NL8601636A - METHOD FOR THE PREPARATION OF RARE EARTH CONTAINING MAGNETIC POWDERS - Google Patents

Description

NL 33608-Kp / dJ / cs

Method for the preparation of rare earth-containing magnetic powders.

The present invention relates to a process for the preparation of rare earth-containing powders, which are used for the production of sintered (agglomerated) permanent magnets.

5 From the publications Postojanie magniti - spravotschnik, isd. Energja, Moskva, 1971, p. 299, Japanese Journal of Appl. Phys., 1971, Vol. 10, No. 11, 1586-91, and Splavi redkih metallov s osobimi fisitscheskimi svojstvami. Redkosemelnie i blagorodnie metalli, Moskva, isd. Nauka, 1983, pages 58-60, 61-64, 64-69, etc., a process for the preparation of powders from rare earth alloys with ferromagnetic metals is known. The starting alloys are prepared by arc or high frequency melting of the high frequency starting metals in an atmosphere of particularly pure argon with homogenization for at least 1 hour at a temperature of 1200 ° C, followed by a low temperature treatment at 200 ° C for 1 hour. In the publications Japanese Journal of Appl. Phys., 1971, Vol. 10, No. 11, 1586-91 and IEEE, Trans.on Magnetics, 1980, no. 5, 991-993, the 20 bars are repeatedly comminuted with a mill in an inert atmosphere, while in Splavi redkih metallov s osobimi fisitscheskimi svojstvami. Redkosemelnie i blagorodnie metalli, Moskva, isd. Nauka, 1983, pp. 56-60, 61-64, 64-69 etc., this reduction is accomplished in ethyl alcohol by means of a centrifugal ball mill.

Disadvantages of this known method are: the high energy consumption in homogenizing the alloy, the need to work in an inert atmosphere, the high purity of the starting materials and the sustained production cycle, while requiring equipment of high quality especially when grinding the alloy.

The present invention now aims to provide a process for the preparation of a magnetic powder containing rare earths in the form of a finely dispersed anisotropic powder, wherein the process operations grind, using 7 1 * 7 * 7 The inert atmosphere, high temperatures, and the difficulties in homogenizing the alloy are avoided, while the high purity starting metals are replaced by salts of the same metals.

To this end, the process according to the invention is characterized in that solutions are mixed for the preparation, which water-soluble salts of rare earth metals, as well as those of iron, nickel, cobalt, copper and palladium, in a concentration of 1x10 up to 1x10 M / l, with an aqueous solution of a sodium borohydride or sodium hypo-phosphite reducer at a concentration of 0.05-1 M / l, at a temperature of 10-90 ° C and a reaction time of 1-30 min , using a permanent magnetic field with an intensity of 1 x 105 to 8 x 105 A / m, followed by washing and drying the prepared powder.

The essence of the invention therefore consists in carrying out the following process steps: preparing the starting solutions of the metal salts at certain concentrations, mixing them with a solution of a sodium borohydride or sodium hypophosphite reducer at a temperature of 10-90 ° C in the presence of a magnetic field with an intensity of 1x10 to 8x10 A / m, while stirring mechanically for 1-30 min, precipitating the prepared powder, washing (once or several times), drying of the finished product and packaging it.

The advantages of the process according to the invention are the following: the need to prepare the alloys by melting is avoided; no inert atmosphere nor a high purity starting metal is required; the work mode step and the equipment for grinding the alloys are unnecessary.

According to the proposed method, a powder with a high dispersion and an anisotropy of the shape of the particles is prepared, due to the possibility of obtaining the alloyed powder in a suitably oriented magnetic field at a lower temperature up to 90 ° C. The ratio between the components in the metal alloy is achieved much more precisely, due to the possibility of preparing the solutions 8 .- => pt ά \ A - / a 0 V 1 ϋ 3 *> - 3 - '2a with a more accurate concentration and performing the reduction in solutions, lacking the diffusion temperature shrinkage in the fusion of the mechanical metal mixture.

The invention is further elucidated by means of the following examples.

EXAMPLE I

An aqueous solution of metal salts in the following concentrations is prepared: 2.5 x 10 µM / l samarium-10 oxide and 0.025 M / l cobalt (II) chloride. Hydrochloric acid is used when dissolving samarium oxide, the solution thus prepared should have a pH value of 1. Dissolution takes place at room temperature or an elevated temperature up to 50 ° C under mechanical mixing.

Furthermore, an aqueous solution of the gear unit at the following concentrations is prepared: 0.13 M / l sodium boron hydride and 1.2 x 10 M / l sodium hydroxide.

The sodium borohydride is dissolved in a previously prepared aqueous solution of caustic soda 20 at the indicated concentration at room temperature and by mechanical mixing.

Both solutions are mixed in a reaction vessel, which is arranged in a magnetic field with an intensity of 5 x 10 A / m for 4 min at room temperature and under mechanical mixing.

The resulting melted powder is decanted, rinsed several times with water and acetone, then filtered and dried in a vacuum dryer. Its specific surface area is 98 m2 / g.

EXAMPLE II

An aqueous solution of the metal salts listed below is prepared in the following concentrations: 5 x 10 M / L-2 -3 samarium oxide, 5 x 10 M / L cobalt (II) chloride, 7.4 x 10 M / L 2 copper dichloride and 1.6 x 10 M / l iron dichloride.

Hydrochloric acid is used in dissolving the samarium oxide, the solution thus prepared should have a pH value of 1. Dissolution takes place at room temperature 8 SQ 1 S3 6 * βϊ * - 4 - temperature or at a slightly elevated temperature up to 50 ° C and under mechanical mixing. The solution indicated in Example 1 is used as the reduction solution.

Both solutions are mixed in a reaction vessel at room temperature for 2 min under mechanical mixing and using a permanent magnetic field at an intensity of 2x10 A / m. The melted powder is decanted, rinsed several times with water or acetone and dried under vacuum.

EXAMPLE III

An aqueous solution of the metal salts listed below is prepared at the following concentrations: 3 x 10 M / l gadolinium chloride and 7.5 x 10 M / l iron dichloride.

The gadolinium chloride is a water-soluble compound, but if required, a minimal amount of hydrochloric acid is added to prepare a true solution.

-4

As a final additive, 2 x 10 M / l * palladium dichloride is added to this solution. This is dissolved in concentrated hydrochloric acid at an elevated temperature. The solution of the metal salts should have an acid content corresponding to a pH of about 1.

An aqueous reduction solution with the following concentrations is prepared: 0.21 M / l sodium hypophosphite and caustic soda to a pH value of 11.

After heating the metal salts-containing solution to 90 ° C, the reducing agent solution is added while maintaining a pH value of about 11 and under mechanical mixing and using a permanent magnetic field.

After a certain reaction time, 15 min, the obtained melted powder is decanted, then rinsed several times with water and dried under vacuum.

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Claims (1)

- 5 - - - '+ + Process for the preparation of rare earth-containing magnetic powders, characterized in that for the preparation, solutions containing water-soluble salts of rare earth metals, as well as those of iron, nickel, cobalt, copper and palladium in a concentration of 1 x 10 -1 to 1 x 10 M / l, are mixed with an aqueous solution of a sodium borohydride or sodium hypophosphite reducer at a concentration of 0.05-1 M / l, at a temperature of 10-90 ° C and a reaction time of 1-30 min, using a permanent magnetic field with an intensity of 55 1 x 10 to 8 x 10 A / m, followed by washing and drying the prepared powder. 3 § 0 1 S 3 S