Spherical-like conductive nickel powder and preparation method thereof

Abstract

The invention belongs to the technical field of conductive nickel powder, and particularly relates to sphere-like conductive nickel powder and a preparation method thereof. According to the preparation method, nickel sulfate is adopted as a starting raw material, complexed with ammonia water and reacted with oxalic acid under ultrasonic-microwave synergy to obtain porous spheroidal nickel oxalate, porous spheroidal nickel powder is obtained through thermal decomposition and hydrogen reduction, the surface of the powder is coated with a sulfur-phosphorus co-doped graphene layer, and meanwhile the oxidation resistance of the powder is improved; a silane coupling agent KH580 is used for carrying out surface treatment on the powder, a layer of compact monomolecular film is formed on the surface of the powder through covalent bonds, and the sphere-like conductive nickel powder prepared through the method has the advantages of being low in resistance, high in electromagnetic shielding value, moderate in apparent density, simple in preparation method, excellent in electrical property, long in service life and suitable for industrial production. And high-frequency scene requirements such as a 5G base station can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of conductive nickel powder, in particular to a kind of spherical conductive nickel powder and preparation method thereof. BACKGROUND

[0002] As a kind of metal powder material with excellent conductivity, chemical stability and functionality, conductive nickel powder has an irreplaceable position in the field of electronic information, new energy, catalysis and the like. In the early days, conductive nickel powder was mainly prepared by atomization method to prepare micron-sized nickel powder. The obtained nickel powder has low purity, irregular morphology and small specific surface area, and is only used in low-end scenarios such as ordinary conductive coating and powder metallurgy, with poor conductivity and consistency. With the development of electronic industry, the requirements for particle size and purity of nickel powder are improved. The reduction method gradually matures, which can prepare nickel powder with high sphericity and narrow particle size distribution, and promotes its application in thick film circuit and electronic paste. In the field of new energy, flexible electronics and 5G, nickel powder is required to have high conductivity, high specific surface area and surface compatibility, which gives rise to the research and development of nano-nickel powder, core-shell structure nickel powder and high specific surface area nickel powder. Surface modification technology has become the key to improving performance.

[0003] Chinese patent application with publication number CN102658370A discloses a preparation method of conductive nickel powder. The invention first prepares a powder by mechanically crushing nickel salt, then decomposes and reduces the powder at 250-350℃ under a reducing atmosphere, and uses the directional action of a magnetic field to make the crude nickel powder produced by decomposition and reduction directionally accumulate. Finally, the crude nickel powder is sintered and reduced at 550-700℃ to obtain conductive nickel powder. In this technical solution, only physical large particle impurities are removed by mechanical crushing and screening, and heavy metal ions and other impurities in the nickel salt cannot be removed. These impurities remain in the nickel powder, forming electron scattering centers, which leads to an increase in resistivity. Moreover, the surface of the nickel powder is not modified, and it is easy to form a loose oxide layer in a humid and acidic environment, which leads to a decrease in conductivity over time. The interface bonding force with the organic matrix is weak, and direct mixing easily leads to agglomeration, which results in discontinuous conductive network in the composite material. SUMMARY

[0004] The present application aims to provide a kind of spherical conductive nickel powder and preparation method thereof. The bulk density of the spherical conductive nickel powder prepared by the present application is 1.2-1.6g / cm 3The spherical conductive nickel powder has good dispersing performance, high specific surface area, low resistance and high shielding value; the porous spherical nickel powder is prepared by taking nickel sulfate as a starting material, complexing with ammonia water, reacting with oxalic acid under the assistance of ultrasonic waves and microwaves, and then reducing under a hydrogen atmosphere; the powder surface is coated with a sulfur-phosphorus co-doped graphene layer; traditional nickel powder is easily oxidized to form an insulating nickel oxide layer; the graphene coating layer can isolate oxygen; the oxidation resistance stability is improved by doping and modifying sulfur and phosphorus; the powder surface is then treated with silane coupling agent KH580 to form a monomolecular film; the porous structure forms C-S bonds and S-S bonds between the mercapto group at one end of KH580 and the sulfur-phosphorus co-doped graphene layer coated on the porous spherical nickel powder; and the other end of the siloxane group is hydrolyzed to form a dense and ordered monomolecular film; the nickel powder is inorganic and has poor compatibility with an organic matrix and is prone to agglomeration; the silane film can improve the compatibility of the nickel powder with the organic matrix and reduce the interfacial tension, so that the nickel powder is uniformly dispersed in the organic system.

[0005] To achieve the above object, in a first aspect, the application provides a kind of spherical conductive nickel powder, the spherical conductive nickel powder is in the surface of porous spherical nickel powder Co-doped graphene layer of sulfur and phosphorus, again by silane coupling agent KH580 processing obtains;The porous spherical nickel powder uses nickel sulfate as starting material, by ammonia water complexing, under the assistance of ultrasonic waves and microwaves with oxalic acid reaction, obtain porous spherical nickel oxalate, again by thermal decomposition, hydrogen reduction preparation obtains.

[0006] In a second aspect, the application provides a kind of spherical conductive nickel powder preparation method, comprising:

[0007] S1, disperse nickel sulfate in deionized water, stir for the first time, filter, collect filtrate, add sulfuric acid solution to adjust pH to 2-3, stir for the second time, add sodium sulfide, stir for the third time, after standing, filter to obtain pretreated nickel sulfate solution;

[0008] S2, drop ammonia water into the pretreated nickel sulfate solution, control pH to 8-9, stir, add oxalic acid, start ultrasonic and microwave assistance, react, filter to obtain porous spherical nickel oxalate, the porous spherical nickel oxalate is put into three-stage steel belt reduction furnace, thermal decomposition is carried out under nitrogen atmosphere to obtain porous spherical nickel oxide, and the porous spherical nickel oxide is reduced under hydrogen atmosphere to obtain porous spherical nickel powder;

[0009] S3, the porous spherical nickel powder is placed in a tube furnace, nitrogen is introduced, carbon disulfide vapor is carried into the tube furnace by nitrogen bubbling, carbon disulfide is added above the tube furnace, the sulfur-doped graphene is grown in situ on the surface of the porous spherical nickel powder by first heating, sodium hypophosphite is added above the tube furnace, the phosphorus vapor diffuses to the surface of the nickel base by second heating, and the porous spherical nickel powder coated with sulfur-phosphorus co-doped graphene is obtained by drying.

[0010] S4, dispersing the sulfur-phosphorus co-doped graphene coated porous spherical nickel powder in a pre-hydrolysis solution of silane coupling agent KH580, performing an ultrasonic assisted reaction, centrifuging, collecting the precipitate, washing, drying, sieving after cooling, and obtaining the spherical conductive nickel powder.

[0011] Preferably, in S1, the mass-volume ratio of the nickel sulfate and the deionized water is 1g: (3-5)mL.

[0012] Preferably, in S1, the temperature of the first stirring is 40-50℃, and the time of the first stirring is 30-60min.

[0013] Preferably, in S1, the time of the second stirring is 5-10min.

[0014] Preferably, in S1, the added amount of the sodium sulfide is 0.002-0.005 times of the mass of the nickel sulfate.

[0015] Preferably, in S1, the temperature of the third stirring is 40-50℃, and the time of the third stirring is 60-90min.

[0016] Preferably, in S1, the time of the standing is 30-60min, and the concentration of the sulfuric acid solution is 0.5-1mol / L.

[0017] Preferably, in S2, the concentration of the ammonia water is 10wt.%-15wt.%.

[0018] Preferably, in S2, the speed of the dropwise addition of the ammonia water is 5-10mL / min.

[0019] Preferably, in S2, the temperature of the stirring is 25-30℃.

[0020] Preferably, in S2, the added amount of the oxalic acid is 2.2-2.4 times of the nickel content in the nickel sulfate.

[0021] Preferably, in S2, the power of the ultrasonic is 500-600W.

[0022] Preferably, in S2, the power of the microwave is 300-400W.

[0023] Preferably, in S2, the temperature of the reaction is 40-50℃, and the time of the reaction is 30-40min; the thermal decomposition process and parameters are as follows: in a nitrogen atmosphere, heating at a rate of 5-10℃ / min to 650-700℃, holding time is 1-2h, and cooling at a rate of 5-15℃ / min to 250-300℃.

[0024] Preferably, the reducing process and parameters are as follows: when the temperature in the furnace drops to 250-300°C, the nitrogen valve is closed, hydrogen is introduced, and the temperature is raised from 250-300°C to 450-500°C at a rate of 3-5°C / min, and then the temperature is kept for 0.5-1 h, and then the temperature is raised to 550-600°C, and the temperature is kept for 1-2 h in a hydrogen atmosphere, and then the temperature is cooled to below 100°C at a rate of 5-15°C / min, and then the hydrogen valve is closed, and the nitrogen is switched on, and then the temperature is cooled to room temperature in the cooling tank at a rate of 5°C / min.

[0025] Preferably, in S3, the first heating has a temperature rising rate of 5-10°C / min, and the temperature is raised to 300-450°C, and the temperature is kept for 1-3 h.

[0026] Preferably, in S3, the second heating has a temperature rising rate of 1-5°C / min, and the temperature is raised to 300-450°C, and the temperature is kept for 1-3 h.

[0027] Preferably, in S3, the drying temperature is 60-80°C, and the drying time is 10-12 h.

[0028] Preferably, in S3, the flow rate of the carbon disulfide vapor is 10-50 mL / h.

[0029] Preferably, in S3, the mass ratio of the porous spherical nickel powder to sodium hypophosphite is 1: (50-100).

[0030] Preferably, in S4, in the silane coupling agent KH580 pre-hydrolysis solution, the solvent is deionized water, and the preparation method is as follows: 0.1-0.2 mol / L hydrochloric acid is added to 95 mL deionized water to adjust the pH to 4-5, 5 mL of silane coupling agent KH580 is added, and stirring is performed for 30 min, and then the temperature is kept at 25-30°C in a constant temperature water bath for 60-90 min to obtain the silane coupling agent KH580 pre-hydrolysis solution.

[0031] Preferably, in S4, the mass-volume ratio of the sulfur-phosphorus co-doped graphene coated on the nickel powder and the silane coupling agent KH580 pre-hydrolysis solution is 1 g: 100 mL.

[0032] Preferably, in S4, the ultrasonic-assisted reaction temperature is 35-40°C, the ultrasonic-assisted reaction time is 4-6 h, and the ultrasonic power is 200-300 W.

[0033] Preferably, in S4, the drying temperature is 70-80°C, and the drying time is 2-3 h.

[0034] Preferably, in S4, the apparent density of the spherical conductive nickel powder is 1.2-1.6 g / cm3 .

[0035] Compared with the prior art, the beneficial effects of the present application are embodied in:

[0036] The present application prepares a kind of high specific surface area, low resistance, high shielding, with porous structure, spherical conductive nickel powder, using nickel sulfate as raw material to prepare porous spherical conductive nickel powder, in situ generation of a layer of sulfur-phosphorus co-doped graphene coating on the surface of powder, tightly coated on the surface of powder, form continuous physical barrier without crack, block the diffusion channel of oxidizing agents such as oxygen, water to nickel powder matrix, the radius of sulfur, phosphorus atom is greater than that of carbon atom, will preferentially occupy the defect site of graphene, form stable covalent bond, passivate defect activity, prevent the adsorption of oxygen and water molecules at defect and oxidation reaction start, improve the oxidation resistance of powder;The surface of powder is treated with silane coupling agent KH580, the mercapto group at one end of KH580 forms C-S bond, S-S bond with the powder, the other end siloxane group is hydrolyzed and self-crosslinked to form a dense, ordered monomolecular film, and the main chain of KH580 has only 3 carbon atoms, the thickness of the monomolecular film formed is nanoscale, at the same time, there is no long-chain alkyl, benzene ring and other insulating structure in the molecule, therefore the transmission path of electrons on the surface of nickel powder will not be blocked by insulating groups, on the one hand, the monomolecular film can improve the dispersibility of nickel powder without blocking the conductive channel and electromagnetic shielding path on the surface of nickel powder, on the other hand, the functional groups on the surface of the film layer can match the resin, rubber and other matrix, and improve the compatibility of nickel powder and matrix. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The scanning electron microscope image of the spherical conductive nickel powder prepared in Example 3.

[0038] Figure 2 It is a preparation flow chart of a kind of spherical conductive nickel powder. DETAILED DESCRIPTION

[0039] The following examples are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0040] The main compounds used in the examples and comparative examples are commercially available and are not further purified.

[0041] Example 1

[0042] As Figure 2 shown, a kind of spherical conductive nickel powder, its preparation method includes:

[0043] S1, 100 g of nickel sulfate was dispersed in 300 mL of deionized water, stirred at 40°C for 60 min, filtered, the filtrate was collected, 0.5 mol / L sulfuric acid solution was added to adjust the pH to 2, stirred for 10 min, 0.2 g of sodium sulfide was added, stirred at 40°C for 90 min, and filtered after standing for 60 min to obtain a pretreated nickel sulfate solution.

[0044] S2, 10 wt.% ammonia water was added dropwise to the pretreated nickel sulfate solution at a rate of 5 mL / min, the pH was controlled to 8, and stirred at 25°C, 49.126 g of oxalic acid was added, the ultrasonic power was set to 500 W, and the microwave power was set to 300 W, under the assistance of ultrasonic and microwave, reacted at 40°C for 40 min, and filtered to obtain porous spherical nickel oxalate; the porous spherical nickel oxalate was put into a three-stage steel belt reduction furnace, heated to 650°C at a rate of 5°C / min under nitrogen protection, and kept for 2 h to perform thermal decomposition, to obtain porous spherical nickel oxide, cooled to 250°C at a rate of 5°C / min, the nitrogen valve was closed, hydrogen was introduced for 30 min, and then raised to 450°C at a rate of 3°C / min, kept for 1 h, and then raised to 550°C, kept for 2 h to perform reduction, cooled to below 100°C at a rate of 5°C / min, the hydrogen valve was closed, switched to nitrogen, and finally cooled to room temperature at a rate of 5°C / min to obtain porous spherical nickel powder.

[0045] S3, 10 g of porous spherical nickel powder was placed in a tube furnace, carbon disulfide vapor was carried into the tube furnace by nitrogen bubbling, and the flow rate was controlled at 10 mL / h; the temperature was raised to 300°C at a rate of 5°C / min, and kept for 3 h to grow sulfur-doped graphene on the surface of the porous spherical nickel powder in situ, after cooling, 50 g of sodium hypophosphite was added above the tube furnace, the temperature was raised to 300°C at a rate of 1°C / min, and kept for 3 h, phosphorus vapor diffused to the surface of the nickel base, and after drying at 60°C for 12 h, sulfur and phosphorus co-doped graphene-coated porous spherical nickel powder was obtained.

[0046] S4, 10 g of sulfur and phosphorus co-doped graphene-coated porous spherical nickel powder was dispersed in 100 mL of silane coupling agent KH580 pre-hydrolysis solution (0.1 mol / L hydrochloric acid was added to 95 mL of deionized water to adjust the pH to 4, 5 mL of silane coupling agent KH580 was added, stirred for 30 min, and aged in a 25°C constant temperature water bath for 90 min), and ultrasonic treatment was performed, under nitrogen protection, reacted at 35°C for 6 h, centrifuged, the precipitate was collected, washed, dried at 70°C for 3 h, and after cooling, screened through a 200 mesh sieve to obtain spherical conductive nickel powder with a loose bulk density of 1.5 g / cm 3 .

[0047] Example 2

[0048] As Figure 2 ​As shown, a kind of spherical conductive nickel powder, its preparation method includes:

[0049] S1, 100g nickel sulfate is dispersed in 400mL deionized water, 45℃ stirring 40min, filtration, collect filtrate, add 1mol / L sulfuric acid solution to adjust pH to 2.5, stirring 5min, add 0.3g sodium sulfide, 45℃ stirring 75min, after standing 45min, filtration, obtain pretreated nickel sulfate solution.

[0050] S2, to the pretreated nickel sulfate solution, drop 15wt.% ammonia water with 10mL / min, control pH to 8.5, 30℃ stirring, add 51.359g oxalic acid, set ultrasonic power to 550W, microwave power to 350W, under the assistance of ultrasonic and microwave, 45℃ reaction 35min, filtration, obtain porous spherical nickel oxalate. The porous spherical nickel oxalate is put into three-stage steel belt reduction furnace, heated to 700℃ at 10℃ / min under nitrogen protection, keep 1h, heat decomposition, obtain porous spherical nickel oxide. Cool to , close nitrogen valve, pass hydrogen for 20min, from 300℃ to 500℃ at 4℃ / min, keep 1h, reheat to 600℃, keep 1h, reduction, cool to below 100℃ at 10℃ / min, close hydrogen valve, switch to nitrogen, finally cool to room temperature at 5℃ / min, obtain porous spherical nickel powder.

[0051] S3, 10g porous spherical nickel powder is placed in tube furnace, carbon disulfide vapor is carried into tube furnace by nitrogen bubbling under nitrogen atmosphere, control flow rate to 35mL / h, heat to 400℃ at 10℃ / min, keep 2h, in-situ growth of sulfur-doped graphene is coated on the surface of porous spherical nickel powder, after cooling, 75g sodium hypophosphite is added above tube furnace, heat to 400℃, keep 2h, phosphorus vapor diffuses to nickel surface, dry at 70℃ for 11h, obtain sulfur and phosphorus co-doped graphene coated porous spherical nickel powder.

[0052] S4, 10g sulfur and phosphorus co-doped graphene coated porous spherical nickel powder is dispersed in 100mL silane coupling agent KH580 prehydrolysis solution (0.2mol / L hydrochloric acid is added to 95mL deionized water to adjust pH to 4.5, 5mL silane coupling agent KH580 is added, stirring 30min, 30℃ constant temperature water bath aging 70min), ultrasonic treatment, 40℃ reaction 5h under nitrogen protection, centrifugal, collect precipitate, wash, 75℃ dry 2.5h, after cooling, pass 200 mesh sieve, obtain spherical conductive nickel powder, loose bulk density is 1.4g / cm 3 .

[0053] ​Example 3

[0054] As shown in Figure 2 , a kind of spherical conductive nickel powder, its preparation method includes:

[0055] S1, 100g of nickel sulfate is dispersed in 500mL deionized water, stirring at 50℃ for 30min, filtration, collect filtrate, add 0.7mol / L sulfuric acid solution to adjust pH to 3, stirring for 5min, add 0.5g sodium sulfide, stirring at 50℃ for 60min, after standing for 30min, filtration, to obtain pretreated nickel sulfate solution.

[0056] S2, to the pretreated nickel sulfate solution, drop 10wt.% ammonia water with 5mL / min, control pH to 9, stirring at 25℃, add 53.592g oxalic acid, set ultrasonic power to 600W, microwave power to 400W, under the assistance of ultrasonic and microwave, reaction at 50℃ for 30min, filtration to obtain porous spherical nickel oxalate. The porous spherical nickel oxalate is put into three-stage steel belt reduction furnace, under nitrogen protection, heated to 700℃ at 5℃ / min, keep for 2h, heat decomposition, to obtain porous spherical nickel oxide, cooled to 250℃ at 15℃ / min, close the nitrogen valve, pass hydrogen for 30min, heated to 450℃ at 5℃ / min, keep for 1h, heated to 600℃ again, keep for 2h, reduction, cooled to below, close the hydrogen valve, switch to nitrogen, finally cooled to room temperature at 5℃ / min, to obtain porous spherical nickel powder.

[0057] S3, 10g of porous spherical nickel powder is put into tube furnace, under nitrogen atmosphere, carbon disulfide vapor is carried into tube furnace by nitrogen bubbling, control flow rate to 50mL / h, heated to 450℃ at 5℃ / min, keep for 1h, in-situ growth of sulfur-doped graphene is coated on the surface of nickel powder, after cooling, 100g of sodium hypophosphite is added above the tube furnace, heated to 450℃ at 5℃ / min, keep for 1h, phosphorus vapor diffuses to the surface of nickel-based material, dried at 80℃ for 10h, to obtain sulfur and phosphorus co-doped graphene coated porous spherical nickel powder.

[0058] S4, 10g of sulfur and phosphorus co-doped graphene coated porous spherical nickel powder is dispersed in 100mL silane coupling agent KH580 pre-hydrolysis solution (0.15mol / L hydrochloric acid is added to 95mL deionized water to adjust pH to 5, 5mL silane coupling agent KH580 is added, stirring for 30min, 30℃ constant temperature water bath aging for 60min), ultrasonic treatment, under nitrogen protection, reaction at 35℃ for 4h, centrifugation, collect the precipitate, washing, dried at 80℃ for 2h, after cooling, pass 200 mesh sieve, to obtain spherical conductive nickel powder, loose bulk density is 1.6g / cm​3 The scanning electron microscope results are shown in Figure 1

[0059] Comparative Example 1

[0060] A kind of spheroidal conductive nickel powder, its preparation method is different from embodiment 3, except that S2 does not use ultrasonic and microwave assisted reaction.

[0061] Comparative Example 2

[0062] A kind of spheroidal conductive nickel powder, its preparation method is different from embodiment 3, except that the porous spheroidal nickel powder prepared by S2 is not coated with sulfur and phosphorus co-doped graphene.

[0063] Comparative Example 3

[0064] A kind of spheroidal conductive nickel powder, its preparation method is different from embodiment 3, except that the porous spheroidal nickel powder coated with sulfur and phosphorus co-doped graphene prepared by S3 is not surface treated with silane coupling agent KH580.

[0065] Performance test:

[0066] The specific surface area of the spheroidal conductive nickel powder prepared in embodiment 1-embodiment 3 and comparative example 1-comparative example 3 was tested by BET specific surface area detection method.

[0067] The resistance value of the spheroidal conductive nickel powder prepared in embodiment 1-embodiment 3 and comparative example 1-comparative example 3 under normal voltage was tested by resistance tester.

[0068] The resistance value of the spheroidal conductive nickel powder prepared in embodiment 1-embodiment 3 and comparative example 1-comparative example 3 under low voltage (≤5V) was tested by resistance tester.

[0069] The electromagnetic shielding value of the spheroidal conductive nickel powder prepared in embodiment 1-embodiment 3 and comparative example 1-comparative example 3 was tested by electromagnetic shielding efficiency testing device.

[0070] The loose bulk density of the spheroidal conductive nickel powder prepared in embodiment 1-embodiment 3 and comparative example 1-comparative example 3 was determined by funnel method.

[0071] The conductivity of the spheroidal conductive nickel powder prepared in embodiment 1-embodiment 3 and comparative example 1-comparative example 3 after 48h salt spray test was tested, and the salt spray test was carried out according to GB / T10125-2021.

[0072] The test results of the above tests are shown in Table 1 and Table 2.

[0073] Table 1 Test results of spheroidal conductive nickel powder of embodiment and comparative example

[0074] ​

[0075] According to the data shown in Table 1, the specific surface area of the nickel powder prepared in Examples 1-3 is above 50 m 2 / g, the resistance value is below 5 mΩ, the electromagnetic shielding value is above 90 dB, and the loose bulk density is 1.2-1.6 g / cm 3 ; the specific surface area of Comparative Example 1 is the lowest, only 35.47 m 2 / g, the resistance value is as high as 8.57 mΩ, which is significantly higher than that of other examples and comparative examples, the electromagnetic shielding value is only 87.21 dB, which is significantly lower than that of other examples and comparative examples, and the loose bulk density of the nickel powder of Comparative Example 3 is below 1.2-1.6 g / cm 3 , only 1.0 g / cm 3 .

[0076] The spherical conductive nickel powder prepared in Examples 1-3 is porous nickel powder, and the porous structure gives the powder a high specific surface area. In Comparative Example 1, no ultrasonic and microwave assisted reaction is used in the preparation of the spherical conductive nickel powder, and the specific surface area of the obtained nickel powder is significantly reduced. This is because, in the reaction process of preparing porous spherical nickel oxalate, the reaction of nickel sulfate and oxalic acid will first form a nanoscale initial crystal nucleus. Without the assistance of ultrasonic and microwave, the crystal nucleus spontaneously attracts and agglomerates to form larger aggregates due to high surface energy. The crystal nucleus in the aggregate is tightly packed, and the original micropores are filled. After thermal decomposition and reduction, the nickel powder still maintains the aggregate morphology, and thus the specific surface area is greatly reduced.

[0077] The spherical conductive nickel powder prepared in Examples 1-3 and Comparative Examples 1-3 shows low resistance under normal voltage conditions and low voltage conditions. Experiments prove that the above-mentioned spherical conductive nickel powder has stable conductive properties and no significant voltage dependence. Experiments prove that the monomolecular film formed by plating a layer of silane coupling agent KH580 on the surface of the nickel powder has no significant effect on the conductive properties of the nickel powder.

[0078] Table 2 Corrosion resistance test results of the spherical conductive nickel powder of Examples and Comparative Examples

[0079]

[0080] According to the data shown in Table 2, the resistance of the spherical conductive nickel powder prepared in Examples 1-3 slightly increased after 48h salt spray test, but the increase was significantly lower than that of the spherical conductive nickel powder prepared in Comparative Examples 1-3. This is because the spherical conductive nickel powder prepared in Examples 1-3 uses sulfur-phosphorus co-doped graphene to generate a coating layer on the surface of the powder in situ, which blocks the intrusion of oxygen and moisture in the air into the powder, resulting in oxidation of the powder; the use of silane coupling agent KH580 to treat the surface of the powder can also improve the oxidation resistance of the powder to some extent, but the main improvement is still due to the sulfur-phosphorus co-doped graphene coating layer.

[0081] The specific surface area of the nickel powder prepared in Comparative Example 1 is reduced, and the number of active sites that can combine with the silane coupling agent mercapto is reduced, so the monomolecular film formed on the surface of the powder is not uniform and not dense, and therefore the resistance of the nickel powder increases more than that of Examples 1-3 after 48h test; Comparative Example 2 does not use sulfur-phosphorus co-doped graphene to generate a layer of coating on the surface of the powder in situ, so the powder is rapidly oxidized in the salt spray environment, resulting in a significant increase in resistance; Comparative Example 3 has a sulfur-phosphorus co-doped graphene coating layer generated on the surface in situ, but is not treated with a silane coupling agent, and the resistance of the nickel powder slightly increases after 48h in the salt spray environment, which is significantly lower than that of Comparative Example 2. In summary, the use of sulfur-phosphorus co-doped graphene to generate a coating layer on the surface of the spherical conductive nickel powder in situ can improve the oxidation resistance of the powder, and the use of silane coupling agent KH580 can also help improve the oxidation resistance of the powder and prolong its service life.

[0082] The above is only a preferred embodiment of the present application, and it should be noted that those skilled in the art can make several improvements and modifications without departing from the technical principles of the present application, and these improvements and modifications should also be considered within the scope of protection of the present application.

Claims

1. A type of spherical conductive nickel powder, characterized in that, The spherical conductive nickel powder is obtained by coating a sulfur-phosphorus co-doped graphene layer on the surface of porous spherical nickel powder, followed by treatment with silane coupling agent KH580; the porous spherical nickel powder is prepared by using nickel sulfate as the starting material, complexing with ammonia water, reacting with oxalic acid under ultrasonic-microwave synergy to obtain porous spherical nickel oxalate, and then preparing it through thermal decomposition and hydrogen reduction.

2. The method for preparing a spherical conductive nickel powder according to claim 1, characterized in that, include: S1. Disperse nickel sulfate in deionized water, stir for the first time, filter, collect the filtrate, add sulfuric acid solution to adjust the pH to 2-3, stir for the second time, add sodium sulfide, stir for the third time, let stand and filter to obtain a pretreated nickel sulfate solution; S2. Add ammonia water dropwise to the pretreated nickel sulfate solution, control the pH to 8-9, stir, add oxalic acid, start the ultrasonic and microwave assisted reaction, filter to obtain porous spherical nickel oxalate, the porous spherical nickel oxalate enters a three-stage steel strip reduction furnace, thermally decomposes under nitrogen protection to obtain porous spherical nickel oxide, the porous spherical nickel oxide is reduced under hydrogen atmosphere to obtain porous spherical nickel powder; S3. Place porous spherical nickel powder in a tube furnace and introduce nitrogen gas. The nitrogen gas bubbles and carries carbon disulfide vapor into the tube furnace. After the first heating, sulfur-doped graphene grows in situ and coats the surface of the nickel powder. Sodium hypophosphite is added above the tube furnace. After the second heating, phosphorus vapor diffuses to the nickel-based surface. After drying, porous spherical nickel powder coated with sulfur and phosphorus co-doped graphene is obtained. S4. The porous spherical nickel powder coated with sulfur and phosphorus co-doped graphene was dispersed in a silane coupling agent KH580 pre-hydrolyzed solution, and the reaction was carried out with ultrasonic assistance. After centrifugation, the precipitate was collected, washed, dried, cooled and sieved to obtain spherical conductive nickel powder.

3. The method for preparing a spherical conductive nickel powder according to claim 2, characterized in that, In step S1, the mass-to-volume ratio of nickel sulfate to deionized water is 1 g: (3~5) mL; the temperature of the first stirring is 40~50℃, and the stirring time is 30~60 min; the stirring time of the second stirring is 5~10 min; the amount of sodium sulfide added is 0.002~0.005 times the mass of nickel sulfate; the temperature of the third stirring is 40~50℃, and the stirring time of the third stirring is 60~90 min; the settling time is 30~60 min; and the concentration of the sulfuric acid solution is 0.5~1 mol / L.

4. The method for preparing a spherical conductive nickel powder according to claim 2, characterized in that, In step S2, the concentration of ammonia is 10 wt.% to 15 wt.%; the rate of ammonia addition is 5 to 10 mL / min; the stirring temperature is 25 to 30°C; the amount of oxalic acid added is 2.2 to 2.4 times the nickel content in nickel sulfate; the ultrasonic power is 500 to 600 W; and the microwave power is 300 to 400 W.

5. The method for preparing a spherical conductive nickel powder according to claim 2, characterized in that, In step S2, the reaction temperature is 40-50℃ and the reaction time is 30-40 min; the thermal decomposition process and parameters are as follows: in a nitrogen atmosphere, the temperature is increased to 650-700℃ at a rate of 5-10℃ / min, the holding time is 1-2 h, and the temperature is cooled to 250-300℃ at a rate of 5-15℃ / min.

6. The method for preparing a spherical conductive nickel powder according to claim 2, characterized in that, In step S2, the reduction process and parameters are as follows: when the furnace temperature drops to 250~300℃, the nitrogen valve is closed, hydrogen is introduced and maintained for 20~30 minutes, the temperature is increased from 250~300℃ to 450~500℃ at a rate of 3~5℃ / min, and held for 0.5~1 hours. Then the temperature is increased to 550~600℃, and the hydrogen atmosphere is maintained for 1~2 hours. The furnace then enters the cooling section and is cooled to below 100℃ at a rate of 5~15℃ / min. The hydrogen valve is closed, and nitrogen is switched to nitrogen. The furnace is then cooled to room temperature at a rate of 5℃ / min in the cooling tank.

7. The method for preparing a spherical conductive nickel powder according to claim 2, characterized in that, In step S3, the heating rate of the first heating is 5~10℃ / min, the temperature is raised to 300~450℃, and the holding time is 1~3h; the heating rate of the second heating is 1~5℃ / min, the temperature is raised to 300~450℃, and the holding time is 1~3h; the drying temperature is 60~80℃, and the drying time is 10~12h.

8. The method for preparing a spherical conductive nickel powder according to claim 2, characterized in that, In step S3, the flow rate of the carbon disulfide vapor is 10~50 mL / h; the mass ratio of the porous spherical nickel powder to sodium hypophosphite is 1:(50~100).

9. The method for preparing a spherical conductive nickel powder according to claim 2, characterized in that, In step S4, the solvent in the pre-hydrolyzed solution of silane coupling agent KH580 is deionized water. The preparation method is as follows: add 0.1~0.2mol / L hydrochloric acid to 95mL of deionized water to adjust the pH to 4~5, add 5mL of silane coupling agent KH580, stir for 30min, and age in a constant temperature water bath at 25~30℃ for 60~90min to obtain the pre-hydrolyzed solution of silane coupling agent KH580.

10. The method for preparing a spherical conductive nickel powder according to claim 2, characterized in that, In step S4, the mass-to-volume ratio of the sulfur-phosphorus co-doped graphene-coated porous spherical nickel powder to the silane coupling agent KH580 pre-hydrolyzed solution is [missing information]. The ultrasonic-assisted reaction temperature is 35-40℃, the ultrasonic-assisted reaction time is 4-6 hours, and the ultrasonic power is 200-300W; the drying temperature is 70-80℃, and the drying time is 2-3 hours; the loose packing density of the spherical conductive nickel powder is 1.2-1.6 g / cm³. 3 .

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