Method for producing nickel nano powder and nickel nano powder produced using the same

Abstract

The present invention provides a method for producing nickel nanopowder, which has a small average particle size and a low agglomeration rate by preventing aggregation between particles. According to one embodiment of the present invention, the method for producing nickel nanopowder includes the steps of providing a nickel salt and a shell-forming material, nucleating and growing nickel core particles from the nickel salt, forming a shell layer on the surface of the nickel core particle using the shell-forming material, and removing the shell layer to form nickel nanopowder.

Description

Technical Field

[0001] The technical idea of the present invention relates to metal powder, and more particularly, to a method for producing nickel nano powder having a uniform particle size by preventing aggregation between particles, and nickel nano powder produced using the same.

Background Art

[0002] A multilayer ceramic capacitor (MLCC) is a chip-shaped capacitor that temporarily charges electricity or removes noise in an electronic circuit. It stores current and stably supplies only the necessary amount of electricity to ensure the correct operation of the electronic device. Currently, the multilayer ceramic capacitor has such a high demand that it is called the rice of the electronics industry. For example, about 1000 pieces are required for a personal computer and about 2000 pieces are required for a television.

[0003] Such a multilayer ceramic capacitor (MLCC) needs to reduce its size and increase its storage capacitance. Therefore, the multilayer ceramic capacitor has a structure in which about 500 ceramic layers and nickel electrode layers are alternately laminated inside. The multilayer ceramic capacitor is formed through a molding process of forming a ceramic sheet on a release film, a printing process of forming an electrode pattern on the ceramic sheet, and a lamination process of cutting the ceramic sheet, removing the release film, and then laminating the ceramic sheet and the nickel electrode layer. An important technology in the multilayer ceramic capacitor is to make the nickel electrode layer as thin as possible, laminate many of them, and form them without cracks at a high temperature of 1000 °C or higher.

[0004] Recently, with the miniaturization and high lamination of the multilayer ceramic capacitor, an ultra-thin layer of the internal electrode has been required. However, when using nickel powder according to the conventional technology, there are problems such as disconnection due to over-sintering and aggregation of the powder.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The technical problem to be achieved by the technical idea of the present invention is to provide a method for producing nickel nano-powder with a small average particle size and a low aggregation rate by preventing aggregation between particles, and nickel nano-powder produced using the same.

[0006] However, such problems are exemplary and the technical idea of the present invention is not limited thereto.

Means for Solving the Problems

[0007] According to one aspect of the present invention, there is provided a method for producing nickel nano-powder with a small average particle size and a low aggregation rate by preventing aggregation between particles, and nickel nano-powder produced using the same.

[0008] According to one embodiment of the present invention, the method for producing the nickel nano-powder may include providing a nickel salt and a shell-forming substance; nucleating and growing nickel core particles from the nickel salt; forming a shell layer on the surface of the nickel core particles using the shell-forming substance; and removing the shell layer to form nickel nano-powder.

[0009] According to one embodiment of the present invention, the shell layer induces non-sintering aggregation of the nickel core particles, and by removing the shell layer, the non-sintering aggregated nickel core particles are individualized to form the nickel nano-powder.

[0010] According to one embodiment of the present invention, the step of providing the nickel salt and the shell-forming substance can provide the nickel salt and the shell-forming substance by vaporizing them at a temperature in the range of 300°C to 1200°C.

[0011] According to an embodiment of the present invention, in the step of providing the nickel salt and the shell-forming substance, the nickel salt and the shell-forming substance may be provided in a weight ratio in the range of 3:1 to 65:1.

[0012] According to an embodiment of the present invention, in the step of providing the nickel salt and the shell-forming substance, the shell-forming substance may be provided in a molar ratio in the range of 0.4 mmol / L to 2.5 mmol / L per volume of the injection gas.

[0013] According to an embodiment of the present invention, the step of nucleating and growing the nickel core particles may be performed by subjecting the nickel salt to a reduction reaction using a reducing gas to form the solid-phase nickel core particles.

[0014] According to an embodiment of the present invention, the step of nucleating and growing the nickel core particles may be performed at a temperature in the range of 800°C to 1200°C.

[0015] According to an embodiment of the present invention, the step of forming the shell layer may be performed by depositing and growing the vaporized shell-forming substance on the surface of the nickel core particles to form the shell layer.

[0016] According to an embodiment of the present invention, the step of forming the shell layer may be performed in a region where the temperature decreases along the direction in which the nickel core particles are transferred.

[0017] According to an embodiment of the present invention, the step of forming the shell layer may be performed at a temperature in the range of 300°C to 1200°C.

[0018] According to an embodiment of the present invention, in the step of forming the shell layer, the free energy of formation of the shell-forming substance may be smaller than the free energy of formation of the nickel salt.

[0019] According to an embodiment of the present invention, in the step of forming the shell layer, the shell-forming material can have an equilibrium vapor pressure in the range of 0.9 kPa to 54 kPa.

[0020] According to an embodiment of the present invention, the step of forming the nickel nano powder can be obtained by selectively removing the shell layer through wet post-treatment.

[0021] According to an embodiment of the present invention, the nickel salt can include at least any one of nickel acetate, nickel bromide, nickel carbonate, nickel chloride, nickel fluoride, nickel hydroxide, nickel iodide, nickel nitrate, nickel oxide, nickel phosphate, nickel silicate, nickel sulfate, and nickel sulfide.

[0022] According to an embodiment of the present invention, the shell-forming material can include a water-soluble metal salt.

[0023] According to an embodiment of the present invention, the shell-forming material can include at least any one of aluminum (Al), barium (Ba), calcium (Ca), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), lithium (Li), magnesium (Mg), manganese (Mn), mercury (Hg), nickel (Ni), potassium (K), rubidium (Rb), silver (Ag), sodium (Na), strontium (Sr), tin (Sn), lanthanum (La), silicon (Si), gallium (Ga), scandium (Sc), titanium (Ti), vanadium (V), zirconium (Zr), yttrium (Y), cadmium (Cd), actinium (Ac), cesium (Cs), hafnium (Hf), and zinc (Zn).

[0024] According to an embodiment of the present invention, the shell-forming material can include at least any one of metal acetate, metal bromide, metal carbonate, metal chloride, metal fluoride, metal hydroxide, metal iodide, metal nitrate, metal oxide, metal phosphate, metal silicate, metal sulfate, and metal sulfide.

[0025] According to an embodiment of the present invention, nickel nanometer powder composed of nickel and formed using the above-described manufacturing method is provided.

[0026] According to an embodiment of the present invention, the nickel nanometer powder can have an average particle size in the range of 30 nm to 200 nm and an aggregation rate in the range of 0.5% to 50%.

[0027] According to an embodiment of the present invention, the nickel nano powder may include a natural oxide layer formed on its surface.

[0028] According to an embodiment of the present invention, the nickel nano powder may contain nickel in the range of 50 wt% to 100 wt%.

[0029] According to an embodiment of the present invention, the nickel nano powder is a nickel nano powder having a core-shell structure, and may include nickel core particles; and a shell layer surrounding the surface of the nickel core particles and composed of a water-soluble metal salt.

[0030] According to an embodiment of the present invention, the method for manufacturing the metal nano powder may include providing a metal salt and a shell-forming substance; nucleating and growing metal core particles from the metal salt; forming a shell layer on the surface of the metal core particles using the shell-forming substance; and removing the shell layer to form a metal nano powder.

Effects of the Invention

[0031] In the case of the technical idea of the present invention, after forming a shell layer composed of a water-soluble metal on the surface of nickel core particles in a high-temperature environment, the shell layer is easily removed by a wet method at a low temperature, thereby preventing aggregation between particles and providing nickel nano powder with a small average particle size and a low aggregation rate.

[0032] The effects of the present invention described above are exemplarily described, and the scope of the present invention is not limited by such effects.

Brief Description of the Drawings

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Best Mode for Carrying Out the Invention

[0046] Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. The embodiments of the present invention are provided to more fully explain the technical idea of the present invention to those having ordinary knowledge in the technical field. The following embodiments can be modified into various other forms, and the scope of the technical idea of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to further enrich and complete the present disclosure and to fully convey the technical idea of the present invention to those skilled in the art. Throughout this specification, the same reference numerals mean the same elements. Further, various elements and regions in the drawings are schematically shown. Therefore, the technical idea of the present invention is not limited by the relative sizes and intervals shown in the accompanying drawings.

[0047] The technical idea of the present invention relates to a method for producing metal nano powder using a vapor phase method. According to the technical idea of the present invention, as an exemplary metal nano powder, nickel nano powder used in multilayer ceramic capacitors can be formed.

[0048] The laminated ceramic capacitor is miniaturized and highly laminated, and as a result, thinning of the nickel electrode layer is required. Due to such thinning of the nickel electrode layer, when using nickel powder with a size of 500 nm or more in the conventional method, problems such as disconnection due to over-sintering and powder aggregation occur. Specifically, for miniaturization and high lamination of the laminated ceramic capacitor, it is required that the nickel powder has a particle size of 100 nm or less, and design technology of a gas-phase reactor is required. For improving the sintering uniformity of the laminated ceramic capacitor, the nickel powder must have a uniform particle size distribution, and improvement of powder classification technology is required. In order to cope with the increase in the sintering temperature of the laminated ceramic capacitor, removal treatment of the oxide film formed on the surface of the nickel powder is required. In order to prevent cracks during sintering of the laminated ceramic capacitor, the nickel powder must have low aggregation characteristics, and for that purpose, surface chemical treatment of the nickel powder is required.

[0049] The nickel electrode layer of the laminated ceramic capacitor is manufactured by printing a fine nickel powder paste on a ceramic layer. The nickel powder is manufactured by dry methods such as evaporation condensation method, thermal decomposition method, gas-phase reaction method, electric explosion method, etc., or wet methods such as liquid-phase reduction method, hydrothermal synthesis method, chemical precipitation method, etc. The dry method can manufacture high-purity and high-quality nano powders, but requires low productivity and high equipment investment costs. The wet method is advantageous for low unit price and mass production, but has the disadvantages that it is difficult to control impurities such as organic substances and difficult to control the particle size. Therefore, the dry method is suitable for use in fields that require high purity and high crystallinity, but cannot use surfactants, and since it is a high-temperature process, strong aggregation between particles occurs, and a classification process for classifying particles by size must be used, resulting in a decrease in yield. Therefore, when the classification process is not performed by preventing aggregation between particles, a high yield can be achieved.

[0050] In the following description, a case where the chemical vapor synthesis (CVS) method is used to produce metal nano-powders is described, but this is exemplary, and the technical idea of the present invention is not limited thereto. The case of using a physical vapor synthesis (PVS) method such as DC plasma or RF plasma is also included in the technical idea of the present invention.

[0051] FIG. 1 is a flowchart showing a method (S100) for producing nickel nano-powders according to the technical idea of the present invention.

[0052] Referring to FIG. 1, the method (S100) for producing the nickel nano-powders includes: a step (S110) of providing a nickel salt and a shell-forming substance; a step (S120) of nucleating and growing nickel core particles from the nickel salt; a step (S130) of forming a shell layer on the surface of the nickel core particles using the shell-forming substance; and a step (S140) of removing the shell layer to form nickel nano-powders.

[0053] The shell layer can induce non-sintering aggregation of the nickel core particles. Further, by removing the shell layer, the non-sintering aggregated nickel core particles can be individualized to form the nickel nano-powders.

[0054] The step (S110) of providing the nickel salt and the shell-forming substance can vaporize and provide the nickel salt and the shell-forming substance. The step (S110) can be performed at a temperature at which the nickel salt changes from a solid phase to a gas phase. The nickel salt and the shell-forming substance can be vaporized and provided at a temperature in the range of, for example, 300°C to 1200°C.

[0055] The nickel salt and the shell-forming substance can be provided in a weight ratio in the range of, for example, 3:1 to 65:1. The nickel salt and the shell-forming substance can be mixed and provided together, or provided individually.

[0056] Further, the shell-forming material can be provided in the range of 0.4 mmol / L to 2.5 mmol / L in terms of molar ratio per volume of the injection gas.

[0057] The vaporized nickel salt and the vaporized shell-forming material can be transferred in the reaction chamber by a carrier gas. The carrier gas can include argon gas or nitrogen gas.

[0058] The step (S120) of nucleating and growing the nickel core particles can be carried out by subjecting the nickel salt to a reduction reaction using a reducing gas, for example, a hydrogen-containing gas, to form the solid nickel core particles. The step (S120) of nucleating and growing the nickel core particles may be carried out at a temperature in the range of, for example, 800°C to 1200°C.

[0059] For example, when the nickel salt is nickel chloride (NiCl2), the nickel core particles can be formed by the following reaction.

[0060] Vaporization reaction of nickel salt: NiCl2(s) ⇒ NiCl2(g)

[0061] Reaction for generating nickel core particles: NiCl2(g) + H2(g) ⇒ Ni(s) + 2HCl(g)

[0062] The reducing gas can include a gas that causes a reduction reaction. The reducing gas can include, for example, hydrogen gas, carbon monoxide gas, magnesium vapor gas, calcium vapor gas, and the like.

[0063] The nickel core particles can contain, for example, 50% by weight or more of nickel, and can contain nickel in the range of, for example, 50% by weight to 100% by weight. The balance can be composed of inevitable impurities such as oxides and chlorides.

[0064] The step (S130) of forming the shell layer may be such that the vaporized shell-forming material is deposited and grown on the surface of the nickel core particles to form the shell layer. The shell-forming material may form the shell layer from a gas phase through a liquid phase to a solid phase, or may change directly from a gas phase to a solid phase to form the shell layer.

[0065] The step (S130) of forming the shell layer may be performed in a region where the temperature decreases along the direction in which the nickel core particles are transferred. The step (S130) may be performed at a temperature below the temperature at which precipitation and growth of the shell-forming material start, and may be performed at a temperature above the temperature at which the nickel nanopowder can be sintered or aggregated. The step (S130) may be performed, for example, at a temperature in the range of 300°C to 1200°C.

[0066] In the step (S130) of forming the shell layer, the free energy of formation of the shell-forming material may be smaller than the free energy of formation of the nickel salt. Also, the free energy of formation of the shell-forming material may be smaller than the free energy of formation of the gaseous chloride (HCl) formed by the reaction of the nickel salt and the reducing gas. Also, the shell-forming material may have, for example, an equilibrium vapor pressure in the range of 0.9 kPa to 54 kPa.

[0067] The steps (S110) to (S130) may be performed using a heat treatment furnace, and may be sequentially performed while the nickel salt, the shell-forming material, and the nickel core particles are transferred in one heat treatment furnace.

[0068] The step (S140) of forming the nickel nanopowder may be such that the shell layer is selectively removed through wet post-treatment without removing the nickel nanopowder. The wet post-treatment may be performed using water, or may be performed using an acidic solution or a basic solution. For such post-treatment, after discharging the nickel nanopowder having the shell layer formed therefrom from the heat treatment furnace, it may be charged into a wet treatment machine and performed.

[0069] The nickel salt can include, for example, at least any one of nickel acetate, nickel bromide, nickel carbonate, nickel chloride, nickel fluoride, nickel hydroxide, nickel iodide, nickel nitrate, nickel oxide, nickel phosphate, nickel silicate, nickel sulfate, and nickel sulfide.

[0070] The shell-forming substance can include a water-soluble metal salt. The shell-forming substance can include, for example, at least any one of aluminum (Al), barium (Ba), calcium (Ca), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), lithium (Li), magnesium (Mg), manganese (Mn), mercury (Hg), nickel (Ni), potassium (K), rubidium (Rb), silver (Ag), sodium (Na), strontium (Sr), tin (Sn), lanthanum (La), silicon (Si), gallium (Ga), scandium (Sc), titanium (Ti), vanadium (V), zirconium (Zr), yttrium (Y), cadmium (Cd), actinium (Ac), cesium (Cs), hafnium (Hf), and zinc (Zn).

[0071] The shell-forming material can include, for example, at least any one of metal acetate, metal bromide, metal carbonate, metal chloride, metal fluoride, metal hydroxide, metal iodide, metal nitrate, metal oxide, metal phosphate, metal silicate, metal sulfate, and metal sulfide. Here, the metal contained in the shell-forming material can include, for example, at least any one of aluminum (Al), barium (Ba), calcium (Ca), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), lithium (Li), magnesium (Mg), manganese (Mn), mercury (Hg), nickel (Ni), potassium (K), rubidium (Rb), silver (Ag), sodium (Na), strontium (Sr), tin (Sn), lanthanum (La), silicon (Si), gallium (Ga), scandium (Sc), titanium (Ti), vanadium (V), zirconium (Zr), yttrium (Y), cadmium (Cd), actinium (Ac), cesium (Cs), hafnium (Hf), and zinc (Zn).

[0072] Nickel nano-powder can be formed by the above-described method (S100) for manufacturing nickel nano-powder. The nickel nano-powder can include a natural oxide layer formed on its surface. The entire reaction section in the above-described method (S100) for manufacturing nickel nano-powder can be maintained in a reducing atmosphere. In such a case, the natural oxide layer may not be formed on the surface of the nickel nano-powder. When the reaction is completed and the nickel nano-powder is transferred from the reducing atmosphere to the air atmosphere, the natural oxide layer may be formed on the surface of the nickel nano-powder.

[0073] The nickel nano powder can contain, for example, 50% by weight or more of nickel, and can contain nickel in the range of, for example, 50% to 100% by weight. The balance can be composed of inevitable impurities such as oxides and chlorides.

[0074] The nickel nano powder can have an average particle size in the range of, for example, 30 nm to 200 nm, and can have an aggregation rate in the range of, for example, 0.5% to 50%.

[0075] The nickel nano powder is a nickel nano powder having a core - shell structure, and can include nickel core particles and a shell layer surrounding the surface of the nickel core particles and composed of a water - soluble metal salt. Such nickel nano powder can remove the shell layer by washing.

[0076] The method for manufacturing nickel nano powder according to the technical idea of the present invention can be extended to methods for manufacturing various metal nano powders.

[0077] Figure 2 is a flowchart showing a method (S200) for manufacturing metal nano powder according to the technical idea of the present invention.

[0078] Referring to Figure 2, the method (S200) for manufacturing metal nano powder includes a step (S210) of providing a metal salt and a shell - forming substance, a step (S220) of nucleating and growing metal core particles from the metal salt, a step (S230) of forming a shell layer on the surface of the metal core particles using the shell - forming substance, and a step (S240) of removing the shell layer to form metal nano powder.

[0079] Figure 3 is a schematic diagram explaining the principle of the method for manufacturing nickel nano powder according to the technical idea of the present invention.

[0080] Referring to FIG. 3, in the comparative example, after nickel particles are formed through nucleation and growth, the nickel particles start to coagulate with each other and are sintering-typed agglomerated in a high-temperature environment. The sintering-typed agglomeration means that the particles are relatively strongly bonded by sintering. Due to such sintering-typed agglomeration, a difference in the size of nickel particles formed when a large number of nickel particles are agglomerated and when a small number of nickel particles are agglomerated will occur. Therefore, through a classification process, nickel particles must be separated into a target size range. Then, through a washing process and surface oxidation, nickel nano-powder is formed. Since the classification process removes nickel particles agglomerated into a large size, there is a problem that the yield of the produced nickel nano-powder decreases.

[0081] On the contrary, in the example of the method for manufacturing nickel nano-powder according to the technical idea of the present invention, after nickel core particles are formed through nucleation and growth, a water-soluble metal substance, that is, a shell-forming substance, coats the surface of the nickel core particles. That is, nickel core particles with a shell layer formed on the surface can be formed. Since the water-soluble metal substance coated on the surface of the nickel core particles can be prevented from being sintered, the nickel core particles are non-sintering-typed coagulated. The non-sintering-typed coagulation means that the nickel particles are relatively weakly bonded by electrostatic bonding or the like. Then, when the nickel particles are washed, the water-soluble metal substance constituting the shell coated on the surface of the nickel particles is removed, and the agglomerated nickel particles are separated from each other. Then, through surface oxidation, nickel nano-powder is formed. In this example, since the classification process is not performed, the nickel particles to be removed can be minimized, so that the yield of the nickel particles increases.

[0082] As the shell-forming substance, the water-soluble metal substance can be selected according to the following criteria.

[0083] 1) Ease of removal: The shell-forming substance must be easily removable from the recovered nickel powder. For example, the shell-forming substance must be easily removable by water, an acidic solution, a basic solution, or the like. Also, those that do not form insoluble compounds are preferred.

[0084] 2) Vaporization vapor pressure: The shell-forming substance must have a sufficient vapor pressure for easy vaporization within a certain temperature range.

[0085] 3) Reactivity: The shell-forming substance is preferably non-reactive with the gas used in the manufacturing process or the gas generated by the reaction. If a reaction occurs, the reaction product must meet this selection criterion. Also, those that do not undergo thermal decomposition at the temperature of the manufacturing process are preferred. If thermal decomposition occurs, the product must meet this selection criterion.

[0086] 4) Solidification vapor pressure: The shell-forming substance must have a sufficient vapor pressure for easy solidification within a certain temperature range. That is, an appropriate amount of the shell-forming substance must be introduced, and precipitation (shell formation) must occur in an appropriate amount at an appropriate temperature. If an excessive amount of the shell-forming substance is required for the formation of the shell, there is a risk that a large amount of energy will be consumed for vaporization or the reaction rate will decrease.

[0087] Hereinafter, experimental examples of selecting a shell-forming substance according to the above selection criteria will be exemplarily described.

[0088] Figure 4 is a table showing the solubility of candidate substances for the shell-forming substance used in the method for producing nickel nano powder according to the technical idea of the present invention.

[0089] Referring to Fig. 4, it shows the solubility of the compounds that can constitute the shell-forming substance in water with respect to cations and anions. In the table, "S" indicates the case of good dissolution, "ss" indicates the case of less dissolution compared to "S", "I" indicates the case of non-dissolution, and "DR" indicates the case where a decomposition reaction occurs.

[0090] Based on the solubility in Fig. 4, assuming that water is used for removal after forming the shell, acetate compounds, bromide compounds, and chloride compounds can be selected as candidate substances for the shell-forming substance.

[0091] Next, since the shell-forming substance requires a substance with a high vaporization vapor pressure, a chloride compound can be selected as a candidate substance for the shell-forming substance.

[0092] Next, since the shell-forming substance requires a substance that is not reactive with the used gas or the generated gas during the manufacturing process, an Ellingham diagram was used.

[0093] Fig. 5 is a graph showing an Ellingham diagram for candidate substances of the shell-forming substance used in the method for manufacturing nickel nano powder according to the technical idea of the present invention.

[0094] Referring to Fig. 5, based on the free energy of formation of the reaction product HCl, since MoCl has a high free energy of formation over the entire temperature range, MoCl has low stability and therefore cannot be selected as a candidate substance for the shell-forming substance. On the contrary, since MgCl2 has a low free energy of formation over the entire range of process temperatures, MgCl2 has high stability and therefore can be selected as a candidate substance for the shell-forming substance.

[0095] Thus, based on the free energy of formation provided by the Ellingham diagram, as candidates for the shell-forming material, MgCl2, LaCl3, LiCl, SrCl3, SiCl4, GaCl3, ScCl3, NaCl, KCl, UCl5, TiCl4, ZnCl2, VCl2, ZrCl4, UCl3, YCl3, RbCl, CdCl2, AlCl3, AcCl3, CaCl2, BaCl2, CsCl, HfCl4, etc. can be selected.

[0096] Next, the candidate materials for the shell-forming material need to have a sufficient vapor pressure to form a shell in the given temperature range under the process conditions. Therefore, based on the boiling point, for example, substances having a boiling point of 300 °C or higher, for example, 700 °C or higher, as candidates for the shell-forming material, MgCl2, LaCl3, LiCl, NaCl, KCl, ZnCl2, YCl3, RbCl, CdCl2, CaCl2, BaCl2, CsCl, etc. can be selected.

[0097] Next, in order to meet the selection criteria of the solidification vapor pressure, it is necessary to consider the equilibrium vapor pressure at different temperatures. Thus, using the Clausius-Clapeyron relation, as candidates for the shell-forming material, NaCl, KCl, ZnCl2, LiCl, CaCl2, MgCl2, CsCl, BaCl2, etc. can be selected.

[0098] FIG. 6 is a schematic diagram showing a metal nanopowder manufacturing apparatus 100 for performing a method for manufacturing nickel nanopowders according to the technical idea of the present invention.

[0099] Referring to FIG. 6, the metal nanopowder manufacturing apparatus 100 can be divided into a vaporization region 110, a reduction reaction region 120, and a shell layer formation region 130.

[0100] In the vaporization region 110, the nickel salt and the shell-forming material can be vaporized, and for example, can have a temperature in the range of 300 °C to 1200 °C.

[0101] In the reduction reaction region 120, the nickel salt can react with the reducing gas to form nickel core particles, and for example, it can have a temperature in the range of 800°C to 1200°C.

[0102] In the shell layer formation region 130, a shell can be formed on the surface of the nickel core particles, and for example, it can have a temperature in the range of 300°C to 1200°C.

[0103] The manufacturing apparatus 100 of the metal nano powder includes a reactor main body 140, a heater unit 150 located outside the reactor main body 140 and providing heat to the reactor main body 140, a carrier gas supply unit 160 located at one end of the reactor main body 140 and supplying a carrier gas, a reducing gas supply unit 170 located at one end of the reactor main body 140 and supplying a reducing gas, and a filter unit 180 located at the other end of the reactor main body 140, filtering the discharged gas to obtain nickel core particles with a shell formed thereon.

[0104] The operating method of the manufacturing apparatus 100 of the metal nano powder is as follows.

[0105] The nickel salt and the shell forming substance 190 are charged into the vaporization region 110 in the reactor main body 140 of the manufacturing apparatus 100 of the metal nano powder. Such charging can be performed by accommodating the nickel salt and the shell forming substance 190 in a storage container, or can be performed using a device such as an injector. Also, the nickel salt and the shell forming substance 190 may be mixed and charged together, or may be charged separately.

[0106] In the vaporization region 110, when the nickel salt and the shell forming substance 190 are heated and vaporized by the heater unit 150, the nickel salt and the shell forming substance are transferred to the reduction reaction region 120 by the carrier gas supplied through the carrier gas supply unit 160.

[0107] In the reduction reaction region 120, the vaporized nickel salt and the shell-forming material can be heated by the heater unit 150 so that the temperature is maintained or increased. The nickel salt is reduced by the reducing gas supplied through the reducing gas supply unit 170 to form nickel core particles. Then, the nickel core particles and the shell-forming material are transferred to the shell layer formation region 130 by the carrier gas.

[0108] In the shell layer formation region 130, the nickel core particles and the shell-forming material can be heated by the heater unit 150 so that the temperature is maintained or gradually decreased. However, this is exemplary, and the heater unit 150 may be omitted. The ambient temperature decreases in the shell layer formation region 130, whereby the shell-forming material adheres to the surface of the nickel core particles to form a shell layer.

[0109] The nickel core particles having the shell layer formed thereon are transferred to the filter unit 180 by the carrier gas and filtered in the filter unit 180.

[0110] Experimental Examples

[0111] Hereinafter, preferred experimental examples are presented to assist in understanding the present invention. However, the following experimental examples are merely for assisting in understanding the present invention, and the present invention is not limited by the following experimental examples.

[0112] In the following experimental examples, NiCl2 hexahydrate was used as the nickel salt, and KCl anhydride or NaCl anhydride was used as the shell-forming material. The nickel salt and the shell-forming material were mixed in various weight ratios and dissolved in distilled water. Then, spray drying was used to form a mixed powder of the solid-phase nickel salt and the shell-forming material, and the mixed powder was provided in the step of providing the nickel salt and the shell-forming material in the production method of the present invention. Then, nickel nano powder was formed using the above-described production method of nickel nano powder.

[0113] In the case of the comparative example, only NiCl2 was used as the nickel salt, vaporized, reacted with hydrogen gas, and vapor-phase deposited to form nickel nano-powder. That is, no shell-forming substance was used in the comparative example.

[0114] Table 1 is a table showing various mixing weight ratios of the nickel salt and the shell-forming substance in the examples of the present invention.

[0115]

Table 1

[0116] Figures 7 and 8 are scanning electron micrographs showing nickel nano-powder formed using the method for producing nickel nano-powder according to the technical idea of the present invention.

[0117] Referring to Figures 7 and 8, in the comparative example, many sintered and combined nickel nano-powders were observed. This is because, since the shell-forming substance was not used, the solidified nickel particles coalesced and sintered with each other at high temperature, and it is analyzed that it is difficult to separate the coalesced nickel particles in subsequent processes.

[0118] Analyzing the case where the KCl anhydrate was used as the shell-forming substance, in Examples 1 and 2, relatively few sintered and combined nickel nano-powders were observed, and almost none were observed in Example 3.

[0119] Analyzing the case where the NaCl anhydrate was used as the shell-forming substance, relatively few sintered and combined nickel nano-powders were observed in Examples 4, 5, and 6.

[0120] Figures 9 and 10 are graphs showing the size distribution of nickel nano-powder formed using the method for producing nickel nano-powder according to the technical idea of the present invention.

[0121] Referring to FIGS. 9 and 10, the size distributions of the nickel nano-powders of the comparative example and Examples 1 to 6 are shown. Based on the graph, the average particle size, particle size distribution, and aggregation rate of the produced nickel nano-powders are shown in Table 2. In Table 2 below, the average particle size was determined using the median diameter value, and the particle size distribution was determined using the geometric standard deviation.

[0122]

Table 2

[0123] Referring to Table 2, compared with the comparative example, the average particle size decreased in the examples, and the aggregation rate also showed a decreasing trend. In Examples 1 to 3 using KCl as the shell-forming substance, it can be seen that the higher the content of NiCl2 hexahydrate, the smaller the average particle size and the lower the aggregation rate. In Examples 4 to 6 using NaCl as the shell-forming substance, the higher the content of NiCl2 hexahydrate, the smaller the average particle size and the lower the aggregation rate. However, in Examples 4 and 5, the aggregation rate was shown to be slightly higher compared to the comparative example.

[0124] FIG. 11 shows the aggregated state of the nickel nano-powders formed using the method for producing nickel nano-powders according to the technical idea of the present invention.

[0125] Referring to FIG. 11, in the scanning electron microscope photographs of the nickel nano-powders of FIGS. 7 and 8, states in which 2, 3, 4, and 5 nickel particles are aggregated are shown. From this, the number of aggregated particles was calculated from the photograph and shown in Table 3.

[0126]

Table 3

[0127] Referring to Table 3, compared with the comparative example, the number of aggregated particles generally decreased in the examples. In particular, in Example 3 using KCl as the shell-forming substance, a significant decrease in aggregated particles was shown.

[0128] When analyzing the above results, the higher the weight ratio of nickel salt (NiCl₂ hexahydrate) to the shell-forming particles (KCl or NaCl), the fewer the sintered nickel particles, and after non-sintered aggregation, individualized nickel nanopowders can be more easily formed. Also, it can be seen that KCl is more effective in preventing the aggregation of nickel particles compared to NaCl. This is analyzed to be because the precipitation amount of NaCl is even less than that of KCl at the same temperature.

[0129] Figure 12 is a scanning electron micrograph showing the surface state of nickel nanopowder after washing with distilled water of nickel nanopowder formed using the method for manufacturing nickel nanopowder according to the technical idea of the present invention.

[0130] Referring to Figure 12, in the comparative example, since no shell-forming substance was used, there was almost no change in the surface state of the nanopowder before and after washing. On the contrary, in the case of Example 3, it can be confirmed that the shell layer was removed by washing with distilled water and the nickel nanopowders were individualized.

[0131] Figure 13 is a graph showing the EDS analysis results of nickel nanopowder after washing with distilled water of nickel nanopowder formed using the method for manufacturing nickel nanopowder according to the technical idea of the present invention.

[0132] Referring to Figure 13, in the case of the comparative example, since no shell-forming substance was used, the potassium content was not shown, and the chlorine content used for the formation of nickel powder decreased by washing.

[0133] In the case of the example, before washing, since there is a shell composed of KCl surrounding the nickel core particles, the contents of potassium and chlorine are shown to be high. After washing, it can be seen that the content of potassium is not shown and the content of chlorine has also decreased significantly. Therefore, it can be understood that the shell is effectively removed by washing in the example to form nickel nano powder. In the said nickel nano powder, the content of nickel was shown to be 56.59 wt% before washing and 99.61 wt% after washing. In the case of the example, the content of chlorine contained in the nickel nano powder was shown to be even lower compared to the comparative example.

[0134] It is obvious to those with ordinary knowledge in the technical field to which the technical idea of the present invention described above belongs that the technical idea of the present invention is not limited to the foregoing examples and the attached drawings, and various substitutions, modifications and changes are possible without departing from the technical idea of the present invention. Aspects according to the present disclosure also include the following aspects. <1> Providing a nickel salt and a shell-forming substance; Nucleating and growing nickel core particles from the nickel salt; Forming a shell layer on the surface of the nickel core particles using the shell-forming substance; Removing the shell layer to form nickel nano powder, a method for manufacturing nickel nano powder. <2> The shell layer induces non-sintering aggregation of the nickel core particles, By removing the shell layer, the non-sintering aggregated nickel core particles are individualized to form the nickel nano powder, the method for manufacturing nickel nano powder according to <1>. <3> In the step of providing the nickel salt and the shell-forming substance, The shell-forming substance is provided in the range of 0.4 mmol / L to 2.5 mmol / L in terms of molar ratio per volume of the injected gas, the method for manufacturing nickel nano powder according to <1>. <4> The step of nucleating and growing the nickel core particles is The nickel salt is subjected to a reduction reaction using a reducing gas to form the solid-phase nickel core particles, the method for manufacturing nickel nano powder according to <1>. <5> The step of forming the shell layer is The vaporized shell-forming substance precipitates and grows on the surface of the nickel core particles to form the shell layer, the method for manufacturing nickel nano powder according to <1>. <6> The step of forming the shell layer is Performed in a region where the temperature decreases along the direction in which the nickel core particles are transferred, the method for manufacturing nickel nano powder according to <1>. <7> In the step of forming the shell layer, The free energy of formation of the shell-forming substance is smaller than the free energy of formation of the nickel salt, the method for manufacturing nickel nano powder according to <1>. <8> The step of forming the nickel nano powder is The shell layer is selectively removed through wet post-treatment, the method for manufacturing nickel nano powder according to <1>. <9> The nickel salt in the method for producing nickel nano powder according to <1> includes at least any one of nickel acetate, nickel bromide, nickel carbonate, nickel chloride, nickel fluoride, nickel hydroxide, nickel iodide, nickel nitrate, nickel oxide, nickel phosphate, nickel silicate, nickel sulfate, and nickel sulfide. <10> The shell-forming substance in the method for producing nickel nano powder according to <1> includes a water-soluble metal salt. <11> The shell-forming substance is aluminum (Al), barium (Ba), calcium (Ca), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), lithium (Li), magnesium (Mg), manganese (Mn), mercury (Hg), nickel (Ni), potassium (K), rubidium (Rb), silver (Ag), sodium (Na), strontium (Sr), tin (Sn), lanthanum (La), silicon (Si), gallium (Ga), scandium (Sc), titanium (Ti), vanadium (V), zirconium (Zr), yttrium (Y), cadmium (Cd), actinium (Ac), cesium (Cs), hafnium (Hf), and zinc (Zn), or includes at least any one of them, or The method for producing nickel nano powder according to <1>, comprising at least any one of metal acetate, metal bromide, metal carbonate, metal chloride, metal fluoride, metal hydroxide, metal iodide, metal nitrate, metal oxide, metal phosphate, metal silicate, metal sulfate, and metal sulfide. <12> A nickel nano powder formed by using the production method according to <1> and composed of nickel, wherein the nickel nano powder has an average particle size in the range of 30 nm to 200 nm, and has an aggregation rate in the range of 0.5% to 50%. <13> The nickel nano powder according to <12>, comprising a natural oxide layer formed on the surface. <14> The nickel nano powder according to <12>, comprising nickel in the range of 50% by weight to 100% by weight. <15> A nickel nano powder having a core-shell structure, comprising nickel core particles, and a shell layer surrounding the surface of the nickel core particles and composed of a water-soluble metal salt. <16> A method for producing a metal nano powder, comprising the steps of providing a metal salt and a shell-forming substance, nucleating and growing metal core particles from the metal salt, forming a shell layer on the surface of the metal core particles using the shell-forming substance, and removing the shell layer to form a metal nano powder.

Claims

1. vaporizing a nickel salt and a shell-forming material to provide them; reducing the vaporized nickel salt by using a reducing gas to cause a reduction reaction to form solid-phase nickel core particles, and nucleating and growing the nickel core particles from the nickel salt; depositing and growing the vaporized shell-forming material on the surface of the nickel core particles to form a shell layer; removing the shell layer to form nickel nano powder, wherein the shell layer induces non-sintering aggregation of the nickel core particles, and by removing the shell layer, the non-sintering aggregated nickel core particles are individualized to form the nickel nano powder. A method for manufacturing nickel nano powder.

2. The step of forming the shell layer is performed in a region where the temperature decreases along the direction in which the nickel core particles are transferred. The method for manufacturing nickel nano powder according to Claim 1.

3. The step of forming the nickel nano powder is selectively removing the shell layer through wet post-treatment. The method for manufacturing nickel nano powder according to Claim 1.

4. The nickel salt includes at least any one of nickel acetate, nickel bromide, nickel carbonate, nickel chloride, nickel fluoride, nickel hydroxide, nickel iodide, nickel nitrate, nickel oxide, nickel phosphate, nickel silicate, nickel sulfate, and nickel sulfide. The method for manufacturing nickel nano powder according to Claim 1.

5. The shell-forming material includes a water-soluble metal salt. The method for manufacturing nickel nano powder according to Claim 1.

6. The shell-forming material is Aluminum (Al), barium (Ba), calcium (Ca), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), lithium (Li), magnesium (Mg), manganese (Mn), mercury (Hg), nickel (Ni), potassium (K), rubidium (Rb), silver (Ag), sodium (Na), strontium (Sr), tin (Sn), lanthanum (La), silicon (Si), gallium (Ga), scandium (Sc), titanium (Ti), vanadium (V), zirconium (Zr), yttrium (Y), cadmium (Cd), actinium (Ac), cesium (Cs), hafnium (Hf), and zinc (Zn), or contains at least any one of them, or The method for producing nickel nano powder according to claim 1, which contains at least any one of metal acetate, metal bromide, metal carbonate, metal chloride, metal fluoride, metal hydroxide, metal iodide, metal nitrate, metal oxide, metal phosphate, metal silicate, metal sulfate, and metal sulfide.

7. The nickel nano powder has an average particle size in the range of 30 nm to 200 nm. The method for producing nickel nano powder according to claim 1.

8. The method for producing nickel nano powder according to claim 1, wherein the nickel nano powder contains a natural oxide layer formed on the surface.

9. The method for producing nickel nano powder according to claim 1, wherein the nickel nano powder contains nickel in the range of 50% by weight to 100% by weight.

10. The nickel nano powder is A nickel nano powder having a core-shell structure, Nickel core particles, and The method for producing nickel nano powder according to claim 1, which includes a shell layer surrounding the surface of the nickel core particles and composed of a water-soluble metal salt.

11. The step of vaporizing and providing a metal salt and a shell-forming substance, A step of nucleating and growing the metal core particles from the metal salt by subjecting the vaporized metal salt to a reduction reaction using a reducing gas to form solid-phase metal core particles; A step of depositing and growing the vaporized shell-forming material on the surface of the metal core particles to form a shell layer; A step of removing the shell layer to form metal nano-powder; and The shell layer induces non-sintering aggregation of the metal core particles, A method for producing metal nano-powder, wherein by removing the shell layer, the non-sintering aggregated metal core particles are individualized to form the metal nano-powder.

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