Preparation method of high-dispersion ultrafine spherical nickel powder

Abstract

The application discloses a preparation method of high-dispersion superfine spherical nickel powder, which comprises the following steps: preparing a nickel salt aqueous solution by mixing a nickel salt, a complexing agent and a dispersing agent, converting a precipitant aqueous solution into a precipitant micro-nano aerosol, adding the precipitant micro-nano aerosol into the nickel salt aqueous solution, performing a gas-liquid phase limited micro-region pre-reaction, obtaining a suspension containing a nickel compound, then performing a homogeneous hydrothermal reaction and vacuum calcination, and obtaining the high-dispersion superfine spherical nickel powder. The application uses low-cost and low-pollution soluble nickel salt as a nickel source, establishes a limited micro-region reaction of aerosol, realizes controllable preparation of high-purity, high-sphericity, high-dispersity and uniform-morphology spherical nickel particles, effectively obtains the high-dispersion superfine spherical nickel powder under the conditions of low cost and low energy consumption, meets the requirements of high-dispersion superfine spherical nickel powder for various scale internal electrode slurries of MLCC, and has good fluidity, which is helpful to preparation of high-performance MLCC internal electrode slurry.

Description

Technical Field

[0001] This invention belongs to the field of preparation technology of ultrafine metal powder materials for electronic pastes, and specifically relates to a method for preparing highly dispersed ultrafine spherical nickel powder. Background Technology

[0002] Currently, multilayer ceramic capacitors (MLCCs) are widely used in consumer electronics, communications, automotive, and military equipment, among other fields. Global production capacity is growing rapidly, leading to a significant year-on-year increase in demand and market size for ultrafine transition metal powders used in MLCCs. Electrode paste is a major factor determining electrode performance, especially internal electrode paste, whose main component is metal powder. Nickel powder has now replaced precious metals as the mainstream material in the market; however, there are stringent requirements for nickel powder in terms of melting point, purity, particle size, morphology, tap density, and electromobility, presenting extremely high technological barriers.

[0003] The main preparation methods for MLCC metal powders in the industry include PVD (evaporation and condensation) and CVD (chemical vapor deposition). In China, the PVD method independently developed by Jiangsu Boqian New Materials is the main method. Its disadvantages are that it requires expensive equipment, relatively high environmental requirements, and relatively complex operation and equipment maintenance, making it difficult to carry out low-cost large-scale production. CVD uses hydrogen to reduce gaseous metal compounds, which has strict process requirements and a high risk factor. The carbonyl nickel thermal decomposition method will cause environmental pollution. Chemical vapor deposition requires expensive equipment and the equipment is subject to severe corrosion.

[0004] Therefore, there is still an urgent need to develop an industrial production method that is more environmentally friendly, lower in cost, and produces nano-nickel powder that meets application requirements, thereby improving the overall performance of internal electrode nickel powder and terminal electrode copper powder. This is of key significance for breaking the foreign technological blockade on high-end powders for electronic devices and helping my country develop high-performance MLCCs. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a method for preparing highly dispersed ultrafine spherical nickel powder, addressing the shortcomings of the prior art. This method converts the solution into an aerosol, enabling a gas-liquid phase confined micro-region pre-reaction. This accelerates the transport rate of nickel salts and the precipitated phase during the reaction, effectively increasing the reaction rate and the number of nuclei, inhibiting the aggregation and growth of nickel-containing compounds, effectively controlling the sphericity and dispersibility of nickel precursor particles, and avoiding irregular particle agglomeration. This yields highly dispersed ultrafine spherical nickel powder, solving the key technical problem of poor sphericity and dispersibility in ultrafine nickel powder prepared by existing technologies.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing highly dispersed ultrafine spherical nickel powder, characterized in that the method includes the following steps:

[0007] Step 1: Prepare an aqueous solution of nickel salt, complexing agent, and dispersant; prepare an aqueous solution of precipitant.

[0008] Step 2: Convert the precipitant aqueous solution prepared in Step 1 into precipitant micro / nano aerosols;

[0009] 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.

[0010] 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;

[0011] 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.

[0012] Step 6: Vacuum calcination is performed on the spherical nickel precursor formed in Step 5 to obtain highly dispersed ultrafine spherical nickel powder.

[0013] This invention first prepares a nickel salt aqueous solution by combining a nickel salt, a complexing agent, and a dispersant, and prepares a precipitant aqueous solution by combining a precipitant. Then, the precipitant aqueous solution is converted into a micro-nano aerosol formed by ultrafine nano-droplets. Under continuous stirring at room temperature, the precipitant micro-nano aerosol is added to the nickel salt aqueous solution to construct a confined micro-region reaction environment for gas-liquid phase confined micro-region pre-reaction. This creates favorable conditions for the nanoscale dispersion of the nickel precursor and the regulation of crystal nucleation and growth, effectively controlling the irregular agglomeration of the nickel precursor during nucleation and growth, and ensuring the sphericity, dispersibility, and uniformity of the spherical nickel powder particles after subsequent high-temperature heat treatment, resulting in nickel-containing nickel powder. A suspension of the nickel-containing compound was prepared, and then the suspension was transferred to a high-pressure reactor. The reaction kinetics of the crystal nucleation and growth process were optimized through homogeneous hydrothermal reaction. After the metal ions precipitated, they first nucleated and grew into nickel-based compound nanoparticles. These nanoparticles spontaneously assembled through intermolecular forces and gradually grew into dense spherical particles through nanoscale reactions, resulting in ultrafine nickel-containing compound particles. Finally, after solid-liquid separation, washing, and drying, spherical nickel precursors formed by the self-assembly of ultrafine nanoblocks were obtained. Finally, high-dispersion ultrafine spherical nickel powder was obtained through vacuum calcination, realizing the control of the morphology and particle size of high-dispersion ultrafine spherical nickel powder.

[0014] The present invention adds a complexing agent to the nickel salt aqueous solution because the complexing agent reduces the release rate of nickel ions through coordination bonding, avoiding the particle inhomogeneity caused by explosive nucleation. At the same time, because the complexing agent molecules are adsorbed onto specific crystal faces through electrostatic interactions or hydrogen bonds, the anisotropic growth rate is regulated, the diffusion path is extended, and the deposition kinetics are changed, guiding the nickel-containing compound particles to tend towards a smaller particle size. Furthermore, a dispersant is added to the nickel salt aqueous solution because the dispersant molecules are adsorbed onto the surface of the nickel-containing compound crystal through surface groups, and the polymer chains form steric hindrance, which can inhibit the agglomeration of nickel-containing compound crystal nuclei. The nickel salt aqueous solution containing the complexing agent and the dispersant meets the requirements for the nucleation and growth of the nickel precursor product and the control of its morphology and particle size.

[0015] This invention utilizes a high-frequency ultrasonic dispersion device to transform an aqueous solution of a precipitant into a micro-nano aerosol formed by ultrafine nano-droplets, thus constructing a confined micro-region reaction environment. Compared to direct mixing or dropwise mixing of solutions, the micro-nano aerosols obtained after transformation by the high-frequency ultrasonic dispersion device have smaller particle sizes and higher specific surface areas, allowing for uniform distribution in the gaseous medium and providing more reaction and adsorption sites. Simultaneously, the device, in conjunction with high-pressure gas, enables long-distance transmission and dispersion, improving reaction efficiency and avoiding the inhomogeneity problems that may occur when mixing solutions. It also allows for effective control of the morphology and particle size of the material.

[0016] In this invention, oxalic acid or ammonium oxalate is used as a precipitant to obtain spherical nickel precursors, which are nickel oxalate. Vacuum calcination of nickel oxalate mainly results in the following reactions: Vacuum calcination inhibits oxidation, promotes the forward reaction, and enhances reduction, resulting in highly dispersed ultrafine spherical nickel powder. Furthermore, the vacuum environment reduces the partial pressure of oxygen in the system, preventing the generated metallic nickel from being re-oxidized to NiO, while also reducing the decomposition products of nickel oxalate, such as CO2, which inhibit the reduction reaction and ensure the stable existence of nickel in its elemental form. Secondly, the thermal decomposition temperature of nickel oxalate is significantly reduced under vacuum conditions, typically from over 400℃ at atmospheric pressure to around 300℃, reducing energy consumption while accelerating the decomposition reaction. Additionally, the carbon generated during calcination... Gases such as O and CO2 escape rapidly under vacuum, avoiding secondary reactions with metallic nickel particles and reducing impurity adsorption, thus increasing the purity of nickel powder to over 99.9%. In addition, compared to the complex process of traditional methods where nickel oxalate is decomposed to obtain nickel oxide, and then reduced with reducing agents such as hydrogen, carbon monoxide, or char to prepare metallic nickel powder, the vacuum roasting method can complete the decomposition of nickel oxalate to metallic nickel in one step, simplifying the process and reducing energy consumption. Furthermore, it eliminates the need for flammable gases such as hydrogen, reducing safety hazards, and the carbon dioxide produced during decomposition can be recycled, meeting clean production requirements.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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

[0032] Figure 1 This is a SEM image of the highly dispersed ultrafine spherical nickel powder prepared in Example 1 of the present invention.

[0033] 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.

[0034] Figure 3 The image shows the XRD pattern of the highly dispersed ultrafine spherical nickel powder prepared in Example 1 of this invention.

[0035] Figure 4 This is a SEM image of the highly dispersed ultrafine spherical nickel powder prepared in Example 2 of the present invention.

[0036] 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

[0037] Example 1

[0038] This embodiment includes the following steps:

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] Figure 3 The image shows the XRD pattern of the highly dispersed ultrafine spherical nickel powder prepared in this embodiment. Figure 3 The 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.

[0049] In this embodiment, the dispersant may also be hexadecyltrimethylammonium bromide or polyvinyl alcohol.

[0050] Example 2

[0051] This embodiment includes the following steps:

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] In this embodiment, the dispersant may also be hexadecyltrimethylammonium bromide or polyvinyl alcohol.

[0061] Example 3

[0062] This embodiment includes the following steps:

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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 140°C for 2 hours.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] In this embodiment, the dispersant may also be hexadecyltrimethylammonium bromide or polyvinyl alcohol.

[0072] 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, and prepare an aqueous solution of precipitant; wherein 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 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 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; 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 suspension of nickel-containing compounds 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, 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.

3. 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.

4. 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.

5. 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 vacuum filtration or centrifugation, and the drying is performed by vacuum drying or freeze drying.

6. 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.

7. 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.

8. 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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