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

Abstract

According to the preparation method of the silver-coated copper powder for the solar low-temperature drying slurry, the silver-coated copper powder which is high in oxidation resistance, good in conductivity, complete in coating and capable of being used for the low-temperature slurry can be prepared through the method, and the preparation method is low in production cost, controllable in technological process and high in practicability.

Description

Technical Field

[0001] The invention relates to the technical field of electronic material functional powders, and 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 a good conductive filler. It can be added to coatings, glues (adhesives), inks, plastics, rubber, etc. to make various conductive, electromagnetic shielding, photovoltaic and other slurries, which are 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] In recent years, the price of silver has skyrocketed, while copper powder is cheap and its conductivity is second only to silver powder. However, copper powder is easily oxidized and has poor stability. If a layer of silver particles is evenly coated on the surface of copper powder to obtain silver-coated copper powder, the excellent conductivity of copper powder can be maintained, its anti-oxidation stability can be improved, and the cost can be greatly reduced.

[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) alkali washing; (2) acid washing; (3) chemical silver plating, washing and vacuum drying to obtain the silver-coated copper powder; 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, which is beneficial 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 another 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, and after mixing evenly, 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 application 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 that the silver-coated copper powder prepared by the existing chemical method still has an uneven coating layer and a high resistivity, the present invention provides a method for preparing silver-coated copper powder for solar low-temperature drying slurry. The method can prepare silver-coated copper powder with strong antioxidant ability, good conductivity, complete coating and can be used for low-temperature slurry. 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) subjecting the copper powder prepared in step (1) to ultrasonic cleaning 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 filtering and cleaning;

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

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

[0018] (8) Adding a solvent 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 reaction kettle and a silver nitrate complex solution is first 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 washed and filtered silver-coated copper powder is placed in a freeze dryer for low-temperature vacuum freeze drying and sifting to obtain a 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 an alkaline solution with a mass concentration of 16%, the amount of the alkaline solution added corresponds to 6 times the weight of the monodisperse copper powder, and then add the prepared copper powder after nitrogen is introduced into the kettle for 5 minutes, and then 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 filtering and cleaning;

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

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

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

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

[0030] ③ Prepare the reducing agent, the mass ratio of the reducing agent to the monodisperse copper powder is 1: (0.2-0.25), add the reducing agent into the reactor with a peristaltic pump, and set the time to add for 28-30min; the reducing agent is one or a mixture of two of glucose, formaldehyde, triethanolamine, glycerol, ascorbic acid, and hydrazine hydrate, and the mixing ratio is arbitrary;

[0031] ④ Add a solution equivalent to 10 times the weight of monodisperse copper powder into 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, taken out and placed in a filter press, and anhydrous ethanol twice the weight of the silver-coated copper powder is added for filtering;

[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 powder was sieved through a 350-mesh sieve to obtain the finished product. 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 the ratio of 1 kg of monodisperse copper powder: 6 L of alkaline solution, the same 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 is 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, step 6) is performed by placing the mixture into a freeze dryer for low-temperature vacuum drying, 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 using 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] 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] Embodiment 1:

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

[0052] 1. Add 12L sodium hydroxide solution to the cleaning kettle, introduce 0.2MPa nitrogen into the kettle for 5 minutes, then add 2kg copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; put the alkali-washed copper powder into 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 into the cleaning kettle, introduce 0.2MPa nitrogen for 5 minutes, then add the alkali-washed copper powder, and clean it for 30 minutes by ultrasonic and high-speed stirring; put the copper powder into 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 into auxiliary material kettle 1, stir and dissolve completely, add 800ml of ammonia water to make the silver nitrate form a complex solution for 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 ultrasound to dissolve evenly, then introduce 0.2MPa nitrogen for 5min and add the cleaned copper powder, maintain ultrasound 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 under stirring and dissolve completely, maintain the temperature at 40±1℃;

[0057] 5. Add the silver nitrate complex solution in the auxiliary material kettle into the reactor within 28-30 minutes using a peristaltic pump. After adding the complexing agent, maintain ultrasonic high-speed stirring for 30 minutes. Then add the glucose solution into the reactor within 28-30 minutes using a peristaltic pump. After adding, maintain ultrasonic stirring for 30 minutes. Put the silver-coated copper powder in the reactor into a centrifuge for cleaning until the conductivity is less than 10μs / cm, take it out and put it into a filter press, add anhydrous ethanol twice the weight of the silver-coated copper powder, and filter it. Put the filtered silver-coated copper powder into a freeze dryer for low-temperature vacuum drying. After drying for 24 hours, pass it 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 obtained 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] Embodiment 2:

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

[0062] 1. Add 12L sodium hydroxide solution to the cleaning kettle, introduce 0.2MPa nitrogen into the kettle for 5 minutes, then add 2kg copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; put the alkali-washed copper powder into 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 into the cleaning kettle, pass 0.2MPa nitrogen for 5 minutes, then add the alkali-washed copper powder, and clean it for 30 minutes by ultrasonic and high-speed stirring; put the copper powder into 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 into auxiliary material kettle 1, stir and dissolve completely, add 600ml of ethylenediamine to make the silver nitrate form a complex solution for 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 ultrasound to dissolve evenly, then introduce 0.2MPa nitrogen for 5min and add the cleaned copper powder, maintain ultrasound 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 under stirring and dissolve completely, maintaining the temperature at 40±1℃;

[0067] 5. Add the silver nitrate complex solution in the auxiliary material kettle into the reactor within 28-30 minutes using a peristaltic pump. After adding the complexing agent, maintain ultrasonic high-speed stirring for 30 minutes. Then add the VC solution into the reactor within 28-30 minutes using a peristaltic pump. After adding, maintain ultrasonic stirring for 30 minutes. Put the silver-coated copper powder in the reactor into a centrifuge for cleaning until the conductivity is less than 10μs / cm, take it out and put it into a filter press, add anhydrous ethanol twice the weight of the silver-coated copper powder, and filter it. Put the filtered silver-coated copper powder into a freeze dryer for low-temperature vacuum drying. After drying for 24 hours, pass it 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, surface area ratio 0.28m 2 / g.

[0069] Figure 2 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 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 through the addition of the reducing agent, the surface of the copper powder particles is coated with a uniform silver layer, and the silver-coated copper powder particles have a smooth surface.

[0071] Embodiment 3:

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

[0073] 1. Add 12L sodium hydroxide solution to the cleaning kettle, introduce 0.2MPa nitrogen into the kettle for 5 minutes, then add 2kg copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; put the alkali-washed copper powder into 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 into the cleaning kettle, pass 0.2MPa nitrogen for 5 minutes, then add the alkali-washed copper powder, and wash it with ultrasonic and high-speed stirring for 30 minutes; put the copper powder into a centrifuge for solid-liquid separation, and wash 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 into auxiliary material kettle 1, stir and dissolve completely, add 600ml of ethylenediamine to make the silver nitrate form a complex solution for 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 ultrasound to dissolve evenly, then introduce 0.2MPa nitrogen for 5min and add the cleaned copper powder, maintain ultrasound 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 under stirring and dissolve completely, maintain the temperature at 40 degrees;

[0078] 5. Add the acid silver complex solution in the auxiliary material kettle into the reactor within 28-30 minutes by using a peristaltic pump. After adding the complexing agent, maintain ultrasonic high-speed stirring for 30 minutes. Then add the glucose solution into the reactor within 28-30 minutes by using a peristaltic pump. After adding, maintain ultrasonic stirring for 30 minutes. Put the silver-coated copper powder in the reactor into a centrifuge for cleaning until the conductivity is less than 10μs / cm, take it out and put it into a filter press, add anhydrous ethanol twice the weight of the silver-coated copper powder, and filter it. Put the filtered silver-coated copper powder into a freeze dryer for low-temperature vacuum drying. After drying for 24 hours, pass it 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, surface area ratio 0.25m 2 / g.

[0080] Embodiment 4:

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

[0082] 1. Add 12L sodium hydroxide solution to the cleaning kettle, introduce 0.2MPa nitrogen into the kettle for 5 minutes, then add 2kg copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; put the alkali-washed copper powder into 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 into the cleaning kettle, pass 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; put the copper powder into 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 into auxiliary material kettle 1, stir and dissolve completely, add 700ml of ethylenediamine to make the silver nitrate form a complex solution for 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 ultrasound to dissolve evenly, then introduce 0.2MPa nitrogen for 5min and add the cleaned copper powder, maintain ultrasound 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 under stirring and dissolve completely, maintaining the temperature at 40±1℃;

[0087] 5. Add the silver nitrate complex solution in the auxiliary material kettle into the reactor within 28-30 minutes using a peristaltic pump. After adding the complexing agent, maintain ultrasonic high-speed stirring for 30 minutes. Then add the VC solution into the reactor within 28-30 minutes using a peristaltic pump. After adding, maintain ultrasonic stirring for 30 minutes. Put the silver-coated copper powder in the reactor into a centrifuge for cleaning until the conductivity is less than 10μs / cm, take it out and put it into a filter press, add anhydrous ethanol twice the weight of the silver-coated copper powder, and filter it. Put the filtered silver-coated copper powder into a freeze dryer for low-temperature vacuum drying. After drying for 24 hours, pass it 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, surface area ratio 0.28m 2 / g.

[0089] Embodiment 5:

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

[0091] 1. Add 12L sodium hydroxide solution to the cleaning kettle, introduce 0.2MPa nitrogen into the kettle for 5 minutes, then add 2kg copper powder, and clean it with ultrasonic and high-speed stirring for 30 minutes; put the alkali-washed copper powder into 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 into the cleaning kettle, introduce 0.2MPa nitrogen for 5 minutes, then add the alkali-washed copper powder, and clean it for 30 minutes by ultrasonic and high-speed stirring; put the copper powder into 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 into auxiliary material kettle 1, stir and dissolve completely, add 700ml of ethylenediamine to make the silver nitrate form a complex solution for use, and maintain the temperature at 30℃±1℃;

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

[0096] 5. Add the silver nitrate complex solution in the auxiliary material kettle into the reactor within 28-30 minutes using a peristaltic pump. After adding the complexing agent, maintain ultrasonic high-speed stirring for 30 minutes. Then add the VC solution into the reactor within 28-30 minutes using a peristaltic pump. After adding, maintain ultrasonic stirring for 30 minutes. Put the silver-coated copper powder in the reactor into a centrifuge for cleaning until the conductivity is less than 10μs / cm, take it out and put it into a filter press, add anhydrous ethanol twice the weight of the silver-coated copper powder, and filter it. Put the filtered silver-coated copper powder into a freeze dryer for low-temperature vacuum drying. After drying for 24 hours, pass it 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 the condition of hydrogen, which is dangerous to a certain extent, while Example 1 is to use nitrogen protection in a liquid phase environment to prevent the oxidation of the copper powder during the reaction process, and a complete layer of silver can be coated on the surface of the copper powder; the silver-coated copper powder is first filtered and low-temperature vacuum freeze-dried to make the silver-coated copper powder have good dispersibility.

[0100] Comparative Example 2:

[0101] Compared with Example 1, the difference is that in Example 2, the special solution A is mixed with the sodium borohydride solution to obtain the silver crystal core dispersion liquid, so that the surface of the silver crystal core dispersion liquid forms copper powder, and then silver is plated on the surface of the copper powder. In Example 1, the copper powder is directly coated with a complete layer of silver on the surface of the copper powder under the protection of nitrogen through chemical reaction, 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 method for preparing a silver-coated copper powder for solar low-temperature drying slurry according to 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 is compared with Example 1, the difference is that Comparative Example 1 is to prepare silver-coated copper powder under hydrogen conditions, which is dangerous, while Example 1 is to protect with nitrogen in a liquid phase environment to prevent oxidation of copper powder during the reaction process, and a complete layer of silver can be coated on the surface of the copper powder through the reducing agent. The silver-coated copper powder is first filtered and vacuum-dried at low temperature to make the silver-coated copper powder have good dispersibility.

[0105] 3. Comparative Example 2 is compared with Example 1. The difference is that in Comparative Example 2, a specially prepared solution A is mixed with a sodium borohydride solution to obtain a silver crystal core dispersion liquid, so that copper powder is formed on the surface of the silver crystal core dispersion liquid, 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 to obtain a particle size D 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing silver-coated copper powder for solar low-temperature drying slurry, characterized in that: The steps include: 1) Select 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 the alkaline solution added corresponds to 6 times the weight of the monodisperse copper powder, and then add the prepared copper powder after nitrogen is introduced into the kettle for 5 minutes, and then ultrasonically and high-speed stirring are used for cleaning 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) placing the copper powder cleaned in the previous step into a centrifuge for solid-liquid separation, and then filtering and cleaning; 3) The copper powder after filter pressing and cleaning is placed in a cleaning kettle for secondary cleaning. First, a 5wt% acid solution with a volume 10 times the weight of the copper powder is added, nitrogen is introduced for 5 minutes, and then the copper powder cleaned in the previous step is added, and ultrasonic cleaning is performed with high-speed stirring for 30 minutes; 4) The copper powder cleaned in the above step is subjected to solid-liquid separation, and then placed in a reactor filled with nitrogen for chemical reduction and silver coating treatment: ① Using a complexing agent to prepare silver nitrate into a complexing solution with a mass ratio of 1:1; the complexing agent is one or a mixture of two of ammonia water, ethylenediamine, EDTA, and ammonium carbonate, and the mixture is in any proportion; ② Use a peristaltic pump to add the complexing solution into the reactor, setting the time to 28-30 minutes; ③ Prepare the reducing agent, the mass ratio of the reducing agent to the monodisperse copper powder is 1: (0.20-0.25), add the reducing agent into the reactor with a peristaltic pump, and set the time to add for 28-30min; the reducing agent is one or a mixture of two of glucose, formaldehyde, triethanolamine, glycerol, ascorbic acid, and hydrazine hydrate, and the mixing ratio is arbitrary; ④ Add a solution equivalent to 10 times the weight of monodisperse copper powder into 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 10 μs / cm, taken out and placed in a filter press, and anhydrous ethanol twice the weight of the silver-coated copper powder is added for filtering; 6) The filtered silver-coated copper powder was placed in a freeze dryer for low-temperature vacuum drying. After drying for 24 hours, the powder was sieved through a 350-mesh sieve to obtain the finished product. 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.

2. The method for preparing silver-coated copper powder for solar low-temperature drying slurry according to claim 1, characterized in that: When performing the cleaning treatment in the cleaning kettle in step 1), first add an alkaline solution with a volume 6 times the weight of the copper powder, in a ratio of 1 kg of copper powder: 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: The nitrogen gas introduced or passed through in step 1), step 3) and step 4) is dry nitrogen gas 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 silver nitrate complex solution in step 4) is added for 28-30 minutes.

7. 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.

8. The method for preparing silver-coated copper powder for solar low-temperature drying slurry according to claim 1, characterized in that: Step 6) is 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.

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

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