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Volume 52, Issue 5
May
Displaying 1-14 of 14 articles from this issue
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Paper
Paper
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Yukihiro Kadogawa, Takayuki Goto2005 Volume 52 Issue 5 Pages 311-316
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSNepheline was synthesized by the TW method. As the starting solution, each aqueous solution of NaNO3 and Al(NO3)39H2O was dissolved in proper amount of distilled water. The constant quantity of Si(OC2H5)4(TEOS) and a small amount of 2M-HCl as catalysis were mixed into the starting solution. A part of NaNO3 was also replaced by KNO3. Nepheline began to form at a certain temperature near 800°C. It was thought that nepheline was produced by a phase transformation of the low-carnegieite under the condition of decreasing of its component. It was also thought that nepheline may be formed by phase transformation of the low-carnegieite in preference to the formation of high-carnegieite through its modification at a certain temperature between 800°C and 900°C, and at a given composition with KNO3 of 15 mole%. In a sample obtained by heating the gel No.7 prepared by replacing the part of NaNO3 of 4.49 × 10-2 mole with KNO3 of 1.35 × 10-2 mole at 1100°C for 30 min, the pure nepheline in a single phase was obtained.View full abstractDownload PDF (633K) -
Mitsuru Nakamura, Makoto Tagusari2005 Volume 52 Issue 5 Pages 317-321
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSFor positive recycling method of cemented carbide scraps, this experiment used block-like scraps by machining process. Recycling process was used by tin impregnation method. This process characterized to react between Co and Sn by heat treatment, and produce brittle Co-Sn intermetallic compounds. Thereafter, it carried out by acid cleaning-stirring and physical milling or powdering. In order to obtain recycled WC powder, this process finished three treatments only. The results summarized as follows;
When the cemented carbides scraps were impregnated by molten Sn bath at 1323 K, it was found to produce a brittle Co-Sn intermetallic compounds. Therefore, Co phase in cemented carbides was transferred to these compounds. The surplus Sn was penetrated into cemented carbides. This treatment was able to get a remarkably brittle WC-Sn alloy. From stirring and cleaning by HCl solution after Sn impregnation, specimens were fractured easily and surplus Sn was resolved to molten alloy. In this experiment, it was able to recover about 60% WC fine powder from 1 to 5 μm.View full abstractDownload PDF (1264K) -
Mitsuru Nakamura, Tsukasa Ono, Ko-ichi Kamada2005 Volume 52 Issue 5 Pages 322-326
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSIn this experiment, the development of recycling method at cemented carbide scraps was researched. First, brittle alloy was obtained by tin impregnation method and then WC fine powder was procured after the physical crushing. Thereafter, the sample followed by the processes of reduction treatment, molding and sintering works. Some properties of recycled cemented carbides were investigated. The results summarized as follows; Recycled WC fine powder suffered the surface oxidation. Therefore it was necessary to be done by reduction treatment at 1073 K-3.6 ks under hydrogen atmosphere. When sintering condition at 1673 K-3.6 ks was treated under vacuum condition, it gained the deflective strength of about 90%, and gained hardness and sintering density about same value compared with commercial alloys. As a result, it was able to recycle only by 7 processes, that is to say, tin impregnation, physical milling, stirring HCl cleaning, reduction, mixing, molding and sintering works.View full abstractDownload PDF (1090K) -
Kazunori Seno, Kenta Takagi, Akira Kawasaki2005 Volume 52 Issue 5 Pages 327-333
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSA photonic crystal is an artificial crystal with a periodic array of dielectric material. Such a crystal possesses a band gap for an electromagnetic wave with wavelengths corresponding to a lattice period. In this study, the photonic crystal with the spherical lattice of hundreds of micrometer-order corresponding to wavelengths of terahertz wave was fabricated by a template method. Monosized spherical copper particles were self-assembled into f.c.c. structure and sintered to form necks between adjacent particles. The array was impregnated with the resin whose dielectric constant was controlled. Subsequently to cure the resin, only the copper particles lattice was etched away by chemical dissolve. The obtained resin-inversed crystals were confirmed to exhibit a photonic stopgap along ‹111› direction by a terahertz wave spectroscopy. The frequency and gap width of measured gaps well agreed with the calculated ones by the plane wave expansion method.View full abstractDownload PDF (1736K) -
Seizo Takahashi, Takanori Shindoh, Mototsugu Katsuta, Tadashi Yamada2005 Volume 52 Issue 5 Pages 334-338
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSAlumina fine powder (0.6 μm) is granulated by 3 mass% PVA. The granule admixed with liquid paraffin are formed by a single-action tooling to columnar-shaped green compact, diameter: 60 mm, height: 60 mm and mass: 450 g. Green density increases according to the content of liquid paraffin. Debinding of green compact admixed with a lot of liquid paraffin is succeeded without cracking on compact by thermal debinding technique after extracting liquid paraffin in an organic solvent to pre-baked compact. Sintered density and dimensional precision of sintered compact formed by flow compaction are improved by liquid paraffin content of 7.5 mass% and by compacting pressure of 98 MPa.View full abstractDownload PDF (1133K) -
Kunio Okimoto, Kazuhiro Kohji, Yoshihiro Isshiki2005 Volume 52 Issue 5 Pages 339-343
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSIt is well known that machinability of sintered iron is improved by impregnation of resin within the open pores. Embrittlement of the sintered iron by the impregnation as well as decreased friction at the contact surface between the chip and the cutting tool are considered to be the causes for the improved machinability. However, there is room for further study on the cause of the improvement in the machinability. It is known that the cutting temperature of wrought material (conventional full-density material) is lowered with increasing thermal properties such as thermal diffusivity α and value of λρc, where λ is the thermal conductivity, ρ is the density and c is the specific heat of the work material. The purpose of this study was to elucidate the effect of resin impregnation on the cutting temperature, and therefore the thermal properties of impregnated sintered iron were investigated. It was found that the thermal properties were lowered by the resin impregnation. However, the degree of reduction in the thermal properties was less than 10%. The experimental results suggest that the small change in thermal properties due to the resin impregnation is not the main cause of the drastically improved machinability.View full abstractDownload PDF (550K)
Special Issue: Biomedical, Biofunctional and Bio-inspired Materials
Summarization
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Kimihiro Yamashita2005 Volume 52 Issue 5 Pages 346
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSDownload PDF (131K)
Paper
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Kimihiro Yamashita, Satoshi Nakamura, Shigeki Kishi, Masahiro Inuzuka, ...2005 Volume 52 Issue 5 Pages 347-350
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSThis report gives a new synthetic method of bioactive yttria-stabilized zirconia (YSZ) ceramics according to the so-called Vector Materials Science (VMS). Although YSZ ceramics have long been clinically used on account of the in vivo bioinertness, a small addition of hydroxyapatite (HA) successfully transformed YSZ to a bioactive material. The transformation was given an explanation by VMS; the resultant tri-calcium phosphate from the chemical reaction during sintering between YSZ and HA was found to induce SBF-active property to YSZ.View full abstractDownload PDF (988K) -
Shunsuke Miyauchi, Katsuko Furukawa, Yoshikazu Umezu, Yasuyuki Ozeki, ...2005 Volume 52 Issue 5 Pages 351-355
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSIn the field of bone tissue engineering, supply of nutrition and oxygen to the cells on and in scaffold is a significant issue. Many studies about the effect of large pores in scaffold on bone formation have been reported. However, there is no scaffold that keeps cells alive and has large suitable size for practical use. In this study, we built multilayer structure graft composed of bead-cell sheets to make a large space for entry of blood vessels. Bead-cell sheets consisted of beta-tricalcium phosphate (beta-TCP) porous beads, human bone marrow stromal cells (HMSCs) and matrices produced by the cells, and the space for vessels was kept with collagen gel. The grafts were implanted subcutaneously in nude mice. After 3 weeks, blood vessels reaching to the central area of graft were observed. In addition, osteogenesis was recognized near the surface. These results should suggest the necessity of preparation of large space or pores for blood vessels, and indicate the good osteoconductivity of bead-cell sheet.View full abstractDownload PDF (1704K) -
Masanobu Kamitakahara, Chikara Ohtsuki, Makoto Oishi, Shin-ichi Ogata, ...2005 Volume 52 Issue 5 Pages 356-359
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSTricalcium phosphate (TCP) ceramics are known as biodegradable materials for use as bone substitutes in orthopedic applications. We recently reported the fabrication of porous α-TCP ceramics with continuous pores ranging from 10 to 50 μm, through a conventional sintering process using a slurry consisting of β-TCP and potato starch. α-TCP shows higher solubility than β-TCP. Therefore, one can expect that biphasic porous ceramics consisting of α- and β-phases of TCP will allow controlled degradation in the body. In the present study, we attempted to synthesize a porous TCP body consisting of a mixture of α- and β-TCP with an additive of Mg, Zn or Fe. It was revealed that the porosity and phase of porous tricalcium phosphate can be controlled by the addition of these additives. The addition of Mg was most effective in decreasing the porosity and α-TCP content. When the Mg content was 0.1 mass%, a porous body consisting of α- and β-TCP with continuous pores ranging from 10 to 50 μm can be prepared by the conventional sintering method.View full abstractDownload PDF (641K) -
Toshiki Miyazaki, Shouji Yasunaga, Eiichi Ishida, Masahiro Ashizuka, C ...2005 Volume 52 Issue 5 Pages 360-363
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSSo-called bioactive ceramics have attractive features such as direct bone-bonding in living body. They are clinically utilized as important bone substitutes. However, their Young's modulus is much higher than that of natural bone. Previous studies reported that the essential condition for materials to show bone-bonding property, i.e. bioactivity, is formation of bone-like apatite on their surfaces after exposure to the body fluid. The same type of apatite formation can be observed even in a simulated body fluid (SBF) with inorganic ion concentrations similar to those of human extracellular fluid. Formation of the surface apatite can be induced both by dissolution of calcium ion (Ca2+) and by silanol (Si-OH) group formed on the surfaces of materials. On the basis of these findings, organic modification of these components would produce bioactive materials with high flexibility. In the present study, we synthesized organic-inorganic hybrids from starch by chemical modification using glycidoxypropyltrimethoxysilane (GPS) and calcium chloride (CaCl2). Acceptance of the apatite formation of the hybrids was examined in SBF. The hybrids formed apatite in SBF within 7 d, even if molar ratio of CaCl2 to GPS was reduced up to 0.01.View full abstractDownload PDF (978K) -
Mitsuhiko Ohta, Isao Tanaka, Atsushi nakahira2005 Volume 52 Issue 5 Pages 364-367
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSACP is expected to be useful for a bioceramic in the body because of its high bioactivities. But there is few report about ACP properties. In this study, synthetic method of ACP was investigated in detail. ACP powders were prepared by sol-gel method in N2 atmosphere. ACP powders prepared by sol-gel method were observed its constitutional phase identified by XRD and thermal behavior was examined by TG/DTA. Effect of heat treatment on ACP structure was investigated. Then, specific surface area of synthesized ACP powders was measured by BET method.View full abstractDownload PDF (616K) -
Kazuyoshi Ohkubo, Yasutaka Sekijima, Satoshi Nakamura, Keiichi Katayam ...2005 Volume 52 Issue 5 Pages 368-372
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSElectrically polarized hydroxyapatite (HA) ceramics have been proved to promote the formation of bone mineral like apatite in vitro and new bone in vivo. To clarify the adsorption properties of the electrically polarized HA powder, column chromatography of the polarized HA powder was carried out. The adsorption tests for bovine serum albumin protein was performed in 0.01 M phosphate buffer solution adjusted to pH 6.60 and 7.40. The adsorption ability of the polarized HA powder was significantly higher than that of non-polarized HA, for both of the adsorbate and pH used in the evaluations. The electrically polarized HA powder could improve the performance of column chromatography techniques.View full abstractDownload PDF (728K)
Review
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Chikara Ohtsuki2005 Volume 52 Issue 5 Pages 373-378
Published: 2005
Released on J-STAGE: April 28, 2006
JOURNAL OPEN ACCESSHydroxyapatite has been used not only as a bone-repairing material in clinical applications but also as a functional material in the biological field, since it shows high biological affinity and specific characteristics on protein adsorption. It is expected that coating of substrates with a layer of hydroxyapatite will increase its potential applications as the hydroxyapatite will be directly exposed to the surrounding environment, allowing it to show its biological and chemical properties without any intervening effects by coverage with an organic polymer matrix. A biomimetic process for depositing hydroxyapatite on the surfaces of organic polymers provides us with a design of novel materials showing various mechanical properties without losing the functionalities of hydroxyapatite. This paper reviews a biomimetic process for coating of hydroxyapatite layers, through exposure of an organic substrate to a solution that mimics human body fluid. The existence of carboxyl groups effectively triggers the heterogeneous nucleation of hydroxyapatite on the examined organic polymer, such as aromatic polyamide and natural silk protein. The rate of hydroxyapatite formation on the examined organic polymer in the biomimetic solutions is increased by incorporation of calcium ions. The resultant layer formed on the organic substrates consists of nano-sized fine particles of hydroxyapatite with low crystallinity. The fine particles provide a high potential for the adsorption of proteins. The adhesive strength of the hydroxyapatite layer on the organic substrate of the aromatic polyamide increased with increasing content of carboxyl groups. These findings indicate that a coating of hydroxyapatite can be achieved on organic polymers under biomimetic condition by a modification of the polymer with carboxyl groups and calcium ions.View full abstractDownload PDF (1747K)
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