Preparation process of high-purity micron copper powder for current sensor

Abstract

This invention relates to the field of current sensor technology, specifically to a process for preparing high-purity micron-sized copper powder for current sensors, comprising the following steps: S1. Raw material pretreatment; S2. Electrolytic purification; S3. Atomization forming; S4. Grading and screening; S5. Rare earth modification; S6. Surface modification. Each process step and functional component of this invention supports and synergistically enhances the other: raw material purification provides a high-purity starting point for electrolytic purification; segmented electrolysis and targeted impurity removal achieve deep purification; vacuum atomization and multi-stage grading ensure uniform particle morphology and size; rare earth modification stabilizes internal impurities; and surface modification constructs external protection. The overall solution achieves a balance of high purity, low oxygen, low resistivity, high sphericity, and high oxidation resistance. The prepared micron-sized copper powder can significantly improve the detection accuracy, signal stability, and service life of current sensors, effectively solving the industry problem that existing copper powders cannot meet the comprehensive performance requirements of current sensors.

Description

Technical Field

[0001] This invention relates to the field of current sensor technology, specifically to the preparation process of high-purity micron-sized copper powder for current sensors. Background Technology

[0002] Current sensors are core sensing components in fields such as power monitoring, new energy control, and industrial automation. Their detection accuracy, response speed, and long-term stability are highly dependent on the material quality of the conductive filler. Micron-sized copper powder is widely used as a key conductive functional material in medium- and low-precision current sensors due to its excellent conductivity, moderate cost, and good processing adaptability.

[0003] In current industrial production, micron-sized copper powder is mostly prepared using electrolysis, atomization, or chemical reduction methods. However, several technical bottlenecks exist in practical applications. First, raw material purity control is insufficient. Electrolysis and smelting processes struggle to efficiently remove low-content harmful impurities such as arsenic, antimony, and bismuth. These impurities tend to agglomerate at grain boundaries, leading to fluctuations in copper powder conductivity and signal transmission distortion, failing to meet the purity requirements for long-term stable sensor operation. Second, conventional atomization and classification processes struggle to simultaneously achieve high sphericity and narrow particle size distribution. Irregular particle morphology and large particle size dispersion result in uneven construction of internal conductive pathways within the sensor, reducing detection linearity and repeatability. Third, copper powder has high chemical reactivity and is prone to surface oxidation under high temperature and humidity environments, causing increased volume resistivity and decreased conductivity, thus affecting the sensor's service life.

[0004] The aforementioned issues collectively make it difficult for commercially available micron-sized copper powder to simultaneously meet the comprehensive requirements of current sensors for high purity, low oxygen, low resistivity, high sphericity, and high environmental stability, thus restricting the performance consistency and reliability of medium- and low-precision current sensors for large-scale applications. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and propose a preparation process for high-purity micron-sized copper powder for current sensors.

[0006] The specific technical solution is as follows: The preparation process of high-purity micron-sized copper powder for current sensors includes the following steps: S1. Raw material pretreatment: Select high-purity cathode copper with a purity of ≥99.995% as raw material, remove the surface oxide layer and impurities, and cut it into copper blocks for later use; S2. Electrolytic purification: The pretreated copper block is used as the anode and the pure titanium plate is used as the cathode. A high-purity electrolyte containing a composite targeted impurity remover is prepared. The electrolysis is controlled in stages. After electrolysis, the product is washed and dried to obtain an intermediate electrolytic copper powder. The composite targeted impurity remover is a mixture of hydroxyethylidene diphosphonic acid, sodium sulfite and tetrabutyl titanate, which can achieve targeted removal of arsenic, antimony and bismuth ions. S3. Atomization Forming: After melting the electrolytic copper powder intermediate in a vacuum induction melting furnace, a high-pressure inert gas atomization method is used to control the oxygen content of the atomization environment to ≤50ppm, thereby obtaining the initial micron-sized copper powder; S4. Grading and screening: The initial micron-sized copper powder is screened using a multi-stage airflow classification method to obtain micron-sized copper powder with uniform particle size; S5. Rare earth modification: The graded copper powder is added to a rare earth modifier and modified under argon protection. After modification, the temperature is lowered to obtain rare earth modified copper powder. The rare earth elements and residual trace impurities form stable intermetallic compounds. S6. Surface modification: Rare earth modified copper powder is treated with a surface activity dynamic regulation-silane coupling agent segmented modification process. After centrifugation and drying, high-purity micron-sized metallic copper powder for current sensors is obtained. The technical specifications of the finished copper powder are: purity ≥ 99.995%, sphericity ≥ 0.92, oxygen content ≤ 30 ppm, and volume resistivity ≤ 4 × 10⁻⁶. -6 Ω·cm, total arsenic, antimony and bismuth content ≤0.0005%, no obvious oxidation after being placed in an environment of 85℃ / 85%RH for 240h, suitable for the detection accuracy and long-term stable operation requirements of medium and low precision current sensors.

[0007] As a further technical solution, the raw material pretreatment in step S1 is as follows: the surface oxide layer and impurities are removed by mechanical grinding combined with anhydrous ethanol wiping. The grinding speed is 300-500 r / min, the wiping is 2-3 times, and the wiping time is 1-2 min each time; and the material is cut into copper blocks with a particle size of 5-10 mm.

[0008] As a further technical solution, in step S2, the pure titanium plate has a purity ≥99.99% and a thickness of 2-3 mm; the high-purity electrolyte is composed of copper sulfate, sulfuric acid, deionized water and a composite targeted impurity remover, wherein the concentration of copper sulfate is 150-200 g / L and the concentration of sulfuric acid is 80-120 g / L; the mass ratio of the three components of the composite targeted impurity remover is 2:1:0.5, and the amount added is 0.05%-0.1% of the total mass of the electrolyte.

[0009] As a further technical solution, step S2, segmented electrolysis, specifically involves: the first stage electrolysis temperature being 55-58℃ and the current density being 200-250A / m. 2 The electrolysis time is 4-6 hours; the second-stage electrolysis temperature is 60-65℃, and the current density is 250-300 A / m³. 2 The electrolysis time is 4-6 hours. After electrolysis, the electrolytic copper powder intermediate is washed with deionized water 3-5 times, then washed with anhydrous ethanol 1-2 times, and then vacuum dried at 80-100℃ for 2-3 hours. The high-purity electrolyte needs to undergo ultrafiltration after preparation. The ultrafiltration membrane has a pore size of 0.1-0.2 μm, an ultrafiltration pressure of 0.1-0.2 MPa, and an ultrafiltration time of 30-60 min to remove impurity particles and complex precipitates formed by the composite targeted impurity remover in the electrolyte.

[0010] As a further technical solution, step S3, atomization forming, specifically involves placing the electrolytic copper powder intermediate into a vacuum induction melting furnace and controlling the vacuum level to 10. -3 -10 -4 The gas is heated to 1100-1200℃ under inert gas protection until it is completely melted; continuous stirring is carried out during the melting process, followed by high-pressure inert gas atomization, wherein the high-pressure inert gas is a mixture of argon and nitrogen in a volume ratio of 3:1-4:1; the atomization pressure is controlled at 3-5 MPa, the atomization temperature at 1050-1150℃, the atomization distance at 80-120 mm, and the cooling rate at 10. 3 -10 4 ℃ / s.

[0011] As a further technical solution, the inert gas flow rate is 15-25 L / min, the stirring speed during the melting process is 100-200 r / min, and the stirring time is 30-60 min; the heating rate of the vacuum induction melting furnace is 50-80℃ / min.

[0012] As a further technical solution, step S4, grading and screening, specifically involves: using a 3-5 level airflow grading method for screening, controlling the grading wind speed at 15-25 m / s, with the wind speed increasing by 2-5 m / s for each grading level; after each grading level, using a laser particle size analyzer to detect the particle size, screening out copper powder with a particle size of 1-50 μm and a particle size variation coefficient ≤5%, and removing particles that are too large or too small.

[0013] As a further technical solution, step S5, rare earth modification, specifically involves: placing the graded and screened copper powder into a modification furnace and heating it to 300-400℃ at a heating rate of 30-50℃ / min; adding a rare earth modifier at a rate of 0.1%-0.5% of the copper powder mass; and maintaining the temperature for 2-4 hours under argon protection with a purity ≥99.999% and an argon flow rate controlled at 10-20L / min; and cooling the modified copper powder to 25±5℃ at a cooling rate of 5-10℃ / min to obtain rare earth modified copper powder.

[0014] As a further technical solution, the preparation method of the rare earth modifier is as follows: a. Select rare earth elements La and Ce, mix them at a mass ratio of 1-2:1, and add them to dilute nitric acid with a concentration of 10%-15%, controlling the solid-liquid ratio of rare earth elements to dilute nitric acid to be 1:5-8 g / mL; b. Heat to 50-60℃ and stir at 150-200r / min for 20-30min until completely dissolved to obtain a rare earth nitrate solution; c. Add citric acid to the rare earth nitrate solution, controlling the molar ratio of citric acid to rare earth elements to be 1.5-2:1, and stir at 150-200 r / min for 10-15 min until homogeneous; d. Adjust the pH of the solution to 5.5-6.5 using 10%-15% dilute ammonia solution to obtain a rare earth complex solution; e. Evaporate and concentrate the rare earth complex solution at 80-100℃ to a viscosity of 5000-8000 mPa·s at 25℃, then transfer it to a muffle furnace and calcine it at 500-600℃ for 2-3 hours. f. After cooling to 25±5℃, grind until the powder particle size is ≤10μm to obtain the rare earth modifier.

[0015] As a further technical solution, the surface modification in step S6 specifically involves: adding rare earth modified copper powder to a 95% ethanol solution, stirring with ultrasound at 20-40 kHz, and then adding a silane coupling agent, with a total addition amount of 0.2%-0.6% of the copper powder mass; after the reaction is complete, centrifuging at 3000-5000 r / min, discarding the supernatant, and vacuum drying the precipitate at 80-100℃ for 3-4 h; The solid-liquid ratio of rare earth modified copper powder to ethanol solution is 1:10-15 g / mL; the ultrasonic stirring time is 30-60 min; and the silane coupling agent is KH-550 or KH-560.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a systematic preparation process involving raw material pretreatment, electrolytic purification, atomization molding, graded screening, rare earth modification, and surface modification. Combined with composite targeted impurity removal agents and gradient parameter control, it achieves synergistic optimization from multiple dimensions, including raw material purification, particle preparation, morphology regulation, and interface modification, making the resulting copper powder fully adaptable to the application requirements of current sensors.

[0017] In the raw material and electrolytic purification stages, high-purity cathode copper with a purity ≥99.995% is selected and mechanically polished and wiped with ethanol to thoroughly remove surface oxide scale and attached impurities, providing a foundation for high-purity preparation. A composite targeted impurity remover containing hydroxyethylidene diphosphonic acid, sodium sulfite, and tetrabutyl titanate is used to form stable complexes with arsenic, antimony, and bismuth ions. Combined with staged electrolysis and ultrafiltration, impurities are removed stepwise and efficiently at different temperatures and current densities. Because the electrolyte undergoes precise ultrafiltration, complex precipitates and suspended particles can be further removed, thereby significantly reducing the total arsenic, antimony, and bismuth content to below 0.0005%, while improving the purity of the copper powder. This solves the problems of difficult deep removal of harmful impurities and fluctuations in conductivity in traditional processes. In the atomization and grading process, vacuum induction melting can strictly control oxygen content and impurity volatilization, while high-pressure inert gas atomization enables rapid solidification to form highly spherical particles. Multi-stage airflow grading achieves precise particle size separation using gradient wind speeds. Because the oxygen content in the atomization environment is ≤50ppm and the cooling rate reaches 10... 3 -10 4 At ℃ / s, particle oxidation and grain growth can be suppressed. Combined with graded wind speed control that increases stepwise, uniform particles with a particle size of 1-50μm, a coefficient of variation of ≤5%, and a sphericity of ≥0.92 can be obtained, thereby solving the problems of irregular morphology, wide particle size distribution, and uneven conductive path of copper powder.

[0018] In the rare earth modification and surface modification process, the rare earth modifier, with La and Ce complexed powder as the core, reacts with copper powder at high temperature under argon protection to form highly stable intermetallic compounds with residual trace impurities, fixing grain boundary impurities and reducing lattice defects. Due to the controlled addition of rare earth and the matching of heating and cooling rates, structural stability can be improved without affecting conductivity. The segmented modification of the silane coupling agent can form a uniform and dense organic protective layer on the surface of copper powder. Due to the combination of ultrasonic dispersion and dynamic control, the coupling agent is completely coated and does not agglomerate, thereby significantly reducing the oxygen content to below 30 ppm and controlling the volume resistivity at 4 × 10⁻⁶. -6 The resistance is within Ω·cm, and the copper powder does not show significant oxidation after 240 hours in an environment of 85℃ / 85%RH, thus solving the problems of easy oxidation, high resistivity, and poor environmental stability of copper powder.

[0019] The various process steps and functional components of this invention support each other and work synergistically: raw material purification provides a high-purity starting point for electrolytic purification; segmented electrolysis and targeted impurity removal achieve deep purification; vacuum atomization and multi-stage grading ensure uniformity of particle morphology and size; rare earth modification stabilizes internal impurities; and surface modification constructs external protection. The overall solution achieves a balance of high purity, low oxygen, low resistivity, high sphericity, and high oxidation resistance. The prepared micron-sized copper powder can significantly improve the detection accuracy, signal stability, and service life of current sensors. At the same time, the process is highly controllable and suitable for large-scale production, effectively solving the industry problem that existing copper powders cannot meet the comprehensive performance requirements of current sensors. Attached Figure Description

[0020] Figure 1 This is a process flow diagram for the preparation of high-purity micron-sized copper powder for current sensors. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention provides a process for preparing high-purity micron-sized metallic copper powder for current sensors, comprising the following steps: S1. Raw material pretreatment: Select high-purity cathode copper with a purity of ≥99.995% as raw material, remove the surface oxide layer and impurities, and cut it into copper blocks for later use; S2. Electrolytic purification: The pretreated copper block is used as the anode and the pure titanium plate is used as the cathode. A high-purity electrolyte containing a composite targeted impurity removal agent is prepared. The electrolysis is controlled in stages. After the electrolysis is completed, the copper powder intermediate is obtained by washing and drying. S3. Atomization Forming: After melting the electrolytic copper powder intermediate in a vacuum induction melting furnace, a high-pressure inert gas atomization method is used to control the oxygen content of the atomization environment to ≤50ppm, thereby obtaining the initial micron-sized copper powder; S4. Grading and screening: The initial micron-sized copper powder is screened using a multi-stage airflow classification method to obtain micron-sized copper powder with uniform particle size; S5. Rare earth modification: The graded copper powder is added to a rare earth modifier, and the modification is carried out under argon protection. After modification, the temperature is lowered to obtain rare earth modified copper powder. S6. Surface modification: Rare earth modified copper powder is treated with a surface activity dynamic regulation-silane coupling agent segmented modification process. After centrifugation and drying, high-purity micron-sized metallic copper powder for current sensors is obtained.

[0023] This invention first pre-treats the raw materials, selecting high-purity cathode copper with a purity ≥99.995% as the raw material. The surface oxide layer and impurities are removed by mechanical grinding combined with wiping with anhydrous ethanol. The preferred grinding speed is 300-500 r / min, the preferred number of wiping cycles is 2-3, and the preferred wiping time is 1-2 min per cycle. After treatment, the copper material is cut into copper blocks with a particle size of 5-10 mm for later use.

[0024] After pretreatment, electrolytic purification is performed, using a copper block as the anode and a pure titanium plate as the cathode. The purity of the pure titanium plate is ≥99.99%, and the thickness is preferably 2-3 mm. The high-purity electrolyte consists of copper sulfate, sulfuric acid, deionized water, and a composite targeted impurity remover. The preferred concentration of copper sulfate is 150-200 g / L, and the preferred concentration of sulfuric acid is 80-120 g / L. The composite targeted impurity remover is a mixture of hydroxyethylidene diphosphonic acid, sodium sulfite, and tetrabutyl titanate, with a mass ratio of 2:1:0.5. The amount added is 0.05%-0.1% of the total mass of the electrolyte, which can achieve targeted removal of arsenic, antimony, and bismuth ions.

[0025] After the high-purity electrolyte is prepared, it needs to be subjected to ultrafiltration. The preferred pore size of the ultrafiltration membrane is 0.1-0.2μm, the preferred ultrafiltration pressure is 0.1-0.2MPa, and the preferred ultrafiltration time is 30-60min to remove impurity particles and complex precipitates formed by the composite targeted impurity remover in the electrolyte.

[0026] The segmented electrolysis is divided into two stages. The preferred electrolysis temperature for the first stage is 55-58℃, and the preferred current density is 200-250A / m. 2 The preferred electrolysis time is 4-6 hours. The preferred electrolysis temperature for the second stage is 60-65℃, and the preferred current density is 250-300 A / m³. 2 The preferred electrolysis time is 4-6 hours. After electrolysis, the electrolytic copper powder intermediate is washed 3-5 times with deionized water, then washed 1-2 times with anhydrous ethanol, and then vacuum dried at 80-100℃ for 2-3 hours to obtain the electrolytic copper powder intermediate.

[0027] Next, atomization molding is performed. The electrolytic copper powder intermediate is placed in a vacuum induction melting furnace, and the vacuum degree is controlled at 10. -3 -10 -4 Pa is heated to 1100-1200℃ under inert gas protection until it is completely melted. The heating rate is preferably 50-80℃ / min, and the mixture is continuously stirred during the melting process. The stirring speed is preferably 100-200 r / min, and the stirring time is preferably 30-60 min.

[0028] Subsequently, a high-pressure inert gas atomization method was employed. The high-pressure inert gas was a mixture of argon and nitrogen in a volume ratio of 3:1-4:1, with an optimal inert gas flow rate of 15-25 L / min. The atomization pressure was controlled at 3-5 MPa, the atomization temperature at 1050-1150℃, the atomization distance at 80-120 mm, and the cooling rate at 10 °C / min. 3 -10 4 At ℃ / s, the oxygen content in the atomization environment is controlled to be ≤50ppm to obtain the initial micron-sized copper powder.

[0029] Next, a grading and screening process was performed using a 3-5 level airflow grading method, with the grading wind speed controlled at 15-25 m / s, increasing by 2-5 m / s for each grading level. After each grading, a laser particle size analyzer was used to detect the particle size, screening out copper powder with a particle size of 1-50 μm and a particle size variation coefficient ≤5%, and removing particles that were too large or too small to obtain uniform micron-sized copper powder.

[0030] Then, rare earth modification is performed. The graded and screened copper powder is placed in a modification furnace and heated to 300-400℃ at a heating rate of 30-50℃ / min. A rare earth modifier is added at a rate of 0.1%-0.5% of the copper powder mass. Under the protection of argon gas with a purity ≥99.999%, the argon flow rate is controlled at 10-20L / min, and the modification is maintained at this temperature for 2-4 hours. After modification, the temperature is lowered to 25±5℃ at a cooling rate of 5-10℃ / min to obtain rare earth modified copper powder.

[0031] The preparation method of rare earth modifier is as follows: a. Select rare earth elements La and Ce, mix them at a mass ratio of 1-2:1, and add them to dilute nitric acid with a concentration of 10%-15%, controlling the solid-liquid ratio of rare earth elements to dilute nitric acid to be 1:5-8 g / mL; b. Heat to 50-60℃ and stir at 150-200r / min for 20-30min until completely dissolved to obtain a rare earth nitrate solution; c. Add citric acid to the rare earth nitrate solution, controlling the molar ratio of citric acid to rare earth elements to be 1.5-2:1, and stir at 150-200 r / min for 10-15 min until homogeneous; d. Adjust the pH of the solution to 5.5-6.5 using 10%-15% dilute ammonia solution to obtain a rare earth complex solution; e. Evaporate and concentrate the rare earth complex solution at 80-100℃ to a viscosity of 5000-8000 mPa・s at 25℃, then transfer it to a muffle furnace and calcine it at 500-600℃ for 2-3 hours; f. After cooling to 25±5℃, grind it until the powder particle size is ≤10μm to obtain the rare earth modifier.

[0032] Finally, surface modification is performed by adding rare earth-modified copper powder to a 95% ethanol solution, with a solid-liquid ratio of 1:10-15 g / mL. The mixture is first ultrasonically stirred at 20-40 kHz for 30-60 min, then a silane coupling agent (KH-550 or KH-560) is added, with a total addition amount of 0.2%-0.6% of the copper powder mass. After the reaction is complete, the mixture is centrifuged at 3000-5000 r / min, the supernatant is discarded, and the precipitate is vacuum dried at 80-100℃ for 3-4 h to obtain high-purity micron-sized metallic copper powder for current sensors.

[0033] The technical specifications of the obtained copper powder are: purity ≥ 99.995%, sphericity ≥ 0.92, oxygen content ≤ 30 ppm, and volume resistivity ≤ 4 × 10⁻⁶. -6 Ω・cm, total arsenic, antimony and bismuth content ≤0.0005%, no obvious oxidation after being placed in an environment of 85℃ / 85%RH for 240h, suitable for the detection accuracy and long-term stable operation requirements of medium and low precision current sensors.

[0034] This invention utilizes a synergistic process of raw material pretreatment, electrolytic purification, atomization molding, grading and screening, rare earth modification, and surface modification, combined with composite targeted impurity removers and rare earth modifiers, to efficiently remove arsenic, antimony, and bismuth impurities, improve the purity, sphericity, and oxidation resistance of copper powder, and reduce oxygen content and volume resistivity. This solves the problems of insufficient purity, high impurity levels, easy oxidation, and unstable conductivity of traditional copper powder, thus meeting the requirements for current sensors.

[0035] To further illustrate the present invention, the following embodiments will be described in detail.

[0036] Example 1: S1 raw material pretreatment: Select high-purity cathode copper with a purity ≥99.995%, mechanically grind it at a speed of 300r / min, wipe it twice with anhydrous ethanol for 1min each time to remove the surface oxide layer and impurities, and cut it into 5mm copper blocks for later use.

[0037] S2 electrolytic purification: A pure titanium plate with a purity ≥99.99% and a thickness of 2mm was selected as the cathode; the electrolyte was prepared with a copper sulfate concentration of 150g / L and a sulfuric acid concentration of 80g / L, and hydroxyethylidene diphosphonic acid, sodium sulfite, and tetrabutyl titanate were added in a mass ratio of 2:1:0.5, with the addition amount being 0.05% of the total electrolyte mass; the electrolyte was ultrafiltered using a 0.1μm ultrafiltration membrane at a pressure of 0.1MPa for 30min; the first stage of electrolysis was carried out at a temperature of 55℃ and a current density of 200A / m. 2 Electrolysis for 4 hours; second-stage electrolysis temperature 60℃, current density 250A / m 2Electrolyze for 4 hours; after electrolysis, wash three times with deionized water and once with anhydrous ethanol, and dry under vacuum at 80°C for 2 hours to obtain an intermediate electrolytic copper powder.

[0038] S3 atomization forming: The intermediate is placed in a vacuum induction melting furnace with a vacuum degree of 10. -3 The gas was heated to 1100℃ at a rate of 50℃ / min and stirred for 30 min at a stirring speed of 100 r / min. A mixture of argon and nitrogen (volume ratio 3:1) was used at a flow rate of 15 L / min. The atomization pressure was 3 MPa, the atomization temperature was 1050℃, the atomization distance was 80 mm, and the cooling rate was 10... 3 At ℃ / s, the oxygen content is controlled to be ≤50ppm to obtain the initial copper powder.

[0039] S4 graded screening: Three-stage airflow classification is adopted, with a classification wind speed of 15m / s and an increase of 2m / s for each stage; laser particle size analyzer is used to screen copper powder with a size range of 1-50μm and a coefficient of variation of ≤5%.

[0040] S5 Rare Earth Modification: Heat to 300℃ at 30℃ / min, add 0.1% rare earth modifier of copper powder by weight, argon purity ≥99.999%, flow rate 10L / min, and hold for 2h; then cool to 25℃ at 5℃ / min to obtain rare earth modified copper powder.

[0041] S6 Surface Modification: Add 95% ethanol at a solid-liquid ratio of 1:10 g / mL, sonicate at 20 kHz for 30 min, add 0.2% KH-550 (by weight of copper powder), centrifuge at 3000 r / min, and vacuum dry at 80 ℃ for 3 h to obtain the finished copper powder.

[0042] Example 2: S1 raw material pretreatment: Select high-purity cathode copper with a purity ≥99.995%, mechanically grind it at a speed of 500r / min, wipe it 3 times with anhydrous ethanol for 2min each time to remove the surface oxide layer and impurities, and cut it into 10mm copper blocks for later use.

[0043] S2 electrolytic purification: A pure titanium plate with a purity ≥99.99% and a thickness of 3mm was selected as the cathode; the electrolyte was prepared with a copper sulfate concentration of 200g / L and a sulfuric acid concentration of 120g / L, and hydroxyethylidene diphosphonic acid, sodium sulfite, and tetrabutyl titanate were added in a mass ratio of 2:1:0.5, with the addition amount being 0.1% of the total electrolyte mass; the electrolyte was ultrafiltered using a 0.2μm ultrafiltration membrane at a pressure of 0.2MPa for 60min; the first stage of electrolysis was carried out at a temperature of 58℃ and a current density of 250A / m. 2 Electrolysis for 6 hours; second-stage electrolysis temperature 65℃, current density 300A / m 2 Electrolyze for 6 hours; after electrolysis, wash 5 times with deionized water and 2 times with anhydrous ethanol, and dry under vacuum at 100℃ for 3 hours to obtain electrolytic copper powder intermediate.

[0044] S3 atomization forming: The intermediate is placed in a vacuum induction melting furnace with a vacuum degree of 10. -4 The gas was heated to 1200℃ at 80℃ / min and stirred at 200r / min for 60min. A mixture of argon and nitrogen (4:1 volume ratio) was used at a flow rate of 25L / min. The atomization pressure was 5MPa, the atomization temperature was 1150℃, the atomization distance was 120mm, and the cooling rate was 10... 4 At ℃ / s, the oxygen content is controlled to be ≤50ppm to obtain the initial copper powder.

[0045] S4 graded screening: Five-level airflow classification is adopted, with a classification wind speed of 25m / s, increasing by 5m / s for each level; laser particle size analyzer is used to screen copper powder with a size range of 1-50μm and a coefficient of variation of ≤5%.

[0046] S5 Rare Earth Modification: Heat to 400℃ at 50℃ / min, add 0.5% rare earth modifier of copper powder by weight, argon purity ≥99.999%, flow rate 20L / min, and hold for 4h; then cool to 25℃ at 10℃ / min to obtain rare earth modified copper powder.

[0047] S6 Surface Modification: Add 95% ethanol at a solid-liquid ratio of 1:15 g / mL, sonicate at 40 kHz for 60 min, add 0.6% KH-560 (copper powder by weight), centrifuge at 5000 r / min, and vacuum dry at 100 ℃ for 4 h to obtain the finished copper powder.

[0048] Example 3: S1 raw material pretreatment: Select high-purity cathode copper with a purity ≥99.995%, mechanically grind it at a speed of 400r / min, wipe it twice with anhydrous ethanol for 1.5min each time to remove the surface oxide layer and impurities, and cut it into 7mm copper blocks for later use.

[0049] S2 electrolytic purification: A pure titanium plate with a purity ≥99.99% and a thickness of 2.5 mm was selected as the cathode; the electrolyte was prepared with a copper sulfate concentration of 175 g / L and a sulfuric acid concentration of 100 g / L, and hydroxyethylidene diphosphonic acid, sodium sulfite, and tetrabutyl titanate were added in a mass ratio of 2:1:0.5, with the addition amount being 0.075% of the total electrolyte mass; the electrolyte was ultrafiltered using a 0.15 μm ultrafiltration membrane at a pressure of 0.15 MPa for 45 min; the first stage electrolysis temperature was 56.5℃, and the current density was 225 A / m. 2 Electrolysis for 5 hours; second-stage electrolysis temperature 62.5℃, current density 275 A / m 2 Electrolyze for 5 hours; after electrolysis, wash 4 times with deionized water and 1 time with anhydrous ethanol, and dry under vacuum at 90℃ for 2.5 hours to obtain an intermediate electrolytic copper powder.

[0050] S3 atomization forming: The intermediate is placed in a vacuum induction melting furnace with a vacuum degree of 5×10. -4 The gas was heated to 1150℃ at a rate of 65℃ / min and stirred at 150 r / min for 45 min. A mixture of argon and nitrogen (volume ratio 3.5:1) was used at a flow rate of 20 L / min. The atomization pressure was 4 MPa, the atomization temperature was 1100℃, the atomization distance was 100 mm, and the cooling rate was 5 × 10⁻⁶. 3 At ℃ / s, the oxygen content is controlled to be ≤50ppm to obtain the initial copper powder.

[0051] S4 graded screening: Four-level airflow classification is adopted, with a classification wind speed of 20m / s and an increase of 3.5m / s for each level; laser particle size analyzer is used to screen copper powder with a size range of 1-50μm and a coefficient of variation of ≤5%.

[0052] S5 Rare Earth Modification: Heat to 350℃ at 40℃ / min, add 0.3% rare earth modifier of copper powder, argon purity ≥99.999%, flow rate 15L / min, and hold for 3h; then cool to 25℃ at 7.5℃ / min to obtain rare earth modified copper powder.

[0053] S6 Surface Modification: Add 95% ethanol at a solid-liquid ratio of 1:12.5 g / mL, sonicate at 30 kHz for 45 min, add 0.4% KH-550 (copper powder by weight), centrifuge at 4000 r / min, and vacuum dry at 90 ℃ for 3.5 h to obtain the finished copper powder.

[0054] Comparative Example 1: Compared to Example 3, no composite targeted impurity remover was added, but the rest of the process and parameters were exactly the same.

[0055] Comparative Example 2: Compared to Example 3, the rare earth modification step was omitted, while the remaining processes and parameters were exactly the same.

[0056] Comparative Example 3: Compared to Example 3, no surface modification step was performed, but the remaining processes and parameters were exactly the same.

[0057] test: Experiment 1: Test of copper powder purity and impurity content: Experimental objective: The purity, oxygen content, and total arsenic, antimony, and bismuth content of the copper powder obtained in the examples and comparative examples were tested to verify the effects of the composite targeted impurity removal agent, segmented electrolysis, and ultrafiltration.

[0058] Test methods The purity of copper powder and the total content of arsenic, antimony and bismuth were determined by inductively coupled plasma mass spectrometry; the oxygen content was determined by pulsed infrared spectroscopy; each group of samples was tested in parallel three times and the average value was taken.

[0059] Experimental data: Table 1 ; The copper powder in Examples 1-3 had a purity ≥99.995%, oxygen content ≤30ppm, and total arsenic, antimony, and bismuth content ≤0.0005%, meeting the required specifications. Comparative Example 1, without the addition of a composite targeted impurity remover, could not effectively remove arsenic, antimony, and bismuth, resulting in a significant increase in impurity content, oxygen content, and purity. Comparative Example 2, without rare earth modification, could not fix trace impurities, leading to a higher impurity content. Comparative Example 3, without surface modification, had minimal impact on purity and impurities, primarily affecting subsequent oxidation resistance and dispersibility.

[0060] Experiment 2: Test of sphericity and particle size uniformity of copper powder: Experimental objective: The sphericity and particle size variation coefficient of copper powder were detected to verify the process effects of atomization, classification, and surface modification.

[0061] Test method: The particle size variation coefficient was detected using a laser particle size analyzer; the sphericity was detected using a scanning electron microscope combined with image analysis software; each group of samples was tested in parallel three times, and the average value was taken.

[0062] Experimental data: Table 2 ; Examples 1-3 showed sphericity ≥ 0.92 and particle size variation coefficient ≤ 5%, exhibiting excellent particle uniformity. Comparative Example 3, without surface modification, showed copper powder particle agglomeration, decreased sphericity, and increased variation coefficient. Comparative Example 1, due to impurities, suffered from poor atomization formation, resulting in a slight decrease in sphericity and uniformity. Comparative Example 2, without rare earth modification, had minimal impact on particle morphology, and its uniformity was close to that of the examples.

[0063] Experiment 3: Test on the conductivity and high-temperature, high-humidity oxidation resistance of copper powder: Experimental objective: The volume resistivity of copper powder and the degree of oxidation after being placed in an environment of 85℃ / 85%RH for 240 hours were measured to verify the effects of rare earth modification and surface modification.

[0064] Test method: Volume resistivity was measured using a four-probe tester; copper powder was placed in a constant temperature and humidity chamber at 85℃ and 85%RH for 240 hours, and the oxidation weight gain rate was calculated by weighing; each group of samples was tested in parallel three times, and the average value was taken.

[0065] Experimental data: Table 3 ; Examples 1-3: Volume resistivity ≤ 4 × 10⁻⁶ -6The resistivity of the copper powder was Ω·cm, with an oxidation weight gain of <0.15%, showing no significant oxidation and excellent conductivity and stability. Comparative Example 2, lacking rare earth modification, could not form stable intermetallic compounds and was easily oxidized under high temperature and humidity, resulting in increased resistivity. Comparative Example 3, without surface modification and a protective layer on the copper powder surface, exhibited the highest oxidation weight gain and a significant decrease in conductivity. Comparative Example 1, due to its high impurity content, had increased lattice defects, leading to increased resistivity and poorer oxidation resistance.

[0066] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not describe all details exhaustively, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification.

Claims

1. A process for preparing high-purity micron-sized copper powder for current sensors, characterized in that, Includes the following steps: S1. Raw material pretreatment: Select high-purity cathode copper with a purity of ≥99.995% as raw material, remove the surface oxide layer and impurities, and cut it into copper blocks for later use; S2. Electrolytic purification: Using a pretreated copper block as the anode and a pure titanium plate as the cathode, a high-purity electrolyte containing a composite targeted impurity remover is prepared. A segmented electrolysis control is employed. After electrolysis, the product is washed and dried to obtain an intermediate electrolytic copper powder. The composite targeted impurity remover is a mixture of hydroxyethylidene diphosphonic acid, sodium sulfite, and tetrabutyl titanate in a mass ratio of 2:1:0.

5. S3. Atomization Forming: After melting the electrolytic copper powder intermediate in a vacuum induction melting furnace, a high-pressure inert gas atomization method is used to control the oxygen content of the atomization environment to ≤50ppm, thereby obtaining the initial micron-sized copper powder; S4. Grading and screening: The initial micron-sized copper powder is screened using a multi-stage airflow classification method to obtain micron-sized copper powder with uniform particle size; S5. Rare earth modification: The graded copper powder is added to a rare earth modifier and modified under argon protection. After modification, the temperature is lowered to obtain rare earth modified copper powder. The rare earth elements and residual trace impurities form stable intermetallic compounds. S6. Surface modification: Rare earth modified copper powder is treated with a surface activity dynamic regulation-silane coupling agent segmented modification process. After centrifugation and drying, high-purity micron-sized metallic copper powder for current sensors is obtained.

2. The preparation process according to claim 1, characterized in that, Step S1, raw material pretreatment, specifically involves removing the surface oxide layer and impurities by mechanical grinding combined with anhydrous ethanol wiping. The grinding speed is 300-500 r / min, the wiping is performed 2-3 times, and each wiping time is 1-2 min. The material is then cut into copper blocks with a particle size of 5-10 mm.

3. The preparation process according to claim 1, characterized in that, In step S2, the pure titanium plate has a purity of ≥99.99% and a thickness of 2-3 mm; the high-purity electrolyte is composed of copper sulfate, sulfuric acid, deionized water and a composite targeted impurity remover, wherein the concentration of copper sulfate is 150-200 g / L and the concentration of sulfuric acid is 80-120 g / L; the amount of composite targeted impurity remover added is 0.05%-0.1% of the total mass of the electrolyte.

4. The preparation process according to claim 1, characterized in that, The step S2 is the step of segmental electrolysis, specifically, the first stage electrolysis temperature is 55-58 DEG C, the current density is 200-250 A / m 2 , the electrolysis time is 4-6 h; the second stage electrolysis temperature is 60-65 DEG C, the current density is 250-300 A / m 2 , the electrolysis time is 4-6 h; after the electrolysis is completed, the electrolytic copper powder intermediate is washed with deionized water for 3-5 times, then washed with anhydrous ethanol for 1-2 times, and vacuum dried at 80-100 DEG C for 2-3 h; The high-purity electrolyte needs to undergo ultrafiltration after preparation. The ultrafiltration membrane has a pore size of 0.1-0.2 μm, an ultrafiltration pressure of 0.1-0.2 MPa, and an ultrafiltration time of 30-60 min to remove impurity particles and complex precipitates formed by the composite targeted impurity remover in the electrolyte.

5. The preparation process according to claim 1, characterized in that, Step S3, atomization molding, specifically involves placing the electrolytic copper powder intermediate into a vacuum induction melting furnace and controlling the vacuum level to 10. -3 -10 -4 The gas is heated to 1100-1200℃ under inert gas protection until it is completely melted; continuous stirring is carried out during the melting process, followed by high-pressure inert gas atomization, wherein the high-pressure inert gas is a mixture of argon and nitrogen in a volume ratio of 3:1-4:1; the atomization pressure is controlled at 3-5 MPa, the atomization temperature at 1050-1150℃, the atomization distance at 80-120 mm, and the cooling rate at 10. 3 -10 4 ℃ / s.

6. The preparation process according to claim 5, characterized in that, The inert gas flow rate is 15-25 L / min, the stirring speed during the melting process is 100-200 r / min, and the stirring time is 30-60 min; the heating rate of the vacuum induction melting furnace is 50-80℃ / min.

7. The preparation process according to claim 1, characterized in that, Step S4, grading and screening, specifically involves: using a 3-5 level airflow grading method for screening, controlling the grading wind speed at 15-25 m / s, with the wind speed increasing by 2-5 m / s for each grading level; after each grading level, using a laser particle size analyzer to detect the particle size, screening out copper powder with a particle size of 1-50 μm and a particle size variation coefficient ≤5%, and removing particles that are too large or too small.

8. The preparation process according to claim 1, characterized in that, Step S5, rare earth modification, specifically involves: placing the graded and screened copper powder into a modification furnace and heating it to 300-400℃ at a heating rate of 30-50℃ / min; adding a rare earth modifier at a rate of 0.1%-0.5% of the copper powder mass; and maintaining the temperature for 2-4 hours under argon protection with a purity ≥99.999% and an argon flow rate controlled at 10-20L / min; after modification, cooling the temperature to 25±5℃ at a cooling rate of 5-10℃ / min to obtain rare earth modified copper powder.

9. The preparation process according to claim 8, characterized in that, The rare earth modifier is prepared as follows: a. Select rare earth elements La and Ce, mix them at a mass ratio of 1-2:1, and add them to dilute nitric acid with a concentration of 10%-15%, controlling the solid-liquid ratio of rare earth elements to dilute nitric acid to be 1:5-8 g / mL; b. Heat to 50-60℃ and stir at 150-200r / min for 20-30min until completely dissolved to obtain a rare earth nitrate solution; c. Add citric acid to the rare earth nitrate solution, controlling the molar ratio of citric acid to rare earth elements to be 1.5-2:1, and stir at 150-200 r / min for 10-15 min until homogeneous; d. Adjust the pH of the solution to 5.5-6.5 using 10%-15% dilute ammonia solution to obtain a rare earth complex solution; e. Evaporate and concentrate the rare earth complex solution at 80-100℃ to a viscosity of 5000-8000 mPa·s at 25℃, then transfer it to a muffle furnace and calcine it at 500-600℃ for 2-3 hours. f. After cooling to 25±5℃, grind until the powder particle size is ≤10μm to obtain the rare earth modifier.

10. The preparation process according to claim 1, characterized in that, Step S6, surface modification, specifically involves adding rare earth-modified copper powder to a 95% ethanol solution, stirring with ultrasound at 20-40 kHz, and then adding a silane coupling agent. The total amount added is 0.2%-0.6% of the copper powder mass. After the reaction is complete, centrifuge at 3000-5000 r / min, discard the supernatant, and vacuum dry the precipitate at 80-100℃ for 3-4 hours. The solid-liquid ratio of rare earth modified copper powder to ethanol solution is 1:10-15 g / mL; the ultrasonic stirring time is 30-60 min; and the silane coupling agent is KH-550 or KH-560.

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