Preparation method of diamond heat-conducting composite material with self-cohesiveness

Abstract

The invention discloses a preparation method of a diamond heat-conducting composite material with self-adhesion, and aims to solve the problems that diamond is poor in dispersing performance and an existing composite heat-conducting material is low in heat conductivity. The composite material comprises modified micron diamond and a high polymer material, and is prepared by adopting a solvent co-extraction method. The modified micron diamond is subjected to non-covalent modification by regulating and controlling the surface energy of the dispersing agent to form a water-based dispersion liquid, so that the surface inertia problem of the diamond is solved. The diamond heat-conducting composite material (including heat-conducting glue and heat-conducting film) with high heat-conducting property and better self-cohesiveness can be directly prepared by taking water / ethanol as a mixed solvent and taking macromolecules as a dispersing agent and a macromolecular matrix and combining a solvent co-extraction method, and the method has the characteristics of simple operation and green and environment-friendly preparation process, and is suitable for large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of heat-conducting materials, in particular to a preparation method of diamond heat-conducting composite material with self-bonding property. BACKGROUND

[0002] With the development of electronic devices towards high integration and high power, the heat generated inside the device increases significantly. If the heat cannot be effectively dissipated, the temperature rise of the chip will seriously affect its performance and service life, and even lead to device failure. Therefore, thermal interface materials (TIM) with high thermal conductivity have important application value in electronic packaging, semiconductor heat dissipation and high-power electronic equipment.

[0003] At present, the traditional thermal interface materials mainly include thermal silicone grease, thermal adhesive, thermal gasket and metal matrix composite materials, etc. However, the existing materials still have many shortcomings in terms of thermal conductivity, interface thermal resistance, mechanical strength and reliability, etc. For example, although the common polymer-based thermal conductive material has good flexibility and processability, due to the low thermal conductivity of the base resin itself, even if it is filled with high thermal conductive filler, the overall thermal conductivity is still difficult to meet the heat dissipation demand of high-power electronic devices. While the metal-based thermal conductive material has excellent thermal conductivity, but it has high density and complex processing, and may cause interface oxidation at high temperature.

[0004] Diamond is considered to be an ideal filler for improving the performance of composite thermal conductive materials due to its ultra-high thermal conductivity (up to 2000 W / m·K or more), excellent insulation performance and chemical stability. However, diamond materials have poor dispersion performance, and the interfacial bonding force between diamond and the base material is weak. Therefore, how to improve the dispersion of diamond and enhance the interfacial bonding capacity with the base material, so as to prepare diamond composite thermal conductive material with high thermal conductivity, is an important topic in the field of thermal interface material research.

[0005] In order to solve the problem of inert surface of diamond thermal conductive filler, for example, a kind of transparent nanocellulose-nano diamond thermal conductive composite film patent with publication number CN106380612A disperses nano diamond in deionized water, mixes with nanocellulose after ultrasonic treatment, and prepares transparent nanocellulose-nano diamond thermal conductive composite film through vacuum filtration and drying. The thermal conductive composite film prepared by this method has the advantages of compactness, simple process and convenient operation.

[0006] However, the thermal conductive composite film prepared in the above patent has obvious thermal anisotropy, the thermal conductivity coefficient in the plane direction can reach 11.46 W / m·K, and the thermal conductivity coefficient in the vertical direction is only 0.1-0.4 W / m·K.

[0007] Patent publication number CN115725273 A discloses a diamond-based thermally conductive filler, its preparation method, a composite thermally conductive material, and an electronic device. This patent involves mixing large-diameter diamond particles and small-diameter thermally conductive particles with a matrix material. The small-diameter particles include a first small-diameter particle and multiple second small-diameter particles. The first small-diameter particles are bonded to the surface of the large-diameter particles, and the second small-diameter particles are randomly distributed within an organic matrix to prepare the composite thermally conductive material. The thermally conductive composite material prepared using this diamond composite filler can significantly improve its thermal conductivity.

[0008] However, during the mixing and dispersion of the organic matrix and thermally conductive filler, the interfacial bonding force between diamond and the matrix material is weak, and local enrichment and agglomeration easily occur among small-diameter particles, leading to phase separation between large-diameter and small-diameter particles. At the same time, local voids / pores are likely to exist between large-diameter particles and the organic matrix, which greatly reduces the thermal conductivity.

[0009] Therefore, it is necessary to improve this method to overcome the aforementioned shortcomings. Summary of the Invention

[0010] The purpose of this invention is to provide a method for preparing a self-adhesive diamond thermally conductive composite material, in order to solve the problems of poor diamond dispersion performance, weak interfacial bonding between diamond and matrix material, thermal conductivity and processing fluidity of composite materials with high filler content, and multi-form and multi-functionality of materials.

[0011] To achieve the above objectives, the present invention provides the following technical solution:

[0012] A method for preparing self-adhesive diamond thermally conductive composite materials.

[0013] The diamond thermally conductive composite material comprises the following components: a modified dispersant, a modified diamond dispersion, and a polymer material;

[0014] Modified diamond dispersion was prepared by non-covalently modifying micron-sized diamond powder with a modified dispersant. The modified diamond dispersion was then used to prepare a modified micron-sized diamond powder thermal conductive adhesive by solvent co-extraction. The modified micron-sized diamond powder thermal conductive adhesive was then combined with polymer materials to prepare a flexible diamond thermal conductive composite film material.

[0015] The modified diamond dispersion is an aqueous dispersion of micron-sized diamond oxide powder with a non-covalently modified dispersant.

[0016] The modified dispersant is one or more of polyvinylpyrrolidone (PVP) whose surface energy is controlled by a water / ethanol mixed solvent.

[0017] Furthermore, the preparation of the modified diamond dispersion includes the following steps:

[0018] A mixed solvent is prepared by mixing water and ethanol, wherein the surface energy of the mixed solvent is 22-72 mJ / m².

[0019] A modified dispersant is prepared by dissolving 1-5 wt% PVP in a mixed solvent; the PVP is one or a mixture of several polyvinylpyrrolidones.

[0020] Micron-sized diamond powder was added to a modified dispersant solution and ultrasonically dispersed for 2 h to prepare a modified diamond dispersion with a concentration of 10-50 mg / mL.

[0021] Furthermore, the modified micron-sized diamond thermal conductive adhesive is prepared by solvent co-extraction of the modified diamond dispersion at a co-evaporation temperature of 70-100℃.

[0022] Furthermore, the preparation of the flexible diamond thermally conductive composite film material includes the following steps:

[0023] Adding 5%-25% polymer materials to the modified micron-sized diamond powder thermal conductive adhesive forms a mixed slurry;

[0024] The mixed slurry is coated onto a substrate at 90°C to form a film. After drying for 3 minutes, a flexible diamond thermal conductive composite film material with controllable thickness can be formed.

[0025] The polymer material is waterborne polyurethane.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] The preparation of modified micron-sized diamond uses PVP as a modified dispersant controlled by a water / ethanol mixed solvent. It is green and environmentally friendly, the raw materials are readily available, the preparation cost is low, and it is suitable for large-scale industrial production.

[0028] This invention utilizes modified PVP non-covalently modified micron-sized diamond. As a linear polymer material, modified PVP can prevent the aggregation of diamonds by utilizing electrostatic repulsion, and can also be directly used as an interface link, effectively solving the problem of poor interfacial compatibility between diamond and polymer matrix.

[0029] This invention utilizes a solvent co-extraction method to prepare a diamond thermally conductive composite material, which solves the problem of poor flowability in thermally conductive materials with high diamond filler content. Furthermore, the diamond thermally conductive composite material prepared by this method exhibits self-adhesion, completely replacing the shortcomings of common thermally conductive adhesives, such as poor gelation and difficulty in post-processing.

[0030] This invention presents a thermally conductive composite material prepared using modified micron-sized diamond and a dispersant. This composite material combines the functions of both a thermally conductive adhesive and a thermally conductive film, overcoming the limitations of traditional materials with their single form. Furthermore, this thermally conductive film exhibits excellent flexibility and self-healing properties. Attached Figure Description

[0031] Figure 1 This is a scanning electron microscope (SEM) image of the modified diamond in Example 4.

[0032] Figure 2 The image shows the X-ray photoelectron spectroscopy (XPS) spectra of diamond and modified diamond in Example 4.

[0033] Figure 3 This is a SEM image of the self-adhesive diamond thermally conductive composite film material in Example 4.

[0034] Figure 4 This is a SEM cross-sectional view of the self-adhesive diamond thermally conductive composite film material in Example 4. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0036] The method for preparing self-adhesive diamond thermally conductive composite materials specifically includes the following steps:

[0037] Modified diamond dispersions were prepared by non-covalently modifying micron-sized diamonds with modified dispersants.

[0038] Modified micron-sized diamond thermally conductive adhesive was prepared by solvent co-extraction of modified diamond dispersion; flexible diamond thermally conductive composite film material was prepared by combining modified micron-sized diamond thermally conductive adhesive with polymer materials.

[0039] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description. It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are conventional methods, and the reagents and materials described are commercially available unless otherwise specified. It should also be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

[0040] Example 1: A method for preparing a self-adhesive diamond thermally conductive composite material based on an aqueous dispersion, the process of which is as follows:

[0041] Preparation of modified dispersant: A certain amount of water and ethanol were weighed in a volume ratio of 100:0 to obtain a mixed solvent with a surface energy of approximately 72 mJ / m². 1% PVP was weighed and dissolved in the mixed solvent, and the mixture was stirred at 500 rpm for 10 h to prepare the modified dispersant.

[0042] Specifically, the PVP content is 1% of the mass of the micron-sized diamond powder.

[0043] Preparation of modified diamond dispersion: 1 g of micron-sized diamond (powder) was added to 100 mL of modified dispersant, and mechanically stirred at 500 rpm for 30 min to mix evenly. The mixture was then ultrasonically dispersed for 2 h to prepare a modified micron-sized diamond dispersion with a concentration of 10 mg / mL.

[0044] Preparation of diamond thermally conductive composite material: Modified micron-sized diamond thermally conductive composite adhesive can be prepared by solvent co-extraction of a 10 mg / mL modified micron-sized diamond dispersion. 5% aqueous polyurethane material is added to the modified micron-sized diamond thermally conductive adhesive to form a mixed slurry. This slurry is then coated onto a substrate at 90℃ and dried for 3 minutes to form a flexible diamond thermally conductive composite film material.

[0045] Specifically, the solvent co-extraction method is performed at a temperature of 100°C.

[0046] Specifically, the coating speed is 10 mm / s.

[0047] Specifically, the substrate for the coating is a polystyrene sheet.

[0048] Example 2: A method for preparing a self-adhesive diamond thermally conductive composite material based on an aqueous dispersion, the process of which is as follows:

[0049] Preparation of modified dispersant: A certain amount of water and ethanol were weighed in a volume ratio of 99:1 to obtain a mixed solvent with a surface energy of approximately 60 mJ / m². 3% PVP was weighed and dissolved in the mixed solvent, and the mixture was stirred at 500 rpm for 10 hours to prepare the modified dispersant.

[0050] Specifically, the PVP content is 3% of the mass of the micron-sized diamond powder.

[0051] Preparation of modified diamond dispersion: 5g of micron-sized diamond powder was added to 100mL of modified dispersant, and mechanically stirred at 500rpm for 30min to mix evenly. The mixture was then ultrasonically dispersed for 2h to obtain a modified micron-sized diamond dispersion with a concentration of 50mg / mL.

[0052] Preparation of diamond thermally conductive composite material: A modified micron-sized diamond thermally conductive composite adhesive can be prepared by solvent co-extraction of a 50 mg / mL modified micron-sized diamond dispersion. 10% aqueous polyurethane material is added to the modified micron-sized diamond thermally conductive adhesive to form a mixed slurry. This slurry is then coated onto a substrate at 90°C and dried for 3 minutes to form a flexible diamond thermally conductive composite film material.

[0053] Specifically, the solvent co-extraction method is performed at a temperature of 100°C.

[0054] Specifically, the coating speed is 10 mm / s.

[0055] Specifically, the substrate for the coating is a polystyrene sheet.

[0056] Example 3: A method for preparing a self-adhesive diamond thermally conductive composite material based on an aqueous dispersion, the process of which is as follows:

[0057] Preparation of modified dispersant: A certain amount of water and ethanol were weighed in a volume ratio of 98:2 to obtain a mixed solvent with a surface energy of approximately 50 mJ / m². 4% PVP was weighed and dissolved in the mixed solvent, and the mixture was stirred at 500 rpm for 10 hours to prepare the modified dispersant.

[0058] Specifically, the PVP content is 4% of the mass of the micron-sized diamond powder.

[0059] Preparation of modified diamond dispersion: 5g of micron-sized diamond powder was added to 100mL of modified dispersant, and mechanically stirred at 500rpm for 30min to mix evenly. The mixture was then ultrasonically dispersed for 2h to obtain a modified micron-sized diamond dispersion with a concentration of 50mg / mL.

[0060] Preparation of diamond thermally conductive composite material: A modified micron-sized diamond thermally conductive composite adhesive can be prepared by solvent co-extraction of a 50 mg / mL modified micron-sized diamond dispersion. 5% aqueous polyurethane material is added to the modified micron-sized diamond thermally conductive adhesive to form a mixed slurry. This slurry is then coated onto a substrate at 90°C and dried for 3 minutes to form a flexible diamond thermally conductive composite film material.

[0061] Specifically, the solvent co-extraction method is performed at a temperature of 100°C.

[0062] Specifically, the coating speed is 10 mm / s.

[0063] Specifically, the substrate for the coating is a polystyrene sheet.

[0064] Example 4: A method for preparing a self-adhesive diamond thermally conductive composite material based on an aqueous dispersion, the process of which is as follows:

[0065] Preparation of modified dispersant: A certain amount of water and ethanol were weighed in a volume ratio of 90:10 to obtain a mixed solvent with a surface energy of approximately 41 mJ / m². 2% PVP was weighed and dissolved in the mixed solvent, and the mixture was stirred at 500 rpm for 10 h to prepare the modified dispersant.

[0066] Specifically, the PVP content is 2% of the mass of the micron-sized diamond powder.

[0067] Preparation of modified diamond dispersion: 4g of micron-sized diamond powder was added to 100mL of modified dispersant, and mechanically stirred at 500rpm for 30min to mix evenly. The mixture was then ultrasonically dispersed for 2h to obtain a modified micron-sized diamond dispersion with a concentration of 40mg / mL.

[0068] Preparation of diamond thermally conductive composite material: A modified micron-sized diamond thermally conductive composite adhesive can be prepared by solvent co-extraction of a 40 mg / mL modified micron-sized diamond dispersion. 15% aqueous polyurethane material is added to the modified micron-sized diamond thermally conductive adhesive to form a mixed slurry. This slurry is then coated onto a substrate at 90°C and dried for 3 minutes to form a flexible diamond thermally conductive composite film material.

[0069] Specifically, the solvent co-extraction method is performed at a temperature of 100°C.

[0070] Specifically, the coating speed is 10 mm / s.

[0071] Specifically, the substrate for the coating is a polystyrene sheet.

[0072] Example 5: A method for preparing a self-adhesive diamond thermally conductive composite material based on an aqueous dispersion, the process of which is as follows:

[0073] Preparation of modified dispersant: A certain amount of water and ethanol were weighed in a volume ratio of 60:40 to obtain a mixed solvent with a surface energy of approximately 29 mJ / m². 5% PVP was weighed and dissolved in the mixed solvent, and the mixture was stirred at 500 rpm for 10 h to prepare the modified dispersant.

[0074] Specifically, the PVP content is 5% of the mass of the micron-sized diamond powder.

[0075] Preparation of modified diamond dispersion: 3g of micron-sized diamond powder was added to 100mL of modified dispersant, and mechanically stirred at 500rpm for 30min to mix evenly. The mixture was then ultrasonically dispersed for 2h to obtain a modified micron-sized diamond dispersion with a concentration of 30mg / mL.

[0076] Preparation of diamond thermally conductive composite material: Modified micron-sized diamond thermally conductive composite adhesive can be prepared by solvent co-extraction of a 30 mg / mL modified micron-sized diamond dispersion. 25% aqueous polyurethane material is added to the modified micron-sized diamond thermally conductive adhesive to form a mixed slurry. This slurry is then coated onto a substrate at 90°C and dried for 3 minutes to form a flexible diamond thermally conductive composite film material.

[0077] Specifically, the solvent co-extraction method is performed at a temperature of 100°C.

[0078] Specifically, the coating speed is 10 mm / s.

[0079] Specifically, the substrate for the coating is a polystyrene sheet.

[0080] Example 6: A method for preparing a self-adhesive diamond thermally conductive composite material based on an aqueous dispersion, the process of which is as follows:

[0081] Preparation of modified dispersant: A certain amount of water and ethanol were weighed in a volume ratio of 0:100 to obtain a mixed solvent with a surface energy of approximately 22 mJ / m². 2% PVP was weighed and dissolved in the mixed solvent, and the mixture was stirred at 500 rpm for 10 hours to prepare the modified dispersant.

[0082] Specifically, the PVP content is 2% of the mass of the micron-sized diamond powder.

[0083] Preparation of modified diamond dispersion: 2g of micron-sized diamond powder was added to 100mL of modified dispersant, and mechanically stirred at 500rpm for 30min to mix evenly. The mixture was then ultrasonically dispersed for 2h to obtain a modified micron-sized diamond dispersion with a concentration of 20mg / mL.

[0084] Preparation of diamond thermally conductive composite material: A modified micron-sized diamond thermally conductive composite adhesive can be prepared by solvent co-extraction of a 20 mg / mL modified micron-sized diamond dispersion. 5% aqueous polyurethane material is added to the modified micron-sized diamond thermally conductive adhesive to form a mixed slurry. This slurry is then coated onto a substrate at 90°C and dried for 3 minutes to form a flexible diamond thermally conductive composite film material.

[0085] Specifically, the solvent co-extraction method is performed at a temperature of 100°C.

[0086] Specifically, the coating speed is 10 mm / s.

[0087] Specifically, the substrate for the coating is a polystyrene sheet.

[0088] Example 7: A method for preparing a self-adhesive diamond thermally conductive composite material based on an aqueous dispersion, the process of which is as follows:

[0089] Preparation of modified dispersant: A certain amount of water and ethanol were weighed in a volume ratio of 60:40 to obtain a mixed solvent with a surface energy of approximately 29 mJ / m². 5% PVP was weighed and dissolved in the mixed solvent, and the mixture was stirred at 500 rpm for 10 h to prepare the modified dispersant.

[0090] Specifically, the PVP content is 5% of the mass of the micron-sized diamond powder.

[0091] Preparation of modified diamond dispersion: 3g of micron-sized diamond powder was added to 100mL of modified dispersant, and mechanically stirred at 500rpm for 30min to mix evenly. The mixture was then ultrasonically dispersed for 2h to obtain a modified micron-sized diamond dispersion with a concentration of 30mg / mL.

[0092] Preparation of diamond thermally conductive composite material: Modified micron-sized diamond thermally conductive composite adhesive can be prepared by solvent co-extraction of a 30 mg / mL modified micron-sized diamond dispersion. The modified micron-sized diamond thermally conductive adhesive is directly coated onto a substrate at 90℃ to form a film, and after drying for 3 minutes, a flexible diamond thermally conductive composite film material is formed.

[0093] Specifically, the solvent co-extraction method is performed at a temperature of 100°C.

[0094] Specifically, the coating speed is 10 mm / s.

[0095] Specifically, the substrate for the coating is a polystyrene sheet.

[0096] Comparative Example 1: Purchase commercial thermally conductive composite materials, PAKCOOL® single-component thermally conductive silicone and PAKCOOL® two-component thermally conductive silicone.

[0097] Comparative Example 2: Purchase commercial thermally conductive composite material, Hon Hai Precision Industry Co., Ltd. HTG-S1400 Series thermally conductive gel.

[0098] Comparative Example 3: Purchase commercial thermally conductive composite materials, specifically the HS series thermally conductive silicone pads from Shenzhen Hanhua Thermal Management Technology Co., Ltd.

[0099] Comparative Example 4: Purchase commercial thermally conductive composite materials, specifically the DC1010-DC1080 series thermally conductive silicone sheets from Hangzhou Dacheng Kehua New Materials Co., Ltd.

[0100] The thermal conductivity of the above materials is shown in the table below.

[0101] Table 1 Thermal conductivity properties of diamond thermally conductive composite materials

[0102] As can be seen from the table above, the modified micron diamond thermally conductive composite adhesive or flexible diamond thermally conductive composite film material prepared in the various embodiments of the present invention have a thermal conductivity of more than 17 W / m·k, and some of them have a thermal conductivity of more than 30 W / m·k.

[0103] The thermal conductivity of the flexible diamond thermally conductive composite film materials is all above 11 W / m·K, and some of them can reach above 24 W / m·K.

[0104] The modified micron-sized diamond thermally conductive composite adhesive or flexible diamond thermally conductive composite film materials prepared in various embodiments of the present invention have thermal conductivity far exceeding that of existing products.

[0105] This invention employs non-covalent modification and solvent surface energy regulation to achieve stable dispersion of micron-sized diamonds in a mixed solvent with a specific surface energy using a modified PVP dispersant, while electrostatic repulsion prevents re-agglomeration. Furthermore, linear polymer PVP, acting as an "interfacial connector," is non-covalently modified to coat the diamond surface, improving its compatibility with polymer matrices (such as aqueous polyurethane) and constructing efficient phonon transport channels.

[0106] The thermally conductive adhesive precursor was prepared by solvent co-extraction, which can maintain good fluidity before the material is cured, thus achieving good processing performance even with high filler content.

[0107] By using a specific material system (modified diamond / water-based polymer) and preparation process (scaling film), the final composite material can be used as a thermally conductive adhesive (self-adhesive) and can also be made into a flexible thermally conductive film. Through design, self-healing properties are achieved, breaking through the limitations of traditional materials.

[0108] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. These terms are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connect" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

Claims

1. A method for preparing a diamond thermally conductive composite material with self-bonding property, characterized in that: the diamond thermally conductive composite material comprises the following components: a modified dispersant, a modified diamond dispersion liquid, and a polymer material; the modified diamond dispersion liquid is prepared by non-covalently modifying micron diamond powder with the modified dispersant, and the modified micron diamond powder thermally conductive glue is prepared by solvent co-extraction method; the flexible diamond thermally conductive composite film material is prepared by compounding the modified micron diamond powder thermally conductive glue and the polymer material.

2. The modified diamond dispersion liquid is an aqueous dispersion liquid of oxidized micron diamond powder non-covalently modified with the modified dispersant.

3. The preparation of the modified diamond dispersion liquid comprises the following steps:

4. mixing water and ethanol to prepare a mixed solvent, wherein the surface energy of the mixed solvent is 22-72 mJ / m²; 2. The method of claim 1, wherein the diamond thermally conductive composite material having self-bonding property is prepared by the steps of: mixing diamond powder, a binder, and a solvent to prepare a mixture; and drying the mixture to remove the solvent.

5. dissolving 1-5 wt% of PVP in the mixed solvent to prepare a modified dispersant; 6. adding micron diamond powder into the modified dispersant solution and ultrasonically dispersing for 2 h to configure a modified diamond dispersion liquid with a concentration of 10-50 mg / mL; 7. the PVP is one or a mixture of several kinds of polyvinylpyrrolidone.

8. The preparation of the modified micron diamond thermally conductive glue: the modified diamond dispersion liquid is prepared by solvent co-extraction method, and the co-evaporation temperature is 70-100℃.

9. The preparation of the flexible diamond thermally conductive composite film material comprises the following steps:

3. The method of claim 1, wherein the diamond thermally conductive composite material having self-bonding property is prepared by mixing and kneading the diamond powder, the thermally conductive filler, the binder, and the solvent.

10. adding 5%-25% of the polymer material into the modified micron diamond powder thermally conductive glue to form a mixed slurry; 4. The method of claim 1, wherein the diamond thermally conductive composite material having self-bonding property is prepared by mixing and kneading the diamond powder, the thermally conductive filler, the binder, and the solvent.

11. coating the mixed slurry on a substrate at 90℃ to form a film, and the flexible diamond thermally conductive composite film material with controllable thickness can be formed after drying for 3 min; 12. the polymer material is aqueous polyurethane. ​ ​

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