KR101828432B1 - Method for controlling shape of metal powder by surface energy controlling and metal powder by the same method - Google Patents

Abstract

The present invention relates to a method for controlling a drying type shape of metal powder via surface energy control. One embodiment of the present invention provides the method for controlling a drying type shape of metal powder via surface energy control, comprising: a step of inputting metal powder into a reactor; a step of supplying steam of metal chloride to the reactor at a predetermined fluid velocity; and a step of performing heat process under a predetermined temperature and time condition of metal powder while the metal chloride steam presents and varying a shape of the metal powder. In the predetermined heat process condition, the metal chloride steam is adsorbed to a specific surface in a molecule state to lower a surface energy such that the shape of the metal powder is changed. Without using an additive such as an interlayer stabilizer, condensation between metal particles during process is not occurring and the shape of the metal powder can be uniformly controlled via a drying type method.

Description

TECHNICAL FIELD The present invention relates to a method for controlling a dry shape of a metal powder through surface energy control and a metal powder produced by the method,

More particularly, the present invention relates to a method of controlling a dry shape of a metal powder by controlling surface energy, and more particularly, to a method of controlling a dry shape of a metal powder by controlling a surface energy of the metal powder, To a controllable technology.

Since the metal microparticles exhibit various physical properties depending on the shape and size, they can be used for electric and magnetic materials, conductive pastes and inks, electrodes for electrodes, capacitors, metal catalysts, heat-resisting heat-dissipating materials, ceramic composite materials, medical materials and materials for defense industry products And the like.

Particularly, spherical metal microparticles have a high packing density, and microparticles on a cubic body have excellent magnetic properties. Depending on the shape of the back particles, the metal particles can have various properties, Controlling the shape of metal particles so that they can be represented is becoming an important issue.

In the prior art, the metal microparticles are synthesized largely in a liquid phase or a gas phase. Specifically, the liquid phase method includes a liquid phase reduction method using a reducing agent and a surfactant, a colloid synthesis method, etc., and the gas phase synthesis method includes a chemical vapor deposition method and a physical vapor deposition method .

In the liquid phase synthesis method, the size of the metal fine particles is uniformly controlled by a bottom-up method in which ions of the metal to be synthesized are supplied with electrons and reduced and grown into metal particles from the solution containing the reducing agent Which is advantageous in that it is easy to control the reaction conditions so as to produce a desired shape.

In this connection, the paper entitled " Shape Control of Platinum Nanoparticles Using a Metal Salt " (hereinafter referred to as non-patent document 1) discloses a precursor for synthesizing platinum nanoparticles, a reducing agent, an interfacial stabilizer and a metal salt (AgNO ₃ ). However, in order to prepare particles having a desired shape and size in addition to a precursor of a metal to be synthesized, an interface stabilizer or the like It is difficult to produce metal fine particles of high purity by containing a large amount of additives, and there is a problem that aggregation of particles is inevitable.

In addition, the gas phase synthesis method is advantageous in producing metal particles having a low degree of aggregation between metal particles and having high crystallinity and purity, and in particular, in the case of the chemical vapor deposition method, the process is most simple and is most widely used for producing highly crystalline metal particles It is a synthetic method that is being used.

In the related article "Synthesis of dispersed superfine fcc nickel single crystals in gas phase" (hereinafter referred to as "non-patent document 2"), there is disclosed a technique for controlling the shape of nickel particles using a gas phase synthesis method, It is difficult to produce high purity metal particles as in the liquid phase method. In order to remove unnecessary contaminants on the surface of the particles, There is a problem that a post-treatment process is required.

 SY Kwak, et al. (2012). "Shape Control of Platinum Nanoparticles Using a Metal Salt" Journal of Korean Powder Metallurgy Institute, Vol. 6, pp. 393-397  Gao, W., et al. (2013). "Synthesis of dispersed superfine fcc nickel single crystals in gas phase" The Journal of Physical Chemistry C 117 (18), pp. 9223-9228

Disclosure of the Invention The present invention has been made to solve the problems of the prior art described above, and it is an object of the present invention to provide a method for producing a metal surface, which is capable of reducing the surface energy of metal particles by using a simple vapor phase synthesis method without using an additive capable of reducing purity, So as to produce a controlled metal powder in a desired shape.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the precise form disclosed. There will be.

According to an aspect of the present invention, there is provided a method of manufacturing a metal powder, comprising: injecting a spherical metal powder into a reactor; Supplying a vapor of a metal chloride to the metal powder to the reactor; And heating the supplied metal chloride so that the vapor of the supplied metal chloride is adsorbed on the surface of the metal powder to change the shape of the metal powder, wherein the shape of the metal powder is controlled by adjusting the temperature and time in the heat treatment step The present invention also provides a method of controlling a dry shape of a metal powder through surface energy control.

In one embodiment of the present invention, the metal powder may be nickel (Ni) or copper (Cu).

In one embodiment of the present invention, the metal chloride may include at least one metal chloride selected from NiCl ₂ , CuCl, CuCl ₂ , MgCl ₂ , PbCl ₂ , and PbCl ₄ .

In one embodiment of the present invention, the heat treatment may be performed at a temperature of 300 ° C to 1400 ° C for 5 minutes to 600 minutes.

In another embodiment of the present invention, the particles of the metal powder produced by the dry shape control method may be particles selected from a truncated octahedron, a truncated hexahedron, and a cube As shown in Fig.

According to the embodiment of the present invention, the shape of the metal powder can be variously controlled by reducing the surface energy by using a simple dry process without using an additive such as a surface stabilizer that lowers the purity of the metal powder. By controlling the surface energy, metal powder of a desired shape can be produced without a post-treatment such as a refining step, thereby reducing the operating time and cost of the process.

Further, the production method according to the present invention has an advantage that uniform shape control can be performed without inducing coagulation of metal particles without using an additive. In addition, by adjusting the heat treatment conditions, the shape of the metal particles can be variously changed to a truncated octahedron or a cube to improve the characteristics of the metal powder. For example, in the case of nickel nanoparticles, the cubic- Is about ten times larger.

It should be understood that the effects of the present invention are not limited to the above effects and include all effects that can be deduced from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is a schematic view for explaining a method of controlling a dry shape of a metal powder by surface energy control according to an embodiment of the present invention.
2 (a) shows spherical nickel nanoparticles, and FIG. 2 (b) and FIG. 2 (c) show spherical nickel nanoparticles annealed at 950 ° C. for 15 minutes and 75 minutes, respectively, Is the FESEM image of.
3 (a) to 3 (c) are diagrams derived by simulation of the equilibrium crystal shape (ECS) of the nickel nanoparticles of FIGS. 2 (a) to 2 (c) by software.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" (connected, connected, coupled) with another part, it is not only the case where it is "directly connected" "Is included. Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises" or "having" and the like refer to the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

The present invention relates to a method for producing a metal powder whose shape is controlled by a dry process through surface energy control,

Introducing the metal powder into the reactor;

Feeding a vapor of a metal chloride (M ₂ Cl _x ) into the reactor to the reactor; And

And heat treating the supplied metal chloride so that the vapor of the metal chloride is adsorbed on the surface of the metal powder to change the shape of the metal powder,

And the shape of the metal powder is controlled by controlling the temperature and the time in the heat treatment step. The present invention can provide a method of controlling a dry shape of a metal powder through surface energy control.

1 is a schematic view for explaining a method of controlling a dry shape of a metal powder by surface energy control according to an embodiment of the present invention. Hereinafter, a method of controlling the dry shape of the metal powder through the surface energy control will be described with reference to the drawings.

In the present invention, the step of introducing the metal powder 1 into the reactor 70 comprises the steps of preparing the metal powder 1 and adjusting the surface energy thereof to prepare the metal powder 10 of the desired shape, . In the present invention, the metal powder (1) may include one kind or an alloy thereof selected from the group consisting of nickel (Ni) and copper (Cu), or at least one kind thereof. In the present invention, the shape of the metal powder (1) may be a spheric shape or a polyhedral shape close to a sphincter shape.

The step of supplying the vapor of the metal chloride to the reactor 70 of the present invention may be a step of controlling the surface energy by adsorbing the metal chloride vapor on the surface of the metal powder 1.

In the present invention, the metal chloride vapor may include at least one selected from the group consisting of NiCl ₂ , CuCl, CuCl ₂ , MgCl ₂ , PbCl ₂ and PbCl _4. However, in order to produce more uniform metal particles It may be desirable to supply one species of metal chloride vapor.

At this time, each of the metals constituting the metal chloride vapor may be a metal which is relatively more oxidized than the metals constituting the metal powder (1).

The metal chloride vapor may be adsorbed on the surface of the metal powder 1 under a predetermined heat treatment condition in a step to be described later to control the surface energy of the metal powder 1. More specifically, the metal chloride vapor is adsorbed on a specific surface of the metal powder surface to lower the surface energy to promote growth of the specific surface, and finally, the shape of the metal powder particle can be changed. Since each of the metals constituting the metal chloride vapor is relatively more oxidized than the metals constituting the metal powder 1, the metal chloride vapor can be relatively oxidized, The oxidation of the metal powders 1 proceeds first and the oxidation reaction of the metal powders 1 does not progress to the surface of the metal powder 1 on the surface of the metal chloride vapor. The surface energy due to the reaction can be lowered.

The vapor of the metal chloride may be generated by evaporating a solid metal chloride in a high temperature furnace provided separately from the reactor 70 and then fed into the reactor 70. Alternatively, the metal powder and the solid metal chloride may be mixed into the same reactor 70 without using a separate furnace, and then the heating unit 50 may be provided in the reactor 70, It may also be possible to form a vapor by evaporating the solid metal chloride by applying heat at a high temperature. However, it should be noted that the method of supplying the vapor of the metal chloride is not limited thereto.

When the metal chloride vapor is generated in a separately prepared high temperature furnace and then fed into the reactor 70, the flow rate of the metal chloride vapor may be 1 sccm / cm ² to 150 sccm / cm ² , more preferably 6 sccm / cm ^{2 2} to 60 sccm / cm < ² >.

The heat treatment step of the present invention is a step of changing the shape by reducing the surface energy by adsorbing the vapor of the metal chloride onto the surface of the metal powder 1 under a predetermined heat treatment condition. That is, the degree of the adsorption of the vapor of the metal chloride onto the surface of the metal powder (1) differs according to the heat treatment conditions. Accordingly, the surface energy of the metal powder (1) varies, Can be controlled. The heat treatment step of the present invention may be performed by the heating means 50 provided in the reactor 70.

The shape of the metal powder through the heat treatment step may be variously changed into a truncated octahedron, a truncated hexahedron, and a cube.

The heat treatment step may be performed at a temperature condition of 300 DEG C to 1400 DEG C for 5 minutes to 600 minutes. If the heat treatment temperature is less than 300 ° C., the temperature inside the reactor may be relatively lower than the temperature of the injected metal chloride gas, so that the vapor of the metal chloride supplied to the reactor is condensed and the shape control of the metal powder by the vapor of the metal chloride It can be difficult. When the heat treatment temperature exceeds 1400 DEG C, coalescence between spherical metal powders may occur and uniform shape control may be difficult. In the present invention, the control of the shape of the metal powder may be influenced by the heat treatment time. If high temperature heat is applied for a long time, sintering of the metal powder may occur, and it is preferable that the heat treatment is performed within the temperature condition and the treatment time range as described above. In addition, in one embodiment, when the spherical metal powder is heat-treated at 950 ° C for 10 minutes to 20 minutes in a metal chloride vapor atmosphere, the shape of the metal powder may be changed from spherical to octahedral, When heat treatment is performed for 80 minutes, a metal powder in the form of a cuboid may be produced.

In addition, it is preferable that the heat treatment step fluidizes and heat-treats the reactor to uniformly control the shape of the metal powder. Specifically, there may be a method of rotating the reactor at a predetermined speed or applying a predetermined vibration But not limited to, The predetermined speed and predetermined vibration means a degree that does not cause problems of damage and stability of the apparatus while allowing uniform shape control.

Also, in the heat treatment step, the pressure in the reactor may be vacuum or atmospheric pressure, but when the shape of the metal powder is to be controlled at normal pressure, vapor of metal chloride must be continuously injected / exhausted.

Hereinafter, specific examples of the present invention will be described.

Example  1 Shape Change of Spherical Nickel Particles with Heat Treatment Time

Nickel nanoparticles having an average size of 200 nm prepared by conventional chemical vapor deposition (CVD) were dispersed by ultrasonic vibration on a sapphire single crystal substrate (C-plane (0001), Crystal Bank). 2 (a) is an FESEM image of the nickel nanoparticles used for shape control. As a result, it can be confirmed that the shape of the nickel nanoparticles before heat treatment is spherical. In the present invention, as shown in FIG. 2 (a), polyhedral nickel nanoparticles which are almost spherical in shape are used. However, the present invention is not limited to this, and the nickel nanoparticles or the copper powders that are commercially available may be used without limitation do.

Nickel chloride (NiCl ₂ , 98%, Aldrich) was charged into a quartz crucible and placed in the center after the base material in which the nickel nanoparticle powder was dispersed was placed in the center of the reactor. Thereafter, the inside of the reactor was purged with nitrogen gas for 30 minutes to prevent reduction of nickel chloride. Next, the temperature of the reactor was changed to 850 캜 to form nickel chloride vapor. After sufficient nickel chloride vapor was formed in the reactor, spherical nickel nanoparticles were heat-treated for 15 minutes and 75 minutes at a temperature of 950 ° C.

After the heat treatment was completed, the shape of the spherical nickel nanoparticles heat-treated on the sapphire substrate was observed using FESEM (MERLIN Compact, Zeiss). In addition, the results obtained by FESEM analysis were used to calculate the relative surface energy of each side of the nickel nanoparticles using Wulffman software.

2 (b) and 2 (c) are FESEM images of nickel particles heat-treated at 950 ° C. in a nickel chloride vapor atmosphere for 15 minutes and 75 minutes, respectively. The shape of the nickel nanoparticles before heat treatment was spherical as shown in FIG. 2 (a), but when it was heat-treated for 15 minutes, it was changed into a truncated octahedron shape as shown in FIG. 2 (b) It can be confirmed that the shape changes to a cuboid shape as shown in Fig. 2 (c).

Experimental ECS of the nickel nanoparticles of Figs. 2 (a) to 2 (c) were generated by software and are shown in Figs. 3 (a) to 3 (c), respectively.

First, referring to the ECS simulation results of the spherical nickel nanoparticles before heat treatment shown in FIG. 3 (a), it can be seen that facets of {100}, {111} and {210} the surface energy was analyzed using non-was proved to be ₁₀₀ γ / γ ₁₁₁ = 1.05 and γ ₂₁₀ / γ ₁₁₁ = 1.01. (Here, 100, 111 and 210 denoted by the subscripts denote the Miller index indicating the crystal face.) However, since the {110} segment face is not observed on the ECS, the γ ₁₁₀ / γ ₁₁₁ must be larger than 1.065, It is found that the size is γ ₁₁₁ <γ ₂₁₀ <γ ₁₀₀ <γ ₁₁₀ .

On the other hand, experimental spherical nickel nanoparticles were heat-treated at 950 ° C for 15 minutes and experimental ECS of the nickel nanoparticles of FIG. 2 (b) was generated by software and shown in FIG. 3 (b) } and {111} to check that the one-piece face is developed, the surface energy ratio was identified as γ ₁₀₀ / γ ₁₁₁ = 1.00. In addition, the relative surface energy magnitude of the sculptured surface was analyzed as γ ₁₀₀ = γ ₁₁₁ <γ ₁₁₀ .

The experimental ECS of the nickel nanoparticles of FIG. 2 (c) obtained by heat-treating the spherical nickel nanoparticles at 950 ° C. for 75 minutes is shown in FIG. 3 (c) } And {111} planes were developed, and the surface energy ratio was confirmed to be γ100 / γ111 = 0.63. Further, the surface energy of the engraved surface is? ₁₀₀ <? ₁₁₁ <? ₁₁₀ Respectively.

As shown in the results of the surface energy analysis, the surface energy ratio of the {100} plane to the {111} plane decreased from 1.05 to 1.0 and 0.63 as the spherical nickel nanoparticles were annealed at predetermined conditions for 15 minutes and 75 minutes . That is, the surface energy is reversed from {100} to {111} after annealing the spherical nickel nanoparticles for 15 minutes in the nickel chloride atmosphere, which is preferentially adsorbed on the {100} plane in the molecular state of the nickel chloride vapor It can be assumed that the {100} plane is stabilized. In this way, the nickel chloride vapor is preferentially adsorbed on a specific surface ({100} plane) to lower the surface energy, so that the shape of the nickel particles can be controlled.

The method for controlling the dry shape of a metal powder by controlling the surface energy according to the present invention is characterized in that the metal powder produced according to the prior art is heat-treated under a predetermined condition in a metal chloride vapor atmosphere to adsorb the metal powder on a specific piece surface of the metal powder particles, And controlling the shape by lowering the angle. The metal powder may exhibit different physical properties depending on the shape of the particles, and the metal powder may be heat treated by the dry shape control method according to the present invention to control the shape of the metal powder to improve the physical properties. This will expand the application field of the metal powder and contribute to improve the properties of the material and the material including the metal powder.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

1: metal powder
10: Shape controlled metal powder
50: Heating means
70: Reactor

Claims (10)

Introducing the metal powder into the reactor;
Supplying a vapor of a metal chloride to the metal powder to the reactor; And
And heat treating the supplied metal chloride so that the vapor of the metal chloride is adsorbed on the surface of the metal powder to change the shape of the metal powder,
Wherein the shape of the metal powder is controlled by controlling the temperature and the time in the heat treatment step,
Wherein the metal powder is nickel (Ni) or copper (Cu).
delete The method according to claim 1,
The metal chloride _{NiCl 2, CuCl, CuCl 2,} MgCl 2, PbCl 2, and dry-control method of a metal powder with a surface energy control, characterized in that it comprises at least one metal chloride selected from PbCl _4.
The method according to claim 1,
Wherein the heat treatment is performed at a temperature of 300 ° C to 1400 ° C for 5 minutes to 600 minutes.
The method according to claim 1,
Wherein the metal powder having the shape changed is any one selected from a truncated octahedron, a truncated hexahedron, and a cube, and controlling the shape of the metal powder by controlling the surface energy.
The method according to claim 1,
Wherein the surface energy of the metal powder is lowered as the vapor of the metal chloride is adsorbed on the surface of the metal powder.
Introducing the metal powder into the reactor;
Supplying a vapor of a metal chloride to the metal powder to the reactor; And
And heat treating the supplied metal chloride so that the vapor of the metal chloride is adsorbed on the surface of the metal powder to change the shape of the metal powder,
Wherein the shape of the metal powder is controlled by controlling the temperature and the time in the heat treatment step,
Wherein the heat treatment step is performed by fluidizing the reactor for uniform shape control. &Lt; RTI ID = 0.0 &gt; 8. &lt; / RTI &gt;
The method according to claim 1,
Wherein the flow rate of the metal chloride vapor supplied to the reactor is 1 sccm / cm ² to 150 sccm / cm ² .
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