Aluminum / carbon fiber / diamond composite material with bonding layer generated in situ under turbulent impact, heat sink and preparation method thereof

Abstract

The application discloses an aluminum / carbon fiber / diamond composite material with a bonding layer generated in situ under turbulent impact, a heat dissipation sheet and a preparation method thereof, and belongs to the technical field of composite material preparation. The aluminum / carbon fiber / diamond composite material is prepared by the following steps: an AlTiSi / carbon fiber master alloy is prepared by stirring casting; the master alloy is melted and infiltrated into a mold filled with diamonds to obtain a composite material heat dissipation sheet; and high and low temperature heat treatment is carried out under atmosphere protection to obtain the final aluminum / carbon fiber / diamond composite material heat dissipation sheet. Under the combined action of in-situ reaction and turbulent impact, the carbon fiber is completely dispersed to form a uniform and fine heat conduction network. In the heat conduction network formed by the carbon material, the large-size diamond is used as the main body, and the micron-scale carbon fiber network is uniformly distributed in the gap of the diamond network. After the joint addition of Ti and Si, the interface reaction of the composite material is sufficient, the interface thermal resistance is small, and the bonding strength is high. Through the adjustment of the particle size and proportion of the diamond and the carbon fiber, a combination with better thermal conductivity and expansion coefficient can be obtained.

Description

Technical Field

[0001] The present invention belongs to the field of novel composite materials, and relates to an aluminum / carbon fiber / diamond composite material with an in-situ generated bonding layer under turbulent impact, a heat sink, and a preparation method thereof. Background Art

[0002] The primary purpose of thermal management is to quickly dissipate the heat generated by semiconductor devices to ensure the proper functioning of core components. Thermal management generally employs a multi-stage heat dissipation model. The primary heat dissipation system requires not only a low thermal expansion coefficient that matches the chip in the direction parallel to the chip plane, but also high thermal conductivity in the direction perpendicular to the chip plane. A secondary heat dissipation system is then used to transfer the heat from the primary heat dissipation material to the air. Because secondary heat dissipation requires heat exchange with the air, a relatively large contact area is often required. Therefore, the density and heat dissipation capacity of the heat sink are equally important.

[0003] With the continuous development of 5G technology, the size of integrated circuit chips and electronic components in base station equipment continues to shrink, while power density is rapidly increasing. This leads to an increase in the heat generated by the equipment, and thermal diffusion becomes a pressing issue. Aluminum, with its advantages such as low price, low density, and corrosion resistance, is the preferred material for secondary heat dissipation systems. Carbon materials such as diamond, carbon fiber, carbon nanotubes, and graphene have thermal conductivity far exceeding that of conventional materials, and also have low linear expansion coefficients and low density. Currently, the thermal conductivity of aluminum-based composite materials is generally low (e.g., CN113802080A and CN103949613A), gradually failing to meet the urgent demand for high thermal conductivity in secondary heat dissipation systems. In addition, traditional aluminum alloy heat sinks are mainly assembled using a rolling and welding process, which has many processes and low production efficiency. If die-casting is used to achieve integrated molding, production efficiency will be greatly improved. However, how to balance the heat sink's thermal conductivity, density, and production efficiency is a major challenge facing current secondary heat dissipation systems.

[0004] Patent CN113444988A discloses a preparation method of a high thermal conductivity dual-carbon material reinforced aluminum-based composite material, which is first coated with a TiC coating on the surface of carbon fiber to prepare TiC-carbon fiber powder, coated with a TiC coating on the surface of diamond to prepare TiC-diamond powder, then the TiC-diamond powder is mixed with aluminum liquid to prepare an intermediate composite material, and finally the TiC-carbon fiber powder and the intermediate composite material are compounded by a gas pressure infiltration method to obtain a high thermal conductivity dual-carbon material reinforced aluminum-based composite material. In order to improve the interface bonding between aluminum and carbon, the carbon fiber and the diamond surface are coated with a TiC coating in advance. However, when the carbon fiber in this patent is coated with the TiC coating, since the carbon fiber is micron-sized and has a large surface area, agglomeration is inevitably likely to occur. When the carbon fiber surface is coated with the TiC coating, the inside of the agglomerate cannot be coated with TiC, and the surface modification effect is lost, thereby causing the carbon fiber to be unable to truly achieve uniform dispersion. Furthermore, the previously proposed TiC coating still leaves room for improvement in its bonding strength with the aluminum substrate. The aluminum substrate and TiC coating cannot form a chemical bond, preferring a physical bond. Furthermore, the morphology and size of the previously proposed TiC coating were not suitable for a perfect bond with the aluminum substrate. Therefore, the present invention was designed to further improve the dispersion of carbon fibers and the bonding strength of the aluminum-carbon interface, thereby facilitating phonon conduction. Summary of the Invention

[0005] To address the issues of insufficient thermal conductivity of existing aluminum-based materials and low heat sink production efficiency, the present invention provides an aluminum / carbon fiber / diamond composite material, a heat sink, and a method for preparing it, which features an in-situ bond layer formed under turbulent impact. This composite material significantly improves thermal conductivity, thereby meeting the growing heat dissipation needs of high-end chips.

[0006] The present invention provides an aluminum / carbon fiber / diamond composite material capable of in-situ generating a bonding layer under turbulent impact. The composite material comprises an AlTiSi alloy as a matrix, and a reinforcement composed mainly of large-scale diamond particles and supplemented by small-scale carbon fibers. The large-scale diamond particles are connected to form a diamond skeleton, and the small-scale carbon fibers are evenly and densely dispersed in the gaps of the diamond skeleton. The large-scale diamond particles and the small-scale carbon fibers are connected to form a dual-scale heat conduction network. Under turbulent impact, a bonding layer is in-situ formed at the junction of the aluminum matrix and the carbon fibers. The bonding layer is a bonding product of Ti, Si and C, and an in-situ bonding layer is also formed at the junction of the aluminum matrix and the diamond particles.

[0007] The present invention also provides a method for preparing an aluminum / carbon fiber / diamond composite material with an in-situ generated bonding layer under turbulent impact, comprising the following steps:

[0008] 1) Melt pure Al, AlTi master alloy, and AlSi master alloy at high temperature, and control the melt temperature at 1200-1500°C;

[0009] 2) A non-contact stirring casting process is used to prepare an AlTiSi / carbon fiber matrix composite material: after the alloying is complete, small-scale carbon fibers are added to the melt while stirring and cooling to 700-900°C, stirring is stopped, and then rapidly cooled to obtain an AlTiSi / carbon fiber matrix composite material; in this process, an in-situ reaction occurs at the interface between the carbon fibers and the aluminum matrix, and then a bonding layer is formed on the surface of the carbon fibers. Due to the small size of the carbon fibers, the surface area is large, and agglomerates are inevitably formed. However, under the turbulent impact formed by high-speed stirring, the agglomerates will be impacted by vortices of different sizes and thus broken, thereby undergoing an in-situ reaction at the new surface of the agglomerates, and then re-crushing and reacting are carried out until the agglomerates are completely broken, achieving uniform dispersion and uniform reaction;

[0010] 3) Select large-scale diamond particles, add a small amount of alcohol, mix them and place them into a graphite mold, which will accumulate to form a diamond skeleton;

[0011] 4) placing the graphite mold into an upper-opening integral mold, and placing the AlTiSi / carbon fiber matrix composite material into the upper end of the integral mold;

[0012] 5) First, evacuate the mold, then raise the temperature to 900-1500°C. The molten AlTiSi / carbon fiber matrix composite material will gradually fill the entire mold. Then, gas is introduced and a positive pressure of 5-15 MPa is maintained, or mechanical pressure is applied to infiltrate the molten blank into the gaps of the diamond skeleton. The mold is then cooled with the furnace to obtain the aluminum / carbon fiber / diamond composite material.

[0013] The present invention also provides a method for preparing a heat sink, which utilizes a preparation method of an aluminum / carbon fiber / diamond composite material that generates a bonding layer in situ under turbulent impact, adopts an atmosphere-protected rapid temperature rise and fall furnace for heat treatment, and heat treats the aluminum / carbon fiber / diamond composite material after demolding at 500 to 600 degrees Celsius for 4 to 6 hours under atmosphere protection, rapidly cools, then heat treats at 250 to 350 degrees Celsius for 1 to 5 hours, and cools with the furnace to obtain the heat sink.

[0014] Furthermore, the large-scale diamond particles have a particle size range of 50 to 800 microns and a volume fraction of 50% to 80%; the small-scale carbon fibers have a diameter of 2 to 20 microns, a length of 20 to 200 microns, and a volume fraction of 1% to 20%.

[0015] Furthermore, the Ti element content ranges from 0.2 to 3 wt.%, and the Si element content ranges from 0.2 to 2 wt.%.

[0016] Furthermore, the large-scale diamond particles have a particle size range of 100 to 150 microns, and the small-scale carbon fibers have a diameter of 5 to 10 microns and a length of 50 to 100 microns.

[0017] Furthermore, the Ti element content ranges from 0.4 to 1 wt.%, and the Si element content ranges from 0.4 to 1 wt.%.

[0018] The method of the present invention is also applicable to the preparation of metal-based composite materials such as copper alloys and magnesium alloys.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are:

[0020] (1) Under the combined action of in-situ reaction and turbulent impact, the carbon fibers are completely broken up to form a uniform and fine heat-conducting network. Due to the small size of the carbon fibers, the surface area is large, and agglomerates are inevitably formed. However, under the turbulent impact formed by high-speed stirring, the agglomerates are impacted by vortices of different sizes and broken up, and then in-situ reaction is carried out on the new surface of the agglomerates. This process is repeated until the agglomerates are completely broken up, achieving uniform dispersion and uniform reaction.

[0021] (2) The interfacial bonding strength formed by the in-situ reaction is higher than the bonding strength between the pre-provided TiC coating and the aluminum substrate. In the present application, a bonding layer, such as a TiC or SiC layer, is formed by in-situ reaction during the stirring casting process. The layer is chemically bonded to the aluminum substrate. Compared with the pre-provided TiC coating, the aluminum substrate and the TiC coating cannot form a chemical bond-level bond, but tend to form a physical bond. In addition, the in-situ reaction can control the size and morphology of the generated bonding layer, forming a thin and uniform bonding layer on the surface of the carbon material, while the directly added titanium carbide layer is difficult to control the morphology of the carbide formed on the surface of the carbon material.

[0022] (3) Carbon materials of different scales work together to build a multi-scale, efficient thermal conductivity network. In the thermal conductivity network formed by carbon materials, large-sized diamonds are the main body, and the gaps in the diamond network are evenly distributed micron-scale carbon fiber networks. Experimental results show that the new composite material has a high thermal conductivity, which can reach about 600 to 900 W / (m·K). In addition, by adjusting the particle size and proportion of diamonds and the proportion of carbon fibers, the expansion coefficient of the resulting composite material can be effectively adjusted to make it closer to the expansion coefficient of the primary heat dissipation system. The composite material has low density, high thermal conductivity, and an adjustable expansion coefficient.

[0023] (4) The interface reaction is sufficient, the interface thermal resistance is small, the bonding strength is high, and the thermal conductivity loss after high and low temperature impact is small. The joint addition of Ti and Si is used to achieve the connection at the aluminum-carbon interface. Ti and Si elements will react with the surface carbon atoms of diamond and carbon fiber during the stirring, infiltration process and high-temperature heat treatment process to form a carbide layer of a certain thickness on the surface of the carbon material. This transition layer can greatly improve the bonding strength of the aluminum-carbon interface on the one hand, and on the other hand, it is also beneficial to the conduction of phonons. The joint addition of Ti and Si is conducive to the control of the thickness and uniformity of this interface layer, thereby achieving a series of advantages such as low interface thermal resistance, high interface bonding strength, and resistance to high and low temperature impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the morphology of the original carbon fiber powder described in the present invention.

[0025] Figure 2 This is the morphology of the original diamond powder described in the present invention.

[0026] Figure 3 This is a fracture picture of the final aluminum / carbon fiber / diamond composite material described in the present invention.

[0027] Figure 4 This is the elemental spectrum result of the final aluminum / carbon fiber / diamond composite material described in the present invention. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] Example 1

[0030] The present invention provides an aluminum / carbon fiber / diamond composite material with an in-situ bonded layer formed under turbulent impact, a heat sink, and a preparation method thereof, comprising the following steps:

[0031] Firstly, AlTiSi / carbon fiber master alloy was prepared by non-contact stirring casting process;

[0032] 1) Pure Al, AlTi master alloy, and AlSi master alloy are melted at a high temperature of 1200 degrees Celsius and cast to obtain an Al-1Ti-0.5Si master alloy;

[0033] 2) Stirring speed is 1500rpm, wait for 5vol.% content of carbon fiber (such as Figure 1As shown, the average diameter of the carbon fibers is 10 microns and the length is 200 microns). After sufficient stirring, the melt is rapidly cooled to 700 degrees Celsius, stirring is stopped, and the ingot is allowed to cool rapidly to obtain an AlTiSi master alloy.

[0034] Secondly, a vacuum pressure furnace is used to melt the AlTiSi / carbon fiber master alloy and infiltrate it into the diamond skeleton. The specific steps are as follows:

[0035] 1) Diamond particles with an average particle size of 500 microns and a content of 50 vol.% (such as Figure 2 As shown in the figure, the diamonds are placed into a graphite mold of the desired thickness, and the diamonds are accumulated to form a loose skeleton.

[0036] 2) Place the above mold into an upper-opening integral mold, and place the AlTiSi / carbon fiber master alloy into the upper end of the upper-opening integral mold;

[0037] 3) First, evacuate the chamber, then heat it to 1200 degrees Celsius. The molten preform will gradually fill the upper opening of the mold. Then, gas is introduced and the positive pressure is maintained at 15 MPa. The molten preform will penetrate into the gaps of the diamond skeleton and cool with the furnace.

[0038] Finally, the composite material after demoulding was heated to 500 degrees Celsius for 5 hours, and then rapidly cooled; then heated to 300 degrees Celsius for 2 hours, and then cooled in the furnace to obtain the desired composite material (such as Figure 3 The final composite material fracture picture is shown. Figure 4 (The results of the elemental energy spectrum of carbides on the diamond surface on the fracture surface).

[0039] Its performance data is shown in Table 1.

[0040] Table 1 Performance data of aluminum-carbon composite material in Example 1

[0041]

[0042] Example 2

[0043] The present invention provides an aluminum / carbon fiber / diamond composite material with an in-situ bonded layer formed under turbulent impact, a heat sink, and a preparation method thereof, comprising the following steps:

[0044] Firstly, AlTiSi / carbon fiber master alloy was prepared by stir casting process;

[0045] 1) Pure Al, AlTi master alloy, and AlSi master alloy are melted at a high temperature of 950 degrees Celsius and cast to obtain an Al-1.2Ti-0.6Si master alloy;

[0046] 2) After stirring at a speed of 2000 rpm and fully stirring a 10 vol.% carbon fiber (with an average carbon fiber diameter of 10 μm and a length of 200 μm), the melt was rapidly cooled to 700°C. Stirring was stopped and the ingot was allowed to cool rapidly to obtain an AlTiSi / carbon fiber master alloy.

[0047] Secondly, a vacuum pressure furnace is used to melt the AlTiSi / carbon fiber master alloy and infiltrate it into the diamond skeleton. The specific steps are as follows:

[0048] 1) Place diamond particles with an average particle size of 120 microns and a content of 70 vol.% into a graphite mold of the desired thickness. The diamonds will accumulate to form a loose skeleton.

[0049] 2) Place the above mold into an upper-opening integral mold, and place the AlTiSi / carbon fiber master alloy into the upper end of the upper-opening integral mold;

[0050] 3) First, evacuate the chamber, then heat it to 1400 degrees Celsius. The molten preform will gradually fill the upper opening of the mold. Then, gas is introduced and the positive pressure is maintained at 15 MPa. The molten preform will penetrate into the gaps of the diamond skeleton and cool with the furnace.

[0051] Finally, an argon-protected rapid temperature rise and fall furnace was used for high and low temperature heat treatment. The demolded composite material was heated to 500 degrees Celsius for 5 hours, and then quickly cooled; then heated to 300 degrees Celsius and kept warm for 2 hours, and cooled with the furnace to obtain the desired composite material.

[0052] Its performance data is shown in Table 2.

[0053] Table 2 Performance data of aluminum-carbon composite material in Example 2

[0054]

[0055]

[0056] Comparative Example 1

[0057] The comparative example of the present invention provides an aluminum-carbon composite material and a preparation method thereof, comprising the following steps:

[0058] Firstly, AlTi / carbon fiber master alloy was prepared by stir casting process;

[0059] 1) Pure Al and AlTi master alloys are melted at a high temperature of 950 degrees Celsius and cast to obtain Al-1.2Ti master alloy;

[0060] 2) After stirring at a speed of 2000 rpm and fully stirring the 10 vol.% carbon fiber (with an average carbon fiber diameter of 10 μm and a length of 200 μm), the melt was rapidly cooled to 700°C. Stirring was stopped and the ingot was allowed to cool rapidly to obtain an AlTi / carbon fiber master alloy.

[0061] Secondly, a vacuum pressure furnace is used to melt the AlTi / carbon fiber master alloy and infiltrate it into the diamond skeleton. The specific steps are as follows:

[0062] 1) Place diamond particles with an average particle size of 120 microns and a content of 70 vol.% into a graphite mold of the desired thickness. The diamonds will accumulate to form a loose skeleton.

[0063] 2) Place the above mold into an upper-opening integral mold, and place the AlTi / carbon fiber master alloy into the upper end of the upper-opening integral mold;

[0064] 3) First, evacuate the chamber, then heat it to 1500 degrees Celsius. The molten preform will gradually fill the upper opening of the mold. Then, gas is introduced and the positive pressure is maintained at 15 MPa. The molten preform will penetrate into the gaps of the diamond skeleton and cool with the furnace.

[0065] Finally, an argon-protected rapid temperature rise and fall furnace was used for high and low temperature heat treatment. The demolded composite material was heated to 500 degrees Celsius for 5 hours, and then quickly cooled; then heated to 300 degrees Celsius and kept warm for 2 hours, and cooled with the furnace to obtain the desired composite material.

[0066] Its performance data is shown in Table 3.

[0067] Table 3 Performance data of aluminum-carbon composite material in comparative example 1

[0068]

[0069] From the comparative data, it can be seen that adding only the alloy element Ti cannot achieve high thermal conductivity, and the thermal conductivity of the material decreases significantly after the hot and cold cycle test. Since the bonding strength between the matrix and carbon is not as good as the effect after the combined addition of Ti and Si, the expansion coefficient is increased.

[0070] The embodiments of the present invention are described in detail, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and spirit of the present invention are still within the scope of protection of the present invention.

Claims

1. An aluminum / carbon fiber / diamond composite material with an in-situ generated bonding layer under turbulent impact, characterized in that: The invention adopts an AlTiSi alloy as a matrix, and a reinforcement mainly composed of large-scale diamond particles and supplemented by small-scale carbon fibers. The large-scale diamond particles are connected to form a diamond skeleton, and the small-scale carbon fibers are evenly and densely dispersed in the gaps of the diamond skeleton. The large-scale diamond particles and the small-scale carbon fibers are connected to form a dual-scale heat conduction network. The large-scale diamond particles have a particle size range of 50 to 800 microns and a volume fraction of 50% to 80%. The small-scale carbon fibers have a diameter of 2 to 20 microns, a length of 20 to 200 microns, and a volume fraction of 1% to 20%. The Ti content of the AlTiSi alloy ranges from 0.2 to 3 wt.%, and the Si content ranges from 0.2 to 2 wt.%. The composite material forms an in-situ bonding layer at the junction of the aluminum matrix and the carbon fibers under the turbulent impact of high-speed stirring of the melt during the preparation process. The bonding layer is a bonding product of Ti, Si and C, and an in-situ bonding layer is also formed at the junction of the aluminum matrix and the diamond particles.

2. The method for preparing an aluminum / carbon fiber / diamond composite material with an in-situ generated bonding layer under turbulent impact according to claim 1, characterized in that: The following steps are involved: 1) Melt pure Al, AlTi master alloy, and AlSi master alloy at high temperature, and control the melt temperature at 1200-1500°C; 2) The AlTiSi / carbon fiber matrix composite was prepared by a non-contact stirring casting process: after alloying was complete, small-scale carbon fibers were added to the melt while stirring and cooling to 700-900°C. Stirring was stopped, and then the melt was rapidly cooled to obtain the AlTiSi / carbon fiber matrix composite. In this process, an in-situ reaction occurs at the interface between the carbon fiber and the aluminum matrix, and then a bonding layer is formed on the surface of the carbon fiber. Due to the small size of the carbon fiber, the surface area is large, and agglomerates are inevitably formed. However, under the turbulent impact formed by high-speed stirring, the agglomerates will be impacted by vortices of different sizes and broken up, so that an in-situ reaction occurs on the new surface of the agglomerate. This process is repeated until the agglomerate is completely broken and uniform dispersion and uniform reaction are achieved. 3) Select large-scale diamond particles, add a small amount of alcohol, mix them and place them into a graphite mold, which will accumulate to form a diamond skeleton; 4) placing the graphite mold into an upper-opening integral mold, and placing the AlTiSi / carbon fiber matrix composite material into the upper end of the integral mold; 5) First, evacuate the mold, then raise the temperature to 900-1500°C. The molten AlTiSi / carbon fiber matrix composite material will gradually fill the entire mold. Then, gas is introduced and a positive pressure of 5-15 MPa is maintained, or mechanical pressure is applied to infiltrate the molten blank into the gaps of the diamond skeleton. The mold is then cooled with the furnace to obtain the aluminum / carbon fiber / diamond composite material.

3. A method for preparing a heat sink, using the method for preparing an aluminum / carbon fiber / diamond composite material with an in-situ generated bonding layer under turbulent impact according to claim 2, characterized in that: The aluminum / carbon fiber / diamond composite material after demoulding is heat treated in an atmosphere-protected rapid heating and cooling furnace, and is heat treated at 500-600 degrees Celsius for 4-6 hours under atmosphere protection, and then rapidly cooled and heat treated at 250-350 degrees Celsius for 1-5 hours, and then cooled in the furnace to obtain the heat sink.

4. The method for preparing an aluminum / carbon fiber / diamond composite material with an in-situ generated bonding layer under turbulent impact according to claim 2, characterized in that: The large-scale diamond particles have a particle size range of 100 to 150 microns, and the small-scale carbon fibers have a diameter of 5 to 10 microns and a length of 50 to 100 microns.

5. The method for preparing an aluminum / carbon fiber / diamond composite material with an in-situ generated bonding layer under turbulent impact according to claim 2, characterized in that: The Ti element content ranges from 0.4 to 1 wt.%, and the Si element content ranges from 0.4 to 1 wt.%.

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