Method for preparing silver nanoparticles based on pulse line evaporation technology
By employing pulsed-line evaporation technology and cooling medium regulation, the problems of silver nanoparticle agglomeration and organic residue were solved, and silver nanoparticles suitable for high-performance conductive inks were prepared, achieving green and environmentally friendly nanomaterial preparation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-29
- Publication Date
- 2026-04-14
Smart Images
Figure CN121847796A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nanomaterial preparation technology, specifically to a physical method for preparing low-agglomeration silver nanoparticles by controlling the cooling medium using pulsed line evaporation technology. Background Technology
[0002] With the rapid development of cutting-edge fields such as flexible electronics, printed circuits, and IoT sensors, conductive inks, as key functional materials for realizing the printing and flexibility of electronic devices, are facing increasingly stringent performance requirements. Modern applications not only demand inks with high conductivity and excellent printability (such as rheological properties, substrate adhesion, and pattern resolution), but also need to consider compatibility with flexible polymer substrates and meet the trends of green, environmentally friendly, low-toxicity, and sustainable manufacturing. Silver nanoparticles, due to their excellent conductivity and outstanding chemical stability, have become a key research direction for the preparation of high-performance conductive inks in recent years. As a conductive functional phase, the size, morphology, dispersion stability, and surface purity of silver nanoparticles directly determine the sintering activity of the ink, the ability to form a conductive network, and the electrical and mechanical properties of the final device. Therefore, developing a simple process for synthesizing silver nanoparticles with controllable morphology and size is crucial for promoting the industrialization of printed electronics.
[0003] Currently, the large-scale preparation of silver nanoparticles is still dominated by chemical reduction methods. While this method offers advantages such as low cost, mild reaction conditions, and ease of mass production, it also has several significant drawbacks: First, the synthesis process requires the introduction of reducing agents (such as sodium borohydride and hydrazine hydrate) and surfactants or dispersants (such as PVP and CTAB) to control particle growth and prevent agglomeration. These organic residues often cannot be completely decomposed during subsequent sintering, easily forming an insulating carbon layer on the particle surface or interface, leading to a significant increase in the resistivity of the conductive ink and affecting device performance. Second, silver nanoparticles prepared by conventional chemical reduction methods are prone to agglomeration, forming irregular polycrystalline aggregates. This not only reduces sintering density but also affects the rheological properties and storage stability of the ink, resulting in poor uniformity of printed patterns and inconsistent linewidths. Furthermore, from an environmental and sustainability perspective, chemical synthesis often involves toxic or flammable reagents, and the treatment of reaction byproducts and wastewater is difficult. It may generate volatile organic compounds (VOCs) and metal-containing wastewater, burdening the environment and failing to align with the development concepts of green chemistry and clean production.
[0004] In contrast, physical preparation methods have attracted widespread attention because they do not require the introduction of additional chemical reagents, can obtain nanoparticles with clean surfaces and high purity, and are generally more environmentally friendly. Among them, pulsed-wire evaporation (PWE) is a promising one-step solid-phase-gas-phase synthesis technology. Its core principle is to apply a transient high-power pulse (high voltage, high current) to a fine metal wire, causing the wire to rapidly heat up to above its evaporation point in a very short time (microseconds), generating high-temperature, high-pressure metal vapor. This vapor rapidly becomes supersaturated in the surrounding cooling medium and undergoes uniform nucleation and condensation, thereby directly generating nanoparticles. This method integrates evaporation, nucleation, and condensation into a single step, and has outstanding advantages such as simple process, fast preparation speed, high yield, and high product purity. It is also easy to implement continuous or semi-continuous production.
[0005] However, despite the unique advantages of PWE technology in principle, current research largely focuses on the influence of electrical parameters (such as pulse voltage, capacitance, and energy input waveform) on the final average size and yield of nanoparticles. There is a lack of systematic and in-depth research and optimized engineering solutions regarding the crucial regulatory role of the cooling medium in silver vapor condensation kinetics, particle nucleation and growth, grain structure formation, and the suppression of particle agglomeration. The properties of the cooling medium (such as solvent polarity, surface tension, and thermal properties (thermal conductivity and specific heat)) directly affect the vapor cooling rate, supersaturation, and collision frequency, thus determining the particle size distribution, morphology (whether it is spherical), crystallinity, and degree of aggregation. Therefore, to fully realize the potential of PWE in preparing highly dispersed, small-sized, well-spherical silver nanoparticles suitable for high-performance conductive inks, it is urgent to develop a new physical preparation method and process that is completely independent of chemical reducing agents and can effectively control the condensation process of silver nanoparticles and suppress their agglomeration behavior through active design and precise control of the cooling medium environment. This is not only key to improving the practical application of PWE technology but also opens up a new technological path for obtaining "green" high-performance conductive ink raw materials. Summary of the Invention
[0006] To address the aforementioned problems, this invention provides a green preparation method for silver nanoparticles based on pulsed-line evaporation technology. The core innovation of this method lies in its complete reliance on physical means, particularly the active design and precise control of the cooling medium, to replace reducing agents and dispersants in traditional chemical synthesis, thereby achieving controllable preparation of silver nanoparticles.
[0007] Specifically, this invention systematically studies the key influence of the type of cooling medium on the condensation behavior of silver vapor. By selecting different types of cooling media, the heat transfer conditions and interparticle interactions during the silver vapor condensation process are altered, thereby suppressing the aggregation behavior of silver nanoparticles and achieving effective control over particle size distribution and dispersion state.
[0008] Thanks to this physical regulation mechanism, the silver nanoparticles prepared in this invention possess the following outstanding characteristics: narrow particle size distribution and controllable average size; near-spherical morphology and high crystallinity; pure surface with no organic residue and low agglomeration. These characteristics ensure good dispersion stability of the nanoparticles in solvents, eliminating the need for complex subsequent purification processes. This invention not only provides an environmentally friendly and simplified preparation process, avoiding the generation of chemical waste and impurities, but also lays a solid technical foundation for the manufacture of high-performance, green printed electronic materials.
[0009] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows:
[0010] Firstly, this invention provides a method for preparing silver nanoparticles based on pulsed-wire evaporation technology. Based on pulsed-wire evaporation technology, this invention introduces a liquid cooling medium during the evaporation of silver metal wires, causing silver vapor to rapidly condense in a liquid environment to form silver nanoparticles. By selecting different types of cooling media, the heat transfer conditions and interparticle interactions during the silver vapor condensation process are altered, thereby suppressing the aggregation behavior of silver nanoparticles and achieving effective control over the particle size distribution and dispersion state. The method specifically includes the following steps:
[0011] (1) A silver wire is loaded into the reaction chamber of the pulsed line evaporator as the evaporation raw material;
[0012] (2) A liquid cooling medium is added to the reaction chamber, wherein the liquid cooling medium is an alcohol solvent, water, or a mixture of water and an alcohol solvent, and the alcohol solvent is one or more of ethanol, propanol, or butanol;
[0013] (3) Apply a pulsed current to the silver wire to make the silver wire evaporate instantaneously to form silver vapor;
[0014] (4) The silver vapor rapidly condenses in the liquid cooling medium to form silver nanoparticles and disperse them in the cooling medium; by adjusting the type of the liquid cooling medium, the degree of aggregation and particle size distribution of the silver nanoparticles can be controlled.
[0015] Further, in step (1), the diameter of the silver wire is 0.1-0.3 mm.
[0016] Furthermore, in step (3), the supply voltage of the pulse current is 200-400V. This supply voltage is set to match the diameter of the silver wire (0.1-0.3mm). If it is too low, it will lead to insufficient vaporization of the silver wire, droplet formation and increased particle size, while if it is too high, it will easily cause excessive plasma formation, secondary agglomeration of particles and widening of particle size distribution.
[0017] Furthermore, in step (3), the evaporation process is repeated (i.e., the number of explosions) 100-800 times, and the evaporation length (i.e. the explosion length) of the silver wire is 20-25 mm.
[0018] Furthermore, when the liquid cooling medium is water, the prepared silver nanoparticles have a d50 of 2.35 µm and a d90 of 23.2 µm. The particle morphology is close to spherical, with high crystallinity and small particle size.
[0019] Furthermore, when the liquid cooling medium is ethanol, the prepared silver nanoparticles have a d50 of 0.22 μm and a d90 of 3.18 μm. The particle morphology is close to spherical, with high crystallinity, small particle size, low agglomeration, and good dispersibility. In terms of particle size distribution, they are significantly superior to silver nanoparticles prepared with water as the liquid cooling medium.
[0020] Secondly, the present invention provides silver nanoparticles prepared using the above method.
[0021] Thirdly, the present invention provides the application of silver nanoparticles prepared by the above method in the preparation of high-performance conductive inks.
[0022] The present invention has the following beneficial effects:
[0023] 1. The entire process uses physical methods, eliminating the need for any toxic chemicals, making it environmentally friendly and avoiding the use of chemical reagents. Chemical methods typically require reducing agents, stabilizers, and organic solvents, which may remain in the product, posing toxicity risks or environmental pollution. Physical methods, on the other hand, require no added chemical reagents, fundamentally eliminating the problem of chemical residues.
[0024] 2. By changing the type of cooling medium, the size and aggregation degree of silver nanoparticles can be effectively controlled.
[0025] 3. The prepared silver nanoparticles (especially those prepared with ethanol as the cooling medium) have a concentrated particle size distribution and good dispersibility, making them suitable for applications such as high-performance conductive inks.
[0026] 4. The process is simple, has good repeatability, and has good prospects for industrial application. Attached Figure Description
[0027] Figure 1 This is a diagram of the experimental setup for pulsed line evaporation (PWE).
[0028] Figure 2 Images of silver colloidal samples prepared in different solvents: deionized water (left) and ethanol (right).
[0029] Figure 3 SEM-EDX image of silver nanoparticles prepared using deionized water as the cooling liquid.
[0030] Figure 4 SEM-EDX image of silver nanoparticles prepared using ethanol as a coolant.
[0031] Figure 5 Particle size distribution of silver particles prepared under different cooling medium conditions. Detailed Implementation
[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0033] Example 1: Preparation of silver nanoparticles under different cooling media conditions
[0034] This embodiment uses a pulsed-line evaporation apparatus (NTi 10C, Nano Technology Inc.) to prepare silver nanoparticles, the structural schematic of which is shown in the figure below. Figure 1 As shown. The method for preparing silver nanoparticles using this device is as follows:
[0035] (1) A silver wire is loaded into the wire feeding system of the pulsed wire evaporation device and the silver wire is fed into the reaction chamber as an evaporation raw material by the wire feeding system. The bottom end of the silver wire is located between the anode and cathode.
[0036] (2) Add liquid cooling medium to the reaction chamber;
[0037] (3) Set the pulse power supply voltage, explosion length and number of explosions on the instrument control panel. When the instrument is running, apply a pulse current to the silver wire to make the silver wire evaporate instantaneously to form silver vapor.
[0038] (4) The silver vapor rapidly condenses in the liquid cooling medium to form silver nanoparticles and disperse them in the cooling medium.
[0039] More specifically, in this embodiment, a silver wire with a diameter of 0.2 mm is selected as the evaporation material, and the pulse power supply voltage is set to 330V, the explosion length is 24 mm, and the number of explosions is 500 on the instrument control panel.
[0040] Deionized water and high-purity ethanol (purity ≥99%) were used as cooling media, respectively, while other process parameters remained consistent. The silver vapor generated by the explosion condensed in the cooling media, yielding a silver nanoparticle dispersion system. Figure 2 The coolant was removed using a rotary evaporator. The resulting sample was dried and placed on a clean silicon wafer for characterization and analysis using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Figure 3 , Figure 4 ).
[0041] The results show that high-purity silver particles were successfully prepared using both deionized water and ethanol as cooling media. The particles had a near-spherical morphology and a particle size in the nanoscale range.
[0042] Example 2: Characterization of the particle size distribution of silver nanoparticles
[0043] The silver nanoparticles obtained in Example 1 were analyzed using a MasterSizer 3000 laser particle size analyzer to determine the particle size distribution of particles prepared with different coolants. The results are as follows: Figure 5 As shown in Table 1 below.
[0044] Table 1. Characterization of particle size distribution of silver particles prepared under different cooling media conditions
[0045]
[0046] Note: d 10 d 50 d 90 These represent 10%, 50%, and 90% of particles smaller than this particle size, respectively.
[0047] The particle size distribution results show that different coolants have a significant impact on the particle size of silver particles. The silver particle sample using water as the coolant has a d50 of 2.35 µm and a d90 as high as 23.2 µm, indicating the presence of numerous large agglomerates and a relatively dispersed particle size distribution. In contrast, the silver particle sample using ethanol as the coolant has a d50 of only 0.22 µm and a d90 that decreases to 3.18 µm, with the particle size distribution clearly concentrated towards smaller particle sizes. This indicates that the ethanol system can effectively suppress the aggregation of silver particles, which is beneficial for obtaining a particle system with better dispersion. This difference is mainly related to the different surface tensions of the solvents and their different effects on particle surface stabilization.
[0048] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. Any changes made by those skilled in the art after reading the specification of the present invention, as long as they are within the scope of the claims of the present invention, will be protected by patent law.
Claims
1. A method for preparing silver nanoparticles based on pulsed-line evaporation technology, characterized in that, Includes the following steps: (1) A silver wire is loaded into the reaction chamber of the pulsed line evaporator as the evaporation raw material; (2) A liquid cooling medium is added to the reaction chamber, wherein the liquid cooling medium is an alcohol solvent, water, or a mixture of water and an alcohol solvent, and the alcohol solvent is one or more of ethanol, propanol, or butanol; (3) Apply a pulsed current to the silver wire to make the silver wire evaporate instantaneously to form silver vapor; (4) The silver vapor rapidly condenses in the liquid cooling medium to form silver nanoparticles and disperse them in the cooling medium.
2. The method for preparing silver nanoparticles based on pulsed line evaporation technology according to claim 1, characterized in that, In step (1), the diameter of the silver wire is 0.1-0.3 mm.
3. The method for preparing silver nanoparticles based on pulsed line evaporation technology according to claim 2, characterized in that, In step (3), the supply voltage of the pulse current is 200-400 V.
4. The method for preparing silver nanoparticles based on pulsed line evaporation technology according to claim 3, characterized in that, In step (3), the evaporation process is repeated 100-800 times, and the evaporation length of the silver wire is 20-25 mm.
5. The method for preparing silver nanoparticles based on pulsed line evaporation technology according to claim 4, characterized in that, When the liquid cooling medium is ethanol, the prepared silver nanoparticles have a d50 of 0.22 μm and a d90 of 3.18 μm.
6. The method for preparing silver nanoparticles based on pulsed line evaporation technology according to claim 4, characterized in that, When the liquid cooling medium is water, the prepared silver nanoparticles have a d50 of 2.35µm and a d90 of 23.2µm.
7. Silver nanoparticles prepared by the method according to any one of claims 1-6.
8. The application of the silver nanoparticles according to claim 7 in the preparation of high-performance conductive ink.