Surface modification method of antioxidant micro-nano copper-based powder

Abstract

The invention discloses a surface modification method for anti-oxidation micro-nano copper-based powder. The surface modification method comprises the following steps: (1) carrying out pretreatment on the micro-nano copper-based powder to remove an oxidation layer on the surface of the copper powder; (2) phosphating treatment is conducted, specifically, phosphoric acid, nitric acid, a surfactant and deionized water are added into the pretreated copper-based powder obtained in the step (1), stirring is conducted, and a phosphating reaction is conducted; after the reaction is finished, filtering and separating the copper-based powder, and cleaning to obtain phosphatized micro-nano copper-based powder; (3) compounding and coating by adding a reducing agent into an organic matter: adding the organic matter, the reducing agent and ethanol or deionized water into the copper phosphide powder obtained in the step (2), stirring and compounding and coating; and (4) post-treatment is conducted, specifically, the compounded and coated micro-nano copper-based powder in the step (3) is cleaned and dried, and the anti-oxidation micro-nano copper-based powder with the modified surface is obtained. According to the method, the micro-nano copper-based powder is good in compactness and high in adhesive force, and has active repairing capacity and good oxidation resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fine metal powder materials for electronic paste, in particular to a surface modification method of an oxidation-resistant micro-nano copper-based powder. BACKGROUND

[0002] The micro-nano copper-based powder includes micro-nano copper powder and micro-nano copper alloy powder, such as micro-nano copper-silver alloy powder, micro-nano copper-nickel alloy powder, and micro-nano copper-zirconium alloy powder. The micro-nano copper-based powder is widely used in the fields of electronics, chemical industry, metallurgy, etc. due to its excellent electrical conductivity, thermal conductivity, and low cost advantage. However, the micro-nano copper-based powder has a large specific surface area and high surface activity, and is prone to react with oxygen and moisture in the air, such as water vapor, to form an oxidation layer, which leads to a decrease in electrical conductivity and poor dispersibility, and seriously affects the product quality and service life, so it needs to be treated by oxidation-resistant surface modification.

[0003] The oxidation-resistant surface modification treatment method of the copper-based powder in the prior art mainly includes two types, each having its own shortcomings:

[0004] One is surface conversion treatment, which is a method of treating the surface of the material by physical and chemical methods to improve the oxidation resistance by changing the composition and structure of the copper powder. Common methods include phosphating and passivation. Phosphating treatment mainly forms a phosphating film on the surface of the copper-based powder to isolate the corrosive medium, but the phosphating film has a microporous structure, and oxygen and moisture can easily penetrate the pores to cause oxidation failure of the copper-based powder during long-term use. Passivation, also known as chromate treatment, is a process in which the metal surface is converted into a chromate film as the main film component, but the passivation layer is prone to decomposition, dissolution, or peeling, and cannot maintain the oxidation resistance effect for a long time. The process is complex, the cost is high, and the environmental protection and application adaptability are poor.

[0005] The second is surface coating treatment, which forms a stable protective film on the surface of the micro-nano copper-based powder to slow down the oxidation rate. The protective layer is generally made of organic matter or metal material. Organic matter coating treatment relies on the coordination of organic matter and copper to form a hydrophobic film to isolate oxygen and water, but the film layer is prone to wear and tear. After the film layer is worn or peeled off, the copper-based powder will quickly oxidize. Metal coating, such as tin-coated copper-based powder or silver-coated copper-tin powder, relies on the physical barrier of the metal layer to block oxygen and moisture, but it has the shortcomings of insufficient integrity and stability of the coating layer, complex process, high cost, limited environmental protection and application adaptability, etc. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a surface modification method of an oxidation-resistant micro-nano copper-based powder, which has good compactness, strong adhesion, active repair ability, long-term stable oxidation resistance, and excellent oxidation resistance performance.

[0007] The technical solution of the present application is to provide a surface modification method of antioxidant micro-nano copper-based powder, comprising the following steps:

[0008] (1) The micro-nano copper-based powder is pretreated or pre-processed to remove the surface oxide layer of the micro-nano copper-based powder;

[0009] (2) Phosphating treatment: phosphoric acid, nitric acid, a surfactant and deionized water are added to the pretreated micro-nano copper-based powder obtained in step (1), stirring and carrying out phosphating reaction; after the reaction is completed, the micro-nano copper-based powder is separated by filtration and washed to obtain phosphated micro-nano copper-based powder;

[0010] (3) Organic compound and reducing agent compounding coating: organic compound, reducing agent and ethanol or deionized water are added to the phosphated micro-nano copper-based powder obtained in step (2), stirring and compounding coating;

[0011] (4) Post-treatment: the compounding coated micro-nano copper-based powder in step (3) is washed and dried to obtain the surface modified antioxidant micro-nano copper-based powder.

[0012] After the above process steps, the surface modification method of the antioxidant micro-nano copper-based powder has the following advantages:

[0013] The present application realizes the synergistic improvement of the compactness, antioxidant stability and adhesion of the coating layer of the micro-nano copper-based powder by constructing the double protection structure of inorganic phosphating and organic compound and reducing agent compounding coating.

[0014] The micro-nano copper-based powder treated by the surface modification method has excellent oxidation resistance: nitric acid as an oxidizing agent can accelerate the dissolution of trace copper ions on the surface of the micro-nano copper-based powder, and react rapidly with phosphate to generate Cu3(PO4)2 (copper phosphate) and CuHPO4 (hydrogen copper phosphate) and other phosphating products. These phosphating products are deposited on the surface of the micro-nano copper-based powder to form a continuous and dense inorganic film, and the porosity of the film is much lower than that of a single organic coating film such as a BTA film. The film can physically block the contact of oxygen and water with the copper matrix, avoid the oxidation reaction of the micro-nano copper-based powder, and the phosphating layer serves as an inorganic barrier, and the density is much better than that of a single organic film. The surfactant can be adsorbed on the surface of the micro-nano copper-based powder through coordination, to form a steric hindrance layer, reduce the film layer porosity, and further enhance the isolation effect, solving the defects of the traditional single phosphating film, such as many pores and poor long-term oxidation resistance. The organic matter can form a stable chelate with the trace copper ions exposed on the phosphating film, to form an organic coating layer outside the phosphating film, further enhance the hydrophobic property, reduce the water vapor adsorption on the surface of the micro-nano copper-based powder, and fill the small pores of the phosphating film, forming a double physical barrier of inorganic and organic.

[0015] The micro-nano copper-based powder treated by the surface modification method has excellent dispersion performance: the initial agglomeration can be broken by pre-treatment and stirring. The phosphating treatment introduces surface charges, and enhances the repulsive force between particles. When Cu3(PO4)2 (copper phosphate) and other products generated by the phosphating reaction are deposited on the surface of the micro-nano copper-based powder, the micro-nano copper-based powder surface will be negatively charged due to the adsorption of phosphate. According to the colloid stability theory, the particles with the same charge will generate electrostatic repulsive force, hindering the particles from approaching each other. At the same time, the surfactant added in the phosphating process can change the surface properties of the powder particles through three types of action mechanisms, such as interface adsorption, electrostatic repulsion and steric hindrance, to weaken the agglomeration force between particles. For example, the hydroxyl groups (-OH) on the surface of the phosphating film can form hydrogen bonds with the pyrrolidone carbonyl groups of the non-ionic surfactant PVP, the end hydroxyl and ether oxygen groups of PEG, the polyoxyethylene chain ether oxygen groups and hydroxyl groups of Tween-80, and Span-80, to further disperse the particles and reduce the agglomeration of the copper-based powder during the phosphating process. When the organic matter and the reducing agent are compounded and coated, the hydrophobic groups of the organic matter stretch outward, so that the surface of the copper-based powder changes from hydrophilic to lipophilic, reducing the hydrophobic attraction between particles. At the same time, the coating layer formed by the organic molecules on the surface of the micro-nano copper-based powder can produce a steric hindrance effect, physically hindering the particle agglomeration, so that the micro-nano copper-based powder has excellent dispersion performance.

[0016] Further, the specific operation of step (1) is as follows: Weigh a certain amount of micro / nano copper-based powder, add a 5%-10% dilute sulfuric acid solution, the solid-liquid ratio of the micro / nano copper-based powder to the dilute sulfuric acid solution is 125-250 g / L, stir at 30℃ or room temperature for 30-60 min to remove the oxide layer on the surface of the copper powder; after stirring, filter to separate the micro / nano copper-based powder, wash the micro / nano copper-based powder with deionized water and anhydrous ethanol until the pH of the filtrate is 6.5-7, and obtain the pretreated micro / nano copper-based powder. After adopting the above steps, the present invention uses a 5%-10% dilute sulfuric acid concentration in the pretreatment in step (1), which can not only efficiently remove the oxide layer such as copper oxide and cuprous oxide on the surface of the micro / nano copper-based powder, but also avoid excessive corrosion of the micro / nano copper-based powder matrix. Washing with deionized water until neutral, followed by washing with anhydrous ethanol, thoroughly removes residual sulfuric acid to prevent excessive acidity in the subsequent phosphating solution. Simultaneously, it rapidly removes surface moisture from the micro / nano copper powder to avoid secondary oxidation after pretreatment, providing a clean surface for the phosphating reaction and further ensuring the excellent antioxidant properties of the micro / nano copper powder. Dilute sulfuric acid dissolves the oxide layer on the copper powder surface (CuO + H₂SO₄ = CuSO₄ + H₂O), eliminating the agglomeration attraction caused by the oxide layer. The local shear force generated by stirring breaks up the hard agglomerates of the micro / nano copper powder. Washing with deionized water and anhydrous ethanol to pH 6.5–7 thoroughly removes residual sulfuric acid and impurity ions, preventing secondary agglomeration caused by ion attraction. At the same time, anhydrous ethanol rapidly replaces surface moisture in the micro / nano copper powder, preventing re-agglomeration due to moisture adsorption after pretreatment, further ensuring the excellent dispersibility of the micro / nano copper powder.

[0017] Further, in step (2), the mass ratio of phosphoric acid to micro / nano copper powder is 0.32g-0.64g / 1g, and the mass ratio of nitric acid to micro / nano copper powder is 0.06g-0.12g / 1g; wherein the surfactant is one or more of PVP, PEG, CTAB, Tween-80, and ammonium dodecylbenzenesulfonate, and the mass ratio of surfactant to micro / nano copper powder is 0.01g-0.03g:1g; the solid-liquid ratio of micro / nano copper powder to deionized water is 125-250g / L. After adopting the above steps, in step (2) phosphating treatment, the use of a compound phosphating solution of phosphoric acid and nitric acid can accelerate the phosphating reaction rate, refine the phosphating film grains, improve the film density, and further ensure the excellent antioxidant properties of micro-nano copper powder. Surfactants such as PVP and PEG can be adsorbed on the surface of micro-nano copper powder through coordination to form a steric hindrance layer, prevent the micro-nano copper powder particles from agglomerating, improve their dispersibility in the liquid phase, and further ensure the excellent dispersion performance of micro-nano copper powder.

[0018] Further, in step (2), the phosphating reaction is carried out by stirring at 40-80℃ for 30-90 min; after the reaction, the micro-nano copper powder is separated by filtration, and the copper powder is washed twice each with deionized water and anhydrous ethanol to obtain phosphated micro-nano copper powder. After adopting the above steps, the reaction temperature is mild. Below this temperature, the phosphating film forms slowly, and above this temperature, the phosphating film is prone to cracking. The thickness of the phosphating film is controllable, and the stirring time, washing materials, and washing times are reasonably designed, which further ensures the excellent antioxidant properties and excellent dispersibility of the micro-nano copper powder.

[0019] Further, in step (3), an organic solution of 0.05-0.2 mol / L is added to the phosphated micro / nano copper powder obtained in step (2). The organic substance is one or more of BTA, TTA, MBT, hexamethyltetramine, and benzimidazole. The solvent is ethanol or deionized water. Then, a reducing agent is added. The reducing agent is one or more of ascorbic acid, citric acid, glucose, formic acid, lactic acid, and hydrazine hydrate. The mass ratio of organic substance to reducing agent is 1.5-2:1. Under stirring conditions, the mixture is reacted at 30-60℃ for 1-4 hours to perform compound coating. After adopting the above steps, the organic matter and reducing agent are combined and coated to achieve a dual synergistic protective effect. The organic matter can form chelates with the trace copper ions exposed in the phosphating film, enhancing the bonding force between the organic layer and the phosphating film. The dense inorganic film physically isolates oxygen and moisture, and the reducing agent can actively repair tiny oxidation points and compensate for film defects. The multiple factors work together to solve the functional defects of single organic coating. The reaction temperature is compatible with the chelation reaction of organic matter and the stability of reducing agent. The appropriate reaction time can ensure uniform coverage of the organic layer, further guaranteeing the excellent antioxidant performance of micro-nano copper powder.

[0020] Further, in step (4), the micro / nano copper-based powder coated in step (3) is filtered and separated, washed twice with anhydrous ethanol, and then dried in a vacuum drying oven at 50-80℃ for 3-6 hours to obtain surface-modified antioxidant micro / nano copper-based powder. Using the above steps improves the washing effect, and the appropriate drying temperature and time prevent carbonization of the organic coating layer, further ensuring the excellent antioxidant and dispersibility properties of the micro / nano copper-based powder.

[0021] Furthermore, the micro / nano copper-based powder includes micro / nano copper powder, micro / nano copper-silver alloy powder, copper-nano copper-tin alloy powder, and micro / nano copper-zirconium alloy powder, etc. After adopting the above steps, the surface modification method for antioxidant micro / nano copper-based powders of the present invention can be adapted to micro / nano copper powder, micro / nano copper-silver alloy powder, copper-nano copper-tin alloy powder, and micro / nano copper-zirconium alloy powder, etc. It can specifically solve the technical problems of micro / nano copper-based powders having large specific surface area and high surface activity, easily reacting with oxygen and moisture in the air to form an oxide layer, leading to decreased conductivity, poor dispersibility, and seriously affecting product quality and service life. It effectively ensures the excellent antioxidant properties and excellent dispersibility of micro / nano copper powder, micro / nano copper-silver alloy powder, copper-nano copper-tin alloy powder, and micro / nano copper-zirconium alloy powder, etc., effectively guaranteeing high product quality and long service life.

[0022] In addition to the advantages and technical effects mentioned above, the surface modification method for antioxidant micro / nano copper powder of the present invention also has the following advantages and technical effects: low cost, green and environmentally friendly, simple process and suitable for large-scale industrial production: for example, the phosphating solution is conventional phosphoric acid and nitric acid, the organic coating agent is low-cost BTA and TTA, etc., plus reducing agent such as ascorbic acid, etc., without introducing heavy metals such as chromates, and without precious metals and high-end organic reagents. For example, the entire process uses deionized water and / or ethanol for washing, the wastewater is easy to treat and there is no harmful gas emission, which is more environmentally friendly; simple process: the whole process takes less time, such as 30-60 min for pretreatment, 30-90 min for phosphating, and 1-4 h for organic coating, which improves the deoxidation efficiency. The organic coating does not require precise dripping as some existing technologies, only stirring for 1-4 h, which greatly reduces costs while ensuring high performance; easy to scale up production, adaptable to industrial mass production, and suitable for large-scale industrial applications. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the thermogravimetric curves of the surface modification method of the present invention in both the embodiment and the comparative example.

[0024] Figure 2 SEM image of raw copper powder without any processing;

[0025] Figure 3 This is a SEM image of copper powder from Comparative Example 1 of the surface modification method of this invention;

[0026] Figure 4 This is a SEM image of copper powder from Comparative Example 2 of the surface modification method of the present invention;

[0027] Figure 5 This is a SEM image of copper powder in Comparative Example 3 of the surface modification method of the present invention;

[0028] Figure 6 This is a SEM image of copper powder from Example 1 of the surface modification method of the present invention. Detailed Implementation

[0029] The present invention will now be further described with reference to the accompanying drawings. It should be noted that the description of these specific embodiments is intended to aid in understanding the present invention, but does not constitute a limitation thereof.

[0030] Example 1

[0031] 250g of micro / nano copper powder was added to 2000ml of 5% dilute sulfuric acid solution and stirred at room temperature using ultrasonic and magnetic stirring (hereinafter referred to as ultrasonic and magnetic stirring) for 30min. After filtration, the powder was washed with deionized water until the pH of the filtrate was 7, and then washed twice with anhydrous ethanol. 2000ml of deionized water, 80g of phosphoric acid, 30g of nitric acid and 5g of PVP were added to the pretreated micro / nano copper powder, and stirred at 65℃ using magnetic stirring (hereinafter referred to as magnetic stirring) for 45min. After filtration, the powder was washed once each with deionized water and anhydrous ethanol to obtain phosphated micro / nano copper powder. 1000ml of ethanol, 11.9g of BTA and 6g of ascorbic acid were added to the phosphated micro / nano copper powder, and the mixture was reacted at 30℃ for 3h. After filtering to separate the copper powder, the powder was washed twice with anhydrous ethanol. The micro / nano copper powder was then dried in a vacuum drying oven at 80℃ for 5h to obtain micro / nano copper powder with excellent antioxidant properties and excellent dispersibility.

[0032] Example 2

[0033] Add 50g of copper-silver alloy powder to 200ml of 10% dilute sulfuric acid solution, sonicate and magnetically stir for 60min at room temperature; after filtration, wash with deionized water until the pH of the filtrate is 6.7, and then wash twice with anhydrous ethanol; add 200ml of deionized water, 16g of phosphoric acid, 4.5g of nitric acid and 1g of PEG to the pretreated micro-nano copper-silver alloy powder, and magnetically stir for 45min at 55℃; after filtration, wash once each with deionized water and anhydrous ethanol to obtain phosphated micro-nano copper-silver alloy powder; add 200ml of deionized water, 2.2g of TTA and 1.2g of citric acid to the phosphated micro-nano copper-silver alloy powder, react at 45℃ for 2h, filter to separate the micro-nano copper-silver alloy powder, wash twice with anhydrous ethanol, and dry the micro-nano copper-silver alloy powder in a vacuum drying oven at 70℃ for 4h to obtain micro-nano copper-silver alloy powder with excellent antioxidant properties and excellent dispersibility.

[0034] Example 3

[0035] 75g of micro / nano copper powder was added to 300ml of 6% dilute sulfuric acid solution and ultrasonically stirred magnetically at 30℃ for 45min. After filtration, the powder was washed with deionized water until the pH of the filtrate was 6.5, and then washed twice with anhydrous ethanol. 375ml of deionized water, 25g of phosphoric acid, 6g of nitric acid and 1.5g of CTAB were added to the pretreated micro / nano copper powder and magnetically stirred at 65℃ for 40min. After filtration, the powder was washed once with deionized water and once with anhydrous ethanol to obtain phosphated micro / nano copper powder. 400ml of ethanol, 4g of MBT and 2.8g of formic acid were added to the phosphated micro / nano copper powder and reacted at 30℃ for 3h. After filtration to separate the copper powder, the powder was washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 60℃ for 5h to obtain micro / nano copper powder with excellent antioxidant properties and excellent dispersibility.

[0036] Example 4

[0037] 1000g of micro / nano copper powder was added to 4000ml of 5% dilute sulfuric acid solution and ultrasonically and magnetically stirred for 30min at room temperature. After filtration, the powder was washed with deionized water until the pH of the filtrate was 7, and then washed twice with anhydrous ethanol. 4000ml of deionized water, 320g of phosphoric acid, 90g of nitric acid and 20g of Tween-80 were added to the pretreated micro / nano copper powder, and the mixture was magnetically stirred at 80℃ for 40min. After filtration, the powder was washed once with deionized water and once with anhydrous ethanol to obtain phosphated micro / nano copper powder. 4000ml of deionized water, 36g of hexamethylenetetramine and 23.8g of lactic acid were added to the phosphated micro / nano copper powder, and the mixture was reacted at 60℃ for 1h. After filtration to separate the micro / nano copper powder, the powder was washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 50℃ for 6h to obtain micro / nano copper powder with excellent antioxidant properties and excellent dispersibility.

[0038] Example 5

[0039] 1200g of micro / nano copper-nickel alloy powder was added to 4800ml of 7.5% dilute sulfuric acid solution and ultrasonically and magnetically stirred for 30min at room temperature. After filtration, the powder was washed with deionized water until the pH of the filtrate was 6.8, and then washed twice with anhydrous ethanol. 4800ml of deionized water, 480g of phosphoric acid, 140g of nitric acid and 30g of Tween-80 were added to the pretreated micro / nano copper-nickel alloy powder, and the mixture was magnetically stirred at 80℃ for 40min. After filtration, the powder was washed once with deionized water and once with anhydrous ethanol to obtain micro / nano copper-nickel phosphide alloy powder. 3000ml of ethanol, 72g of BTA and 48g of glucose were added to the micro / nano copper-nickel alloy powder, and the mixture was reacted at 60℃ for 1h. After filtration to separate the micro / nano copper-nickel alloy powder, the powder was washed twice with anhydrous ethanol and then dried in a vacuum drying oven at 60℃ for 6h to obtain micro / nano copper-nickel alloy powder with excellent antioxidant properties and excellent dispersibility.

[0040] Example 6

[0041] 90g of micro / nano copper-zirconium alloy powder was added to 360ml of 10% dilute sulfuric acid solution and ultrasonically and magnetically stirred for 30min at room temperature. After filtration, the powder was washed with deionized water until the pH of the filtrate was 6.9, and then washed twice with anhydrous ethanol. 380ml of deionized water, 32g of phosphoric acid, 9g of nitric acid and 2g of ammonium dodecylbenzenesulfonate were added to the pretreated micro / nano copper-zirconium alloy powder, and the mixture was magnetically stirred at 80℃ for 40min. After filtration, the powder was washed once with deionized water and once with anhydrous ethanol to obtain micro / nano copper-zirconium phosphate alloy powder. 36ml of ethanol, 3.8g of benzimidazole and 1.9g of hydrazine hydrate were added to the micro / nano copper-zirconium phosphate alloy powder, and the mixture was reacted at 60℃ for 1h. After filtration to separate the micro / nano copper-zirconium alloy powder, the powder was washed twice with anhydrous ethanol. The micro / nano copper-zirconium alloy powder was dried in a vacuum drying oven at 75℃ for 6h to obtain micro / nano copper-zirconium alloy powder with excellent antioxidant properties and excellent dispersibility.

[0042] Comparative Example 1 (Single Phosphating Treatment)

[0043] The copper powder from Example 1 was subjected to pickling pretreatment and phosphating treatment only, without subsequent organic coating.

[0044] Comparative Example 2 (Single BTA Encapsulation)

[0045] The phosphating step in Example 1 is omitted, and the organic coating removes the ascorbic acid reagent.

[0046] Comparative Example 3 (Single Ascorbic Acid Coating)

[0047] The phosphating step in Example 1 is omitted, and the organic coating removes the reagent BTA.

[0048] TGA test: The oxidation resistance of copper powder was tested by measuring the TG curves of copper powder pretreated only by acid pickling, Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, which showed the onset temperature and weight gain trend of oxidation in air. The results are as follows: Figure 1 .from Figure 1 It can be seen that the antioxidant properties of copper powders in Comparative Examples 1, 2, and 3 are improved compared to those treated only with acid washing, but the effect is not particularly significant. However, the antioxidant properties of the micro / nano copper powder in Example 1 are significantly improved, indicating that constructing a dual-protective structure—an inorganic phosphating base followed by a complex coating of organic matter and a reducing agent—has a positive effect on improving the antioxidant properties of micro / nano copper powders. TGA testing shows that its oxidation initiation temperature is much higher than that of single phosphating treatment and single organic coating, and its long-term antioxidant stability is significantly improved.

[0049] As can be seen from the various SEM images, Figure 2The raw powder shown has a thin oxide layer on its surface, which indicates poor antioxidant properties. Figure 3 The SEM results of Comparative Example 1, which only underwent phosphating treatment, show that there are shortcomings of the phosphating treatment described in the background art. However, as an inorganic base layer process of the present invention, the phosphating sample has a smooth and clean surface, which provides an anchor point for subsequent organic compound coating with reducing agent. Furthermore, the phosphating design using nitric acid and phosphoric acid does not introduce other metal ions such as traditional manganese, iron and zinc phosphating and chromate passivation, which can ensure the purity of micro and nano copper powder. Figure 4 Comparative Example 2, which shows SEM results of only BTA coating, reveals that the sample surface is covered with a thin, flocculent coating layer, which is loose and easily peeled off. Figure 5 The SEM results of Comparative Example 2, which only involved ascorbic acid coating, show that its organic layer is easily detached due to friction, exhibiting the shortcomings of organic coating in the surface coating described in the background art. The method of this invention addresses these shortcomings. Figure 3 and Figure 4 Based on this, by adding a reducing agent, the bonding force between the organic layer and the phosphating film is enhanced. The reducing agent's reducing properties can actively repair tiny oxidation points. Even if the film layer is locally damaged, the reducing agent can quickly repair the oxidation points. These multiple factors synergistically address the defects of single phosphating treatment and the functional deficiencies of single organic coating, ultimately resulting in... Figure 6 The SEM results of Example 1 of this invention show a micro / nano copper-based powder with uniform coating, strong adhesion, and excellent antioxidant properties. Furthermore, this micro / nano copper-based powder is lower in cost and more environmentally friendly compared to metal coatings. Figure 6 The SEM results of Example 1 of the present invention show that the micro-nano copper-based powder particles are distinct, indicating that it has excellent dispersion performance.

[0050] It's easy to understand that phosphoric acid is also called orthophosphoric acid. PVP stands for polyvinylpyrrolidone. BTA stands for benzotriazole. Ascorbic acid is vitamin C. PEG stands for polyethylene glycol. TTA stands for methylbenzotriazole. CTAB stands for cetyltrimethylammonium bromide or cetyltrimethylammonium bromide. MBT stands for 2-mercaptobenzothiazole. Tween-80 stands for polyoxyethylene sorbitan monooleate. In this invention, phosphoric acid and nitric acid are expressed in grams (g) rather than by volume because their densities can easily deviate from the effective component content measured by volume due to variations in concentration and temperature. Using grams allows for precise control of the ratio with micro / nano copper-based powders, ensuring repeatability of the phosphating reaction and the quality of the phosphating film, which also aligns with industry practice.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for surface modification of an antioxidant micro-nano copper-based powder, characterized in that: The method comprises the following steps: (1) removing the surface oxide layer of the micro-nano copper-based powder for pretreatment; (2) phosphating treatment: adding phosphoric acid, nitric acid, a surfactant and deionized water into the pretreated micro-nano copper-based powder obtained in step (1), stirring and performing phosphating reaction; after the reaction is completed, the micro-nano copper-based powder is separated by filtration and is cleaned to obtain phosphated micro-nano copper-based powder; (3) organic compound and reducing agent compounding coating: adding an organic compound, a reducing agent and ethanol or deionized water into the micro-nano phosphated copper-based powder obtained in step (2), stirring and performing compounding coating; (4) post-treatment: cleaning and drying the micro-nano copper-based powder coated in step (3) to obtain the surface-modified anti-oxidation micro-nano copper-based powder. 2.The method for surface modification of antioxidant micro-nano copper-based powder according to claim 1, characterized in that: In step (1), a certain amount of micro-nano copper-based powder is weighed, a 5%-10% dilute sulfuric acid solution is added, the solid-liquid ratio of the micro-nano copper-based powder to the dilute sulfuric acid solution is 125-250 g / L, and stirring is performed at 30 DEG C or room temperature for 30-60 min to remove the surface oxide layer of the micro-nano copper-based powder; after the stirring is completed, the micro-nano copper-based powder is separated by filtration, the micro-nano copper-based powder is washed with deionized water and anhydrous ethanol until the pH of the filtrate is 6.5-7, and the pretreated micro-nano copper-based powder is obtained. 3.The method for surface modification of antioxidant micro-nano copper-based powder according to claim 1, characterized in that: In step (2), the mass ratio of phosphoric acid to the micro-nano copper-based powder is 0.32 g-0.64 g / 1 g, and the mass ratio of nitric acid to the micro-nano copper-based powder is 0.06 g-0.12 g / 1 g; the surfactant is one or more of PVP, PEG, CTAB, Tween-80 and dodecyl benzene sulfonic acid ammonium, and the mass ratio of the surfactant to the micro-nano copper-based powder is 0.01 g-0.03 g:1 g; the solid-liquid ratio of the micro-nano copper-based powder to deionized water is 125-250 g / L. 4.The method for surface modification of antioxidant micro-nano copper-based powder according to claim 3, characterized in that: In step (2), the phosphating reaction is performed by stirring at 40-80 DEG C for 30-90 min; after the reaction is completed, the micro-nano copper-based powder is separated by filtration, and the copper powder is washed with deionized water and anhydrous ethanol respectively for 2 times to obtain the phosphated micro-nano copper-based powder. 5.The method for surface modification of antioxidant micro-nano copper-based powder according to claim 1, characterized in that: In step (3), 0.05-0.2 mol / L of an organic compound solution is added into the phosphated micro-nano copper-based powder obtained in step (2), the organic compound is one or more of BTA, TTA, MBT, hexamethylene tetramine and benzimidazole, the solvent is ethanol or deionized water, a reducing agent is further added, the reducing agent is one or more of ascorbic acid, citric acid, glucose, formic acid, lactic acid, hydrazine hydrate and dimethylamine borane, the mass ratio of the organic compound to the reducing agent is 1.5-2:1, and the compounding coating is performed by stirring at 30-60 DEG C for 1-4 h. 6.The method for surface modification of antioxidant micro-nano copper-based powder according to claim 1, characterized in that: In step (4), the micro-nano copper-based powder coated in step (3) is separated by filtration, washed with anhydrous ethanol for 2 times, and then dried in a vacuum drying oven at 50-80 DEG C for 3-6 h to obtain the surface-modified anti-oxidation micro-nano copper-based powder.

7. The method of surface modification of antioxidant micro-nano copper-based powder according to any one of claims 1-6, characterized in that: The micro-nano copper-based powder includes micro-nano copper powder, micro-nano copper-silver alloy powder, micro copper-tin alloy powder and micro-nano copper-zirconium alloy powder.

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