Preparation method of high-crystallinity nano nickel powder

Abstract

The invention discloses a preparation method of high-crystallinity nanometer nickel powder, and belongs to the technical field of multilayer ceramic capacitors, and the preparation method comprises the following steps: preparing nanometer nickel powder by adopting a gas phase evaporation condensation method, and coating a silicon dioxide layer on the surface of the nanometer nickel powder through surface modification. By optimizing a dispersing agent system, dispersion of the nano nickel powder is remarkably improved, and the coating effect of a silicon dioxide layer on the surface of the nano nickel powder is optimized. The high-crystallinity nano nickel powder prepared by the preparation method has excellent oxidation resistance and thermal shrinkage resistance, and the matching property with a ceramic medium is remarkably improved. The high-crystallinity nano nickel powder prepared by the method can be widely applied to an inner electrode of a high-performance multilayer ceramic capacitor, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of multilayer ceramic capacitors, and in particular to a method for preparing highly crystalline nano nickel powder. Background Art

[0002] In recent years, with the rapid development of 5G communication technology and new energy vehicles, market demand for multilayer ceramic capacitors (MLCCs) has continued to rise. To adapt to the trend of miniaturization and thinness in portable electronic devices such as smartphones and tablets, MLCC products are rapidly developing towards miniaturization and high specific capacitance. However, two key technical issues remain in MLCC preparation: First, during high-temperature sintering, the difference in thermal expansion coefficients between the metal nickel inner electrode layer and the ceramic dielectric layer leads to a mismatch in shrinkage, which easily causes internal stress cracks and interface defects; second, during the sintering process, the metal nickel inner electrode layer is easily oxidized. These problems seriously restrict the reliability and service life of MLCC devices. Therefore, developing new nickel powder preparation processes to effectively improve the material's oxidation resistance and thermal shrinkage properties has become an urgent need in the current development of MLCC technology. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing highly crystalline nano nickel powder, and to improve the oxidation resistance and thermal shrinkage of the prepared highly crystalline nano nickel powder.

[0004] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are: A method for preparing highly crystalline nano nickel powder, comprising: S1. In a nitrogen atmosphere, nickel is evaporated by vapor evaporation and condensation, and then the vapor is condensed to obtain nano nickel powder with an average diameter of 60-600 nm; S2, the nano nickel powder is acidified with dilute hydrochloric acid, a dispersant is added, and then reacted with a sodium silicate aqueous solution, and aged to obtain a highly crystalline nano nickel powder; The dispersant at least comprises sodium hexametaphosphate, and the mass ratio of the nano nickel powder to the dispersant is 1:1-5.

[0005] The present invention first prepares nano-nickel powder using a vapor-phase evaporation-condensation method, then removes the surface oxide layer of the nano-nickel powder. After dispersion with a dispersant, the nano-nickel powder is coated with a high-dielectric inorganic substance to obtain a highly crystalline nano-nickel powder. The highly crystalline nano-nickel powder prepared by the present invention has good dispersion stability. The high-dielectric inorganic substance coated on its surface not only effectively isolates the air by forming a dense protective layer, significantly improving the anti-oxidation performance of the highly crystalline nano-nickel powder, but also improves the heat shrinkage resistance of the highly crystalline nano-nickel powder by reducing local high-temperature fluidity.

[0006] Preferably, the mass concentration of the dilute hydrochloric acid is 1-2 mol / L, and the usage ratio of the nano-nickel powder to the dilute hydrochloric acid is 1 g:1-5 mL.

[0007] Preferably, the mass ratio of the nano nickel powder to the dispersant is 1:1-5.

[0008] Preferably, the dispersant includes at least one of sodium hexametaphosphate, N-(1-pyridinium oxide-2-yl)acetamide and acetic acid-N-succinimide ester. The present invention uses sodium hexametaphosphate, N-(1-pyridinium oxide-2-yl)acetamide and acetic acid-N-succinimide ester as a dispersant, utilizes the steric effect to prevent the formation of nano nickel powder agglomerates, and achieves excellent dispersion effect. Then, the surface of the nano nickel powder particles is coated with an inorganic substance with high dielectric properties, which not only helps to improve the oxidation resistance of the prepared high crystalline nano nickel powder, but also can effectively fill the pores between the nano nickel powder particles through the inorganic substance, suppressing the shrinkage phenomenon of the prepared high crystalline nano nickel powder during the MLCC sintering process, and reducing the thermal shrinkage of the high crystalline nano nickel powder.

[0009] More preferably, the mass ratio of sodium hexametaphosphate to N-(1-oxypyridin-2-yl)acetamide is 1:0.06-0.2.

[0010] More preferably, the mass ratio of sodium hexametaphosphate to N-succinimidyl acetate is 1:0.01-0.05.

[0011] Preferably, the mass concentration of the sodium silicate aqueous solution is 3-20%, and the usage ratio of the nano nickel powder to the sodium silicate aqueous solution is 1 g: 20-100 mL.

[0012] Preferably, a method for preparing high-crystalline nickel powder comprises: S1. In a nitrogen atmosphere, nickel is heated and evaporated by a vapor evaporation and condensation method, and then the vapor is condensed to obtain nano nickel powder; S2. Add dilute hydrochloric acid to the nano-nickel powder and stir evenly, ultrasonically vibrate for 20-40 minutes, let it stand for 2-5 hours, filter, wash with deionized water 2-5 times, add dispersant and N,N-dimethylformamide and stir evenly, then add ultrapure water and ultrasonically vibrate for 20-40 minutes, add ammonia water to adjust the pH to 9-10, then add dilute hydrochloric acid to adjust the pH to 7-8 at 70-90°C, slowly add sodium silicate aqueous solution, stir the reaction for 1-4 hours, age for 4-6 hours, discard the supernatant, wash with deionized water 2-5 times, and vacuum dry for 8-24 hours to obtain highly crystalline nano-nickel powder.

[0013] More preferably, the mass concentration of the dilute hydrochloric acid in step S2 is 1-2 mol / L, and the usage ratio of the nano-nickel powder to the dilute hydrochloric acid is 1 g:1-5 mL.

[0014] More preferably, the mass ratio of the nanometer nickel powder and the dispersant in step S2 is 1:1-5.

[0015] More preferably, the dispersant in step S2 comprises at least one of sodium hexametaphosphate, N-(1-oxidized pyridine-2-yl)acetamide, acetic acid-N-succinimide ester and phthalimidyl acetone. The present application further uses phthalimidyl acetone as the dispersant to participate in the preparation of the high-crystalline nanometer nickel powder, which helps to increase the particle spacing of the nanometer nickel powder, realizes the uniform dispersion and stability of the nanometer nickel powder particles, and makes the silicon dioxide crystals deposit on the surface of the nanometer nickel powder particles, which not only helps to improve the oxidation resistance of the prepared high-crystalline nanometer nickel powder, but also improves the sintering thermal shrinkage performance by reducing the local high-temperature fluidity of the nanometer nickel powder, thereby improving the stability of the high-crystalline nanometer nickel powder in the application of the electrode layer of the multilayer ceramic capacitor.

[0016] More preferably, the mass ratio of the sodium hexametaphosphate and the N-(1-oxidized pyridine-2-yl)acetamide is 1:0.06-0.2.

[0017] More preferably, the mass ratio of the sodium hexametaphosphate and the acetic acid-N-succinimide ester is 1:0.01-0.05.

[0018] More preferably, the mass ratio of the sodium hexametaphosphate and the phthalimidyl acetone is 1:0.03-0.08.

[0019] More preferably, the amount ratio of the dispersant and the N,N-dimethylformamide in step S2 is 1g:1-5mL.

[0020] More preferably, the amount ratio of the nanometer nickel powder and the ultrapure water in step S2 is 1g:50-200mL.

[0021] More preferably, the mass concentration of the ammonia water in step S2 is 20-30%.

[0022] More preferably, the mass concentration of the sodium silicate aqueous solution in step S2 is 3-20%, and the amount ratio of the nanometer nickel powder and the sodium silicate aqueous solution is 1g:20-100mL.

[0023] The present application also discloses the high-crystalline nanometer nickel powder prepared by the preparation method.

[0024] The present application also discloses the application of the high-crystalline nanometer nickel powder in the multilayer ceramic capacitor.

[0025] The present invention utilizes at least one of sodium hexametaphosphate, N-(1-pyridin-2-oxy)acetamide, N-succinimidyl acetate, and phthalimidoacetone as a dispersant to enhance the dispersibility of nano-nickel powder. A silicon dioxide layer is then coated on the surface of the nano-nickel powder to produce highly crystalline nano-nickel powder. This method has the following beneficial effects: the highly crystalline nano-nickel powder prepared by the present invention exhibits excellent oxidation resistance and low thermal shrinkage, with an initial oxidation temperature of 413.78-468.81°C, a maximum oxidation temperature of 474.50-537.61°C, and a thermal shrinkage of 4.9-9.9%. Therefore, the present invention provides a method for preparing highly crystalline nano-nickel powder with excellent oxidation resistance and low thermal shrinkage. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the SEM image of highly crystalline nano-nickel powder.

[0027] Figure 2 This is the SEM image of a single particle of highly crystalline nano-nickel powder.

[0028] Figure 3 This is the oxygen element distribution diagram. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below in conjunction with specific embodiments. The examples provided are only for illustrating the present invention and are not intended to limit the scope of the present invention. The examples provided below can serve as a guide for further improvements by those skilled in the art and are not intended to limit the present invention in any way.

[0030] The experimental methods in the following examples are conventional methods unless otherwise specified. The materials and reagents used in the following examples are commercially available unless otherwise specified.

[0031] Example 1: Preparation of highly crystalline nano nickel powder, including: S1. In a nitrogen atmosphere, nickel is heated and evaporated by a vapor evaporation and condensation method, and then the vapor is condensed to obtain nano nickel powder; S2. Add dilute hydrochloric acid to the nano-nickel powder and stir evenly, ultrasonically vibrate for 30 minutes, let it stand for 3 hours, filter, wash with deionized water three times, add dispersant and N,N-dimethylformamide and stir evenly, then add ultrapure water and ultrasonically vibrate for 30 minutes, add ammonia water to adjust the pH to 10, then add dilute hydrochloric acid to adjust the pH to 8 at 85°C, slowly add sodium silicate aqueous solution, stir to react for 2 hours, age for 4 hours, discard the supernatant, wash with deionized water three times, and vacuum dry for 12 hours to obtain highly crystalline nano-nickel powder. The mass concentration of dilute hydrochloric acid is 2 mol / L, and the amount ratio of nano-nickel powder to dilute hydrochloric acid is 1 g:2 mL; the dispersant is sodium hexametaphosphate, and the mass ratio of nano-nickel powder to dispersant is 1:2; the amount ratio of dispersant to N,N-dimethylformamide is 1 g:2 mL; the amount ratio of nano-nickel powder to ultrapure water is 1 g:100 mL; the mass concentration of ammonia water is 25%; the mass concentration of sodium silicate aqueous solution is 10%, and the amount ratio of nano-nickel powder to sodium silicate aqueous solution is 1 g:50 mL.

[0032] Example 2: Compared with Example 1, this embodiment has the same conditions as Example 1, except that the dispersant used in step S2 is changed to a mixture of sodium hexametaphosphate, N-(1-pyridin-2-oxide)acetamide and acetic acid-N-succinimidyl ester, the mass ratio of sodium hexametaphosphate to N-(1-pyridin-2-oxide)acetamide is 1:0.2, and the mass ratio of sodium hexametaphosphate to acetic acid-N-succinimidyl ester is 1:0.05.

[0033] Example 3: Compared with Example 1, this embodiment is the same as Example 1, except that the dispersant used in step S2 is changed to a mixture of sodium hexametaphosphate, N-(1-pyridin-2-oxide)acetamide and acetic acid-N-succinimidyl ester, the mass ratio of sodium hexametaphosphate to N-(1-pyridin-2-oxide)acetamide is 1:0.06, and the mass ratio of sodium hexametaphosphate to acetic acid-N-succinimidyl ester is 1:0.05.

[0034] Example 4: Compared with Example 1, this embodiment is the same as Example 1, except that the dispersant used in step S2 is changed to a mixture of sodium hexametaphosphate, N-(1-pyridin-2-oxide)acetamide and acetic acid-N-succinimidyl ester, the mass ratio of sodium hexametaphosphate to N-(1-pyridin-2-oxide)acetamide is 1:0.2, and the mass ratio of sodium hexametaphosphate to acetic acid-N-succinimidyl ester is 1:0.01.

[0035] Example 5: Compared with Example 1, this embodiment is the same as Example 1, except that the dispersant used in step S2 is changed to a mixture of sodium hexametaphosphate, N-(1-pyridin-2-oxide)acetamide, acetic acid-N-succinimidyl ester and phthalimidoacetone, the mass ratio of sodium hexametaphosphate to N-(1-pyridin-2-oxide)acetamide is 1:0.2, the mass ratio of sodium hexametaphosphate to acetic acid-N-succinimidyl ester is 1:0.05, and the mass ratio of sodium hexametaphosphate to phthalimidoacetone is 1:0.08.

[0036] Example 6: Compared with Example 1, this embodiment is the same as Example 1, except that the dispersant used in step S2 is changed to a mixture of sodium hexametaphosphate, N-(1-pyridin-2-oxide)acetamide, acetic acid-N-succinimidyl ester and phthalimidoacetone, the mass ratio of sodium hexametaphosphate to N-(1-pyridin-2-oxide)acetamide is 1:0.2, the mass ratio of sodium hexametaphosphate to acetic acid-N-succinimidyl ester is 1:0.05, and the mass ratio of sodium hexametaphosphate to phthalimidoacetone is 1:0.03.

[0037] Comparative Example 1: Compared with Example 1, this comparative example is the same as Example 1, except that the dispersant used in step S2 is changed to a mixture of sodium hexametaphosphate and N-(1-pyridin-2-oxide)acetamide, and the mass ratio of sodium hexametaphosphate to N-(1-pyridin-2-oxide)acetamide is 1:0.2.

[0038] Comparative Example 2: Compared with Example 1, this comparative example has the same conditions as Example 1 except that the dispersant used in step S2 is changed to a mixture of sodium hexametaphosphate and acetic acid-N-succinimidyl ester, and the mass ratio of sodium hexametaphosphate to acetic acid-N-succinimidyl ester is 1:0.05.

[0039] Comparative Example 3: Compared with Example 1, this comparative example has the same conditions as Example 1 except that the dispersant used in step S2 is changed to a mixture of sodium hexametaphosphate and phthalimidoacetone, and the mass ratio of sodium hexametaphosphate to phthalimidoacetone is 1:0.08.

[0040] Experimental example: 1. Material characterization The nano-nickel powder prepared in Example 1 was ultrasonically dispersed in anhydrous ethanol to form a suspension. Two drops of the suspension were added to a copper mesh for an electron microscope. After the anhydrous ethanol evaporated, the microscopic morphology of the sample was observed using a scanning electron microscope, and the element distribution analysis was performed using the electron probe provided in the electron microscope.

[0041] Figure 1 This is a SEM image of nano-nickel powder. The size of the nano-nickel powder is 60-400nm, and the shape is spherical or quasi-spherical, with a sphericity of >90%, high crystallinity, and a grain size of 30-80nm.

[0042] Figure 2 This is the SEM image of a single nano-nickel powder. Figure 3 is the oxygen element distribution diagram. Figure 2 It can be seen that the nano nickel powder is clearly visible and the surface shows an obvious coating structure. Figure 3 As a result, oxygen is evenly distributed on the outer surface of the highly crystalline nano-nickel powder. This may be due to the oxidation of the nano-nickel powder during the preparation process to form an oxide layer with a thickness of 1.5-5 nm.

[0043] 2. Antioxidant properties The oxidation resistance of the highly crystalline nano-nickel powders prepared in Examples 1-6 and Comparative Examples 1-3 was tested using a simultaneous thermal analyzer. The parameters were set as follows: in an air atmosphere, the temperature was increased from room temperature to 1000°C at a rate of 10°C / min. The oxidation resistance results for the highly crystalline nano-nickel powders prepared in Examples 1-6 and Comparative Examples 1-3 were obtained. Table 1 shows the oxidation temperatures (°C).

[0044] Table 1 Oxidation temperature (℃)

[0045] As shown in Table 1, compared with Example 1, the initial oxidation temperature of Examples 2-4 of the present invention is higher, and the fastest oxidation temperature is postponed thereupon. This is because in the preparation of high-crystalline nano nickel powder, Examples 2-4 additionally use N-(1-pyridinium oxide-2-yl) acetamide and acetic acid-N-succinimide ester as dispersants, which contribute to improving the dispersion stability of the nano nickel powder, improving the coating effect of the silicon dioxide layer, and avoiding the oxidation of the nickel powder caused by air infiltration during the temperature rise process, thereby improving the antioxidant properties of the high-crystalline nano nickel powder. Compared with Examples 3-4, Example 2 has higher initial oxidation temperature and the fastest oxidation temperature. This is because in the preparation of high-crystalline nano nickel powder, the usage amounts of N-(1-pyridinium oxide-2-yl) acetamide and acetic acid-N-succinimide ester are different. Compared with Comparative Examples 1-2, Example 2 has a higher initial oxidation temperature and a higher fastest oxidation temperature. This is because, in the preparation of highly crystalline nano-nickel powder, Comparative Example 1 only uses N-(1-pyridin-2-oxide)acetamide as a dispersant, while Comparative Example 2 only uses N-succinimidyl acetate as a dispersant. This indicates that, compared with the use of either N-(1-pyridin-2-oxide)acetamide or N-succinimidyl acetate alone, the coordinated use of appropriate amounts of N-(1-pyridin-2-oxide)acetamide and N-succinimidyl acetate helps improve the oxidation resistance of the prepared highly crystalline nano-nickel powder.

[0046] Compared with Example 2, the initial oxidation temperature and the fastest oxidation temperature of Examples 4-5 of the present invention are higher, because in the preparation of high-crystalline nano nickel powder, Examples 4-5 further use phthalimidoacetone as a dispersant; Compared with Example 5, the initial oxidation temperature and the fastest oxidation temperature are higher, because in the preparation of high-crystalline nano nickel powder, the amount of phthalimidoacetone used is different; Compared with Comparative Example 3, the initial oxidation temperature and the fastest oxidation temperature are higher, because in the preparation of high-crystalline nano nickel powder, Comparative Example 3 only uses phthalimidoacetone as a dispersant, without using N-(1-pyridin-2-oxide) acetamide and acetic acid-N-succinimide ester. This shows that the present invention further uses phthalimidoacetone in the dispersant, which helps to further enhance the antioxidant properties of the prepared high-crystalline nano nickel powder.

[0047] 3. Heat shrinkage performance Under a nitrogen atmosphere, the thermal shrinkage properties of the highly crystalline nano-nickel powders prepared in Examples 1-6 and Comparative Examples 1-3 were tested using a thermomechanical analyzer. The temperature was increased from room temperature to 1200°C at a heating rate of 5°C / min. The thermal shrinkage rates in the range of 400-700°C are shown in Table 2.

[0048] Table 2 Thermal shrinkage (%)

[0049] As shown in Table 2, the present invention embodiment 2-4 is compared with Example 1, and the heat shrinkage is lower, because in the preparation of high crystalline nano nickel powder, embodiment 2-4 additionally uses N-(1-pyridinium oxide-2-yl) acetamide and acetic acid-N-succinimide ester as dispersant, which helps to improve the dispersion stability of nano nickel powder, promotes the coating effect of silicon dioxide layer, reduces the local high temperature fluidity of nano nickel powder, thereby reducing the heat shrinkage of high crystalline nano nickel powder. Example 2 is compared with Example 3-4, and the heat shrinkage is lower, because in the preparation of high crystalline nano nickel powder, the usage amount of N-(1-pyridinium oxide-2-yl) acetamide and acetic acid-N-succinimide ester is different. Example 2 is compared with Comparative Example 1-2, and the heat shrinkage is lower, because in the preparation of high crystalline nano nickel powder, Comparative Example 1 only additionally uses N-(1-pyridinium oxide-2-yl) acetamide as dispersant, and Comparative Example 2 only additionally uses acetic acid-N-succinimide ester as dispersant. This shows that compared with the use of N-(1-pyridin-2-oxide)acetamide or N-succinimidyl acetate alone, the synergistic use of appropriate amounts of N-(1-pyridin-2-oxide)acetamide and N-succinimidyl acetate helps to reduce the thermal shrinkage of the prepared highly crystalline nano-nickel powder.

[0050] Compared with Example 2, Examples 4-5 of the present invention have a lower thermal shrinkage rate, which is due to the fact that in the preparation of high-crystalline nano-nickel powder, Examples 4-5 further use phthalimidoacetone as a dispersant; Compared with Example 5, Example 4 has a lower thermal shrinkage rate, which is due to the different amounts of phthalimidoacetone used in the preparation of high-crystalline nano-nickel powder; Compared with Comparative Example 3, Example 4 has a lower thermal shrinkage rate, which is due to the fact that in the preparation of high-crystalline nano-nickel powder, Comparative Example 3 only uses phthalimidoacetone as a dispersant, without using N-(1-pyridin-2-oxide)acetamide and acetic acid-N-succinimidyl ester. This shows that the present invention further uses phthalimidoacetone in the dispersant, which helps to further enhance the thermal shrinkage of the prepared high-crystalline nano-nickel powder.

[0051] The conventional operations in the operating steps of the present invention are well known to those skilled in the art and will not be described in detail here.

[0052] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any changes and modifications made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing highly crystalline nano nickel powder, comprising: S1. In a nitrogen atmosphere, nickel is evaporated by vapor evaporation and condensation, and then the vapor is condensed to obtain nano nickel powder with an average diameter of 60-600 nm; S2, the nano nickel powder is acidified with dilute hydrochloric acid, a dispersant is added, and then reacted with a sodium silicate aqueous solution, and aged to obtain a highly crystalline nano nickel powder; The dispersant includes at least sodium hexametaphosphate, and the mass ratio of the nano nickel powder to the dispersant is 1:1-5.

2. The method for preparing a highly crystalline nano nickel powder according to claim 1, wherein The mass concentration of the dilute hydrochloric acid is 1-2 mol / L, and the usage ratio of nickel to dilute hydrochloric acid is 1 g:1-5 mL.

3. The method for preparing a highly crystalline nano nickel powder according to claim 1, wherein The mass ratio of the nickel to the dispersant is 1:1-5.

4. The method for preparing a highly crystalline nano nickel powder according to claim 1, wherein The dispersant includes at least one of sodium hexametaphosphate, N-(1-pyridin-2-yl)acetamide and N-succinimidyl acetate.

5. The method for preparing a highly crystalline nano nickel powder according to claim 4, wherein: The mass ratio of the sodium hexametaphosphate to N-(1-oxypyridin-2-yl)acetamide is 1:0.06-0.

2.

6. The method for preparing a highly crystalline nano nickel powder according to claim 4, wherein: The mass ratio of the sodium hexametaphosphate to N-succinimidyl acetate is 1:0.01-0.

05.

7. The method for preparing a highly crystalline nano nickel powder according to claim 1, wherein The mass concentration of the sodium silicate aqueous solution is 3-20%.

8. The method for preparing a highly crystalline nano nickel powder according to claim 1, wherein The usage ratio of the nickel and sodium silicate aqueous solution is 1g:20-100mL.

9. Highly crystalline nano nickel powder prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the highly crystalline nano nickel powder according to claim 9 in multilayer ceramic capacitors.

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