Silver powder and preparation method thereof

Abstract

The invention belongs to the technical field of metal powder, and particularly relates to silver powder and a preparation method thereof. The preparation method of the silver powder comprises the steps that under illumination, a reduction solution is added into a silver ion oxidation solution for a reaction, and the reduction solution contains a quantum dot material. According to the method, the quantum dot material added into the reduction solution serves as a light-sensitive material, electron holes are generated under illumination, oxidation-reduction reaction is participated, reaction energy barriers are reduced, and the particle size uniformity of the silver powder prepared through the liquid-phase reduction method is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal powders, and in particular relates to silver powder and a preparation method thereof. Background Art

[0002] Silver has excellent electrical and thermal conductivity, unique antibacterial properties, catalytic properties and chemical stability, and is widely used in electronics, photovoltaics, biomedicine and chemical industries. In recent years, with the rapid development of electronic technology, the research and development of electronic materials has also seen unprecedented development. Conductive paste is a very important branch of electronic materials, among which conductive silver paste has attracted much attention due to its many excellent properties. For example, a large amount of silver paste is used in the production of solar cell modules, sheet (or round) ceramic capacitors and other electronic components, automotive glass heating wires, etc.

[0003] The morphology, dispersibility, particle size, and tap density of silver powder have an important influence on the usability of silver paste. There are many methods for preparing silver powder, such as chemical reduction, electrochemical deposition, electrolysis, sputtering, vibration ball milling, sol-gel method, etc. At present, chemical reduction is the most common method for preparing micron-level ultrafine silver powder. Usually, photovoltaic silver paste and high-end electronic silver paste require silver powder with good dispersibility and uniform particle size. Therefore, the technical key to producing silver powder is how to control its particle size, particle size distribution and morphology during mass production. Summary of the invention

[0004] The present invention is based on the inventor's discovery and understanding of the following facts and problems:

[0005] At present, many researchers have used liquid phase chemical reduction to prepare a variety of silver powders, including spherical or quasi-spherical, flake, and linear. However, the silver powder prepared by this method has poor dispersibility, rough surface, wide particle size distribution, and poor use effect.

[0006] The present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, an embodiment of the present invention provides a method for preparing silver powder, which is simple, efficient and easy to operate, and the prepared silver powder has better particle size uniformity, and the conductive paste prepared with the silver powder has higher conductivity.

[0007] A method for preparing silver powder according to an embodiment of the present invention comprises: adding a reducing solution into a silver ion oxidation solution for reaction under light, wherein the reducing solution contains a quantum dot material.

[0008] The advantages and technical effects brought by the preparation method of the silver powder of the embodiment of the present invention are as follows: 1. In the method of the embodiment of the present invention, quantum dot material is introduced into the reducing solution. As a photosensitive material, it generates electron holes under light and participates in the redox reaction, which can reduce the reaction energy barrier and improve the uniformity of the silver powder prepared by the liquid phase reduction method; 2. In the method of the embodiment of the present invention, the introduced quantum dot material is used as a nucleation site. After the silver ions are reduced, they preferentially nucleate into elemental silver on the surface of the quantum dots and finally grow into silver particles, which further improves the particle size uniformity of the silver powder; 3. The method of the embodiment of the present invention is simple, efficient, easy to operate, and suitable for promotion and application in industrial production.

[0009] In some embodiments, the quantum dot material includes at least one of CdTe or CdS; and / or the reducing solution also includes sodium hypophosphite and a surfactant, and the surfactant includes at least one of sodium dodecylbenzene sulfonate, polyethylene glycol or polyvinyl pyrrolidone.

[0010] In some embodiments, the concentration of sodium hypophosphite in the reducing solution is 0.3-1.2 mol / L, the concentration of the surfactant is 1-10 g / L, and the concentration of the quantum dot material is 1-20 g / L.

[0011] In some embodiments, the silver ion oxidizing solution comprises silver nitrate, nitric acid and sodium nitrate.

[0012] In some embodiments, the concentration of silver nitrate in the silver ion oxidation solution is 0.3-1.2 mol / L, the concentration of nitric acid is 1-20 g / L, and the concentration of sodium nitrate is 0.02-0.1 mol / L.

[0013] In some embodiments, the molar ratio of hypophosphite in the reducing solution to silver ions in the silver ion oxidizing solution is 0.8-1.2:1.

[0014] In some embodiments, the intensity of the light is 80-120 mW / cm 2 ; and / or, the reaction temperature is 20 to 30°C and the reaction time is 20 to 50 min.

[0015] In some embodiments, the preparation method further comprises performing centrifugal cleaning and drying after the reaction is completed.

[0016] The silver powder provided in the embodiment of the present invention is prepared by the above-mentioned preparation method.

[0017] The advantages and technical effects brought by the silver powder of the embodiment of the present invention are that the silver powder of the embodiment of the present invention is prepared by the above method, has a uniform particle size, and can effectively improve the conductivity of the conductive paste when used in the preparation of conductive paste in the field of photovoltaic and electronic devices.

[0018] In some embodiments, the particle size D50 of the silver powder is 0.8-3 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a SEM image of the silver powder prepared in Example 1 of the present invention;

[0020] Figure 2 is a particle size distribution diagram of the silver powder prepared in Example 1 of the present invention;

[0021] Figure 3 is a particle size distribution diagram of the silver powder prepared in Example 2 of the present invention;

[0022] Figure 4 is a particle size distribution diagram of the silver powder prepared in Example 3 of the present invention;

[0023] Figure 5 3 is a particle size distribution diagram of the silver powder prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0024] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0025] A method for preparing silver powder according to an embodiment of the present invention comprises: adding a reducing solution into a silver ion oxidation solution for reaction under light, wherein the reducing solution contains a quantum dot material.

[0026] In the method for preparing silver powder of the embodiment of the present invention, quantum dot material is introduced into the reducing solution. As a photosensitive material, the quantum dot material generates electron holes under light and participates in the redox reaction, which can reduce the reaction energy barrier and improve the uniformity of the silver powder prepared by the liquid phase reduction method. The introduced quantum dot material serves as a nucleation site, and the silver ions are preferentially nucleated into elemental silver on the surface of the quantum dots after being reduced, and finally grow into silver particles, which further improves the particle size uniformity of the silver powder. The method is simple, efficient, easy to operate, and suitable for promotion and application in industrial production.

[0027] In some embodiments, preferably, the quantum dot material includes at least one of CdTe or CdS; and / or, the reducing solution further includes sodium hypophosphite and a surfactant, and the surfactant includes at least one of sodium dodecylbenzene sulfonate, polyethylene glycol or polyvinyl pyrrolidone. Further preferably, the concentration of sodium hypophosphite in the reducing solution is 0.3-1.2 mol / L, the concentration of the surfactant is 1-10 g / L, and the concentration of the quantum dot material is 1-20 g / L.

[0028] In the embodiment of the present invention, the quantum dot material serves as the nucleation site of silver and mainly affects the particle size of the silver powder. The concentration of the quantum dot material in the reducing solution is optimized to ensure that the prepared silver powder has a suitable particle size. If the concentration of the quantum dot material is too low, the silver powder particle size will be too large, and even the reaction cannot be completely carried out. If the concentration of the quantum dot material is too high, the silver powder particle size will be too small, and even nano-scale silver powder will be formed, which is not conducive to the preparation of silver powder with better particle size uniformity.

[0029] In some embodiments, preferably, the silver ion oxidation solution comprises silver nitrate, nitric acid and sodium nitrate. Further preferably, the concentration of silver nitrate in the silver ion oxidation solution is 0.3-1.2 mol / L, the concentration of nitric acid is 1-20 g / L, and the concentration of sodium nitrate is 0.02-0.1 mol / L.

[0030] In some embodiments, preferably, the molar ratio of hypophosphite in the reducing solution to silver ions in the silver ion oxidizing solution is 0.8-1.2:1.

[0031] In the embodiment of the present invention, the dosage ratio of the reducing solution and the silver ion oxidation solution is preferably selected. If the molar ratio of the hypophosphite in the reducing solution is too high, reagent waste will be caused and the difficulty of sample cleaning will be increased; if the molar ratio of the hypophosphite in the reducing solution is too low, the reaction will be incomplete and silver ions will exist in the solution.

[0032] In some embodiments, preferably, the intensity of the light is 80 to 120 mW / cm 2 ; and / or, the reaction temperature is 20 to 30°C and the reaction time is 20 to 50 min.

[0033] In the embodiment of the present invention, the intensity of light mainly affects the growth rate of the silver powder. The intensity of light is optimized to ensure that the silver powder grows at an appropriate speed, which is convenient for controlling its morphology. If the intensity of light is too low, the growth rate of the silver powder will be reduced, making the morphology of the silver powder difficult to control. If the intensity of light is too high, the growth rate of the silver powder will be too fast, defects will easily occur, and the production energy consumption will be too high, thereby increasing the manufacturing cost of the silver powder.

[0034] In some embodiments, preferably, the reducing solution is poured into or flows into the silver ion oxidation solution at a flow rate of 10 to 100 L / min. Further preferably, the reducing solution is added to the silver ion oxidation solution and then stirred.

[0035] In some embodiments, preferably, the preparation method further comprises centrifuging, washing and drying after the reaction is completed.

[0036] The silver powder provided in the embodiment of the present invention is prepared by the above-mentioned preparation method.

[0037] The advantages and technical effects brought by the silver powder of the embodiment of the present invention are that the silver powder of the embodiment of the present invention is prepared by the above method, has a uniform particle size, and can effectively improve the conductivity of the conductive paste when used in the preparation of conductive paste in the field of photovoltaic and electronic devices.

[0038] In some embodiments, preferably, the particle size D50 of the silver powder is 0.8-3 μm.

[0039] The technical solution of the present invention is described in detail below in conjunction with specific embodiments and drawings.

[0040] Example 1

[0041] (1) preparing a silver ion oxidation solution: wherein the concentration of silver nitrate is 0.8 mol / L, the concentration of nitric acid is 10 g / L, and the concentration of sodium nitrate is 0.06 mol / L;

[0042] (2) preparing a reducing solution: wherein the concentration of sodium hypophosphite is 0.8 mol / L; the concentration of polyethylene glycol is 5 g / L; and the concentration of CdTe is 10 g / L;

[0043] (3) At 100 mW / cm 2 Under the light intensity of , the same volume of reducing solution was poured into the silver ion oxidation solution and allowed to stand at 25°C for 30 min;

[0044] (4) After the reaction is completed, centrifugal cleaning and drying are performed to obtain silver powder.

[0045] The silver powder obtained in this embodiment was scanned by SEM, and the results were as follows: Figure 1 As shown, the silver powder is spherical in shape and has a relatively uniform particle size.

[0046] The particle size of the silver powder obtained in this embodiment is statistically analyzed, and the particle size distribution is as follows: Figure 2 As shown, from Figure 2 It can be seen that the particle size of the silver powder prepared in this embodiment is mostly distributed between 1.058 and 2.480 μm, the particle size is nearly normally distributed, and the particle size uniformity is good.

[0047] Example 2

[0048] (1) preparing a silver ion oxidation solution: wherein the concentration of silver nitrate is 0.3 mol / L, the concentration of nitric acid is 1 g / L, and the concentration of sodium nitrate is 0.02 mol / L;

[0049] (2) preparing a reducing solution: wherein the concentration of sodium hypophosphite is 0.3 mol / L; the concentration of polyethylene glycol is 1 g / L; and the concentration of CdS is 1 g / L;

[0050] (3) At 100 mW / cm 2Under the light intensity of , the same volume of reducing solution was poured into the silver ion oxidation solution, and the reaction was stirred at 25°C for 30 minutes;

[0051] (4) After the reaction is completed, centrifugal cleaning and drying are performed to obtain silver powder.

[0052] The particle size of the silver powder obtained in this embodiment is statistically analyzed, and the particle size distribution is as follows: Figure 3 As shown, from Figure 3 It can be seen that the particle size of the silver powder prepared in this embodiment is mostly distributed between 1 and 5 μm, with good uniformity.

[0053] Example 3

[0054] (1) preparing a silver ion oxidation solution: wherein the concentration of silver nitrate is 1.2 mol / L, the concentration of nitric acid is 20 g / L, and the concentration of sodium nitrate is 0.1 mol / L;

[0055] (2) preparing a reducing solution: wherein the concentration of sodium hypophosphite is 1.2 mol / L; the concentration of polyethylene glycol is 10 g / L; and the concentration of CdTe is 20 g / L;

[0056] (3) At 100 mW / cm 2 Under the light intensity of , the same volume of reducing solution was flowed into the silver ion oxidation solution at a flow rate of 50 L / min, and the reaction was stirred at 25°C for 30 min;

[0057] (4) After the reaction is completed, centrifugal cleaning and drying are performed to obtain silver powder.

[0058] The particle size of the silver powder obtained in this embodiment is statistically analyzed, and the particle size distribution is as follows: Figure 4 As shown, from Figure 4 It can be seen that the particle size of the silver powder prepared in this embodiment is mostly distributed between 0.758 and 0.987 μm, with good uniformity.

[0059] Comparative Example 1

[0060] The preparation method of this comparative example is the same as that of Example 1, except that in step (2), the prepared reducing solution does not contain CdTe.

[0061] The particle size of the silver powder obtained in this comparative example was statistically analyzed, and the particle size distribution was as follows: Figure 5 As shown, from Figure 5 It can be seen that the particle size distribution of the silver powder prepared in this comparative example is relatively wide and the uniformity is poor.

[0062] The tap density of the silver powders obtained in Examples 1 to 3 and Comparative Example 1 was tested with reference to standard GB / T 5162-2021. The results are shown in Table 1.

[0063] Table 1

[0064] <![CDATA[Tap density (g / cm 3 )]]> Example 1 5.1 Example 2 4.9 Example 3 4.6 Comparative Example 1 3.3

[0065] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0066] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A method for preparing silver powder, characterized in that: include: Under light, a reducing solution is added into a silver ion oxidation solution for reaction, wherein the reducing solution contains a quantum dot material.

2. The method for preparing silver powder according to claim 1, characterized in that: The quantum dot material includes at least one of CdTe and CdS; and / or the reducing solution further includes sodium hypophosphite and a surfactant, and the surfactant includes at least one of sodium dodecylbenzene sulfonate, polyethylene glycol or polyvinyl pyrrolidone.

3. The method for preparing silver powder according to claim 2, characterized in that: The concentration of sodium hypophosphite in the reducing solution is 0.3-1.2 mol / L, the concentration of the surfactant is 1-10 g / L, and the concentration of the quantum dot material is 1-20 g / L.

4. The method for preparing silver powder according to claim 1, characterized in that: The silver ion oxidation solution contains silver nitrate, nitric acid and sodium nitrate.

5. The method for preparing silver powder according to claim 4, characterized in that: The concentration of silver nitrate in the silver ion oxidation solution is 0.3-1.2 mol / L, the concentration of nitric acid is 1-20 g / L, and the concentration of sodium nitrate is 0.02-0.1 mol / L.

6. The method for preparing silver powder according to any one of claims 2 to 5, characterized in that: The molar ratio of the hypophosphite in the reducing solution to the silver ions in the silver ion oxidizing solution is 0.8-1.2:

1.

7. The method for preparing silver powder according to claim 1, characterized in that: The intensity of the light is 80-120 mW / cm 2 ; and / or, the reaction temperature is 20 to 30°C and the reaction time is 20 to 50 min.

8. The method for preparing silver powder according to claim 1, characterized in that: The preparation method further comprises performing centrifugal cleaning and drying after the reaction is completed.

9. A silver powder, characterized in that: The preparation method is described in any one of claims 1 to 8.

10. The silver powder according to claim 9, characterized in that The particle size D50 of the silver powder is 0.8-3 μm.

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