A method for preparing diamond / aluminum composite material

Abstract

The present invention provides a method for preparing a diamond / aluminum composite material, relating to the technical field of composite materials. The method comprises: filling a mixed powder containing aluminum powder and diamond powder into a graphite mold with a pouring gate, then placing the graphite mold containing the mixed powder in a gas pressure infiltration furnace, and placing an aluminum block above the graphite mold; evacuating the gas pressure infiltration furnace, heating the graphite mold and the aluminum block to melt the aluminum block; using inert gas to increase pressure so that the molten aluminum liquid penetrates through the pouring gate into the gaps between the mixed powders; maintaining the temperature and pressure of the gas pressure infiltration furnace to control the interfacial reaction between the aluminum and diamond; stopping heating and then cooling to obtain the diamond / aluminum composite material. The present invention can control the diamond content in the aluminum / diamond mixed powder and the diamond content in the composite material to obtain a diamond / aluminum composite material with a wide performance range and a density greater than 99%, thereby reducing raw material costs and expanding the application field of this composite material.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and in particular relates to a method for preparing a diamond / aluminum composite material. The method can regulate the diamond content in the diamond / aluminum composite material. Background Art

[0002] With the rapid development of electronic information technology and micro-nano manufacturing technologies, the characteristic dimensions of electronic components have been reduced to the micro-nanoscale. The high integration and high power of electronic components have made heat dissipation a major bottleneck restricting the development of electronic devices. Therefore, the development of high-performance thermal management materials has become a key driving force for the development of the electronic information industry. Diamond / aluminum composites, due to their excellent thermophysical properties, good mechanical properties, and low density, are a research hotspot for the next generation of thermal management materials.

[0003] Liquid-phase diamond / aluminum composites have the advantages of high density and easy control of interfacial reactions. The density and thermal conductivity of diamond / aluminum composites prepared by gas pressure infiltration are as high as 99.2% and 1021 W / mK, respectively (N. Li et al. Mater. Today Phys. 28 (2022) 100901), which has good application prospects. However, due to the natural stacking of diamond powder, the volume fraction of diamond in the diamond / aluminum composite prepared by liquid phase method is usually above 50% (WB Johnson, J. Mater. Res. 8 (1993) 1169-1173 (pressureless infiltration); PW Ruch et al. Compos. Sci. Technol. 66 (2006) 2677-2685 (pressure infiltration); IE Monje et al. Compos. Part A 48 (2013) 9-14 (gas pressure infiltration), and it is difficult to vary the diamond content over a large range by regulating the stacking method of diamond powder. Due to the addition of the superhard diamond phase, the machining and welding of high-volume-fraction diamond / aluminum composites are greatly limited. The high price of diamond powder is also one of the main reasons why diamond / aluminum composites are difficult to apply on a large scale. Although high-thermal-conductivity diamond / aluminum composites can be obtained by adding high-volume-fraction diamond, the thermal conductivity requirements of diamond / aluminum composites vary depending on the application scenario. Adding too much diamond powder can sometimes lead to excessive performance and increased costs.

[0004] In order to overcome the defects of the existing liquid phase method for preparing diamond / aluminum composite materials, that is, the diamond content in the diamond / aluminum composite materials is high and cannot be controlled, the present invention proposes a preparation method of the diamond / aluminum composite materials, which can control the diamond content in the diamond / aluminum composite materials according to actual application requirements.

[0005] The present invention provides a method for preparing a diamond / aluminum composite material, comprising the following steps:

[0006] 1) Weighing aluminum powder and diamond powder, then ball milling to obtain a mixed powder;

[0007] 2) Filling the mixed powder obtained in step 1) into a graphite mold with a gate, then placing the graphite mold filled with the mixed powder in a gas pressure infiltration furnace, and placing an aluminum block on top of the graphite mold;

[0008] 3) After the pressure impregnation furnace is evacuated, the graphite mold containing the mixed powder and the aluminum block in step 2) are heated to a temperature above the melting point of the aluminum block, and the aluminum block is melted;

[0009] 4) Use inert gas to increase the pressure in the gas pressure infiltration furnace, so that the molten aluminum liquid penetrates into the gaps between the mixed powders through the graphite mold gate under pressure. The gas pressure infiltration furnace is kept hot and pressurized to control the interface reaction between aluminum and diamond;

[0010] 5) stopping heating and cooling the mixture to room temperature in the furnace to obtain the diamond / aluminum composite material.

[0011] Preferably, in step 1), the mass ratio of aluminum powder to diamond powder is (0.1-10):1, and the total mass of the aluminum powder and diamond powder is 10-500 g. Existing liquid-phase methods for preparing diamond / aluminum composite materials typically do not mix aluminum powder with diamond powder. The present invention allows the temperature of the graphite mold loaded with aluminum / diamond powder to be controlled below the melting point of the aluminum powder, without affecting the subsequent penetration of molten aluminum into the gaps between the mixed powders. This reduces the amount of diamond added to 10%.

[0012] Preferably, in step 1), the particle size of the aluminum powder is 10-500 μm, and the particle size of the diamond powder is 50-700 μm. The diamond powder can be uncoated diamond powder or metal-coated diamond powder.

[0013] Preferably, in step 1), the ball milling time is 5 to 60 minutes, and the ball milling speed is 50 to 200 rpm.

[0014] Preferably, in step 2), the aluminum block is made of one of pure aluminum, aluminum-silicon alloy, 1050 aluminum alloy, and 1100 aluminum alloy. The aluminum block has a mass of 50-1000 g and a volume 5-20 times the volume of the graphite mold. Excess molten aluminum cannot enter the graphite mold and remains above the mold. After the reaction is complete, the diamond / aluminum composite material inside the graphite mold shrinks during cooling. The molten aluminum above the graphite mold can continue to enter the graphite mold through the gate. This excess molten aluminum reduces shrinkage cavities in the diamond / aluminum composite material and improves its density.

[0015] Preferably, in step 2), the graphite mold is made of high-purity graphite, the diameter of the gate above the graphite mold is 3-10 mm, and the distribution density is 2-5 gates / cm 2 .

[0016] Preferably, in step 3), the pressure infiltration furnace is evacuated to a vacuum level of ≤1 Pa. The aluminum block is heated at a rate of 10-50°C / minute, at a temperature of 600-1000°C, and held at this temperature for 5-60 minutes. More preferably, the heating temperature is 50-1000°C above the melting point of the aluminum block. It should be noted that during the melting of the aluminum block above the mold in step 3), the aluminum powder in the graphite mold must not melt. Otherwise, the molten aluminum will not be able to enter the gaps between the aluminum / diamond mixed powder in the graphite mold during the pressurization process in step 4). A heating element (such as a resistance wire) can be placed in the upper portion of the pressure infiltration furnace chamber so that the heating element heats the aluminum block, while the temperature of the graphite mold below the aluminum block remains relatively low. This allows the aluminum block to melt without melting the aluminum powder.

[0017] Preferably, in step 4), the inert gas is one of nitrogen and argon, the pressure in the pressure infiltration furnace is pressurized to 0.3-3 MPa, and the holding time is 5-60 minutes. During the holding period, the molten aluminum and diamond come into contact and undergo an interfacial reaction, forming a compact structure and increasing the density of the diamond / aluminum composite material. The duration of the interfacial reaction can be controlled by controlling the holding time.

[0018] The present invention also provides a diamond / aluminum composite material prepared by the method, wherein the volume fraction of diamond in the diamond / aluminum composite material is 10-70%.

[0019] The present invention also provides an apparatus for implementing the method, comprising a graphite mold, an aluminum block, and a pressure infiltration furnace. The graphite mold is a fully enclosed structure with several gates on its top. The mold is filled with aluminum powder and diamond powder. The aluminum block is placed above the graphite mold, and the graphite mold and aluminum block are placed together in the pressure infiltration furnace chamber. A heating resistor is installed above the furnace chamber, at the same height as the aluminum block.

[0020] The present invention has the following beneficial effects:

[0021] The present invention utilizes a liquid phase method to prepare a diamond / aluminum composite material. By controlling the diamond content in the diamond / aluminum mixed powder, the diamond content of the resulting diamond / aluminum composite material can be precisely controlled. This method can produce diamond / aluminum composite materials with a diamond volume fraction of 10-70% and a density exceeding 99%, while also enabling the thermal conductivity of the diamond / aluminum composite material to be regulated within a wide performance range of 300-800 W / mK. This method can reduce the machining difficulty and material cost of the diamond / aluminum composite material while improving the surface weldability of the composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 Schematic diagram of the device used in the method for preparing the diamond / aluminum composite material of the present invention;

[0024] Among them, 1-graphite mold; 11-gate; 12-aluminum powder; 13-diamond powder; 2-aluminum block; 3-air pressure infiltration furnace; 31-heating resistance wire.

[0025] Figure 2 This is a surface morphology of the diamond / aluminum composite material prepared in Example 1 of the present invention;

[0026] Figure 3 This is a surface morphology of the diamond / aluminum composite material prepared in Example 2 of the present invention;

[0027] Figure 4 This is a surface morphology of the diamond / aluminum composite material prepared in Comparative Example 1 of the present invention;

[0028] Figure 5 This is a surface morphology of the diamond / aluminum composite material prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0030] Figure 1The diagram below shows the apparatus used in the method for preparing the diamond / aluminum composite material of the present invention. The apparatus comprises a graphite mold 1, an aluminum block 2, and a pressure infiltration furnace 3. The graphite mold 1 is a fully enclosed structure with several gates 11 on its top. The graphite mold 1 is filled with aluminum powder 12 and diamond powder 13. An aluminum block 2 is placed above the graphite mold 1, and the graphite mold 1 and aluminum block 2 are placed together in the furnace chamber of the pressure infiltration furnace 3. A heating resistor 31 is provided at the top of the furnace chamber, and the heating resistor 31 is located at the same height as the aluminum block 2. When heating is turned on, the aluminum block 2 is heated and melts, while the temperature of the graphite mold 1 is relatively low, and the aluminum powder therein does not melt.

[0031] The present invention provides a method for preparing a diamond / aluminum composite material, comprising the following steps:

[0032] 1) Weighing aluminum powder and diamond powder, then ball milling to obtain a mixed powder;

[0033] 2) Filling the mixed powder obtained in step 1) into a graphite mold with a gate, then placing the graphite mold filled with the mixed powder in a gas pressure infiltration furnace, and placing an aluminum block of a certain mass above the graphite mold;

[0034] 3) After the gas pressure impregnation furnace is evacuated, the gas pressure impregnation furnace heats the graphite mold and aluminum block in the furnace chamber through the heating resistance wire. When the heating temperature reaches above the melting point of aluminum or aluminum alloy, the aluminum block melts;

[0035] 4) Use inert gas to increase the pressure in the gas pressure infiltration furnace. The temperature of the graphite mold filled with aluminum / diamond powder is controlled below the melting point of the aluminum powder. Under the action of pressure, the molten aluminum liquid penetrates into the gaps between the mixed powders through the graphite mold gate. The gas pressure infiltration furnace is kept hot and pressurized to control the interface reaction between aluminum and diamond.

[0036] 5) Stop heating and cool the furnace to room temperature. The volume of the diamond / aluminum composite material in the graphite mold shrinks during the cooling process. The molten aluminum above the graphite mold can continue to enter the graphite mold through the gate, increasing the density of the composite material, thereby obtaining the diamond / aluminum composite material.

[0037] The present invention controls the volume fraction of diamond in the prepared diamond / aluminum composite material by controlling the diamond content in the diamond / aluminum mixed powder, thereby effectively reducing the machining difficulty and material cost of the diamond / aluminum composite material and improving the surface weldability of the composite material.

[0038] In order to better understand the present invention, specific examples are described in detail below. It should be noted that the following examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0039] Example 1

[0040] Step 1: Weigh 60 g of aluminum powder with a particle size of 80 μm and 40 g of diamond powder with a particle size of 120 μm and a surface coated with metal zirconium;

[0041] Step 2: Use a ball mill to mix the aluminum powder and diamond powder for 15 minutes at a ball milling speed of 60 rpm;

[0042] Step 3: Fill the powder mixed by ball milling in step 2) into a graphite mold with a gate. The diameter of the gate above the graphite mold is 3 mm and the distribution density is 5 / cm 2 , then put the graphite mold filled with the mixed powder into a gas pressure infiltration furnace, and place a 100 g Al-12wt.%Si alloy block on top of the graphite mold;

[0043] Step 4: Evacuate the pressure impregnation furnace to a vacuum degree of 0.1 Pa;

[0044] Step 5: Heat the graphite mold and aluminum block containing the mixed powder in step 3) to 650°C at a heating rate of 30°C / min;

[0045] Step 6: Use argon gas to increase the pressure in the pressure infiltration furnace to 0.5 MPa, and infiltrate the molten aluminum liquid into the gaps of the mixed powder through the graphite mold gate under pressure;

[0046] Step 7: Maintain the temperature and pressure in the gas pressure infiltration furnace for 10 minutes to control the interface reaction between aluminum and diamond;

[0047] Step 8: Stop heating and cool to room temperature in the furnace to obtain a diamond / aluminum composite material. Figure 2 This is the surface morphology of the diamond / aluminum composite material prepared in Example 1. Diamonds are uniformly distributed within the aluminum matrix. Testing using the Archimedean drainage method combined with the law of mixing revealed a diamond volume fraction of 10%, a thermal conductivity of 304 W / mK, and a density of 99%.

[0048] Example 2

[0049] Step 1: Weigh 20 g of aluminum powder with a particle size of 80 μm and 20 g of diamond powder with a particle size of 270 μm and a titanium coating on the surface;

[0050] Step 2: Use a ball mill to mix the aluminum powder and diamond powder for 15 minutes at a ball milling speed of 60 rpm;

[0051] Step 3: Fill the powder mixed by ball milling in step 2) into a graphite mold with a gate. The diameter of the gate above the graphite mold is 4 mm and the distribution density is 4 / cm 2, then put the graphite mold filled with the mixed powder into a gas pressure infiltration furnace, and place a pure aluminum block with a mass of 70 g on top of the graphite mold;

[0052] Step 4: Evacuate the pressure impregnation furnace to a vacuum degree of 0.1 Pa;

[0053] Step 5: Heat the graphite mold and aluminum block containing the mixed powder in step 3) to 800°C at a heating rate of 30°C / min;

[0054] Step 6: Use argon gas to increase the pressure in the pressure infiltration furnace to 1 MPa, and infiltrate the molten aluminum liquid into the gaps of the mixed powder through the graphite mold gate under pressure;

[0055] Step 7: Maintain the temperature and pressure in the gas pressure infiltration furnace for 20 minutes to control the interface reaction between aluminum and diamond;

[0056] Step 8: Stop heating and cool to room temperature in the furnace to obtain a diamond / aluminum composite material. Figure 3 The surface morphology of the diamond / aluminum composite material prepared in Example 2 was tested by the Archimedean drainage method combined with the law of mixing, and the diamond volume fraction was 23%, the thermal conductivity was 320 W / mK, and the density was 99.1%.

[0057] Example 3

[0058] Step 1: Weigh 4 g of aluminum powder with a particle size of 80 μm and 12 g of diamond powder with a particle size of 270 μm;

[0059] Step 2: Use a ball mill to mix the aluminum powder and diamond powder for 15 minutes at a ball milling speed of 60 rpm;

[0060] Step 3: Fill the powder mixed by ball milling in step 2) into a graphite mold with a gate. The diameter of the gate above the graphite mold is 4 mm and the distribution density is 4 / cm 2 , then put the graphite mold filled with the mixed powder into a gas pressure infiltration furnace, and place a 50 g pure aluminum block on top of the graphite mold;

[0061] Step 4: Evacuate the pressure impregnation furnace to a vacuum degree of 0.1 Pa;

[0062] Step 5: Heat the graphite mold and aluminum block containing the mixed powder in step 3) to 900°C at a heating rate of 30°C / min;

[0063] Step 6: Use argon gas to increase the pressure in the pressure infiltration furnace to 1 MPa, and infiltrate the molten aluminum liquid into the gaps of the mixed powder through the graphite mold gate under pressure;

[0064] Step 7: Maintain the temperature and pressure in the gas pressure infiltration furnace for 20 minutes to control the interface reaction between aluminum and diamond;

[0065] Step 8: Stop heating and allow the furnace to cool to room temperature to obtain a diamond / aluminum composite material. The volume fraction of diamond, measured by the Archimedean drainage method combined with the law of mixing, was found to be 34%, with a thermal conductivity of 354 W / mK and a density of 99.1%.

[0066] Through Examples 1-3, the volume fraction of diamond in the composite material can be estimated based on the volume ratio of the diamond / aluminum mixed powder. The calculation formula is:

[0067] The volume fraction of diamond in the composite material = 50% × the volume content of diamond in the mixed powder.

[0068] Comparative Example 1

[0069] Step 1: Fill diamond powder with a particle size of 270 μm into a graphite mold with a gate. The diameter of the gate above the graphite mold is 4 mm, and the distribution density is 4 pieces / cm 2 , then put the graphite mold filled with diamond powder into the gas pressure infiltration furnace, and place a pure aluminum block with a mass of 100 g on top of the graphite mold;

[0070] Step 4: Evacuate the pressure impregnation furnace to a vacuum degree of 0.1 Pa;

[0071] Step 5: Heat the graphite mold and aluminum block containing diamond powder in step 3) to 850°C at a heating rate of 30°C / min;

[0072] Step 6: Use argon gas to increase the pressure in the pressure infiltration furnace to 1.5 MPa, and infiltrate the molten aluminum liquid into the gaps between the diamond powder through the graphite mold gate under pressure;

[0073] Step 7: Maintain the temperature and pressure in the gas pressure infiltration furnace for 20 minutes to control the interface reaction between aluminum and diamond;

[0074] Step 8: Stop heating and cool to room temperature in the furnace to obtain a diamond / aluminum composite material. Figure 4 The surface morphology of the diamond / aluminum composite material prepared in Comparative Example 1, in which the diamond content is much higher than that in the embodiment, is shown. The diamond volume fraction, as determined by the Archimedean drainage method combined with the law of mixing, is 53%, the thermal conductivity is 722 W / mK, and the density is 99.3%.

[0075] Comparative Example 2

[0076] Step 1: Fill the graphite mold with a gate with a diameter of 4 mm and a distribution density of 4 diamond powder with a particle size of 70 μm into the graphite mold. 2 , continuously vibrate the graphite mold until it can no longer be filled with diamond powder, then place the graphite mold filled with diamond powder in a gas pressure infiltration furnace, and place a pure aluminum block with a mass of 100 g on top of the graphite mold;

[0077] Step 4: Evacuate the pressure impregnation furnace to a vacuum degree of 0.1 Pa;

[0078] Step 5: Heat the graphite mold and aluminum block containing diamond powder in step 3) to 900°C at a heating rate of 50°C / min;

[0079] Step 6: Use argon gas to increase the pressure in the pressure infiltration furnace to 1 MPa, and infiltrate the molten aluminum liquid into the gaps between the diamond powder through the graphite mold gate under pressure;

[0080] Step 7: Maintain the temperature and pressure in the gas pressure infiltration furnace for 20 minutes to control the interface reaction between aluminum and diamond;

[0081] Step 8: Stop heating and cool to room temperature in the furnace to obtain a diamond / aluminum composite material. Figure 5 The surface morphology of the diamond / aluminum composite material prepared in Comparative Example 2 was tested by the Archimedean drainage method combined with the mixing law to obtain a diamond volume fraction of 65%, a thermal conductivity of 498 W / mK, and a density of 99.1%.

[0082] Comparative Examples 1 and 2 demonstrate that when only diamond powder is added to the graphite mold, the resulting diamond / aluminum composite material generally contains more than 50% diamond. Therefore, the diamond volume fraction of the diamond / aluminum composite materials prepared in Examples 1, 2, and 3 is significantly lower than that of the diamond / aluminum composite materials prepared in Comparative Examples 1 and 2, demonstrating that the present invention can effectively control the diamond volume fraction in the diamond / aluminum composite material and reduce the material cost of the diamond / aluminum composite material.

[0083] Comparative Example 3

[0084] In step 3, no aluminum block was placed above the graphite mold, and the argon pressurization in step 6 was omitted. All other steps were the same as in Example 1. That is, without the additional aluminum block or pressurization, the graphite mold containing the diamond and aluminum powders was heated directly. Without the addition of molten aluminum, a diamond / aluminum composite material could not be prepared, and the final mixed powder remained unchanged.

[0085] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a diamond / aluminum composite material, characterized in that: The following steps are involved: 1) Weighing aluminum powder and diamond powder, then ball milling to obtain a mixed powder; In step 1), the mass ratio of the aluminum powder to the diamond powder is (0.1-10):1, and the total mass of the aluminum powder and the diamond powder is 10-500 g; the particle size of the aluminum powder is 10-500 μm, and the particle size of the diamond powder is 50-700 μm; 2) Filling the mixed powder obtained in step 1) into a graphite mold with a gate, then placing the graphite mold filled with the mixed powder in a gas pressure infiltration furnace, and placing an aluminum block on top of the graphite mold; 3) After the pressure infiltration furnace is evacuated, the graphite mold containing the mixed powder and the aluminum block in step 2) are heated to a temperature above the melting point of the aluminum block, and the aluminum block is melted; 4) Use inert gas to increase the pressure in the gas pressure infiltration furnace, so that the molten aluminum liquid penetrates into the gaps between the mixed powders through the graphite mold gate under pressure. The gas pressure infiltration furnace is kept hot and pressurized to control the interface reaction between aluminum and diamond; 5) stopping heating and cooling the mixture to room temperature in the furnace to obtain the diamond / aluminum composite material, wherein the volume fraction of diamond in the diamond / aluminum composite material is 10-70%.

2. The method for preparing the diamond / aluminum composite material according to claim 1, wherein: In step 2), the material of the aluminum block is selected from one of pure aluminum, aluminum-silicon alloy, 1050 aluminum alloy and 1100 aluminum alloy.

3. The method for preparing the diamond / aluminum composite material according to claim 2, wherein: In step 2), the mass of the aluminum block is 50-1000 g, and the volume of the aluminum block is 5-20 times the volume of the graphite mold.

4. The method for preparing the diamond / aluminum composite material according to claim 1, wherein: In step 2), the graphite mold is made of high-purity graphite, the diameter of the gate above the graphite mold is 3-10 mm, and the distribution density is 2-5 gates / cm 2 .

5. The method for preparing the diamond / aluminum composite material according to claim 1, wherein: In step 3), the pressure infiltration furnace is evacuated to a vacuum degree of ≤1 Pa, the aluminum block is heated at a rate of 10-50°C / min, the heating temperature is 600-1000°C, and the holding time is 5-60 minutes.

6. The method for preparing the diamond / aluminum composite material according to claim 1, wherein: In step 4), the inert gas is one of nitrogen and argon, the pressure of the pressure infiltration furnace after pressurization is 0.3-3 MPa, and the heat and pressure holding time is 5-60 minutes.

7. A device for implementing the method according to any one of claims 1 to 6, characterized in that: The device comprises a graphite mold, an aluminum block and a gas pressure infiltration furnace, wherein, The graphite mold is a fully enclosed structure with several gates on the top. The graphite mold is filled with aluminum powder and diamond powder. An aluminum block is placed on top of the graphite mold, and the graphite mold and the aluminum block are placed together in the furnace chamber of the gas pressure impregnation furnace; A heating resistance wire is provided on the upper part of the furnace chamber, and the heating resistance wire and the aluminum block are located at the same height.

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