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    2.
    发明专利
    未知

    公开(公告)号：DE3775801D1

    公开(公告)日：1992-02-20

    申请号：DE3775801

    申请日：1987-03-25

    Applicant: BASF AG

    Inventor： MUELLER NORBERT ,  OHLINGER MANFRED ,  WALTER EGON

    IPC: C01G37/027 ,  G11B5/706

    Abstract: Ferromagnetic CrO2 (I) is produced by mixing Cr2O3 and CrO3 in water, with addn. of modifier(s) (II), and then heating the mixt. at 240-500 deg. C and 100-700 bar. (II) is added in a predetermined amt. of a dust-tight package, made of material which is soluble or disintegrates in water.

    5.
    发明专利
    未知

    公开(公告)号：DE3680905D1

    公开(公告)日：1991-09-19

    申请号：DE3680905

    申请日：1986-10-18

    Applicant: BASF AG

    Inventor： MUELLER NORBERT ,  BOETTCHER BERNHARD ,  OHLINGER MANFRED ,  REINICKE HELMUT ,  HONECKER GERHARD

    IPC: H01F1/11 ,  C01G37/02 ,  C01G37/027 ,  G11B5/706 ,  H01F1/10

    Abstract: Prodn. of Cr2O3 is effected by thermal decompsn. of hydrous NH4 bichromate (I) at 450-750 deg.C in a restricted combustion chamber such that the ratio of the vol. of the combustion chamber in l, to the flow rate of (I) in kg/min. is 1-6:1. Pref. decompsn. is effected in a combustion chamber attached to the feed inlet of a rotary furnace, the material emerging from the combustion chamber being post-reacted in the furnace at sub-decompsn. temp. before being discharged from the other end. The combustion chamber has a dia./length ratio of 1:2 2:1. The ratio of the dia. of the combustion chamber to the dia. of the furnace is 1-3:4.

    PREPARATION OF FERROMAGNETIC CHROMIUM DIOXIDE
    6.
    发明专利
    PREPARATION OF FERROMAGNETIC CHROMIUM DIOXIDE 未知

    公开(公告)号：CA1269234A

    公开(公告)日：1990-05-22

    申请号：CA488306

    申请日：1985-08-08

    Applicant: BASF AG

    Inventor： OHLINGER MANFRED ,  MUELLER NORBERT ,  RUDOLF PETER ,  WETTSTEIN EUGEN

    IPC: H01F1/11 ,  C01G37/027 ,  C09D5/23 ,  C09D7/12 ,  G11B5/706 ,  G11B7/24

    Abstract: The invention relates to a process for the preparation of a ferromagnetic chromium dioxide by converting oxides of trivalent and hexavalent chromium under a pressure of from 100 to 700 bar and at a temperature of from 200.degree. to 600.degree.C in the presence of water, an antimony modifier and acicular iron oxide particles or acicular iron particles in an amount of not more than 15% by weight comprising adding an antimony compound as a modifier in the form of a water-soluble salt in an amount of at least 0.1% by weight but less than 4% by weight, based on the resulting chromium dioxide and said iron oxide or iron particles to a mixture of hexavalent chromium oxide and water, adding trivalent chromium oxide thereto and subjecting the resultant mixture to said pressure and temperature, with a proviso that the water-soluble antimony compound contains at least one organic molecular moiety anion which is oxidized by the oxide of hexavalent chromium with the evolution of gas when said antimony compound is added to a mixture of said hexavalent chromium oxide and water. This process allows the preparation of ferromagnetic chromium dioxides having a high coercive force while at the same time reducing the amount of modifiers required for this purpose.

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