Preparation method of diamond skeleton for thermal management material

Abstract

A preparation method of a diamond skeleton for a thermal management material comprises the following steps: mixing raw materials: uniformly mixing graphite powder, a pore-forming agent and a catalyst material, and pressing into a blank body; performing high-temperature and high-pressure sintering: performing vacuum treatment on the blank body obtained in the step (a), then putting the blank body into a cubic press, heating to 1500-1700 DEG C under the pressure of 5.0-7.0 GPa, and keeping the temperature for 10-60 minutes, so that the graphite is converted into diamond, and meanwhile, the pore-forming agent is volatilized to form pores; impurity removal: soaking the sintered body obtained in the step (b) with an acid solution, and removing the residual metal catalyst and pore-forming agent to obtain a diamond skeleton with uniform porosity; a high-strength diamond framework is prepared by utilizing phase change from graphite to diamond under high-temperature and high-pressure conditions and adding a pore-forming agent to form a porous structure with uniform gaps, so that the thermal expansion coefficient can be effectively controlled, the high thermal shock resistance is realized, and meanwhile, the problem that more interfaces are generated among diamond crystals in a traditional sintering mode can be avoided; the thermal conductivity and the overall strength are improved.

Description

Technical Field

[0001] This invention relates to the field of thermal management materials, and more particularly to a method for preparing a diamond framework for thermal management materials. Background Technology

[0002] Diamond, metal and ceramic composites are the core preferred materials in the field of high-end thermal management. With the ultra-high thermal conductivity of diamond and the excellent interfacial compatibility of metals and ceramics, a precise balance between thermal conductivity and mechanical stability can be achieved.

[0003] This composite material combines the low expansion properties of diamond with the impact resistance and ease of processing of metals and ceramics. It efficiently conducts the dense heat generated during the operation of electronic devices, addressing the stringent requirements for heat dissipation efficiency and structural reliability in high-end chips and aerospace components. With a thermal conductivity of 500-1000 W / (m·K) and a coefficient of thermal expansion matching key semiconductor materials, it maintains stable performance even under extreme conditions. This provides core thermal management support for the miniaturization and high-power development of high-end equipment. With the popularization of technologies such as 5G, artificial intelligence, and new energy vehicles, market demand will continue to expand.

[0004] The main method for preparing diamond thermal management materials is to mix high thermal conductivity metal or ceramic materials with coated diamond single crystals and then sinter them at high temperature. In the sintered product, the diamond single crystal particles are metal or ceramic, and there is no bonding between the diamond crystals, resulting in many diamond-metal or diamond-ceramic interfaces. The presence of these interfaces affects the improvement of thermal conductivity. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a method for preparing a diamond framework for thermal management materials.

[0006] The technical solution of this invention is: a method for preparing a diamond framework for thermal management materials, comprising the following steps: (a) Raw material mixing: Graphite powder, pore-forming agent and catalyst material are put into a mixer and mixed evenly. The mixer is a horizontal double-helix conical mixer and is pressed into a blank by a press with a hydraulic system. After the blank is pressed, it is automatically demolded by a demolding mechanism and the blank is taken out. (b) High temperature and high pressure sintering: The preforms obtained in step (a) are placed in a vacuum furnace for vacuum treatment. The preforms are evenly placed on a support and sent into the vacuum furnace in batches for vacuum treatment. Then they are placed in a six-sided press and heated to 1500-1700℃ under a pressure of 5.0-7.0 GPa. The temperature is held for 10-60 minutes to convert graphite into diamond. At the same time, the pore-forming agent volatilizes and forms uniform pores inside the sintered body. (c) Impurity removal: Soak the sintered body obtained in step (b) in an acid solution. Place a batch of sintered bodies into a special container, which is a polyacrylic acid washing tank or a polyvinyl chloride acid washing tank, for batch soaking to remove the metal catalyst and pore-forming agent remaining after high-temperature pressing. Take out the sintered body and put it into an oven for drying to obtain a diamond skeleton with uniform porosity.

[0007] Preferably, in step (a), the pore-forming agent is Zn powder, which has the characteristics of low melting point (419.5℃), easy volatility (boiling point 907℃), and easy oxidation / acid solubility, and the catalyst material is Fe-Co-Ni alloy powder.

[0008] Preferably, in step (a), the amount of pore-forming agent added accounts for 10%-15% of the total mass of the raw materials, the amount of catalyst material added accounts for 5%-8% of the total mass of the raw materials, and the remainder is graphite powder, which accounts for 77%-85% of the total mass of the raw materials.

[0009] Preferably, the graphite powder in step (a) has a particle size of 1-5 micrometers. The ultra-fine particle size of the graphite powder is used to control the microporous structure, while avoiding its mutual influence with Zn powder during the sintering process.

[0010] Preferably, the specific sintering process parameters in step (b) are: pressure 5.5 GPa, temperature 1500℃, and holding at the temperature for 20-30 minutes after sintering.

[0011] Preferably, the acid solution in step (c) is dilute hydrochloric acid, which should completely cover the sintered body during soaking, and the soaking time should be no less than 24 hours.

[0012] The beneficial technical effects of this invention are as follows: This invention utilizes the phase transformation from graphite to diamond under high temperature and high pressure conditions, and simultaneously adds Zn powder to form a porous structure with uniform voids to prepare a high-strength diamond framework. The coefficient of thermal expansion is controlled to be close to 1 PPM / K, which has high thermal shock resistance. At the same time, it can avoid the problem of generating more interfaces between diamond crystals in the traditional sintering method, improve the bonding between diamond crystals, and achieve a thermal conductivity of 500-650 W / (m·K), thereby improving the strength of the framework. Attached Figure Description

[0013] Figure 1 These are product images of the diamond skeleton of this invention; Figure 2 yes Figure 1 A magnified view of a portion of the surface; Figure 3 yes Figure 1 A schematic diagram showing the internal pore structure through surface polishing (arrows in the diagram point to the pores). Detailed Implementation

[0014] Example 1: A method for preparing a diamond framework for thermal management materials, the preparation method is as follows:

[0015] Prepare the raw materials: carbon source (graphite powder), pore-forming agent (Zn powder) and catalyst material (Fe-Co-Ni alloy powder). The particle size of the graphite powder is 1 micrometer. The amount of Zn powder added accounts for 10% of the total mass of the raw materials. The amount of Fe-Co-Ni alloy powder added accounts for 5% of the total mass of the raw materials, and the remainder is graphite powder.

[0016] Fe-Co-Ni alloy powder consists of 50 parts by weight of iron (Fe), 20 parts by weight of cobalt (Co), and 30 parts by weight of nickel (Ni).

[0017] The above raw materials are mixed evenly in a mixing device to ensure that the graphite powder, Zn powder and Fe-Co-Ni alloy powder are fully dispersed. Then, the mixture is pressed into a blank using a press. The shape and size of the blank can be designed according to actual needs, such as a circular blank with a diameter of 10 mm and a thickness of 5 mm.

[0018] The pressed preform is placed in a vacuum furnace for vacuum treatment to remove residual gas and moisture. Then the preform is transferred to a six-sided press for high-temperature and high-pressure sintering. The pressure is set at 5.0 GPa, the temperature is raised to 1500℃, and held for 30 minutes. During this process, graphite is transformed into diamond under the action of Fe-Co-Ni alloy powder, while some of the pore-forming agent Zn powder volatilizes to form a uniform pore structure.

[0019] After sintering, the sintered body is removed and immersed in an acid solution for impurity removal. The acid solution is dilute hydrochloric acid, and the immersion time is 24 hours. During this time, it can be stirred appropriately to ensure a full reaction and remove residual Fe-Co-Ni alloy powder and Zn powder volatilization residue.

[0020] The sintered body was then repeatedly rinsed with deionized water until neutral, and then dried to obtain a high-strength diamond framework with uniform porosity.

[0021] Example 2: A method for preparing a diamond framework for thermal management materials, the preparation method is as follows:

[0022] Prepare the raw materials: carbon source (graphite powder), pore-forming agent (Zn powder) and catalyst material (Fe-Co-Ni alloy powder). The particle size of the graphite powder is 5 micrometers. The amount of Zn powder added accounts for 15% of the total mass of the raw materials. The amount of Fe-Co-Ni alloy powder added accounts for 8% of the total mass of the raw materials, and the remainder is graphite powder.

[0023] Fe-Co-Ni alloy powder consists of 50 parts by weight of iron (Fe), 20 parts by weight of cobalt (Co), and 30 parts by weight of nickel (Ni).

[0024] The above raw materials are mixed evenly in a mixing device to ensure that the graphite powder, Zn powder and Fe-Co-Ni alloy powder are fully dispersed. Then, the mixture is pressed into a blank using a press. The shape and size of the blank can be designed according to actual needs, such as a circular blank with a diameter of 10 mm and a thickness of 5 mm.

[0025] The pressed preform is placed in a vacuum furnace for vacuum treatment to remove residual gas and moisture. Then the preform is transferred to a six-sided press for high-temperature and high-pressure sintering. The pressure is set at 7.0 GPa, the temperature is raised to 1700℃, and held for 20 minutes. During this process, graphite is transformed into diamond under the action of Fe-Co-Ni alloy powder, while some of the pore-forming agent Zn powder volatilizes to form a uniform pore structure.

[0026] After sintering, the sintered body is removed and immersed in an acid solution for impurity removal. The acid solution is dilute hydrochloric acid, and the immersion time is 24 hours. During this time, it can be stirred appropriately to ensure a full reaction and remove residual Fe-Co-Ni alloy powder and Zn powder volatilization residue.

[0027] The sintered body was then repeatedly rinsed with deionized water until neutral, and then dried to obtain a high-strength diamond framework with uniform porosity.

[0028] Example 3: A method for preparing a diamond framework for thermal management materials, the preparation method is as follows:

[0029] Prepare the raw materials: carbon source (graphite powder), pore-forming agent (Zn powder) and catalyst material (Fe-Co-Ni alloy powder). The particle size of the graphite powder is 3 micrometers. The amount of Zn powder added accounts for 12% of the total mass of the raw materials. The amount of Fe-Co-Ni alloy powder added accounts for 6% of the total mass of the raw materials, and the remainder is graphite powder.

[0030] Fe-Co-Ni alloy powder consists of 50 parts by weight of iron (Fe), 20 parts by weight of cobalt (Co), and 30 parts by weight of nickel (Ni).

[0031] A pore-forming agent content below 10% may not be able to form sufficient pores, while a content above 15% may lead to a decrease in the strength of the skeleton structure. A content of 12% can achieve a balance and has the best effect.

[0032] The above raw materials are mixed evenly in a mixing device to ensure that the graphite powder, Zn powder and Fe-Co-Ni alloy powder are fully dispersed. Then, the mixture is pressed into a blank using a press. The shape and size of the blank can be designed according to actual needs, such as a circular blank with a diameter of 10 mm and a thickness of 5 mm.

[0033] The pressed preform is placed in a vacuum furnace for vacuum treatment to remove residual gas and moisture. Then the preform is transferred to a six-sided press for high-temperature and high-pressure sintering. The pressure is set at 5.5 GPa, the temperature is raised to 1500℃, and held for 25 minutes. During this process, graphite is transformed into diamond under the action of Fe-Co-Ni alloy powder, while some of the pore-forming agent Zn powder volatilizes to form a uniform pore structure.

[0034] After sintering, the sintered body is removed and immersed in an acid solution for impurity removal. The acid solution is dilute hydrochloric acid, and the immersion time is 24 hours. During this time, it can be stirred appropriately to ensure a full reaction and remove residual Fe-Co-Ni alloy powder and Zn powder volatilization residue.

[0035] The sintered body is then repeatedly rinsed with deionized water until neutral, and then dried to obtain a high-strength diamond framework with uniform porosity. The coefficient of thermal expansion is controlled to be close to 1 PPM / K, which has high thermal shock resistance. At the same time, it can avoid the problem of many interfaces between diamond crystals in traditional sintering methods, improve the bonding between diamond crystals, and achieve a thermal conductivity of 500-650 W / (m·K).

[0036] This diamond framework can be used in thermal management materials, such as as a reinforcing phase in composite materials, exhibiting high thermal conductivity and good structural stability.

[0037] For details of the skeleton products obtained in Examples 1 to 3, please refer to the appendix of the instruction manual. Figure 1 , Figure 2 yes Figure 1 A magnified view of a portion of the surface; Figure 3 yes Figure 1 A schematic diagram showing the internal pore structure through surface polishing. Figure 3 The middle arrow points to the gaps between porous diamond particles, while Figure 3 The image also shows the tight bond between adjacent diamond particles, which are integrated into one.

[0038] Experimental testing showed that the thermal expansion coefficient of the diamond framework obtained by this method is controlled to be close to 1 PPM / K, which has high thermal shock resistance. At the same time, it can avoid the problem of many interfaces between diamond crystals in the traditional sintering method, improve the bonding between diamond crystals, and achieve a thermal conductivity of 500-650 W / (m·K), while also ensuring the strength of the framework.

[0039] This diamond framework can be used in thermal management materials, such as as a reinforcing phase in composite materials, exhibiting high thermal conductivity and good structural stability.

Claims

1. A method for preparing a diamond framework for thermal management materials, characterized in that, Includes the following steps: (a) Raw material mixing: Graphite powder, pore-forming agent and catalyst material are mixed evenly and pressed into a blank; (b) High temperature and high pressure sintering: The preform obtained in step (a) is subjected to vacuum treatment, and then placed in a six-sided press. Under a pressure of 5.0-7.0 GPa, the temperature is raised to 1500-1700℃ and held for 10-60 minutes to convert graphite into diamond. At the same time, the pore-forming agent evaporates to form pores. (c) Impurity removal: Soak the sintered body obtained in step (b) in an acid solution to remove residual metal catalyst and pore-forming agent, and obtain a diamond framework with uniform porosity.

2. The method for preparing a diamond framework for thermal management materials according to claim 1, characterized in that: In step (a), the pore-forming agent is Zn powder and the catalyst material is Fe-Co-Ni alloy powder.

3. The method for preparing a diamond framework for thermal management materials according to claim 2, characterized in that: In step (a), the amount of pore-forming agent added accounts for 10%-15% of the total mass of the raw materials, the amount of catalyst material added accounts for 5%-8% of the total mass of the raw materials, and the remainder is graphite powder.

4. The method for preparing a diamond framework for thermal management materials according to claim 1, characterized in that: The particle size of the graphite powder in step (a) is 1-5 micrometers.

5. The method for preparing a diamond framework for thermal management materials according to claim 1, characterized in that: The specific sintering process parameters in step (b) are: pressure 5.5 GPa, temperature 1500℃, and holding time 20-30 minutes.

6. The method for preparing a diamond framework for thermal management materials according to claim 1, characterized in that: The acid solution in step (c) is dilute hydrochloric acid, and the soaking time is no less than 24 hours.

Images