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Volume 43, Issue 12
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[in Japanese]1996 Volume 43 Issue 12 Pages 1378
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (85K) -
Takashi Shinohara1996 Volume 43 Issue 12 Pages 1379-1385
Published: December 15, 1996
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSThe magnetic characterirtics and ferromagnetic resonance linewidth of garnet system {Gdz-Y3-2x-zCa2X}[Fe2-ylny](Fe3-xVx)O12 was investigated as function of x, y, and z. 4 π Ms temperature stability depends on Tmax strongly. Putting Tmax to around 20C, 4 π Ms temperature coefficient α will be as low as 0.05% / °C. In this system, ferromagnetic resonance linewidth Δ H is very low and, Δ H is found to be composed with Δ Hint 0.2 Oe, Δ Hrelax 2.7⋅Z⋅Oe, and Δ Hani 0-30 Oe.
It is shown that some combinations of x, y, and z displayed higher stability of 4 7r Ms temperature change and resulted in very low ferromagnetic resonance linewidth .View full abstractDownload PDF (440K) -
Etsuo Otsuki1996 Volume 43 Issue 12 Pages 1386-1392
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIt is exemplified that a novel approach for controlling the electromagnetic properties and microstructure has given excellent results in the development of new Mn-Zn ferrites.
The investigation about the effects of nanostructural improvement on the electromagnetic properties was performed by introducing a new method of power loss analysis, which is characterized by plotting the power loss versus reciprocal of electrical resistivity at the secondary peak temperature of the permeability. An eddy current loss obtained by this analysis is two times larger than the calculated one. The residual loss was identified as a loss factor which is not related to the resistivity and closely associated with frequency as well as applied magnetic field.
Sintering conditions influences the distribution of additives in the microstructure, which is responsible for the loss factors.View full abstractDownload PDF (1699K) -
Takafumi Satoh, Etsuo Otsuki1996 Volume 43 Issue 12 Pages 1393-1398
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA control of nano-structure in sintering process is necessary to decrease the power loss of Mn-Zn ferrites.
The purpose of this paper is to investigate the forming process of nano-structure during sintering as well as the structural change of spinel matrix and grain boundary which are affected by the oxygen partial pressure of sintering atmosphere by using High-Resolution Transmission Electron Microscopy(HRTEM).
As a result, it was revealed by the TEM images(bright, dark-field and lattice-fringe images) and the electron diffraction analyses that the thickness of the grain boundary layers was found to increase with increasing oxygen partial pressure of sintering atmosphere. And the reduction of power loss by adding SiO2 and CaO is thought of due to the formation of highly resisitive grain boundary layers.View full abstractDownload PDF (7360K) -
Taku Murase, Katsuhiko Igarashi, Jun Sawai, Takeshi Nomura1996 Volume 43 Issue 12 Pages 1399-1404
Published: December 15, 1996
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe gradual lowering of initial permeability(μi) with increasing frequency is said to be a relaxation phenomenon. The lowering of μi with frequency is improved by CuO substitution for MgO in MgZn ferrite. From the measuring results of the temperature dependence of tan δ, the activation enegy of the relaxation is calculated as approximately 0.43eV. The effect of the parameters in making process on the lattice defects was investigated with special reference to electric conductivity, microstructure and disaccommodation. From the results of time disaccommodation, the change in permeability for MgCuZn ferrites was found to be larger than that of MgZn ferrite. Furthermore, the lowering of permeability with time for both ferrites was regarded as being over 500 hours.View full abstractDownload PDF (3462K) -
Hidehiko Kobayashi, Hikaru Minowa, Koichi Kakizaki, Nobuyuki Hiratsuka1996 Volume 43 Issue 12 Pages 1405-1410
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA new technique for preparing metal/ferrite composite powder by the pyrolysis of ferrous oxalate and nickel oxalate powders derived from coprecipitation has been proposed. The technique was carried out as follows ; pyrolysis of the coprecipitated powder under NH3 gas flow and subsequent pyrolysis of mixtures of ferrite and (Fe3Ni)N powders under N2 gas flow. (Ni-Fe)/Fe3O4 composite powder was prepared by heating the coprecipitated powder of NiC2O4/FeC2Oa=0. 5-r2. 0 (molar ratio) at 350°C for 1h in NH3 gas, followed by heating at 500°C for 1 h in N2 gas. It was found that the thermal stability of (Ni-Fe)/Fe3O4 composite powder was affected by the composition of (Ni-Fe)alloy in the composite powder.View full abstractDownload PDF (1508K) -
Nobuyuki Hiratsuka, Hiroaki Tomimori, Takahiro Minakawa, Koichi Kakiza ...1996 Volume 43 Issue 12 Pages 1411-1414
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFerromagnetic ultra metallic fine particles of Fe, Ni and Co were prepared by a gas evaporation method in the pressure of nitrogen gas from 0.5-4Torr. Fine structures of these particles were revealed by a transmission electron microscope and a scanning electron microscope (SEM). Magnetic properties of the particles were measured by a vibrating sample magnetometer. The Fe, Ni and Co ultra fine particles observed by SEM were regarded as spheres and their surfaces were composed of oxide layers Fe3O4, NiO and CoO, respectively. The maximum coercivity was 1320, 1160 and 290Oe, respectively, for Co (425Å), Fe (310Å) and Ni (415Å) at room temperature. The exchange magnetic anisotropy between the cobalt core and the cobalt oxide shell was observed when the Co ultra fine particles were cooled in an applied field of 7kOe from room temperature to 77K.View full abstractDownload PDF (2978K) -
Shigeru Ito, Sachiko Shinmura, Takashi Hosokoshi, Kazuo Akashi1996 Volume 43 Issue 12 Pages 1415-1419
Published: December 15, 1996
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSince Fe4N decomposes at 670°C, sintering of Fe4N powder has not been performed under atmospheric pressure. In this study, Fe4N powders have been sintered below the decomposition temperature applying hipping pressure. The sealed capsule containing Fe4N powder was hipped at 450-550°C for 2 hours under 50-200 MPa. The decomposition of Fe4N was confirmed at 550°C. Therefore, hipping temperature was restricted below 500°C. The maximum relative density 97% was obtained for the specimen hipped at 500°C under the maximum pressure of 200MPa. The specimen obtained at 450°C has a higher saturation magnetization than that obtained at 500°C. The maximum saturation magne-tization 182emu/g was measured for a specimen obtained at 450°C under 200 MPa. The saturation magnetization was decreased to 151 emu/g by the addition of small amount of oxygen (0.33wt%) to Fe4N raw powder. In addition, the corrosion resistance of the hipped Fe4N was higher than that of steel.View full abstractDownload PDF (1457K) -
Mitsushi Fujiki, Shinichi Kikkawa, Masao Takahashi, Fumikazu Kanamaru, ...1996 Volume 43 Issue 12 Pages 1420-1425
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFour kinds of Fe metal/A1N multilayered thin films were deposited by rf-sputter deposition at room temperature. Both Fe and AIN layers have almost the same thickness and their total film thikness was about 1u m. They have stacking sequences of 1, 3, 8 and 35 times, respectively. They showed an anisotropic magnetic behavior; soft ferromagnetic and mostly paramagnetic when a magnetic field was applied along and vertically against the film surface, respectively. Larger saturation magnetization in 10 to 20% than that of α-Fe was observed on the multilayers in the 3 and the 8 times stacking. Larger internal magnetic field component in about 10% than that of α-Fe was present in Mossbauer spectra for these films. Formation of both iron nitride and aluminum metal were detected at the interface of the multilayers by XAFS, Mössbauer spectrocopy and XPS even though the films were prepared at room temperature.View full abstractDownload PDF (370K) -
Shigemi Sato, Min-Cheol Chu, Yasuyoshi Kobayashi, Kotoji Ando1996 Volume 43 Issue 12 Pages 1429-1434
Published: December 15, 1996
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSMullite/SiC composite ceramics containing 20 vol% SiC particles (0.12-1.71μm) were prepared by hot-pressing at 1650°C under 35 MPa for 4h. The effect of SiC particle size on mechanical properties such as bending strength and plastic deformation behavior at high temperatures was investigated as a function of cross-head speed. Bending strength and yield stress of mullite/SiC composite ceramics were higher than those of monolithic mullite at high temperatures. Bending strength and yield stress at 1300°C decreased with decreasing cross-head speed. At 1300°C, mullite/SiC composite ceramics with SiC grain size of 0.56-0.76 μm showed the highest bending strength and yield stress, which are 30-80% higher than those of monolithic mullite. On the other hand, mullite/SiC composite ceramics with SiC grain size of 0.18 μm showed maximum plastic deformation.View full abstractDownload PDF (3767K) -
Minato Ando1996 Volume 43 Issue 12 Pages 1435-1438
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSJoinning ceramic to metal without interlayer was tried using process from emulsifying of suspension to sintering. Alumina-kerosene suspension (0) was mixed with iron oxide-molybdenum-water suspension (W) and (W/O) emulsion was formed. After casting the emulsion, the (W)particles submerged to bottom due to difference in density between (O) and(W). The dried body was sintered in a reducing atmosphere and transformed to double layer consisting of alumina ceramic and iron-molybdenum alloy. At the area between these layers, protrusions of the alloy were locked in the alumina ceramic and this was considered to be a source of joint strength.View full abstractDownload PDF (5049K) -
Tsutomu Yamamoto, Kazuhiro Tezuka, Mikio Iwasa1996 Volume 43 Issue 12 Pages 1439-1443
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSErosive wear of WC based alloys with different cobalt content or Vickers hardness (Hv) was investigated by blasting SiC particles on specimen surface of the alloys. The erosive wear volumes were measured by the weight variation of the specimen and the profile of erosive wear scar obtained by surface profilemeter, which were expressed as Vd and Vp, respectively. V d of the alloys was also compared with that of commercial ceramics.
The results obtained were as follows: (1) The value of V d which decreased with the decrease of cobalt content in the alloys was nearly equal to that of V p. (2) V d decreased with the increase of Hv. Namely, Vd was estimated as a secondray function of Hv. (3) Vd of the alloys with low cobalt content of 0-2mass%, however, was smaller than that of B4C and SiC ceramics having nearly the same hardness.View full abstractDownload PDF (3027K) -
Yoshio Ukyo, Akihiko Suda, Hideyuki Masaki1996 Volume 43 Issue 12 Pages 1444-1448
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe sintering behavior of Y-α'-sialon powder during hot-pressing was investigated. Y-α'-sialon powder was consolidated by hot-pressing without any additive. Although the intermediate phases were formed during sintering, only Y-α'-sialon was observed as crystalline phase after sintering. The lattice constant of Y-α'-sialon was constant before and after sintering. This means that the solid solubility of Y- α'-sialon remains constant during sintering.View full abstractDownload PDF (4300K) -
Yoshihisa Kishimoto, Masami Ueda, Osamu Yamashita1996 Volume 43 Issue 12 Pages 1449-1454
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe iron-cobalt based alloys (especially Permendur) have been widely used for the application requiring high saturation induction, high permeability, low coercive force and high Curie temperature. Although the quantity of material so used has not been large, the reduction in the size and weight of apparatus that can be accomplished by its use has had an important effect on technical developments. Magnetic characteristics of Fe-50Co ring samples produced by the conventional powder metallurgy process with spray drying method were investigated. After pure elemental powders of iron and cobalt were mixed, these powders were granulated by spray drying method using organic binder consisting of polyvinylalcohol (PVA) and plasticizer in the range from O.1wt% to 0.5wt% of PVA, in order to improve the powder flowability during feeding and compacting. The resulting magnetic properties are superior to those of the MIM (Metal Injection Molding) 49Fe-49Co-2V alloy, and its magnetic induction at a magnetic field of 2000A/m exhibits the same value as that of commercial wrought 49Fe-49Co-2V alloy. Results show that the present method is an excellent process of producing near-net-shape parts with high saturation induction and low coercivity.View full abstractDownload PDF (4482K) -
Hideaki Itoh, Kazuyoshi Sugiyama, Hiroyasu Iwahara, Hiromichi Sakamoto1996 Volume 43 Issue 12 Pages 1455-1460
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDiamond coated cutting tool was prepared by microwave plasma CVD in the CO-H2 reactant system using silicon nitride substrate. A graded interfacial textrue between diamond film and silicon nitride substrate was formed by acid and microflawing pretreatments of the substrate and by the sub-sequent two-stage CVD treatment The correlation among the graded microstructure, film thickness distribution and cutting performance of the coated specimens was investigated. Long life of the silicon nitride cutting tool with thick diamond coating was verified by the milling test using Al-20wt%Si alloy as work material.View full abstractDownload PDF (3109K) -
Naomichi Miyagawa, Nobuhiro Shinohara, Hirotsugu Takizawa, Tadashi End ...1996 Volume 43 Issue 12 Pages 1461-1465
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPorous SiC ceramics have been fabricated by using SiO2-Al2O3 based glass beads. SiC powder with the anerage grain size of 0.6 μm was mixed with 5-20 wt.% glass beads by dry mixing. The average particle size of the glass beads was about 45 μm. The mixed powder was compressed into plate form and sinterd at 1970°C for 2 hours in Ar atmosphere. The resultant materials had porosities ranging from 25 to 50 %. Large spherical pores connecting through micro-sized open pores were observed in their microstructures. It has been concluded that the occurence of open pores was orginated in the formation of gas phase through the reaction, SiC+2SiO2→3SiO(g)+CO(g), in Ar atmosphere. The alumina element in the glass beads contributed to the densification of SiC matrix through the formation of liquid phase and as a result, the materials had high bending strength in spite of their high porosity.View full abstractDownload PDF (2083K) -
Hisashi Ito, Yuji Yamasaki, Ken-ichi Takagi, Hidenori Kuroki1996 Volume 43 Issue 12 Pages 1466-1472
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMullite ceramics containing 20-40 mass% zirconia were rapidly solidified (RS) to obtain amorphous ceramic powder using a Plasma Centrifugal Atomization (PCA) process. The RS and, for comparison, non RS powder were hot-pressed at various temperatures ranging from 1623 to 1823 K Transverse rupture strengths (TRS) of the hot pressed compacts were measured between 293 and 1473 K. The averaged TRS of the RS compacts at room temperature increased with increasing zirconia content However the TRS of the non RS compacts exhibited a peak value at 30 mass% zirconia content. Although the TRS for both materials decreased with increasing temperature, the RS material still had higher values than non RS material at elevated temperature. The improvement in the strength was attributed to a very fine microstructure in the RS compacts produced from amorphous powder.View full abstractDownload PDF (1982K) -
Masayuki Kato, Naotaka Yamamoto, Toshikazu Takeda, Koji Hayashi1996 Volume 43 Issue 12 Pages 1473-1478
Published: December 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFeSi2(β phase) semiconducting iron silicide, which is expected to be widely used as a thermoelectric material in high temperature environment, is formed below 1259K by the peritectoid reaction of FeSi(ε) and Fe2Si5(α) two metallic phases. Because the transformation of ε+α→β caused by this peritectoid reaction occurs considerably slowly, the iron silicide material which is produced by sintering of the powder at temperatures above 1259K has to be isothermally heat-treated for at least 180ks at about 1120K after the sintering so that the transformation occurs completely.
We have found that the transformation was drastically accelerated by the addition of a small amount of Pd in the same way as Cu; the isothermal heat-treatment time necessary for the completion of the transformation was reduced to about 1/60. The sintering time needed for the almost full densification of the powder by pressure DCL sintering (DCL; direct current loading) was also reduced. A hypothesis for the mechanisms was proposed.View full abstractDownload PDF (2687K)
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