Nanoscale cobaltosic oxide as well as preparation method and application thereof

Abstract

The invention relates to nanoscale cobaltosic oxide and a preparation method and application thereof.The preparation method comprises the steps that a cobalt salt mixed solution and a complexing agent solution are added into a base solution in a parallel flow mode, a co-precipitation reaction is conducted, and a cobalt carbonate wet material is obtained through aging; the cobalt salt mixed solution comprises a surfactant and a cobalt salt solution; and sequentially carrying out crushing and heat treatment on the cobalt carbonate wet material to obtain the nanoscale cobaltosic oxide. According to the preparation method disclosed by the invention, the nano cobalt carbonate which is in the shape of primary particles and is relatively good in sphericity and relatively high in dispersity is firstly prepared, and then the spherical nanoscale cobaltosic oxide which is uniform in size, high in yield and good in flowability can be obtained through the working procedures of crushing, heat treatment and the like, and the spherical nanoscale cobaltosic oxide still can keep good dispersity and is relatively low in agglomeration degree; the adopted preparation method is simple and low in cost, and industrial large-scale production can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of cobalt tetroxide preparation, and particularly to a nano cobalt tetroxide, a preparation method thereof and an application thereof. Background Art

[0002] At present, energy in China is increasingly tense. As a clean energy, the development and application of electric power have also received much attention from the country. Cobalt tetroxide (Co3O4) is a transition metal oxide of the VIIIth subgroup, with a typical spinel structure, and it has characteristics such as rich resources, high energy storage efficiency, good catalytic activity and environmental friendliness. Especially nano cobalt tetroxide has a wide range of applications and can be widely used in fields such as lithium ion batteries, capacitors, catalysts and magnetic materials. In addition, with the rapid development of China's communication and electronic information industries, the demand for lithium ion secondary batteries is increasing continuously. As the main raw material of lithium cobaltate, the cathode material of lithium ion batteries, cobalt tetroxide is the focus of attention of scientific researchers. Therefore, it is particularly important to find a suitable cobalt tetroxide raw material that meets standards such as fast lithium ion transmission ability, mechanical robustness and high surface-to-volume ratio.

[0003] At present, the preparation routes of cobalt tetroxide include solid phase method, gas phase method and liquid phase method. The solid phase method includes direct heat solid phase method and indirect heat solid phase method; the gas phase method includes chemical vapor deposition method and spray pyrolysis method, etc.; the liquid phase method includes hydrothermal method, dissolution method, sol-gel method or microemulsion method, etc.; and there are also some combined route methods, such as liquid phase precipitation-thermal decomposition method or hydrothermal-microemulsion method, etc. Different preparation routes have different characteristics, and according to the applications of cobalt tetroxide in different fields, the preparation routes are different.

[0004] Taking the application of ultrafine cobalt powder as an example, currently, the cobalt tetroxide commonly used in the preparation of ultrafine cobalt powder is directly calcined from fine-grained cobalt carbonate. After heat treatment of fine-grained cobalt carbonate, it is easy to agglomerate and the yield is low. Therefore, the obtained nano cobalt tetroxide has problems such as poor morphology and uneven size. During the preparation of ultrafine cobalt powder and the subsequent preparation of high-cobalt cemented carbide, it will lead to the formation of abnormally large grains, and then lead to the occurrence of cobalt pool phenomenon in high-cobalt cemented carbide.

[0005] CN117886370A discloses a preparation method of nano cobalt tetroxide, which includes using cobalt solution, sodium hydroxide solution, ammonia water solution and hydrogen peroxide solution. By controlling the addition amount of the hydrogen peroxide solution, part of the synthesized Co(OH)₂ is oxidized to CoOOH. Since the crystal forms of Co(OH)₂ and CoOOH are different, the synthesized micron-sized composite particles are formed by the agglomeration of nano-sized Co(OH)₂ and nano-sized CoOOH through intermolecular forces. Then, by increasing the solid-liquid ratio of the synthesis slurry, the micron-sized composite particles collide with each other and break to form nano-sized Co(OH)₂ and CoOOH mixed particles. Then, through calcination, nano cobalt tetroxide products are obtained. Although the above method can obtain nano-sized powders, it has serious problems of interparticle agglomeration, and the agglomerates are irregular in shape, with poor particle uniformity and relatively poor fluidity.

[0006] Therefore, how to provide a simple preparation method of nano cobalt tetroxide with high yield, which can achieve industrial large-scale production, and the nano cobalt tetroxide has characteristics such as uniform morphology, uniform size, low agglomeration degree and high fluidity has become an urgent problem to be solved at present. Summary of the Invention

[0007] To solve the above technical problems, the present invention provides a nano cobalt tetroxide, its preparation method and application. The present invention first prepares nano cobalt carbonate with a morphology of primary particles, good sphericity and high dispersibility. Subsequently, through processes such as crushing and heat treatment, spherical nano cobalt tetroxide with uniform size, high yield and good fluidity can be obtained, and good dispersibility can still be maintained, and the agglomeration degree is low. The adopted preparation method is simple and low-cost, and can achieve industrial large-scale production.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a preparation method of nano cobalt tetroxide, and the preparation method includes the following steps:

[0010] (1) The cobalt salt mixed solution and the complexing agent solution are added to the bottom liquid in a parallel flow manner for coprecipitation reaction, and after aging, wet cobalt carbonate is obtained;

[0011] The cobalt salt mixed solution includes a surfactant and a cobalt salt solution;

[0012] (2) The wet cobalt carbonate obtained in step (1) is sequentially subjected to crushing and heat treatment to obtain nano cobalt tetroxide.

[0013] In the present invention, a cobalt salt solution containing a surfactant and a complexing agent solution are first added in parallel flow to a bottom liquid, and a coprecipitation reaction is first carried out to obtain a wet material with the target nano cobalt carbonate particle size. Then aging is carried out. Aging helps to improve the crystallinity and chemical uniformity of nano cobalt carbonate, and optimize its particle size, morphology and pore structure, thereby improving its own performance. And through aging, the stability of individual nano particles can also be improved, and the aggregation between particles can be reduced. Based on this, nano cobalt carbonate with a primary particle morphology, good sphericity and high dispersibility can be obtained in advance. Subsequently, a crushing process is immediately carried out. The nano cobalt carbonate is pre-crushed to obtain spherical nano cobalt carbonate with a suitable particle size. After heat treatment, the preparation of spherical nano cobalt tetroxide with uniform size, high yield and good fluidity can be achieved, and good dispersibility can still be maintained, and the degree of aggregation is low.

[0014] As a preferred technical solution of the present invention, in the cobalt salt solution of step (1), the concentration of cobalt ions is 110 g / L - 130 g / L, such as 110 g / L, 112 g / L, 115 g / L, 118 g / L, 120 g / L, 122 g / L, 125 g / L, 128 g / L or 130 g / L, etc.

[0015] Preferably, the cobalt salt solution of step (1) includes any one or a combination of at least two of cobalt chloride solution, cobalt nitrate solution or cobalt sulfate solution.

[0016] Preferably, in the cobalt salt mixed solution of step (1), the mass ratio of the surfactant to cobalt in the cobalt salt solution is (0.01 - 0.08):1, such as 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1 or 0.08:1, etc.

[0017] Preferably, the surfactant includes any one or a combination of at least two of Tween 80, polyvinylpyrrolidone or sodium citrate.

[0018] Preferably, the concentration of the complexing agent solution in step (1) is 180 g / L - 230 g / L, such as 180 g / L, 185 g / L, 190 g / L, 195 g / L, 200 g / L, 205 g / L, 210 g / L, 215 g / L, 220 g / L, 225 g / L or 230 g / L, etc.

[0019] Preferably, the complexing agent solution of step (1) includes any one or a combination of at least two of ammonium bicarbonate solution, sodium bicarbonate solution, sodium hydroxide solution or sodium carbonate solution.

[0020] As a preferred technical solution of the present invention, the bottom liquid in step (1) accounts for 40%-55% of the volume of the reaction vessel, such as 40%, 42%, 45%, 48%, 50%, 52% or 55%, etc.

[0021] It should be noted that in the present invention, there are no specific requirements and special limitations on the volume of the reaction vessel, and those skilled in the art can make adaptive selection and adjustment according to the actual amount of the prepared product. For example, it can be 50L-200L.

[0022] Preferably, the bottom liquid in step (1) includes any one or a combination of at least two of ammonium bicarbonate solution, sodium bicarbonate solution, sodium hydroxide solution or sodium carbonate solution.

[0023] Preferably, the concentration of the bottom liquid in step (1) is 60g / L-230g / L, such as 60g / L, 70g / L, 80g / L, 90g / L, 100g / L, 110g / L, 120g / L, 130g / L, 140g / L, 150g / L, 160g / L, 170g / L, 180g / L, 190g / L, 200g / L, 210g / L, 220g / L or 230g / L, etc.

[0024] In the present invention, by controlling the concentration of the bottom liquid to be 60g / L-230g / L, the average particle size of nano cobalt carbonate is further controlled within the target range, providing a key raw material basis for preparing spherical nano cobalt tetroxide with uniform size, high yield, good fluidity and good dispersibility. If the concentration of the bottom liquid is too low, at the initial stage of the coprecipitation reaction, the nucleation rate slows down and the number of crystal nuclei is small. As the reaction proceeds, the particles will grow into larger particles, thus affecting the preparation of nano cobalt tetroxide. If the concentration of the bottom liquid is too high, it will lead to an increase in the collision probability of reactants, easily resulting in an increase in particle size, and nano particles are also prone to agglomeration, thus affecting the preparation and performance of nano cobalt carbonate materials. In addition, it will also cause problems such as non-uniform particle morphology, decreased crystallinity, increased impurities, difficult reaction control and decreased yield, and the equipment burden is increased, and the equipment maintenance difficulty is also increased.

[0025] As a preferred technical solution of the present invention, the flow rate of the cobalt salt mixed solution in step (1) is 100L / h-300L / h, such as 100L / h, 120L / h, 150L / h, 180L / h, 200L / h, 220L / h, 250L / h, 280L / h or 300L / h, etc.

[0026] Preferably, the flow rate of the complexing agent solution in step (1) is 130 L / h - 450 L / h, such as 130 L / h, 150 L / h, 180 L / h, 200 L / h, 220 L / h, 250 L / h, 280 L / h, 300 L / h, 320 L / h, 350 L / h, 380 L / h, 400 L / h, 420 L / h or 450 L / h, etc.

[0027] Preferably, stirring is included during the coprecipitation reaction in step (1).

[0028] Preferably, the rotation speed of the stirring in step (1) is 350 r / min - 450 r / min, such as 350 r / min, 380 r / min, 400 r / min, 420 r / min or 450 r / min, etc.

[0029] Preferably, the temperature of the coprecipitation reaction in step (1) is 38 °C - 45 °C, such as 38 °C, 39 °C, 40 °C, 41 °C, 42 °C, 43 °C, 44 °C or 45 °C, etc.

[0030] Preferably, the pH value of the coprecipitation reaction in step (1) is 7 - 8.5, such as 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4 or 8.5, etc.

[0031] Preferably, the aging time in step (1) is 1 h - 3 h, such as 1 h, 1.5 h, 2 h, 2.5 h or 3 h, etc.

[0032] In the present invention, after the coprecipitation reaction is completed, aging can make the crystallinity of nano cobalt carbonate higher and the stability better; further, regulating the aging time to 1 h - 3 h can optimize the particle size and morphology of nano cobalt carbonate. If the aging time is too short, the crystallinity of nano cobalt carbonate will be low, and the stability will be poor, and it is easy to agglomerate and the dispersibility will be poor. If the aging time is too long, more impurities existing in the reaction system will be introduced, the purity of the powder will be reduced, and it will be difficult to remove in the later stage, thus affecting the use performance of nano cobalt tetroxide.

[0033] It should be noted that within the aging time period (1 h - 3 h) in the present invention, the particle size of nano cobalt carbonate will not continue to grow.

[0034] In the present invention, the parameters of the coprecipitation reaction (temperature, stirring rotation speed and pH value) and the aging time are regulated, so as to control the preparation of nano cobalt carbonate with a morphology of primary particles, good sphericity and high dispersibility.

[0035] Preferably, in the cobalt carbonate wet material described in step (1), the average particle size D50 of cobalt carbonate is 400 nm - 1000 nm, such as 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm, etc.

[0036] In the cobalt carbonate wet material of the present invention, the average particle size D50 of nano cobalt carbonate is the particle size when the coprecipitation reaction stops.

[0037] It should be noted that in the present invention, there are no specific requirements and special limitations on the time of the coprecipitation reaction. After the coprecipitation reaction starts, the particle size is detected every half hour on average. As long as the average particle size D50 of nano cobalt carbonate in the cobalt carbonate wet material is 400 nm - 1000 nm, the coprecipitation reaction can be stopped and the aging can be started.

[0038] As a preferred technical solution of the present invention, before the crushing described in step (2), there are also steps of washing and drying.

[0039] Preferably, the detergent used for washing includes ammonium bicarbonate solution.

[0040] Preferably, the concentration of the ammonium bicarbonate solution is 30 g / L - 75 g / L, such as 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, or 75 g / L, etc.

[0041] Preferably, the washing is stopped when the content of impurity ions is below 200 ppm.

[0042] In the present invention, the impurity ions include Cl contained in the reaction raw materials - .

[0043] Preferably, the drying temperature is 100 °C - 150 °C, such as 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, or 150 °C, etc.

[0044] It should be noted that in the present invention, there are no specific requirements and special limitations on the drying time, as long as the cobalt carbonate wet material can be completely dried.

[0045] As a preferred technical solution of the present invention, the crushing time described in step (2) is 10 s - 120 s, such as 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s, 110 s, or 120 s, etc.

[0046] In the present invention, the regulation of the crushing time is 10 s - 120 s, which can control the particle size of the crushed powder to be uniform, with good sphericity and high dispersibility. If the crushing time is too long, it is easy to cause agglomeration of the powder and poor dispersibility. If the crushing time is too short, the particle size of cobalt tetroxide will be relatively large, failing to meet the preparation requirements.

[0047] Preferably, the crushing method in step (2) includes any one of ball milling, crusher crushing, ultrasonic crushing or jet milling.

[0048] Preferably, the heat treatment holding temperature in step (2) is 450 °C - 800 °C, such as 450 °C, 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, 750 °C or 800 °C, etc.

[0049] Preferably, the heating rate of the heat treatment in step (2) is 7 °C / min - 12 °C / min, such as 7 °C / min, 8 °C / min, 9 °C / min, 10 °C / min, 11 °C / min or 12 °C / min, etc.

[0050] Preferably, the heat treatment holding time in step (2) is 60 min - 180 min, such as 60 min, 80 min, 100 min, 120 min, 150 min or 180 min, etc.

[0051] Preferably, the gas used in the heat treatment in step (2) includes air.

[0052] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0053] (1) Mix a cobalt salt solution with a cobalt ion concentration of 110 g / L - 130 g / L and a surfactant uniformly to obtain a cobalt salt mixed solution. The mass ratio of the surfactant to cobalt in the cobalt salt solution is (0.01 - 0.08):1. Add the cobalt salt mixed solution and a complexing agent solution with a concentration of 180 g / L - 230 g / L into a bottom liquid with a concentration of 60 g / L - 230 g / L under stirring in a co-current manner. Carry out a coprecipitation reaction under the conditions of a rotation speed of 350 r / min - 450 r / min, a temperature of 38 °C - 45 °C, and a pH value of 7 - 8.5. When the average particle size D50 of nano-cobalt carbonate in the wet cobalt carbonate material is 400 nm - 1000 nm, stop the coprecipitation reaction, and after aging for 1 h - 3 h, obtain a wet cobalt carbonate material;

[0054] Among them, the flow rate of the cobalt salt mixed solution is 100 L / h - 300 L / h, and the flow rate of the complexing agent is 130 L / h - 450 L / h; the bottom liquid accounts for 40% - 55% of the volume of the reaction vessel;

[0055] (2) Wash the cobalt carbonate wet material described in step (1) until the content of impurity ions is below 200 ppm. After drying at 100 °C - 150 °C, crush it for 10 s - 120 s. Under air conditions, heat it to 450 °C - 800 °C at a heating rate of 7 °C / min - 12 °C / min and heat-treat for 60 min - 180 min to obtain nano-sized cobalt tetroxide.

[0056] In a second aspect, the present invention also provides a nano-sized cobalt tetroxide, which is prepared according to the preparation method described in the first aspect.

[0057] As a preferred technical solution of the present invention, the average particle size D50 of the nano-sized cobalt tetroxide is 300 nm - 800 nm, such as 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm or 800 nm, etc.

[0058] In a third aspect, the present invention also provides an application of the nano-sized cobalt tetroxide. The nano-sized cobalt tetroxide prepared by the preparation method described in the first aspect, or the nano-sized cobalt tetroxide described in the second aspect is applied to the fields of catalysts, battery materials, gas sensors or magnetic materials.

[0059] Compared with the prior art, the present invention has at least the following beneficial effects:

[0060] By regulating the process parameters of the coprecipitation reaction and optimizing the overall preparation process, the present invention makes the morphology of the initially prepared nano-sized cobalt carbonate be primary particles with good sphericity and high dispersibility. Subsequently, by combining the crushing and heat-treatment processes, the preparation of spherical nano-sized cobalt tetroxide with uniform size, high yield and good fluidity can be achieved, and it can still maintain good dispersibility, low degree of agglomeration, and the average particle size D50 is 300 nm - 800 nm, meeting the preparation requirements of the present invention. Specific Embodiments

[0061] To facilitate the understanding of the present invention, the following examples are listed. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0062] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

[0063] Example 1

[0064] This example provides a preparation method of nano-sized cobalt tetroxide, and the preparation method includes the following steps:

[0065] (1) Prepare a cobalt chloride solution with a cobalt ion concentration of 120 g / L as the cobalt salt solution, add Tween 80 as the surfactant (the addition amount of Tween 80 is in a mass ratio of 0.05:1 to the cobalt in the cobalt chloride solution) to obtain a cobalt salt mixed solution; prepare an ammonium bicarbonate solution with a concentration of 230 g / L as the complexing agent; prepare an ammonium bicarbonate solution with a concentration of 60 g / L as the bottom liquid (precipitant); prepare an ammonium bicarbonate solution with a concentration of 50 g / L as the detergent;

[0066] Carry out the reaction in a 200 L reactor. First, add 80 L of the bottom liquid (ammonium bicarbonate solution with a concentration of 60 g / L) to the reactor. Subsequently, under the conditions of a reaction temperature of 45 °C and a stirring speed of 450 r / min, add the cobalt salt mixed solution (cobalt chloride solution + Tween 80) and the complexing agent solution (ammonium bicarbonate solution with a concentration of 230 g / L) into the reactor in parallel through a peristaltic pump at flow rates of 100 L / h and 160 L / h respectively, and carry out the coprecipitation reaction at a stirring speed of 450 r / min. Among them, the pH value of the coprecipitation reaction fluctuates within the range of 8.0 ± 0.5. When the average particle size D50 of nano-cobalt carbonate in the wet cobalt carbonate material is 980 nm, stop the coprecipitation reaction. After aging for 2.5 h, obtain the wet cobalt carbonate material;

[0067] (3) Put the wet cobalt carbonate material into a centrifuge and wash it with ammonium bicarbonate at room temperature with a concentration of 50 g / L. After the test result of Cl - is below 200 ppm, dry the washed wet material at 130 °C, and then ultrasonically crush it for 60 s to obtain spherical cobalt carbonate powder. Heat-treat it in air (compressed air, air pressure 8 Nm 3 / h) at 650 °C for 120 min. After mixing and screening to remove iron, obtain nano-scale cobalt tetroxide.

[0068] Example 2

[0069] This example provides a method for preparing nano-scale cobalt tetroxide, and the preparation method includes the following steps:

[0070] (1) Prepare a cobalt chloride solution with a cobalt ion concentration of 115 g / L as the cobalt salt solution, add Tween 80 as the surfactant (the addition amount of Tween 80 is in a mass ratio of 0.08:1 to the cobalt in the cobalt chloride solution) to obtain a cobalt salt mixed solution; prepare an ammonium bicarbonate solution with a concentration of 225 g / L as the complexing agent; prepare an ammonium bicarbonate solution with a concentration of 210 g / L as the bottom liquid (precipitant); prepare an ammonium bicarbonate solution with a concentration of 50 g / L as the detergent;

[0071] The reaction is carried out in a 200 L reactor. First, 90 L of the bottom liquid (ammonium bicarbonate solution with a concentration of 210 g / L) is added to the reactor. Subsequently, under the conditions of a reaction temperature of 42 °C and a stirring speed of 450 r / min, the cobalt salt mixed solution (cobalt chloride solution + Tween 80) and the complexing agent solution (ammonium bicarbonate solution with a concentration of 225 g / L) are added to the reactor in parallel flow through a peristaltic pump at a flow rate of 100 L / h and 160 L / h respectively, and a coprecipitation reaction is carried out under the condition of 450 r / min. Among them, the pH value of the coprecipitation reaction fluctuates within the range of 8.0 ± 0.5. When the average particle size D50 of nano-cobalt carbonate in the wet cobalt carbonate material is 460 nm, the coprecipitation reaction is stopped. After aging for 2.5 h, wet cobalt carbonate material is obtained;

[0072] (3) The wet cobalt carbonate material is put into a centrifuge and washed with ammonium bicarbonate at room temperature with a concentration of 50 g / L. After the test result of Cl - is below 200 ppm, the washed wet material is dried at 130 °C, and then crushed by a crusher for 60 s to obtain spherical cobalt carbonate powder. It is heat-treated in air (compressed air, air pressure 8 Nm 3 / h) at 650 °C for 120 min. After mixing and sieving to remove iron, nano-cobalt ferrite is obtained.

[0073] Example 3

[0074] This example provides a method for preparing nano-cobalt ferrite, and the preparation method includes the following steps:

[0075] (1) Prepare a cobalt chloride solution with a cobalt ion concentration of 130 g / L as the cobalt salt solution, add sodium citrate as the surfactant (the addition amount of sodium citrate is in a mass ratio of 0.01:1 to the cobalt in the cobalt chloride solution) to obtain a cobalt salt mixed solution; prepare an ammonium bicarbonate solution with a concentration of 180 g / L as the complexing agent; prepare an ammonium bicarbonate solution with a concentration of 230 g / L as the bottom liquid (precipitating agent); prepare an ammonium bicarbonate solution with a concentration of 50 g / L as the detergent;

[0076] The reaction is carried out in a 200 L reactor. First, 100 L of the bottom liquid (ammonium bicarbonate solution with a concentration of 230 g / L) is added to the reactor. Subsequently, under the conditions of a reaction temperature of 38 °C and a stirring speed of 350 r / min, the cobalt salt mixed solution (cobalt chloride solution + sodium citrate) and the complexing agent solution (ammonium bicarbonate solution with a concentration of 180 g / L) are added to the reactor in parallel flow through a peristaltic pump at a flow rate of 300 L / h and 450 L / h respectively, and a coprecipitation reaction is carried out under the condition of 350 r / min. Among them, the pH value of the coprecipitation reaction fluctuates within the range of 8.0 ± 0.5. When the average particle size D50 of nano-cobalt carbonate in the wet cobalt carbonate material is 470 nm, the coprecipitation reaction is stopped. After aging for 1.5 h, wet cobalt carbonate material is obtained;

[0077] (3) Put the wet cobalt carbonate into a centrifuge and wash it with ammonium bicarbonate at room temperature of 50 g / L. After the test result of Cl - is below 200 ppm, dry the washed wet material at 130 °C, and then crush it with a crusher for 120 s to obtain spherical cobalt carbonate powder. Heat-treat it at 800 °C in air (compressed air, air pressure 8 Nm 3 / h) for 60 min. After mixing and sieving to remove iron, nano-scale cobalt tetroxide is obtained.

[0078] Example 4

[0079] This example provides a method for preparing nano-scale cobalt tetroxide. The difference between this preparation method and that of Example 1 is that the concentration of the bottom liquid is 40 g / L, and the rest of the preparation methods and parameters are the same as those of Example 1.

[0080] Example 5

[0081] This example provides a method for preparing nano-scale cobalt tetroxide. The difference between this preparation method and that of Example 1 is that the concentration of the bottom liquid is 260 g / L, and the rest of the preparation methods and parameters are the same as those of Example 1.

[0082] Example 6

[0083] This example provides a method for preparing nano-scale cobalt tetroxide. The difference between this preparation method and that of Example 1 is that the aging time is 5 h, and the rest of the preparation methods and parameters are the same as those of Example 1.

[0084] Example 7

[0085] This example provides a method for preparing nano-scale cobalt tetroxide. The difference between this preparation method and that of Example 1 is that the aging time is 0.5 h, and the rest of the preparation methods and parameters are the same as those of Example 1.

[0086] Example 8

[0087] This example provides a method for preparing nano-scale cobalt tetroxide. The difference between this preparation method and that of Example 1 is that the ultrasonic crushing time is 150 s, and the rest of the preparation methods and parameters are the same as those of Example 1.

[0088] Comparative Example 1

[0089] This comparative example provides a method for preparing nano-scale cobalt tetroxide. The difference between this preparation method and that of Example 1 is that in step (2), the dried powder is first heat-treated and then crushed, that is, the order of the heat-treatment and crushing steps is reversed, and the rest of the preparation methods and parameters are the same as those of Example 1.

[0090] The nano cobalt tetroxide prepared in Examples 1-8 and Comparative Example 1 was tested for particle size using a laser diffraction particle size analyzer (Malvern 3000), and the test results are shown in Table 1.

[0091] Table 1

[0092]

[0093]

[0094] It can be seen from the test results that:

[0095] (1) It can be seen from Examples 1-3 that in the present invention, nano cobalt carbonate with a morphology of primary particles, good sphericity and high dispersibility is first prepared, and then through processes such as crushing and heat treatment, spherical nano cobalt tetroxide with uniform size, high yield and good fluidity can be obtained. The average particle size D50 of the nano cobalt tetroxide is 300 nm - 800 nm, and it can maintain good dispersibility and low degree of agglomeration, meeting the preparation requirements of the present invention; among them, the bottom liquid concentration, aging time, crushing duration and the process of crushing and heat treatment also play a crucial role in the preparation of nano cobalt tetroxide.

[0096] (2) It can be seen from Example 1 and Examples 4-5 that in the present invention, the concentration of the bottom liquid is regulated to be 60 g / L - 230 g / L, thereby regulating the average particle size of nano cobalt carbonate within the target range, providing a key raw material basis for the preparation of spherical nano cobalt tetroxide with uniform size, high yield, good fluidity and good dispersibility.

[0097] (3) It can be seen from Example 1 and Examples 6-7 that in the present invention, the aging time is regulated to be 1 h - 3 h, which can optimize the particle size and morphology of nano cobalt carbonate. If the aging time is too short, the crystallinity of nano cobalt carbonate will be low, and its stability will be poor, and it is easy to agglomerate and the dispersibility will be poor, and D100 will increase. If the aging time is too long, more impurities existing in the reaction system will be introduced, the purity of the powder will be reduced, and it will be difficult to remove in the later stage, thereby affecting the use performance of nano cobalt tetroxide.

[0098] (4) It can be seen from Example 1 and Example 8 that in the present invention, the crushing time is regulated to be 10 s - 120 s, which can control the particle size of the crushed powder to be uniform, with good sphericity and high dispersibility. If the crushing time is too long, although the particle size of nano cobalt tetroxide can be further refined, it is easy to cause the powder to agglomerate, form aggregates, and the dispersibility is poor, and D100 is relatively large, thereby affecting the use performance of nano cobalt tetroxide.

[0099] (5) It can be seen from Example 1 and Comparative Example 1 that the dispersion effect of the nanoparticles obtained by first crushing and then performing heat treatment in the present invention is significantly better than that of first performing heat treatment and then crushing. Crushing after heat treatment easily causes agglomeration of the nanoparticles.

[0100] In summary, the present invention first prepares nano cobalt carbonate with a morphology of primary particles, good sphericity and high dispersibility, and then through processes such as crushing and heat treatment, spherical nano cobalt ferrite with uniform size, high yield and good fluidity can be obtained, and it can still maintain good dispersibility and low degree of agglomeration; the preparation method adopted is simple and low-cost, and large-scale industrial production can be realized.

[0101] The applicant declares that the above is only the specific implementation manner 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 thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing nano-scale cobalt tetroxide, characterized in that: The preparation method comprises the following steps: (1) adding the cobalt salt mixed solution and the complexing agent solution to the bottom liquid in parallel to carry out a coprecipitation reaction, and aging to obtain a cobalt carbonate wet material; The cobalt salt mixed solution includes a surfactant and a cobalt salt solution; (2) The wet cobalt carbonate material described in step (1) is crushed and heat-treated in sequence to obtain nano-scale cobalt tetroxide.

2. The preparation method according to claim 1, characterized in that: In the cobalt salt solution of step (1), the concentration of cobalt ions is 110 g / L-130 g / L; Preferably, in the cobalt salt mixed solution of step (1), the mass ratio of the surfactant to the cobalt in the cobalt salt solution is (0.01-0.08):1; Preferably, the surfactant comprises any one of Tween 80, polyvinyl pyrrolidone or sodium citrate or a combination of at least two thereof; Preferably, the concentration of the complexing agent solution in step (1) is 180 g / L-230 g / L; Preferably, the complexing agent solution in step (1) comprises any one of ammonium bicarbonate solution, sodium bicarbonate solution, sodium hydroxide solution or sodium carbonate solution, or a combination of at least two thereof.

3. The preparation method according to claim 1 or 2, characterized in that: The base liquid in step (1) accounts for 40%-55% of the volume of the reaction container; Preferably, the base solution in step (1) comprises any one of ammonium bicarbonate solution, sodium bicarbonate solution, sodium hydroxide solution or sodium carbonate solution, or a combination of at least two thereof; Preferably, the concentration of the base solution in step (1) is 60 g / L-230 g / L.

4. The preparation method according to any one of claims 1 to 3, characterized in that The flow rate of the cobalt salt mixed solution in step (1) is 100L / h-300L / h; Preferably, the flow rate of the complexing agent solution in step (1) is 130 L / h-450 L / h; Preferably, the coprecipitation reaction in step (1) includes stirring; Preferably, the stirring speed in step (1) is 350 r / min-450 r / min; Preferably, the temperature of the coprecipitation reaction in step (1) is 38°C-45°C; Preferably, the pH value of the coprecipitation reaction in step (1) is 7-8.5; Preferably, the aging time in step (1) is 1h-3h; Preferably, in the cobalt carbonate wet material in step (1), the average particle size D50 of nano-cobalt carbonate is 400nm-1000nm.

5. The preparation method according to any one of claims 1 to 4, characterized in that: Before the crushing in step (2), washing and drying steps are also included; Preferably, the detergent used in the washing comprises an ammonium bicarbonate solution.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The crushing time in step (2) is 10s-120s; Preferably, the heat treatment in step (2) is carried out at a holding temperature of 450°C-800°C; Preferably, the heating rate of the heat treatment in step (2) is 7°C / min-12°C / min; Preferably, the heat treatment time in step (2) is 60 min to 180 min; Preferably, the gas used for the heat treatment in step (2) includes air.

7. The preparation method according to claim 1, characterized in that: The preparation method comprises the following steps: (1) uniformly mixing a cobalt salt solution having a cobalt ion concentration of 110 g / L-130 g / L and a surfactant to obtain a cobalt salt mixed solution, wherein the mass ratio of the surfactant to the cobalt in the cobalt salt solution is (0.01-0.08):1, adding the cobalt salt mixed solution and a complexing agent solution having a concentration of 180 g / L-230 g / L to a base liquid having a concentration of 60 g / L-230 g / L under stirring, and performing a coprecipitation reaction at a speed of 350 r / min-450 r / min, a temperature of 38° C.-45° C., and a pH value of 7-8.5, until the average particle size D50 of nano-cobalt carbonate in the cobalt carbonate wet material is 400 nm-1000 nm, stopping the coprecipitation reaction, and aging for 1 h-3 h to obtain a cobalt carbonate wet material; The flow rate of the cobalt salt mixed solution is 100L / h-300L / h, the flow rate of the complexing agent is 130L / h-450L / h; the base liquid accounts for 40%-55% of the volume of the reaction container; (2) The wet cobalt carbonate material of step (1) is washed until the content of impurity ions is below 200 ppm, dried at 100° C.-150° C., crushed for 10 s-120 s, and heated to 450° C.-800° C. at a heating rate of 7° C. / min-12° C. / min in air for 60 min-180 min to obtain nano-scale cobalt tetroxide.

8. A nano-scale cobalt trioxide, characterized in that: The nano-scale cobalt trioxide is prepared according to the preparation method according to any one of claims 1 to 7.

9. The nano-scale cobalt trioxide according to claim 8, characterized in that: The average particle size D50 of the nano-scale cobalt tetroxide is 300nm-800nm.

10. An application of nano-scale cobalt tetroxide, characterized in that: The nano-scale cobalt tetroxide prepared by the preparation method according to any one of claims 1 to 7, or the nano-scale cobalt tetroxide according to claim 8 or 9 is applied to the field of catalysts, battery materials, gas sensors or magnetic materials.

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