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Patent Agency Ranking
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公开(公告)号：DE2919662A1
公开(公告)日：1980-11-27
申请号：DE2919662
申请日：1979-05-16
Applicant: BASF AG
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公开(公告)号：DE2705967A1
公开(公告)日：1978-08-17
申请号：DE2705967
申请日：1977-02-12
Applicant: BASF AG
Inventor： BECKER HANS-JUERGEN DIPL CHEM , JAECKH CHRISTOF DIPL CHEM DR , KOESTER EBERHARD DIPL PHYS DR , LOESER WERNER DIPL ING DR , OHLINGER MANFRED DIPL CHEM DR , STECK WERNER DIPL CHEM DR
Abstract: A process for the manufacture of an acicular magnetic iron oxide containing from 0.5 to 10 percent by weight of cobalt and up to 24 percent by weight of divalent iron, each based on the amount of iron(III) oxide, wherein an aqueous suspension of gamma-iron(III) oxide, containing cobalt(II) and iron(II) ions, the suspension having a hydroxyl ion concentration of more than 3.6x10-6 moles/liter, is heated at from 50 DEG to 100 DEG C. for at least 15 minutes, and the resulting precipitate is filtered off, washed until neutral, dried at below 100 DEG C. and thereafter heated at from 100 DEG to 200 DEG C. The products thus obtained give, even when their cobalt content is low, a very high coercive force, while the effect of temperature on the coercive force and residual induction is very slight.
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