JP4295860B2 - Method for producing metal powder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for producing metal powder, and specifically, Ni, Cu, Ag suitable for various uses such as conductive paste fillers used in electronic parts and the like, Ti material bonding materials, and catalysts. The present invention relates to a method and apparatus suitable for producing ultrafine metal powders such as
[0002]
[Prior art]
Among the Ni, Cu, and Ag, Ni powder is particularly attracting attention as an internal electrode for multilayer ceramic capacitors because it is less expensive than conventional Pd powder. Above all, the Ni powder production method by metal chloride hydrogen reduction is suitable for mass production because the production process is simpler than the wet method. Among these Ni powders, the particle size is 1 μm or less, and the particle size is 0.5 μm or less, due to the demands for thinner and lower resistance internal electrodes accompanying the downsizing of multilayer ceramic capacitors and the increase in capacity. Ni ultrafine powder is demanded.
[0003]
FIG. 3 shows a conventional example of an apparatus for producing ultrafine metal powder as described above. This manufacturing apparatus mainly includes a vertical reduction furnace 20, and the inside of the reduction furnace 20 is divided into an upper evaporation chamber 20A and a lower reaction chamber 20B by a crucible 21. The top of the reduction furnace 20 has an inert gas supply port 22 for supplying an inert gas to the evaporation chamber 20A. A reducing gas supply pipe 23 extending from the top to the reaction chamber 20B is provided through the evaporation chamber 20A. Between the reducing gas supply pipe 23 and the crucible 21, a metal chloride gas inlet 24 that connects the evaporation chamber 20 </ b> A and the reaction chamber 20 </ b> B is formed. Around the furnace wall, heating means 25A and 25B for heating the evaporation chamber 20A and the reaction chamber 20B are arranged, respectively.
[0004]
The case where Ni ultrafine powder is produced by this production apparatus will be described. Solid nickel chloride is introduced into the evaporation chamber 20A, and this is heated and evaporated (sublimated) by the heating means 25A. A certain nickel chloride gas is continuously generated. On the other hand, an inert gas is supplied to the evaporation chamber 20A from the inert gas supply port 22, hydrogen gas as a reducing gas is supplied to the reaction chamber 20B through the reducing gas supply pipe 23, and further reacted by the heating means 25B. The chamber 20B is maintained at a predetermined reduction temperature. The inert gas supplied into the evaporation chamber 20A flows into the reaction chamber 20B from the metal chloride gas inlet 24 together with the nickel chloride gas. In the reaction chamber 20B, nickel chloride gas is reduced by hydrogen gas to generate Ni powder. The inert gas supplied to the evaporation chamber 20A is used as a carrier gas for transferring the metal chloride gas to the reaction chamber 20B.
[0005]
The metal chloride gas and reducing gas (in the above case, nickel chloride gas and hydrogen gas) generate metal atoms as soon as they come into contact with each other, and the metal atoms collide or aggregate to form ultrafine metal particles. It is thought that the particles grow as the vapor phase chemical reaction proceeds on the surface of the grown or generated ultrafine metal particles. For this reason, the particle diameter of the metal powder to be produced is affected by conditions such as the partial pressure and temperature of the metal chloride gas in the atmosphere in the reaction step.
[0006]
[Problems to be solved by the invention]
The conventional manufacturing apparatus adopts a form in which the metal chloride gas (nickel chloride gas in the above specific example) generated in the evaporation chamber 20A is introduced from the evaporation chamber 20A to the reaction chamber 20B by the carrier gas. There is a problem.
The metal chloride gas partial pressure in the evaporation chamber 20A and the supply amount of the metal chloride gas to the reaction chamber 20B are not stable, and the particle size of the metal powder produced in the reaction chamber 20B is controlled within a desired range. Is considered difficult. For this reason, a method for stably producing a high-quality metal powder having a narrow particle size distribution is desired.
The present invention aims at the following points in the case of obtaining a metal ultrafine powder by reducing a metal chloride gas obtained by evaporating a solid metal chloride.
1) To provide an apparatus for stably supplying a metal chloride gas to a reaction section.
2) To provide a gas phase chemical reaction apparatus for ultrafine metal powder using the apparatus of 1) above.
3) To provide a method for producing ultrafine metal powder using the apparatus of 2) above.
[0007]
[Means for Solving the Problems]
The present invention heats and evaporates a solid metal chloride to produce a metal chloride gas, supplies the metal chloride gas and the reducing gas to the reaction section, and performs a gas phase chemical reaction by the metal chloride gas and the reducing gas. the cause was to a method for producing a metal powder to obtain a metal powder, a feed pipe made through the reaction section by circulating an inert gas, utilizing a negative pressure caused by flow of inert gas, the supply pipe A metal chloride gas is sucked from a metal chloride gas introduction section provided in the middle, and a metal chloride gas accompanied by an inert gas is supplied to the reaction section .
[0008]
According to this manufacturing method, the generated metal chloride gas is introduced into the supply pipe in which the carrier gas is flowing into the reaction section using negative pressure, and is supplied from the supply pipe to the reaction section by the carrier gas. The amount of the metal chloride gas introduced into the supply pipe is determined by the magnitude of the negative pressure when the evaporation amount of the metal chloride gas and the flow rate of the carrier gas are constant. Therefore, the amount of the metal chloride gas supplied to the reaction section and the partial pressure of the metal chloride gas can be controlled by using the magnitude of the negative pressure as a control factor. Therefore, the supply amount and partial pressure of the metal chloride gas can be controlled easily and with high accuracy, and as a result, the particle size of the metal powder produced in the reaction section can be controlled accurately.
[0009]
The metal ultrafine powder that can be produced by the metal powder production method of the present invention is nickel, Cu, Ag, or the like, and these ultrafine powders are suitable for various uses such as conductive paste filler, Ti material bonding material, and catalyst. ing. Among these, the present invention is particularly suitable for producing Ni ultrafine powder.
[0010]
As the carrier gas in the present invention, an inert gas such as argon gas or nitrogen gas is preferably used. However, a reducing gas may be mixed in the carrier gas, and further, the reducing gas may be used as the carrier gas. You can also.
In addition, as the reducing gas used when producing the metal powder, a reducing gas such as hydrogen gas or hydrogen sulfide gas can be used, but hydrogen gas is preferable in view of the influence on the produced metal powder.
Furthermore, examples of the metal chloride of the present invention include nickel chloride and CuCl ₂ .
[0011]
Next, the apparatus for producing metal powder of the present invention is suitable for carrying out the method for producing metal powder of the present invention, and generates metal chloride gas by heating and evaporating solid metal chloride. An evaporating part, a reaction part for causing a gas phase chemical reaction with a metal chloride gas and a reducing gas to obtain a metal powder, a carrier gas directly flowing to the reaction part, and a metal chloride gas introducing part, A supply pipe for supplying the metal chloride gas introduced from the introduction part to the reaction part by a carrier gas, and the metal chloride gas introduction part in the supply pipe has a negative pressure for sucking the metal chloride gas. A generation means is provided.
[0012]
According to this manufacturing apparatus, the metal chloride gas generated in the evaporation section is introduced into the supply pipe at a negative pressure generated by the negative pressure generating means, and is transferred to the reaction section by the carrier gas. The metal chloride gas comes into contact with the reducing gas in the reaction section and causes a gas phase chemical reaction to become metal powder. The amount of metal chloride gas supplied to the reaction section and the partial pressure of the metal chloride gas are controlled by the magnitude of the negative pressure generated by the negative pressure generating means. These controls are performed when the carrier gas reacts via the supply pipe. Since it is directly flowed to the part, it can be carried out easily and with high accuracy. For this reason, in this invention, it is set as the preferable form that the magnitude | size of the negative pressure generated by the negative pressure generation means is adjustable.
[0013]
The negative pressure generating means according to the present invention can be constituted by an introduction port formed as a metal chloride gas introduction part to the supply pipe. However, in order to generate a sufficient negative pressure, it is preferable to provide a venturi mechanism for generating a negative pressure using the flow velocity of the carrier gas in the supply pipe adjacent to the introduction port.
[0014]
Moreover, in the manufacturing apparatus of this invention, it is set as the preferable form that the supply pipe has penetrated the evaporation part from a viewpoint with which the size reduction and simplification of an apparatus are achieved. In this case, the metal chloride gas introduction part provided in the supply pipe is arranged in the evaporation part.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a metal powder manufacturing apparatus according to an embodiment. The apparatus is mainly composed of a cylindrical vertical reduction furnace 1, and the inside of the reduction furnace 1 is divided into an upper evaporation chamber (evaporation part) 1A and a lower reaction chamber (reaction part) 1B by a partition 2 constituting a crucible. It is divided. The evaporation chamber 1A and the reaction chamber 1B are heated to predetermined temperatures by heating means 3A and 3B arranged around the reduction furnace 1, respectively. A reducing gas supply pipe 4a for supplying a reducing gas to the reaction chamber 1B is connected to the upper part of the furnace wall constituting the reaction chamber 1B. In addition, a recovery tube 4b for recovering the generated ultrafine metal powder is provided at the lower end of the reaction chamber 1B.
[0016]
A supply pipe 5 for supplying a metal chloride gas to the reaction chamber 1B is disposed at the upper part of the reduction furnace 1. The supply pipe 5 extends along the axis of the reduction furnace 1 from the top of the reduction furnace 1 through the evaporation chamber 1A to the top of the reaction chamber 1B. The lower end of the supply pipe 5 is configured as a nozzle 5a that discharges a metal chloride gas into the reaction chamber 1B.
[0017]
As shown in FIG. 2 (a), a venturi mechanism (negative pressure generating means) in which the thickness of the supply pipe 5 bulges inwardly at the substantially central portion of the extension part of the supply pipe 5 in the evaporation chamber 1A. 6 is configured. The thickest part of the venturi mechanism 6 is provided with a plurality of metal chloride gas inlets 7 communicating with the inside of the supply pipe 5 and the evaporation chamber 1A at equal intervals in the circumferential direction.
[0018]
Next, a specific example of an embodiment for producing Ni ultrafine powder using the metal powder production apparatus will be described.
First, solid nickel chloride (solid metal chloride) is put into the evaporation chamber 1A, and this is heated and evaporated (sublimated) by the heating means 3A. The heating temperature of nickel chloride by the heating means 3A is suitably around 900 ° C. In the evaporation chamber 1A, nickel chloride gas, which is a metal chloride gas, is continuously generated. On the other hand, an inert gas (argon gas or nitrogen gas) is flowed to the supply pipe 5 and pumped to the reaction chamber 1B, and hydrogen gas as a reducing gas is flowed to the reducing gas supply pipe 4a to be supplied to the reaction chamber 1B. The reaction chamber 1B is heated to a predetermined reduction temperature (around 1000 ° C.) by the heating means 3B.
[0019]
The inert gas flowing in the supply pipe 5 toward the reaction chamber 1B generates a negative pressure when passing through the venturi mechanism 6. Due to the generation of the negative pressure, the nickel chloride gas generated in the evaporation chamber 1 </ b> A is sucked into the supply pipe 5 from the metal chloride gas inlet 7. The nickel chloride gas introduced into the supply pipe 5 is discharged from the nozzle 5a into the reaction chamber 1B together with the inert gas. In the reaction chamber 1B, the nickel chloride gas accompanying the inert gas causes a gas phase chemical reaction with the hydrogen gas, and Ni ultrafine powder is generated.
[0020]
The generated Ni ultrafine powder is cooled at the lower part of the reaction chamber 1B together with an inert gas, hydrochloric acid gas by-produced by a gas phase chemical reaction, and the like, and then separated and recovered from the mixed gas through the recovery pipe 4b. The separated and recovered Ni ultrafine powder is further subjected to a washing and drying step, and then the Ni ultrafine powder according to the present invention is obtained.
[0021]
According to the present embodiment, the metal chloride gas (nickel chloride gas in the above specific example) generated in the evaporation chamber 1A is introduced into the supply pipe 5 using the negative pressure generated by the venturi mechanism 6, and the reaction chamber 1B. The amount of the metal chloride gas introduced into the supply pipe 5 is determined by the magnitude of the negative pressure generated in the venturi mechanism 6 when the amount of evaporation of the metal chloride gas and the flow rate of the carrier gas are constant. Thus, by using the magnitude of the negative pressure by the venturi mechanism 6 as a control factor, the supply amount of the metal chloride gas to the reaction chamber 1B and the partial pressure of the metal chloride gas can be controlled. Therefore, the supply amount and partial pressure of the metal chloride gas can be controlled easily and with high accuracy. As a result, the particle size of the metal powder produced in the reaction chamber 1B can be accurately controlled, and Ni ultrafine powder having a particle size of 0.5 μm or less, for example, can be produced. In this case, the negative pressure generated by the venturi mechanism 6 can be controlled by the narrow state in the supply pipe 5 associated with the thickness and length.
[0022]
In the above manufacturing apparatus, the evaporation chamber 1A and the reaction chamber 1B are adjacent to each other in the vertical direction, and the supply pipe 5 penetrates the evaporation chamber 1A. Therefore, the apparatus can be reduced in size and simplified.
[0023]
In the above embodiment, an inert gas is used as the carrier gas. However, a reducing gas (hydrogen gas that is a reducing gas in the above specific example) or another gas (chlorine gas in the above specific example) is mixed in the carrier gas. In addition, a reducing gas may be used as a carrier gas.
[0024]
The venturi mechanism 6 of the above embodiment is an example of a negative pressure generating means for introducing the metal chloride gas into the supply pipe 5. As the negative pressure generating means, the metal chloride gas can be introduced into the supply pipe 5. Any form is acceptable. 2B to 2D show modified examples of the venturi mechanism. The venturi mechanism of FIG. 2B is configured by a funnel-shaped throttle member 10 provided on the upstream side of the metal chloride gas inlet 7. The venturi mechanism of FIG. 2C is configured by reducing the diameter of the nozzle 5a of the supply pipe 5 and constricting it, and connecting the metal chloride gas introduction port 7 to the inner pipe 11 passing through the supply pipe 5. Yes. Further, in the venturi mechanism of FIG. 2D, the throttle valve 12 constitutes a venturi mechanism. In this case, the amount of the metal chloride gas introduced can be arbitrarily controlled by adjusting the magnitude of the negative pressure according to the opening of the throttle valve 12. Therefore, the particle size control of the metal powder to be generated can be easily performed with high accuracy.
[0025]
【Example】
Examples of the present invention will be described below.
Solid nickel chloride as a starting material is charged into the evaporation chamber 1A of the metal powder production apparatus shown in FIG. 1, and the evaporation chamber 1A is heated to 900 ° C. by the heating means 3A to evaporate the solid nickel chloride. Nickel gas was generated. Further, the reaction chamber 1B was heated to 1000 ° C. by the heating means 3B. Next, argon gas is allowed to flow through the supply pipe 5, nickel chloride gas is supplied to the reaction chamber 1B at 0.3 Nl / min, and hydrogen gas is supplied from the reducing gas supply pipe 4a to the reaction chamber 1B. Ni ultrafine powder was continuously generated in 1B. Next, nitrogen gas, hydrochloric acid vapor by-produced by the reaction, and Ni ultrafine powder were introduced from the collection tube 4b to the oil scrubber, and only Ni ultrafine powder was separated and recovered. Next, the recovered Ni ultrafine powder was washed with xylene, washed with water and dried to obtain Ni ultrafine powder. This ultrafine Ni powder had an average particle size of 0.3 μm and was a spherical particle having a substantially uniform shape, and was extremely high quality.
[0026]
【The invention's effect】
As described above, according to the present invention, the metal chloride gas generated by heating and evaporating the solid metal chloride is applied to the supply pipe in which the carrier gas is directly flowed to the reaction section. Therefore, the particle size of the metal powder to be generated can be easily controlled with high accuracy. Therefore, a high quality metal powder having a narrow particle size distribution can be stably obtained.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an apparatus for producing metal powder according to an embodiment of the present invention.
2A is a longitudinal sectional view showing a venturi mechanism according to an embodiment of the present invention, and FIGS. 2B to 2D are longitudinal sectional views showing modified examples of the venturi mechanism. FIG.
FIG. 3 is a longitudinal sectional view showing a conventional example of a conventional metal powder production apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Reduction furnace, 1A ... Evaporation chamber (evaporation part), 1B ... Reaction chamber (reaction part),
5 ... supply pipe, 6 ... venturi mechanism (negative pressure generating means),
7: Metal chloride gas inlet.

Claims (4)

A solid metal chloride is heated and evaporated to generate a metal chloride gas, the metal chloride gas and the reducing gas are supplied to the reaction section, and a gas phase chemical reaction between the metal chloride gas and the reducing gas is performed. A method for producing a metal powder that is caused to wake up to obtain a metal powder,
Is passed through an inert gas supply tube made through the above reaction section, the utilizing negative pressure by the flow of inert gas, the metal from the metal chloride gas introducing portion provided on the way of the supply pipe A method for producing metal powder, comprising sucking a chloride gas and supplying the metal chloride gas accompanying the inert gas to the reaction section . The method for producing metal powder according to claim 1, wherein the supply amount of the metal chloride gas is adjusted by adjusting the negative pressure. The method for producing metal powder according to claim 1 or 2, wherein the metal is nickel and the reducing gas is hydrogen. The method for producing a metal powder according to any one of claims 1 to 3, wherein a particle diameter of the metal powder is 0.5 µm or less.

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