and preservation when the Na-bentonite containing smectite 5 mass %.

Abstract: Biomaterials have been developed and used for bone grafting. Here, we study a fabrication of composite for bone tissue engineering by combining tricalcium phosphate and collagen. This tricalcium phosphate and collagen composite material may be applicable for use as a bone substitute. The β-tricalcium phosphate (β-TCP) is the one of the most investigated biomaterials due to its biocompatibility and good bioactivity. The β-TCP is used in a filling purpose to the bone defect region such as bone fractures. It is known that β-TCP substitutes it for a self bone in the body. The ingredient of the real bone is made of hydroxyapatite and collagen. In this study, the purpose was at giving the mechanical property and biological property which were near to a bone with β-TCP and collagen this time. We evaluate what kind of action collagen addition.

Abstract: The oxidation behavior of tantalum diboride (TaB2) powder at high temperature was investigated in order to determine the possibility of the use of advanced high temperature structural materials. Unfortunately, monolithic TaB2 were known to be chemical stability up to high temperatures. To date, there have been few reports regarding the properties of TaB2 ceramics. The samples were oxidized at room temperature to 1273 K for 5 minutes to 25 hours in air. The weight changes were measured to estimate the oxidation resistance. The oxidation of samples oxidized for short oxidation time of 5 minutes started at 873 K, and the weight gain increased with increasing oxidation temperature. On the other hand, at the oxidation time of above 1 hour, a maximum weight gain value at 973 to 1073 K was observed. However, even if the oxidation temperature was increased an additional weight change slightly occurred. The weight gain of the sample oxidized at 1273 K for 5 minutes to 25 hours was about 40 to 20 % of the theoretical oxidation mass change. According to the powder X-ray diffraction date, the oxidized TaB2 sample was changed to Ta2O5 at 873 K. Finally, the TaB2 showed a good oxidation resistance at high temperature, because the surface film of tantalum oxide (Ta2O5) formed by oxidation acted as an oxidation resistant layer.

Abstract: Boron carbide composites in Si-B-C System have been widely studied and applied in excellent engineering materials. These materials are usually used at high temperature. Unfortunately, amorphous Si-B-C ceramics have been few reports regarding the properties of Si-B-B4C ceramics. In this study, the preparation of crystallized Si-B-C system compounds using Si, B, and B4C powders was investigated to determine their potentially for applications as high hardness composites. The samples were prepared at 1673 K for 2 hours in Ar atmosphere. The sintered bodies were cut into 5 х 5 х 10 mm blocks and polished with diamond disk for Vickers hardness. The samples were subjected to X-ray diffraction (XRD) analysis for phase evolution using a powder X-ray diffractometer. The fracture surfaces of the specimens were observed using a scanning electron microscope (SEM) included an energy dispersive X-ray fluorescence spectrometer (EDX) system to estimate the microstructures.

Abstract: Several boride sintered bodies such as TiB2, ZrB2, and SiB6 were previously reported. In the present study, the sinterability and physical properties of chromium boride (CrB2) containing chromium carbide (Cr3C2) sintered bodies were investigated in order to determine its new advanced material. The samples were sintered at desired temperature for 1 hour in vacuum under a pressure by hot pressing. The relative density of sintered bodies was measured by Archimedes’ method. The relative densities of CrB2 addition of 0, 5, 10, 15 and 20 mass % Cr3C2 composites were 92 to 95 %. The Vickers hardness of the CrB2 with 10 and 15 mass % Cr3C2 composites were about 14 and 15 GPa at room temperature, respectively. The Vickers hardness at high temperature of the CrB2 addition of 10 mass % Cr3C2 composite decreased with increasing measurement temperature. The Vickers hardness at 1273 K of the sample was 6 GPa. The Vickers hardness of CrB2 addition of Cr3C2 composites was higher than monolithic CrB2 sintered body. The powder X-ray diffraction analysis detected CrB and B4C phases in CrB2 containing Cr3C2 composites.

Abstract: Mechanochemical synthesis of zinc ferrite, ZnFe2O4, was attempted from a powder mixture of iron (III) oxide, alpha-Fe2O3 and zinc (II) oxide, ZnO. Nanocrystalline zinc ferrite, ZnFe2O4 powders were successfully synthesized only by milling for 30 hours. The X-ray diffraction spectrum of the as-milled powders (without heating) showed twelve ZnFe2O4 peaks and four weak peaks of coexisting unreacted Fe2O3. The crystallite size of the mechanochemicallysynthesized ZnFe2O4 was 26.3 nm. Evidence of the ZnFe2O4 formation was absent for the powders milled for 10 and 20 hours; milling lowered the crystallinity of the starting materials. Heating after milling enhanced the formation of ZnFe2O4, the crystal growth of ZnFe2O4 and the unreacted starting materials. The unreacted starting materials decreased their amounts by heating at higher temperatures.