Nano-copper powder and method for preparing the same

Abstract

The application provides a kind of nano copper powder and its preparation method, and the preparation method comprises the following steps: mixing copper salt solution and soluble carbonate solution, reacting at 0-35 DEG C to obtain basic copper carbonate slurry; the basic copper carbonate slurry is filtered to obtain filter cake, and the filter cake is dried at 0-35 DEG C to obtain amorphous basic copper carbonate powder; the amorphous basic copper carbonate powder is reduced by hydrogen to obtain nano copper powder.The application synthesizes amorphous basic copper carbonate precursor by liquid phase, and further uses hydrogen as reducing agent to reduce at low temperature, obtains nano copper powder with particle size of 20-100 nm, has low cost, uniform size of nano copper powder, and no sintering agglomeration behavior.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano powder material preparation technology, and particularly relates to a nano copper powder and its preparation method. Background Technology

[0002] Nano-copper powder refers to a type of metallic copper powder with a size between 10 nm and 100 nm. Metallic copper has good thermal conductivity, electrical conductivity, and ductility, and its powder materials are often used in the preparation of conductive pastes, powder metallurgy, and mechanical lubrication. Nano-copper has a large specific surface area and strong chemical activity. Compared with ordinary micron-sized copper powder, nano-copper powder has a lower sintering temperature, more active chemical properties, and better dispersibility. Therefore, it has potential applications in low-temperature (<250℃) sintering of photovoltaics, mechanical lubrication, and the recovery of precious metals from precious metal ion solutions.

[0003] Currently, methods for synthesizing nano-copper powder include physical vapor deposition (PVD), liquid-phase reduction, and gas atomization. PVD involves vaporizing metallic copper at high temperatures, then condensing it with an inert gas, classifying it, and collecting the nano-copper powder. This method yields copper powder with high sphericity and good dispersibility, but it requires expensive equipment and consumes large amounts of inert gas, resulting in high production costs. Gas atomization involves melting metallic copper, then atomizing and condensing it with an inert gas in a Venturi nozzle, classifying it to obtain nano-copper powder. This method produces nano-copper powder with relatively uniform size, but the yield is low and the production cost is high. Liquid-phase reduction involves reducing copper hydroxide or cuprous oxide in solution with reducing agents such as hydrazine hydrate, sodium borohydride, and formaldehyde to obtain nano-copper. This method has low equipment costs and low energy consumption, but the resulting copper powder is prone to agglomeration, and the reaction parameters are difficult to control, making large-scale synthesis of nano-copper powder difficult.

[0004] Patent CN111889692A proposes a process for obtaining basic copper carbonate by reacting sodium carbonate and copper salt, and then further reducing it with hydrogen to obtain ultrafine copper powder. In this method, the temperature for synthesizing basic copper carbonate in the liquid phase is 50℃~90℃. The basic copper carbonate is then further reduced with hydrogen at 350℃~600℃ to obtain copper powder with a size of about 10 μm. The copper powder exhibits significant agglomeration.

[0005] In summary, the current technical challenges in synthesizing nano-copper powder include: nano-copper is highly reactive and easily agglomerates during the synthesis process; and the technology for synthesizing nano-copper powder involves high equipment investment and high production costs. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an ultrafine spherical copper powder and its preparation method. This is a new process for synthesizing nano copper powder using hydrogen, which can solve the technical problems mentioned in the background.

[0007] To address the aforementioned technical problems, this invention provides a method for preparing nano-copper powder, the method comprising the following steps: S1. Mix copper salt solution and soluble carbonate solution, and react at 0℃~35℃ to obtain basic copper carbonate slurry; S2. Filter the basic copper carbonate slurry to obtain a filter cake, and dry the filter cake at 0℃~35℃ to obtain amorphous basic copper carbonate powder. S3. Reduce amorphous basic copper carbonate powder with hydrogen to obtain nano copper powder.

[0008] In the above preparation method, the soluble carbonate in S1 is one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, or ammonium bicarbonate, and the copper salt includes one of copper sulfate, copper nitrate, copper formate, and copper acetate.

[0009] In the above preparation method, the reaction temperature in S1 is 10℃~30℃.

[0010] In the above preparation method, the drying temperature in step S2 is 0℃~35℃ and the drying time is 10 min~600 min.

[0011] In the above preparation method, the drying temperature is 10℃~30℃ and the time is 30 min~300 min.

[0012] In the above preparation method, the reduction temperature in step S3 is 150℃~250℃, and the reduction time is 0.5 h~10 h.

[0013] In the above preparation method, the reduction temperature is 160℃~210℃ and the reduction time is 2 h~6 h.

[0014] Based on a general technical concept, the present invention provides a nano-copper powder prepared by the preparation method described above.

[0015] Furthermore, the aforementioned nano-copper powder has a particle size of 20 nm to 100 nm.

[0016] Compared with the prior art, the advantages of the present invention are as follows: This invention provides an ultrafine spherical copper powder and its preparation method. The method involves synthesizing an amorphous basic copper carbonate precursor in the liquid phase, and then reducing it at low temperature using hydrogen as a reducing agent to obtain nano-copper powder. This method is characterized by low cost, uniform size of the nano-copper powder, and no sintering or agglomeration. Attached Figure Description

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0018] Figure 1 The SEM morphology of the amorphous basic copper carbonate powder obtained in step (2) of Example 1 is shown.

[0019] Figure 2 The TEM morphology of copper powder reduced from amorphous basic copper carbonate obtained in step (3) of Example 1 is shown.

[0020] Figure 3 The thermogravimetric curves are the corresponding thermogravimetric curves for the thermal decomposition of amorphous basic copper carbonate in N2 atmosphere in Example 1.

[0021] Figure 4 The image shows the SEM morphology of the spiky basic copper carbonate obtained in step (2) of Comparative Example 1.

[0022] Figure 5 The image shows the SEM morphology of copper powder obtained by reducing micron-sized spiky basic copper carbonate at 160℃ in Comparative Example 1.

[0023] Figure 6 This is the thermogravimetric curve corresponding to the thermal decomposition of the spiky basic copper carbonate in Comparative Example 1 under N2 atmosphere.

[0024] Figure 7 The TEM morphology of copper powder reduced from amorphous basic copper carbonate in Example 2 is shown.

[0025] Figure 8 These are the XRD patterns of amorphous basic copper carbonate from Example 1, spiky basic copper carbonate from Comparative Example 1, and reduced copper powder from Examples 1-4. Detailed Implementation

[0026] The present invention will be further described below with reference to specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0027] The materials, reagents, and instruments used in the following examples are all commercially available. Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art.

[0028] This invention provides a method for preparing nano-copper powder, the method comprising the following steps: S1. Mix copper salt solution and soluble carbonate solution, and react at 0℃~35℃ to obtain basic copper carbonate slurry; S2. Filter the basic copper carbonate slurry to obtain a filter cake, and dry the filter cake at 0℃~35℃ to obtain amorphous basic copper carbonate powder. S3. Reduce amorphous basic copper carbonate powder with hydrogen to obtain nano copper powder.

[0029] In step S2 above, the prepared amorphous basic copper carbonate powder is loose and porous, allowing hydrogen to fully penetrate; the reduction process releases H2O and CO2 gases, which play an in-situ blocking role in particle agglomeration, ultimately yielding elemental copper powder with a particle size of 20 nm to 100 nm and high powder purity.

[0030] Furthermore, the reaction temperature in S1 is 10℃~30℃. The drying temperature is 10℃~30℃, and the time is 30 min~300 min. This invention maintains the reaction temperature at a lower temperature, resulting in more stable amorphous basic copper carbonate, which can suppress the production of micron-sized spiky crystalline basic copper carbonate. The obtained amorphous nano-sized basic copper carbonate is unstable in aqueous solution and easily grows into spiky spherical basic copper carbonate with a structure of about 4 μm. When the spiky basic copper carbonate is used as a precursor for further reduction with hydrogen, it still retains the spiky structure. However, when this invention uses amorphous basic copper carbonate powder as a precursor for reduction, the resulting copper powder inherits the nanostructure of the precursor, and the product is nano-copper powder.

[0031] Furthermore, the reduction temperature in step S3 is 150℃~250℃, and the reduction time is 0.5 h~10 h. Copper carbonate is difficult to reduce with hydrogen. When the temperature is higher than 250℃, the generated copper nanoparticles sinter and grow, and the product is no longer copper nanoparticles. Preferably, the temperature is 160~210℃, and the reduction time is 2 h~6 h. The generated amorphous basic copper carbonate can be reduced to copper nanoparticles in a hydrogen atmosphere. Since carbon dioxide and water vapor are generated during the reaction, compared with the reduction of copper oxide as a precursor, it is an endothermic reaction, which avoids the sintering of copper nanoparticles.

[0032] Example 1 The present invention discloses an ultrafine spherical copper powder, the preparation method of which includes the following steps: (1) Weigh 270 g of copper sulfate pentahydrate and dissolve it in 1.2 L of deionized water. Separately, take 120 g of anhydrous sodium carbonate and add it to 1.2 L of water to form a slurry. Keep the solution temperature at 10℃ and the stirring speed at 600 rpm. Add the copper sulfate solution to the sodium carbonate solution to obtain basic copper carbonate slurry.

[0033] (2) Filter the basic copper carbonate slurry to obtain a filter cake, and dry the filter cake at 10°C for 600 min to obtain amorphous basic copper carbonate powder.

[0034] (3) Amorphous basic copper carbonate powder was reduced with hydrogen at 160℃ for 6 h to obtain 65.9 g of nano copper powder.

[0035] Figure 1 The image shows the SEM morphology of the amorphous basic copper carbonate powder obtained in step (2) of Example 1. From... Figure 1 It can be seen that the basic copper carbonate obtained by liquid-phase synthesis at a low temperature of 10℃ and drying at 10℃ has an amorphous structure of about 150 nm.

[0036] Figure 2 The TEM morphology of copper powder reduced from amorphous basic copper carbonate obtained in step (3) of Example 1 is shown. Figure 2 As can be seen from this, the copper powder prepared according to this embodiment has a particle size in the range of 20 nm to 100 nm.

[0037] Figure 3 The figure shows the thermogravimetric curves for the thermal decomposition of amorphous basic copper carbonate in a N2 atmosphere. As can be seen from the figure, amorphous basic copper carbonate has poor crystallinity, loses a large amount of water at low temperatures, and its decomposition temperature is lower than that of crystalline basic copper carbonate.

[0038] Comparative Example 1 The preparation method of the ultrafine spherical copper powder in this comparative example includes the following steps: (1) Weigh 270 g of copper sulfate pentahydrate and dissolve it in 1.2 L of deionized water. Separately, take 120 g of anhydrous sodium carbonate and add it to 1.2 L of water to form a slurry. Keep the solution temperature at 40℃ and the stirring speed at 600 rpm. Add the copper sulfate solution to the sodium carbonate solution to obtain basic copper carbonate slurry.

[0039] (2) Filter the basic copper carbonate slurry to obtain a filter cake, and dry the filter cake at 10°C for 600 min to obtain spiky basic copper carbonate.

[0040] (3) Reduce amorphous basic copper carbonate powder with hydrogen at 160℃ for 6 h to obtain copper powder.

[0041] Figure 4 The image shows the SEM morphology of the spiky basic copper carbonate obtained in step (2) of Comparative Example 1. As can be seen from the image, the basic copper carbonate synthesized at 40℃ recrystallizes due to the high temperature, resulting in a micron-sized spiky spherical structure.

[0042] Figure 5 This is the SEM morphology of copper powder obtained by reducing micron-sized spiky spherical basic copper carbonate at 160℃. As can be seen from the image, the copper powder inherits the spiky spherical structure and has a particle size of approximately 4 micrometers.

[0043] Figure 6 This is the thermogravimetric curve corresponding to the thermal decomposition of spiky basic copper carbonate in an N2 atmosphere. As can be seen from the figure, the spiky basic copper carbonate has intact crystals, few pores, and almost no free adsorbed water; it is difficult to remove at low temperatures, with a characteristic weight loss at 258℃, indicating that dehydration is concentrated in the high-temperature range.

[0044] Example 2 The present invention discloses an ultrafine spherical copper powder, the preparation method of which includes the following steps: (1) Weigh 220 g of copper formate tetrahydrate and dissolve it in 1.2 L of deionized water. Separately, add 200 g of sodium bicarbonate to 1.2 L of water to form a slurry. Keep the solution temperature at 30℃ and the stirring speed at 600 rpm. Add the copper formate tetrahydrate solution to the sodium bicarbonate solution to obtain basic copper carbonate slurry.

[0045] (2) Filter the basic copper carbonate slurry to obtain a filter cake, and dry the filter cake at 30°C for 30 min to obtain amorphous basic copper carbonate powder.

[0046] (3) Amorphous basic copper carbonate powder was reduced with hydrogen at 210℃ for 3 h to obtain 65.1 g of nano copper powder.

[0047] Figure 7 The image shows the TEM morphology of copper powder reduced from amorphous basic copper carbonate. As can be seen from the image, the nano-copper powder has a size of 10–100 nm and exhibits good dispersibility.

[0048] Example 3 The present invention discloses an ultrafine spherical copper powder, the preparation method of which includes the following steps: (1) Weigh 260 g of copper nitrate trihydrate and dissolve it in 1.2 L of deionized water. Separately, add 150 g of anhydrous potassium carbonate to 1.2 L of water to form a solution. Keep the solution temperature at 10℃ and the stirring speed at 600 rpm. Add the copper nitrate solution to the potassium carbonate solution to obtain basic copper carbonate slurry.

[0049] (2) Filter the basic copper carbonate slurry to obtain a filter cake, and dry the filter cake at 10°C for 600 min to obtain amorphous basic copper carbonate powder.

[0050] (3) Amorphous basic copper carbonate powder was reduced with hydrogen at 200℃ for 4 h to obtain 67.2 g of nano copper powder.

[0051] Example 4 The present invention discloses an ultrafine spherical copper powder, the preparation method of which includes the following steps: (1) Weigh 230 g of copper acetate monohydrate and dissolve it in 1.2 L of deionized water. Separately, add 300 g of ammonium bicarbonate to 1.2 L of water to form a solution. Keep the solution temperature at 20℃ and the stirring speed at 600 rpm. Add the copper acetate monohydrate solution to the ammonium bicarbonate solution to obtain basic copper carbonate slurry.

[0052] (2) Filter the basic copper carbonate slurry to obtain a filter cake, and dry the filter cake at 20°C for 180 min to obtain amorphous basic copper carbonate powder.

[0053] (3) Amorphous basic copper carbonate powder was reduced with hydrogen at 180℃ for 5 h to obtain 66.3 g of nano copper powder.

[0054] Figure 8 These are the XRD patterns of amorphous basic copper carbonate, spiky basic copper carbonate, and the reduced copper powder from Examples 1-4. As can be seen from the figures: As can be seen from the figures, the spiky basic copper carbonate exhibits sharp discrete diffraction peaks resulting from ordered crystals, while the XRD pattern of amorphous basic copper carbonate lacks a regular long-range lattice, showing only broadened diffuse bulges without sharp characteristic peaks. The nano-copper powders from Examples 1 to 4 demonstrate that the process of this invention can completely reduce amorphous basic copper carbonate powder, avoiding the significant particle growth and agglomeration caused by high-temperature sintering.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for preparing nano-copper powder, characterized in that, The preparation method includes the following steps: S1. Mix copper salt solution and soluble carbonate solution, and react at 0℃~35℃ to obtain basic copper carbonate slurry; S2. Filter the basic copper carbonate slurry to obtain a filter cake, and dry the filter cake at 0℃~35℃ to obtain amorphous basic copper carbonate powder. S3. Reduce amorphous basic copper carbonate powder with hydrogen to obtain nano copper powder.

2. The preparation method according to claim 1, characterized in that, The soluble carbonate in S1 includes one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, or ammonium bicarbonate, and the copper salt includes one of copper sulfate, copper nitrate, copper formate, and copper acetate.

3. The preparation method according to claim 1, characterized in that, The reaction temperature in S1 is 10℃~20℃.

4. The preparation method according to claim 1, characterized in that, The drying temperature in S2 is 10℃~30℃, and the time is 10 min~600 min.

5. The preparation method according to claim 4, characterized in that, The drying temperature is 10℃~20℃, and the time is 30 min~300 min.

6. The preparation method according to claim 1, characterized in that, The reduction temperature in S3 is 150℃~250℃, and the reduction time is 0.5h~10h.

7. The preparation method according to claim 6, characterized in that, The reduction temperature is 160℃~210℃, and the reduction time is 2 h~6 h.

8. A nano-copper powder prepared by the preparation method according to any one of claims 1 to 7.

9. The nano-copper powder according to claim 8, characterized in that, The particle size of the nano-copper powder is 20 nm to 100 nm.

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