CN114535590A

CN114535590A - Method for preparing cobalt powder from cobalt carbonate

Info

Publication number: CN114535590A
Application number: CN202210079007.1A
Authority: CN
Inventors: 朱治军; 王朝安; 张志平; 杜晗
Original assignee: Anhui Hanrui New Material Co ltd
Current assignee: Anhui Hanrui New Material Co ltd
Priority date: 2022-01-24
Filing date: 2022-01-24
Publication date: 2022-05-27
Anticipated expiration: 2042-01-24
Also published as: CN114535590B

Abstract

The invention provides a method for preparing cobalt powder from cobalt carbonate, which comprises the steps of reacting cobalt carbonate with hydrogen at a reduction temperature to obtain cobalt powder, then continuously introducing the hydrogen, and cooling to the normal temperature. Wherein, the reduction temperature and the content of crystal form in the cobalt powder have a corresponding relation. The preparation method has the advantages of simple process and relatively accurate control of the crystal form proportion.

Description

Method for preparing cobalt powder from cobalt carbonate

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 carbonate.

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 structure in a stable state at a high temperature; and the hexagonal close packed structure is in a stable state at room temperature. The phase transition temperature of pure cobalt is 417 ℃. 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 requirement of ball milling and not influence the alloy performance, the control of the relative content of crystal forms is very important when cobalt powder is prepared, and the phase component proportion of a final product is difficult to control in a small range only through 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 a 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 narrow range.

In order to solve the above problems, we have always sought 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 carbonate, 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 carbonate comprises the steps of carrying out reduction reaction on cobalt carbonate powder and 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 face-centered cubic phase in the cobalt powder is shown in the following table, the content of the close-packed hexagonal phase in the cobalt powder is Y, Y = 1-X:

cobalt powder face centered cubic phase content (X)	Corresponding reduction temperature (T)
		X≤10%	250℃≤T≤330℃
10%＜X≤20%	330℃＜T≤370℃
		20%＜X≤30%	370℃＜T≤390℃
30%＜X≤40%	390℃＜T≤410℃
		40%＜X≤50%	410℃＜T≤420℃
50%＜X≤60%	420℃＜T≤450℃
		60%＜X≤70%	450℃＜T≤480℃
70%＜X≤80%	480℃＜T≤500℃
		80%＜X≤90%	500℃＜T≤520℃
90%＜X≤100%	520℃＜T≤550℃

As a further improvement of the technical scheme, when the temperature of a reaction system 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; preferably, the cooling speed is less than or equal to 5 ℃/min.

As a further improvement of the technical scheme, the Fisher size of the cobalt carbonate powder is 0.8-1.0 μm.

As a further improvement of the technical scheme, the method comprises the following steps:

step one, heating and dehydrating cobalt carbonate powder in a hydrogen atmosphere; the common industrial cobalt carbonate contains a large amount of adsorbed water and bound water, and water is removed before the reduction reaction.

Preferably, before dehydration, the cobalt carbonate powder is placed in an inert atmosphere to isolate air, wherein the inert atmosphere can adopt nitrogen or a zero-group element gas, and then hydrogen is introduced to ensure the safety of production. When the water content is small, dehydration is preferably performed during temperature rise; under the condition of large water content, the water content is kept for a period of time at a certain dehydration temperature so as to ensure the removal of water.

Step two, heating the dehydrated cobalt carbonate powder to a reduction temperature, and carrying out reduction reaction on the cobalt carbonate powder and hydrogen to obtain cobalt powder;

and step three, cooling the cobalt powder to the normal temperature.

As a further improvement of the technical scheme, in the step I, the cobalt carbonate powder is heated and dehydrated, and in order to uniformly heat the raw material, the heating rate is 4-6 ℃.

As a further improvement of the technical scheme, the dehydration temperature is 120-150 ℃ for complete dehydration.

As a further improvement of the technical scheme, in order to improve the stability of the reduction reaction, hydrogen is introduced in the temperature rising process in the second step.

As a further improvement of the technical proposal, in order to remove the moisture generated in the reaction, hydrogen is introduced in the cooling process.

As a further improvement of the technical proposal, the purity of the introduced hydrogen in the preparation process is more than 90 percent (V/V).

As a further improvement of the technical scheme, the rate of introducing hydrogen in the reduction reaction process is 1.3-1.6L/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 the cobalt powder with the crystal form ratio in a smaller range can be obtained only by controlling the reduction temperature. The invention has the advantages of simple process and relatively accurate control of the crystal form proportion of the cobalt powder.

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 inner diameter quartz tube slide rail tube furnace, and a 5cm x 4cm x 3cm stainless steel boat made of Cr25Ni20 was used, and 70g of cobalt carbonate was charged into the boat and shaken, the fischer-tropsch size of the cobalt carbonate powder was 0.80 μm, and the water content (adsorbed water) of the cobalt carbonate powder was 2.6%.

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 carbonate powder is measured by adopting a drying and weighing method, and the Fisher particle size of the cobalt carbonate powder and the cobalt powder is measured by adopting a WLP-208A average particle size measuring instrument.

Example 1

And introducing argon into the furnace at the speed of 1.0L/min for 30min, detecting that the oxygen content in the tail gas is lower than 0.1%, starting introducing hydrogen and heating, wherein the hydrogen flow is 1.5L/min, and the heating speed is 5 ℃/min. Setting the reduction temperature to 480 ℃, heating to 480 ℃ and reducing for 165min to obtain the cobalt powder. Then cooling, adopting a furnace cooling mode, wherein the cooling speed is less than 4 ℃/min.

The Fisher granularity of the obtained cobalt powder is 1.71 mu m, and the obtained cobalt powder is obtained by XRD detection and quantitative calculation: the FCC content was 70.2%, the HCP content was 29.8%.

Example 2

Introducing argon into the furnace at the speed of 1.0L/min for 30min, detecting that the oxygen content in the tail gas is lower than 0.1%, starting introducing hydrogen and heating, wherein the hydrogen flow is 1.4L/min, the heating speed is 4 ℃/min, the reduction temperature is set to 330 ℃, and the temperature is increased to 330 ℃ for reduction for 170min to obtain the cobalt powder. Then, cooling by adopting a furnace cooling mode, wherein the cooling speed is less than 4 ℃/min.

The Fisher granularity of the obtained cobalt powder is 0.63 mu m, and XRD detection and quantitative calculation are carried out: the FCC content was 9.2%, the HCP content was 90.8%.

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

1. A method for preparing cobalt powder from cobalt carbonate is characterized in that the cobalt carbonate powder and hydrogen are subjected to reduction reaction at a reduction temperature T to prepare cobalt powder, and then the cobalt powder is cooled to normal temperature; wherein the corresponding relation between the reduction temperature T and the content X of the face-centered cubic phase in the cobalt powder is shown in a table I,

TABLE I

。

2. The method for preparing cobalt powder from cobalt carbonate as claimed in claim 1, wherein the cooling rate is less than or equal to 10 ℃/min when the temperature of the reaction system is above 400 ℃.

3. The method for preparing cobalt powder from cobalt carbonate according to claim 2, wherein the cooling rate is preferably less than or equal to 5 ℃/min.

4. The method for preparing cobalt powder from cobalt carbonate according to any one of claims 1 to 3, wherein the Fisher size of the cobalt carbonate powder is 0.80 to 1.0 μm.

5. The method for preparing cobalt powder from cobalt carbonate according to claim 4, characterized in that it comprises the following steps:

step one, heating and dehydrating cobalt carbonate powder in a hydrogen atmosphere;

step two, heating the dehydrated cobalt carbonate powder to the reduction temperature, and carrying out reduction reaction on the cobalt carbonate powder and hydrogen to obtain cobalt powder;

and step three, cooling the cobalt powder to the normal temperature.

6. The method of claim 5, wherein the temperature raising rate in the first step is 4-6 ℃.

7. The method of claim 6, wherein the dehydration temperature is 120-150 ℃.

8. The method for preparing cobalt powder from cobalt carbonate according to claim 5, wherein hydrogen is introduced during the cooling process.

9. The method for preparing cobalt powder from cobalt carbonate according to claim 5, wherein the purity of the introduced hydrogen gas is more than 90% (V/V) during the preparation process.

10. The method for preparing cobalt powder from cobalt carbonate according to claim 5, wherein the rate of introducing hydrogen gas during the reduction reaction is 1.3-1.6L/min.