JP2014231624A - METHOD FOR PRODUCING Fe-Ni ALLOY POWDER, Fe-Ni ALLOY POWDER AND MAGNET - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing Fe-Ni alloy powder capable of artificially synthesizing Fe-Ni alloy powder having higher coercive force in a stable way.SOLUTION: Provided is a method for producing Fe-Ni alloy powder comprising: a precursor preparation step S1 of preparing a powdery precursor composed of a mixture of an Fe-containing compound made of an Fe-containing inorganic compound and an Ni-containing compound made of an Ni-containing inorganic compound; an alloying step S2 of mixing the precursor and a reducing agent capable of reducing the precursor and heating the obtained mixed powder at 320°C or lower to obtain alloy powder including the Fe-Ni alloy; and a cleaning step S3 of cleaning the alloy powder and removing impurities. The molar fraction of Fe in the precursor lies in the range of 0.5 to 0.9.

Description

  The present invention relates to a method for producing an Fe—Ni alloy powder, an Fe—Ni alloy powder, and a magnet.

The ordered alloy of Fe: Ni = 1: 1 is called tetrathenite, and has attracted attention as a new magnet material that does not use rare metals and rare earths. Tetrathenite is known to have a high coercivity. The coercive force of a normal Fe—Ni alloy is 100 A / m or less, whereas natural tetrathenite present in iron meteorite has a high coercive force of about 100 kA / m. Specifically, natural tetrathenite exists in the grain boundary layer of iron meteorite and is produced through a cooling process at a very slow cooling rate of −10 ⁻⁶ ° ^C./year from a molten state at a high temperature. It is considered a thing.

In recent years, attempts have been made to artificially synthesize Fe-Ni alloys containing tetrathenite. For example, in Patent Document 1, precursor particles containing a reducing agent and having a Fe: Ni molar ratio of 1: 1 are heated in a hydrogen atmosphere to reduce the precursor particles, and the structure of the alloy particles is L1. method for producing an L1 ₀ type iron-nickel alloy particles are ordered in ₀ type, magnet made from the L1 ₀ type iron-nickel alloy particles is disclosed.

WO2012 / 141205 publication

  However, the artificially synthesized Fe—Ni alloy has a much lower coercive force than natural tetrathenite. Therefore, development of a manufacturing method capable of stably artificially synthesizing Fe—Ni alloy powder having a higher coercive force is desired.

  The present invention has been made in view of the above background, and is intended to provide a method for producing an Fe—Ni alloy powder capable of stably artificially synthesizing an Fe—Ni alloy powder having a higher coercive force. It is what was done.

One aspect of the present invention is a precursor preparation step of preparing a powdery precursor composed of a mixture of an Fe-containing compound comprising an inorganic compound containing Fe and a Ni-containing compound comprising an inorganic compound containing Ni When,
An alloying step of mixing the precursor and a reducing agent capable of reducing the precursor, and heating the obtained mixed powder at a temperature of 320 ° C. or less to obtain an alloy powder containing an Fe—Ni alloy;
A cleaning step of cleaning the alloy powder and removing impurities,
The Fe molar fraction in the precursor is in the range of 0.5 to 0.9, in the method for producing Fe-Ni alloy powder.

  Another aspect of the present invention lies in an Fe—Ni alloy powder having a coercive force of 40 kA / m or more and being an artificial composite.

  Yet another embodiment of the present invention lies in a magnet characterized by using an Fe—Ni alloy powder.

  Tetrathenite having a high coercive force is an ordered alloy having a Fe: Ni molar ratio of 1: 1. Therefore, when the production of tetrathenite is intended, the general idea is to make the Fe: Ni molar ratio in the precursor close to 1: 1. However, as a result of intensive studies by the present inventors, surprisingly, the amount of Fe in the Fe-Ni alloy obtained with respect to the amount of Fe in the precursor is reduced, and due to this, The knowledge that the coercive force of the obtained Fe-Ni alloy powder was reduced was obtained. As a result of further detailed research based on this knowledge, the amount of Fe in the obtained Fe-Ni alloy is increased and the coercive force is improved by intentionally increasing the amount of Fe contained in the precursor. I came to the conclusion that I could do it.

  That is, the manufacturing method of the Fe-Ni alloy powder includes the precursor preparation step, the alloying step, and the cleaning step, and the precursor prepared in the precursor preparation step The Fe mole fraction is in the range of 0.5 to 0.9.

  Therefore, the method for producing the Fe—Ni alloy powder makes it possible to stably artificially synthesize an Fe—Ni alloy powder having a high coercive force of 40 kA / m or more. When the Fe mole fraction in the precursor is less than 0.5, Ni is excessively increased and tetrathenite is hardly generated, and the coercive force is greatly reduced. On the other hand, when the Fe mole fraction in the precursor exceeds 0.9, Fe is excessively increased and Fe oxide is easily generated, and the coercive force is lowered.

  The Fe—Ni alloy powder has a coercive force of 40 kA / m or more despite being an artificial composition. Therefore, the Fe—Ni alloy powder is useful as an alternative to a magnet material that uses rare metal or rare earth.

  The magnet is made of the Fe-Ni alloy powder. Therefore, the magnet can exhibit a high coercive force of 40 kA / m or more without using a rare metal or a rare earth. Therefore, the magnet is useful for increasing the density, power saving, and resource saving of magnetic devices.

It is explanatory drawing which showed the flow of each process in the manufacturing method of the Fe-Ni alloy powder of an Example. It is explanatory drawing which showed an example of the flow of the precursor preparation process in the manufacturing method of the Fe-Ni alloy powder of an Example. It is explanatory drawing which showed an example of the flow of the alloying process in the manufacturing method of the Fe-Ni alloy powder of an Example. It is explanatory drawing which showed an example of the heating conditions of the alloying process in the manufacturing method of the Fe-Ni alloy powder of an Example.

  In the Fe—Ni alloy powder manufacturing method, the Fe mole fraction in the precursor is obtained by calculating the number of moles of Fe and the number of moles of Ni contained in the precursor, and the number of moles of Fe / (total number of moles of Fe and Ni ). The number of moles of Fe and the number of moles of Ni contained in the precursor can be determined by fluorescent X-ray analysis.

  The Fe mole fraction in the precursor makes it easier to stably obtain an Fe—Ni alloy powder having a larger coercive force, and makes it easier to stably obtain an Fe—Ni alloy powder having a larger residual magnetic flux density. In view of the above, preferably more than 0.5, more preferably 0.55 or more, still more preferably 0.6 or more, even more preferably 0.65 or more, still more preferably 0.7 or more, most preferably 0. .7 and above. On the other hand, the Fe mole fraction in the precursor is preferably 0.88 or less, more preferably 0.86 or less, further preferably 0.84 or less, from the viewpoint of suppressing a decrease in coercive force due to an increase in Fe content. More preferably, it can be 0.82 or less, and even more preferably, it can be 0.8 or less.

  The Fe-containing compound constituting the precursor can be used without particular limitation as long as it is an inorganic compound containing Fe. Similarly, the Ni-containing compound constituting the precursor can be used without particular limitation as long as it is an inorganic compound containing Ni. Note that the Fe-containing compound and the Ni-containing compound constituting the precursor both include not only anhydrous but also hydrate.

Examples of the Fe-containing compound include Fe chloride such as FeCl ₂ .2H ₂ O and FeCl ₃ (which may include hydrates, hereinafter omitted), FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , Fe (NO ₃ ) ₂ , FeSO _{4 and the} like. Examples of the Ni-containing compound include Ni chlorides such as NiCl ₂ .2H ₂ O (which may include hydrates, omitted below), NiO, Ni (NO ₃ ) ₂ , NiSO _{4 and the} like. These can be used alone or in combination of two or more.

  As the Fe-containing compound and the Ni-containing compound, those that do not contain oxygen atoms can be used except for oxygen atoms in the structured water. In this case, Fe and oxygen atoms are hardly bonded in the alloying process, and it is difficult to produce Fe oxide, which is advantageous in improving the coercive force.

Specifically, Fe chloride can be preferably used as the Fe-containing compound, and Ni chloride can be preferably used as the Ni-containing compound. This is because there is an advantage that an Fe—Ni alloy powder having a high coercive force is easily obtained. In particular, when the Fe chloride is FeCl ₂ · 2H ₂ O and the Ni chloride is NiCl ₂ · 2H ₂ O, the Fe—Ni alloy powder has a small coercive force variation and stably has a high coercive force. There is an advantage that it is easy to obtain.

  The precursor preparing step is not particularly limited as long as the precursor having the Fe mole fraction described above can be prepared. The precursor preparation step is, for example, an Fe-containing starting compound that is a starting material for preparing a precursor and is composed of an inorganic compound that contains Fe, and an inorganic material that is a starting material for preparing a precursor and contains Ni A solution-forming step in which a Ni-containing starting compound composed of a compound is dissolved and / or dispersed in a solvent to form a solution, a resulting solution is dried to remove the solvent, and a solidification step in which the solvent is dried. A pulverizing step of pulverizing a solid material to prepare a powdery precursor.

  In this case, since the starting material is once in solution, a powdery precursor composed of a mixture in which the Fe-containing compound and the Ni-containing compound are uniformly mixed can be prepared relatively easily. Therefore, tetrathenite is easily generated in the subsequent alloying step, and it becomes easy to obtain an Fe—Ni alloy powder having a high coercive force and a residual magnetic flux density.

In this case, the feed amounts of the Fe-containing starting compound and the Ni-containing starting compound may be adjusted so that the Fe mole fraction in the obtained precursor is in the range of 0.5 to 0.9. Both the Fe-containing starting compound and the Ni-containing starting compound can contain not only an hydrate but also a hydrate. Examples of Fe-containing starting compounds include Fe chlorides such as FeCl ₂ .4H ₂ O and FeCl ₃ .6H ₂ O, Fe (NO ₃ ) ₂ , FeSO _{4 and the} like. Examples of Ni-containing starting compounds include Ni chlorides such as NiCl ₂ .6H ₂ O, Ni (NO ₃ ) ₂ , NiSO _{4 and the} like. These can be used alone or in combination of two or more.

  The drying step can be performed in a vacuum atmosphere from the viewpoint of preventing oxidation of Fe and improving the solvent evaporation rate. The temperature at the time of drying can be about 105-120 degreeC, for example. Moreover, the said grinding | pulverization process can be performed in inert gas, such as argon and helium, from a viewpoint of oxidation prevention of Fe, prevention of reaction with the water | moisture content in air, etc.

  In the alloying step, the mixing ratio of the precursor and the reducing agent can be in the range of precursor: reducing agent = 2: 1 to 1: 1 in terms of mass ratio. In this case, there is an advantage that the reduction reaction easily proceeds with an appropriate amount of the reducing agent, the reduction rate does not become too fast, and Fe and Ni easily take an ordered structure after the reduction.

  The reducing agent is not particularly limited as long as the precursor can be reduced by heating at a temperature of 320 ° C. or lower. If it exceeds 320 ° C., the reduction rate becomes too fast, and it becomes difficult to form an ordered structure of Fe and Ni, and it becomes difficult to obtain an Fe—Ni alloy powder having a high coercive force.

Specific examples of the reducing agent include calcium hydride (CaH ₂ ). These can be used alone or in combination of two or more. When the Fe-containing compound constituting the precursor is Fe chloride such as FeCl ₂ · 2H ₂ O and the Ni-containing compound constituting the precursor is Ni chloride such as NiCl ₂ · 2H ₂ O, the reducing agent Calcium hydride can be preferably used. In this case, the reactivity at a temperature of 320 ° C. or less is good, which is advantageous.

  The heating temperature when heating the mixed powder of the precursor and the reducing agent is preferably 320 ° C. or less, more preferably less than 320 ° C., and even more preferably 315 ° C. or less in consideration of the phase transformation temperature of tetrathenite. Even more preferably, it can be 310 ° C. or lower. On the other hand, the heating temperature when heating the mixed powder of the precursor and the reducing agent is preferably 260 ° C. or higher, more preferably 270 ° C. or higher, from the viewpoint of reactivity and the like. Note that the alloying step can be performed in an inert gas such as argon or helium from the viewpoint of preventing oxidation of Fe and preventing reaction with moisture in the air.

  In addition to the Fe—Ni alloy, the alloy powder obtained in the alloying step may contain impurities such as residues caused by a soft magnetic component containing a large amount of Fe and a reducing agent. Therefore, in the cleaning step, the alloy powder is cleaned to remove impurities. Specifically, the impurities can be eluted from the alloy powder using an acid such as hydrochloric acid or sulfuric acid, followed by washing with water. Moreover, drying, grinding | pulverization, classification, etc. can also be implemented with respect to the alloy powder after washing | cleaning as needed.

  The Fe—Ni alloy powder is an artificial composite and has a coercive force of 40 kA / m or more. This Fe-Ni alloy powder can be suitably manufactured by carrying out the above-described method for manufacturing an Fe-Ni alloy powder. Note that the phrase “artificial compound” is intended to distinguish it from natural tetrathenite, which is mainly present in iron meteorites.

  The coercive force of the Fe-Ni alloy powder is preferably 45 kA / m or more, more preferably 48 kA / m or more, still more preferably 50 kA / m or more, and even more preferably 52 kA, from the viewpoint of usefulness as a magnet material. / M or more. The coercive force of the Fe—Ni alloy powder is preferably as high as possible from the viewpoint of usefulness as a magnet material, and the upper limit of the coercive force is not particularly limited.

The Fe—Ni alloy powder can have a residual magnetic flux density of 0.25 T or more. In this case, since the maximum energy product (BH) _max of the magnet can be increased, it is excellent in usefulness as a permanent magnet material.

  From the viewpoint of usefulness as a permanent magnet material, the residual magnetic flux density of the Fe—Ni alloy powder is preferably 0.28 T or more, more preferably 0.3 T or more, still more preferably 0.31 T or more, and even more preferably. Can be 0.32T or more. The residual magnetic flux density of the Fe—Ni alloy powder is preferably as high as possible from the viewpoint of usefulness as a permanent magnet material, and the upper limit of the residual magnetic flux density is not particularly limited.

  The magnet is made of the Fe-Ni alloy powder. Specifically, the magnet can be configured as a sintered magnet obtained by baking and solidifying the Fe—Ni alloy powder at a high temperature. The magnet may be configured as a bonded magnet obtained by solidifying the Fe—Ni alloy powder with a binder (binder) such as a plastic resin.

  Hereinafter, it demonstrates more concretely using an Example.

  As shown in FIG. 1, the manufacturing method of the Fe-Ni alloy powder of this example includes a precursor preparation step S1, an alloying step S2, and a cleaning step S3. As shown in FIG. 2, the precursor preparation step S1 is a powdery precursor composed of a mixture of an Fe-containing compound made of an inorganic compound containing Fe and a Ni-containing compound made of an inorganic compound containing Ni. Is a step of preparing At this time, the Fe mole fraction in the precursor is in the range of 0.5 to 0.9. In the alloying step S2, as shown in FIG. 3, a precursor and a reducing agent capable of reducing the precursor are mixed, and the obtained mixed powder is heated at a temperature of 320 ° C. or less, thereby forming an Fe—Ni alloy. This is a step of obtaining an alloy powder. The cleaning step S3 is a step of cleaning the alloy powder and removing impurities. Details will be described below.

  As shown in FIG. 1, various Fe—Ni alloy powders were manufactured by performing a precursor preparation step S1, an alloying step S2, and a cleaning step S3 in this order.

(Precursor preparation process)
As shown in FIG. 2, FeCl ₂ .4H ₂ O as an Fe-containing starting compound and NiCl ₂ .6H ₂ O as an Ni-containing starting compound were dissolved in ion-exchanged water as a solvent to form a solution. The obtained solution was dried in a constant temperature bath at 120 ° C. in a vacuum atmosphere to remove the solvent, and was dried until the precipitate deposited by removing the solvent turned yellow. The dried product thus obtained was pulverized using a mortar in a glove box having an argon gas atmosphere.

According to the above procedure, six types of precursors used to prepare the Fe—Ni alloy powders of Sample 1 to Sample 6 were prepared. Each precursor is composed of a mixture of FeCl ₂ .2H ₂ O and NiCl ₂ .2H ₂ O. Each of the precursors was obtained by adjusting the amounts of FeCl ₂ .4H ₂ O and NiCl ₂ .6H ₂ O as starting compounds to the Fe: Ni molar ratio shown in Table 1 to be described later at the time of preparing the precursor. Is. The Fe mole fraction in each precursor is a value shown in Table 1, respectively.

(Alloying process)
Each prepared precursor and calcium hydride (CaH ₂ ) as a reducing agent were uniformly mixed using a mortar so that the mass ratio of precursor: calcium hydride = 4: 3. Then, each obtained mixed powder was heated on the heating conditions shown in FIG. That is, the heating conditions in this example were as follows: the temperature was raised from room temperature to 310 ° C. over 4 hours, then cooled to 270 ° C. over 20 hours, and then allowed to cool naturally to room temperature. did. The mixing and heating were both performed in an argon gas atmosphere. This reduced each precursor and obtained each alloy powder containing a Fe-Ni alloy.

(Washing process)
Each obtained alloy powder was put in a container, and hydrochloric acid was added to the supernatant until the supernatant became blue-green transparent with stirring, followed by washing with water. Thereafter, the washed powder was dried.

  Thus, Fe—Ni alloy powders of Sample 1 to Sample 6 were produced.

(Fe mole fraction in the sample)
The Fe mole fraction in each sample was calculated using a fluorescent X-ray analyzer.

(Measurement of coercive force and residual magnetic flux density)
Using a vibrating sample magnetometer (VSM), the coercive force and residual magnetic flux density of each sample were measured.

  Table 1 lists the amounts of Fe and Ni charged at the time of preparing the precursor, the Fe mole fraction in the precursor, the Fe mole fraction in the sample, the coercive force, and the residual magnetic flux density.

  According to Table 1, the following can be said. That is, as can be seen from the results of Samples 3, 5, and 6, when the Fe mole fraction in the precursor is less than 0.5, the amount of Fe in the resulting Fe-Ni alloy is greatly reduced, so Fe-Ni It can be seen that the coercivity of the alloy powder is greatly reduced. This is because it becomes difficult to produce tetrathenite because of excessive Ni. On the other hand, as shown in the results of Sample 1 to Sample 4, when the Fe mole fraction in the precursor is in the range of 0.5 to 0.9, 40 kA / m or more Fe-Ni alloy powder having a high coercive force is obtained. That is, according to this example, it can be seen that it is possible to stably artificially synthesize Fe—Ni alloy powder having a higher coercive force. As shown in the results of Sample 4, it can be seen that when the Fe mole fraction in the precursor exceeds 0.9, the coercive force is reduced. This is because Fe is excessively increased and Fe oxide is easily generated.

Further, as shown in Table 1, it can be seen that the Fe—Ni alloy powders of Samples 1 to 4 have a coercive force of 40 kA / m or more and a residual magnetic flux density of 0.25 T or more. . From this, it can be said that the Fe-Ni alloy powder obtained by the manufacturing method of the Fe-Ni alloy powder of this example can increase the maximum energy product (BH) _max of the magnet and is useful as a permanent magnet material. .

  Moreover, the magnet produced using the Fe-Ni alloy powder obtained by the manufacturing method of the Fe-Ni alloy powder of this example shows a high coercive force of 40 kA / m or more without using a rare metal or a rare earth. Therefore, it can be said that the magnetic device is useful for increasing the density, saving power, saving resources, and the like.

  As mentioned above, although the Example of this invention was described in detail, this invention is not limited to the said Example, A various change is possible within the range which does not impair the meaning of this invention.

S1 precursor preparation process S2 alloying process S3 cleaning process

Claims (6)

A precursor preparation step (S1) for preparing a powdery precursor composed of a mixture of an Fe-containing compound composed of an inorganic compound containing Fe and a Ni-containing compound composed of an inorganic compound containing Ni;
An alloying step (S2) of mixing the precursor and a reducing agent capable of reducing the precursor and heating the resulting mixed powder at a temperature of 320 ° C. or less to obtain an alloy powder containing an Fe—Ni alloy. When,
A cleaning step (S3) for cleaning the alloy powder and removing impurities,
The method for producing an Fe—Ni alloy powder, wherein the Fe mole fraction in the precursor is in the range of 0.5 to 0.9.   The method for producing Fe-Ni alloy powder according to claim 1, wherein the Fe-containing compound is Fe chloride, and the Ni-containing compound is Ni chloride. The Fe-containing compound is FeCl ₂ · 2H ₂ O, the Ni-containing compound is NiCl ₂ · 2H ₂ O, and the reducing agent is calcium hydride. The manufacturing method of Fe-Ni alloy powder as described in 2.   An Fe—Ni alloy powder having a coercive force of 40 kA / m or more and being an artificial composite.   The Fe-Ni alloy powder according to claim 4, which has a residual magnetic flux density of 0.25T or more.   A magnet comprising the Fe-Ni alloy powder according to claim 4 or 5.

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