Nickel-coated graphite composite powder and preparation method thereof

Abstract

The invention discloses nickel-coated graphite composite powder and a preparation method thereof, and relates to the technical field of composite materials. The preparation method comprises the following steps: taking a carbon raw material as a starting point, mixing a nitrogen source, a phosphorus source and a sulfur source, performing high-temperature treatment to obtain modified artificial graphite powder, adding the modified artificial graphite powder into a plating solution mixed with nickel salt, a reducing agent, a complexing agent and a stabilizing agent, and optimizing process parameters. The nickel-coated graphite composite powder which is complete in coating, excellent in anti-aging performance and electromagnetic shielding performance and simple and efficient in preparation process is prepared. The nickel-coated graphite composite powder can be widely applied to multiple fields of electromagnetic shielding materials, conductive fillers and the like.

Description

A nickel-coated graphite composite powder and its preparation method Technical Field

[0001] This application relates to the field of composite materials technology, and in particular to a nickel-coated graphite composite powder and its preparation method. Background Technology

[0002] Nickel-coated graphite composite powder is widely used in industry due to its combination of the good electrical and thermal conductivity of nickel and the excellent lubricity of graphite. However, existing nickel-coated graphite composite powder preparation technologies mostly adopt the following method: after surface degreasing, roughening and sensitization of graphite powder, it is pre-plated with other metals, then reduced nickel plating, and finally washed, filtered and dried to obtain nickel-coated graphite composite powder.

[0003] For example, Chinese patent application CN113059155A discloses a method for preparing nickel-coated graphite composite powder material for conductive silicone. The preparation process is as follows: 1) Degreasing, cleaning, filtering and drying the surface of graphite powder; 2) Activating the cleaned graphite powder, cleaning, filtering and drying; 3) Placing the graphite powder treated in step 2) into a chemical plating solution for chemical plating, filtering, washing and drying to obtain the nickel-coated graphite composite powder material for conductive silicone.

[0004] This method uses graphite powder instead of carbon as raw material, and the pretreatment steps are relatively complicated. The nickel coating is also easily incomplete, which makes the graphite structure easily oxidized and degraded in high temperature or corrosive environments. As a result, the aging resistance and electromagnetic shielding performance are not good enough, and there is a lot of room for optimization and improvement. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a nickel-coated graphite composite powder and its preparation method. Starting with carbon raw materials, nitrogen, phosphorus, and sulfur sources are mixed and treated at high temperature to obtain modified artificial graphite powder. The modified artificial graphite powder is then added to a plating bath containing nickel salt, reducing agent, complexing agent, and stabilizer. By optimizing process parameters, a nickel-coated graphite composite powder with complete coating, excellent anti-aging properties, and electromagnetic shielding performance is obtained. The preparation process is simple and efficient, and it can be widely used in electromagnetic shielding materials, conductive fillers, and other fields.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] In a first aspect, this application provides a nickel-coated graphite composite powder, which includes modified artificial graphite powder and nickel powder coated on the surface of the modified artificial graphite powder; the modified artificial graphite powder is obtained by mixing carbon raw materials with nitrogen, phosphorus and sulfur sources and then treating them at high temperature; the nickel powder is obtained by in-situ reduction of nickel salt on the surface of the modified artificial graphite powder.

[0008] At high temperatures, nitrogen, phosphorus, and sulfur sources undergo thermal decomposition, releasing reactive nitrogen, reactive phosphorus, and reactive sulfur. These reactive species react with carbon atoms on the surface of carbon raw materials at high temperatures, introducing nitrogen, phosphorus, and sulfur atoms into the graphite structure formed by carbon raw materials at high temperatures by replacing some carbon atoms in the formed graphite lattice or filling the interstices of the formed graphite lattice, thus achieving a doping effect. At the same time, high temperatures further promote graphitization reconstruction, reduce lattice defects, and form a more regular doped graphite structure, thus obtaining modified artificial graphite powder.

[0009] In modified artificial graphite powder, the doping of nitrogen, phosphorus, and sulfur significantly enhances surface activity. This not only allows for the physical adsorption of nickel ions, but the doped nitrogen, phosphorus, and sulfur atoms can also form stable coordination bonds with nickel ions in subsequently added nickel salts. This bonding effect ensures that nickel ions from the nickel salts are more firmly adsorbed and tightly bound to the surface of the modified artificial graphite powder. Consequently, when nickel ions are reduced in situ to nickel powder, the nickel powder coating on the surface of the modified artificial graphite powder becomes more compact, complete, and less prone to detachment, resulting in a greater performance improvement.

[0010] In one feasible implementation, the nitrogen source includes any one of urea, dicyandiamide, and melamine; the phosphorus source includes any one of ammonium dihydrogen phosphate and diammonium hydrogen phosphate; and the sulfur source includes any one of sulfur, thiourea, and ammonium sulfide.

[0011] The nitrogen, phosphorus, and sulfur sources used in this application are all prone to decomposition at high temperatures, ensuring that the modification reaction is stable and controllable. This allows for the efficient release of nitrogen, phosphorus, and sulfur elements, which then combine with the carbon in the graphite structure formed by the carbon raw materials at high temperatures to obtain modified artificial graphite powder.

[0012] In one feasible implementation, the mass ratio of the carbon raw material, nitrogen source, phosphorus source and sulfur source is (90~95):(2-5):(1-2):(1-3).

[0013] In the process of preparing modified artificial graphite powder, the proportion of carbon raw materials is much higher than that of nitrogen, phosphorus and sulfur sources. This is to ensure that the nitrogen, phosphorus and sulfur sources can provide enough active sites to bind with nickel ions, and will not cause the structure of the modified artificial graphite powder to become disordered due to excessive doping.

[0014] In one feasible implementation, the carbon raw material includes either petroleum coke or needle coke.

[0015] In this application, petroleum coke and needle coke have high carbon content, few impurities, and good graphitization potential, which can provide a high-quality artificial graphite powder matrix for subsequent nickel ion reduction to nickel powder for coating.

[0016] In one feasible implementation, the nickel salt includes any one of nickel sulfate, nickel nitrate, nickel acetate tetrahydrate, and nickel chloride.

[0017] The nickel salt used in this application has good solubility in aqueous solution and can stably provide nickel ions to meet the ion requirements for in-situ reduction reaction on the surface of modified artificial graphite powder. Moreover, the nickel salt used will not produce difficult-to-remove impurities during the reduction process, which can ensure the purity of the reduced nickel powder and not affect the performance of the final nickel-coated graphite composite powder.

[0018] Secondly, this application provides a method for preparing nickel-coated graphite composite powder, comprising the following steps:

[0019] Weigh out carbon raw materials, nitrogen source, phosphorus source and sulfur source in proportion, then mix and grind them together for 1-2 hours to obtain mixed graphite powder;

[0020] The mixed graphite powder was kept at 2800-3200℃ for 2-4 hours under nitrogen protection, and then cooled to room temperature to obtain modified artificial graphite powder.

[0021] Mix nickel salt, deionized water, reducing agent, complexing agent, and stabilizer in proportion, and adjust the pH value to 10-12 to obtain the plating solution;

[0022] Modified artificial graphite powder is added to the plating solution, the temperature is controlled at 65-90℃, the stirring speed is 100-200rpm, and the stirring is carried out for 3-5 hours to obtain a graphite powder mixture.

[0023] The obtained graphite powder mixture is filtered to obtain filter residue. The filter residue is washed with deionized water 3-5 times and then dried in a vacuum drying oven at 100-120℃ for 1-3 hours to finally obtain nickel-coated graphite composite powder.

[0024] The preparation method of nickel-coated graphite composite powder provided in this application is simple and controllable, resulting in a product with high coating uniformity and purity, suitable for large-scale production. The mixing and grinding of carbon raw materials, nitrogen source, phosphorus source, and sulfur source for 1-2 hours ensures sufficient contact between the carbon raw material and all dopant sources, forming the basis for subsequent uniform modification. High-temperature treatment under nitrogen protection prevents oxidation of the various raw materials and the resulting modified artificial graphite powder, while simultaneously promoting better doping of nitrogen, phosphorus, and sulfur elements into the graphitized structure formed by the high temperature of the carbon source, resulting in modified artificial graphite powder with nitrogen, phosphorus, and sulfur doped into its structure. After the modified artificial graphite powder is added to the plating bath, under appropriate temperature control and slow, prolonged stirring, nickel ions are more uniformly adsorbed, reduced, and deposited on the surface of the modified artificial graphite powder, coordinating with the doped nitrogen, phosphorus, and sulfur elements.

[0025] In one feasible implementation, the reducing agent includes either sodium borohydride or hydrazine hydrate.

[0026] Under optimized process parameters, the reducing agent reduces nickel ions adsorbed on the modified artificial graphite powder or nickel ions combined with nitrogen, phosphorus and sulfur doped on the modified artificial graphite powder to elemental nickel, which is deposited on the surface of the modified artificial graphite powder to form a coating layer. This process does not cause oxidation or structural damage to the modified artificial graphite powder and has high reduction efficiency.

[0027] In one feasible implementation, the complexing agent includes any one of citric acid, tartaric acid, and ethylenediaminetetraacetic acid.

[0028] Under optimized process parameters, the complexing agent forms a stable complex with nickel ions, avoiding the rapid reduction of nickel ions that would lead to particle agglomeration. This ensures that the reduced nickel powder is deposited on the surface of the modified artificial graphite powder in a fine and uniform form, guaranteeing a uniform and dense coating layer.

[0029] In one feasible implementation, the stabilizer includes either thiourea or potassium iodide.

[0030] The addition of stabilizers suppresses side reactions in the plating solution, thereby improving the stability of the entire process of nickel powder coating modified artificial graphite powder. At the same time, it inhibits excessive growth of nickel grains, avoids porosity or unevenness in the nickel powder coating layer, and ensures the density of the coating layer.

[0031] In one feasible implementation, the mass ratio of nickel salt, deionized water, reducing agent, complexing agent and stabilizer in the plating solution is (10-20):(50-60):(15-25):(5-15):(0.1-0.5).

[0032] Beneficial technical effects:

[0033] This application obtains modified artificial graphite powder by mixing carbon raw materials with nitrogen, phosphorus and sulfur sources and treating them at high temperature. The modified artificial graphite powder is then added to a plating solution containing nickel salt, reducing agent, complexing agent and stabilizer. By optimizing the process parameters, a nickel-coated graphite composite powder with complete coating, excellent anti-aging properties and electromagnetic shielding properties, and a simple and efficient preparation process is obtained.

[0034] At high temperatures, nitrogen, phosphorus, and sulfur sources undergo thermal decomposition, releasing reactive nitrogen, phosphorus, and sulfur. These reactive species react with carbon atoms on the surface of the carbon raw materials at high temperatures, introducing nitrogen, phosphorus, and sulfur atoms into the graphite structure formed by the carbon raw materials at high temperatures by replacing some carbon atoms in the formed graphite lattice or filling the interstitial spaces, thus achieving a doping effect. Furthermore, the doped nitrogen, phosphorus, and sulfur atoms form stable chemical bonds with carbon atoms, reducing lattice defects and forming a more regular doped graphite structure. This makes the graphite structure more stable under high-temperature or corrosive environments, less prone to oxidation and degradation, ultimately yielding modified artificial graphite powder, thereby improving the aging resistance of nickel-coated graphite composite powder. Moreover, due to the doping of nitrogen, phosphorus, and sulfur, the surface activity of the modified artificial graphite powder is significantly enhanced. It can not only physically adsorb nickel ions, but the doped nitrogen, phosphorus, and sulfur atoms can also form stable coordination bonds with nickel ions in subsequently added nickel salts. This bonding effect allows nickel ions in the nickel salts to be more firmly adsorbed and tightly bound to the surface of the modified artificial graphite powder. Furthermore, when nickel ions are reduced to nickel powder in situ, the nickel powder coating layer on the surface of the modified artificial graphite powder becomes tighter, more complete, and less prone to falling off, thus greatly improving the electromagnetic shielding performance. Attached Figure Description

[0035] Figure 1 is a SEM image of the modified artificial graphite powder prepared in Example 1.

[0036] Figure 2 is a SEM image of the nickel-coated graphite composite powder prepared in Example 1.

[0037] Figure 3 is a schematic diagram of the preparation method of nickel-coated graphite composite powder provided in this application. Detailed Implementation

[0038] To facilitate understanding of the content described in this application, the technical solutions described herein are further explained below with reference to specific embodiments; however, this application is not limited thereto. All equivalent transformations or simple substitutions made based on the substantive content of this application should fall within the protection scope of this application.

[0039] The singular forms “for,” “or,” “a,” “any,” and “the” used in this application are intended to include the plural forms unless the context clearly indicates otherwise.

[0040] The preparation method of nickel-coated graphite composite powder provided in this application will be described in detail below with reference to different embodiments.

[0041] Example 1

[0042] As shown in Figure 3, a method for preparing nickel-coated graphite composite powder includes the following steps:

[0043] 1. Weigh out petroleum coke, urea, ammonium dihydrogen phosphate and sulfur according to the proportion, then mix and grind them together for 1 hour to obtain mixed graphite powder;

[0044] The mass ratio of petroleum coke, urea, ammonium dihydrogen phosphate, and sulfur is 95:2:1:2.

[0045] 2. The mixed graphite powder was kept at 2800℃ for 4 hours under nitrogen protection, and then cooled to room temperature to obtain modified artificial graphite powder, the morphology of which is shown in Figure 1.

[0046] 3. Mix nickel sulfate, deionized water, sodium borohydride, citric acid and thiourea in proportion, and adjust the pH value to 10 to obtain the plating solution;

[0047] The mass ratio of nickel sulfate, deionized water, sodium borohydride, citric acid, and thiourea is 19.9:50:15:5:0.1.

[0048] 4. Add the modified artificial graphite powder to the plating solution, control the temperature at 65℃, stir at 100rpm, and stir for 5 hours to obtain a graphite powder mixture.

[0049] 5. The obtained graphite powder mixture was filtered to obtain filter residue. The filter residue was washed three times with deionized water and then dried in a vacuum drying oven at 100°C for 3 hours to finally obtain nickel-coated graphite composite powder, the morphology of which is shown in Figure 2.

[0050] Example 2

[0051] As shown in Figure 3, a method for preparing nickel-coated graphite composite powder includes the following steps:

[0052] 1. Weigh out needle coke, dicyandiamide, diammonium hydrogen phosphate and thiourea in proportion, then mix and grind them together for 2 hours to obtain mixed graphite powder;

[0053] The mass ratio of needle coke, dicyandiamide, diammonium hydrogen phosphate and thiourea is 90:5:2:3.

[0054] 2. The mixed graphite powder was kept at 3200℃ for 2 hours under nitrogen protection, and then cooled to room temperature to obtain modified artificial graphite powder.

[0055] 3. Mix nickel nitrate, deionized water, sodium borohydride, tartaric acid and potassium iodide in proportion, and adjust the pH value to 12 to obtain the plating solution;

[0056] The mass ratio of nickel nitrate, deionized water, sodium borohydride, tartaric acid, and potassium iodide is 14.5:60:20:5:0.5.

[0057] 4. Add the modified artificial graphite powder to the plating solution, control the temperature at 90℃, stir at 200rpm, and stir for 3 hours to obtain a graphite powder mixture.

[0058] 5. The obtained graphite powder mixture was filtered to obtain filter residue. The filter residue was washed 5 times with deionized water and then dried in a vacuum drying oven at 120℃ for 1 hour to finally obtain nickel-coated graphite composite powder.

[0059] Example 3

[0060] As shown in Figure 3, a method for preparing nickel-coated graphite composite powder includes the following steps:

[0061] 1. Weigh out petroleum coke, melamine, ammonium dihydrogen phosphate and ammonium sulfide in proportion, then mix and grind them together for 1.5 hours to obtain mixed graphite powder;

[0062] The mass ratio of petroleum coke, melamine, ammonium dihydrogen phosphate, and ammonium sulfide is 92:4:1:3.

[0063] 2. The mixed graphite powder was kept at 3000℃ for 3 hours under nitrogen protection, and then cooled to room temperature to obtain modified artificial graphite powder.

[0064] 3. Mix nickel acetate tetrahydrate, deionized water, hydrazine hydrate, ethylenediaminetetraacetic acid and thiourea in proportion, and adjust the pH value to 11 to obtain the plating solution;

[0065] The mass ratio of nickel acetate tetrahydrate, deionized water, hydrazine hydrate, ethylenediaminetetraacetic acid, and thiourea is 20:50:19.7:10:0.3.

[0066] 4. Add modified artificial graphite powder to the plating solution, control the temperature at 75℃, stir at 150 rpm, and stir for 4 hours to obtain a graphite powder mixture.

[0067] 5. The obtained graphite powder mixture was filtered to obtain filter residue. The filter residue was washed with deionized water 4 times and then dried in a vacuum drying oven at 110℃ for 2 hours to finally obtain nickel-coated graphite composite powder.

[0068] Example 4

[0069] As shown in Figure 3, a method for preparing nickel-coated graphite composite powder includes the following steps:

[0070] 1. Weigh out needle coke, urea, diammonium hydrogen phosphate and sulfur in proportion, then mix and grind them together for 1.2 hours to obtain mixed graphite powder;

[0071] The mass ratio of needle coke, urea, diammonium hydrogen phosphate and sulfur is 93:3:1:3;

[0072] 2. The mixed graphite powder was kept at 2900℃ for 3.5h under nitrogen protection, and then cooled to room temperature to obtain modified artificial graphite powder;

[0073] 3. Mix nickel chloride, deionized water, sodium borohydride, citric acid and potassium iodide in proportion, and adjust the pH value to 10.5 to obtain the plating solution;

[0074] The mass ratio of nickel chloride, deionized water, sodium borohydride, citric acid, and potassium iodide is 19.8:52:18:10:0.2.

[0075] 4. Add the modified artificial graphite powder to the plating solution, control the temperature at 80℃, stir at 120rpm, and stir for 3.5h to obtain a graphite powder mixture.

[0076] 5. The obtained graphite powder mixture was filtered to obtain filter residue. The filter residue was washed three times with deionized water and then dried in a vacuum drying oven at 105℃ for 1.5h to finally obtain nickel-coated graphite composite powder.

[0077] Example 5

[0078] As shown in Figure 3, a method for preparing nickel-coated graphite composite powder includes the following steps:

[0079] 1. Weigh out petroleum coke, dicyandiamide, ammonium dihydrogen phosphate and thiourea in proportion, then mix and grind them together for 1.6 hours to obtain mixed graphite powder;

[0080] The mass ratio of petroleum coke, dicyandiamide, ammonium dihydrogen phosphate, and thiourea is 91:4:2:3.

[0081] 2. The mixed graphite powder was kept at 3100℃ for 2.5h under nitrogen protection, and then cooled to room temperature to obtain modified artificial graphite powder.

[0082] 3. Mix nickel sulfate, deionized water, sodium borohydride, tartaric acid and potassium iodide in the specified proportions, and adjust the pH value to 11.5 to obtain the plating solution;

[0083] The mass ratio of nickel sulfate, deionized water, sodium borohydride, tartaric acid, and potassium iodide is 10:58:22:9.7:0.3.

[0084] 4. Add the modified artificial graphite powder to the plating solution, control the temperature at 85℃, stir at 180 rpm, and stir for 4.5 hours to obtain a graphite powder mixture.

[0085] 5. The obtained graphite powder mixture was filtered to obtain filter residue. The filter residue was washed 5 times with deionized water and then dried in a vacuum drying oven at 115℃ for 2.5h to finally obtain nickel-coated graphite composite powder.

[0086] Example 6

[0087] As shown in Figure 3, a method for preparing nickel-coated graphite composite powder includes the following steps:

[0088] 1. Weigh out needle coke, melamine, diammonium hydrogen phosphate and ammonium sulfide in proportion, then mix and grind them together for 2 hours to obtain mixed graphite powder;

[0089] The mass ratio of needle coke, melamine, diammonium hydrogen phosphate and ammonium sulfide is 94:2:2:2;

[0090] 2. The mixed graphite powder was kept at 3200℃ for 4 hours under nitrogen protection, and then cooled to room temperature to obtain modified artificial graphite powder.

[0091] 3. Mix nickel acetate tetrahydrate, deionized water, hydrazine hydrate, ethylenediaminetetraacetic acid and thiourea in proportion, and adjust the pH value to 11 to obtain the plating solution;

[0092] The mass ratio of nickel acetate tetrahydrate, deionized water, hydrazine hydrate, ethylenediaminetetraacetic acid, and thiourea is 10:50:25:14.6:0.4.

[0093] 4. Add modified artificial graphite powder to the plating solution, control the temperature at 70℃, stir at 160 rpm, and stir for 5 hours to obtain a graphite powder mixture.

[0094] 5. The obtained graphite powder mixture was filtered to obtain filter residue. The filter residue was washed with deionized water 4 times and then dried in a vacuum drying oven at 120℃ for 3 hours to finally obtain nickel-coated graphite composite powder.

[0095] Comparative Example 1

[0096] A method for preparing nickel-coated graphite composite powder includes the following steps:

[0097] 1. Weigh out the petroleum coke, then mix and grind it together for 1 hour to obtain carbon raw material powder;

[0098] 2. The carbon raw material powder was kept at 2800℃ for 4 hours under nitrogen protection, and then cooled to room temperature to obtain artificial graphite powder.

[0099] 3. Mix nickel sulfate, deionized water, sodium borohydride, citric acid and thiourea in proportion, and adjust the pH value to 10 to obtain the plating solution;

[0100] The mass ratio of nickel sulfate, deionized water, sodium borohydride, citric acid, and thiourea is 19.9:50:15:5:0.1.

[0101] 4. Add artificial graphite powder to the plating solution, control the temperature at 65℃, stir at 100rpm, and stir for 5 hours to obtain a graphite powder mixture.

[0102] 5. The obtained graphite powder mixture was filtered to obtain filter residue. The filter residue was washed three times with deionized water and then dried in a vacuum drying oven at 100°C for 3 hours to finally obtain nickel-coated graphite composite powder.

[0103] Comparative Example 2

[0104] A method for preparing nickel-coated graphite composite powder includes the following steps:

[0105] 1. Weigh out petroleum coke, melamine, ammonium dihydrogen phosphate and ammonium sulfide in proportion, then mix and grind them together for 1.5 hours to obtain mixed graphite powder;

[0106] The mass ratio of petroleum coke, melamine, ammonium dihydrogen phosphate, and ammonium sulfide is 92:4:1:3.

[0107] 2. The mixed graphite powder was kept at 3000℃ for 3 hours under nitrogen protection, and then cooled to room temperature to obtain modified artificial graphite powder.

[0108] 3. Mix nickel acetate tetrahydrate, deionized water, hydrazine hydrate and thiourea in proportion, and adjust the pH value to 11 to obtain the plating solution;

[0109] The mass ratio of nickel acetate tetrahydrate, deionized water, hydrazine hydrate, and thiourea is 14.7:65:20:0.3.

[0110] 4. Add modified artificial graphite powder to the plating solution, control the temperature at 75℃, stir at 150 rpm, and stir for 4 hours to obtain a graphite powder mixture.

[0111] 5. The obtained graphite powder mixture was filtered to obtain filter residue. The filter residue was washed with deionized water 4 times and then dried in a vacuum drying oven at 110℃ for 2 hours to finally obtain nickel-coated graphite composite powder.

[0112] Comparative Example 3

[0113] A method for preparing nickel-coated graphite composite powder includes the following steps:

[0114] 1. Weigh out needle coke, then mix and grind them together for 2 hours to obtain carbon raw material powder;

[0115] 2. The carbon raw material powder was kept at 3200℃ for 4 hours under nitrogen protection, and then cooled to room temperature to obtain artificial graphite powder.

[0116] 3. Mix nickel acetate tetrahydrate, deionized water, hydrazine hydrate and thiourea in proportion, and adjust the pH value to 11 to obtain the plating solution;

[0117] The mass ratio of nickel acetate tetrahydrate, deionized water, hydrazine hydrate, and thiourea is 10:64.6:25:0.4.

[0118] 4. Add artificial graphite powder to the plating solution, control the temperature at 70℃, stir at 160 rpm, and stir for 5 hours to obtain a graphite powder mixture.

[0119] 5. The obtained graphite powder mixture was filtered to obtain filter residue. The filter residue was washed with deionized water 4 times and then dried in a vacuum drying oven at 120℃ for 3 hours to finally obtain nickel-coated graphite composite powder.

[0120] The resistivity changes of the nickel-coated graphite composite powders prepared in each embodiment and comparative example before and after aging (aging for 500 hours in an environment of 85℃ and 85%RH) were detected using a resistivity meter to demonstrate their anti-aging performance. Simultaneously, the electromagnetic shielding performance of the nickel-coated graphite composite powders prepared in each embodiment and comparative example was tested using a vector network analyzer. The overall test results are shown in Table 1.

[0121] Table 1. Test results of nickel-coated graphite composite powders prepared in the examples and comparative examples.

[0122]

[0123] As shown in Table 1, the aging resistance and electromagnetic shielding performance of the nickel-coated graphite composite powders prepared in Examples 1 to 6 are generally better than those in Comparative Examples 1 to 3.

[0124] The main reason is that this application obtains modified artificial graphite powder by mixing carbon raw materials with nitrogen, phosphorus and sulfur sources and treating them at high temperature. Then, the modified artificial graphite powder is added to a plating solution mixed with nickel salt, reducing agent, complexing agent and stabilizer. By optimizing the process parameters, a nickel-coated graphite composite powder with complete coating, excellent anti-aging performance and electromagnetic shielding performance, and simple and efficient preparation process is obtained.

[0125] At high temperatures, nitrogen, phosphorus, and sulfur sources undergo thermal decomposition, releasing reactive nitrogen, phosphorus, and sulfur. These reactive species react with carbon atoms on the surface of the carbon raw materials at high temperatures, introducing nitrogen, phosphorus, and sulfur atoms into the graphite structure formed by the carbon raw materials at high temperatures by replacing some carbon atoms in the formed graphite lattice or filling the interstitial spaces, thus achieving a doping effect. Furthermore, the doped nitrogen, phosphorus, and sulfur atoms form stable chemical bonds with carbon atoms, reducing lattice defects and forming a more regular doped graphite structure. This makes the graphite structure more stable under high-temperature or corrosive environments, less prone to oxidation and degradation, ultimately yielding modified artificial graphite powder, thereby improving the aging resistance of nickel-coated graphite composite powder. Moreover, due to the doping of nitrogen, phosphorus, and sulfur, the surface activity of the modified artificial graphite powder is significantly enhanced. It can not only physically adsorb nickel ions, but the doped nitrogen, phosphorus, and sulfur atoms can also form stable coordination bonds with nickel ions in subsequently added nickel salts. This bonding effect allows nickel ions in the nickel salts to be more firmly adsorbed and tightly bound to the surface of the modified artificial graphite powder. Furthermore, when nickel ions are reduced to nickel powder in situ, the nickel powder coating layer on the surface of the modified artificial graphite powder becomes tighter, more complete, and less prone to falling off, thus greatly improving the electromagnetic shielding performance.

[0126] In contrast, Comparative Example 1 did not involve mixing carbon raw materials with nitrogen, phosphorus, and sulfur sources and then treating them at high temperatures to obtain modified artificial graphite powder; instead, it only produced artificial graphite powder by high-temperature treatment of petroleum coke. Therefore, the resulting artificial graphite powder had low surface activity, failing to effectively physically adsorb nickel ions and lacking nitrogen, phosphorus, and sulfur atoms capable of forming stable coordinate bonds with them. Consequently, its anti-aging properties and electromagnetic shielding performance were both poor.

[0127] In Comparative Example 2, the plating solution formulation was incomplete and lacked a complexing agent. Therefore, it was difficult to avoid the rapid reduction of nickel ions, which led to particle agglomeration. Consequently, it was difficult to ensure that the reduced nickel powder was deposited on the surface of the modified artificial graphite powder in a fine and uniform form. As a result, the coating layer was not uniform and dense enough, and the anti-aging performance and electromagnetic shielding performance were also affected.

[0128] In Comparative Example 3, since the carbon raw materials were not mixed with nitrogen, phosphorus and sulfur sources and treated at high temperature to obtain modified artificial graphite powder, and the plating solution used did not contain a complexing agent, the nickel-coated graphite composite powder obtained had the worst anti-aging performance and electromagnetic shielding performance for the same reasons as above.

[0129] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.

[0130] Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the equivalents of the appended claims.

Claims

1. A nickel-coated graphite composite powder, characterized in that, The nickel-coated graphite composite powder includes modified artificial graphite powder and nickel powder coated on the surface of the modified artificial graphite powder; the modified artificial graphite powder is obtained by mixing carbon raw materials with nitrogen, phosphorus and sulfur sources and then treating them at high temperature; the nickel powder is obtained by in-situ reduction of nickel salt on the surface of the modified artificial graphite powder.

2. The nickel-coated graphite composite powder according to claim 1, characterized in that, The nitrogen source includes any one of urea, dicyandiamide, and melamine; the phosphorus source includes any one of ammonium dihydrogen phosphate and diammonium hydrogen phosphate; and the sulfur source includes any one of sulfur, thiourea, and ammonium sulfide.

3. The nickel-coated graphite composite powder according to claim 1, characterized in that, The mass ratio of the carbon raw material, nitrogen source, phosphorus source and sulfur source is (90~95):(2-5):(1-2):(1-3).

4. The nickel-coated graphite composite powder according to claim 1, characterized in that, The carbon raw material includes either petroleum coke or needle coke.

5. The nickel-coated graphite composite powder according to claim 1, characterized in that, The nickel salt includes any one of nickel sulfate, nickel nitrate, nickel acetate tetrahydrate, and nickel chloride.

6. A method for preparing nickel-coated graphite composite powder as described in any one of claims 1-5, comprising the following steps: Weigh carbon raw materials, nitrogen source, phosphorus source and sulfur source in proportion, then mix and grind them together for 1-2 hours to obtain mixed graphite powder; keep the mixed graphite powder at 2800-3200℃ for 2-4 hours under nitrogen protection, then cool to room temperature to obtain modified artificial graphite powder; mix nickel salt, deionized water, reducing agent, complexing agent and stabilizer in proportion, adjust the pH value to 10-12 to obtain plating solution; add modified artificial graphite powder to plating solution, control the temperature at 65-90℃, stir at 100-200rpm, stir for 3-5 hours to obtain graphite powder mixture; filter the obtained graphite powder mixture to obtain filter residue, wash the filter residue with deionized water 3-5 times, and then dry it in a vacuum drying oven at 100-120℃ for 1-3 hours to finally obtain nickel-coated graphite composite powder.

7. The method for preparing nickel-coated graphite composite powder according to claim 6, characterized in that, The reducing agent includes either sodium borohydride or hydrazine hydrate.

8. The method for preparing nickel-coated graphite composite powder according to claim 6, characterized in that, The complexing agent includes any one of citric acid, tartaric acid, and ethylenediaminetetraacetic acid.

9. The method for preparing nickel-coated graphite composite powder according to claim 6, characterized in that, The stabilizer includes either thiourea or potassium iodide.

10. The method for preparing nickel-coated graphite composite powder according to claim 6, characterized in that, In the plating solution, the mass ratio of nickel salt, deionized water, reducing agent, complexing agent and stabilizer is (10-20):(50-60):(15-25):(5-15):(0.1-0.5).

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