JP5680866B2 - Method for producing nitrogen-containing metal powder - Google Patents

Description

  The present invention relates to a method for producing a nitrogen-containing metal powder used for producing a tantalum electrolytic capacitor or a niobium electrolytic capacitor.

As a capacitor used in an electronic circuit of an electronic device, a tantalum electrolytic capacitor or a niobium electrolytic capacitor having a low ESR and a high capacity may be used for the purpose of achieving low voltage driving, high frequency, and low noise.
A tantalum electrolytic capacitor is manufactured by forming a dielectric film on the surface by chemical conversion treatment of tantalum powder, and connecting a cathode electrode to the dielectric film through an electrolyte layer made of an electrolytic solution or a conductive polymer. . A niobium electrolytic capacitor is also manufactured by a similar method.
In recent years, the surface area of tantalum powder or niobium powder (hereinafter referred to as “tantalum powder or the like”) has been increased in order to achieve higher capacity. However, when the surface area of tantalum powder or the like is increased, the amount of oxygen adsorbed on the surface increases, and thus the amount of crystalline oxide that causes leakage current of the dielectric film is increased during the manufacture of the capacitor. In recent years, in order to realize a high capacity, since the dielectric film tends to be thin with respect to the operating voltage, leakage current is more likely to occur. Therefore, when the capacity of the capacitor is increased, the leakage current increases and the reliability may be impaired.

Therefore, in order to suppress the influence of oxygen and improve the reliability of the high-capacitance capacitor, it has been proposed that tantalum powder or the like contains nitrogen.
As a method for producing a tantalum powder containing nitrogen, for example, in Patent Document 1, potassium fluoride of tantalum or potassium fluoride of niobium is reduced in a molten diluted salt using a reducing agent. A method of introducing a nitrogen-containing gas into a molten diluted salt by bubbling is disclosed.
Further, Patent Document 2 discloses that tantalum potassium fluoride salt or niobium fluoride potassium salt is reduced with a reducing agent in a molten diluted salt, while nitrogen is formed on the surface of the molten diluted salt. A method for distributing the contained gas is disclosed.
In the production of tantalum powder, it is a common practice to prepare agglomerated particles that are easy to handle by further heat-treating the powder obtained by reduction in molten diluted salt. Therefore, as in the methods described in Patent Documents 1 and 2, when nitrogen is appropriately contained in the tantalum powder or the like before the heat treatment, a decrease in the surface area during the heat treatment can be suppressed, and reliability when used as a capacitor is improved. It is thought to improve.

Japanese Patent No. 4049964 Japanese Patent No. 4187533

  However, in the production methods described in Patent Documents 1 and 2, even when production is performed under completely the same controllable conditions, the nitrogen content in the nitrogen-containing metal powder may vary greatly from production to production. If the nitrogen content of the nitrogen-containing metal powder is not constant, the mechanical properties of the nitrogen-containing metal powder and the performance of the resulting electrolytic capacitor may not be constant, leading to a decrease in quality.

  Further, tantalum powder for tantalum capacitors has a required nitrogen content depending on characteristics such as a specific surface area and a primary particle diameter. Therefore, a means for easily adjusting the nitrogen content to a desired amount has been demanded. However, in the nitrogen supply methods described in Patent Literatures 1 and 2, the nitrogen content of the obtained nitrogen-containing metal powder may deviate greatly from the desired amount.

Then, the 1st objective of this invention is to provide the manufacturing method of the nitrogen containing metal powder which can suppress the dispersion | variation in the nitrogen content of the nitrogen containing metal powder for every manufacture easily, and can adjust nitrogen content easily. .
The second object of the present invention is to provide a method for producing a nitrogen-containing metal powder that can easily adjust the nitrogen content of the obtained nitrogen-containing metal powder within an appropriate range.

As a result of investigation by the present inventor, the nitrogen content of the nitrogen-containing metal powder varies from production to production in the production methods described in Patent Literatures 1 and 2 because the amount of nitrogen gas taken into the molten diluted salt is different. I found out. That is, in the production methods described in Patent Documents 1 and 2, in order to obtain fine and uniform primary particles, the raw materials put into the diluted salt are sufficiently stirred and dispersed quickly, but can be controlled. Even if the conditions are completely the same, it is difficult to control the stirring state to be constant. Therefore, it is presumed that the nitrogen gas intake amount of the diluted salt becomes excessive or insufficient for each production, and the nitrogen content of the nitrogen-containing metal powder varies.
And based on this knowledge, in order to achieve the first object, as a result of examining a nitrogen supply method that hardly causes a difference in the amount of nitrogen in the molten diluted salt even if a difference in stirring state occurs, The first invention and the second invention have been reached.

The first invention has the following aspects [1] to [3].
C. in [1] molten diluent salt, when the tantalum compound or niobium compound is reduced with a reducing agent, a nitrogen supply agent is added, a nitrogen supply agent is a solid body, wherein the solid is melted A nitrogen supply formed from a solid nitrogen-containing compound using a molding material that can be melted in a diluted salt; the diluted salt is sodium chloride, potassium chloride or potassium fluoride; the reducing agent is an alkali Metals, alkaline earth metals or hydrides thereof; the solid nitrogen-containing compound is ammonium chloride or urea; and the molding material is potassium chloride, sodium chloride, lithium chloride, potassium fluoride or sodium fluoride A method for producing a nitrogen-containing metal powder, characterized in that
[2] The method for producing a nitrogen-containing metal powder according to [1], wherein the molding material coats a solid nitrogen-containing compound in the previous period.
[3] The method for producing a nitrogen-containing metal powder according to [1] or [2], wherein the molding material is the same component as the diluted salt.

In the method for producing a nitrogen-containing metal powder of the first invention and the second invention, variation in the nitrogen content of the nitrogen-containing metal powder for each production can be easily suppressed, and the nitrogen content can be easily adjusted.
In the method for producing a nitrogen-containing metal powder of the third invention, the nitrogen content of the obtained nitrogen-containing metal powder can be easily adjusted within an appropriate range.

It is the schematic which shows an example of the reaction apparatus used by the 1st, 3rd embodiment of the manufacturing method of the nitrogen containing metal powder of this invention. It is a figure explaining the stirring blade used with the reaction apparatus shown in FIG. It is the schematic which shows an example of the reaction apparatus used by 2nd Embodiment of the manufacturing method of the nitrogen containing metal powder of this invention. It is the schematic which shows the other example of the sealing means used in 2nd Embodiment of the manufacturing method of the nitrogen-containing metal powder of this invention.

"Nitrogen-containing metal powder"
As a form of nitrogen in the nitrogen-containing metal powder produced by the method for producing a nitrogen-containing metal powder of the present invention, it is preferable that nitrogen is in a solid solution in the metal. Here, it is preferable that the metal is at least one selected from the group consisting of niobium, tantalum, and niobium-tantalum alloy because a high-capacity capacitor can be obtained when this is used as an anode electrode raw material for a solid electrolytic capacitor. .
When nitrogen is dissolved in the metal, the lattice constant of the metal crystal changes. Therefore, the solid solution of nitrogen in the metal can be confirmed by shifting the position of the X-ray diffraction peak. For example, when 3000 ppm of nitrogen is dissolved in tantalum, the interplanar spacing d = 0.23375 nm of the (110) plane of metallic tantalum increases by about 0.1% to d = 0.23400 nm.
Examples of the form of nitrogen in the nitrogen-containing metal powder include a form of crystalline nitride in which nitrogen is formed with a metal, but an increase in crystalline nitride is not preferable because the leakage current of the capacitor increases.

The nitrogen content of the nitrogen-containing metal powder is preferably 500 to 10000 ppm, more preferably 800 to 6000 ppm, and still more preferably 1000 to 4000 ppm.
Here, the nitrogen content is a value determined by the following method. For example, using a commercially available oxygen / nitrogen analyzer (Horiba EMGA520), a sample is heated in an helium gas by impulse melting and the generated gas is quantified by TCD (thermal conductivity method) (JIS H1585). Desired.
When the nitrogen content of the nitrogen-containing metal powder is 500 ppm or more, the sintering speed can be moderately suppressed when the nitrogen-containing metal powder is sintered, and pores suitable for the capacitor can be formed. On the other hand, if the nitrogen content is 10000 ppm or less, the distribution of nitrogen in the nitrogen-containing metal powder can be made uniform, an increase in nitride crystals can be suppressed, and the leakage current of the capacitor can be reduced.
In order to bring the content of the nitrogen-containing metal powder into the above range, for example, in the production method described later, the nitrogen supply agent or the amount of nitrogen introduced is referred to as a tantalum compound or niobium compound (hereinafter referred to as “metal raw material”). The target nitrogen content should be equivalent to the mass of the metal in the metal). Furthermore, when the accuracy of the nitrogen content of the nitrogen-containing metal powder is required, the nitrogen supply amount when the target nitrogen content is 100% by mass with respect to the mass of the metal in the metal raw material is 100 to 100%. What is necessary is just to adjust with 500 mass%.
Here, the nitrogen supply amount is preferably determined in consideration of the recovery rate of the nitrogen-containing metal powder and the efficiency of the added nitrogen. For example, there is a difference in the recovery rate between the amount of the metal raw material and the amount of the nitrogen-containing metal powder obtained, and when the reaction temperature is low, the reaction time is short, or the target nitrogen content is high, nitrogen It is necessary to set a large amount of supply, preferably 100 to 300% by mass, and more preferably 100 to 150% by mass.
When it is desired to produce a nitrogen-containing tantalum powder having a nitrogen content of 2000 ppm, for example, in the production method described later, 200 kg of potassium fluorinated tantalate (K ₂ TaF ₇ ) is used as a metal salt, and the recovery rate and nitrogen efficiency are increased. Assuming 100%, about 150 L (185 g) of nitrogen may be introduced in the standard state (STP).

The specific surface area measured by the BET method of the nitrogen-containing metal powder is preferably 1.0 m ² / g or more because a capacitor having a higher capacity can be obtained. Specifically, when the metal is tantalum is preferably 1.0~10.0m ² / g, when the metal is niobium, be a 2.0~20.0m ² / g preferable.
Further, when the nitrogen amount [ppm] in the nitrogen-containing metal powder is W and the specific surface area [m ² / g] is S, W / S is preferably 150 to 3000, and preferably 150 to 2000. Is more preferable. If W / S is 150 or more, the effect of adding nitrogen is sufficiently exhibited, the leakage current is further reduced, and if it is 3000 or less, formation of crystalline nitride can be prevented. In particular, since the temperature used for heat treatment or the like decreases as S increases, when S = 1.3 to 1.6, W / S = 1500 to 2500 and S = 1.6 to 1 when the metal is tantalum. .9 is W / S = 1000 to 1900, S = 2.0 to 2.5 is W / S = 700 to 1100, S = 2.8 to 3.2 is W / S = 500 to 900, S = 3 .2 to 4.0, W / S = 400 to 600, S = 4.2 to 5.0, W / S = 300 to 500, S = 5.0 to 10.0, W / S = 150 to 300 Is preferred.

  The nitrogen-containing metal powder preferably has a mode diameter (maximum frequency diameter) of 30 to 150 μm. Here, when the nitrogen-containing metal powder is a porous powder by agglomeration of fine primary particles corresponding to the specific surface area, the particle diameter is a volume measured by a laser diffraction / scattering method. The standard particle size. When the mode diameter of the nitrogen-containing metal powder is within the above range, the handling is good and the capacitor is more suitable for the capacitor.

"Production method of nitrogen-containing metal powder"
Hereinafter, an embodiment of a method for producing a nitrogen-containing metal powder of the present invention will be described. The following embodiments are specifically shown for better understanding of the gist of the invention, and do not limit the present invention.

<First Embodiment>
1st Embodiment is embodiment about the manufacturing method of the nitrogen-containing metal powder of 1st invention.

(Reactor)
In the method for producing a nitrogen-containing metal powder of the present embodiment, a reaction apparatus 1 shown in FIG. 1 is used.
The reactor 1 includes a reactor 10a, a metal raw material inlet 20, a reducing agent inlet 30, a nitrogen supplier inlet 40 provided on the upper surface of the reactor 10a, and an agitator 50 for stirring the inside of the reactor 10a. It comprises.

  The stirrer 50 includes a stirring blade 51, a rotating shaft 52 that fixes the stirring blade 51, and a motor 53 that rotationally drives the rotating shaft 52. In the present embodiment, two pitched paddle blades arranged so as to be inclined with respect to the horizontal direction as shown in FIG.

In the present embodiment, the width W of the stirring blade 51 is uniform. The width W of the stirring blade 51 is preferably 10 to 50%, more preferably 15 to 25% with respect to the rotation radius of the stirring blade 51. If the width W of the agitating blade 51 is 10% or more with respect to the rotation radius of the agitating blade 51, in order to obtain fine and uniform primary particles, the raw materials put into the diluted salt are sufficiently agitated quickly and uniformly. It can be sufficiently expected to function as an agitating blade dispersed in the glass, and if it is 50% or less, the rotational speed for functioning as an agitating blade can be achieved without excessive stirring resistance.
The length (rotating radius) of the stirring blade 51 in the longitudinal direction is preferably 30 to 80%, more preferably 40 to 70%, with respect to the inner diameter of the reactor 10a. If the length in the longitudinal direction of the stirring blade 51 is 30% or more with respect to the inner diameter of the reactor 10a, in order to obtain fine and uniform primary particles, the raw material that has been sufficiently stirred and introduced into the diluted salt is used. It is sufficient as a stirring blade to disperse quickly and uniformly, and if it is 80% or less, it is possible to prevent undesired turbulent flow due to excessive stirring resistance.

  The stirring blade 51 is preferably inclined at an angle θ of 30 to 90 ° with respect to the horizontal direction over the entire length direction. When stirring with a pitched paddle blade inclined at an angle θ in the above range, there is a large discharge flow that is a flow from the stirring blade 51 toward the inner peripheral surface of the reactor 10a, and a circulating flow (shaft) that is a flow that circulates the contents in the vertical direction. Flow) is reduced. In such a stirring state, the generated nitrogen-containing metal powder is allowed to settle in the lower part of the reactor 10a, and the reaction with the newly introduced metal raw material can be suppressed. Can be prevented.

  As shown in FIG. 2, the corner C between the surface 51a and the side surface 51b of the stirring blade 51 is preferably rounded. For example, when the thickness of the portion having no curvature radius at the cross-sectional end in the rotation direction of the stirring blade is 20 mm to 30 mm, the curvature radius of the corner C is preferably 3 to 10 mm. If the curvature radius of the corner C is 3 mm or more and 10 mm or less, the nitrogen content of the nitrogen-containing metal powder can be made more uniform.

(Production method)
In the method for producing a nitrogen-containing metal powder according to this embodiment, first, the reactor 10a of the reaction apparatus 1 is filled with a diluted salt.
Here, as the diluted salt, for example, sodium chloride, potassium chloride, potassium fluoride and the like are used. A diluted salt may be used individually by 1 type, and may use 2 or more types together.
The amount of the diluted salt is preferably 2 to 10 times the total mass of the metal raw material and the reducing agent described later. If the amount of diluted salt is more than twice the total mass of the metal raw material and the reducing agent, the concentration of the metal raw material can be lowered moderately, the reaction rate is suppressed, and the resulting nitrogen-containing metal powder is prevented from becoming coarse. it can. On the other hand, if the amount of the diluted salt is 10 times or less with respect to the total mass of the metal raw material and the reducing agent, an excessive decrease in the reaction rate can be prevented and sufficient productivity can be secured.

Next, a rare gas such as argon is introduced into the reactor 10a to exclude air, and the reactor 10a is heated to melt the diluted salt (hereinafter, the molten diluted salt is referred to as “molten salt”). After melting, the stirring blade 51 is rotated by the motor 53 via the rotating shaft 52 to stir the molten salt.
The heating temperature is preferably 750 to 900 ° C. If the heating temperature is 750 ° C. or higher, the diluted salt can be sufficiently melted, and if it is 900 ° C. or lower, the diluted salt can be melted while suppressing excessive consumption of energy.

  The number of revolutions of the stirring blade 51 when melting the diluted salt is preferably 100 to 200 revolutions / minute, and more preferably 120 to 160 revolutions / minute. If the number of revolutions of the stirring blade 51 when melting the diluted salt is 100 revolutions / minute or more, the temperature distribution is sufficiently uniform, and if it is 200 revolutions / minute or less, stirring is possible with economical power. .

Next, a metal raw material is introduced into the reactor 10a from the metal raw material inlet 20, and a solid nitrogen-containing compound is formed from a nitrogen material inlet 40 or a metal raw material inlet 20 as a molding material that is melted in molten salt. Is fed into the reactor 10a. In the introduction of the nitrogen supply agent, for example, a method in which a target amount is mixed and supplied in advance with a metal raw material, a method in which a load cell is installed separately from the metal raw material and supplied simultaneously or with a time difference, a screw feeder, etc. A method of supplying continuously or intermittently with the metal raw material simultaneously or separately can be applied.
The charged metal raw material is melted in the molten salt while being diffused by stirring. In addition, while the charged nitrogen supplier is diffused by stirring, the molding material is first melted, and then the exposed solid nitrogen-containing compound is melted and dispersed. Thereby, nitrogen is supplied into the molten salt.

The metal raw material is a tantalum compound or a niobium compound. Examples of the tantalum compound include potassium tantalum fluoride (K ₂ TaF ₇ ) and halides (eg, tantalum pentachloride, lower tantalum chloride, etc.).
Examples of niobium compounds include potassium fluoride salts of niobium (K ₂ NbF ₇ , K ₂ NbF ₆ ) or halides (eg, niobium pentachloride, lower niobium chloride, etc.).

The solid-like nitrogen-containing compounds contained in the nitrogen supply agent, for example, ammonium chloride, urea, hydrazine, etc. azide and the like.
Specific examples of the molding material include potassium chloride, sodium chloride, lithium chloride, potassium fluoride, sodium fluoride, and the like. Among these, the same component as the molten salt (diluted salt) is preferable because it does not affect the composition of the molten salt. Nitrogen supply agent can be added without using molding material, but bubbling of nitrogen generated by gasification until the nitrogen supply agent is dissolved in the molten salt and re-contact with the molten salt surface It is preferable to use a molding material in order to reduce the amount as much as possible.

The content of the solid nitrogen-containing compound in the nitrogen supply agent is preferably 25 to 95% by mass, and more preferably 35 to 85% by mass. If the content of the solid nitrogen-containing compound is 25% by mass or more, nitrogen can be sufficiently supplied with a small addition amount, and if it is 95% by mass or less, the shape of the nitrogen supply agent is maintained until the molten salt is reached. Thus, the rate at which the solid nitrogen-containing compound is exposed can be suppressed.
The mode diameter of the nitrogen supply agent is preferably 0.5 to 20 mm, and more preferably 1 to 8 mm. If the mode diameter of the nitrogen supply agent is 20 mm or less, it can be diffused quickly, and if it is 0.5 mm or more, the handleability is excellent.

  As a method for preparing the nitrogen supply agent, for example, a method in which a solid nitrogen-containing compound and a molding material are mixed and then molded into a cylindrical shape or a spherical shape with a tableting machine or the like, a solid nitrogen-containing compound and a molding material are used. A method of kneading into a paste with water, alcohol, etc., then molding and drying with an extrusion molding machine, etc., and coating a molding material with a coating device etc. with water, alcohol, etc. as a binder using a solid mass of a nitrogen-containing compound as a core And a method of coating a molding material with a hybridizer (manufactured by Nara Machinery) without using a binder on a solid obtained by spray cooling of a solid nitrogen-containing compound.

  Although the amount of nitrogen supply or nitrogen added varies depending on the type of nitrogen supply used, the target nitrogen content may be introduced with respect to the mass of the metal in the metal raw material. Furthermore, when the accuracy of the nitrogen content of the nitrogen-containing metal powder is required, the recovery rate of the nitrogen-containing metal powder and the efficiency of the added nitrogen are taken into consideration, and the target is based on the mass of the metal in the metal raw material. It is preferable to adjust the nitrogen supply amount at 100 to 500% by mass when the nitrogen content is 100% by mass.

  The number of rotations of the stirring blade 51 when adding the metal raw material and the nitrogen supply agent is preferably 100 to 200 rotations / minute, and more preferably 140 to 170 rotations / minute. If the rotation speed of the stirring blade 51 when adding the metal raw material and the nitrogen supply agent is 100 revolutions / minute or more, the nitrogen supply agent can be further diffused throughout the reactor 10a. However, even if it stirs over 200 rotations / min, since the effect of making it high rotation is saturated, it is useless.

Next, a reducing agent is introduced into the reactor 10a from the reducing agent inlet 30, and the metal raw material is reduced by the reducing agent.
The metal tantalum or metal niobium produced by the reduction easily takes in the nitrogen in the molten salt to produce a solid solution in which tantalum and nitrogen are in solid solution or a solid solution in which niobium and nitrogen are in solid solution. Since the produced solid solution has a specific gravity larger than that of the molten salt, it settles in the lower part of the reactor 10a.

  As the reducing agent, alkali metals such as sodium, magnesium and calcium, alkaline earth metals, hydrides thereof and the like can be used. Among these, sodium is preferable.

  The amount of reducing agent added varies depending on the type of metal raw material to be used, but the metal raw material can be sufficiently reduced as long as it is equal to or more than the reaction equivalent with the metal raw material. It is also possible to use it.

  The reaction melt obtained by adding the metal raw material and the reducing agent to the molten salt is stirred by the stirring blade 51. In this case, the rotation speed of the stirring blade 51 is preferably 100 to 200 rotations / minute, and more preferably 140 to 170 rotations / minute. If the rotation speed of the stirring blade 51 during the reduction is 100 revolutions / minute or more, the metal raw material can be reduced in a state in which the nitrogen supply agent is further diffused throughout the reactor 10a, and is 200 revolutions / minute or less. If so, the nitrogen-containing metal powder produced in the lower part of the reactor 10a can be settled more rapidly. Further, the amount of nitrogen contained in the nitrogen-containing metal powder can be adjusted by adjusting the rotation speed of the stirring blade 51 during the reduction.

The introduction of the metal raw material and the nitrogen supply agent and the introduction of the reducing agent are repeated a predetermined number of times. Thus, a solid solution in which tantalum and nitrogen are dissolved or a solid solution in which niobium and nitrogen are dissolved is deposited in the lower part of the reactor 10a.
Thereafter, the supply of the metal raw material, the nitrogen supply agent and the reducing agent is stopped, and the molten salt is cooled. Next, the agglomerates deposited at the bottom of the reactor 10a are washed with water, pickled, and the molten salt is removed and dried.
Examples of the acid used for pickling include mineral acids such as nitric acid, hydrochloric acid, and hydrofluoric acid, and hydrogen peroxide.
It is preferable that the drying temperature in the case of drying is 80-150 degreeC. If the drying temperature is 80 ° C. or higher, it can be sufficiently dried in a short time, and if it is 150 ° C. or lower, the energy consumption during drying can be reduced.
The nitrogen-containing metal powder can be obtained by the above production method.

(Heat treatment)
The obtained nitrogen-containing metal powder may be subjected to heat treatment and / or deoxygenation treatment.
The heat treatment is a treatment for heating the nitrogen-containing metal powder obtained by the above production method. By this heat treatment, the nitrogen-containing metal powder can be aggregated to form aggregated particles.
It is preferable that the heat processing temperature is 800-1400 degreeC, and 900-1200 degreeC is further more preferable. If the heat treatment temperature is 800 ° C. or higher, it can be sufficiently aggregated in a short time, and if it is 1400 ° C. or lower, excessive coarsening can be prevented.
The heat treatment time is preferably 0.1 to 2 hours. If the heat treatment time is 0.1 hour or longer, sufficient agglomeration can be achieved. However, since aggregation is almost complete in 2 hours, it is useless to spend a longer time.
In the heat treatment, water functioning as a binder may be added to the nitrogen-containing metal powder in advance and granulated and dried. By adding water, it is possible to agglomerate firmly. Furthermore, since it can be agglomerated while maintaining a high surface area, it is preferable to add about 10 to 300 ppm of phosphorus, boron, or the like to the nitrogen-containing metal powder in advance.
The heating atmosphere can be, for example, a vacuum atmosphere, a rare gas atmosphere, a nitrogen-containing gas atmosphere, or the like. Among these, when it is set as nitrogen-containing gas atmosphere, nitrogen can be further contained in nitrogen-containing metal powder also in heat processing. Therefore, when the nitrogen content of the nitrogen-containing metal powder obtained by the above production method is insufficient, it can be finely adjusted by further containing nitrogen by heat treatment. Here, as the nitrogen-containing gas, for example, nitrogen gas, ammonia gas, or the like is used.

(Deoxygenation treatment)
The deoxygenation treatment is a treatment for removing oxygen contained in the nitrogen-containing metal powder obtained by the above production method or the aggregated particles obtained by heat treatment in a rare gas atmosphere by reacting with a reducing agent in excess of the natural oxide film. .
In the deoxygenation treatment, a nitrogen-containing gas such as nitrogen gas or ammonia gas may be supplied together with the reaction of the reducing agent to further contain nitrogen in the nitrogen-containing metal powder. In particular, when the nitrogen content of the nitrogen-containing metal powder is less than the desired amount, a nitrogen-containing gas having a nitrogen amount corresponding to the difference from the target nitrogen content is supplied and reacted during the deoxygenation treatment. The target nitrogen content can be adjusted.
When the nitrogen-containing gas is supplied, almost all of the nitrogen of the supplied nitrogen-containing gas is taken into the metal, so the supply amount of the nitrogen-containing gas is set according to the target nitrogen content.
Note that if the amount of nitrogen supplied here is more than 30% by mass or more of the entire desired amount, nitride crystals are formed, which may reduce the performance as a capacitor. It is preferable to reduce the amount as much as possible and increase the accuracy of nitrogen addition in the reduction.

The reducing agent used in the deoxygenation treatment may be the same as the reducing agent used in the production of the nitrogen-containing metal powder, but magnesium is particularly preferable.
The temperature of the deoxygenation treatment is preferably not less than the melting point of the reducing agent and not more than the boiling point. If the temperature of the deoxygenation treatment is not less than the melting point of the reducing agent and not more than the boiling point, the reducing agent can be volatilized appropriately. When the reducing agent is magnesium, 650 to 1000 ° C is preferable, and 700 to 890 ° C is more preferable.
The deoxygenation treatment may be performed once, but it is preferably repeated twice or more in order to sufficiently deoxygenate.

  After the deoxygenation treatment, it is preferable not to supply nitrogen to the apparatus that performs the deoxygenation treatment. When nitrogen is supplied to the deoxygenation apparatus after the deoxygenation process, nitride crystals are easily generated.

(Function and effect)
As described above, the nitrogen supply agent to be added to the molten salt in the present manufacturing method is such that the solid nitrogen-containing compound melts after the molding material melts in the molten salt, so the nitrogen supply rate to the molten salt is high. It is suppressed. Therefore, even if gently stirred, it can be sufficiently diffused in the molten salt in the state of a nitrogen supply agent or a solid nitrogen-containing compound, and nitrogen can be uniformly generated in the molten salt. Moreover, excessive contact between the metal raw material and nitrogen can be avoided by adjusting the amount of nitrogen introduced into the molten salt to a constant amount. Therefore, since the amount of nitrogen taken into tantalum or niobium is less dependent on the stirring state, variations in the nitrogen content of the nitrogen-containing metal powder from production to production can be easily suppressed. And since the dispersion | variation in the nitrogen content of the nitrogen-containing metal powder for every manufacture becomes small, it becomes possible for the tantalum powder for tantalum capacitors to adjust arbitrarily the nitrogen content calculated | required for every characteristic.

<Second Embodiment>
2nd Embodiment is embodiment about the manufacturing method of the nitrogen-containing metal powder of 2nd invention.
(Reactor)
In the manufacturing method of the nitrogen-containing metal powder of this embodiment, the reaction apparatus 2 shown in FIG. 3 is used.
The reaction apparatus 2 of the present embodiment includes a reactor 10b, a metal raw material inlet 20 and a reducing agent inlet 30 provided on the upper surface of the reactor 10b, an agitator 50, and an inert gas inside the reactor 10b. An inert gas introduction pipe 60 to be introduced, a nitrogen-containing gas supply means 70 for supplying a nitrogen-containing gas to the reactor 10b, and a sealing means 80 for sealing the inside of the reactor 10b to a predetermined pressure are provided.
The stirrer 50 used in the present embodiment is the same as the stirrer 50 used in the first embodiment. That is, the width W and the length (rotational radius) of the stirring blade 51 used in the present embodiment are the same as the width W and the length in the longitudinal direction of the stirring blade 51 used in the first embodiment.

Also in this embodiment, the angle θ of the stirring blade 51 is preferably 30 to 90 °. The amount of nitrogen contained in the nitrogen-containing metal powder can be adjusted by adjusting the angle θ of the stirring blade 51. As the angle θ of the stirring blade 51 is increased, the reaction melt S obtained by adding the metal raw material and the reducing agent to the molten salt spirals around the rotating shaft 52, and a part of the stirring blade 51 is reacted and melted. The liquid surface of the reaction melt S is exposed to the outside of the liquid S to be sheared. Due to this shearing, nitrogen in contact with the liquid surface is taken into the reaction melt S as fine bubbles. Therefore, as the angle θ of the stirring blade 51 is increased, the amount of nitrogen contained in the nitrogen-containing metal powder can be increased. In particular, when the angle θ is 30 ° or more, the amount of nitrogen contained in the nitrogen-containing metal powder can be increased.
Further, if the angle θ is 30 to 90 °, the generated nitrogen-containing metal powder is allowed to settle in the lower part of the reactor 10b as in the first embodiment, and the reaction with the newly added metal raw material is performed. Since it can suppress, the coarse particle formation of the nitrogen-containing metal powder obtained can be prevented.

The amount of nitrogen contained in the nitrogen-containing metal powder can be adjusted by adjusting the radius of curvature of the corner C of the stirring blade 51. The preferable range of the radius of curvature varies depending on the thickness, angle θ, rotation speed, and the like of the stirring blade 51. However, if the curvature radius of the angle C is decreased, the stirring Reynolds number when stirring with the stirring blade 51 is increased (that is, turbulent flow). Therefore, the liquid surface is likely to be renewed. Therefore, the amount of nitrogen taken into the molten salt increases, and the amount of nitrogen contained in the nitrogen-containing metal powder increases.
Thus, since the nitrogen content in the nitrogen-containing metal powder varies depending on the radius of curvature of the stirring blade 51, the radius of curvature is appropriately selected according to the target nitrogen content, but with respect to the thickness of the portion without the radius of curvature. The radius of curvature is preferably selected to be 10 to 50%, more preferably 10 to 30%. For example, when the thickness of the portion having no curvature radius is 20 mm to 30 mm, the curvature radius is preferably 3 to 10 mm.

A nitrogen-containing gas introduction pipe 11 and a pressure equalizing pipe 12 connected to the nitrogen-containing gas supply means 70 and an inert gas discharge pipe 13 connected to the sealing means 80 are attached to the reactor 10b.
An end portion 11a on the reactor 10b side of the nitrogen-containing gas introduction tube 11 is disposed so as to be positioned below the liquid surface of the diluted salt S in the reactor 10b, and an end of the pressure equalizing tube 12 on the reactor 10b side. The part 12a is disposed so as to be located below the liquid surface of the diluted salt S.

The nitrogen-containing gas supply means 70 includes a non-shrinkable and non-expandable container 71 made of metal or the like, and a shrinkable and expandable nitrogen-containing gas storage bag 72 made of resin or the like.
In this nitrogen-containing gas supply means 70, when the nitrogen-containing gas supplied from the nitrogen-containing gas storage bag 72 is taken into the reaction melt S, the nitrogen in the container 71 is fed from the reactor 10 b through the pressure equalizing pipe 12. An inert gas flows into the outside of the containing gas storage bag 72. Therefore, the pressure inside and outside the nitrogen-containing gas storage bag 72 can be made substantially equal, and the nitrogen-containing gas can be continuously supplied.

The sealing means 80 has a structure in which outside air does not enter the inert gas discharge pipe 13. In the present embodiment, the sealing means 80 includes a container 81 in which a hole 81b is formed in the upper surface 81a and contains a low volatile liquid (for example, oil or liquid paraffin) 82, and a liquid of the low volatile liquid 82 inside the container 81. And a float lid 83 disposed on the surface.
The upper part of the float lid 83 is a space 83a, and the space 83a does not communicate with the inside of the container 81, but communicates with the inside of the reactor 10b through the inert gas discharge pipe 13. ing. The float lid 83 has no bottom, and the low volatile liquid 82 enters the inside of the float lid 83, and an interface between the space 83 a and the low volatile liquid 82 is formed inside the float lid 83. . As a result, a liquid-sealed state can be achieved, and external air does not enter the inert gas discharge pipe 13.

(Production method)
In the method for producing a nitrogen-containing metal powder of the present embodiment, first, the reactor 10b of the reactor 2 is filled with a diluted salt. Here, the kind and amount of the diluted salt are the same as those in the first embodiment.
Next, an inert gas such as argon (excluding nitrogen gas) is introduced into the reactor 10b and the container 71 of the nitrogen-containing gas supply means 70 through the inert gas introduction pipe 60 to exclude air. At this time, the nitrogen-containing gas introduction pipe 11 is closed by a cock (not shown).
The introduction amount of the inert gas may be appropriately adjusted depending on the capacity of the reactor 10b to be used, but in order to control the introduction amount of the nitrogen-containing gas described later to a predetermined amount, for example, the inside of the reactor 10b It is preferable to set the pressure to an external pressure + 1 kPa and set the pressure inside the nitrogen-containing gas supply means 70 to the pressure inside the reactor 10b + 0.5 to 2 kPa.

  Next, the reactor 10b is heated to melt the diluted salt to prepare a molten salt. After melting, the stirring blade 51 is rotated by driving means (not shown) such as a motor to stir the molten salt. The heating temperature is the same as in the first embodiment.

In the second embodiment, it is preferable to adjust the rotational speed of the stirring blade 51 so that a spiral around the rotation shaft 52 is formed and a part of the stirring blade 51 is exposed.
Specifically, the rotation speed of the stirring blade 51 when supplying the nitrogen-containing gas is preferably 100 to 200 rotations / minute, and more preferably 140 to 170 rotations / minute. If the rotation speed of the stirring blade 51 when supplying the nitrogen-containing gas is 100 revolutions / minute or more, the nitrogen supply agent can be more diffused throughout the reactor 10b. However, even if it stirs over 200 rotations / min, since the effect of making it high rotation is saturated, it is useless.
In addition, when the rotation speed is high, the metal raw material and the reducing agent can be quickly and uniformly dispersed in the molten salt, and further, the contact between nitrogen and the molten salt is promoted. The amount can be increased. However, since high-speed rotation also increases bubble entrapment, variations in contact between nitrogen and molten salt occur. Further, when the rotation speed is high, the sealing mechanism of the rotating shaft becomes complicated, and it becomes difficult to achieve a balance with the sealing performance in a high temperature reaction. Also from this point, the rotation speed of the stirring blade 51 is preferably 100 to 200 rotations / minute.

  Subsequently, a metal salt is introduced into the reactor 10b from the metal raw material inlet 20. The introduced metal salt is melted in the molten salt while being diffused by stirring, and then the reducing agent is introduced into the reactor 10 b from the reducing agent inlet 30 and gently stirred by the stirring blade 51. At that time, the same metal salt and reducing agent as those used in the first embodiment are used.

Next, a cock (not shown) is opened, and a nitrogen-containing gas is introduced into the reaction melt S from the nitrogen-containing gas introduction pipe 11.
Any nitrogen-containing gas may be used as long as it can supply a nitrogen-containing gas to the reaction melt S. For example, a nitrogen-containing gas, or nitrogen that generates nitrogen gas by heating, such as ammonia or urea, is generated. Gas.
In order to efficiently contain nitrogen in the metal, the nitrogen gas concentration in the nitrogen-containing gas is preferably 50% by volume or more, and in order to do so, pure nitrogen having a nitrogen concentration of about 100% or It is preferable to use one obtained by appropriately diluting this with argon or the like. If the nitrogen gas concentration in the nitrogen-containing gas is less than 10% by volume, the metal may not be sufficiently contained in the metal.

The amount of the nitrogen-containing gas supplied to the reaction melt S is the capacity of the reactor 10b, the volume of the reaction melt S, the diameter of the end portion 11a of the nitrogen-containing gas introduction pipe 11, the target nitrogen content, and the nitrogen content. What is necessary is just to select suitably by the nitrogen amount etc. which remain | survive in the gas supply means 70. For example, when 200 kg of K ₂ TaF ₇ is used as the metal salt and nitrogen-containing metal powder is to contain 2000 ppm of nitrogen, at least about 150 L (185 g) of nitrogen is introduced in the standard state (STP). For this purpose, the internal pressure of the reactor 10b is set to the external pressure + 1 kPa, and nitrogen gas having a purity of 99.999 vol% may be supplied to the reaction melt S (capacity 500 L).

The introduction of the metal salt and the introduction of the reducing agent are repeated a predetermined number of times. At that time, the nitrogen-containing gas is continuously supplied from the nitrogen-containing gas introduction pipe 11 to the reaction melt S.
In the present embodiment, the end 11a of the nitrogen-containing gas introduction pipe 11 is located below the liquid surface of the reaction melt S, so that the nitrogen-containing gas is near the end 11a of the nitrogen-containing gas introduction pipe 11. The reaction melt S is introduced. Since the space above the reaction melt S of the reactor 10b is filled with an inert gas, the contact between the reaction melt S and the nitrogen-containing gas is substantially the end 11a of the nitrogen-containing gas introduction pipe 11. Nearby.

Metal tantalum or metal niobium produced by reduction in reaction melt S easily incorporates nitrogen from the introduced nitrogen-containing gas to produce a solid solution in which tantalum and nitrogen are in solid solution or a solid solution in which niobium and nitrogen are in solid solution. To do. Since the produced solid solution has a specific gravity greater than that of the molten salt, it settles in the lower part of the reactor 10b.
Due to the solid solution of the reduced metal and the introduced nitrogen, the nitrogen-containing gas in the nitrogen-containing gas storage bag 72 is consumed. Since the reactor 10b and the container 71 are communicated with each other by the pressure equalizing pipe 12, the gas flows into the container 71 from the reactor 10b and is compressed by the flowing gas, so that the volume of the nitrogen-containing gas storage bag 72 is reduced. Thereby, the inside of the nitrogen-containing gas storage bag 72 does not become negative pressure, and the nitrogen-containing gas can be continuously supplied from the nitrogen-containing gas storage bag 72.

  Thereafter, the introduction of the metal salt and the reducing agent and the introduction of the nitrogen-containing gas are stopped, and the reaction melt S is cooled. Next, as in the first embodiment, the agglomerates deposited at the bottom of the reactor 10b are washed with water, pickled, and dried to obtain a nitrogen-containing metal powder. The obtained nitrogen-containing metal powder may be subjected to heat treatment and / or deoxygenation treatment as in the first embodiment.

(Function and effect)
In the method for producing a nitrogen-containing metal powder of the second embodiment, since the nitrogen-containing gas is supplied from the nitrogen-containing gas storage bag 72 to the reaction melt S, the supply amount of the nitrogen-containing gas is limited. Therefore, the nitrogen content of the nitrogen-containing metal powder is unlikely to become excessive. Therefore, it is possible to easily suppress the variation in the nitrogen content for each production while uniformizing and refining the primary particles of the nitrogen-containing metal powder.

<Third Embodiment>
3rd Embodiment is embodiment about the manufacturing method of the nitrogen-containing metal powder of 3rd invention.
(Reactor)
In the method for producing a nitrogen-containing metal powder of the present embodiment, the reactor 1 used in the first embodiment is used. However, the nitrogen supply agent inlet 40 is used as the nitrogen-containing gas supply port 40, and for the stirring blade 51, the radius of curvature of the cross-sectional end in the rotation direction of the stirring blade is defined.
That is, in this embodiment, the curvature radius of the cross-sectional end (corner C) in the rotation direction of the stirring blade 51 is 3 to 10 mm, preferably 4 to 7 mm. If the radius of curvature is less than 3 mm, the nitrogen content of the obtained nitrogen-containing metal powder may be excessive, and if it exceeds 10 mm, the nitrogen content of the obtained nitrogen-containing metal powder may be insufficient.
Moreover, in this embodiment, it is preferable that the thickness of the part without a curvature radius in the cross-sectional end of the stirring blade rotation direction of the stirring blade 51 is 20-30 mm.
Also in this embodiment, the width W of the stirring blade 51 is 10 to 50% with respect to the rotation radius of the stirring blade 51, similarly to the stirring blade 51 used in the first embodiment. It is preferable. Moreover, it is preferable that the length (rotation radius) of a longitudinal direction is 30 to 80% with respect to the internal diameter of the reactor 10a. Moreover, it is preferable that angle (theta) with respect to a horizontal direction is 30-90 degrees.

(Production method)
In the method for producing a nitrogen-containing metal powder according to this embodiment, first, the reactor 10a is filled with a diluted salt. Here, the kind and amount of the diluted salt are the same as those in the first embodiment.
Next, a rare gas such as argon is introduced into the reactor 10a to exclude air, and the reactor 10a is heated to melt the diluted salt to obtain a molten salt. Then, the molten salt is stirred by rotating the stirring blade 51 via the rotating shaft 52 by the motor 53. The heating temperature and the rotation speed of the stirring blade at that time are the same as in the first embodiment.
Next, after the metal salt is introduced into the reactor 10a from the metal raw material inlet 20, the reducing agent is introduced into the reactor 10a from the reducing agent inlet 30 and stirred in the stirring blade 51 to react the reaction melt. Get. At that time, the same metal salt and reducing agent as those used in the first embodiment are used.
Next, nitrogen-containing gas is introduced from the nitrogen-containing gas supply port 40 to the upper side of the reaction melt in the reactor 10a. Examples of the nitrogen-containing gas include the same as those used in the second embodiment.

  In the present embodiment, during the supply of the nitrogen-containing gas, the reaction melt is stirred by the stirring blade 51 at a rotation speed of 100 to 200 rotations / minute, preferably 140 to 170 rotations / minute. When the rotational speed of the stirring blade is less than 100 revolutions / minute, the nitrogen content of the obtained nitrogen-containing metal powder may be insufficient, and when it exceeds 200 revolutions / minute, the nitrogen content of the obtained nitrogen-containing metal powder. May become excessive.

  Thereafter, the introduction of the metal salt and the reducing agent and the introduction of the nitrogen-containing gas are stopped, and the reaction melt S is cooled. Next, as in the first embodiment, the agglomerates deposited at the bottom of the reactor 10a are washed with water, pickled, and dried to obtain a nitrogen-containing metal powder. The obtained nitrogen-containing metal powder may be subjected to heat treatment and / or deoxygenation treatment as in the first embodiment.

(Function and effect)
As a result of investigation by the present inventors, the rotation speed of the stirring blade 51 at the time of supplying the nitrogen-containing gas is set to 100 to 200 rotations / minute, and the sectional end curvature radius in the rotation direction of the stirring blade 51 is set to 3 to 10 mm. The nitrogen content of the resulting nitrogen-containing metal powder can be adjusted to a desired amount. Since the shape and rotation speed of the stirring blade 51 can be easily adjusted, in the present embodiment, the nitrogen content of the obtained nitrogen-containing metal powder can be easily adjusted within an appropriate range.
For example, when the rotation speed is increased, the spiral of the reaction melt around the rotation axis becomes deeper, and a part of the stirring blade 51 is exposed to the outside of the reaction melt so as to shear the liquid surface of the reaction melt. Become. Due to this shearing, nitrogen in contact with the liquid surface is taken into the reaction melt as fine bubbles. If the shear is not appropriate, it is not easy to adjust the amount of nitrogen to be taken in. However, by adjusting the shape of the stirring blade 51, an appropriate shear state can be adjusted.

<Other embodiments>
In addition, this invention is not limited to the said embodiment.
In the first embodiment, the nitrogen supply agent is charged into the reactor 10a together with the metal raw material, but may be charged into the reactor 10a before the metal raw material is charged, or into the reactor 10a after the metal raw material is charged. You may throw it in.
In the first embodiment, the metal raw material may be melted in advance and charged into the reactor 10a in a molten state. In that case, the molten metal raw material may be supplied by being pushed in with nitrogen gas.
The thickness of the stirring blade 51 may be non-uniform, and the width W of the stirring blade 51 may be non-uniform. For example, the width may become wider toward the tip of the stirring blade 51.
Further, the stirring blade 51 may not be flat, for example, may be curved so that the tip of the stirring blade 51 is rearward when rotating, or the tip of the stirring blade 51 is bent upward or downward. May be.
Further, the angle θ may not be inclined at 30 ° to 90 ° over the entire length direction of the stirring blade 51. However, since nitrogen is easily taken into the reaction melt S, it is preferable that 50% or more of the stirring blade 51 in the longitudinal direction is inclined at 30 ° to 90 °.
Further, the stirring blade 51 used in the above embodiment is not limited to the pitched paddle blade inclined with respect to the horizontal direction, and a screw blade, a turbine blade, or a specially shaped stirring blade can be used, but the structure is simple. Paddle blades are suitable because sufficiently uniform stirring can be achieved even at relatively low speeds.

In the second embodiment, in the sealing means 80, the container 81 does not have an upper surface, and may have an open structure.
Further, instead of the sealing means 80, a sealing means 90 shown in FIG. The sealing means 90 includes a lower container 91 whose side wall is a double wall 91a, and a float lid 92 inserted between the double walls 91a, and discharges inert gas to the bottom surface 91b of the lower container 91. The pipe 13 is connected, and the double wall 91a is filled with the low volatile liquid 93. In the sealing means 90, the gap between the lower container 91 and the float lid 92 is sealed with the low volatile liquid 93, thereby exhibiting a sealing function.

Further, in the second embodiment, the reactor 10b and the nitrogen-containing gas supply means 70 are connected via the nitrogen-containing gas introduction pipe 11 and the pressure equalizing pipe 12, but the nitrogen-containing gas to the reactor 10b is not connected. There is no particular limitation as long as the supply amount can be controlled. For example, a gas flow meter may be provided without using the pressure equalizing pipe 12 to control the supply amount of the nitrogen-containing gas, or the container 71 can be pressurized and a differential pressure valve is provided in the pressure equalizing pipe 12 to react. The supply amount of the nitrogen-containing gas may be controlled based on the differential pressure between the vessel 10b and the container 71.
Further, the nitrogen-containing gas supply amount can be limited using the sealing means 90 without using the container 71, the nitrogen-containing gas storage bag 72, the nitrogen-containing gas introduction pipe 11, and the pressure equalizing pipe 12. That is, the mass of the float lid 92 is adjusted in the sealing means 90, and when the supply amount of the nitrogen-containing gas reaches a desired amount, the nitrogen-containing gas escapes to the outside like a safety valve so that the nitrogen-containing gas supply amount is reduced. You may restrict. When the supply amount of the nitrogen-containing gas is limited by the sealing means 90, it is preferable to supply the nitrogen-containing gas to the upper side of the reaction melt S of the reactor 10b.

  Hereinafter, the first invention will be described in more detail with reference to Example 1 and Comparative Example 1.

Example 1
250 kg of potassium fluoride and 250 kg of potassium chloride are put into the reactor 10a (capacity 800L) of the reactor 1 shown in FIG. 1, and after removing water at 200 ° C. for 1 hour, the melt is carried out at 800 ° C. and the stirring blade 51 is rotated 150 times. Stir at / min. Thereby, potassium fluoride and potassium chloride were used as molten salts.
Next, while maintaining the rotation speed of the stirring blade 51 at 150 rpm, 200 g of nitrogen supply agent (particle size: about 700 to 2500 μm) was introduced into the reactor 10a from the nitrogen supply inlet 40, and 5 minutes later, 2.5 kg of potassium tantalum iodide was introduced from the metal raw material inlet 20, and 27 g of nitrogen supply agent (particle size: about 700 to 2500 μm) was introduced from the nitrogen supplier inlet 40. Here, as a nitrogen supply agent, what shape | molded the mixture of 18 g of ammonium chloride in 4.5 g of potassium fluoride and 4.5 g of potassium chloride was used.
Then, 1 minute later, 750 g of sodium was added from the reducing agent inlet 30. The rotation speed of the stirring blade 51 at this time was also 150 rpm.
After repeating the addition of this potassium tantalum fluoride, 18 g of ammonium chloride formed with potassium fluoride and potassium chloride, and sodium 40 times, the solid solution of tantalum and nitrogen precipitated in the reactor 10a was washed with water, It pickled using 5 mass% hydrofluoric acid aqueous solution, and it dried at 120 degreeC, and obtained nitrogen-containing tantalum powder (A1).
Also, nitrogen-containing tantalum powders (A2) to (A10) were obtained by the same method as above.

(Comparative Example 1)
In the same manner as in Example 1, tantalum fluoride potassium and sodium were introduced, and nitrogen gas was continuously introduced from the nitrogen supply agent inlet 40 onto the molten salt liquid surface at 30 L / min without using a nitrogen supplier. However, after repeating 40 times, a nitrogen-containing tantalum powder (B1) was obtained in the same manner as in Example 1.
Also, nitrogen-containing tantalum powders (B2) to (B10) were obtained by the same method as above.

[Measurement of nitrogen content in nitrogen-containing tantalum powder]
About nitrogen-containing tantalum powders (A1) to (A10) and (B1) to (B10) obtained by the production methods of Example 1 and Comparative Example 1, respectively, the nitrogen content was determined by the following method. (Ppm) was measured.
That is, using an oxygen / nitrogen analyzer (Horiba EMGA520), the sample was impulse-heated and heated in helium gas, and the generated gas was quantified by TCD (thermal conductivity method) (JIS H1685). The measurement results are shown in Table 1.

In the production method of Example 1 using ammonium chloride formed with potassium fluoride and potassium chloride as a nitrogen supply source, the difference in nitrogen content of (A1) to (A10) is small, and the nitrogen-containing tantalum powder for each production The variation in nitrogen content was small.
On the other hand, in Comparative Example 1 using nitrogen gas as a nitrogen supply source, the difference in nitrogen content of (B1) to (B10) is large, and the variation in nitrogen content of the nitrogen-containing tantalum powder from production to production is large. It was.

  Hereinafter, the second invention will be described in more detail with reference to Examples 2 and 3 and Comparative Examples 2 and 3.

(Example 2)
Argon gas was introduced at a rate of 5 L / min into the reactor 10b (capacity 800 L) of the reactor 2 shown in FIG. 3 and degassed, 250 kg of potassium fluoride and 250 kg of potassium chloride were added, and water was removed at 200 ° C. for 1 hour. Then, the mixture was melted at 800 ° C., and the stirring blade 51 was stirred at 150 rpm. Thereby, potassium fluoride and potassium chloride were used as molten salts.
Next, while stirring with the stirring blade 51 was continued, 2.5 kg of potassium tantalum fluoride was introduced into the reactor 10 b from the metal raw material inlet 20, and 750 g of sodium was added from the reducing agent inlet 30 one minute later. After stirring for 2 minutes, pure nitrogen gas (purity 99.999%) as a nitrogen-containing gas was supplied to the reaction melt S from the nitrogen-containing gas supply means at an internal pressure of the reactor +1.5 kPa. The supply amount of nitrogen gas was limited by using the nitrogen-containing gas supply means.
This addition of potassium tantalum fluoride and sodium was repeated 40 times. The total amount of pure nitrogen introduced was 140 g with respect to 100 kg of potassium tantalum fluoride. After completion of the reaction, the solid solution of tantalum and nitrogen precipitated in the reactor 10b is washed with water, pickled with an aqueous hydrofluoric acid solution having a concentration of 5% by mass, dried at 120 ° C., and nitrogen-containing tantalum powder (A11) Got.
Also, nitrogen-containing tantalum powders (A12) to (A15) were obtained by the same method as above.

Example 3
Argon gas was introduced at a rate of 5 L / min into the reactor 10b (capacity 800 L) of the reactor 2 shown in FIG. 3 and degassed, 250 kg of potassium fluoride and 250 kg of potassium chloride were added, and water was removed at 200 ° C. for 1 hour. Then, the mixture was melted at 800 ° C., and the stirring blade 51 was stirred at 150 rpm. Thereby, potassium fluoride and potassium chloride were used as molten salts.
Next, while stirring with the stirring blade 51 was continued, 2.5 kg of potassium tantalum fluoride was introduced into the reactor 10b from the metal raw material inlet 20, and 750 g of sodium was added from the reducing agent inlet 11b after 1 minute. After stirring for 2 minutes, pure nitrogen gas (purity 99.999%) as nitrogen-containing gas was introduced into the reaction melt S from the nitrogen-containing gas supply means 70 at an internal pressure of the reactor 10b of +0.9 kPa. By using the nitrogen-containing gas supply means 70, the supply amount of nitrogen gas was limited.
This addition of potassium tantalum fluoride and sodium was repeated 40 times. The total amount of pure nitrogen introduced was 120 g with respect to 100 kg of potassium tantalum fluoride. After the completion of the reaction, the produced solid solution of tantalum and nitrogen was washed with water, pickled with a 5% by mass hydrofluoric acid aqueous solution, and dried at 120 ° C. to obtain nitrogen-containing tantalum powder (A16).
Also, nitrogen-containing tantalum powders (A17) to (A20) were obtained by the same method as above.

(Comparative Example 2)
Without using the nitrogen-containing gas supply means 70 in the reaction apparatus 2 shown in FIG. 3, pure nitrogen gas (purity 99.999%) was introduced to the upper side of the reaction melt S at a flow rate of 12 L / min during the reaction. Nitrogen-containing tantalum powders (B11) to (B15) were obtained in the same manner as in Example 2 except for continuing.

(Comparative Example 3)
Without using the nitrogen-containing gas supply means 70 in the reaction apparatus 2 shown in FIG. 3, pure nitrogen gas (purity 99.999%) was supplied directly to the reaction melt S at a flow rate of 20 L / min throughout the reaction. Nitrogen-containing tantalum powders (B16) to (B20) were obtained in the same manner as in Example 2 except that bubbling was performed.

[Measurement of nitrogen content in nitrogen-containing tantalum powder]
Nitrogen content of nitrogen-containing tantalum powders (A11) to (A20) and (B11) to (B20) obtained by the production methods of Examples 2 and 3 and Comparative Examples 2 and 3 (Ppm) was measured in the same manner as the nitrogen-containing tantalum powder of Example 1 and Comparative Example 1. The measurement results are shown in Table 2.

In the production method of Example 2 in which the supply amount of nitrogen gas is limited using the nitrogen-containing gas supply means 70, the difference in nitrogen content of (A11) to (A15) is small, and the nitrogen-containing metal tantalum powder for each production is different. The variation in nitrogen content was small.
Also in the manufacturing method of Example 3 in which the supply amount of nitrogen gas was limited using the nitrogen-containing gas supply means 70, the difference in nitrogen content of (A16) to (A20) was small, and the nitrogen-containing tantalum powder for each manufacture The variation in nitrogen content was small.
On the other hand, in the production method of Comparative Example 2 in which the nitrogen-containing gas supply means 70 is not used and the supply amount of nitrogen gas is not limited, the difference in nitrogen content between (B11) to (B15) is large. The variation of the nitrogen content of the nitrogen-containing tantalum powder was large.
Also in the production method of Comparative Example 3 in which the nitrogen-containing gas supply means 70 was not used and the supply amount of nitrogen gas was not limited, the difference in nitrogen content of (B16) to (B20) was large, and the nitrogen content for each production The variation in nitrogen content of tantalum powder was large.

  Hereinafter, the third invention will be described in more detail with reference to Examples 4 to 9 and Comparative Examples 4 to 8.

Example 4
250 kg of potassium fluoride and 250 kg of potassium chloride are charged into the reactor 10a (capacity 800 L) of the reactor 1 shown in FIG. 1, water is removed at 200 ° C. for 1 hour, and then melted at 800 ° C. The mixture was stirred at 150 revolutions / minute to obtain a molten salt of potassium fluoride and potassium chloride. At that time, as a stirring blade, a pitched paddle blade that is widened toward the tip, the rotation radius is 50 cm, the blade width is 5 cm on the rotating shaft side, 15 cm at the tip, the thickness is uniform 20 mm, and the angle θ is 45 °. A uniform one having a radius of curvature of a corner C of 3 mm was used.
Next, while the rotation speed of the stirring blade 51 is maintained at 150 rpm, nitrogen gas is continuously introduced from the nitrogen supply port 40 onto the surface of the molten salt at a rate of 15 L / min. 2.5 kg of potassium tantalum was introduced from the metal raw material inlet 20, and 750 g of sodium was added from the reducing agent inlet 30 one minute later. The rotation speed of the stirring blade 51 at this time was also 150 rpm.
After the addition of this potassium tantalum fluoride and sodium was repeated 40 times, the solid solution of tantalum and nitrogen precipitated in the reactor 10 was washed with water, pickled with an aqueous hydrofluoric acid solution, and dried at 120 ° C. Thus, a nitrogen-containing tantalum powder (A21) was obtained.

(Example 5)
Nitrogen-containing tantalum powder (A22) was obtained in the same manner as in Example 4 except that the radius of curvature of the corner C of the stirring blade 51 when supplying nitrogen gas was 5 mm and the rotation speed was 150 rotations / minute.

(Example 6)
Nitrogen-containing tantalum powder (A23) was obtained in the same manner as in Example 4 except that the radius of curvature of the corner C of the stirring blade 51 during the supply of nitrogen gas was 10 mm and the rotation speed was 150 rotations / minute.

(Example 7)
Nitrogen-containing tantalum powder (A24) was obtained in the same manner as in Example 4 except that the radius of curvature of the corner C of the stirring blade 51 during the supply of nitrogen gas was 5 mm and the rotation speed was 120 rpm.

(Example 8)
Nitrogen-containing tantalum powder (A25) was obtained in the same manner as in Example 4 except that the radius of curvature of the corner C of the stirring blade 51 during the supply of nitrogen gas was 10 mm and the rotation speed was 200 rotations / minute.

Example 9
Nitrogen-containing tantalum powder (A26) was obtained in the same manner as in Example 4 except that the radius of curvature of the corner C of the stirring blade 51 when supplying nitrogen gas was 5 mm and the rotation speed was 100 rotations / minute.

(Comparative Example 4)
Nitrogen-containing tantalum powder (B21) in the same manner as in Example 4 except that the thickness of the stirring blade 51 at the time of supplying nitrogen gas was 20 mm, the radius of curvature of the corner C was 3 mm, and the rotation speed was 210 rpm. Got.

(Comparative Example 5)
Nitrogen-containing tantalum powder (B22) in the same manner as in Example 4 except that the thickness of the stirring blade 51 at the time of nitrogen gas supply was 20 mm, the radius of curvature of the corner C was 5 mm, and the rotation speed was 90 rpm. Got.

(Comparative Example 6)
Nitrogen-containing tantalum powder (B23) in the same manner as in Example 4 except that the thickness of the stirring blade 51 at the time of nitrogen gas supply was 20 mm, the radius of curvature of the corner C was approximately 0 mm, and the rotation speed was 150 rpm. )

(Comparative Example 7)
Nitrogen-containing tantalum powder (B24) in the same manner as in Example 4 except that the thickness of the stirring blade 51 at the time of nitrogen gas supply was 30 mm, the radius of curvature of the corner C was approximately 0 mm, and the rotation speed was 150 rpm. )

(Comparative Example 8)
Nitrogen-containing tantalum powder (B24) in the same manner as in Example 4 except that the thickness of the stirring blade 51 when supplying nitrogen gas was 30 mm, the radius of curvature of the corner C was 15 mm, and the rotation speed was 150 revolutions / minute. Got.

  In Examples 4 to 9 and Comparative Examples 4 to 8, the target was to adjust the nitrogen content of the nitrogen-containing tantalum powder to a range of 1000 to 4000 ppm.

[Measurement of nitrogen content in nitrogen-containing tantalum powder]
Nitrogen content of nitrogen-containing tantalum powders (A21) to (A26) and (B21) to (B25) obtained by the production methods of Examples 4 to 9 and Comparative Examples 4 to 8 (Ppm) was measured by the method using the oxygen / nitrogen analyzer described above. Table 3 shows the measurement results.

The rotation speeds of the stirring blades 51 during the supply of nitrogen gas are 150 rotations / minute, 120 rotations / minute, and 160 rotations / minute, respectively, and the curvature radii of the corners C of the stirring blades 51 are 3 mm and 5 mm, respectively. In the manufacturing method of Examples 4-9 which was 10 mm, the nitrogen content of the nitrogen-containing tantalum powder was in the target range.
On the other hand, in the manufacturing method of Comparative Example 4 in which the rotation speed of the stirring blade 51 during the supply of nitrogen gas was 210 rotations / minute, the nitrogen content of the nitrogen-containing tantalum powder was excessive.
In the manufacturing method of Comparative Example 5 in which the rotation speed of the stirring blade 51 at the time of supplying nitrogen gas was 90 rotations / minute, the nitrogen content of the nitrogen-containing tantalum powder was insufficient.
In the manufacturing methods of Comparative Examples 6 and 7 in which the radius of curvature of the corner C of the stirring blade 51 was approximately 0 mm, the nitrogen content of the nitrogen-containing tantalum powder was excessive.
In the manufacturing method of Comparative Example 8 in which the radius of curvature of the corner C of the stirring blade 51 was 15 mm, the nitrogen content of the nitrogen-containing tantalum powder was insufficient.

DESCRIPTION OF SYMBOLS 1, 2 Reactor 10a, 10b Reactor 11 Nitrogen containing gas introduction pipe 12 Pressure equalizing pipe 13 Inert gas discharge pipe 20 Metal raw material inlet 30 Reducing agent inlet 40 Nitrogen supply agent inlet (Nitrogen containing gas inlet)
DESCRIPTION OF SYMBOLS 50 Stirrer 51 Stirring blade 52 Rotating shaft 53 Motor 60 Inert gas introduction pipe 70 Nitrogen-containing gas supply means 71 Container 72 Nitrogen-containing gas storage bag 80, 90 Sealing means 81 Container 81a Upper surface 81b Hole 82 Low volatile liquid 83 Float lid 91 Bottom Side container 91a Double wall 92 Float lid 93 Low volatile liquid

Claims (3)

At molten in dilute salt, a tantalum compound or niobium compound, when is reduced with a reducing agent, a nitrogen supply agent is added, a nitrogen supply agent is a solid body, wherein the solid is diluted salt melted A nitrogen supplier in which a solid nitrogen-containing compound is molded using a molding material that can be melted in; the diluting salt is sodium chloride, potassium chloride or potassium fluoride; the reducing agent is an alkali metal, alkali An earth metal or a hydride thereof; the solid nitrogen-containing compound is ammonium chloride or urea; and the molding material is potassium chloride, sodium chloride, lithium chloride, potassium fluoride or sodium fluoride; The manufacturing method of the nitrogen-containing metal powder characterized by the above-mentioned.   The method for producing a nitrogen-containing metal powder according to claim 1, wherein the molding material is the same component as the diluted salt.   The method for producing a nitrogen-containing metal powder according to claim 1 or 2, wherein the molding material covers the solid nitrogen-containing compound.

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