KR101476612B1 - Metal powders coated with multilayer graphene and/or nano graphite layer - Google Patents

Abstract

The present invention provides a metal powder whose surface is coated with multilayer graphene and / or a nano-graphite layer. The metal powder isolates and protects metal powder having high reactivity with respect to a reaction gas or an aqueous solution in the atmosphere, The stability can be remarkably improved and the oxidation reaction, the hydration reaction, the carbonate formation reaction and the like can be suppressed, and expensive metallic materials can be substituted for expensive metal materials in various electronic parts and devices, It is effective.

Description

METAL POWDERS COATED WITH MULTILAYER GRAPH AND / OR NANO GRAPHITE LAYER [0002]

The present invention relates to a method of coating a surface of a metal powder with a multilayer graphene and / or a nano-graphite layer so as to shield the metal powder surface from oxygen, moisture, carbon dioxide, A hydration reaction, a carbonate formation reaction, and a corrosion reaction with respect to the metal powder, thereby preventing deterioration of the physical and chemical properties of the metal powder.

Metal materials such as Ag, Au, Cu, Al, Cr, Mo, W, Zn, Ni, Fe and Co have excellent electrical conductivity, contact materials for various applications. As a method of forming an electrode pattern or an electrode contact pattern in these elements and parts, a thin film patterning method and a thick film processing method using a metal powder paste are used.

In the thin film patterning method, a target metal material thin film is formed by a thin film process such as a plasma sputtering method, and then the formed thin film is patterned by various processes including a photo-lithography process, ). Such a thin film patterning method has many problems including a vacuum deposition process, a photoresist application process, an exposure process, a development process, and an etching process, so that the productivity of the process is low, the process cost is high, There is a problem that an additional cost is incurred to treat the contaminated by-products.

The thick film process may be performed by pattern printing in the form of electrodes or electrodes using a paste or a slurry prepared by mixing a metal powder and an organic vehicle or by using a uniformly coated thick film ) Is pattern-developed to produce a thick-film electrode or electrode contact shape. The electrode or electrode contact thick film thus formed is cured at room temperature or is calcined by heating at a high temperature to add the organic solution and sintering the metal powder added to the paste or slurry.

The thick film process using the metal powder paste or slurry has a simpler process step than the thin film patterning process and has a high productivity because of the thick film coating process at room temperature and atmospheric pressure, and is excellent in economical efficiency and used in various electronic parts. For example, in the case of forming an electrode contact pattern between an ITO electrode and a flexible printed circuit board in a touch panel of a display device, a paste containing Ag powder is printed, and then the paste is printed at room temperature or at a temperature of 60 to 100 DEG C And is used in a process of forming a contact between electrodes. The photosensitive paste containing the Ag powder used for the BUS electrode of the PDP is printed on the front side in the form of a thick film, exposed and developed in the form of an electrode pattern, and then heated to a temperature at which the Ag powder is sintered to form an electrode. In addition, they are used in solar cells, LEDs, RFIDs, thick film printing antennas, power semiconductors, and high thermal conductive pastes.

Though the thick film process including the metal powder has advantages of low equipment investment cost and process cost, most of these thick film processes use a high temperature heat treatment process in the atmosphere. Most of the metal powders are oxidized, hydrated or carbonated There is a problem that the material usable as the electrode material is limited to the Ag metal powder in which the oxidation reaction, the hydration reaction, and the carbonate formation reaction do not occur at atmospheric conditions.

The Ag material is very expensive compared to metal materials such as Cu, Al, Cr, Mo, W, Zn, Ni, Fe, and Co. Therefore, in order to lower the cost of a product or a part, However, there is a high need for a method of suppressing oxidation, hydration, and carbonate formation reaction during heating of these metal powders to room temperature or heat treatment temperature.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

In particular, the inventors of the present invention have studied a variety of in-depth studies and have come up with the development of metallic powder coated with multilayer graphene and / or nanographite layer as described below, Compared with existing metal powders, it has been confirmed that oxides, hydrates, and carbonate formation reactions are suppressed and that the original properties of the metal powders can be maintained even after a process accompanied by a high temperature, thereby completing the present invention.

Accordingly, the present invention provides a metal powder characterized in that a multilayer graphene and / or a nano graphite layer is coated on the surface.

The metal powder according to the present invention can prevent the surface of the metal powder from various solutions as well as oxygen, water and carbon dioxide in the atmosphere, as described above, due to the multilayer graphene and / or nano graphite layer coated on the surface thereof , It is possible to prevent the oxidation reaction, the hydration reaction, the carbonate formation reaction, and the corrosion reaction from occurring on the metal powder, thereby preventing the deterioration of the physical and chemical properties of the metal powder.

Therefore, the metal powder according to the present invention is preferably used as a precursor for producing electrodes or electrode contacts of various electronic components including information display devices, solar cells, LEDs, RFIDs, thick film printing antennas, power semiconductors, high thermal conductive pastes and the like Lt; / RTI >

In one specific example, the metal powder comprises one element selected from the group consisting of Cu, Al, Cr, Mo, W, Zn, Ag, Ni, Fe and Co, . ≪ / RTI >

Such a metal powder may have a size of, for example, from 0.01 μm to 100 μm, and more specifically, a size range of 0.1 μm to 40 μm, which is a size range used as an electrode of an electronic component. More specifically, , And may have a size of from 2 탆 to 5 탆 used for most electronic parts.

The metal powder may have various shapes such as a spherical shape, a rod shape, a plate shape, and an irregular shape. Among them, the spherical shape is particularly preferable, for example, the printing property and the thick film application performance of the paste and slurry produced by mixing the metal powder and the organic solution are excellent in the spherical powder.

On the other hand, graphene has been reported to be a layered material composed of a mono-element layer in which carbon atoms are arranged in a hexagonal shape, and can serve as a diffusion barrier for almost all elements when there is no defect in the layer [Jong Min Move it. al., " High-Resolution EM of Colloidal Nanocrystal Growth Using Graphene Liquid Cells ", Science, Vol. 336, p61-64 (2012)).

According to the present invention, such graphene is coated on the surface of metal particles in the form of multilayer graphene and / or nanographite layer.

Therefore, the multilayer graphene and / or nano graphite layer can block and isolate the metal powder from the atmospheric oxygen, moisture, reaction gas such as CO ₂ / CO or the aqueous solution, and consequently the oxidation resistance, hydration resistance, The carbonate formation reaction resistance is remarkably improved as compared with the uncoated metal powder. A variety of metal powders, including Cu, Al, Cr, Mo, W, Zn, Ag, Ni, Fe, and Co, which easily deteriorate due to oxidation reaction in a high temperature process in the atmosphere, , The chemical properties can be maintained during the process and during the storage process and the original properties can be used as is.

In order for the graphene-coated metal powder to effectively exhibit its protective film properties, for example, in a thick film process, a partial defect in the coating layer may occur due to mechanical impact or the like during the process, . In addition, the resistance of the coating layer to the oxidation reaction depends mainly on the defect and thickness of such a coating layer.

First, when the multi-layered graphene or nano graphite layer contains defects at the atomic level or the macro level, the reaction material diffuses to the surface of the metal powder through the defects and oxidation reaction, hydration reaction, and carbonate formation reaction occur do. Therefore, the coating layer should not contain any defects through which substances causing oxidation, hydration or carbonate formation reaction can pass. Since graphene composed of a carbon single layer is likely to cause defects in the coating layer during the manufacturing process or the process, a multi-layer graphene layer composed of at least two graphene layers is required.

In addition, when the graphene and graphite materials are heated in an air atmosphere, the coating layer gradually disappears by reacting with oxygen in the atmosphere, and eventually the metal powder is exposed to atmospheric oxygen. In this process, the amount of oxidation of the graphene and graphite layers increases exponentially with temperature and increases linearly with the holding time. Therefore, when the process temperature is increased or the process time is increased, it is necessary to increase the number of stacked graphenes in order to maintain the protective function during the formation process of the electrode or the electrode contact. Therefore, in order to shield and protect the metal powder from the reaction gas or the reactive aqueous solution in the atmosphere, it is preferable to determine the thickness of the multilayer graphene or nano graphite layer according to the process temperature and time conditions.

For example, when the temperature of the step of using the metal powder of the present invention as a precursor is as low as 200 占 폚 or less, the process time is as short as several minutes, or the partial pressure of oxygen in the process atmosphere is significantly lower than the partial pressure of oxygen in the atmosphere, When the potential is low, even a multilayer graphene coating of two to five layers can sufficiently serve as a protective film. However, when the process temperature is as high as about 300 DEG C to 600 DEG C, the reaction time is as long as several minutes to several hours, or the process atmosphere has high oxidation potential such as atmospheric or oxygen atmosphere, Based on the total weight of the nano-particles.

In this case, as the number of graphene layers increases, the electrical conductivity of the metal powder is shielded from the reactants, but the electrical conductivity through the coating layer is reduced. Therefore, the thickness of the coating layer on the actual powder surface depends on the optimum factors It should be set up to have performance. It is known that the electrical conductivity in the direction perpendicular to the graphene layer is reduced by a factor of 100 compared with the electrical conductivity in the direction parallel to the graphene layer in the graphite. Therefore, as the thickness of the coating layer is increased, the electrical resistance value in the thickness direction of the coating layer is increased, and the performance as the electrode or the electrode contact material is lowered.

On the other hand, in order for the metal powder coated with the multi-layer graphene and / or the nano graphite to exhibit, for example, as a precursor for producing an electrode or an electrode contact effectively, / RTI > and / or to form a coating of the nanographite layer. The individually coated powder can form a dense film during the thick film formation and the firing process, because it can exhibit excellent electrical characteristics as a precursor for producing the electrode material and the electrode contact.

Examples of the method for forming the multilayer graphene or nano graphite layer include a high temperature chemical vapor deposition (CVD) method in which a metal powder is exposed to a hydrocarbon gas at a high temperature to coat the metal powder, a carbon source such as carbon black, Various methods such as a method of coating by immersion in a solution in which graphene oxide is dispersed and a method of coating by immersion may be used. Among these methods, in the high temperature CVD coating process, since the metal powder has a high temperature, the diffusion of the metal element is actively generated, and the powder is mutually sintered. Therefore, a method capable of forming a multilayer graphene or nano graphite layer in a state where the metal powder is kept independently is preferable.

Metal powder such as Cu, Al, Cr, Mo, Ag, W, Zn or the like having a weak catalytic characteristic or low carbon solubility for the decomposition reaction of hydrocarbon gas when coating a multilayer graphene or nano- graphite layer by high- Co, Pt, Pd, Ru, Re, and Ni, which are excellent in catalytic properties for the decomposition reaction of hydrocarbon gas and have sufficient solubility in carbon to obtain the desired thickness of the coating layer, It may be desirable to further coat a metal layer such as Ir.

Thus, in one specific example,

A core comprising one element selected from the group consisting of Al, Cr, Mo, Ag, W and Zn, or containing an alloy of two or more elements; And

A shell on which an outer surface of the core is coated with a transition metal catalyst element selected from the group consisting of Ni, Co, Pt, Pd, Ru, Re and Ir;

And a core-shell structure including the core-shell structure.

In this case, the thickness of the shell may be 0.001 to 0.5 times the core radius.

In some cases, the metal powder may be coated with a multilayer graphene or nano-graphite layer in such a manner that the metal powder is brought into contact with the carbon black and / or the carbon organic material and heated, reacted, and cooled.

The present invention also provides a paste or slurry for an electroconductive electrode prepared by adding a metal powder coated on the surface of the multilayer graphene and / or nano graphite layer and an electrode or electrode contact formed using such paste or slurry do.

A method of manufacturing a paste or slurry for an electrically conductive electrode by using a metal powder and a method of manufacturing an electrode or an electrode contact using the metal powder are well known in the art, so a detailed description thereof will be omitted herein.

Such electrodes or electrode contacts are used in various electronic components. The electronic component includes an information display device, a touch panel for an information display device, a photovoltaic device, a multi-layer ceramic capacitor, a chip varistor, an LED, an RFID, an electronic package, But is not limited to, a flat panel display device, and examples of the flat panel display device include LCDs, PDPs, OLEDs, and the like.

As described above, the metal powder coated with the multi-layered graphene and / or nano-graphite layer according to the present invention isolates and protects the metal powder having high reactivity with respect to the reaction gas or aqueous solution in the atmosphere, The oxidation reaction, the hydration reaction, the carbonate formation reaction, and the like can be suppressed, and the expensive Ag metal can be substituted as a low-cost metal material in various electronic parts and devices, and the manufacturing cost can be greatly reduced have.

1 is a schematic diagram of a metal powder coated with a multilayer graphene layer;
2 is a schematic view showing a process of coating a multilayer graphene or nano-graphite layer on a metal powder by high-temperature CVD;
3 is a schematic view of a composite powder coated with a catalyst layer capable of promoting the decomposition reaction of hydrocarbon gas on the surface of a metal powder;
4 is a schematic diagram of a rotating reaction furnace that can be used to prevent sintering between powders when coating multi-layer graphene or nano-graphite layers with metal powder by high temperature CVD;
5 is a schematic diagram of a fluidized bed reactor that may be used to prevent sintering between powders when coating multi-layer graphene or nano-graphite layers with metal powder by high temperature CVD;
6 is an electron micrograph showing a shape in which graphene is separated from a metal powder when the powder coated with the multilayer graphene is fractured;
FIG. 7 is a TGA analysis result of a Ni powder coated on a particle surface of Ni powder and an Ni powder not coated according to another embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings according to the embodiments of the present invention, but the scope of the present invention is not limited thereto.

1 is a schematic cross-sectional view of a metal powder coated with a nano-graphene layer according to an embodiment of the present invention.

Referring to FIG. 1, the surface of the metal powder is coated with multilayer graphene having a number of layers less than 5 or a nanographite layer having 5 or more and less than 100 layers. The metal powder is not particularly limited, but may be a metal powder for manufacturing an electrode or an electrode contact applied to various electric parts and devices including information display devices, touch panels, solar cells, ceramic multilayer capacitors, RFID, flexible printed substrates, For example, Cu, Al, Cr, Mo, W, Zn, Ag, Ni, Fe, Co, etc., which are excellent in electric conductivity and low in cost, can be used as the precursor Or a variety of materials including their selective alloys can be used.

FIG. 2 schematically shows process steps of coating multi-layer graphene or nano-graphite on the surface of a metal powder by a high-temperature CVD process.

First, the metal powder is charged into a reactor, and the inside of the reactor is evacuated by a vacuum pump to lower the partial pressure of the oxygen gas present in the reactor to a low partial pressure that does not oxidize the metal powder, Or reducing gas is continuously purged by purging the oxygen gas from the inside of the reactor so that the partial pressure of at least these gases does not oxidize or nitrify the metal powder.

The optimum partial pressure of oxygen in the reactor depends on the kind of the metal powder. In the case of the Cu powder having a relatively low formation energy of the oxide, it is preferable to maintain the partial pressure of 10 ^-3 torr or less, and the formation energy of the oxide In the case of the material, it is desirable to keep it at 10 ^-6 torr or less.

When the partial pressure of oxygen in the reactor is lowered to a desired value or less by such vacuum evacuation or atmospheric pressure purging, a reducing gas such as Ar-H ₂ or N ₂ -H ₂ is supplied into the reactor and the temperature is increased to the reaction temperature . At this time, the reduction reaction of the metal powder occurs during the heating process, and the oxide present on the surface of the metal powder must be reduced. Therefore, the temperature raising rate is appropriately selected within the range of 1 占 폚 / min to 30 占 폚 / min depending on the oxidation state of the surface of the metal powder and the kind of the powder.

When the metal powder is heated and reaches the reaction temperature, hydrocarbon gas and hydrogen gas, which are the raw materials of graphene and nano graphite, are introduced into the reaction chamber by using argon, which is inert gas or nitrogen gas, which is inert gas, as a carrier gas Supply. The hydrocarbon gas is methane (CH _4), ethane (C ₂ H _6), propane (C ₃ H _8), butane (C ₄ H _10), ethylene (C ₂ H _4), propylene (C ₃ H _6), etc. Can be used. However, gas or liquid in which carbon is deposited on the surface of the metal powder due to decomposition reaction at the surface of the metal powder at the reaction temperature can be used.

The reaction temperature is preferably a temperature range in which the decomposition reaction of the hydrocarbon gas is selectively generated on the surface of the metal powder. The reaction temperature depends on the kind of the hydrocarbon gas and the catalytic performance for the decomposition reaction of the metal powder. For example, in the case of the Ni metal powder, when the methane gas is used, decomposition is carried out in a temperature range of 500 ° C. to 1100 ° C. Since the reaction is actively generated, a temperature range of 600 ° C to 950 ° C is preferable.

The thickness of the multilayer graphene or nanographite layer formed on the surface of the metal powder depends on the amount of carbon generated by the decomposition reaction of the hydrocarbon gas into the metal powder. When the carbon-solidified metal powder is cooled from the reaction temperature, supersaturated carbon precipitates on the surface of the metal powder to form a multilayer graphene or nano-graphite layer. Therefore, as the holding time of the specimen increases at the reaction temperature, the thickness of the multilayer graphene and nanographite layer increases because the amount of diffusion of the hydrocarbon into the powder increases due to the decomposition reaction of the hydrocarbon at the surface of the metal powder. If the Ni metal powder is increased in the methane gas atmosphere at a reaction temperature of 850 ° C for 5 minutes to 30 minutes, the thickness of the coating layer may vary from 2 to 5 in terms of the number of graphene layers The thickness of the nanographite is increased up to 100 graphene layers.

On the other hand, the partial pressure of the hydrocarbon gas at the reaction temperature influences the decomposition reaction of the hydrocarbon gas and the high carbon content into the metal powder. As the partial pressure of the hydrocarbon gas increases, the carbon concentration on the metal surface increases and the amount of carbon employed increases. In order to form multi-layer graphene or nanographite of excellent characteristics, it is preferable that the partial pressure of hydrocarbons is such that the carbon concentration generated by the decomposition reaction at the metal surface is equal to or lower than the solubility limit concentration of the metal powder at the reaction temperature. When a multilayer graphene or nano graphite layer is coated with methane gas on the surface of the Ni metal powder at a temperature of 850 占 폚, the partial pressure of methane gas is preferably in the range of 5 torr to 200 torr.

On the other hand, in the metal powder, Cu, Al, Cr, Mo, W, Zn and the like have weak catalytic function for the decomposition reaction of the hydrocarbon gas or have no catalytic function. In the case of the Cu powder, although the catalyst performance for the decomposition reaction is retained, since the solubility limit for carbon is small, it is possible to form a multilayer graphene layer, but it is difficult to form a thick nano graphite layer. On the other hand, Al, Cr, Mo, W, Zn and the like have no catalytic function for the decomposition reaction of hydrocarbon gas, and it is difficult to form multilayer graphene or nano graphite coating layer on the surfaces of these metal powders by CVD.

The surface of such Al, Cr, Mo, W, Zn and the like is provided with a transition metal catalyst metal element which is excellent in catalytic properties for the decomposition reaction of hydrocarbon gas and has a sufficiently high solubility to carbon, It is possible to form metal layers such as Ni, Co, Pt, Pd, Ru, Re and Ir as shown in FIG. 3 to form multilayer graphene and nano graphite layers therebetween. In such a core-shell structure, the thickness of the metal coating layer (shell) is preferably 0.001 to 0.5 times the radius of the base metal (core), more preferably 0.001 to 0.1 times.

Referring again to FIG. 2, when the carbon powder-solidified metal powder is cooled to a room temperature at a high reaction temperature, a multi-layered graphene or nano-graphite layer is deposited on the surface of the metal powder to form a coating layer. At this time, it is also possible to use a method in which the cooling temperature profile of the sample is cooled directly from the reaction temperature to room temperature, or maintained at a constant holding temperature as shown by the dotted line in Fig. 2, and then cooled to room temperature.

At this stage, the cooling rate of the sample affects the thickness of the multilayer graphene or nano-graphite layer. When the cooling rate is high, the time required for the carbon dissolved in the metal powder to diffuse to the surface of the metal powder is shortened, The thickness of the coating layer is reduced. On the other hand, when the cooling rate of the sample is slowed or maintained at a constant temperature during the cooling process, since the carbon dissolved in the metal powder provides a time for diffusing and precipitating to the surface, the thickness of the multilayer graphene or nano- .

The cooling rate of the specimen for forming multilayer graphene or nano graphite is preferably in the range of 0.1 占 폚 / min to 20 占 폚 / min, and cooling in the range of 1 占 폚 / min to 5 占 폚 / min is preferable It is more preferable to obtain a coating layer. The holding temperature in the cooling process is preferably 200 占 폚 to 500 占 폚, more preferably 300 占 폚 to 400 占 폚, since it is necessary to set the temperature at which the carbon can be diffused sufficiently fast in the metal powder, Lt; 0 > C to obtain a thermodynamically stable coating layer.

When the metal powder is maintained in a reducing atmosphere at a high temperature, sintering occurs at the contact portion between the powders, which causes the use performance of the coated powder to deteriorate. The oxide is removed from the surface of the metal powder in a reducing atmosphere at a high temperature, so that element diffusion on the surface is actively generated, thereby promoting sintering at the contact portion between the powders. The paste or slurry prepared by mixing the sintered powder with, for example, an organic solution has problems such as uniformity of the thickness of the thick film, poor coating performance and speed, and filling property, which may deteriorate the electrical conductivity of the prepared electrode pattern or electrode contact pattern It causes. In order to prevent these metal powders from contacting and sintering, it may be preferable to use a high temperature CVD reactor as shown in Fig. That is, while the reaction vessel is being rotated, the metal powder is maintained in a state where the metal powder continuously flows at a high reaction temperature, thereby preventing sintering between powders.

Another method of preventing sintering between metal powders at a high temperature reaction temperature is to suspend the metal powder by the reaction gas and the carrier gas to inhibit sintering by preventing the powders from contacting each other. For example, by using the fluidized bed reaction apparatus shown in FIG. 5, the decomposition reaction of the hydrocarbon gas is generated on the surface of the metal powder in a state where the powder is suspended and heated by the reaction gas and the carrier gas introduced from below. In a method other than the gas flow method, a method of preventing the sintering by using an ultrasonic vibrator or a mechanical oscillator to flow the powder continuously may be used.

FIG. 6 is a photograph showing an external shape of a powder broken by applying an external force to Ni powder coated with multilayer graphene in the manufacturing process of FIG. 4 by scanning electron microscope.

Referring to FIG. 6, it can be seen that graphene is observed outside the Ni powder (deep white). That is, when the Ni metal powder is fractured by plastic deformation due to external force, the multi-layered graphene layer is broken, and a part of the coating layer is loosened and attached to the surface of the powder. As shown in FIG. 6, it can be seen that the multi-layer graphene can be formed on the surface of the independent metal powder through the high-temperature CVD method.

FIG. 7 is a graph illustrating the effect of improving the resistance to oxidation of a multi-layered graphene coating layer by using a thermogravimetric analysis in which the Ni powder coated with the multilayer graphene is heated in an oxygen atmosphere to be.

7, it can be seen that the weight increase of the multi-layer graphene-coated Ni powder occurs at a higher temperature than the uncoated Ni powder. Here, the increase of the powder weight is due to the oxidation reaction between the oxygen gas in the atmosphere and the Ni powder. Based on the weight increase of 2%, the Ni powder was measured at about 440 ° C and the multi-layer graphene-coated powder at 590 ° C, which prevented the contact between oxygen and Ni metal in the atmosphere, This is considered to contribute to increase the oxidation resistance. As a result, the multilayer graphene and nano graphite coating layer formed through the present manufacturing process shows that the metal powder can maintain the oxidation resistance up to a high temperature.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Accordingly, the above description is intended to illustrate the present invention, and the scope of the present invention is not limited thereto.

Claims (13)

Wherein the nanographite layer is formed of a multilayer graphene having a structure in which 2 to 5 grapins are stacked on the surface and / or a structure in which 6 to 100 grapins are stacked. The metal powder according to claim 1, wherein the metal powder is a precursor for producing an electrode pattern or an electrode contact pattern. The metal powder according to claim 1, wherein the metal powder contains one element selected from the group consisting of Cu, Al, Cr, Mo, W, Zn, Ag, Ni, Fe and Co, And a metal powder. The metal powder according to claim 1, wherein the metal powder has a size of 0.01 to 100 탆. delete The metal powder according to claim 1, wherein the multi-layer graphene or nano-graphite layer is formed by a chemical vapor deposition (CVD) process at a temperature of 600 ° C to 950 ° C. The method of claim 6, wherein the high-temperature chemical vapor deposition process is methane (CH _4), ethane (C ₂ H _6), propane (C ₃ H _8), butane (C ₄ H _10), ethylene (C ₂ H ₄₎ and propylene (C ₃ H ₆ ) is used as the metal powder. The method according to claim 1,
A core comprising one element selected from the group consisting of Al, Cr, Mo, Ag, W and Zn, or containing an alloy of two or more elements; And
A shell on which an outer surface of the core is coated with a transition metal catalyst element selected from the group consisting of Ni, Co, Pt, Pd, Ru, Re and Ir;
And a core-shell structure including the core-shell structure. 9. The metal powder according to claim 8, wherein the thickness of the shell is 0.001 to 0.5 times the core radius. 7. The method according to claim 6, wherein in order to prevent sintering between the metal powders in the high temperature chemical vapor deposition process, a coating layer is formed under the conditions of rotating the reactor, floating the metal powder, or vibrating the metal powder, So as to be coated in an independent state. The metal powder according to claim 1, wherein the multilayer graphene and / or nano graphite layer is coated on the metal powder in such a manner that the metal powder and the carbon black or the carbon organic material are heated, reacted, and cooled. A paste or slurry for an electroconductive electrode, which is prepared by adding a multilayer graphene according to claim 1 and / or a metal powder coated with a nanographite layer. An electrode or an electrode contact formed using the paste or slurry according to claim 12.

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