Preparation method of high-purity superfine cobalt monoboride powder

Abstract

The invention belongs to the technical field of preparation of high-purity cobalt boride, and particularly provides a preparation method of high-purity superfine cobalt boride powder, which comprises the following steps: 1) mixing Co3O4 with isopropanol, sanding and crushing to obtain Co3O4 slurry; b4C and isopropanol are mixed, sanded and crushed to obtain B4C slurry; then mixing the Co3O4 slurry with the B4C slurry and carbon black at a high speed to obtain a mixture; 2) sintering the mixture under the protection of inert gas to obtain a sintered material, and 3) scattering and sieving the sintered material to obtain the CoB. The CoB prepared by the invention has the advantages of low impurity content, small particle size and uniformity.

Description

Technical Field

[0001] This application belongs to the field of high-purity cobalt boride preparation technology, and in particular relates to a method for preparing high-purity ultrafine cobalt boride powder. Background Technology

[0002] CoB is an intermetallic compound that possesses both the high hardness and chemical stability of ceramics and the excellent electrical conductivity of metals, while also exhibiting magnetic and microwave absorption properties. Published methods for synthesizing CoB include liquid-phase synthesis, solid-state sintering, and direct elemental synthesis. The liquid-phase method uses borohydrides such as NaBH4 as the boron source and cobalt salts such as CoCl2 as the cobalt source, preparing cobalt monoboride at low temperatures in water or organic solvents. This method can synthesize high-purity nanoscale particles at low temperatures, but mass production faces challenges such as the disposal of large amounts of process wastewater and the inability to completely restore the particle size to its original primary size after drying.

[0003] Solid-state sintering uses cobalt oxides or hydroxides as the cobalt source and borohydrides such as NaBH4 as the boron source. After solid-state mixing and pressing, the mixture is sintered at high temperature and washed with water to obtain ultrafine CoB powder. Although this method has low raw material and process costs, CoB reacts slowly with water to produce cobalt hydroxide and boric acid, which increases the oxygen content in the product and limits its application. Direct elemental synthesis uses elemental cobalt and elemental boron to synthesize CoB at high temperatures. Whether the reaction is carried out in an atmosphere furnace or a high-temperature plasma rapid reaction, the synthesized particles are relatively large and need to be crushed to obtain ultrafine powder. Moreover, the cost of elemental boron raw materials is too high, resulting in poor overall economic efficiency.

[0004] For example, CN106179349A discloses a method for preparing ultrafine nano-CoB powder. Cobalt acetate ((CH3COO)2Co) is used as the cobalt source, NaBH4 as the boron source, and polyol and water as solvents. CoB is obtained through a liquid-phase reaction at room temperature, followed by filtration, washing, and drying to obtain the final product. This method can synthesize CoB at low temperatures, but large-scale production faces challenges in handling large amounts of waste liquid and in restoring the original primary particle size to its original caking state after filter cake drying.

[0005] For example, CN102442706A discloses a method for preparing CoB powder, which involves mixing cobalt oxide or hydroxide with borohydride, pressing the mixture into briquettes, reacting it at 400-800℃, and then washing and drying it to obtain the finished product. This method has low raw material and process costs, but during the washing process, CoB reacts slowly with water, leading to an increase in the oxygen content of the finished product.

[0006] For example, CN118221126A discloses a method for preparing ultrafine CoB, which uses elemental cobalt, elemental boron, and a binder for granulation, heats the granules with high-temperature plasma to obtain CoB, and then crushes them to obtain ultrafine cobalt boride powder. This method has high raw material costs for elemental boron, cannot directly obtain ultrafine powder, and carries a high risk of introducing impurities during the crushing process.

[0007] Although existing technologies attempt to optimize processes, they still cannot simultaneously meet the four core indicators of low oxygen content, low metal impurities, fine particle size, and low cost. Summary of the Invention

[0008] To address the aforementioned issues and further improve the performance of high-purity cobalt boride products, this application provides a method for preparing high-purity ultrafine cobalt boride powder. The prepared cobalt boride powder exhibits high purity (≥99.5%), low free carbon (≤0.2%), low metal impurities (Fe≤100ppm, Zn≤10ppm, Cu≤10ppm), low oxygen content (≤0.2%), and is micron-sized (D50=1-2μm).

[0009] This application provides a method for preparing high-purity ultrafine cobalt boride powder, comprising the following steps: 1) Co3O4 and isopropanol are mixed and milled to obtain Co3O4 slurry; B4C and isopropanol are mixed and milled to obtain B4C slurry; then the Co3O4 slurry, B4C slurry, and carbon black are mixed at high speed to obtain a mixture. 2) The mixture is sintered under inert gas protection to obtain sintered material; 3) Take the sintered material, break it up, and sieve it to obtain the final product.

[0010] Furthermore, in step 1), the molar ratio of Co3O4 slurry, B4C slurry, and carbon black is 4:(2.8-3.2):(12.8-13.2).

[0011] Furthermore, in step 1), the crushing is performed by high-speed ball milling, and the grinding media is silicon nitride balls.

[0012] Furthermore, in step 1), the particle size D50 of the Co3O4 slurry is 200-500 nm. And / or, the Co3O4 is lithium-ion grade; And / or, the mass ratio of Co3O4 to isopropanol is (1.5-3):(7.5-8).

[0013] Furthermore, in step 1), the agitator and inner wall of the high-speed mixing device are coated with tungsten carbide.

[0014] Furthermore, in step 1), the particle size D50 of the B4C slurry is 200-600 nm; And / or, the grinding media used for milling the mixture of B4C and isopropanol is cubic boron nitride or diamond; And / or, the mass ratio of B4C to isopropanol is (1.5-3):(7-8.5).

[0015] Furthermore, in step 1), the carbon black is lithium-ion grade carbon black; And / or, the specific surface area of ​​the carbon black is 40-80 m². 2 / g.

[0016] Furthermore, in step 2), sintering involves heating to 1100-1450℃ and holding at that temperature for 1-10 hours.

[0017] Furthermore, in step 2), the inert gas is an Ar atmosphere.

[0018] Furthermore, in step 2), the container used in the sintering process is a high-purity graphite crucible.

[0019] Compared with the prior art, this application has the following beneficial effects: 1. This application uses lithium-ion grade Co3O4 as the cobalt source, which is easier to break down to the submicron level. The reaction process generates submicron-sized cobalt particles, which is beneficial for boron diffusion, thereby reducing the reaction temperature and holding time. Furthermore, it uses high-purity submicron-sized B4C as the boron source. Firstly, its cost is much lower than that of elemental boron. Secondly, B4C is an excellent boronizing agent, with a faster boronizing rate and lower required temperature compared to boron sources such as boron anhydride.

[0020] 2. All parts of the equipment used in this application that come into contact with materials (except for the vibrating screen) are lined with ceramic or coated with Teflon to minimize the introduction of metal impurities during the process. In addition, due to the low-temperature reaction and the addition of carbon black, the connection, diffusion and growth of adjacent particles can be effectively blocked, and ultrafine powder can be obtained directly without crushing. Attached Figure Description

[0021] Figure 1 This is an XRD pattern of the CoB product obtained in Example 1 of this application.

[0022] Figure 2 This is a SEM image of the CoB product obtained in Example 1 of this application. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0024] This application, based on extensive experimental research, provides a method for preparing high-purity, ultrafine cobalt boride powder, comprising the following steps: 1) Co3O4 and isopropanol are mixed and milled to obtain Co3O4 slurry; B4C and isopropanol are mixed and milled to obtain B4C slurry; then the Co3O4 slurry, B4C slurry, and carbon black are mixed at high speed to obtain a mixture. 2) The mixture is sintered under inert gas protection to obtain sintered material; 3) Take the sintered material, break it up, and sieve it to obtain the final product.

[0025] Furthermore, in step 1), the molar ratio of Co3O4 slurry, B4C slurry, and carbon black is 4:(2.8-3.2):(12.8-13.2).

[0026] In some specific embodiments, in step 1), the molar ratio of Co3O4 slurry, B4C slurry and carbon black can be 4:(2.8-3):(12.8-13) or 4:(3-3.2):(13-13.2). More preferably, the molar ratio of Co3O4 slurry, B4C slurry, and carbon black can be 4:2.8:12.8, 4:2.85:12.8, 4:2.9:12.8, 4:2.95:12.8, 4:3:12.8, 4:3.05:12.8, 4:3.1:12.8, 4:3.15:12.8, 4:3.2:12.8, 4:2.8:12.85, 4:2.85:12.9, 4:2.9:12.95, 4:2.95:13, 4:3:13.05, 4:3.05:13.1, 4:3.1:13.15, or 4:3.15:13.2. Under normal circumstances, a molar ratio of Co3O4 slurry, B4C slurry, and carbon black of 4:3.05:12.95 can achieve better experimental results.

[0027] Furthermore, in step 1), the crushing is performed by high-speed ball milling, and the grinding media is silicon nitride balls.

[0028] Furthermore, in step 1), the particle size D50 of the Co3O4 slurry is 200-500 nm. And / or, the Co3O4 is lithium-ion grade; And / or, the mass ratio of Co3O4 to isopropanol is (1.5-3):(7.5-8).

[0029] In some specific embodiments, in step 1), the particle size D50 of the Co3O4 slurry can be 200-250nm, 250-300nm, 300-350nm, 350-400nm, 400-450nm, or 450-500nm. More preferably, the particle size D50 of the Co3O4 slurry can be 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm, 290nm, 300nm, 310nm, 320nm, 330nm, 340nm, 350nm, 360nm, 370nm, 380nm, 390nm, 400nm, 410nm, 420nm, 430nm, 440nm, 450nm, 460nm, 470nm, 480nm, 490nm, or 500nm.

[0030] Under normal circumstances, when the particle size D50 of the Co3O4 slurry is 310 nm in step 1), better product performance can be obtained.

[0031] In some specific embodiments, the mass ratio of Co3O4 to isopropanol can be 1.5:8.5, 2:8, 2.5:7.5, or 3:7. More preferably, under normal circumstances, a mass ratio of Co3O4 to isopropanol of 3:7 can achieve better technical results.

[0032] Furthermore, in step 1), the agitator and inner wall of the high-speed mixing device are coated with tungsten carbide.

[0033] Furthermore, in step 1), the particle size D50 of the B4C slurry is 200-600 nm; And / or, the grinding media used for milling the mixture of B4C and isopropanol is cubic boron nitride or diamond.

[0034] And / or, the mass ratio of B4C to isopropanol is (1.5-3):(7-8.5).

[0035] In some specific embodiments, in step 1), the particle size D50 of the B4C slurry can be 200-250nm, 250-300nm, 300-350nm, 350-400nm, 400-450nm, 450-500nm, 500-550nm, or 550-600nm. More preferably, the particle size D50 of the B4C slurry can be 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm, 290nm, 300nm, 310nm, 320nm, 330nm, 340nm, 350nm, 360nm, 370nm, 380nm, 390nm, 400nm, 410nm, 420nm, 430nm, 440nm, 450nm, 460nm, 470nm, 480nm, 490nm, 500nm, 510nm, 520nm, 330nm, 540nm, 550nm, 560nm, 570nm, 580nm, 590nm, or 600nm. Under normal circumstances, B4C slurry with a particle size D50 of 230nm, 350nm, or 580nm can achieve better results.

[0036] Furthermore, in step 1), the carbon black is lithium-ion grade carbon black; And / or, the specific surface area of ​​the carbon black is 40-80 m². 2 / g.

[0037] In some specific embodiments, the specific surface area of ​​the carbon black can be 40-50 m². 2 / g、50-60m 2 / g、60-70m 2 / g、70-80m 2 / g. More preferably, the specific surface area of ​​the carbon black can be 40m². 2 / g、45m 2 / g, 50m 2 / g、55m 2 / g、60m 2 / g、65m 2 / g、70m 2 / g、75m 2 / g、80m 2 / g. Under normal circumstances, the specific surface area of ​​the carbon black is 60m². 2 / g or 65m 2 When the ratio is / g, better technical results can be achieved.

[0038] Furthermore, in step 2), sintering involves heating to 1100-1450℃ and holding at that temperature for 1-10 hours.

[0039] Furthermore, in step 2), the inert gas is an Ar atmosphere.

[0040] Furthermore, in step 2), the container used in the sintering process is a high-purity graphite crucible.

[0041] Example 1 The method for preparing high-purity ultrafine cobalt boride powder in this embodiment includes the following steps: 1) Lithium-ion grade Co3O4 and isopropanol were milled and crushed in a high-speed ball mill at a mass ratio of 3:7 to obtain a Co3O4 slurry. The grinding media was silicon nitride balls. The particle size D50 of the obtained Co3O4 slurry was measured to be 310 nm. The obtained Co3O4 slurry was freeze-dried to obtain well-dispersed Co3O4 powder. 2) Lithium-ion grade B4C and isopropanol were milled and crushed in a high-speed ball mill at a mass ratio of 2:8 to obtain a B4C slurry. The grinding media was diamond. The particle size D50 of the obtained B4C slurry was measured to be 230 nm. The obtained B4C slurry was freeze-dried to obtain well-dispersed B4C powder. Then, Co3O4 powder, B4C powder, and a specific surface area of ​​65 m² were added. 2 / g of lithium-ion battery grade carbon black was mixed at high speed in a high-speed mixer at a molar ratio of 4:3.05:12.95 to obtain a mixture. 2) Place the mixture into a high-purity graphite crucible, then push the high-purity graphite crucible into an atmosphere furnace. Evacuate the furnace to below 100 Pa and then stop evacuation. Then, fill the furnace with argon gas to atmospheric pressure and begin sintering. The heating curve during sintering is as follows: room temperature to 900℃, 5℃ / min; hold at 900℃ for 1 h; 900℃ to 1200℃, 3℃ / min; hold at 1200℃ for 4 h to obtain the sintered material. The argon gas flow rate during the heating and cooling processes is 10 L / min. 3) Take the sintered material, break it up, and pass it through a 325-mesh sieve to obtain the final product.

[0042] Example 2 The method for preparing high-purity ultrafine cobalt boride powder in this embodiment includes the following steps: 1) Lithium-ion grade Co3O4 and isopropanol were milled and crushed in a high-speed ball mill at a mass ratio of 3:7 to obtain a Co3O4 slurry. The grinding media was silicon nitride balls. The particle size D50 of the obtained Co3O4 slurry was measured to be 310 nm. The obtained Co3O4 slurry was freeze-dried to obtain well-dispersed Co3O4 powder. 2) Lithium-ion grade B4C and isopropanol were milled and crushed in a high-speed ball mill at a mass ratio of 2:8 to obtain a B4C slurry. The grinding media was diamond. The particle size D50 of the obtained B4C slurry was measured to be 350 nm. The obtained B4C slurry was freeze-dried to obtain well-dispersed B4C powder. Then, Co3O4 powder, B4C powder, and a specific surface area of ​​65 m² were added. 2 / g of lithium-ion battery grade carbon black was mixed at high speed in a high-speed mixer at a molar ratio of 4:3.05:12.95 to obtain a mixture. 2) Place the mixture into a high-purity graphite crucible, then push the high-purity graphite crucible into an atmosphere furnace. Evacuate the furnace to below 100 Pa and then stop evacuation. Then, fill the furnace with argon gas to atmospheric pressure and begin sintering. The heating curve during sintering is as follows: room temperature to 900℃, 5℃ / min; hold at 900℃ for 1 h; 900℃ to 1200℃, 3℃ / min; hold at 1200℃ for 4 h to obtain the sintered material. The argon gas flow rate during the heating and cooling processes is 10 L / min. 3) Take the sintered material, break it up, and pass it through a 325-mesh sieve to obtain the final product.

[0043] Example 3 The method for preparing high-purity ultrafine cobalt boride powder in this embodiment includes the following steps: 1) Lithium-ion grade Co3O4 and isopropanol were milled and crushed in a high-speed ball mill at a mass ratio of 3:7 to obtain a Co3O4 slurry. The grinding media was silicon nitride balls. The particle size D50 of the obtained Co3O4 slurry was measured to be 310 nm. The obtained Co3O4 slurry was freeze-dried to obtain well-dispersed Co3O4 powder. 2) Lithium-ion grade B4C and isopropanol were milled and crushed in a high-speed ball mill at a mass ratio of 2:8 to obtain a B4C slurry. The grinding media was cubic boron nitride. The particle size D50 of the obtained B4C slurry was measured to be 580 nm. The obtained B4C slurry was freeze-dried to obtain well-dispersed B4C powder. Then, Co3O4 powder, B4C powder, and a specific surface area of ​​65 m² were added. 2 / g of lithium-ion battery grade carbon black was mixed at high speed in a high-speed mixer at a molar ratio of 4:3.05:12.95 to obtain a mixture. 2) Place the mixture into a high-purity graphite crucible, then push the high-purity graphite crucible into an atmosphere furnace. Evacuate the furnace to below 100 Pa and then stop evacuation. Then, fill the furnace with argon gas to atmospheric pressure and begin sintering. The heating curve during sintering is as follows: room temperature to 900℃, 5℃ / min; hold at 900℃ for 1 h; 900℃ to 1200℃, 3℃ / min; hold at 1200℃ for 4 h to obtain the sintered material. The argon gas flow rate during the heating and cooling processes is 10 L / min. 3) Take the sintered material, break it up, and pass it through a 325-mesh sieve to obtain the final product.

[0044] control group Co powder with an average particle size of 3 μm and B powder produced by the magnesia-reduction process with an average particle size of 5 μm were mixed uniformly at a molar ratio of 1:1.1. The mixed material was added to a high-purity graphite crucible, and then the graphite crucible assembly was pushed into an atmosphere furnace. The furnace was evacuated to below 100 Pa and then the evacuation was stopped. Argon gas was then introduced to atmospheric pressure, and the temperature was raised. The heating curve used was as follows: room temperature to 900℃, 5℃ / min; 900℃ held for 1 h; 900℃ to 1400℃, 3℃ / min; 1350℃ held for 4 h. The argon gas flow rate during the heating and cooling processes was 10 L / min.

[0045] Performance testing 1. The purity, particle size, specific surface area, and impurity content of the CoB products obtained in Examples 1-3 and the control group were tested, and the results are shown in Table 1 and Table 2.

[0046] Table 1. Test results of purity, particle size, specific surface area, and impurity content of the CoB product from Example 1 of this application. Table 2 Comparison of CoB product index data between Examples 1-3 of this application and the control group. Analysis of Tables 1 and 2 shows that the CoB of this application can achieve a particle size much smaller than that of conventional elemental synthesis methods without the need for crushing, and the content of metal impurities is also lower.

[0047] 2. The CoB product obtained in Example 1 was subjected to XRD and scanning electron microscopy tests, and the results are as follows: Figure 1 and Figure 2 As shown, from Figure 1 It can be seen that the CoB prepared in this application has high purity and is free of other impurity peaks and phases. Furthermore, from... Figure 2 It can be seen that the CoB finished product has uniform particles and good morphology.

[0048] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing high-purity ultrafine cobalt boride powder, characterized in that: Includes the following steps: 1) Co3O4 and isopropanol are mixed and milled to obtain Co3O4 slurry; B4C and isopropanol are mixed and milled to obtain B4C slurry; then the Co3O4 slurry, B4C slurry, and carbon black are mixed at high speed to obtain a mixture. 2) The mixture is sintered under inert gas protection to obtain sintered material; 3) Take the sintered material, break it up, and sieve it to obtain the final product.

2. The method for preparing high-purity ultrafine cobalt boride powder according to claim 1, characterized in that: In step 1), the molar ratio of Co3O4 slurry, B4C slurry, and carbon black is 4:(2.8-3.2):(12.8-13.2).

3. The method for preparing high-purity ultrafine cobalt boride powder according to claim 1, characterized in that: In step 1), the crushing process involves high-speed ball milling, with silicon nitride balls as the grinding media.

4. The method for preparing high-purity ultrafine cobalt boride powder according to claim 1, characterized in that: In step 1), the particle size D50 of the Co3O4 slurry is 200-500 nm; And / or, the Co3O4 is lithium-ion grade; And / or, the mass ratio of Co3O4 to isopropanol is (1.5-3):(7.5-8).

5. The method for preparing high-purity ultrafine cobalt boride powder according to claim 1, characterized in that: In step 1), the stirring paddle and inner wall of the high-speed mixing device were coated with tungsten carbide.

6. The method for preparing high-purity ultrafine cobalt boride powder according to claim 1, characterized in that: In step 1), the particle size D50 of the B4C slurry is 200-600 nm; And / or, the grinding media used for milling the mixture of B4C and isopropanol is cubic boron nitride or diamond; And / or, the mass ratio of B4C to isopropanol is (1.5-3):(7-8.5).

7. The method for preparing high-purity ultrafine cobalt boride powder according to claim 1, characterized in that: In step 1), the carbon black is lithium-ion grade carbon black; And / or, the specific surface area of ​​the carbon black is 40-80 m². 2 / g.

8. The method for preparing high-purity ultrafine cobalt boride powder according to claim 1, characterized in that: In step 2), sintering involves heating to 1100-1450℃ and holding at that temperature for 1-10 hours.

9. The method for preparing high-purity ultrafine cobalt boride powder according to claim 8, characterized in that: In step 2), the inert gas is an Ar atmosphere.

10. The method for preparing high-purity ultrafine cobalt boride powder according to claim 1, characterized in that: In step 2), the container used in the sintering process is a high-purity graphite crucible.

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