Preparation method of silver-coated copper powder for solar low-temperature drying slurry

Abstract

The invention discloses a method for preparing silver-coated copper powder for solar low-temperature drying slurry. By this method, silver-coated copper powder with strong antioxidant ability, good conductivity, complete coating and can be used for low-temperature slurry can be prepared. The preparation method has low production cost, controllable process and strong practicality.

Description

Technical Field

[0001] The invention relates to the technical field of electronic material functional powders, in particular to a method for preparing silver-coated copper powder for solar low-temperature drying slurry. Background Art

[0002] Silver-coated copper powder is an excellent conductive filler. When added to coatings, glues (adhesives), inks, plastics, rubber, etc., it can be made into various conductive, electromagnetic shielding, photovoltaic, and other slurries. It is widely used in electronics, electromechanics, printing, aviation, etc. In this project, the silver-coated copper powder is mainly used together with nano-silver powder in photovoltaic low-temperature silver paste.

[0003] Silver prices have skyrocketed in recent years, while copper powder is inexpensive and second only to silver in conductivity. However, copper powder is susceptible to oxidation and has poor stability. Silver-coated copper powder, evenly coated with a layer of silver particles, can maintain the copper powder's excellent conductivity and improve its antioxidant stability while significantly reducing costs.

[0004] At present, the preparation methods of silver-clad copper mainly include electroplating, mechanical method, physical melting method, chemical vapor deposition method, chemical reduction method, and displacement deposition method:

[0005] For example, Chinese application No. 202410196832.9 discloses a method for preparing ultrafine silver-coated copper powder, comprising the following steps: (1) alkaline washing; (2) acid washing; (3) chemical silver plating, and the silver-coated copper powder is obtained by washing and vacuum drying. Compared with the traditional silver plating in air or inert gas atmosphere, the invention adopts a hydrogen reducing atmosphere, which can greatly reduce the possibility of re-oxidation of the copper powder after acid washing, and is conducive to the replacement reaction of copper and silver, thereby evenly distributing active silver on the surface of the copper powder, ensuring the uniformity and density of subsequent reduction silver plating, and improving the oxidation resistance of the silver-coated copper powder.

[0006] For example, Chinese application No. 202410346573.3 provides a method for preparing silver-coated copper powder for low-temperature curing slurry, by mixing a special solution A and a sodium borohydride solution at a constant temperature of 0°C and stirring to obtain a silver crystal core dispersion; and on this basis, sodium borohydride solution and copper sulfate solution are simultaneously added and stirred for 1 to 2 minutes to form copper powder on the surface of the silver crystal core dispersion; then a special solution B is added, mixed evenly, and then ascorbic acid solution is added at a rate of 20 to 25 ml / min to coat the surface of the copper powder liquid with a silver layer having good morphology, density and uniformity; in this way, submicron silver-coated copper powder is directly prepared in the liquid phase, reducing the risk of oxidation of the copper powder intermediate, and making the prepared silver-coated copper powder suitable for use in low-temperature curing slurries and conductive adhesive coatings with high printing performance and high conductivity.

[0007] At present, the silver-clad copper used in low-temperature slurry is mainly imported, with high prices and long procurement cycles. Therefore, silver-clad copper powder has broad market prospects. Summary of the Invention

[0008] In view of the problems of uneven coating and high resistivity of silver-coated copper powder prepared by existing chemical methods, the present invention provides a method for preparing silver-coated copper powder for solar low-temperature drying slurry. By this method, silver-coated copper powder with strong antioxidant ability, good conductivity, complete coating and can be used for low-temperature slurry can be prepared. The preparation method has low production cost, controllable process and strong practicality.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A method for preparing silver-coated copper powder for solar low-temperature drying slurry comprises the following steps:

[0011] (1) Selecting monodisperse copper powder as raw material;

[0012] (2) ultrasonically cleaning the copper powder prepared in step (1) in a cleaning kettle;

[0013] (3) placing the copper powder cleaned in step (2) into a centrifuge for solid-liquid separation, and then filtering and cleaning;

[0014] (4) placing the copper powder washed in step (3) into a cleaning kettle for secondary ultrasonic cleaning;

[0015] (5) placing the copper powder cleaned in step (4) into a centrifuge for solid-liquid separation, and then filter-filtering for cleaning;

[0016] (6) preparing silver nitrate into a complex solution using a complexing agent;

[0017] (7) Prepare the required reducing agent;

[0018] (8) Add 10 times the weight of the copper powder into the reaction kettle;

[0019] (9) The copper powder after solid-liquid separation is placed in a reactor and a silver nitrate complex solution is added using a peristaltic pump;

[0020] (10) Add the prepared reducing agent into the reactor using a peristaltic pump;

[0021] (11) The silver-coated copper powder is placed in a centrifuge for cleaning, and then filtered by adding anhydrous ethanol;

[0022] (12) The silver-coated copper powder after cleaning and filter pressing is placed in a freeze dryer for low-temperature vacuum freeze drying and sifting to obtain the finished product.

[0023] The present invention relates to a method for preparing silver-coated copper powder for solar low-temperature drying slurry, comprising the following steps:

[0024] 1) Use monodisperse copper powder as raw material: When cleaning in a cleaning kettle, first add a 16% alkaline solution, the amount of which corresponds to 6 times the weight of the monodisperse copper powder. After nitrogen is introduced into the kettle for 5 minutes, add the prepared copper powder and clean it with ultrasonic and high-speed stirring for 30 minutes until the conductivity is less than 10μs / cm and the pH is 7-8. The particle size of the monodisperse copper powder selected is D 50 3-4μm, tapped: 5-6g / cm 3 ;

[0025] 2) placing the copper powder cleaned in the previous step into a centrifuge for solid-liquid separation, and then filter pressing for cleaning;

[0026] 3) The copper powder after filter pressing and cleaning was placed in a cleaning kettle for secondary cleaning. First, a 5 wt% acid solution with a volume 10 times the weight of the copper powder was added, nitrogen was introduced for 5 minutes, and then the copper powder cleaned in the previous step was added. The cleaning was carried out under ultrasonication and high-speed stirring for 30 minutes.

[0027] 4) The copper powder cleaned in the previous step is subjected to solid-liquid separation, and then placed in a reactor ventilated with nitrogen for chemical reduction and silver coating treatment:

[0028] ① Using a complexing agent to prepare a complexing solution with a mass ratio of 1:1 with silver nitrate; the complexing agent is one or a mixture of two of ammonia water, ethylenediamine, EDTA, and ammonium carbonate, and the mixture can be in any proportion;

[0029] ② Use a peristaltic pump to add the complexing solution to the reactor, setting the time to 28-30 minutes;

[0030] ③ Prepare a reducing agent with a mass ratio of reducing agent to monodisperse copper powder of 1:(0.2-0.25), add the reducing agent to the reactor using a peristaltic pump, and set the addition time to 28-30 minutes; the reducing agent is one or a mixture of two of glucose, formaldehyde, triethanolamine, glycerol, ascorbic acid, and hydrazine hydrate, and the mixture can be in any proportion;

[0031] ④ Add a solution equivalent to 10 times the weight of the monodisperse copper powder to the reactor, wherein the solution is a 20wt% solution of one or two of gelatin, PVP, polyethylene glycol, gum arabic, and Tween 80, and the mixture can be in any proportion;

[0032] 5) The coated silver-coated copper powder is placed in a centrifuge for cleaning until the conductivity is less than 10 μs / cm, then taken out and placed in a filter press, and filtered by adding anhydrous ethanol twice the weight of the silver-coated copper powder;

[0033] 6) The filtered silver-coated copper powder was placed in a freeze dryer for low-temperature vacuum drying. After drying for 24 hours, the finished product was passed through a 350-mesh sieve. The bulk density of the obtained silver-coated copper powder was 2.3-3.0 g / cm 3 , tap density 4.0-5.0g / cm 3 , particle size D 50 3.0-4.5μm, specific surface area 0.2-0.4m 2 / g.

[0034] In the present invention:

[0035] Furthermore, the amount of the alkaline solution added in step 1) corresponds to 6 volumes of the weight of the monodisperse copper powder, which is based on a ratio of 1 kg of monodisperse copper powder to 6 L of alkaline solution, and the same applies below.

[0036] Furthermore, the alkaline solution in step 1) is selected from sodium carbonate, sodium hydroxide, and potassium hydroxide.

[0037] Furthermore, the acid solution in step 3) is selected from one of sulfuric acid, ammonium sulfate, acetic acid, nitric acid, and hydrochloric acid, or a mixture of two of them, and the mixture can be in any proportion.

[0038] Furthermore, the introduction of nitrogen or the passage of nitrogen in step 1), step 3), and step 4) is the introduction of dry nitrogen at a pressure of 0.2 MPa.

[0039] Furthermore, the silver nitrate complex solution in step 4) is added for 28-30 minutes.

[0040] Furthermore, the reducing agent in step 4) is added for 30 minutes, and stirring is maintained for 30 minutes after the reducing agent is added.

[0041] Furthermore, the product is placed in a freeze dryer for low-temperature vacuum drying in step 6), wherein the freezing temperature of the freeze dryer is -80°C and the drying temperature is 35°C.

[0042] The present invention also relates to a silver-coated copper powder for solar low-temperature drying slurry, which is obtained by adopting the above-mentioned preparation method of the silver-coated copper powder for solar low-temperature drying slurry. The bulk density of the silver-coated copper powder is 2.3-3.0 g / cm 3 , tap density 4.0-5.0g / cm 3 , particle size D 50 3.0-4.5μm, specific surface area 0.2-0.4m 2 / g.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] 1. The present invention discloses a method for preparing silver-coated copper powder for solar low-temperature drying slurry. By this method, silver-coated copper powder with strong antioxidant ability, good conductivity, complete coating and can be used for low-temperature slurry can be prepared. The preparation method has low production cost, controllable process and strong practicality.

[0045] 2. The silver-coated copper powder for solar low-temperature drying slurry obtained by the present invention has uniform particle distribution, smooth surface and high powder tap density compared with the existing copper powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a 20,000-fold local scanning electron microscope image of the silver-coated copper powder prepared in Example 1 of the present invention;

[0047] Figure 2 This is a 20,000-fold local scanning electron microscope image of the silver-coated copper powder prepared in Example 2 of the present invention;

[0048] Figure 3 This is a 20,000-fold local scanning electron microscope image of the silver-coated copper powder prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0049] The preferred implementation cases of the present invention are further described in detail below, but the present invention is not limited to the implementation cases.

[0050] Example 1:

[0051] A method for preparing silver-coated copper powder for solar low-temperature drying slurry comprises the following steps:

[0052] 1. Add 12L of sodium hydroxide solution to the cleaning kettle, introduce 0.2MPa nitrogen into the kettle for 5 minutes, then add 2kg of copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; place the alkali-washed copper powder in a centrifuge for solid-liquid separation, and clean it until the conductivity is less than 10μs / cm and the pH is 7-8;

[0053] Add 20L of 5% dilute sulfuric acid solution to the cleaning kettle, introduce 0.2MPa nitrogen for 5 minutes, then add the alkali-washed copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; place the copper powder in a centrifuge for solid-liquid separation, and clean it until the conductivity is less than 10μs / cm for later use;

[0054] 2. Add 10L of deionized water and 787.5g of silver nitrate to auxiliary material kettle 1, stir and dissolve completely, add 800ml of ammonia water to form a complex solution of silver nitrate for later use, and maintain the temperature at 30℃±1℃;

[0055] 3. Add 40L of deionized water and 200g of PVP into the reactor, stir at high speed with ultrasonic wave to dissolve evenly, then introduce 0.2MPa nitrogen for 5 minutes, add the cleaned copper powder, maintain ultrasonic wave and stirring, and control the temperature in the reactor at 40±1℃;

[0056] 4. Add 10L of deionized water into auxiliary material kettle 2, add 500g of glucose while stirring and dissolve completely, maintaining the temperature at 40±1℃;

[0057] 5. The silver nitrate complex solution in the auxiliary material kettle is added to the reactor by a peristaltic pump within 28-30 minutes. After the complexing agent is added, ultrasonic high-speed stirring is maintained for 30 minutes. Then, the glucose solution is added to the reactor by a peristaltic pump within 28-30 minutes. After the addition is completed, ultrasonic stirring is maintained for 30 minutes. The silver-coated copper powder in the reactor is placed in a centrifuge for cleaning until the conductivity is less than 10μs / cm. The powder is taken out and placed in a filter press. Anhydrous ethanol twice the weight of the silver-coated copper powder is added and filtered. The filtered silver-coated copper powder is placed in a freeze dryer for low-temperature vacuum drying. After drying for 24 hours, it is sieved through a 350-mesh sieve to obtain the finished product.

[0058] Technical indicators of silver-coated copper powder: bulk density 2.70g / cm 3 , tap density 4.10g / cm 3 , particle size D 50 3.30μm, specific surface area 0.26m 2 / g.

[0059] Figure 1 This is a 20,000-fold local scanning electron microscope image of the silver-coated copper powder prepared in Example 1. It can be seen that the silver powder is evenly coated on the surface of the copper powder, there are no protrusions on the surface of the silver-coated copper powder particles, and the particles are evenly dispersed.

[0060] Example 2:

[0061] A method for preparing silver-coated copper powder for solar low-temperature drying slurry comprises the following steps:

[0062] 1. Add 12L of sodium hydroxide solution to the cleaning kettle, introduce 0.2MPa nitrogen into the kettle for 5 minutes, then add 2kg of copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; place the alkali-washed copper powder in a centrifuge for solid-liquid separation, and clean it until the conductivity is less than 10μs / cm and the pH is 7-8;

[0063] Add 20L of 5% dilute acetic acid solution to the cleaning kettle, introduce 0.2MPa nitrogen for 5 minutes, then add the alkali-washed copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; place the copper powder in a centrifuge for solid-liquid separation, and clean it until the conductivity is less than 10μs / cm for later use;

[0064] 2. Add 10L of deionized water and 787.5g of silver nitrate to auxiliary material kettle 1, stir and dissolve completely, add 600ml of ethylenediamine to form a complex solution of silver nitrate for later use, and maintain the temperature at 40℃±1℃;

[0065] 3. Add 40L of deionized water and 200g of PVP into the reactor, stir at high speed with ultrasonic wave to dissolve evenly, then introduce 0.2MPa nitrogen for 5 minutes, add the cleaned copper powder, maintain ultrasonic wave and stirring, and control the temperature in the reactor at 40±1℃;

[0066] 4. Add 10L of deionized water into auxiliary material kettle 2, add 400g of VC while stirring and dissolve completely, maintaining the temperature at 40±1℃;

[0067] 5. The silver nitrate complex solution in the auxiliary material kettle is added to the reactor by a peristaltic pump within 28-30 minutes. After the complexing agent is added, ultrasonic high-speed stirring is maintained for 30 minutes. Then, the VC solution is added to the reactor by a peristaltic pump within 28-30 minutes. After the addition is completed, ultrasonic stirring is maintained for 30 minutes. The silver-coated copper powder in the reactor is placed in a centrifuge for cleaning until the conductivity is less than 10μs / cm. The powder is taken out and placed in a filter press. Anhydrous ethanol twice the weight of the silver-coated copper powder is added for filtration. The filtered silver-coated copper powder is placed in a freeze dryer for low-temperature vacuum drying. After drying for 24 hours, it is sieved through a 350-mesh sieve to obtain the finished product.

[0068] Technical indicators of silver-coated copper powder: bulk density 2.74g / cm 3 , tap density 4.20g / cm 3 , particle size D 50 3.20μm, specific surface area 0.28m 2 / g.

[0069] Figure 2 This is a 20,000-fold local scanning electron microscope image of the silver-coated copper powder prepared in Example 2. It can be seen that the dispersant PVP can make the silver-coated copper powder particles dispersed evenly without agglomeration.

[0070] Figure 3 This is a 20,000-fold local scanning electron microscope image of the silver-coated copper powder obtained in Example 2. It can be seen that due to the addition of the reducing agent, the surface of the copper powder particles is evenly coated with a silver layer, and the surface of the silver-coated copper powder particles becomes smooth.

[0071] Example 3:

[0072] A method for preparing silver-coated copper powder for solar low-temperature drying slurry comprises the following steps:

[0073] 1. Add 12L of sodium hydroxide solution to the cleaning kettle, introduce 0.2MPa nitrogen into the kettle for 5 minutes, then add 2kg of copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; place the alkali-washed copper powder in a centrifuge for solid-liquid separation, and clean it until the conductivity is less than 10μs / cm and the pH is 7-8;

[0074] Add 20L of 5% dilute acetic acid solution to the cleaning kettle, introduce 0.2MPa nitrogen for 5 minutes, then add the alkali-washed copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; place the copper powder in a centrifuge for solid-liquid separation, and clean it until the conductivity is less than 10μs / cm for later use;

[0075] 2. Add 10L of deionized water and 787.5g of silver nitrate to auxiliary material kettle 1, stir and dissolve completely, add 600ml of ethylenediamine to form a complex solution of silver nitrate for later use, and maintain the temperature at 40℃±1℃;

[0076] 3. Add 40L of deionized water and 200g of PVP into the reactor, stir at high speed with ultrasonic wave to dissolve evenly, then introduce 0.2MPa nitrogen for 5 minutes, add the cleaned copper powder, maintain ultrasonic wave and stirring, and control the temperature in the reactor at 40±1℃;

[0077] 4. Add 10L of deionized water into auxiliary material kettle 2, add 500g of glucose while stirring and dissolve completely, maintaining the temperature at 40 degrees;

[0078] 5. The acid silver complex solution in the auxiliary material kettle is added to the reactor within 28-30 minutes using a peristaltic pump. After the complexing agent is added, ultrasonic high-speed stirring is maintained for 30 minutes. Then, the glucose solution is added to the reactor within 28-30 minutes using a peristaltic pump. After the addition is completed, ultrasonic stirring is maintained for 30 minutes. The silver-coated copper powder in the reactor is placed in a centrifuge for cleaning until the conductivity is less than 10μs / cm. The powder is taken out and placed in a filter press. Anhydrous ethanol twice the weight of the silver-coated copper powder is added and filtered. The filtered silver-coated copper powder is placed in a freeze dryer for low-temperature vacuum drying. After drying for 24 hours, it is sieved through a 350-mesh sieve to obtain the finished product.

[0079] Technical indicators of silver-coated copper powder: bulk density 2.80g / cm 3 , tap density 4.50g / cm 3 , particle size D 50 3.40μm, specific surface area ratio 0.25m 2 / g.

[0080] Example 4:

[0081] A method for preparing silver-coated copper powder for solar low-temperature drying slurry comprises the following steps:

[0082] 1. Add 12L of sodium hydroxide solution to the cleaning kettle, introduce 0.2MPa nitrogen into the kettle for 5 minutes, then add 2kg of copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; place the alkali-washed copper powder in a centrifuge for solid-liquid separation, and clean it until the conductivity is less than 10μs / cm and the pH is 7-8;

[0083] Add 20L of 5% dilute sulfuric acid solution to the cleaning kettle, introduce 0.2Mpa nitrogen for 5 minutes, then add the alkali-washed copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; place the copper powder in a centrifuge for solid-liquid separation, and clean it until the conductivity is less than 10μs / cm for later use;

[0084] 2. Add 10L of deionized water and 787.5g of silver nitrate to auxiliary material kettle 1, stir and dissolve completely, add 700ml of ethylenediamine to form a complex solution of silver nitrate for later use, and maintain the temperature at 30℃±1℃;

[0085] 3. Add 40L of deionized water and 200g of PVP into the reactor, stir at high speed with ultrasonic wave to dissolve evenly, then introduce 0.2MPa nitrogen for 5 minutes, add the cleaned copper powder, maintain ultrasonic wave and stirring, and control the temperature in the reactor at 40±1℃;

[0086] 4. Add 10L of deionized water into auxiliary material kettle 2, add 400g of VC while stirring and dissolve completely, maintaining the temperature at 40±1℃;

[0087] 5. The silver nitrate complex solution in the auxiliary material kettle is added to the reactor by a peristaltic pump within 28-30 minutes. After the complexing agent is added, ultrasonic high-speed stirring is maintained for 30 minutes. Then, the VC solution is added to the reactor by a peristaltic pump within 28-30 minutes. After the addition is completed, ultrasonic stirring is maintained for 30 minutes. The silver-coated copper powder in the reactor is placed in a centrifuge for cleaning until the conductivity is less than 10μs / cm. The powder is taken out and placed in a filter press. Anhydrous ethanol twice the weight of the silver-coated copper powder is added for filtration. The filtered silver-coated copper powder is placed in a freeze dryer for low-temperature vacuum drying. After drying for 24 hours, it is sieved through a 350-mesh sieve to obtain the finished product.

[0088] Technical indicators of silver-coated copper powder: bulk density 2.74g / cm 3 , tap density 4.20g / cm 3 , particle size D 50 3.20μm, specific surface area 0.28m 2 / g.

[0089] Example 5:

[0090] A method for preparing silver-coated copper powder for solar low-temperature drying slurry comprises the following steps:

[0091] 1. Add 12L of sodium hydroxide solution to the cleaning kettle, introduce 0.2MPa nitrogen into the kettle for 5 minutes, then add 2kg of copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; place the alkali-washed copper powder in a centrifuge for solid-liquid separation, and clean it until the conductivity is less than 10μs / cm and the pH is 7-8;

[0092] Add 20L of 5% dilute sulfuric acid solution to the cleaning kettle, introduce 0.2MPa nitrogen for 5 minutes, then add the alkali-washed copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; place the copper powder in a centrifuge for solid-liquid separation, and clean it until the conductivity is less than 10μs / cm for later use;

[0093] 2. Add 10L of deionized water and 787.5g of silver nitrate to auxiliary material kettle 1, stir and dissolve completely, add 700ml of ethylenediamine to form a complex solution of silver nitrate for later use, and maintain the temperature at 30℃±1℃;

[0094] 3. Add 40L of deionized water and 200g of gelatin into the reactor, stir at high speed with ultrasound to dissolve evenly, then introduce 0.2MPa nitrogen for 5 minutes, add the cleaned copper powder, maintain ultrasound and stirring, and control the temperature in the reactor at 40±1℃;

[0095] 4. Add 10L of deionized water into auxiliary material kettle 2, add 400g of VC while stirring and dissolve completely, maintaining the temperature at 40±1℃;

[0096] 5. The silver nitrate complex solution in the auxiliary material kettle is added to the reactor by a peristaltic pump within 28-30 minutes. After the complexing agent is added, ultrasonic high-speed stirring is maintained for 30 minutes. Then, the VC solution is added to the reactor by a peristaltic pump within 28-30 minutes. After the addition is completed, ultrasonic stirring is maintained for 30 minutes. The silver-coated copper powder in the reactor is placed in a centrifuge for cleaning until the conductivity is less than 10μs / cm. The powder is taken out and placed in a filter press. Anhydrous ethanol twice the weight of the silver-coated copper powder is added for filtration. The filtered silver-coated copper powder is placed in a freeze dryer for low-temperature vacuum drying. After drying for 24 hours, it is sieved through a 350-mesh sieve to obtain the finished product.

[0097] Technical indicators of silver-coated copper powder: bulk density 2.78g / cm 3 , tap density 4.25g / cm 3 , particle size D 50 3.26μm, specific surface area ratio 0.28m 2 / g.

[0098] Comparative Example 1:

[0099] Compared with Example 1, the difference is that Comparative Example 1 is to prepare the silver-coated copper powder under hydrogen conditions, which is dangerous. Example 1 is to use nitrogen protection in a liquid phase environment to prevent the copper powder from oxidizing during the reaction process, and to coat the surface of the copper powder with a complete layer of silver; the silver-coated copper powder is first filtered and vacuum-freeze-dried at low temperature to make the silver-coated copper powder well dispersed.

[0100] Comparative Example 2:

[0101] Compared with Example 1, the difference is that in Comparative Example 2, a special solution A is mixed with a sodium borohydride solution to obtain a silver crystal core dispersion, and copper powder is formed on the surface of the silver crystal core dispersion, and then silver is plated on the surface of the copper powder. In Example 1, a complete layer of silver is coated on the surface of the copper powder by chemical reaction under nitrogen protection, and the obtained particle size is D 50 3.0-5.0μm silver-coated copper powder.

[0102] Result analysis:

[0103] 1. Through Examples 1-5, it can be seen that the preparation method of the silver-coated copper powder for solar low-temperature drying slurry of the present invention has a bulk density of 2.30-3.0 g / cm 3 , tap density 3.6-5.0g / cm 3 , particle size D 50 3.0-5.0μm, specific surface area 0.2-0.4m 2 / g.

[0104] 2. Comparative Example 1 differs from Example 1 in that the silver-coated copper powder was produced in the presence of hydrogen, which is somewhat hazardous. In Example 1, nitrogen was used as a protective layer in the liquid phase to prevent oxidation of the copper powder during the reaction. The reducing agent allowed a complete layer of silver to be coated on the surface of the copper powder. The silver-coated copper powder was first filter-pressed and freeze-dried in a low-temperature vacuum to ensure good dispersibility.

[0105] 3. Comparative Example 2 is compared with Example 1. The difference is that in Comparative Example 2, a special solution A is mixed with a sodium borohydride solution to obtain a silver crystal core dispersion, and copper powder is formed on the surface of the silver crystal core dispersion, and then silver is plated on the surface of the copper powder. In Example 1, a monodispersed copper powder is directly used under nitrogen protection, and the copper powder is treated with acid and alkali, and then a complete layer of silver is coated on the surface of the copper powder through a chemical reaction, so that the particle size D is obtained. 50 3.0-5.0μm silver-coated copper powder.

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing silver-coated copper powder for solar low-temperature drying slurry, characterized by: The steps include: 1) Use monodisperse copper powder as raw material: When cleaning in a cleaning kettle, first add an alkaline solution with a mass concentration of 16%. The amount of alkaline solution added corresponds to 6 times the weight of the monodisperse copper powder. After nitrogen is introduced into the kettle for 5 minutes, the prepared copper powder is added. Ultrasonic cleaning and high-speed stirring are performed for 30 minutes until the conductivity is less than 10μs / cm and the pH is 7-8. The particle size of the monodisperse copper powder selected is D 50 3-4μm, tapped: 5-6g / cm 3 ; 2) Place the copper powder cleaned in the previous step into a centrifuge for solid-liquid separation, and then filter press for cleaning; 3) The copper powder after filter pressing was placed in a cleaning kettle for secondary cleaning. First, a 5 wt% acid solution with a volume 10 times the weight of the copper powder was added, nitrogen was introduced for 5 minutes, and then the copper powder cleaned in the previous step was added. The cleaning was carried out under ultrasonication and high-speed stirring for 30 minutes. 4) The copper powder cleaned in the previous step is subjected to solid-liquid separation and then placed in a nitrogen-filled reactor for chemical reduction and silver coating treatment: ① Using a complexing agent to prepare a complexing solution with a mass ratio of 1:1 with silver nitrate; the complexing agent is one or a mixture of two of ammonia water, ethylenediamine, EDTA, and ammonium carbonate, and the mixture can be in any proportion; ② Use a peristaltic pump to add the complexing solution to the reactor, setting the time to 28-30 minutes; ③ Prepare the reducing agent with a mass ratio of reducing agent to monodisperse copper powder of 1:(0.20-0.25), add the reducing agent to the reactor with a peristaltic pump, and set the addition time to 28-30 minutes; the reducing agent is one or a mixture of two of glucose, formaldehyde, triethanolamine, glycerol, ascorbic acid, and hydrazine hydrate, and the mixing ratio can be any ratio; ④ Add a solution equivalent to 10 times the weight of the monodisperse copper powder to the reactor, wherein the solution is a 20wt% solution of one or two of gelatin, PVP, polyethylene glycol, gum arabic, and Tween 80, and the mixture can be in any proportion; 5) The coated silver-coated copper powder is placed in a centrifuge for cleaning until the conductivity is less than 10μs / cm. It is then taken out and placed in a filter press. Anhydrous ethanol twice the weight of the silver-coated copper powder is added for filtration. 6) Place the filtered silver-coated copper powder into a freeze dryer for low-temperature vacuum drying. After drying for 24 hours, sieve it through a 350-mesh sieve to obtain the finished product. The bulk density of the obtained silver-coated copper powder is 2.3-3.0 g / cm 3 , tap density 4.0-5.0 g / cm 3 , particle size D 50 3.0-4.5μm, specific surface area 0.2-0.4 m 2 / g.

2. The method for preparing silver-coated copper powder for solar low-temperature drying slurry according to claim 1, characterized in that: In step 1), during the cleaning process in the cleaning kettle, an alkaline solution having a volume 6 times the weight of the copper powder is first added, in a ratio of 1 kg of copper powder to 6 L of alkaline solution.

3. The method for preparing silver-coated copper powder for solar low-temperature drying slurry according to claim 1, characterized in that: The alkaline solution in step 1) is selected from sodium carbonate, sodium hydroxide, and potassium hydroxide.

4. The method for preparing silver-coated copper powder for solar low-temperature drying slurry according to claim 1, characterized in that: The acid solution in step 3) is selected from sulfuric acid, ammonium sulfate, acetic acid, nitric acid, hydrochloric acid, or a mixture of two of them, and the mixture can be in any proportion.

5. The method for preparing silver-coated copper powder for solar low-temperature drying slurry according to claim 1, characterized in that: In step 1), step 3), and step 4), the introduction of nitrogen or the passage of nitrogen is the introduction of dry nitrogen at a pressure of 0.2 MPa.

6. The method for preparing silver-coated copper powder for solar low-temperature drying slurry according to claim 1, characterized in that: The reducing agent in step 4) is added for 30 minutes, and stirring is maintained for 30 minutes after the reducing agent is added.

7. The method for preparing silver-coated copper powder for solar low-temperature drying slurry according to claim 1, characterized in that: Step 6) placing the product into a freeze dryer for low-temperature vacuum drying, wherein the freeze dryer has a freezing temperature of -80°C and a drying temperature of 35°C.

8. A silver-coated copper powder for solar low-temperature drying of slurry, characterized by: The silver-coated copper powder is obtained by the preparation method of a solar low-temperature drying slurry according to any one of claims 1 to 7, wherein the bulk density of the silver-coated copper powder is 2.3-3.0 g / cm 3 , tap density 3.6-5.0 g / cm 3 , particle size D 50 3.0-4.5μm, specific surface area 0.2-0.4 m 2 / g.

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