公开(公告)号：US20220375663A1

公开(公告)日：2022-11-24

申请号：US17764229

申请日：2020-09-29

申请人： THE UNIVERSITY OF TOKYO ,  DOWA HOLDINGS CO., LTD.

发明人： Shin-ichi OHKOSHI ,  Asuka NAMAl ,  Hiroko TOKORO ,  Marie YOSHIKIYO ,  Kazuhiro YAMAGA ,  Yasuto MIYAMOTO ,  Yuki MINEYAMA ,  Kenji SAKANE ,  Tetsuya KAWAHITO

IPC分类号： H01F1/11 ,  C01G49/06 ,  B82Y40/00 ,  B82Y30/00 ,  B82Y25/00

摘要： A raw material solution containing trivalent iron ions, or trivalent iron ions and ions of a metal element that partially substitutes Fe sites, and an alkaline aqueous solution for neutralizing the raw material solution are added to a reaction system to adjust the pH of the reaction system from 1.0 to 3.0 or lower. Hydroxycarboxylic acid is added to the obtained reaction solution and the pH of the reaction system is then neutralized from 7.0 to 10.0 or lower. The obtained precipitate of a substituent metal element-containing iron oxyhydroxide is coated with silicon oxide, followed by heating so as to form particles of ε-iron oxide in which Fe sites are partially substituted by other metal elements, and then, a slurry containing the particles is classified. The iron-based oxide magnetic powder has a particle shape close to a perfect sphere and is suitable for use in a magnetic recording medium.

公开(公告)号：US20210300779A1

公开(公告)日：2021-09-30

申请号：US16979241

申请日：2019-03-26

申请人： DOWA ELECTRONICS MATERIALS CO., LTD. ,  THE UNIVERSITY OF TOKYO

发明人： Shin-ichi OHKOSHI ,  Asuka NAMAI ,  Kenji SAKANE ,  Tetsuya KAWAHITO

IPC分类号： C01G49/06 ,  H01F1/11

摘要： [Problem] To provide a method for producing iron based oxide magnetic powder that has a narrow particle size distribution and a small content of fine particles that do not contribute to the magnetic recording characteristics, and consequently has a narrow coercive force distribution and is suitable for the enhancement of the recording density of the magnetic recording medium. [Solution] ε-Type iron based oxide magnetic powder is obtained by a wet method, then a tetraalkylammonium salt as a surface modifier is added to a slurry containing the magnetic powder to make a concentration of 0.009 mol/kg or more and 1.0 mol/kg or less, and simultaneously to make pH of 11 or more and 14 or less, and the slurry is subjected to a dispersion treatment and then classified, so as to provide iron based oxide magnetic powder having a narrow particle size distribution and a narrow coercive force distribution.