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Volume 18, Issue 6
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[in Japanese]1972 Volume 18 Issue 6 Pages 209-216
Published: February 25, 1972
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (579K) -
Koichi Haneda, Hiroshi Kojima1972 Volume 18 Issue 6 Pages 217-222
Published: February 25, 1972
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSAn investigation on the influence of replacement of Fe3+ with Cr3+ on the magnetic properties of BaFe12O19 was made. The specimens BaFe12-x CrxO19 (x=0-3.0) were prepared by the ordinary powder metallurgy method. By X-ray investigation, it was proved that a continuous series of solid solutions of the type BaFe12-xCrxO19 are formed, at least up to x=3.0. The lattice parameter a0 and the volume of the unit cell V0 decreased monotonically with increasing Cr concentration. Curie temperature Tc and the intrinsic coercive force iHc, saturation magnetization Is, and anisotropy constant K, at room temperature were measured for various compositions. The temperature dependence of magnetization was also carried out between the liquid-nitrogen and Curie temperature. These magnetic parameters, except for iHc, decreased monotonically with the increasing amount of substituted ions. But extremely high intrinsic coercive forces under the effect of Cr (iHc=8000 Oe at x=3.0) were obtained. Intrinsic coercive force of the hard ferrites is expected to increase greatly as the particle size varies from multidomain to single domain. The critical radius Rc for single domain particles was calculated for each composition. It becomes larger when the Cr concentration is increased. But from the changes of K and Is against x, the increase in anisotropy field could not be expected. It can then be concluded that single-domain behavior is easily obtained in higher Cr concentration powder, even though under the same milling condition. The similar results can be obtained in case of SrFe12-x CrxO19 (x=0-4.0).View full abstractDownload PDF (411K) -
Tôru Miyazaki, Yûnoshin Imai, Takao Kawakita1972 Volume 18 Issue 6 Pages 223-228
Published: February 25, 1972
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSGrowth of oxide particles during annealing at 1100-1300°C in dispersion strengthened alloy, Fe-25%Cr-28%Ni-3vol.%oxide (a-Al2O3, MgO, Er2O3, TiO2 and ZrO2) prepared by the method of powder metallurgy were investigated. Results obtained are as follow;
(1) Oxide particles are coagulated by annealing at 1100-1300°C in air and in hydrogen stream.Rates of the particle coagulation are smaller in hydrogen stream than in air. Activation energies for the coagulation are larger in hydrogen stream than in air. Volume fraction of the oxide particle increases with heating, and increment of the volume fraction is larger in air than in hydrogen stream. It seemed that these particles change to complex compounds during annealing.
(2) The coagulation of the particle in these alloys come about in a mechanism of the particlemigration along the grain boundary, while the particles react on impure oxides such as Cr2O3 mixed in the preparation of the alloys.View full abstractDownload PDF (7782K) -
Yasutoshi Saito, Kohei Nishimura, Isao Sakamoto, Tsutomu Yamamura, Yos ...1972 Volume 18 Issue 6 Pages 229-237
Published: February 25, 1972
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe electromotive force measurements were made on the stacked pellet type galvanic cells consisting of the 0.85 ZrO2-0.15 CaO electrolyte with the electrodes including Fe-FeO (wiistite), FeO-Fe2O4 (magnetite), Fe2O4-Fe2O3 (hematite), Ni-NiO and Co-CoO two-phase coexisting systems at temperatures of 630°to 1100°C, in order to obtain the relative partial molar free energies of oxygen for the two-phase oxide systems. The data obtained were in good agreement with the accepted values, which proved that the cells functioned satisfactorily.
The feasibility of employing the solid electrolyte galvanic cell method, especially the open cell staccked pellet technique, was discussed. The careful consideration of several factors made it possible to obtain equilibrium values of the electromotive force.View full abstractDownload PDF (716K)
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