CN106077692A - A kind of preparation method of metallic cobalt microsphere - Google Patents

Abstract

The present invention relates to a kind of preparation method of metal cobalt microsphere, and the steps are as follows: (1) prepare cobalt source mother liquor by cobalt nitrate and EDTA, then add ammoniacal liquor and water, make the pH value of solution 12.4; Then above-mentioned solution is transferred to reaction Add a high-purity metal cobalt plate into the kettle as a substrate, and react hydrothermally at 90-120°C, then rinse and dry; (2) Send the above-mentioned micron-sized spherical cobalt hydroxide together with the metal cobalt plate directly into the muffle furnace, and the heating rate Control at 1-10°C per minute, the final temperature at 250-350°C, and the holding time for 3-5 hours; (3) Send the micron-sized spherical cobalt tetroxide cooled to about 200°C together with the metal cobalt plate directly into the reduction furnace. Control at 0.24-0.35Mpa, control the heating rate at 10-20°C per minute, control the final temperature at 600-800°C, and hold the holding time for 2-3 hours; (4) Use an ion fan to eliminate the static electricity of the metal cobalt microspheres after cooling, Then, the metal cobalt microspheres are subjected to multi-stage airflow winnowing to eliminate large particles larger than 20 μm.

Description

A kind of preparation method of metal cobalt microsphere

technical field

The invention relates to a preparation method of metal cobalt microspheres.

Background technique

The existing application fields of spherical metal powder include powder metallurgy, 3D metal printing, battery, electronic packaging, precision preparation, etc. At present, the preparation methods of spherical metal particles are mainly crushing method (obtaining fine powder by crushing coarse particles or molten liquid) and synthesis method (obtaining fine powder by reaction, nucleation and growth, collection and post-treatment of ions, atoms and molecules). body method) two categories. For the former, the pulverization method can be roughly divided into three categories: gas atomization method and centrifugal atomization method based on droplet jet solidification into balls; shredding or punching remelting method based on mechanical shearing into balls; uniform droplet injection method and pulsed orifice jetting. The main disadvantages of the above method are that the particle agglomeration is very serious under electrostatic action, there are many impurities, the particle size distribution range is too large, the sphericity of the microparticles is not high, and it is difficult to prepare metal balls with a size of less than 100 μm. Therefore, subsequent treatments such as further sieving are required, which increases the cost of the above method.

The synthesis method is currently more effective in the preparation of spherical ultrafine cobalt powder is the hydrogen reduction method. The cobalt powder prepared by this method has a small particle size, uniformity, good fluidity and mixing effect, so the cobalt powder produced in China basically belongs to the hydrogen reduction method. cobalt powder. Hydrogen reduction methods include high-temperature solid-phase hydrogen reduction method and high-pressure hydrogen reduction method. The high-temperature solid-phase hydrogen reduction method is to reduce cobalt oxides or precipitated products with hydrogen at high temperature to obtain metal cobalt powder. This is the current industrial method for preparing cobalt powder, but its products generally have serious agglomeration and coarse particles. The oxygen content is higher, and it is difficult to obtain ultra-fine cobalt powder. The high-pressure hydrogen reduction method is to prepare ultra-fine cobalt powder by reducing cobalt solution or slurry with hydrogen under high pressure conditions. The hydrogen pressure required by this method is high, and the purity can only reach about 95%. It is difficult to meet the requirements of ultrafine cobalt powder products, and the shape is dendritic, and the spherical cobalt powder is very little.

In response to the above problems, the business community and scientific research institutions in universities have made many attempts and researches from the following aspects.

The first is the high-temperature solid-phase hydrogen reduction method. In the early days, cobalt oxide obtained after cobalt oxalate oxidation was generally used for hydrogen reduction. Cobalt powder prepared by direct reduction of cobalt oxalate is more common. Yuan Ping of Zhuzhou Cemented Carbide Factory in "Study on the Effect of Cobalt Oxalate Precipitation Process on the Particle Size of Cobalt Powder" (Cemented Carbide, 2001, Volume 18, Issue 1), the morphology of cobalt oxalate determines the morphology of cobalt powder, The crystal grains of cobalt oxalate are rod-like fiber structure, and the chain shape of cobalt powder is shorter and irregular granular _; the main influencing factors of cobalt oxalate precipitation process on the particle size of cobalt powder are the density of CoCl2 solution and the temperature during reaction, followed by adding The flow rate of ammonium oxalate; the conditions for producing fine-grained cobalt oxalate and cobalt powder are low solution density, low reaction temperature and high flow rate, otherwise the particles will be coarse. Jinchuan Nonferrous Metals Group Nickel and Cobalt New Product Company Wang Jinrui and others proposed the use of a pit furnace device in the "Experimental Research on the Preparation of Cobalt Powder by Cobalt Oxalate Reduction" (Gansu Metallurgy, Volume 26, Issue 3, September 2004), using hydrogen and Nitrogen is a mixed reducing atmosphere for reduction. Under the condition of controlling temperature, reduction time and reducing gas flow rate, the loose ratio of cobalt powder is controlled at 0.4-0.6g/cm ³ , the hydrogen loss is less than 0.3%, and the appearance of cobalt powder is Very good dendritic structure. Huang Liwei and others of Beijing General Research Institute of Mining and Metallurgy proposed that cobalt oxalate is oxidized to cobalt oxide and re- The particle size of the cobalt powder for hydrogen reduction is related to the oxidation temperature of cobalt oxalate, and related to the oxidation process equipment and operation method. The cobalt powder obtained by the direct reduction of cobalt oxalate is finer than the cobalt powder obtained by oxidation and re-reduction of cobalt oxalate. During the production process, β-Co phase cobalt powder is naturally produced, but under appropriate conditions, the main phase can be produced as α-Co cobalt powder. In addition, some people have changed the precursors. For example, Luo Chongling, the State Key Laboratory of Powder Metallurgy of Central South University, etc., adopted a steel belt type in the "Process Discussion on the Preparation of Ultrafine Spherical Cobalt Powder from Cobalt Carbonate" (Cemented Carbide, Issue 02, 2007). A continuous reduction furnace uses cobalt carbonate as raw material to prepare cobalt powder by hydrogen reduction method; the prepared cobalt powder is spherical or quasi-spherical, not dendritic; Du Xiaohua of Sichuan University et al. Preparation of ultrafine spherical cobalt powder by reduction method" (Thermal Processing Technology, 2013, Volume 42, Issue 24) proposes that the precursor is CoCO ₃ prepared by room temperature ball milling solid-phase chemical reaction method, then roasted at medium temperature, and reduced with hydrogen to obtain ultrafine cobalt powder. Spherical cobalt powder, adopting ball milling in this method causes its agglomeration to be very serious.

In terms of actual production, Zhejiang Huayou Cobalt Industry Co., Ltd. is currently the largest cobalt chemical manufacturer in China, and has applied for and owned a number of related cobalt industry production patents. One of its core patents is "A Method for Preparing Ultrafine Spherical Cobalt Powder" (ZL200810121121.6), which proposes a method of continuously producing monodisperse, ultrafine spherical cobalt powder using cobalt ore as raw material and adopting homogeneous precipitation-thermal reduction method , is characterized in that it includes the step of providing 60-160g/L cobalt salt solution and precipitating agent solution, and described precipitating agent selects a kind of in ammonium bicarbonate, ammonium carbonate, is made into mass concentration 80-200g after dissolving and filtering /L solution, and carry out as follows: (a). Add polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), cetyltrimethylammonium bromide (CTAB), One or more of polyethylene glycol PEG (1000) and water-soluble starch are used as a homogeneous cobalt salt solution; (b). Use a homogeneous cobalt salt solution and a precipitant solution with a theoretical reaction volume of 1.1 to 1.3 times Feed into the reactor by cocurrent feeding method, control the synthesis reaction temperature at 40-90°C, the reaction pH value at 6.0-8.5, the feeding speed at 200-1000L/h, the stirring speed at 500-1500rpm, and obtain superfine Spherical cobalt carbonate precipitate; (c). Ultrafine spherical cobalt carbonate powder is obtained after the precipitate is filtered, washed, and flash-dried, with a particle size of 0.6-1.0 μm; the filtered tail liquid is comprehensively treated by integrated film and evaporative crystallization , fresh water is returned to production, and by-products are recovered in the form of crystalline salts. The integrated membrane treatment is reverse osmosis + electrodialysis treatment; (d). The above-mentioned cobalt carbonate powder is sent to a reduction furnace and carried out at 400-550 ° C. Continuous thermal reduction to obtain ultrafine spherical cobalt powder. Then there are related invention patents on precursors, such as carbonate "A Preparation Method for Spherical Carbonate" (ZL 201010209990.1) and "A Method for Continuously Preparing Large-Size Spherical Cobalt Carbonate" (Application No.: 201510151958.5) ; cobalt oxyhydroxide "Preparation method of spherical cobalt oxyhydroxide-cobalt trioxide composite material" (application number: 201510152081.1); cobalt hydroxide, etc. Among them, cobalt hydroxide is relatively mature in technology, and "A method for preparing spherical cobalt hydroxide without complexing agent system" (ZL200910307676.4) proposes to use pure water as the bottom liquid, and oxidize cobalt liquid and hydroxide under stirring. The sodium solution is added to the bottom liquid at the same time to cause a precipitation reaction, and the pH value of the solution is maintained at 5-7 during the co-current dropwise addition of cobalt liquid and sodium hydroxide, and the pH value of the solution at the end is 10.5-13.5; then add to the solution Antioxidant to prevent its oxidation, cobalt hydroxide slurry is washed and dried to obtain spherical cobalt hydroxide product; "A method for continuous preparation of cobalt hydroxide with high loose ratio" (ZL 201310290589.9) proposes to use cobalt-containing ore as raw material , and purified by leaching to obtain a cobalt chloride solution; using NaOH as the bottom liquid, add NaOH, cobalt chloride and complexing agent solutions into the reaction kettle in parallel, and quickly control the pH value at 8-12 during the parallel flow process, and control the temperature At 30-90°C, the stirring speed is 200-1000rpm, after reacting for 6-40 hours, open the overflow valve of the reactor and start continuous production. The product is excellent, the shape is porous spherical, and the particle size is normally distributed.

As for the high-pressure hydrogen reduction method, Sherritt is the pioneer in the preparation of metal cobalt powder by high-pressure hydrogen reduction. Since the 1950s, it has successfully adopted wet pressurized hydrogen reduction technology to produce high-grade cobalt powder directly from ammonium sulfate solution. Pure metal cobalt powder, the obtained product has a coarse particle size. my country's Shanghai Smelter has also used this process for the production of cobalt powder since 1985. Westaim Company, formerly part of Sherritt Company, began to improve the technology in 1992 to produce ultrafine cobalt powder with submicron narrow particle size distribution. The improved process is as follows: first dissolve metal cobalt in sulfuric acid to generate CoSO ₄ solution, and then add liquid ammonia to convert it into ammonium cobalt sulfate. During the process of adding ammonia, part of basic cobalt sulfate is also generated. The formation of some basic cobalt sulfate can promote the nucleation reaction. The last step is to replace and precipitate ultrafine cobalt powder from the supersaturated solution. The particle size of cobalt powder produced by high-pressure hydrogen reduction can be adjusted from submicron to micron. Compared with the oxalate precipitation-thermal decomposition process, it can produce spherical, ultra-fine, and high-tap density cobalt powder is its advantage. At present, UMICORE also adopts the high-pressure hydrogen reduction method to produce high-quality cobalt powder for the high-end cemented carbide market. The cobalt powders produced by the two methods have different crystal structures, and the hardness of the chemically precipitated cobalt powder is higher than that of the oxalate thermal decomposition method. Domestic research in this area is less. Zan Linhan, School of Materials Science and Engineering, Kunming University of Science and Technology published "Preparation of Ultrafine Cobalt Powder by Hydrogen Reduction Method" in "Journal of Materials Science and Engineering" (2010, Volume 28, Issue 126), and proposed the use of CoSO ₄ plus excess NaOH The prepared Co(OH) ₂ slurry, under the low hydrogen partial pressure (1MPa), the hydrothermal hydrogen reduction method has produced the spherical ultrafine cobalt powder with an average particle size of 120nm and a purity of 96%; and the ultrafine cobalt powder is subjected to secondary High temperature (700 degrees Celsius) hydrogen reduction, the particle size only grows to about 200nm, and the purity is as high as 99.68%. By controlling the secondary reduction temperature, cobalt powder with two structures of hexagonal close-packed and face-centered cubic can be obtained. Co(OH) ₂ The mechanism of slurry hydrogen reduction was preliminarily explored. Drawing on the idea of reducing reaction in the liquid phase, certain attempts have also been made in domestic universities, such as "Research on the Preparation Technology and Surface Modification Technology of Ultrafine Cobalt Powder" by Liu Pengcheng of Lanzhou University of Technology (2006, master's thesis of Lanzhou University of Technology ) proposed a polyol liquid-phase reduction method, and realized a one-step reduction method in the liquid phase to prepare ultra-fine cobalt powder; the precursor Co(OH) ₂ prepared by different cobalt salts has a certain impact on the subsequent reaction, but the impact is not great ; The product has the characteristics of high purity, fine particle size, uniform distribution, and spherical shape. Bi Dandan of Central South University in "Research on the Preparation of Ultrafine Cobalt Powder by Polyol Method" (2008, Master's Thesis of Central South University) used cobalt oxalate powder calcined at 300 degrees Celsius as a precursor to prepare cobalt tetroxide powder with relatively high purity by reducing it with glycerol. Spherical cobalt powder with high and uniform particle size distribution has no inheritance from the morphology of the precursor.

The production links involved in the technology disclosed in this patent can provide intermediate products as commodities with high economic value, and the metal cobalt microspheres produced by this process have less agglomeration and high bulk density.

Contents of the invention

In order to achieve the above-mentioned purpose, the object of the present invention provides a method for preparing cobalt metal microspheres, the cobalt metal microspheres produced by the method have the advantages of high purity, less agglomeration, reasonable particle size distribution, high bulk density and bulk density.

In order to achieve the above purpose, the preparation idea of the present invention: induce the growth of micron-sized spherical cobalt hydroxide on the metal substrate in a hydrothermal environment; use the principle of shape inheritance, thermally decompose the spherical cobalt hydroxide at a specific temperature into micron-scale spherical cobalt tetroxide; finally, under the reduction furnace, use natural gas to reduce cobalt tetroxide to obtain metal cobalt microspheres. The advantage of the above scheme is that the product of each step can become a raw material for a specific purpose, the reaction operation and process are simple and easy to control, and the quality of the product can be guaranteed.

The purpose of the present invention is achieved by the following technical solutions, a method for preparing metal cobalt microspheres, the method comprising the following steps:

(1) Preparation of micron-sized spherical cobalt hydroxide by hydrothermal method

First prepare the cobalt source mother liquor from cobalt nitrate and EDTA, the molar concentration of cobalt nitrate is 2molL ^-1 , and the concentration of EDTA is 1molL ^-1 , then add ammonia and water to make the pH of the solution about 12.4; then transfer the above solution to water Add a metal cobalt plate with a purity of >99.99% as a substrate in a thermal reaction kettle, conduct a hydrothermal reaction at 90-120 degrees Celsius for 5-20 hours in a holding furnace, take out the metal cobalt plate and repeatedly rinse it with deionized water and ethanol, After drying for 1-2 hours, the micron-sized spherical cobalt hydroxide attached to the metal cobalt plate can be obtained;

(2) Thermal decomposition treatment to obtain micron-sized spherical cobalt tetroxide

The above-mentioned micron-sized spherical cobalt hydroxide and metal cobalt plate are directly sent into the muffle furnace, the heating rate is controlled at 1-10°C per minute, the final temperature is controlled at 250-350°C, the holding time is 3-5 hours, and then naturally cooled to about 200°C;

(3) Reduction of natural gas to obtain metal cobalt microspheres

Send the micron-sized spherical cobalt tetroxide cooled to about 200°C together with the metal cobalt plate directly into the reduction furnace. The time is 2-3 hours, and the hot tail gas is directly discharged into the holding furnace where the reaction kettle is placed;

(4) Multi-stage air selection to eliminate large particles

An ion fan is used to eliminate the static electricity of the metal cobalt microspheres after cooling, and then the metal cobalt microspheres are subjected to multi-stage airflow air selection to eliminate large particles above 20 μm.

Gain effect of the present invention is as follows:

1. The method for preparing cobalt metal microspheres of the present invention is different from methods such as hydrogen reduction method and metal high-temperature annealing and solidification, and its equipment, process difficulty and energy consumption cost are greatly reduced, which is conducive to improving product competitiveness.

2, the preparation method of a kind of metal cobalt microsphere of the present invention adopts step-by-step production, is conducive to the quality monitoring of each link, and the intermediate product (micron-order spherical cobalt hydroxide and micron-order spherical cobalt tetroxide) of each production link can also be produced simultaneously Sales are conducive to the timely adjustment of production according to market demand.

3. A metal template is used in the preparation method of the metal cobalt microspheres of the present invention, which is beneficial to the collection of particles, avoids secondary pollution, is beneficial to the improvement of product purity, and enhances automatic production.

4. In the preparation method of metal cobalt microspheres of the present invention, the excess heat of the high-temperature reduction reaction is supplied to the holding furnace in the early stage of production in the form of tail gas, which reduces energy consumption and is conducive to energy saving and environmental protection.

5. In the preparation method of the cobalt metal microspheres of the present invention, multi-stage airflow selection is adopted to eliminate large particles and an ion fan is used to eliminate the static electricity of the cobalt metal microspheres after cooling, which effectively reduces the agglomeration of the product and improves the bulk density.

Description of drawings

The schematic diagram of the relationship between pH value and cobalt ion concentration in Fig. 1 solution.

Figure 2 XRD diffraction pattern of micron-sized spherical Co(OH) ₂ on a cobalt plate. (a, 5h; b, 10h; c, 15h; d, 20h)

Fig. 3 Schematic diagram of the change of the average diameter of micron-sized spherical Co(OH) ₂ with time.

Figure 4. Thermogravimetric curve of micron-sized spherical Co(OH) ₂ .

Fig. 5 SEM photo of micron-sized spherical Co ₃ O ₄ obtained by pyrolysis treatment. (a, 250°C; b, 300°C; c, 350°C)

Figure 6 Energy spectrum test of micron-scale spherical Co ₃ O ₄ .

Fig. 7 Scanning electron micrograph of metal cobalt microsphere product.

detailed description

A preparation method of metal cobalt microspheres provided by the present invention comprises the following four key process steps.

The first step is to prepare micron-sized spherical cobalt hydroxide by hydrothermal method. The preparation of various forms of nano-micron cobalt hydroxide by hydrothermal method has been generally recognized. The key to preparing spherical cobalt hydroxide is to carry out the precipitation and dissolution equilibrium of cobalt hydroxide in the system gently, that is, to control the reasonable pH value and the concentration of cobalt ions in the solution at a lower temperature. In this process, there are cobalt ions, ammonium ions, hydroxide ions, EDTA, ammonia molecules, cobalt hydroxide and other substances in the solution, and there are various reaction balances between the above molecules or ions, and complex ions are generated. By calculating the corresponding equilibrium coefficient and complexation equilibrium constant, we obtained the relationship between cobalt ion and pH value, as shown in Figure 1. In order to ensure the uniform nucleation and uniform growth of cobalt hydroxide in the system, it is very effective to maintain its low concentration Necessary, that is, require most of the cobalt ions to exist in the form of complexes, and the concentration of the cobalt ions in the solution is reduced to 0.01molL ^-1 (the horizontal line where the logarithm of the cobalt ion concentration is -2 in the figure), and the pH value should be over 12.38. Therefore, the steps are as follows: first, prepare the cobalt source mother liquor from cobalt nitrate hexahydrate and EDTA, then add ammonia and water, the initial concentration of cobalt ions in the solution is 2molL ^-1 , the concentration of EDTA is 1molL ^-1 , and the pH value of the solution is about 12.4 Then the above solution is transferred to the hydrothermal reaction kettle, and the metal cobalt plate as the substrate is added, and the hydrothermal reaction is carried out at 90 degrees Celsius in the holding furnace for several hours, and the metal cobalt plate is taken out and rinsed repeatedly with deionized water and ethanol and drying for 2 hours, the micron-sized spherical cobalt hydroxide attached to the metal cobalt plate can be obtained. Considering the yield, we are particularly concerned about the time of the hydrothermal reaction. Figure ₂ is the XRD diffraction pattern of the Co(OH) powder on the cobalt plate during the hydrothermal reaction time. From 5-20 hours, it is found that the cobalt hydroxide crystal form is basically There is no change, so 5 hours is taken in practice, and it is found that the radius of cobalt hydroxide microspheres increases with the prolongation of time, and the specific law is shown in Figure 3.

The second step is thermal decomposition treatment to obtain micron-sized spherical cobalt tetroxide. From micron-scale spherical Co(OH) ₂ to micron-scale spherical cobalt tetroxide is a thermal decomposition reaction. During the reaction, it is hoped to keep the original shape unchanged, that is, the water vapor generated by thermal decomposition can be released stably and slowly without destroying The original spherical structure. The key to this step is to establish a reasonable temperature regime. The temperature regime includes heating rate, maximum temperature and holding time, etc. Generally speaking, for this sample, the heating rate is controlled at 1°C per minute. The maximum temperature can be obtained by thermogravimetric analysis to know the state of its thermal decomposition. As shown in Figure 4, the TG thermogravimetric curve shows that between 20°C and 175°C, the sample has about 7% mass loss, which is caused by the removal of adsorbed water from the sample. And as the temperature increases, the water loss rate increases rapidly between 45°C and 175°C. A large amount of weight loss, about 10.9%, occurs between 175°C and 400°C, which is because the precursor is dehydroxylated and oxidized to oxides. After 400°C, the TG curve tends to be stable, indicating that the reaction of the precursor has been completed. Therefore, the precursor can be calcined at 250°C, 300°C and 350°C to produce black Co ₃ O ₄ . Figure 5 is a scanning electron micrograph of micron-sized spherical Co(OH) ₂ heat-treated at the above temperature for 5 hours in a muffle furnace. The three pictures are all micro-nano spheres, and there is inheritance of morphology. Among them, it is found in Figure 5a that the samples obtained by heat treatment at 250°C have good dispersion and small size. As shown in Figure 5b, the sample at 300 °C has a good dispersion and a slight increase in the size of the nanospheres. However, in Fig. 5c, the sample at 350 °C has a cohesive phenomenon, and the dispersion is greatly reduced to a size of 2 μm. Thus, it can be seen that a high sintering temperature is not conducive to the dispersibility of the product, and an excessively high temperature leads to sintering. Considering the dispersibility and yield, 300°C is the best temperature. At the same time, the energy spectrum EDS test shows that the sample is indeed Co ₃ O ₄ , and the mass ratio of Co and O is close to the theoretical value of the chemical formula Co ₃ O ₄ . The test location and results Figure 6. According to the detection requirements _of Co3O4 in the nonferrous metal industry standard YS/T _633-2007 , the technical indicators of cobalt metal microspheres prepared under this process are as follows:

The third step is to reduce Co ₃ O ₄ by natural gas to obtain metal cobalt microspheres, which involves a set of natural gas reduction furnace equipment. The device is composed of heating furnace body, reduction furnace tube, material pushing device, natural gas flow meter, control device, multi-channel intelligent temperature control, electric control system and so on. Unlike general hydrogen reduction furnaces, safety and economy are improved by using natural gas. Especially for the heating device part, the previous process is heat-treated in a muffle furnace, so the micron-sized spherical cobalt tetroxide cooled to about 200°C can be directly sent into the reduction furnace together with the metal cobalt plate using the pusher device. By controlling the air pressure at 0.35Mpa, the content of CH ₄ in the reduction furnace tube is guaranteed to make it fully reduced. The reduction temperature in the central section is controlled at 600°C, the holding time is 3 hours, and the heating rate is controlled at 10-20°C per minute. At the end of the reduction process, the hot tail gas containing higher temperature in the furnace is directly discharged into the holding furnace where the reaction kettle is placed by controlling the air pressure.

The fourth step is multi-stage air selection to eliminate large particles. After the reduction reaction in the previous process, during the cooling and collection process, the surface temperature of the metal cobalt microspheres is low and the interior is high, and the thermal stress direction is from the inside to the outside, with the possibility of expansion. Secondly, during the entire reduction reaction process, The water vapor generated by the reaction brings a large number of charged groups, and these groups are likely to be adsorbed on the surface defect points of the metal cobalt microspheres, causing the metal cobalt microspheres to be charged with static electricity, resulting in the cooling of the metal cobalt microsphere products. Contains a small amount of agglomeration, large particles or secondary particles with particle growth. We plan to use ion fan-multi-stage air separation-ion fan combination to remove large particles, and remove the secondary agglomeration and large particles that grow up during the spheroidization cooling process. For the first time, the ion fan was used to eliminate the static electricity of the metal cobalt microspheres after cooling, creating conditions for the subsequent multi-stage airflow winnowing of the metal cobalt microspheres to eliminate large particles above 20 μm; the second ion blower was to eliminate the airflow winnowing after the collision newly generated static electricity. After passing through the above process, the metal cobalt microsphere product is completely separated from the metal cobalt plate, and the static electricity is basically eliminated, and as shown in Figure 7, there are no particles larger than 20 μm at all. The median particle size of metal cobalt microsphere products is 5±2μm, and the particle size <4.00μm accounts for more than 20wt%, and its particle size distribution (<4.00μm accounts for ≥20wt%; <7.0μm accounts for ≥60wt%; <20μm accounts for 100wt%) It basically conforms to the Westman equation of the packing theory of size particles, which is beneficial to the application of various close packing occasions.

According to the industry standard YS/T255-2009, the technical indicators of cobalt metal microspheres prepared under this process are as follows:

Claims (1)

1. the preparation method of a metallic cobalt microsphere, it is characterised in that the step that the method includes is as follows:

(1) hydro-thermal method prepares micron-size spherical cobalt hydroxide

First being prepared cobalt source mother solution by cobalt nitrate and EDTA, cobalt nitrate substance withdrawl syndrome is 2molL^-1, EDTA concentration is 1molL^-1, then adding ammonia and water, the pH value making solution is 12.4；Then above-mentioned solution is transferred in hydrothermal reaction kettle, The metallic cobalt plate of addition purity ＞ 99.99% is as substrate, and in holding furnace, 90-120 degree Celsius of lower hydro-thermal reaction 5-20 hour, takes Go out metallic cobalt plate and it is rinsed repeatedly with deionized water and ethanol, is dried 1-2 hour, i.e. can obtain being attached to metal Micron-size spherical cobalt hydroxide on cobalt plate；

(2) thermal decomposition process obtains micron-size spherical Cobalto-cobaltic oxide

Being sent directly in Muffle furnace together with metallic cobalt plate by above-mentioned micron-size spherical cobalt hydroxide, programming rate controls at 1-10 DEG C Per minute, final temperature controls at 250-350 DEG C, and then temperature retention time 3-5 hour naturally cools to about 200 DEG C；

(3) natural gas reduction obtains metallic cobalt microsphere

The micron-size spherical Cobalto-cobaltic oxide that will be cooled to about 200 DEG C is sent directly into reduction furnace, air pressure control together with metallic cobalt plate System is at 0.24-0.35Mpa, and programming rate controls at 10-20 DEG C per minute, and final temperature controls at 600-800 DEG C, temperature retention time 2-3 hour, hot exhaust gas was directly discharged in the holding furnace of placing response still；

(4) Multi-stage airflow selecting crude drugs with winnower eliminates bulky grain

After using ion blower elimination to cool down, the electrostatic of metallic cobalt microsphere, then carries out Multi-stage airflow selecting crude drugs with winnower by metallic cobalt microsphere and disappears Except bulky grains more than 20 μm.