JPS59157205A - Production of metallic magnetic powder - Google Patents

Abstract

PURPOSE:To obtain metallic magnetic powder having excellent oxidative stability by adding an aq. soln. prepd. by adding further a complexing agent to an Ni salt, etc. into an alkaline suspension of powder consisting essentially of iron oxide, metallic iron, etc. CONSTITUTION:A soln. formed by adding a complexing agent to an aq. soln. contg. an Ni salt or the Ni salt and a Cu salt is prepd. Such soln. is added into an alkaline suspension of powder consisting essentially of iron oxyhydroxide, iron oxide or metallic iron. An Ni complex compd. or the Ni complex compd. and a copper complex compd. are stuck on the surface of the above-described powder. The powder is then subjected to a heating reduction treatment and the metallic magnetic powder consisting of the metallic magnetic powder composed essentially of iron and the surface protective layer composed essentially of Ni or Ni and Cu formed on the particle surface thereof is obtd. The metallic magnetic powder having excellent oxidative stability is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing metal magnetic powder mainly useful for magnetic recording.

Metallic magnetic powder, mainly composed of iron, has a high coercive force and has been used for high-density recording, but it has inferior oxidation stability compared to oxide-based magnetic powder, and its magnetic properties tend to deteriorate over time. It has the disadvantage of being wet. In order to avoid such drawbacks, the inventors added an aqueous solution containing a nickel salt or a nickel salt and a copper salt to an alkaline suspension of a powder such as iron oxyhydroxide to coat the surface of the powder particles. By adhering nickel hydroxide or nickel hydroxide and copper hydroxide, and then subjecting it to stress and heat treatment, the metal magnetic powder mainly consisting of iron and the nickel or nickel and copper formed on the surface of the particles are combined. We have already proposed a method for obtaining metal magnetic powder consisting of a surface protective layer mainly composed of .

The metal magnetic powder obtained by this method has improved oxidation stability due to the surface protective layer mainly composed of nickel or nickel and nickel, resulting in less deterioration of magnetic properties over time. This invention was developed with the aim of obtaining a metal magnetic powder with even better oxidation stability by roughly improving the method related to the proposed method described in Section 2. The most significant feature of this invention is that a complexing agent is added to an aqueous solution containing a salt and a copper salt. A solution obtained by adding a complexing agent to an aqueous solution containing a nickel salt or a nickel salt and a copper salt is added to the suspension, and then neutralized to form a nickel complex compound or a nickel complex compound and a copper complex compound on the particle surface of the powder. and then heated and reduced to obtain a metal magnetic powder consisting of a metal magnetic powder mainly composed of iron and a surface protective layer mainly composed of nickel or nickel and copper formed on the particle surface. The present invention relates to a method for producing metal magnetic powder characterized by the following.

In this invention, when a complexing agent is added to an aqueous solution containing a nickel salt or a nickel salt and a copper salt, a water-soluble nickel complex compound or a nickel complex compound and a 1lijl complex compound are formed, and these compounds are stable against alkalis. Therefore, when it is added to an alkaline suspension of powder such as iron oxyhydroxide, crystals do not precipitate, but only when the liquid is neutralized by blowing carbon dioxide gas etc. into it, crystals precipitate and form on the particle surface of the powder. adhere to. In this way, the nickel complex compound or two, the nickel complex compound and the copper complex compound that are precipitated and adhered to the particle surface have a uniform coating property, so they are finally heated and reduced. The surface protective layer formed mainly of nickel or nickel and copper is also uniform, which provides better oxidation stability.

Examples of powders mainly composed of iron oxyhydroxide, iron oxide, or metallic iron used as starting materials in this invention include cl -Fe001(, β-Fe001-1
.

7-Fe001-1. ct-Fc203,1-F'e2
03. In addition to Fe30a and those corresponding to intermediate types thereof, and metallic iron, these include Ni, Go, Cr, M
n, Mg, Ca, Zn.

Examples include those containing metal components such as Sn and Si.
In particular, those with good acicular properties are preferably used.

In this invention, first, an alkaline solution of the above-mentioned powder (1) I-11] or more is prepared, and to this is added nickel salt such as nickel sulfate, nickel nitrate, nickel chloride G, or this nickel salt, steel sulfate, copper nitrate, A solution prepared by adding a complexing agent to an aqueous solution containing a copper salt such as copper chloride is added.

Here, whether to use a nickel salt alone or a combination of a nickel salt and a copper salt may be appropriately determined depending on the required degree of oxidation stability of the final target gold-plated magnetic powder. The combined use of nickel salt and copper salt provides better oxidation stability of the finally obtained metal magnetic powder than the use of nickel salt alone. The side content of Cu is 50% by weight or more, especially 60 to 90% by weight.
The oxidation stability of the metal magnetic powder is improved when the weight percentage is reduced.

As the complexing agent added to the aqueous solution containing these salts, alkali metal salts such as citric acid and tartaric acid are used, and an aqueous solution thereof is prepared in advance and mixed with the aqueous solution containing the above-mentioned salts. As a result of this mixing, a corresponding nickel complex compound or a copper complex compound thereof is rapidly formed, and these compounds remain stably dissolved even after addition of the alkaline suspension.

Next, when carbon dioxide gas is blown into the alkaline suspension or an acid such as hydrochloric acid is added to neutralize the liquid, the nickel complex compound or the copper complex compound is precipitated into crystals such as iron oxyhydroxide. It adheres to the surface of powder particles. It is preferable that the amount of M applied is 01 to 10% by weight based on metallic iron (compared to metallic nickel or metallic copper).

In addition, after or at the time of adhering the above nickel complex compound or (or this and the copper complex compound), in an alkaline state 7-shu solution (sodium orthosilicate, sodium metasilicate, potassium metasilicate, A water-soluble silicate such as water glass with a heavy composition or various water-soluble aluminum salts are added, and as in the case of the complex compound described above, silicic acid and silicic acid are deposited on the powder surface together with the complex compound. It is preferable to deposit an aluminum compound.In particular, the silicic acid film prevents sintering between powder particles and maintains the particle shape (acicularity) of the starting material during the heat reduction treatment in the subsequent process. As a result, the magnetic properties of the finally obtained metal magnetic powder (gives good results).The amount of adhesion should be such that the weight in terms of silicon atoms relative to metal iron is 0.1 to 15% by weight. It is desirable.

``After forming a nickel complex compound or a copper complex compound thereof and preferably a silicic acid film as described in 1, heat reduction treatment is performed.
Prior to the reduction treatment of the tobacco, it is preferable to heat it at a temperature of 300 to LOOO°C. The hydroxide is converted into an oxide by this heat treatment.

Further, such heat treatment facilitates alloying σ of metal nickel and iron formed in the subsequent heat reduction treatment, and also promotes alloying of nickel and copper. Thermal reduction treatment after heat treatment is generally carried out at a temperature of 300 to 600°C in hydrogen gas, and when the starting material is mainly composed of iron oxyhydroxide or iron oxide, it is converted into powder mainly composed of iron. At the same time as being reduced, the complex compound attached to the surface is reduced to metallic nickel or nickel and copper, and when the starting material is made of metallic iron, the nickel complex compound attached to the surface is similarly reduced. be done.

The metal magnetic powder obtained in this way consists of a metal magnetic powder mainly composed of iron and a surface protective layer mainly composed of nickel or nickel and copper formed on the surface of the particle. Since it is very uniform and in the form of a thin film, it has better oxidation stability and good initial magnetic properties.

In addition, in order to further improve the oxidation stability of the metal magnetic powder of the present invention obtained in this way, after the above-mentioned thermal reduction treatment, the powder is dispersed in an organic solvent such as toluene and air is blown thereto. It is desirable to provide a fine oxide film on the powder surface by a method such as mulching.

EXAMPLES Below, examples of the present invention will be described in more detail.

Example 1 28 g of α-iron oxyhydroxide powder with an average particle diameter of 0.5 μm and a qt ratio of 15 was suspended in 3 tons of 01N caustic soda aqueous solution σ
I set it. In this iL Shu solution, 2 mol/l of nickel sulfate (
NiSO4) aqueous solution IQmt (Ni is 6 compared to Fe
．． A mixed solution of 6% by weight) and 2 mol/l aqueous sodium citrate solution t o +nz was added. While stirring this, blow in carbon dioxide to adjust the pH of the liquid.
The mixture was neutralized until it became 8 or more particles, and a complex compound of nickel and citric acid was precipitated and adhered to the surface of the α-iron oxyhydroxide particles.

Next, the α-oxyhydroxide powder to which the complex compound had adhered was washed with water, dried, and then heat-treated in air at a temperature of 300°C for 2 hours to obtain iron oxide powder.
Suspended in o o mt of water, 5Qm of 1 mol/l of an aqueous solution of sodium chloride (Na4Si04) was added.
After adding and mixing t, carbonic acid was blown into pl-I.
LO and Ff were neutralized. Thereafter, the madder suspension was washed with water, dried, and then heated in air at 800° C. for 2 hours, and then heated and reduced in a hydrogen stream at 500° C. for 2 hours. A fine oxide film was formed by immersing the reduced product in toluene and stirring while blowing air into it.

The metal magnetic powder of the present invention thus obtained has an average particle diameter of 03 μm, a uniaxial ratio of 10, and a saturation magnetization of 44:
L: 32 cmu/g1 coercive force was 1370 2) qstead, square shape was 0.51.

Example 2 Instead of using a mixture of a 2 mol/1 nickel sulfate aqueous solution and a 2 mol/1 sodium citrate aqueous solution, 10 mt of a 2 mol/L nickel sulfate aqueous solution and 10 mt of a 2 mol/l sodium tartrate aqueous solution were used. A metal magnetic powder of the present invention was produced in exactly the same manner as in Example 1, except that a mixed solution of the present invention was used.

The average particle diameter of this powder is 0.3 μm, the uniaxial ratio is 10, the saturation magnetization is 132 emu/g, and the coercive force is 138
5 oersted, square type is 0.51 and a.

Example 3 Instead of using a mixture of 2 mol/7 nickel sulfate aqueous solution and 2 mol/1° sodium citrate aqueous solution,
An aqueous solution containing 0.30 mol/l of nickel sulfate and 0.645 mol/l of copper sulfate (2Qmt(Fe), whereas the total amount of Ni and Cu corresponds to 66% double healing, and the combination of Ni and Cu corresponds to The proportion of Cu in the total intake is 70
wt%) and 0.945 mol/l of sodium tartrate IJ
A metal magnetic powder of the present invention was prepared in exactly the same manner as in Example 1, except that a mixture with a 20 mA aqueous solution of aluminum was used. The average particle size of this powder was 03 μITI, the fineness was 10, the magnetization was 130 C111 u/g1, the coercive force was 1400 oersted, and the square shape was 0.51.

Example 4 28 g of α-oxyhydroxide iron powder having an average particle diameter of 05 μm and a uniaxial ratio of 15 was added to 3 L of 01N caustic/noda aqueous solution @7. This hard work! In solution A, 2 mol/1 nickel sulfate aqueous solution t o mt and 2 mol/L sodium citrate l)
A mixture of 10 mA of rum aqueous solution was added. Then,
50 mt of a 1 mol/1 sodium orthosilicate aqueous solution was added and mixed, and carbon dioxide gas was blown into this to adjust the pH of the liquid to 10.
Neutralized until below.

After that, the suspended matter was washed with water and dried, and then 80%
Heat treatment was performed at a temperature of 0°C for 2 hours, and further heat reduction treatment was performed at 500°C for 2 hours in a water-+:air flow.

A fine oxide film was formed by immersing the reduced product in toluene and then blowing a magnet into it.

The metal magnetic powder of the present invention thus obtained has an average particle diameter of 03 μm, an axial ratio of 10, and a saturation magnetization amount of L.
30 emu/g', coercive force 1400 oersted, square shape 0.51. Met.

Example 5 The same as Example 4 except that a suspension was used [Thus, the metal magnetic powder of the present invention was prepared. The average particle size of this powder is 030
μm uniaxial ratio is 8, saturation magnetization is 130 emu/g,
, + dumb magnetic force is 1495 oersted, li 3! i number・
It was 051.

Comparative Example 1 Instead of using one volume of a mixed solution of 2 mol/1 nickel sulfate aqueous solution and 2 mol/1 sodium citrate aqueous solution,
A metal magnetic powder was obtained in the same manner as in Example 1, except that a mol/l aqueous solution of nickel sulfate 1 (mz) was gradually added and neutralization by blowing carbon dioxide after the addition was not performed. The average particle diameter is 0.3 Jm, and the axial ratio is 10
, the saturation magnetization is 135 em u/g, and the coercive force is 14
10 oersted, square shape H: 052.

Comparative Example 2 Instead of using a mixed solution of a 2 mol/L nickel sulfate aqueous solution and a 2 mol/L sodium citrate aqueous solution, 10 n1t of a 2 mol/L nickel sulfate aqueous solution was gradually added. A metal magnetic powder was prepared in the same manner as in Example 4. The average particle diameter of this powder is 03 μm, uniaxial ratio t
Yo10, the saturation magnetization is L32emu/g, and the coercive force is 14
It was 50 oersted and the square shape was 0.52.

Comparative Example 3 Step of precipitating a complex compound of nickel and citric acid on the particle surface of α-oxyiron hydroxide powder and subsequent washing with water,
Drying and heat treatment (to produce iron oxide powder)] - Exactly the same as in Example 1 except that 6 culms were used (1.g of strained gold + fi powdered rice powder. The average particle size of this powder was 03 μm, uniaxial ratio is 10, and the amount of saturation magnetization is L 2 s emu/g.

The coercive force was 1530 oersted, and the square shape was 0.52.

The metal magnetic powder according to each of the above examples and comparative examples was heated at 6σ℃.
, the deterioration rate of saturation magnetization after being left in an atmosphere of 90% RH for 7 days; the result of examining [(initial saturation magnetization - saturation magnetization after oral administration)/initial saturation magnetization) x 100% is , were as follows.

Degradation rate of saturation magnetization Example 1 38% Example 2 39% Example 3 26% Example 4 41% Example 5 41% Comparative example 1 48% Comparative example 2 51% Comparative example 3 109% From the above results As is clear, the metal magnetic powder of the present invention has excellent oxidation stability and exhibits less decline in magnetic properties after storage over time.

Claims (1)

[Claims] tL) Alkaline suspension of powder mainly composed of iron oxyhydroxide, iron oxide or (metallic iron) l-Adding a complexing agent to an aqueous solution containing nickel salt or nickel salt and copper salt /P7. After adding a solution consisting of iron, it is neutralized to attach a nickel complex compound or a nickel button compound and a copper complex compound to the particle surface of the powder, and then heat reduction treatment is performed to obtain a metal magnetic powder mainly composed of iron. and a surface protective layer mainly composed of nickel or nickel and steel formed on the surface of the particles.