Abstract: A process for the preparation of finely divided and acicular hexagonal ferrites of the general formula AMe.sub.x Fe.sub.12-x O.sub.19, where x is .ltoreq.4, A is barium and/or strontium and Me is indium or equimolar amounts of zinc or cobalt and titanium, and their use for the production of magnetic recording media and plastoferrites.

Abstract: The preparation of acicular ferrimagnetic iron oxides which contain cobalt and phosphate ions and, if desired, further additives, and their use for manufacturing magnetic recording media.

Abstract: A process for the preparation of cobalt-containing isotropic magnetic iron oxides which are based on gamma-iron(III) oxide, contain from 2 to 7% by weight of cobalt(II) ions and less than 2% by weight of Fe(II) ions, the percentages in each case being based on the iron oxide, and have a particle length of from 0.08 to 0.30 .mu.m, a length/width ratio of from 1.5 to 3.5:1 and a specific remanent magnetization after saturation of not less than 60 nTm.sup.3 /g.

Abstract: Acicular metal particles consisting essentially of iron are prepared by reducing .alpha.-iron(III) oxide obtained--by dehydration--from acicular iron(III) oxide hydroxide prepared in the presence of phosphate ions and having a shape-stabilizing surface coating.

Abstract: Finely divided ferrite powder of the general formulaCo.sub.x Fe.sub.3-x O.sub.4.5-0.5 xwhere x is from greater than zero to one, having an essentially isotropic particle shape, is prepared by oxidation of ferrite powder of the composition Co.sub.x Fe.sub.3-x O.sub.4, where x has the same limits, with an oxygen-containing gas at from 150.degree. to 500.degree. C.

Abstract: Ferrimagnetic particles which are useful as magnetic material for magnetic recording media and consist of a core of a magnetic material exhibiting multiaxial anisotropy and a coating which surrounds the core and is composed of a magnetic material possessing uniaxial anisotropy, and a process for their preparation.

Abstract: A magnetic dispersion which can be applied to a non-magnetic base to produce a recording medium is prepared by dispersing a magnetically anisotropic material in a polymer binder and in an organic solvent by a method wherein the magnetically anisotropic material is worked in a jet mill before and/or during dispersing.

Abstract: Magnetic recording media are produced by preparing a dispersion consisting of finely divided magnetic material, a dispersant, the conventional additives and a solution or a dispersion of a polymeric binder, applying the dispersion in the form of a layer onto a non-magnetizable base, orienting the anisotropic magnetic material by means of a magnetic field and drying the applied layer, by a process in which the dispersant employed is obtained by reactingA. from 70 to 95 parts by weight of a reaction product ofI. from 0.5 to 1.5 moles of an oxoalcohol of 6 to 20 carbon atoms,II. from 6 to 18 moles of ethylene oxide andIII. from 2 to 10 moles of propylene oxide, withB. from 5 to 30 parts by weight of a polyphosphoric acid having a P.sub.2 O.sub.5 content of from 80 to 88%.

Abstract: Magnetic recording media are produced by dispersing timely divided anisotropic magnetic material in a polymeric binder to a non-magnetizable base.

Abstract: A process for the preparation of acicular ferrimagnetic iron oxides by reducing gamma-iron(III) oxide hydroxide to magnetite, at from 280.degree. to 620.degree. C., by means of an organic compound which is decomposable at this temperature in the presence of iron oxide, and, optionally, a stream of reducing gas, and, if desired, then oxidizing the magnetite with oxygen-containing gases, at from 150.degree. to 450.degree. C., to acicular ferrimagnetic iron oxide of the formula FeO.sub.x, where x is from above 1.33 to 1.50, wherein the organic compound used for the reduction is a non-polar glycerol ester of a fatty acid which is introduced into the aqueous reaction suspension during the preparation of the gamma-iron(III) oxide hydroxide.

Abstract: Acicular ferromagnetic chromium dioxide particles having a pH greater than 4 and a process for their preparation.

Abstract: Acicular ferromagnetic metal particles consisting essentially of iron are prepared by a process wherein acicular iron(III) oxide hydroxide provided with a shape-stabilizing surface coating, or iron(III) oxide obtained therefrom by dehydration, is reduced by means of a decomposable organic compound and hydrogen.

Abstract: A process for stabilizing pyrophoric acicular metal particles consisting essentially of iron, by reaction with oxygen-containing gases in two stages, wherein, in the first stage, up to 1/3 of the passivating layer present in the final state is formed at from 25.degree. to 45.degree. C. and, in a subsequent second stage, the remainder of the passivating layer is formed at from 50.degree. to 70.degree. C.

Abstract: A process for the preparation of barium ferrite of the formula BaFe.sub.12 O.sub.19 by reacting an aqueous solution or suspension of a barium salt and an aqueous solution of an iron(III) salt with an aqueous sodium carbonate solution, removing the solvent, heating the dry salt mixture to below the melting point of the sodium salt present, but to not less than 680.degree. C., and isolating the resulting finely divided, platelet-like barium ferrite from the barium ferrite/sodium salt mixture by leaching with water.

Abstract: A process for the manufacture of acicular magnetic iron oxide consisting of a core of gamma-iron(III) oxide and a ferrite shell which contains, based on the total amount of magnetic material, from 0.2 to 12 percent by weight of cobalt(II) ions and from 0.1 to 15 percent by weight of iron(II) ions, wherein a solution containing cobalt(II) hydroxide and iron(II) hydroxide is applied to acicular gamma-iron(III) oxide particles and the latter are heated at 100.degree.-220.degree. C.

Abstract: An iron oxide pigment having a coating of a silane of the formulaR.sub.n Si(OR').sub.4-nwhereinR is an, in some cases, branched or oxygen-bridge-containing alkyl or alkenyl moiety of 1 to 18 carbon atoms, or an aryl moiety,R' is an, in some cases, branched and, in some cases, oxygen-bridge-containing alkyl moiety of 1 to 8,n=1 to 3,or a hydrolysis product thereof; a magnetic tape containing such coated iron oxide pigment and a process for coating such iron oxide pigment. There is particularly disclosed the treatment of iron oxide magnetic pigments to thereby improve their wear resistance and dispersibility in organic mediums.

Abstract: A process for the manufacture of acicular ferrimagnetic iron oxide by reducing heat-treated acicular iron(III) oxide hydroxide with an organic compound which decomposes in the presence of iron oxide at from 450.degree. to 650.degree. C., followed by at least partial oxidation with an oxygen-containing gas at from 200.degree. to 500.degree. C., wherein the iron(III) oxide hydroxide employed is heat-treated at from 450.degree. to 700.degree. C. and has a surface area, measured by the BET method, of from 10 to 23 m.sup.2 /g.

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.degree. to 650.degree. 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.degree. to 500.degree. 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.degree. to 700.degree. C.

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.

Abstract: An iron oxide pigment having a coating of a silane of the formulaR.sub.n Si(OR').sub.4-nwhereinR is an, in some cases, branched or oxygen-bridge-containing alkyl or alkenyl moiety of 1 to 18 carbon atoms, or an aryl moiety,R' is an, in some cases, branched and, in some cases, oxygen-bridge-containing alkyl moiety of 1 to 8,N=1 to 3,Or a hydrolysis product thereof; a magnetic tape containing such coated iron oxide pigment and a process for coating such iron oxide pigment. There is particularly disclosed the treatment of iron oxide magnetic pigments to thereby improve their wear resistance and dispersibility in organic mediums.