A method for synthesizing submicron-sized flake-shaped silver powder

Abstract

This invention discloses a method for synthesizing submicron-sized flake-like silver powder, comprising the following steps: S1, preparing a silver nitrate solution using silver nitrate and a solvent selected from one or more of ethylene glycol, glycerol, N,N-dimethylformamide, n-octanol, and n-heptol; S2, adding a dispersant and a flake-forming agent to the silver nitrate solution; S3, carrying out a reduction reaction in a sealed reactor; S4, post-processing the reaction solution to obtain silver powder. This invention employs a one-step solvothermal method, which is simple to operate. The solvent simultaneously acts as a reducing agent, eliminating the need for additional reducing agents, thus reducing the introduction of exogenous impurities. The product has high purity, regular morphology, and is entirely submicron-sized flake-like silver powder with a particle size of 200-600 nm. This invention also boasts high silver source utilization, with a yield exceeding 95%.

Description

Technical Field

[0001] This invention relates to a method for synthesizing silver powder, specifically a method for synthesizing submicron-sized flake-shaped silver powder. Background Technology

[0002] Silver powder, due to its excellent electrical and thermal conductivity and oxidation resistance, is widely used in the electronics industry. However, the requirements for the morphology and size of the silver powder vary depending on the application. When flake-shaped silver powder is stacked, the particles form line and surface contacts, resulting in a larger contact area compared to the point contacts between block or near-spherical ultrafine silver powder particles. Therefore, it exhibits lower packing resistivity and better conductivity. In silver paste systems, flake-shaped silver powder is further divided into micron-sized and submicron-sized particles. Submicron-sized flake-shaped silver powder (particle size 100nm~1μm) is more suitable for high-precision, high-efficiency screen printing.

[0003] Currently, the main methods for preparing flake silver powder include ball milling, photo-induced method, template method, and chemical reduction method. Among them, ball milling requires first using a reduction method to prepare micro-nano silver particles of suitable particle size, and then obtaining flake silver powder through mechanical ball milling. However, mechanical ball milling has many variables, and it is difficult to control the flake formation effect of different batches of silver powder. Impurities are easily introduced during the ball milling process, and the powder may be cold-welded, making it difficult to meet the product particle size standard.

[0004] Invention patent CN101947655A discloses a method for preparing triangular silver nanosheets, which uses a dual reduction system with sodium borohydride and trisodium citrate as reducing agents, polyvinylpyrrolidone as a surfactant and protective agent, and finally adds hydrogen peroxide to regulate the crystal morphology to obtain triangular silver nanosheets with a particle size of 50nm to 120nm. However, this method has complicated steps, and the reaction rate of sodium borohydride as a reducing agent is too fast, making the reaction process difficult to control. Summary of the Invention

[0005] To overcome the above-mentioned shortcomings, the present invention aims to provide a method for synthesizing submicron-sized flake silver powder. This method introduces fewer exogenous impurities, produces products with high purity, controllable morphology, and uses simple process equipment.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a method for synthesizing submicron-sized flake-like silver powder, comprising the following steps:

[0007] S1. Prepare a silver nitrate solution by mixing silver nitrate with a solvent, wherein the solvent is selected from one or more of ethylene glycol, glycerol, N,N-dimethylformamide, n-octanol, and n-heptol.

[0008] S2. Add dispersant and crystal modifier to silver nitrate solution;

[0009] S3. The reduction reaction is carried out in a closed reactor.

[0010] S4. Post-process the reaction solution to obtain silver powder.

[0011] Furthermore, in S1, the concentration of the silver nitrate solution is 40–500 mmol / L.

[0012] Furthermore, in S2, the dispersant is selected from one or more of oleic acid, linoleic acid, polyvinylpyrrolidone, and methyl oleate.

[0013] Furthermore, in S2, based on 100 parts by mass of silver nitrate, the dispersant is 5 to 100 parts.

[0014] Furthermore, in S2, the wafer control agent is hydrogen peroxide, and based on 100 parts by mass of silver nitrate, the wafer control agent is 1 to 100 parts.

[0015] Further, in S2, after adding the dispersant and wafer regulator, stir for 1 to 5 minutes.

[0016] Furthermore, in S3, the reaction temperature of the reaction solution in the reactor is 130–170°C.

[0017] Furthermore, in S3, the reaction time of the reaction solution in the reactor is 8–16 hours.

[0018] Furthermore, in S4, the post-treatment of the reaction solution includes the following steps:

[0019] S41. After the reaction solution is removed, it settles naturally. The supernatant is discarded, and the reaction product is retained.

[0020] S42. Add deionized water to the reaction product, ultrasonically stir and wash, and discard the supernatant.

[0021] S43. Wash the reaction product with ethanol and discard the supernatant.

[0022] S44. The reaction product is dried in a vacuum oven and then ground to obtain silver powder.

[0023] The beneficial effects of this invention are:

[0024] 1) This invention uses a one-step solvothermal method, which is simple to operate. The solvent also acts as a reducing agent, so there is no need to add an additional reducing agent, which reduces the amount of exogenous impurities introduced. The product has high purity and regular morphology. All of them are submicron-sized flake silver powder with a particle size of 200-600nm.

[0025] 2) The present invention has a high silver source utilization rate, with a yield of over 95%. Attached Figure Description

[0026] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a scanning electron microscope image of the silver powder prepared in Example 1 of the present invention;

[0029] Figure 2 This is a scanning electron microscope image of the silver powder prepared in Example 2 of the present invention;

[0030] Figure 3 This is a scanning electron microscope image of the silver powder prepared in Example 3 of the present invention;

[0031] Figure 4 This is a scanning electron microscope image of the silver powder prepared in Example 4 of the present invention;

[0032] Figure 5 This is a scanning electron microscope image of the silver powder prepared in Comparative Example 1 of the present invention;

[0033] Figure 6 This is a scanning electron microscope image of the silver powder prepared in Comparative Example 2 of the present invention;

[0034] Figure 7 This is a flowchart of the method for synthesizing submicron-sized flake silver powder according to the present invention. Detailed Implementation

[0035] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] See appendix Figure 7 As shown, a method for synthesizing submicron-sized flake-like silver powder includes the following steps:

[0037] S1. Prepare a silver nitrate solution using silver nitrate and a solvent selected from one or more of ethylene glycol, glycerol, N,N-dimethylformamide, n-octanol, and n-heptanol. The concentration of the silver nitrate solution is 40–500 mmol / L. For example, the concentrations of the silver nitrate solution are 40 mmol / L, 70 mmol / L, 100 mmol / L, 200 mmol / L, 300 mmol / L, 400 mmol / L, and 500 mmol / L.

[0038] In this invention, the solvent in the reaction is also a reducing agent, eliminating the need for additional reducing agents, resulting in fewer impurities introduced during the preparation process and higher product purity. The solvent can also be common organic solvents such as aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, alcohols, ethers, esters, ketones, etc.

[0039] S2. Add dispersant and wafer regulator to silver nitrate solution. Stir for 1-5 minutes after adding dispersant and wafer regulator to ensure that dispersant and wafer regulator are fully dissolved in silver nitrate solution.

[0040] The dispersant is selected from one or more of oleic acid, linoleic acid, polyvinylpyrrolidone, and methyl oleate. Based on 100 parts by mass of silver nitrate, the dispersant comprises 5 to 100 parts. The wafer control agent is hydrogen peroxide, and based on 100 parts by mass of silver nitrate, the wafer control agent comprises 1 to 100 parts. For example, the dispersant comprises 5 parts, 10 parts, 30 parts, 50 parts, 80 parts, and 100 parts, and the wafer control agent comprises 1 part, 10 parts, 30 parts, 50 parts, 80 parts, and 100 parts.

[0041] S3. The reduction reaction is carried out in a reactor; the reaction temperature in the reactor is 130–170°C, and the reaction time is 8–16 h. For example, the reaction temperature in the reactor is 130°C, 140°C, 150°C, 160°C, or 170°C; and the reaction time is 8 h, 10 h, 12 h, 14 h, or 16 h.

[0042] S4. Post-treatment reaction solution to obtain silver powder. The post-treatment reaction solution includes the following steps:

[0043] S41. After the reaction solution is removed, it settles naturally. The supernatant is discarded, and the reaction product is retained.

[0044] S42. Add deionized water to the reaction product and ultrasonically stir and wash for 10-20 minutes. Discard the supernatant and repeat the washing process three times.

[0045] S43. Add ethanol to the reaction product and wash for 10-20 minutes. Discard the supernatant and repeat the washing process three times.

[0046] S44. The reaction product is placed in a vacuum oven and dried for 6-10 hours. Finally, the dried sample is pulverized to obtain silver powder.

[0047] Example

[0048] The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized by conventional methods and can be used directly without further processing. The instruments used in the examples are also commercially available.

[0049] Example 1

[0050] S1. Preparation of the reaction system solution: Measure 60 mL of N,N-dimethylformamide into a 100 mL beaker, add 0.41 g of silver nitrate, and stir until completely dissolved;

[0051] S2. Weigh 0.14g of polyvinylpyrrolidone and add it to the above silver nitrate solution. Stir until completely dissolved, and finally add 0.1mL of hydrogen peroxide (30%). Mix and stir for 5min.

[0052] S3. Pour the reaction system into the reactor, set the temperature to 130℃, and the reaction time to 8 hours;

[0053] S4. After the reaction is complete, cool the reactor to below 40°C, open the reactor, remove the reaction solution, and allow it to settle naturally. Discard the supernatant, leaving the reaction product. Sonicate the reaction product with 50 mL of deionized water for 15 min. After complete sedimentation, discard the supernatant and repeat the washing process three times. Then, sonicate the product with 50 mL of anhydrous ethanol for 15 min. After complete sedimentation, discard the supernatant and repeat the washing process three times. After washing, place the product in a 45°C vacuum oven to dry for 6 hours. After drying, grind and crush the sample to obtain 0.25 g of well-dispersed submicron-sized flake silver powder, with a yield of 96.02%. See Appendix. Figure 1 As shown, the morphology was tested using scanning electron microscopy, and the particle size was mainly distributed in the range of 200–600 nm.

[0054] Example 2

[0055] S1. Preparation of the reaction system solution: Measure 60 mL of ethylene glycol into a 100 mL beaker, add 0.82 g of silver nitrate, and stir until completely dissolved;

[0056] S2. Weigh 0.28g of oleic acid and add it to the above solution. Stir for 3 minutes, and finally add 0.2mL of hydrogen peroxide (30%). Mix and stir for 5 minutes.

[0057] S3. Pour the reaction system into the reactor, set the temperature to 140℃, and the reaction time to 8 hours;

[0058] S4. After the reaction is complete, cool the reactor to below 40°C, open the reactor, remove the reaction solution and allow it to settle naturally. Discard the supernatant, leaving the reaction product. Sonicate the product with 50 mL of deionized water for 15 min. After complete sedimentation, discard the supernatant and repeat the washing process three times. Then, sonicate the product with 50 mL of anhydrous ethanol for 15 min. After complete sedimentation, discard the supernatant and repeat the washing process three times. After washing, place the product in a 45°C vacuum oven to dry for 6 hours. After drying, grind and crush the sample to obtain 0.50 g of well-dispersed submicron-sized flake silver powder, with a yield of 96.02%. See Appendix. Figure 2 As shown, the morphology was tested using scanning electron microscopy, and the particle size was mainly distributed in the range of 200–600 nm.

[0059] Example 3

[0060] S1. Preparation of the reaction system solution: Measure 60 mL of glycerol into a 100 mL beaker, add 1.64 g of silver nitrate, and stir until completely dissolved;

[0061] S2. Weigh 0.56g of methyl oleate and add it to the above silver nitrate solution. Stir for 3 minutes, and finally add 0.4mL of hydrogen peroxide (30%). Mix and stir for 5 minutes.

[0062] S3. Finally, pour the reaction system into the reactor, set the temperature to 150℃, and the reaction time to 10 hours.

[0063] S4. After the reaction is complete, cool the reactor to below 40°C, open the reactor, remove the reaction solution, and allow it to settle naturally. Discard the supernatant, leaving the reaction product. Sonicate the product with 50 mL of deionized water for 15 min. After complete sedimentation, discard the supernatant and repeat the washing three times. Then sonicate with 50 mL of anhydrous ethanol for 15 min. After complete sedimentation, discard the supernatant and repeat the washing three times. After washing, place the product in a 45°C vacuum oven to dry for 6 hours. After drying, grind and crush the sample to obtain 1.01 g of well-dispersed submicron-sized flake silver powder. Yield: 96.98%. See Appendix. Figure 3 As shown, the morphology was tested using scanning electron microscopy, and the particle size was mainly distributed in the range of 200–600 nm.

[0064] Example 4

[0065] S1. Preparation of the reaction system solution: Measure 60 mL of n-octanol into a 100 mL beaker, add 3.28 g of silver nitrate, and stir until completely dissolved;

[0066] S2. Weigh 1.12g of linoleic acid and add it to the above solution. Stir for 3 minutes, and finally add 0.8mL of hydrogen peroxide (30%). Mix and stir for 5 minutes.

[0067] S3. Pour the reaction system into the reactor, set the temperature to 160℃, and the reaction time to 12 hours;

[0068] S4. After the reaction is complete, cool the reactor to below 40°C, open the reactor, remove the reaction solution, and allow it to settle naturally. Discard the supernatant, leaving the reaction product. Sonicate the product with 50 mL of deionized water for 15 min. After complete sedimentation, discard the supernatant and repeat the washing process three times. Then, sonicate the product with 50 mL of anhydrous ethanol for 15 min. After complete sedimentation, discard the supernatant and repeat the washing process three times. After washing, place the product in a 45°C vacuum oven to dry for 6 hours. After drying, grind and crush the sample to obtain 1.99 g of well-dispersed submicron-sized flake silver powder, with a yield of 95.54%. See Appendix. Figure 4 As shown, the morphology was tested using scanning electron microscopy, and the particle size was mainly distributed in the range of 200–600 nm.

[0069] Comparative Example 1

[0070] S1. Preparation of the reaction system solution: Measure 60 mL of methanol into a 100 mL beaker, add 3.28 g of silver nitrate, and stir until completely dissolved;

[0071] S2. Add 7.31g of fructose and stir until completely dissolved. Weigh 1.12g of linoleic acid and add it to the above silver nitrate solution. Mix and stir for 5 minutes until homogeneous.

[0072] S3. Pour the reaction system into the reactor, set the temperature to 140℃, and the reaction time to 6 hours;

[0073] S4. After the reaction is complete, cool the reactor to below 40°C, open the reactor, remove the reaction solution and allow it to settle naturally. Discard the supernatant, leaving the reaction product. Sonicate the product with 50 mL of deionized water for 15 min. After complete sedimentation, discard the supernatant and repeat the washing three times. Then sonicate with 50 mL of anhydrous ethanol for 15 min. After complete sedimentation, discard the supernatant and repeat the washing three times. After washing, place the product in a 45°C vacuum oven to dry for 6 hours. After drying, grind and crush the sample to obtain 1.69 g of nano-sized silver powder, with a yield of 81.14%. See Appendix. Figure 5 As shown, the morphology was tested using a scanning electron microscope, revealing that the silver powder had a wide particle size distribution and poor dispersion.

[0074] Comparative Example 2

[0075] S1. Preparation of the reaction system solution: Measure 60 mL of water into a 100 mL beaker, add 3.28 g of silver nitrate, and stir until completely dissolved;

[0076] S2. Add 7.31g of glucose and stir until completely dissolved. Weigh 2.24g of ethyl oleate and add it to the above solution. Stir for 3 minutes. Finally, add 0.8mL of hydrogen peroxide (30%) and stir for 5 minutes until well mixed.

[0077] S3. Finally, pour the reaction system into the reactor, set the temperature to 160℃, and the reaction time to 8 hours.

[0078] S4. After the reaction is complete, cool the reactor to below 40°C, open the reactor, remove the reaction solution, and allow it to settle naturally. Discard the supernatant, leaving the reaction product. Sonicate the product with 50 mL of deionized water for 15 min. After complete sedimentation, discard the supernatant and repeat the washing process three times. Then, sonicate the product with 50 mL of anhydrous ethanol for 15 min. After complete sedimentation, discard the supernatant and repeat the washing process three times. After washing, place the product in a 45°C vacuum oven to dry for 6 hours. After drying, grind and crush the sample to obtain 1.89 g of nano-sized silver powder, with a yield of 90.74%. See Appendix. Figure 6 As shown, the morphology was tested using a scanning electron microscope, revealing that the silver powder had a wide particle size distribution and poor dispersion.

[0079] From the experimental data and scanning electron microscope images of Examples 1-4 and Comparative Examples 1-2, it can be seen that:

[0080] 1) The preparation process of this invention introduces fewer impurities, resulting in high product purity;

[0081] 2) The particle size of the flake silver powder of the present invention is controllable, and the particle size is mainly distributed in the range of 200-600 nm;

[0082] 3) The present invention has a high silver source utilization rate, with a yield of over 95%.

[0083] Therefore, this invention provides a method for synthesizing submicron-sized flake silver powder with minimal introduction of exogenous impurities, high product purity, controllable morphology, and simple process equipment.

[0084] In addition, information on the reagents used in this invention is shown in the table below:

[0085]

[0086] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for synthesizing sub-micron flaky silver powder, characterized in that, The method comprises the following steps: S1, preparing a silver nitrate solution by using silver nitrate and a solvent selected from one or more of ethylene glycol, glycerol, N,N-dimethylformamide, n-octanol and n-heptanol; S2, adding a dispersant and a wafer control agent into the silver nitrate solution, the wafer control agent being hydrogen peroxide, and the wafer control agent being 1-100 parts by mass based on 100 parts of silver nitrate; S3, performing a reduction reaction in a closed reaction kettle; S4, post-treating the reaction solution to obtain silver powder.

2. The method for synthesizing submicron-sized flake-like silver powder according to claim 1, characterized in that, In S1, the concentration of the silver nitrate solution is 40-500 mmol / L.

3. The method for synthesizing submicron-sized flake-like silver powder according to claim 1, characterized in that, In S2, the dispersant is selected from one or more of oleic acid, linoleic acid, polyvinylpyrrolidone and methyl oleate.

4. The method for synthesizing submicron-sized flake-like silver powder according to claim 1, characterized in that, In S2, the dispersant is 5-100 parts by mass based on 100 parts of silver nitrate.

5. The method for synthesizing submicron-sized flake-like silver powder according to claim 1, characterized in that, In S2, the reaction solution is stirred for 1-5 minutes after the dispersant and the wafer control agent are added.

6. The method for synthesizing submicron-sized flake-like silver powder according to claim 1, characterized in that, In S3, the reaction temperature of the reaction solution in the reaction kettle is 130-170°C.

7. The method for synthesizing submicron-sized flake-like silver powder according to claim 1, characterized in that, In S3, the reaction time of the reaction solution in the reaction kettle is 8-16 hours.

8. The method for synthesizing submicron-sized flake-like silver powder according to claim 1, characterized in that, In S4, the post-treatment of the reaction solution comprises the following steps: S41, taking out the reaction solution and allowing it to naturally settle, discarding the supernatant and leaving the reaction product; S42, adding deionized water to the reaction product and stirring it under ultrasonic waves to clean it, and discarding the supernatant; S43, adding ethanol to the reaction product to clean it, and discarding the supernatant; S44, placing the reaction product in a vacuum oven to dry it, and grinding and crushing it to obtain silver powder.

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