A room-temperature photochemical preparation method for nano-tungsten copper composite materials

Abstract

The application discloses a kind of room temperature photochemical preparation method of nano tungsten copper composite material belongs to the field of composite material.Copper ion and sodium ascorbate constitute photosensitive reduction system, and under the illumination of ultraviolet light, primary copper nanoparticles are generated.Amine group in auxiliary agent forms polydentate coordination to copper nanoparticles, and each amine group-containing auxiliary agent molecular chain can anchor multiple nanoparticles, and the entanglement of different amine group-containing auxiliary agent molecular chains forms a spatial network between nanoparticles;Amide unit in amine group-containing auxiliary agent is used to adjust the distance between amine groups, so that the distance between nanoparticles is maintained appropriately.The above two effects enable the primary nanoparticles to continue to grow and connect under continuous light, forming a dense structure.The long molecular chain of amine group-containing auxiliary agent can also form a wrap around tungsten nanoparticles, solving the problem of weak tungsten-copper interface bonding, so that the copper produced by photochemical reaction can spread and deposit on the tungsten surface.

Description

Technical Field

[0001] This invention relates to a method for preparing nano-tungsten-copper composite materials in a one-step process at room temperature using a photochemical reaction. This invention belongs to the field of composite materials. Background Technology

[0002] Tungsten-copper composites possess high hardness, high strength, low coefficient of thermal expansion, good arc resistance, and excellent electrical and thermal conductivity, making them widely used in defense, aerospace, and civilian industries, particularly in high-voltage circuit contact components, welding electrodes, electronic packaging, and heat dissipation devices. However, due to the significant differences in the physicochemical properties of tungsten and copper, the tungsten and copper phases in tungsten-copper composites cannot effectively dissolve, hindering interfacial bonding and densification, thus limiting the continuous improvement of high performance. Recent studies have shown that using tungsten and copper nanoparticles as starting materials to prepare tungsten-copper composites with nanoscale grain structures can effectively improve their overall performance. This is because nanoparticles have a higher specific surface area and surface energy, resulting in more thorough interfacial bonding and a greater tendency for densification during sintering. Simultaneously, the rearrangement process of nano-W particles during liquid-phase sintering provides higher capillary forces, accelerating the densification of tungsten-copper composites. Nanoscale W and Cu particles also contribute to improving the uniformity of the material's microstructure, thereby significantly improving its physical and mechanical properties.

[0003] Currently, there are two main methods for preparing nano-tungsten-copper composite materials. One method involves powder metallurgy infiltration, where dealloying is used to prepare a W framework with open nanopores. Molten Cu then enters the W framework via capillary action, filling its voids to form the nano-tungsten-copper composite material. The other method involves liquid-phase sintering, where high-energy ball milling repeatedly deforms and breaks down the raw materials, achieving submicron-level mixing through mechanical alloying. The resulting nano-tungsten-copper composite material is then obtained through cold pressing and sintering. To address the issue of uneven Cu distribution due to cold welding during mechanical alloying, a mechanical-chemical alloying technique can be used to mix the raw materials. This method first mechanically grinds W and Cu oxides, utilizing the brittleness of the metal oxides to obtain smaller, more uniform nano-mixed powders. Then, a chemical reduction method is used to obtain metallic W and Cu. Additionally, wet chemical methods can also prepare well-dispersed nano-tungsten-copper composite powders. The precursor solution is sprayed, gelled, or precipitated, followed by calcination and reduction to convert metal ions in the solution into metal nanoparticles.

[0004] Unfortunately, all the methods described above require high-temperature processes (typically >950℃) in their preparation. Nanocrystals have poor thermal stability and are prone to unstable growth under heating conditions, causing the product's structure, composition, and phase distribution to deviate from the initial design. For example, during liquid-phase sintering, nano-W particles can rapidly grow to micrometer sizes, losing the performance enhancement benefits of nanoscale effects. Simultaneously, abnormal grain growth at higher temperatures can easily lead to uneven phase and grain size distribution in the final product, affecting the material's physical and mechanical properties. Therefore, there is an urgent need to develop new methods that can simultaneously achieve nanoscale formation and maintain stability in tungsten-copper materials, overcoming existing technological bottlenecks. Summary of the Invention

[0005] This invention proposes a novel method for obtaining nano-tungsten-copper composite materials in one step using a photochemical reaction at room temperature, thereby completely avoiding the high-temperature process at the preparation mechanism level and resolving the contradictions of existing technologies. The specific implementation process of this invention is as follows:

[0006] (1) Preparation of copper deposition solution: Mix copper salt, amine-containing auxiliary agent, and sodium ascorbate to prepare copper deposition solution. Among them, copper chloride or copper sulfate can be selected as copper salt, and its concentration range is generally between 10mM and 60mM; the concentration of sodium ascorbate is generally between 50mM and 200mM; after the addition of amine-containing auxiliary agent, the amine concentration is controlled between 25mM and 140mM.

[0007] Amine-containing additives can be prepared as follows: Pentaethylenehexamine (PEHA) and acrylamide (AAm) are dissolved in water to form a mixed solution, wherein the molar ratio of PEHA to acrylamide is controlled between 1:12 and 1:24, and the absolute concentration of PEHA is not less than 100 mM. A 10% (w / w) ammonium persulfate or potassium persulfate solution is added to this mixture. The volume of the ammonium persulfate or potassium persulfate solution is 5-10% of the total liquid volume. The mixture is allowed to stand for one day to allow the polymerization reaction to occur fully. Finally, water is added to dilute the solution until the amine concentration in the product is uniformly 0.5 M.

[0008] (2) Deposition Preparation: Spread the nano-tungsten powder evenly into a thin layer on the substrate, with a layer thickness generally not exceeding 10 μm. Add the copper deposition solution to the substrate, ensuring the copper deposition solution completely covers the nano-tungsten powder, and maintain a thickness of at least 400 μm between the deposition solution surface and the substrate surface. Figure 1 ).

[0009] (3) Photochemical deposition: The deposition solution and tungsten powder layer are vertically irradiated with a 365nm ultraviolet light source, and the irradiation intensity on the sample surface is not less than 100mM / cm. 2Irradiate continuously for 5-20 minutes to fully reduce Cu ions in the deposition solution and deposit them in the interstices of W powder, forming a nano-tungsten-copper composite material. For cases requiring large amounts of Cu deposition, the deposition solution can be replaced after each deposition for multiple depositions. For cases requiring thicker WCu composite materials, the sample can be washed with deionized water after Cu deposition, followed by a layer of W powder. Repeat the above process until a satisfactory thickness is obtained. Figure 2 ).

[0010] (4) In step (3) above, spatially selective preparation of nano-tungsten-copper composite materials can also be performed. By focusing ultraviolet light onto a specific location in the tungsten powder layer using a projection device, copper can be selectively deposited at that location. The surrounding unlit areas do not react. After deposition, the tungsten powder layer can be rinsed with a large amount of deionized water to remove the unreacted parts, leaving only the nano-tungsten-copper composite material with copper deposited in the specific area. This allows for the preparation of nano-tungsten-copper composite materials of a certain shape.

[0011] The room temperature photochemical preparation principle of nano-tungsten copper composite materials is as follows ( Figure 3 ):

[0012] Copper ions and sodium ascorbate form a photosensitive reduction system, producing primary copper nanoparticles under ultraviolet light. The amine groups in the additive form multidentate coordination with the copper nanoparticles; each amine-containing additive molecular chain can anchor multiple nanoparticles, and the entanglement of different amine-containing additive molecular chains creates a spatial network between the nanoparticles. The amide units in the amine-containing additive adjust the inter-amine spacing, maintaining an appropriate distance between the nanoparticles. These two effects allow the primary nanoparticles to continue growing and connecting under continuous light irradiation, forming a dense structure. The long molecular chains of the amine-containing additive can also encapsulate tungsten nanoparticles, solving the problem of weak bonding at the tungsten-copper interface, allowing the copper produced by the photochemical reaction to spread and deposit on the tungsten surface. Attached Figure Description

[0013] Figure 1 Preparation work for depositing copper in a tungsten powder layer.

[0014] Figure 2 Schematic diagrams of photochemical deposition methods for preparing nano-tungsten-copper composite materials under different modes.

[0015] Figure 3 A schematic diagram illustrating the working principle of preparing amine-containing additives in nano-tungsten-copper composite materials by photochemical deposition.

[0016] Figure 4Microscopic characterization of the nano-tungsten-copper composite material prepared in Example 1. (A) Dark-field microscopy image of W powder thin layer; (B) Dark-field microscopy image of W powder thin layer after Cu deposition; (C) Dark-field microscopy image of commercial tungsten-copper sample; (D) Scanning electron microscopy image of the prepared nano-tungsten-copper composite material; (E) W elemental distribution in region (D); (F) Cu elemental distribution in region (D).

[0017] Figure 5 The effect of multiple depositions on Cu morphology in Example 2. (A) Scanning electron microscope image of the sample surface after multiple depositions; (B) W element distribution in region (A); (C) Cu element distribution in region (A).

[0018] Figure 6 The effect of multilayer deposition on sample thickness in Example 3. (A) Port morphology of a 4-layer deposited sample; (B) Port morphology of a 6-layer deposited sample.

[0019] Figure 7 The regionally selective Cu deposition process in Example 4.

[0020] Figure 8 Limitations of using small molecule amines to assist copper deposition in Comparative Example 1. (A) Dark-field micrograph of the deposited sample surface; (B) Scanning electron microscope image of the deposited sample surface.

[0021] Figure 9 Limitations of using unoptimized amine-based additives to assist copper deposition in Comparative Example 2. (A) Dark-field micrograph of the deposited sample surface; (B) Scanning electron microscope image of the deposited sample surface. Detailed Implementation

[0022] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to the following embodiments. All of the following embodiments use a 365nm ultraviolet light source.

[0023] Example 1:

[0024] 0.3873 g of PEHA and 2.1324 g of AAm were dissolved in 16.5 mL of water to form a mixture. 1 mL of a 10% (w / w) ammonium persulfate solution was added to this mixture, and the mixture was allowed to stand for one day. A 0.5 M amine concentration was obtained and named P3A. Copper chloride, P3A, and sodium ascorbate were mixed to prepare a copper deposition solution. The concentrations were: copper chloride 20 mM, amine 30 mM, and sodium ascorbate 100 mM.

[0025] A substrate coated with a 200 nm tungsten nanoparticle layer was immersed in this deposition solution, with the liquid layer thickness maintained at 1 mm. The irradiation intensity received by the sample surface was 500 mM / cm. 2Irradiation for 10 minutes. Photochemical deposition was performed twice by changing the deposition solution. Optical microscopy characterization of the sample revealed that the red Cu phase filled the voids between the W particles after deposition. Comparison with commercial tungsten-copper samples prepared by powder metallurgy showed that both exhibited similar interwoven network structures; however, the W and Cu phases in the composite material prepared in this invention were at the nanoscale, exhibiting significantly finer microstructure than the commercial tungsten-copper sample. Scanning electron microscopy confirmed that the W and Cu particles in the composite material prepared in this invention formed an interwoven and relatively dense continuous structure, with particle sizes maintained in the range of 100-200 nm. Image analysis showed a density >99.7% (…). Figure 4 ).

[0026] Example 2:

[0027] A copper deposition solution was prepared by mixing copper chloride, P3A, and sodium ascorbate. The concentrations of copper chloride (20 mM), amino groups (30 mM), and sodium ascorbate (100 mM) were used. A substrate coated with a 200 nm tungsten nanoparticle layer was immersed in this deposition solution, maintaining a layer thickness of 1 mm. The irradiation intensity received by the sample surface was 500 mM / cm². 2 Irradiation was performed for 10 minutes. A total of 8 photochemical deposition processes were carried out by changing the deposition solution.

[0028] Scanning electron microscopy revealed that after eight depositions, a large amount of Cu was deposited on the surface of the W particles, forming a shell-like structure that completely obscured the underlying W layer. If only two depositions were performed, as in Example 1, Cu could only barely fill the gaps between the W particles; both elements were still detectable in all regions, albeit in different relative amounts. This verifies that the Cu layer thickness, relative tungsten and copper content, and spatial distribution can be controlled by the number of depositions. Figure 5 ).

[0029] Example 3:

[0030] 0.3873 g of PEHA and 2.8432 g of AAm were dissolved in 15.8 mL of water to form a mixture. 1 mL of a 10% (w / w) ammonium persulfate solution was added to this mixture, and the mixture was allowed to stand for one day. A 0.5 M amine concentration was obtained, named P4A. Copper sulfate, P4A, and sodium ascorbate were mixed to prepare a copper deposition solution. The concentrations were: copper sulfate 20 mM, amine 25 mM, and sodium ascorbate 100 mM. A substrate coated with a 200 nm tungsten nanoparticle layer was immersed in this deposition solution. The tungsten layer thickness was approximately 3 μm, and the liquid layer thickness was maintained at 1 mm. The irradiation intensity on the sample surface was 500 mM / cm². 2 Irradiation was performed for 10 minutes. A total of 4 photochemical deposition processes were carried out by changing the deposition solution.

[0031] The sample surface was washed with deionized water, and the powder deposition process was repeated to prepare two sets of samples: one set containing four layers of W powder and the other containing six layers of W powder. Scanning electron microscopy showed that the total thickness of the four-layer W powder sample was approximately 12 μm, and the total thickness of the six-layer W powder sample was approximately 17 μm. This indicates that the thickness of the tungsten-copper composite material can be controlled through multilayer deposition, and the total thickness of the material generally increases proportionally with the number of deposition cycles. Figure 6 ).

[0032] Example 4:

[0033] 0.3873 g of PEHA and 1.4216 g of AAm were dissolved in 17.2 mL of water to form a mixture. 1 mL of a 10% (w / w) ammonium persulfate solution was added to this mixture, and the mixture was allowed to stand for one day. An auxiliary agent solution with an amino group concentration of 0.5 M was obtained and named P2A. Copper sulfate, P2A, and sodium ascorbate were mixed to prepare a copper deposition solution. The copper sulfate concentration was 40 mM, the amino group concentration was 100 mM, and the sodium ascorbate concentration was 200 mM. A substrate with a 200 nm tungsten nanoparticle layer was immersed in this deposition solution, maintaining a layer thickness of 400 μm. A circular light field was selectively projected onto a specific area of ​​the sample using a dynamic light processing projection device equipped with a 365 nm ultraviolet LED light source, with the sample surface receiving an irradiation intensity of 100 mM / cm². 2 Irradiation for 15 minutes. Photochemical deposition was performed twice by changing the deposition solution.

[0034] The sample surface was repeatedly rinsed with deionized water. The W-powder particles in the un-illuminated areas, lacking adhesion, were washed away, while those in the illuminated areas remained, forming a circular tungsten-copper composite material. This demonstrates that the method can simultaneously control the macroscopic geometry of the obtained sample. Figure 7 ).

[0035] Comparative Example 1:

[0036] 0.3873 g of PEHA was dissolved in 19.6 mL of water to form a mixture. Without adding AAM, a PEHA solution with an amino group concentration of 0.5 M was obtained and named POA. Copper chloride, POA, and sodium ascorbate were mixed to prepare a copper deposition solution. The concentrations were: copper chloride 20 mM, amino group 60 mM, and sodium ascorbate 100 mM.

[0037] A substrate coated with a 200 nm tungsten nanoparticle layer was immersed in this deposition solution, with the liquid layer thickness maintained at 1 mm. The irradiation intensity received by the sample surface was 500 mM / cm. 2Irradiation for 10 minutes. Photochemical deposition was performed twice, with the deposition solution changed. Optical microscopy revealed a large amount of orange granular material after deposition; electron microscopy showed that this was Cu polycrystalline particle growth on the W powder surface. The above experiments indicate that small-molecule polyamines alone cannot solve the wetting problem at the tungsten-copper interface; Cu does not deposit in the interstices of W particles but tends to grow as a separate phase. Figure 8 The product density based on image analysis is <90%.

[0038] Comparative Example 2:

[0039] 0.3873 g of PEHA and 0.7108 g of AAm were dissolved in 17.9 mL of water to form a mixture. 1 mL of a 10% (w / w) ammonium persulfate solution was added to this mixture, and the mixture was allowed to stand for one day. A 0.5 M amine concentration was obtained and named P1A. Copper chloride, P1A, and sodium ascorbate were mixed to prepare a copper deposition solution. The concentrations were: copper chloride 20 mM, amine 60 mM, and sodium ascorbate 100 mM.

[0040] A substrate coated with a 200 nm tungsten nanoparticle layer was immersed in this deposition solution, with the liquid layer thickness maintained at 1 mm. The irradiation intensity received by the sample surface was 500 mM / cm. 2 Irradiation for 10 minutes. Photochemical deposition was performed twice, with the deposition solution changed. Optical microscopy revealed that the voids in the W powder layer after deposition were filled with a red Cu phase. Electron microscopy showed that Cu deposition caused some W powder to co-aggregate into small spheres, but plate-like Cu crystals were also observed. This indicates that when the amine-containing additive composition is not optimal, it can only partially promote the W / Cu interface bonding; at this point, a large amount of deposited Cu tends to form its own phase. Figure 9 The product density based on image analysis is <90%.

Claims

1. A method for the room temperature photochemical preparation of nanosized tungsten copper composites, characterized in that, The method comprises the following steps: (1) configuring a copper deposition solution: mixing copper salt, amine-containing auxiliary agent and sodium ascorbate to prepare a copper deposition solution; wherein the copper salt is copper chloride or copper sulfate, the concentration of which is between 10 mM and 60 mM; the concentration of sodium ascorbate is between 50 mM and 200 mM; the amine concentration of the amine-containing auxiliary agent after addition is controlled between 25 mM and 140 mM; The amine-containing auxiliary agent is prepared as follows: pentethylenehexamine (PEHA) and acrylamide (AAm) are dissolved in water to form a mixed solution, wherein the molar ratio of PEHA to AAm is controlled between 1:12 and 1:24, and the concentration of PEHA is not less than 100 mM; 10% ammonium persulfate or potassium persulfate solution is added to the mixed solution; the volume of the ammonium persulfate or potassium persulfate solution is 5-10% of the mixed solution; the mixed solution is left to stand for one day to allow the polymerization reaction to fully occur; (2) deposition preparation: uniformly spreading nano tungsten powder on the substrate to form a thin layer, the thickness of which is not more than 10 μm; adding the copper deposition solution to the substrate, the copper deposition solution should cover the nano tungsten powder, and the thickness of the copper deposition solution to the substrate surface should be at least 400 μm; (3) Photochemical deposition: a 365 nm ultraviolet light source is vertically irradiated to the deposition liquid and tungsten powder layer, the light source intensity is not less than 100 mM / cm 2 ; irradiate for 5-20 min, so that the Cu ions in the deposition liquid are fully reduced and deposited in the gap of the W powder to form a nano tungsten copper composite material.

2. The method according to claim 1, wherein the method is characterized by, In the case of a large amount of Cu deposition, the deposition solution is replaced after one deposition for multiple depositions.

3. The method according to claim 1, wherein the method is characterized by, In the case of thicker WCu composite material, the sample is cleaned with deionized water after Cu deposition, and then a layer of W powder is laid; the photochemical deposition and cleaning and powder laying operations are repeated until the target thickness is obtained.

4. The method according to claim 1, wherein the method is characterized by, By focusing ultraviolet light on a specific position of the tungsten powder layer through a projection device, copper can be selectively deposited at that position; no reaction occurs in the surrounding unlit area; after deposition, the unreacted part of the tungsten powder layer is washed away with deionized water, leaving only the nano tungsten copper composite material with copper deposited in the specific area; thus, a nano tungsten copper composite material with a certain shape is prepared.

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