WO2018128153A1 - METHOD FOR PRODUCING MnAL ALLOY - Google Patents

Abstract

[Problem] To reduce variation in the composition of a MnAl alloy precipitated by molten salt electrolysis, and obtain high magnetic properties. [Solution] In a method for producing MnAl alloy by electrolyzing a molten salt containing a Mn compound and an Al compound to precipitate a MnAl alloy, the Mn compound is additionally introduced to the molten salt during electrolysis. According to the present invention, the concentration of the Mn compound is maintained by the additional introduction of the Mn compound, and thus variation in the composition of the precipitated MnAl alloy is reduced and stable production conditions can be maintained.

Description

Method for producing MnAl alloy

The present invention relates to a method for producing an MnAl alloy, and more particularly to a method for producing an MnAl alloy using a molten salt electrolysis method.

As a manufacturing method of MnAl alloy, melting methods such as arc melting method and high-frequency induction melting method are known, and the molten metal obtained by melting is cooled and solidified using casting method, atomizing method, roll quenching method, etc. By doing so, a MnAl-based alloy is obtained. For example, Patent Document 1, MnAl based ferromagnetic material to τ phase having a tetragonal crystal structure of L1 ₀ type as a main component as a main phase have been reported. Patent Document 2 proposes a Mn—Al—C-based magnetic material and discloses that an alloy obtained by a melting method becomes a MnAl-based ferromagnetic material having a τ phase as a main phase.

In the MnAl-based alloy manufacturing method using the melting method, the stoichiometric ratio of the τ phase is originally Mn: Al = 1: 1, but the ε phase (hcp) to the τ phase is as completely as possible by heat treatment in the subsequent process. In order to transform, it is necessary to include a large amount of ε phase during the rapid cooling in the previous step. For this reason, it is important that the alloy composition at the time of melting is Mn: Al = 55: 45, resulting in the problem that Mn-excess τ phase is generated.

On the other hand, in a Mn—Al—C-based magnetic material, by adding carbon, it is possible to obtain a τ phase directly without heat treatment by dissolving and quenching without passing the ε phase as an intermediate product phase. it can. However, when carbon is added, there is a problem that a heterogeneous phase of Mn ₃ AlC is slightly generated.

A molten salt electrolysis method is also known as a method for producing a MnAl-based alloy. Non-Patent Document 1 discloses that an MnAl alloy is deposited on the surface of an electrode by electrolyzing a molten salt containing an Al compound as a main component and added with an Mn compound. Non-Patent Document 2 discloses a MnAl system in which the addition amount of a Mn compound added to a molten salt containing an Al compound as a main component is adjusted, and electrolysis is performed under a predetermined condition to have a τ phase exhibiting ferromagnetism as a main phase. It has been reported that magnetic materials are deposited.

Japanese Patent Publication No.34-30435 Japanese Patent Publication No. 37-57224

J. Uchida et al., Tetsu-to-hagane Vol. 77 (1991) No.7 p.931. G.R. Stafford et al., J. Alloy Compd. 200 (1993) 107-113.

In the conventional method for producing an MnAl alloy using the molten salt electrolysis method, the MnAl content is lower than 55% by adjusting the amount of the Mn compound added to the molten salt containing the Al compound as a main component. An alloy is obtained, and a τ-phase single-phase MnAl-based magnetic material close to the stoichiometric ratio can be obtained. However, as the electrolysis proceeds, the concentration of the Mn compound in the molten salt gradually decreases, so that the composition of the deposited MnAl alloy varies, and stable manufacturing conditions cannot be maintained.

The present invention has been made in view of the above, and aims to reduce the variation in the composition of the precipitated MnAl alloy and to obtain high magnetic properties in a method for producing an MnAl alloy using a molten salt electrolysis method. And

As a result of intensive studies by the present inventors to solve the above-mentioned problems and achieve the object, by stabilizing the concentration of the Mn compound in the molten salt, the variation in the composition of the precipitated MnAl alloy is reduced, and the result And found that high magnetic properties can be obtained. The present invention has been made based on such technical knowledge, and a method for producing a MnAl alloy according to the present invention includes a MnAl alloy in which a MnAl alloy is precipitated by electrolyzing a molten salt containing a Mn compound and an Al compound. In this production method, the Mn compound is additionally added to the dissolved salt during electrolysis.

According to the present invention, since the concentration of the Mn compound is maintained by additionally adding the Mn compound, variation in the composition of the deposited MnAl alloy is reduced, and stable manufacturing conditions can be maintained. The concentration of the Mn compound in the molten salt is preferably maintained at 0.2 mass% or more by adding the Mn compound. According to this, it becomes possible to stably manufacture a MnAl alloy having high magnetic properties. The molten salt may further contain an alkali metal halide, and may further contain a rare earth halide or an alkaline earth halide. The temperature of the molten salt during electrolysis is preferably 150 ° C. or more and 600 ° C. or less, and the amount of electricity per 1 cm ^{2 of} electrode area is preferably 30 mAh or more and 120 mAh. Here, various magnetic properties can be imparted to the MnAl alloy depending on the temperature of the molten salt during electrolysis. Specifically, ferromagnetism can be imparted to the MnAl alloy by setting the temperature of the molten salt during electrolysis to 150 ° C. or more and less than 400 ° C. By setting the temperature of the molten salt during electrolysis to 400 ° C. or higher and lower than 600 ° C., metamagnetism can be imparted to the MnAl alloy. By setting the temperature of the molten salt during electrolysis to 600 ° C. or more and 700 ° C. or less, ferromagnetism can be imparted and the remanent magnetization can be increased as compared with a MnAl alloy produced at less than 600 ° C.

In the present invention, the MnAl alloy deposited by electrolysis may be heat treated. If heat treatment is performed on the precipitated MnAl alloy, various magnetic properties can be imparted to the MnAl alloy depending on the heat treatment conditions. Specifically, metamagnetism can be imparted to the MnAl alloy by setting the temperature of the heat treatment to 400 ° C. or more and less than 600 ° C., and by setting the temperature of the heat treatment to 600 ° C. or more and 700 ° C. or less, Residual magnetization can be increased as compared to MnAl alloys. The atmosphere for the heat treatment is preferably in an inert gas or in a vacuum.

In the present invention, the powdered MnAl alloy may be precipitated by performing electrolysis at an electric quantity of 50 mAh or more per 1 mass% of the Mn compound concentration in the molten salt and per 1 cm ^{2 of} the electrode area. According to this, while being able to obtain high productivity, it becomes possible to obtain arbitrary product shapes by compression-molding the powdered MnAl alloy.

As described above, according to the present invention, in the method for producing a MnAl alloy using the molten salt electrolysis method, it is possible to reduce variation in the composition of the deposited MnAl alloy and obtain high magnetic properties.

FIG. 1 is a schematic view of an electrodeposition apparatus for producing a MnAl alloy. FIG. 2 is a table showing manufacturing conditions and evaluation results of the examples. FIG. 3 is a table showing manufacturing conditions and evaluation results of the examples. FIG. 4 is a table showing manufacturing conditions and evaluation results of the examples. FIG. 5 is a table showing manufacturing conditions and evaluation results of the examples. FIG. 6 is a table showing manufacturing conditions and evaluation results of the examples. FIG. 7 is a table showing manufacturing conditions and evaluation results of the examples.

Hereinafter, preferred embodiments of the present invention will be described. The present invention is not limited by the contents of the embodiments and examples described below. In addition, the constituent elements shown in the embodiments and examples described below may be appropriately combined or may be appropriately selected.

FIG. 1 is a schematic view of an electrodeposition apparatus for producing a MnAl alloy.

The electrodeposition apparatus shown in FIG. 1 includes an alumina crucible 2 arranged inside a stainless steel sealed container 1. The alumina crucible 2 holds the molten salt 3, and the molten salt 3 in the alumina crucible 2 is heated by an electric furnace 4 disposed outside the sealed container 1. A cathode 5 and an anode 6 immersed in the molten salt 3 are provided in the alumina crucible 2, and a current is supplied to the cathode 5 and the anode 6 via a constant current power supply device 7. The cathode 5 is a plate-like body made of Cu, and the anode 6 is a plate-like body made of Al. The molten salt 3 in the alumina crucible 2 can be stirred by the stirrer 8. In addition, the inside of the sealed container 1 is filled with an inert gas such as N ₂ supplied via the gas path 9.

The molten salt 3 contains at least a Mn compound and an Al compound. MnCl ₂ can be used as the Mn compound, and AlCl ₃ , AlF ₃ , AlBr _3, or AlNa ₃ F ₆ can be used as the Al compound. The Al compound may be AlCl ₃ alone, or a part thereof may be substituted with AlF ₃ , AlBr _3, or AlNa ₃ F ₆ .

In addition to the Mn compound and Al compound described above, another halide may be added to the molten salt 3. As another halide, it is preferable to select an alkali metal halide such as NaCl, LiCl or KCl, and the alkali metal halide includes rare earth halides such as LaCl ₃ , DyCl ₃ , MgCl ₂ and CaCl ₂ , alkaline earths. A halide or the like may be added.

The molten salt 3 can be obtained by charging such an Mn compound, Al compound and another halide into the alumina crucible 2 and heating and melting them in the electric furnace 4. Further, it is preferable that the molten salt 3 is sufficiently stirred by the stirrer 8 immediately after melting so that the composition distribution of the molten salt 3 becomes uniform.

The electrolysis of the molten salt 3 is performed by passing a current between the cathode 5 and the anode 6 via the constant current power supply device 7. Thereby, a MnAl alloy can be deposited on the cathode 5. The heating temperature of the molten salt 3 during electrolysis depends on the composition of the molten salt 3 and the characteristics of the target MnAl alloy, but is preferably 150 ° C. or higher and 600 ° C. or lower. The amount of electricity is also preferably 30 mAh or more and 120 mAh per 1 cm ^{2 of} electrode area, although it depends on the composition of the molten salt 3 and the characteristics of the target MnAl alloy. During electrolysis, it is preferable to fill the inside of the sealed container 1 with an inert gas such as N ₂ .

In addition, the current flowing between the cathode 5 and the anode 6 is reduced to a powder in the cathode 5 by setting the amount of electricity per 1 mass% of the Mn compound in the molten salt 3 and the amount of electricity per 1 cm ^{2 of} electrode area to 50 mAh or more. A shaped MnAl alloy can be deposited. This is because the higher the concentration of the Mn compound in the molten salt 3 is, the more the precipitation is promoted, and the more the amount of electricity per unit electrode area is, the more the precipitation is promoted. As a result, the above numerical range (50 mAh or more) is satisfied. This is because the deposited MnAl alloy tends to be powdered. If the MnAl alloy deposited on the cathode 5 is in the form of a powder, the MnAl alloy deposition does not stop even when electrolysis is performed for a long time, so that the productivity of the MnAl alloy can be increased. Moreover, it becomes possible to obtain arbitrary product shapes by compression-molding the obtained powdered MnAl alloy.

The initial concentration of the Mn compound in the molten salt 3 is preferably 0.2 mass% or more, and more preferably 0.2 mass% or more and 3 mass% or less. And in this embodiment, the density | concentration of the Mn compound in the molten salt 3 is maintained by adding the Mn compound additionally during electrolysis. The additional Mn compound to be added may be in the form of a powder or a pellet formed by molding the powder, and this may be added to the molten salt 3 continuously or periodically. Thus, if the Mn compound is additionally added during the electrolysis of the molten salt 3, the decrease in the concentration of the Mn compound accompanying the progress of electrolysis is suppressed, and the concentration of the Mn compound in the molten salt 3 is maintained at a predetermined value or more. Can do. Thereby, it becomes possible to suppress the dispersion | variation in the composition of the MnAl alloy to precipitate.

Predetermined magnetic properties can be imparted to the MnAl alloy by heat treatment of the MnAl alloy deposited by electrolysis. Specifically, if the heat treatment temperature is 400 ° C. or more and less than 600 ° C. and the heat treatment time is about 0.5 hour, the MnAl alloy can be given metamagnetism, and the heat treatment temperature is 600 ° C. or more and 700 ° C. If the heat treatment time is about 0.5 hours, the remanent magnetization of the MnAl alloy can be increased. The atmosphere for the heat treatment is preferably in an inert gas or in a vacuum. When the heat treatment temperature is 400 ° C. or more and less than 600 ° C., sharp metamagnetism can be obtained by performing the heat treatment for a longer time. In addition, when the heat treatment temperature is 600 ° C. or higher, if the heat treatment time exceeds a predetermined time, it becomes non-magnetic.

In addition, when the heating temperature of the molten salt 3 during electrolysis is 400 ° C. or higher and 700 ° C. or lower, heat treatment is effectively performed during electrolysis. Depending on the temperature, various magnetic properties can be imparted to the MnAl alloy. Specifically, by setting the heating temperature of the molten salt 3 during electrolysis to 400 ° C. or more and less than 600 ° C., the MnAl alloy can be given metamagnetism, and the heating temperature of the molten salt 3 during electrolysis is 600 ° C. or more. By setting the temperature to 700 ° C. or lower, the remanent magnetization can be increased as compared with the MnAl alloy before the heat treatment.

Metamagnetism refers to the property of a primary phase transition from paramagnetism (PM) or anti-ferromagnetism (AFM) to ferromagnetism (FM) by a magnetic field. First-order phase transition by a magnetic field refers to having a point at which the change in magnetization related to the magnetic field becomes discontinuous. Metamagnetic materials are classified into PM-FM transition type metamagnetic materials that transition from paramagnetic to ferromagnetic by a magnetic field, and AFM-FM transition type metamagnetic materials that transition from antiferromagnetic to ferromagnetic by a magnetic field. A PM-FM transition type metamagnetic material undergoes a primary phase transition only near the Curie temperature, whereas an AFM-FM transition type metamagnetic material has a primary phase at or below the Neel temperature at which the antiferromagnetic state disappears. Metastasis occurs. Since the MnAl alloy manufactured by the method according to the present embodiment is an AFM-FM transition type metamagnetic material, it exhibits metamagnetism at a wide range of temperatures.

As described above, the MnAl alloy manufacturing method according to the present embodiment maintains the concentration of the Mn compound in the molten salt by additionally introducing the Mn compound during electrolysis. Variations in composition can be suppressed. In addition, if the deposited MnAl alloy is heat-treated, it is possible to give the MnAl alloy predetermined magnetic properties. Furthermore, by adjusting the concentration of the Mn compound in the molten salt 3 and the amount of electricity per unit electrode area, the MnAl alloy deposited on the cathode 5 can be powdered.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

<Comparative Example 1>
First, an electrodeposition apparatus having the structure shown in FIG. 1 was prepared. The cathode 5 is a Cu plate having a thickness of 3 mm cut so that the immersion area in the molten salt 3 is 5 cm × 8 cm, and the anode 6 is 3 mm in thickness cut so that the immersion area in the molten salt 3 is 5 cm × 8 cm. An Al plate was used.

Next, 50 mol% each of anhydrous AlCl _{3 as} an Al compound and NaCl as another halide are weighed, and 0.1 mass% of MnCl ₂ previously dehydrated as a Mn compound is weighed, so that the total weight becomes 1200 g. The alumina crucible 2 was charged. Therefore, the amount of MnCl ₂ is 1.2 g. The dehydration treatment was performed by heating MnCl ₂ hydrate at about 400 ° C. for 4 hours or more in an inert atmosphere such as N ₂ gas.

The alumina crucible 2 charged with the material was moved to the inside of the sealed container 1, and the material was heated to 350 ° C. by the electric furnace 4 to obtain a molten salt 3. Next, the rotating blades of the stirrer 8 were allowed to settle in the molten salt 3 and stirred for 0.5 hours at a rotational speed of 400 rpm. Thereafter, a constant current of 60 mA / cm ² (2.4 A) per unit electrode area was applied between the cathode 5 and the anode 6 for 0.5 hour, and the current and heating were stopped. Then, before the molten salt 3 was cooled and solidified, the electrode was removed, and the cathode 5 was ultrasonically cleaned with acetone. A film-like electrodeposit was deposited on the surface of the cathode 5. The film-like electrodeposit was recovered by dissolving and removing Cu constituting the cathode 5 with concentrated nitric acid. The collected electrodeposits were pulverized in a mortar to obtain a sample of Comparative Example 1 in a powder form.

FIG. 2 shows the electrolysis conditions, the form of the electrodeposit, the concentration unevenness and the magnetic characteristics of Comparative Example 1. As shown in FIG. 2, the sample of Comparative Example 1 showed ferromagnetism, but its residual magnetization was almost 0 emu / g. The residual magnetization was measured using a vibrating sample magnetometer (VSM, manufactured by Tamagawa Seisakusho). Further, density unevenness was evaluated as follows. First, the cross section of the obtained film or the cross section of the powder molding is cut by ion milling to remove the influence of oxidation and the like, and then the elements of Mn and Al using EPMA (Electron Probe Micro Analyzer). Mapping was performed. Specifically, element mapping (256 points × 256 points) is performed in a 50 μm square region, and the maximum and minimum values of the Mn: Al ratio in the region are less than 2.5 at%. % Or more and less than 5.0 at% was evaluated as Δ, and 5.0 at% or more was evaluated as ×. As shown in FIG. 2, in the sample of Comparative Example 1, the evaluation of density unevenness was x.

<Comparative Examples 2 to 15>
Samples of Comparative Examples 2 to 5 were prepared in the same manner as Comparative Example 1 except that the concentration of MnCl _{2 as} the Mn compound was changed. Samples of Comparative Examples 6 to 15 were prepared in the same manner as Comparative Examples 1 to 5, except that the energization time was 1 hour or 4 hours. As shown in FIG. 2, the electrodeposits were also film-like in Comparative Examples 2 to 15. In addition, in the samples of Comparative Examples 2 to 15, the evaluation of density unevenness was x.

Thus, in Comparative Examples 1 to 15, ferromagnetic film deposits were obtained. Although the residual magnetization of the electrodeposits tended to increase as the initial concentration of the Mn compound increased, the residual magnetization obtained was relatively small. This is presumably because Mn in the molten salt is consumed with the progress of electrolysis, so that the Mn ratio in the produced electrodeposit is reduced. As a result, a ferromagnetic τ phase having a low Mn ratio and a nonmagnetic γ2 phase or γ brass phase having a low Mn ratio are generated, which is considered to reduce the residual magnetization. On the other hand, when the initial concentration of the Mn compound was too large, 3 mass%, in Comparative Examples 5 and 10 having a short energization time, the residual magnetization was slightly reduced. This is because if the initial concentration of the Mn compound is too high, the Mn compound is saturated with respect to the molten salt, so that it is dispersed in the molten salt as a solid, and the current density is reduced to, for example, less than 30 mA / cm ^2. This is probably because the electrochemical reaction is inhibited.

<Examples 1 to 5>
Samples of Examples 1 to 5 were prepared in the same manner as Comparative Examples 6 to 10, respectively, except that MnCl ₂ as a Mn compound was additionally added during electrolysis.

Additional charging of MnCl ₂ was performed as follows. First, MnCl ₂ hydrate was dehydrated in advance in an inert atmosphere such as N ₂ gas at about 400 ° C. for 4 hours or more, and the resulting anhydrous MnCl ₂ was pulverized in an inert atmosphere using a mortar. The obtained powder was formed into a cylindrical pellet having a diameter of 5 mm to produce anhydrous MnCl ₂ pellets. The pellets thus obtained were additionally charged into the molten salt 3 during electrolysis. The additional charging of pellets was performed every 10 minutes, and the charging amount per one time was 0.38 g in Examples 1 to 5.

As shown in FIG. 2, the samples of Examples 1 to 5 showed ferromagnetism, and the residual magnetization was larger than that of the corresponding Comparative Examples 6 to 10, respectively. Further, in Examples 4 and 5 in which the initial Mn compound concentration was 1 mass% or more, the form of the MnAl alloy deposited on the cathode 5 was not only film-like but mostly powdery. Further, in the samples of Examples 1 to 5, the evaluation of density unevenness was all “good”.

In addition, although a part of the powdered electrodeposit remains on the cathode 5, the rest is deposited on the bottom of the alumina crucible 2. For this reason, the powdered electrodeposits settled in the molten salt 3 are collected by filtration, the molten salt is decanted, and the mixture of the powdered electrodeposits and the molten salt remaining at the bottom is cooled and solidified, and then acetone is added. And then recovered by filtration. The powdered electrodeposits obtained by any of the recovery methods were mixed together with the powdered sample obtained by pulverizing the film-like electrodeposited material to obtain an evaluation sample.

As described above, in Examples 1 to 3, ferromagnetic film-like deposits were obtained, and in Examples 4 and 5, both ferromagnetic film-like deposits and powder-like deposits were obtained. In Examples 1 to 5, the amount of electricity per concentration of 1 mass% of the Mn compound in the molten salt and the electrode area per 1 cm ² are 6 mAh, 12 mAh, 30 mAh, 60 mAh and 180 mAh, respectively.

The remanent magnetization of the electrodeposit was increased when the initial concentration of the Mn compound was 0.1 to 1 mass% and slightly decreased at 3 mass%. This is because when the initial concentration of the Mn compound is too low as 0.1 mass%, the Mn ratio of the deposited product is low even when the initial concentration is maintained, and the ferromagnetic τ phase with a low Mn ratio, A non-magnetic γ2 phase or γ brass phase with a low Mn ratio is likely to be formed, so that a film-like electrodeposit is easily formed. If the initial concentration of the Mn compound is appropriate to be 0.2 mass% or more, a τ phase is generated. Further, since the operation of maintaining the initial concentration of the Mn compound was performed, it is considered that the τ phase that could not be formed into a film was obtained as a powdered electrodeposit. On the other hand, if the initial concentration of the Mn compound is as high as 3 mass%, the additional amount of the Mn compound added exceeds the amount of Mn consumed by the electrolysis, and the Mn compound is saturated with respect to the molten salt. Dispersion is thought to cause an electrochemical reaction.

<Examples 6 to 10>
Samples of Examples 6 to 10 were prepared in the same manner as Comparative Examples 11 to 15 except that MnCl ₂ as a Mn compound was additionally added during electrolysis. The pellets used and the charging conditions were the same as in Examples 1 to 5, respectively.

As shown in FIG. 2, the samples of Examples 6 to 10 also showed ferromagnetism, and the remanent magnetization was larger than the corresponding Comparative Examples 11 to 15, respectively. Further, in any of Examples 6 to 10, the form of the MnAl alloy deposited on the cathode 5 was not only film-like but mostly powdery. In addition, in the samples of Examples 6 to 10, the evaluation of density unevenness was all good.

Thus, in Examples 6 to 10, both ferromagnetic film deposits and powder deposits were obtained. The remanent magnetization of the obtained ferromagnetic electrodeposit increased when the initial concentration of the Mn compound increased from 0.1 to 1 mass%, and decreased slightly at 3 mass%. This is because when the initial concentration of the Mn compound is too low at 0.1 mass%, the Mn ratio of the produced electrodeposit is lowered, and a ferromagnetic τ phase with a low Mn ratio or a nonmagnetic γ2 phase with a low Mn ratio. Alternatively, when the γ brass phase is easily generated and the initial concentration of the Mn compound is as high as 3 mass%, the additional amount of the Mn compound added exceeds the amount of Mn consumed by the electrolysis, and the Mn compound is saturated with respect to the molten salt. It is considered that the electrochemical reaction is inhibited by being dispersed in the molten salt as a solid substance.

<Examples 11 to 16>
Samples of Examples 11 to 16 were produced in the same manner as in Examples 4 and 9, except that the energization time was set to 0.5 hour and the obtained precipitate was heat-treated. All the deposits were film-like. The heat treatment was performed by raising the temperature of the powdered sample to 300 ° C. to 700 ° C. over 1 hour in an N ₂ gas flow and maintaining this state for 0.5 hour.

As shown in FIG. 3, the samples of Examples 11, 15 and 16 with the heat treatment temperatures of 300 ° C., 600 ° C. and 700 ° C. showed ferromagnetism, whereas the heat treatment temperatures were 400 ° C., 500 ° C. and The samples of Examples 12-14 at 550 ° C. showed metamagnetism. Even when the remanent magnetization was 0 emu / g, when magnetizing with a magnetic field of a certain strength (magnetic field induced ferromagnetic transition), it was determined as metamagnetic and the magnetic field was used as a response magnetic field. The response magnetic field was an intercept between the tangent line of the magnetization curve at the transition and the magnetic field axis. Further, the metamagnetic response magnetic field tended to be lower as the heat treatment temperature was higher. In addition, in the samples of Examples 11 to 16, the evaluation of density unevenness was all good.

<Examples 17 to 19>
Samples of Examples 17 to 19 were produced in the same manner as in Examples 4 and 9, except that the energization time was set to 0.5 hour, 2 hours, and 3 hours, respectively. As shown in FIG. 3, the sample of Example 17 was film-like, and the samples of Examples 18 and 19 were film-like and powdery. In Examples 17 to 19, the amount of electricity per concentration of 1 mass% of the Mn compound in the molten salt and per 1 cm ^{2 of} the electrode area is 30 mAh, 120 mAh, and 180 mAh, respectively.

As described above, when the energization time was short, the electrodeposit was film-like, but when the energization time was lengthened, the electrodeposition became powdery. This is because, when electrolysis is performed at an electric quantity of 60 mAh / cm ² per 1 mass% of the Mn compound concentration, the film thickness of the film-like deposit becomes about 10 to 20 μm as the energization time becomes longer, compared with the electrode surface in the initial state. The flatness is lost, and it is considered that the powdered electrodeposits are formed by starting dendrite growth on the convex and concave portions. In addition, in the samples of Examples 17 to 19, the evaluation of density unevenness was all good.

Note that Example 17 has the same conditions as Examples 11 to 16, except that the heat treatment is omitted. As shown in FIG. 3, compared with Example 17 in which heat treatment was not performed, Example 11 (heat treatment temperature: 300 ° C.), Example 15 (heat treatment temperature: 600 ° C.), and Example 16 (heat treatment temperature: A larger remanent magnetization was obtained at 700 ° C. In particular, in Examples 15 and 16 in which the heat treatment temperatures were 600 ° C. and 700 ° C., the increase in remanent magnetization was remarkable.

<Comparative Examples 16 to 21>
Samples of Comparative Examples 16 to 21 were prepared in the same manner as Examples 11 to 16, respectively, except that no additional MnCl ₂ was added during the electrolysis.

As shown in FIG. 3, the sample of Comparative Example 16 showed ferromagnetism, but no magnetism was observed in the samples of Comparative Examples 17-21. In the samples of Comparative Examples 16 to 21, the density unevenness was evaluated as x. As described above, even when heat treatment was performed after electrolysis, high magnetic properties could not be obtained and concentration unevenness was large unless additional addition of MnCl ₂ was performed during electrolysis.

<Examples 20 to 25>
Samples of Examples 20 to 25 were produced in the same manner as in Example 9, except that the obtained precipitate was heat-treated for 0.5 hour. The electrodeposits were both filmy and powdery.

As shown in FIG. 3, the samples of Examples 20, 24 and 25 having heat treatment temperatures of 300 ° C., 600 ° C. and 700 ° C. showed ferromagnetism, whereas the heat treatment temperatures were 400 ° C., 500 ° C. and The samples of Examples 21 to 23 at 550 ° C. showed metamagnetism. In addition, the samples of Examples 20, 24, and 25 that exhibited ferromagnetism had increased residual magnetization compared to the sample of Example 9 that was not subjected to heat treatment. In particular, in Example 24 where the heat treatment temperature was 600 ° C., the increase in residual magnetization was significant. Further, the metamagnetic response magnetic field tended to be lower as the heat treatment temperature was higher. Also in the samples of Examples 20 to 25, the evaluation of density unevenness was all good.

<Examples 26 to 30>
Samples of Examples 26 to 30 were produced in the same manner as Examples 17, 4, 18, 19 and 9, except that the amount of electricity per unit electrode area was 30 mAh / cm ² .

As shown in FIG. 4, even when the current density was reduced to 30 mA / cm ² , a ferromagnetic film electrodeposition was obtained. In addition, the samples of Examples 26 and 27 were film-like, and the samples of Examples 28 to 30 were film-like and powdery. In addition, in the samples of Examples 26 to 30, the evaluation of density unevenness was all good. In Examples 26 to 30, the amount of electricity per concentration of 1 mass% of the Mn compound in the molten salt and per 1 cm ^{2 of} the electrode area are 15 mAh, 30 mAh, 60 mAh, 90 mAh, and 120 mAh, respectively.

<Examples 31 to 35>
The same as in Examples 26 to 30 except that the amount of electricity per unit electrode area was 120 mAh / cm ² and the energization time was 0.2 hours, 0.4 hours, 0.5 hours, 1 hour and 2 hours, respectively. Thus, samples of Examples 26 to 30 were produced.

As shown in FIG. 4, even when the current density was increased to 120 mA / cm ² , a ferromagnetic film electrodeposit was obtained. In addition, the samples of Examples 31 and 32 were film-like, and the samples of Examples 33 to 35 were film-like and powdery. In addition, in the samples of Examples 31 to 35, the density unevenness evaluation was all good. In Examples 31 to 35, the electric quantities per 1 mass% of the Mn compound in the molten salt and 1 cm ^{2 of} the electrode area are 24 mAh, 48 mAh, 60 mAh, 120 mAh, and 240 mAh, respectively.

<Examples 36 to 48>
Samples of Examples 36 to 48 were prepared in the same manner as in Example 9 except that the type and ratio of the Al compound and the type and ratio of the halide were changed. The types and ratios of Al compounds and the types and ratios of halides are as shown in FIGS.

As shown in FIGS. 4 and 5, the residual magnetization is higher in the case where the halide is NaCl than in the case where the halide is KCl, and in the case where the halide is LiCl than in the case where the halide is NaCl. However, when KCl and LiCl were combined as in Example 39, the remanent magnetization became larger. Moreover, even if AlCl ₃ which is an Al compound is replaced by a small amount with AlF ₃ or AlBr ₃ , a ferromagnetic powder electrodeposit is obtained. Even when cryolite (AlNa ₃ F ₆ ) was used as in Example 44, a powdered electrodeposit was obtained. In Examples 45 and 46, the residual magnetization slightly increased by containing a small amount of rare earth halides LaCl ₃ and DyCl ₃ . As in Examples 47 and 48, ferromagnetic powder electrodeposits were obtained even when a small amount of alkaline earth halide was contained. Also, in the samples of Examples 36 to 48, the evaluation of density unevenness was all good.

<Examples 49 to 56>
Examples 49 to 56 are the same as Example 9 except that the temperature of the molten salt during electrolysis was set to 150 ° C., 200 ° C., 300 ° C., 400 ° C., 450 ° C., 500 ° C., 550 ° C. and 600 ° C., respectively. A sample of was prepared. However, in Examples 55 and 56, the ratio of AlCl ₃ and NaCl was adjusted to 49:51 in consideration of the temperature of the molten salt.

As shown in FIG. 5, when the temperature of the molten salt during electrolysis is in the range of 150 ° C. to 350 ° C., the higher the temperature, the higher the residual magnetization of the ferromagnetic deposit. This is because when the temperature of the molten salt is too low, the Mn ratio in the electrodeposit is decreased, and a ferromagnetic τ phase having a low Mn ratio and a nonmagnetic γ2 phase or γ brass phase having a low Mn ratio are likely to be generated. Because. On the other hand, metamagnetism was observed in the temperature range of 400 ° C. or more and less than 600 ° C., and the response magnetic field of metamagnetism tended to decrease as the temperature of the molten salt increased. Further, when the temperature was 600 ° C., it became ferromagnetic and a very large remanent magnetization was obtained. Therefore, in order to obtain a sufficient remanent magnetization, the temperature of the molten salt during electrolysis may be set to 150 ° C. or more, 350 ° C. or less, or about 600 ° C. Furthermore, in order to obtain metamagnetism, the temperature of the molten salt during electrolysis may be 400 ° C. or higher and lower than 600 ° C. In the samples of Examples 49 to 56, the density unevenness evaluation was all good.

<Examples 57 to 60>
Except that the current density is set at the time of electrolysis respectively ^{15mA / cm 2, 30mA / cm} 2, 120mA / cm 2 and 150 mA / cm ^2, to prepare a sample of Examples 57-60 in the same manner as in Example 9.

As shown in FIG. 5, in the range current density of ^{15mA / cm 2 ~ 60mA / cm} 2 at the time of electrolysis, the residual magnetization of Analyte conductive ferromagnetic higher the current density, increased, the current density 150 mA / When it was raised to cm ² , the remanent magnetization was significantly reduced. This is because if the current density is too low, the Mn ratio in the deposit decreases, and a ferromagnetic τ phase with a low Mn ratio, a nonmagnetic γ2 phase or a γ brass phase with a low Mn ratio is likely to be generated. It is considered that this is because if the current density is too high, the formation of the τ phase itself is difficult to occur. Therefore, in order to obtain a sufficient residual magnetization, the current density during electrolysis 30 mA / cm ² or more, it may be set to 120 mA / cm ² or less. In addition, in the samples of Examples 57 to 60, the density unevenness evaluation was all good.

<Examples 61 to 73>
Samples of Examples 61 to 73 were prepared in the same manner as in Example 23 except that the type and ratio of the Al compound and the type and ratio of the halide were changed. The types and ratios of Al compounds and the types and ratios of halides are as shown in FIGS.

As shown in FIGS. 5 and 6, it was found that metamagnetism can be obtained by heat treatment at a predetermined temperature even if the type and ratio of the Al compound and the type and ratio of the halide are changed. Further, in the samples of Examples 61 to 73, the evaluation of density unevenness was all good.

<Examples 74 to 81>
Examples 74 to 81 are the same as Example 23 except that the temperature of the molten salt during electrolysis was set to 150 ° C, 200 ° C, 300 ° C, 400 ° C, 450 ° C, 500 ° C, 550 ° C, and 600 ° C, respectively. A sample of was prepared. However, in Examples 80 and 81, the ratio of AlCl ₃ and NaCl was adjusted to 49:51 in consideration of the temperature of the molten salt.

As shown in FIG. 7, when the temperature of the molten salt during electrolysis is 150 ° C. to 550 ° C., metamagnetism can be obtained by heat treatment at a predetermined temperature, and the temperature of the molten salt during electrolysis is 600 ° C. For example, it was found that ferromagnetism can be obtained by heat treatment at a predetermined temperature. In addition, in the samples of Examples 74 to 81, the evaluation of density unevenness was all good.
<Examples 82 to 85>
Except that the current density is set at the time of electrolysis respectively ^{15mA / cm 2, 30mA / cm} 2, 120mA / cm 2 and 150 mA / cm ^2, to prepare a sample of Examples 82-85 in the same manner as in Example 23.

As shown in FIG. 7, even when the current density during electrolysis was changed, it was found that metamagnetism can be obtained by heat treatment at a predetermined temperature. Further, in the samples of Examples 82 to 85, the density unevenness evaluation was all good.

DESCRIPTION OF SYMBOLS 1 Airtight container 2 Alumina crucible 3 Molten salt 4 Electric furnace 5 Cathode 6 Anode 7 Constant current power supply device 8 Stirrer 9 Gas path

Claims (10)

A method for producing a MnAl alloy in which a MnAl alloy is precipitated by electrolyzing a molten salt containing a Mn compound and an Al compound, wherein the Mn compound is additionally charged into the molten salt during electrolysis. . 2. The method for producing an MnAl alloy according to claim 1, wherein electrolysis is performed while the concentration of the Mn compound in the molten salt is maintained at 0.2 mass% or more by additionally charging the Mn compound. The method for producing a MnAl alloy according to claim 1 or 2, wherein the MnAl alloy deposited by electrolysis is subjected to a heat treatment. 4. The method for producing an MnAl alloy according to claim 3, wherein the MnAl alloy is given metamagnetism by setting the temperature of the heat treatment to 400 ° C. or higher and lower than 600 ° C. The method for producing a MnAl alloy according to claim 3, wherein the residual magnetization of the MnAl alloy is increased by setting the temperature of the heat treatment to 600 ° C or higher and 700 ° C or lower. The method for producing an MnAl alloy according to any one of claims 3 to 5, wherein an atmosphere of the heat treatment is in an inert gas or a vacuum. The powdered MnAl alloy is precipitated by performing electrolysis at an electric quantity of 50 mAh or more per 1 mass% of the Mn compound concentration in the molten salt and per 1 cm ^{2 of} electrode area. The manufacturing method of the MnAl alloy as described in any one of thru | or 6. The method for producing a MnAl alloy according to any one of claims 1 to 7, wherein the molten salt further contains an alkali metal halide. The method for producing an MnAl alloy according to claim 8, wherein the molten salt further contains a rare earth halide or an alkaline earth halide. 10. The temperature of the molten salt during electrolysis is 150 ° C. or more and 700 ° C. or less, and the amount of electricity per 1 cm ^{2 of} electrode area is 30 mAh or more and 120 mAh, 10. The manufacturing method of this MnAl alloy.

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