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Volume 50, Issue 2
Displaying 1-14 of 14 articles from this issue
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Tsuyoshi Morishita, Kenji Miyake, Hidenori Kuroki2003 Volume 50 Issue 2 Pages 79-85
Published: February 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effect of the carbon content and sintering conditions on the wear resistant properties of ferrous sintered materials were investigated in order to develop rotary engine side seal. Wear test was conducted using cast iron as the mating material. The specimens were made by pressing the mixture of reduced iron powder and natural graphite powder. The compacts were sintered in H2 at 1393 K for 1.2 ks. In the wear test, the wear amount of the couple "3mass%C specimen and cast iron disk" was minimum.
The specimen of 3 mass% C showed the brittleness, which have a Fe3C network structure and nodular α phase iron. The brittleness of this specimens was overcome changing the structures into spheroidal Fe3C and redusing a phase iron by special heat treatment. The heat treatment is that specimens were hold or slow cooling around the spherodizing of Fe3C and the carbon potential was kept in the range from 0.7% to 0.9%. The specimens sintered on these conditions were rolled into side seals of the rotary engines with 1.0 mm in thickness and 186 mm in radius of curvature.View full abstractDownload PDF (4080K) -
Minato Andou, Yutaka Higashida, Hideo Okuma2003 Volume 50 Issue 2 Pages 86-90
Published: February 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe dielectric properties of titanite-based ceramics at millimeter wave frequency range were investigated. The specimens were fabricated by usual solid sintering process. Part of Ti elements in titanite was replaced by Mn, Sn, and Zr. The specimens derived from nominal composition of CaTi0.95Zr0.05SiO5 had dielectric loss tangent, 0.22, and relative permittivity, 36. The plot of complex permittivity is exactly on the anti-reflection curve in ε'-ε" plane for a sheet of typical electromagnetic absorber. A sheet with thickness, 0.19 mm, had reflection loss of 32 dB at 58 GHz.View full abstractDownload PDF (1601K) -
Wei Zhang, Nobutaka Sato, Kazuyoshi Yoshimura, Koji Kosuge, Akihiro Mi ...2003 Volume 50 Issue 2 Pages 91-95
Published: February 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAt the transition temperature (Tv≈42 K) YbInCu4 with AuBe5-type structure exhibits a first-order isostructural valence transition from Yb3+ free ion state at high temperatures (HT) to the Fermi liquid state with an intermediate valence (Yb2.9+) at low temperatures (LT). In the LT phase a metamagnetic transition from the Fermi-liquid state to the Yb3+ state can also be induced by high magnetic field at Hv≈30 T. We will discuss the valence transition in the Yb1-xYxInCu4 system by measurements of susceptibility and high field magnetization in this paper. With increasing x, Tv and Hv decrease, while the Pauli paramagnetic susceptibility X(0) in the LT phase increases, resulting in suppression of the valence transition at x=0.3, indicating that the state of Yb3+ is stabilized down to very low temperatures. We found that the Kondo temperature TK of the LT phase is proportional to Tv according to the susceptibility measurements, which means that the stability of intermediate valence phase would be reduced by the Y substitution. According to the high field magnetization measurements in the range of T<Tv, Hv is decreased with increasing temperature.View full abstractDownload PDF (373K) -
Norimitsu Hirose, Shin-ichi Tanaka, Toshiyuki Tanaki, Junichi Asami2003 Volume 50 Issue 2 Pages 96-103
Published: February 15, 2003
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn this study, the relationships between porosity and Young's moduli measured by an acoustic pulse method, a resonance frequency technique, a tensile test and a bending test of sintered irons were investigated. Moreover, tensile strength and proof stress were measured by tensile test, and these values and Young's modulus were evaluated against porosity.
Young's moduli measured by the acoustic pulse method, resonance frequency technique and tensile test, except for the bending test, were nearly equal at the same porosity. In the case of the bending test, the moment of inertia of the area was a linear function of porosity. Young's modulus measured by the bending test, which was corrected by use of the above relation, was equal to that by other method. Young's modulus measured by the bending test was 0.7-0.8 times of Young's modulus measured by the tensile test.
Young's modulus (E), tensile strength (Ts) and proof stress (Ps) against porosity (P) are expressed as E=(E0-KE⋅P) (1-P), Ts=(Tso-KTs⋅P)(1-P) and Ps=(Pso-Kps⋅P)(1-P), respectively. Here, E0, Tso and Pso are Young's modulus, tensile strength and proof stress at P=0, and KE, KTS and KPS are the experimental coefficients of each relation. Moreover, we found that the relationships among Young's modulus, tensile strength and proof stress are in positive correlation.View full abstractDownload PDF (539K) -
[in Japanese]2003 Volume 50 Issue 2 Pages 106
Published: February 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (112K) -
Balachandran Jayadevan, Akira Hobo, Oscar Perales Perez, Chinnaperuma ...2003 Volume 50 Issue 2 Pages 107-113
Published: February 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSynthesis of nanometer size core-shell structured NiCo particles via the modified polyol process is described. Cobalt particles of about 20 nm with hcp crystal structure was synthesized by the use of appropriate type of glycol, hydroxyl ions, adsorbing ions, nucleating agents and other reaction conditions, which otherwise were few microns in diameter and fcc in structure. It is proposed that the suitable control of those factors permitted the enhancement of the metal forming reaction rate. The room temperature (RT) saturation magnetization (M5) and coercivity (Hc) of the fcc-cobalt particles of few hundred nanometer in diameter ranged from 135 to 150emu/g and 35 to161 Oe, respectively. However, the 20 nm hcp-Co particles reported a M5 of 67 emu/g and Hc, 535 Oe. On the other hand, the nickel metal particles of few tens of nanometer in diameter were synthesized by modifying the ethylene glycol EG-Ni(II) solution chemistry, which otherwise were sub micron in size and had plate-like morphology. The nickel particles were polycrystalline with fcc structure. The M5 and Hc at RT ranged from 38 to 55 emu/g and 100 to 170 Oe, respectively. Though nickel was reduced easily than the cobalt in the absence of hydroxyl ions in EG, the reaction kinetics was reversed in the presence of hydroxyl ions. Thus, the unconstrained control of the reaction kinetics through the manipulation of the reaction parameters permitted the co-reduction of Ni and Co ions and facilitated the synthesis of nanocrystalline core-shell structured NiCo particles. The TEM-EDX analysis revealed that the core was rich in Co and the shell was rich in Ni. The magnetic properties of the particles depended on the Ni to Co ratio and the M, of these particles ranged between 50 and 150emu/g.View full abstractDownload PDF (6919K) -
Balachandran Jeyadevan, Chinnaperuma Gaunden Puddhur Nallasamy Chinna ...2003 Volume 50 Issue 2 Pages 114-119
Published: February 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSHere, we describe the growth assisted (a) co-precipitation and (b) oxidation methods to achieve CoFe2O4 nanoparticles with high coercivity (Hc) and moderate magnetization (Ms) at room temperature (RT). The particle size is closely related to the relative interdependence between the nucleation and growth steps, which can be manipulated by the solution chemistry and precipitation conditions. Based on this premise, the particles synthesized by optimizing reaction parameters such as, reaction temperature, NaOH concentration and feed rate of metal ion supply source into the alkali solution, was used as seed to prepare particles as large as 40 nm in diameter. On the other hand, by optimizing the reaction parameters such as, concentrations of NaOH and oxidizing agent KNO3, and the ratio of Fe3+/ (Fe3+Fe2+), particles ranging from 15 to 110 nm were synthesized using the oxidation method. The He was enhanced from 0.56 kOe to 2.29 kOe at RT for particles synthesized via growth-assisted coprecipitation method using 1.13 mol of NaOH, metal ion feed rate of 0.06 mollh at 98°C. Using the above single domain CoFe2O4 nanoparticles as seed during in-situ growth improved the He further to 2.9 kOe. On the other hand, among the particles synthesized with the growth assisted oxidation method, particles with diameter around 35 nm recorded the highest He of 2.02 kOe. The relation between He and particle diameter of CoFe2O4 synthesized using the above two methods was studied. The results suggested that size classified particles with 40 nm diameter obtained from the seeded particles showed the highest He of 4.3 kOe.View full abstractDownload PDF (3386K) -
Masaru Yokoyama, Tomohiro Tanaka, Shinichiro Ishibashi, Toshihiko Sato2003 Volume 50 Issue 2 Pages 120-124
Published: February 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe investigated the magnetic properties of field cooled CoCa ferrite (Co1-xCaxFe2O4) nanoparticles. The magnetizations and coercivities of field cooled Co1-xCaxFe2O4 nanoparticles show the maximum at x=0.2 in the nominal composition x ranged from 0 to 0.4. In x=0.1 to 0.4, the coercivities monotonically increase with decreasing cooling rate, while field cooled CoFe2O4 nanoparticles, which corresponds to x=0 in Co1-xCaxFe2O4, do not depend on the cooling rate in our condition (1.25°C/min-15°C/min). The enhanced coercivities should be attributed to the filed cooling condition. The induced magnetic anisotropy of field cooled Co1-xCaxFe2O4 nanoparticles would originate from the surface layer.View full abstractDownload PDF (341K) -
Shinichiro Ishibashi, Toshihiko Sato, Takashi Shimanuki, Shunji Okuda, ...2003 Volume 50 Issue 2 Pages 125-129
Published: February 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThere is no and end with the troubles such as in hospital accidents caused by the microorganisms such as Legionella pneumophila, Serratia marcescens, Pseudomonas aeruginosa, etc., not to speak of Staphylococcus aureus. The methods to remove these microorganisms come into operation with various kind of countermeasures, e.g. application of disinfectants, tools, microorganisms as objectives in the individual hospitals, dispensaries, and medical facilities. Meanwhile for removal of microorganisms, removal methods to be made use of in a wide range of utilization are required. Therefore in this study, ultra-fine ferromagnetic ferrite particles are first of all thrown into physiological saline solution. Secondly a concussion contacting test, bubbling test, and other such treatments were conducted. By so doing, this brought about good sterilization effect. Meanwhile when general stray bacilli are allowed to pass through a suspended liquid after a filter was dipped in the liquid by the use of a dehydrated filter, and good sterilization effect was obtained.View full abstractDownload PDF (410K) -
Toshihiko Sato, Shinichiro Ishibashi, Yokoyama Masaru, Shunji Okuda, R ...2003 Volume 50 Issue 2 Pages 130-135
Published: February 15, 2003
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSA bacterial removing effect of ultrafine ferrite particles prepared by chemical coprecipitation has been investigated. The ten kinds of ferrite nanoparticles were tested, and CdFe2O4, CuFe2O4, ZnFe2O4, Ca0.5Zn0.5Fe2O4 and Ni0.5Zn0.5Fe2O4 showed the effects to reduce bacterial titers of L. pneumophila, S. aureus, P. aeruginosa, B. subtilis and E. cob. in the liquid culture. The crystal structure of ZnFe2O4, Ca0.5Zn0.5Fe2O4 and Ni0.5Zn0.5Fe2O4 analized by XRD method was the spinel structure, while CdFe2O4 and CuFe2O4 are composed of the spinel structure and small amounts of byproducts. These ferrite particles shared common physical properties, ie, average size of ferrite particles with bacterial removing effects was uniformly less than 15 nm, specific surface area was more than 140m2/g, saturation magnetization was less than 0.35 T and coercivity was less than 6.4kA/m.View full abstractDownload PDF (5260K) -
Osamu Kimura, Yoshitaka Murakami, Masafumi Matsumoto, Mitsuo Sakakura, ...2003 Volume 50 Issue 2 Pages 136-142
Published: February 15, 2003
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSMagnetic properties were studied for Hexagonal ferrites, namely, Z, W and Y type hexagonal ferrites, whose basal planes contain the easy direction of magnetization. Increase in the degree of crystal orientation of these ferrites is known as an effective method to enhance their permeabilities. Accordingly, we have already obtained highly crystaloriented samples by applying a hot-forging process, on the plate-like ferrite particles obtained by the molten-salt process. Here, we applied a rotational horizontal magnetic field to these particles in a die during a wet molding process to align the plates of the particles vertical to the pressing direction. After then, the pressed compacts were hot-pressed in a furnace to obtain highly crystal-oriented samples. The degrees of crystal orientation of these samples are expected to be comparable with those obtained by the hot-forging process using the same molten-salt powders above mentioned.View full abstractDownload PDF (2048K) -
Taro Kamiki, Syunsuke Saito, Kong Sok Hyun, Shigeki Nakagawa2003 Volume 50 Issue 2 Pages 143-148
Published: February 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMn-Zn spinel ferrite thin films were prepared on a Pt underlayer by reactive facing-targets sputtering to increase the deposition rate to improve the productivity. The film prepared at PO2 of 25% crystallized and possessed 4πMs of 3.4 kG. The discharge voltage changed with PO2 because of the oxidation of the target surface. The discharge voltage-current characteristics were examined to clarify the extent of oxidation of the targets. It was found that a proper discharge voltage is required to prepare Mn-Zn ferrite films. Although saturation magnetization increased with increase in substrate temperature, the surface roughness also increased. By thinning the Mn-Zn ferrite films and inserting the hyperoxidized layer that showed flat surface as the interlayer, the surface roughness of the film decreased from 4.4 nm to 2.8 run. Saturation magnetization was improved from 3.4 kG to 4.8 kG in the same preparation condition (Ts=400°C, PO2=25%) by adjusting the inlet position of O2 gas. By using the new method, the deposition rate increased to be 16 times that of the conventional method.View full abstractDownload PDF (3005K) -
Atsushi Kominato, Koichi Kakizaki, Nobuyuki Hiratsuka2003 Volume 50 Issue 2 Pages 149-153
Published: February 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe c-axis oriented Ba-ferrite thin films without underlayer were prepared, and their magnetic properties and crystal structures were investigated. Ba-ferrite thin films were deposited on fused quartz substrates, which were kept at room temperature, using rf diode magnetron sputtering apparatus. Two kinds of Ba-ferrite target disks were used; one was FeBa ratio of 6.5 and another was that of 16. The films with a thickness of 20 nm were deposited by using the target with Fe/Ba ratio of 16, and then annealed at 800°C for 5 hrs in air. They were not crystallized, but the films deposited by using the target with Fe/Ba ratio of 6.5 and then annealed at 800°C for 5 hrs in air were crystallized. Thus using target with Fe/Ba ratio of 6.5 is found to be useful for reduction of thickness. Moreover, the c-axis of Ba-ferrite films was oriented perpendicular to the film surface that was caused by the effect of { 111 } oriented Fe3O4 formed at interface between film and substrate. It was confirmed that the {111} oriented Fe3O4 was formed because of diffusion of Ba ions to the substrate.View full abstractDownload PDF (369K) -
Keisuke Mizuno, Shigeki Nakagawa2003 Volume 50 Issue 2 Pages 154-158
Published: February 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMagnetoplumbite type Sr-ferrite (SrM) thin films with high magneto crystalline anisotropy were deposited on Pt underlayers. It was found that Pt underlayer is effective to enhance crystallization and the c-axis orientation perpendicular to the film plane. In order to get high crystallization and high coercivity and large squareness ratio, high substrate temperature (> 500 °C) and large thickness of magnetic layer (> 50 nm) were required. In this study, SrM/Pt bilayers were prepared using mixture gasses of Ar and Kr as sputtering gas. Ar and Kr mixture gasses was effective to deposit SrM films with high c-axis orientation and better crystallization even though their thickness below 20 nm. SrM layer sputter-deposited using Ar and Kr mixture gas revealed high perpendicular coercivity Hc⊥ around 3 kOe. SrM layer were able to be dethickness below 20 nm, and crystallized at substrate temperature 450 °C.View full abstractDownload PDF (1472K)
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