Diamond with Al3BC coating, diamond / aluminum composite material and preparation method of diamond / aluminum composite material

Abstract

The invention relates to a diamond with an Al3BC coating, a diamond / aluminum composite material and a preparation method of the diamond / aluminum composite material, and relates to the technical field of composite materials. According to the main technical scheme, the preparation method of the diamond with the Al3BC coating comprises the steps that diamond particles are subjected to surface graphitization treatment, so that nanoscale graphite layers are formed on the surfaces of the diamond particles, and the diamond particles with the nanoscale graphite layers on the surfaces are obtained; the diamond particles with the nanoscale graphite layers on the surfaces, a boron source and aluminum powder are mixed, and a mixture is obtained; under a protective atmosphere, heating the mixture to an in-situ reaction temperature, and carrying out an in-situ reaction to obtain an in-situ reaction product; and carrying out post-treatment on the in-situ reaction product to obtain the diamond with the Al3BC coating. And the diamond with the Al3BC coating and the aluminum material are subjected to composite treatment, and the diamond / aluminum composite material is obtained. The method is used for solving the bottleneck problems that an existing diamond surface coating is low in heat conductivity and prone to interface reaction with aluminum.

Description

Technical Field

[0001] This invention relates to the field of composite material preparation technology, and in particular to a diamond / aluminum composite material with an Al3BC coating and its preparation method. Background Technology

[0002] With the rapid development of electronic technology, the demand for high-power, highly integrated electronic devices in fields such as defense technology, information and communication, and artificial intelligence is becoming increasingly urgent. Traditional thermal management materials are insufficient to meet the development requirements of current high-power, highly integrated devices, thus necessitating the development of a new generation of thermal management materials with superior comprehensive performance. Compared to graphene and carbon nanotubes, diamond possesses isotropic thermal conductivity, with a maximum thermal conductivity reaching 2000 W / m². -1 K -1 Its coefficient of thermal expansion is only 2×10 -6 K -1 It is an ideal material with high thermal conductivity.

[0003] Diamond / aluminum composites, prepared by combining diamond and aluminum, possess advantages such as high thermal conductivity, low coefficient of thermal expansion, and low density, showing broad application prospects in aerospace, electronic packaging, and other fields. However, the wetting angle at the diamond-aluminum interface is 150°, making it difficult for the interface to bond well during composite formation, severely limiting the utilization of diamond's high thermal conductivity. Furthermore, the low chemical compatibility between diamond and aluminum makes them prone to interfacial reactions at high temperatures, leading to the formation of the Al4C3 phase. The Al4C3 phase is susceptible to hydrolysis, which can compromise the safety of the composite material under humid conditions. Therefore, optimizing the diamond-aluminum interface is a primary issue in preparing high-performance composite materials to ensure high thermal conductivity and stability.

[0004] Diamond surface coating offers the advantage of precisely controlling and designing the interfacial structure of composite materials without negatively impacting the thermal conductivity of the matrix, making it a crucial method for interface control and improvement of interfacial issues. Studies have shown that coating the surface of diamond particles can inhibit the formation of Al4C3 during composite material preparation, thereby enhancing the thermal conductivity and moisture resistance of the composite material.

[0005] Currently, commonly used coatings are metals such as W, Ti, Cr, and Mo, and their carbides, which help improve the interfacial bonding of composite materials. However, these coatings have low intrinsic thermal conductivity, and under high-temperature preparation environments, aluminum reacts with the coating at the interface, leading to interface damage and hindering the composite material from achieving the desired thermal conductivity. Furthermore, after the coating elements diffuse into the aluminum matrix, the aluminum matrix re-contacts with diamond, potentially forming easily hydrolyzable Al4C3 at the interface. Reports indicate that during composite sintering, the Ti coating reacts with diamond to form the TiC phase, which subsequently reacts with the aluminum matrix and dissolves into it, preventing the formation of the ideal interfacial structure. Summary of the Invention

[0006] In view of this, the present invention provides a diamond with an Al3BC coating, a diamond / aluminum composite material and a method for preparing the same, the main purpose of which is to prepare a diamond with an Al3BC coating, so as to solve the bottleneck problem of low thermal conductivity and easy interfacial reaction with aluminum in existing diamond surface coatings.

[0007] To achieve the above objectives, the present invention mainly provides the following technical solutions: On one hand, embodiments of the present invention provide a method for preparing diamond with an Al3BC coating, which includes the following steps: Surface graphitization treatment step: The diamond particles are subjected to surface graphitization treatment to form a nanoscale graphite layer on the surface of the diamond particles, thereby obtaining diamond particles with a nanoscale graphite layer on the surface; wherein, the thickness of the nanoscale graphite layer is in the nanometer range. In-situ reaction step: Diamond particles with a nanoscale graphite layer on the surface, boron source and aluminum powder are mixed to obtain a mixture; under a protective atmosphere, the mixture is heated to the in-situ reaction temperature to carry out an in-situ reaction, so that aluminum, boron source and graphite layer react in-situ to generate an Al3BC coating attached to the diamond surface, and an in-situ reaction product is obtained. Post-processing step: The in-situ reaction product is post-processed to obtain diamond with an Al3BC coating.

[0008] Preferably, prior to the surface graphitization treatment step, the method further includes: Cleaning and drying steps: The diamond particles are ultrasonically cleaned, then filtered and subsequently air-dried and oven-dried. Preferably, acetone is used as the cleaning solvent for the ultrasonic cleaning process.

[0009] Preferably, the diamond particles are primary diamond particles or crushed diamond particles; and / or the particle size of the diamond particles is 50-950 μm.

[0010] Preferably, in the surface graphitization treatment step: The surface graphitization treatment temperature is 1050℃-1450℃, preferably 1200℃; the vacuum degree of the surface graphitization treatment is ≤1×10⁻⁶. -2 Pa; the surface graphitization treatment time is 1-4 hours, preferably 2 hours; and / or The diamond particles were placed in a graphite crucible and then subjected to surface graphitization treatment in a vacuum high-temperature furnace.

[0011] Preferably, in the in-situ reaction step: the boron source includes boric acid and boron powder; The ratio of diamond, boron powder, boric acid, and aluminum powder by molar mass is (3-6):(4-5):(1-1.5):(2-4). Preferably, the boron powder is amorphous boron powder or crystalline boron powder; Preferably, the boric acid powder has a particle size of 10-200 micrometers; Preferably, the aluminum powder has a particle size of 10-200 micrometers; Preferably, the boric acid powder particles are nearly spherical; Preferably, the aluminum powder particles are nearly spherical.

[0012] Preferably, in the in-situ reaction step: The in-situ reaction temperature is 1100-1300℃; the in-situ reaction time is 2-6 hours; and / or The mixture is placed in a magnesium oxide crucible for in-situ reaction; and / or The protective atmosphere is made of an inert gas, preferably argon.

[0013] Preferably, the post-processing step includes: The in-situ reaction product is crushed and sieved to obtain sieved particulate product. The sieved particulate product was purified in a dilute alkaline solution to remove unreacted aluminum; after washing, the particulate product was purified in a dilute acid solution to remove byproducts; finally, after washing, filtering and drying, granular diamond with an Al3BC coating was obtained.

[0014] On the other hand, embodiments of the present invention provide a diamond with an Al3BC coating, wherein the diamond with the Al3BC coating is prepared by any of the above-described methods for preparing diamonds with an Al3BC coating. Preferably, the diamond with the Al3BC coating is granular with a particle size ranging from 50 to 950 μm.

[0015] Preferably, the thickness of the Al3BC coating in the diamond with the Al3BC coating ranges from 100 to 300 nm.

[0016] In another aspect, embodiments of the present invention provide a method for preparing a diamond / aluminum composite material, wherein diamond with an Al3BC coating and aluminum material are compositely treated to obtain a diamond / aluminum composite material; wherein the diamond with an Al3BC coating is prepared by any of the above-described methods for preparing diamond with an Al3BC coating. Preferably, the aluminum material is aluminum or an aluminum alloy; Preferably, diamond and aluminum materials with Al3BC coating are composite treated using any one of the following methods: powder metallurgy, gas pressure infiltration, or mechanical pressure melting infiltration.

[0017] In another aspect, embodiments of the present invention provide a diamond / aluminum composite material, wherein the diamond / aluminum composite material includes an aluminum matrix and diamond particles dispersed in the aluminum matrix; wherein the diamond particles and the aluminum matrix form a multilayer interface structure with aluminum-Al3BC-diamond. Preferably, the diamond / aluminum composite material has a thermal conductivity of 500 W / m at room temperature. -1 K -1 Up to 720Wm -1 K -1 ; Preferably, the diamond / aluminum composite material is prepared by the diamond / aluminum composite material preparation method described above.

[0018] Compared with the prior art, the diamond and diamond / aluminum composite materials with Al3BC coatings of the present invention and their preparation methods have at least the following beneficial effects: On one hand, embodiments of the present invention provide a method for preparing diamond with an Al3BC coating, mainly including the following steps: surface graphitization treatment of diamond particles to form a nanoscale graphite layer on the surface of the diamond particles, obtaining diamond particles with a nanoscale graphite layer on the surface; mixing the diamond particles with the nanoscale graphite layer, a boron source, and aluminum powder to obtain a mixture; heating the mixture to an in-situ reaction temperature under a protective atmosphere to carry out an in-situ reaction, so that the aluminum, boron source, and graphite layer react to generate an Al3BC coating attached to the diamond surface, obtaining an in-situ reaction product; and post-processing the in-situ reaction product to obtain diamond with an Al3BC coating. Regarding the above steps, it should be noted that the present invention directly generates an Al3BC coating on the surface of diamond through an in-situ reaction using the above steps, and the coating thickness can be optimized by adjusting the reaction time. This is because the Al3BC phase has high stability and high intrinsic thermal conductivity, and does not undergo interfacial reaction with the aluminum matrix under high temperature conditions. The Al3BC phase is prepared through an in-situ carbothermal reaction, a process that enables it to form an excellent interface with strong adhesion, high continuity, and few surface defects between itself and diamond particles. Therefore, the diamond with an Al3BC coating prepared in this embodiment of the invention can solve the bottleneck problems of low thermal conductivity and easy interfacial reaction with aluminum in existing diamond surface coatings.

[0019] On the other hand, embodiments of the present invention provide a method for preparing a diamond / aluminum composite material, which involves composite treatment of diamond with an Al3BC coating and aluminum material as described above to obtain a diamond / aluminum composite material. Here, because the present invention uses the aforementioned Al3BC-coated diamond in the preparation of the diamond / aluminum composite material, the diamond / aluminum composite material exhibits good interfacial bonding, high thermal conductivity, and good stability in humid environments.

[0020] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0021] Figure 1 These are morphological images and X-ray photoelectron spectroscopy spectra of diamond particles with nanoscale graphite layers on their surfaces; among them, Figure 1Figure (a) is a morphology diagram of diamond particles with a nanoscale graphite layer on the surface in Example 1; Figure (b) is an X-ray photoelectron spectrum of diamond particles with a nanoscale graphite layer on the surface in Example 1; Figure (c) is a morphology diagram of diamond particles with a nanoscale graphite layer on the surface in Example 2; Figure (d) is an X-ray photoelectron spectrum of diamond particles with a nanoscale graphite layer on the surface in Example 2; Figure (e) is a morphology diagram of diamond particles with a nanoscale graphite layer on the surface in Example 3; and Figure (f) is an X-ray photoelectron spectrum of diamond particles with a nanoscale graphite layer on the surface in Example 3.

[0022] Figure 2 The surface morphology and X-ray diffraction energy spectrum of the diamond with an Al3BC coating in Example 1 are shown; wherein, Figure 2 Figures (a) and (b) show the surface morphology of diamond with an Al3BC coating. Figure 2 Figure (c) is the X-ray diffraction energy spectrum of diamond with an Al3BC coating.

[0023] Figure 3 It is the surface morphology of diamond / aluminum composite materials; among which, in Figure 3 In the figure, (a) shows the surface morphology of the diamond / aluminum composite material prepared in Example 1; (b) shows the surface morphology of the diamond / aluminum composite material prepared in Example 2; (c) shows the surface morphology of the diamond / aluminum composite material prepared in Comparative Example 2; (d) shows the surface morphology of the diamond / aluminum composite material prepared in Comparative Example 4; (e) shows the surface morphology of the diamond / aluminum composite material prepared in Example 3; and (f) shows the surface morphology of the diamond / aluminum composite material prepared in Comparative Example 5.

[0024] Figure 4 The surface morphology of the diamond / aluminum composite material after immersion in 3.5 wt.% NaCl solution for 500 h is shown; among them, in Figure 4 In the figure, (a) shows the surface morphology of the diamond / aluminum composite material prepared in Example 1 after soaking in 3.5 wt.% NaCl solution for 500 h; (b) shows the surface morphology of the diamond / aluminum composite material prepared in Comparative Example 1 after soaking in 3.5 wt.% NaCl solution for 500 h. Detailed Implementation

[0025] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0026] This invention relates to a diamond with an Al3BC coating, a diamond / aluminum composite material, and a method for preparing the same. The invention involves graphitizing the surface of diamond under vacuum conditions, followed by an in-situ reaction of boron powder, boric acid, aluminum powder, and diamond under an argon atmosphere. This uniformly generates an Al3BC coating on each surface of the diamond particles. The diamond / aluminum composite material is then prepared using processes such as powder metallurgy, gas pressure infiltration, or mechanical pressure melting. The composite material prepared by this invention exhibits good interfacial bonding, high thermal conductivity of the Al3BC coating, excellent corrosion resistance, and does not react with aluminum, effectively solving the bottleneck problem of low thermal conductivity and easy interfacial reaction between traditional diamond surface coatings and aluminum. The main components of this invention are as follows: On one hand, embodiments of the present invention provide a method for preparing diamond with an Al3BC coating, comprising the following steps: Cleaning and drying steps: The diamond particles are ultrasonically cleaned, then filtered and subsequently air-dried and oven-dried. Preferably, acetone is used as the cleaning solvent for the ultrasonic cleaning process.

[0027] Preferably, the diamond particles are raw diamond particles or crushed diamond particles.

[0028] Preferably, the diamond particles have a particle size of 50-950 μm.

[0029] Surface graphitization treatment step: The diamond particles are subjected to surface graphitization treatment to form a nanoscale graphite layer on the surface of the diamond particles (the thickness of the nanoscale graphite layer is in the nanometer range), thereby obtaining diamond particles with a nanoscale graphite layer on the surface.

[0030] Specifically, diamond particles are placed in a graphite crucible and heated in a vacuum high-temperature furnace to form a nanoscale graphite layer on the diamond surface.

[0031] Preferably, the surface graphitization treatment temperature is 1050℃-1450℃, more preferably 1200℃; the vacuum degree of the surface graphitization treatment is ≤1×10⁻⁶. -2 Pa; the surface graphitization treatment time is 1-4 hours, preferably 2 hours.

[0032] The following explanation addresses this step: Diamond is a tetrahedron. If the diamond particles are directly reacted in the next in-situ reaction, it is difficult to prepare a continuous coating on all faces of the diamond particles. Therefore, graphitizing the surface of the diamond particles promotes the preparation of a continuous coating on all faces during the in-situ reaction step.

[0033] In-situ reaction step: Diamond particles with a nanoscale graphite layer on the surface, boron source, and aluminum powder are mixed to obtain a mixture; under a protective atmosphere, the mixture is heated to the in-situ reaction temperature to carry out an in-situ reaction, so that the aluminum, boron source, and graphite layer react in-situ to generate an Al3BC coating attached to the diamond, and the in-situ reaction product is obtained. (It should be noted that because the temperature of the in-situ reaction is very high, the in-situ reaction product sticks together in a large piece, so it needs to be crushed in the post-processing step.)

[0034] Preferably, in the in-situ reaction step: the boron source includes boric acid and boron powder; wherein, the ratio of diamond, boron powder, boric acid and aluminum powder by molar mass is (3-6):(4-5):(1-1.5):(2-4).

[0035] The boron powder is selected from amorphous or crystalline boron powder. The boric acid powder has a particle size of 10-200 micrometers. The aluminum powder has a particle size of 10-200 micrometers. The boric acid powder particles are nearly spherical. The aluminum powder particles are nearly spherical.

[0036] In the in-situ reaction step: the temperature of the in-situ reaction is 1100-1300℃; the time of the in-situ reaction is 2-6 hours. The mixture is placed in a magnesium oxide crucible for in-situ reaction. Argon is used as the protective atmosphere.

[0037] Post-processing step: The in-situ reaction product is post-processed to obtain diamond with an Al3BC coating.

[0038] Preferably, in this step, the in-situ reaction product is crushed and sieved (by sieving, some of the reaction product fragments are separated from the diamond; the sieve aperture is determined according to the selected diamond particle size) to obtain sieved particulate product; the sieved particulate product is placed in a dilute alkaline solution (5-15% sodium hydroxide solution by mass) for purification to remove unreacted aluminum; then it is placed in a dilute acid solution (5-15% nitric acid by mass) for purification to remove byproducts; finally, after ultrasonic cleaning with anhydrous ethanol, filtration and drying, granular diamond with an Al3BC coating is obtained.

[0039] On the other hand, embodiments of the present invention provide a diamond with an Al3BC coating, wherein the Al3BC-coated diamond is prepared by the preparation method of Al3BC-coated diamond described in any one of the above-mentioned methods. The Al3BC-coated diamond is granular with a particle size ranging from 50 to 950 μm. The thickness of the Al3BC coating in the Al3BC-coated diamond ranges from 100 to 300 nm.

[0040] In another aspect, embodiments of the present invention provide a method for preparing a diamond / aluminum composite material, wherein diamond with an Al3BC coating and aluminum material are compositely treated to obtain a diamond / aluminum composite material; wherein the diamond with an Al3BC coating is prepared by any of the above-described methods for preparing diamond with an Al3BC coating; preferably, the aluminum material is aluminum or an aluminum alloy; preferably, any one of powder metallurgy, gas pressure infiltration, and mechanical pressure melting infiltration is used to composite the diamond with an Al3BC coating and the aluminum material.

[0041] In another aspect, embodiments of the present invention provide a diamond / aluminum composite material, wherein the diamond / aluminum composite material is prepared by the above-described method for preparing diamond / aluminum composite materials. The diamond / aluminum composite material comprises an aluminum matrix and diamond particles dispersed in the aluminum matrix; wherein the diamond particles and the aluminum matrix form a multilayer interface structure with aluminum-Al3BC-diamond; preferably, the thermal conductivity of the diamond / aluminum composite material at room temperature is 500 W / m². -1 K -1 Up to 720 Wm -1 K -1 .

[0042] The present invention will be further illustrated below with specific embodiments: Example 1 This example describes the preparation of a diamond / aluminum composite material with an Al3BC coating, comprising the following steps: Cleaning and drying steps: Pour raw diamond particles with a particle size of 425-500μm into acetone, ultrasonically clean for 30 minutes, filter and air dry, and then dry in a drying oven at 45℃ for 8 hours to obtain clean diamond particles.

[0043] Surface graphitization treatment steps: Weigh 300g of diamond particles, place them in a graphite crucible, put the crucible into a vacuum high-temperature furnace, and evacuate the furnace to a vacuum level of 1×10⁻⁶. -2 After Pa, the temperature was raised to 1250℃ and held for 3 hours before being cooled in the furnace to obtain diamond particles with a nanoscale graphite layer on the surface. The morphology of the diamond particles with the nanoscale graphite layer is as follows: Figure 1 As shown in Figure (a); the X-ray photoelectron spectrum of diamond particles with a nanoscale graphite layer on the surface is as follows. Figure 1 As shown in Figure (b).

[0044] In-situ reaction procedure: Weigh 36g of diamond particles with a nanoscale graphite layer on the surface, 43g of amorphous boron powder, 62g of boric acid, and 54g of aluminum powder. Mix the powders evenly and transfer them to a magnesium oxide crucible. Place the crucible in a tube furnace, introduce argon gas at a flow rate of 2L / min for 1 hour, then raise the temperature to 1200℃ and hold for 4 hours. After heating, cool with the furnace to obtain the in-situ reaction product.

[0045] Post-processing steps: The in-situ reaction product mass was removed from the crucible, crushed, and sieved to obtain diamonds with an Al3BC coating. The sieved coated diamonds were then placed in a 10 wt.% NaOH solution and stirred to remove unreacted aluminum. Subsequently, the coated diamonds were ultrasonically cleaned in anhydrous ethanol, filtered, and dried. 15 vol.% nitric acid was heated to 80°C in a water bath, and the coated diamonds were then poured into the nitric acid solution to remove residual boron oxide and other byproducts. The coated diamonds were then transferred to anhydrous ethanol for ultrasonic cleaning, filtered, and dried to obtain Al3BC coated diamonds (particle size 425-500 μm) with a coating thickness of 150-300 nm. Figure 2 Figures (a), (b), and (c) show that the Al3BC coating is uniformly distributed on the diamond surface.

[0046] Preparation of diamond / aluminum composite material: Granular diamond with an Al3BC coating was weighed at a volume fraction of 60 vol.% and filled into a high-strength graphite mold. The mold was compacted for 30 minutes using a vibratory compaction table. After compaction, the aluminum block and mold cover were assembled sequentially. The selected aluminum block was 1060 pure aluminum. The mold was placed in a vacuum pressure impregnation furnace, and the vacuum in the furnace was evacuated to 1×10⁻⁶. -2 Pa, heated to 750℃ at 10℃ / min, held for 30min, then pressurized and held at 20MPa for 30min, followed by furnace cooling to obtain a dense 60 vol.% diamond / aluminum composite material. The surface morphology of the diamond / aluminum composite material prepared in this embodiment is as follows. Figure 3 As shown in Figure (a), it can be seen that the diamond particles are uniformly distributed in the Al matrix and the interface bonding is good.

[0047] Example 2 This embodiment prepares a diamond / aluminum composite material with an Al3BC coating, including the following steps: Cleaning and drying steps: Pour raw diamond particles with a particle size of 800-950μm into acetone, ultrasonically clean for 30 minutes, filter and air dry, and then dry in a drying oven at 50℃ for 8 hours to obtain clean diamond particles.

[0048] Surface graphitization treatment steps: Weigh 200g of diamond particles, place them in a graphite crucible, put the crucible into a vacuum high-temperature furnace, and evacuate the furnace to a vacuum level of 1×10⁻⁶. -2 After Pa, the temperature was raised to 1450℃ and held for 1 hour before being cooled in the furnace to obtain diamond particles with a nanoscale graphite layer on the surface. The morphology of the diamond particles with the nanoscale graphite layer is as follows: Figure 1 As shown in Figure (c), the X-ray photoelectron spectrum of diamond particles with a nanoscale graphite layer on their surface is as follows. Figure 1 As shown in Figure (d) of the document.

[0049] In-situ reaction procedure: Weigh 72g of diamond particles with a nanoscale graphite layer on the surface, 54g of amorphous boron powder, 62g of boric acid, and 54g of aluminum powder. Mix the powders evenly and transfer them to a magnesium oxide crucible. Place the crucible in a tube furnace, introduce argon gas at a flow rate of 2L / min for 1 hour, then raise the temperature to 1300℃ and hold for 2 hours. After heating, cool with the furnace to obtain the in-situ reaction product.

[0050] Post-processing steps: The in-situ reaction product block was removed from the crucible, crushed, and sieved to obtain coated diamond. The sieved coated diamond was then placed in a 10 wt.% NaOH solution and stirred to remove unreacted aluminum. Subsequently, the coated diamond was ultrasonically cleaned in anhydrous ethanol, filtered, and dried. Nitric acid (15 vol.%) was heated to 80°C in a water bath, and the coated diamond was then poured into the nitric acid solution to remove residual boron oxide and other byproducts. The coated diamond was then transferred to anhydrous ethanol for ultrasonic cleaning, filtered, and dried to obtain Al3BC coated diamond (particle size 800-950 μm) with a coating thickness of 100-250 nm.

[0051] Preparation of diamond / aluminum composite material: Granular diamonds with an Al3BC coating were weighed according to a volume fraction of 64 vol.% and filled into a graphite mold. The mold was compacted for 20 min using a vibratory compaction table. After compaction, a 1060 aluminum block was placed in the mold, positioned above the diamond particles. The mold was then placed in a pneumatic impregnation furnace, and the vacuum level in the furnace was increased to 1 × 10⁻⁶. - 2 The temperature was increased to 750℃ at a rate of 10℃ / min, held for 30 min, then pressurized with argon gas and held at 5 MPa for 30 min. After impregnation, the furnace was cooled to room temperature, and after demolding, a dense 64 vol.% diamond / aluminum composite material was obtained. The surface morphology of the diamond / aluminum composite material prepared in this embodiment is as follows. Figure 3 As shown in Figure (b), it can be seen that the diamond is uniformly dispersed in the Al matrix, with good interfacial bonding and no cracking.

[0052] Example 3 This embodiment prepares a diamond / aluminum composite material with an Al3BC coating, including the following steps: Cleaning and drying steps: Pour raw diamond particles with a particle size of 50-70μm into acetone, ultrasonically clean for 40 minutes, filter and air dry, and then dry in a drying oven at 60℃ for 8 hours to obtain diamond particles with clean surfaces.

[0053] Surface graphitization treatment steps: Weigh 200g of diamond particles, place them in a graphite crucible, put the crucible into a vacuum high-temperature furnace, and evacuate the furnace to a vacuum level of 1×10⁻⁶. -2 After Pa, the temperature was increased to 1050℃ at a heating rate of 10℃ / min, held at that temperature for 4 hours, and then cooled in the furnace to obtain diamond particles with a nanoscale graphite layer on the surface. The morphology of the diamond particles with the nanoscale graphite layer is as follows: Figure 1 Figure (e) shows the X-ray photoelectron spectrum of diamond particles with a nanoscale graphite layer on their surface. Figure 1 As shown in Figure (f).

[0054] In-situ reaction procedure: Weigh 120g of diamond particles with a nanoscale graphite layer on the surface, 87g of amorphous boron powder, 124g of boric acid, and 108g of aluminum powder. Mix the powders evenly and transfer them to a magnesium oxide crucible. Place the crucible in a tube furnace, purge with argon gas at a flow rate of 2L / min for 1 hour, then heat to 1100℃ at a heating rate of 10℃ / min and hold at that temperature for 6 hours. After heating, cool with the furnace to obtain the in-situ reaction product.

[0055] Post-processing steps: The in-situ reaction product mass was removed from the crucible, crushed, and sieved to obtain diamonds with an Al3BC coating. The sieved coated diamonds were then placed in a 10 wt.% NaOH solution and stirred to remove unreacted aluminum. Subsequently, the coated diamonds were ultrasonically cleaned in anhydrous ethanol, filtered, and dried. Nitric acid (15 vol.%) was heated to 80°C in a water bath, and the coated diamonds were then poured into the nitric acid solution to remove residual boron oxide and other byproducts. The coated diamonds were then transferred to anhydrous ethanol for ultrasonic cleaning, filtered, and dried to obtain Al3BC coated diamonds (particle size 50-70 μm) with a coating thickness of 200-400 nm.

[0056] Preparation of diamond / aluminum composite material: Granular diamond with an Al3BC coating was weighed according to a volume fraction of 50 vol.% and mixed evenly with 6061 aluminum powder. The mixed powder was then transferred to a steel mold and cold-pressed into a blank. The powder blank was placed in a vacuum hot press furnace and evacuated to a vacuum of 1×10⁻⁶. -2Pa, then heated to 640℃ and held for 1.5 h, followed by applying 100 MPa pressure to densify the composite material. After furnace cooling to room temperature, it was demolded to obtain a dense 50 vol.% diamond / aluminum composite material, with the surface morphology as shown in the figure. Figure 3 As shown in Figure (e), it can be seen that the diamond particles in the composite material are evenly distributed and there are no obvious defects on the surface.

[0057] Comparative Example 1 Comparative Example 1 prepared a diamond / aluminum composite material, which differed from Example 1 in that the diamond with Al3BC coating in Example 1 was replaced with untreated raw diamond, while the rest were the same.

[0058] The thermal conductivity of the diamond / aluminum composite samples prepared in Example 1 and Comparative Example 1 was measured. The thermal conductivity of the diamond / aluminum composite sample in Example 1 was 667 W / m². -1 K -1 The thermal conductivity of the diamond / aluminum composite sample in Comparative Example 1 was 732 W / m. -1 K -1 .

[0059] The diamond / aluminum composite material samples from Example 1 and Comparative Example 1 were immersed in a 3.5 wt.% NaCl solution for 500 h, and the thermal conductivity of the composite materials was measured again. It was found that the thermal conductivity of the diamond / aluminum composite material sample from Example 1 was 650 W / m². -1 K -1 The thermal conductivity decreased by 2.5%; the thermal conductivity of the diamond / aluminum composite sample in Comparative Example 1 was 641 W / m². -1 K -1 The thermal conductivity decreased by 12.4%. This shows that the Al3BC coating prevents the formation of the easily hydrolyzed Al4C3 phase at the interface, thus preventing the significant decrease in thermal conductivity caused by interface cracking due to Al4C3 phase hydrolysis.

[0060] Figure 4 The surface morphology of the diamond / aluminum composite material after immersion in 3.5 wt.% NaCl solution for 500 h is shown; among them, in Figure 4 In Figure (a), the surface morphology of the diamond / aluminum composite material prepared in Example 1 after immersion in 3.5 wt.% NaCl solution for 500 h is shown; Figure (b) shows the surface morphology of the diamond / aluminum composite material prepared in Comparative Example 1 after immersion in 3.5 wt.% NaCl solution for 500 h. It can be seen that after 500 h of corrosion, the interface between the diamond particles and the Al matrix in Example 1 shows good bonding; however, the interface between the diamond particles and the Al matrix in Comparative Example 1 shows severe cracking.

[0061] Comparative Example 2 This comparative example prepares a diamond / aluminum composite material, including the following steps: Preparation of TiC-coated diamond: Weigh 100g of Ti-coated diamond with a particle size of 800-950μm (the Ti coating is prepared on the surface of the diamond using magnetron sputtering, and the thickness of the Ti coating is 100-200nm), and place it in a graphite crucible. Place the graphite crucible in a vacuum high-temperature furnace, and evacuate the furnace to a vacuum level of 1×10⁻⁶. -2 After Pa, the temperature was raised to 1100℃, held for 3 hours, and then cooled in the furnace to obtain diamond with a continuous TiC coating (coating thickness of 100-200nm) on the surface.

[0062] Preparation of diamond / aluminum composite material: The TiC-coated diamond particles were weighed according to a volume fraction of 64 vol.% and filled into a graphite mold. The mold was compacted for 20 minutes using a vibratory compaction table. After compaction, 1060 pure aluminum blocks were filled on top of the diamond particles. The mold was placed in the cavity of a pneumatic infiltration furnace, and the vacuum level in the furnace cavity was increased to 1×10⁻⁶. -2 To remove excess gas, the temperature was increased to 750℃ at a rate of 10℃ / min, held for 30 min, and then pressurized with argon gas. The mixture was held at 5 MPa for 30 min. After impregnation, the furnace was cooled to room temperature. After demolding, a dense 64 vol.% diamond / aluminum composite material was obtained. The surface morphology of the composite material is as follows: Figure 3 As shown in Figure (c), it can be seen that the diamond particle composite material has good interfacial bonding.

[0063] The thermal conductivity of the diamond / aluminum composite samples prepared in Example 2 and Comparative Example 2 was measured. The thermal conductivity of the diamond / aluminum composite sample prepared in Example 2 was 713 W / m². -1 K -1 The thermal conductivity of the diamond / aluminum composite sample prepared in Comparative Example 2 was 647 W / m. -1 K -1 .

[0064] The diamond / aluminum composite material samples from Example 2 and Comparative Example 2 were immersed in a 3.5 wt.% NaCl solution for 1000 h, and the thermal conductivity of the composite materials was measured again. The thermal conductivity of the diamond / aluminum composite material sample from Example 2 was 687 W / m². -1 K -1 The thermal conductivity decreased by 3.7%; the thermal conductivity of the diamond / aluminum composite sample in Comparative Example 2 was 610 W / m². -1 K -1The thermal conductivity decreased by 5.7%. This indicates that, compared to the more stable Al3BC coating, the TiC coating diffuses into the aluminum matrix during the composite material melting and infiltration process, causing diamond and aluminum to re-contact and form a small amount of easily hydrolyzable Al4C3 phase at the interface, which reduces the corrosion resistance of the composite material.

[0065] Comparative Example 3 This comparative example prepares a diamond / aluminum composite material. The difference between Comparative Example 3 and Example 2 is that the diamond is Cr-coated diamond (prepared by magnetron sputtering, with a particle size of 800-950 μm and a surface coating thickness of 100-200 nm). The other steps are the same as in Example 2.

[0066] The thermal conductivity of the diamond / aluminum composite samples prepared in Example 2 and Comparative Example 3 was measured.

[0067] The thermal conductivity of the diamond / aluminum composite sample in Example 2 was 713 W / m. -1 K -1 The thermal conductivity of the diamond / aluminum composite sample in Comparative Example 3 was 662 W / m. -1 K -1 The diamond / aluminum composite material samples from Example 2 and Comparative Example 3 were immersed in a 3.5 wt.% NaCl solution for 1000 h, and the thermal conductivity of the composite materials was measured again. The thermal conductivity of the diamond / aluminum composite material from Example 2 was 687 W / m². -1 K -1 The thermal conductivity decreased by 3.7%; the thermal conductivity of the diamond / aluminum composite material in Comparative Example 3 was 614 W / m². -1 K -1 The thermal conductivity decreased by 7.3%. This indicates that the Cr coating rapidly diffuses into the aluminum matrix during the composite material melting and infiltration process, forming a metallic compound. This leads to the re-contact of diamond and aluminum, resulting in the formation of an easily hydrolyzable Al4C3 phase at the interface, thus reducing the corrosion resistance of the composite material. Compared to the metallic coating, the Al3BC coating exhibits superior high-temperature stability.

[0068] Comparative Example 4 This comparative example prepares a diamond / aluminum composite material. The difference between Comparative Example 4 and Example 2 is that the diamond is W-coated diamond (prepared by magnetron sputtering, with a particle size of 800-950 μm and a surface coating thickness of 100-200 nm). Other steps are the same as in Example 2.

[0069] The surface morphology of the diamond / aluminum composite material prepared in this comparative example is as follows: Figure 3 As shown in Figure (d) of the document.

[0070] The thermal conductivity of the diamond / aluminum composite samples prepared in Example 2 and Comparative Example 4 was measured.

[0071] The thermal conductivity of the diamond / aluminum composite sample in Example 2 was 713 W / m. -1 K -1 The thermal conductivity of the diamond / aluminum composite sample in Comparative Example 3 was 673 W / m. -1 K -1 The diamond / aluminum composite material samples from Example 2 and Comparative Example 4 were immersed in a 3.5 wt.% NaCl solution for 1000 h, and the thermal conductivity of the composite materials was measured again. The thermal conductivity of the diamond / aluminum composite material from Example 2 was 687 W / m². -1 K -1 The thermal conductivity decreased by 3.7%; the thermal conductivity of the diamond / aluminum composite material in Comparative Example 4 was 645 W / m². -1 K -1 The thermal conductivity decreased by 6.1%. This indicates that the W coating rapidly diffuses into the aluminum matrix during the composite material melting and infiltration process, forming a metallic compound. This leads to the re-contact between diamond and aluminum, resulting in the formation of an easily hydrolyzed Al4C3 phase at the interface, thus reducing the corrosion resistance of the composite material. Compared to the metallic coating, the Al3BC coating exhibits superior high-temperature stability.

[0072] Comparative Example 5 This comparative example prepares a diamond / aluminum composite material. The difference between Comparative Example 5 and Example 3 is that the diamond used is uncoated raw diamond with a particle size of 50-70 μm, while the other steps are the same as in Example 3.

[0073] The surface morphology of the diamond / aluminum composite sample prepared in this comparative example is as follows: Figure 3 As shown in Figure (f), it can be seen that there are obvious defects on the surface of the composite material. This is achieved by comparing the surface morphology of the sample from Example 3 with that of Comparative Example 5. Figure 3 Figures (e) and (f) show that in the sample of Example 3, the diamond particles are tightly bonded to the aluminum matrix, the composite material has high density, and the thermal conductivity is 545 W / m². -1 K -1 In contrast, in the sample of Comparative Example 5, multiple cracks appeared at the interface between the diamond particles and the aluminum matrix. The composite material had low density and extremely poor interfacial bonding, resulting in ineffective heat transfer and a thermal conductivity of only 385 W / m². -1 K -1 .

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing diamond with an Al3BC coating, characterized in that, It includes the following steps: Surface graphitization treatment step: The diamond particles are subjected to surface graphitization treatment to form a nanoscale graphite layer on the surface of the diamond particles, thereby obtaining diamond particles with a nanoscale graphite layer on the surface; wherein, the thickness of the nanoscale graphite layer is in the nanometer range. In-situ reaction step: Diamond particles with a nanoscale graphite layer on the surface, boron source and aluminum powder are mixed to obtain a mixture; under a protective atmosphere, the mixture is heated to the in-situ reaction temperature to carry out an in-situ reaction, so that aluminum, boron source and graphite layer react in-situ to generate an Al3BC coating attached to the diamond surface, and an in-situ reaction product is obtained. Post-processing step: The in-situ reaction product is post-processed to obtain diamond with an Al3BC coating.

2. The method for preparing diamond with an Al3BC coating according to claim 1, characterized in that, Prior to the surface graphitization treatment step, the method further includes: Cleaning and drying steps: The diamond particles are ultrasonically cleaned, then filtered and subsequently air-dried and oven-dried. Preferably, acetone is used as the cleaning solvent for the ultrasonic cleaning process.

3. The method for preparing diamond with an Al3BC coating according to claim 1 or 2, characterized in that, The diamond particles are raw diamond particles or crushed diamond particles; and / or The diamond particles have a particle size of 50-950 μm.

4. The method for preparing diamond with an Al3BC coating according to any one of claims 1-3, characterized in that, In the surface graphitization treatment step: The surface graphitization treatment temperature is 1050℃-1450℃, preferably 1200℃; the vacuum degree of the surface graphitization treatment is ≤1×10⁻⁶. -2 Pa; the surface graphitization treatment time is 1-4 hours, preferably 2 hours; and / or The diamond particles were placed in a graphite crucible and then subjected to surface graphitization treatment in a vacuum high-temperature furnace.

5. The method for preparing diamond with an Al3BC coating according to any one of claims 1-4, characterized in that, In the in-situ reaction step: the boron source includes boric acid and boron powder; The ratio of diamond, boron powder, boric acid, and aluminum powder by molar mass is (3-6):(4-5):(1-1.5):(2-4). Preferably, the boron powder is amorphous boron powder or crystalline boron powder; Preferably, the boric acid powder has a particle size of 10-200 micrometers; Preferably, the aluminum powder has a particle size of 10-200 micrometers; Preferably, the boric acid powder particles are nearly spherical; Preferably, the aluminum powder particles are nearly spherical.

6. The method for preparing diamond with an Al3BC coating according to any one of claims 1-5, characterized in that, In the in-situ reaction step: The in-situ reaction temperature is 1100-1300℃; the in-situ reaction time is 2-6 hours; and / or The mixture is placed in a magnesium oxide crucible for in-situ reaction; and / or The protective atmosphere is made of an inert gas, preferably argon.

7. The method for preparing diamond with an Al3BC coating according to any one of claims 1-6, characterized in that, The post-processing steps include: The in-situ reaction product is crushed and sieved to obtain sieved particulate product. The sieved particulate product was purified in a dilute alkaline solution to remove unreacted aluminum; after washing, the particulate product was purified in a dilute acid solution to remove byproducts; finally, after washing, filtering and drying, granular diamond with an Al3BC coating was obtained.

8. A diamond with an Al3BC coating, characterized in that, The Al3BC coated diamond is prepared by the method for preparing Al3BC coated diamond according to any one of claims 1-7; Preferably, the diamond with the Al3BC coating is granular with a particle size range of 50-950 μm; Preferably, the thickness of the Al3BC coating in the diamond with the Al3BC coating ranges from 100 to 300 nm.

9. A method for preparing a diamond / aluminum composite material, characterized in that, A diamond / aluminum composite material is obtained by composite treatment of diamond with Al3BC coating and aluminum material; wherein the diamond with Al3BC coating is prepared by the preparation method of diamond with Al3BC coating according to any one of claims 1-7. Preferably, the aluminum material is aluminum or an aluminum alloy; Preferably, diamond and aluminum materials with Al3BC coating are composite treated using any one of the following methods: powder metallurgy, gas pressure infiltration, or mechanical pressure melting infiltration.

10. A diamond / aluminum composite material, characterized in that, The diamond / aluminum composite material includes an aluminum matrix and diamond particles dispersed in the aluminum matrix; wherein, the diamond particles and the aluminum matrix form a multilayer interface structure with aluminum-Al3BC-diamond. Preferably, the diamond / aluminum composite material has a thermal conductivity of 500 W / m at room temperature. -1 K -1 Up to 720Wm -1 K -1 ; Preferably, the diamond / aluminum composite material is prepared by the method for preparing the diamond / aluminum composite material according to claim 9.

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