Preparation method of nano spherical cobalt powder
Through low temperature and high ammonium synthesis conditions, wet synthesis and hydrogen reduction steps, the problems of complex and high cost of ultrafine cobalt powder production process in the existing technology were solved, and nanospherical cobalt powder with D50≤0.2μm were successfully prepared, which is suitable for the preparation of high-performance WC-Co carbide tools.
Patent Information
- Application Number
- CN202510140397.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-08
- Publication Date
- 2025-06-27
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
The prior art is difficult to effectively produce ultrafine cobalt powder with a particle size of less than 1.0 μm, resulting in complex production processes and high cost.
Spherical nanocobalt carbonate particles were prepared by wet synthesis and high temperature slurry using low-temperature and high-temperature slurry, and nanospherical cobalt powder was obtained by hydrogen reduction.
It realizes the simplicity and control of the production process, reduces production costs, and obtains nanospherical cobalt powder with D50≤0.2μm, which is suitable for the preparation of high-performance WC-Co carbide tools.
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Figure CN120205802A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of preparation of nano / ultrafine metal powders in metal functional materials, and particularly relates to a method for preparing nano cobalt powder for WC-Co cemented carbide tools. Background Art
[0002] WC-Co cemented carbide has characteristics such as high temperature resistance, high hardness, high wear resistance, and corrosion resistance, and is widely used in fields such as mining tools, dies, and machine tool cutters. At present, most cemented carbide tools are made of submicron / micron-scale cemented carbide. However, during the cutting of difficult-to-machine materials, higher requirements are put forward for the mechanical properties of cemented carbide tools, such as hardness, fracture strength, fracture toughness, heat resistance, and impact resistance. In order to obtain high-performance WC-Co cemented carbide tools, it is necessary to study the preparation process of tool materials.
[0003] The binder used for preparing WC-Co cemented carbide is cobalt powder, and the role of cobalt powder in the preparation of ultrafine-grained WC-Co cemented carbide is crucial. Using spherical cobalt powder with ultrafine / nano-scale particle size can not only accelerate the sintering process and reduce energy consumption, but also reduce the sintering densification temperature of the alloy to inhibit abnormal growth of WC grains, which helps to obtain high-performance ultrafine and nano-crystalline WC-Co cemented carbide.
[0004] At present, the hydrogen reduction method is generally used in China to prepare spherical ultrafine / nano cobalt powder, mainly producing fine-grained cobalt powder with an average particle size between 1 and 2 μm, and there is less ultrafine cobalt powder with a particle size below 1.0 μm. In order to produce ultrafine cobalt powder, new production processes of cobalt powder are being explored at home and abroad, such as thermal decomposition method, high-pressure water mist method, carbonyl method, electrolysis method, polyol method, etc.; although ultrafine cobalt powder with an average particle size less than 1 μm can be prepared by these methods, some methods for producing ultrafine cobalt powder have complex processes and high raw material costs, and some other methods require expensive equipment and high production costs. Summary of the Invention
[0005] To overcome the deficiencies of the existing production processes, the purpose of the present invention is to provide a method for preparing nano-spherical cobalt powder with a simple and easy-to-control production process and easy industrial production to the art, as shown in Figure 1 , and the purpose of the present invention can be achieved through the following technical solutions:
[0006] (1) Solution preparation: Using cobalt sulfate as the raw material, prepare a cobalt solution with a cobalt concentration of 1.8 - 2.0 mol / L as solution A; prepare an ammonium bicarbonate solution with a concentration of 3.0 - 3.2 mol / L as solution B.
[0007] (2) Wet synthesis: At the beginning of the synthesis reaction, a peristaltic pump is used to add solutions A and B into the reaction kettle in a co-current manner, and the synthesis reaction is carried out under stirring. When the reaction kettle is full, the supernatant is extracted after standing to concentrate the synthesis slurry. When the slurry density in the reaction kettle reaches a certain value, the kettle is divided to reduce the solid content of the slurry in the reaction kettle. During the reaction process, the flow rates of solutions A and B, the reaction temperature of 30-35 °C, the stirring frequency, and the volume of the supernatant extracted each time are strictly controlled. When the laser particle size of the synthesis material reaches a certain value, the synthesis is stopped.
[0008] (3) High-temperature pulping: After the synthesis reaction is completed, the solid and liquid of the synthesis product are separated, and the synthesized cobalt carbonate solid is subjected to high-temperature pulping treatment on another reaction kettle.
[0009] (4) Stirring and crushing: The cobalt carbonate slurry after high-temperature pulping is wet-crushed by increasing the stirring frequency.
[0010] (5) Washing and drying: The crushed material is washed and dried to obtain spherical nano cobalt carbonate.
[0011] (6) Hydrogen reduction: The dried spherical nano cobalt carbonate is subjected to hydrogen reduction to obtain a nano spherical cobalt powder product.
[0012] Preferably, in the step (2), the synthesis reaction is carried out on an A1 reaction kettle. The effective volume of the A1 reaction kettle is 50 L, the flow rate of solution A is 6-8 L / h, the flow rate of solution B is 10-14 L / h, and the molar ratio of ammonium bicarbonate to cobalt sulfate added to the reaction kettle is 2.5-2.7. The reaction temperature is 30-35 °C, the stirring frequency of the reaction kettle motor is 15-20 Hz, and the volume of the supernatant extracted each time is 25-30 L. When the slurry density in the reaction kettle > 1.4 g / cm 3 When it reaches 20-21 µm, the synthesis is stopped. 50
[0013] Preferably, in the step (3), a centrifuge is used to separate the solid and liquid of the synthesis slurry. The pulping reaction is carried out on an A2 reaction kettle. The effective volume of the A2 reaction kettle is 20 L. The synthesized cobalt carbonate and pure water are configured into a slurry with a density ≥ 1.5 g / L and subjected to pulping treatment in the reaction kettle. The pulping temperature ≥ 90 °C, the stirring frequency of the reaction kettle motor is 25-30 Hz, and the pulping time is 2-3 h.
[0014] Preferably, in the step (4), the wet crushing is carried out on an A2 reaction kettle. After the pulping reaction is completed, the stirring frequency of the A2 reaction kettle motor is adjusted to 50 Hz, and the crushing step is started. The temperature during crushing ≥ 90 °C, and the crushing time is 1 h.
[0015] Preferably, in the step (5), the washing device is a filter press, the drying device is a vacuum drying oven, the drying temperature is 100-120°C, and the moisture content of the dried material is ≤0.2%.
[0016] Preferably, in the step (6), the reducing gas used in the reduction step is hydrogen, and the reduction temperature is 350-400°C.
[0017] Preferably, in the step (6), the indexes of the nano-spherical cobalt powder are: D 50 ≤0.2 μm, and the microscopic morphology is spherical granular.
[0018] The characteristics of this method are as follows: This method uses cobalt sulfate and ammonium bicarbonate as raw materials, and through the synthesis conditions of low temperature and high ammonium (i.e., ammonium bicarbonate), spherical cobalt carbonate particles containing a large amount of complex ammonium are prepared. Then, the synthesized spherical cobalt carbonate is slurried with hot pure water. Under the action of hot pure water, the complex ammonium will overflow from the inside of the spherical cobalt carbonate, causing the spherical cobalt carbonate to transform into micron-porous cobalt carbonate spherical particles composed of nano-spherical cobalt carbonate particles. Then, by increasing the stirring frequency, the micron cobalt carbonate particles collide with each other and are broken into nano-spherical cobalt carbonate particles. The obtained nano-spherical cobalt carbonate particles are reduced with hydrogen to obtain nano-spherical cobalt powder products. This method for preparing nano-spherical cobalt powder has simple raw materials and processes and is easy to industrialize. Description of the Drawings
[0019] Figure 1 is the process flow chart of the preparation of nano-spherical cobalt powder;
[0020] Figure 2 is the microscopic morphology diagram of micron-scale cobalt carbonate before high-temperature slurrying in Example 1;
[0021] Figure 3 is the microscopic morphology diagram of micron-scale porous cobalt carbonate spherical particles composed of nano-spherical cobalt carbonate particles after high-temperature slurrying in Example 1;
[0022] Figure 4 is the microscopic morphology diagram of the nano-spherical cobalt prepared in Example 1;
[0023] Figure 5 is the microscopic morphology diagram of the nano-spherical cobalt prepared in Example 2;
[0024] Figure 6 is the microscopic morphology diagram of the nano-spherical cobalt prepared in Example 3; Detailed Embodiments
[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Embodiment 1
[0026] The production steps are the same as above and will not be elaborated here. The specific parameters in each step are as follows:
[0027] Using cobalt sulfate as the raw material, a cobalt solution with a cobalt concentration of 1.8 mol / L is prepared as solution A; a ammonium bicarbonate solution with a concentration of 3.0 mol / L is prepared as solution B.
[0028] The synthesis reaction is carried out on an A1 reactor with an effective volume of 50 L. At the beginning of the synthesis, solutions A and B are added to the reactor in parallel using a peristaltic pump, and the synthesis reaction is carried out under stirring. The flow rate of solution A is 6 L / h, the flow rate of solution B is 10 L / h, the molar ratio of ammonium bicarbonate to cobalt sulfate added to the reactor is 2.5, the reaction temperature is 30 °C, and the stirring frequency of the reactor motor is 20 Hz. When the synthesis reaches 3 h, the reactor is full, the stirring is stopped, and the slurry in the reactor is left to stand. After the solid-liquid separation of the materials in the reactor, 25 - 30 L of the supernatant is extracted to complete one operation of standing and extracting the supernatant, and then this operation is repeated. After this operation is carried out 6 times, the sub-reactor operation is carried out, and about 50% of the synthesized slurry is separated out of the reactor. When the laser particle size D of the synthesized material 50 reaches 20 - 21 µm, the synthesis is stopped.
[0029] After the synthesis reaction is completed, a centrifuge is used to carry out solid-liquid separation on the synthesized slurry, and the microscopic morphology of the obtained micron-sized cobalt carbonate is shown in Figure 2 , and the slurrying reaction is carried out on an A2 reactor. The effective volume of the A2 reactor is 20 L. The synthesized cobalt carbonate and pure water are configured into a slurry with a density ≥ 1.5 g / L, and the slurrying treatment is carried out in the reactor. The slurrying temperature ≥ 90 °C, the stirring frequency of the reactor motor is 30 Hz, and the slurrying time is 2 h.
[0030] The wet crushing is carried out on the A2 reactor. After the slurrying reaction is completed, the stirring frequency of the A2 reactor motor is adjusted to 50 Hz, and the crushing step is started. The temperature during crushing ≥ 90 °C, the crushing time is 1 h, and the microscopic morphology of the micron-sized loose cobalt carbonate spherical particles composed of nano-spherical cobalt carbonate particles after high-temperature slurrying is shown in Figure 3 .
[0031] The washing equipment is a filter press, and the drying equipment is a vacuum drying oven. The drying temperature is 100 - 120 °C, and the moisture content of the dried material ≤ 0.2%.
[0032] The reducing gas used in the reduction step is hydrogen, and the reduction temperature is 350 °C to obtain D 50 ≤0.2 μm, and the microscopic morphology is spherical particulate nano-spherical cobalt powder. The microscopic morphology of the prepared nano-spherical cobalt powder is shown in Figure 4 . Example 2
[0033] The production steps are the same as above and will not be elaborated here. The specific parameters in each step are as follows:
[0034] Using cobalt sulfate as the raw material, a cobalt solution with a cobalt concentration of 1.9 mol / L is prepared as solution A; a ammonium bicarbonate solution with a concentration of 3.1 mol / L is prepared as solution B.
[0035] The synthesis reaction is carried out on an A1 reactor with an effective volume of 50 L. At the start of the synthesis, solutions A and B are added into the reactor in a co-current manner using a peristaltic pump, and the synthesis reaction is carried out under stirring. The flow rate of solution A is 7 L / h, the flow rate of solution B is 11.6 L / h, the molar ratio of ammonium bicarbonate to cobalt sulfate added into the reactor is 2.7, the reaction temperature is 33 °C, the stirring frequency of the reactor motor is 18 Hz. When the synthesis is carried out for 3 h, the reactor is full, the stirring is stopped, and the slurry in the reactor is allowed to stand. When the solid-liquid in the reactor is stratified, 25 - 30 L of the supernatant is extracted to complete one operation of standing and extracting the supernatant, and then this operation is repeated. When this operation is carried out 5 times, the operation of separating the kettle is carried out, and about 50% of the synthesized slurry is separated out of the reactor. When the laser particle size D 50 of the synthesized material reaches 20 - 21 µm, the synthesis is stopped.
[0036] After the synthesis reaction is completed, a centrifuge is used to carry out solid-liquid separation on the synthesized slurry. The slurrying reaction is carried out on an A2 reactor with an effective volume of 20 L. The synthesized cobalt carbonate and pure water are configured into a slurry with a density ≥ 1.5 g / L, and the slurrying treatment is carried out in the reactor. The slurrying temperature ≥ 90 °C, the stirring frequency of the reactor motor is 28 Hz, and the slurrying time is 2.5 h.
[0037] The wet crushing is carried out on the A2 reactor. After the slurrying reaction is completed, the stirring frequency of the A2 reactor motor is adjusted to 50 Hz, and the crushing step is started. The temperature during crushing ≥ 90 °C, and the crushing time is 1 h.
[0038] The washing equipment is a filter press, and the drying equipment is a vacuum drying oven. The drying temperature is 100 - 120 °C, and the moisture content of the dried material ≤ 0.2%.
[0039] The reducing gas used in the reduction step is hydrogen, and the reduction temperature is 380 °C to obtain D 50 ≤0.2 μm, and the microscopic morphology is spherical particulate nano-spherical cobalt powder.
[0040] The microscopic morphology of the prepared nano-spherical cobalt powder is shown in Figure 5 . Example 3
[0041] The production steps are the same as above and will not be elaborated here. The specific parameters in each step are as follows:
[0042] Using cobalt sulfate as the raw material, a cobalt solution with a cobalt concentration of 2.0 mol / L is prepared as solution A; a ammonium bicarbonate solution with a concentration of 3.2 mol / L is prepared as solution B.
[0043] The synthesis reaction is carried out on an A1 reactor with an effective volume of 50 L. At the beginning of the synthesis, solutions A and B are added into the reactor in parallel by a peristaltic pump, and the synthesis reaction is carried out under stirring. The flow rate of solution A is 8 L / h, the flow rate of solution B is 13 L / h, the molar ratio of ammonium bicarbonate to cobalt sulfate added into the reactor is 2.6, the reaction temperature is 35 °C, and the stirring frequency of the reactor motor is 15 Hz. When the synthesis reaches 2 h, the reactor is full, the stirring is stopped, and the slurry in the reactor is allowed to stand. After the solid-liquid separation of the materials in the reactor, 25 - 30 L of the supernatant is extracted to complete one operation of standing and extracting the supernatant, and then this operation is repeated. After this operation is carried out 5 times, the sub-pot operation is carried out, and about 50% of the synthesized slurry is separated out of the reactor. When the laser particle size D50 of the synthesized material reaches 20 - 21 µm, the synthesis is stopped.
[0044] After the synthesis reaction is completed, a centrifuge is used to carry out solid-liquid separation on the synthesized slurry. The slurry reaction is carried out on an A2 reactor with an effective volume of 20 L. The synthesized cobalt carbonate and pure water are configured into a slurry with a density ≥ 1.5 g / L, and the slurry treatment is carried out in the reactor. The slurry temperature ≥ 90 °C, the stirring frequency of the reactor motor is 25 Hz, and the slurry time is 3 h.
[0045] The wet crushing is carried out on the A2 reactor. After the slurry reaction is completed, the stirring frequency of the A2 reactor motor is adjusted to 50 Hz, and the crushing step is started. The temperature during crushing ≥ 90 °C, and the crushing time is 1 h.
[0046] The washing equipment is a filter press, and the drying equipment is a vacuum drying oven. The drying temperature is 100 - 120 °C, and the moisture content of the dried material ≤ 0.2%.
[0047] The reducing gas used in the reduction step is hydrogen, the reduction temperature is 400 °C, and nano-spherical cobalt powder with D 50 ≤ 0.2 µm and a microscopic morphology of spherical particles is prepared.
[0048] The microscopic morphology of the prepared nano-spherical cobalt powder is shown in Figure 6 .
Claims
1. A method for preparing nano-spherical cobalt powder, the method being characterized by the following specific steps: (1) Liquid preparation Using cobalt sulfate as raw material, a cobalt solution with a cobalt concentration of 1.8-2.0 mol / L is prepared as solution A; an ammonium bicarbonate solution with a concentration of 3.0-3.2 mol / L is prepared as solution B; (2) Wet synthesis At the beginning of the synthesis reaction, the A and B solutions are added to the reactor in parallel by a peristaltic pump, and the synthesis reaction is carried out under stirring. When the reactor is full, the supernatant is extracted after standing to concentrate the synthetic slurry. When the slurry density in the reactor reaches a certain value, the solid content of the slurry in the reactor is reduced by splitting the reactor. During the reaction, the flow rate of A and B solutions, the reaction temperature of 30~35℃, the stirring intensity and the volume of the supernatant extracted each time are controlled. When the laser particle size of the synthetic material reaches a certain value, the synthesis is stopped; (3) High temperature pulping After the synthesis reaction is completed, the solid and liquid of the synthesis product are separated, and the synthesized cobalt carbonate solid is subjected to high-temperature slurry treatment in another reactor; (4) Mixing and crushing The high-temperature slurried cobalt carbonate slurry is wet-crushed by increasing the stirring intensity; (5) Washing and drying The crushed material is washed and dried to obtain spherical nano cobalt carbonate; (6) Hydrogen reduction The dried spherical nano-cobalt carbonate is reduced with hydrogen to obtain a nano-spherical cobalt powder product.
2. The method for preparing nano spherical cobalt powder according to claim 1, characterized in that: In the step (2), the synthesis reaction is carried out in the A1 reactor, the effective volume of the A1 reactor is 50L, the flow rate of the A solution is 6-8L / h, the flow rate of the B solution is 10-14 L / h, and the ratio of the amount of ammonium bicarbonate added to the reactor to the amount of cobalt sulfate is 2.5-2.7, and the stirring intensity of the reactor is 15-20Hz. The volume of the supernatant extracted each time is 25-30L. When the slurry density in the reactor is greater than 1.4g / cm3, the solid content of the slurry in the reactor is reduced by splitting the reactor.
3. The method for preparing nano spherical cobalt powder according to claim 1, characterized in that: When the laser particle size (D50) of the synthesized material reaches 20-21 µm, the synthesis is stopped.
4. The method for preparing nano spherical cobalt powder according to claim 1, characterized in that: In the step (3), a centrifuge is used to separate the solid and liquid of the synthetic slurry. The slurry reaction is carried out in an A2 reactor, the effective volume of the A2 reactor is 20L, the synthetic cobalt carbonate and pure water are configured into a slurry with a density of ≥1.5g / L, and the slurry treatment is carried out in the reactor, the slurry temperature is ≥90°C, the stirring intensity is 25~30Hz, and the slurry time is 2~3h.
5. The method for preparing nano spherical cobalt powder according to claim 1, characterized in that: In the step (4), wet crushing is carried out on the A2 reactor. After the slurry reaction is completed, the stirring intensity of the A2 reactor is adjusted to 50 Hz, and the crushing step is started. During the crushing, the temperature of the reactor slurry is maintained at ≥ 90°C, and the crushing time is 1 hour.
6. The method for preparing nano spherical cobalt powder according to claim 1, characterized in that: In the step (5), the washing equipment is a filter press, the drying equipment is a vacuum drying oven, the drying temperature is 100-120° C., and the moisture content of the material after drying is ≤0.2%.
7. The method for preparing nano spherical cobalt powder according to claim 1, characterized in that: In the step (6), the reducing gas used in the reduction step is hydrogen, and the reduction temperature is 350-400°C.
8. The method for preparing nano spherical cobalt powder according to claim 1, characterized in that: In the step (6), the nano-spherical cobalt powder has an index of D50≤0.2 μm and a microscopic morphology of spherical particles.