JP2003193117A - Method of producing iron-rhodium magnetic powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide iron-rhodium magnetic powder whose alloy composition can correctly be controlled to develop its use by applying peculiar magnetic properties of the conventional iron-rhodium magnetic powder, and to provide a synthesis method therefor. <P>SOLUTION: In the method of producing iron-rhodium magnetic powder consisting of iron and rhodium, iron-rhodium magnetic powder in which x in the case the iron-rhodium alloy components are expressed by Fe<SB>1-x</SB>Rh<SB>x</SB>is 0.4 to <0.8, and the grain sizes lie within the range of 20 nm to 200 μm is produced by using an aqueous solution containing the ions of iron and rhodium. <P>COPYRIGHT: (C)2003,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a magnetic powder containing iron and rhodium as constituent elements at least.

[0002]

2. Description of the Related Art Iron-rhodium alloys are known for having unique magnetic properties ("Physics of Ferromagnetic Materials", by Toshinobu Chikagu,
Shokabo etc.). The present inventors believe that it is indispensable to make this alloy into fine particles for practical use, and as a result of repeated studies, as a basic process of synthesizing iron-rhodium-based magnetic powder, the raw materials iron and rhodium were used. Mix the compounds containing
By developing a process in which an alloy powder is obtained by adding an alkali to obtain a precipitate containing these components and heating them in a reducing atmosphere, the particle size is in the range of 20 nm to less than 200 μm. Has succeeded in producing an iron-rhodium-based magnetic powder.

[0003] However, the iron-rhodium-based magnetic powder produced by the above-mentioned synthesis method goes through a coprecipitation step using an alkali. Therefore, depending on the type of alkali used and the pH at the time of coprecipitate formation, rhodium is used. Hydroxide is hardly generated, and it may be difficult to accurately control the composition of iron and rhodium.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a method of manufacturing an iron-rhodium-based magnetic powder for the purpose of accurately controlling the composition of an iron-rhodium-based magnetic powder. We worked on improvement and succeeded.

[0005]

As a basic process, the present inventors prepare an aqueous solution containing at least iron and rhodium ions, heat this aqueous solution to remove moisture, and contain at least iron and rhodium. A steamed product was prepared. Next, the steamed product was reduced by heating to obtain an iron-rhodium-based magnetic powder.

As a result, the iron-rhodium alloy magnetic powder produced by the above-described method for producing a magnetic powder is an iron-rhodium alloy magnetic powder containing at least iron and rhodium as constituent elements, and the iron-rhodium alloy component is Fe When expressed as _1-x Rh _x, it was an iron-rhodium-based magnetic powder in which x was 0.4 or more and less than 0.8 and the particle size was in the range of 20 nm or more and less than 200 μm.

Further, it has been found that the iron-rhodium-based magnetic powder produced by the above-described production method exhibits unique magnetic properties similar to those of the iron-rhodium-based magnetic powder produced by the conventional production method.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail below. In the production method of the present invention, iron as a raw material,
By dissolving a compound containing at least rhodium and an additive element in an aqueous solution and neutralizing with an alkali, a precipitate containing these components is obtained and heated in a reducing atmosphere to obtain an alloy powder. The process was used. Hereinafter, the manufacturing method will be described step by step.

(Preparation of Precipitate) At least an iron salt and a rhodium salt and an additional element are dissolved in water to prepare a solution containing at least iron ions and rhodium ions. The iron salts used at that time include iron nitrate, iron sulfate, iron chloride,
Rhodium salts such as iron acetate include rhodium nitrate, rhodium chloride and rhodium acetate. Palladium, ruthenium, iridium, platinum, gold,
It may include silver, osmium, aluminum, titanium, silicon, boron, rare earth elements and compounds thereof.

There are two types of additives: a component which forms a solid solution with iron and rhodium by reduction in a stream of hydrogen, and a component which is not reduced by reduction in the stream of hydrogen and remains in an oxide state.

[0011] Examples of the solid solution component include palladium, ruthenium, iridium, platinum, gold, silver and osmium. These solid-soluble components are preferable as additive elements for controlling the transition temperature.

The components which do not form a solid solution include aluminum,
Examples include titanium, silicon, boron, and rare earths. These have an effect mainly on micronization since they hinder the particle growth during the reduction and the subsequent heat treatment step.

In the present invention, the composition of iron, rhodium and additional elements was first examined. As a result, the iron-rhodium alloy component in the iron-rhodium alloy powder was changed to Fe _1-x Rh _x M
When represented as _y , it is preferable that x is 0.4 or more and less than 0.8. This is because if x is less than 0.4, the magnetic transition becomes difficult to be observed because the abundance ratio of iron exhibiting ferromagnetism becomes large, and if x is 0.8 or more, there is no magnetism. Because the proportion of rhodium in the reaction is relatively large,
This is because the saturation magnetization does not show a significant change.

Further, y is preferably 0.001 or more and 0.1 or less. The magnetic transition temperature of the iron-rhodium-based magnetic powder when no additional element is added is about 120 ° C.
When y is 0.001 or less, no significant change in transition temperature is observed, and no effect of temperature control by the added element is observed. When y is 0.1 or more, it becomes difficult to measure the transition temperature. This is because, when M has the effect of lowering the transition temperature, in addition to the low transition temperature of the obtained iron-rhodium-based magnetic powder, the iron-rhodium-based magnetic powder exhibits temperature hysteresis, This is because cooling cannot be performed until the ferromagnetic state is reached within the measurement temperature range. On the other hand, if M has the effect of raising the transition temperature, the transition temperature may exceed the measurement temperature range.
Further, when y is 0.1 or more, the ratio of the unreacted additional element having no magnetism becomes relatively large, and thus a significant change in the saturation magnetization tends to be reduced.

As additional elements other than iron and rhodium, palladium, ruthenium, iridium, platinum, gold, silver, osmium, aluminum, titanium, silicon, boron, rare earth elements and compounds thereof may be included. These additional elements are effective in adjusting the magnetic transition temperature described later.

The aqueous solution was heated to remove water, and was heated and steamed to produce a product containing at least iron and rhodium.

(Oxidation Step) It is preferable that the above-mentioned product is heated and oxidized in air to remove water and the like contained in the precipitate in advance. The heat treatment temperature is preferably in the range of 200 ° C. to 500 ° C., but omitting the oxidation step does not significantly affect the properties of the final iron-rhodium alloy magnetic powder.

(Surface Treatment Step) The above-mentioned oxide may be dispersed in a surface treatment agent to perform a surface treatment. Examples of the surface treating agent include a sodium silicate aqueous solution and a boric acid solution.

(Reduction Step) The above oxide is reduced by heating in a hydrogen stream to produce an iron-rhodium alloy powder. Next, after cooling to room temperature while flowing hydrogen gas, the gas is switched to nitrogen gas and taken out into the air.

The reduction temperature is from 300.degree.
A range of 0 ° C. is preferred. When the temperature is lower than this temperature, particularly, iron is not sufficiently reduced, and it is difficult to form a uniform iron-rhodium alloy. If the temperature is too high, the particle size becomes too large due to sintering.

Next, the magnetic characteristics will be described. Iron-rhodium alloys are known to exhibit unique temperature dependence of magnetic properties. That is, at temperatures below about 150 ° C,
Although it shows almost no spontaneous magnetization and the saturation magnetization is almost zero, in a temperature range of about 150 ° C. to 200 ° C., the saturation magnetization rapidly increases to about 100-130 emu / g. The temperature at which the saturation magnetization changes sharply is called the magnetic transition temperature.

When an iron-rhodium alloy exhibiting ferromagnetism by magnetic transition is cooled to a temperature lower than the magnetic transition temperature, it returns to antiferromagnetism while substantially following the original curve in the case of bulk.
The saturation magnetization becomes zero. In the case of the iron-rhodium-based magnetic powder, the saturation magnetization remains even when the temperature becomes lower than the magnetic transition temperature, and the saturation magnetization shows temperature hysteresis.

Further, it is known that the magnetic transition temperature varies depending on the alloy composition of iron and rhodium and the addition of the above-mentioned palladium and iridium.

Further, the X-ray diffraction spectrum will be described. Iron-rhodium alloy has a CsCl type crystal structure,
It is known that the maximum intensity peak appears near 43 degrees in the X-ray diffraction spectrum. The iron-rhodium-based magnetic powder of the present invention showed an X-ray diffraction spectrum corresponding to the iron-rhodium alloy. Further, peaks corresponding to metallic rhodium and metallic iron may be observed. This X-ray diffraction spectrum and the above-mentioned magnetic properties were examined in detail, and the iron-rhodium-based magnetic powder of the present invention showed that
It is unknown how the metal rhodium is distributed, but if temperature hysteresis is observed in the magnetic properties, the peak corresponding to the metal rhodium in addition to the iron-rhodium alloy in the X-ray diffraction spectrum It turned out to be observed.

[0025]

The present invention will be described below with reference to examples. Example 1 0.00092 mol of iron (III) nitrate and 0.1%
001 mol of rhodium (III) nitrate was dissolved in 50 cc of water. This aqueous solution was heated at 100 ° C. to remove water, and a steamed product containing iron and rhodium was produced.

Next, the steamed product was heated at 250 ° C. for 2 hours to remove oxides of iron and rhodium.

This surface-treated oxide is placed in a hydrogen stream at 500 ° C.
For 2 hours to produce an iron-rhodium alloy powder. Next, the mixture was cooled to room temperature while flowing hydrogen gas, and taken out into the air to obtain an iron-rhodium alloy magnetic powder.

The iron and rhodium contents were examined by X-ray fluorescence. As a result, when expressed as Fe _1-x Rh _x , x was 0.521.
Met. The particle size of the iron-rhodium-based magnetic powder was about 50 μm.

FIG. 1 shows the temperature dependence of the saturation magnetization of the iron-rhodium based magnetic powder. Table 1 shows the results in which the main magnetic characteristics such as the magnetic transition temperature and the saturation magnetization changed by the magnetic transition are summarized.

Example 2 In the preparation of the iron-rhodium-based magnetic powder of Example 1, 0.00092 mol of iron nitrate (I
A coprecipitate was formed in the same manner as in Example 1 except that 0.0008 mol of iron (III) nitrate was used in place of II). A rhodium alloy was prepared.

The iron and rhodium contents were examined by X-ray fluorescence. As a result, when expressed as Fe _1-x Rh _x , x was 0.588.
Met. The particle size of the iron-rhodium-based magnetic powder was about 45 μm.

FIG. 2 shows the temperature dependence of the saturation magnetization of the iron-rhodium-based magnetic powder. Table 1 shows the results in which the main magnetic characteristics such as the magnetic transition temperature and the saturation magnetization changed by the magnetic transition are summarized.

Example 3 In the preparation of the iron-rhodium-based magnetic powder of Example 1, 0.00092 mol of iron nitrate (I
A coprecipitate was formed in the same manner as in Example 1 except that 0.001 mol of iron (III) nitrate was used in place of II). A rhodium alloy was prepared.

As a result of examining the iron and rhodium contents by X-ray fluorescence, when expressed as Fe _1-x Rh _x , x was 0.506.
Met.

FIG. 3 shows the temperature dependence of the saturation magnetization of the iron-rhodium-based magnetic powder. Table 1 shows the results in which the main magnetic characteristics such as the magnetic transition temperature and the saturation magnetization changed by the magnetic transition are summarized.

Comparative Example 1 In the preparation of the iron-rhodium-based magnetic powder of Example 1, 0.00092 mol of iron nitrate (I
II) and 50 cc of 0.001 mol of rhodium (III) nitrate
In addition to the aqueous solution dissolved in water, a 0.05 mol aqueous sodium hydroxide solution was prepared and mixed with the aqueous solution to produce a precipitate containing at least iron and rhodium. P at this time
H was about 12. The suspension containing the precipitate is washed with water,
The filtered and dried product was replaced with the steamed product in Example 1, and the subsequent steps were the same as in Example 1 and reduced by heating to produce an iron-rhodium alloy.

The iron and rhodium contents were examined by X-ray fluorescence. As a result, when expressed as Fe _1-x Rh _x , x was 0.25.
It was 4.

FIG. 4 shows the temperature dependence of the saturation magnetization of the iron-rhodium-based magnetic powder. Table 1 shows the results in which the main magnetic characteristics such as the magnetic transition temperature and the saturation magnetization changed by the magnetic transition are summarized.

Comparative Example 2 In the preparation of the iron-rhodium-based magnetic powder of Example 1, 0.00092 mol of iron nitrate (I
II), instead of 0.001 mol of rhodium (III) nitrate,
A coprecipitate was formed in the same manner as in Example 1 except that only 0.002 mol of iron (III) nitrate and 0.001 mol of rhodium (III) nitrate were used, washed with water, filtered and dried. It was reduced by heating to produce an iron-rhodium alloy.

The content of iron and rhodium was examined by X-ray fluorescence. As a result, when expressed as Fe _1-x Rh _x , x was 0.326.
Met.

FIG. 5 shows the temperature dependence of the saturation magnetization of the iron-rhodium-based magnetic powder. Table 1 shows the results in which the main magnetic characteristics such as the magnetic transition temperature and the saturation magnetization changed by the magnetic transition are summarized.

<Measurement Result of Temperature Dependence of Saturation Magnetization Amount of Iron-Rhodium Alloy Magnetic Powder> FIGS.
4 to 5 show the temperature dependence of the saturation magnetization of the iron-rhodium-based alloy magnetic powders manufactured in Comparative Examples 1 and 2, respectively.

Fe _{0 . 479} Rh _{0 .} Example 1 represented by ₅₂₁
As shown in FIG. 1, the iron-rhodium alloy magnetic powder exhibits a saturation magnetization of about 10 emu / g at a temperature of about 100 ° C. or less. This saturation magnetization is considered to be due to the appearance of saturation magnetization due to iron present in addition to the iron-rhodium alloy magnetic powder.

On the other hand, when the temperature of the magnetic powder is raised to 80 ° C. or higher, the iron-rhodium-based alloy magnetic powder is changed from antiferromagnetic to ferromagnetic by magnetic transition at a temperature of 100 to 120 ° C., and the saturation magnetization is about 110 emu. / G rapidly increases. When the temperature is further raised to 300 ° C., the saturation magnetization slightly decreases.

Next, when the temperature is lowered from 300 ° C., the original magnetization curve is followed until about 80 ° C. at which the magnetic transition occurs.
Below 0 ° C., it does not follow the original curve and shows hysteresis. That is, for example, at 10 ° C. where the magnetic transition starts, about 110 e
It shows a saturation magnetization of mu / g, and shows a saturation magnetization of about 30 emu / g even when the temperature is lowered to room temperature of 20 ° C. When the temperature is further lowered to about 100 ° C., the saturation magnetization becomes about 10 emu / g, which is almost the initial value, indicating that the iron-rhodium alloy magnetic powder returns to the antiferromagnetic state before the temperature rise. .

[0046] Figure 2, the iron of the second embodiment having a composition of Fe _{0. 412} Rh _{0. 588} - shows the temperature dependence of the saturation magnetization amount of rhodium-based alloy magnetic powder. The saturation magnetization before magnetic transition is about 5e
The saturation magnetization increases to 80 emu / g due to the magnetic transition at 100 to 120 ° C. The reason why the saturation magnetization after the magnetic transition is smaller than that of the magnetic powder of Example 1 is considered to be that the content of rhodium that does not show magnetism is larger than that of the magnetic powder of Example 1. However, even in this magnetic powder, remarkable hysteresis is still observed due to the magnetic transition.

[0047] Figure 3 is a third embodiment of the iron with a composition of Fe _{0. 494} Rh _{0. 506} - shows the temperature dependence of the saturation magnetization amount of rhodium-based alloy magnetic powder. The saturation magnetization before magnetic transition is about 60e
The saturation magnetization increases to 120 emu / g due to the magnetic transition at 100 to 120 ° C. The reason why the saturation magnetization before the magnetic transition is large as compared with Examples 1 and 2 is considered that the saturation magnetization due to iron present in addition to the iron-rhodium alloy magnetic powder is relatively large. Can be

FIG. 4 shows the temperature dependence of the saturation magnetization of the iron-rhodium based magnetic powder of Comparative Example 1. This magnetic powder is F
represented by e _{0. 746} Rh _{0. 254.} This is presumably because the production of rhodium hydroxide was difficult due to the high pH at the time of preparation of the precipitate. This iron-rhodium based magnetic powder,
No magnetic transition is exhibited, and the saturation magnetization monotonically decreases with increasing temperature.

FIG. 5 shows the temperature dependence of the saturation magnetization of the iron-rhodium based magnetic powder of Comparative Example 2. This magnetic powder is F
represented by e _{0. 689} Rh _{0. 326.} This iron-rhodium-based magnetic powder does not show a magnetic transition, and as the temperature increases,
The saturation magnetization decreases monotonically.

FIG. 6 shows an X-ray diffraction diagram of the iron-rhodium alloy magnetic powder of Example 1. A sharp diffraction peak based on the iron-rhodium alloy is observed. Further, in addition to the iron-rhodium alloy, a minute diffraction peak based on a small amount of unreacted metal rhodium is also observed. In the iron-rhodium-based magnetic powder of the present invention, it is unknown how this metal rhodium is distributed, but when temperature hysteresis is observed in the magnetic properties, in the X-ray diffraction spectrum, It is known that peaks corresponding to metal rhodium in addition to the rhodium alloy are observed. FIG. 7 shows an X-ray diffraction diagram of the iron-rhodium-based magnetic powder of Comparative Example 1. Although this iron-rhodium-based magnetic powder does not show a magnetic transition, a sharp diffraction peak based on the iron-rhodium alloy is observed. From this, it can be seen that although an iron-rhodium alloy was formed in this magnetic powder, it did not exhibit magnetic transition.

Composition, magnetic transition temperature (Ttrs), saturation magnetization due to magnetic transition of iron-rhodium alloy magnetic powders prepared in Examples 1 to 3 and iron-rhodium alloy magnetic powders of Comparative Examples 1 and 2. Change (ΔMtrs), saturation magnetization before magnetic transition (Mint), saturation magnetization after magnetic transition (Mt)
ras), and the saturation magnetization (Mrmt) at 20 ° C. when the temperature rises above the magnetic transition temperature and falls below the temperature at which the magnetic transition occurs, and ΔMd which is the difference between Mrmt and Mint.
If is summarized in Table 1.

The magnetic transition temperature was defined as an intermediate temperature between the temperature at which the magnetic transition starts and the temperature at which the magnetic transition ends. When the temperature is further increased after the magnetic transition, the saturation magnetization decreases. Therefore, the saturation magnetization after the magnetic transition is the maximum saturation magnetization after the transition.

[0053]

[Table 1]

As is clear from Table 1, the iron-rhodium based magnetic powders shown in the examples show a magnetic transition at about 120 ° C. Further, the iron-rhodium-based magnetic powder shown in the comparative example,
No magnetic transition temperature was observed. Further, the iron-rhodium-based magnetic powder shown in the examples has a variation in saturation magnetization due to magnetic transition (ΔMtrs), a saturation magnetization before magnetic transition (Mint), a saturation magnetization after magnetic transition (Mtras), And the saturation magnetization (Mrm) at 20 ° C. when the temperature is raised to a temperature equal to or higher than the magnetic transition temperature and is lowered to a temperature equal to or lower than the temperature at which the magnetic transition occurs.
t) are observed, but in the iron-rhodium-based magnetic powder having a large palladium content shown in the comparative example, only the saturation magnetization (Mrmt) at 20 ° C. is observed, and no other characteristics are observed. . Saturation magnetization after magnetic transition (Mtr
as) tends to decrease as the rhodium content increases. This is presumably because the relative amount of rhodium that does not exhibit magnetism increases, and the saturation magnetization per unit weight of the alloy decreases. Also, the saturation magnetization (Mint) before the magnetic transition tends to decrease as the rhodium content increases. This is also thought to be because the content of iron exhibiting ferromagnetism is relatively reduced. On the other hand, the amount of change in the saturation magnetization due to the magnetic transition (ΔMtr
s) indicates the maximum in the case of the first embodiment.

In this embodiment, the variation (ΔMtrs) of the saturation magnetization due to the magnetic transition is 66 emu / g to 92 emu.
/ G, but by changing the added element and the heat treatment conditions similarly to the magnetic transition temperature, 10 emu / g to 200 em
It can be prepared in the range of u / g.

When the X-ray diffraction spectrum of the iron-rhodium alloy powder used in Examples 1 to 3 and Comparative Example was measured, an X-ray diffraction spectrum specific to the ordered iron-rhodium alloy was observed. . Iron with a composition ratio of 1: 1
It is known that the crystal structure of the rhodium ordered alloy is a cesium chloride type structure, but in the iron-rhodium-based alloy powder of the present invention, at least an X-ray diffraction spectrum specific to the iron-rhodium ordered alloy is provided. Observed.

[0057]

As described above, the iron-rhodium-based alloy powder of the present invention can accurately control the alloy composition of iron and rhodium, and can exhibit the unique magnetic properties of the iron-rhodium-based magnetic powder. It is a great help to take full advantage. Therefore, the alloy powder of the present invention is an alloy powder particularly suitable for a medium requiring temperature control, and its industrial utility value is extremely large.

[Brief description of the drawings]

FIG. 1 is a diagram showing the temperature dependence of the saturation magnetization of the iron-rhodium-based magnetic powder of Example 1.

FIG. 2 is a diagram showing the temperature dependence of the saturation magnetization of the iron-rhodium-based magnetic powder of Example 2.

FIG. 3 is a graph showing the temperature dependence of the saturation magnetization of the iron-rhodium-based magnetic powder of Example 3.

FIG. 4 is a diagram showing the temperature dependence of the saturation magnetization of the iron-rhodium-based magnetic powder of Comparative Example 1.

FIG. 5 is a diagram showing the temperature dependence of the saturation magnetization of the iron-rhodium-based magnetic powder of Comparative Example 2.

FIG. 6 is an X-ray diffraction diagram of the iron-rhodium-based magnetic powder of Example 1.

FIG. 7 is an X-ray diffraction diagram of the iron-rhodium-based magnetic powder of Comparative Example 1.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Shinichi Kitahata             1-88 Usutora, Ibaraki-shi, Osaka             Kusel Corporation F term (reference) 4K017 AA04 BA02 BA06 BB02 BB06                       DA02 EH01 EH18 FB06                 5E040 AA11 CA01 HB17 NN01 NN06

Claims (3)

[Claims] 1. A steel, iron and at least constituent elements rhodium - a process for the preparation of a rhodium-based magnetic powder, iron - rhodium alloy component Fe _{1 -} when expressed as _x Rh _x, x is 0.4 Not more than 0.8 and the particle size is 20 n
A method for producing an iron-rhodium-based alloy powder, characterized in that an iron-rhodium-based magnetic powder having a diameter of not less than m and not more than 200 μm is prepared using an aqueous solution containing at least iron and rhodium ions. Wherein iron, iron and at least constituent elements rhodium - a rhodium alloy powder, iron - when a rhodium-based alloy components, expressed as _{Fe 1-x Rh x M y} , adding M is any element Wherein x is 0.4 or more and less than 0.8, and y is 0.001 or more and less than 0.1, and the particle size is in a range of 20 nm to 200 μm. The magnetic characteristic can be controlled by changing the values of x and y.
A method for producing the iron-rhodium-based magnetic powder according to the above. 3. An aqueous solution containing at least iron and rhodium is heated and vaporized, and the obtained product is reduced by heating to reduce iron-
3. The method for producing an iron-rhodium-based magnetic powder according to claim 1, wherein a rhodium-based magnetic powder is obtained.