A green preparation method of micro-nano spherical silver powder
Micro- and nano-spherical silver powders were prepared by combining a liquid-phase chemical reduction method with xanthan gum and sodium carboxymethyl cellulose dispersant. This method solves the problems of high cost, uneven particle size, and difficulty in shape control in traditional methods, and achieves efficient and environmentally friendly preparation of micro- and nano-spherical silver powders, which are suitable for conductive pastes and biological applications.
Patent Information
- Application Number
- CN202410911544.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-09
- Publication Date
- 2025-11-11
- Estimated Expiration
- 2044-07-09
AI Technical Summary
Traditional methods for preparing micro- and nano-sized spherical silver powder are costly, have uneven particle size distribution, and are difficult to control in terms of shape. Furthermore, chemical methods are prone to generating impurities during preparation, which are harmful to the environment.
A liquid-phase chemical reduction method was adopted, using xanthan gum and sodium carboxymethyl cellulose as composite dispersants. Silver nitrate solution was added to the reducing agent-dispersant mixture under light-protected conditions, and the mixture was added dropwise and allowed to mature. Then, it was filtered, washed, and dried to prepare micro-nano spherical silver powder.
Micro- and nano-spherical silver powders with uniform particle size, high sphericity, and surface nanostructure were prepared, which improved sintering activity. The process is simple, efficient, and low-cost, making it suitable for commercial mass production.
Smart Images
Figure CN118699389B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of nanomaterial preparation technology, specifically relating to a green preparation method for micro-nano spherical silver powder. Background Technology
[0002] With the rapid development of nanotechnology, micro and nanomaterials have shown broad application prospects in many fields due to their unique physical and chemical properties. Among them, micro and nano spherical silver powder plays a core role in conductive pastes and biological applications. However, traditional methods for preparing micro and nano spherical silver powder often suffer from problems such as high cost, uneven particle size distribution, and difficulty in shape control, which limit their widespread application in practice.
[0003] Traditional methods for preparing micro / nano spherical silver powder mainly fall into two categories: physical methods and chemical methods. Physical methods primarily involve mechanical ball milling, laser ablation, ultrasound, and irradiation to prepare nano-silver powder; however, these methods often require sophisticated equipment and are costly. Chemical methods mainly utilize liquid-phase chemical reduction, dissolving silver salts (such as silver nitrate) in water and adding a chemical reducing agent (such as hydrazine hydrate) for reduction to obtain silver powder. Although chemical methods are less expensive, they are prone to generating impurities during preparation, the chemical reagents used are environmentally harmful, and controlling particle size distribution and morphology is more difficult. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a green preparation method for micro-nano spherical silver powder.
[0005] The technical solution of the present invention is as follows:
[0006] A green preparation method for micro / nano spherical silver powder includes the following steps:
[0007] (1) Under light-protected conditions, silver nitrate was added to deionized water to prepare a silver nitrate solution;
[0008] (2) First, prepare a dispersant solution containing xanthan gum / sodium carboxymethyl starch and sodium carboxymethyl cellulose, and allow it to swell fully. Then, add ascorbic acid to obtain a reducing agent-dispersant mixed solution containing 0.02-0.1 wt% sodium carboxymethyl cellulose.
[0009] (3) Under light-protected conditions, while stirring, add silver nitrate solution to the reducing agent-dispersant mixed solution at a volume ratio of 1:1. After the addition is complete, allow it to mature to obtain silver paste solution.
[0010] (4) The silver paste solution is filtered, washed and dried in sequence to obtain the final micro-nano spherical silver powder.
[0011] In a preferred embodiment of the present invention, in step (1), the concentration of the silver nitrate solution is 0.05-0.5 mol / L.
[0012] More preferably, in step (1), the concentration of the silver nitrate solution is 0.1-0.2 mol / L.
[0013] In a preferred embodiment of the present invention, in step (2), the concentrations of xanthan gum and sodium carboxymethyl cellulose in the dispersant solution are both 0.04-0.1 wt%.
[0014] More preferably, the final concentration of ascorbic acid in the reducing agent-dispersant mixed solution is 0.05-2 mol / L.
[0015] More preferably, the final concentration of ascorbic acid in the reducing agent-dispersant mixed solution is 0.1-0.5 mol / L.
[0016] In a preferred embodiment of the present invention, step (3) is as follows: under a light-protected environment at 25-45°C, the silver nitrate solution is added to the reducing agent-dispersant mixed solution at a volume ratio of 1:1 and a rate of 1-100 mL / s with a stirring rate of 100-600 r / min. After the addition is complete, the mixture is allowed to mature for 2-15 min to obtain the silver paste solution.
[0017] More preferably, in step (4), the washing process includes washing with deionized water and washing with ethanol in sequence.
[0018] More preferably, in step (4), the drying is performed in a forced-air drying oven at 50-80°C for 6-8 hours.
[0019] A micro / nano spherical silver powder is prepared by the above-described method.
[0020] The beneficial effects of this invention are:
[0021] 1. The micro-nano spherical silver powder prepared by this invention is formed by the self-assembly of silver nanosheets with a thickness of about 20-80nm, resulting in particles with a particle size range of 1-2μm. Its surface nanostructure can greatly improve the sintering activity of the silver powder.
[0022] 2. This invention belongs to the liquid-phase chemical reduction method. Adding a composite dispersant (xanthan gum and sodium carboxymethyl cellulose) to the reducing agent solution can promote the formation of silver nanosheets and their self-assembly into micro-nano spherical silver powder, which can effectively prevent the agglomeration of the formed silver powder.
[0023] 3. No seed crystals are introduced in this invention. The material is self-assembled in one step, and no additional pH adjustment is required during the reaction process. The preparation method has the advantages of being simple, efficient, low-cost, and having a large process window, which is conducive to subsequent commercial mass production. Attached Figure Description
[0024] Figure 1 This is a 2000x SEM image of the micro / nano spherical silver powder prepared in Example 1 of the present invention (one small division on the scale bar in the image represents 2 μm).
[0025] Figure 2 This is a 20,000x SEM image of the micro-nano spherical silver powder prepared in Example 1 of the present invention (one small division on the scale bar represents 200 nm).
[0026] Figure 3 The image shows a SEM image of silver paste prepared using the micro-nano spherical silver powder obtained in Example 1 of this invention as a conductive phase after sintering at 190°C (1 small division on the scale bar in the image represents 2 μm).
[0027] Figure 4 This is a 10,000x SEM image of the micro / nano spherical silver powder prepared in Example 2 of the present invention (one small division on the scale bar represents 500 nm).
[0028] Figure 5 This is a 20,000x SEM image of the comparative silver powder prepared in Comparative Example 1 of this invention (one small division on the scale bar represents 200 nm).
[0029] Figure 6 The image shows a SEM image of silver paste prepared using the silver powder obtained in Comparative Example 1 of this invention as the conductive phase, after curing at 190°C (the first small division on the scale bar in the image is 2 μm).
[0030] Figure 7 This is a 20,000x SEM image of the comparative silver powder prepared in Comparative Example 2 of this invention (one small division on the scale bar represents 200 nm). Detailed Implementation
[0031] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.
[0032] Example 1
[0033] (1) Weigh a certain amount of silver nitrate and add 500 mL of deionized water under light-protected conditions to prepare a 0.15 mol / L silver nitrate solution.
[0034] (2) First, prepare a 500 mL dispersant solution containing 0.05 wt% xanthan gum and 0.05 wt% sodium carboxymethyl cellulose, and allow it to swell for more than 12 hours. Then, add ascorbic acid to make the final concentration 0.3 mol / L to obtain a reducing agent-dispersant mixed solution.
[0035] (3) Under the dark environment at 25℃, silver nitrate solution was added to a reducing agent-dispersant mixed solution with a stirring rate of 400r / min at a rate of 20mL / s. After the addition was completed, it was aged for 5min to obtain silver paste solution.
[0036] (4) The silver paste solution was filtered, washed and dried in sequence to obtain the final micro-nano spherical silver powder. The washing method was to wash with deionized water 3 times and anhydrous ethanol 2 times; the drying conditions were to dry in a forced-air drying oven at 60℃ for 6 hours.
[0037] Example 2
[0038] (1) Weigh a certain amount of silver nitrate and add 500 mL of deionized water under light-protected conditions to prepare a 0.25 mol / L silver nitrate solution.
[0039] (2) First, prepare a 500 mL dispersant solution containing 0.05 wt% sodium carboxymethyl starch and 0.05 wt% sodium carboxymethyl cellulose, and allow it to swell for more than 12 hours. Then, add ascorbic acid to make the final concentration 0.3 mol / L to obtain a reducing agent-dispersant mixed solution.
[0040] (3) Under the dark environment at 25℃, silver nitrate solution was added to a reducing agent-dispersant mixed solution with a stirring rate of 400r / min at a rate of 20mL / s. After the addition was completed, it was aged for 5min to obtain silver paste solution.
[0041] (4) The silver paste solution was filtered, washed and dried in sequence to obtain the final micro-nano spherical silver powder. The washing method was to wash with deionized water 3 times and anhydrous ethanol 2 times; the drying conditions were to dry in a forced-air drying oven at 60℃ for 6 hours.
[0042] Comparative Example 1
[0043] (1) Weigh a certain amount of silver nitrate and add 500 mL of deionized water under light-protected conditions to prepare a 0.15 mol / L silver nitrate solution.
[0044] (2) First, prepare a 500 mL dispersant solution containing 0.05 wt% xanthan gum and 0.05 wt% sodium carboxymethyl cellulose, and allow it to swell for more than 12 hours. Then, add ascorbic acid to make the final concentration 0.3 mol / L to obtain a reducing agent-dispersant mixed solution.
[0045] (3) In a light-protected environment at 25℃, the reducing agent-dispersant mixed solution was added to a silver nitrate solution with a stirring rate of 400r / min at a rate of 20mL / s. After the addition was completed, the solution was allowed to mature for 5min to obtain a silver paste solution.
[0046] (4) The silver paste solution was filtered, washed and dried in sequence to obtain the final comparison silver powder. The washing method was to wash with deionized water 3 times and anhydrous ethanol 2 times; the drying conditions were to dry in a forced-air drying oven at 60℃ for 6 hours.
[0047] The difference between Comparative Example 1 and Example 1 is that solutions A and B are added in different ways.
[0048] Comparative Example 2
[0049] (1) Weigh a certain amount of silver nitrate and add 500 mL of deionized water under light-protected conditions to prepare a 0.15 mol / L silver nitrate solution.
[0050] (2) First, prepare 500 mL of xanthan gum solution containing 0.05 wt% and allow it to swell for more than 12 hours. Then, add ascorbic acid to make the final concentration 0.3 mol / L to obtain a reducing agent-dispersant mixed solution.
[0051] (3) Under the dark environment at 25℃, silver nitrate solution was added to a reducing agent-dispersant mixed solution with a stirring rate of 400r / min at a rate of 20mL / s. After the addition was completed, it was aged for 5min to obtain silver paste solution.
[0052] (4) The silver paste solution was filtered, washed and dried in sequence to obtain the final comparison silver powder. The washing method was to wash with deionized water 3 times and anhydrous ethanol 2 times; the drying conditions were to dry in a forced-air drying oven at 60℃ for 6 hours.
[0053] The difference between Comparative Example 2 and Example 1 is that only a single dispersant was added to the reducing agent solution.
[0054] Depend on Figure 1 and Figure 2 It can be seen that the micro-nano spherical silver powder prepared in Example 1 of the present invention is formed by the self-assembly of silver nanosheets with a thickness of 20-80 nm, and the whole is spherical with a relatively smooth surface. Its surface nanoscale structure makes it highly active for sintering. Figure 3 As shown, the silver paste prepared using it as a conductive phase exhibits a distinct sintering neck at 190°C.
[0055] Depend on Figure 4 It can be seen that the surface of the micro-nano spherical silver powder prepared in Example 2 of the present invention still exhibits a nanostructure, but the sphericity is not as good as that of the micro-nano spherical silver powder prepared in Example 1.
[0056] The addition method is the opposite of that in Example 1, such as... Figure 5 As shown, the obtained comparative silver powder is generally spherical with a relatively rough surface and almost no surface nanostructure, such as... Figure 6 As shown, silver paste prepared using it as a conductive phase cannot achieve a sintering process at 190°C; Figure 7 It can be seen that when xanthan gum, a single dispersant, is added to Comparative Example 2, the resulting comparative silver powder exhibits an overall twin cloud-like appearance, with the surface composed of a large number of thin silver flakes. The nanostructure is relatively obvious, but the dispersibility and sphericity are poor.
[0057] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.
Claims
1. A green preparation method for micro / nano spherical silver powder, characterized in that: Includes the following steps: (1) Under light-protected conditions, silver nitrate is added to deionized water to prepare a silver nitrate solution with a concentration of 0.15-0.25 mol / L; (2) First, prepare a dispersant solution containing xanthan gum / sodium carboxymethyl starch and sodium carboxymethyl cellulose, and allow it to swell fully. Then, add ascorbic acid to obtain a reducing agent-dispersant mixed solution containing 0.02-0.1 wt% sodium carboxymethyl cellulose. The concentrations of xanthan gum and sodium carboxymethyl cellulose in the dispersant solution are both 0.04-0.1 wt%, and the final concentration of ascorbic acid in the reducing agent-dispersant mixed solution is 0.05-2 mol / L. (3) In a light-protected environment at 25-45℃, the silver nitrate solution is added to the reducing agent-dispersant mixed solution at a volume ratio of 1:1 and a rate of 1-100 mL / s with a stirring rate of 100-600 r / min. After the addition is complete, the mixture is allowed to mature for 2-15 min to obtain the silver paste solution. (4) The silver paste solution is filtered, washed and dried in sequence to obtain the final micro-nano spherical silver powder.
2. The green preparation method as described in claim 1, characterized in that: The final concentration of ascorbic acid in the reducing agent-dispersant mixed solution is 0.1-0.5 mol / L.
3. The green preparation method as described in claim 1, characterized in that: In step (4), the washing process includes washing with deionized water and washing with ethanol in sequence.
4. The green preparation method as described in claim 1, characterized in that: In step (4), the drying is performed in a forced-air drying oven at 50-80℃ for 6-8 hours.
5. A micro / nano spherical silver powder, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 4.
Citation Information
Patent Citations
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