JPS5860504A - Magnetic powder and method of manufacturing the same - Google Patents

Abstract

PURPOSE:To attain magnetic powder with high coercive force and high intensity of saturated magnetization by adding rare-metal elements together with Co to Fe. CONSTITUTION:Magnetic powder contains Co, R.E. with Fe being a main ingredient. Co/Fe is 0.1-7wt% in atomic ratio, rare-metal elements/Co is 7-50wt% and iron consists of a needle crystal iron oxide, maghematitie (gammaFe2O3) or pure iron. Ce, Y, La, Sm, Pr, Cd, Tb, Dy, Ho, etc. can be used as rare-metal elements singularly or in the form of a mixture containing two or more among them. When both rare-metal elements and Co are used combinedly relative to iron oxide powder, the coercive force is improved up to a level of 700-800 oersted and the intensity of saturated magnetization sigmas becomes 80-90emu/g. Using of metal iron powder increases the coercive force up to a level of 1,100-1,300 oersted and results in metal powder with superior square ratio (sigmar/sigmas) and dispersibility.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic powder and its production, and more specifically, the present invention relates to a magnetic powder and its production, and more specifically, the present invention relates to a magnetic powder having excellent magnetism, a small spread of coercive force distribution, a high coercive force, and a large saturation magnetization σB. The present invention relates to a stable iron oxide powder that has powder properties such as high dispersibility, high orientation, and high filling properties, as well as its production.

The use of magnetic iron oxide, Fe, Oq + r Fe 205 powder or iron powder in magnetic tapes, magnetic disks, etc. has been widely used for a long time, and as a means of improving these, trace amounts of CO CO-containing compounds have also been added alone or together with Ou, Zn, etc., by thinly coating the surface of iron oxide crystals, and when iron hydroxide or goethite is being formed.

The behavior of Co added in a small amount to ferrite is truly interesting, and C02+ has the essential property of causing large magnetic anisotropy when added to the B position of Fe, 04.

The manner in which CO is added to Fe may be one in which Oof is uniformly distributed, or one in which a portion of CO is deposited on the surface of the powder particles.

The inventors succeeded in further improving the properties of the magnetic powder by adding a rare earth element to Fe along with the addition of Cof, and by manufacturing it by a specific method, the shape ratio was improved. By synthesizing particles that are large, uniform in size, and free of pores, we have achieved the development of unprecedentedly superior powder particles.

Rare earth elements are already yco5. Sm00610eC! o
A magnet with a large coercive force has been developed that is used as a powder magnet such as 6tPrCo5, and a part of this CO is replaced with Cu, but a mixture of Co and rare earth elements is added to iron instead of CO. The improvement in magnetism was quite surprising. In other words, its characteristics are a small spread of coercive force distribution, a large coercive force, and a large saturation magnetization (σB).
It also has high saturation magnetic flux, high high-density recording performance, excellent coercive force (Hc), and squareness ratio (σ, /σ5). Rare earth metals can be added to iron, aluminum, copper, or their alloys in small amounts to make crystals finer, or to improve or improve mechanical and chemical properties such as heat resistance and oxidation resistance. However, the only way to add it was to push it into the molten metal, making it extremely difficult to add it in any desired amount. Alternatively, it has been discovered that the magnetic properties of magnetic powder can be greatly improved by coating the surface of the iron powder. Furthermore, by using rare earth metals not only alone but also in combination with t-CO, it is possible to develop heat resistance and even better magnetic properties.

The magnetic powder according to the present invention has FEF as its main component.
NiC! o, R, E, i j) Co/Fe is 0.1 to 7% by weight in atomic proportion, preferably 0.5 to 3% by weight, rare earth element/Co is 7 to 50% by weight in atomic proportion %
, preferably 10 to 40% by weight. The main components of iron include acicular iron oxide, maghematite (γPe
20B) or iron, most preferably acicular iron oxide and acicular iron powder.

Examples of rare earth metal compounds include Ce, Y, and La.

Sm, Pr, Cd, Tby Er, Dy, Ho
etc., and these can be used alone or as a mixture of two or more. Mitsushmetal (Lancel 7 is also available as an additive for pyrotechnic alloys or metals (!% steel, aluminum, etc.), which is currently easily available as a commercial product. Among the rare earth elements, OeνE!m and Gd Particularly desirable are mixtures with

In addition to the above three components, the magnetic powder according to the present invention further contains C! By adding one or more of u, Zr, Ti, or V, the properties can be improved and an excellent magnetic powder can be obtained.

It is thought that by adding rare earth elements to iron oxide or at the time of goethite formation, the product maghematite or iron powder generally has an improved coercive force and therefore an improved volume resistivity.

For example, when rare earth metals and cobalt are used together with iron oxide powder, compared to when cobalt is simply added or when cobalt is used together with copper and zinc, the
The coercive force was about 700 to 80
The saturation magnetization σ has been improved to about 0 process level, and the saturation magnetization σ is 7.
0-85 emu/g is 80-90 emu
/ g. In addition, in the case of metallic iron powder, the coercive force, which was about 1000 to 1150 oersted at most, easily increases to about 1100 to 1600 oersted, and moreover, the squareness ratio (σr/σ,) is superior in dispersibility. It becomes metal powder.

The rare earth metal to be added may be added separately from Co or other additive components, but FL2Co, , ,
It can also be added as an alloy such as RCo5 (where 釠 stands for rare earth). Similarly, alloys with other components such as R
(Co, 5~.95Cu o~., 2Fe, .4'''-
[1,26zrO~0. [16) It can also be added as 5-9. In this case Co, Ou, H
For example, when the three components are ” (Coo, A~0.91
>CuO,1~G,2FeO,114~0.25
) Preferably 5 to 9 C added in addition to rare earth metals
Addition of iron oxide, iron powder magnetic material, etc., makes it have a dense structure with few voids, improves the temperature characteristics showing stability at high temperatures, and improves the manufacturing process, such as reduction and oxidation. This contributes to the prevention of deformation and destruction of needle-shaped crystals in processes such as

The magnetic powder according to the present invention also has a sufficiently large shape ratio, has uniform particle sizes, and satisfies the conditions required for magnetic powder, such as having uniform particle sizes and good dispersion during the production of magnetic paint. R is added, but n largely depends on the manufacturing method.

A typical manufacturing method will be explained below. First, Fe(OH
), Co(OH), and a rare earth metal dihydroxide, a water-soluble silicate or a water-soluble aluminum salt is added to an aqueous solution containing dihydroxide of a rare earth metal, and then an oxygen-containing gas is passed through the aqueous solution to remove CO and a rare earth metal. The desired product can be produced by forming the acicular α-Fe OOH particle crystals contained therein and reducing the acicular crystals obtained by sifting in a reducing gas. As the ferrous salt aqueous solution used in this case, ferrous sulfate aqueous solution and ferrous chloride aqueous solution are the most easily available and preferred from the viewpoint of handling, and salts of organic acids are also effective. Cobalt and rare earth metals can also be used as sulfates, nitrates or halides (
It is preferable to use it as a chloride or fluoride.

As the silicates and aluminum salts to be added to the solution, sodium and potassium silicates, commercially available colloidal silica, aluminum sulfates and chlorides, and commercially available colloidal alumina aqueous solutions can be used. The purpose of adding these silicates and aluminum salts is to promote the uniform formation of iron hydroxide crystal nuclei and flocs that are generated when an alkali is added to the iron compound and the additive metal compound, to suppress α~Pe00H crystal growth, and to suppress the growth of α~Pe00H crystals and during high-temperature treatment. The purpose is to prevent deformation of the crystal. Therefore, the amount of salts added in c) AI, 8A is small, AI! Or as Si, it is expressed as 0.0% by atomic weight based on the total amount of iron, cobalt and rare earth metals.
It may be 1 to 1.5%. The use of a large amount of silicate or aluminum salt is not preferred as it tends to produce particulate Fe, 04 and dilutes the magnetic properties of the alloy.

The n α-Pe 00H needle crystals obtained by the above method are further washed with water, separated from the grain, and reduced at 150 to 45.0°C to obtain gold R# powder, or are produced during the reduction. Fe, 0
4f-oxidize to γFe2O, powder. The powder thus obtained contains 0.1 to t O atoms, usually 0.2 to 0.7 atoms, of Si t or AJ based on the total metal content.

Alternatively, iron oxyhydroxide (Fe0OH), iron oxide (
Powder of Fe2O, or Fe, 04) is generated in advance, and the surface is coated with Re(000,!+ ~0.
95C'O~0.2Fe(1,04~.,25
"l+"-0,O5)? '-9゜FLe(COOj"-
[1,960,1~+1.2 0.04”-0,2!l
)S~? (Cu Fe and Re are rare earth metals) or cobalt,
The surface is coated or adsorbed with a solution of salts such as copper, Zr, Ti, V, etc., then an alkali is added and mixed with stirring, and if necessary, silicates and aluminum salts are added and stirred and mixed, followed by washing with water and r. Separate. The precipitate is reduced or further oxidized to obtain the desired magnetic powder.

The finer the metal powder, the greater the risk of spontaneous ignition; however, the following method is known to be effective in suppressing ignition, and this method is related to the present invention. It can also be applied to processing magnetic powder. That is, the material is first exposed to nitrogen containing about 1% oxygen, then oxidized by increasing oxygen, and finally left in air to form a thin oxide film.

The present invention will be explained in more detail below using examples. Unless otherwise specified, all percentages are based on weight.

Example 1 Aqueous solution 141 containing 1.5 mol/l of ferric sulfate obtained by adding cobalt sulfate and samarium sulfate to contain 2 atomic % of co and 0.3 % of Sm with respect to Fe was added with 3 N
Add about 141 liters of NaOH aqueous solution, then add water to 30
I made it J. Sodium silicate (Si028.5%) 22
g (si/ Fe+ Co +8m 0.5 atomic%
) was added, stirred and mixed, and the pH was adjusted to 13. At a temperature of 50° C., air was passed through at a rate of 2 DJ per minute for 15 hours to produce acicular α-FeOOH containing Co and Sm. The precipitate was washed with water, separated from P, dried, and ground. The needle-like crystals obtained in this way have the following components, and from electron micrographs, the average long axis length is 0.75 μm, and the shape ratio (long axis/short axis) is F! It was i4.

Co/Fe 1.96 atoms Sm
/ Fe O, 34-8i / (F
e +Oo+Sm )0.61 @Next, the above α-
300g of Fe00H powder in a retort with one end open
31 H2 gas at 0℃! The mixture was reduced at a rate of 1/min to obtain triiron tetroxide (magnetite) powder. From the electron micrograph, the average long axis is 0.6 μm, the shape ratio (long axis, 1 axis) F! 1
It was 1.

In addition, the magnetic properties are Coercive force Hc”7200e Saturation magnetization σt-90emu/1 Met.

Example 2゜200g of magnetite powder obtained in Example 1 was placed in air,
It was oxidized at 280° C. for 80 minutes to obtain r(peo) (maghematite). Electron micrograph 3 The average long axis was 0.6 μm, and the shape ratio (long axis/short axis) was 10.

Furthermore, the magnetic properties are Coercive force Hc=520oe Saturation magnetization σ = 80 emu/11.

Example 3゜Dry cake iog of α-Pe00H powder obtained in Example 1
was reduced at 350° C. with hydrogen at a rate of 317 min for 7 hours to obtain a magnetic powder with a °9O content (/Fe 2 ) of 1.9 at %. The magnetic properties were as follows: Coercive force Hc"42500e Residual flux density or = 65 em u/1 Saturation magnetic flux density σ5 = 158" Squareness ratio σγ/σs = 0.41.

Example 4 Instead of Sm, Oe, Pr, La, Y,
Tb.

Br, Dy, Ho and Mitsushmetal (S
The method of Examples 1-6 was repeated using mO,9,Gd O,1). As a result, a powder with almost the same magnetic characteristics and sound as when using Sm was obtained.

Example 5゜Co2.5 at%, CuO, 15 at%,
Aqueous solution 14 containing 1.5 mol/11 of ferrous sulfate to which n each n of sulfate was added so as to contain 0.5 atoms of Sm.
To 11, add about 141 ml of 3N NaOH aqueous solution, and further add water to make 30 I! And so. Aluminum sulfate (AI 8.
j%) 501r (Al/Fe/Co/Cu = 0.3%) was added and mixed with stirring, and the pH was adjusted to 12.
After adjusting the temperature to 50 to 60° C., air was passed through the reactor at a rate of 20/min for 15 hours to produce needle-shaped α-Fe 00H. This precipitate was washed with water, separated, dried, and pulverized.

This powder has the following composition, and from an electron micrograph, the average long axis is approximately 0.7 μm, and the shape ratio (long axis/short axis) is approximately 14.
Met.

Co/Fe = 195 atomic% Sm/
Fe=0.37-AJ/(Fe+O
o+C! u+sm)=0.4Cu/Co
= 21 above α-PeOOH powder 300
1r was poured into a glass cylindrical reactor, and 570"
The mixture was reduced by passing H2 gas through it at a rate of 61/min to obtain triiron tetroxide. This powder has an average major axis length of 0.6 μm and a shape ratio (major axis/minor axis) β10 from an electron micrograph, and its magnetic properties are as follows.

Coercive force HC' = 7300e Saturation magnetization σs = 91 emu/g Example 6゜ 200 gr of magnetite powder obtained in Example 5 was placed in air,
It was oxidized at 275°C for 80 minutes to obtain rFe20° (maghematite). From the electron micrograph, the average major axis length is 0.6
The shape ratio (major axis/minor axis) was 10, and the magnetic properties were as follows.

Coercive force HC = 5400e Saturation magnetic flux density σs '' = 84 'emu/g Example Z The α-FeOOH powder dry cake iog obtained in Example 5 was taken and passed through H2 gas at a rate of 3/min at 350°C for 7 hours. A magnetic powder with a Co/Pe atomic % of about 1.95% and the following magnetic properties was obtained.

Coercive force He: 12800e Residual flux density σr = 67 emu/g Saturation magnetic flux density σS 2165 emu/g Squareness ratio σr
/σs ””0.41 Example 8° Co2.2 atomic %, CuO, 6 atomic percent relative to Fe,
1.5 mol/11 of ferrous sulfate to which each sulfate was added so as to contain 0.4 atomic % of Sm and 0.3 atomic % of Zr.
Aqueous solution containing 14I! To this, 5N NaOH aqueous solution 1411 was added, and water was further added to make 301. Sodium silicate (8
Add 40228, 5%) 45.9・t, mix, and adjust the pH.
to 12! 20I at 50-60℃ after conditioning! Air was aerated for 15 hours at a rate of 1.5 min to produce needle-shaped α-F'eOOH. This precipitate was washed with water, separated, dried, and pulverized. This needle-shaped crystal has the following composition, and as seen from an electron micrograph, the average major axis length is approximately 0.7 μm, and the shape ratio (major axis/minor axis) is −1.
It was 4.

Co/Fe = 195 atomic% Sm
/Fe=0.3981/CF
e+Co+Cu+8m+ZF) = 0J5Cu/
Co = 0jZr / Co
= 0.14 above C1-PeoOH powder 3
0 powder was packed into an all-glass cylindrical reactor, and 30
31 H2 gas at 0'C! The mixture was reduced to obtain triiron tetroxide. From an electron micrograph, this particle has an average major axis length of 0. It had a diameter of 6 μm, a shape ratio (major axis/minor axis) of about 10, and had the following magnetic properties.

Coercive force Hc” = 7500e Saturation magnetic flux density σs = 95 emu/.!i
i' Example 9 Magnetite powder obtained in Example 8 200,! oxidize in air at 275"C for 80 minutes to obtain γF.
e2O3 maghematite was obtained.

The particles had an average major axis length of 0.6 μm, a shape ratio (major axis/minor axis ratio) of approximately 10, and the following magnetic properties.

Coercive force He: 6000e Saturation flux density σ, = 88 emu / 11 Examples
10° 10 g of the dried αFe0OH powder obtained in Example 8 was reduced to 360°C with H2 gas at a rate of 3/min for 4 hours until the co content (relative to Fe) was reduced to 1. A magnetic powder containing 9 atom % was obtained.

The magnetic properties are coercive force He = 14000e residual flux density 0γ = 70 emu / 1 saturation magnetic flux density It
'U', s = 170 emu/nonagonal ratio - σγ/σ, = 0.1.

Example 11゜In the method of Examples 8 to 10, Lr h is substituted for Zr.
, or V was used, and the same method was repeated to obtain substantially the same magnetic powder.

Example 12゜In the method of Examples 5 to 1o, Ce, Y is substituted for Sm.
2 Pr, La Others Y, Td, Br,
When the same method was repeated except for using Dy or Mitsushmetal, a magnetic powder similar to that of the powder was obtained.

Example 13゜Acicular crystal αFe0OH180j produced by a conventionally known method
i (2 mol) was dispersed in 91 water and stirred.

On the other hand, each of the following compounds was mixed with the respective amount of N (!:I
) CO8047H20? 5.211r CLISO45H202,I FirFeSO47H
z0 4. ! flrZr80a4H200,
61r Sm2(804)s 8H203, 99r1/dissolved in water and stirred, added to 91 water in which Fe0OH was dispersed, total? OA'.

After stirring for 30 minutes, add N-NaOH solution dropwise.
H to 8, then water glass (840228, 5%)
51 (Sr / (Fe+, α>, +Cu, 10Zr
+8m)=0.56%) was added and stirred at 60°C for 60 minutes.

After washing the precipitate with water, filtering, and drying, 9011r was heated at 350°C.
It was reduced with H2 gas.

Then, it was oxidized at 280° C. for 80 minutes to obtain γFe·2011 in an amount of 87 and 0.6% based on the total metal. From the electron micrograph, the average long axis of the particles is 0.7 μm, and the axial ratio is 10:1.
The coercive force Hc = 740 Oersted saturation magnetization σs = 90 emu/Ji'.

Example 14 10 g of the precipitate obtained in Example 13 was roasted and reduced with hydrogen at 450°C to obtain the following magnetic iron powder.

Coercive force = 1280 Oersted residual magnetic flux density σr = 68 emu / ji Saturation magnetic flux density σs = 166 emu / monogonal ratio σr/σ
s=0.41

Claims (1)

[Scope of Claims] 1. Magnetism characterized by having iron as a main component, coexisting with cobalt and rare earth elements, and containing AJ or Si in an amount of 0.1 to 0.7 atomic weight % based on the total amount of metals. powder. 10 2. The magnetic powder according to claim 1, wherein Co/Fe is 0.1 to 7 at % and rare earth metal/Co is 7 to 50 at %. 3. Contains iron as the main component, cobalt and rare earth elements, does not contain copper, and contains 0.1-M O, 7 atoms of AJ or Si based on the total amount of metals listed in 15 above. Characteristic magnetic powder. 4. Co/Fe 0.1-7 atomic%, rare earth elements. The magnetic powder according to claim 3, wherein the element/Co content is 7 to 50 at % and the O/Co content is 7 to 30 at %. 5 Mainly composed of iron, coexisting with cobalt, rare earth elements, and copper, and further containing at least one selected from Zi, Ti, and V, in an amount of 0.1 to 1.0 atomic % based on the total metal content. A magnetic powder characterized by containing A7 or Si. (5, Co/Fe is 0.1 to 10 at%, rare earth element/CO is 7 to 50 at%, Ou/Co is 10 to 60 at%, M/Co (where M is selected from ZrlTi and 7. The magnetic powder according to claim 5, wherein the amount of at least one compound (representing at least one kind) is 0.5 to 5 atomic %. prepared hydroxide and optionally Z
At least one selected from the group consisting of r, Ti and V
After adding a water-soluble silicate or a water-soluble aluminum salt to an aqueous solution with a pH of 10 or more containing a seed hydroxide,
Oxygen-containing gas is passed through the aqueous solution to form acicular crystals α- containing Co, rare earth elements, and other metals added.
A method for producing magnetic powder containing iron as a main component, which comprises reducing the needle-like crystals that have been produced and separated into Fe00H particles in a reducing gas. 8. A method for producing magnetic powder in which FeoOH particles containing added metal are reduced and then further oxidized.