JP2019104982A - METHOD FOR PRODUCING PtCo ALLOYED POWDER THROUGH HYDRAZINE REDUCTION - Google Patents

Abstract

To provide a novel method for producing PtCo alloyed powder that has been an alloy sufficiently uniform at a minute level.SOLUTION: A method for producing PtCo alloyed powder includes the steps of: adding a mixed aqueous solution (PtCo solution) of platinum chloride and cobalt chloride at 50°C-100°C and a reducing agent solution comprising hydrazine and ammonia into a stirred reaction bath solution at 50°C-100°C, then while keeping temperature at 50°C-100°C, performing stirring after the end of the addition process, to deposit and precipitate Pt and Co; and subjecting the precipitation of Pt and Co to a hydrogen treatment.SELECTED DRAWING: None

Description

  The present invention relates to a method of producing PtCo alloy powder by hydrazine reduction.

With the recent oxide-based magnetic material targets, the heating temperature during sintering is limited by the addition of a low melting point component such as B ₂ O ₃ . However, when the sintering temperature is lowered, the interdiffusion ability of metal components such as Pt and Co is lowered, alloying is difficult to proceed, and it becomes difficult to maintain the homogeneity of the target.

  It is desirable that the magnetic material target has a large amount of leaked magnetic flux (PTF) leaking to the target surface during magnetron sputtering. Coarse-grained Co powder is mixed with the raw material of the target material in order to improve the PTF, but it also causes difficulties in maintaining the homogeneity of the target.

  As means for producing Pt powder, methods by atomization, hydrazine reduction, electrolysis and the like are known. Among them, the method by hydrazine reduction (for example, Patent Document 1) is effective in terms of initial investment, running cost, and quality stability. Patent Document 1 discloses a method of simultaneously adding a chloroplatinic acid aqueous solution and an ammonia / hydrazine aqueous solution to an ammoniacal aqueous solution as a hydrazine reduction method.

  Patent Document 2 discloses a technique for producing a nickel powder in which a cobalt coating layer is formed on the surface of nickel particles. In the technique of Patent Document 2, when hydrazine reduction is performed, it is taught that an alkaline region of about pH 10 to pH 12 is used (paragraph 0030 of Patent Document 2). However, a technique for forming a cobalt coating layer on the surface of Pt powder is neither disclosed nor suggested.

Patent No. 4079983 JP, 2015-81377, A

  As described above, maintenance of the homogeneity of the oxide-based magnetic material target containing Pt or Co is achieved by the reduction of the sintering temperature by the addition of the low melting point element, and the addition of the coarse-grained Co powder to improve the PTF. It is getting more and more difficult. However, if preparing a PtCo alloy powder that has become a sufficiently uniform alloy at a fine level and using it as a raw material powder for the target material, it will be easier to maintain the homogeneity of the target, or It is expected to improve.

  As described above, hydrazine reduction is known as a means for producing Pt powder. However, according to the study based on Patent Document 2, when hydrazine reduction is used as a means for producing Co powder, Co is much more difficult to be reduced than Pt, and therefore conditions of strong alkalinity (pH 10 to 12) The reaction at is essential. In order to obtain strong alkaline conditions, as disclosed in paragraph 0030 of Patent Document 2, NaOH, KOH, or the like is used as a modifier, but the remaining elements such as Na, K, etc. Negative impact on characteristics. Therefore, for example, by means of producing Co powder by hydrazine reduction based on the teaching of Patent Document 2 and mixing Pt powder and hydrazine powder separately after that, the remaining elements such as Na and K are avoided. However, the PtCo mixed powder produced in this manner is not suitable as a raw material for a target material.

  Accordingly, it is an object of the present invention to provide a novel manufacturing method for producing a PtCo alloy powder which is a sufficiently uniform alloy at a fine level.

  As a result of earnest research, according to a method including steps to be described later, the inventors of the present invention have a sufficiently uniform alloy at a fine level while avoiding residual Na and K by a wet reduction method excellent in productivity. It has been found that it is possible to produce a PtCo alloy powder to reach the present invention.

Therefore, the present invention includes the following (1):
(1)
Add a mixed aqueous solution of platinum chloride and cobalt chloride (PtCo solution) at 50 ° C. to 100 ° C. and an aqueous solution of a reducing agent containing hydrazine and ammonia into the stirred reaction solution at 50 ° C. to 100 ° C. Maintaining at 50 ° C. to 100 ° C. and stirring after completion of addition to precipitate Pt and Co for precipitation;
Hydrogenating the precipitate of Pt and Co,
A method of producing PtCo alloy powder, including:
(2)
The method according to (1), wherein the hydrogen treatment is a treatment in which the precipitate of Pt and Co is heated to 500 to 1000 ° C. in a hydrogen stream and held for 1 to 6 hours, and then cooled.
(3)
The production method according to any one of (1) to (2), wherein the stirring after completion of the addition is performed for 8 to 24 hours.
(4)
The manufacturing method in any one of (1)-(3) in which the stirring after completion | finish of addition is performed by pH of the range of pH 4-10.
(5)
The production method according to any one of (1) to (4), wherein the addition of the PtCo solution and the reducing agent aqueous solution is performed simultaneously or alternately, continuously or intermittently.
(6)
The addition of the PtCo solution takes place at one or more points of the reaction bath solution,
The production method according to any one of (1) to (5), wherein the addition of the reducing agent aqueous solution is performed at one or more places of the reaction bath aqueous solution.
(7)
The manufacturing method in any one of (1)-(6) whose reaction bath aqueous solution is water or dilute ammonia aqueous solution.
(8)
The aqueous reaction bath solution being stirred is a 70 ° C. to 100 ° C. reaction bath aqueous solution,
The PtCo solution to be added is a PtCo solution at 70 ° C. to 100 ° C.
The manufacturing method according to any one of (1) to (7), wherein the stirring after the completion of the addition is stirring maintained at 70 ° C. to 100 ° C.
(9)
Stirring is performed by means of stirring blades provided in the reaction bath aqueous solution,
The stirring blade is provided with the rotation axis parallel to the substantially vertical direction,
The production method according to any one of (1) to (8), wherein the stirring is performed at the tip of the outer periphery of the rotating stirring blade so as to have a stirring speed of 40 cm / sec or more.

  According to the present invention, it is possible to produce a PtCo alloy powder which is a sufficiently uniform alloy at a fine level while avoiding Na and K residues by a wet reduction method which is excellent in productivity. The PtCo alloy powder obtained by the present invention can be suitably used as a raw material powder for producing a sputtering target material.

FIG. 1 is a photograph showing the result of SEM observation of PtCo powder (after hydrogen reduction). FIG. 2 is a photograph showing the results of EDS mapping of PtCo powder (after hydrogen reduction).

  The present invention will be described in detail by way of specific embodiments.

[Production of PtCo alloy powder by hydrazine reduction]
In the preparation of the PtCo alloy powder according to the present invention, a mixed aqueous solution of platinum chloride and cobalt chloride (PtCo solution) at 50 ° C. to 100 ° C., hydrazine and ammonia are added to a stirred reaction solution at 50 ° C. to 100 ° C. Adding reducing agent aqueous solution containing, maintaining at 50 ° C. to 100 ° C. and stirring even after completion of addition to precipitate Pt and Co and precipitating, hydrogenating the precipitation of Pt and Co, and It can be implemented by a method.

  Originally, in order to precipitate Co, when hydrazine reduction was used, a reaction under strongly alkaline conditions should be essential. However, when precipitation is performed simultaneously with Pt in the above process, Pt is precipitated at a high recovery rate, and Co is also precipitated at a sufficiently high recovery rate, so that precipitation of Pt and Co can be obtained. . In this process, since NaOH and KOH used to make strong alkaline conditions are not used, Na and K derived from these do not remain in principle, and as a raw material for sputtering target materials, A suitable raw material powder is obtained.

[Mixed aqueous solution of platinum chloride and cobalt chloride]
A mixed aqueous solution of platinum chloride and cobalt chloride (PtCo solution) can be obtained by known means. In a preferred embodiment, the concentration of platinum chloride (PtCl ₂ ) can be, for example, 50 to 150 g / L, preferably 80 to 120 g / L as platinum concentration, and the concentration of cobalt chloride (CoCl ₂ ) is The cobalt concentration can be, for example, 5 to 50 g / L, preferably 15 to 40 g / L.

  The mixed aqueous solution of platinum chloride and cobalt chloride (PtCo solution) is, for example, at a temperature of 50 ° C. to 100 ° C., preferably 60 ° C. to 100 ° C., more preferably 70 ° C. to 100 ° C. prior to addition to the reaction bath aqueous solution. Heat it up. By setting the temperature to 50 ° C. or higher, the reaction activity can be enhanced and the reduction can be reduced. From the viewpoint of reaction activity, the temperature is preferably 70 ° C. or higher. By setting the temperature to 100 ° C. or less, it is possible to reduce the efficiency decrease due to the autolysis of hydrazine and to prevent the liquid amount reduction due to the evaporation of the reaction bath.

[Reductant aqueous solution containing hydrazine and ammonia]
The aqueous reducing agent solution containing hydrazine and ammonia is preferably an aqueous solution of hydrazine and ammonia and can be prepared by known means. The reducing agent aqueous solution contains a component that reduces the reducing power of hydrazine (such as an oxidizing agent), a component that promotes the destabilization of hydrazine (such as a strong alkali), and a component that reduces the alkali component of ammonia (such as an acid). Preferably not. The aqueous reducing agent solution can be prepared, for example, by mixing hydrazine monohydrate, aqueous ammonia and water immediately before use. The hydrazine concentration in the reducing agent aqueous solution can be, for example, 5 to 12% by mass, preferably 9 to 11% by mass. The ammonia concentration in the reducing agent aqueous solution can be, for example, 15 to 25% by mass, preferably 18 to 22% by mass.

  The temperature of the aqueous solution of the reducing agent containing hydrazine and ammonia is a temperature at which the temperature of the aqueous solution of the reaction bath can be maintained within the above-mentioned predetermined range, and the amount of volatilization of the components of the aqueous solution of the reducing agent is particularly restricted. There is no. The temperature of the reducing agent aqueous solution can be, for example, room temperature, for example, 4 ° C to 40 ° C, preferably 10 ° C to 30 ° C.

[Reaction bath solution]
The PtCo solution and the reducing agent aqueous solution are added to the reaction bath aqueous solution, and precipitation of Pt and Co proceeds in the reaction bath aqueous solution. As the reaction bath aqueous solution, for example, water or dilute aqueous ammonia can be used. However, in the case of using dilute aqueous ammonia, since a large amount of ammonia is volatilized in order to stir while heating to a predetermined temperature, the reductive deposition reaction uses water as a reaction bath aqueous solution, and It does not differ greatly, and it is preferable to use water from the viewpoint of work environment. Although water may contain a small amount of ammonia or salts within the range that does not interfere with the practice of the present invention, it is preferable to use pure water as water from the viewpoint of producing high purity PtCo alloy powder.

[Temperature of reaction bath solution]
The reaction bath aqueous solution is heated to a temperature of, for example, 50 ° C. to 100 ° C., preferably 60 ° C. to 100 ° C., more preferably 70 ° C. to 100 ° C. prior to the addition. By setting the temperature to 50 ° C. or higher, the reaction activity can be enhanced and the reduction can be reduced. From the viewpoint of reaction activity, the temperature is preferably 70 ° C. or higher. By setting the temperature to 100 ° C. or less, it is possible to reduce the efficiency decrease due to the autolysis of hydrazine and to prevent the liquid amount reduction due to the evaporation of the reaction bath.

  In a preferred embodiment, the aqueous reaction bath solution is heated to the above temperature range prior to the addition, and the above temperature range is maintained even after the addition is started, and the addition is completed. Continue after the

[PH of reaction solution]
In a preferred embodiment, the reaction bath aqueous solution can be, for example, in the range of pH 4 to 10, preferably pH 5 to 9 after addition is started and after addition is completed. By setting the pH to 4 or more, the reaction activity of hydrazine can be sufficiently extracted, and the reduction can be reduced. By setting the pH to 10 or less, the decrease in efficiency due to the autolysis of hydrazine can be reduced.

[Aspect of addition to reaction bath aqueous solution]
The PtCo solution and the reducing agent aqueous solution are added to the stirred reaction water solution. The addition of the PtCo solution and the reducing agent aqueous solution can be performed, for example, simultaneously or alternately, continuously or intermittently, preferably simultaneously and continuously. That is, although it is preferable to add simultaneously and continuously, the addition of either or both of the PtCo solution and the reducing agent aqueous solution is intermittently performed, and the time difference is within the range where the PtCo alloy powder is favorably generated. It may be.

  The addition of the PtCo solution and the reducing agent aqueous solution can be performed at one or a plurality of places of the reaction bath aqueous solution, respectively, and preferably can be added to a plurality of places, respectively. As a plurality of places, for example, two or more places can be used. Although there is no upper limit of the addition location, it may be, for example, 100 or less and 10 or less.

  The addition can take place, for example, on top of the stirred aqueous reaction bath solution, or may take place in the region from top to bottom. For example, precipitation of Pt and Co may be performed in the vicinity of the upper surface of the reaction bath aqueous solution, and may be added to a position where precipitation occurs rapidly.

[Rate and amount of addition to reaction bath solution]
In a preferred embodiment, the addition of the PtCo solution can be performed at an addition rate of, for example, 50 to 200 mL / min, preferably 80 to 120 mL / min, per liter of the reaction bath aqueous solution. In a preferred embodiment, the total addition amount of the PtCo solution is in the range of 50 to 200 g, preferably about 100 g, and in the range of 10 to 80 g of Co, per liter of the reaction bath aqueous solution. It can be about 35 g. The addition of the reducing agent aqueous solution can be performed, for example, at an addition rate of 20 to 200 mL / min, preferably 80 to 120 mL / min, per liter of the reaction bath aqueous solution. In a preferred embodiment, the total addition of the aqueous reducing agent solution is in the range of 0.5 to 1.5 ml as hydrazine monohydrate, 2.0 to 5.0 ml as aqueous 29% ammonia, per gram of Pt. can do. The ratio of the addition rate [mL / min] of the reducing agent aqueous solution to the addition rate [mL / min] of the PtCo solution is, for example, in the range of 0.3 to 0.7, preferably 0.4 to 0.6. it can.

[Stirring of reaction solution]
In a preferred embodiment, the aqueous reaction bath solution is allowed to stir prior to the addition, and this stirring is continued after the addition is started and also after the addition is completed. In a preferred embodiment, it is preferred to maintain the temperature range mentioned above during this stirring, preferably to the pH range mentioned above. That is, by setting the maintenance temperature to 50 ° C. or higher, the reaction activity can be enhanced, and the reduction can be reduced. From the viewpoint of reaction activity, the temperature is preferably 70 ° C. or higher. By setting the maintenance temperature to 100 ° C. or less, it is possible to reduce the decrease in efficiency due to the autolysis of hydrazine and to prevent the liquid amount reduction due to the evaporation of the reaction bath.

  Such stirring can be performed by a known means, for example, using a water pump or using bubbling by blowing in an inert gas such as nitrogen or argon which does not affect the reaction. Although it is possible, in order to achieve homogeneous propagation of the reaction conditions throughout the reaction system, means by a stirring blade or a stirrer is preferable.

[Stirring speed]
In a preferred embodiment, the stirring is carried out by means of a stirring blade provided in the aqueous reaction bath solution. For example, the stirring blade can be provided with the rotation axis parallel to the substantially vertical direction, and the stirring is performed so that the stirring speed is 40 cm / sec or more at the tip of the outer periphery of the rotating stirring blade. It will be. The stirring speed can be 40 cm / sec or more, preferably 100 cm / sec or more, and the upper limit is not particularly limited as long as it does not impair the workability, for example, 400 cm / sec or less, 350 cm / sec or less , 300 cm / sec or less and 250 cm / sec or less. By setting it as 40 cm / sec or more, reaction of a solution can be homogenized and bias of a component by local reaction can be reduced. It is preferable to set it as 400 cm / sec or less from the viewpoint of loss due to splashing and efficiency of energy.

[Stirring after completion of addition]
In a preferred embodiment, the stirring after the addition is carried out, for example, for 8 to 24 hours, preferably for 12 to 16 hours. By setting the stirring time after the completion of addition to 8 hours or more, a sufficient reaction maturation time can be given to reduce the reduction. The stirring after completion of the addition can be carried out for 24 hours or more, but preferably 24 hours or less from the viewpoint of effective use of energy and time. As described above, also in the stirring after the completion of the addition, it is preferable to maintain the above-mentioned temperature range, it is preferable to maintain the above-mentioned pH range, and it is preferable to maintain the above-mentioned stirring speed. That is, by setting the maintenance temperature to 50 ° C. or higher, the reaction activity can be enhanced, and the reduction can be reduced. From the viewpoint of reaction activity, the temperature is preferably 70 ° C. or higher. By setting the maintenance temperature to 100 ° C. or less, it is possible to reduce the decrease in efficiency due to the autolysis of hydrazine and to prevent the liquid amount reduction due to the evaporation of the reaction bath.

Precipitation of Pt and Co
By the above addition and stirring, Pt and Co precipitate and precipitate. In a preferred embodiment, of the Pt contained in the added PtCo solution, the ratio of Pt precipitated and precipitated (Pt recovery rate) is 99% or more, preferably 99.5% or more, more preferably 99.9. % Or more. In a preferred embodiment, the proportion (Co recovery rate) of Co precipitated and precipitated out of Co contained in the added PtCo solution is 70% or more, preferably 74% or more, more preferably 80% or more. be able to. According to the present invention, it is possible to precipitate and precipitate Co with such a high recovery rate, which is originally considered to be not precipitated by reduction under strong alkaline conditions. The Pt recovery rate and the Co recovery rate can be calculated by the procedure described in the examples.

  The precipitated Pt and Co precipitates can be separated from the liquid phase and recovered by known means. As such separation means, for example, filtration, centrifugation, sedimentation, and drying can be mentioned.

[Hydrogen treatment]
Precipitation The precipitates of Pt and Co recovered by precipitation are subjected to hydrogen treatment. By this hydrogen treatment, the precipitation of Pt and Co becomes the whole PtCo alloy powder. The hydrogen treatment can be performed, for example, by raising the temperature of recovered PtCo precipitate to 500 to 1000 ° C. in a hydrogen stream and holding it for 1 to 6 hours, and then lowering the temperature. The heating can be performed to reach the predetermined temperature, for example, in a time of 1 to 5 hours, preferably 2 to 4 hours. Since the heating rate has a relatively small effect on the quality of the alloy, it may be carried out so as to reach the predetermined temperature in a shorter or longer time. The predetermined temperature may be, for example, 500 to 1000 ° C., preferably 750 to 850 ° C. By setting this temperature to 500 ° C. or more, the reduction reaction can be sufficiently advanced. By setting this temperature to 1000 ° C. or less, a powder having good crushability can be obtained. The holding at the predetermined temperature may be, for example, holding for 1 to 6 hours, preferably 1 to 3 hours. The temperature drop from the predetermined temperature can be performed, for example, by natural cooling in a hydrogen stream, and can be performed, for example, by cooling for 3 hours or more, preferably 12 hours or more. Since the temperature lowering rate has a relatively small effect on the quality of the alloy, it may be allowed to cool for a shorter time. The hydrogen flow can be, for example, a flow rate of 0.1 to 2.0 L / min, preferably 0.5 to 1.0 L / min.

[PtCo alloy powder]
In a preferred embodiment, the PtCo alloy powder can have such characteristics as high surface area and low concentration of gas components without any bias in the dispersibility of Pt and Co. The ratio of the content of Pt to Co contained in the PtCo alloy powder can be adjusted by the ratio of the content in the added PtCo solution. For example, the value of Co / Pt weight ratio is 1/1. The ratio may be in the range of ̃1 / 10, or in the range of 1⁄4 to 1⁄6.

  The PtCo alloy powder of the present invention is obtained by subjecting a precipitate of Pt and Co deposited by hydrazine reduction (PtCo precipitate) to hydrogen treatment. The PtCo alloy powder is converted into an alloy powder or an alloy powder containing fine single Pt metal and single Co metal by hydrogen treatment, and the remaining elements such as Na and K are completely avoided, so the target is a target. It is an alloy powder that can be suitably used as a raw material for materials.

  Hereinafter, the present invention will be described in detail by way of examples. The present invention is not limited to the examples illustrated below.

[Examples 1 to 4]
First, a 1000 ml glass beaker containing 200 ml of pure water was placed on a hot plate and heated while stirring with a stirring blade to prepare a solution (1). As the stirring blade, a Teflon (registered trademark) T-shaped blade having a blade length of 4 cm from the center (the outer end is 25.12 cm at one round) was used. The stirring rotational speed and the temperature will be described later because they are condition fluctuation factors.
Next, 200 ml of a platinum chloride / cobalt chloride solution of 100 g of Pt and 23 g of Co / L was prepared. The solution was heated on a hot plate to prepare a solution (2). Temperature will be described later because it is a condition variable.
Next, 68 ml of 29% ammonia water, 20 ml of 98% hydrazine monohydrate and pure water were mixed to prepare 100 ml (Liquid (3)).
Then, the liquid (2) and the liquid (3) were simultaneously added to the liquid (1) prepared above. The addition rate was 20 ml / min for solution (2) and 10 ml / min for solution (3).
It heated at 80 degreeC for 16 to 20 hours after completion | finish of said addition.
Thus, the solution (2) and the solution (3) were added to the solution (1) to precipitate Pt and Co. The deposited Pt and Co precipitates were collected by filtration. The concentration of Pt and Co remaining in the filtrate was measured, and the Pt recovery rate and the Co recovery rate were calculated by the following equations.
[Pt recovery rate] = 100 x (Pt input amount-filtrate Pt amount) / (Pt input amount)
[Co recovery rate] = 100 × (Co input amount-filtrate Co amount) / (Co input amount)
The details of the conditions of the above Examples 1 to 4 and the results thereof are summarized in the following Table 1.

  In Table 1, when the liquid (1) stirring rotational speed is 100 rpm, the tip speed of the stirring blade (stirring speed) is calculated to be 41.9 cm / sec, and the liquid (1) stirring rotational speed is 150 rpm In the case, the stirring speed is calculated to be 62.8 cm / sec.

[result]
As shown in Table 1, it was found that by simultaneously reducing Pt and Co with hydrazine, Pt and Co were simultaneously deposited to obtain PtCo powder, without using strongly alkaline conditions (for example, pH 10 or more). . The Pt recovery rate in this method was very high, and the Co recovery rate was sufficiently high.

[Example 5]
First, a 2000 ml glass beaker containing 400 ml of pure water was placed on a hot plate and heated while stirring with a stirring blade to prepare a solution (1). The stirring rotational speed and the temperature will be described later because they are condition fluctuation factors.
Next, 400 ml of a platinum chloride-cobalt chloride solution of 100 g of Pt and 23 g of Co / L was prepared. The solution (2) was prepared by heating on a hot plate. Temperature will be described later because it is a condition variable.
Next, 136 ml of 29% ammonia water, 40 ml of 98% hydrazine monohydrate and pure water were mixed to prepare 200 ml (Liquid (3)).
Then, the solution (2) and the solution (3) were simultaneously added to the solution (1). The addition rate was 40 ml / min for solution (2) and 20 ml / min for solution (3), respectively.
After completion of the above addition, the mixture was heated at 80 ° C. for 16 hours.
Thus, the solution (2) and the solution (3) were added to the solution (1) to precipitate Pt and Co. Precipitation The precipitated Pt and Co precipitates were collected by filtration. The concentration of Pt and Co remaining in the filtrate was measured, and the Pt recovery rate and the Co recovery rate were calculated in the same manner as in Example 1.
The details of the conditions of Example 5 described above and the results thereof are summarized in Table 2 below.

  In Table 2, when the liquid (1) stirring rotation speed is 250 rpm, the stirring speed is calculated to be 104.6 cm / sec.

[result]
As shown in Table 2 above, the method of simultaneously precipitating and precipitating Pt and Co by hydrazine reduction is carried out by scaling up twice and the Pt recovery rate and the Co recovery rate are sufficiently improved. It turned out that it is a method that can be further scaled up.

Example 6: Hydrogen reduction
The powder obtained in Example 5 was placed in a tubular furnace, heated to 800 ° C. in a 1 L / min hydrogen stream for 3 hours, held at 800 ° C. for 2 hours, and allowed to cool to recover PtCo powder.
SEM observation of the obtained powder was performed. FIG. 1 is a photograph showing the result of SEM observation. The obtained powder was observed by EDS (energy dispersive X-ray spectrometer) mapping. FIG. 2 is a photograph showing the results of EDS mapping.
It was found from FIG. 2 that the colored portions showing Co were uniformly dispersed. Since it was estimated that Pt was present in the whole of the visual field from the composition separately confirmed, as a result, it was confirmed that there was no bias in the dispersion of Pt and Co.
It was 0.06% (600 ppm) when oxygen concentration (oxygen content) was measured by LECO analysis about the obtained powder | flour. Similarly, the Co concentration (Co content) was 15.7%. That is, Co was present in the metal state, not in the oxide state in its entirety.
Combining this measurement result of the oxygen concentration and the observation result of the dispersibility of Pt and Co, it is possible for PtCo powder to be fine even if the whole amount of Pt and Co is in an alloyed state or even if a single metal is present. It was found that the material was in a sufficiently uniformly dispersed state at

  According to the present invention, it is possible to produce a PtCo alloy powder which is a sufficiently uniform alloy at a fine level while avoiding Na and K residues by a wet reduction method which is excellent in productivity. The present invention is an industrially useful invention.

Claims (9)

Add a mixed aqueous solution of platinum chloride and cobalt chloride (PtCo solution) at 50 ° C. to 100 ° C. and an aqueous solution of a reducing agent containing hydrazine and ammonia into the stirred reaction solution at 50 ° C. to 100 ° C. Maintaining at 50 ° C. to 100 ° C. and stirring after completion of addition to precipitate Pt and Co for precipitation;
Hydrogenating the precipitate of Pt and Co,
A method of producing PtCo alloy powder, including:   The production method according to claim 1, wherein the hydrogen treatment is a treatment in which the precipitate of Pt and Co is heated to 500 to 1000 ° C in a hydrogen stream and held for 1 to 6 hours, and then cooled.   The manufacturing method according to any one of claims 1 to 2, wherein the stirring after the completion of the addition is performed for 8 to 24 hours.   The method according to any one of claims 1 to 3, wherein the stirring after completion of the addition is performed at a pH in the range of pH 4 to 10.   The method according to any one of claims 1 to 4, wherein the addition of the PtCo solution and the aqueous reducing agent solution is performed simultaneously or alternately, continuously or intermittently. The addition of the PtCo solution takes place at one or more points of the reaction bath solution,
The method according to any one of claims 1 to 5, wherein the addition of the reducing agent aqueous solution is carried out at one or more places of the reaction bath aqueous solution.   The production method according to any one of claims 1 to 6, wherein the aqueous reaction bath solution is water or a dilute aqueous ammonia solution. The aqueous reaction bath solution being stirred is a 70 ° C. to 100 ° C. reaction bath aqueous solution,
The PtCo solution to be added is a PtCo solution at 70 ° C. to 100 ° C.
The production method according to any one of claims 1 to 7, wherein the stirring after completion of the addition is stirring maintained at 70 ° C to 100 ° C. Stirring is performed by means of stirring blades provided in the reaction bath aqueous solution,
The stirring blade is provided with the rotation axis parallel to the substantially vertical direction,
The method according to any one of claims 1 to 8, wherein the stirring is performed at a tip of the outer periphery of the rotating stirring blade so as to have a stirring speed of 40 cm / sec or more.