Method for preparing nano copper powder based on microwave-assisted reduction method and application

Abstract

The invention discloses a method for preparing nano copper powder based on a microwave-assisted reduction method and application. The method comprises the following steps: a) preparing a copper ion solution; b) adding a dispersing agent and a surfactant; c) adding a reducing agent; d) microwave heating reaction; e) separating and purifying a product; and f) drying. According to the method, directional reduction and morphology regulation and control of copper ions are achieved through the synergistic effect of a microwave field and chemical reduction, the specific surface area of the obtained product reaches 25-35 m < 2 > / g, the oxygen content is lower than 0.8 wt%, and excellent performance is shown in the fields of electronic packaging and conductive ink; the method has the characteristics of short reaction time (shortened by 90% compared with the traditional method), low energy consumption (less than 0.5 kWh / kg), no harmful by-product and the like, and meets the requirements of green chemical industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterial preparation, and in particular to a method for preparing nano copper powder based on a microwave-assisted reduction method and application thereof. Background Art

[0002] Nano-copper powders, due to their high electrical and thermal conductivity, and excellent antibacterial properties, have important applications in electronics, electrical appliances, catalysts, and antimicrobial agents. High-purity copper pastes made from nano-copper powders can replace precious metal silver pastes in the electronics industry, effectively reducing costs in the manufacture of conductive inks and electronic pastes.

[0003] Currently, the main methods for preparing nano-copper powder include chemical reduction, thermal decomposition, microemulsion, and electrochemical methods. However, these methods have problems such as harsh reaction conditions, long reaction times, high energy consumption, uneven particle size, and severe agglomeration, which limit the industrial production and application of nano-copper powder. The specific comparison results are shown in Table 1.

[0004] Table 1:

[0005] Preparation method Reaction time Average particle size <![CDATA[Specific surface area (m 2 / g)]]> Copper purity Specific energy consumption (kWh / kg) Traditional chemical reduction method 2-4 hours 150nm 12-18 98.5％ 8.2 Microemulsion method 6-8 hours 80nm 20-25 99.0％ 12.5 Method of the present invention 5 minutes 65nm 25-30 99.8％ 3.1 ;

[0006] Microwave-assisted chemical reactions have the advantages of uniform heating, fast speed, and high selectivity, which can effectively improve the shortcomings of traditional methods. However, the application of microwave technology in the preparation of nano-copper powders is still lacking in systematic research and application.

[0007] Therefore, developing a new method for preparing nano-copper powder using microwave technology that is simple, efficient, and highly controllable has important theoretical significance and practical value. Summary of the Invention

[0008] In view of this, the present invention provides a method for preparing nano copper powder based on a microwave-assisted reduction method and its application.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] A method for preparing nano copper powder based on microwave-assisted reduction method comprises the following steps:

[0011] a) preparing a copper ion solution: dissolving a soluble copper salt in deionized water to obtain a copper ion solution;

[0012] b) adding a dispersant and a surfactant: adding a dispersant and a surfactant to the copper ion solution of step a), stirring uniformly to form a stable solution;

[0013] c) adding a reducing agent: adding a reducing agent to the solution in proportion while stirring, and continuing to stir to form a uniform reaction mixture;

[0014] d) microwave heating reaction: transferring the reaction mixture of step c) into a microwave reaction vessel and heating;

[0015] e) Product separation and purification: After the reaction is completed, cool, centrifuge and separate the product, wash and remove impurities;

[0016] f) Drying: Dry the product at low temperature to obtain nano copper powder.

[0017] Preferably, in step a), the soluble copper salt is one or more of copper sulfate or copper chloride;

[0018] Wherein, the concentration of soluble copper salt is 0.1-0.5 mol / L, preferably 0.2 mol / L.

[0019] Preferably, in step b), the dispersant is polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG);

[0020] Among them, the mass ratio of dispersant / copper salt is 1:5 to 1:2, and the optimal mass ratio of PVP / copper salt is 1:4.

[0021] Preferably, in step b), the surfactant is sodium dodecyl sulfate (SDS).

[0022] Preferably, in step c), the reducing agent is one or more of hydrazine hydrate or ethylene glycol;

[0023] The molar ratio of reducing agent to copper salt is 2:1 to 5:1, and the molar ratio of hydrazine hydrate to copper salt is preferably 3:1.

[0024] Preferably, in step d), the microwave power is 400-800 W, the heating time under the microwave power is 1-10 minutes, and the microwave heating temperature is 60-100° C.;

[0025] The microwave field strength is 10-30kV / m and the power density is 0.5-2.0W / cm 3 .

[0026] Preferably, in the step f), the obtained nano copper powder particles have a particle size of 50-100 nm, and are characterized by uniform particle size and a network structure;

[0027] Its network structure meets the following requirements: node density ≥ 3×10 3 pieces / μm 2 , porosity 50-70%;

[0028] The drying temperature at low temperature is 40-50°C and the drying time is 10-12 hours.

[0029] A method for preparing nano-copper powder based on microwave-assisted reduction and its application in high-performance and high-purity copper slurry, comprising the nano-copper powder in step f), a binder and a solvent;

[0030] The specific preparation method is as follows:

[0031] 1) Adding nano copper powder to a mixture of an organic binder and a solvent under stirring;

[0032] 2) Using ball milling or ultrasonic treatment to fully disperse the nano copper powder to form a uniform copper slurry;

[0033] 3) Adjust the viscosity to ensure that the copper paste has good coating properties.

[0034] Preferably, in step 2), 20-100 kHz ultrasonic waves are applied with a sound intensity range of 10-100 W / L.

[0035] Preferably, it can also be used to manufacture electronic materials such as conductive inks and electronic pastes.

[0036] Compared with the prior art, the present invention has achieved the following technical effects:

[0037] (1) Preparation of nano-copper powder by microwave-assisted reduction: Nano-copper powder was prepared using microwave heating technology for the first time, which significantly improved the reduction reaction efficiency and shortened the reaction time;

[0038] (2) Preparation of network-structured nano-copper powder: The prepared nano-copper particles have a network structure, which improves the conductivity and performance stability of the material;

[0039] (3) Process parameter optimization: By systematically studying the effects of microwave power, reaction time, temperature and other parameters on the product, a highly controllable preparation method was established;

[0040] (4) Green and environmentally friendly: The reaction process is pollution-free and uses environmentally friendly reducing agents such as hydrazine hydrate and ethylene glycol, which is in line with the concept of green chemistry;

[0041] (5) Application of high-performance copper paste: Nano copper powder was successfully applied to the preparation of high-purity copper paste, which improved the conductivity and stability of the paste and has important application value;

[0042] (6) Simple operation: This method is easy to operate and has a short reaction time, which is 90% shorter than that of traditional methods, and has low energy consumption of <0.5kWh / kg;

[0043] (7) Synergistic effect of microwave field and chemical reduction: This method realizes the directional reduction and morphology control of copper ions through the synergistic effect of microwave field and chemical reduction. The specific surface area of the obtained product reaches 25-35m 2 / g, with an oxygen content of less than 0.8wt%, it exhibits excellent performance in the fields of electronic packaging and conductive inks. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a flow chart of the present invention;

[0045] Figure 2 This is the SEM image of the nano copper powder prepared by the present invention;

[0046] Figure 3 This is a diagram showing the effect of microwave field intensity on product morphology in the present invention. DETAILED DESCRIPTION

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0048] The present invention discloses a method for preparing nano copper powder based on a microwave-assisted reduction method, comprising the following steps:

[0049] a) preparing a copper ion solution: dissolving a soluble copper salt in deionized water to obtain a copper ion solution;

[0050] b) adding a dispersant and a surfactant: adding a dispersant and a surfactant to the copper ion solution of step a), stirring uniformly to form a stable solution;

[0051] c) adding a reducing agent: adding a reducing agent to the solution in proportion while stirring, and continuing to stir to form a uniform reaction mixture;

[0052] d) Microwave heating reaction: the reaction mixture of step c) is transferred to a microwave reaction vessel, the microwave power is 400-800W, the heating time is 1-10 minutes at the microwave power, the microwave heating temperature is 60-100°C; the microwave field intensity is 10-30kV / m, the power density is 0.5-2.0W / cm 3 ;

[0053] e) Product separation and purification: After the reaction is completed, the product is cooled, centrifuged, and washed three times with deionized water and anhydrous ethanol to remove unreacted reagents and impurities;

[0054] f) Drying: Dry the product at a low temperature of 40 to 50° C. for 10 to 12 hours to obtain nano copper powder.

[0055] In step a), the soluble copper salt is one or more of copper sulfate or copper chloride;

[0056] Wherein, the concentration of soluble copper salt is 0.1-0.5 mol / L, preferably 0.2 mol / L.

[0057] In step b), the dispersant is polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG);

[0058] Among them, the mass ratio of dispersant / copper salt is 1:5 to 1:2, and the optimal mass ratio of PVP / copper salt is 1:4.

[0059] In step b), the surfactant is sodium dodecyl sulfate (SDS).

[0060] In step c), the reducing agent is one or more of hydrazine hydrate or ethylene glycol;

[0061] The molar ratio of reducing agent to copper salt is 2:1 to 5:1, and the molar ratio of hydrazine hydrate to copper salt is preferably 3:1.

[0062] Microwave frequency 2.45GHz and Cu 2 + The dipole relaxation frequency of the hydrated ions matches, generating selective heating with a local temperature gradient of up to 10 3 K / s, promoting nucleation rate (>1×10 20 nuclei / (m 3 ·s));

[0063] In step f), the obtained nano copper powder particles have a particle size of 50-100 nm, and are characterized by uniform particle size and a network structure;

[0064] Its network structure meets the following requirements: node density ≥ 3×10 3 pieces / μm 2 , porosity 50-70%;

[0065] The network structure formation mechanism is caused by the non-equilibrium conditions caused by microwaves:

[0066] Surface energy anisotropy (Δγ=0.15J / m 2 );

[0067] Directed attachment growth (OA mechanism) is dominant (>80%);

[0068] Ostwald ripening was inhibited (<5%);

[0069] The drying temperature at low temperature is 40-50°C and the drying time is 10-12 hours.

[0070] The present invention also discloses a method for preparing nano copper powder based on microwave assisted reduction and its application in high performance and high purity copper slurry, which is prepared from the nano copper powder in step f), a binder and a solvent;

[0071] The specific preparation method is as follows:

[0072] 1) Adding nano copper powder to a mixture of an organic binder and a solvent under stirring;

[0073] 2) Using ball milling or ultrasonic treatment to fully disperse the nano copper powder to form a uniform copper slurry;

[0074] 3) Adjust the viscosity to ensure that the copper paste has good coating properties.

[0075] In step 2), applying 20-100 kHz ultrasonic waves with a sound intensity range of 10-100 W / L;

[0076] It can be used in high-performance and high-purity copper pastes and can also be used to manufacture electronic materials such as conductive inks and electronic pastes.

[0077] Example 1: Preparation of nano copper powder using hydrazine hydrate as reducing agent

[0078] 1. Reagents and Materials:

[0079] Copper salt: copper sulfate pentahydrate (CuSO4·5H2O), analytical grade;

[0080] Reducing agent: hydrazine hydrate (N2H4·H2O), analytical grade;

[0081] Dispersant: polyvinylpyrrolidone (PVP, K30), analytical grade;

[0082] Solvent: deionized water.

[0083] 2. Preparation steps:

[0084] a) Prepare copper salt solution: Weigh 12.5 g of copper sulfate pentahydrate and dissolve it in 250 ml of deionized water to obtain 0.2 mol / L of Cu 2+ solution;

[0085] b) Adding a dispersant: Add the Cu 2+ Add 2.5 g of PVP to the solution and stir for 30 minutes until it is completely dissolved to form a uniform blue solution;

[0086] c) Adding a reducing agent: Slowly add 50 ml of 1 mol / L hydrazine hydrate solution while stirring. Continue stirring for 15 minutes until the color of the solution gradually changes from blue to dark brown.

[0087] d) Microwave heating reaction: The mixed solution of step c) was transferred to a microwave reaction vessel, placed in a microwave reactor, and the microwave power was set to 600 W, the reaction time was 5 minutes, and the temperature was controlled at 80° C.;

[0088] e) Product Isolation and Purification: After the reaction, the container was removed, cooled to room temperature, and centrifuged at 8000 rpm for 10 minutes. The supernatant was discarded, and the precipitate was washed three times with deionized water and anhydrous ethanol to remove unreacted reagents and by-products.

[0089] f) Drying: The washed product was placed in a vacuum drying oven and dried at 40° C. for 12 hours to obtain red nano-copper powder.

[0090] 3. Characterization of results:

[0091] Particle size analysis: Transmission electron microscopy (TEM) observation showed that the obtained nano-copper particles were spherical, with a particle size distribution of 50-80nm, and a network structure formed between the particles;

[0092] Crystal structure: X-ray diffraction (XRD) test confirmed that the product is pure copper crystal, without impurity peaks such as copper oxide;

[0093] Specific surface area: According to BET test, the specific surface area of nano copper powder is 25m 2 / g.

[0094] The comparison table of reaction time and copper conversion rate is shown in Table 2:

[0095] Table 2: Comparison of reaction time and copper conversion rate

[0096] Reaction time (min) Copper conversion rate 1 38％ 3 72％ 5 98％ 7 99％ .

[0097] Example 2: Preparation of Nano-Copper Powder Using Ethylene Glycol as Reducing Agent

[0098] 1. Reagents and Materials:

[0099] Copper salt: copper chloride dihydrate (CuCl2·2H2O), analytical grade;

[0100] Reducing agent: ethylene glycol (C2H6O2), analytical grade;

[0101] Dispersant: polyethylene glycol (PEG-400), analytical grade;

[0102] Surfactant: sodium dodecyl sulfate (SDS), analytical grade;

[0103] Solvent: deionized water.

[0104] 2. Preparation steps:

[0105] a) Prepare copper salt solution: Weigh 8.5 g of copper chloride dihydrate and dissolve it in 250 ml of deionized water to obtain 0.2 mol / L of Cu 2+ solution;

[0106] b) Adding dispersant and surfactant: Add the Cu 2+ 2 g of PEG-400 and 0.5 g of SDS were added to the solution and stirred for 20 min to form a homogeneous solution;

[0107] c) Adding a reducing agent: Add 100 ml of ethylene glycol while stirring and continue stirring for 10 minutes;

[0108] d) Microwave heating reaction: The mixed solution of step c) was transferred to a microwave reaction vessel, placed in a microwave reactor, and the microwave power was set to 700 W, the reaction time was 8 minutes, and the temperature was controlled at 90° C.;

[0109] e) Product separation and purification: After the reaction is completed, the product is cooled to room temperature, centrifuged, and washed three times with deionized water and anhydrous ethanol respectively;

[0110] f) Drying: The product was placed in a vacuum drying oven and dried at 50° C. for 10 hours to obtain nano-copper powder.

[0111] 3. Characterization of results:

[0112] Particle size analysis: Scanning electron microscopy (SEM) observations show that the nano-copper particles have a particle size distribution of 60-100 nm, presenting a network structure with tightly connected particles.

[0113] Thermogravimetric analysis (TGA): The mass loss is small below 200 °C, indicating that the product has good thermal stability.

[0114] Example 3: Nano copper powder used in the preparation of high-purity copper slurry

[0115] 1. Preparation of high-purity copper slurry:

[0116] Raw materials: nano copper powder prepared in Example 1, with a mass fraction of 70%; an organic binder (such as ethyl cellulose solution), and a solvent (such as xylene).

[0117] step:

[0118] 1) Adding nano copper powder to a mixture of an organic binder and a solvent under stirring;

[0119] 2) Using ball milling or ultrasonic treatment to fully disperse the nano copper powder to form a uniform copper slurry;

[0120] 3) Adjust the viscosity to ensure that the copper paste has good coating properties.

[0121] 2. Performance testing:

[0122] Conductivity: Copper paste was coated on the substrate and its resistivity was measured after drying. The results showed low resistivity and excellent conductivity.

[0123] Stability: The copper slurry has good stability after being placed at room temperature for 30 days without obvious sedimentation or stratification.

[0124] During the microwave reaction, 40kHz ultrasonic waves were applied at a power density of 50W / L;

[0125] Improved performance:

[0126] The particle size distribution is narrowed to 50-70nm;

[0127] The specific surface area is increased to 32m 2 / g;

[0128] The resistivity of copper paste is reduced to 2.1×10 -6 Ω·m (reduced by 18%)

[0129] Implementation effect:

[0130] The comparison of copper paste properties is shown in Table 3;

[0131] Table 3: Comparison of copper paste performance indicators

[0132] Performance indicators Traditional copper paste Copper paste of the present invention Improvement Resistivity (Ω·m) <![CDATA[5.8×10 -6 ]]> <![CDATA[2.5×10 -6 ]]> 56.9％ Sintering temperature (℃) 350 280 Reduce 70℃ Adhesion (MPa) 8.2 12.5 52.4％ Storage stability (months) 3 6 100％ .

[0133] Example 4: Effect of reaction conditions on the particle size of nano-copper powder

[0134] Microwave power gradient control experiment:

[0135] Three-stage power control:

[0136] Initial stage (0-1min): 800W rapid nucleation;

[0137] Growth stage (1-4min): 600W directional growth;

[0138] Stabilization stage (4-5 min): 400W structural relaxation;

[0139] Effect:

[0140] A monodisperse network structure was obtained (PDI = 0.15);

[0141] The copper paste printing line width can reach 20μm (traditional method>50μm);

[0142] Example 5: Effect of microwave power on nano-copper particles (one)

[0144] 1. Reagents and Materials:

[0145] Copper salt: copper sulfate pentahydrate (CuSO4·5H2O), analytical grade;

[0146] Reducing agent: hydrazine hydrate (N2H4·H2O), analytical grade;

[0147] Dispersant: polyvinylpyrrolidone (PVP, K30), analytical grade;

[0148] Solvent: deionized water.

[0149] 2. Preparation steps:

[0150] a) Prepare copper salt solution: Weigh 12.5 g of copper sulfate pentahydrate and dissolve it in 250 ml of deionized water to obtain 0.2 mol / L of Cu 2+ solution;

[0151] b) Adding a dispersant: Add the Cu 2+ Add 2.5 g of PVP to the solution and stir for 30 minutes until it is completely dissolved to form a uniform blue solution;

[0152] c) Adding a reducing agent: Slowly add 50 ml of 1 mol / L hydrazine hydrate solution while stirring. Continue stirring for 15 minutes until the color of the solution gradually changes from blue to dark brown.

[0153] d) Microwave heating reaction: The mixed solution of step c) was transferred to a microwave reaction vessel, placed in a microwave reactor, set the microwave power to 400 W, the reaction time to 5 minutes, and the temperature to 80° C.;

[0154] e) Product Isolation and Purification: After the reaction, the container was removed, cooled to room temperature, and centrifuged at 8000 rpm for 10 minutes. The supernatant was discarded, and the precipitate was washed three times with deionized water and anhydrous ethanol to remove unreacted reagents and by-products.

[0155] f) Drying: The washed product was placed in a vacuum drying oven and dried at 40° C. for 12 hours to obtain red nano-copper powder. (two)

[0157] 1. Reagents and Materials:

[0158] Copper salt: copper sulfate pentahydrate (CuSO4·5H2O), analytical grade;

[0159] Reducing agent: hydrazine hydrate (N2H4·H2O), analytical grade;

[0160] Dispersant: polyvinylpyrrolidone (PVP, K30), analytical grade;

[0161] Solvent: deionized water.

[0162] 2. Preparation steps:

[0163] a) Prepare copper salt solution: Weigh 12.5 g of copper sulfate pentahydrate and dissolve it in 250 ml of deionized water to obtain 0.2 mol / L of Cu 2+ solution;

[0164] b) Adding a dispersant: Add the Cu 2+ Add 2.5 g of PVP to the solution and stir for 30 minutes until it is completely dissolved to form a uniform blue solution;

[0165] c) Adding a reducing agent: Slowly add 50 ml of 1 mol / L hydrazine hydrate solution while stirring. Continue stirring for 15 minutes until the color of the solution gradually changes from blue to dark brown.

[0166] d) Microwave heating reaction: The mixed solution of step c) was transferred to a microwave reaction vessel, placed in a microwave reactor, and the microwave power was set to 600 W, the reaction time was 5 minutes, and the temperature was controlled at 80° C.;

[0167] e) Product Isolation and Purification: After the reaction, the container was removed, cooled to room temperature, and centrifuged at 8000 rpm for 10 minutes. The supernatant was discarded, and the precipitate was washed three times with deionized water and anhydrous ethanol to remove unreacted reagents and by-products.

[0168] f) Drying: The washed product was placed in a vacuum drying oven and dried at 40° C. for 12 hours to obtain red nano-copper powder. (three)

[0170] 1. Reagents and Materials:

[0171] Copper salt: copper sulfate pentahydrate (CuSO4·5H2O), analytical grade;

[0172] Reducing agent: hydrazine hydrate (N2H4·H2O), analytical grade;

[0173] Dispersant: polyvinylpyrrolidone (PVP, K30), analytical grade;

[0174] Solvent: deionized water.

[0175] 2. Preparation steps:

[0176] a) Prepare copper salt solution: Weigh 12.5 g of copper sulfate pentahydrate and dissolve it in 250 ml of deionized water to obtain 0.2 mol / L of Cu 2+ solution;

[0177] b) Adding a dispersant: Add the Cu 2+ Add 2.5 g of PVP to the solution and stir for 30 minutes until it is completely dissolved to form a uniform blue solution;

[0178] c) Adding a reducing agent: Slowly add 50 ml of 1 mol / L hydrazine hydrate solution while stirring. Continue stirring for 15 minutes until the color of the solution gradually changes from blue to dark brown.

[0179] d) Microwave heating reaction: The mixed solution of step c) was transferred to a microwave reaction vessel, placed in a microwave reactor, and the microwave power was set to 800 W, the reaction time was 5 minutes, and the temperature was controlled at 80° C.;

[0180] e) Product Isolation and Purification: After the reaction, the container was removed, cooled to room temperature, and centrifuged at 8000 rpm for 10 minutes. The supernatant was discarded, and the precipitate was washed three times with deionized water and anhydrous ethanol to remove unreacted reagents and by-products.

[0181] f) Drying: The washed product was placed in a vacuum drying oven and dried at 40° C. for 12 hours to obtain red nano-copper powder.

[0182] 3. Results:

[0183] Influence of microwave power: As the microwave power increases, the particle size of nano-copper particles decreases, but too high a power can easily cause excessive aggregation.

[0184] Example 6: Effect of reaction time on nano-copper particles (one)

[0186] 1. Reagents and Materials:

[0187] Copper salt: copper sulfate pentahydrate (CuSO4·5H2O), analytical grade;

[0188] Reducing agent: hydrazine hydrate (N2H4·H2O), analytical grade;

[0189] Dispersant: polyvinylpyrrolidone (PVP, K30), analytical grade;

[0190] Solvent: deionized water.

[0191] 2. Preparation steps:

[0192] a) Prepare copper salt solution: Weigh 12.5 g of copper sulfate pentahydrate and dissolve it in 250 ml of deionized water to obtain 0.2 mol / L of Cu 2+ solution;

[0193] b) Adding a dispersant: Add the Cu 2+ Add 2.5 g of PVP to the solution and stir for 30 minutes until it is completely dissolved to form a uniform blue solution;

[0194] c) Adding a reducing agent: Slowly add 50 ml of 1 mol / L hydrazine hydrate solution while stirring. Continue stirring for 15 minutes until the color of the solution gradually changes from blue to dark brown.

[0195] d) Microwave heating reaction: The mixed solution of step c) was transferred to a microwave reaction vessel, placed in a microwave reactor, and the microwave power was set to 600 W, the reaction time was 3 minutes, and the temperature was controlled at 80° C.;

[0196] e) Product Isolation and Purification: After the reaction, the container was removed, cooled to room temperature, and centrifuged at 8000 rpm for 10 minutes. The supernatant was discarded, and the precipitate was washed three times with deionized water and anhydrous ethanol to remove unreacted reagents and by-products.

[0197] f) Drying: The washed product was placed in a vacuum drying oven and dried at 40° C. for 12 hours to obtain red nano-copper powder. (two)

[0199] 1. Reagents and Materials:

[0200] Copper salt: copper sulfate pentahydrate (CuSO4·5H2O), analytical grade;

[0201] Reducing agent: hydrazine hydrate (N2H4·H2O), analytical grade;

[0202] Dispersant: polyvinylpyrrolidone (PVP, K30), analytical grade;

[0203] Solvent: deionized water.

[0204] 2. Preparation steps:

[0205] a) Prepare copper salt solution: Weigh 12.5 g of copper sulfate pentahydrate and dissolve it in 250 ml of deionized water to obtain 0.2 mol / L of Cu 2+ solution;

[0206] b) Adding a dispersant: Add the Cu 2+ Add 2.5 g of PVP to the solution and stir for 30 minutes until it is completely dissolved to form a uniform blue solution;

[0207] c) Adding a reducing agent: Slowly add 50 ml of 1 mol / L hydrazine hydrate solution while stirring. Continue stirring for 15 minutes until the color of the solution gradually changes from blue to dark brown.

[0208] d) Microwave heating reaction: The mixed solution of step c) was transferred to a microwave reaction vessel, placed in a microwave reactor, and the microwave power was set to 600 W, the reaction time was 5 minutes, and the temperature was controlled at 80° C.;

[0209] e) Product Isolation and Purification: After the reaction, the container was removed, cooled to room temperature, and centrifuged at 8000 rpm for 10 minutes. The supernatant was discarded, and the precipitate was washed three times with deionized water and anhydrous ethanol to remove unreacted reagents and by-products.

[0210] f) Drying: The washed product was placed in a vacuum drying oven and dried at 40° C. for 12 hours to obtain red nano-copper powder. (three)

[0212] 1. Reagents and Materials:

[0213] Copper salt: copper sulfate pentahydrate (CuSO4·5H2O), analytical grade;

[0214] Reducing agent: hydrazine hydrate (N2H4·H2O), analytical grade;

[0215] Dispersant: polyvinylpyrrolidone (PVP, K30), analytical grade;

[0216] Solvent: deionized water.

[0217] 2. Preparation steps:

[0218] a) Prepare copper salt solution: Weigh 12.5 g of copper sulfate pentahydrate and dissolve it in 250 ml of deionized water to obtain 0.2 mol / L of Cu 2+ solution;

[0219] b) Adding a dispersant: Add the Cu 2+ Add 2.5 g of PVP to the solution and stir for 30 minutes until it is completely dissolved to form a uniform blue solution;

[0220] c) Adding a reducing agent: Slowly add 50 ml of 1 mol / L hydrazine hydrate solution while stirring. Continue stirring for 15 minutes until the color of the solution gradually changes from blue to dark brown.

[0221] d) Microwave heating reaction: The mixed solution of step c) was transferred to a microwave reaction vessel, placed in a microwave reactor, and the microwave power was set to 600 W, the reaction time was 7 minutes, and the temperature was controlled at 80° C.;

[0222] e) Product Isolation and Purification: After the reaction, the container was removed, cooled to room temperature, and centrifuged at 8000 rpm for 10 minutes. The supernatant was discarded, and the precipitate was washed three times with deionized water and anhydrous ethanol to remove unreacted reagents and by-products.

[0223] f) Drying: The washed product was placed in a vacuum drying oven and dried at 40° C. for 12 hours to obtain red nano-copper powder.

[0224] 3. Results:

[0225] Effect of reaction time: Properly extending the reaction time is beneficial to particle growth, while too long a time will cause the particles to grow and agglomerate.

[0226] Example 7: Effect of reaction temperature on nano-copper particles (one)

[0228] 1. Reagents and Materials:

[0229] Copper salt: copper sulfate pentahydrate (CuSO4·5H2O), analytical grade;

[0230] Reducing agent: hydrazine hydrate (N2H4·H2O), analytical grade;

[0231] Dispersant: polyvinylpyrrolidone (PVP, K30), analytical grade;

[0232] Solvent: deionized water.

[0233] 2. Preparation steps:

[0234] a) Prepare copper salt solution: Weigh 12.5 g of copper sulfate pentahydrate and dissolve it in 250 ml of deionized water to obtain 0.2 mol / L of Cu 2+ solution;

[0235] b) Adding a dispersant: Add the Cu 2+ Add 2.5 g of PVP to the solution and stir for 30 minutes until it is completely dissolved to form a uniform blue solution;

[0236] c) Adding a reducing agent: Slowly add 50 ml of 1 mol / L hydrazine hydrate solution while stirring. Continue stirring for 15 minutes until the color of the solution gradually changes from blue to dark brown.

[0237] d) Microwave heating reaction: The mixed solution of step c) was transferred to a microwave reaction vessel, placed in a microwave reactor, and the microwave power was set to 600 W, the reaction time was 5 minutes, and the temperature was controlled at 60° C.;

[0238] e) Product Isolation and Purification: After the reaction, the container was removed, cooled to room temperature, and centrifuged at 8000 rpm for 10 minutes. The supernatant was discarded, and the precipitate was washed three times with deionized water and anhydrous ethanol to remove unreacted reagents and by-products.

[0239] f) Drying: The washed product was placed in a vacuum drying oven and dried at 40° C. for 12 hours to obtain red nano-copper powder. (two)

[0241] 1. Reagents and Materials:

[0242] Copper salt: copper sulfate pentahydrate (CuSO4·5H2O), analytical grade;

[0243] Reducing agent: hydrazine hydrate (N2H4·H2O), analytical grade;

[0244] Dispersant: polyvinylpyrrolidone (PVP, K30), analytical grade;

[0245] Solvent: deionized water.

[0246] 2. Preparation steps:

[0247] a) Prepare copper salt solution: Weigh 12.5 g of copper sulfate pentahydrate and dissolve it in 250 ml of deionized water to obtain 0.2 mol / L of Cu 2+ solution;

[0248] b) Adding a dispersant: Add the Cu 2+ Add 2.5 g of PVP to the solution and stir for 30 minutes until it is completely dissolved to form a uniform blue solution;

[0249] c) Adding a reducing agent: Slowly add 50 ml of 1 mol / L hydrazine hydrate solution while stirring. Continue stirring for 15 minutes until the color of the solution gradually changes from blue to dark brown.

[0250] d) Microwave heating reaction: The mixed solution of step c) was transferred to a microwave reaction vessel, placed in a microwave reactor, and the microwave power was set to 600 W, the reaction time was 5 minutes, and the temperature was controlled at 80° C.;

[0251] e) Product Isolation and Purification: After the reaction, the container was removed, cooled to room temperature, and centrifuged at 8000 rpm for 10 minutes. The supernatant was discarded, and the precipitate was washed three times with deionized water and anhydrous ethanol to remove unreacted reagents and by-products.

[0252] f) Drying: The washed product was placed in a vacuum drying oven and dried at 40° C. for 12 hours to obtain red nano-copper powder. (three)

[0254] 1. Reagents and Materials:

[0255] Copper salt: copper sulfate pentahydrate (CuSO4·5H2O), analytical grade;

[0256] Reducing agent: hydrazine hydrate (N2H4·H2O), analytical grade;

[0257] Dispersant: polyvinylpyrrolidone (PVP, K30), analytical grade;

[0258] Solvent: deionized water.

[0259] 2. Preparation steps:

[0260] a) Prepare copper salt solution: Weigh 12.5 g of copper sulfate pentahydrate and dissolve it in 250 ml of deionized water to obtain 0.2 mol / L of Cu 2+ solution;

[0261] b) Adding a dispersant: Add the Cu 2+ Add 2.5 g of PVP to the solution and stir for 30 minutes until it is completely dissolved to form a uniform blue solution;

[0262] c) Adding a reducing agent: Slowly add 50 ml of 1 mol / L hydrazine hydrate solution while stirring. Continue stirring for 15 minutes until the color of the solution gradually changes from blue to dark brown.

[0263] d) Microwave heating reaction: The mixed solution of step c) was transferred to a microwave reaction vessel, placed in a microwave reactor, and the microwave power was set to 600 W, the reaction time was 5 minutes, and the temperature was controlled at 100° C.;

[0264] e) Product Isolation and Purification: After the reaction, the container was removed, cooled to room temperature, and centrifuged at 8000 rpm for 10 minutes. The supernatant was discarded, and the precipitate was washed three times with deionized water and anhydrous ethanol to remove unreacted reagents and by-products.

[0265] f) Drying: The washed product was placed in a vacuum drying oven and dried at 40° C. for 12 hours to obtain red nano-copper powder.

[0266] 3. Results:

[0267] Influence of reaction temperature: Higher temperature is conducive to increasing the reaction rate, but too high temperature will cause particle oxidation.

[0268] In summary, the optimal conditions are: microwave power 600 W, reaction time 5 minutes, and temperature 80°C, which can obtain nano-copper powder with uniform particle size and good dispersibility.

[0269] Through the above examples 1-7, it can be seen that the method of the present invention has the following advantages:

[0270] Fast reaction speed: Microwave heating accelerates the reaction process and the preparation time is short, only 1-10 minutes;

[0271] Strong controllability of particle size: By adjusting the reaction conditions and additives, the particle size and morphology of nano copper powder can be controlled;

[0272] Excellent product performance: The prepared nano copper powder has uniform particle size and a network structure, which is beneficial to improving the conductivity of copper slurry;

[0273] The process is simple and environmentally friendly: the reaction conditions are mild, no high temperature or high pressure is required, the operation is simple, and no harmful substances are emitted during the reaction;

[0274] Suitable for industrial production: the process is easy to scale up, the production cost is low, and it has broad application prospects.

[0275] The above description is merely a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing nano copper powder based on microwave-assisted reduction, characterized in that: The following steps are involved: a) preparing a copper ion solution: dissolving a soluble copper salt in deionized water to obtain a copper ion solution; b) adding a dispersant and a surfactant: adding a dispersant and a surfactant to the copper ion solution of step a), stirring uniformly to form a stable solution; c) adding a reducing agent: adding a reducing agent to the solution in proportion while stirring, and continuing to stir to form a uniform reaction mixture; d) microwave heating reaction: transferring the reaction mixture of step c) into a microwave reaction vessel and heating; e) Product separation and purification: After the reaction is completed, cool, centrifuge and separate the product, wash and remove impurities; f) Drying: Dry the product at low temperature to obtain nano copper powder.

2. The method for preparing nano copper powder based on microwave-assisted reduction according to claim 1, wherein: In step a), the soluble copper salt is one or more of copper sulfate and copper chloride; Wherein, the concentration of soluble copper salt is 0.1-0.5 mol / L, preferably 0.2 mol / L.

3. The method for preparing nano copper powder based on microwave-assisted reduction according to claim 1, wherein: In the step b), the dispersant is polyvinyl pyrrolidone (PVP) or polyethylene glycol (PEG); Among them, the mass ratio of dispersant / copper salt is 1:5 to 1:2, and the optimal mass ratio of PVP / copper salt is 1:

4.

4. The method for preparing nano copper powder based on microwave-assisted reduction according to claim 1, wherein: In the step b), the surfactant is sodium dodecyl sulfate (SDS).

5. The method for preparing nano copper powder based on microwave-assisted reduction according to claim 1, wherein: In the step c), the reducing agent is one or more of hydrazine hydrate and ethylene glycol; The molar ratio of reducing agent to copper salt is 2:1 to 5:1, and the molar ratio of hydrazine hydrate to copper salt is preferably 3:

1.

6. The method for preparing nano copper powder based on microwave-assisted reduction according to claim 1, characterized in that: In the step d), the microwave power is 400-800W, the heating time is 1-10 minutes under the microwave power, and the microwave heating temperature is 60-100°C; The microwave field strength is 10-30kV / m and the power density is 0.5-2.0W / cm 3 .

7. The method for preparing nano copper powder based on microwave-assisted reduction according to claim 1, characterized in that: In the step f), the obtained nano copper powder particles have a particle size of 50-100 nm, and are characterized by uniform particle size and a network structure; Its network structure meets the following requirements: node density ≥ 3×10 3 pieces / μm 2 , porosity 50-70%; The drying temperature at low temperature is 40-50°C and the drying time is 10-12 hours.

8. The use of the method for preparing nano-copper powder based on microwave-assisted reduction according to claims 1-7 in high-performance and high-purity copper slurry, characterized in that: Made from the nano copper powder, binder and solvent in step f); The specific preparation method is as follows: 1) Adding nano copper powder to a mixture of an organic binder and a solvent under stirring; 2) Using ball milling or ultrasonic treatment to fully disperse the nano copper powder to form a uniform copper slurry; 3) Adjust the viscosity to ensure that the copper paste has good coating properties.

9. The method for preparing nano copper powder based on microwave-assisted reduction according to claim 8, characterized in that: In the step 2), 20-100 kHz ultrasonic waves are applied with a sound intensity range of 10-100 W / L.

10. Application of the method for preparing nano-copper powder based on microwave-assisted reduction method according to claim 8 in high-performance and high-purity copper slurry, characterized in that: It can also be used to manufacture electronic materials such as conductive inks and electronic pastes.

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