JP3504481B2 - Method for producing Ni powder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a method for producing a metal powder such as Ni, Cu or Ag suitable for various applications such as a conductive paste filler used in electronic parts and the like, a Ti material bonding material, and a catalyst. Regarding the device.

[0002]

2. Description of the Related Art Conductive metal powders such as Ni, Cu and Ag are useful for forming internal electrodes of laminated ceramic capacitors, and Ni powders have recently attracted attention as such applications. Above all, Ni ultra-fine powder manufactured by a dry manufacturing method is regarded as promising. Due to the demand for thinner internal electrodes, lower resistance, etc., along with the miniaturization and large capacity of capacitors, the particle size is 0.5 μm or less as well as 1 μm or less.
There is a demand for ultrafine powder having a size of μm or less.

Conventionally, various manufacturing methods for manufacturing the above-mentioned metal powder have been proposed. For example, Japanese Examined Patent Publication No. 59-7765 discloses a method in which solid nickel chloride is heated and vaporized to form nickel chloride vapor, and hydrogen gas is sprayed at high speed on this to cause nuclei growth in an interface unstable region. Further, in JP-A-4-365806, nickel chloride vapor obtained by evaporating solid nickel chloride (hereinafter referred to as N
The partial pressure of iCl ₂ gas) is 0.05 to 0.3,
A method of gas phase reduction at 1004 ° C to 1453 ° C is disclosed. According to these manufacturing methods, spherical Ni ultrafine powder having an average particle diameter of 0.1 to several μm is produced.

[0004]

However, in each of the methods for producing a metal powder according to the above-mentioned proposal, since solid nickel chloride is used as a starting material, there are the following essential problems. Since vaporization (sublimation) of solid NiCl ₂ by heating is essential, stable generation of vapor is difficult. As a result, the partial pressure of NiCl ₂ gas fluctuates, and the particle size of the produced Ni powder is not stable. If the amount of solid NiCl ₂ in the evaporation part fluctuates during the operation of the process, the evaporation rate fluctuates, and stable production cannot be performed. Since solid NiCl ₂ has water of crystallization, not only dehydration treatment is required before use but also insufficient dehydration causes oxygen contamination of the produced Ni powder. Since the evaporation rate of solid NiCl ₂ is slow, a large amount of carrier gas (inert gas such as nitrogen gas) is required to transfer NiCl ₂ gas to the reduction process, and extra heating is required to heat nitrogen gas. Energy is required. For this reason, the concentration (partial pressure) of the NiCl ₂ gas in the reduction step cannot be increased, the production rate of Ni powder is slow, and a large reaction container is required.

Therefore, the present invention has been made in view of the above circumstances, and is a method and an apparatus for producing a metal powder capable of achieving the following objects. 1) A powder (ultrafine powder) of Ni, Cu, Ag or the like having an average particle diameter of 0.1 to 1.0 μm is stably manufactured. 2) The reaction is easily controlled without a heating evaporation (sublimation) step. 3) The whole process can be controlled by the gas flow rate, and a metal powder having a target particle size can be arbitrarily produced. 4) Consumption of gas and energy is small.

The present invention has an average particle size of 0.1 to 1.0 μm.
The method for producing a Ni powder for forming an internal electrode of a monolithic ceramic capacitor, comprising:
The chlorination step of continuously generating iCl ₂ gas and the NiCl ₂ gas generated in the chlorination step are brought into contact with hydrogen gas,
and a reducing step of continuously reducing iCl _{2, in} which a partial pressure of 0.5 to 1.0 of NiCl ₂ gas is ejected from a nozzle provided in the reducing furnace at a linear velocity of 1 to 30 m / sec. The chemical equivalent of chlorine gas supplied to the chlorination step.
Prepare 1.0 to 3.0 times the hydrogen gas in the reduction furnace.
1 / the linear velocity of the NiCl ₂ gas ejected from the nozzle
It is characterized by ejecting at a linear velocity of 50 to 1/300 .

In the process of producing metal powder by gas phase reaction,
At the moment when the metal chloride gas and the reducing gas come into contact with each other, metal atoms are generated, and the metal atoms collide and aggregate with each other to generate ultrafine particles and grow. The particle size of the metal powder produced is determined by the conditions such as the partial pressure and temperature of the metal chloride gas in the atmosphere of the reduction process. According to the manufacturing method of the metal powder of the present invention, the amount of from the amount of NiCl ₂ gas in accordance with the supply amount of chlorine gas is generated, NiCl ₂ gas supplied to the reduction step by controlling the supply amount of chlorine gas Can be controlled. Further, since NiCl ₂ gas is generated by the reaction between chlorine gas and metallic Ni , unlike the method of generating NiCl ₂ gas by heating and evaporating solid NiCl ₂ , the use of carrier gas should be reduced. Not only can it be used, but it can be not used depending on the manufacturing conditions. Therefore, the manufacturing cost can be reduced by reducing the amount of carrier gas used and the heating energy accompanying it.

In addition, by mixing an inert gas with the NiCl ₂ gas generated in the chlorination step,
The partial pressure of NiCl ₂ gas can be controlled. In particular,
In the method for producing Ni powder of the present invention, the reduction step is performed
The reduction furnace was equipped with NiCl ₂ gas at a pressure of 0.5 to 1.0.
Since it ejects from the nozzle at a linear velocity of 1 to 30 m / sec,
The particle size of the metallic Ni powder can be stabilized, and the particle size can be set within an appropriate range .

[0009]

Even in the apparatus for producing metal powder having the above-mentioned structure, the amount of metal chloride gas corresponding to the supply amount of chlorine gas is generated, and since the chlorination furnace and the reduction furnace are directly connected, By controlling the supply amount, the amount of metal chloride gas supplied to the reduction furnace can be controlled. Also,
The chlorination furnace is provided with an inert gas supply pipe from which the inert gas can be supplied to the chlorination furnace, so that the partial pressure of the metal chloride gas in the reduction furnace can be controlled. Therefore, even in the metal powder production apparatus of the present invention, the particle size of the metal powder can be controlled by controlling the supply amount of chlorine gas or the partial pressure of the metal chloride gas supplied to the reduction furnace. The particle size can be stabilized, and the same function and effect as the above can be obtained such that the particle size can be arbitrarily set.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to an example of manufacturing Ni, with reference to the drawings. A. Chlorination Step The chlorination step is preferably performed by a chlorination furnace 1 as shown in FIG. On the upper end surface of the chlorination furnace 1, the raw material metal Ni (M)
The raw material supply pipe 11 for supplying the is provided. Also,
A chlorine gas supply pipe 14 is connected to the upper side of the chlorination furnace 1,
An inert gas supply pipe 15 is connected to the lower side portion. A heating means 10 is arranged around the chlorination furnace 1, and a transfer pipe / nozzle 17 is connected to the lower end surface of the chlorination furnace 1. The chlorination furnace 1 may be of a vertical type or a horizontal type, but the vertical type is preferable in order to uniformly perform the solid-gas contact reaction. The flow rate of chlorine gas is measured and continuously introduced through the chlorine gas supply pipe 14. Chlorination furnace 1
The other members are preferably made of quartz glass. The transfer pipe / nozzle 17 is connected to the upper end surface of the reduction furnace 2 described later,
It has a function of transferring NiCl ₂ gas or the like generated in the chlorination furnace 1 to the reduction furnace 2. The lower end of the transfer pipe / nozzle 17 projects into the reduction furnace 2 and functions as a NiCl ₂ jet nozzle. A net 16 as shown in FIG. 1 may be provided at the bottom of the chlorination furnace 1, and metal Ni (M) may be deposited on the net 16.

The form of metallic Ni (M) as a starting material is not limited, but from the viewpoint of contact efficiency and prevention of increase in pressure loss, granular, lumpy, plate-like or the like having a particle size of about 5 mm to 20 mm is preferable, and its purity. Is preferably 99.5% or more.
The packed bed height of the metal Ni (M) in the chlorination furnace 1 is converted from the supplied chlorine gas into NiCl ₂ gas based on the chlorine supply rate, the chlorination furnace temperature, the continuous operation time, the shape of the metal Ni (M), and the like. It may be set appropriately within a range sufficient to be maintained. The temperature in the chlorination furnace 1 is set to 800 ° C. or higher in order to promote the reaction sufficiently, and N
It should be 1483 ° C. or lower, which is the melting point of i. Considering the reaction rate and the durability of the chlorination furnace 1, practically 900 ° C to 11
The range of 00 ° C is preferred.

In the method for producing metal powder according to the present invention,
Continuous supply of chlorine gas to the chlorination furnace 1 filled with metallic nickel (M) results in continuous generation of NiCl ₂ gas.
Then, since the chlorine gas supply amount controls the generation amount of NiCl ₂ gas, it controls the reduction reaction described later, and as a result, the target product Ni powder can be produced. The details of the chlorine gas supply will be described more specifically in the section of the reduction step below.

The NiCl ₂ gas generated in the chlorination step is directly transferred to the reduction step through the transfer pipe / nozzle 17, or in some cases, an inert gas such as nitrogen or argon is supplied from the inert gas supply pipe 15 to the NiCl ₂ gas. 1 for gas
Mol% to 30 mol% are mixed, and this mixed gas is transferred to the reduction step. The supply of this inert gas becomes a factor for controlling the particle size of the Ni powder. Excessive mixing of the inert gas causes not only a great consumption of the inert gas but also energy loss, which is uneconomical. From such a viewpoint, the NiCl ₂ gas partial pressure of the mixed gas passing through the transfer pipe / nozzle 17 is set in the range of 0.5 to 1.0 when the total pressure is 1.0, and particularly, the particle diameter is 0. Ni with a small particle size of 2 μm to 0.5 μm
When producing powder, a partial pressure of about 0.6 to 0.9 is suitable. Then, as described above, the amount of NiCl ₂ gas generated can be arbitrarily adjusted by the chlorine gas supply amount, and the partial pressure of the NiCl ₂ gas can also be arbitrarily adjusted by the inert gas supply amount.

B. Reduction Step NiCl ₂ gas generated in the chlorination step is continuously transferred to the reduction step. The reduction process is performed by the reduction furnace 2 as shown in FIG.
It is desirable to use. At the upper end of the reduction furnace 2,
The nozzle of the transfer pipe / nozzle 17 described above (hereinafter, simply referred to as the nozzle 17) is projected downward. A hydrogen gas supply pipe (reducing gas supply pipe) 21 is connected to the upper end surface of the reduction furnace 2, and a cooling gas supply pipe 22 is connected to the lower side of the reduction furnace 2. A heating means 20 is arranged around the reduction furnace 2. As will be described later, the nozzle 17 has a function of ejecting NiCl ₂ gas (which may contain an inert gas) from the chlorination furnace 1 into the reduction furnace 2 at a preferable flow rate.

When the reduction reaction by NiCl ₂ gas and hydrogen gas progresses, a downwardly extending luminous flame (hereinafter referred to as flame), which is similar to the combustion flame of gaseous fuel such as LPG, from the tip of the nozzle 17. F is formed. The hydrogen gas supply amount to the reduction furnace 2 is 1.0 to 3.0 of the chemical equivalent of NiCl ₂ gas, that is, the chemical equivalent of chlorine gas supplied to the chlorination furnace 1.
It is about twice, preferably about 1.1 to 2.5 times, but not limited to this. However, excessive supply of hydrogen gas causes a large hydrogen flow in the reduction furnace 2, disturbs the NiCl ₂ jet flow from the nozzle 17, causes a non-uniform reduction reaction, and causes unconsumed gas release. It is uneconomical. Further, the temperature of the reduction reaction may be higher than or equal to the temperature sufficient for completion of the reaction, but solid N 2
Since it is easier to handle the i powder, the melting point of Ni or less is preferable. Considering the reaction rate, the durability of the reduction furnace 2, and the economical efficiency, 900 ° C to 1100 ° C is practical, but it is not limited to this.

The chlorine gas introduced into the chlorination step as described above becomes substantially the same molar amount of NiCl ₂ gas, which is used as the reducing raw material. NiCl ₂ gas or NiCl
Ni obtained by adjusting the linear velocity of the gas flow ejected from the tip of the nozzle 17 of the ₂ -inert gas mixed gas
The particle size of the powder P can be optimized. That is, if the nozzle diameter is constant, the particle size of the Ni powder P generated in the reduction furnace 2 can be adjusted to a target range by the chlorine supply amount and the inert gas supply amount to the chlorination step. The linear velocity of the gas flow at the tip of the nozzle 17 (the total of NiCl ₂ gas and the inert gas (calculated value converted into the gas supply amount at the reducing temperature)) is about 1 m / sec at the reducing temperature of 900 ° C. to 1100 ° C. 0.1 μm set to 30 m / s
In the case of producing a Ni powder having a small particle diameter of about 0.3 μm, the particle size is about 5 m / sec to 25 m / sec, and 0.4 μm.
Approximately 1 when producing Ni powder of ˜1.0 μm
The range of m / sec to 15 m / sec is suitable. Hydrogen gas reduction furnace 2
The linear velocity in the axial direction is about 1/50 to 1/300, preferably 1/80 of the ejection velocity (linear velocity) of NiCl ₂ gas.
~ 1/250 is good. Therefore, the NiCl ₂ gas is substantially injected into the static hydrogen atmosphere from the nozzle 17. The outlet of the hydrogen gas supply pipe 21 is preferably not directed to the flame side.

In the production method of the present invention, when the chlorine gas supply flow rate to the chlorination step is increased, the Ni produced in the reduction step is increased.
The particle size of the powder becomes small, and conversely, when the supply flow rate of chlorine gas is reduced, the particle size increases. Furthermore, by adjusting the partial pressure of the NiCl ₂ gas with an inert gas mixed with the NiCl ₂ gas near the outlet of the chlorination furnace 2 as described above, specifically, 1 mol% to NiCl ₂ gas Thirty
By mixing in the range of mol% and increasing the partial pressure, for example, the particle size of the produced Ni powder can be increased.
If the partial pressure of Cl ₂ gas is lowered, the particle size of the Ni powder produced can be reduced.

C. Cooling Step A cooling step can be provided in the method for producing metal powder of the present invention. As shown in FIG. 1, the cooling process can be performed in a space portion on the opposite side of the nozzle 17 in the reduction furnace 2,
Alternatively, another container connected to the outlet of the reduction furnace 2 can be used. The cooling in the present invention means Ni in the gas flow (including hydrochloric acid gas) generated by the reduction reaction.
It is an operation performed to stop or suppress the growth of particles, and specifically means an operation of rapidly cooling the gas flow near 1000 ° C. after the reduction reaction to about 400 ° C. to 800 ° C. Of course, you may cool to the temperature below this.

As a preferable example for cooling, an inert gas may be blown into the space below from the tip of the flame. Specifically, the cooling gas supply pipe 2
The gas flow can be cooled by blowing in nitrogen gas from 2. By blowing an inert gas, it is possible to control the particle size while preventing the Ni powder P from aggregating.
By providing the cooling gas supply pipe at one position or at a plurality of positions by changing the position in the vertical direction of the reduction furnace 2, it is possible to arbitrarily change the cooling conditions, and thereby more accurately control the particle size. You can

D. Collection Step The mixed gas of the Ni powder P, the hydrochloric acid gas, and the inert gas that has undergone the above steps is transferred to the collection step, where the Ni powder P is separated and collected from the mixed gas. For separation and recovery, for example, a bag filter, an underwater trapping / separating means, an oil trapping / separating means, and a magnetic separating means are suitable, but not limited thereto. For example, when the Ni powder P is collected by a bag filter, the mixed gas of the Ni powder P generated in the cooling step, hydrochloric acid gas and an inert gas is guided to the bag filter, and only the Ni powder P is collected, and then the cleaning step is performed. You may send it. When the collection and separation in oil is used, it is preferable to use normal paraffin having 10 to 18 carbon atoms or light oil. When collecting in water or oil, the collection liquid contains a polyoxyalkylene glycol, polyoxypropylene glycol or a derivative thereof (monoalkyl ether, monoester), or a surfactant such as sorbitan or sorbitan monoester, A known antioxidant such as a phenol-based or amine-based metal deactivator represented by benzotriazole or a derivative thereof, and when one or more of these antioxidants are added at about 10 ppm to 1000 ppm, prevention of aggregation of metal powder particles and Effective for rust prevention.

E. Other Embodiments In the above embodiment, the reduction process is one process, but the reduction process may be divided into a plurality of processes. Figure 2
Shows an example in which one reduction process is divided into two processes, and the same components as those shown in FIG. 1 are designated by the same reference numerals. As shown in FIG. 2, the cooling gas supply pipe 22
Is not provided in the reducing furnace 2 ′ of the first reducing step, but is provided only in the reducing furnace 2 of the second reducing step. The amount of hydrogen gas supplied to the first reduction step is 0.5 to 0.5 of the chemical equivalent of NiCl _2.
0.9 times, supplementing the shortage hydrogen gas in the second reduction step, the total amount is 1.0 to 2.5 of the NiCl ₂ gas amount.
By supplying twice as much hydrogen gas, it becomes possible to control the particle size more accurately and in a wide range. In this case, an appropriate amount of NiCl ₂ gas may be replenished near the outlet of the reduction furnace 2 ′ if necessary.

By dividing the reduction step into a plurality of steps in this way, the gas flow in the reduction furnaces 2, 2'can be made close to a laminar flow. As a result, the reduction furnace 2, 2 '
It is possible to make the residence time of the Ni particles in the inside uniform,
The i-particle growth can be made uniform. This allows
The particle diameter of the generated Ni powder can be made uniform. Further, it is preferable that the total volume of all the reducing furnaces when the reducing step is divided into a plurality of steps is the same as the volume of the reducing furnaces when not dividing. As a result, only the residence time distribution can be made closer to that of extrusion mixing without changing the average residence time of the Ni powder contained in the gas flow passing through all the reduction furnaces, and more precise particle size control is possible. Become.

As described above, in the conventional production method in which solid NiCl ₂ is used as a starting material, and this is evaporated to be used in the reduction reaction, it is extremely difficult to control the solid-gas conversion rate, and a process of sublimation of solid NiCl ₂ is performed. The NiCl ₂ gas supplied to the inside of the reduction furnace is NiC.
Although a large amount of inert gas flow to the vaporization section of l ₂ must be used, it was difficult to increase the partial pressure of NiCl ₂ gas, and the process control was extremely difficult. In the method, since the amount of NiCl ₂ gas generated can be controlled by the amount of chlorine gas supplied, process control is easy and stable control is possible. According to the manufacturing method of the present invention, C other than Ni
Powders of u, Ag and the like can also be produced by using the respective metals as starting materials and selecting the temperatures of chlorination and reduction.

[0025]

EXAMPLES The present invention will now be described in more detail with reference to specific examples. Example 1 A chlorination furnace 1 of the apparatus for producing metal powder shown in FIG.
Then, 15 kg of Ni powder having an average particle size of 5 mm was filled in, the temperature of the atmosphere in the furnace was set to 1100 ° C., chlorine gas was introduced at a flow rate of 4 Nl / min, and metallic Ni was chlorinated to generate NiCl ₂ gas. 10% of chlorine gas supply (molar ratio)
Nitrogen gas was mixed, and this NiCl ₂ -nitrogen mixed gas was introduced into the reducing furnace 2 heated to an ambient temperature of 1000 ° C. from the nozzle 17 at a flow rate of 2.3 m / sec (1000 ° C. conversion). At the same time, the flow rate of hydrogen gas from the top of the reduction furnace 2 was 7 Nl /
NiCl ₂ gas was supplied to reduce the NiCl ₂ gas. And
The produced gas containing Ni powder produced by the reduction reaction was mixed with nitrogen gas in the cooling step and cooled. Next, a mixed gas of nitrogen gas-hydrochloric acid vapor-Ni powder was introduced into an oil scrubber, and the Ni powder was separated and collected. Then, the collected N
The i powder was washed with xylene and then dried to obtain a product Ni powder. This Ni powder has an average particle size of 0.70 μm (BET
(Measured by the method) was spherical. The particle size obtained from the SEM photograph was 0.80 μm, which was almost the same as the particle size obtained by the BET method. This means that the surface of the Ni powder obtained in this example is smooth as in the SEM photograph example shown in FIG. As a result of performing stable operation for 10 hours by the method of this example, the hydrogen gas supply amount and the nitrogen gas supply amount per 1 g of Ni powder were 0.668 Nl /
and 0.038 Nl / g.

Example 2 Using the manufacturing apparatus shown in FIG. 1, the temperature conditions were the same as in Example 1, and Ni powder was manufactured under the gas flow rate conditions shown in Table 1. As shown in Table 1, it was confirmed that the particle diameter of the produced Ni powder became smaller as the flow rate of chlorine gas increased.

Example 3 Using the manufacturing apparatus shown in FIG. 1, the temperature conditions were the same as in the example, and Ni powder was manufactured under the gas flow rate conditions shown in Table 1. As shown in Table 1, by reducing the partial pressure of NiCl ₂ gas, N
The particle size of the i powder can be made fine.

[0028]

[Table 1]

[0029]

As described above, according to the present invention, the following effects can be obtained. By controlling the supply amount of chlorine gas, the supply amount of metal chloride gas can be controlled, and stable operation of the entire process becomes possible. This makes it possible to reliably control the particle size of the metal powder produced. Ni, Cu, A having an average particle size of 0.1 to 1.0 μm
It is possible to easily produce g of metal powder. In particular, it is possible to easily manufacture a powder of 0.2 to 0.4 μm, which is said to be difficult to manufacture. Nitrogen gas and hydrogen gas can be used efficiently,
The production cost of metal powder can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an example of an apparatus for producing metal powder according to the present invention.

FIG. 2 is a vertical cross-sectional view showing another example of the metal powder manufacturing apparatus of the present invention.

FIG. 3 is an SEM photograph example of Ni powder manufactured according to the present invention.

[Explanation of symbols]

1 ... Chlorination furnace, 2, 2 '... Reduction furnace, 11 ... Raw material supply pipe, 14 ... Chlorine gas supply pipe, 17 ... Transfer pipe and nozzle, 15 ... Inert gas supply pipe, 21 ... Hydrogen gas supply pipe (reducing gas supply pipe), 22 ... Cooling gas supply pipe, M
... Ni particles, P ... Ni powder.

Continuation of front page (56) Reference JP-A-6-122906 (JP, A) JP-A-5-247506 (JP, A) JP-A-5-163512 (JP, A) JP-A-5-247507 (JP , A) JP-A-64-73009 (JP, A) Fukukaihei 4-73939 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22F 9/28

Claims (4)

(57) [Claims] 1. A NiC obtained by bringing chlorine gas into contact with metallic Ni.
a chlorination step of generating l ₂ gas continuously, the NiCl ₂ gas produced in the chlorination step is contacted with hydrogen gas, NiC
and a reducing step of continuously reducing l _{2 in} which a partial pressure of 0.5 to 1.0 of NiCl 2 gas is jetted from a nozzle provided in the reducing furnace at a linear velocity of 1 to 30 m / sec.
However, the chemical equivalent of chlorine gas supplied to the chlorination step is 1.
The reduction furnace was equipped with 0 to 3.0 times the hydrogen gas.
1/50 of the linear velocity of the NiCl ₂ gas ejected from the nozzle
A method for producing a Ni powder for forming an internal electrode of a laminated ceramic capacitor having an average particle diameter of 0.1 to 1.0 μm, characterized in that the powder is ejected at a linear velocity of ˜1 / 300 . 2. The method for producing Ni powder according to claim 1, further comprising a cooling step of cooling the gas containing the Ni powder generated in the reducing step with an inert gas. 3. The method for producing Ni powder according to claim 1, wherein the particle size of the Ni powder is controlled by adjusting the flow rate of chlorine gas introduced into the chlorination step. 4. The method for producing Ni powder according to claim 1, wherein the reducing step is performed by ejecting the NiCl ₂ gas into a hydrogen atmosphere.