A nano-copper powder and a preparation method of a silver-copper core-shell structure thereof

Abstract

The application discloses a kind of nano copper powder and its silver-copper core-shell structure preparation method, comprising the following steps: S11.Arabian gum is dissolved in deionized water, and uniform magnetic stirring is obtained at constant temperature 70-80 DEG C to obtain solvent;The mass ratio of arabian gum and deionized water is 1:15-20;S12.Copper sulfate pentahydrate and glucose are sequentially added to the solvent obtained in step S11, and uniform magnetic stirring is carried out at constant temperature 70-80 DEG C;The mass ratio of copper sulfate pentahydrate and deionized water is 1:3-4;The mass ratio of copper sulfate pentahydrate and glucose is 1:1-2.Using cheap and environmentally friendly glucose and ascorbic acid continuous two-step reduction reaction, mainly solve the problem of long time and incomplete reduction of glucose in the first reduction, ascorbic acid secondary reduction can quickly reduce the product Cu2O of incomplete reduction of glucose into nano copper, improve the reduction efficiency and purity, and the purity of nano copper powder is higher than 99.9%.

Description

Technical Field

[0001] This invention relates to the field of metal composite materials technology, specifically to a method for preparing nano-copper powder and its silver-copper core-shell structure. Background Technology

[0002] High-purity nano-copper powder, with its excellent electrical and thermal conductivity, non-toxicity, and low price, is widely used in electronic pastes and other applications. However, the ultra-large surface area and ultra-high surface activity of nanoparticles make them highly susceptible to oxidation, reducing conductivity and operational stability. Therefore, preparing high-quality nano-copper powder and using an inert metal core-shell structure for protection to give it high oxidation resistance is of great significance for its application. Although the physical method for preparing nano-copper powder is simple in principle, it results in low copper powder purity, uneven particle size, and high equipment requirements. The chemical method, with its lower equipment investment, simpler process, and higher yield, is the preferred solution for preparing high-quality nano-copper powder. Chinese patents CN102978667B and CN200910022137.6 disclose an electrochemical method for preparing nano-copper powder. However, this method tends to cause the powder to adhere to the cathode, making scraping and collection difficult. Furthermore, the copper powder adhered to the electrode plate tends to grow, resulting in uneven particle size. The above problems can be overcome by using liquid-phase reduction, but most of the reducing agents used are hydrazine hydrate, as described in Chinese patents CN105945302B and CN108728871B, which are expensive or pollute the environment. Huang Fudong et al. (Research on the process of two-step synthesis of nano-copper by liquid-phase reduction [J], Precision Molding Engineering, 2019, 11(5)) used glucose and sodium hypophosphite to reduce and prepare copper powder. Although it did not have an impact on the environment, the purity of the prepared copper powder was not high, and the particle size was large and irregular. Chinese patent CN116652173A disclosed a method for preparing nano-copper powder by atomization, which uses airflow to pulverize and classify copper powder multiple times. The steps are numerous, the energy consumption is high, the production capacity is low, and it is not conducive to actual production. Chinese patent CN116100039A disclosed a method for preparing nano-copper powder by combining dialysis and modifier. The two dialysis times are long, and inert gas needs to be passed and high temperature needs to be maintained during reduction, resulting in low overall efficiency. Chinese patent CN202210328593.9 discloses a method for preparing nano-copper powder using a combination of supergravity reaction technology and chemical reduction. This method involves large equipment investment, numerous reaction materials, cumbersome steps, and a long overall time. To date, although many nano-copper powder preparation technologies have been proposed, it is difficult to simultaneously meet requirements regarding purity, particle size distribution, particle dispersion, antioxidant properties, efficiency, and environmental friendliness, severely impacting its application in high-quality printed electronic pastes. Therefore, it is necessary to invent a high-quality nano-copper powder and its efficient silver-copper core-shell structure preparation method to meet the performance and production needs of industrial printed electronic pastes. Summary of the Invention

[0003] 1. The technical problem to be solved:

[0004] To address the aforementioned technical problems, this invention provides a method for preparing nano-copper powder and its silver-copper core-shell structure.

[0005] 2. Technical Solution:

[0006] A method for preparing nano-copper powder includes the following steps:

[0007] S11. Dissolve gum arabic in deionized water and stir magnetically at a constant temperature of 70-80℃ to obtain a homogeneous solvent; the mass ratio of gum arabic to deionized water is 1:15-20.

[0008] S12. Add copper sulfate pentahydrate and glucose sequentially to the solvent obtained in step S11, and stir magnetically at a constant temperature of 70-80℃ until homogeneous; the mass ratio of copper sulfate pentahydrate to deionized water is 1:3-4; the mass ratio of copper sulfate pentahydrate to glucose is 1:1-2.

[0009] S13. Add sodium hydroxide to the solution obtained in step S12 in small amounts several times to adjust the pH value of the solution to 6-8, and stir the reaction magnetically at a constant temperature of 70-80℃ to obtain a reduced suspension solution;

[0010] S14. Add ascorbic acid to the suspension obtained in step S13, with the mass ratio of copper sulfate pentahydrate to ascorbic acid being 1:1-2; then add sodium hydroxide in small amounts several times to adjust the pH of the solution to 6-8, and stir the reaction magnetically at a constant temperature of 70-80℃ to obtain a suspension of nano-copper powder. After centrifugation, ultrasonic cleaning with deionized water, and freeze-drying, spherical nano-copper powder is obtained.

[0011] Preferably, the speed of the constant temperature magnetic stirring in step S11 is 450-600 r / min, and the stirring time is 15-30 min.

[0012] Preferably, the constant temperature magnetic stirring time in step S12 is 15-30 min.

[0013] Preferably, the constant temperature magnetic stirring reaction time in step S13 is 1-2 hours.

[0014] Preferably, the constant temperature magnetic stirring reaction time in step S14 is 0.5-2 hours.

[0015] Spherical copper nanoparticles were prepared by the above method.

[0016] A method for preparing a silver-copper core-shell structure of nano-copper powder includes the following steps:

[0017] S21. The spherical copper nanoparticles prepared by the above method are dispersed in deionized water, and ammonium sulfate and ammonia are added sequentially. After deoxidation, potassium sodium tartrate is added, and the mixture is magnetically stirred at room temperature to obtain a copper nanoparticle suspension. The mass ratio of copper nanoparticles to deionized water is 1:20-50; the mass ratio of ammonium sulfate to copper nanoparticles is 1:3-5; the mass ratio of ammonia to copper nanoparticles is 1:2-3; and the mass ratio of potassium sodium tartrate to copper nanoparticles is 1:3-5.

[0018] S22. Dissolve silver nitrate in deionized water, and add ammonia dropwise until the solution becomes clear to obtain a silver ammonia solution;

[0019] S23. The silver ammonia solution prepared in step S22 is added dropwise to the nano-copper powder suspension prepared in step S21. The mixture is stirred magnetically at room temperature, and after centrifugation, washing, and vacuum freeze-drying, silver-coated nano-copper powder is obtained.

[0020] Preferably, in step S22, the mass ratio of silver nitrate to deionized water is 1:20-30, and the mass ratio of silver nitrate to ammonia is 1:1.5-2.

[0021] Preferably, in step S23, the silver ammonia solution is added dropwise to the nano copper powder suspension in S21 at a dropping rate of 2-3 ml / min, and the magnetic stirring time is 1-1.5 h.

[0022] Preferably, the centrifugation speed in step S23 is 6000-9000 r / min; the washing is performed by ultrasonic cleaning with deionized water, repeated 3-5 times; and the vacuum freeze-drying temperature is -60~-40℃.

[0023] 3. Beneficial effects:

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] (1) The low-cost and environmentally friendly glucose and ascorbic acid are used in a continuous two-step reduction reaction. This mainly solves the problems of long reduction time and incomplete reduction of glucose in the first step. The secondary reduction of ascorbic acid can quickly reduce Cu2O, the product of incomplete reduction of glucose, into nano-copper, thereby improving the reduction efficiency and purity. The purity of nano-copper powder is higher than 99.9%.

[0026] (2) By adding gum arabic as a dispersant, the problem of agglomeration of nano-copper powder particles is solved, resulting in high dispersibility. Sodium hydroxide is added multiple times during the reaction to adjust the pH value and control the reaction rate, so that the nano-spherical copper powder has a uniform particle size distribution of 20~30 nm and good sphericity consistency.

[0027] (3) Silver is an excellent conductive metal. The conductivity of high-purity nano-copper is similar to that of silver. Using silver-coated high-purity nano-copper can ensure that the overall conductivity will not decrease. The dense silver plating can also effectively prevent the oxidation of high-purity nano-copper from affecting the conductivity. In electronic paste applications, silver-coated nano-copper can effectively solve the problem of silver migration and enhance the stability of the use of silver-coated nano-copper electrodes.

[0028] (4) The raw materials used to prepare nano copper powder are low in cost, non-toxic and non-polluting, low in energy consumption, simple in preparation method, short in reduction time, easy to promote and scale up production, and improve antioxidant properties through silver-coated copper core-shell structure, while avoiding the high cost of using nano pure silver powder. Attached Figure Description

[0029] Figure 1 This is a SEM image of the nano-copper powder prepared in Example 1;

[0030] Figure 2 This is the XRD pattern of the nano-copper powder prepared in Example 1;

[0031] Figure 3 This is the Raman spectrum of the nano-copper powder prepared in Example 1;

[0032] Figure 4 This is the EDS image of the silver-coated nano-copper powder prepared in Example 1;

[0033] Figure 5 This is a thermogravimetric curve of the nano-copper and silver-copper core-shell structures prepared in Example 1;

[0034] Figure 6 The image shows the XRD pattern of the nano-copper powder prepared in Comparative Example 1.

[0035] Figure 7 The XRD pattern of the nano-copper powder prepared in Comparative Example 2 is shown.

[0036] Figure 8 This is the XRD pattern of the nano-copper powder prepared in Comparative Example 3. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings.

[0038] As attached Figure 1 To be continued Figure 8 As shown,

[0039] Example 1

[0040] Preparation of spherical copper nanoparticles: Take a 100ml clean beaker, add 30ml of deionized water and 2g of gum arabic, and place it in a preheated 75℃ magnetically stirred water bath. Stir at 600r / min for 15min to obtain a solvent. Add 10g of copper sulfate pentahydrate and 10g of glucose to the solvent successively, and stir magnetically at a constant temperature for 15min. Then add sodium hydroxide to the solution in small amounts several times to maintain the pH value at 7, and react at a constant temperature for 1h. Add 10g of ascorbic acid to the solution, and add sodium hydroxide in small amounts several times to maintain the pH value at 7, and react magnetically at a constant temperature for 0.5h to obtain a suspension of copper nanoparticles. After centrifugation at 8000r / min, ultrasonic washing with deionized water three times, and freeze-drying at -60℃, highly dispersed spherical copper nanoparticles are obtained.

[0041] SEM morphology of spherical copper nanoparticles as follows Figure 1 As shown. XRD pattern as follows. Figure 2 As shown, this indicates the absence of impurity phase peaks, with an average particle size of approximately 20 nm. The Raman spectrum is as follows: Figure 3 As shown (without trace impurity peaks), energy dispersive spectroscopy analysis indicates that the purity of the spherical copper powder is 99.9%.

[0042] Further preparation of the silver-copper core-shell structure of the nano-copper powder: 1.5g of nano-copper powder was dispersed in 30ml of deionized water, 0.5g of ammonium sulfate was added, and after dissolution, 0.824ml of ammonia water was added. After thorough stirring, 4.5g of potassium sodium tartrate was added. In a separate clean beaker, 1g of silver nitrate was mixed with 20ml of deionized water, and 1.65ml of ammonia water (25%) was slowly added to the silver nitrate solution, stirring continuously until the solution became clear. The silver ammonia solution was added dropwise to the nano-copper powder suspension at a rate of 2ml / min, and magnetically stirred for 1h. After centrifugation at 6000r / min, ultrasonic washing with deionized water was repeated 5 times, and highly dispersible spherical silver-coated nano-copper powder was obtained by vacuum freeze-drying at -40℃.

[0043] EDS spectrum of silver-coated nano-copper powder as shown in the figure. Figure 4 As shown, it contains 71.56% silver and 28.44% copper (mass fraction). Figure 5 Thermogravimetric analysis curves of nano-copper powder and silver-copper core-shell structure demonstrate that the silver-copper core-shell structure exhibits high oxidation resistance. A sheet resistance of 0.05 mΩ / □ was achieved by printing a film electrode on a silica substrate.

[0044] Example 2

[0045] Preparation of spherical copper nanoparticles: Take a 100ml clean beaker, add 37.5ml of deionized water and 2g of gum arabic, and place it in a preheated 70℃ magnetically stirred water bath. Stir at 550r / min for 20min to obtain a solvent. Add 10g of copper sulfate pentahydrate and 15g of glucose to the solvent successively, and stir magnetically at a constant temperature for 20min. Add sodium hydroxide in small amounts several times to maintain the pH at 7, and react at a constant temperature for 1.5h. Add 15g of ascorbic acid, and add sodium hydroxide in small amounts several times to maintain the pH at 7, and react magnetically at a constant temperature for 1h to obtain a copper nanoparticle suspension. Centrifuge at 9000r / min and ultrasonically wash with deionized water four times. Obtain highly dispersible spherical copper nanoparticles by vacuum freeze-drying at -50℃. Energy dispersive spectroscopy analysis shows that the spherical copper nanoparticles have a purity of 99.95% and high dispersibility, with an average particle size of approximately 25nm.

[0046] Further preparation of silver-copper core-shell structure for nano-copper powder: 1.5g of nano-copper powder was dispersed in 37.5ml of deionized water, 0.375g of ammonium sulfate was added, and after dissolution, 0.66ml of ammonia water was added. After thorough stirring, 6g of potassium sodium tartrate was added. In a separate beaker, 1g of silver nitrate was mixed with 25ml of deionized water, and 1.92ml of ammonia water (25%) was slowly added to the silver nitrate solution, stirring continuously until the solution became clear. The silver ammonia solution was added dropwise to the nano-copper powder suspension at a rate of 1.5ml / min, and magnetically stirred for 1.2h. After centrifugation at 9000r / min and ultrasonic washing with deionized water four times, highly dispersed spherical silver-coated nano-copper powder was obtained by vacuum freeze-drying at -50℃. The EDS spectrum of the silver-coated nano-copper powder showed that it contained 70.53% silver and 29.47% copper (mass fraction). The sheet resistance of the film electrode printed on the silica substrate was 0.03mΩ / □, and it exhibited high oxidation resistance.

[0047] Example 3

[0048] Preparation of spherical copper nanoparticles: Take a 100ml clean beaker, add 40ml deionized water and 2g gum arabic, and place it in a preheated 80℃ magnetically stirred water bath. Stir at 600r / min for 30min to obtain a solvent. Add 10g copper sulfate pentahydrate and 20g glucose to the solvent sequentially, and stir magnetically at 80℃ for 30min. Add sodium hydroxide in small amounts several times to maintain the pH at 8, and react at 80℃ for 2h. Add 20g ascorbic acid, and add sodium hydroxide in small amounts several times to maintain the pH at 8, and react magnetically at 80℃ for 1h to obtain a copper nanoparticle suspension. Centrifuge at 9000r / min and ultrasonically wash with deionized water five times. Obtain highly dispersible spherical copper nanoparticles by vacuum freeze-drying at -60℃. Energy dispersive spectroscopy analysis shows that the spherical copper nanoparticles have a purity of 99.93% and high dispersibility, with an average particle size of approximately 30nm.

[0049] Further preparation of silver-copper core-shell structure for nano-copper powder: 1.5g of nano-copper powder was dispersed in 75ml of deionized water, 0.3g of ammonium sulfate was added, and after dissolution, 0.55ml of ammonia water was added. After thorough stirring, 7.5g of potassium sodium tartrate was added. In a separate beaker, 1g of silver nitrate was mixed with 30ml of deionized water, and 2.2ml of ammonia water (25%) was slowly added to the silver nitrate solution, stirring continuously until the solution became clear. The silver ammonia solution was added dropwise to the nano-copper powder suspension at a rate of 1ml / min, and magnetically stirred for 1.5h. After centrifugation at 9000r / min and ultrasonic cleaning with deionized water five times, highly dispersed spherical silver-coated nano-copper powder was obtained by vacuum freeze-drying at -60℃. The EDS spectrum of the silver-coated nano-copper powder showed that it contained 73.36% silver and 26.64% copper (mass fraction). The sheet resistance of the film electrode printed on the silica substrate was 0.08mΩ / □, and it exhibited high oxidation resistance.

[0050] Comparative Example 1

[0051] Take a 100ml clean beaker, add 30ml deionized water and 2g gum arabic, and place it in a preheated 75℃ magnetically stirred water bath. Stir at 600 rpm for 15 minutes to obtain a solvent. Add 10g copper sulfate pentahydrate and 10g glucose to the solvent successively, stirring for 15 minutes each time. Then, add sodium hydroxide in small amounts several times to adjust the pH to 7, and react at a constant temperature for 24 hours to obtain a suspension of nano-copper powder. Centrifuge at 8000 rpm and ultrasonically wash with deionized water five times. Obtain highly dispersed nano-copper powder by vacuum freeze-drying at -60℃. The XRD pattern is as follows. Figure 6 As shown, the purity of the nano copper powder is only 83.4%, and the average particle size is about 25 nm.

[0052] Comparative Example 2

[0053] Take a 100ml clean beaker, add 30ml deionized water and 2g gum arabic, and place it in a preheated 75℃ magnetically stirred water bath. Stir at 600 rpm for 15 minutes to obtain a solvent. Add 10g copper sulfate pentahydrate and 10g ascorbic acid to the solvent successively, stirring for 15 minutes. Then, add sodium hydroxide in small amounts several times to adjust the pH to 7, and react at a constant temperature for 24 hours to obtain a suspension of nano-copper powder. Centrifuge at 8000 rpm and ultrasonically wash with deionized water five times. Obtain highly dispersed nano-copper powder by vacuum freeze-drying at -60℃. The XRD pattern is as follows. Figure 7 As shown, the purity of the nano copper powder is only 91.3%, and the average particle size is about 33 nm.

[0054] Comparative Example 3

[0055] Take a 100ml clean beaker, add 30ml deionized water and 2g gum arabic, and place it in a preheated 75℃ magnetically stirred water bath. Stir at 600 rpm for 15 minutes to obtain a solvent. Add 10g copper sulfate pentahydrate to the solvent and dissolve it. Then, add 10g glucose and 10g ascorbic acid and stir for 15 minutes. Add sodium hydroxide in small amounts several times to adjust the pH to 7, and react at a constant temperature for 24 hours to obtain a suspension of nano-copper powder. Centrifuge at 8000 rpm and ultrasonically wash with deionized water five times. Freeze-dry at -60℃ to obtain highly dispersed nano-copper powder. The XRD pattern is as follows: Figure 8 As shown, the purity of the nano copper powder is only 83.4%, and the average particle size is about 28 nm.

[0056] Although the present invention has been disclosed above with reference to preferred embodiments, these are not intended to limit the invention. Any person skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims of this application.

Claims

1. A method for preparing a silver-copper core-shell structure of nano-copper powder, characterized in that, Prepared by a method including the following steps: (1) Preparation of spherical nano-copper powder: S11. Dissolve gum arabic in deionized water and magnetically stir at a constant temperature of 70-80℃ and a rotation speed of 450-600 r / min for 15-30 min to obtain a solvent; the mass ratio of gum arabic to deionized water is 1:15-20. S12. Add copper sulfate pentahydrate and glucose sequentially to the solvent obtained in step S11, and stir magnetically at a constant temperature of 70-80℃ for 15-30 min; the mass ratio of copper sulfate pentahydrate to deionized water is 1:3-4; the mass ratio of copper sulfate pentahydrate to glucose is 1:1-2. S13. Add sodium hydroxide to the solution obtained in step S12 in small amounts several times to adjust the pH value of the solution to 6-8, and stir magnetically at a constant temperature of 70-80℃ for 1-2 hours to obtain a reduced suspension solution; S14. Add ascorbic acid to the suspension obtained in step S13, wherein the mass ratio of copper sulfate pentahydrate to ascorbic acid is 1:1-2; then add sodium hydroxide in small amounts several times to adjust the pH of the solution to 6-8, and stir magnetically at a constant temperature of 70-80℃ for 0.5-2 hours to obtain a nano copper powder suspension. S15. The nano-copper powder suspension described in S14 is centrifuged, ultrasonically cleaned with deionized water, and freeze-dried to obtain spherical nano-copper powder with a purity of over 99.9% and an average particle size of 20-30 nm. (2) Preparation of silver-copper core-shell structure for nano-copper powder: S21. The spherical nano-copper powder obtained in step (1) is dispersed in deionized water, and ammonium sulfate and ammonia are added in sequence, followed by potassium sodium tartrate. After magnetic stirring at room temperature, a nano-copper powder suspension is obtained; the mass ratio of nano-copper powder to deionized water is 1:20-50; the mass ratio of ammonium sulfate to nano-copper powder is 1:3-5; the mass ratio of ammonia to nano-copper powder is 1:2-3; the mass ratio of potassium sodium tartrate to nano-copper powder is 1:3-5. S22. Dissolve silver nitrate in deionized water, and add ammonia dropwise until the solution becomes clear to obtain a silver ammonia solution; the mass ratio of silver nitrate to deionized water is 1:20-30, and the mass ratio of silver nitrate to ammonia is 1:1.5-2; S23. The silver ammonia solution prepared in step S22 is added dropwise to the nano copper powder suspension prepared in step S21 at a dropping rate of 2-3 ml / min. The mixture is magnetically stirred at room temperature for 1-1.5 h. After centrifugation, ultrasonic cleaning with deionized water 3-5 times, and vacuum freeze-drying at -60~-40℃, the silver-copper core-shell structured powder of the nano copper powder is obtained. The silver-copper core-shell structure powder of the nano-copper powder contains 71.56% silver and 28.44% copper by mass, or 70.53% silver and 29.47% copper by mass, or 73.36% silver and 26.64% copper by mass.

2. The method for preparing the silver-copper core-shell structure of nano-copper powder according to claim 1, characterized in that, The sheet resistance of the film electrode formed by printing it on the silicon dioxide substrate is 0.03, 0.05, or 0.08 mΩ / □.

Images