Spherical copper powder coated with nano thin layer on surface as well as preparation method and application of spherical copper powder

Abstract

The invention discloses spherical copper powder coated with a nanometer thin layer on the surface and a preparation method and application of the spherical copper powder. The method comprises the following steps that (S1) mixing is conducted, specifically, pure copper powder and a salt solution are mixed, and a mixed solution is prepared; (S2) precipitation: under a stirring condition, adjusting the mixed solution in the step (S1) to be alkaline, separating out a precipitate after the precipitate is formed, and drying to obtain a solid 1; and (S3) high-temperature treatment: carrying out high-temperature treatment on the solid 1 in the step (S2) under argon shielding gas to obtain a solid 2. The coating layer of the prepared copper powder coated with cobalt oxide on the surface is uniform, and the thickness of the cobalt oxide coating layer is nanoscale. The thickness of the coating layer can be adjusted by adjusting and controlling the concentration of the salt solution, so that the laser reflectivity of the copper powder is adjusted. When the prepared copper powder with the surface coated with cobalt oxide is applied to 3D printing, the printability is remarkably improved, and the strength of a printed part is far higher than that of an untreated copper powder printed part.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation, and particularly relates to a spherical copper powder with a surface-coated nano-thin layer, a preparation method thereof, and an application thereof. Background Art

[0002] Copper has excellent electrical conductivity, thermal conductivity, good ductility and corrosion resistance, which makes copper have broad application prospects in applications such as electronic components, electrical equipment and heat exchangers. Laser powder bed fusion (LPBF) is one of the most common additive manufacturing technologies, which can manufacture complex geometries that are difficult to achieve by traditional processing methods. However, due to the extremely high laser reflectivity and thermal conductivity of pure copper, energy loss and insufficient heat input are caused, so it is difficult to prepare dense copper samples using a laser LPBF device with a laser wavelength in the range of 1000 - 1100 nm. To solve the problem of insufficient heat input caused by the high laser reflectivity of pure copper, researchers have explored a series of strategies. For example, the literature (S.D. Jadhav et al, J. Mater. Process. Technol, doi.org / 10.1016 / j.jmatprotec.2019.02.022) reported the production of relatively high-density pure copper samples using a high-power single-mode fiber laser, but when exposed to high-power laser for a long time, the optical mirror is easily damaged. Another example is the literature (A. Singh et al, Opt. Laser Technol, doi.org / 10.1016 / j.optlastec.2022.108310) which reported the use of a new type of LPBF device with a green-band wavelength laser for preparing dense copper samples. However, due to the poor stability and high cost of the green-band laser, its application and development are limited. In addition, coating copper powder with nanoparticles with high laser absorption rate is considered an effective method to overcome the high laser reflectivity of copper powder and enhance heat input. Currently, the modification of copper powder is mainly achieved by coating nanoparticles on copper powder through ball milling mixing, and this method inevitably results in the phenomenon of agglomeration and uneven mixing of nanoparticles.

[0003] Improving the laser absorption rate of copper powder is one of the key technologies for preparing high-performance copper parts. Therefore, it is particularly important to develop a copper powder with excellent 3D printing performance. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a copper powder with a surface-coated cobalt oxide, a preparation method thereof, and an application thereof. The copper powder with a surface-coated cobalt oxide prepared by the present invention has a significantly reduced laser reflectivity at a wavelength of 1080 nm and does not affect the powder fluidity, thus solving the problem that pure copper powder is difficult to be 3D printed and formed, and significantly improving the performance of 3D printed copper parts.

[0005] To achieve the above-mentioned invention object, the technical solution of the present invention is as follows:

[0006] A method for preparing copper powder, the method comprising the following steps:

[0007] (S1) Mixing: Mix copper powder with a salt solution to prepare a mixed solution;

[0008] (S2) Precipitation: Under stirring conditions, adjust the mixed solution in step (S1) to be alkaline, form a precipitate, separate the precipitate, and obtain solid 1 after drying;

[0009] (S3) High-temperature treatment: Subject solid 1 in step (S2) to high-temperature treatment under an inert gas atmosphere to obtain solid 2.

[0010] According to an embodiment of the present invention, the preparation method further includes step (S4), washing, solid-liquid separation, and drying of solid 2 in step (S3) to obtain the copper powder. For example, solid 2 in step (S3) is washed by ultrasonic waves with water, the solid mixture is separated by precipitation, and the coated copper powder is obtained after drying.

[0011] According to an embodiment of the present invention, in step S1, the copper powder is preferably pure copper powder, preferably spherical copper powder.

[0012] According to an embodiment of the present invention, in step S1, the pure copper powder can be prepared by methods such as aerosol and rotating electrode, or can be spherical powder obtained by any other method.

[0013] According to an embodiment of the present invention, in step S1, the particle size of the copper powder can be 15 - 53 μm.

[0014] According to an embodiment of the present invention, in step S1, the salt solution can be a cobalt salt solution, such as cobalt chloride solution and cobalt nitrate solution. Preferably, the concentration of the salt solution is 0.01 - 0.1 g / mL, and examples are 0.01 g / mL, 0.016 g / mL, 0.032 g / mL, 0.048 g / mL, 0.06 g / mL, 0.0801 g / mL, 0.1 g / mL.

[0015] According to an embodiment of the present invention, in step S1, the solid-liquid ratio of the copper powder to the salt solution is 1 g:(0.1 - 1) mL, and examples are 1 g:0.1 mL, 1 g:0.2 mL, 1 g:0.4 mL, 1 g:0.5 mL, 1 g:0.8 mL, 1 g:1 mL.

[0016] According to an embodiment of the present invention, in step S2, the mixed solution in step (S1) is adjusted to a pH of 8 - 10, for example, 8, 9, 9.3, 9.5, 10.

[0017] In one embodiment of the present invention, the pH is adjusted to 8 - 10 by adding an alkali solution to the mixed solution. For example, the alkali solution can be a sodium hydroxide solution. Preferably, the concentration of the sodium hydroxide solution can be 0.5 - 2 mol / L. Exemplarily, the sodium hydroxide solution is 0.5 mol / L, 0.75 mol / L, 1 mol / L, 2 mol / L.

[0018] According to an embodiment of the present invention, in step S2, the stirring is carried out under a magnetic stirrer. Stirring can also be carried out by other means.

[0019] According to an embodiment of the present invention, in step S2, the stirring time is 1 - 5 hours, for example, 1 hour, 3 hours, 5 hours.

[0020] According to an embodiment of the present invention, in steps S2 and S4, the drying is carried out using a vacuum oven to remove the moisture in the powder.

[0021] According to an embodiment of the present invention, in step S3, the temperature of the high-temperature treatment is 300 - 500 °C, for example, 300 °C, 350 °C, 400 °C, 450 °C, 500 °C; the heat preservation time of the high-temperature treatment is 1 - 5 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours.

[0022] According to an embodiment of the present invention, in step S3, the heating rate of the high-temperature treatment is 1 - 15 °C / min, for example, 1 °C / min, 5 °C / min, 10 °C / min, 15 °C / min.

[0023] According to an embodiment of the present invention, in step S3, the inert atmosphere can be, for example, one of argon and nitrogen.

[0024] In one embodiment of the present invention, the high-temperature treatment is to rise from room temperature to 300 - 500 °C at a heating rate of 1 - 15 °C / min, keep warm for 1 - 5 hours, and then cool with the furnace.

[0025] In the present invention, the alkali solution reacts with the cobalt chloride solution to form cobalt hydroxide precipitate, which is uniformly attached to the surface of the copper powder under stirring. After high-temperature treatment, a cobalt oxide coating with a nanoscale thickness is formed on the surface of the prepared pure copper powder.

[0026] According to an embodiment of the present invention, in step S4, the number of times of ultrasonic water washing is not limited, as long as the residual ionic substances on the powder surface can be removed. Exemplarily, it is repeated 2 - 3 times.

[0027] According to an embodiment of the present invention, in step S4, the cleaning method is not limited to this, and other cleaning methods can also be used, as long as the ionic substances attached to the surface of the powder can be removed.

[0028] According to an embodiment of the present invention, in steps S2 and S4, the drying time is not limited, as long as the surface is dried. Exemplarily, the drying time can be 3 - 12 hours.

[0029] The present invention provides copper powder with a cobalt oxide coating on the surface prepared by the above method.

[0030] According to an embodiment of the present invention, the surface of the copper powder has a cobalt oxide coating layer, that is, copper powder with a cobalt oxide coating on the surface.

[0031] According to an embodiment of the present invention, the coating amount of cobalt oxide can be 0.2 - 1.0 wt%, and exemplarily it can be 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, 1.0 wt%.

[0032] According to an embodiment of the present invention, the thickness of the cobalt oxide coating layer is 200 - 400 nm.

[0033] The present invention also provides the application of the above copper powder with a cobalt oxide coating on the surface in 3D printing.

[0034] The present invention also provides a manufactured product, which contains the above copper powder with a cobalt oxide coating on the surface and / or is prepared from the above copper powder with a cobalt oxide coating on the surface.

[0035] The present invention also provides a preparation method of the above manufactured product, which includes performing 3D printing on the above copper powder with a cobalt oxide coating on the surface to prepare the manufactured product.

[0036] The present invention also provides a method for reducing the laser reflectivity of copper powder, which includes coating a cobalt oxide layer on the surface of the copper powder to obtain the copper powder with a cobalt oxide coating on the surface.

[0037] Advantages of the present invention:

[0038] (1) The cobalt oxide coating layer of the copper powder with a cobalt oxide coating on the surface prepared by the present invention is uniform, and the thickness of the cobalt oxide coating layer is nanoscale. The present invention can adjust the thickness of the surface coating layer by regulating the concentration of the salt solution, thereby adjusting the laser reflectivity of the copper powder.

[0039] (2) The copper powder with a cobalt oxide coating on the surface prepared by the present invention can be applied to 3D printed parts. Moreover, the printability of the copper powder with a cobalt oxide coating on the surface of the present invention is significantly improved, and the strength of the printed parts is much higher than that of the printed parts made of copper powder without coating treatment. Description of the Drawings

[0040] Figure 1 It is a schematic structural diagram of a tensile spline.

[0041] Figure 2 It is a laser reflectivity diagram of pure copper powder and copper powder with cobalt copper oxide coated on the surface in Example 1.

[0042] Figure 3 It is an XRD diffraction pattern of copper powder with cobalt copper oxide coated on the surface and pure copper powder in Example 1.

[0043] Figure 4 It is an SEM image of copper powder with cobalt copper oxide coated on the surface in Example 1.

[0044] Figure 5 In it, a and b are SEM images of the overall section and the local section of the copper powder with cobalt copper oxide coated on the surface obtained in Example 1 respectively.

[0045] Figure 6 It is an SEM image of pure copper powder. Detailed implementation manners

[0046] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only for exemplarily illustrating and explaining the present invention, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0047] Unless otherwise specified, the raw materials and reagents used in the following embodiments are all commercially available products, or can be prepared by known methods.

[0048] Example 1

[0049] The preparation method of the copper powder with cobalt oxide coated on the surface in this example is as follows:

[0050] (S101) Add 50 g of spherical copper powder with a particle size of 15 - 53 μm (purchased from Jirui Metal Materials (Shandong) Co., Ltd.) to 20 mL of cobalt chloride aqueous solution with a concentration of 0.079 g / mL (1.5885 g of cobalt chloride hexahydrate dissolved in 20 mL of water);

[0051] (S102) Continuously stir the mixture for 3 hours, and at the same time gradually add 0.5 mol / L sodium hydroxide solution until the pH of the solution is 9 and it becomes alkaline. After the stirring ends, let it stand for 10 minutes, pour out the upper clear liquid, and dry the lower precipitate in a vacuum drying oven at 85 °C;

[0052] (S103) Use a tube furnace to heat the solid obtained in step (S102) to 450 °C under argon protection gas at a heating rate of 5 °C / min, keep it warm for 2 hours, and finally take it out after naturally cooling to room temperature;

[0053] (S104) Add the solid obtained in step (S103) to deionized water and wash it under ultrasonic treatment. Repeat this cleaning process three times. Take out the solid and dry it in an oven at 85 °C to obtain copper powder with cobalt oxide coated on its surface.

[0054] Perform a laser reflectivity test on the copper powder with cobalt oxide coated on its surface prepared in this example and pure copper powder (the spherical copper powder in step S101). The test results are as Figure 2 shown. The results in the figure show that, compared with the untreated copper powder, the laser reflectivity of the copper powder with cobalt oxide coated on its surface according to the present invention is significantly reduced.

[0055] Perform an XRD test on the copper powder with cobalt oxide coated on its surface prepared in this example and pure copper powder (the spherical copper powder in step S101). The test results are as Figure 3 shown. The results in the figure show that the XRD diffraction pattern of the copper powder with cobalt oxide coated on its surface has obvious characteristic diffraction peaks of cobalt oxide at diffraction angles of 36.5° and 42.4°. This indicates that a cobalt oxide coating layer has been successfully formed on the surface of the copper powder.

[0056] Perform an SEM test on the copper powder with cobalt oxide coated on its surface prepared in this example (the coating amount is 1 wt%). The results are as Figure 4 shown. Comparing with Figure 6 the SEM image of the pure copper powder (the spherical copper powder in step S101), it can be seen that there is a coating layer on the surface of the copper powder prepared in this example.

[0057] Perform a cross-section test on the copper powder with cobalt oxide coated on its surface prepared in this example. The test results are as Figure 5 shown. From Figure 5 it can be seen that the surface of the copper powder is coated with a thin layer with a thickness of 200 - 400 nm.

[0058] Example 2

[0059] The difference between Example 2 and Example 1 is that in step (S101), the mass of cobalt chloride hexahydrate becomes 0.3177 g (i.e., add 20 mL of cobalt chloride aqueous solution with a concentration of 0.015885 g / mL), and copper powder with cobalt oxide coated on its surface with a coating amount of 0.2 wt% is prepared.

[0060] Example 3

[0061] The difference between Example 3 and Example 1 is that in step (S101), the mass of cobalt chloride hexahydrate becomes 0.6344 g (i.e., add 20 mL of cobalt chloride aqueous solution with a concentration of 0.0317 g / mL), and copper powder with cobalt oxide coated on its surface with a coating amount of 0.4 wt% is prepared.

[0062] Example 4

[0063] Example 4 is different from Example 1 in that in step (S101), the mass of cobalt chloride hexahydrate becomes 0.9531 g (i.e., 20 mL of an aqueous cobalt chloride solution with a concentration of 0.04765 g / mL is added), and copper powder with a cobalt oxide coating amount of 0.6 wt% on the surface is prepared.

[0064] Example 5

[0065] Example 5 is different from Example 1 in that in step (S102), the stirring time is reduced to 1 hour.

[0066] Example 6

[0067] Example 6 is different from Example 1 in that in step (S102), the stirring time is increased to 5 hours.

[0068] Example 7

[0069] Example 7 is different from Example 1 in that in step (S102), 0.75 mol / L sodium hydroxide solution is added dropwise until the pH of the solution reaches 9.3.

[0070] Example 8

[0071] Example 8 is different from Example 1 in that in step (S102), 1 mol / L sodium hydroxide solution is added dropwise until the pH of the solution reaches 9.5.

[0072] Test Example 1

[0073] The copper powder with a cobalt oxide coating on the surface and pure copper powder (spherical copper powder in step S101) prepared in Examples 1 - 8 were subjected to a laser reflectivity test. The test results of the reflectivity of the samples at a laser wavelength of 1080 nm are shown in Table 1 below.

[0074] Table 1

[0075]

[0076] It can be seen from Table 1 that the copper powder with a cobalt oxide coating on the surface prepared in the present invention significantly reduces the laser reflectivity of the powder, and with the increase of the cobalt oxide coating amount, the laser reflectivity shows a downward trend.

[0077] Test Example 2

[0078] The copper powder with cobalt oxide-coated surface prepared in Example 1 and pure copper powder (the spherical copper powder in Step S101) were used in 3D printing, and the tensile properties of the prepared parts were tested. The printing conditions were as follows: laser power 325 W, scanning speed 200 mm / s, scanning line spacing 0.1 mm, powder layer thickness 0.03 mm, protective atmosphere argon, and the oxygen content in the forming cavity was maintained at <100 ppm. The pure copper powder was also printed with the above parameters, and a sheet sample of 50 mm * 6 mm * 2 mm was printed and processed into a tensile sheet sample by wire cutting for tensile experiments. The dimensions of the tensile specimen were as shown in Figure 1 shown. The test results are shown in Table 2 below.

[0079] Table 2

[0080] Yield strength (MPa) Tensile strength (MPa) Elongation rate (%) Pure copper powder 89 121 7.9 Example 1 382 451 7.6

[0081] The results in Table 2 show that when pure copper powder is used in 3D printing, due to its high laser reflectivity and high thermal conductivity, there are many internal defects in the prepared samples, so the performance of the samples is poor. However, when the copper powder with cobalt oxide-coated surface of the present invention is used in 3D printing, the laser reflectivity of the copper powder after coating with cobalt oxide is reduced, and there are fewer internal defects in the prepared samples. The yield strength and tensile strength of the samples are greatly improved.

[0082] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing copper powder, characterized in that: The method comprises the following steps: (S1) mixing: mixing copper powder and salt solution to prepare a mixed solution; (S2) precipitation: under stirring conditions, adjusting the mixed solution of step (S1) to be alkaline, forming a precipitate, separating the precipitate, and drying to obtain a solid 1; (S3) High temperature treatment: The solid object 1 in step (S2) is subjected to high temperature treatment under an inert atmosphere to obtain a solid object 2.

2. The preparation method according to claim 1, characterized in that In step S1, the salt solution is a cobalt salt solution, preferably a cobalt chloride solution or a cobalt nitrate solution. Preferably, the concentration of the salt solution is 0.01 to 0.1 g / mL. Preferably, in step S1, the solid-liquid ratio of the copper powder to the salt solution is 1 g: (0.1-1) mL.

3. The preparation method according to claim 1, characterized in that: In step S2, the mixed solution of step (S1) is adjusted to a pH of 8-10.

4. The preparation method according to any one of claims 1 to 3, characterized in that: In step S3, the temperature of the high temperature treatment is 300-500° C.; the insulation time of the high temperature treatment is 1-5 hours.

5. The copper powder with surface coated with cobalt oxide prepared by the method according to any one of claims 1 to 4.

6. The copper powder according to claim 5, characterized in that The copper powder has a cobalt oxide coating layer on its surface. Preferably, the coating amount of the cobalt oxide may be 0.2-1.0 wt%. Preferably, the thickness of the cobalt oxide coating layer is 200-400 nm.

7. Use of the copper powder according to claim 5 or 6 in 3D printing.

8. A manufactured article, comprising the copper powder according to claim 5 or 6 and / or prepared from the copper powder according to claim 5 or 6.

9. The method for preparing a product according to claim 8, characterized in that: The preparation method comprises 3D printing the copper powder according to claim 5 or 6 to prepare the product.

10. A method for reducing the laser reflectivity of copper powder, comprising coating a cobalt oxide layer on the surface of the copper powder to obtain copper powder with the surface coated with cobalt oxide.

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