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

Abstract

The invention discloses a preparation method of high-tap-density high-dispersity superfine silver powder, and belongs to the technical field of conductive silver paste, and the preparation method comprises the following steps: mixing a refiner, a reducing agent, alkali liquor and a silver salt oxidation solution, and performing oxidation-reduction reaction under mechanical stirring and ultrasonic stirring to obtain silver powder liquid; the method comprises the following steps: washing a silver powder material with water until the conductivity is less than or equal to 50us / cm, then hydraulically drying the silver powder material in a vacuum state under mechanical stirring and ultrasonic stirring, washing with alcohol, and then hydraulically drying the silver powder material in the vacuum state under mechanical stirring and ultrasonic stirring to obtain superfine silver powder; under mechanical stirring and ultrasonic stirring, hot alcohol is adopted for dissolving a dispersing agent to obtain a dispersing agent solution, then the dispersing agent solution is adopted for dispersing the superfine silver powder, vacuum drying is conducted, and the high-tap-density and high-dispersity superfine silver powder is obtained. The superfine silver powder is high in tap density and small in particle size, meets the electrical property requirement of silver paste on the back face of a metal electrode on a crystalline silicon solar cell, and is high in yield.

Description

Technical Field

[0001] The invention belongs to the technical field of conductive silver paste, and in particular relates to a method for preparing ultrafine silver powder with high tapping density and high dispersibility. Background Art

[0002] Silver powder is the main component of silver paste on the back of the metal electrode on crystalline silicon solar cells. As a conductive functional item, silver powder is directly related to the electrical properties of the silver paste on the back of the metal electrode on crystalline silicon solar cells. The existing ultrafine silver powder is usually prepared by the traditional liquid phase reduction method, but due to the small particle size, large specific surface area and high surface activity of the prepared ultrafine silver powder, it is easy to agglomerate, thereby reducing the surface activity of the silver powder and the yield is low. Summary of the invention

[0003] One of the purposes of the present invention is to provide a method for preparing ultrafine silver powder with high tap density and high dispersibility. The ultrafine silver powder obtained by the method has high tap density and small particle size, meets the electrical performance requirements of silver paste on the back of the metal electrode on crystalline silicon solar cells, and has high yield.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for preparing ultrafine silver powder with high tapping density and high dispersibility, the method comprising the following steps:

[0006] Step S1, at a temperature of 48 to 62° C., a refining agent, a reducing agent and an alkali solution are mixed with a silver salt oxidation solution having a molar concentration of 0.15 to 0.25 mol / L, and then, under mechanical stirring and ultrasonic stirring, an oxidation-reduction reaction is performed for 1.2 to 1.7 hours to obtain a silver powder solution;

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

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

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

[0010] Step S3, under mechanical stirring and ultrasonic stirring, using 40-60° C. alcohol to dissolve the dispersant to obtain a dispersant solution, then using the dispersant solution to disperse the ultrafine silver powder, and then vacuum drying at a temperature of 77-82° C. for 20-24 hours to obtain a highly tapped and highly dispersible ultrafine silver powder.

[0011] Furthermore, in step S1, the mass concentration of the alkali solution is 30-50%, and the temperature is 28-38°C.

[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 refiner 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 alkali solution is one of sodium hydroxide and sodium carbonate.

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

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

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

[0019] Furthermore, in the step S3, the dispersion time is 20 to 60 minutes.

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

[0021] Furthermore, in step S3, the D10 of the highly tapped and highly dispersible ultrafine silver powder is 0.310-0.350 um, the D50 is 0.74-0.96 um, the D90 is 1.51-2.10, and the tap density is 4.6-5.6 g / cm 3 , the ignition reduction is 0.80~1.00%.

[0022] In summary, the solution proposed by the present invention has the following technical effects:

[0023] The invention effectively controls the small particle size of silver powder particles by adding a refiner in the redox reaction; uses alcohol to wash away the water mixed in the silver powder material, reduces the water content of the silver powder, and reduces the degree of silver powder agglomeration during the washing process; in the dispersion process, hot alcohol and a dispersant are used to reduce the agglomeration of the silver powder generated during reduction, the aging of the silver powder during washing, and the agglomeration of the silver powder with limited dispersibility, thereby improving the dispersion effect of the silver powder; at the same time, in the redox, washing and dispersion processes, mechanical stirring and ultrasonic stirring are used simultaneously to further reduce the agglomeration of the silver powder during the redox, washing and dispersion processes; the high-tapped and high-dispersibility ultrafine silver powder of the invention has a D10 of 0.310-0.350 um, a D50 of 0.74-0.96 um, a D90 of 1.51-2.10, and a tap density of 4.6-5.6 g / cm 3 The burning reduction is 0.80-1.00%, which meets the electrical performance requirements of the silver paste on the back of the metal electrode on the crystalline silicon solar cell and has a high yield. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Embodiment 1:

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

[0027] The mass concentration of sodium hydroxide is 40%, and the temperature is 33° C. The rotation speed of the mechanical stirring is 250 rpm, and the ultrasonic power of the ultrasonic stirring is 350W.

[0028] Step S2, washing the silver powder material with water until the conductivity of the silver powder material reaches 50 us / cm, and then using compressed air to pressurize the silver powder material under vacuum, mechanical stirring and ultrasonic stirring, and then washing it with alcohol, and then continuing to pressurize the silver powder material under vacuum at 5.0 MPa, mechanical stirring and ultrasonic stirring, using compressed air to pressurize the silver powder material to obtain ultrafine silver powder.

[0029] The mass ratio of silver powder to alcohol is 1:2. The speed of mechanical stirring is 250 rpm, and the ultrasonic power of ultrasonic stirring is 350W.

[0030] Step S3, under mechanical stirring and ultrasonic stirring, using 40°C alcohol to dissolve oleic acid dispersant to obtain oleic acid dispersant solution, and then using oleic acid dispersant solution, the entire dispersion process uses 40°C hot alcohol, the ultrafine silver powder is dispersed for 40 minutes, and then dried at 80°C under a vacuum state of 5.0MPa for 22 hours to obtain high-tapped and high-dispersibility ultrafine silver powder. The speed of mechanical stirring is 250 rpm, and the ultrasonic power of ultrasonic stirring is 350W.

[0031] The yield of the highly tapped and highly dispersible ultrafine silver powder of this embodiment reaches 97.5%.

[0032] Embodiment 2:

[0033] Step S1, at a temperature of 48° C., in a mass ratio of 800:1:120:536, a refining agent aluminum nitrate, a reducing agent formaldehyde and sodium carbonate are mixed with a silver carbonate oxidation solution having a molar concentration of 0.15 mol / L, and an oxidation-reduction reaction is carried out for 1.2 hours under mechanical stirring and ultrasonic stirring to obtain a silver powder solution.

[0034] The mass concentration of sodium carbonate is 30%, and the temperature is 28° C. The rotation speed of the mechanical stirring is 200 rpm, and the ultrasonic power of the ultrasonic stirring is 300W.

[0035] Step S2, washing the silver powder material with water until the conductivity of the silver powder material is 45 us / cm, then, in a vacuum state, with mechanical stirring and ultrasonic stirring, using compressed air, the silver powder material is hydraulically dried, and then washed with alcohol, and then continued in a vacuum state of 1.0 MPa, with mechanical stirring and ultrasonic stirring, using compressed air, the silver powder material is hydraulically dried to obtain ultrafine silver powder.

[0036] The mass ratio of silver powder to alcohol is 1:3. The speed of mechanical stirring is 200 rpm, and the ultrasonic power of ultrasonic stirring is 300W.

[0037] Step S3, under mechanical stirring and ultrasonic stirring, using 50°C alcohol to dissolve stearic acid dispersant to obtain a stearic acid dispersant solution, and then using the stearic acid dispersant solution to disperse the ultrafine silver powder for 20 minutes, and then drying at a temperature of 77°C and a vacuum state of 3.0MPa for 20 hours to obtain highly tapped and highly dispersible ultrafine silver powder. The speed of mechanical stirring is 200 rpm, and the ultrasonic power of ultrasonic stirring is 300W.

[0038] The yield of the highly tapped and highly dispersible ultrafine silver powder of this embodiment reaches 97%.

[0039] Embodiment 3:

[0040] Step S1, at a temperature of 62° C., in a mass ratio of 850:1.5:150:600, a refining agent aluminum nitrate, a reducing agent hydrogen peroxide and sodium carbonate are mixed with a silver carbonate oxidation solution having a molar concentration of 0.25 mol / L, and an oxidation-reduction reaction is carried out for 1.7 hours under mechanical stirring and ultrasonic stirring to obtain a silver powder solution.

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

[0042] Step S2, washing the silver powder material with water until the conductivity of the silver powder material reaches 35 us / cm, and then, under vacuum, with mechanical stirring and ultrasonic stirring, using compressed air to pressurize the silver powder material dry, and then washing it with alcohol, and then continuing to pressurize the silver powder material dry under vacuum at 10 MPa, with mechanical stirring and ultrasonic stirring, using compressed air to obtain ultrafine silver powder.

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

[0044] Step S3, under mechanical stirring and ultrasonic stirring, using 60°C alcohol to dissolve the hexadecanoic acid dispersant to obtain a hexadecanoic acid dispersant solution, and then using the hexadecanoic acid dispersant solution to disperse the ultrafine silver powder for 60 minutes, and then drying at a temperature of 82°C and a vacuum state of 7.0MPa for 24 hours to obtain a highly tapped and highly dispersible ultrafine silver powder. The speed of the mechanical stirring is 300 rpm, and the ultrasonic power of the ultrasonic stirring is 400W.

[0045] The yield of the highly tapped and highly dispersible ultrafine silver powder of this embodiment reaches 96.8%.

[0046] Embodiment 4:

[0047] Step S1, at a temperature of 60° C., in a mass ratio of 840:1.4:145:590, a refining agent copper, a reducing agent ascorbic acid and sodium hydroxide are mixed with a silver nitrate oxidation solution with a molar concentration of 0.18 mol / L, and an oxidation-reduction reaction is carried out for 1.6 hours under mechanical stirring and ultrasonic stirring to obtain a silver powder solution.

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

[0049] Step S2, washing the silver powder material with water until the conductivity of the silver powder material is 40us / cm, and then using compressed air to pressurize the silver powder material under vacuum, mechanical stirring and ultrasonic stirring, and then washing it with alcohol, and then continuing to pressurize the silver powder material under vacuum at 7MPa, mechanical stirring and ultrasonic stirring, using compressed air to pressurize the silver powder material to obtain ultrafine silver powder.

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

[0051] Step S3, under mechanical stirring and ultrasonic stirring, using 60°C alcohol to dissolve the hexadecanoic acid dispersant to obtain a hexadecanoic acid dispersant solution, and then using the hexadecanoic acid dispersant solution to disperse the ultrafine silver powder for 45 minutes, and then drying at a temperature of 78°C and a vacuum state of 6.0MPa for 23 hours to obtain a highly tapped and highly dispersible ultrafine silver powder. The speed of the mechanical stirring is 280 rpm, and the ultrasonic power of the ultrasonic stirring is 380W.

[0052] The yield of the highly tapped and highly dispersible ultrafine silver powder of this embodiment reaches 97%.

[0053] Table 1 Particle size, tap density and ignition loss of high-dispersion ultrafine silver powder of Examples 1 to 4

[0054]

[0055]

[0056] Please note that the technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above embodiments only express several implementation methods of the present application, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several variations and improvements can be made, which all belong to the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be based on the attached claims.

Claims

1. A method for preparing highly vibrated and highly dispersible ultrafine silver powder, characterized in that: The preparation method comprises the following steps: Step S1, at a temperature of 48 to 62° C., a refining agent, a reducing agent and an alkali solution are mixed with a silver salt oxidation solution having a molar concentration of 0.15 to 0.25 mol / L, and then, under mechanical stirring and ultrasonic stirring, an oxidation-reduction reaction is performed for 1.2 to 1.7 hours to obtain a silver powder solution; In the step S1, the mass ratio of the silver salt oxidation solution, the refiner, the reducing agent and the alkali solution is 800-850:1-1.5:120-150:536-600; Step S2, washing the silver powder material with water until the conductivity of the silver powder material is ≦50us / cm, and then using compressed air to pressurize the silver powder material under vacuum, mechanical stirring and ultrasonic stirring, and then washing it with alcohol, and then continuing to pressurize the silver powder material under vacuum, mechanical stirring and ultrasonic stirring, using compressed air to pressurize the silver powder material to obtain ultrafine silver powder; In the step S2, the mass ratio of the silver powder to the alcohol is 1:2-4; Step S3, under mechanical stirring and ultrasonic stirring, using 40-60° C. alcohol to dissolve the dispersant to obtain a dispersant solution, then using the dispersant solution to disperse the ultrafine silver powder, and then vacuum drying at a temperature of 77-82° C. for 20-24 hours to obtain a highly tapped and highly dispersible ultrafine silver powder.

2. The preparation method according to claim 1, characterized in that: In step S1, the mass concentration of the alkali solution is 30-50%, and the temperature is 28-38°C.

3. The preparation method according to claim 2, characterized in that: In the step S1, the silver salt in the silver salt oxidation solution is one of silver nitrate and silver carbonate; In the step S1, the refiner is one of copper and aluminum nitrate; In the step S1, the reducing agent is one of hydrazine hydrate, formaldehyde, hydrogen peroxide and ascorbic acid; In the step S1, the alkali of the alkali solution is one of sodium hydroxide and sodium carbonate.

4. The preparation method according to claim 3, characterized in that: In the step S1, step S2 and step S3, the rotation speed of the mechanical stirring is 200-300 rpm; the ultrasonic power of the ultrasonic stirring is 300-400W.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In the step S2, the vacuum degree of the vacuum state is 1.0-10 MPa.

6. The preparation method according to claim 5, characterized in that: In the step S3, the dispersant is one or more of oleic acid, stearic acid and hexadecanoic acid.

7. The preparation method according to claim 6, characterized in that: In the step S3, the dispersion time is 20 to 60 minutes.

8. The preparation method according to claim 7, characterized in that: In the step S3, the vacuum degree of the vacuum drying is 3.0-7.0 MPa.

9. The preparation method according to claim 8, characterized in that: In step S3, the D10 of the highly tapped and highly dispersible ultrafine silver powder is 0.310-0.350 um, the D50 is 0.74-0.96 um, the D90 is 1.51-2.10, and the tap density is 4.6-5.6 g / cm 3 , the ignition reduction is 0.80~1.00%.

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