Hollow-structure micro-nano silver powder and preparation method and application thereof

Abstract

The invention relates to hollow-structure micro-nano silver powder and a preparation method and application thereof. The preparation method comprises the following steps that (1) gas is introduced into a nano-metal colloidal solution for gas adsorption; (2) mixing the nano-metal colloidal solution obtained in the step (1), silver salt and a surface dispersing agent, and continuously introducing gas to obtain a micro-nano silver powder precursor; and (3) the micro-nano silver powder precursor and a reducing agent are mixed for a reduction reaction, and the hollow-structure micro-nano silver powder is obtained. The hollow structure is ingeniously formed in the silver powder material in the silver nitrate liquid-phase reduction process through the gas adsorption-desorption process of the nano metal colloidal solution, and the preparation method has the advantages of being simple in process, low in manufacturing cost, low in energy consumption, stable in product structure and environmentally friendly. The micro-nano silver powder with the hollow structure is narrow in particle size distribution, high in activity and low in sintering temperature, and has great application value in the fields of solar photovoltaics, 5G electronics and the like.

Description

Technical Field

[0001] This invention relates to the field of metal materials technology, and in particular to a hollow structure micro / nano silver powder, its preparation method, and its uses. Background Technology

[0002] Micro-nano silver powder refers to powder materials composed of silver particles at the micrometer (1μm-100μm) or nanometer (1nm-100nm) scale. Due to its excellent electrical and thermal conductivity and surface plasmon resonance effect, it has important application value in fields such as solar photovoltaic, electronic packaging, and flexible electronics.

[0003] In recent years, hollow-structured micro / nano silver powders have attracted widespread attention due to their unique physicochemical properties. The hollow structure allows for significant reduction in material density and increase in specific surface area by controlling the shell thickness and internal cavity size, thereby enhancing surface plasmon resonance, light absorption, and carrier transport efficiency. This characteristic shows great potential, especially in the photovoltaic industry: the high specific surface area of ​​hollow silver powder endows it with abundant surface active sites, significantly improving the electrochemical activity of electrode materials; simultaneously, its unique shell structure, due to uniform thermal stress distribution during sintering, enables lower sintering temperatures (typically 20℃-50℃ lower than solid silver powder). This not only reduces energy consumption but also avoids thermal damage to flexible substrates or heat-sensitive devices, providing crucial material support for the development of next-generation low-temperature solar cells (such as perovskite cells and flexible thin-film cells).

[0004] However, existing methods for preparing hollow silver powder still face challenges: traditional chemical reduction methods are prone to structural collapse due to rapid deposition of silver ions; template methods (such as hard template SiO2 or soft template bubbles) can achieve controllable structure, but have problems such as complex template removal process and residual pollution; while vapor deposition methods are costly and difficult to scale up.

[0005] Therefore, developing an efficient and controllable hollow micro / nano silver powder preparation technology is of great significance for promoting its application in fields such as solar photovoltaics, flexible electronics, and electronic devices. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a hollow structure micro / nano silver powder, its preparation method, and its applications. The preparation method of the hollow structure micro / nano silver powder provided by the present invention utilizes the adsorption-desorption process of a nano-metal colloidal solution under certain temperature control conditions. This ingeniously enables the formation of a hollow structure within the silver powder material during the liquid-phase reduction of silver nitrate, thereby preparing a micro / nano silver powder material with high activity and low sintering temperature. This material has significant application value in fields such as solar photovoltaics and 5G electronics.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing hollow structured micro / nano silver powder, the preparation method comprising the following steps:

[0009] (1) Gas adsorption is performed by introducing gas into the nano-metal colloidal solution;

[0010] (2) Mix the nano-metal colloidal solution, silver salt, and surface dispersant from step (1), and continue to pass gas through to obtain the micro-nano silver powder precursor;

[0011] (3) Mix the micro-nano silver powder precursor and the reducing agent to carry out a reduction reaction to obtain the hollow structure micro-nano silver powder.

[0012] This invention utilizes the adsorption-desorption process of gas in a nano-metal colloidal solution. After the gas is adsorbed on the surface of the nano-metal colloidal solution, it can serve as a nucleation site for subsequent silver salt deposition. During the reduction process, the silver salt nucleates and grows, simultaneously encapsulating the adsorbed gas in the colloidal solution. By controlling the reaction temperature, the encapsulated colloid undergoes gas desorption and release, thereby preparing a hollow-structured micro / nano silver powder. Subsequent sintering or etching is unnecessary to obtain the hollow-structured micro / nano silver powder. The preparation method provided by this invention has the advantages of simple process, low manufacturing cost, low energy consumption, stable product structure, and environmental friendliness.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0014] Preferably, the nano-metal colloidal solution in step (1) comprises nano-metal colloids and water.

[0015] Preferably, the nano-metal colloid includes any one or a combination of at least two of nano-platinum colloid, nano-gold colloid, nano-palladium colloid, or nano-rhodium colloid. Typical but non-limiting combinations include combinations of nano-platinum colloid and nano-gold colloid, combinations of nano-gold colloid and nano-palladium colloid, combinations of nano-palladium colloid and nano-rhodium colloid, combinations of nano-platinum colloid and nano-palladium colloid, combinations of nano-gold colloid and nano-rhodium colloid, combinations of nano-platinum colloid, nano-gold colloid, and nano-palladium colloid, or combinations of nano-platinum colloid, nano-gold colloid, nano-palladium colloid, and nano-rhodium colloid.

[0016] In this invention, the ability of nano-metal colloids to adsorb gases is utilized to provide sites for the nucleation of silver powder. Other non-metallic nanocolloids (such as silica colloids or carbon nanosphere colloids) do not have this property and cannot form sites for gas structures. They need to be removed by sintering or etching after the reduction step, which results in problems such as complex template removal process and residual pollution.

[0017] The nano-metal colloidal solution used in this invention is prepared by the following method.

[0018] After diluting a noble metal salt (such as chloropalladium acid, chloroplatinic acid, chlororhodium acid, etc.) to a certain volume, add the stabilizer polyethylene glycol, then add ascorbic acid, and heat to boiling using microwave method to obtain a noble metal nanocolloid solution.

[0019] Preferably, the median particle size of the metal particles in the nano-metal colloidal solution is ≤10nm, for example, it can be 10nm, 8nm, 6nm, 5nm, 4.5nm, 4nm, 3.5nm, 3nm, 2.5nm, 2nm, 1.5nm or 1nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] This invention further controls the median particle size of metal particles in the nano-metal colloidal solution to ≤10nm. The median particle size of the metal particles affects the particle size and hollow state of the hollow micro-nano silver powder. If the median particle size of the metal particles is too large, it will cause the silver powder particle size to become uncontrollable and the hollow structure to disappear.

[0021] Preferably, the metal particle content in the nano-metal colloidal solution is 0.1 mg / L-3 mg / L, for example, it can be 0.1 mg / L, 0.5 mg / L, 1 mg / L, 1.5 mg / L, 2 mg / L, 2.5 mg / L or 3 mg / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the gas includes any one or a combination of at least two of air, hydrogen, nitrogen, or oxygen. Typical but non-limiting combinations include combinations of air and hydrogen, hydrogen and nitrogen, nitrogen and oxygen, air, hydrogen and oxygen, hydrogen, nitrogen and oxygen, air, hydrogen and nitrogen, or air, hydrogen, nitrogen and oxygen.

[0023] Preferably, during the gas introduction process in step (1), the temperature is controlled at 10℃-25℃, accompanied by stirring. For example, it can be 10℃, 12℃, 15℃, 18℃, 20℃, 22℃, 24℃ or 25℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the stirring time is 0.2h-1h, for example, it can be 0.2h, 0.5h, 0.8h or 1h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the silver salt in step (2) includes silver nitrate.

[0026] Preferably, the surface dispersant comprises any one or a combination of at least two of polyvinylpyrrolidone, stearic acid, gum arabic, triethanolamine, or polyvinyl alcohol. Typical but non-limiting combinations include combinations of polyvinylpyrrolidone and stearic acid, combinations of stearic acid and gum arabic, combinations of gum arabic and triethanolamine, combinations of triethanolamine and polyvinyl alcohol, combinations of polyvinylpyrrolidone, gum arabic, triethanolamine, and polyvinyl alcohol, or combinations of polyvinylpyrrolidone, stearic acid, gum arabic, triethanolamine, and polyvinyl alcohol.

[0027] Preferably, the mass ratio of the nano-metal colloidal solution, silver salt, and surface dispersant in step (2) is 500-2000:100:0.2-20, for example, it can be 1000:100:0.5, 2000:100:10 or 800:100:15, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] The present invention further controls the mass ratio of nano-metal colloidal solution, silver salt, and surface dispersant to (500-2000):100:(0.2-20). If the content of nano-metal colloidal solution is too low, the particle size distribution will be too wide and a hollow structure cannot be formed; if the content of nano-metal colloidal solution is too high, the preparation cost will be too high and the reduction system will be unstable.

[0029] Preferably, the mixing temperature in step (2) is 15℃-30℃, for example, it can be 15℃, 18℃, 20℃, 22℃, 24℃, 25℃, 28℃ or 30℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the mixing time in step (2) is 0.2h-1h, for example, it can be 0.2h, 0.5h, 0.8h or 1h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the pH of the mixture in step (2) is 2-6, for example, it can be 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5 or 6, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] This invention controls the pH of the mixture to 2-6 by adding an acid or alkali. The acid used can be nitric acid or sulfuric acid, and the alkali used can be ammonia, etc.

[0033] Preferably, the reducing agent in step (3) includes any one or a combination of at least two of ascorbic acid, hydrazine hydrate, or formaldehyde. Typical but non-limiting combinations include a combination of ascorbic acid and hydrazine hydrate, a combination of hydrazine hydrate and formaldehyde, a combination of ascorbic acid and formaldehyde, and a combination of ascorbic acid, hydrazine hydrate, and formaldehyde.

[0034] Preferably, the mass ratio of the silver salt to the reducing agent is 1:0.5-2, for example, it can be 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8 or 1:2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the temperature of the reduction reaction is 35℃-60℃, for example, it can be 35℃, 38℃, 40℃, 42℃, 45℃, 48℃, 50℃, 52℃, 55℃, 58℃ or 60℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0036] The present invention further controls the temperature of the reduction reaction to 35℃-60℃. Within this temperature range, the stability of the entire reduction system can be guaranteed, ensuring the smooth preparation of hollow micro-nano silver powder. If the temperature of the reduction reaction is too high, the reaction rate will be too fast, the particle size will be too small, and a hollow structure cannot be formed. If the temperature of the reduction reaction is too low, a silver mirror phenomenon will occur, and micro-nano silver powder cannot be formed.

[0037] Preferably, the reduction reaction time is 0.2h-1h, for example, it can be 0.2h, 0.5h, 0.8h or 1h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] Preferably, after the reduction reaction and before obtaining hollow micro / nano silver powder, solid-liquid separation, washing, and drying are also performed.

[0039] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:

[0040] (1) Gas is introduced into a nano-metal colloidal solution with a metal content of 0.1 mg / L-3 mg / L and a median particle size of ≤10 nm, and the mixture is stirred at 10℃-25℃ for 0.2 h-1 h to carry out gas adsorption;

[0041] The gas includes any one or a combination of at least two of the following: air, hydrogen, nitrogen, or oxygen.

[0042] (2) Mix the nano-metal colloidal solution, silver nitrate, and surface dispersant after step (1) in a mass ratio of 500-2000:100:0.2-20, and continue to pass the gas from step (1) through the mixture. Control the temperature during the mixing process to be 15℃-30℃, the pH to be 2-6, and the time to be 0.2h-1h to obtain the micro-nano silver powder precursor.

[0043] (3) Mix the micro-nano silver powder precursor and the reducing agent at a mass ratio of 1:0.5-2, and carry out the reduction reaction at 35℃-60℃ for 0.2h-1h. After centrifugation, washing, and drying at 50℃-70℃ for 10h-20h, the hollow structure micro-nano silver powder is obtained.

[0044] Secondly, the present invention provides a hollow structure micro / nano silver powder, which is prepared according to the preparation method described in the first aspect, and the median particle size of the hollow structure micro / nano silver powder is 0.3 μm-3 μm.

[0045] The hollow structure micro / nano silver powder provided by this invention has the characteristics of narrow particle size distribution, high activity and low sintering temperature. At the same time, due to its unique spatial structure, it can reduce the amount of precious metals in the slurry and improve the rheological properties of the slurry, making the application performance more stable. Its preferred median particle size D50 is 1.2μm-2.0μm.

[0046] Thirdly, the present invention provides an application of hollow structure micro / nano silver powder as described in the second aspect, wherein the hollow structure micro / nano silver powder is used in the fields of solar photovoltaic, electronic packaging or flexible electronics.

[0047] The hollow structure micro-nano silver powder provided by this invention has great application value in fields such as solar photovoltaics and 5G electronics.

[0048] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0049] Compared with the prior art, the present invention has at least the following beneficial effects:

[0050] (1) This invention utilizes the adsorption-desorption process of gas by a nano-metal colloidal solution. After the gas is adsorbed on the surface of the nano-metal colloidal solution, it can serve as a nucleation site for subsequent silver salt deposition. During the reduction process, the silver salt nucleates and grows, simultaneously encapsulating the adsorbed gas in the colloidal solution. By controlling the reaction temperature, the encapsulated colloid is desorbed and released, thereby preparing a hollow-structured micro / nano silver powder. No subsequent sintering or etching is required to obtain the hollow-structured micro / nano silver powder. The preparation method provided by this invention has the advantages of simple process, low manufacturing cost, low energy consumption, stable product structure, and environmental friendliness.

[0051] (2) The hollow micro-nano silver powder provided by this invention has the characteristics of narrow particle size distribution, high activity, and low sintering temperature. At the same time, due to its unique spatial structure, it can reduce the amount of precious metals in the slurry and improve the rheological properties of the slurry, making the application performance more stable. It has great application value in the fields of solar photovoltaic, 5G electronics and other fields. Attached Figure Description

[0052] Figure 1 This is a SEM image of the hollow structure micro / nano silver powder prepared in Example 1 of this invention;

[0053] Figure 2 This is a SEM image of the hollow structure micro / nano silver powder prepared in Example 2 of this invention;

[0054] Figure 3 This is a SEM image of the hollow structured micro / nano silver powder prepared in Comparative Example 1 of this invention. Detailed Implementation

[0055] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0056] Unless otherwise specified, all reagents and consumables used in the following examples and comparative examples were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used were conventional methods and techniques in the art.

[0057] Example 1

[0058] This embodiment provides a method for preparing hollow structured micro / nano silver powder, the preparation method including the following steps:

[0059] (1) Nitrogen gas was introduced into a nano-palladium colloidal solution with a metal particle content of 0.2 mg / L and a median particle size of 3 nm, and the mixture was stirred at 15 °C for 0.2 h to carry out gas adsorption;

[0060] (2) Mix the nano-palladium colloidal solution, silver nitrate and polyvinylpyrrolidone after step (1) in a mass ratio of 2000:100:15, continue to introduce nitrogen gas, control the temperature during the mixing process to be 30℃, pH to be 5, and time to be 0.2h, and obtain the micro-nano silver powder precursor.

[0061] (3) The precursor of micro-nano silver powder and the reducing agent were mixed at a mass ratio of silver nitrate to ascorbic acid of 1:1.2 and the reduction reaction was carried out at 60°C for 0.5h. After centrifugation, washing and drying at 50°C for 12h, the hollow structure micro-nano silver powder was obtained.

[0062] SEM images of the prepared hollow micro / nano silver powder are shown below. Figure 1 As shown, from Figure 1 As indicated by the black arrow, the silver powder has a hollow structure with a particle size D50 of 1.5 μm.

[0063] Example 2

[0064] This embodiment provides a method for preparing hollow structured micro / nano silver powder, the preparation method including the following steps:

[0065] (1) Hydrogen gas was introduced into a nano-palladium colloidal solution with a metal particle content of 0.25 mg / L and a median particle size of 5 nm, and the mixture was stirred at 20 °C for 1 h to carry out gas adsorption.

[0066] (2) Mix the nano-palladium colloid, silver nitrate and polyvinyl alcohol after step (1) in a mass ratio of 1000:100:10, and continue to introduce air and hydrogen. Control the temperature during the mixing process to be 20℃, pH to be 6, and time to be 0.5h to obtain micro-nano silver powder precursor.

[0067] (3) The precursor of micro-nano silver powder and the reducing agent were mixed at a mass ratio of silver nitrate to ascorbic acid of 1:1.5, and the reduction reaction was carried out at 55°C for 1 hour. After centrifugation, washing, and drying at 55°C for 15 hours, the hollow structure micro-nano silver powder was obtained.

[0068] SEM images of the prepared hollow micro / nano silver powder are shown below. Figure 2 As shown, from Figure 2 As can be seen from this, the silver powder has a hollow structure and its particle size is 1.6 μm.

[0069] Example 3

[0070] This embodiment provides a method for preparing hollow structured micro / nano silver powder, the preparation method including the following steps:

[0071] (1) Air was introduced into a mixture of nano-platinum colloidal solution with a metal particle content of 0.17 mg / L and a median particle size of 10 nm and nano-rhodium colloidal solution (mass ratio 1:1), and the mixture was stirred at 25 °C for 0.5 h to carry out gas adsorption.

[0072] (2) Mix the nano-platinum colloidal solution, silver nitrate and stearic acid after step (1) in a mass ratio of 1500:100:20, continue to introduce air, control the temperature during the mixing process to be 15℃, pH to be 3, and time to be 0.3h, to obtain the micro-nano silver powder precursor;

[0073] (3) The micro-nano silver powder precursor and the reducing agent were mixed at a mass ratio of 1:2 of silver nitrate and reducing agent (ascorbic acid and formaldehyde in a mass ratio of 1:1). The mixture was subjected to a reduction reaction at 45°C for 0.5 h. After centrifugation, washing, and drying at 60°C for 12 h, the hollow structure micro-nano silver powder with a particle size of 1.4 μm was obtained.

[0074] Example 4

[0075] This embodiment provides a hollow structure micro / nano silver powder. The only difference from Embodiment 1 is that, when preparing the hollow structure micro / nano silver powder, the median particle size of the metal particles in the nano-platinum colloid in step (1) is 20 nm.

[0076] Example 5

[0077] This embodiment provides a hollow structure micro / nano silver powder. The only difference from Embodiment 1 is that, when preparing the hollow structure micro / nano silver powder, the mass ratio of the nano-metal colloidal solution, silver nitrate and polyvinylpyrrolidone in step (2) is 3000:100:15.

[0078] Example 6

[0079] This embodiment provides a hollow structure micro / nano silver powder. The only difference from Embodiment 1 is that, when preparing the hollow structure micro / nano silver powder, the mass ratio of the nano-metal colloidal solution, silver nitrate and polyvinylpyrrolidone in step (2) is 200:100:15.

[0080] Example 7

[0081] This embodiment provides a hollow structure micro / nano silver powder. The only difference from Embodiment 1 is that the temperature of the reduction reaction in step (3) is 10°C when preparing the hollow structure micro / nano silver powder.

[0082] Example 8

[0083] This embodiment provides a hollow structure micro / nano silver powder. The only difference from Embodiment 1 is that the temperature of the reduction reaction in step (3) is 70°C when preparing the hollow structure micro / nano silver powder.

[0084] Comparative Example 1

[0085] This comparative example provides a hollow structure micro / nano silver powder, which differs from Example 1 only in that gas is not introduced in step (1) when preparing the hollow structure micro / nano silver powder.

[0086] SEM images of the prepared hollow micro / nano silver powder are shown below. Figure 3 As shown, solid silver powder with strong crystallinity is generated.

[0087] Comparative Example 2

[0088] This comparative example provides a hollow structure micro / nano silver powder, which differs from Example 1 only in that, when preparing this hollow structure micro / nano silver powder, the nano-platinum colloid is replaced with an equal amount of silica gel.

[0089] Test method: The particle size of the micro-nano silver powder prepared in the test examples and comparative examples is shown in Table 1 below.

[0090] Table 1

[0091]

[0092] The test results show that:

[0093] (1) As can be seen from Examples 1-3, this invention utilizes the adsorption-desorption process of gas by a nano-metal colloidal solution. After the gas is adsorbed on the surface of the nano-metal colloidal solution, it can serve as a nucleation site for subsequent silver salt deposition. The silver salt nucleates and grows while simultaneously encapsulating the adsorbed gas in the colloidal solution. By controlling the reaction temperature, the encapsulated colloid is desorbed and released, thereby preparing a hollow-structured micro / nano silver powder. No subsequent sintering or etching is required to obtain the hollow-structured micro / nano silver powder. The preparation method provided by this invention has the advantages of simple process, low manufacturing cost, low energy consumption, stable product structure, and environmental friendliness.

[0094] (2) By comparing Example 1 and Example 4, it can be seen that the present invention further controls the median particle size of the metal particles in the nano-metal colloidal solution to ≤10nm. The median particle size of the metal particles affects the particle size of the hollow micro-nano silver powder. If the median particle size of the metal particles is too large, the particle size of the powder will be uncontrollable, and the colloidal adsorption-desorption process will be limited, resulting in a decrease in the proportion of hollow silver powder.

[0095] (3) A comparison of Examples 1 and 5-6 shows that by further controlling the mass ratio of nano-metal colloidal solution, silver salt, and surface dispersant to (500-2000):100:(0.2-20), the present invention achieves the following results: if the content of nano-metal colloidal solution is too low, the particle size will be too large, and the adsorption-desorption process of the colloid will be limited, leading to a decrease in the proportion of hollow silver powder; if the content of nano-metal colloidal solution is too high, the particle size will be too small, and the preparation cost will be too high.

[0096] (4) By comparing Example 1 with Examples 7-8, it can be seen that by further controlling the temperature of the reduction reaction to 25℃-60℃, the present invention can ensure that the colloidal adsorption-desorption process is controllable and the entire reduction system is controllable. If the temperature of the reduction reaction is too high, the reaction rate is too fast and it is easy to produce fluffy ultrafine black silver powder. If the temperature of the reduction reaction is too low, the reaction rate is too slow and it is easy to produce silver mirror phenomenon, which in turn leads to the production of silver flakes.

[0097] (5) As can be seen from Example 1 and Comparative Examples 1-2, the present invention utilizes the property of nano-metal colloidal solution to adsorb gas, providing sites for silver powder nucleation. Other non-metallic nanocolloids (such as silica gel or carbon nanosphere colloids) do not have this property and cannot form sites for gas structures. They need to be removed by sintering or etching after the reduction step to generate solid silver powder with strong crystallinity.

[0098] In summary, this invention utilizes the adsorption-desorption process of gas in a nano-metal colloidal solution. After the gas is adsorbed on the surface of the nano-metal colloidal solution, it serves as a nucleation site for subsequent silver salt deposition. The silver salt nucleates and grows while simultaneously encapsulating the adsorbed gas in the colloidal solution. By controlling the reaction temperature, the encapsulated colloid undergoes gas desorption and release, thereby preparing a hollow-structured micro / nano silver powder. Subsequent sintering or etching is unnecessary to obtain the hollow-structured micro / nano silver powder. The preparation method provided by this invention has advantages such as simple process, low manufacturing cost, low energy consumption, stable product structure, and environmental friendliness. The obtained hollow-structured micro / nano silver powder has significant application value in fields such as solar photovoltaics and 5G electronics.

[0099] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing hollow-structured micro / nano silver powder, characterized in that, The preparation method includes the following steps: (1) Gas adsorption is performed by introducing gas into the nano-metal colloidal solution; (2) Mix the nano-metal colloidal solution, silver salt and surface dispersant after step (1), and continue to pass gas through to obtain micro-nano silver powder precursor; (3) Mix the micro-nano silver powder precursor and the reducing agent to carry out a reduction reaction to obtain the hollow structure micro-nano silver powder.

2. The preparation method according to claim 1, characterized in that, The nano-metal colloidal solution in step (1) comprises nano-metal colloids and water; Preferably, the nano-metal colloid includes any one or a combination of at least two of nano-platinum colloid, nano-gold colloid, nano-palladium colloid, or nano-rhodium colloid; Preferably, the median particle size of the metal particles in the nano-metal colloid is ≤10nm; Preferably, the metal particle content in the nano-metal colloidal solution is 0.1 mg / L-3 mg / L; Preferably, the gas includes any one or a combination of at least two of air, hydrogen, nitrogen, or oxygen.

3. The preparation method according to claim 1 or 2, characterized in that, During the gas introduction process described in step (1), the temperature is controlled at 10℃-25℃, and stirring is carried out simultaneously. Preferably, the stirring time is 0.2h-1h.

4. The preparation method according to any one of claims 1-3, characterized in that, The silver salt mentioned in step (2) includes silver nitrate; Preferably, the surface dispersant comprises any one or a combination of at least two of polyvinylpyrrolidone, stearic acid, gum arabic, triethanolamine, or polyvinyl alcohol.

5. The preparation method according to any one of claims 1-4, characterized in that, In step (2), the mass ratio of the nano-metal colloidal solution, silver salt, and surface dispersant is 500-2000:100:0.2-20. Preferably, the mixing temperature in step (2) is 15℃-30℃; Preferably, the mixing time in step (2) is 0.2h-1h; Preferably, the pH of the mixture in step (2) is 2-6.

6. The preparation method according to any one of claims 1-5, characterized in that, The reducing agent in step (3) includes any one or a combination of at least two of ascorbic acid, hydrazine hydrate, or formaldehyde; Preferably, the mass ratio of the silver salt to the reducing agent is 1:(0.5-2); Preferably, the temperature of the reduction reaction is 35℃-60℃; Preferably, the reduction reaction takes 0.2 h to 1 h.

7. The preparation method according to any one of claims 1-6, characterized in that, The process after the reduction reaction, before obtaining hollow micro / nano silver powder, includes solid-liquid separation, washing, and drying.

8. The preparation method according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: (1) Gas is introduced into a nano-metal colloidal solution with a metal content of 0.1 mg / L-3 mg / L and a median particle size of ≤5 nm, and the mixture is stirred at 10℃-25℃ for 0.2 h-1 h to carry out gas adsorption; The gas includes any one or a combination of at least two of the following: air, hydrogen, nitrogen, or oxygen. (2) Mix the nano-metal colloidal solution, silver nitrate and surface dispersant after step (1) in a mass ratio of 500-2000:100:0.2-20, and continue to pass the gas in step (1) through the mixture. Control the temperature during the mixing process to be 15℃-30℃, the pH to be 2-6, and the time to be 0.2h-1h to obtain the micro-nano silver powder precursor. (3) Mix the micro-nano silver powder precursor and the reducing agent at a mass ratio of 1:0.5-2, and carry out the reduction reaction at 35℃-60℃ for 0.2h-1h. After centrifugation, washing, and drying at 50℃-70℃ for 10h-20h, the hollow structure micro-nano silver powder is obtained.

9. A hollow-structured micro / nano silver powder, characterized in that, The hollow structure micro / nano silver powder is prepared by the preparation method according to any one of claims 1-8, and the median particle size of the hollow structure micro / nano silver powder is 0.1 μm-3 μm.

10. The use of the hollow structure micro / nano silver powder as described in claim 9, characterized in that, The hollow structure micro / nano silver powder is used in solar photovoltaic, electronic packaging, or flexible electronics.

Images