CN119176550B

CN119176550B - A graphene thermal interface material with multi-level pore structure and preparation method thereof

Info

Publication number: CN119176550B
Application number: CN202411687538.4A
Authority: CN
Inventors: 陈琛; 杨泓; 高超; 蔡盛赢; 赵博; 王勇霖
Original assignee: Zhejiang Xiejie Thermal Management Technology Co ltd
Current assignee: Zhejiang Xiejie Thermal Management Technology Co ltd
Priority date: 2024-11-25
Filing date: 2024-11-25
Publication date: 2025-03-25
Anticipated expiration: 2044-11-25
Also published as: CN119176550A

Abstract

The present invention discloses a graphene thermal interface material with a multi-level pore structure and a preparation method thereof. The material has a unique multi-level pore distribution structure, and achieves high compression rebound rate and low interface thermal resistance. The present invention cleverly utilizes the slow reduction of aminoguanidine carbonate to graphene oxide and its own thermal foaming characteristics. After the composite film is formed by mixing with graphene oxide, slow reduction occurs during the drying process, so that cross-linking occurs between graphene oxide sheets, and primary pores are formed as water evaporates; in low-temperature heat treatment, aminoguanidine carbonate decomposes in the 50-100°C range to produce gas, and the gas is generated to form secondary pores, and graphene oxide above 100°C further loses oxygen-containing groups, which promotes the formation of tertiary pores; finally, the pore structure is further developed under high-temperature treatment to form a final multi-level pore structure. The graphene material with the multi-level pore structure has high compression rebound characteristics, has excellent gap-filling effect on the thermal interface, and has broad application prospects in high-performance interface heat dissipation.

Description

Graphene thermal interface material with hierarchical pore structure and preparation method thereof

Technical Field

The invention relates to the field of thermal interface materials, in particular to a graphene thermal interface material with a hierarchical pore structure and a preparation method thereof.

Background

Graphene, as a two-dimensional material, has great potential in the field of thermal interface materials in terms of its unique structure and excellent physicochemical properties. Firstly, the graphene has extremely high thermal conductivity and can rapidly transfer heat, so that the working temperature of electronic equipment is effectively reduced, and the performance and stability of the electronic equipment are improved. Secondly, the thickness of graphene is extremely thin, being only a monolayer or few layers of atoms, which makes it hardly increase the volume and weight of the device when applied. In addition, the graphene has high mechanical strength and good flexibility, is easy to process into various shapes, and meets the requirements of different equipment.

Despite the many advantages of graphene in the field of thermal interface materials, its practical application still faces some challenges. Firstly, the preparation cost of graphene is high, and particularly, the large-area high-quality graphene film is limited to be popularized in large-scale industrial application. Secondly, although graphene has extremely high heat conduction performance in the horizontal direction, the coefficient of heat conduction in the vertical direction is low, and the conventional high-orientation graphene film is difficult to exert the self advantage of graphene in thermal interface application. Moreover, the graphene film is in rigid butt joint with the radiating surface, so that the interface thermal resistance is increased, and the radiating performance in the vertical direction is further limited. In view of these problems, there have been studies attempting to improve the problem of poor vertical thermal conductivity by introducing a pleated structure, a porous structure or a vertically oriented structure, but generally involve complicated preparation processes, use environmentally unfriendly chemical reagents, and are difficult to popularize in a large area. Thus, there are still many difficulties in developing a green, low cost, high vertical thermal conductivity graphene thermal interface material.

Disclosure of Invention

Aiming at the problems in the background technology, the invention provides a graphene thermal interface material with a hierarchical pore structure, which shows excellent compression rebound resilience and high equivalent vertical heat conductivity.

Specifically, the invention adopts the following technical scheme:

According to the technical scheme, the graphene thermal interface material with the multi-level pore structure comprises wrinkled graphene sheets, wherein the thickness of each graphene sheet is 20-500 nm, the oxygen content is lower than 0.5%, the overall thickness of the graphene material is 0.2-2 mm, the density is 0.08-0.32 g/cm ³, the graphene thermal interface material comprises primary pores with the size of 10-50 nm, secondary pores with the size of 1-10 mu m and tertiary pores with the size of 100-300 mu m, the primary pores are arranged in the wrinkled in the graphene sheets, the secondary pores and the tertiary pores are arranged among the graphene sheets, and the volume ratio of the primary pores, the secondary pores and the tertiary pores in the graphene thermal interface material is 16% -28%, 35% -42% and 20% -28% respectively.

The multistage pore structure effectively realizes the balance of high elasticity and high equivalent thermal conductivity. Generally, the higher the degree of orientation of the graphene sheet, the better the thermal conductivity in that direction, but the compressibility thereof is significantly reduced, even rendered inelastic, due to the rigidity of the graphene sheet. Too high rigidity can lead to the existence of an air layer between material interfaces, so that the interface thermal resistance is remarkably increased. Accordingly, the introduction of the porous structure can effectively enhance compression elasticity, but vertical thermal conductivity is also greatly impaired. In the method, 10-50 nm holes are mainly formed in folds in the graphene sheets, influence on vertical heat conduction is small, but the degree of freedom of the graphene sheets can be improved, the rigidity of the graphene sheets is reduced, meanwhile, the orientation of the graphene sheets in the vertical direction is guaranteed, 1-10 mu m holes are mainly formed among the graphene sheets, a small-sized air bag is formed, the whole structure is prevented from being collapsed, material rebound is facilitated, and Kong Lingsan of 100-300 mu m are distributed in the whole film, so that space is provided for compression deformation of the graphene sheets. The reasonable density range is to avoid irreversible deformation of the graphene sheet caused by excessive pores at low density and high rigidity caused by excessive density. The thermal impedance of the material is obviously lower than that of the traditional heat conduction silica gel gasket (basically more than 0.3K cm ²/W), and the material has obvious advantages in realizing high-efficiency vertical heat dissipation performance.

The reasonable thickness of the graphene sheet is used for obtaining high flexibility and high compression resilience, so that interface gaps are filled through compression in the application of a thermal interface, an air layer is prevented from being introduced through rigid contact, and interface thermal resistance is effectively reduced. Too low a thickness of the graphene sheet can lead to insufficient compression strength, after compression, the graphene sheet is difficult to rebound, too high a thickness leads to too high rigidity of the graphene sheet, and compression cannot be completed to realize effective joint filling. The oxygen content is controlled to be lower than 0.5% so as to reduce the defects of graphene and improve the intrinsic heat conduction performance.

The second technical scheme of the invention is to provide a preparation method of the graphene thermal interface material, which specifically comprises the following steps:

(1) Dissolving aminoguanidine carbonate in deionized water to form an aminoguanidine carbonate solution having a concentration of 20 wt%;

(2) Adding 0.5-2 parts by mass of the aminoguanidine carbonate solution obtained in the step (1) into 100 parts by mass of graphene oxide solution with the concentration of 2wt%, and uniformly stirring and mixing;

(3) Forming a film by using the mixed solution obtained in the step (2), and drying for 10-24 hours at room temperature to obtain a dried film with the thickness of 0.05-0.5 mm;

(4) Placing the dried film obtained in the step (3) at 200-250 ℃ for heating foaming to obtain a primary foaming film;

(5) And (3) placing the preliminary foaming film obtained in the step (4) in an argon atmosphere, and heating to 2800-3200 ℃ at 5 ℃ per minute for 0.5-3 hours to obtain the graphene thermal interface material with the hierarchical pore structure.

The step (1) adopts aminoguanidine carbonate as a reducing agent, so that the conventional hydrazine hydrate reducing agent is avoided, and the method is more environment-friendly and safer (also referred to in patent CN 103420365B). On the other hand, the phenomenon of reducing graphene oxide by aminoguanidine carbonate is greatly different from that of hydrazine hydrate, and the reduction speed of the aminoguanidine carbonate is low, so that the gas generated by the reaction is slowly released, and a large amount of gas is not generated in a short time like that of the hydrazine hydrate, so that the volume of the graphene oxide film is severely expanded. The method comprises the steps of mixing aminoguanidine carbonate with graphene oxide, carrying out slow reduction reaction on the aminoguanidine carbonate and the graphene oxide in a film coating process, enabling the aminoguanidine carbonate and the graphene oxide to cross-link in a film coating process, enabling the graphene oxide to form primary holes in the film coating process along with moisture volatilization, decomposing the aminoguanidine carbonate between 50 ℃ and 100 ℃ to generate gas in low-temperature heat treatment, generating the gas to form secondary holes, enabling the graphene oxide to further lose oxygen-containing groups to form gas to promote the formation of tertiary holes, and finally further developing a hole structure under high-temperature treatment to form a final multi-stage hole structure.

Further, the average thickness of the graphene oxide in the step (2) is 0.8-100 nm.

Further, the film forming method in the step (3) comprises a casting method, a knife coating method and a spin coating method.

Further, the heating foaming method in the step (4) is to heat up to 200-250 ℃ in an oven at 5 ℃ per min, and keep the temperature for 1-3 hours.

Further, the heating foaming method in the step (4) can be that the temperature is raised to 50 ℃ in an oven at 2 ℃ per minute for 1-3 hours, then the temperature is raised to 200-250 ℃ at 5 ℃ per minute for 1-3 hours.

The aminoguanidine carbonate has a decomposition temperature of about 50-100 ℃ and undergoes a thermal decomposition reaction at that temperature. Heating to 200 ℃ can cause the aminoguanidine carbonate to be rapidly thermally decomposed to generate gas, and the gas is introduced into a porous structure. Heating to 50 ℃ and preserving heat is performed firstly to further enable aminoguanidine carbonate and graphene oxide to undergo a reduction reaction in a low-temperature region, and then heating is performed to undergo a decomposition reaction, so that a richer mesoporous structure can be obtained.

The invention has the beneficial effects that:

(1) The unique hierarchical pore structure is that the hierarchical pore structure which is mainly distributed at 10-50 nm, 1-10 mu m and 100-300 mu m is introduced on the basis of a conventional graphene film, so that the graphene thermal interface material has the characteristics of light weight, compression resistance and high flexibility. The three-dimensional heat conduction network is constructed by the wrinkled graphene film, so that the efficient transfer of heat in the vertical direction is ensured.

(2) The low interface thermal resistance is that the wrinkled porous graphene microstructure is beneficial to filling gaps among heating interfaces, the graphene sheet effectively fills tiny undulation on the surface of a heating surface, an air layer is obviously reduced, the interface thermal resistance is reduced, and the overall equivalent thermal conductivity is higher than that of a conventional heat conduction gasket.

(3) The cost performance is high, the high-performance graphene thermal interface material can be prepared in batches by simply improving the conventional graphene film preparation process, and the requirement on equipment is low.

(4) The environment-friendly type waste water treatment method has the advantages that the main raw materials are only water, graphene oxide and aminoguanidine carbonate, the high-toxicity and high-pollution chemical reagent is not involved, the waste water can reach the discharge requirement through simple treatment, and the environment pressure is low.

Drawings

FIG. 1 is an SEM sectional view of a graphene thermal interface material obtained in example 1;

FIG. 2 is a graph showing the size distribution of the graphene thermal interface material obtained in example 1;

FIG. 3 is a graph showing thermal impedance curves of the graphene thermal interface material obtained in example 1 at different pressures;

fig. 4 shows the thermal resistance of the graphene thermal interface material obtained in example 1 after 5 times of repeated disassembly and assembly.

Detailed Description

The following examples are provided to further illustrate embodiments of the invention.

It should be understood that the described embodiments are merely some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

The raw materials used in the invention are conventional commercial products unless otherwise specified, and the methods used in the invention are conventional methods in the art unless otherwise specified.

The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Furthermore, technical terms involved in the present invention are explained as follows:

As is known in the art, the pore size distribution is measured by mercury intrusion method, and the horizontal axis of the pore size distribution curve represents the pore size and the vertical axis represents the mercury intrusion amount (quantitative representation of volume ratio). The thermal resistance is the sum of the thermal resistance of the material itself and the thermal resistance between contact surfaces, and is measured by using an ASTM D5470 method, and the equipment is an LW-9389MD interface material thermal resistance and thermal conductivity coefficient measuring instrument.

Casting film coating is a process of forming a uniform film by pouring a liquid film coating material onto a substrate and utilizing its fluidity. Blade coating is a method of uniformly coating a liquid coating material on a substrate with a blade, and removing excess material by movement of the blade to form a thin film of a certain thickness. Spin coating is a process in which a liquid coating material is uniformly distributed on the surface of a substrate by centrifugal force by rotating the substrate to form a thin film. After the graphene oxide film is prepared by the three methods, a fold structure is spontaneously formed in the graphene oxide sheets along with the volatilization of water in the drying process, and the folded graphene oxide sheets are stacked to form the graphene oxide dry film.

Examples

(2) Adding 2 parts by mass of the aminoguanidine carbonate solution obtained in the step (1) into 100 parts by mass of graphene oxide solution with the concentration of 2wt%, and uniformly stirring and mixing, wherein the thickness of the graphene oxide is 0.8 nm;

(3) Forming a film by using the mixed solution obtained in the step (2) through a tape casting method, and drying for 12 hours at room temperature to obtain a dried film with the thickness of 0.05 mm;

(4) Placing the dried film obtained in the step (3) in an oven for heating and foaming, heating to 200 ℃ at 2 ℃ per min, and preserving heat for 1h to obtain a primary foaming film;

(5) And (3) placing the preliminary foaming film obtained in the step (4) in an argon atmosphere, and heating to 2800 ℃ at 5 ℃ per min, and carrying out high-temperature treatment on the preliminary foaming film to 1h to obtain the graphene thermal interface material with the hierarchical pore structure.

The microstructure of the obtained graphene thermal interface material is shown in fig. 1, and the material consists of a wrinkled graphene sheet, and has pore structures with different pore diameters inside. The overall thickness of the material is 0.3 mm, the density is 0.12 g/cm ³, and the material comprises a pore structure (the size distribution is shown in figure 2) with the main distribution of the sizes of 10-50 nm, 1-10 mu m and 100-300 mu m. The average thickness of the graphene sheets is 20 nm, and the oxygen content is 0.01%. The thermal resistance of the material at different pressures is shown in FIG. 3, and as the pressure increases, the thermal resistance decreases, and the thermal resistance is 0.129K cm ²/W at 50psi, which is significantly lower than that of conventional thermal conductive gaskets (generally 0.5-2K cm ²/W). And as shown in fig. 4, the material can be repeatedly disassembled and assembled, and the thermal impedance change in 5 times of disassembly and assembly is not more than 5 percent. The specific properties are shown in Table 1.

Examples

(2) Adding 0.5 part by mass of the aminoguanidine carbonate solution obtained in the step (1) into 100 parts by mass of graphene oxide solution with the concentration of 2wt%, and uniformly stirring and mixing, wherein the thickness of the graphene oxide is 0.8 nm;

(3) Forming a film by using the mixed solution obtained in the step (2) through a tape casting method, and drying for 24 hours at room temperature to obtain a dried film with the thickness of 0.05 mm;

(4) Placing the dried film obtained in the step (3) in an oven for heating and foaming, heating to 250 ℃ at 2 ℃ per min, and preserving heat for 3 hours to obtain a primary foaming film;

(5) And (3) placing the preliminary foaming film obtained in the step (4) in an argon atmosphere, and heating to 2800 ℃ at 5 ℃ per min, and performing high-temperature treatment on the preliminary foaming film for 3h to obtain the graphene thermal interface material with the hierarchical pore structure.

The obtained graphene thermal interface material consists of a wrinkled graphene sheet, the overall thickness is 0.2 mm, the density is 0.16 g/cm ³, the graphene thermal interface material comprises a pore structure with the sizes mainly distributed in 10-50 nm, 1-10 mu m and 100-300 mu m, the average thickness of the graphene sheet is 20nm, the oxygen content is 0.01%, and specific performances are shown in a table 1.

Examples

(2) Adding 0.5 part by mass of the aminoguanidine carbonate solution obtained in the step (1) into 100 parts by mass of graphene oxide solution with the concentration of 2wt%, and uniformly stirring and mixing, wherein the thickness of the graphene oxide is 10 nm;

(3) Forming a film by using the mixed solution obtained in the step (2) through a tape casting method, and drying for 10 hours at room temperature to obtain a dried film with the thickness of 0.1 mm;

(4) Placing the dried film obtained in the step (3) in an oven for heating and foaming, heating to 50 ℃ at2 ℃ per min, preserving heat for 1h, heating to 250 ℃ at 5 ℃ per min, and preserving heat for 1h to obtain a primary foaming film;

(5) And (3) placing the preliminary foaming film obtained in the step (4) in an argon atmosphere, and heating to 2800 ℃ at 5 ℃ per min, and performing high-temperature treatment on the preliminary foaming film to 0.5 h to obtain the graphene thermal interface material with the multi-stage pore structure.

The obtained graphene thermal interface material consists of wrinkled graphene sheets, the overall thickness is 0.2 mm, the density is 0.32 g/cm ³, the graphene thermal interface material comprises pore structures with the sizes mainly distributed in 10-50 nm, 1-10 mu m and 100-300 mu m, the average thickness of the graphene sheets is 80 nm, the oxygen content is 0.01%, and specific performances are shown in table 1.

Examples

(2) Adding 0.5 part by mass of the aminoguanidine carbonate solution obtained in the step (1) into 100 parts by mass of graphene oxide solution with the concentration of 2wt%, and uniformly stirring and mixing, wherein the thickness of the graphene oxide is 100 nm;

(3) Forming a film by using the mixed solution obtained in the step (2) through a knife coating method, and drying for 24 hours at room temperature to obtain a dried film with the thickness of 0.5 mm;

(4) Placing the dried film obtained in the step (3) in an oven for heating and foaming, heating to 50 ℃ at2 ℃ per min, preserving heat for 3 hours, heating to 200 ℃ at 5 ℃ per min, and preserving heat for 3 hours to obtain a primary foaming film;

The obtained graphene thermal interface material consists of a wrinkled graphene sheet, the overall thickness is 2 mm, the density is 0.16 g/cm ³, the graphene thermal interface material comprises a pore structure with the size mainly distributed in 10-50 nm, 1-10 mu m and 100-300 mu m, the average thickness of the graphene sheet is 500 nm, the oxygen content is 0.02%, and specific performances are shown in a table 1.

Examples

(3) Forming a film by using the mixed solution obtained in the step (2) through a spin coating method, and drying for 24 hours at room temperature to obtain a dried film with the thickness of 0.05 mm;

(5) And (3) placing the preliminary foaming film obtained in the step (4) in an argon atmosphere, and heating to 3200 ℃ at 5 ℃ per min, and carrying out high-temperature treatment on the preliminary foaming film to 0.5 h, so as to obtain the graphene thermal interface material with the multi-stage pore structure.

The obtained graphene thermal interface material consists of wrinkled graphene sheets, the overall thickness is 0.45 mm, the density is 0.08 g/cm ³, the graphene thermal interface material comprises pore structures with the sizes mainly distributed in 10-50 nm, 1-10 mu m and 100-300 mu m, the average thickness of the graphene sheets is 20 nm, the oxygen content is 0.01%, and specific performances are shown in table 1.

(1) Dissolving hydrazine hydrate in deionized water to form a hydrazine hydrate solution with the concentration of 20 wt%;

(2) Adding 0.5 part by mass of the hydrazine hydrate solution obtained in the step (1) into 100 parts by mass of graphene oxide solution with the concentration of 2wt%, and uniformly stirring and mixing, wherein the thickness of the graphene oxide is 10 nm;

(3) Forming a film by using the mixed solution obtained in the step (2) through a knife coating method, and drying for 10 hours at room temperature to obtain a dried film with the thickness of 0.1 mm;

(4) Placing the dried film obtained in the step (3) in an oven for heating and foaming, heating to 50 ℃ at2 ℃ per min, preserving heat for 1h, then heating to 200 ℃ at 5 ℃ per min, and preserving heat for 1h to obtain a primary foaming film;

(5) And (3) placing the preliminary foaming film obtained in the step (4) in an argon atmosphere, heating to 2800 ℃ at 5 ℃ per min, and carrying out high-temperature treatment on the preliminary foaming film to 0.5 h to obtain the graphene thermal interface material with the pore structure.

In the preparation process, the solution viscosity is obviously increased along with stirring in the mixing process of the step (2), the fluidity is poor, the operation difficulty is high in the blade coating process of the step (3), and the film cannot be continuously formed. The whole thickness of the obtained part of graphene thermal interface material is 0.13 mm, and the density is 0.5 g/cm ³. The average thickness of the graphene sheet is 1-3 μm, the oxygen content is 0.01%, and specific properties are shown in table 1.

It can be found that the pore volume of 10-50 nm is far more than 1-10 μm and 100-300 μm, because hydrazine hydrate has a much higher reducibility than aminoguanidine carbonate, the reduction reaction starts to occur in the step (2), and the graphene oxide starts to form a fold structure in the solution. After the film is coated, a pore structure is formed in the wrinkles, and meanwhile, graphene sheets are stacked due to a strong reduction reaction of graphene oxide. Therefore, no obvious gas is generated in the heating in the step (4), and the large holes of 100-300 mu m generated in the high-temperature treatment in the step (5) are also obviously smaller than those in the examples 1-5. This relatively dense structure has lower compressibility and higher thermal resistance, and is not suitable for use as a thermal interface.

Table 1 summary of performance of various embodiments

The foregoing embodiments have been presented for the purpose of illustrating the general principles of the invention and are merely exemplary of the invention, and are not intended to limit the invention to the particular form disclosed.

Claims

1. A graphene thermal interface material with a multi-level pore structure, characterized in that it is composed of wrinkled graphene sheets, the thickness of the graphene sheets is 20-500 nm, the oxygen content is less than 0.5%, the overall thickness of the graphene material is 0.2-2 mm, and the density is 0.08-0.32 g/cm ³ ; the graphene thermal interface material comprises primary pores with a size of 10-50 nm, secondary pores with a size of 1-10 μm, and tertiary pores with a size of 100-300 μm; the primary pores exist in the wrinkles in the graphene sheets, and the secondary pores and tertiary pores exist between the graphene sheets; in the graphene thermal interface material, the volume proportions of the primary pores, secondary pores and tertiary pores are 16%-28%, 35%-42%, and 20%-28%, respectively.

2. A method for preparing the graphene thermal interface material according to claim 1, characterized in that it comprises the following steps:

(1) dissolving aminoguanidine carbonate in deionized water to form an aminoguanidine carbonate solution with a concentration of 20 wt %;

(2) adding 0.5 to 2 parts by weight of the aminoguanidine carbonate solution obtained in step (1) to 100 parts by weight of a 2 wt% graphene oxide solution, and stirring to mix well;

(3) forming a film using the mixed solution obtained in step (2), and drying at room temperature for 10 to 24 hours to obtain a dry film with a thickness of 0.05 to 0.5 mm;

(4) heating the dried film obtained in step (3) at 200-250° C. for foaming to obtain a preliminary foamed film;

(5) The preliminary foamed film obtained in step (4) is placed in an argon atmosphere, heated to 2800-3200°C at 5°C/min for high temperature treatment for 0.5-3 h to obtain a graphene thermal interface material with a multi-level pore structure.

3. The preparation method according to claim 2, characterized in that the average thickness of the graphene oxide in step (2) is 0.8~100 nm.

4. The preparation method according to claim 2, characterized in that the film forming method in step (3) comprises a casting method, a blade coating method, and a spin coating method.

5. The preparation method according to claim 2, characterized in that the heating and foaming method in step (4) is to increase the temperature to 200-250°C at 5°C/min and keep the temperature for 1-3 hours.

6. The preparation method according to claim 2, characterized in that the heating and foaming method in step (4) is to heat the mixture to 50°C at 2°C/min and keep it at that temperature for 1-3 hours in an oven, then heat the mixture to 200-250°C at 5°C/min and keep it at that temperature for 1-3 hours.