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公开(公告)号：DE2735316A1
公开(公告)日：1979-02-08
申请号：DE2735316
申请日：1977-08-05
Applicant: BASF AG
Inventor： BRODT RUDOLF DIPL CHEM DR , JAKUSCH HELMUT DIPL PHYS DR , KOESTER EBERHARD DIPL PHYS DR , LOESER WERNER DIPL ING DR , OHLINGER MANFRED DIPL CHEM DR , SARNECKI WILHELM DIPL-CHEM DR , STECK WERNER DIPL CHEM DR
Abstract: A process for the manufacture of acicular ferrimagnetic iron oxide by dehydrating acicular iron(III) oxide hydroxides to give acicular iron(III) oxides, then reducing these iron(III) oxides at from 300 DEG to 650 DEG C. by means of an organic compound which decomposes in this temperature range, and oxidizing the reduced product with an oxygen-containing gas at from 200 DEG to 500 DEG C., wherein the acicular iron(III) oxide hydroxides employed consist of a mixture of goethite and lepidocrocite, containing at least 60% of the latter, and the dehydration is carried out at from 250 DEG to 700 DEG C.
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公开(公告)号：DE2714588A1
公开(公告)日：1978-10-12
申请号：DE2714588
申请日：1977-04-01
Applicant: BASF AG
Inventor： STECK WERNER DIPL CHEM DR , BRODT RUDOLF DIPL CHEM DR , SARNECKI WILHELM DIPL CHEM DR , JAKUSCH HELMUT DIPL PHYS DR , OHLINGER MANFRED DIPL CHEM DR , KOESTER EBERHARD DIPL PHYS DR
IPC: G11B5/706 , B22F9/22 , C09D5/23 , C09D7/12 , C21B15/00 , G11B5/712 , G11B5/714 , H01F1/06 , B22F9/00
Abstract: A process for the manufacture of acicular ferromagnetic iron particles by reducing acicular iron(III) oxide hydroxides which consist of pure synthetic lepidocrocite or a mixture of synthetic goethite and at least 70% by weight of synthetic lepidocrocite. The iron(III) oxide hydroxides used carry, on their surface, an alkaline earth metal cation and an anion of a monobasic, dibasic or tribasic aliphatic carboxylic acid of up to 6 carbon atoms or an organic compound containing at least two groups capable of chelating the alkaline earth metal cation, and are produced in such a way that they consist of at least 70 percent by weight of lepidocrocite and have a length-to-width ratio of not less than 15:1. Reduction of such iron(III) oxide hydroxides gives iron particles with pronounced shape anisotropy, which exhibit both good magnetic properties and a narrow field strength distribution.
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公开(公告)号：DE2743298A1
公开(公告)日：1979-04-05
申请号：DE2743298
申请日：1977-09-27
Applicant: BASF AG
Inventor： JAECKH CHRISTOPHER DIPL CHEM D , STECK WERNER DIPL CHEM DR , BRODT RUDOLF DIPL CHEM DR , OHLINGER MANFRED DIPL CHEM DR , LOESER WERNER DIPL ING DR , KOESTER EBERHARD DIPL PHYS DR
Abstract: Acicular ferromagnetic metal particles essentially contain iron and carry, on their surface, from 0.02 to 0.6% by weight of boron in the form of a borate. Such particles may be obtained by reducing an acicular iron oxide with a gaseous reducing agent at from 250 to 500 DEG C, if boron oxyacid or an inorganic salt thereof is deposited on the said iron oxide before reduction. The acicular, ferromagnetic particles are principally used in magnetic recording media and the invention seeks to overcome the difficulty of providing such particles distinguished by a narrow particle size spectrum and pronounced acicular shape.
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公开(公告)号：DE2735315A1
公开(公告)日：1979-02-15
申请号：DE2735315
申请日：1977-08-05
Applicant: BASF AG
Inventor： BRODT RUDOLF DIPL CHEM DR
Abstract: A ferrous salt soln. is treated with 0.05-1% (w.r.t. the wt. of Fe2+ ions) of cuprous or cupric ions and/or 0.05-1% Pb4+ ions; NH4OH or alkali(ne earth) hydroxides; oxidising gases; more Fe2+ cpds.; and more alkali to obtain a pH of 4.8-6, so that lepidocrocite is pptd. The lepidocrocite is reduced to magnetite and then oxidised to acicular gamma-Fe2O3 (I). The lepidocrocite is pref. dewatered at 300-620 degrees C prior to redn. The process is used for mfr. of (I) with high coercive force, good crystallinity, and good mechanical and magnetic stability for magnetic recording tapes.
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