JP2009024204A - Carbide-coated nickel powder and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide carbide-coated nickel powder which contains nitrogen atoms in the skeleton and is suitable to an internal electrode material for a laminated ceramic capacitor, a multilayer ceramic substrate or the like, and to provide a method for producing the carbide-coated nickel powder. <P>SOLUTION: The carbide-coated nickel powder is coated with carbide, in which the coating amount of the carbide is 1 to 70 wt.% and the ratio of nitrogen atoms included in the skeleton is 15 to 30 wt.% per the whole carbide, and has the average particle diameter of 50 to 200 nm. The nickel powder is produced by adding a compound forming ammonium ions to an aqueous solution in which a polymer dispersant as a polymer of a nickel salt and amino acid is dissolved, so as to form a nickel ammonia complex, next adding a compound to form carbonate ions thereto, heating the same, subsequently removing moisture, so as to be dry matter, and firing the dry matter in a nitrogen atmosphere. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to nickel powder coated with a carbide containing nitrogen suitable for internal electrode materials such as multilayer ceramic capacitors and multilayer ceramic substrates, and a method for producing the same.

  Nickel powder having a small particle diameter is used as a thick film conductor material for forming an electric circuit such as a multilayer ceramic capacitor (hereinafter referred to as MLCC) or a multilayer ceramic substrate.

  The MLCC has a structure in which a plurality of ceramic dielectric layers and internal electrode layers are alternately stacked. The internal electrode layer is formed by dispersing a metal powder of a conductive material in a binder to form a paste, printing the paste on a ceramic green sheet, laminating a plurality of the printed substrates, heating and pressing, and then heating in a reducing atmosphere. It is produced by firing.

  Conventionally, noble metal powders such as Pd and Ag-Pd have been used as internal electrode materials for MLCCs. Since noble metals can be fired in the air, they can be suitably used for the production of MLCC, but there is a problem that the material is expensive. Therefore, the internal electrode material has been replaced with a relatively inexpensive nickel powder.

  However, since nickel powder is inferior in oxidation resistance as compared with the case where noble metal powder is used, there is a problem that a part of nickel powder is oxidized at the time of firing and diffuses into the ceramic dielectric layer.

By the way, the firing temperature at the time of manufacturing MLCC requires heating of 1100 ° C. or more when, for example, BaTiO ₃ widely used as a material for the ceramic dielectric layer is used. However, since the thermal shrinkage starting temperature of nickel powder is 400 to 500 ° C., when co-fired with the ceramic dielectric layer, distortion occurs due to the difference in thermal shrinkage between the laminated ceramic dielectric layer and the nickel layer. As a result, delamination and cracks occur, and the performance of the MLCC deteriorates.

  Therefore, various methods for suppressing delamination and cracks caused by using nickel powder have been proposed.

  Mix nickel chloride gas and titanium tetrachloride gas, and react these gases with the reducing gas of nickel chloride and oxidizing gas of titanium tetrachloride to prepare titanium oxide-coated nickel powder by simultaneously synthesizing nickel and titanium dioxide. A method has been proposed (Patent Document 1: Japanese Patent Laid-Open No. 2005-240076). However, in this method, since titanium oxide is formed not only on the surface of the prepared nickel powder but also inside the nickel powder, there is a problem that the oxide remains as an impurity when the electrode is formed. In addition, a special vacuum device is required for gasifying the nickel chloride.

  In addition, a method of preparing oxide-coated nickel powder using an ang mill, a hybridizer, or the like has been proposed (Patent Document 2: Japanese Patent Laid-Open No. 11-343501). However, the oxide-coated nickel powder prepared using ONGMILL or a hybridizer has a weak adhesion between the oxide particles and the nickel particles, so the oxide particles are easy to peel off from the nickel particles, and the heat shrinkage rate is improved. Is considered very low.

  In addition, as a method for increasing the sintering start temperature of nickel powder, a technique for incorporating sulfur into nickel powder has been proposed (Patent Document 3: Japanese Patent Laid-Open No. 11-80817). However, in the sulfur-containing nickel powder prepared according to the present proposal, sulfur may diffuse into the dielectric layer during sintering, which may deteriorate the electrical characteristics of the dielectric layer.

As a technique for improving the problems caused by the oxide-coated nickel powder and sulfur-containing nickel powder as described above, a method of coating the nickel powder with carbon has been proposed.
In this method, the surface of the nickel powder is coated with carbon to improve the heat resistance of the nickel powder and raise the sintering start temperature.

  There has been proposed a method in which a nickel layer and a hydrocarbon gas such as hexane are brought into contact with each other under a temperature condition of 300 to 600 ° C. to coat a carbon layer on the surface of the nickel powder. (Patent Document 4: Japanese Patent Application Laid-Open No. 2005-8960) By using the carbon-coated nickel powder prepared by this method as the MLCC internal electrode material, the sintering start temperature is higher than that of the nickel powder not coated with carbon. To rise. However, the set temperature range of the surface reaction by the contact between the hydrocarbon gas and the nickel powder shown in this proposal is also the sintering start temperature of the nickel powder not coated with carbon. There is no mention in the proposal that carbon coating on the surface of nickel powder always takes precedence over sintering of nickel powder, and that carbon coating reaction and sintering of nickel powder occur simultaneously in the reaction system. The proposed method is still not sufficient. Moreover, in order to process nickel powder with high temperature hydrocarbon gas, a special apparatus is required and it cannot be said that it is a simple method.

  In addition, a method of forming a carbon coating layer on the surface of the nickel powder by heating after mixing the nickel powder and the polyol has been proposed (Patent Document 5: JP-A-2005-154904). However, in the method of heating after mixing the nickel powder and the polyol, the nickel particles are finer than the nickel particles shown in the examples, and the nickel particles having an average particle diameter of 50 to 200 nm required for MLCC are obtained. In consideration of the application of the above, it is considered difficult to uniformly coat the surface of the nickel particles with carbon while releasing the aggregation so as not to crush the nickel particles which are relatively soft metals.

  Therefore, in order to uniformly coat the nickel powder with carbon while preventing particle aggregation, it is considered preferable to coat the surface of the nickel powder with carbon simultaneously with the preparation of the nickel powder.

  The following methods have been proposed as techniques for simultaneously preparing nickel powder and carbon coating.

After adding ammonia to a polymer dispersant aqueous solution containing nickel acetate and heating to prepare a nickel hydroxide colloidal aqueous solution, the colloidal aqueous solution is dried and baked to prepare nickel particles coated with carbon. (Non-Patent Document 1). According to this method, nickel fine particles can be prepared and simultaneously the surfaces of the nickel fine particles can be uniformly coated with carbon.
However, Non-Patent Document 1 only describes a method for preparing carbon-coated nickel fine particles having a particle diameter of 10 nm or less, and the present inventors conducted a supplementary test of this method. It was difficult to prepare carbon-coated nickel powder having a particle size of 50 to 200 nm.
Usually, when ammonia is added to an aqueous nickel salt solution and heated, very fine nickel hydroxide particles are generated. Therefore, even in Non-Patent Document 1, only fine nickel hydroxide particles can be produced, and as a result, it is considered that preparation of carbon-coated nickel powder having a particle diameter of 50 to 200 nm was difficult.

JP 2005-240076 A Japanese Patent Laid-Open No. 11-343501 Japanese Patent Laid-Open No. 11-80817 JP 2005-8960 A JP 2005-154904 A Yongping Chen, 6 others, “Novel Synthesis of Nanoporous Nickel Oxide and Nickel Nanoparticulates / Amorphous Carbon Composites et 200th, L 700-701

  In recent years, with the miniaturization of electronic devices, MLCCs tend to be miniaturized, and the film thicknesses of dielectric layers and internal electrode layers have become 1 μm or less. For this reason, the particle size has been reduced along with the thinning, and nickel powder having an average particle size of 50 to 200 nm is particularly required. At the same time, there is a need for nickel powder that can suppress the occurrence of delamination and cracks.

However, the conventionally proposed coating of nickel powder with oxides and the method of incorporating sulfur into nickel powder have the effect of increasing the sintering start temperature and suppressing the occurrence of delamination and cracks. There is a problem that the product or contained sulfur component diffuses into the ceramic dielectric layer and deteriorates the characteristics of MLCC.
On the other hand, a method of coating nickel powder with carbon has been proposed in order to suppress diffusion of oxides and sulfur into the ceramic dielectric layer and raise the sintering start temperature. This is a method in which the surface of the nickel powder is coated with carbon to improve the heat resistance of the nickel powder and to increase the sintering start temperature.

  However, it has been difficult to prepare carbon-coated nickel powder having an average particle diameter of 50 to 200 nm required for MLCC and excellent in heat resistance by the conventional method.

  The present invention has been made to solve the above-described problems, and has an average particle diameter in the range of 50 to 200 nm, and is excellent in heat resistance and can be suitably used as an internal electrode of a multilayer ceramic capacitor. An object is to provide a powder and a method for producing the same.

  The inventors focused on the carbon component that coats the nickel powder, and as a result of earnestly examining what kind of carbide to coat the nickel powder to improve heat resistance, the following invention can achieve the object. I found.

  That is, the present invention is a nickel powder having an average particle diameter of 50 to 200 nm coated with a carbide containing nitrogen (Invention 1).

  Moreover, this invention is nickel powder with an average particle diameter of 50-200 nm coated with the carbide | carbonized_material whose nitrogen is 15-30 wt% with respect to all the carbide | carbonized_materials (invention 2).

  Further, the present invention is a nickel powder having an average particle diameter of 50 to 200 nm coated with a carbide having a carbide coating amount of 1 to 70 wt% and nitrogen of 15 to 30 wt% with respect to the total carbide (the present invention). 3).

  In addition, the present invention adds a compound that generates ammonium ions to an aqueous solution in which a polymer dispersant that is a polymer of nickel salt and amino acid is dissolved to form a nickel ammonia complex, and then a compound that generates carbonate ions. Addition and heating, removing moisture to obtain a dried product, and then firing the dried product in a nitrogen atmosphere. Production of nickel powder coated with carbide containing nitrogen atoms in the skeleton This is a method (Invention 4).

  Since the nickel powder according to the present invention is a nickel powder having an average particle diameter of 50 to 200 nm coated with a carbide containing nitrogen atoms in the skeleton, it has excellent heat resistance and can be suitably used for MLCC.

  The configuration of the present invention will be described in more detail as follows.

  Hereinafter, the nickel powder having an average particle diameter of 50 to 200 nm coated with a carbide in which the amount of the carbide of the present invention is 1 to 70 wt% and the nitrogen atoms contained in the skeleton are 15 to 30 wt% with respect to the total carbide The manufacturing method will be described in detail.

  When producing nickel powder coated with a carbide containing nitrogen atoms in the skeleton according to the embodiment of the present invention, an aqueous nickel salt solution is first prepared. Here, as the nickel salt, for example, an aqueous solution containing a nickel salt soluble in water such as nickel chloride and nickel acetate is used.

  The concentration of the nickel salt aqueous solution used in the production method of the present invention is preferably 0.05 to 2 mol / L.

  Next, an aqueous solution of a polymer dispersant, which is an amino acid polymer, is prepared and added to the aqueous nickel salt solution. A polymeric dispersant, which is a polymer of amino acids, is a relatively high molecular weight compound that is classified as a protein. From the viewpoint of availability, bovine-derived gelatin, porcine-derived gelatin, and other gelatin derivatives are more preferred. Is preferred.

  In the production method of the present invention, the addition amount of the polymer dispersant which is a polymer of amino acids is 0.1 times or more by mass with respect to the nickel salt, preferably 0.2 to 10 times the mass of the nickel salt. Is preferred. When the addition amount of the polymer dispersant, which is an amino acid polymer, is less than 0.1 times, the nickel oxide produced by decarboxylation from nickel carbonate when baked cannot be completely reduced. Further, the sintering of the nickel powder after firing is likely to proceed, and the particle size distribution becomes wide. When it exceeds 10 times, the nitrogen-containing carbon content of the nickel powder obtained after firing becomes high, and it becomes difficult to use it suitably for the MLCC internal electrode.

Next, the compound which produces | generates an ammonium ion is added to the mixed aqueous solution of the polymer dispersing agent which is a polymer of the said nickel salt and an amino acid, and nickel salt aqueous solution is prepared.
As the compound that generates ammonium ions, aqueous ammonia, hexamethylenetetramine, urea, or the like can be used.

  It is preferable that the addition amount of the compound which produces | generates the ammonium ion used with the manufacturing method of this invention is 1-10 mol with respect to 1 mol of nickel salts. When the amount of ammonia is less than 1 mol, the nickel ammonia complex is not sufficiently formed, gelled nickel carbonate is generated, and the particle size distribution of the nitrogen-containing carbon-coated nickel powder after firing becomes wide.

  Next, a compound that generates carbonate ions is prepared. As the compound that generates carbonate ions, an aqueous solution containing sodium carbonate, sodium hydrogen carbonate, urea or the like is used.

  In the production method of the present invention, the amount of the compound that generates carbonate ions is preferably 1 to 10 mol with respect to 1 mol of the nickel salt. When the amount of the compound that generates carbonate ions is less than 1 mol, fine nickel hydroxide is generated from the nickel ammonia complex that has not reacted with the compound that generates carbonate ions, and the carbon-coated nickel obtained after firing The particle diameter of the powder becomes fine.

  It is preferable to prepare an aqueous solution containing at least one of nickel carbonate (which may include basic nickel carbonate) and nickel hydroxide by mixing and heating the aqueous nickel salt solution and the aqueous compound solution that generates carbonate ions. .

  In the present invention, urea can be used as a compound having both functions of a compound that generates ammonium ions and a compound that generates carbonate ions. By using urea, the step of adding a compound that generates ammonium ions and the step of adding a compound that generates carbonate ions can be performed at the same time. In this case, the amount added is the sum of the amounts added in both steps. And it is sufficient.

  In the production method of the present invention, the reaction temperature of the nickel salt aqueous solution and the compound that generates carbonate ions is preferably 50 ° C. or higher.

  Next, the moisture of the nickel carbonate and nickel hydroxide-containing aqueous solution is removed, and a mixed dried product of a polymer dispersant, which is an amino acid polymer, and nickel carbonate and / or nickel hydroxide is prepared. Washing with water and drying may be performed according to a conventional method.

  Next, the dried product is put in an atmospheric furnace and heat-treated in a nitrogen gas atmosphere to prepare nickel powder coated with a carbide containing the target nitrogen atom in the skeleton.

  In the production method of the present invention, the dried nickel carbonate and / or basic nickel carbonate is fired in a nitrogen atmosphere, the firing temperature is preferably 350 to 700 ° C., and the firing time is preferably 1 to 5 hours.

  The average particle diameter of the nickel powder according to the present invention is 50 to 200 nm. When the average particle diameter of the nickel powder is out of the above range, fine nickel particles and coarse nickel particles are contained. When nickel powder containing fine particles is used in a multilayer ceramic capacitor, the sintering temperature is shifted to the low temperature side due to the fine nickel particles, making it difficult to suppress delamination and cracks. In addition, when nickel powder containing coarse particles is used in a multilayer ceramic capacitor, coarse particles break through the dielectric layer between the electrodes, making it difficult to suppress delamination and cracks. The average particle diameter of the nickel powder is preferably 50 to 150 nm.

  The standard deviation of the particle diameter of the nickel powder according to the present invention is preferably 0.5 to 100 nm. More preferably, it is 0.5-50 nm. When the average particle size and standard deviation of the particle size of the nickel powder coated with the carbide containing nitrogen atoms in the skeleton are out of the above ranges, fine nickel particles and coarse nickel particles will be contained. . When nickel powder containing fine particles is used in a multilayer ceramic capacitor, the sintering temperature is shifted to the low temperature side due to the fine nickel particles, making it difficult to suppress delamination and cracks. In addition, when nickel powder containing coarse particles is used in a multilayer ceramic capacitor, coarse particles break through the dielectric layer between the electrodes, making it difficult to suppress delamination and cracks. The standard deviation of the particle diameter is more preferably 0.5 to 50 nm.

In the nickel powder according to the present invention, the nitrogen contained in the carbide is preferably 15 to 30 wt% with respect to the total carbide. When the nitrogen contained in the carbide is less than 15 wt% or more than 30 wt% with respect to the total carbide, the heat resistance becomes insufficient, which is not preferable. The nitrogen content in the carbide is more preferably 20-30 wt%.
Here, the carbide in which a nitrogen atom is included in the skeleton will be described. Usually, a carbonized carbon-based carbide is formed by carbonizing an organic polymer under arbitrary conditions. At this time, when nitrogen atoms are contained in the organic polymer, a network-like carbide is formed in which nitrogen atoms are replaced with carbon atoms according to carbonization conditions such as heating temperature and atmospheric gas during heating. The structure of this network is one of the important factors affecting the heat resistance that is the subject of the present invention. The significance of the present invention is that a carbide having a structure in which a nitrogen atom having a content within the above-described range is substituted with a carbon atom is treated by using a polymer dispersant that is a polymer of amino acids under appropriate carbonization conditions. The nickel powder can be prepared, and the nickel powder is excellent in heat resistance.

  In the nickel powder according to the present invention, the amount of carbide to be coated is preferably 1 to 70 wt%. When the nitrogen-containing carbon content is less than 1 wt%, the nickel powder cannot be completely covered with the carbide, so the heat resistance is low, and it becomes difficult to suppress delamination and cracks. Moreover, when there is more carbon content than 70 wt%, it will become difficult for the nickel in an electrode to contact, and it will become difficult to form a uniform electrode layer. As for the quantity of the carbide | carbonized_material to coat | cover, 5-60 wt% is more preferable.

  Hereinafter, the present invention will be described in detail with reference to examples.

  The nickel particle shape and carbide coating state were observed with a transmission electron microscope. The average particle size of the nickel particles was measured by measuring the particle size of 300 particles shown in the electron micrograph, and the average particle size was shown. The standard deviation of the particle diameter was obtained from statistical analysis on the particles of an image taken by electron microscope observation.

  The carbon content was measured using “Carbon Sulfur Analyzer: EMIA-2200” (manufactured by HORIBA).

  The nitrogen content in the carbide was measured with “EMGA-620W” (manufactured by HORIBA).

  The composition of the particles was identified using “X-ray diffractometer RINT-2500” (manufactured by Rigaku Corporation, tube: Cu).

  Thermal analysis was measured using “EXSTAR 6000 TG / DTA6300” (manufactured by SII).

<Example 1>
A nickel chloride aqueous solution was prepared by dissolving 1.3 g of nickel chloride (manufactured by Wako Pure Chemical Industries) in 25 ml of pure water. A gelatin aqueous solution was prepared by dissolving 5 g of gelatin (manufactured by Wako Pure Chemical Industries) in 50 ml of pure water. After mixing and stirring the gelatin aqueous solution with the nickel chloride aqueous solution, 5 g of 25% aqueous ammonia (manufactured by Wako Pure Chemical Industries, Ltd.) was added. An aqueous solution in which 1.0 g of sodium hydrogen carbonate (manufactured by Wako Pure Chemical Industries) was dissolved in 25 ml of pure water was added to this solution, and then heated at 90 ° C. for 2 hours. The solution was put into a dryer and dried at 80 ° C. for 20 hours, and then calcined at 550 ° C. in a nitrogen atmosphere.
The obtained particles were confirmed to have metallic nickel and amorphous carbon by X-ray diffraction. The average particle diameter of nickel was 69 nm, and the standard deviation was 12 nm, and the particle size distribution was very narrow. When the surface of nickel was observed with a transmission electron microscope, the surface of metallic nickel was completely covered with carbide. The carbide content was 57 wt% with respect to the entire powder. The nitrogen content in the carbide was 28 wt%.

<Example 2>
A nickel chloride aqueous solution was prepared by dissolving 1.3 g of nickel chloride (manufactured by Wako Pure Chemical Industries) in 25 ml of pure water. A gelatin aqueous solution was prepared by heating and dissolving 1 g of gelatin (Wako Pure Chemical Industries) in 50 ml of pure water. After mixing and stirring the nickel chloride aqueous solution and the gelatin aqueous solution, 3 g of 25% aqueous ammonia (manufactured by Wako Pure Chemical Industries) was added. To this solution, an aqueous solution in which 1 g of sodium hydrogen carbonate (manufactured by Wako Pure Chemical Industries) was dissolved in 25 ml of pure water was added, and then heated at 90 ° C. for 2 hours. The solution was put into a dryer and dried at 80 ° C. for 20 hours, and then calcined at 600 ° C. in a nitrogen atmosphere.
From the X-ray diffraction, the obtained particles were confirmed to have metallic nickel and amorphous carbon. The average particle diameter of nickel was 72 nm, and the standard deviation was 15 nm. The particle size distribution was very narrow. When the surface of nickel was observed with a transmission electron microscope, the surface of metallic nickel was completely covered with carbide. Carbide content was 46 wt% with respect to the whole powder. The nitrogen content in the carbide was 20 wt%.

<Example 3>
A nickel chloride aqueous solution was prepared by dissolving 1.3 g of nickel chloride (manufactured by Wako Pure Chemical Industries) in 25 ml of pure water. A gelatin aqueous solution was prepared by dissolving 0.3 g of gelatin (Wako Pure Chemical Industries, Ltd.) in 50 ml of pure water by heating. After mixing and stirring the nickel chloride aqueous solution and the gelatin aqueous solution, 3 g of 25% aqueous ammonia (manufactured by Wako Pure Chemical Industries) was added. To this solution, an aqueous solution in which 1 g of sodium hydrogen carbonate (manufactured by Wako Pure Chemical Industries) was dissolved in 25 ml of pure water was added, and then heated at 90 ° C. for 2 hours. The solution was put into a dryer and dried at 80 ° C. for 20 hours, and then calcined at 600 ° C. in a nitrogen atmosphere.
From X-ray diffraction, the resulting particles were composed of metallic nickel and amorphous carbon. Nickel had an average particle diameter of 110 nm and a standard deviation of 46 nm, which was a narrow particle size distribution. As a result of TEM observation, the surface of the metallic nickel was completely covered with carbon. The carbide content was 9 wt% with respect to the whole powder. The nitrogen content in the carbide was 21 wt%.

<Comparative Example 1>
A nickel chloride aqueous solution was prepared by dissolving 1.3 g of nickel chloride (manufactured by Wako Pure Chemical Industries) in 25 ml of pure water. A starch aqueous solution was prepared by dissolving 5 g of polyvinyl alcohol (manufactured by Wako Pure Chemical Industries) in 50 ml of pure water. After mixing and stirring the nickel chloride aqueous solution and the polyvinyl alcohol aqueous solution, 5 g of 25% ammonia water (manufactured by Wako Pure Chemical Industries, Ltd.) was added. An aqueous solution in which 1.0 g of sodium hydrogen carbonate (manufactured by Wako Pure Chemical Industries) was dissolved in 25 ml of pure water was added to this solution, and then heated at 90 ° C. for 2 hours. The solution was put into a dryer and dried at 80 ° C. for 20 hours, and then calcined at 550 ° C. in a nitrogen atmosphere.
The obtained particles were confirmed to have metallic nickel and amorphous carbon by X-ray diffraction. The particle diameter of nickel was 500 nm or more, and the distribution was very wide. When the surface of nickel was observed with a transmission electron microscope, the surface of metallic nickel was completely covered with carbide. The carbide content was 52 wt% with respect to the whole powder. The nitrogen content in the carbide was 0 wt%.

<Comparative Example 2>
A nickel chloride aqueous solution was prepared by dissolving 1.3 g of nickel chloride (manufactured by Wako Pure Chemical Industries) in 25 ml of pure water. To this solution, 5 g of 25% aqueous ammonia (manufactured by Wako Pure Chemical Industries) was added. An aqueous solution in which 1.0 g of sodium hydrogen carbonate (manufactured by Wako Pure Chemical Industries) was dissolved in 25 ml of pure water was added to this solution, and then heated at 90 ° C. for 2 hours to prepare a solution containing basic nickel carbonate. The solution was put into a dryer and dried at 80 ° C. for 20 hours, and then calcined at 550 ° C. in a nitrogen atmosphere.
From the X-ray diffraction, it was confirmed that the obtained particles were composed only of nickel oxide. Carbon was not confirmed when the nickel surface was observed with a transmission electron microscope. The carbide content was 0 wt% with respect to the entire powder.

<Test of heat resistance>
The heat resistance test was performed by thermogravimetric analysis of the nickel powder obtained in Example 1 and the nickel powder obtained in Comparative Example 1. The thermogravimetric analysis was performed by weighing 10 mg of each sample in an aluminum pan and raising the temperature from room temperature to 600 ° C. at a rate of 10 ° C./min while flowing air at 300 cc / min. The comparison result of the thermogravimetric analysis is shown in FIG.
It can be seen that the amount of carbide is reduced as it is heated. In contrast to the nickel powder obtained in Comparative Example 1, the temperature at which the weight reduction starts in the nickel powder of Example 1 rises to the high temperature side, and clearly heat-resistant. It can be seen that the performance is improved.

  Since nickel powder with an average particle diameter of 50 to 200 nm coated with a carbide containing nitrogen according to the present invention is excellent in heat resistance, it can be suitably used for an internal electrode of MLCC.

2 is a graph showing the results of thermogravimetric analysis of the nickel powder obtained in Example 1 and the nickel powder obtained in Comparative Example 1. FIG.

Claims (4)

A nickel powder having an average particle diameter of 50 to 200 nm covered with a carbide containing nitrogen. The nickel powder according to claim 1, wherein nitrogen is 15 to 30 wt% with respect to the total carbides. The nickel powder according to claim 1 or 2, wherein the coating amount of the carbide is 1 to 70 wt%. A compound that generates ammonium ions is added to an aqueous solution in which a polymer dispersant that is a polymer of nickel salt and amino acid is dissolved to form a nickel ammonia complex, and then a compound that generates carbonate ions is added and heated. The method for producing nickel powder according to any one of claims 1 to 3, wherein after the moisture is removed to obtain a dried product, the dried product is fired in a nitrogen atmosphere.