Graphite film-p-phenylenediamine-silver composite material and preparation method thereof

Abstract

The invention discloses a graphite film-p-phenylenediamine-silver composite material and a preparation method thereof.The structure of the composite material is that p-phenylenediamine molecules are introduced to the upper face and the lower face of a flake graphite film, silver is deposited on the flake graphite film with the p-phenylenediamine molecules, amino in the p-phenylenediamine molecules and the silver form an amino-silver complex, and the composite material is prepared. The preparation method comprises the following steps: carrying out surface plasma treatment on the flake graphite film; putting the flake graphite film into absolute ethyl alcohol containing p-phenylenediamine, adding isoamyl nitrite while magnetically stirring under the protection of nitrogen, taking out the flake graphite film, washing, drying in vacuum, and electrosilvering the flake graphite film to obtain the graphite film-p-phenylenediamine-silver composite material, the thermal conductivity of the composite material is increased, and the interface bonding between the graphite film and a silver base is good.

Description

Technical Field

[0001] The present invention relates to the field of thermal management of composite materials, and particularly to a graphite film-p-phenylenediamine-silver composite material and a preparation method thereof. Background Art

[0002] Graphite film has unique advantages as an electronic heat dissipation material, with a thermal conductivity as high as 600 - 1200 (W / (m﹒K)). At the same time, the heat dissipation graphite film is light in specific gravity, so it has broad application prospects in the field of electronic device heat dissipation. At the same time, silver has very excellent thermal conductivity and excellent welding performance. The combination of graphite film and silver has broad application prospects in the field of electronic packaging.

[0003] In the graphite film / silver composite material, the heat conduction modes of the graphite film and the metal are different. The graphite film is mainly phonon heat transfer while silver is mainly electron heat transfer. When the heat conducts at the graphite film-silver interface, certain losses will occur due to the transformation of the two modes, that is, the interface thermal resistance effect. How to design the structure at the graphite film-silver interface to improve the phonon-electron coupling rate and thus reduce the interface thermal resistance is an important means to improve the thermal conductivity of the graphite film-silver composite material. On the other hand, considering that the wettability between the graphite film itself and silver is poor and the interface bonding effect is weak, this weak interface bonding will have a fatal impact on the composite material. Because the temperature rise and fall during the heat dissipation process and the bending during the assembly process are likely to directly generate tiny gaps between the graphite film and silver, thereby increasing the interface thermal resistance between the graphite film and silver. Summary of the Invention

[0004] The present invention provides a graphite film-p-phenylenediamine-silver composite material and a preparation method thereof, aiming to simultaneously solve the problems of high interface thermal resistance, low interface bonding strength between the graphite film and silver, and difficulty in bending the composite material in the existing technical solutions.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A graphite film-p-phenylenediamine-silver composite material, the structure of the composite material is that p-phenylenediamine molecules are introduced on the upper and lower surfaces of the flaky graphite film, silver is deposited on the flaky graphite film with p-phenylenediamine molecules, and the amino group in the p-phenylenediamine molecule forms an amino silver complex with silver, forming a silver-flaky graphite film-silver composite material, also called a graphite film-p-phenylenediamine-silver composite material.

[0006] The preparation method of the graphite film-p-phenylenediamine-silver composite material includes the following steps:

[0007] S1. Perform surface plasma treatment on the flaky graphite film.

[0008] S2. Dissolve p-phenylenediamine in absolute ethanol, put in the flaky graphite film, evacuate the air, introduce nitrogen for protection, and magnetically stir for 10 min to obtain a mixed solution.

[0009] S3. Under nitrogen protection, add isoamyl nitrite to the above-mentioned mixed solution. After magnetic stirring evenly, heat it to 60 - 100 °C and carry out magnetic stirring reaction at a constant temperature for 10 - 20 h.

[0010] S4. Take out the flaky graphite film in S3, wash it with ethanol, and vacuum dry it at 50 - 100 °C for 2 - 6 h.

[0011] S5. Electroplate silver on the dried flaky graphite film for 30 s - 2 min to obtain a graphite film - p - phenylenediamine - silver composite material.

[0012] Furthermore, the thickness of the flaky graphite film is 10 - 300 μm, and the density is 1.7 - 2.3 g / cm 3 。

[0013] Furthermore, the surface plasma treatment of the flaky graphite film in step S1 is specifically as follows: soak the flaky graphite film in absolute ethanol and stir for 10 min, wash it with deionized water and dry it; after drying, carry out plasma treatment. The process parameters of the plasma surface treatment are: use an air atmosphere, the gas flow rate is 100 - 800 sccm, the power is 10 - 300 W, and the treatment time is 10 s - 20 min.

[0014] Furthermore, the mass ratio of p - phenylenediamine to the flaky graphite film in step S2 is 0.2 - 5:1.

[0015] Furthermore, the molar ratio of isoamyl nitrite to p - phenylenediamine in step S3 is 1 - 4:1.

[0016]

[0017] In the above molar ratio formula: n 1 is the amount of substance of isoamyl nitrite, n 2 is the amount of substance of p - phenylenediamine, v is the liquid volume of isoamyl nitrite, ω is the mass fraction of isoamyl nitrite (ω = 97%), ρ is the solution density of isoamyl nitrite (ρ = 0.872 g / cm 3 ), m is the mass of p - phenylenediamine, M 1 and M 2 are the molar masses of isoamyl nitrite and p - phenylenediamine respectively (M 1＝ 117.15 g / mol; M 2＝ 108.14 g / mol).

[0018] Further, in step S5, the electroplating solution includes 30-60 g / L of silver nitrate, 200-300 g / L of sodium thiosulfate, and 30-60 g / L of potassium metabisulfite. The concentration ratio of silver nitrate: sodium thiosulfate: potassium metabisulfite is 1:5.56:1, the pH value is 6-7, the constant current mode is adopted, and the current density is 0.5-0.8 A / dm 2 , and the plating time is 30 s - 2 min.

[0019] The principle of the present invention is that through the interaction between the amino group of p-phenylenediamine molecule and silver, a "chemical bridge" is established between silver and the graphite film.

[0020] p-Phenylenediamine is an aromatic amine containing two amino (-NH 2 ) groups, which are located at the para positions of the benzene ring respectively. It has relatively low activity itself, and it is rather difficult to react with silver to form an amino silver complex. However, the diazonium salt (aniline) formed by the diazotization reaction of isoamyl nitrite and p-phenylenediamine is adsorbed on the graphite film. This diazonium salt has relatively high activity and contains a reactive functional group amino (-NH 2 ). The amino group is a very reactive functional group, and the nitrogen atom in it has a lone pair of electrons, which can act as a coordinating atom to form a coordination bond with a metal. This reaction is usually not a direct redox reaction, but is based on the complexing ability of the amino group in the aniline molecule towards silver ions.

[0021] Silver ion Ag+ is a typical Lewis acid and can accept an electron pair. When silver is deposited or exists in ionic form, it tends to interact with the lone pair of electrons in the ligand to form a coordination bond.

[0022] The amino group in the p-phenylenediamine molecule coordinates with silver ions through the lone pair of electrons of its nitrogen atom to form an amino silver complex [Ag(NH 2 )x] + , where x≥1. The nitrogen atom in the amino group provides electron density through the lone pair of electrons to coordinate with silver ions. The coordination bond forms a covalent bond, but the source of its electrons is completely provided by the ligand (here the amino group). The presence of the amino group in p-phenylenediamine provides multiple coordination sites and enhances the stability of the complex.

[0023] Therefore, the amino group does not react with the silver deposited on the graphite film after the reduction reaction during electroplating. Instead, during electroplating, silver ions migrate from the electroplating solution to the surface of the graphite film, and the lone pair of electrons in the amino group can act as a Lewis base to react with silver ions (Ag +)A coordination bond is formed. The empty orbitals of silver ions (such as 5s and 4d) accept the lone pair electrons from nitrogen atoms, thus undergoing a complexation reaction to form a stable silver ammine complex. The formation of the coordination bond reduces the free energy of the system, enabling the complex to stably exist in the electroplating solution. This reaction may occur before the reduction of silver ions to silver atoms or may occur simultaneously with the reduction process of silver ions.

[0024] Beneficial effects:

[0025] In the present invention, the surface of the graphite film is roughened by plasma activation. Meanwhile, chemical molecules containing amino benzene are physically and chemically adsorbed on the graphite film through a diazotization reaction. Subsequently, silver is deposited on the modified graphite film by electroplating to form a silver-graphite film-silver composite material. Specifically: First, the conjugated small molecules chemically adsorbed on the surface of the graphite film construct a p-π conjugate system through chemical linkage, enhancing the action of electrons participating in energy transfer at the graphite film / Ag interface, promoting the electron-phonon coupling at the interface, and thus effectively reducing the interfacial thermal resistance. This increases the thermal conductivity of the composite material; Second, the plasma roughens the surface of the graphite film. The roughened grooves and the silver layer form a mechanical bite, improving the interfacial bonding. Coupled with the p-π conjugate system structure constructed at the interface, it helps to enhance the interfacial bonding between the graphite film and the silver matrix. Description of the drawings

[0026] Figure 1 It is a schematic diagram of the preparation process of the composite material of the present invention.

[0027] Figure 2 It is a schematic diagram of the structure of the composite material of the present invention.

[0028] Figure 3 It is a SEM image of the surface of the silver-plated composite material after bending in Example 1. Detailed implementation manners

[0029] Example 1:

[0030] As Figure 1 shown, 1.2 g of a graphite film with a thickness of 70 μm and a density of 2.1 g / cm 3 is selected. The graphite film is soaked in absolute ethanol and stirred for 10 min, then washed with deionized water and dried; after drying, it is subjected to plasma treatment. An air atmosphere is used, the gas flow rate is 300 sccm, the power is 120 W, and the treatment time is 20 s. 1.2 g of p-phenylenediamine is dissolved in 300 ml of absolute ethanol, the treated graphite film is put in, poured into a three-necked flask, the air is evacuated, nitrogen is introduced for protection, after magnetic stirring for 10 min, 3.5 ml of isoamyl nitrite is slowly added, and the temperature is raised to 80 °C for reaction for 18 h. After the reaction is completed, the flaky graphite film is taken out, washed with ethanol, and vacuum dried at 60 °C for 5 h. Subsequently, the graphite film is electroplated at 0.65 A / dm 2Electroplating was carried out for 40 s at a current density of [value not provided], and the concentration ratio of silver nitrate: sodium thiosulfate: potassium metabisulfite in the electroplating solution was 1:5.56:1, obtaining a graphite film silver-based composite material with an in-plane thermal conductivity of 1906 (W / (m﹒K)). The structural schematic diagram is as Figure 2 . The composite material was subjected to a bending test. The composite material was fixed on a metal fixture with a bending radius of 10 mm, and a bending experiment with a bending degree of 90° was carried out on the composite material at a rate of 20 times per minute. After 30 bends, it did not crack. The SEM image of the surface of the silver-plated composite material at the bent part is shown in Figure 3 . As can be seen from the figure, there are no obvious voids on the microscopic surface after bending, indicating that the material has good bending performance.

[0031] Example 2:

[0032] As Figure 1 shown, 1.2 g of a graphite film with a thickness of 70 μm and a density of 2.1 g / cm 3 was selected. The graphite film was soaked in absolute ethanol and stirred for 10 min, then washed with deionized water and dried. After drying, it was subjected to plasma treatment. An air atmosphere was used, the gas flow rate was 300 sccm, the power was 120 W, and the treatment time was 20 s. 1.2 g of p-phenylenediamine was dissolved in 300 ml of absolute ethanol, the treated graphite film was put in, poured into a three-necked flask, the air was evacuated, nitrogen was introduced for protection, after magnetic stirring for 10 min, 6 ml of isoamyl nitrite was slowly added, and the temperature was raised to 80 °C and reacted for 18 h. After the reaction was completed, the flaky graphite film was taken out, washed with ethanol, and vacuum dried at 60 °C for 5 h. Subsequently, the graphite film was electroplated at a current density of 0.65 A / dm 2 for 40 s, and the concentration ratio of silver nitrate: sodium thiosulfate: potassium metabisulfite in the electroplating solution was 1:5.56:1, obtaining a graphite film silver-based composite material with an in-plane thermal conductivity of 1864 (W / (m﹒K)). The structural schematic diagram is as Figure 2 . The composite material was subjected to a bending test. The composite material was fixed on a metal fixture with a bending radius of 10 mm, and a bending experiment with a bending degree of 90° was carried out on the composite material at a rate of 20 times per minute. After 20 bends, it did not crack.

[0033] Example 3:

[0034] Select a graphite film with a thickness of 70 μm and a density of 2.1 g / cm 31.2 g of the graphite film was immersed in absolute ethanol and stirred for 10 min, then washed with deionized water and dried. After drying, plasma treatment was carried out. An air atmosphere was used, the gas flow rate was 500 sccm, the power was 50 W, and the treatment time was 1 min. 1.2 g of p-phenylenediamine was dissolved in 300 ml of absolute ethanol, the treated graphite film was put in, and then poured into a three-necked flask. The air was evacuated, nitrogen was introduced for protection. After magnetic stirring for 10 min, 3.5 ml of isoamyl nitrite was slowly added, and the temperature was raised to 80 °C and reacted for 18 h. After the reaction was completed, the flaky graphite film was taken out, washed with ethanol, and vacuum dried at 60 °C for 5 h. Subsequently, the graphite film was electroplated at a current density of 0.65 A / dm 2 for 40 s. The concentration ratio of silver nitrate: sodium thiosulfate: potassium metabisulfite in the electroplating solution was 1:5.56:1, and a graphite film silver-based composite material with an in-plane thermal conductivity of 1785 (W / (m﹒K)) was obtained. The composite material was subjected to a bending test. The composite material was fixed on a metal fixture with a bending radius of 10 mm, and a bending experiment with a bending degree of 90° was carried out on the composite material at a rate of 20 times per minute. After 40 bends, it did not crack.

[0035] Example 4:

[0036] A graphite film with a thickness of 70 μm and a density of 2.1 g / cm 3 1.2 g was selected. The graphite film was immersed in absolute ethanol and stirred for 10 min, then washed with deionized water and dried. After drying, plasma treatment was carried out. An air atmosphere was used, the gas flow rate was 300 sccm, the power was 120 W, and the treatment time was 20 s. 1.2 g of p-phenylenediamine was dissolved in 300 ml of absolute ethanol, the treated graphite film was put in, and then poured into a three-necked flask. The air was evacuated, nitrogen was introduced for protection. After magnetic stirring for 10 min, 3.5 ml of isoamyl nitrite was slowly added, and the temperature was raised to 80 °C and reacted for 18 h. After the reaction was completed, the flaky graphite film was taken out, washed with ethanol, and vacuum dried at 60 °C for 5 h. Subsequently, the graphite film was electroplated at a current density of 0.65 A / dm 2 for 2 min. The concentration ratio of silver nitrate: sodium thiosulfate: potassium metabisulfite in the electroplating solution was 1:5.56:1, and a graphite film silver-based composite material with an in-plane thermal conductivity of 1508 (W / (m﹒K)) was obtained. The composite material was subjected to a bending test. The composite material was fixed on a metal fixture with a bending radius of 10 mm, and a bending experiment with a bending degree of 90° was carried out on the composite material at a rate of 20 times per minute. After 10 bends, it did not crack.

[0037] Comparative Example 1:

[0038] A graphite film with a thickness of 70 μm and a density of 2.1 g / cm 31.2 g of the graphite film was immersed in absolute ethanol and stirred for 10 min, then washed with deionized water and dried. After drying, plasma treatment was carried out. An air atmosphere was used, the gas flow rate was 300 sccm, the power was 120 W, and the treatment time was 20 s. Subsequently, the graphite film was electroplated for 40 s at a current density of 0.65 A / dm 2 . The concentration ratio of silver nitrate: sodium thiosulfate: potassium metabisulfite in the electroplating solution was 1:5.56:1, and a silver-based composite material of the graphite film with an in-plane thermal conductivity of 1480 (W / (m·K)) was obtained. The composite material was subjected to a bending test. The composite material was fixed on a metal fixture with a bending radius of 10 mm, and a bending experiment with a bending degree of 90° was carried out on the composite material at a rate of 20 times per minute. It cracked after 1 bending.

[0039] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A graphite film-p-phenylenediamine-silver composite material, characterized in that: The structure of the composite material is that p-phenylenediamine molecules are introduced into the upper and lower surfaces of the flaky graphite film, silver is deposited on the flaky graphite film with the p-phenylenediamine molecules, and the amino groups in the p-phenylenediamine molecules form amino-silver complexes with silver to form a silver-flaky graphite film-silver composite material, also called a graphite film-p-phenylenediamine-silver composite material.

2. A method for preparing a graphite film-p-phenylenediamine-silver composite material, characterized in that: The steps include: S1. Plasma treatment of the surface of the flake graphite film; S2, dissolving p-phenylenediamine in anhydrous ethanol, placing in a flake graphite film, removing air, introducing nitrogen for protection, and magnetically stirring for 10 minutes to obtain a mixed solution; S3. Add isoamyl nitrite to the above mixture under nitrogen protection, stir evenly with a magnetic stirrer, heat to 60-100°C, and stir with a constant temperature magnetic stirrer for 10-20h; S4, taking out the flake graphite film in S3, washing it with ethanol, and vacuum drying it at 50-100°C for 2-6h; S5. The dried flaky graphite film is electroplated with silver for 30 seconds to 2 minutes to obtain a graphite film-p-phenylenediamine-silver composite material.

3. The method for preparing the graphite film-p-phenylenediamine-silver composite material according to claim 2, characterized in that: The thickness of the graphite film is 10-300 μm, and the density is 1.7-2.3 g / cm 3 .

4. The method for preparing the graphite film-p-phenylenediamine-silver composite material according to claim 2, characterized in that: The surface plasma treatment of the flaky graphite film in step S1 is specifically as follows: the flaky graphite film is immersed in anhydrous ethanol and stirred for 10 minutes, washed with deionized water and dried; after drying, plasma treatment is performed, and the plasma surface treatment process parameters are: using air atmosphere, a gas flow rate of 100-800sccm, a power of 10-300W, and a treatment time of 10s-20min.

5. The method for preparing the graphite film-p-phenylenediamine-silver composite material according to claim 2, characterized in that: In step S2, the mass ratio of p-phenylenediamine to the flaky graphite film is 0.2-5:

1.

6. The method for preparing the graphite film-p-phenylenediamine-silver composite material according to claim 2, characterized in that: In step S3, the molar ratio of isoamyl nitrite to p-phenylenediamine is 1-4:

1.

7. The method for preparing the graphite film-p-phenylenediamine-silver composite material according to claim 2, characterized in that: In step S5, the electroplating solution includes 30-60 g / L of silver nitrate, 200-300 g / L of sodium thiosulfate, and 30-60 g / L of potassium pyrosulfite, wherein the concentration ratio of silver nitrate: sodium thiosulfate: potassium pyrosulfite is 1:5.56:1, the pH value is 6-7, and the constant current mode is adopted, and the current density is 0.5-0.8 A / dm 2 , plating time 30s-2min.

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