Spherical ultrafine nickel powder and method for preparing the same

Abstract

The application provides a kind of spherical superfine nickel powder and its preparation method, the preparation method of spherical superfine nickel powder includes: (1) mixing soluble nickel salt, water-soluble binder and water, complexation reaction is generated, Ni 2+ Binder complex solution is obtained; (2) mixing submicron NiO powder, Ni 2+ Binder complex solution and solvent, then spray granulation is carried out, spherical NiO agglomerated particles are obtained; (3) spherical NiO agglomerated particles obtained are heated and reduced in reducing atmosphere, spherical superfine nickel powder is obtained. In the preparation method of spherical superfine nickel powder provided by the application, through the synergistic effect of Ni 2+ Binder in the process of granulation and reduction, while ensuring the forming strength of spherical agglomerated particles, spherical superfine nickel powder with high sphericity and small particle size is directly prepared by using the in-situ nucleation of Ni 2+ Binder and the physical barrier effect formed by pyrolysis of binder to inhibit morphology collapse and grain growth.

Description

Technical Field

[0001] This invention belongs to the field of metal powder preparation technology, and relates to a method for preparing spherical ultrafine nickel powder, and more particularly to a spherical ultrafine nickel powder and its preparation method. Background Technology

[0002] In existing technologies for preparing metal powders such as nickel, cobalt, and copper powders via chemical reduction, the reduction and spheroidization processes are usually independent. On the one hand, grain growth and morphology deterioration are commonly accompanied by reduction, making it difficult to directly obtain spherical metal powders with good morphology. On the other hand, to achieve powder spheroidization, the reduction product needs to undergo secondary heating and melting, which is not only energy-intensive but also prone to introducing oxidation and impurity contamination.

[0003] Spray granulation technology can prepare ultrafine powder into spherical agglomerates with controllable particle size, which is a method for preparing spherical powder. However, in the existing spray granulation-reduction process, the binder used in spray granulation only plays the role of particle bonding in the granulation stage and is removed by thermal decomposition in the subsequent reduction process. During the reduction process, the agglomerates are prone to problems such as morphological collapse and abnormal grain growth, making it difficult to directly obtain ultrafine spherical nickel powder with high sphericity and small particle size.

[0004] In summary, the existing spray granulation-reduction process for preparing nickel powder suffers from the problem that during the heating and reduction process, spherical agglomerates are prone to morphological collapse and abnormal grain growth, making it difficult to directly obtain spherical ultrafine nickel powder with high sphericity and small particle size. Therefore, it is crucial to develop a novel type of spherical ultrafine nickel powder and its preparation method. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a spherical ultrafine nickel powder and its preparation method. In the preparation method provided by the present invention, Ni... 2+ - The synergistic effect of the binder in the granulation and reduction processes ensures the molding strength of the spherical agglomerated particles while utilizing Ni 2+ In-situ nucleation and the physical barrier formed by the pyrolysis of the binder inhibited morphological collapse and grain growth, and spherical ultrafine nickel powder with high sphericity and small particle size was directly prepared.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing spherical ultrafine nickel powder, the method comprising: (1) Mix soluble nickel salt, water-soluble binder and water, so that the Ni released from the soluble nickel salt is ionized. 2+ It undergoes a complexation reaction with a water-soluble binder to obtain Ni. 2+ - Adhesive composite solution; (2) Mixing submicron NiO powder and Ni obtained in step (1) 2+ - The binder composite solution and solvent are mixed to obtain a slurry, and then the obtained slurry is spray-granulated to obtain spherical NiO agglomerated particles; (3) The spherical NiO agglomerates obtained in step (2) are heated and reduced in a reducing atmosphere, and then air-flow crushed in a protective atmosphere to obtain spherical ultrafine nickel powder.

[0007] In the preparation method provided by this invention, Ni in soluble nickel salt is used... 2+ Complexation and coordination with water-soluble binders enable Ni 2+ Uniformly anchored at the molecular scale within a polymer network formed by a water-soluble binder, thereby improving Ni 2+ Uniform dispersion of Ni on water-soluble binders 2+ It can be uniformly distributed among submicron NiO powders along with the water-soluble binder, which is beneficial to ensuring Ni during subsequent heating and reduction processes. 2+ Uniform in-situ reduction and nucleation optimizes the sphericity of spherical ultrafine nickel powder.

[0008] The Ni used in the preparation method provided by this invention 2+ - The binder composite solution played a synergistic role in both the spray granulation and subsequent heating reduction stages, achieving significantly better technical results than conventional binders; firstly, in spray granulation, Ni 2+ Ni in binder composite solution 2+ - The binder can bind submicron NiO powder into spherical agglomerates, providing sufficient mechanical strength to ensure that the agglomerates can withstand subsequent conveying, loading, and other processes; secondly, during the heating and reduction process, Ni... 2+ - Ni anchored in the binder 2+ During the reduction process, it is reduced in situ to metallic nickel and forms crystal nuclei in situ, growing together with the nickel grains generated by the reduction of submicron NiO powder. This in-situ nucleation effect can increase the nucleus density within the reduction system, refine the product grains, and simultaneously improve the morphological collapse of spherical NiO agglomerates caused by volume shrinkage during the reduction process; furthermore, Ni 2+ - The binder in the binder pyrolyzes during heating to form a carbon-containing structure, which can generate a physical barrier effect through the interfacial interaction with nickel grains, further inhibiting the growth of nickel grains.

[0009] In summary, in the preparation method provided by this invention, Ni 2+ - The synergistic effect of the binder in the granulation and reduction processes ensures the molding strength of the spherical agglomerated particles while utilizing Ni 2+In-situ nucleation and the physical barrier formed by the pyrolysis of the binder inhibited morphological collapse and grain growth, and spherical ultrafine nickel powder with high sphericity and small particle size was directly prepared.

[0010] In some embodiments, the soluble nickel salt in step (1) includes any one or a combination of at least two of nickel nitrate, nickel acetate, nickel sulfate, or nickel chloride. Typical but non-limiting combinations include a combination of nickel nitrate and nickel acetate, a combination of nickel sulfate and nickel chloride, a combination of nickel acetate and nickel sulfate, a combination of nickel nitrate, nickel acetate, and nickel sulfate, or a combination of nickel nitrate, nickel sulfate, and nickel chloride.

[0011] In some embodiments, the water-soluble binder in step (1) comprises a component that can react with Ni 2+ Functional groups that undergo complexation.

[0012] In some embodiments, the water-soluble binder in step (1) includes polyvinyl alcohol (PVA) and / or sodium carboxymethyl cellulose (CMC-Na).

[0013] In this invention, when the water-soluble binder includes polyvinyl alcohol, the hydroxyl groups on the polyvinyl alcohol molecular chain can react with Ni. 2+ A network reaction occurs.

[0014] In some embodiments, during the mixing in step (1), Ni in the soluble nickel salt 2+ The molar ratio of the repeating unit in the water-soluble adhesive is (0.05~0.5):1, for example, it can be 0.05:1, 0.08:1, 0.10:1, 0.15:1, 0.20:1, 0.25:1, 0.30:1, 0.35:1, 0.45:1 or 0.50:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0015] In some embodiments, the mixing in step (1) includes: initially mixing a water-soluble binder with water to obtain an initial mixture with a mass concentration of 1wt% to 5wt%; then mixing a soluble nickel salt with the obtained initial mixture to obtain a mixed solution.

[0016] In this invention, the initial mixture obtained after initial mixing has a mass concentration of 1wt% to 5wt%, for example, it can be 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, or 5wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] In some embodiments, the remixing method includes stirring.

[0018] In some embodiments, the temperature of the complexation reaction in step (1) is 60°C to 80°C and the time is 1h to 3h.

[0019] In this invention, the temperature of the complexation reaction in step (1) is 60℃~80℃, for example, it can be 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃ or 80℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] In this invention, the complexation reaction time in step (1) is 1h to 3h, for example, it can be 1.0h, 1.2h, 1.4h, 1.6h, 2.0h, 2.2h, 2.6h, 2.8h or 3.0h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] In some embodiments, stirring is performed during the complexation reaction described in step (1).

[0022] In some embodiments, the method for preparing the submicron NiO powder in step (2) includes: using nickel nitrate or nickel sulfate as raw materials, and preparing the submicron NiO powder by chemical precipitation or spray pyrolysis.

[0023] In some embodiments, the D50 particle size of the submicron NiO powder in step (2) is 200nm~600nm, for example, it can be 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm or 600nm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] In some implementations, the mixing method in step (2) includes ball milling and / or stirring.

[0025] In some embodiments, the solvent in step (2) includes water.

[0026] In some embodiments, the solid content of the slurry in step (2) is 60wt% to 80wt%, for example, it can be 60wt%, 62wt%, 64wt%, 66wt%, 68wt%, 70wt%, 72wt%, 74wt%, 76wt%, 78wt% or 80wt%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0027] In some embodiments, the D50 particle size of the spherical NiO agglomerates obtained in step (2) is 1 μm to 5 μm, for example, it can be 1.0 μm, 1.2 μm, 1.8 μm, 2.0 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3.0 μm, 3.4 μm, 3.6 μm, 4.0 μm, 4.4 μm, 4.8 μm or 5.0 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0028] In some embodiments, the reducing atmosphere in step (3) includes a reducing atmosphere composed of reducing gases, or a reducing atmosphere composed of reducing gases and protective gases.

[0029] In some embodiments, in a reducing atmosphere composed of a reducing gas and a protective gas, the volume fraction of the reducing gas is not less than 50%, for example, it can be 50%, 55%, 60%, 70%, 75%, 80%, 90%, 95% or 100%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0030] In some embodiments, the heating reduction in step (3) includes sequential heating and holding, wherein the holding temperature is 400℃~600℃ and the holding time is 1h~4h.

[0031] In this invention, the insulation temperature is 400℃~600℃, for example, it can be 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃ or 600℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] In this invention, the heat preservation time is 1h to 4h, for example, it can be 1.0h, 1.5h, 2.0h, 2.5h, 3.0h, 3.5h or 4.0h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] In some embodiments, the heating rate is 2°C / min to 10°C / min, for example, it can be 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min or 10°C / min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0034] In some embodiments, after the heating and reduction in step (3), the furnace is cooled to 5°C to 40°C. For example, the values ​​may be 5°C, 8°C, 15°C, 18°C, 20°C, 22°C, 28°C, 30°C, 32°C, 35°C, 38°C or 40°C, but are not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] In some embodiments, the protective atmosphere in step (3) includes nitrogen and / or an inert gas, the inert gas including any one or a combination of at least two of argon, helium or neon, typical but non-limiting combinations including a combination of argon and helium, a combination of helium and neon, a combination of argon and neon, or a combination of argon, helium and neon.

[0036] In a second aspect, the present invention provides a spherical ultrafine nickel powder, wherein the spherical ultrafine nickel powder is obtained by the preparation method described in the first aspect.

[0037] In some embodiments, the D50 particle size of the spherical ultrafine nickel powder is 0.6 μm to 0.8 μm, for example, it can be 0.60 μm, 0.62 μm, 0.64 μm, 0.66 μm, 0.68 μm, 0.70 μm, 0.72 μm, 0.74 μm, 0.76 μm, 0.78 μm or 0.80 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0038] In some embodiments, the sphericity of the spherical ultrafine nickel powder is not less than 0.90, for example, it can be 0.90, 0.91, 0.92, 0.94, 0.95, 0.96, 0.99 or 1.00, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0039] In some embodiments, the purity of the spherical ultrafine nickel powder is ≥99.5%, for example, it can be 99.5%, 99.6%, 99.7%, 99.9% or 100%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0040] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0041] Compared with the prior art, the present invention has the following beneficial effects: (1) In the preparation method provided by the present invention, Ni in soluble nickel salt is used. 2+ Complexation and coordination with water-soluble binders enable Ni 2+Uniformly anchored at the molecular scale within a polymer network formed by a water-soluble binder, thereby improving Ni 2+ Uniform dispersion of Ni on water-soluble binders 2+ It can be uniformly distributed among submicron NiO powders along with the water-soluble binder, which is beneficial to ensuring Ni during subsequent heating and reduction processes. 2+ Uniform in-situ reduction and nucleation optimizes the sphericity of spherical ultrafine nickel powder; (2) In the preparation method provided by the present invention, the Ni used 2+ - The binder composite solution played a synergistic role in both the spray granulation and subsequent heating reduction stages, achieving significantly better technical results than conventional binders; firstly, in spray granulation, Ni 2+ Ni in binder composite solution 2+ - The binder can bind submicron NiO powder into spherical agglomerates, providing sufficient mechanical strength to ensure that the agglomerates can withstand subsequent conveying, loading, and other processes; secondly, during the heating and reduction process, Ni... 2+ - Ni anchored in the binder 2+ During the reduction process, it is reduced in situ to metallic nickel and forms crystal nuclei in situ, growing together with the nickel grains generated by the reduction of submicron NiO powder. This in-situ nucleation effect can increase the nucleus density within the reduction system, refine the product grains, and simultaneously improve the morphological collapse of spherical NiO agglomerates caused by volume shrinkage during the reduction process; furthermore, Ni 2+ - The binder in the binder pyrolyzes during heating to form a carbon-containing structure, which can generate a physical barrier effect through the interfacial interaction with nickel grains, further inhibiting the growth of nickel grains; (3) In the preparation method provided by the present invention, Ni 2+ - The synergistic effect of the binder in the granulation and reduction processes ensures the molding strength of the spherical agglomerated particles while utilizing Ni 2+ In-situ nucleation and the physical barrier formed by the pyrolysis of the binder inhibited morphological collapse and grain growth, and spherical ultrafine nickel powder with high sphericity and small particle size was directly prepared. Detailed Implementation

[0042] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0043] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0044] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0045] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0046] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0047] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0048] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0049] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0050] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0051] Example 1 This embodiment provides a method for preparing spherical ultrafine nickel powder, the preparation method being as follows: (1) Add water-soluble binder (polyvinyl alcohol) to water to obtain a preliminary mixture with a mass concentration of 3wt%; then mix soluble nickel salt (nickel nitrate) with the obtained preliminary mixture by stirring to obtain a mixed solution; stir the obtained mixed solution at 70℃ for 2 hours to allow the Ni from the soluble nickel salt to ionize. 2+ It undergoes a complexation reaction with a water-soluble binder to obtain Ni. 2+ - Adhesive composite solution; During the remixing, the Ni content in the soluble nickel salt is controlled. 2+ The molar ratio of repeating units in the water-soluble binder in the initial mixture is 0.2:1; (2) Using nickel nitrate as raw material, submicron NiO powder with a D50 particle size of 350 nm was prepared by spray pyrolysis. By stirring and mixing submicron NiO powder and the Ni obtained in step (1) 2+ - A binder composite solution and water were mixed to obtain a slurry with a solid content of 70 wt%. The obtained slurry was then spray-granulated to obtain spherical NiO agglomerates with a D50 particle size of 3 μm. (3) In a reducing atmosphere (a reducing atmosphere composed of H2 and Ar, with a volume fraction of H2 of 80%), the spherical NiO agglomerates obtained in step (2) are heated to 450°C at a rate of 5°C / min and held for 2.5h. Then, they are cooled to 25°C in the furnace and then subjected to airflow crushing in a nitrogen atmosphere to obtain spherical ultrafine nickel powder.

[0052] Example 2 This embodiment provides a method for preparing spherical ultrafine nickel powder, the preparation method being as follows: (1) Add water-soluble binder (sodium carboxymethyl cellulose) to water to obtain a preliminary mixture with a mass concentration of 1.5 wt%; then mix soluble nickel salt (nickel sulfate) with the obtained preliminary mixture by stirring to obtain a mixed solution; stir the obtained mixed solution at 60°C for 3 hours to allow the Ni from the soluble nickel salt to ionize. 2+ It undergoes a complexation reaction with a water-soluble binder to obtain Ni. 2+ - Adhesive composite solution; During the remixing, the Ni content in the soluble nickel salt is controlled. 2+ The molar ratio of repeating units in the water-soluble binder in the initial mixture is 0.1:1; (2) Using nickel sulfate as raw material, submicron NiO powder with a D50 particle size of 200 nm was prepared by chemical precipitation method; Submicron NiO powder and Ni obtained in step (1) are mixed by ball milling and / or stirring.2+ - A binder composite solution and water were mixed to obtain a slurry with a solid content of 65wt%. The obtained slurry was then spray-granulated to obtain spherical NiO agglomerates with a D50 particle size of 1μm. (3) In a reducing atmosphere (a reducing atmosphere composed of H2 and Ar, with a volume fraction of H2 of 60%), the spherical NiO agglomerates obtained in step (2) are heated to 400°C at a rate of 2°C / min and held for 4 hours. Then, they are cooled to 5°C in the furnace and then subjected to airflow crushing in a nitrogen atmosphere to obtain spherical ultrafine nickel powder.

[0053] Example 3 This embodiment provides a method for preparing spherical ultrafine nickel powder, the preparation method being as follows: (1) Add water-soluble binder (polyvinyl alcohol) to water to obtain a preliminary mixture with a mass concentration of 5 wt%; then mix soluble nickel salt (nickel nitrate) with the obtained preliminary mixture by stirring to obtain a mixed solution; stir the obtained mixed solution at 80°C for 1 h to allow the Ni from the soluble nickel salt to ionize. 2+ It undergoes a complexation reaction with a water-soluble binder to obtain Ni. 2+ - Adhesive composite solution; During the remixing, the Ni content in the soluble nickel salt is controlled. 2+ The molar ratio of repeating units in the water-soluble binder in the initial mixture is 0.5:1; (2) Using nickel nitrate as raw material, submicron NiO powder with a D50 particle size of 600 nm was prepared by spray pyrolysis. By stirring and mixing submicron NiO powder and the Ni obtained in step (1) 2+ - A binder composite solution and water were mixed to obtain a slurry with a solid content of 80wt%. The obtained slurry was then spray-granulated to obtain spherical NiO agglomerates with a D50 particle size of 5μm. (3) In a reducing atmosphere (a reducing atmosphere composed of H2 and Ar, with a volume fraction of H2 of 90%), the spherical NiO agglomerates obtained in step (2) are heated to 600°C at a rate of 10°C / min and held for 1 hour, then cooled to 40°C in the furnace, and then air-flow crushed in a nitrogen atmosphere to obtain spherical ultrafine nickel powder.

[0054] Example 4 This embodiment provides a method for preparing spherical ultrafine nickel powder, except that in step (1) of the preparation method, the Ni content in the soluble nickel salt is controlled. 2+ Except for the molar ratio of repeating units in the water-soluble binder in the initial mixture being 0.02:1, everything else is the same as in Example 1.

[0055] Example 5 This embodiment provides a method for preparing spherical ultrafine nickel powder, except that in step (1) of the preparation method, the Ni content in the soluble nickel salt is controlled. 2+ Except for the molar ratio of repeating units in the water-soluble binder in the initial mixture being 0.8:1, everything else is the same as in Example 1.

[0056] Example 6 This embodiment provides a method for preparing spherical ultrafine nickel powder. Except for step (2) of the preparation method, in which a slurry with a solid content of 40 wt% is obtained, the rest is the same as in Example 1.

[0057] Example 7 This embodiment provides a method for preparing spherical ultrafine nickel powder. Except for step (2) of the preparation method, in which a slurry with a solid content of 90 wt% is obtained, the rest are the same as in Example 1.

[0058] Example 8 This embodiment provides a method for preparing spherical ultrafine nickel powder. Except for step (2) of the preparation method, in which spherical NiO agglomerated particles with a D50 particle size of 0.8 μm are obtained after spray granulation, the rest is the same as in Example 1.

[0059] Example 9 This embodiment provides a method for preparing spherical ultrafine nickel powder. Except for step (2) of the preparation method, in which spherical NiO agglomerated particles with a D50 particle size of 10 μm are obtained after spray granulation, the rest are the same as in Example 1.

[0060] Example 10 This embodiment provides a method for preparing spherical ultrafine nickel powder. Except for step (3) of the preparation method, in which the final temperature of heating the spherical NiO agglomerates obtained in step (2) is 300°C, that is, the holding temperature is 300°C, the rest is the same as in embodiment 1.

[0061] Example 11 This embodiment provides a method for preparing spherical ultrafine nickel powder. Except for step (3) of the preparation method, in which the final temperature of heating the spherical NiO agglomerates obtained in step (2) is 800℃, that is, the holding temperature is 800℃, the rest is the same as in Example 1.

[0062] Comparative Example 1 This comparative example provides a method for preparing nickel powder, except that step (1) of the preparation method is omitted, which involves "further mixing the soluble nickel salt (nickel nitrate) with the obtained initial mixture to obtain a mixed solution, and stirring the obtained mixed solution at 70°C for 2 hours to allow the soluble nickel salt to ionize into Ni." 2+ It undergoes a complexation reaction with a water-soluble binder to obtain Ni.2+ - Binder composite solution", and in step (2) "Ni obtained in step (1) 2+ Except for replacing “adhesive composite solution” with “initial mixture obtained in step (1)”, everything else is the same as in Example 1.

[0063] Comparative Example 2 This comparative example provides a method for preparing nickel powder, except that step (1) of the preparation method is omitted, and the "Ni obtained in step (1)" in step (2) is... 2+ Except for replacing “adhesive composite solution” with “a 3 wt% polyvinylpyrrolidone aqueous solution”, everything else is the same as in Example 1.

[0064] Nickel powder was prepared using the methods provided in the above embodiments and comparative examples. The sphericity, D50 particle size, and purity of the prepared nickel powder were tested. The sphericity was tested using a field emission scanning electron microscope, and the sphericity of the nickel powder is shown in Table 1. The D50 particle size was tested using a laser particle size analyzer, and the D50 particle size of the nickel powder is shown in Table 1. The purity was tested using an inductively coupled plasma atomic emission spectrometer to determine the content of impurity elements (excluding O) in the sample, and the purity of the nickel powder was calculated by the difference method, and the purity of the nickel powder is shown in Table 1.

[0065] Table 1 From Table 1, we can obtain: (1) The nickel powder prepared by the method of preparing spherical ultrafine nickel powder provided in Examples 1 to 3 has high sphericity, small particle size and high purity; (2) By comparing Example 1 with Examples 4 and 5, it can be seen that in the preparation method of spherical ultrafine nickel powder provided by the present invention, the Ni in the soluble nickel salt in step (1) 2+ When the molar ratio of repeating units in the water-soluble binder is (0.05~0.5):1, the nickel powder obtained by the above preparation method has better overall performance. This is because when the molar ratio is in this range, Ni... 2+ The anchoring density on the molecular chain of the water-soluble binder is moderate, which can provide sufficient in-situ crystal nuclei for subsequent reduction, and also ensure the physical barrier effect of the binder forming carbon-containing structures during the heating process. (3) By comparing Example 1 with Examples 6 and 7, it can be seen that in the preparation method of spherical ultrafine nickel powder provided by the present invention, when the solid content of the slurry obtained in step (2) is 60wt%~80wt%, the nickel powder obtained by the preparation method has better comprehensive performance. This is because the viscosity and fluidity of the slurry in this solid content range are better. Combined with spray granulation, it is more conducive to forming spherical NiO agglomerates of uniform size, which is more conducive to obtaining spherical ultrafine nickel powder. (4) By comparing Example 1 with Examples 8 and 9, it can be seen that in the preparation method of spherical ultrafine nickel powder provided by the present invention, when the D50 particle size of the spherical NiO agglomerates obtained in step (2) is 10μm~50μm, the nickel powder obtained by the preparation method has better comprehensive performance. This is because the spherical NiO agglomerates in this particle size range have better internal mass transfer and heat transfer uniformity, which is beneficial to improving the morphological collapse caused by volume shrinkage during the heating and reduction process of spherical NiO agglomerates. (5) By comparing Example 1 with Examples 10 and 11, it can be seen that in the preparation method of spherical ultrafine nickel powder provided by the present invention, when the final temperature of heating in step (3), that is, the temperature of heat preservation, is 400℃~800℃, the nickel powder obtained by the preparation method has better comprehensive performance. This is because when the temperature of heat preservation is in this range, NiO can be fully reduced to metallic nickel, and the carbon-containing structure formed by the pyrolysis of the binder can stably play a physical barrier role. (6) As can be seen from the comparison between Example 1 and Comparative Examples 1 and 2, in the preparation method provided by the present invention, Ni in the soluble nickel salt is used to prepare the product. 2+ Complexation coordination with water-soluble binders enables Ni 2+ Uniformly anchored at the molecular scale within a polymer network formed by a water-soluble binder, thereby improving Ni 2+ Uniform dispersion of Ni on water-soluble binders 2+ It can be uniformly distributed among submicron NiO powders along with the water-soluble binder, which is beneficial to ensuring Ni during subsequent heating and reduction processes. 2+ Uniform in-situ reduction and nucleation optimizes the sphericity of spherical ultrafine nickel powder; The Ni used in the preparation method provided by this invention 2+ - The binder composite solution played a synergistic role in both the spray granulation and subsequent heating reduction stages, achieving significantly better technical results than conventional binders; firstly, in spray granulation, Ni 2+ Ni in binder composite solution 2+ - The binder can bind submicron NiO powder into spherical agglomerates, providing sufficient mechanical strength to ensure that the agglomerates can withstand subsequent conveying, loading, and other processes; secondly, during the heating and reduction process, Ni... 2+ - Ni anchored in the binder2+ During the reduction process, it is reduced in situ to metallic nickel and forms crystal nuclei in situ, growing together with the nickel grains generated by the reduction of submicron NiO powder. This in-situ nucleation effect can increase the nucleus density within the reduction system, refine the product grains, and simultaneously improve the morphological collapse of spherical NiO agglomerates caused by volume shrinkage during the reduction process; furthermore, Ni 2+ - The binder in the binder pyrolyzes during heating to form a carbon-containing structure, which can generate a physical barrier effect through the interfacial interaction with nickel grains, further inhibiting the growth of nickel grains; In summary, in the preparation method provided by this invention, Ni 2+ - The synergistic effect of the binder in the granulation and reduction processes ensures the molding strength of the spherical agglomerated particles while utilizing Ni 2+ In-situ nucleation and the physical barrier formed by the pyrolysis of the binder inhibited morphological collapse and grain growth, and spherical ultrafine nickel powder with high sphericity and small particle size was directly prepared.

[0066] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing spherical ultrafine nickel powder, characterized in that, The preparation method includes: (1) Mix soluble nickel salt, water-soluble binder and water, so that the Ni released from the soluble nickel salt is ionized. 2+ It undergoes a complexation reaction with a water-soluble binder to obtain Ni. 2+ - Adhesive composite solution; (2) Mixing submicron NiO powder and Ni obtained in step (1) 2+ - The binder composite solution and solvent are mixed to obtain a slurry, and then the obtained slurry is spray-granulated to obtain spherical NiO agglomerated particles; (3) The spherical NiO agglomerates obtained in step (2) are heated and reduced in a reducing atmosphere, and then air-flow crushed in a protective atmosphere to obtain spherical ultrafine nickel powder.

2. The preparation method according to claim 1, characterized in that, The soluble nickel salt in step (1) includes any one or a combination of at least two of nickel nitrate, nickel acetate, nickel sulfate, or nickel chloride; And / or, the water-soluble binder of step (1) comprises a component that can react with Ni 2+ Functional groups that undergo complexation; And / or, the water-soluble binder in step (1) includes polyvinyl alcohol and / or sodium carboxymethyl cellulose.

3. The preparation method according to claim 1, characterized in that, In the mixing described in step (1), Ni in the soluble nickel salt 2 + The molar ratio of repeating units in the water-soluble adhesive is (0.05~0.5):

1.

4. The preparation method according to claim 1, characterized in that, The mixing in step (1) includes: initially mixing water-soluble binder and water to obtain an initial mixture with a mass concentration of 1wt%~5wt%; then mixing soluble nickel salt with the obtained initial mixture to obtain a mixed solution.

5. The preparation method according to claim 1, characterized in that, The temperature for the complexation reaction in step (1) is 60℃~80℃, and the time is 1h~3h; And / or, stirring is performed during the complexation reaction described in step (1).

6. The preparation method according to claim 1, characterized in that, The D50 particle size of the submicron NiO powder in step (2) is 200nm~600nm.

7. The preparation method according to claim 1, characterized in that, The solid content of the slurry in step (2) is 60wt%~80wt%; And / or, the D50 particle size of the spherical NiO agglomerates obtained in step (2) is 1 μm to 5 μm.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The heating and reduction in step (3) includes sequential heating and holding, wherein the holding temperature is 400℃~600℃ and the holding time is 1h~4h.

9. A spherical ultrafine nickel powder, characterized in that, The spherical ultrafine nickel powder is obtained by the preparation method according to any one of claims 1 to 8.

10. The spherical ultrafine nickel powder according to claim 9, characterized in that, The spherical ultrafine nickel powder has a D50 particle size of 0.6μm~0.8μm; And / or, the sphericity of the spherical ultrafine nickel powder is not less than 0.90; And / or, the purity of the spherical ultrafine nickel powder is ≥99.5%.

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