CN107150127B - Preparation method of spherical cobalt powder - Google Patents

Abstract

The invention relates to the technical field of cobalt material preparation, and specifically discloses a preparation method of spherical cobalt powder. The method includes at least the following steps: Step S01. Mix the cobalt salt solution and the precipitant solution in parallel to carry out a precipitation reaction; Step S02. Under an oxidizing atmosphere, dynamically roast the precipitate obtained by the reaction in Step S01; Step S03. Under a reducing atmosphere, the product obtained in step S02 is calcined; wherein, the dynamic calcination temperature is 400-800°C, and the calcination time is 4-8h. The spherical cobalt powder obtained by the invention has the characteristics of high purity, good dispersibility, small particle size, uniform and controllable particle size, good sphericity, regular appearance, etc. The method of the invention is suitable for industrialized large-scale production of spheroidized cobalt powder materials.

Description

Preparation method of spherical cobalt powder

technical field

The invention relates to the technical field of cobalt material preparation, in particular to a preparation method of spherical cobalt powder.

Background technique

Cobalt powder is widely used in cemented carbide and battery materials due to its excellent physical and chemical properties. Whether it is the cemented carbide industry or the battery material industry, there are strict requirements for the purity, dispersibility and surface morphology of cobalt powder. Strip shape will affect the mechanical properties and service life of cemented carbide to a certain extent.

At present, there are many methods for preparing ultrafine cobalt powder at home and abroad, mainly including polyol reduction method, electrolysis method, precipitation-thermal dissociation method, hydrogen reduction method, etc. Among them, the hydrogen reduction method has become one of the main methods for domestic production of cobalt powder due to its relatively simple process flow and is more suitable for industrial production. poor. Since the precursor has a great influence on the particle morphology of the hydrogen-reduced cobalt powder, the morphology of the precursor and the cobalt powder have a certain inheritance. Therefore, researchers at home and abroad have carried out a lot of research on the precursor of the hydrogen reduction method.

The invention patent with the application number of 200710075929.0 discloses a manufacturing process of ultra-fine cobalt powder. The process is specifically as follows: cobalt carbonate is first subjected to high-energy ball milling to obtain ultra-fine cobalt carbonate precursor, and then in the atmosphere of reducing gas, reduction preparation Ultrafine spherical cobalt powder. However, this ball milling production process is easy to introduce impurities and affect the quality of cobalt powder.

Another example is the invention patent with the application number of 201010196228.4, which discloses a preparation method of nearly spherical aggregated cobalt powder. In the method, ammonium bicarbonate is used as a precipitant, and co-current with the cobalt salt solution is added to the reactor to generate a precursor, and then the obtained cobalt carbonate is placed in a reduction furnace for thermal decomposition and hydrogen reduction, thereby obtaining nearly spherical aggregated cobalt powder.

This method focuses on controlling the formation of the precursor, and the control of the reduction process is not precise, and the spheroidization effect of the obtained cobalt powder is not very ideal.

SUMMARY OF THE INVENTION

Aiming at the problems of poor shape and unsatisfactory spheroidization in the above-mentioned prior art, the purpose of the embodiments of the present invention is to provide a preparation method of spherical cobalt powder.

In order to achieve the above-mentioned purpose of the invention, the embodiment of the present invention adopts the following technical solutions:

A preparation method of spherical cobalt powder, comprising at least the following steps:

Step S01. co-currently mixing the cobalt salt solution and the precipitant solution to carry out a precipitation reaction;

Step S02. Under an oxidizing atmosphere, dynamically roast the precipitate obtained by the reaction in step S01;

Step S03. In a reducing atmosphere, the product obtained in Step S02 is calcined;

Wherein, the dynamic roasting temperature is 400-800 DEG C, and the roasting time is 4-8h.

The preparation method of spherical cobalt powder provided by the above embodiments of the present invention combines dynamic roasting and hydrogen reduction, without adding any surfactant, and only dynamic roasting can obtain a precursor (Co ₃ O ₄ ) with good fluidity , thereby providing a precursor with good fluidity for hydrogen reduction calcination, and the finally obtained cobalt powder has the characteristics of good dispersibility, small particle size, uniform and controllable particle size, high spheroidization, and regular morphology.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

Fig. 1 is the process flow diagram of the preparation method of spherical cobalt powder provided by the embodiment of the present invention;

2 is a SEM image of Co ₃ O ₄ prepared by the method for preparing spherical cobalt powder provided in Example 1 of the present invention.

3 is a SEM image of the cobalt powder prepared by the method for preparing spherical cobalt powder provided in Example 1 of the present invention.

4 is a SEM image of Co ₃ O ₄ prepared by the preparation method of spherical cobalt powder provided in Example 2 of the present invention.

5 is a SEM image of cobalt powder prepared by the preparation method of spherical cobalt powder provided in Example 2 of the present invention.

6 is a SEM image of Co ₃ O ₄ prepared by the preparation method of spherical cobalt powder provided in Example 3 of the present invention.

7 is a SEM image of the cobalt powder prepared by the method for preparing spherical cobalt powder provided in Example 3 of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

The embodiment of the present invention provides a preparation method of spherical cobalt powder, comprising at least the following steps:

Step S01. co-currently mixing the cobalt salt solution and the precipitant solution to carry out a precipitation reaction;

Step S02. Under an oxidizing atmosphere, dynamically roast the precipitate obtained by the reaction in step S01;

Step S03. In a reducing atmosphere, the product obtained in Step S02 is calcined;

Wherein, the dynamic roasting temperature is 400-800 DEG C, and the roasting time is 4-8h.

In a preferred embodiment, the reaction equipment in the above step S01 is a reaction kettle. Since the reaction kettle is equipped with a stirring device, and the stirring speed is uniform and controllable, it plays an important role in realizing the rapid and uniform mixing of the reaction mixture and avoiding the formation of large particle precursors. In the embodiment of the present invention, the stirring speed is controlled to be 150-250 rpm.

In a preferred embodiment, the cobalt salt and the precipitant are added in a mass ratio of 1:(1.5-2.0), and the precipitant is controlled to be slightly excessive, which is beneficial to the complexation of the cobalt salt and the nucleation of cobalt carbonate.

In a preferred embodiment, the cobalt salt is configured as a cobalt salt solution with a concentration of 80-120 g/L, and the precipitant is configured as a precipitant solution with a concentration of 180-250 g/L.

In a preferred embodiment, ammonium bicarbonate is used as the precipitating agent, mainly because this type of precipitating agent will eventually decompose into gas without introducing impurities, and will not adversely affect the purity of the product.

Preferably, the cobalt salt is cobalt chloride, mainly because the chloride ion is easy to clean after the reaction, and it is not easy to remove other substances to react, and impurities will not be introduced.

In a preferred embodiment, the reaction in step S01 needs to be kept in the range of 40-55° C., which can significantly improve the chemical activity of the reactants and increase the reaction rate.

In the whole reaction, the pH of the reaction mixture has a certain influence on the realization of the technical effect of the present invention. Therefore, during the reaction in the embodiment of the present invention, the pH value needs to be adjusted between 6.98 and 7.30, so as to achieve the control of the combination rate of the cobalt salt and the precipitant.

In any embodiment, in order to ensure that the obtained precursor tricobalt tetroxide has good fluidity, in the dynamic roasting process, it is necessary to perform preheating and predecomposition in an orderly manner, and the product obtained in step S01 is placed in a boiling furnace and fluidized. In the furnace or rotary kiln and other equipment, it moves and decomposes under the airflow flowing in the furnace, so as to achieve the effect of modifying the morphology of the precursor tricobalt tetroxide, so that the precursor tricobalt tetroxide has good dispersibility at the same time. The flowing airflow here is an oxidizing airflow, specifically air or oxygen.

In a preferred embodiment, the calcination temperature is 350-550° C., the calcination time is 1-4 hours, and the reducing atmosphere can completely reduce cobalt tetroxide to cobalt powder at the calcination temperature and calcination time.

In the embodiment of the present invention, after the reaction in the above step S01 is completed, the reaction product further includes the steps of centrifuging or filtering, washing, and drying the reaction product cobalt carbonate.

The preparation method of spherical cobalt powder provided in the embodiment of the present invention does not require any surfactant, and uses ammonium bicarbonate as a precipitant, and does not introduce any other impurities into the product. More importantly, it increases dynamic performance before reduction. The roasting process optimizes the sphericity of the precursor and reduces the irregularity of the powder, so that the prepared precursor powder has a regular morphology, high sphericity and uniform particle size, and finally makes the cobalt powder obtained from the precursor reduction. It has the characteristics of high purity, good dispersibility, small particles, uniform and controllable particle size, good sphericity, and regular morphology. At the same time, the process is simple and easy to implement, can be continuously produced, has high production efficiency, can ensure the stability of product batch quality, and is suitable for large-scale industrial production.

Further, the cobalt powder material synthesized by the preparation method of spherical cobalt powder provided in the embodiment of the present invention can be applied to the field of lithium ion batteries or cemented carbide.

In order to better reflect the preparation method of the spherical cobalt powder provided in the embodiment of the present invention, the following is further described through a plurality of embodiments.

Example 1

(1) the cobalt chloride solution with a concentration of 80g/L and an ammonium bicarbonate solution with a concentration of 180g/L;

(2) be 2 times of cobalt chloride consumption by ammonium bicarbonate consumption, add ammonium bicarbonate solution and cobalt chloride solution in the reactor in parallel, be warming up to 45 ℃;

(3) stirring at a stirring speed of 200 rpm, keeping the reaction temperature at 45° C. and pH value of 7.0 to 7.1, and reacting for 2 h to obtain ultra-fine spherical cobalt carbonate precipitate;

(4) The ultrafine spherical cobalt carbonate was centrifuged, washed and dried, and then dynamically calcined in an oxygen atmosphere at a calcination temperature of 400 °C for 8 h to obtain a black precursor Co ₃ O ₄ ultrafine powder. After testing, in the precursor Co ₃ O ₄ ultrafine powder obtained in Example 1, the particle size is less than or equal to 1.0 μm. And carry out SEM scanning on the obtained Co ₃ O ₄ ultrafine powder, and the scanning results are shown in Figure 2 of the specification;

(5) The obtained Co ₃ O ₄ ultrafine powder was placed in a reducing atmosphere of hydrogen, and calcined at 420 °C for 2 h to obtain ultrafine spherical cobalt powder with a particle size of about 0.5 μm. After scanning by SEM, its morphology is shown in Figure 3 shown.

Example 2

(1) The cobalt chloride solution with a concentration of 100g/L and an ammonium bicarbonate solution with a concentration of 200g/L are configured;

(2) be 1.5 times of cobalt chloride consumption by ammonium bicarbonate consumption, add ammonium bicarbonate solution and cobalt chloride solution in the reactor in parallel, be warming up to 50 ℃;

(3) stirring at a stirring speed of 250 rpm, keeping the reaction temperature at 50° C. and pH value of 7.1-7.2, and reacting for 3 h to obtain ultrafine spherical cobalt carbonate precipitate;

(4) The ultrafine spherical cobalt carbonate is centrifuged, washed and dried, and then dynamically calcined in an oxygen atmosphere at a calcination temperature of 800 °C for 4 h to obtain a black precursor Co ₃ O ₄ ultrafine powder. After testing, the particle size of the precursor Co ₃ O ₄ ultrafine powder obtained in Example 2 is ≤1.0 μm. And carry out SEM scanning on the obtained Co ₃ O ₄ ultrafine powder, and the scanning results are shown in Figure 4 of the description;

(5) The obtained Co ₃ O ₄ ultrafine powder was placed in a reducing atmosphere of hydrogen, and calcined at 420 °C for 2 h to obtain ultrafine spherical cobalt powder with a particle size of about 0.5 μm. After scanning by SEM, its morphology is shown in Figure 5 shown.

Example 3

(1) The cobalt chloride solution with a concentration of 120g/L and an ammonium bicarbonate solution with a concentration of 220g/L are configured;

(2) be 1.8 times of cobalt chloride consumption by ammonium bicarbonate consumption, add ammonium bicarbonate solution and cobalt chloride solution in the reactor in parallel, be warming up to 40 ℃;

(3) stirring at a stirring speed of 150 rpm, keeping the reaction temperature at 40° C. and pH value of 7.2 to 7.3, and reacting for 3 h to obtain ultrafine spherical cobalt carbonate precipitate;

(4) The ultrafine spherical cobalt carbonate was centrifuged, washed and dried, and then dynamically calcined in an oxygen atmosphere at a calcination temperature of 550 °C for 7 h to obtain a black precursor Co ₃ O ₄ ultrafine powder. After testing, the particle size of the precursor Co ₃ O ₄ ultrafine powder obtained in Example 3 is ≤1.0 μm. And carry out SEM scanning on the obtained Co ₃ O ₄ ultrafine powder, and the scanning results are shown in Figure 6 of the specification;

(5) The obtained Co ₃ O ₄ ultrafine powder was placed in a reducing atmosphere of hydrogen, and calcined at 52 °C for 2 h to obtain ultrafine spherical cobalt powder with a particle size of about 0.5 μm. After scanning by SEM, its morphology is shown in Figure 7 shown.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements or improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (7)

1. a preparation method of spherical cobalt powder, comprising at least the following steps: Step S01. co-currently mixing the cobalt salt solution and the precipitant solution to carry out a precipitation reaction; Step S02. Under an oxidizing atmosphere, dynamically roast the precipitate obtained by the reaction in step S01; Step S03. In a reducing atmosphere, the product obtained in Step S02 is calcined; Wherein, the dynamic roasting temperature is 400～800℃, and the roasting time is 4～8h; The dynamic roasting is to make the product obtained in step S02 move and decompose under a flowing airflow; the flowing airflow is air or oxygen; Described precipitating agent is ammonium bicarbonate; The calcination temperature is 350-550° C.; the mass ratio of the cobalt salt and the precipitating agent is 1:(1.5-2.0). 2 . The method for preparing spherical cobalt powder according to claim 1 , wherein the temperature of the precipitation reaction is 40-55° C. 3 . 3 . The method for preparing spherical cobalt powder according to claim 1 , wherein the pH value of the reaction solution is controlled at 6.98-7.30. 4 . 4 . The method for preparing spherical cobalt powder according to claim 1 , wherein the reaction time is 2 to 3 hours. 5 . 5 . The method for preparing spherical cobalt powder according to claim 1 , wherein the reaction process is accompanied by a step of stirring, and the stirring speed of the stirring is 150-250 rpm. 6 . 6 . The method for preparing spherical cobalt powder according to claim 1 , wherein the calcination time is 1-4 hours. 7 . 7 . The method for preparing spherical cobalt powder according to claim 1 , wherein the concentration of the cobalt salt solution is 80-120 g/L, and/or the concentration of the precipitating agent is 180-250 g/L. 8 .

Images