CN114433861A - Method for preparing cobalt powder from cobalt oxalate - Google Patents
Method for preparing cobalt powder from cobalt oxalate Download PDFInfo
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- CN114433861A CN114433861A CN202210079006.7A CN202210079006A CN114433861A CN 114433861 A CN114433861 A CN 114433861A CN 202210079006 A CN202210079006 A CN 202210079006A CN 114433861 A CN114433861 A CN 114433861A
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- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
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Abstract
The invention provides a method for preparing cobalt powder from cobalt oxalate, which comprises the following steps: firstly, heating cobalt oxalate powder to a reduction temperature under the condition of introducing hydrogen. And step two, reacting the cobalt oxalate powder with hydrogen at a reduction temperature to obtain cobalt powder, and then cooling to the normal temperature. The reduction temperature and the crystal form content in the cobalt powder have a corresponding relation, and the crystal form of the cobalt powder is controlled within a certain proportion range by controlling the reduction temperature. The preparation method has the advantages of simple process and relatively accurate control of the crystal form proportion.
Description
Technical Field
The invention relates to the field of cobalt powder preparation by hydrogen reduction, in particular to a method for preparing cobalt powder by hydrogen reduction of cobalt oxalate.
Background
Cobalt is often used as an important component phase in cemented carbide, diamond tools and magnetic materials due to its unique chemical properties. Cobalt belongs to an isomeric polymorphic metal, and crystal form transformation can occur under specific conditions. Studies have shown that cobalt has two stable crystal forms: a Face Centered Cubic (FCC) structure in a stable state at a high temperature, and a Hexagonal Close Packed (HCP) structure in a stable state at a room temperature. The face-centered cubic cobalt has 12 slip systems, has better plasticity, and can ensure that the hard alloy shows better toughness when responding to external force impact. The hexagonal close-packed cobalt has only 3 sliding systems, shows more brittleness and is beneficial to the crushing and mixing of cobalt powder and tungsten carbide during ball milling. In order to meet the requirements of ball milling and not influence the alloy performance, the control of the relative content of crystal forms is particularly important when cobalt powder is prepared, but the phase composition ratio of a final product is difficult to control in a small range only by qualitative research in the conventional method.
Patent application No. CN101653830B discloses a method for preparing superfine cobalt powder with a close-packed hexagonal structure (HCP) or a face-centered cubic structure (FCC) by hydrogen reduction, which combines high-pressure hydrogen reduction and high-temperature solid-phase hydrogen reduction, controls the secondary hydrogen reduction temperature to obtain the cobalt powder with the close-packed hexagonal structure or the face-centered cubic structure, has more complex preparation process, and does not disclose a technical scheme that the proportion of the close-packed hexagonal structure to the face-centered cubic structure can be obtained in a narrower range.
In order to solve the above problems, we have been seeking an ideal technical solution.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a method for preparing cobalt powder from cobalt oxalate, which can control the crystal form proportion in the cobalt powder in a smaller range.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for preparing cobalt powder from cobalt oxalate comprises the following steps: firstly, heating cobalt oxalate powder to a reduction temperature under the condition of introducing hydrogen to prevent cobalt oxalate hydrate from being decomposed into cobalt powder or cobalt oxide; reacting the cobalt oxalate powder with hydrogen at a reduction temperature T to obtain cobalt powder, and then cooling to normal temperature; the corresponding relation between the reduction temperature T and the content X of the close-packed hexagonal phase in the cobalt powder is shown in the following table, wherein the content of the face-centered cubic phase in the cobalt powder is Y, and Y = 1-X:
| content (wt.) | Reduction temperature |
| 85%<X≤100% | 280℃≤T≤300℃ |
| 70%＜X≤85% | 300℃＜T≤330℃ |
| 55%＜X≤70% | 330℃＜T≤340℃ |
| 40%＜X≤55% | 340℃＜T≤370℃ |
| 25%＜X≤40% | 370℃＜T≤390℃ |
| 10%＜X≤25% | 390℃＜T≤440℃ |
| 0%＜X≤10% | 440℃＜T≤550℃ |
The reaction equipment can be a reduction furnace commonly used in the metal powder smelting industry, such as a quartz tube slide rail tube furnace, a single tube furnace, a double tube furnace, a fifteen tube furnace and the like, and in order to improve the use safety, the hydrogen purity is preferably more than 90% (V/V), and the best purity is more than 99% (V/V).
As a further improvement of the technical scheme, when the temperature is above 400 ℃, the cobalt powder is prevented from generating phase change due to too fast temperature reduction, the crystal form proportion of the cobalt powder cannot be accurately controlled, and the temperature reduction speed during cooling is less than or equal to 10 ℃/min. More preferably, the temperature is close to the phase transition temperature of cobalt powder at 400-430 ℃, and the cooling speed is less than or equal to 10 ℃/min during cooling.
As a further improvement of the technical proposal, when the temperature of the reaction system is 400-430 ℃, the cooling speed is 1-5 ℃/min.
As a further improvement of the technical proposal, when the temperature of the reaction system is 400-430 ℃, the cooling speed is 1-3 ℃/min.
As a further improvement of the technical proposal, the Fisher size of the cobalt oxalate powder is 1.3-2.0 μm.
As a further improvement of the technical scheme, the common industrial cobalt oxalate contains a large amount of adsorbed water, and the method also comprises the step of placing the cobalt oxalate powder in an inert atmosphere, raising the temperature to the dehydration temperature and removing the adsorbed water, wherein the inert atmosphere can adopt nitrogen or a group zero element gas. In order to heat evenly, the temperature can be slowly increased, and dehydration can be carried out in the temperature increasing process.
As a further improvement of the technical scheme, in order to ensure the removal of the water adsorbed by the cobalt oxalate, the dehydration temperature is 100-150 ℃.
As a further improvement of the technical scheme, in order to heat the raw material uniformly, the temperature rise rate in the step of removing the adsorbed water is 3-10 ℃/min.
As a further improvement of the technical scheme, in order to heat the raw materials uniformly, the heating rate is 3-8 ℃/min.
As a further improvement of the technical scheme, the temperature of the reduction reaction is kept stable, the generation of side reactions is reduced, and the rate of introducing hydrogen into the reaction system in the reaction process of the step two is 1-2L/min.
As a further improvement of the technical scheme, when the temperature of the reaction system is more than 150 ℃, the cooling speed in the cooling in the second step is 1-5 ℃/min; preferably, the cooling rate in the second step is 1-3 ℃/min.
Compared with the prior art, the preparation method has outstanding substantive characteristics and obvious progress, and particularly, the preparation method has simple process, and can obtain the cobalt powder with the crystal form proportion in a smaller range only by controlling the reduction temperature. The invention has the advantages of simple process and relatively accurate control of the crystal form proportion.
Detailed Description
The technical solution of the present invention is further described in detail by the following embodiments.
In each example, cobalt carbonate was prepared by hydrogen reduction of cobalt carbonate in a 89mm internal diameter quartz tube slide rail tube furnace, and a 5cm 4cm 3cm stainless steel boat made of Cr25Ni20 was used, 25g of cobalt oxalate powder was placed in the boat and shaken, the water content of the cobalt oxalate powder was 2.3% (adsorbed water), and the fisher's particle size of the cobalt oxalate was 1.57 μm.
The cobalt powder crystal form is characterized by adopting a Bruker D8 advanced X-ray diffractometer, and the crystal form proportion is calculated according to the standard YB/T5320-2006.
The water content of the cobalt oxalate is measured by adopting a drying and weighing method, and the Fisher particle sizes of the cobalt oxalate powder and the cobalt powder are measured by adopting a WLP-208A average particle size measuring instrument.
Example 1
Introducing argon into the furnace for 30min, detecting that the oxygen content in the tail gas is lower than 0.1%, slowly heating to 120 ℃ for dehydration, wherein the heating speed is 5 ℃/min.
And introducing hydrogen into the furnace to continuously raise the temperature, wherein the hydrogen flow is 1.5L/min, the temperature raising speed is 5 ℃/min, the temperature is raised to the set reduction temperature of 350 ℃, and the reduction is carried out for 165min at the temperature of 350 ℃.
After the reaction is finished, the product is cooled along with the furnace, the cooling speed is less than 3 ℃/min, after the product is cooled to the room temperature, the hydrogen is closed, and the product is taken out and sealed in vacuum.
The Fischer-Tropsch particle size of the obtained cobalt powder is 0.9 mu m, and the results of XRD detection and quantitative calculation show that the HCP content is 47.4 percent and the FCC content is 52.6 percent.
Example 2
Introducing argon into the furnace for 30min, detecting that the oxygen content in the tail gas is lower than 0.1%, slowly heating to 120 ℃ for dehydration, wherein the heating speed is 5 ℃/min.
And introducing hydrogen into the furnace to continuously raise the temperature, wherein the hydrogen flow is 1.5L/min, the temperature raising speed is 5 ℃/min, the temperature is raised to the set reduction temperature of 400 ℃, and the reduction is carried out for 165min at the temperature of 400 ℃.
After the reaction is finished, cooling the product along with the furnace at a cooling speed of less than 3 ℃/min, cooling to room temperature, closing hydrogen, taking out the product, and carrying out vacuum sealing storage.
The Fischer-Tropsch particle size of the obtained cobalt powder is 0.96 mu m, and XRD detection and quantitative calculation results show that the HCP content is 18.9 percent and the FCC content is 81.1 percent.
Example 3
And introducing argon into the furnace for 30min, detecting that the oxygen content in the tail gas is lower than 0.1%, slowly heating to 120 ℃, and heating at the speed of 5 ℃/min.
And introducing hydrogen into the furnace to continuously raise the temperature, wherein the hydrogen flow is 1.5L/min, the temperature raising speed is 5 ℃/min, the temperature is raised to the set reduction temperature of 480 ℃, and the reduction is carried out for 165min at the temperature of 480 ℃.
After the reaction is finished, cooling the product along with the furnace at a cooling speed of less than 3 ℃/min, cooling to room temperature, closing hydrogen, taking out the product, and carrying out vacuum sealing storage.
The Fisher granularity of the obtained cobalt powder is 1.95 mu m, and the obtained cobalt powder is obtained by XRD detection and quantitative calculation: HCP content 5.2%, FCC content 94.8%.
Example 4
And introducing argon into the furnace for 30min, detecting that the oxygen content in the tail gas is lower than 0.1%, slowly heating to 120 ℃, and heating at the speed of 5 ℃/min.
And introducing hydrogen into the furnace to continuously raise the temperature, wherein the hydrogen flow is 1.5L/min, the temperature raising speed is 5 ℃/min, the temperature is raised to the set reduction temperature of 500 ℃, and the reduction is carried out for 165min at the temperature of 500 ℃.
After the reaction is finished, cooling the product along with the furnace at a cooling speed of less than 3 ℃/min, cooling to room temperature, closing hydrogen, taking out the product, and carrying out vacuum sealing storage.
The Fisher granularity of the obtained cobalt powder is 2.03 mu m, and the obtained cobalt powder is obtained by XRD detection and quantitative calculation: HCP content 4%, FCC content 96%.
Example 5
And introducing argon into the furnace for 30min, detecting that the oxygen content in the tail gas is lower than 0.1%, slowly heating to 120 ℃, and heating at the speed of 5 ℃/min.
And introducing hydrogen into the furnace to continuously raise the temperature, wherein the hydrogen flow is 1.5L/min, the temperature raising speed is 5 ℃/min, the temperature is raised to the set reduction temperature of 300 ℃, and the reduction is carried out for 165min at the temperature of 300 ℃.
After the reaction is finished, cooling the product along with the furnace at a cooling speed of less than 3 ℃/min, cooling to room temperature, closing hydrogen, taking out the product, and carrying out vacuum sealing storage.
The Fisher granularity of the obtained cobalt powder is 0.84 mu m, and the obtained cobalt powder is obtained by XRD detection and quantitative calculation: HCP content 100%, FCC content 0%.
Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and not to limit the same; although the present invention has been described in detail with reference to preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention; without departing from the spirit of the present invention, it is intended to cover all aspects of the invention as defined by the appended claims.
Claims (10)
1. A method for preparing cobalt powder from cobalt oxalate is characterized by comprising the following steps: step one, heating cobalt oxalate powder to a reduction temperature under the condition of introducing hydrogen; reacting the cobalt oxalate powder with hydrogen at a reduction temperature T to obtain cobalt powder, and then cooling to normal temperature; wherein the corresponding relation between the reduction temperature T and the content X of the close-packed hexagonal phase in the cobalt powder is shown in a table I,
TABLE I
。
2. The method for preparing cobalt powder from cobalt oxalate according to claim 1, wherein when the temperature of the reaction system is above 400 ℃, the cooling rate in the second step is less than or equal to 10 ℃/min; preferably, when the temperature of the reaction system is 400-430 ℃, the cooling speed during the cooling in the second step is less than or equal to 10 ℃/min; preferably, the cooling speed is 1-5 ℃/min.
3. The method for preparing cobalt powder from cobalt oxalate as recited in claim 2, wherein the cooling rate is 1-3 ℃/min.
4. The method for preparing cobalt powder from cobalt oxalate according to any one of claims 1 to 3, wherein the Fisher's particle size of the cobalt oxalate powder is 1.3-2.0 μm.
5. The method for preparing cobalt powder from cobalt oxalate as recited in claim 4, further comprising the step of removing adsorbed water by heating the cobalt oxalate powder to a dehydration temperature in an inert atmosphere.
6. The method of claim 5, wherein the dehydration temperature is 100-150 ℃.
7. The method for preparing cobalt powder from cobalt oxalate according to claim 5 or 6, wherein the temperature increase rate in the step of removing adsorbed water is 3-10 ℃/min.
8. The method for preparing cobalt powder from cobalt oxalate as recited in claim 7, wherein the temperature increase rate is 3-8 ℃/min.
9. The method for preparing cobalt powder from cobalt oxalate as recited in claim 5, wherein the rate of hydrogen gas introduction into the reaction system in the second step is 1-2L/min.
10. The method for preparing cobalt powder from cobalt oxalate as recited in claim 5, wherein in the second step, when the temperature of the reaction system is above 150 ℃, the cooling rate is 1-5 ℃/min; preferably, the cooling rate in the second step is 1-3 ℃/min.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101653830A (en) * | 2009-11-09 | 2010-02-24 | 昆明贵金属研究所 | Method for preparing superfine cobalt powder in close-packed hexagonal structure or face-centered cubic structure by hydrogen reduction |
| CN102049524A (en) * | 2009-10-29 | 2011-05-11 | 北京有色金属研究总院 | Method for preparing nano Epsilon-Co powder |
| WO2016190669A1 (en) * | 2015-05-26 | 2016-12-01 | 부경대학교 산학협력단 | Method for recovering cobalt powder from lithium-cobalt oxide |
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- 2022-01-24 CN CN202210079006.7A patent/CN114433861B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102049524A (en) * | 2009-10-29 | 2011-05-11 | 北京有色金属研究总院 | Method for preparing nano Epsilon-Co powder |
| CN101653830A (en) * | 2009-11-09 | 2010-02-24 | 昆明贵金属研究所 | Method for preparing superfine cobalt powder in close-packed hexagonal structure or face-centered cubic structure by hydrogen reduction |
| WO2016190669A1 (en) * | 2015-05-26 | 2016-12-01 | 부경대학교 산학협력단 | Method for recovering cobalt powder from lithium-cobalt oxide |
Non-Patent Citations (3)
| Title |
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| 傅小明,戴起勋,吴晓东: "草酸钴还原过程的相变研究" * |
| 昝林寒;杨滨;汪云华;赵家春;范兴祥;: "氢还原法制备超细钴粉" * |
| 罗崇玲;易茂中;谭兴龙;: "碳酸钴制备超细球形钴粉的工艺探讨" * |
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