Spherical nickel powder with high crystallinity and uniform shape and preparation method thereof

Abstract

The invention discloses spherical nickel powder with high crystallinity and uniform shape and a preparation method thereof, and relates to the technical field of metal powder materials. The preparation method comprises the following steps: dissolving nickel nitrate hexahydrate in deionized water to form a nickel nitrate solution, adding a dispersing agent into the nickel nitrate solution, stirring to obtain a mixed solution, adjusting the p H value of the mixed solution to obtain a precursor solution, adding a reducing agent into the precursor solution in an inert gas protection environment, and stirring to obtain a precursor solution; and stirring and reacting to obtain the spherical nickel powder. The nickel powder prepared through the method is uniform in shape, excellent in crystallinity and excellent in oxidation resistance, in addition, nickel paste prepared from the spherical nickel powder prepared through the method has the good shrinkage characteristic, and the reliability of electronic components such as energy-saving equipment, automobiles and smartphones can be remarkably improved through the characteristics.

Description

Technical Field

[0001] The invention belongs to the technical field of metal powder materials, and particularly relates to spherical nickel powder with high crystallinity and uniform shape and a preparation method thereof. Background Art

[0002] Nickel particles are widely used in various fields such as conductive paste, secondary battery materials, catalysts, and internal electrode materials of multilayer ceramic capacitors. In particular, in the field of ceramic capacitors, with the trend of miniaturization and thinning of electronic devices, the particle size of nickel particles is gradually changing from the current mainstream 200-400nm to 100nm, and the demand for 100nm nickel particles is increasing. From the perspective of manufacturing uniform slurry, it is urgent to obtain spherical nickel powder with uniform shape.

[0003] The manufacturing methods of nickel powder include chemical reduction, chemical vapor deposition, physical vapor deposition, hydrothermal, polyol and spray thermal decomposition. In the chemical reduction method, a reducing agent such as hydrazine can be used to reduce the nickel chloride salt dissolved in water to obtain spherical nickel particles. Alternatively, after the nickel oxide particles are generated, they can be reduced to nickel with a reducing agent to obtain spherical nickel particles. Japanese Patent 2015-161014 discloses a nickel powder and a production and processing method thereof. The invention uses a triazine thiol metal salt compound as a triazine thiol compound, disperses nickel particles in water to prepare a nickel slurry, mixes the prepared nickel slurry with a solution containing triazine thiol, and the mixed nickel slurry is filtered to obtain nickel powder. The obtained nickel powder is suitable for nickel inner electrodes of multilayer ceramic capacitors, which can effectively prevent the occurrence of structural defects such as delamination and cracks. Japanese Patent 2015-158000 discloses a nickel powder without coarse particles suitable for the internal electrodes of thin-layer laminated ceramic capacitors and a method for manufacturing the same. The invention forms a highly dispersed state of nickel powder in a water slurry, then wet-classifies the state, then heat-treats it in a reducing atmosphere, and finally dry-classifies it to form a thin film of laminated ceramics, thereby obtaining a suitable nickel powder suitable for forming the internal electrodes of curved capacitors.

[0004] If the above method is adopted to manufacture, cheap, high productivity, very fine spherical nickel particles can be obtained. However, owing to mainly using nickel chloride, chlorine easily remains as impurities. In addition, the crystallinity of the nickel powder manufactured by chemical reduction method is usually lower than that of the nickel powder manufactured by gas phase methods such as chemical vapor deposition, physical vapor deposition and spray thermal decomposition. Although the nickel powder manufactured by gas phase method has higher crystallinity and better performance, the nickel powder particle size distribution produced by these methods is wider, and it is necessary to adjust the particle size by classification operation, resulting in lower yield and higher production cost.

[0005] Therefore, how to provide a method for producing spherical nickel powder that is free of impurities such as chlorine and has high crystallinity is an urgent problem to be solved in this field. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for producing spherical nickel powder with high crystallinity by reducing nickel nitrate in a nitric acid solution without mixing impurities such as chlorine. Specifically, the technical solution of the present invention includes the following contents:

[0007] A method for preparing spherical nickel powder with high crystallinity and uniform shape, the method comprising the following steps:

[0008] Nickel nitrate hexahydrate is dissolved in deionized water to form a nickel nitrate solution, a dispersant is added to the nickel nitrate solution and stirred for 10 to 30 minutes to obtain a mixed solution, the pH value of the mixed solution is adjusted to obtain a precursor solution, a reducing agent is added to the precursor solution in an inert gas protection environment, and the spherical nickel powder is obtained by stirring the reaction.

[0009] Furthermore, the concentration of the nickel nitrate solution is 0.01-1.00M.

[0010] Further, examples of the dispersant include gum arabic, hydroxypropylcellulose, polyvinyl pyrrolidone, gelatin and polyethylene glycol.

[0011] Preferably, the dispersant is gum arabic.

[0012] Furthermore, the concentration of the dispersant is 1 to 20 g / L.

[0013] Furthermore, the reducing agent includes any one of reducing agents having a hydroxyl group such as L-ascorbic acid, hydrazine, formalin, hydroquinone, phenylhydrazine or ethylene glycol.

[0014] Furthermore, the molar ratio of the reducing agent to nickel nitrate hexahydrate is 0.5-2:1.

[0015] Furthermore, the pH value of the precursor solution is 1-4.

[0016] Preferably, the pH value of the precursor solution is 1-2.

[0017] Furthermore, the stirring reaction temperature is 20 to 80° C., and the stirring reaction time is 5 to 60 minutes.

[0018] Furthermore, the stirring speed is 100-500 rpm.

[0019] Furthermore, the inert gas is one of nitrogen or argon.

[0020] Furthermore, the average particle size of the spherical nickel powder is 100 to 1000 nm.

[0021] Furthermore, the spherical nickel powder is made into an electrode paste to obtain an electrode with a smaller volume shrinkage after firing.

[0022] Furthermore, the spherical nickel powder is applied to internal electrodes of laminated ceramic capacitors.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) According to the present invention, spherical nickel powder having uniform particle shape, excellent crystallinity and excellent oxidation resistance can be prepared.

[0025] (2) The nickel powder prepared by the wet reduction method of the present invention has high diffraction peak orientation and good crystallinity, and is suitable as a raw material powder for nickel paste.

[0026] (3) The nickel paste made from the spherical nickel powder prepared according to the present invention is not only low in cost, but also has good shrinkage characteristics. When it is used as the internal electrode of a multilayer ceramic capacitor, it can significantly enhance the reliability of electronic components such as energy-saving devices, automobiles and smart phones. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a scanning electron microscope image of nickel powder.

[0028] Figure 2 is the relationship between nickel nitrate concentration and nickel powder particle size.

[0029] Figure 3 is the relationship between dispersant concentration and nickel powder particle size.

[0030] Figure 4 This is the X-ray diffraction pattern of nickel powder.

[0031] Figure 5 is the shrinkage change of nickel paste. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be clearly and completely described below through the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0033] Unless otherwise specified, the raw materials and reagents used in the present invention are commercially available or can be prepared by known methods.

[0034] Example 1

[0035] A method for preparing spherical nickel powder with high crystallinity and uniform shape comprises the following steps:

[0036] 3 g of nickel nitrate hexahydrate was dissolved in 1 L of deionized water to form a nickel nitrate solution with a concentration of 0.01 M. 20 g of gum arabic was added to the nickel nitrate solution and stirred for 30 min to obtain a mixed solution. The pH value of the mixed solution was adjusted to 1 to obtain a precursor solution. 1.82 g of ascorbic acid was added to the precursor solution in a nitrogen protection environment. The mixture was stirred at 500 rpm for 60 min at 50°C to obtain spherical nickel powder.

[0037] Example 2

[0038] A method for preparing spherical nickel powder with high crystallinity and uniform shape comprises the following steps:

[0039] 30 g of nickel nitrate hexahydrate was dissolved in 1 L of deionized water to form a nickel nitrate solution with a concentration of 0.1 M. 10 g of hydroxypropyl cellulose was added to the nickel nitrate solution and stirred for 10 min to obtain a mixed solution. The pH value of the mixed solution was adjusted to 3 to obtain a precursor solution. 1.65 g of hydrazine was added to the precursor solution in an argon protection environment. The reaction was stirred at 100 rpm for 30 min at 80 ° C to obtain spherical nickel powder.

[0040] Example 3

[0041] A method for preparing spherical nickel powder with high crystallinity and uniform shape comprises the following steps:

[0042] 150 g of nickel nitrate hexahydrate was dissolved in 0.5 L of deionized water to form a nickel nitrate solution with a concentration of 1 M. 1 g of polyvinyl pyrrolidone was added to the nickel nitrate solution and stirred for 15 min to obtain a mixed solution. The pH value of the mixed solution was adjusted to 4 to obtain a precursor solution. 113.6 g of hydroquinone was added to the precursor solution in a nitrogen protection environment. The reaction was stirred at 200 rpm for 5 min at 20°C to obtain spherical nickel powder.

[0043] Example 4

[0044] A method for preparing spherical nickel powder with high crystallinity and uniform shape comprises the following steps:

[0045] 150 g of nickel nitrate hexahydrate was dissolved in 0.5 L of deionized water to form a nickel nitrate solution with a concentration of 1 M, 5 g of gum arabic was added to the nickel nitrate solution and stirred for 20 min to obtain a mixed solution, the pH value of the mixed solution was adjusted to 2 to obtain a precursor solution, 32 g of ethylene glycol was added to the precursor solution in a nitrogen protection environment, and the reaction was stirred at 350 rpm at 60 ° C for 40 min to obtain spherical nickel powder.

[0046] Example 5

[0047] A method for preparing spherical nickel powder with high crystallinity and uniform shape comprises the following steps:

[0048] 145 g of nickel nitrate hexahydrate was dissolved in 1 L of deionized water to form a nickel nitrate solution with a concentration of 0.5 M. 15 g of gelatin was added to the nickel nitrate solution and stirred for 25 min to obtain a mixed solution. The pH value of the mixed solution was adjusted to 2 to obtain a precursor solution. 43.26 g of ethylene glycol was added to the precursor solution in a nitrogen protection environment. The reaction was stirred at 300 rpm at 50 ° C for 50 min to obtain spherical nickel powder.

[0049] Test Example 1: Nickel powder morphology

[0050] Nickel powder was prepared by Example 1, and a scanning electron microscope image of the nickel powder was taken. Figure 1 As shown in the scanning electron microscope image, the nickel powder has a nearly spherical shape and a nearly monodisperse distribution.

[0051] Test Example 2: Relationship between nickel nitrate concentration and nickel powder particle size

[0052] Nickel powder was prepared by changing the concentration of nickel nitrate in Example 1, and the relationship between the concentration of nickel nitrate and the particle size of nickel powder was observed. Figure 2 The results in the figure show that the D 50 The value increases with the increase of nickel nitrate concentration, which means that by adjusting the concentration of nickel nitrate, the particle size of nickel powder can be controlled to vary within the range of 100 to 1000 nm.

[0053] Test Example 3: Relationship between dispersant concentration and nickel powder particle size

[0054] Nickel powder was prepared by changing the concentration of the dispersant (gum arabic) in Example 1, and the relationship between the concentration of the dispersant and the particle size of the nickel powder was observed. The results are as follows: Figure 3 When the molar ratio of ascorbic acid to nickel nitrate is 1, increasing the concentration of the dispersant will increase the D 50 The change from 1000nm to 100nm indicates that changing the concentration of dispersant can effectively adjust the D 50 .

[0055] Test Example 4: Nickel powder X-ray diffraction test

[0056] Figure 4 It is the X-ray diffraction pattern of nickel powder measured by powder X-ray diffraction. Figure 4(a) is an X-ray diffraction pattern of nickel powder prepared from nickel nitrate according to Example 1 of the present invention, Figure 4 (b) is an X-ray diffraction pattern of nickel powder prepared from nickel chloride by the existing method. It can be seen from the figure that both show only the diffraction peak of nickel. In addition, the (111) diffraction peak of the nickel powder prepared by Example 1 is higher, and the ratio of the (111) diffraction peak to the (200) diffraction peak is greater than that of the nickel powder prepared by the existing method, indicating that the nickel powder prepared from nickel nitrate by the present invention has higher crystallinity.

[0057] Test Example 5: Nickel paste shrinkage determination

[0058] 2 g of ethyl cellulose and 43 g of terpineol were mixed with 55 g of nickel powder prepared in Example 1, and kneaded with a high-speed stirrer to prepare a nickel paste. The temperature was then controlled to rise in the range of 500 to 1200° C., and the shrinkage was measured with a thermomechanical analyzer. The measurement results are as follows: Figure 5 shown. Figure 5 In the figure, ● represents the shrinkage rate of the nickel paste prepared by the nickel powder of Example 1 of the present invention, and ▲ represents the shrinkage rate of the nickel paste prepared by the nickel powder prepared by the existing method. It can be seen from the figure that at 600°C, the shrinkage rate of the nickel powder prepared by the present invention is 3%, while the shrinkage rate of the nickel powder prepared by the existing method is 5%; at 1000°C, the shrinkage rate of the nickel powder prepared by the present invention is 7%, while the shrinkage rate of the nickel powder prepared by the existing method is 12%. These results show that the nickel powder prepared by the present invention significantly improves the shrinkage characteristics of the nickel paste.

[0059] In summary, compared with the nickel powder prepared by the existing method, the nickel powder prepared by the present invention not only has higher crystallinity, but also shows lower shrinkage.

[0060] The above-described embodiments provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected.

Claims

1. A method for preparing spherical nickel powder with high crystallinity and uniform shape, characterized in that: The method comprises the following steps: Nickel nitrate hexahydrate is dissolved in deionized water to form a nickel nitrate solution, a dispersant is added to the nickel nitrate solution and stirred for 10 to 30 minutes to obtain a mixed solution, the pH value of the mixed solution is adjusted to obtain a precursor solution, a reducing agent is added to the precursor solution in an inert gas protection environment, and the spherical nickel powder is obtained by stirring the reaction.

2. The method for preparing a spherical nickel powder with high crystallinity and uniform shape as claimed in claim 1, characterized in that: The concentration of the nickel nitrate solution is 0.01-1.00M.

3. The method for preparing a spherical nickel powder with high crystallinity and uniform shape as claimed in claim 1, characterized in that: The dispersant includes any one of gum arabic, hydroxypropyl cellulose, polyvinyl pyrrolidone or gelatin.

4. The method for preparing a spherical nickel powder with high crystallinity and uniform shape as claimed in claim 1, characterized in that: The reducing agent includes any one of reducing agents having a hydroxyl group, such as L-ascorbic acid, hydrazine, formalin, hydroquinone, phenylhydrazine or ethylene glycol.

5. The method for preparing a spherical nickel powder with high crystallinity and uniform shape as claimed in claim 1, characterized in that: The concentration of the dispersant is 1-20 g / L.

6. The method for preparing a spherical nickel powder with high crystallinity and uniform shape as claimed in claim 1, characterized in that: The pH value of the precursor solution is 1-4.

7. The method for preparing a spherical nickel powder with high crystallinity and uniform shape as claimed in claim 1, characterized in that: The stirring reaction is carried out at a temperature of 20 to 80° C. and for a time of 5 to 60 minutes.

8. The method for preparing a spherical nickel powder with high crystallinity and uniform shape as claimed in claim 1, characterized in that: The inert gas includes nitrogen or argon.

9. A spherical nickel powder prepared by the method for preparing a spherical nickel powder with high crystallinity and uniform shape according to any one of claims 1 to 8, characterized in that: The average particle size of the spherical nickel powder is 100-1000 nm.

10. The spherical nickel powder according to claim 9, characterized in that The spherical nickel powder is applied to internal electrodes of a laminated ceramic capacitor.

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