SU1734947A1 - Process for making cobalt-plated magnetic particles based on gamma-iron oxide for working layer of magnetic recording medium - Google Patents

Abstract

Use: manufacture of magnetic powders for magnetic media recording, video and computing. SUMMARY OF THE INVENTION: In the manufacture of cobalt magnetic particles, solutions of ferrous sulfate, potassium hydroxide, and zinc salts are mixed. The content of zinc is 0.5-1.5% by weight. The mixture is oxidized with atmospheric oxygen, filtered, washed and dried. The precipitate is reduced at 500 - 550 ° C. C and oxidized to gamma iron oxide at 330-370 ° C. C. Preparing an aqueous suspension of cobalt salt and gamma-iron oxide. Suspension disaggregate with to the size of the agglomerates 10-30 microns. The suspension is filtered, dried and subjected to heat treatment in a nitrogen atmosphere at 380 ° C. C. Positive effect: the resulting magnetic particles provide magnetic carriers with higher thermal stability, coercive force and orienting ability. 1 tab. sl C

Description

The invention relates to magnetic recording, and in particular to the technology of manufacturing magnetic powders for magnetic information carriers, and can be used in the manufacture of magnetic media for sound recording, video recording and computer technology.

The purpose of the invention is to increase the coercive force and orientation ability of magnetic particles.

The invention is based on the introduction of a zinc salt solution in the process of mixing solutions of ferrous sulfate and potassium hydroxide before crystallization & - FeOOH.a cobalt salts - in an aqueous suspension of gamma-iron oxide. The suspension is then subjected to disaggregation; it is disaggregated within seconds up to a value of agglomerates of 10-30 μm. The content of zinc added is 0.5-1.5 wt.%. The introduction of zinc as a modifying agent allows increasing the orientation and thermal stability of cobalted magnetic particles by increasing the axial ratio. The disaggregation process, as well as the addition of zinc in the powder synthesis process, allows cobalt ions to be positioned in a thin surface layer, which leads to an increase in the coercive force and orientation

 Yu

Jb vi

due to the production of more uniformly sized magnetic particles.

PRI me R 1. Obtaining cobalted magnetic particles in a known manner. 60 liters of iron sulfate solution with a concentration of 110-114 g / l are loaded into a 100-liter reactor, heated to 35-41 ° C, and sodium hydroxide solution is added with a concentration of 188-182 g / l in an amount of 7 liters to obtain the sulfate solution concentration iron 53-57 g / l. Then, the resulting solution is passed through an air bubbler in the amount of 43-47 l / min, carried out the oxidation of iron oxide hydrate to iron oxide monohydrate for 5-6 hours. The resulting germinal suspension is heated to 48-52 ° C, introduced air through the bubbler in the amount of 88-92 l / min for 7 hours while simultaneously feeding an alkali solution with a concentration of 120 g / l in the amount of 13 l and maintaining the pH of the process equal to 5.0-6.0. After completion of the synthesis, the pigment is treated with sodium hydroxide solution to pH 8.0-9.0, filtered and washed with water to pH 6.5-7.5. The resulting needle-like crystals of a-FeOOH are dried at 90 ° C, reduced to y-ResSC in an oven at 500-550 ° C, oxidized at 330-370 ° C to y-Fe203. The precipitation of zinc and cobalt hydroxides is carried out from solutions of the salts of these elements with sodium hydroxide solution. In a reactor with a capacity of 100 l load 32 l of a mixture of solutions of acetates of cobalt and zinc with a concentration of 60-70 g / l each. With continuous stirring, crushed gamma iron oxide is introduced in the amount of 5.85 kg. Disperse for 1 hour at room temperature. After that, a solution of sodium hydroxide with a concentration of 65-75 g / l is added until the pH of the reaction mixture is reached 8.0-9.0. Stir for 1 hour at room temperature. After the pH of the medium is reached, the reaction mixture is filtered, washed to pH 605-7.5 and dried. The obtained powder is subjected to additional heat treatment for 30 minutes in a nitrogen atmosphere at 380 ° C. The amount of added zinc and cobalt additives is 1.9-2.0% by mass.

PRI mme R 2. Obtaining cobalted magnetic particles by the proposed method. A 100 liter reactor is charged with 20 l of potassium hydroxide solution with a concentration of 430–450 g / l, 60 l of iron sulphate solution with a concentration of 124–128 g / l of zinc sulfate solution with a concentration of 61–65 g / l, which is calculated as zinc. is 0.5 wt.%. The process is carried out under a nitrogen atmosphere. Excess potassium hydroxide after

precipitation 40 g / l, pH 13.5. The contents of the reactor are heated to 50-55 ° C and air is supplied at a speed of 30 m3 / h with continuous stirring at a speed of 250 rpm. The end of the oxidation process is recorded by the change in the redox potential from 900 to 100 mV. 150 g of stearic acid is added to the resulting suspension and stirred for 2 hours. Freshly prepared goethite suspension is fed to a press filter, where it is washed with water from sulphate ions and excess alkali to pH 9.5. Thermal processing of the obtained goethite is carried out by high-temperature reduction of magnetite to ResSch at 500-550 ° C and subsequent oxidation to gamma-iron oxide y-FezOa.- Then a suspension is prepared consisting of 32 l of 30-40 g / l of cobalt acetate which, in terms of cobalt, is 1.0 wt.% and such an amount of gamma-iron oxide magnetic powder that the solids content is 10 wt.%. The prepared suspension goes through a disaggregation stage by grinding in a working container with multi-directionally rotating rotors for up to 30 µm agglomerates. At the same time, the cobalt salt is adsorbed on the surface of gamma-iron oxide particles. The resulting suspension is treated with a solution of potassium hydroxide with a concentration of 65-75 g / l to achieve a pH of the reaction mixture of 8.0-9.0, after which the suspension is filtered, dried and subjected to heat treatment in a nitrogen atmosphere for 30 minutes at 330-370 ° C

Examples 3-7 are carried out analogously to example 2 by varying the duration of disaggregation, the size of the agglomerates and the content of zinc injected.

Characteristics obtained in examples 1-7 cobalt magnetic particles in the table.

As can be seen from the results shown in the table, samples 2–4 have the best orientation and coercive force, in the manufacture of which the distinctive features of the invention are used. Upon leaving the time interval for disaggregation, as well as the content of additives, the powders are obtained with worse properties. Example 7 is provided to prove the need for the joint administration of zinc and cobalt to achieve the objective of the invention.

Inventions

A method of manufacturing cobalt magnetic particles based on gamma-iron oxide for a working layer of magnetic information carriers, including mixing solutions of ferrous sulphate and alkali metal hydroxide, oxidizing the resulting mixture with air oxygen, filtering, washing, drying, recovering the precipitate at 500-550 ° С and its oxidation to gamma-iron oxide at 330-370 ° C, the introduction of zinc and cobalt compounds and heat treatment at 380 ° C, characterized in that, in order to increase the coercive force and orienting ability of magnesium Particles, zinc compounds are introduced in the process of mixing solutions of ferrous sulphate and potassium hydroxide based on the content of injected zinc 0.5-1.5 May. %, and after introducing the cobalt compound into the aqueous suspension of gamma iron oxide, it is disaggregated within

with up to the size of agglomerates 10-30 microns.

Claims (1)

Fo mule of invention A method of manufacturing cobalted magnetic particles based on gamma-ox5 iron oxide for the working layer of magnetic information carriers, including mixing solutions of ferrous sulfate and alkali metal hydroxide, oxidizing the resulting mixture with oxygen, filtering, washing, drying, sediment recovery at 500-550 ° C and its oxidation to gamma-iron oxide at 330-370 ° C, the introduction of zinc and cobalt compounds and heat treatment at 380 ° C, characterized in that, in order to increase the coercive force and orienting ability of the magnetic particles, the zinc compound is introduced in the process of mixing solutions of iron sulfate and potassium hydroxide, based on the content of the introduced zinc of 0.5-1.5 May. %, And after the introduction of the cobalt compound in the aqueous suspension of iron oxide gamma disaggregate it for 10 ^'3 -10' ⁵ 10 to a value of 10-30 micron agglomerates. Example Content, wt.% Duration of processing, s Particle size, microns Ns, E Hf Thermostability in NS,% Thermostability in RF,% Orientation, dB zinc cobalt one 1.95 1.95 3600 - 530 2500 36 19.6 1,2 2 0.50 1.00 10 ' ³ thirty 556 2690 21 15.9 5.5 3 1,50 3.00 s- ⁵ 10 708 2480 33 18.2 2,5 four 1.10 2,30 W ⁴ twenty 630.5 2650 27 16.8 5,0 5 0.23 0.78 10 ' ⁷ fifty 538 2710 19 15.0 6.3 6 1.85 3.62 10 ' ¹ 10 770 2457 45 20.5 1,5 I 7 2,30 10 ' ⁴ twenty 690 2695 35 20,0 0.7