Compositions – Magnetic – Iron-oxygen compound containing
Patent
1995-11-16
1997-11-18
Bonner, Melissa
Compositions
Magnetic
Iron-oxygen compound containing
252 6257, 423594, C04B 3536, C04B 3538, C04B 3540, C04B 3546
Patent
active
056884303
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a soft ferrite raw material powder, its sintered body, and their production method and apparatus. More particularly, the present invention relates to a soft ferrite raw material powder, its ferrite sintered body, a method of producing directly a ferrite powder by atomizing and roasting a solution containing chlorides of metal elements constituting the ferrite, an apparatus for this method, and a production method of a ferrite sintered body.
BACKGROUND ART
Recently, the reduction of the size and weight of power transformers used for a switching power supply, etc., has been required and for this reason, the driving frequency has been expanded to a high frequency range beyond the conventional range of from 100 KHz to 500 KHz, and the future application in the MHz range has been examined. However, because an eddy current loss, which becomes a particular problem in the high frequency range among the power loss, is proportional to the square of the driving frequency, the power loss increases with the increase of the frequency, so that exothermy cannot be neglected. Various proposals have been made in the past to solve such a problem. Among them, some represent that high performance can be expected for a soft ferrite sintered body necessary for accomplishing high characteristics by a fine structure in which texture fluctuation of individual crystal particles is less, and which has small amounts of impurities and has a high density.
Particularly because the reduction of the crystal particle diameter of the sintered body is effective, Japanese Unexamined Patent Publication (Kokai) No. 1-224265 teaches to produce a fine sintered body having a mean crystal diameter of 5 .mu.m so as to restrict the power loss in the high frequency range. Another improvement example which uses fine powder prepared by a hydrothermal synthesis method as the raw material powder has been reported (refer to "Nikkei Material & Technology", 125, (1993) 24). The soft ferrite raw material powder for obtaining such a sintered body must have smaller amounts of impurities, must have uniform components and small variance of particle size distribution and must be fine particles. Therefore, improvements and development have been continued.
A method of atomizing and thermally decomposing a pickling waste liquor of steel is known as one of the iron oxide methods of obtaining soft ferrite raw materials. In this case, if various metallic ions constituting the ferrite are mixed in the pickling water liquor, a ferrite powder can be obtained by atomization and thermal decomposition. According to the ordinary atomization thermal decomposition method, however, components having a high vapor pressure such as zinc evaporate, and a homogeneous composition cannot be obtained so easily. Therefore, Japanese Unexamined Patent Publication (Kokai) No. 55-144421 discloses a production method of a soft ferrite sintered body which mixes Fe and Mn ions, which have stable high temperature thermal decomposition characteristics, as the soft ferrite raw material powder in the form of an aqueous chloride solution, prepares a mixed oxide containing Fe--Mn in a predetermined composition by atomization thermal decomposition (roasting), then mixes zinc oxide powder, and thereafter conducts pulverization, granulation, molding and sintering.
On the other hand, as a method of producing a composite oxide for the Zn-containing soft ferrite raw material powder, Japanese Unexamined Patent Publication (Kokai) No. 63-156017 discloses a method which sprays a chloride solution containing the ferrite raw materials in a predetermined composition to a fluidization roasting furnace to conduct a high temperature oxidation reaction, withdraws the powder with the decomposition products, and recovers the soft ferrite raw material powder by a dust collector.
As an improvement of Japanese Unexamined Patent Publication (Kokai) No. 63-156017 described above, Japanese Unexamined Patent Publication (Kokai) No. 1-192708 discloses a method which atomizes and mix
REFERENCES:
patent: 5462686 (1995-10-01), Sugiyama et al.
Chemical Abstracts citation 122:44708, abstract for JP 6-260321, Sep. 16, 1994.
Chemical Abstracts citation 122:229036, absract for JP 6-333724, Dec. 2, 1994.
Aritome Kiyoshi
Hasegawa Fumihiko
Ikeda Yoshimasa
Ito Kaoru
Kawahito Kenji
Bonner Melissa
Nippon Steel Corporation
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