Spherical nickel oxide material and preparation method thereof

Abstract

The invention provides a spherical nickel oxide material and a preparation method thereof. The preparation method comprises the following steps: S1, carrying out first mixing on raw materials including a nickel salt solution and an alkali solution to obtain a first mixed solution; s2, performing second mixing on raw materials including the first mixed solution, a surfactant and a dispersing agent to obtain a second mixed solution; s3, sequentially carrying out third mixing and aging reaction on raw materials comprising the second mixed solution and an oxalate solution to obtain a third mixed solution; and S4, sequentially centrifuging, washing, drying and roasting 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; the roasting temperature is 300 to 550 DEG C; according to the preparation method, the needle-shaped spherical nickel oxide material with uniform particle size can be obtained, so that the surface activity and the specific surface energy of the nickel oxide material are enhanced, and the nickel oxide material can be better applied to the fields of gas sensitive materials and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of nickel oxide material preparation, in particular to a spherical nickel oxide material and a preparation method thereof. Background Art

[0002] Nickel oxide is primarily used industrially as a raw material for the preparation of battery electrodes, catalysts, semiconductors, nickel-zinc ferrites, and glass and ceramic pigments. The morphological characteristics of its particles largely determine the powder's performance. Nickel oxide is low-cost and has a tunable eight-electron structure in its 3d orbitals, making it an effective catalyst for the electrochemical nitrogen reduction reaction under mild conditions. Embedding or doping nickel oxide with highly conductive metals with catalytic properties is an effective method for obtaining high-performance electrocatalysts. Nickel oxide is also a p-type oxide semiconductor. Due to metal ion vacancies, it forms a p-type semiconductor at high temperatures. At high temperatures (above 600°C), its resistivity is related to the oxygen partial pressure in the atmosphere: the higher the oxygen concentration, the lower the resistivity. The relationship between the resistivity of nickel oxide and oxygen molecules is used to detect oxygen concentration. The gas-sensing properties of nickel oxide are also related to its particle size: smaller particles have a larger specific surface area. Similarly, a larger contact area with the gas being measured results in higher detection sensitivity and shorter response and recovery times. Therefore, using ultrafine nickel oxide particles to prepare resistive gas sensors can significantly improve their performance.

[0003] Chinese patent application publication number CN117779054A discloses a method for electrochemically synthesizing nickel oxide. The method uses at least one of nickel particles, nickel fibers, nickel films, nickel sheets, and nickel foam as a metallic nickel precursor. The metallic nickel precursor acts as both a cathode and an anode and is placed in an electrolyte for voltage pulse oxidation to produce nickel oxide. The preparation process is complex, and the reactants, nickel particles and nickel films, must be prepared in specific forms, placing certain requirements on the raw material form. Furthermore, electrochemical synthesis methods consume a lot of energy.

[0004] Chinese patent application publication number CN117843046A discloses a method for preparing high-purity nano-nickel oxide. The method involves using a nickel salt solution and a precipitant solution in a multiphase interfacial reactor under the action of a surfactant to produce a nano-nickel oxide precursor slurry. The nano-nickel oxide precursor slurry is aged, filtered, and washed to produce a nano-nickel oxide precursor filter cake. This filter cake is then dried in an oven and calcined in a muffle furnace to produce a 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 purpose of the present invention is to provide a spherical nickel oxide material and a preparation method thereof, so as to solve the problems in the prior art of complex preparation process and reaction conditions of spherical nickel oxide and uneven prepared spherical nickel oxide particles.

[0007] To achieve the above-mentioned object, according to one aspect of the present invention, a method for preparing a 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 mixed liquid; step S2, second mixing raw materials including the first mixed liquid, a surfactant, and a dispersant to obtain a second mixed liquid; step S3, sequentially performing a third mixing and aging reaction on raw materials including the second mixed liquid and an oxalate solution to obtain a third mixed liquid; and step S4, sequentially centrifuging, washing, drying, and calcining the third mixed liquid to obtain a spherical nickel oxide material; wherein the pH value of the first mixed liquid is 5.0-6.8; and the calcination temperature is 300-550°C.

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

[0009] Furthermore, in the above step S2, the mass ratio of the surfactant to the first mixed liquid 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 mixed liquid is 0.05 to 1:1000; and / or the dispersant is a polyethylene glycol dispersant and / or a polycarboxylate dispersant.

[0010] Furthermore, in the above 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 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 the above step S1, the first mixing is performed by third stirring under ultrasonic conditions, wherein the temperature of the third stirring is 20 to 55° C., and the rotation speed of the third stirring is 100 to 500 r / min.

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

[0013] Furthermore, in the above 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 to 1 mol / L based on the oxalate ions in the oxalate solution; and / or the molar ratio of the oxalate solution to the nickel salt solution is 0.5 to 2:1 based on the oxalate ions in the oxalate solution and the nickel ions in the nickel salt solution.

[0014] Furthermore, the above-mentioned step S3 also includes adding the oxalate solution to the second mixed liquid through a peristaltic pump, the propulsion speed of the peristaltic pump is 1 to 2 mL / min; and / or, performing the second mixing through a fourth stirring, the rotation speed of the fourth stirring is 100 to 300 r / min, and the time of the fourth stirring is 15 to 120 min.

[0015] Furthermore, in the above step S4, the centrifuged mixture is washed 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 roasting time is 300-720 min.

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

[0017] By applying the technical solution of the present invention, a nickel oxide material with a needle-like spherical morphology and uniform particle size can be prepared by the preparation method of the present application, thereby enhancing the surface activity and specific surface energy of the spherical nickel oxide material, and thus better applied to fields such as gas-sensitive materials. Specifically, the addition of an alkaline solution in step S1 can regulate the pH value of the first mixed solution and form a slanted 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 has a low surface activity energy, so it is easier to form in this environment. And according to Young's equation, the lower the interfacial tension, the more conducive to 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 regulate 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 be adsorbed on the surface of the nickel oxalate precipitate particles generated subsequently to form a protective film, increase the electrostatic repulsion between the particles, thereby improving the dispersion effect, and thus 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, the oxalate ions in the oxalate solution react with the nickel ions in the nickel salt solution in the second mixed solution to form a nickel oxalate precipitate. In step S4, a nickel oxalate precipitate is obtained by centrifugation, impurities on the surface of the nickel oxalate precipitate are removed by washing, and residual solvent after washing is removed by drying. Finally, by roasting and controlling the roasting temperature within the above range, the nickel oxalate can be promoted to decompose and obtain nickel oxide, while improving the morphology of nickel oxide to obtain a pure nickel oxide material with a spherical structure. In addition, the preparation method of the present application is not only simple in steps and preparation conditions and easy to operate, but also no harmful gases are generated during the preparation process, thereby eliminating the need to additionally increase the tail gas treatment step. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0019] Figure 1 shows an SEM image of the spherical nickel oxide material in Example 1 of the present application;

[0020] Figure 2 The SEM image of the spherical nickel oxide material in Comparative Example 1 of the present application is shown. DETAILED DESCRIPTION

[0021] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

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

[0023] In a typical embodiment of the present application, a method for preparing a spherical nickel oxide material is provided, which comprises: step S1, performing a first mixing of raw materials including a nickel salt solution and an alkaline solution to obtain a first mixed liquid; step S2, performing a second mixing of raw materials including the first mixed liquid, a surfactant and a dispersant to obtain a second mixed liquid; step S3, performing a third mixing and aging reaction on raw materials including the second mixed liquid and an oxalate solution in sequence to obtain a third mixed liquid; and step S4, performing a centrifugal, washing, drying and roasting on the third mixed liquid in sequence to obtain a spherical nickel oxide material; wherein the pH value of the first mixed liquid is 5.0 to 6.8; and the roasting temperature is 300 to 550°C.

[0024] The preparation method of the present application can be used to prepare a nickel oxide material with a needle-like spherical morphology and uniform particle size, thereby enhancing the surface activity and specific surface energy of the spherical nickel oxide material, and thus better applied to fields such as gas-sensitive materials. Specifically, adding an alkaline solution in step S1 can regulate the pH value of the first mixed solution and form a slant-acidic reaction environment. In the above reaction environment, the surface activity energy and interfacial tension of the solution are low, and the nickel oxide with a spherical structure has a low surface activity energy, so it is easier to form in this environment. And according to Young's equation, the lower the interfacial tension, the more conducive to 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 regulate 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 be adsorbed on the surface of the nickel oxalate precipitate particles generated subsequently to form a protective film, increase the electrostatic repulsion between the particles, thereby improving the dispersion effect, and thus 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, the oxalate ions in the oxalate solution react with the nickel ions in the nickel salt solution in the second mixed solution to form a nickel oxalate precipitate. In step S4, a nickel oxalate precipitate is obtained by centrifugation, impurities on the surface of the nickel oxalate precipitate are removed by washing, and residual solvent after washing is removed by drying. Finally, by roasting and controlling the roasting temperature within the above range, the nickel oxalate can be promoted to decompose and obtain nickel oxide, while improving the morphology of nickel oxide to obtain a pure nickel oxide material with a spherical structure. In addition, the preparation method of the present application is not only simple in steps and preparation conditions and easy to operate, but also no harmful gases are generated during the preparation process, thereby eliminating the need to additionally increase the tail gas treatment step.

[0025] In one embodiment of the present application, the above-mentioned step S2 also includes a first stirring of the raw materials including the first mixed liquid and the surfactant to obtain a fourth mixed liquid; and a second stirring of the raw materials including the fourth mixed liquid and the dispersant to obtain a second mixed liquid; wherein the rotation speeds of the first stirring and the second stirring are each independently 100 to 500 r / min, preferably 200 to 350 r / min, and the time of the first stirring and the second stirring are each independently 5 to 40 minutes, preferably 15 to 30 minutes.

[0026] It is preferred to control the rotation speed and time of the first stirring and the second stirring within the above range, which helps to fully disperse the surfactant and dispersant in the nickel salt solution to obtain a second mixed solution with uniform components, thereby helping to improve the uniformity and consistency of the nickel oxide particle morphology in the subsequent aging reaction.

[0027] In one embodiment of the present application, in the above step S2, the mass ratio of the surfactant to the first mixed liquid 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 mixed liquid 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 polycarboxylate dispersant.

[0028] The type of surfactant and the mass ratio of the surfactant to the first mixed liquid are preferably within the above ranges, as this helps the surfactant better adsorb onto the particle surfaces to form a protective film, thereby further increasing the electrostatic repulsion between the particles. The type of dispersant and the mass ratio of the dispersant to the first mixed liquid are preferably within the above ranges, as this helps further reduce particle agglomeration, thereby improving the uniformity of the nickel oxide morphology.

[0029] It is further preferred that the mass ratio of the surfactant to the dispersant is 1 to 4:1, which helps to improve the synergistic effect between the two, thereby further enhancing the dispersion effect, and further helping the subsequent nickel oxide to better form a spherical structure.

[0030] In one embodiment of the present application, in the above 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 to 0.1 mol / L, preferably 0.05 to 0.1 mol / L, calculated as 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] The type and molar concentration of the nickel salt solution are preferably within the above ranges, which facilitates the formation of nickel oxalate precipitate during the reaction with the oxalate solution. The type of the alkaline solution is preferably within the above ranges, which facilitates the adjustment of the pH value and adjusts the reaction environment to a slightly acidic state, thereby facilitating the production of spherical nickel oxide material.

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

[0033] The temperature and stirring speed of the third stirring are preferably controlled within the above ranges, and combined with the use of ultrasound, this helps to effectively promote uniform mixing of the alkaline solution and the nickel salt solution while maintaining the stability of the pH of the reaction system.

[0034] The above mixing was all carried out under ultrasonic conditions.

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

[0036] It is preferred to control the temperature and time of the aging reaction within the above ranges, which helps to promote the precipitation reaction between the nickel salt solution and the oxalate solution to form nickel oxalate precipitate.

[0037] In one embodiment of the present application, in the above 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, preferably 0.15-0.45 mol / L, calculated as oxalate ions in the oxalate solution; and / or, the molar ratio of the oxalate solution to the nickel salt solution is 0.5-2:1, preferably 0.8-1.7:1, calculated as oxalate ions in the oxalate solution and nickel ions in the nickel salt solution.

[0038] The type and molar concentration of the oxalate solution are preferably within the above ranges to facilitate sufficient reaction between oxalate ions and nickel ions to form nickel oxalate. This allows for precise control of morphology and size during the reaction. The molar ratio of the oxalate solution to the nickel salt solution is preferably controlled within the above range to facilitate the formation of fine needle-like structures, allowing the nickel oxide to further evolve into the desired spherical structure in subsequent processes while maintaining its needle-like characteristics, thereby achieving a high specific surface area and high activity.

[0039] In one embodiment of the present application, the above-mentioned step S3 also includes adding the oxalate solution to the second mixed liquid through a peristaltic pump, and the propulsion speed of the peristaltic pump is 1 to 2 mL / min; and / or, performing the second mixing through a fourth stirring, the rotation speed of the fourth stirring is 100 to 300 r / min, preferably 150 to 250 r / min, and the time of the fourth stirring is 15 to 120 min, preferably 30 to 90 min.

[0040] Preferably, a peristaltic pump is used and its propulsion speed is controlled within the above range, which helps the oxalate solution react with the nickel salt solution at a stable and uniform rate, alleviates the rapid change in local pH caused by the addition of a large amount of oxalate solution, and thus improves the morphological consistency and dimensional uniformity of the nickel oxide material. Preferably, the speed and time of the fourth stirring are controlled within the above range to help uniformly disperse the components in the mixed solution, promote the full reaction of oxalate ions and nickel ions, and form a well-dispersed nickel oxalate precipitate.

[0041] In one embodiment of the present application, in the above step S4, the third mixed liquid is washed 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 roasting time is 300-720 min, preferably 360-720 min.

[0042] The washing treatment is preferably used to help remove unreacted reagents, by-products and impurities in the centrifuged mixture. Among them, water can wash away most water-soluble impurities, while the use of ethanol helps to further clean the organic matter remaining on the surface of the centrifuged mixture, especially the residual surfactant and dispersant that are not easily soluble in the aqueous phase.

[0043] The drying temperature and time are preferably within the above ranges to help remove moisture from the washed material and reduce structural damage caused by water evaporation during the subsequent calcination process. The calcination time is preferably within the above range to help fully decompose the nickel oxalate and obtain a needle-shaped, spherical, ultrafine nickel oxide powder material.

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

[0045] The nickel oxide material prepared by the above-described preparation method has a spherical structure, a D50 particle size within the aforementioned range, and a uniform particle size distribution. This method can improve the surface activity and specific surface energy of the nickel oxide powder material, thereby improving its application in fields such as gas-sensing materials. The D50 particle size is the particle size corresponding to the cumulative particle size distribution percentage reaching 50% in the sample.

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

[0047] Example 1

[0048] 200 mL of a nickel sulfate solution having a nickel ion molar concentration of 0.05 mol / L was placed in a 500 mL reactor and subjected to a third stirring at 40° C. and at a speed of 300 r / min under ultrasonic conditions. While stirring, a potassium hydroxide solution was added dropwise to obtain a first mixed solution, and the pH value of the first mixed solution was adjusted to be maintained at 6.5.

[0049] A surfactant, sodium lignin sulfonate, was added to the first mixed solution and stirred for a first time at 300 r / min for 30 minutes to obtain a fourth mixed solution, wherein the mass ratio of the surfactant to the first mixed solution was 0.6:1000. A dispersant, polyethylene glycol, was further added to the fourth mixed solution and stirred for a second time at 300 r / min for 30 minutes to obtain a second mixed solution, wherein the mass ratio of the dispersant to the first mixed solution was 0.5:1000.

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

[0051] After the third mixed liquid is centrifuged, a centrifuged mixture is obtained, which is then washed with deionized water 3 times and then washed with ethanol 5 times. The washed mixture is placed in a vacuum drying oven and dried at 70°C for 500 minutes. The dried mixture is placed in a crucible and then in a muffle furnace, calcined at 500°C for 480 minutes, and cooled with the furnace to obtain a nickel oxide material. The nickel oxide material is a needle-shaped spherical ultrafine nickel oxide powder material. The morphology and particle size are uniform and the particle size distribution range is narrow as observed by SEM. Figure 1 shown.

[0052] Example 2

[0053] 300 mL of a nickel sulfate solution having a nickel ion molar concentration of 0.08 mol / L was placed in a 500 mL reactor and subjected to a third stirring at 50° C. and at a speed of 350 r / min under ultrasonic conditions. While stirring, a potassium hydroxide solution was added dropwise to obtain a first mixed solution, and the pH value of the first mixed solution was adjusted to maintain at 6.0.

[0054] A surfactant, sodium lignin sulfonate, was added to the first mixed solution and stirred for a first time at 350 r / min for 20 minutes to obtain a fourth mixed solution, wherein the mass ratio of the surfactant to the first mixed solution was 0.6:1000. A dispersant, polyethylene glycol, was further added to the fourth mixed solution and stirred for a second time at 350 r / min for 20 minutes to obtain a second mixed solution, wherein the mass ratio of the dispersant to the first mixed solution was 1:1000.

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

[0056] The third mixed liquid 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 minutes. The dried mixture was placed in a crucible and then in a muffle furnace, calcined at 550°C for 360 minutes, and cooled in the furnace to obtain a nickel oxide material. This nickel oxide material is a needle-shaped, spherical ultrafine nickel oxide powder material, whose morphology is mainly spherical.

[0057] Example 3

[0058] 300 mL of a nickel sulfate solution having a nickel ion molar concentration of 0.02 mol / L was placed in a 500 mL reactor and subjected to a third stirring at 20° C. and at a speed of 100 r / min under ultrasonic conditions. While stirring, a potassium hydroxide solution was added dropwise to obtain a first mixed solution, and the pH value of the first mixed solution was adjusted to maintain at 5.0.

[0059] A surfactant, sodium lignin sulfonate, was added to the first mixed solution and stirred for a first time at 500 r / min for 5 minutes to obtain a fourth mixed solution, wherein the mass ratio of the surfactant to the first mixed solution was 0.2:1000. A dispersant, polyethylene glycol, was further added to the fourth mixed solution and stirred for a second time at 500 r / min for 5 minutes to obtain a second mixed solution, wherein the mass ratio of the dispersant to the first mixed solution was 0.05:1000.

[0060] 60 mL of ammonium oxalate solution with a molar concentration of oxalate ions of 0.05 mol / L was measured and added dropwise to the second mixed liquid at a propulsion speed of 2.5 ml / min using a peristaltic pump to make the molar ratio of nickel ions to oxalate ions in the solution system be 2:1. Subsequently, the fourth stirring was performed at a speed of 200 r / min for 30 min. After stopping the stirring, the aging reaction was performed at 20°C for 120 min to obtain a third mixed liquid.

[0061] The third mixed liquid 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 minutes. The dried mixture was placed in a crucible and then in a muffle furnace, calcined at 300°C for 720 minutes, and cooled in the furnace to obtain a nickel oxide material. This nickel oxide material is a needle-shaped, spherical ultrafine nickel oxide powder material, whose morphology is mainly spherical.

[0062] Example 4

[0063] The difference from Example 1 is that the pH value of the first mixed solution 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 a spherical nickel oxide material is finally obtained.

[0066] Example 6

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

[0072] Example 9

[0073] The difference from Example 1 is that the mass ratio of the dispersant to the first mixed liquid 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., the aging reaction time is 30 min, and spherical nickel oxide material is finally obtained.

[0076] Example 11

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

[0078] Example 12

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

[0080] Example 13

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

[0082] Example 14

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

[0084] Example 15

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

[0086] Comparative Example 1

[0087] The difference from Example 1 is that the pH value of the first mixed solution is 7.2, and the elliptical nickel oxide material is finally obtained, such as Figure 2 shown.

[0088] Comparative Example 2

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

[0090] Test method:

[0091] Determination of D50 particle size: A laser particle size analyzer is used to detect the particle size distribution of the material.

[0092] Determination of specific surface area: Use a specific surface area detector to detect the specific surface area of the material.

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

[0094] Table 1

[0095]

[0096]

[0097] Among them, the morphology of the nickel oxide material in the embodiment is mainly spherical, while the morphology of the nickel oxide material in comparative example 1 is an elliptical structure. The morphology of the nickel oxide material in comparative example 2 has a smaller content of spherical structures and contains more fine and unformed structures.

[0098] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0099] The preparation method of the present application can be used to prepare a nickel oxide material with a needle-like spherical morphology and uniform particle size, thereby enhancing the surface activity and specific surface energy of the spherical nickel oxide material, and thus better applied to fields such as gas-sensitive materials. Specifically, adding an alkaline solution in step S1 can regulate the pH value of the first mixed solution and form a slant-acidic reaction environment. In the above reaction environment, the surface activity energy and interfacial tension of the solution are low, and the nickel oxide with a spherical structure has a low surface activity energy, so it is easier to form in this environment. And according to Young's equation, the lower the interfacial tension, the more conducive to 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 regulate 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 be adsorbed on the surface of the nickel oxalate precipitate particles generated subsequently to form a protective film, increase the electrostatic repulsion between the particles, thereby improving the dispersion effect, and thus 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, the oxalate ions in the oxalate solution react with the nickel ions in the nickel salt solution in the second mixed solution to form a nickel oxalate precipitate. In step S4, a nickel oxalate precipitate is obtained by centrifugation, impurities on the surface of the nickel oxalate precipitate are removed by washing, and residual solvent after washing is removed by drying. Finally, by roasting and controlling the roasting temperature within the above range, the nickel oxalate can be promoted to decompose and obtain nickel oxide, while improving the morphology of nickel oxide to obtain a pure nickel oxide material with a spherical structure. In addition, the preparation method of the present application is not only simple in steps and preparation conditions and easy to operate, but also no harmful gases are generated during the preparation process, thereby eliminating the need to additionally increase the tail gas treatment step.

[0100] The above are merely embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a spherical nickel oxide material, characterized in that: The preparation method comprises: Step S1, mixing raw materials including a nickel salt solution and an alkaline solution to obtain a first mixed solution; Step S2, performing a second mixing of the raw materials including the first mixed liquid, the surfactant and the dispersant to obtain a second mixed liquid; Step S3, sequentially subjecting the raw materials including the second mixed solution and the oxalate solution to a third mixing and aging reaction to obtain a third mixed solution; and Step S4, centrifuging, washing, drying and calcining the third mixed solution in sequence to obtain a 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°C.

2. The preparation method according to claim 1, characterized in that The step S2 further includes: performing a first stirring on the raw material including the first mixed liquid and the surfactant to obtain a fourth mixed liquid; performing a second stirring on the raw material including the fourth mixed liquid and the dispersant to obtain the second mixed liquid; The rotation speeds of the first stirring and the second stirring are independently 100 to 500 r / min, and the time of the first stirring and the second stirring are independently 5 to 40 minutes.

3. The preparation method according to claim 1 or 2, characterized in that In step S2, the mass ratio of the surfactant to the first mixed solution 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 mixed liquid is 0.05 to 1:1000; and / or, the dispersant is a polyethylene glycol dispersant and / or a polycarboxylate dispersant.

4. The preparation method according to any one of claims 1 to 3, 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 to 0.1 mol / L based on 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.

5. The preparation method according to any one of claims 1 to 4, characterized in that In the step S1, the first mixing is performed by third stirring under ultrasonic conditions, wherein the temperature of the third stirring is 20 to 55° C., and the rotation speed of the third stirring is 100 to 500 r / min.

6. The preparation method according to any one of claims 1 to 5, characterized in that In step S3, the temperature of the aging reaction is 20-55° C., and the time of the aging reaction is 30-120 minutes.

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

8. The preparation method according to any one of claims 1 to 7, characterized in that The step S3 also includes adding the oxalate solution to the second mixed liquid through a peristaltic pump, the propulsion speed of the peristaltic pump is 1 to 2 mL / min; and / or, performing the second mixing through a fourth stirring, the rotation speed of the fourth stirring is 100 to 300 r / min, and the time of the fourth stirring is 15 to 120 min.

9. The preparation method according to any one of claims 1 to 8, characterized in that In the step S4, the centrifuged mixture is washed 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 roasting time is 300-720 min.

10. 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 9, and the D50 particle size of the spherical nickel oxide material is ≤15 μm.

Images