Silver particles, method for their production and use thereof

Abstract

The application discloses silver particles and a preparation method and application thereof. The preparation method comprises the following steps: S1: dispersing a silver source in an alcohol amine solution, and adding a dispersing agent to form a bottom solution; a molar ratio of silver ions in the silver source to alcohol amine compounds in the alcohol amine solution is 1:0.05-5; S2: performing a hydrothermal reaction on the bottom solution and an organic amine solution to prepare the silver particles; a molar ratio of silver ions in the silver source to organic amine compounds in the organic amine solution is 1:0.005-0.15. The size and particle diameter of the silver particles are controlled by controlling the amount of the alcohol amine solution and the organic amine solution, so that small particle diameter silver particles are filled into the gaps between large particle diameter silver particles, thereby improving the tap density of the silver powder.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal powder preparation, in particular to a silver particle and a preparation method and application thereof. BACKGROUND

[0002] Silver paste prepared by the spherical silver powder has the advantages of good fluidity, easy printing, small sintering shrinkage, and dense film formed, and is widely used in various fields. The most commonly used method for preparing spherical silver powder is liquid phase chemical reduction method, which usually mixes reducing liquid and oxidizing liquid, and reduces silver ions to elemental silver through oxidation-reduction reaction. In this synthesis process, researchers mainly control the rate of oxidation-reduction and the growth direction of silver powder by controlling the type of reducing agent, the amount of dispersing agent, the pH of the reaction process, the reaction temperature and other conditions, so as to control the particle size and morphology of silver powder. However, in the actual research process, it is found that this method has limited control over particle size, especially it is difficult to synthesize small particle size and uniformly dispersed silver powder (≤3 μm), and the particle size and morphology of the silver powder synthesized based on this method are not uniform.

[0003] In the existing synthesis technology, the particle size of silver powder is adjusted through three processes of preparation of crystal seeds, preparation of silver-containing precursor deposition, and oxidation-reduction preparation of nano-silver colloidal particles, and different solutions such as oxidizing solution, reducing solution, dispersing agent solution, complexing agent, and precipitating agent need to be configured in multiple steps. The synthesis process is complex, time-consuming, and leads to high production cost. SUMMARY

[0004] The present application aims to at least solve one of the above technical problems in the prior art. To this end, the purpose of the present application is to provide a silver particle and a preparation method and application thereof.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present application is:

[0006] In a first aspect of the present application, a preparation method of a silver particle is provided, comprising the following steps:

[0007] S1: dispersing a silver source in an alcohol amine solution to form a bottom solution after adding a dispersing agent; the molar ratio of silver ions in the silver source to alcohol amine compounds in the alcohol amine solution is 1:0.05-5;

[0008] S2: hydrothermal reaction of the bottom solution with an organic amine solution to obtain the silver particle; the molar ratio of silver ions in the silver source to organic amine compounds in the organic amine solution is 1:0.005-0.15.

[0009] In the present application, the number of silver particles of different sizes can be adjusted by controlling the amount of different reducing agents in the preparation process. Small-sized silver particles are generated by the reaction of silver source and alcohol amine solution, and large-sized silver particles are generated by the reaction of silver source and organic amine solution. The addition of dispersant before the generation of large-sized silver particles is beneficial to improve the dispersion degree of small-sized silver particles, so that they can be effectively filled into the gap of large-sized silver particles during the generation of large-sized silver particles. The proportion of large-sized and small-sized silver particles in the product can be matched with each other, thereby improving the tap density of the packed silver particles. If the amount of alcohol amine solution in the preparation process is too large, the product will be agglomerated. If the amount of organic amine added is too large, the maximum diameter (D100) of silver particles will be significantly increased, which is not conducive to improving the tap density of the packed silver particles.

[0010] In some embodiments of the present application, the molar ratio of silver ions in the silver source to alcohol amine compounds in the alcohol amine solution is 1:0.5-5, such as 1:1-4.5, 1:1-4.0, 1:1-3.5, 1:1-3.0.

[0011] In some embodiments of the present application, the molar ratio of silver ions in the silver source to organic amine compounds in the organic amine solution is 1:0.01-0.15, such as 1:0.02-0.13, 1:0.03-0.12, 1:0.04-0.11, 1:0.05-0.10, 1:0.06-0.09, etc.

[0012] In some embodiments of the present application, the mass ratio of silver atoms in the silver source to dispersant is 1:0.01-10, such as 1:0.05-8, 1:0.1-7, 1:0.5-6, 1:1-5, etc.

[0013] In some embodiments of the present application, the molar concentration of silver source in the base solution is 0.008-5 mol / L, such as 0.1 mol / L, 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L, 4.5 mol / L.

[0014] In some embodiments of the present application, the pH of the organic amine solution is 9-14, such as 10-13, 10.5, 11, 11.5, 12, 12.5, etc.

[0015] In some embodiments of the present application, at least one of pH adjusters such as sodium carbonate, sodium hydroxide, ammonia, monoethanolamine, and triethanolamine can be used to adjust the pH of the organic amine solution.

[0016] In some embodiments of the present application, the silver source is a soluble silver salt, including at least one of silver nitrate, silver perchlorate, silver acetate, silver oxalate, silver chlorate, silver hexafluorophosphate, silver tetrafluoroborate, silver hexafluoroarsenate, silver sulfate.

[0017] In some embodiments of the present application, the alcohol amine compound in the alcohol amine solution is selected from at least one of diethanolamine, methyldiethanolamine, ethanolamine, dimethylethanolamine, diglycolamine, isopropanolamine, triisopropanolamine, oleic acid diethanolamide, stearic acid diethanolamide, lauric acid diethanolamide, and octadecyl diethanolamine.

[0018] In some embodiments of the present application, the dispersing agent includes at least one of polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, sodium citrate, sodium dodecyl sulfate, cetyltrimethylammonium bromide, gelatin, methylcellulose, citric acid, Tween 60, propionic acid, octanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, acrylic acid, oleic acid, linoleic acid, arachidonic acid, and ricinoleic acid.

[0019] In some embodiments of the present application, the organic amine compound in the organic amine solution is selected from at least one of triethylamine, N-ethyldiisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, cyclohexylamine, dimethyloctylamine, dimethyldecylamine, tris(3,6-dioxaheptyl)amine, and octylamine.

[0020] In some embodiments of the present application, the temperature of the hydrothermal reaction is 70-240°C, such as 90-210°C, 90-155°C, 100-200°C, etc., and the time of the hydrothermal reaction is 0.5-12h, such as 1-10h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, etc. The hydrothermal reaction can be temperature-controlled by methods known in the art, such as placing the hydrothermal reactor in an oven. To improve the uniformity of the reaction, the hydrothermal reaction can be performed with stirring or after sufficient stirring, and the stirring rate can be controlled at 200-500rpm.

[0021] In some embodiments of the present application, the method for preparing silver particles further includes a purification treatment of the hydrothermal reaction product, and the purification treatment includes washing, drying, etc. As a drying condition, for example, 73°C can be set for 10 hours. Through the drying, a dried powder is obtained.

[0022] In a second aspect of the present application, a silver particle prepared by the method for preparing silver particles is provided.

[0023] In some embodiments of the present application, the average particle size of the silver particles is 1.00-2.20μm, such as 1.10-2.15μm, as measured by a laser diffraction particle size distribution measuring device.

[0024] In some embodiments of the present application, the particle size distribution of the silver particles satisfies the following relationships: D50 is between 0.9 and 1.7 μm, D100 is between 3.5 and 8.5 μm, and Span is between 1.8 and 2.0, as determined by a laser diffraction particle size distribution measuring device.

[0025] In some embodiments of the present application, the number of silver particles with an average particle size greater than 0.2 μm / the number of silver particles with an average particle size less than 0.2 μm is between 0.25 and 0.65, as determined by a field emission scanning electron microscope (SEM).

[0026] In some embodiments of the present application, the tap density of the silver particles is between 6.60 g / m 3 In some embodiments of the present application, the tap density of the silver particles is between 6.60 g / m 3 .

[0027] In a third aspect of the present application, a conductive silver paste is provided, comprising a conductive phase, a binding phase and a solvent, wherein the conductive phase is the above-mentioned silver particles.

[0028] In some embodiments of the present application, the binding phase is at least one of tributyl citrate and diethylene glycol butyl ether acetate. Any commonly used binding phase in the art can be used.

[0029] In some embodiments of the present application, the solvent is at least one of DBE or dimethyl silicone oil. Any commonly used solvent in the art can be used.

[0030] In a fifth aspect of the present application, the above-mentioned silver particles or conductive silver paste is used in the preparation of a solar cell or an electronic component.

[0031] In some embodiments of the present application, the solar cell further comprises a panel glass, and a coating layer prepared from the above-mentioned conductive silver paste is provided on the panel glass. The conductive silver paste of the present application can be well printed on a substrate such as a panel glass by a screen printing process.

[0032] In some embodiments of the present application, the electronic component comprises at least one of a thin film switch, a flexible printed circuit board, an electromagnetic shield, a potentiometer or a wireless radio frequency identification system. The conductive silver paste of the present application has a good application prospect in various electronic components.

[0033] The present application has the following advantages:

[0034] The preparation method of the present application controls the proportion of silver particles of different sizes by controlling the amount of alcohol amine solution and organic amine solution, controls the morphology of silver powder such as particle size distribution, fills small particle size silver particles into the gap between large particle size silver particles, and thus improves the tap density of silver powder. By optimizing the use ratio of alcohol amine solution and organic amine solution, the yield and purity of silver powder can also be improved, and the occurrence of side reactions can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 SEM image of silver powder prepared for Example 1 of the present application.

[0036] Figure 2 SEM image of silver powder prepared for Example 1 of the present application after sizing.

[0037] Figure 3 SEM image of silver powder prepared for Example 2 of the present application.

[0038] Figure 4 SEM image of silver powder prepared for Example 2 of the present application after sizing.

[0039] Figure 5 SEM image of silver powder prepared for Example 3 of the present application.

[0040] Figure 6 SEM image of silver powder prepared for Example 3 of the present application after sizing.

[0041] Figure 7 SEM image of silver powder prepared for Example 4 of the present application.

[0042] Figure 8 SEM image of silver powder prepared for Example 4 of the present application after sizing.

[0043] Figure 9 SEM image of silver powder prepared for Comparative Example 1 of the present application.

[0044] Figure 10 SEM image of silver powder prepared for Comparative Example 1 of the present application after sizing.

[0045] Figure 11 SEM image of silver powder prepared for Comparative Example 2 of the present application.

[0046] Figure 12 SEM image of silver powder prepared for Comparative Example 2 of the present application after sizing.

[0047] Figure 13 SEM image of silver powder prepared for Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0048] The application will be further described in detail by specific examples. The raw materials, reagents or devices used in the examples and comparative examples are commercially available or can be obtained by prior art methods unless otherwise specified. The test or test method is the conventional method in the art unless otherwise specified.

[0049] The materials in the following examples or comparative examples are prepared as follows:

[0050] The alcohol amine solution is prepared by selecting dimethyl ethanolamine with 98% active ingredient content;

[0051] The organic amine solution is prepared by selecting octylamine with 98% active ingredient content;

[0052] The dispersant is prepared by selecting oleic acid with 98.5% content.

[0053] The pH value regulator solution is prepared by selecting sodium hydroxide solution with 40% mass fraction.

[0054] Example 1

[0055] A silver particle is prepared in this example, and the specific process is as follows:

[0056] 2g of silver carbonate (the molar amount of silver ions is 0.0145mol) is taken into the inner container of the hydrothermal reactor, and 2.468g of dimethyl ethanolamine (the molar ratio of dimethyl ethanolamine to Ag is 2.25:1) and 0.1246g of oleic acid are added into the inner container in sequence, and the inner container is placed on a magnetic stirrer and opened at 300rpm until the stirring is uniform to obtain a bottom solution;

[0057] 0.0084g of sodium hydroxide solution is added into 0.152g of octylamine to adjust the pH value of the octylamine to 12 to obtain a reducing agent solution;

[0058] The reducing agent solution is poured into the inner container of the hydrothermal reactor and mixed with the bottom solution (the molar ratio of octylamine to Ag is 0.0798:1), and the magnetic stirring is opened at 300rpm for 10min, and then the inner container is placed in a 105℃ oven for 3h after being loaded into the hydrothermal reactor;

[0059] After the reaction, the inner container of the hydrothermal reactor is washed with deionized water and alcohol after the hydrothermal reactor is cooled to room temperature (25℃), and then dried (the drying temperature is 55℃, and the drying time is 2.5h) to obtain silver particles, and the purity of the silver powder is 99.99% and the yield is 78%.

[0060] The prepared silver powder is characterized by scanning electron microscopy (SEM), and the results are shown in Figure 1 .

[0061] The silver particles were tested for particle size distribution, with an average particle size of 1.332 μm, a D50 of 1.12 μm, a D100 of 5.3 μm, and a Span of 1.84. The tap density of the silver particles was also tested, and the results showed that the tap density of the silver particles was 6.95 g / m 3 .

[0062] Example 2

[0063] In this example, a silver particle was prepared as follows:

[0064] 2 g of silver carbonate (0.0145 mol of silver ions) was added to the inner container of the hydrothermal reactor. 4.388 g of dimethyl ethanolamine (molar ratio of dimethyl ethanolamine to Ag was 4:1) and 0.1246 g of oleic acid were added to the inner container in sequence. The inner container was placed on a magnetic stirrer and stirred at 300 rpm until the bottom liquid was uniform.

[0065] 0.0084 g of sodium hydroxide solution was added to 0.152 g of octylamine to adjust the pH of the octylamine to 12 to obtain a reducing agent solution.

[0066] The reducing agent solution was poured into the inner container of the hydrothermal reactor and mixed with the bottom liquid (molar ratio of octylamine to Ag was 0.0798:1). After stirring at 300 rpm for 10 min, the inner container was placed in a hydrothermal reactor and placed in a 105°C oven for 3 h.

[0067] After the reaction, the hydrothermal reactor was allowed to cool to room temperature (25°C). Deionized water and alcohol were added to the inner container of the hydrothermal reactor in sequence for washing, drying (drying temperature was 55°C, and drying time was 2.5 h), to obtain silver particles. The purity of the silver powder was 99.99%, and the yield was 76.60%.

[0068] The prepared silver powder was characterized by scanning electron microscopy (SEM), and the results are shown in Figure 2 .

[0069] The silver particles were tested for particle size distribution, with an average particle size of 1.332 μm, a D50 of 1.12 μm, a D100 of 5.3 μm, and a Span of 1.84. The tap density of the silver particles was also tested, and the results showed that the tap density of the silver particles was 6.95 g / m 3 .

[0070] Example 3

[0071] In this example, a silver particle was prepared as follows:

[0072] Take 2 g of silver carbonate (silver ion molar mass is 0.0145 mol) as added to the inner container of the hydrothermal reactor, 2.468 g of dimethyl ethanolamine (molar ratio of dimethyl ethanolamine to Ag is 2.25:1) and 0.0365 g of oleic acid are added to the inner container in turn, and the inner container is placed on a magnetic stirrer and started at 300 rpm until the stirring is uniform to obtain a bottom solution;

[0073] 0.0084 g of sodium hydroxide solution is added to 0.152 g of octylamine, and the pH value of the octylamine is adjusted to 12 to obtain a reducing agent solution;

[0074] The reducing agent solution is poured into the inner container of the hydrothermal kettle and mixed with the bottom solution (molar ratio of octylamine to Ag is 0.0798:1), and the inner container is placed in a 105°C oven for 3 h after being stirred at 300 rpm for 10 min.

[0075] After the reaction, the inner container of the hydrothermal kettle is washed with deionized water and alcohol, dried (drying temperature is 55°C, and drying time is 2.5 h) after the hydrothermal kettle is cooled to room temperature (25°C), and silver particles are obtained, with a silver powder purity of 99.99% and a yield of 77.80%.

[0076] The silver powder obtained is subjected to scanning electron microscopy (SEM) characterization, and the results are shown in Figure 3 .

[0077] In this example, the silver particles are tested for particle size distribution, with an average particle size of 1.87 μm, a D50 of 1.41 μm, a D100 of 8.0 μm, and a span of 1.997. At the same time, the tap density of the silver particles is tested, and the results show that the tap density of the silver particles is 6.85 g / m 3 .

[0078] Example 4

[0079] A silver particle is prepared in this example, and the specific process is as follows:

[0080] Take 2 g of silver carbonate (silver ion molar mass is 0.0145 mol) as added to the inner container of the hydrothermal reactor, 2.468 g of dimethyl ethanolamine (molar ratio of dimethyl ethanolamine to Ag is 2.25:1) and 0.1246 g of oleic acid are added to the inner container in turn, and the inner container is placed on a magnetic stirrer and started at 300 rpm until the stirring is uniform to obtain a bottom solution;

[0081] 0.0084 g of sodium hydroxide solution is added to 0.152 g of octylamine, and the pH value of the octylamine is adjusted to 12 to obtain a reducing agent solution;

[0082] The reducing agent solution was poured into the inner container of the autoclave and mixed with the bottom liquid (the molar ratio of octylamine to Ag was 0.12:1). After stirring at 300 rpm for 10 min, the inner container was placed in the autoclave and put in a 105°C oven for 3 h;

[0083] After the reaction, the inner container of the autoclave was washed with deionized water and alcohol, and dried (drying temperature: 55°C, drying time: 2.5 h) to obtain silver particles. The purity of the silver powder was 99.99%, and the yield was 76.8%.

[0084] The silver powder obtained was characterized by scanning electron microscopy (SEM), and the results are shown in Figure 4 .

[0085] In this example, the particle size distribution of the silver particles was tested, and the average particle size was 2.11 μm, D50 was 1.63 μm, D100 was 8.0 μm, and Span was 1.95. The tap density of the silver particles was also tested, and the results showed that the tap density of the silver particles was 6.62 g / m 3 .

[0086] Comparative Example 1

[0087] In this comparative example, a kind of silver particles was prepared, which was different from Example 1 in that the molar ratio of dimethyl ethanolamine to Ag was 8:1. The purity of the silver powder was 92.40%, and the yield was 72%.

[0088] The silver powder obtained was characterized by scanning electron microscopy (SEM), and the results are shown in Figure 5 .

[0089] In this example, the particle size distribution of the silver particles was tested, and the average particle size was 3.06 μm, D50 was 2.426 μm, D100 was 15.0 μm, and Span was 2.13. The tap density of the silver particles was also tested, and the results showed that the tap density of the silver particles was 5.89 g / m 3 .

[0090] It can be seen that too high a dosage of the alcohol amine solution will cause the product to be significantly agglomerated.

[0091] Comparative Example 2

[0092] In this comparative example, a kind of silver particles was prepared, which was different from Example 1 in that the molar ratio of octylamine to Ag was 0.3:1. The purity of the silver powder was 89.60%, and the yield was 68%.

[0093] The silver powder obtained was characterized by scanning electron microscopy (SEM), and the results are shown in Figure 6 .

[0094] The silver particles were tested for particle size distribution, with an average particle size of 4.83 μm, D50 of 3.298 μm, D100 of 27.0 μm, and Span of 2.45. The tap density of the silver particles was also tested, and the results showed that the tap density of the silver particles was 5.71 g / m 3 .

[0095] It can be seen that too high a dosage of the organic amine solution can cause the D100 of the silver particles to increase significantly.

[0096] Comparative Example 3

[0097] This comparative example prepared a kind of silver particles, which differed from Example 1 in that the molar ratio of dimethyl ethanolamine to Ag was 6:1, and the molar ratio of octylamine to Ag was 0.25:1. The silver powder purity was 93.30%, and the yield was 69.60%.

[0098] The prepared silver powder was subjected to scanning electron microscopy (SEM) characterization, and the results are shown in Figure 7 .

[0099] In this example, the silver particles were tested for particle size distribution, with an average particle size of 11.23 μm, D50 of 8.1 μm, D100 of 35.0 μm, and Span of 2.81. The tap density of the silver particles was also tested, and the results showed that the tap density of the silver particles was 5.32 g / m 3 .

[0100] It can be seen that when the dosages of both the alcohol amine solution and the organic amine solution are too high, the silver powder exhibits obvious agglomeration, with extremely poor dispersibility, and the average particle size, D50, and D100 of the silver particles all increase significantly.

[0101] Test Example

[0102] The silver particles prepared in the examples and comparative examples were counted, and the counting method was as follows: 1 um was taken as the scale, and the silver particles prepared in the examples and comparative examples were counted. The counting method was as follows: 9%-15% of the area of the SEM image of the silver powder was selected as the counting object, so as to ensure that the number of particles selected from each image remained consistent, and the number of silver particles with a particle size of 0.2 μm or more (inclusive) and less than 0.2 μm was counted. The test images are shown in Figure 2 、 4 , 6, 8, 10, and 12, and the results are shown in Table 1.

[0103] Table 1

[0104]

[0105] Among them, Comparative Example 3 was severely agglomerated, and its particle condition could not be determined.

[0106] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications, etc. made without departing from the spirit and principles of the present application should be equivalent replacement manners and should be included in the protection scope of the present application.

Claims

1. A method for preparing silver particles, characterized in that: S1: The silver source is dispersed in an alkanolamine solution, and a dispersant is added to form a base solution; the molar ratio of silver ions in the silver source to alkanolamine compounds in the alkanolamine solution is 1:0.05~5; S2: The base liquid is subjected to a hydrothermal reaction with an organic amine solution to obtain the silver particles; the molar ratio of silver ions in the silver source to organic amine compounds in the organic amine solution is 1:0.005~0.15; The alkanolamine compound in the alkanolamine solution is selected from at least one of diethanolamine, methyldiethanolamine, ethanolamine, dimethylethanolamine, diethylene glycolamine, isopropanolamine, triisopropanolamine, oleic acid diethanolamide, stearic acid diethanolamide, lauric acid diethanolamide, and octadecyl diethanolamine; The organic amine compound in the organic amine solution is selected from at least one of triethylamine, N-ethyldiisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, cyclohexylamine, dimethyloctylamine, dimethyldecylamine, tris(3,6-dioxaheptyl)amine, and octylamine; The particle size distribution of the silver particles satisfies the following relationship: D50 is between 0.9 and 1.7 μm, D100 is between 3.5 and 8.5 μm, and Span is between 1.8 and 2.0 μm; The temperature of the hydrothermal reaction is 70–240°C; The pH of the organic amine solution is 9; The molar concentration of the silver source in the substrate is 0.008 mol / L.

2. The method for preparing silver particles according to claim 1, characterized in that: The mass ratio of silver atoms to dispersant in the silver source is 1:0.01~10.

3. The silver particles prepared by the method of claim 1 or 2, as determined by field emission scanning electron microscopy, have a ratio of 0.25 to 0.65 between the number of silver particles with a diameter greater than 0.2 μm and the number of silver particles with a diameter less than 0.2 μm.

4. The silver particles according to claim 3, characterized in that: The tap density of the silver particles is 6.60 g / cm³. 3 above.

5. A conductive silver paste, comprising a conductive phase, a binder phase, and a solvent, wherein the conductive phase is silver particles as described in any one of claims 3 to 4.

6. The use of the silver particles according to any one of claims 3 to 4 or the conductive silver paste according to claim 5 in the preparation of solar cells or electronic components.

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