Spherical nickel oxide material and method for producing the same

Abstract

The application provides a spherical nickel oxide material and a preparation method thereof. The preparation method comprises the following steps: S1, mixing raw materials including a nickel salt solution and an alkali solution to obtain a first mixed solution; S2, mixing raw materials including the first mixed solution, a surfactant and a dispersant to obtain a second mixed solution; S3, sequentially performing third mixing and aging reaction on raw materials including the second mixed solution and an oxalate solution to obtain a third mixed solution; and S4, sequentially performing centrifugation, washing, drying and calcination on the third mixed solution to obtain the spherical nickel oxide material; wherein the pH value of the first mixed solution is 5.0-6.8; and the calcination temperature is 300-550 DEG C. The nickel oxide material with needle-like spherical morphology and uniform particle size can be obtained through the above preparation method, so that the surface activity and specific surface energy of the nickel oxide material are enhanced, and the nickel oxide material is better applied in the field of gas-sensitive materials and the like.

Description

Technical Field

[0001] This invention relates to the field of nickel oxide material preparation technology, and more specifically, to a spherical nickel oxide material and its preparation method. Background Technology

[0002] Nickel oxide is mainly used industrially as a raw material for preparing battery electrodes, catalysts, semiconductors, nickel-zinc ferrites, glass and ceramic colorants, etc. The morphology of its particles largely determines the performance of the powder. Nickel oxide is low in cost and possesses a tunable octet structure in its 3d orbitals, making it an effective catalyst for electrochemical nitrogen reduction reactions under mild conditions. Embedding or doping highly conductive metals with catalytic properties onto nickel oxide is an effective method to obtain high-performance electrocatalysts. Meanwhile, nickel oxide is a p-type oxide semiconductor. Due to the formation of a p-type semiconductor at high temperatures due to metal ion vacancies, its resistivity at high temperatures (above 600℃) is related to the partial pressure of oxygen in the atmosphere; that is, the higher the oxygen concentration, the lower the resistivity. The relationship between the resistivity of nickel oxide materials and oxygen molecule concentration can be used to detect oxygen concentration. The gas-sensitive properties of nickel oxide materials are also related to their particle size; the smaller the particle size, the larger the specific surface area. Similarly, the larger the contact area of ​​the measured gas, the higher the detection sensitivity and the shorter the response and recovery time. Therefore, using ultrafine nickel oxide materials to prepare resistive gas-sensitive materials can significantly improve their performance.

[0003] Chinese patent application CN117779054A discloses a method for electrochemically synthesizing nickel oxide. This method uses at least one of nickel particles, nickel fibers, nickel films, nickel sheets, and nickel foam as a nickel precursor. The nickel precursor simultaneously serves as both the cathode and anode and is subjected to voltage pulse oxidation treatment in an electrolyte to obtain nickel oxide. The preparation process is complex, and the reactants, such as nickel particles and nickel films, require specific morphologies, thus placing certain requirements on the raw material form. Furthermore, the electrochemical synthesis method is energy-intensive.

[0004] Chinese patent application CN117843046A discloses a method for preparing high-purity nano-nickel oxide. The method involves using a multiphase interface reactor with a surfactant to obtain a nano-nickel oxide precursor slurry using a nickel salt solution and a precipitant solution. After aging the nano-nickel oxide precursor slurry, it is filtered and washed to obtain a nano-nickel oxide precursor filter cake. This filter cake is then dried in an oven and calcined in a muffle furnace to obtain granular nano-nickel oxide powder.

[0005] Therefore, there is an urgent need to develop a method for preparing spherical ultrafine nickel oxide powder materials with simple preparation process and conditions. Summary of the Invention

[0006] The main objective of this invention is to provide a spherical nickel oxide material and its preparation method, so as to solve the problems of complex preparation process and reaction conditions and uneven spherical nickel oxide particles obtained in the prior art.

[0007] To achieve the above objectives, according to one aspect of the present invention, a method for preparing spherical nickel oxide material is provided, the method comprising: step S1, first mixing raw materials including a nickel salt solution and an alkaline solution to obtain a first mixture; step S2, second mixing raw materials including the first mixture, a surfactant, and a dispersant to obtain a second mixture; step S3, sequentially subjecting raw materials including the second mixture and an oxalate solution to a third mixing and aging reaction to obtain a third mixture; and step S4, sequentially centrifuging, washing, drying, and calcining the third mixture to obtain spherical nickel oxide material; wherein the pH value of the first mixture is 5.0–6.8; and the calcination temperature is 300–550°C.

[0008] Furthermore, step S2 above also includes: first stirring the raw materials including the first mixture and the surfactant to obtain the fourth mixture; second stirring the raw materials including the fourth mixture and the dispersant to obtain the second mixture; wherein the rotation speed of the first stirring and the second stirring are each independently 100-500 r / min, and the stirring time of the first stirring and the second stirring are each independently 5-40 min.

[0009] Further, in step S2 above, the mass ratio of the surfactant to the first mixture is 0.2 to 1:1000; and / or, the surfactant is a sulfonic acid surfactant and / or a sulfate surfactant; and / or, the mass ratio of the dispersant to the first mixture is 0.05 to 1:1000; and / or, the dispersant is a polyethylene glycol dispersant and / or a human polycarboxylate dispersant.

[0010] Further, in step S1 above, the nickel salt solution is selected from any one or more of nickel nitrate solution, nickel chloride solution, and nickel sulfate solution; the molar concentration of the nickel salt solution is 0.02 to 0.1 mol / L based on the nickel ions in the nickel salt solution; and / or, the alkaline solution is selected from any one or more of ammonia water, sodium hydroxide solution, and potassium hydroxide solution.

[0011] Furthermore, in step S1 above, the first mixing is carried out under ultrasonic conditions by a third stirring, wherein the temperature of the third stirring is 20-55°C and the speed of the third stirring is 100-500 r / min.

[0012] Furthermore, in step S3 above, the aging reaction temperature is 20–55°C, and the aging reaction time is 30–120 min.

[0013] Further, in step S3 above, the oxalate solution is selected from any one or more of sodium oxalate solution, ammonium oxalate solution, and potassium oxalate solution; the molar concentration of the oxalate solution is 0.05 to 1 mol / L based on the oxalate ions in the oxalate solution; and / or, based on the oxalate ions in the oxalate solution and the nickel ions in the nickel salt solution, the molar ratio of the oxalate solution to the nickel salt solution is 0.5 to 2:1.

[0014] Furthermore, step S3 above also includes adding the oxalate solution to the second mixture using a peristaltic pump, the pump speed being 1-2 mL / min; and / or performing the second mixing by a fourth stirring, the stirring speed being 100-300 r / min, and the stirring time being 15-120 min.

[0015] Further, in step S4 above, the mixture after centrifugation is washed sequentially with water and ethanol respectively; and / or, the drying temperature is 40-70°C and the drying time is 480-720 min; and / or, the calcination time is 300-720 min.

[0016] According to another aspect of the present invention, a spherical nickel oxide material is provided, which is prepared by the above-described preparation method, and the D50 particle size of the spherical nickel oxide material is ≤15μm.

[0017] By applying the technical solution of this invention, a needle-like spherical nickel oxide material with uniform particle size can be prepared using the preparation method of this application. This enhances the surface activity and specific surface energy of the spherical nickel oxide material, thus enabling its better application in fields such as gas-sensitive materials. Specifically, in step S1, adding an alkaline solution can adjust the pH value of the first mixture and create a slightly acidic reaction environment. In this reaction environment, the surface activity energy and interfacial tension of the solution are low, and the spherical nickel oxide structure has low surface activity energy, making it easier to form in this environment. Furthermore, according to Young's equation, the lower the interfacial tension, the more favorable it is for the formation of a spherical structure. At the same time, in the above reaction environment, the reaction rate is relatively mild, which is conducive to uniform nucleation and regulation of ion behavior, thereby helping to better control the morphology of the nickel oxide material to be spherical, and making the particle size and distribution of the nickel oxide material more uniform. The surfactant added in step S2 can adsorb onto the surface of the subsequently generated nickel oxalate precipitate particles to form a protective film, increasing the electrostatic repulsion between particles, thereby improving the dispersion effect and helping the subsequent nickel oxide to form a spherical structure. At the same time, the addition of a dispersant can reduce particle agglomeration through its electrostatic repulsion or steric hindrance. In step S3, oxalate ions in the oxalate solution react with nickel ions in the nickel salt solution in the second mixture to form nickel oxalate precipitate. In step S4, the nickel oxalate precipitate is obtained by centrifugation, impurities on the surface of the precipitate are removed by washing, and residual solvent is removed by drying. Finally, calcination is performed at a temperature controlled within the aforementioned range to promote the decomposition of nickel oxalate to obtain nickel oxide, while improving the morphology of the nickel oxide, resulting in a pure nickel oxide material with a spherical structure. Furthermore, the preparation method of this application is not only simple and easy to operate in terms of steps and preparation conditions, but also produces no harmful gases during the preparation process, thus eliminating the need for additional tail gas treatment steps. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 SEM images of the spherical nickel oxide material in Example 1 of this application are shown;

[0020] Figure 2 SEM images of the spherical nickel oxide material in Comparative Example 1 of this application are shown. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] As analyzed in the background section of this application, the existing technology has the problems of complex preparation process and reaction conditions for spherical nickel oxide and uneven spherical nickel oxide particles. In order to solve the above problems, this application provides a spherical nickel oxide material and its preparation method.

[0023] In a typical embodiment of this application, a method for preparing spherical nickel oxide material is provided. The method includes: step S1, mixing raw materials including a nickel salt solution and an alkaline solution to obtain a first mixture; step S2, mixing raw materials including the first mixture, a surfactant, and a dispersant to obtain a second mixture; step S3, sequentially mixing and aging raw materials including the second mixture and an oxalate solution to obtain a third mixture; and step S4, sequentially centrifuging, washing, drying, and calcining the third mixture to obtain spherical nickel oxide material; wherein the pH value of the first mixture is 5.0–6.8; and the calcination temperature is 300–550°C.

[0024] The preparation method of this application can prepare nickel oxide materials with needle-like spherical morphology and uniform particle size, thereby enhancing the surface activity and specific surface energy of spherical nickel oxide materials, and thus better applying them to fields such as gas-sensitive materials. Specifically, adding an alkaline solution in step S1 can adjust the pH value of the first mixture and form a slightly acidic reaction environment. In the above reaction environment, the surface activity energy and interfacial tension of the solution are low, and the spherical nickel oxide structure has low surface activity energy, so it is easier to form in this environment. Furthermore, according to Young's equation, the lower the interfacial tension, the more favorable it is for the formation of spherical structures. At the same time, in the above reaction environment, the reaction rate is relatively mild, which is conducive to uniform nucleation, regulating ion behavior, and thus helping to better control the morphology of the nickel oxide material to be spherical, while making the particle size and distribution of the nickel oxide material more uniform. The surfactant added in step S2 can adsorb on the surface of the subsequently generated nickel oxalate precipitate particles to form a protective film, increasing the electrostatic repulsion between particles, thereby improving the dispersion effect and helping the subsequent nickel oxide to form a spherical structure. At the same time, the addition of a dispersant can reduce particle agglomeration through its electrostatic repulsion or steric hindrance. In step S3, oxalate ions in the oxalate solution react with nickel ions in the nickel salt solution in the second mixture to form nickel oxalate precipitate. In step S4, the nickel oxalate precipitate is obtained by centrifugation, impurities on the surface of the precipitate are removed by washing, and residual solvent is removed by drying. Finally, calcination is performed at a temperature controlled within the aforementioned range to promote the decomposition of nickel oxalate to obtain nickel oxide, while improving the morphology of the nickel oxide, resulting in a pure nickel oxide material with a spherical structure. Furthermore, the preparation method of this application is not only simple and easy to operate in terms of steps and preparation conditions, but also produces no harmful gases during the preparation process, thus eliminating the need for additional tail gas treatment steps.

[0025] In one embodiment of this application, step S2 further includes: first stirring the raw materials comprising the first mixture and the surfactant to obtain a fourth mixture; and second stirring the raw materials comprising the fourth mixture and the dispersant to obtain a second mixture; wherein the rotation speed of the first stirring and the second stirring are each independently 100-500 r / min, preferably 200-350 r / min, and the stirring time of the first stirring and the second stirring are each independently 5-40 min, preferably 15-30 min.

[0026] Preferably controlling the rotation speed and time of the first and second stirrings within the above range helps the surfactant and dispersant to be fully dispersed in the nickel salt solution, resulting in a second mixture with uniform composition, which in turn helps to improve the uniformity and consistency of the morphology of nickel oxide particles in the subsequent aging reaction.

[0027] In one embodiment of this application, in step S2 above, the mass ratio of the surfactant to the first mixture is 0.2 to 1:1000, preferably 0.3 to 1:1000; and / or, the surfactant is a sulfonic acid surfactant and / or a sulfate surfactant; preferably, the sulfonic acid surfactant is sodium lignin sulfonate and / or lignin-based polyoxyethylene sulfonate, and preferably, the sulfate surfactant is sodium fatty alcohol polyoxyethylene ether sulfate or triethanolamine fatty alcohol polyoxyethylene ether sulfate; and / or, the mass ratio of the dispersant to the first mixture is 0.05 to 1:1000, preferably 0.1 to 0.5:1000; and / or, the dispersant is a polyethylene glycol dispersant and / or a human polycarboxylate dispersant.

[0028] Preferring a specific type of surfactant and a specific mass ratio of surfactant to the first mixture within the aforementioned range helps the surfactant to better adsorb onto the particle surface and form a protective film, thereby further increasing the electrostatic repulsion between particles. Similarly, preferring a specific type of dispersant and a specific mass ratio of dispersant to the first mixture within the aforementioned range helps to further reduce particle agglomeration, thereby improving the uniformity of the nickel oxide morphology.

[0029] Further optimization of the surfactant-dispersant mass ratio to 1-4:1 helps to improve the synergistic effect of the two, thereby further enhancing the dispersion effect and helping the nickel oxide to form a better spherical structure in the subsequent process.

[0030] In one embodiment of this application, in step S1 above, the nickel salt solution is selected from any one or more of nickel nitrate solution, nickel chloride solution, and nickel sulfate solution; the molar concentration of the nickel salt solution is 0.02 to 0.1 mol / L, preferably 0.05 to 0.1 mol / L, based on the nickel ions in the nickel salt solution; and / or, the alkaline solution is selected from any one or more of ammonia water, sodium hydroxide solution, and potassium hydroxide solution.

[0031] Preferring the type and molar concentration of the nickel salt solution within the above-mentioned range helps to better form nickel oxalate precipitate during the reaction with the oxalate solution. Preferring the type of alkaline solution within the above-mentioned range helps to better adjust the pH value and make the reaction environment slightly acidic, which is beneficial to obtaining spherical nickel oxide material.

[0032] In one embodiment of this application, in step S1 above, the first mixing is carried out by a third stirring under ultrasonic conditions, wherein the temperature of the third stirring is 20-55°C, preferably 25-55°C, and the speed of the third stirring is 100-500 r / min, preferably 200-350 r / min.

[0033] It is preferable to control the temperature and stirring speed of the third stirring within the above range. Combined with the use of ultrasound, this helps to effectively promote the uniform mixing of the alkaline solution and the nickel salt solution, while maintaining the pH stability of the reaction system.

[0034] All the above mixing was carried out under ultrasonic conditions.

[0035] In one embodiment of this application, in step S3 above, the aging reaction temperature is 20-55°C, preferably 25-55°C, and the aging reaction time is 30-120 min, preferably 60-120 min.

[0036] Preferably controlling the temperature and time of the aging reaction within the above range helps to promote the precipitation reaction between the nickel salt solution and the oxalate solution, forming nickel oxalate precipitate.

[0037] In one embodiment of this application, in step S3 above, the oxalate solution is selected from any one or more of sodium oxalate solution, ammonium oxalate solution, and potassium oxalate solution; the molar concentration of the oxalate solution is 0.05 to 1 mol / L, preferably 0.15 to 0.45 mol / L, based on the oxalate ions in the oxalate solution and the nickel ions in the nickel salt solution; and / or, the molar ratio of the oxalate solution to the nickel salt solution is 0.5 to 2:1, preferably 0.8 to 1.7:1, based on the oxalate ions in the oxalate solution and the nickel ions in the nickel salt solution.

[0038] Preferably, the type and molar concentration of the oxalate solution are within the above-mentioned range, which facilitates the full reaction of oxalate ions and nickel ions to form nickel oxalate. Precise control of morphology and size is achieved during the reaction process. Preferably, controlling the molar ratio of the oxalate solution to the nickel salt solution is within the above-mentioned range, which helps to form a fine needle-like structure, thereby allowing the nickel oxide to further evolve into the desired spherical structure in subsequent processes while maintaining the needle-like characteristics, thus achieving high specific surface area and high activity.

[0039] In one embodiment of this application, step S3 further includes adding oxalate solution to the second mixture using a peristaltic pump, wherein the peristaltic pump has a propulsion speed of 1 to 2 mL / min; and / or performing a second mixing by a fourth stirring, wherein the stirring speed is 100 to 300 r / min, preferably 150 to 250 r / min, and the stirring time is 15 to 120 min, preferably 30 to 90 min.

[0040] Using a peristaltic pump and controlling its propulsion speed within the aforementioned range helps the oxalate solution react with the nickel salt solution at a stable and uniform rate, mitigating the rapid local pH changes caused by the addition of a large amount of oxalate solution, thereby improving the morphological consistency and dimensional uniformity of the nickel oxide material. Controlling the speed and time of the fourth stirring action within the aforementioned range also helps to ensure uniform dispersion of the components in the mixture, promotes the full reaction of oxalate ions and nickel ions, and forms a well-dispersed nickel oxalate precipitate.

[0041] In one embodiment of this application, in step S4 above, the third mixture is washed sequentially with water and ethanol respectively; and / or, the drying temperature is 40-70°C, preferably 50-70°C, and the drying time is 480-720 min, preferably 500-720 min; and / or, the calcination time is 300-720 min, preferably 360-720 min.

[0042] The washing process described above is preferred as it helps to remove unreacted reagents, byproducts and impurities from the mixture after centrifugation. Water can wash away most of the water-soluble impurities, while ethanol helps to further clean the organic matter remaining on the surface of the mixture after centrifugation, especially residual surfactants and dispersants that are not easily soluble in the aqueous phase.

[0043] The preferred drying temperature and time, within the above range, help remove moisture from the washed material and reduce structural damage caused by moisture evaporation during subsequent calcination. The preferred calcination time, within the above range, helps to fully decompose nickel oxalate, yielding needle-like spherical ultrafine nickel oxide powder material.

[0044] In another typical embodiment of this application, a spherical nickel oxide material is provided, which is prepared by the above-described preparation method, and the D50 particle size of the spherical nickel oxide material is ≤15μm.

[0045] The nickel oxide material prepared by the above method has a spherical structure, a D50 particle size within the aforementioned range, and a uniform particle size distribution. This improves the surface activity and specific surface energy of the nickel oxide powder material, thus enabling its better application in fields such as gas-sensitive materials. The D50 particle size is the particle size corresponding to a cumulative particle size distribution percentage of 50% in the sample.

[0046] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0047] Example 1

[0048] Take 200 mL of nickel sulfate solution with a nickel ion molar concentration of 0.05 mol / L and place it in a 500 mL reactor. Stir for the third time at 40 °C and under ultrasonic conditions at a speed of 300 r / min. While stirring, add potassium hydroxide solution dropwise to obtain the first mixture and adjust the pH value of the first mixture to maintain it at 6.5.

[0049] Sodium lignosulfonate, a surfactant, was added to the first mixture and stirred at 300 rpm for 30 minutes to obtain a fourth mixture; wherein the mass ratio of surfactant to the first mixture was 0.6:1000. Polyethylene glycol, a dispersant, was then added to the fourth mixture and stirred at 300 rpm for 30 minutes to obtain a second mixture; wherein the mass ratio of dispersant to the first mixture was 0.5:1000.

[0050] 50 mL of ammonium oxalate solution with a molar concentration of 0.3 mol / L was measured and added dropwise to the second mixture using a peristaltic pump at a rate of 2.0 mL / min, so that the molar ratio of nickel ions to oxalate ions in the solution system was 0.67:1. Then, the mixture was stirred for 90 min at a speed of 250 r / min. After stirring was stopped, the mixture was aged at 40 °C for 120 min to obtain the third mixture.

[0051] The third mixture was centrifuged to obtain a centrifuged mixture, which was then washed three times with deionized water and five times with ethanol. The washed mixture was placed in a vacuum drying oven and dried at 70°C for 500 min. The dried mixture was then placed in a crucible and placed in a muffle furnace, where it was calcined at 500°C for 480 min and cooled with the furnace to obtain nickel oxide material. This nickel oxide material is a needle-like, spherical, ultrafine nickel oxide powder. SEM images showed that its morphology and particle size were uniform, with a narrow particle size distribution. Figure 1 As shown.

[0052] Example 2

[0053] Take 300 mL of nickel sulfate solution with a nickel ion molar concentration of 0.08 mol / L and place it in a 500 mL reactor. Stir for the third time at 50 °C and under ultrasonic conditions at a speed of 350 r / min. While stirring, add potassium hydroxide solution dropwise to obtain the first mixture and adjust the pH value of the first mixture to maintain it at 6.0.

[0054] Sodium lignosulfonate, a surfactant, was added to the first mixture and stirred at 350 rpm for 20 minutes to obtain a fourth mixture; wherein the mass ratio of surfactant to the first mixture was 0.6:1000. Polyethylene glycol, a dispersant, was then added to the fourth mixture and stirred at 350 rpm for 20 minutes to obtain a second mixture; wherein the mass ratio of dispersant to the first mixture was 1:1000.

[0055] 91 mL of ammonium oxalate solution with a molar concentration of 0.45 mol / L was measured and added dropwise to the second mixture using a peristaltic pump at a rate of 2.5 mL / min, so that the molar ratio of nickel ions to oxalate ions in the solution system was 0.59:1. Then, the mixture was stirred for a fourth time at a speed of 200 r / min for 30 min. After stirring was stopped, the mixture was aged at 50 °C for 90 min to obtain the third mixture.

[0056] The third mixture was centrifuged to obtain a centrifuged mixture, which was then washed three times with deionized water and five times with ethanol. The washed mixture was placed in a vacuum drying oven and dried at 50°C for 720 min. The dried mixture was then placed in a crucible and placed in a muffle furnace, where it was calcined at 550°C for 360 min and cooled with the furnace to obtain nickel oxide material. This nickel oxide material is a needle-like spherical ultrafine nickel oxide powder, with a predominantly spherical morphology.

[0057] Example 3

[0058] Take 300 mL of nickel sulfate solution with a nickel ion molar concentration of 0.02 mol / L and place it in a 500 mL reactor. Stir for the third time at 20 °C and under ultrasonic conditions at a speed of 100 r / min. While stirring, add potassium hydroxide solution dropwise to obtain the first mixture and adjust the pH value of the first mixture to maintain it at 5.0.

[0059] Sodium lignosulfonate, a surfactant, was added to the first mixture and stirred at 500 rpm for 5 minutes to obtain a fourth mixture; wherein the mass ratio of surfactant to the first mixture was 0.2:1000. Polyethylene glycol, a dispersant, was then added to the fourth mixture and stirred at 500 rpm for 5 minutes to obtain a second mixture; wherein the mass ratio of dispersant to the first mixture was 0.05:1000.

[0060] 60 mL of ammonium oxalate solution with a molar concentration of 0.05 mol / L was measured and added dropwise to the second mixture using a peristaltic pump at a rate of 2.5 mL / min, so that the molar ratio of nickel ions to oxalate ions in the solution system was 2:1. Then, the mixture was stirred for a fourth time at a speed of 200 r / min for 30 min. After stirring was stopped, the mixture was aged at 20 °C for 120 min to obtain the third mixture.

[0061] The third mixture was centrifuged to obtain a centrifuged mixture, which was then washed three times with deionized water and five times with ethanol. The washed mixture was placed in a vacuum drying oven and dried at 70°C for 480 min. The dried mixture was then placed in a crucible and placed in a muffle furnace, where it was calcined at 300°C for 720 min and cooled with the furnace to obtain nickel oxide material. This nickel oxide material is a needle-like spherical ultrafine nickel oxide powder, with a predominantly spherical morphology.

[0062] Example 4

[0063] The difference from Example 1 is that the pH value of the first mixture is 5.0, and spherical nickel oxide material is finally obtained.

[0064] Example 5

[0065] The difference from Example 1 is that the calcination temperature is 300°C, and spherical nickel oxide material is finally obtained.

[0066] Example 6

[0067] The difference from Example 1 is that the mass ratio of surfactant to first mixture is 1:1000, and spherical nickel oxide material is finally obtained.

[0068] Example 7

[0069] The difference from Example 1 is that the mass ratio of surfactant to first mixture is 0.1:1000, and spherical nickel oxide material is finally obtained.

[0070] Example 8

[0071] The difference from Example 1 is that the mass ratio of the dispersant to the first mixture is 1:1000, and spherical nickel oxide material is finally obtained.

[0072] Example 9

[0073] The difference from Example 1 is that the mass ratio of dispersant to the first mixture is 1.5:1000, and spherical nickel oxide material is finally obtained.

[0074] Example 10

[0075] The difference from Example 1 is that the aging reaction temperature is 55°C and the aging reaction time is 30 min, ultimately yielding spherical nickel oxide material.

[0076] Example 11

[0077] The difference from Example 1 is that the aging reaction temperature is 15°C and the aging reaction time is 130 min, ultimately yielding spherical nickel oxide material.

[0078] Example 12

[0079] The difference from Example 1 is that the volume of the nickel salt solution is 150 mL and the molar concentration is 0.1 mol / L, and the volume of the oxalate solution is 80 mL and the molar concentration is 0.094 mol / L, so that the molar ratio of oxalate ions to nickel ions in the second mixture is 0.5:1, and finally spherical nickel oxide material is obtained.

[0080] Example 13

[0081] The difference from Example 1 is that the volume of the nickel salt solution is 150 mL and the molar concentration is 0.1 mol / L, and the volume of the oxalate solution is 50 mL and the molar concentration is 0.12 mol / L, so that the molar ratio of oxalate ions to nickel ions in the second mixture is 0.4:1, and finally spherical nickel oxide material is obtained.

[0082] Example 14

[0083] The difference from Example 1 is that the oxalate solution was added dropwise to the second mixture using a peristaltic pump at a rate of 1.0 ml / min, followed by a fourth stirring at 100 r / min for 120 min. After stirring was stopped, an aging reaction was carried out to obtain the third mixture, and finally spherical nickel oxide material was obtained.

[0084] Example 15

[0085] The difference from Example 1 is that the oxalate solution was added dropwise to the second mixture using a peristaltic pump at a rate of 3 ml / min, followed by a fourth stirring at 400 r / min for 10 min. After stirring was stopped, an aging reaction was carried out to obtain the third mixture, and finally spherical nickel oxide material was obtained.

[0086] Comparative Example 1

[0087] The difference from Example 1 is that the pH value of the first mixture is 7.2, ultimately yielding an elliptical nickel oxide material, such as... Figure 2 As shown.

[0088] Comparative Example 2

[0089] The difference from Example 1 is that the calcination temperature is 650°C, and spherical nickel oxide material is finally obtained.

[0090] Test method:

[0091] D50 particle size determination: The particle size distribution of the material was detected using a laser particle size analyzer.

[0092] Specific surface area determination: The specific surface area of ​​the material is measured using a specific surface area meter.

[0093] The nickel oxide materials of the above embodiments and comparative examples were subjected to performance tests, and the test results are shown in Table 1.

[0094] Table 1

[0095]

[0096]

[0097] In the examples, the nickel oxide material is mainly spherical, while the nickel oxide material in Comparative Example 1 has an elliptical structure. The nickel oxide material in Comparative Example 2 has less spherical structure and more fragmented and irregular structures.

[0098] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0099] The preparation method of this application can prepare nickel oxide materials with needle-like spherical morphology and uniform particle size, thereby enhancing the surface activity and specific surface energy of spherical nickel oxide materials, and thus better applying them to fields such as gas-sensitive materials. Specifically, adding an alkaline solution in step S1 can adjust the pH value of the first mixture and form a slightly acidic reaction environment. In the above reaction environment, the surface activity energy and interfacial tension of the solution are low, and the spherical nickel oxide structure has low surface activity energy, so it is easier to form in this environment. Furthermore, according to Young's equation, the lower the interfacial tension, the more favorable it is for the formation of spherical structures. At the same time, in the above reaction environment, the reaction rate is relatively mild, which is conducive to uniform nucleation, regulating ion behavior, and thus helping to better control the morphology of the nickel oxide material to be spherical, while making the particle size and distribution of the nickel oxide material more uniform. The surfactant added in step S2 can adsorb on the surface of the subsequently generated nickel oxalate precipitate particles to form a protective film, increasing the electrostatic repulsion between particles, thereby improving the dispersion effect and helping the subsequent nickel oxide to form a spherical structure. At the same time, the addition of a dispersant can reduce particle agglomeration through its electrostatic repulsion or steric hindrance. In step S3, oxalate ions in the oxalate solution react with nickel ions in the nickel salt solution in the second mixture to form nickel oxalate precipitate. In step S4, the nickel oxalate precipitate is obtained by centrifugation, impurities on the surface of the precipitate are removed by washing, and residual solvent is removed by drying. Finally, calcination is performed at a temperature controlled within the aforementioned range to promote the decomposition of nickel oxalate to obtain nickel oxide, while improving the morphology of the nickel oxide, resulting in a pure nickel oxide material with a spherical structure. Furthermore, the preparation method of this application is not only simple and easy to operate in terms of steps and preparation conditions, but also produces no harmful gases during the preparation process, thus eliminating the need for additional tail gas treatment steps.

[0100] The above are merely embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing spherical nickel oxide material, characterized in that, The preparation method includes: Step S1: The raw materials, including nickel salt solution and alkaline solution, are first mixed to obtain a first mixture; Step S2: The raw materials including the first mixture and the surfactant are first stirred to obtain a fourth mixture; the raw materials including the fourth mixture and the dispersant are second stirred to obtain a second mixture. Step S3 involves sequentially subjecting the raw materials, including the second mixture and the oxalate solution, to a third mixing and aging reaction to obtain a third mixture; and Step S4: The third mixture is centrifuged, washed, dried and calcined in sequence to obtain spherical nickel oxide material; The first mixture has a pH value of 5.0 to 6.8; the calcination temperature is 300 to 550°C. The mass ratio of the surfactant to the dispersant is 1~4:1; The mass ratio of the surfactant to the first mixture is 0.2~1:1000; The mass ratio of the dispersant to the first mixture is 0.05~1:1000; The surfactant is a sulfonic acid surfactant and / or a sulfate ester surfactant; The dispersant is a polyethylene glycol dispersant and / or a polycarboxylate dispersant; Step S3 further includes adding the oxalate solution to the second mixture using a peristaltic pump, wherein the peristaltic pump has a propulsion speed of 1~2 mL / min; The morphology of the spherical nickel oxide material is needle-shaped and spherical.

2. The preparation method according to claim 1, characterized in that, In step S2, the rotation speed of the first stirring and the second stirring are each independently 100~500 r / min, and the stirring time of the first stirring and the second stirring are each independently 5~40 min.

3. The preparation method according to claim 1 or 2, characterized in that, In step S1, the nickel salt solution is selected from any one or more of nickel nitrate solution, nickel chloride solution, and nickel sulfate solution; the molar concentration of the nickel salt solution is 0.02~0.1 mol / L based on the nickel ions in the nickel salt solution; and / or, the alkaline solution is selected from any one or more of ammonia water, sodium hydroxide solution, and potassium hydroxide solution.

4. The preparation method according to claim 1 or 2, characterized in that, In step S1, the first mixing is carried out under ultrasonic conditions by a third stirring, wherein the temperature of the third stirring is 20~55℃ and the rotation speed of the third stirring is 100~500r / min.

5. The preparation method according to claim 1 or 2, characterized in that, In step S3, the aging reaction temperature is 20~55℃, and the aging reaction time is 30~120min.

6. The preparation method according to claim 1 or 2, characterized in that, In step S3, the oxalate solution is selected from any one or more of sodium oxalate solution, ammonium oxalate solution, and potassium oxalate solution; the molar concentration of the oxalate solution is 0.05~1 mol / L, based on the oxalate ions in the oxalate solution. And / or, based on the oxalate ions in the oxalate solution and the nickel ions in the nickel salt solution, the molar ratio of the oxalate solution to the nickel salt solution is 0.5 to 2:

1.

7. The preparation method according to claim 1 or 2, characterized in that, Step S3 further includes performing the third mixing by a fourth stirring, wherein the speed of the fourth stirring is 100~300 r / min and the time of the fourth stirring is 15~120 min.

8. The preparation method according to claim 1 or 2, characterized in that, In step S4, the centrifuged mixture is washed sequentially with water and ethanol; and / or, the drying temperature is 40~70℃ and the drying time is 480~720min; and / or, the calcination time is 300~720min.

9. A spherical nickel oxide material, characterized in that, The spherical nickel oxide material is prepared by the preparation method according to any one of claims 1 to 8, wherein the D50 particle size of the spherical nickel oxide material is ≤15μm, and the morphology of the spherical nickel oxide material is needle-shaped spherical.

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