Preparation method of nickel-coated graphite composite powder material for conductive silica gel

Abstract

The invention discloses a preparation method of a nickel-coated graphite composite powder material for conductive silica gel, and relates to the technical field of nickel-coated graphite composite powders.The preparation method comprises the following preparation steps that 1, 1 g of graphite is pretreated; 2, fully mixing the pretreated graphite with 500mL of a nickel sulfate solution with the concentration of 200g / L, adjusting the pH value to 11-11.5 by using ammonia water, stirring for 25-40 minutes under the condition of water bath heating at 60-75 DEG C, and adding ammonia water at any time to adjust the pH value until the reaction is complete; 3, washing the solution with distilled water until the solution is neutral, and drying to obtain nickel-coated graphite composite powder; and 4, carrying out modification treatment on the nickel-coated graphite composite powder. According to the preparation method of the nickel-coated graphite composite powder material for the conductive silica gel, the nickel-coated graphite composite powder is treated through HC1 and H2O2, and impurities on the surface of the nickel-coated graphite composite powder can be removed.

Description

Technical Field

[0001] The present invention relates to the technical field of nickel-coated graphite composite powder, and specifically to a preparation method of a nickel-coated graphite composite powder material for conductive silica gel. Background Art

[0002] Common conductive fillers for conductive silica gel include pure silver powder, silver-coated copper powder, silver-coated aluminum powder, silver-coated glass powder, nickel-coated copper powder, nickel-coated graphite powder, etc. Pure silver powder, as a conductive compound of conductive filler, has good electrical conductivity and oxidation resistance, but its scope of use is limited due to silver particle migration and high price. In order to overcome the defects of pure silver powder, conductive composite powders such as silver-coated copper powder, silver-coated aluminum powder, and silver-coated glass powder have been developed successively. However, the price of silver-based conductive composite powders is still relatively high, and silver-based conductive composite powders do not have magnetic conductivity, so the magnetic shielding effect is poor. Nickel is a metal material with both electrical conductivity and magnetic conductivity. Therefore, using nickel as an inexpensive conductive silica gel filler has become a research hotspot in recent years.

[0003] Chinese Patent with Publication No. CN113059155A discloses a preparation method of a nickel-coated graphite composite powder material for conductive silica gel. The preparation process is as follows: 1) Degrease the surface of graphite powder, wash, filter by suction, and dry; 2) Activate the washed graphite powder, wash, filter by suction, and dry; 3) Place the graphite powder treated in step 2) into a chemical plating solution for chemical plating, filter by suction, wash, and dry to obtain a nickel-coated graphite composite powder material for conductive silica gel. This scheme has a simple preparation process, good coating effect of the prepared nickel-coated graphite composite powder, and high production efficiency, and is suitable for large-scale industrial production. However, the mechanical properties and electrical conductivity of the nickel-coated graphite composite powder prepared by the above prior art scheme need to be further improved; for this reason, the present invention provides a preparation method of a nickel-coated graphite composite powder material for conductive silica gel to solve the above technical problems. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a preparation method of a nickel-coated graphite composite powder material for conductive silica gel, which solves the problems mentioned in the above background art.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A preparation method of a nickel-coated graphite composite powder material for conductive silica gel includes the following preparation steps:

[0006] Step 1: Pretreat 1 g of graphite.

[0007] Step 2: fully mix the pretreated graphite with 500 mL of a 200 g / L nickel sulfate solution, adjust the pH value to 11-11.5 with aqueous ammonia, stir for 25-40 min in a 60-75 ° C water bath, and add aqueous ammonia to adjust the pH value at any time until the reaction is complete;

[0008] Step 3, washing the solution with distilled water until it is neutral, and drying it to obtain nickel-coated graphite composite powder;

[0009] Step 4: Modify the nickel-coated graphite composite powder.

[0010] Preferably, in step 1, graphite pretreatment includes the following processing steps:

[0011] S1, oil removal treatment;

[0012] S2, sensitization treatment;

[0013] S3. Activation treatment.

[0014] Preferably, the specific operation of the oil removal treatment is:

[0015] S11, immerse 1g of graphite in 460-500mL of a sodium hydroxide solution with a concentration of 100g / L, heat to 60-70°C, and stir to react for 25-30min;

[0016] S12, perform vacuum filtration and separation, then wash with deionized water 2-3 times, and then dry in a vacuum drying oven at 55-60° C. for 1.5-2 h.

[0017] Preferably, the specific operation of the sensitization treatment is:

[0018] S21, slowly add 5g / L SnCl2 to the HCl solution, and after it is completely dissolved, add distilled water and deoiled graphite in sequence, and perform magnetic stirring;

[0019] S22, perform vacuum filtration separation, wash with deionized water 2-3 times, and then place in a vacuum drying oven at 55-60°C to dry for 1.5-2h.

[0020] Preferably, the specific operation of the activation treatment is:

[0021] S31, placing the sensitized graphite in a 0.02-0.05 g / L PdCl2 solution, raising the temperature to 30-40°C, adding HCl solution dropwise, adjusting the pH value of the solution to 1-2, and stirring for 20-30 min;

[0022] S32. Perform vacuum filtration separation, wash with deionized water 2 - 3 times, and then place in a vacuum drying oven at 55 - 60 °C for drying for 1.5 - 2 h.

[0023] Preferably, in the fourth step, the specific modification method for the nickel-coated graphite composite powder is as follows:

[0024] (1) Pour 6.5 - 12 g of a mixed solution of HC1 and H2O2 into 4.5 - 7.5 g of the nickel-coated graphite composite powder, and stir for 30 - 40 min;

[0025] (2) After filtration, wash with deionized water 3 - 5 times;

[0026] (3) Add 1.2 - 2.5 g of ethylenediamine, stir well until fully mixed, and then filter, wash, and dry.

[0027] Preferably, in (1), the molar ratio of HC1 to H2O2 is (2 - 3):1.

[0028] Preferably, in (3), stir at a speed of 500 - 900 r / min for 25 - 45 min, the drying temperature is 50 - 60 °C, and the drying time is 50 - 80 min.

[0029] Beneficial effects

[0030] The present invention provides a preparation method of a nickel-coated graphite composite powder material for conductive silica gel. Compared with the prior art, it has the following beneficial effects:

[0031] (1). In the preparation method of the nickel-coated graphite composite powder material for conductive silica gel, sodium hydroxide can remove acidic impurities on the surface of graphite, purify the surface of graphite, and at the same time can activate the surface of graphite to a certain extent, generating more active sites on its surface, which is beneficial to subsequent reactions or composites with other substances, thereby improving the bonding force between the nickel layer and graphite and effectively improving the compressive performance of the composite powder; Sn 2+ is adsorbed on the active sites on the surface of graphite after the previous treatment, providing a transition layer for the subsequent metal deposition process, enabling metallic nickel to deposit better on the surface of graphite, enhancing the bonding force between graphite and metal, and improving the hardness of the composite powder; PdCl2 will react with the adsorbed Sn 2+ to generate palladium particles attached to the surface of graphite, catalyzing the reduction reaction of nickel ions in the subsequent electroless nickel plating process, enabling nickel to uniformly coat the surface of graphite, thereby enhancing the mechanical strength of the composite material and improving the compatibility and dispersibility among other components in the conductive adhesive, thus improving the electrical conductivity.

[0032] (2) The preparation method of the nickel-coated graphite composite powder material for conductive silica gel can remove impurities on the surface of the nickel-coated graphite composite powder by treating it with HCl and H2O2. HCl can react with some metal oxides and dissolve them, while H2O2 has oxidizing properties and can oxidize and decompose some organic impurities, thus purifying the surface of the composite powder. At the same time, HCl can corrode the surface of the nickel layer, producing tiny pits or defects and increasing the surface roughness. H2O2 can undergo an oxidation-reduction reaction with the nickel surface, forming some active functional groups on the surface. These active sites and functional groups are beneficial for the composite powder to interact better with other components in subsequent applications, improving the bonding force between it and the matrix material, and thus enhancing the mechanical properties of the material. After being modified by HCl and H2O2, the surface properties of the nickel-coated graphite composite powder are improved, its dispersibility in systems such as conductive adhesives is enhanced, and the agglomeration phenomenon between the composite powder particles is reduced, enabling it to be more evenly dispersed in the conductive adhesive, thereby improving the stability and consistency of the conductive performance of the conductive adhesive. Description of the Drawings

[0033] Figure 1 SEM images before and after graphite pretreatment provided for the preparation method of a nickel-coated graphite composite powder material for conductive silica gel according to the present invention. Detailed Embodiments

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] Example 1

[0036] A preparation method of a nickel-coated graphite composite powder material for conductive silica gel includes the following preparation steps:

[0037] Step 1. Pretreat 1 g of graphite:

[0038] S1. Degreasing treatment: Immerse 1 g of graphite in 460 mL of sodium hydroxide solution with a concentration of 100 g / L, heat it to 60 °C, and stir for reaction for 25 min; perform vacuum filtration separation, then wash it twice with deionized water, and then place it in a vacuum drying oven at 55 °C for drying for 1.5 h;

[0039] S2. Sensitization treatment: Slowly add 5 g / L of SnCl2 to the HC1 solution. After complete dissolution, add distilled water and the degreased graphite in sequence, and perform magnetic stirring; conduct vacuum filtration and separation, wash twice with deionized water, and then place in a vacuum drying oven at 55 °C for drying for 1.5 h;

[0040] S3. Activation treatment: Place the sensitized graphite in a 0.02 g / L PdCl2 solution, raise the temperature to 30 °C, add the HCl solution dropwise, adjust the pH value of the solution to 1, and stir for 20 min; conduct vacuum filtration and separation, wash twice with deionized water, and then place in a vacuum drying oven at 55 °C for drying for 1.5 h;

[0041] Step 2: Thoroughly mix the pretreated graphite with 500 mL of a nickel sulfate solution with a concentration of 200 g / L, adjust the pH value to 11 with ammonia water, stir at 60 °C under a water bath heating condition for 25 min, and add ammonia water at any time to adjust the pH value until the reaction is complete;

[0042] Step 3: After rinsing the solution with distilled water until it is neutral, dry it to obtain the nickel-coated graphite composite powder;

[0043] Step 4: Modify the nickel-coated graphite composite powder: Take 4.5 g of the nickel-coated graphite composite powder, pour 6.5 g of a mixed solution of HC1 and H2O2 with a molar ratio of 2:1 into it, and stir for 30 min; filter, and then wash three times with deionized water; add 1.2 g of ethylenediamine, stir at a rotation speed of 500 r / min for 25 min, then filter and wash, and finally place in a drying oven at 50 °C for drying for 50 min.

[0044] Example 2

[0045] A preparation method of a nickel-coated graphite composite powder material for conductive silica gel includes the following preparation steps:

[0046] Step 1: Pretreat 1 g of graphite:

[0047] S1. Degreasing treatment: Immerse 1 g of graphite in 480 mL of a sodium hydroxide solution with a concentration of 100 g / L, raise the temperature to 65 °C, and stir and react for 28 min; conduct vacuum filtration and separation, then wash three times with deionized water, and then place in a vacuum drying oven at 58 °C for drying for 1.8 h;

[0048] S2. Sensitization treatment: Slowly add 5 g / L of SnCl2 to the HC1 solution. After complete dissolution, add distilled water and the degreased graphite in sequence, and perform magnetic stirring; conduct vacuum filtration and separation, wash twice with deionized water, and then place in a vacuum drying oven at 57 °C for drying for 1.7 h;

[0049] S3. Activation treatment: Place the sensitized graphite in a PdCl2 solution with a concentration of 0.03 g / L, raise the temperature to 35 °C, add HCl solution dropwise, adjust the pH value of the solution to 1.5, and stir for 25 min; perform vacuum filtration separation, wash twice with deionized water, and then place in a vacuum drying oven at 58 °C for drying for 1.7 h;

[0050] Step 2. Thoroughly mix the pretreated graphite with 500 mL of a nickel sulfate solution with a concentration of 200 g / L, adjust the pH value to 11.2 with ammonia water, stir for 30 min under the condition of water bath heating at 65 °C, and add ammonia water at any time to adjust the pH value until the reaction is complete;

[0051] Step 3. After rinsing the solution with distilled water until it is neutral, dry it to obtain nickel-coated graphite composite powder;

[0052] Step 4. Modify the nickel-coated graphite composite powder: Take 5.5 g of the nickel-coated graphite composite powder, pour 8.5 g of a mixed solution of HCl and H2O2 with a molar ratio of 2.5:1 into it, and stir for 35 min; filter, and then wash 4 times with deionized water; add 2.2 g of ethylenediamine, stir at a speed of 700 r / min for 35 min, then filter and wash, and finally place in a drying oven at 55 °C for drying for 65 min.

[0053] Example 3

[0054] A preparation method of a nickel-coated graphite composite powder material for conductive silica gel, comprising the following preparation steps:

[0055] Step 1. Pretreat 1 g of graphite:

[0056] S1. Degreasing treatment: Immerse 1 g of graphite in 500 mL of a sodium hydroxide solution with a concentration of 100 g / L, raise the temperature to 70 °C, and stir and react for 30 min; perform vacuum filtration separation, then wash 3 times with deionized water, and then place in a vacuum drying oven at 60 °C for drying for 2 h;

[0057] S2. Sensitization treatment: Slowly add 5 g / L of SnCl2 to the HCl solution. After complete dissolution, add distilled water and the degreased graphite in sequence, and perform magnetic stirring; perform vacuum filtration separation, wash 3 times with deionized water, and then place in a vacuum drying oven at 60 °C for drying for 2 h;

[0058] S3. Activation treatment: Place the sensitized graphite in a PdCl2 solution with a concentration of 0.05 g / L, raise the temperature to 40 °C, add HCl solution dropwise, adjust the pH value of the solution to 2, and stir for 30 min; perform vacuum filtration separation, wash 3 times with deionized water, and then place in a vacuum drying oven at 60 °C for drying for 2 h;

[0059] Step 2: Thoroughly mix the pretreated graphite with 500 mL of nickel sulfate solution with a concentration of 200 g / L, adjust the pH value to 11.5 with ammonia water, stir for 40 min under the condition of water bath heating at 75 °C, and add ammonia water at any time to adjust the pH value until the reaction is complete;

[0060] Step 3: After rinsing the solution with distilled water until it is neutral, dry it to obtain nickel-coated graphite composite powder;

[0061] Step 4: Modify the nickel-coated graphite composite powder: Take 7.5 g of nickel-coated graphite composite powder, pour 12 g of a mixed solution of HC1 and H2O2 with a molar ratio of 3:1 into it, and stir for 40 min; filter, and then wash it 5 times with deionized water; add 2.5 g of ethylenediamine, stir at a speed of 900 r / min for 45 min, then filter and wash, and finally place it in a drying oven at 60 °C and dry for 80 min.

[0062] Comparative Example 1

[0063] Compared with Example 1, the difference is that the pretreatment step of graphite in Example 1 is replaced with:

[0064] S1: Place 1 g of graphite powder in 50 mL of sodium hydroxide solution with a concentration of 20 g / L, carry out mechanical heating and stirring, control the heating temperature at 60 °C, and the stirring time is 25 min;

[0065] S2: Place the degreased graphite powder in 100 mL of nickel acetate methanol solution with a mass concentration of 90 g / L, and then pour the sodium borohydride solution with a mass concentration of 20 g / L into the activation solution for activation, and the activation treatment time is 30 min.

[0066] Comparative Example 2

[0067] Compared with Example 1, the difference is that the nickel-coated graphite composite powder in Example 1 is not subjected to modification treatment.

[0068] Shore hardness test: Conduct the test in accordance with GB / T531-2009; the results are shown in Table 1.

[0069] Tensile strength test: Conduct the test in accordance with GB / T528-2008; the results are shown in Table 1.

[0070] Resistivity test: First, the prepared silver paste was coated on a glass slide to obtain a conductive circuit with a length of 25 mm, a width of 10 mm, and a thickness of approximately 50 μm. The size of the circuit was controlled by a polyimide tape fixed on the glass substrate. Then, the coated silver paste was vacuum-cured at a temperature of 120 °C for 2 h. Finally, it was detected using an RTS-9 dual-electrical measurement four-probe tester; the results are shown in Table 1.

[0071] Table 1

[0072] Hardness / Shore A Tensile strength / MPa Volume resistivity / Ω·cm Example 1 53 1.46 <![CDATA[0.82×10 -3 > Example 2 50 1.42 <![CDATA[0.81×10 -3 > Example 3 52 1.46 <![CDATA[0.81×10 -3 > Comparative example 1 46 1.31 <![CDATA[1.37×10 -3 > Comparative example 2 44 1.27 <![CDATA[1.21×10 -3 >

[0073] As Figure 1 shown, the surface of the graphite before pretreatment was relatively rough, and the surface of the graphite after pretreatment was significantly smoother.

[0074] Meanwhile, the content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

[0075] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0076] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a nickel-coated graphite composite powder material for conductive silica gel, characterized in that, It includes the following preparation steps: Step 1: Pretreat 1 g of graphite; Step 2: Thoroughly mix the pretreated graphite with 500 mL of nickel sulfate solution with a concentration of 200 g / L, adjust the pH value to 11 - 11.5 with ammonia water, stir for 25 - 40 min under the condition of water bath heating at 60 - 75 °C, and add ammonia water at any time to adjust the pH value until the reaction is complete; Step 3: After rinsing the solution with distilled water until it is neutral, dry it to obtain nickel-coated graphite composite powder; Step 4: Modify the nickel-coated graphite composite powder.

2. The preparation method of a nickel-coated graphite composite powder material for conductive silicone according to claim 1, characterized in that: In the said Step 1, the graphite pretreatment includes the following treatment steps: S1: Degreasing treatment; S2: Sensitization treatment; S3: Activation treatment.

3. The preparation method of a nickel-coated graphite composite powder material for conductive silica gel according to claim 2, characterized in that: The specific operation of the said degreasing treatment is: S11: Immerse 1 g of graphite in 460 - 500 mL of sodium hydroxide solution with a concentration of 100 g / L, heat up to 60 - 70 °C, and stir and react for 25 - 30 min; S12: Conduct vacuum filtration separation, then wash with deionized water 2 - 3 times, and then place it in a vacuum drying oven at 55 - 60 °C for drying for 1.5 - 2 h.

4. The preparation method of a nickel-coated graphite composite powder material for conductive silica gel according to claim 3, characterized in that: The specific operation of the said sensitization treatment is: S21: Slowly drop 5 g / L of SnCl2 into the HC1 solution. After complete dissolution, add distilled water and the graphite after degreasing treatment in sequence, and conduct magnetic stirring; S22: Conduct vacuum filtration separation, wash with deionized water 2 - 3 times, and then place it in a vacuum drying oven at 55 - 60 °C for drying for 1.5 - 2 h.

5. The preparation method of a nickel-coated graphite composite powder material for conductive silica gel according to claim 4, characterized in that: The specific operation of the said activation treatment is: S31: Place the graphite after sensitization treatment in a PdCl2 solution with a concentration of 0.02 - 0.05 g / L, raise the temperature to 30 - 40 °C, dropwise add the HCl solution, adjust the pH value of the solution to 1 - 2, and stir for 20 - 30 min; S32: Conduct vacuum filtration separation, wash with deionized water 2 - 3 times, and then place it in a vacuum drying oven at 55 - 60 °C for drying for 1.5 - 2 h.

6. The preparation method of a nickel-coated graphite composite powder material for conductive silica gel according to claim 1, characterized in that: In the said Step 4, the specific modification method for the nickel-coated graphite composite powder is: (1) Pour 6.5 - 12 g of the mixed solution of HC1 and H2O2 into 4.5 - 7.5 g of nickel-coated graphite composite powder, and stir for 30 - 40 min; (2) After filtration, wash with deionized water 3 - 5 times; (3) Add 1.2 - 2.5 g of ethylenediamine, stir well and mix evenly, then filter, wash, and dry.

7. The preparation method of a nickel-coated graphite composite powder material for conductive silica gel according to claim 6, characterized in that: In the said (1), the molar ratio of HC1 to H2O2 is (2 - 3):

1.

8. The preparation method of a nickel-coated graphite composite powder material for conductive silica gel according to claim 6, characterized in that: In the said (3), stir at a speed of 500 - 900 r / min for 25 - 45 min, the drying temperature is 50 - 60 °C, and the drying time is 50 - 80 min.

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