Preparation method of high-tap-density and high-dispersibility superfine silver powder

Abstract

The application discloses a preparation method of high-tap-density high-dispersibility superfine silver powder and belongs to the technical field of conductive silver paste materials, and comprises the following steps: mixing a refining agent, a reducing agent and an alkali liquor with a silver salt oxidizing solution, and then performing an oxidation-reduction reaction under mechanical stirring and ultrasonic stirring to obtain a silver powder material liquid; after water washing of the silver powder material liquid is completed until the conductivity is less than or equal to 50 us / cm, the silver powder material liquid is pressed dry under a vacuum state, alcohol washing is performed on the silver powder material liquid under mechanical stirring and ultrasonic stirring, then the silver powder material liquid is continuously pressed dry under the vacuum state, and superfine silver powder is obtained; under mechanical stirring and ultrasonic stirring, a hot alcohol is used to dissolve a dispersant to obtain a dispersant solution, the superfine silver powder is dispersed by using the dispersant solution, and vacuum drying is performed to obtain high-tap-density high-dispersibility superfine silver powder. The superfine silver powder disclosed by the application has high tap density and small particle size, can meet the electrical performance requirements of a metal electrode back silver paste on a crystalline silicon solar cell, and has high yield.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of conductive silver paste, and particularly relates to a preparation method of high-tap high-dispersibility superfine silver powder. BACKGROUND

[0002] Silver powder is the main component of the back silver paste of the metal electrode of a crystalline silicon solar cell, and as the conductive functional item, the silver powder is directly related to the electrical performance of the back silver paste of the metal electrode of the crystalline silicon solar cell. The existing superfine silver powder is usually prepared by using the traditional liquid phase reduction method. However, the prepared superfine silver powder has small particle size, large specific surface area and high surface activity, and is easy to be agglomerated, thereby reducing the surface activity of the silver powder and lowering the yield. SUMMARY

[0003] One of the purposes of the application is to provide a preparation method of high-tap high-dispersibility superfine silver powder, which has high tap density, small particle size, meets the electrical performance requirements of the back silver paste of the metal electrode of the crystalline silicon solar cell and has high yield.

[0004] In order to achieve the above purpose, the application adopts the following technical scheme:

[0005] The preparation method of high-tap high-dispersibility superfine silver powder comprises the following steps:

[0006] Step S1, mixing a refining agent, a reducing agent and a lye with a silver salt oxidation solution with a molar concentration of 0.15-0.25 mol / L at a temperature of 48-62℃, and then performing oxidation-reduction reaction for 1.2-1.7h under mechanical stirring and ultrasonic stirring to obtain a silver powder material liquid;

[0007] In the step S1, the mass ratio of the silver salt oxidation solution, the refining agent, the reducing agent and the lye is 800-850: 1-1.5: 120-150: 536-600;

[0008] Step S2, washing the silver powder material with water until the electrical conductivity of the silver powder material is ≦50 us / cm, and then drying the silver powder material liquid by using compressed air under vacuum and mechanical stirring and ultrasonic stirring, washing the silver powder material liquid with alcohol, and then drying the silver powder material liquid by using compressed air under vacuum and mechanical stirring and ultrasonic stirring to obtain superfine silver powder;

[0009] In the step S2, the mass ratio of the silver powder material and the alcohol is 1: 2-4;

[0010] Step S3, under mechanical stirring and ultrasonic stirring, using alcohol of 40-60℃ to dissolve dispersant to obtain dispersant solution, then using the dispersant solution to disperse superfine silver powder, and then vacuum drying at 77-82℃ for 20-24h to obtain high tapability and high dispersibility superfine silver powder.

[0011] Further, in the step S1, the mass concentration of the lye is 30-50%, and the temperature is 28-38℃.

[0012] Further, in the step S1, the silver salt in the silver salt oxidation solution is one of silver nitrate and silver carbonate.

[0013] In the step S1, the refining agent is one of copper and aluminum nitrate.

[0014] In the step S1, the reducing agent is one of hydrazine hydrate, formaldehyde, hydrogen peroxide and ascorbic acid.

[0015] In the step S1, the alkali of the lye is one of sodium hydroxide and sodium carbonate.

[0016] Further, in the step S1, step S2 and step S3, the rotating speed of the mechanical stirring is 200-300rpm; and the ultrasonic power of the ultrasonic stirring is 300-400W.

[0017] Further, in the step S2, the vacuum degree of the vacuum state is 1.0-10MPa.

[0018] Further, in the step S3, the dispersant is one or several of oleic acid, stearic acid and hexadecanoic acid.

[0019] Further, in the step S3, the dispersing time is 20-60min.

[0020] Further, in the step S3, the vacuum degree of the vacuum drying is 3.0-7.0MPa.

[0021] Further, in the step S3, the D10 of the high tapability and high dispersibility superfine silver powder is 0.310-0.350um, the D50 is 0.74-0.96um, the D90 is 1.51-2.10, the tap density is 4.6-5.6g / cm 3 , and the loss on ignition is 0.80-1.00%.

[0022] In summary, the scheme provided by the application has the following technical effects:

[0023] The present application effectively controls the small particle size of silver powder by adding a refining agent in the oxidation-reduction reaction, reduces the moisture content of the silver powder and the degree of silver powder agglomeration in the washing process by washing away the moisture in the silver powder material with alcohol, reduces the agglomeration of the silver powder generated in the reduction, the aging of the silver powder in the washing and the limited agglomeration of the dispersion capacity in the dispersion process by using hot alcohol and a dispersing agent in the dispersion process, and further reduces the agglomeration of the silver powder in the oxidation-reduction, washing and dispersion processes by using mechanical stirring and ultrasonic stirring simultaneously in the oxidation-reduction, washing and dispersion processes. 3 The D10 of the high-tap high-dispersibility ultra-fine silver powder is 0.310-0.350 um, the D50 is 0.74-0.96 um, the D90 is 1.51-2.10, the tap density is 4.6-5.6 g / cm DETAILED DESCRIPTION

[0024] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0025] Embodiment 1

[0026] Step S1, at a temperature of 55℃, the refining agent copper, the reducing agent hydrazine hydrate and sodium hydroxide are mixed with the silver nitrate oxidation solution with a molar concentration of 0.20 mol / L according to a mass ratio of 820:1.2:135:568, and then, under mechanical stirring and ultrasonic stirring, the oxidation-reduction reaction is carried out for 1.5 h to obtain a silver powder material liquid.

[0027] The mass concentration of sodium hydroxide is 40%, and the temperature is 33℃. The mechanical stirring speed is 250 revolutions / min, and the ultrasonic stirring power is 350W.

[0028] Step S2, the silver powder material is washed with water until the conductivity of the silver powder material is 50 us / cm, then, under vacuum, the silver powder material liquid is dried by compressed air under mechanical stirring and ultrasonic stirring, then washed with alcohol, and then, under vacuum at 5.0 MPa, the silver powder material liquid is dried by compressed air under mechanical stirring and ultrasonic stirring to obtain ultra-fine silver powder.

[0029] The mass ratio of silver powder material and alcohol is 1:2. The rotating speed of mechanical stirring is 250 r / min, and the ultrasonic power of ultrasonic stirring is 350 W.

[0030] In step S3, the stearic acid dispersant is dissolved in 50℃ alcohol to obtain a stearic acid dispersant solution under mechanical stirring and ultrasonic stirring. The superfine silver powder is dispersed for 20 min using the stearic acid dispersant solution, and then dried at 77℃ under a vacuum state of 3.0 MPa for 20 h to obtain the superfine silver powder with high tap density and high dispersibility. The rotating speed of mechanical stirring is 200 r / min, and the ultrasonic power of ultrasonic stirring is 300 W.

[0031] The yield of the superfine silver powder with high tap density and high dispersibility in this embodiment reaches 97.5%.

[0032] Example 2:

[0033] In step S1, the refining agent aluminum nitrate, the reducing agent formaldehyde, and sodium carbonate are mixed with the silver carbonate oxidized solution with a molar concentration of 0.15 mol / L at a temperature of 48℃ and a mass ratio of 800:1:120:536. Then, the oxidizing-reducing reaction is performed for 1.2 h under mechanical stirring and ultrasonic stirring to obtain a silver powder material liquid.

[0034] The mass concentration of sodium carbonate is 30%, and the temperature is 28℃. The rotating speed of mechanical stirring is 200 r / min, and the ultrasonic power of ultrasonic stirring is 300 W.

[0035] In step S2, the silver powder material is washed with water until the conductivity of the silver powder material reaches 45 us / cm. Then, the silver powder material liquid is dried by compressed air under a vacuum state and mechanical stirring and ultrasonic stirring. Then, the silver powder material liquid is washed with alcohol. Then, the silver powder material liquid is dried by compressed air under a vacuum state of 1.0 MPa and mechanical stirring and ultrasonic stirring to obtain the superfine silver powder.

[0036] The mass ratio of silver powder material and alcohol is 1:3. The rotating speed of mechanical stirring is 200 r / min, and the ultrasonic power of ultrasonic stirring is 300 W.

[0037] In step S3, the stearic acid dispersant is dissolved in 50℃ alcohol to obtain a stearic acid dispersant solution under mechanical stirring and ultrasonic stirring. The superfine silver powder is dispersed for 20 min using the stearic acid dispersant solution, and then dried at 77℃ under a vacuum state of 3.0 MPa for 20 h to obtain the superfine silver powder with high tap density and high dispersibility. The rotating speed of mechanical stirring is 200 r / min, and the ultrasonic power of ultrasonic stirring is 300 W.

[0038] The yield of the high tap density and high dispersibility ultra-fine silver powder of the embodiment reaches 97%.

[0039] Embodiment 3

[0040] In step S1, the refining agent aluminum nitrate, the reducing agent hydrogen peroxide and sodium carbonate are mixed with the silver carbonate oxidized solution with a molar concentration of 0.25 mol / L at a mass ratio of 850:1.5:150:600 at a temperature of 62℃, and then a redox reaction is performed for 1.7 h under mechanical stirring and ultrasonic stirring to obtain a silver powder material solution.

[0041] The mass concentration of the sodium carbonate is 50% and the temperature is 38℃. The mechanical stirring speed is 300 rpm and the ultrasonic stirring power is 400 W.

[0042] In step S2, the silver powder material is washed with water until the conductivity of the silver powder material is 35 us / cm, and then the silver powder material solution is dried by compressed air under vacuum, mechanical stirring and ultrasonic stirring, and then washed with alcohol, and then dried by compressed air under vacuum, mechanical stirring and ultrasonic stirring at 10 MPa to obtain ultra-fine silver powder.

[0043] The mass ratio of the silver powder material and the alcohol is 1:3.5. The mechanical stirring speed is 300 rpm and the ultrasonic stirring power is 400 W.

[0044] In step S3, the palmitic acid dispersant is dissolved in alcohol at 60℃ to obtain a palmitic acid dispersant solution, and then the ultra-fine silver powder is dispersed in the palmitic acid dispersant solution for 60 min, and then dried at a temperature of 82℃ under vacuum at 7.0 MPa for 24 h to obtain high tap density and high dispersibility ultra-fine silver powder. The mechanical stirring speed is 300 rpm and the ultrasonic stirring power is 400 W.

[0045] The yield of the high tap density and high dispersibility ultra-fine silver powder of the embodiment reaches 96.8%.

[0046] Embodiment 4

[0047] In step S1, the refining agent copper, the reducing agent ascorbic acid and sodium hydroxide are mixed with the silver nitrate oxidized solution with a molar concentration of 0.18 mol / L at a mass ratio of 840:1.4:145:590 at a temperature of 60℃, and then a redox reaction is performed for 1.6 h under mechanical stirring and ultrasonic stirring to obtain a silver powder material solution.

[0048] The mass concentration of the sodium hydroxide is 45% and the temperature is 36℃. The mechanical stirring speed is 280 rpm and the ultrasonic stirring power is 380 W.

[0049] Step S2, the silver powder material is washed with water until the conductivity of the silver powder material is 40 us / cm, then the silver powder material is dried by compressed air under vacuum state with mechanical stirring and ultrasonic stirring, then the silver powder material is washed with alcohol, then the silver powder material is dried by compressed air under vacuum state with mechanical stirring and ultrasonic stirring at 7 MPa, to obtain superfine silver powder.

[0050] The mass ratio of the silver powder material and the alcohol is 1:4. The rotating speed of the mechanical stirring is 280 rpm, and the ultrasonic power of the ultrasonic stirring is 380 W.

[0051] Step S3, the palmitic acid dispersant is dissolved in alcohol at 60℃ to obtain a palmitic acid dispersant solution, then the superfine silver powder is dispersed in the palmitic acid dispersant solution for 45 min, then the high tapability and high dispersibility superfine silver powder is obtained by drying at 78℃ under vacuum state at 6.0 MPa for 23 h. The rotating speed of the mechanical stirring is 280 rpm, and the ultrasonic power of the ultrasonic stirring is 380 W.

[0052] The yield of the high tapability and high dispersibility superfine silver powder of the embodiment reaches 97%.

[0053] Table 1 Particle size, tap density and ignition loss of the high tapability and high dispersibility superfine silver powder of Example 1-Example 4

[0054]

[0055]

[0056] Note that the technical features of the above embodiments can be combined in any manner. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combinations of the technical features do not contradict, they should be considered as the scope of the description. The above embodiments only express several implementation manners of the application, the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be noted that for those skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which are all within the scope of the application. Therefore, the patent protection scope of the application should be subject to the appended claims.

Claims

1. A method for preparing a high tapability and high dispersibility ultrafine silver powder, characterized by, The preparation method comprises the following steps: In step S1, the silver salt in the silver salt oxidation solution is one of silver nitrate and silver carbonate; In step S1, the reducing agent is one of hydrazine hydrate, formaldehyde, hydrogen peroxide and ascorbic acid; In step S1, the alkali of the alkali solution is one of sodium hydroxide and sodium carbonate. In step S1, step S2 and step S3, the rotating speed of the mechanical stirring is 200-300 rpm; the ultrasonic power of the ultrasonic stirring is 300-400 W. In step S2, the vacuum degree of the vacuum state is 1.0-10 MPa. In step S3, the dispersing time is 20-60 min. The high tap density and high dispersibility superfine silver powder has D10 of 0.310-0.350 μm, D50 of 0.74-0.96 μm, D90 of 1.51-2.10 μm, and tap density of 4.6-5.6 g / cm 3 , and burning loss of 0.80-1.00%.

2. The production method according to claim 1, characterized by, In step S3, the vacuum degree of the vacuum drying is 3.0-7.0 MPa.

3. The preparation method according to claim 2, characterized in that, ​ ​ ​ 4. The preparation method according to claim 3, characterized in that, ​ 5. The production method according to any one of claims 1 to 4, characterized by, ​ 6. The preparation method according to claim 5, characterized in that, ​ 7. The preparation method according to claim 6, characterized in that, ​ 8. The preparation method according to claim 7, characterized in that, ​

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