Preparation process of high-purity micron-sized metal nickel powder based on automobile current sensor

Abstract

This invention relates to the field of current sensor technology, specifically to a process for preparing high-purity micron-sized nickel powder for automotive current sensors. The process includes sequential raw material pretreatment, synergistic treatment, and post-treatment steps. These steps are not simply additive but form a complete synergistic system: purification ensures purity, passivation ensures dispersion, spheroidization ensures morphology, and modification ensures performance. Combined with post-treatment vacuum drying, precision sieving, and vacuum packaging, the final product quality and batch consistency are further stabilized. The entire process can be continuously manufactured, achieving high yield and lower energy consumption. The resulting nickel powder simultaneously meets the requirements of high purity, narrow particle size, high sphericity, high oxidation resistance, high hydrophobicity, and high interfacial bonding strength, perfectly adapting to the long-term stable operation requirements of automotive current sensors. This significantly improves sensor accuracy, reliability, and lifespan, combining technological advancement with industrial practicality.

Description

Technical Field

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

[0002] Nickel powder possesses excellent electrical and thermal conductivity and chemical stability, making it a key functional material for manufacturing core conductive components and signal acquisition units in automotive current sensors. Automotive current sensors impose stringent requirements on the purity, particle size uniformity, sphericity, dispersibility, and interfacial compatibility of nickel powder. Typically, it needs a nickel content ≥99.99%, a particle size controlled between 1–3 μm, and a sphericity ≥0.94, while also exhibiting good oxidation resistance and hydrophobicity to ensure the sensor's detection accuracy and lifespan under long-term high and low temperature alternation, vibration, and humid conditions.

[0003] Currently, the industrial production of micron-sized metallic nickel powder mostly uses electrolytic nickel as raw material, which is prepared through processes such as crushing, purification, spheroidization, and modification. However, existing processes generally suffer from several technical bottlenecks. Traditional purification processes have limited efficiency in removing trace impurities such as Fe, Cu, S, and C; conventional spheroidization methods are prone to problems such as particle adhesion, wide particle size distribution, and low sphericity, which cannot meet the high-precision requirements of sensors for particle morphology. Commercially available conventional nickel powder is prone to oxidation at high temperatures, has weak adhesion to the substrate, and is prone to agglomeration when exposed to moisture, directly affecting the stability and reliability of sensor signals.

[0004] Therefore, developing a process for preparing micron-sized metallic nickel powder with high purity, high sphericity, uniform particle size, and excellent interfacial properties has become an urgent technical problem to be solved in the field of automotive electronic functional materials. 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 metallic nickel powder based on automotive current sensors.

[0006] The specific technical solution is as follows: The preparation process of high-purity micron-level metallic nickel powder based on automotive current sensors includes sequential raw material pretreatment, co-processing and post-processing steps; The raw material pretreatment is as follows: industrial-grade electrolytic nickel blocks with a nickel content of ≥99.5% are selected as raw materials. After mechanical grinding and ultrasonic cleaning to remove the surface oxide scale and oil, they are crushed into coarse nickel powder of 50-100μm for later use. The synergistic processing sequentially includes purification, purification-spheroidization synergistic adaptation, plasma spheroidization, and gradient composite modification-interface anchoring. The purification process employs a complexation-hydrogen reduction-catalysis synergistic process to remove Fe, Cu, S, and C impurities from the crude nickel powder, with lanthanum nitrate added as a catalyst during the complexation and impurity removal stage. The purification-spheroidization synergistic adaptation process involves passivating the purified nickel powder to form a 20-50 nm ultrathin passivation film on its surface. The plasma spheroidization process uses a thermal field stabilization-gas-solid coupling synergistic process to produce micron-sized nickel powder with a particle size of 1-3 μm, sphericity ≥0.94, and a particle size distribution satisfying (D90-D10) / D50≤0.6. The gradient composite modification-interface anchoring process employs a gradient modification design of "bottom layer anchoring, middle layer anti-oxidation, and surface hydrophobicity," forming a firmly bonded gradient composite modification layer on the nickel powder surface, suitable for the high-temperature and vibration-prone working environment of automotive current sensors. The post-processing involves vacuum drying, precision sieving, and multi-index testing of the modified nickel powder, followed by vacuum packaging to obtain the finished product. The finished product meets the following standards: nickel content ≥99.99%, particle size 1-3μm, and sphericity ≥0.94.

[0007] As a further technical solution, in the raw material pretreatment, the ultrasonic cleaning power is 150-200W and the cleaning time is 15-20min; the crushing adopts airflow crushing method; the grinding adopts diamond grinding wheel, grinding speed is 2000-2500r / min, grinding time is 10-15min, and the surface roughness of the raw material after grinding is ≤0.8μm; the ultrasonic cleaning adopts deionized water, and the surface of the raw material is free of oil and oxide scale residue after cleaning.

[0008] As a further technical solution, in the purification process, the amount of lanthanum nitrate catalyst added is 0.3%-0.5% of the mass of crude nickel powder; the purification process specifically includes three steps in sequence: complexation and impurity removal, filtration and washing, and hydrogen reduction for deep impurity removal. The complexation and impurity removal process involves adding crude nickel powder to a complexation reactor, adding deionized water and a compound complexing agent, controlling the reaction temperature at 60-80℃ and the stirring speed at 300-400 r / min, and reacting for 2-3 hours. The compound complexing agent is a mixture of EDTA-2Na and sodium citrate in a mass ratio of 2:1, and the amount added is 5%-8% of the mass of the crude nickel powder. The amount of deionized water added is 5-8 times the mass of the crude nickel powder. The filtration and washing process involves using vacuum filtration to achieve solid-liquid separation, and washing the filter residue repeatedly with deionized water 3-5 times, with each washing session lasting 10-15 minutes. The hydrogen reduction deep impurity removal process involves placing the washed nickel powder into a reduction furnace, introducing hydrogen gas, controlling the furnace temperature at 400-500℃, the hydrogen flow rate at 50-80mL / min, the heating rate at 5-10℃ / min, the cooling rate at 8-12℃ / min, and holding the furnace at this temperature for 3-4 hours to complete the deep impurity removal.

[0009] As a further technical solution, the purification-spheroidization synergistic adaptation treatment specifically involves: placing the purified nickel powder into a passivation reactor, adding a zinc dihydrogen phosphate passivating agent solution with a mass fraction of 0.8%-1.2%, controlling the reaction temperature at 30-40℃ and the stirring speed at 150-200 r / min, reacting for 30-40 min, followed by vacuum filtration and drying at 80-100℃ for 1-1.5 h; the amount of passivating agent added is 10%-15% of the mass of the purified nickel powder.

[0010] As a further technical solution, the plasma spheroidization process optimizes the gas-solid two-phase flow and avoids particle agglomeration by adding an airflow distribution plate and a particle disperser; the plasma torch outlet temperature is controlled at 5000-8000K, and the carrier gas is a mixture of argon and hydrogen in a volume ratio of 9:1. The plasma spheroidizing process specifically includes five steps in sequence: feed pretreatment, gas-solid coupling pretreatment, plasma spheroidizing, cooling and collection, and particle size screening. The feed pretreatment involves drying at 120-150℃ and a vacuum degree ≤-0.08MPa for 2-3 hours until the moisture content of the nickel powder is ≤0.1%. In the gas-solid coupling pretreatment, the airflow distribution plate has a pore size of 0.5-1mm and an opening rate of 30%-40%, the disperser speed is 800-1000r / min, and the dispersion accuracy is ≤10μm. The power control of the plasma spheroidization process is 50-60kW, the carrier gas flow rate is 10-15L / min, and the feed rate is 20-30g / min; the cooling and collection adopts a gradient cooling method with a temperature gradient of 800℃, 400℃, and 200℃, and the cooling time for each stage is 10-15s, with the matching cyclone separator rotating at 2000-2500r / min. The particle size screening uses a precision sieve with 1μm and 3μm pore sizes, a sieve speed of 10-15 r / min, a sieve time of 30-40 min, and a sieve accuracy of ≤0.1μm. Unqualified products can be returned to the plasma spheroidization process for reprocessing.

[0011] As a further technical solution, the specific steps of the gradient composite modification-interface anchoring treatment are as follows: a. Bottom layer anchoring: Add spherical nickel powder to 1.5%-2.0% by mass of silane coupling agent KH-560 anchoring liquid, react at 50-60℃ and 250-300r / min for 1-1.5h, and then vacuum filter and dry at low temperature. b. Intermediate layer anti-oxidation: Add the anchored nickel powder to the anti-oxidation modified liquid containing nano titanate coupling agent NDZ-311 and antioxidant 1010 at a material-to-liquid ratio of 1:5-8, and react at 40-50℃ and 200-250r / min for 0.5-1h. After the reaction, vacuum filter and low-temperature vacuum dry. c. Surface hydrophobicity: Add 0.8%-1.2% of nano-silane coupling agent KH-550 hydrophobic modification liquid to the modified nickel powder in a material-liquid ratio of 1:6-8, react at 35-45℃ and 180-220r / min for 40-60min, and then vacuum filter and vacuum dry to solidify.

[0012] As a further technical solution, the anchoring liquid solvent is prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 2:3, and the amount of anchoring liquid added is 20%-25% of the mass of spherical nickel powder; the vacuum filtration pressure after anchoring, anti-oxidation, and hydrophobic treatment is 0.1-0.15MPa, the filter cake thickness is 5-8mm, the filtration time is 15-20min, and the moisture content of the nickel powder after each drying step is ≤0.1%.

[0013] As a further technical solution, the antioxidant modified liquid contains 1.0%-1.5% NDZ-311 and 0.1%-0.2% antioxidant 1010; the hydrophobic modified liquid contains nano-silane coupling agent KH-550 with a particle size of 50-100nm; the anchoring liquid, antioxidant modified liquid, and hydrophobic modified liquid all need to be degassed in advance, with a degassed temperature of 25-30℃, a degassed time of 20-30min, a degassed vacuum degree ≤-0.08MPa, and then allowed to stand for 10-15min after degassed for later use.

[0014] As a further technical solution, in the post-processing, the vacuum drying conditions are a temperature of 80-100℃, a vacuum degree of ≤-0.09MPa, and a drying time of 1-2h, and the moisture content of the nickel powder after drying is ≤0.1%; the precision sieving adopts a graded sieving mode, with a sieving speed of 10-15r / min and a sieving time of 30-40min.

[0015] As a further technical solution, the vacuum packaging uses an aluminum foil vacuum bag with a thickness of 0.15-0.2mm. Before packaging, argon gas is filled in at a pressure of 0.02-0.03MPa and a filling time of 5-10s. After packaging, the overall vacuum degree is ≤-0.09MPa.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a three-stage continuous process of raw material pretreatment, synergistic treatment, and post-treatment, combined with parameter control and functional component matching at each step, to achieve full-process optimization from raw materials to finished products. Each process step supports and synergistically enhances the overall performance of high-purity micron-sized nickel powder.

[0017] The raw material pretreatment method, which combines diamond wheel grinding with ultrasonic cleaning, can thoroughly remove oxide scale and oil stains from the surface of electrolytic nickel blocks. Combined with airflow pulverization, it produces coarse nickel powder with uniform particle size, providing a stable raw material foundation for subsequent purification and spheroidization. This solves the problems of incomplete purification and easy spheroidization adhesion caused by surface contamination and uneven initial particle size. In the purification stage, lanthanum nitrate is introduced as a catalyst, combined with a complexation-hydrogen reduction deep impurity removal process, which significantly enhances the efficiency of impurity complexation and reduction, resulting in a stable increase in nickel purity. The content of Fe, Cu, S, and C impurities is reduced to extremely low levels, solving the problem of insufficient purification depth and difficulty in meeting high purity requirements in traditional processes.

[0018] By employing a purification-spheroidization synergistic passivation treatment, an ultra-thin passivation film of 20–50 nm is formed on the surface of nickel powder, effectively inhibiting particle agglomeration and oxidation during high-temperature spheroidization. Combined with a plasma spheroidization process incorporating an airflow distribution plate and particle disperser, a synergistic effect of thermal field stability and gas-solid coupling is achieved, enabling precise control of nickel powder particle size at 1–3 μm, sphericity ≥0.94, and particle size distribution (D90-D10) / D50 ≤0.6. This solves the problems of low sphericity, wide particle size distribution, and high particle irregularity in conventional spheroidization processes. The gradient composite modification-interface anchoring treatment adopts a three-layer structure design: bottom anchoring, middle anti-oxidation, and surface hydrophobicity. The bottom silane coupling agent strengthens the bonding force between nickel powder and subsequent substrates, the middle titanate and antioxidant improve high-temperature stability, and the surface nano-silane imparts excellent hydrophobicity. The synergy of these three elements significantly improves the oxidation resistance and moisture resistance of nickel powder, solving the problems of easy oxidation, moisture absorption, and poor interfacial bonding of nickel powder used in automotive sensors.

[0019] The various process steps in this invention are not simply superimposed, but rather form a complete and synergistic system: purification ensures purity, passivation ensures dispersion, spheroidization ensures morphology, and modification ensures performance. Combined with post-processing vacuum drying, precision sieving, and vacuum packaging, this further stabilizes the quality and batch consistency of the finished product. The entire process can be continuously manufactured, with high yield and lower energy consumption. The resulting nickel powder simultaneously meets the requirements of high purity, narrow particle size, high sphericity, high oxidation resistance, high hydrophobicity, and high interfacial bonding strength, perfectly adapting to the long-term stable operation requirements of automotive current sensors. This significantly improves sensor accuracy, reliability, and lifespan, combining technological advancement with industrial practicality. Attached Figure Description

[0020] Figure 1 This is a process flow diagram for the preparation of high-purity micron-sized nickel powder based on automotive 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 nickel powder based on automotive current sensors, comprising sequential raw material pretreatment, co-processing, and post-processing steps.

[0023] This invention first pre-treats the raw materials, selecting industrial-grade electrolytic nickel blocks with a nickel content ≥99.5% as the raw material. After mechanical grinding and ultrasonic cleaning to remove surface oxide scale and oil, the material is pulverized into coarse nickel powder for later use. Grinding is performed using a diamond grinding wheel, with a preferred grinding speed of 2000-2500 r / min and a preferred grinding time of 10-15 min, resulting in a surface roughness of ≤0.8 μm. Ultrasonic cleaning is performed with a preferred power of 150-200 W and a preferred cleaning time of 15-20 min, using deionized water. After cleaning, the raw material surface is free of oil and oxide scale residue. Pulverization is performed using an airflow milling method, resulting in coarse nickel powder with a particle size of 50-100 μm.

[0024] After the raw material pretreatment is completed, a synergistic treatment is carried out, which includes purification treatment, purification-spheroidization synergistic adaptation treatment, plasma spheroidization treatment, and gradient composite modification-interface anchoring treatment.

[0025] The purification process employs a complexation-hydrogen reduction-catalysis synergistic process to remove Fe, Cu, S, and C impurities from crude nickel powder. Lanthanum nitrate is added as a catalyst during the complexation purification stage. The amount of lanthanum nitrate added is 0.3%-0.5% of the crude nickel powder mass. The purification process specifically includes three steps: complexation purification, filtration and washing, and hydrogen reduction for deep purification. In the complexation purification step, crude nickel powder is added to a complexation reactor along with deionized water and a compound complexing agent. The reaction temperature is controlled at 60-80℃, the stirring speed at 300-400 r / min, and the reaction time is 2-3 h. The compound complexing agent is a mixture of EDTA-2Na and sodium citrate at a mass ratio of 2:1, and the amount added is 5%-8% of the crude nickel powder mass. The amount of deionized water added is 5-8 times the mass of the crude nickel powder. In the filtration and washing step, vacuum filtration is used to achieve solid-liquid separation. The filter residue is repeatedly washed with deionized water 3-5 times, with each washing lasting 10-15 min. The hydrogen reduction deep impurity removal process involves placing the washed nickel powder into a reduction furnace, introducing hydrogen gas, controlling the furnace temperature at 400-500℃, the hydrogen flow rate at 50-80mL / min, the heating rate at 5-10℃ / min, the cooling rate at 8-12℃ / min, and holding at this temperature for 3-4 hours to complete the deep impurity removal.

[0026] The purification-spheroidization synergistic adaptation treatment involves passivating the purified nickel powder to form an ultrathin passivation film of 20-50 nm on its surface. The purified nickel powder is placed in a passivation reactor, and a zinc dihydrogen phosphate passivating agent solution with a mass fraction of 0.8%-1.2% is added. The reaction temperature is controlled at 30-40℃, the stirring speed at 150-200 r / min, and the reaction is carried out for 30-40 min. Subsequently, the mixture is vacuum filtered and dried at 80-100℃ for 1-1.5 h. The amount of passivating agent added is 10%-15% of the mass of the purified nickel powder.

[0027] Plasma spheroidization employs a thermal field stabilization-gas-solid coupling synergistic process to produce micron-sized nickel powder with a particle size of 1-3 μm, a sphericity ≥0.94, and a particle size distribution satisfying (D90-D10) / D50≤0.6. The plasma spheroidization process utilizes an added airflow distribution plate and a particle disperser. The plasma torch outlet temperature is controlled at 5000-8000 K, and the carrier gas is a mixture of argon and hydrogen at a volume ratio of 9:1. The plasma spheroidization process specifically includes five steps: feed pretreatment, gas-solid coupling pretreatment, plasma spheroidization, cooling and collection, and particle size screening. Feed pretreatment involves drying at 120-150℃ under a vacuum of ≤-0.08 MPa for 2-3 hours until the nickel powder moisture content is ≤0.1%. In the gas-solid coupling pretreatment, the airflow distribution plate has a pore size of 0.5-1 mm and an opening rate of 30%-40%, the disperser rotates at 800-1000 r / min, and the dispersion accuracy is ≤10 μm. The plasma spheroidization process uses a power control of 50-60kW, a carrier gas flow rate of 10-15L / min, and a feed rate of 20-30g / min. Cooling and collection employs a gradient cooling method with temperature gradients of 800℃, 400℃, and 200℃, each with a cooling time of 10-15s. A cyclone separator is used at a speed of 2000-2500r / min. Particle size screening utilizes a precision sieve with 1μm and 3μm pore sizes, a screening speed of 10-15r / min, a screening time of 30-40min, and a screening accuracy of ≤0.1μm. Defective products can be returned to the plasma spheroidization process for reprocessing.

[0028] The gradient composite modification-interface anchoring treatment employs a gradient modification design with a bottom anchoring layer, a middle anti-oxidation layer, and a surface hydrophobic layer, forming a firmly bonded gradient composite modification layer on the nickel powder surface. For the bottom anchoring layer, spherical nickel powder is added to an anchoring solution containing 1.5%-2.0% (w / w) of silane coupling agent KH-560, and reacted at 50-60℃ and 250-300 r / min for 1-1.5 h. After the reaction, it is vacuum filtered and dried under low-temperature vacuum. The anchoring solution solvent is prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 2:3, and the amount of anchoring solution added is 20%-25% of the mass of the spherical nickel powder. For the middle anti-oxidation layer, the anchored nickel powder is added to an anti-oxidation modification solution containing nano-titanium ester coupling agent NDZ-311 and antioxidant 1010 at a material-to-liquid ratio of 1:5-8, and reacted at 40-50℃ and 200-250 r / min for 0.5-1 h. After the reaction, it is vacuum filtered and dried under low-temperature vacuum. The antioxidant modification solution contains 1.0%-1.5% NDZ-311 and 0.1%-0.2% antioxidant 1010. For the surface hydrophobic layer, the modified nickel powder is added to the nano-silane coupling agent KH-550 hydrophobic modification solution at a ratio of 1:6-8 (0.8%-1.2% by mass). The reaction is carried out at 35-45℃ and 180-220 r / min for 40-60 min, followed by vacuum filtration and vacuum drying for curing. The nano-silane coupling agent KH-550 in the hydrophobic modification solution has a particle size of 50-100 nm. The anchoring solution, antioxidant modification solution, and hydrophobic modification solution all require pre-degassing treatment at 25-30℃ for 20-30 min, with a degassing vacuum degree ≤-0.08 MPa. After degassing, the solution is allowed to stand for 10-15 min before use. After anchoring, anti-oxidation, and hydrophobic treatment, the vacuum filtration pressure is 0.1-0.15MPa, the filter cake thickness is 5-8mm, the filtration time is 15-20min, and the moisture content of the nickel powder after each drying step is ≤0.1%.

[0029] After co-processing, post-processing is carried out. The modified nickel powder is vacuum dried, precision sieved, and tested for multiple indicators before being vacuum packaged to obtain the finished product. Vacuum drying conditions are: temperature 80-100℃, vacuum degree ≤ -0.09MPa, drying time 1-2h, and the moisture content of the dried nickel powder ≤ 0.1%. Precision sieving adopts a graded sieving mode, with a sieving speed of 10-15r / min and a sieving time of 30-40min. The finished product qualification standards are: nickel content ≥ 99.99%, particle size 1-3μm, and sphericity ≥ 0.94. Vacuum packaging uses aluminum foil vacuum bags with a thickness of 0.15-0.2mm. Before packaging, argon gas is filled at a pressure of 0.02-0.03MPa for 5-10s, and the overall vacuum degree after packaging is ≤ -0.09MPa.

[0030] The preparation process provided by this invention, through raw material pretreatment, multi-step synergistic processing and refined post-processing, can prepare high-purity micron-sized metallic nickel powder suitable for automotive current sensors. The nickel purity can reach over 99.99%, and the particle size and sphericity meet the requirements of sensor use. At the same time, the gradient modification layer can improve the oxidation resistance, hydrophobicity and interfacial bonding performance of the nickel powder, extend the service life of the sensor and improve the detection accuracy.

[0031] Example 1: Raw material pretreatment: Industrial-grade electrolytic nickel blocks with a nickel content ≥99.5% were selected as raw materials and polished with diamond wheels at a speed of 2000 r / min for 10 min, resulting in a surface roughness ≤0.8 μm. Ultrasonic cleaning with deionized water was then performed at a power of 150 W for 15 min, leaving no oil or oxide scale residue on the surface. The cleaned nickel blocks were then pulverized into coarse nickel powder of 50 μm using an airflow milling method for later use.

[0032] Collaborative processing: (1) Purification process: Impurities are removed using a complexation-hydrogen reduction-catalysis synergistic process, with lanthanum nitrate added at 0.3% of the mass of crude nickel powder. In the complexation purification process, crude nickel powder is added to a complexation reactor, along with 5 times the mass of deionized water and 5% of the mass of crude nickel powder in a compound complexing agent. The compound complexing agent is a mixture of EDTA-2Na and sodium citrate at a mass ratio of 2:1. The reaction temperature is controlled at 60℃, the stirring speed at 300r / min, and the reaction is carried out for 2 hours. In the filtration and washing process, vacuum filtration is used for separation. The filter residue is washed repeatedly with deionized water 3 times, with each washing time lasting 10 minutes. In the hydrogen reduction deep purification process, the washed nickel powder is placed in a reduction furnace, and hydrogen gas is introduced. The furnace temperature is 400℃, the hydrogen flow rate is 50mL / min, the heating rate is 5℃ / min, the cooling rate is 8℃ / min, and the temperature is maintained for 3 hours to complete the deep purification.

[0033] (2) Purification-spheroidization synergistic adaptation treatment: The purified nickel powder is placed in a passivation reactor, and zinc dihydrogen phosphate passivating agent solution with a mass fraction of 10% of the purified nickel powder and a mass fraction of 0.8% is added. The reaction temperature is controlled at 30℃ and the stirring speed is 150r / min. The reaction is carried out for 30min, followed by vacuum filtration and drying at 80℃ for 1h to form a 20nm ultrathin passivation film on the surface of the nickel powder.

[0034] (3) Plasma spheroidization treatment: The plasma torch outlet temperature is controlled at 5000K, and the carrier gas is a mixture of argon and hydrogen at a volume ratio of 9:1. The feed pretreatment is to dry at 120℃ and vacuum degree ≤-0.08MPa for 2h until the moisture content of the nickel powder is ≤0.1%. In the gas-solid coupling pretreatment, the airflow distribution plate has a hole diameter of 0.5mm and an opening rate of 30%, the disperser speed is 800r / min, and the dispersion accuracy is ≤10μm. The power of the plasma spheroidization process is controlled at 50kW, the carrier gas flow rate is 10L / min, and the feed rate is 20g / min. The cooling and collection adopts a gradient cooling method with a temperature gradient of 800℃, 400℃, and 200℃, and a cooling time of 10s for each stage. The matching cyclone separator speed is 2000r / min. The particle size screening adopts a precision sieve with 1μm and 3μm apertures, a screening speed of 10r / min, a screening time of 30min, and a screening accuracy of ≤0.1μm.

[0035] (4) Gradient composite modification-interface anchoring treatment: The anchoring solution was degassed for 20 min at 25℃ and vacuum degree ≤ -0.08MPa, and then allowed to stand for 10 min before use. The solvent of the anchoring solution was anhydrous ethanol and deionized water at a volume ratio of 2:3. The anchoring solution was a silane coupling agent KH-560 solution with a mass fraction of 1.5%. The bottom anchoring solution was made by adding spherical nickel powder to 20% of its mass of the anchoring solution and reacting for 1 h at 50℃ and 250 r / min. The vacuum filtration pressure was 0.1 MPa, the filter cake thickness was 5 mm, the filtration time was 15 min, and the solution was dried at low temperature under vacuum until the moisture content was ≤ 0.1%. The antioxidant modification solution was degassed for 20 min at 25℃ and vacuum degree ≤ -0.08MPa, and then allowed to stand for 10 min before use. The antioxidant modification solution contained 1.0% NDZ-311 and 0.1% antioxidant 1010. For the intermediate anti-oxidation layer, the anchored nickel powder was added to the anti-oxidation modification liquid at a material-to-liquid ratio of 1:5. The reaction was carried out at 40℃ and 200 r / min for 0.5 h, followed by vacuum filtration at a pressure of 0.1 MPa, a filter cake thickness of 5 mm, and a filtration time of 15 min. The mixture was then vacuum dried at low temperature until the moisture content was ≤0.1%. The hydrophobic modification liquid was pre-degassed at 25℃ and a vacuum degree ≤-0.08 MPa for 20 min, and then allowed to stand for 10 min before use. The hydrophobic modification liquid was a 0.8% (w / w) solution of nano-silane coupling agent KH-550 with a particle size of 50 nm. For the surface hydrophobic layer, the intermediate-layer modified nickel powder was added to the hydrophobic modification liquid at a material-to-liquid ratio of 1:6. The reaction was carried out at 35℃ and 180 r / min for 40 min, followed by vacuum filtration at a pressure of 0.1 MPa, a filter cake thickness of 5 mm, and a filtration time of 15 min. The mixture was then vacuum dried and cured until the moisture content was ≤0.1%.

[0036] Post-processing: The modified nickel powder was vacuum dried at 80℃ and a vacuum degree ≤-0.09MPa for 1 hour, with a moisture content ≤0.1% after drying. Precision sieving was then performed using a graded sieving method at a speed of 10 r / min and a sieving time of 30 min. After passing multiple tests, the powder was vacuum-packed in 0.15mm thick aluminum foil vacuum bags. Before packaging, argon gas was introduced at a pressure of 0.02MPa for 5 seconds. After packaging, the overall vacuum degree was ≤-0.09MPa, yielding the finished nickel powder.

[0037] Example 2: Raw material pretreatment: Industrial-grade electrolytic nickel blocks with a nickel content ≥99.5% were selected as raw materials and polished with diamond wheels at a speed of 2500 r / min for 15 min, resulting in a surface roughness ≤0.8 μm. Ultrasonic cleaning with deionized water was then performed at a power of 200 W for 20 min, leaving no oil or oxide scale residue on the surface. The cleaned nickel blocks were then pulverized into 100 μm coarse nickel powder using an airflow milling method for later use.

[0038] Collaborative processing: (1) Purification process: Impurities are removed using a complexation-hydrogen reduction-catalysis synergistic process, with lanthanum nitrate added at 0.5% of the mass of crude nickel powder. In the complexation purification process, crude nickel powder is added to a complexation reactor, along with 8 times the mass of deionized water and 8% of the mass of crude nickel powder in a compound complexing agent. The compound complexing agent is a mixture of EDTA-2Na and sodium citrate at a mass ratio of 2:1. The reaction temperature is controlled at 80℃, the stirring speed at 400r / min, and the reaction is carried out for 3 hours. In the filtration and washing process, vacuum filtration is used for separation. The filter residue is washed repeatedly with deionized water 5 times, with each washing time lasting 15 minutes. In the hydrogen reduction deep purification process, the washed nickel powder is placed in a reduction furnace, and hydrogen gas is introduced. The furnace temperature is 500℃, the hydrogen flow rate is 80mL / min, the heating rate is 10℃ / min, the cooling rate is 12℃ / min, and the temperature is maintained for 4 hours to complete the deep purification.

[0039] (2) Purification-spheroidization synergistic adaptation treatment: The purified nickel powder is placed in a passivation reactor, and zinc dihydrogen phosphate passivating agent solution with a mass fraction of 15% and a mass fraction of 1.2% of the purified nickel powder is added. The reaction temperature is controlled at 40℃ and the stirring speed is 200r / min. The reaction is carried out for 40min, followed by vacuum filtration and drying at 100℃ for 1.5h to form a 50nm ultrathin passivation film on the surface of the nickel powder.

[0040] (3) Plasma spheroidization treatment: The plasma torch outlet temperature is controlled at 8000K, and the carrier gas is a mixture of argon and hydrogen in a volume ratio of 9:1. The feed pretreatment is drying at 150℃ and vacuum degree ≤-0.08MPa for 3h until the moisture content of the nickel powder is ≤0.1%. In the gas-solid coupling pretreatment, the airflow distribution plate has a hole diameter of 1mm and an opening rate of 40%, the disperser speed is 1000r / min, and the dispersion accuracy is ≤10μm. The power of the plasma spheroidization process is controlled at 60kW, the carrier gas flow rate is 15L / min, and the feed rate is 30g / min. The cooling and collection adopts a gradient cooling method with a temperature gradient of 800℃, 400℃, and 200℃, and a cooling time of 15s for each stage. The matching cyclone separator speed is 2500r / min. The particle size screening adopts a precision sieve with 1μm and 3μm apertures, a screening speed of 15r / min, a screening time of 40min, and a screening accuracy of ≤0.1μm.

[0041] (4) Gradient composite modification-interface anchoring treatment: The anchoring solution was degassed for 30 min at 30℃ and vacuum degree ≤ -0.08 MPa, and then allowed to stand for 15 min before use. The solvent of the anchoring solution was anhydrous ethanol and deionized water at a volume ratio of 2:3. The anchoring solution was a 2.0% mass fraction of silane coupling agent KH-560 solution. The bottom anchoring solution was made by adding spherical nickel powder to 25% of its mass of the anchoring solution and reacting at 60℃ and 300 r / min for 1.5 h. The vacuum filtration pressure was 0.15 MPa, the filter cake thickness was 8 mm, the filtration time was 20 min, and the solution was dried at low temperature under vacuum until the moisture content was ≤ 0.1%. The antioxidant modification solution was degassed for 30 min at 30℃ and vacuum degree ≤ -0.08 MPa, and then allowed to stand for 15 min before use. The antioxidant modification solution contained 1.5% mass fraction of NDZ-311 and 0.2% mass fraction of antioxidant 1010. For the intermediate anti-oxidation layer, the anchored nickel powder was added to the anti-oxidation modification liquid at a material-to-liquid ratio of 1:8. The reaction was carried out at 50℃ and 250 r / min for 1 hour, followed by vacuum filtration at a pressure of 0.15 MPa, a filter cake thickness of 8 mm, and a filtration time of 20 minutes. The mixture was then vacuum dried at low temperature until the moisture content was ≤0.1%. The hydrophobic modification liquid was pre-degassed at 30℃ and a vacuum degree ≤-0.08 MPa for 30 minutes, and then allowed to stand for 15 minutes before use. The hydrophobic modification liquid was a 1.2% (w / w) solution of nano-silane coupling agent KH-550 with a particle size of 100 nm. For the surface hydrophobic layer, the intermediate-layer modified nickel powder was added to the hydrophobic modification liquid at a material-to-liquid ratio of 1:8. The reaction was carried out at 45℃ and 220 r / min for 60 minutes, followed by vacuum filtration at a pressure of 0.15 MPa, a filter cake thickness of 8 mm, and a filtration time of 20 minutes. The mixture was then vacuum dried and cured until the moisture content was ≤0.1%.

[0042] Post-processing: The modified nickel powder was vacuum dried at 100℃ and a vacuum degree ≤-0.09MPa for 2 hours, with a moisture content ≤0.1% after drying. Precision sieving was then performed using a graded sieving method at a speed of 15 r / min and a sieving time of 40 min. After passing multiple tests, the powder was vacuum-packed in 0.2 mm thick aluminum foil vacuum bags. Before packaging, argon gas was introduced at a pressure of 0.03 MPa for 10 seconds. After packaging, the overall vacuum degree was ≤-0.09 MPa, yielding the finished nickel powder.

[0043] Example 3: Raw material pretreatment: Industrial-grade electrolytic nickel blocks with a nickel content ≥99.5% were selected as raw materials and polished with diamond wheels at a speed of 2250 r / min for 12 min, resulting in a surface roughness ≤0.8 μm. Ultrasonic cleaning with deionized water was then performed at a power of 175 W for 18 min, leaving no oil or oxide scale residue on the surface. The cleaned nickel blocks were then pulverized into coarse nickel powder of 75 μm using an airflow milling method for later use.

[0044] Collaborative processing: (1) Purification process: Impurities are removed using a complexation-hydrogen reduction-catalysis synergistic process, with lanthanum nitrate added at 0.4% of the mass of crude nickel powder. In the complexation impurity removal process, crude nickel powder is added to a complexation reactor, along with 6.5 times the mass of deionized water and 6.5% of the mass of crude nickel powder in a compound complexing agent. The compound complexing agent is a mixture of EDTA-2Na and sodium citrate at a mass ratio of 2:1. The reaction temperature is controlled at 70℃, the stirring speed at 350r / min, and the reaction time is 2.5h. In the filtration and washing process, vacuum filtration is used for separation. The filter residue is washed repeatedly with deionized water 4 times, with each washing time lasting 12min. In the hydrogen reduction deep impurity removal process, the washed nickel powder is placed in a reduction furnace, and hydrogen gas is introduced. The furnace temperature is 450℃, the hydrogen flow rate is 65mL / min, the heating rate is 7.5℃ / min, the cooling rate is 10℃ / min, and the temperature is maintained for 3.5h to complete the deep impurity removal.

[0045] (2) Purification-spheroidization synergistic adaptation treatment: The purified nickel powder was placed in a passivation reactor, and zinc dihydrogen phosphate passivating agent solution with a mass of 12.5% ​​and a mass fraction of 1.0% of the purified nickel powder was added. The reaction temperature was controlled at 35℃ and the stirring speed was 175r / min. The reaction was carried out for 35min, followed by vacuum filtration and drying at 90℃ for 1.25h to form a 35nm ultrathin passivation film on the surface of the nickel powder.

[0046] (3) Plasma spheroidization treatment: The plasma torch outlet temperature is controlled at 6500K, and the carrier gas is a mixture of argon and hydrogen in a volume ratio of 9:1. The feed pretreatment is to dry at 135℃ and vacuum degree ≤-0.08MPa for 2.5h until the moisture content of the nickel powder is ≤0.1%. In the gas-solid coupling pretreatment, the airflow distribution plate has a hole diameter of 0.75mm and an opening rate of 35%, the disperser speed is 900r / min, and the dispersion accuracy is ≤10μm. The power of the plasma spheroidization process is controlled at 55kW, the carrier gas flow rate is 12.5L / min, and the feed rate is 25g / min. The cooling and collection adopts a gradient cooling method with a temperature gradient of 800℃, 400℃, and 200℃, and a cooling time of 12s for each stage. The matching cyclone separator speed is 2250r / min. The particle size screening adopts a precision sieve with 1μm and 3μm apertures, a screening speed of 12r / min, a screening time of 35min, and a screening accuracy of ≤0.1μm.

[0047] (4) Gradient composite modification-interface anchoring treatment: The anchoring solution was degassed for 25 min at 27℃ and vacuum degree ≤ -0.08 MPa, and then allowed to stand for 12 min before use. The anchoring solution solvent was anhydrous ethanol and deionized water at a volume ratio of 2:3. The anchoring solution was a silane coupling agent KH-560 solution with a mass fraction of 1.75%. The bottom anchoring solution was made by adding spherical nickel powder to the anchoring solution at a mass fraction of 22.5%. The reaction was carried out at 55℃ and 275 r / min for 1.25 h. The vacuum filtration pressure was 0.125 MPa, the filter cake thickness was 6.5 mm, the filtration time was 18 min, and the solution was dried at low temperature under vacuum until the moisture content was ≤ 0.1%. The antioxidant modification solution was degassed for 25 min at 27℃ and vacuum degree ≤ -0.08 MPa, and then allowed to stand for 12 min before use. The antioxidant modification solution contained 1.25% NDZ-311 and 0.15% antioxidant 1010. For the intermediate anti-oxidation layer, the anchored nickel powder was added to the anti-oxidation modification liquid at a material-to-liquid ratio of 1:6.5. The reaction was carried out at 45℃ and 225 r / min for 0.75 h, with vacuum filtration at a pressure of 0.125 MPa, a filter cake thickness of 6.5 mm, and a filtration time of 18 min. The mixture was then vacuum dried at low temperature until the moisture content was ≤0.1%. The hydrophobic modification liquid was pre-degassed at 27℃ and a vacuum degree ≤-0.08 MPa for 25 min, and then allowed to stand for 12 min before use. The hydrophobic modification liquid was a 1.0% (w / w) solution of nano-silane coupling agent KH-550 with a particle size of 75 nm. For the surface hydrophobic layer, the intermediate-layer modified nickel powder was added to the hydrophobic modification liquid at a material-to-liquid ratio of 1:7. The reaction was carried out at 40℃ and 200 r / min for 50 min, with vacuum filtration at a pressure of 0.125 MPa, a filter cake thickness of 6.5 mm, and a filtration time of 18 min. The mixture was then vacuum dried and cured until the moisture content was ≤0.1%.

[0048] Post-processing: The modified nickel powder was vacuum dried at 90℃ and a vacuum degree ≤-0.09MPa for 1.5h, with a moisture content ≤0.1% after drying. Precision sieving was then performed using a graded sieving method at a speed of 12r / min and a sieving time of 35min. After passing multiple tests, it was vacuum-packed in 0.175mm thick aluminum foil vacuum bags. Before packaging, argon gas was introduced at a pressure of 0.025MPa for 7s. After packaging, the overall vacuum degree was ≤-0.09MPa, yielding the finished nickel powder.

[0049] Comparative Example 1: The same preparation process as in Example 3 was used, except that no lanthanum nitrate catalyst was added during the complexation and impurity removal stage of the purification treatment. All other steps and parameters were the same as in Example 3.

[0050] Comparative Example 2: The same preparation process as in Example 3 was used, except that the purification-spheroidization synergistic adaptation step was omitted, and plasma spheroidization was performed directly after purification. The remaining steps and parameters were the same as in Example 3.

[0051] Comparative Example 3: The same preparation process as in Example 3 was used, except that the gradient composite modification-interface anchoring treatment step was omitted, and post-treatment was performed directly after plasma spheroidization. The remaining steps and parameters were the same as in Example 3.

[0052] test: Experiment 1: Detection of purity and impurity content in nickel powder: 1.1 Experimental Objective: The nickel content and the contents of Fe, Cu, S, and C impurities in the nickel powder prepared in Examples 1-3 and Comparative Examples 1-3 were tested to verify the effect of lanthanum nitrate catalyst on the purification effect.

[0053] 1.2 Test Methods: The contents of nickel, Fe, and Cu in nickel powder were detected by inductively coupled plasma atomic emission spectrometry, and the contents of S and C were detected by high-frequency infrared carbon-sulfur analyzer. Each sample was tested in parallel three times and the average value was taken.

[0054] 1.3 Experimental Data: Table 1 ; The nickel powders in Examples 1-3 all had a nickel content ≥99.99%, and the impurity contents of Fe, Cu, S, and C were all below 1.5 ppm, demonstrating excellent purification effects. In Comparative Example 1, due to the absence of lanthanum nitrate as a catalyst, the complexation-hydrogen reduction impurity removal efficiency decreased significantly, resulting in a nickel content of 99.956% and a significant increase in impurity content, failing to meet the requirements for high-purity nickel powder. Comparative Examples 2-3 did not affect the purification process; the nickel purity and impurity content showed no significant difference compared to Example 3, indicating that lanthanum nitrate is the key to improving the purification effect.

[0055] Experiment 2: Detection of nickel powder particle size, sphericity, and particle size distribution: 2.1 Experimental Objective: The particle size, sphericity, and (D90-D10) / D50 values ​​of nickel powder prepared in Examples 1-3 and Comparative Examples 1-3 were tested to verify the influence of plasma spheroidization optimization and passivation treatment on the morphology of nickel powder.

[0056] 2.2 Test Methods: Particle size distribution was detected using a laser particle size analyzer, and sphericity was detected using a scanning electron microscope combined with image analysis software. 500 particles were randomly selected from each sample for testing, and the average value was taken.

[0057] 2.3 Experimental Data: Table 2 ; The nickel powder particles in Examples 1-3 had a particle size of 1-3 μm, a sphericity ≥0.94, and a particle size distribution (D90-D10) / D50 ≤0.6, meeting the requirements. Comparative Example 2, without passivation treatment, showed a tendency for nickel powder particles to agglomerate, a sphericity reduced to 0.86, and a wider particle size distribution. Comparative Examples 1 and 3 showed no significant impact, indicating that passivation treatment and optimization of the plasma spheroidization structure are key to ensuring the morphology of the nickel powder.

[0058] Experiment 3: Testing of the oxidation resistance and hydrophobic properties of nickel powder: 3.1 Experimental Objective: The oxidation weight gain and contact angle of nickel powder prepared in Examples 1-3 and Comparative Examples 1-3 were tested to verify the effect of gradient composite modification-interface anchoring treatment on the stability of nickel powder.

[0059] 3.2 Test Methods: Antioxidant properties test: Nickel powder was heated in a 200℃ forced-air drying oven for 24 hours, and the oxidation weight gain rate was calculated. Hydrophobicity test: The water contact angle of the nickel powder tablets was measured using a contact angle meter. Each sample was tested in parallel 5 times, and the average value was taken.

[0060] 3.3 Experimental Data: Table 3 ; The nickel powders in Examples 1-3 exhibited an oxidation weight gain rate of less than 0.13% and a water contact angle greater than 110°, demonstrating excellent oxidation resistance and hydrophobicity. Comparative Example 3, without gradient modification treatment and lacking both an anti-oxidation and hydrophobic layer, showed an oxidation weight gain rate of 0.86% and a contact angle of only 42.3°, completely losing its oxidation resistance and hydrophobicity. Comparative Examples 1 and 2 showed no significant impact, indicating that gradient composite modification-interface anchoring treatment is the core innovative feature for improving the environmental stability of nickel powder.

[0061] 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 preparation process for high-purity micron-sized nickel powder based on automotive current sensors, characterized in that, This includes sequential raw material pretreatment, co-processing, and post-processing steps; The raw material pretreatment is as follows: industrial-grade electrolytic nickel blocks with a nickel content of ≥99.5% are selected as raw materials. After mechanical grinding and ultrasonic cleaning to remove the surface oxide scale and oil, they are crushed into coarse nickel powder of 50-100μm for later use. The synergistic treatment sequentially includes purification treatment, purification-spheroidization synergistic adaptation treatment, plasma spheroidization treatment, and gradient composite modification-interface anchoring treatment. The purification treatment employs a complexation-hydrogen reduction-catalysis synergistic process to remove Fe, Cu, S, and C impurities from the crude nickel powder, with lanthanum nitrate added as a catalyst during the complexation and impurity removal stage. The purification-spheroidization synergistic adaptation treatment involves passivating the purified nickel powder to form a 20-50 nm ultrathin passivation film on its surface. The plasma spheroidization treatment uses a thermal field stabilization-gas-solid coupling synergistic process to obtain micron-sized nickel powder with a particle size of 1-3 μm, sphericity ≥0.94, and a particle size distribution satisfying (D90-D10) / D50≤0.

6. The gradient composite modification-interface anchoring treatment employs a bottom-layer anchoring, middle-layer anti-oxidation, and surface hydrophobic gradient modification design to form a firmly bonded gradient composite modification layer on the nickel powder surface. The post-processing involves vacuum drying, precision sieving, and multi-index testing of the modified nickel powder, followed by vacuum packaging to obtain the finished product. The finished product meets the following standards: nickel content ≥99.99%, particle size 1-3μm, and sphericity ≥0.

94.

2. The preparation process according to claim 1, characterized in that, In the raw material pretreatment, the ultrasonic cleaning power is 150-200W and the cleaning time is 15-20min; the pulverization adopts airflow pulverization method; the grinding adopts diamond grinding wheel, grinding speed is 2000-2500r / min, grinding time is 10-15min, and the surface roughness of the raw material after grinding is ≤0.8μm; the ultrasonic cleaning adopts deionized water, and the surface of the raw material is free of oil and oxide scale residue after cleaning.

3. The preparation process according to claim 1, characterized in that, In the purification process, the amount of lanthanum nitrate catalyst added is 0.3%-0.5% of the mass of crude nickel powder; the purification process specifically includes three steps in sequence: complexation and impurity removal, filtration and washing, and hydrogen reduction for deep impurity removal. The complexation and impurity removal process involves adding crude nickel powder to a complexation reactor, adding deionized water and a compound complexing agent, controlling the reaction temperature at 60-80℃ and the stirring speed at 300-400 r / min, and reacting for 2-3 hours. The compound complexing agent is a mixture of EDTA-2Na and sodium citrate in a mass ratio of 2:1, and the amount added is 5%-8% of the mass of the crude nickel powder. The amount of deionized water added is 5-8 times the mass of the crude nickel powder. The filtration and washing process involves using vacuum filtration to achieve solid-liquid separation, and washing the filter residue repeatedly with deionized water 3-5 times, with each washing session lasting 10-15 minutes. The hydrogen reduction deep impurity removal process involves placing the washed nickel powder into a reduction furnace, introducing hydrogen gas, controlling the furnace temperature at 400-500℃, the hydrogen flow rate at 50-80mL / min, the heating rate at 5-10℃ / min, the cooling rate at 8-12℃ / min, and holding the furnace at this temperature for 3-4 hours to complete the deep impurity removal.

4. The preparation process according to claim 1, characterized in that, The purification-spheroidization synergistic adaptation treatment specifically involves: placing the purified nickel powder into a passivation reactor, adding a zinc dihydrogen phosphate passivating agent solution with a mass fraction of 0.8%-1.2%, controlling the reaction temperature at 30-40℃ and the stirring speed at 150-200 r / min, reacting for 30-40 min, followed by vacuum filtration and drying at 80-100℃ for 1-1.5 h; the amount of passivating agent added is 10%-15% of the mass of the purified nickel powder.

5. The preparation process according to claim 1, characterized in that, The plasma spheroidization process is achieved by adding an airflow distribution plate and a particle disperser; the plasma torch outlet temperature is controlled at 5000-8000K, and the carrier gas is a mixture of argon and hydrogen in a volume ratio of 9:

1. The plasma spheroidizing process specifically includes five steps in sequence: feed pretreatment, gas-solid coupling pretreatment, plasma spheroidizing, cooling and collection, and particle size screening. The feed pretreatment involves drying at 120-150℃ and a vacuum degree ≤-0.08MPa for 2-3 hours until the moisture content of the nickel powder is ≤0.1%. In the gas-solid coupling pretreatment, the airflow distribution plate has a pore size of 0.5-1mm and an opening rate of 30%-40%, the disperser speed is 800-1000r / min, and the dispersion accuracy is ≤10μm. The power control of the plasma spheroidization process is 50-60kW, the carrier gas flow rate is 10-15L / min, and the feed rate is 20-30g / min; the cooling and collection adopts a gradient cooling method with a temperature gradient of 800℃, 400℃, and 200℃, and the cooling time for each stage is 10-15s, with the matching cyclone separator rotating at 2000-2500r / min. The particle size screening uses a precision sieve with 1μm and 3μm pore sizes, a sieve speed of 10-15 r / min, a sieve time of 30-40 min, and a sieve accuracy of ≤0.1μm. Unqualified products can be returned to the plasma spheroidization process for reprocessing.

6. The preparation process according to claim 1, characterized in that, The specific steps of the gradient composite modification-interface anchoring treatment are as follows: a. Bottom layer anchoring: Add spherical nickel powder to 1.5%-2.0% by mass of silane coupling agent KH-560 anchoring liquid, react at 50-60℃ and 250-300r / min for 1-1.5h, and then vacuum filter and dry at low temperature. b. Intermediate layer anti-oxidation: Add the anchored nickel powder to the anti-oxidation modified liquid containing nano titanate coupling agent NDZ-311 and antioxidant 1010 at a material-to-liquid ratio of 1:5-8, and react at 40-50℃ and 200-250r / min for 0.5-1h. After the reaction, vacuum filter and low-temperature vacuum dry. c. Surface hydrophobicity: Add 0.8%-1.2% of nano-silane coupling agent KH-550 hydrophobic modification liquid to the modified nickel powder in a material-liquid ratio of 1:6-8, react at 35-45℃ and 180-220r / min for 40-60min, and then vacuum filter and vacuum dry to solidify.

7. The preparation process according to claim 6, characterized in that, The anchoring solution is prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 2:

3. The amount of anchoring solution added is 20%-25% of the mass of spherical nickel powder. After anchoring, anti-oxidation, and hydrophobic treatment, the vacuum filtration pressure is 0.1-0.15 MPa, the filter cake thickness is 5-8 mm, the filtration time is 15-20 min, and the moisture content of the nickel powder after each drying step is ≤0.1%.

8. The preparation process according to claim 6, characterized in that, The antioxidant modified liquid contains 1.0%-1.5% NDZ-311 and 0.1%-0.2% antioxidant 1010. The hydrophobic modified liquid contains nano-silane coupling agent KH-550 with a particle size of 50-100nm. The anchoring liquid, antioxidant modified liquid, and hydrophobic modified liquid all need to be degassed in advance. The degassed temperature is 25-30℃, the degassed time is 20-30min, the degassed vacuum degree is ≤-0.08MPa, and the liquid is allowed to stand for 10-15min after degassed for later use.

9. The preparation process according to claim 1, characterized in that, In the post-processing, the vacuum drying conditions are: temperature 80-100℃, vacuum degree ≤-0.09MPa, drying time 1-2h, and the moisture content of the nickel powder after drying is ≤0.1%; the precision sieving adopts a graded sieving mode, with a sieving speed of 10-15r / min and a sieving time of 30-40min.

10. The preparation process according to claim 1, characterized in that, The vacuum packaging uses aluminum foil vacuum bags with a thickness of 0.15-0.2mm. Before packaging, argon gas is filled in at a pressure of 0.02-0.03MPa and a filling time of 5-10s. After packaging, the overall vacuum degree is ≤-0.09MPa.

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