日本応用磁気学会誌
Online ISSN : 1880-4004
Print ISSN : 0285-0192
ISSN-L : 0285-0192
22 巻 , S_1_ISFA_97 号
選択された号の論文の141件中1~50を表示しています
Ferrite industry/research in Asia
Physics of magnetic materials
Process and evaluation
  • Peter MICZAJKA
    1998 年 22 巻 S_1_ISFA_97 号 p. S1_71-73
    発行日: 1998年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      For the granulation of ferrites according to the Vacuum Hot Steam Process (VHSP) a high-pasty material is used as starting material. Homogenizing and dispersing of the mixing components are made in an intensive mixer with rotating mixing pan and high-speed rotor by using high shearing forces. Granulation is made by drying. Superheated steam is passed through the material as drying medium under vacuum. The adjustment of the granule size can be reproduced. The granules are distinguished by an increased density, considerably improved homogeneity, higher abrasive resistance, homogeneous moisture distribution in the interior.
  • Geun-Min Jeong, Sung-Soo Kim
    1998 年 22 巻 S_1_ISFA_97 号 p. S1_74-76
    発行日: 1998年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      This study investigates the grain growth behavior (normal and abnormal) in Mn-Zn ferrite system with respect to the addition of CaO and SiO2. The powders of (Mn0.76Zn0.24O)0.94(Fe2O3)1.06 composition and average particle size of 0.94 μm are prepared by milling the calcined powder in an attritor. CaO and SiO2 are added in the range from 0 to 1.5 wt%, respectively. In the specimen containing a very low additive content (less than 0.02 wt% CaO and 0.007 wt% SiO2), a typical normal grain growth is observed. In the specimens containing 0.08 wt% CaO and 0.011 wt% SiO2, however, a few grains grow abnormally, while the growth of other grains is almost suppressed. In the specimen of a little more additive content (1.5 wt% CaO and 1.5 wt% SiO2), the grains are faceted in the liquid matrix and abnormal grain structure is developed. The results are discussed on the basis of growth kinetics determined by two-dimensional nucleation at the singluar interfaces of faceted grains.
  • K. TANAKA, M. MAKITA, K. HIRAO, N. SOGA
    1998 年 22 巻 S_1_ISFA_97 号 p. S1_77-79
    発行日: 1998年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      We have examined the effect of heat treatment temperature and time on magnetic properties of rapidly quenched oxides with compositions close to ZnFe2O4. These oxides show high magnetization even at room temperature as we reported previously. In particular, attention is focused on oxide with nominal composition of 60ZnO•40Fe2O3. It is suggested that the high magnetization is brought about by iron ion clusters with Zn2+ ions occupying octahedral sites as well as solid solution of Fe3O4 in ZnFe2O4. As the heat treatment temperature increases, the room temperature magnetization decreases sluggishly below 500°C and decreases sharply above 600°C when the heat treatment time is 2 h. It is proposed that the decrease of magnetization below 500°C corresponds to disappearance of iron ion clusters while the rapid decrease of magnetization above 600°C is caused by oxidation of Fe2+ to form ZnFe2O4 with normal spinel structure.
  • D. J. FATEMI, V. G. HARRIS, J. P. KIRKLAND
    1998 年 22 巻 S_1_ISFA_97 号 p. S1_80-82
    発行日: 1998年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      We have produced MnZn-ferrite via high-energy ball-milling of the elemental oxides MnO, ZnO, and Fe2O3. X-ray diffraction indicates a pure phase spinel forms after 1250 min. of ball-milling, with all diffraction peaks being indexed to the fd3m space group having a lattice parameter 8.422 Å(8.429Å after 2400 min. milling). Extended x-ray absorption fine structure (EXAFS) analysis reveals that the conversion of metal ions from their elemental oxide structures to the spinel phase occurs nearlinear with milling time with 50% of the oxides converted after approximately 500 minutes. Multiple-scattering EXAFS modeling indicates an increase in the inversion parameter for the milled ferrite with a abnormally high fraction of Zn cations residing on the B sublattice.
  • B. PARVATHEESWARA RAO, P.S.V. SUBBA RAO, ATMARAM LAKSHMAN, K.H. RAO
    1998 年 22 巻 S_1_ISFA_97 号 p. S1_83-85
    発行日: 1998年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      With a useful combination of magnetic and electrical properties, Ni0.65 Zn0.35 Fe2 O4 is a desirable composition for power transformer cores in Switched Mode Power Supplies (SMPS). The present investigation is aimed at studying electrical and microstructural aspects of this composition under different sintering conditions. Room temperature DC resistivity of the ferrite has been found to decrease slowly and gradually with an increase either in sintering temperature or in sintering time below the sintering schedule of 1250°C / 2 hrs and for the above the decrease has been observed to be rapid. The observed variations have been attributed to microstructural changes brought about by the sintering conditions. Temperature dependence of resistivity shows two regions thus indicating the presence of atleast two conduction mechanisms in the system. Conclusions have been drawn towards optimisation of sintering schedule required for the development of transformer cores for SMPS applications.
  • Hiroshi Yamamoto, Masahiro Chono
    1998 年 22 巻 S_1_ISFA_97 号 p. S1_86-88
    発行日: 1998年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      This experiment was carried out to investigate the effect of Na2O and SrO additives on the magnetic and physical properties of SrZn2-W type hexagonal ferrite. The specimens were prepared by the conventional manufacturing methods without the atmosphere control. It was found that the magnetic properties of SrO • 2ZnO8Fe2O3 were considerably improved on adding 1.33wt% Na2O and 0.67wt% SrO after semisintering treatment. The optimum condition of making magnet with suitable properties are as follows : chemical analysis composition: Sr2+0.953Zn2+1.595Na+0.271Fe2+0.080Fe3+16.157O27 ; semisintering condition : 1300°C x 1h in air ; sintering condition : 1250°C x 0.5h in air. The magnetic properties are : Jm = 0.415 T, Jr = 0.375 T, HcJ = 123.4 kA/m, HcB = 118.6 kA/m, (BH)max = 22.8 kJ/m3, Tc = 361°C, HA = 1084 kA/m, KA = 2.25 x 105J/m3 and nB = 33.8μB. The magnetic properties of this compound powder heated at 1100°C after milling are σ5 = 82.9x10-6Wb·m/kg and HcJ = 199 kA/m, and they are useful as the bonded magnet material.
  • S. Shinmura, S. Ito, K. Akashi
    1998 年 22 巻 S_1_ISFA_97 号 p. S1_89-91
    発行日: 1998年
    公開日: 2011/12/15
    ジャーナル オープンアクセス
      Fe4N powder has been sintered at below the decomposition temperature applying a hipping pressure, and the influence of oxygen content on saturation magnetization of hipped Fe4N has been studied. The hipping temperature was restricted below 500°C, because Fe4N was decomposed at 550°C. The maximum relative density of 97% was obtained for the Fe4N hipped at 500°C under 200MPa. The Fe4N hipped at 450°C under 200MPa revealed the maximum saturation magnetization of 182emu/g with a high relative density of 95%. It was confirmed that the presence of oxygen decreased saturation magnetization of Fe4N. The Vickers hardness was measured as Hv5.5 × 102, and the corrosion resistance was higher than that of steel.
Magnetic recording and magneto-optics
Thin films
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