Preparation method of high-dispersion superfine spherical nickel powder

Abstract

The invention discloses a preparation method of high-dispersion superfine spherical nickel powder, which comprises the following steps: preparing nickel salt, a complexing agent and a dispersing agent into a nickel salt aqueous solution, converting a precipitant aqueous solution into precipitant micro-nano aerosol, adding the precipitant micro-nano aerosol into the nickel salt aqueous solution, and carrying out gas-liquid phase confinement micro-zone pre-reaction to obtain the high-dispersion superfine spherical nickel powder. And carrying out homogeneous hydrothermal reaction and vacuum roasting to obtain the high-dispersion superfine spherical nickel powder. According to the method, low-cost and low-pollution soluble nickel salt is used as a nickel source, aerosol confinement microcell reaction is established, controllable preparation of spherical nickel particles with high purity, high sphericity degree, high dispersity and uniform morphology is achieved, the high-dispersion superfine spherical nickel powder is effectively obtained under the conditions of low cost and low energy consumption, and the method is suitable for industrial production. The high-dispersion superfine spherical nickel powder meets the requirements of high-dispersion superfine spherical nickel powder required by inner electrode slurry of various sizes for the MLCC, meanwhile, the high-dispersion superfine spherical nickel powder has good fluidity, and preparation of high-performance inner electrode slurry of the MLCC is facilitated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ultra-fine metal powder material preparation for electronic paste, and particularly relates to a preparation method of high-dispersion ultra-fine spherical nickel powder. BACKGROUND

[0002] At present, chip multi-layer ceramic capacitors (MLCC) are widely used in many fields such as consumer electronics, communication industry, automobile industry, military equipment, etc., and the global production capacity is growing rapidly, so the demand and market size of transition metal ultra-fine powder for MLCC are also increasing year by year. Electrode paste is the main factor determining the performance of the electrode, especially the internal electrode paste, the main component of which is metal powder material. At present, nickel powder has replaced precious metals to occupy the market mainstream, but nickel powder has strict requirements on the performance characteristics such as melting point, purity, particle size, morphology, tap density and electromigration rate, and has very high technical barriers.

[0003] The main preparation methods of MLCC metal powder in the industry include PVD (evaporation condensation process) and CVD (chemical vapor deposition method). The PVD method independently developed by Jiangsu Boqian New Material Co., Ltd. is mainly used in China, which has the disadvantages of high equipment cost, relatively high environmental requirements, and relatively complex operation and equipment maintenance, so it is difficult to produce on a large scale at low cost; CVD hydrogen reduction of gaseous metal compounds has strict process requirements and high risk; the thermal decomposition of carbonyl nickel pollutes the environment; and the chemical vapor deposition method requires expensive equipment and the equipment is severely corroded.

[0004] Therefore, there is still an urgent need to develop an industrial production method that is more environmentally friendly, has lower cost, and can meet the application requirements of the prepared nano-nickel powder, improve the comprehensive performance of the internal electrode nickel powder and the end electrode copper powder, and has key significance for breaking the foreign technical blockade of high-end powder for electronic devices and helping China to develop high-performance MLCC. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a preparation method of high-dispersion ultra-fine spherical nickel powder to solve the key technical problems of poor sphericity and dispersity of the prepared ultra-fine nickel powder in the prior art.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is: a preparation method of high-dispersion ultra-fine spherical nickel powder, characterized in that the method comprises the following steps: Step one, preparing a nickel salt aqueous solution by mixing nickel salt, complexing agent and dispersant, and preparing a precipitant aqueous solution by mixing precipitant; Step two, converting the precipitant aqueous solution prepared in step one into a precipitant micro-nano aerosol; Step three, adding the precipitant micro-nano aerosol converted in step two to the nickel salt aqueous solution obtained in step one under the condition of continuous stirring, carrying out gas-liquid phase limited micro-zone pre-reaction, and obtaining a suspension containing nickel compound; Step four, transferring the suspension containing nickel compound obtained in step three to a high-pressure reaction kettle and sealing, and then carrying out homogeneous hydrothermal reaction; Step five, after the homogeneous hydrothermal reaction in step four is completed and the high-pressure reaction kettle is cooled to room temperature, carrying out solid-liquid separation, washing and drying on the suspension after reaction, and obtaining spherical nickel precursor; Step six, vacuum calcining the spherical nickel precursor formed in step five, and obtaining high-dispersion ultra-fine spherical nickel powder.

[0007] Firstly, the present application prepares a nickel salt aqueous solution by mixing nickel salt, complexing agent and dispersant, and prepares a precipitant aqueous solution by mixing precipitant, then converts the precipitant aqueous solution into a micro-nano aerosol formed by ultra-fine micro-nano droplets, adds the precipitant micro-nano aerosol to the nickel salt aqueous solution under the condition of continuous stirring at room temperature, constructs a limited micro-zone reaction environment, carries out gas-liquid phase limited micro-zone pre-reaction, creates favorable conditions for nanoscale dispersion and regulation of crystal nucleation and growth of nickel precursor, effectively controls irregular agglomeration of nickel precursor in the nucleation and growth process, ensures the sphericity, dispersity and uniformity of spherical nickel powder particles after subsequent high-temperature heat treatment, obtains a suspension containing nickel compound, then transfers the suspension containing nickel compound to a high-pressure reaction kettle, optimizes the reaction kinetics conditions of the crystal nucleation and growth process through homogeneous hydrothermal reaction, and the metal ions are deposited first to form nickel-based compound nanoparticles, these nanoparticles spontaneously assemble through intermolecular forces, gradually grow into spherical particles with dense structure through nanoscale reaction, and ultra-fine particles containing nickel compound are obtained, finally, solid-liquid separation, washing and drying are carried out to obtain spherical nickel precursor formed by self-assembly of ultra-fine nanoblocks, and finally vacuum calcining is carried out to obtain high-dispersion ultra-fine spherical nickel powder, thereby realizing the regulation of the morphology and particle size of high-dispersion ultra-fine spherical nickel powder.

[0008] The application adds a complexing agent in the aqueous nickel salt solution, because the complexing agent reduces the release rate of nickel ions by coordination bonding, avoids the uneven phenomenon of particles caused by explosive nucleation, and because the complexing agent molecules are adsorbed on specific crystal planes of the crystal by electrostatic action or hydrogen bonds, the anisotropic growth rate is regulated, the diffusion path is prolonged and the deposition kinetics is changed, and the nickel-containing compound particles tend to be smaller in size; and a dispersing agent is added in the aqueous nickel salt solution, because the dispersing agent molecules are adsorbed on the surface of the nickel-containing compound crystal by the surface groups, and the polymer chain forms steric hindrance, which can inhibit the agglomeration of the nickel-containing compound crystal nucleus, and the aqueous nickel salt solution containing the complexing agent and the dispersing agent meets the needs of regulating the nucleation and growth and the morphology and particle size of the product nickel precursor.

[0009] The high-frequency ultrasonic dispersion device converts the aqueous precipitant solution into a precipitant micro-nano aerosol formed by ultrafine micro-nano droplets, and constructs a limited micro-zone reaction environment.

[0010] In the application, oxalic acid or ammonium oxalate is used as a precipitant, and the obtained spherical nickel precursor is nickel oxalate. Vacuum calcination has the effects of inhibiting oxidation, promoting the forward reaction, and strengthening reduction, and the high-dispersion ultrafine spherical nickel powder is obtained. Secondly, the thermal decomposition temperature of nickel oxalate under vacuum conditions is significantly reduced, usually from above 400 DEG C under normal pressure to about 300 DEG C, which reduces energy consumption and accelerates the decomposition reaction. In addition, compared with the complex process of preparing metal nickel powder by decomposing nickel oxalate to obtain nickel oxide, and then reducing the nickel oxide with a reducing agent such as hydrogen, carbon monoxide or carbon, the vacuum calcination method can complete the decomposition of nickel oxalate to metal nickel in one step, simplify the process flow, and reduce energy consumption.

[0011] The above-mentioned method for preparing highly dispersed ultrafine spherical nickel powder is characterized in that, in step one, the nickel salt is nickel nitrate or nickel acetate, the complexing agent is trisodium citrate or citric acid, the dispersant is hexadecyltrimethylammonium bromide, polyethylene glycol or polyvinyl alcohol, the concentration of nickel ions in the aqueous solution of the nickel salt is 60 g / L to 100 g / L, the concentration ratio of the complexing agent to the nickel salt is 0.45 to 0.9:1, the mass fraction of the dispersant is 1% to 5%, the precipitant is oxalic acid or ammonium oxalate, the concentration of the precipitant in the aqueous solution of the precipitant is 40 g / L to 80 g / L, and the mass ratio of the precipitant to the nickel salt is 0.6 to 0.85:1. This invention selects nickel salts, complexing agents, dispersants, and precipitants to prepare aqueous solutions of nickel salts and precipitants. The final morphology of the metal oxide is determined by the interaction of the chemical properties of anions and cations with crystal growth kinetics. This process involves the synergistic effects of selective adsorption on crystal faces, nucleation rate regulation, and structure-directing effects. Specifically, in the gas-liquid phase confined micro-region pre-reaction, the complexing agent influences the nucleation, growth, and final morphology of the precipitate from thermodynamic and kinetic perspectives by regulating the release rate of metal ions and their adsorption on the particle surface. The advantages of using trisodium citrate and citric acid are that both can form stable complexes, slowly releasing metal ions, and the complexation strength can be controlled by adjusting the pH, thus precisely regulating the microstructure of the particles. They are environmentally friendly, food-grade, non-toxic, easily degradable, and low-cost. By controlling the composition of the dispersant, an adsorption layer can be formed, effectively preventing aggregation and playing a role in morphology regulation. After addition, the prepared nickel oxalate particles are observed to be uniform spherical particles; they are also non-toxic or low-toxic, commonly found in daily consumer goods. By controlling the concentration of nickel ions, according to the concentration of the precipitant and... The reactant ratios were determined after process optimization. Oxalic acid and ammonium oxalate, used as precipitants, have low solubility. The concentrations of all reactants were determined primarily under conditions of maximum precipitant solubility. If the concentration is too low, the amount of reaction product is too small, resulting in low efficiency. If the concentration is too high, the reactants cannot completely dissolve, and the reaction system becomes heterogeneous, affecting the reaction pathway. If it becomes supersaturated, the crystal growth rate may exceed the nucleation rate, leading to excessively large or irregularly shaped product particles. A low ratio of complexing agent to nickel salt concentration leads to a high concentration of free metal ions, resulting in a rapid partial precipitation reaction and the formation of large or unevenly sized particles. A high ratio leads to excessive complexation of metal ions, while a low concentration of free metal ions may inhibit precipitation. Furthermore, excessive complexing agent may adsorb onto the surface of the precipitated particles, affecting crystal growth and the primary particle self-assembly process, leading to particle agglomeration. The amount of complexing agent added is a crucial factor in controlling particle size. The selected range was obtained through experimental optimization; within this range, particles with good dispersibility, excellent sphericity, and uniform particle size can be obtained.The amount of dispersant added is another crucial factor in controlling particle size. The range of dispersant addition selected above was obtained through experimental optimization. Within this range, particles with good dispersibility, excellent sphericity, and uniform particle size can be obtained. When the amount of dispersant added is less than 1%, it has virtually no effect on particle size and dispersibility. Excessive addition leads to excessive adsorption of the dispersant on the particle surface, inhibiting crystal directional growth, resulting in uneven particle size and increased difficulty in subsequent powder washing. The reaction rate of oxalate ion precipitation of nickel ions is relatively mild. By controlling the reaction process and precisely controlling the balance between nucleation and growth, side reactions such as the formation of nickel hydroxide can be reduced. Furthermore, nickel oxalate has a low thermal decomposition temperature, and the decomposition products are mainly nickel oxide, nickel, carbon monoxide, and carbon dioxide. The gaseous products can escape during thermal decomposition, minimizing the introduction of other impurities and improving powder purity. Therefore, the amount of dispersant added needs to be precisely controlled. Under optimal conditions, the nickel precursor exhibits the best uniformity, morphology, and particle size. Controlling the mass ratio of the precipitant to the nickel salt, which is equivalent to controlling the mass ratio of the nickel salt aqueous solution to the precipitant aqueous solution, ensures the reaction proceeds fully.

[0012] The above-mentioned method for preparing highly dispersed ultrafine spherical nickel powder is characterized in that the conversion in step two is carried out using a high-frequency ultrasonic dispersion device, with an ultrasonic frequency of 10kHz~20kHz, a liquid inlet flow rate of 110mL / h~350mL / h, and a gas flow rate of 15L / min~30L / min. The precipitant micro-nano aerosol is composed of uniform micron-sized ultrafine droplets. This invention utilizes high-frequency ultrasound to convert the solution into ultrafine nano aerosols. Precise control of the ultrasonic frequency, liquid inlet flow rate, and gas flow rate is required to regulate the uniformity and particle size of the sol particles, effectively enhancing the transport and reaction kinetics during the reaction between the nickel source and the precipitant. Simultaneously, it constructs a large number of micro-nano reaction regions, thereby inhibiting the aggregation and ripening process of nickel-containing compound nanoparticles, which helps to control the morphology and particle size of the product.

[0013] The method for preparing highly dispersed ultrafine spherical nickel powder described above is characterized in that the gas-liquid phase confined micro-region pre-reaction in step three is carried out at room temperature, and the region size of the gas-liquid phase confined micro-region pre-reaction is 5μm~20μm. Traditional precipitation reactions require heating to promote the forward reaction, improve reaction efficiency, enhance particle crystallinity, and reduce side reactions. This invention does not require heating and can efficiently obtain particles with excellent dispersibility and good crystallinity at room temperature. The region size of the gas-liquid phase confined micro-region pre-reaction is 5μm~20μm, much smaller than the macroscopic space of conventional reactors, such as stirred tanks. This micron-level confinement characteristic confines the gas-phase reactants within a very small area, forming an efficient microscopic contact interface with the liquid phase, enhancing molecular diffusion and reaction rate. The core advantage lies in the microdroplets formed by atomization. With a large specific surface area, sufficient gas-liquid interface contact, and a shortened diffusion distance between the precipitant and metal ions to the micrometer level, the mass transfer rate is greatly improved, avoiding the agglomeration problem caused by local overconcentration in the traditional precipitation process, and the product particles are more uniform. The micro-regions with a size of 5μm~20μm are equivalent to micro-reactors. The reaction environment within each microdroplet, such as concentration and pH, is highly uniform, and the nucleation and growth processes are highly synchronized. By controlling atomization parameters, such as droplet size and spray speed, the product morphology can be precisely controlled, and the particle dispersion is good, avoiding the morphological differences caused by uneven mixing in conventional reactions.

[0014] The method for preparing highly dispersed ultrafine spherical nickel powder described above is characterized in that the homogeneous hydrothermal reaction in step four is carried out at a temperature of 100℃~140℃ for 2h~6h. In this invention, a suspension of nickel-containing compounds is transferred to a high-pressure reactor for a homogeneous hydrothermal reaction. Precursors prepared by precipitation methods typically have low crystallinity and contain impurity ions, with most compounds exhibiting an amorphous nanoparticle structure. After undergoing a high-temperature, high-pressure hydrothermal process, secondary spherical particles are formed. The reaction temperature and time then need to be strictly controlled to prevent excessively high temperatures and long reaction times from causing particles to easily grow along specific crystal planes, transforming into other particle morphologies or exhibiting overlapping and growth phenomena, thus obtaining a solution of ultrafine nickel-containing compound particles.

[0015] The above-mentioned method for preparing highly dispersed ultrafine spherical nickel powder is characterized in that the solid-liquid separation in step five is performed by vacuum filtration or centrifugation, and the drying is performed by vacuum drying or freeze drying. In this invention, solid-liquid separation is performed by vacuum filtration or centrifugation to remove unreacted solution, collect the nickel-containing compound obtained from the reaction, and wash with deionized water and anhydrous ethanol to remove impurities. The wastewater discharged after washing with deionized water can be recycled into a wastewater recycling system, avoiding the wastewater discharge problem present in liquid-phase reactions. Vacuum drying or freeze drying thoroughly removes residual solution; however, care should be taken to prevent over-drying and aggregation during vacuum drying.

[0016] The method for preparing highly dispersed ultrafine spherical nickel powder described above is characterized in that, in step five, the average particle size of the primary particles of the spherical nickel precursor is 20 nm to 30 nm, and the average particle size of the secondary particles is 500 nm to 700 nm. In this invention, primary particles refer to the first-formed, indivisible original particles in the powder, with no obvious internal pores, high surface energy, and directly generated nanoparticles by the reaction; secondary particles are independent particles formed by the spontaneous aggregation of two or more primary particles.

[0017] The above-mentioned method for preparing highly dispersed ultrafine spherical nickel powder is characterized in that the vacuum calcination process in step six is ​​as follows: the temperature is raised to 290℃~400℃ at a heating rate of 5℃~10℃ and then held for 1h~3h; the thickness of the spherical nickel precursor laid in the vacuum calcination is 5mm~20mm. This invention controls the parameters of vacuum calcination to minimize the temperature gradient between powder sample layers, resulting in a more uniform sintering process. This allows adsorbed water and crystal water in the product to slowly escape, providing sufficient diffusion time, reducing particle porosity, and preventing thermal shock aging of heating elements due to rapid heating. It also balances efficiency and powder quality, ensuring complete calcination of the nickel precursor to obtain high-purity, ultrafine spherical nickel powder. By controlling the layer thickness, it ensures uniform heating of the sample, preventing excessively thick layers from causing gas accumulation inside or in the lower layers, forming particle pores and reducing particle density. Simultaneously, this thickness can shorten the heat treatment cycle and reduce energy consumption while maintaining quality. Insufficient layer thickness results in low yield per batch, increasing energy consumption for the same production volume.

[0018] The method for preparing highly dispersed ultrafine spherical nickel powder described above is characterized in that the particle size of the highly dispersed ultrafine spherical nickel powder in step six is ​​400 nm to 600 nm. In this invention, after vacuum calcination, the nickel precursor decomposes into nickel, causing particle shrinkage and a smaller particle size.

[0019] Compared with the prior art, the present invention has the following advantages: 1. This invention converts the solution into an aerosol for pre-reaction in a confined micro-region of gas and liquid phases. Compared with direct incorporation or dropwise addition of solution, aerosols diffuse more easily and have smaller average particle size and higher specific surface area, greatly accelerating the transport rate of nickel salts and precipitated phases during the reaction. This effectively increases the reaction rate and the number of nuclei. At the same time, the constructed confined micro-regions inhibit the aggregation and growth of nickel-containing compounds, effectively controlling the sphericity and dispersibility of nickel precursor particles, and avoiding irregular agglomeration of particles. The method for obtaining highly dispersed ultrafine spherical nickel powder is novel, low-cost, simple, energy-efficient, and can be operated continuously with easily controllable process conditions. It focuses on solving the key technical problems of poor sphericity and dispersibility of ultrafine nickel powder prepared by existing technologies, reducing raw material and equipment costs, ensuring environmentally friendly process routes, and reducing potential hazards in production.

[0020] 2. This invention uses atomization precipitation-hydrothermal preparation of highly dispersed ultrafine spherical nickel powder, which is beneficial to the uniformity of nickel grain size and shape, controllable particle size, dispersibility and sphericity. The resulting highly dispersed ultrafine spherical nickel powder has high purity, good crystallinity, good sphericity, uniform morphology and good dispersibility. A series of spherical nickel particles formed by the self-assembly of nanoparticles with controllable particle size can be obtained.

[0021] 3. This invention uses vacuum calcination to decompose the nickel precursor into metallic nickel in one step, which is conducive to the forward reaction, reduces the decomposition byproducts of nickel oxalate, lowers the precursor decomposition temperature, reduces the safety hazards caused by hydrogen reduction, simplifies the process, and reduces energy consumption.

[0022] 4. The overall process of this invention is simple and does not require high-energy-consuming CVD and PVD processes, thus reducing energy consumption. The process is environmentally friendly and suitable for mass industrial production. It can be operated continuously and the process conditions are easy to control, which is beneficial for preparing highly dispersed ultrafine spherical nickel powder with uniform size and shape, controllable particle size, high dispersibility and high sphericity.

[0023] 5. Under low cost and low energy consumption conditions, this invention effectively obtains nickel particles with high sphericity, while meeting the requirements of ultrafine nickel powder particle size, uniformity and flowability for MLCC internal electrode slurry. This is conducive to the preparation of high-performance MLCC internal electrode slurry, breaking the foreign monopoly on ultrafine nickel powder in the high-end electronics field, effectively promoting the process of domestic substitution of imported powder research and development, and contributing to the healthy development of the domestic high-end electronics field.

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0025] Figure 1 This is a SEM image of the highly dispersed ultrafine spherical nickel powder prepared in Example 1 of the present invention.

[0026] Figure 2 This is a particle size distribution chart of the highly dispersed ultrafine spherical nickel powder prepared in Example 1 of the present invention.

[0027] Figure 3 The image shows the XRD pattern of the highly dispersed ultrafine spherical nickel powder prepared in Example 1 of this invention.

[0028] Figure 4 This is a SEM image of the highly dispersed ultrafine spherical nickel powder prepared in Example 2 of the present invention.

[0029] Figure 5 This is a SEM image of the highly dispersed ultrafine spherical nickel powder prepared in Example 3 of the present invention. Detailed Implementation

[0030] Example 1 This embodiment includes the following steps: Step 1: Prepare a nickel salt aqueous solution with a nickel acetate concentration of 60 g / L, a citric acid to nickel acetate concentration ratio of 0.6:1, and a polyethylene glycol mass fraction of 5%; and prepare a precipitant aqueous solution with an ammonium oxalate concentration of 40 g / L. Step 2: The aqueous solution of the precipitant prepared in Step 1 is converted into precipitant micro-nano aerosols using a high-frequency ultrasonic dispersion device, and the ultrasonic frequency is 10kHz~20kHz. Step 3: At room temperature, the precipitant micro-nano aerosol converted in Step 2 is added to the nickel salt aqueous solution obtained in Step 1 under continuous stirring. The liquid inlet volume is 15%, the gas flow rate is 20 L / min, and the mass ratio of precipitant to nickel salt is 0.6:1. Gas-liquid phase confined micro-region pre-reaction is carried out, and the region size of the gas-liquid phase confined micro-region pre-reaction is 5 μm to 20 μm, to obtain a suspension containing nickel compounds. Step 4: Transfer the suspension of nickel-containing compounds obtained in Step 3 to a high-pressure reactor and seal it. Then, carry out a homogeneous hydrothermal reaction at a reaction temperature of 120°C for 4 hours. Step 5: After the homogeneous hydrothermal reaction in Step 4 is completed and the high-pressure reactor is cooled to room temperature, the resulting suspension is filtered and washed, and then placed in a vacuum drying oven at 80°C for vacuum drying to obtain a light blue spherical nickel precursor. Step 6: The spherical nickel precursor formed in Step 5 is calcined in vacuum at a heating rate of 10℃ / min and a temperature of 290℃ for 3 hours, wherein the thickness of the spherical nickel precursor is 20mm, to obtain highly dispersed ultrafine spherical nickel powder.

[0031] Testing revealed that the average particle size of the primary particles of the spherical nickel precursor prepared in this embodiment was 20 nm, and the average particle size of the secondary particles was 500 nm.

[0032] Figure 1 This is a SEM image of the highly dispersed ultrafine spherical nickel powder prepared in this embodiment. Figure 1 As can be seen from the above, the highly dispersed ultrafine spherical nickel powder prepared in this embodiment has good sphericity and good monodispersity.

[0033] Figure 2 This is a particle size distribution chart of the highly dispersed ultrafine spherical nickel powder prepared in this embodiment, from... Figure 2 As can be seen from the data, the average particle size of the highly dispersed ultrafine spherical nickel powder prepared in this embodiment is 400 nm, and there is no obvious agglomeration phenomenon.

[0034] Figure 3 The image shows the XRD pattern of the highly dispersed ultrafine spherical nickel powder prepared in this embodiment. Figure 3The top line shows the XRD pattern of the highly dispersed ultrafine spherical nickel powder prepared in this embodiment; the second line is the Ni standard card; and the third line is the NiO standard card. Figure 3 As can be seen from the above, the highly dispersed ultrafine spherical nickel powder prepared in this embodiment exhibits a pure nickel phase with no impurities present.

[0035] In this embodiment, the dispersant may also be hexadecyltrimethylammonium bromide or polyvinyl alcohol.

[0036] Example 2 This embodiment includes the following steps: Step 1: Prepare a nickel salt aqueous solution with a nickel acetate concentration of 80 g / L, a citric acid to nickel acetate concentration ratio of 0.45:1, and a polyethylene glycol mass fraction of 3%; and prepare a precipitant aqueous solution with an ammonium oxalate concentration of 60 g / L. Step 2: The aqueous solution of the precipitant prepared in Step 1 is converted into precipitant micro-nano aerosols using a high-frequency ultrasonic dispersion device, and the ultrasonic frequency is 10kHz~20kHz. Step 3: At room temperature, the precipitant micro-nano aerosol converted in Step 2 is added to the nickel salt aqueous solution obtained in Step 1 under continuous stirring. The liquid inlet volume is 10%, the gas flow rate is 15 L / min, and the mass ratio of precipitant to nickel salt is 0.7:1. Gas-liquid phase confined micro-region pre-reaction is carried out, and the region size of the gas-liquid phase confined micro-region pre-reaction is 5 μm to 20 μm, to obtain a suspension containing nickel compounds. Step 4: Transfer the nickel-containing compound suspension obtained in Step 3 to a high-pressure reactor and seal it. Then, carry out a homogeneous hydrothermal reaction at a reaction temperature of 100°C for 6 hours. Step 5: After the homogeneous hydrothermal reaction in Step 4 is completed and the high-pressure reactor is cooled to room temperature, the suspension obtained after the reaction is filtered and washed, and then placed in a vacuum drying oven at a temperature of 60°C for vacuum drying to obtain a light blue spherical nickel precursor. Step 6: The spherical nickel precursor formed in Step 5 is calcined in vacuum at a heating rate of 5℃ / min and a temperature of 320℃ for 2 hours, wherein the thickness of the spherical nickel precursor is 5mm, to obtain highly dispersed ultrafine spherical nickel powder.

[0037] Testing revealed that the average particle size of the primary particles of the spherical nickel precursor prepared in this embodiment was 25 nm, and the average particle size of the secondary particles was 600 nm.

[0038] Figure 4 This is a SEM image of the highly dispersed ultrafine spherical nickel powder prepared in this embodiment. Figure 4 As can be seen from the above, the highly dispersed ultrafine spherical nickel powder prepared in this embodiment has good shape, good monodispersity, uniform particle size, no obvious agglomeration, and an average particle size of 500 nm.

[0039] In this embodiment, the dispersant may also be hexadecyltrimethylammonium bromide or polyvinyl alcohol.

[0040] Example 3 This embodiment includes the following steps: Step 1: Prepare a nickel salt aqueous solution with a nickel nitrate concentration of 100 g / L, a trisodium citrate to nickel nitrate salt concentration ratio of 0.9:1, and a polyethylene glycol mass fraction of 1%; and prepare a precipitant aqueous solution with an oxalic acid concentration of 80 g / L. Step 2: The aqueous solution of the precipitant prepared in Step 1 is converted into precipitant micro-nano aerosols using a high-frequency ultrasonic dispersion device, and the ultrasonic frequency is 10kHz~20kHz. Step 3: At room temperature, the precipitant micro-nano aerosol converted in Step 2 is added to the nickel salt aqueous solution obtained in Step 1 under continuous stirring. The liquid inlet volume is 30%, the gas flow rate is 30 L / min, and the mass ratio of precipitant to nickel salt is 0.85:1. Gas-liquid phase confined micro-region pre-reaction is carried out, and the region size of the gas-liquid phase confined micro-region pre-reaction is 5 μm to 20 μm, to obtain a suspension containing nickel compounds. Step 4: Transfer the suspension of nickel-containing compounds obtained in Step 3 to a high-pressure reactor and seal it. Then, carry out a homogeneous hydrothermal reaction at a reaction temperature of 140°C for 2 hours. Step 5: After the homogeneous hydrothermal reaction in Step 4 is completed and the high-pressure reactor is cooled to room temperature, the resulting suspension is filtered and washed, and then placed in a freeze-drying oven for freeze-drying to obtain a light blue spherical nickel precursor. Step 6: The spherical nickel precursor formed in Step 5 is calcined in vacuum at a heating rate of 8℃ / min and a temperature of 400℃ for 1 hour, wherein the thickness of the spherical nickel precursor is 10mm, to obtain highly dispersed ultrafine spherical nickel powder.

[0041] Testing revealed that the average particle size of the primary particles of the spherical nickel precursor prepared in this embodiment was 30 nm, and the average particle size of the secondary particles was 700 nm.

[0042] Figure 5 This is a SEM image of the highly dispersed ultrafine spherical nickel powder prepared in this embodiment. Figure 5 As can be seen from the above, the highly dispersed ultrafine spherical nickel powder prepared in this embodiment has good shape, good monodispersity, uniform particle size, no obvious agglomeration, and an average particle size of 600 nm.

[0043] In this embodiment, the dispersant may also be hexadecyltrimethylammonium bromide or polyvinyl alcohol.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing highly dispersed ultrafine spherical nickel powder, characterized in that, The method includes the following steps: Step 1: Prepare an aqueous solution of nickel salt, complexing agent, and dispersant; prepare an aqueous solution of precipitant. Step 2: Convert the precipitant aqueous solution prepared in Step 1 into precipitant micro / nano aerosols; Step 3: Add the precipitant micro-nano aerosol converted in Step 2 to the nickel salt aqueous solution obtained in Step 1 under continuous stirring to carry out gas-liquid phase confined micro-region pre-reaction and obtain a suspension containing nickel compounds. Step 4: Transfer the nickel-containing compound suspension obtained in Step 3 to a high-pressure reactor and seal it, then carry out a homogeneous hydrothermal reaction; Step 5: After the homogeneous hydrothermal reaction in Step 4 is completed and the high-pressure reactor is cooled to room temperature, the suspension after the reaction is subjected to solid-liquid separation, washing and drying to obtain spherical nickel precursor. Step 6: Vacuum calcination is performed on the spherical nickel precursor formed in Step 5 to obtain highly dispersed ultrafine spherical nickel powder.

2. The method for preparing highly dispersed ultrafine spherical nickel powder according to claim 1, characterized in that, In step one, the nickel salt is nickel nitrate or nickel acetate, the complexing agent is trisodium citrate or citric acid, the dispersant is hexadecyltrimethylammonium bromide, polyethylene glycol or polyvinyl alcohol, the concentration of nickel ions in the aqueous solution of the nickel salt is 60 g / L to 100 g / L, the concentration ratio of the complexing agent to the nickel salt is 0.45 to 0.9:1, the mass fraction of the dispersant is 1% to 5%, the precipitant is oxalic acid or ammonium oxalate, the concentration of the precipitant in the aqueous solution of the precipitant is 40 g / L to 80 g / L, and the mass ratio of the precipitant to the nickel salt is 0.6 to 0.85:

1.

3. The method for preparing highly dispersed ultrafine spherical nickel powder according to claim 1, characterized in that, The conversion in step two is carried out using a high-frequency ultrasonic dispersion device with an ultrasonic frequency of 10kHz to 20kHz, a liquid inlet flow rate of 110mL / h to 350mL / h, and a gas flow rate of 15L / min to 30L / min. The precipitant micro-nano aerosol is composed of uniform micron-sized ultrafine droplets.

4. The method for preparing highly dispersed ultrafine spherical nickel powder according to claim 1, characterized in that, The gas-liquid phase confined micro-region pre-reaction described in step three is carried out at room temperature, and the region size of the gas-liquid phase confined micro-region pre-reaction is 5μm~20μm.

5. The method for preparing highly dispersed ultrafine spherical nickel powder according to claim 1, characterized in that, The homogeneous hydrothermal reaction in step four is carried out at a temperature of 100℃~140℃ for 2h~6h.

6. The method for preparing highly dispersed ultrafine spherical nickel powder according to claim 1, characterized in that, The solid-liquid separation in step five is performed by filtration or centrifugation, and the drying is performed by vacuum drying or freeze drying.

7. The method for preparing highly dispersed ultrafine spherical nickel powder according to claim 1, characterized in that, The average particle size of the primary particles of the spherical nickel precursor in step five is 20 nm to 30 nm, and the average particle size of the secondary particles is 500 nm to 700 nm.

8. The method for preparing highly dispersed ultrafine spherical nickel powder according to claim 1, characterized in that, The vacuum calcination process described in step six is ​​as follows: the temperature is increased to 290℃~400℃ at a heating rate of 5℃~10℃ and then held for 1h~3h; the thickness of the spherical nickel precursor laid in the vacuum calcination is 5mm~20mm.

9. The method for preparing highly dispersed ultrafine spherical nickel powder according to claim 1, characterized in that, The particle size of the highly dispersed ultrafine spherical nickel powder mentioned in step six is ​​400nm~600nm.

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