A continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material and a preparation method thereof

Abstract

This invention provides a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material and its preparation method, comprising the following steps: pre-treating mesophase pitch-based carbon fibers by graphitization, placing them above a mixture of silicon powder and silica powder, and heating them at 1400-1600℃ for 1-2 minutes under negative pressure and an inert atmosphere to obtain modified carbon fiber bundles containing a continuous SiC interface layer; placing them in a volume-adjustable fixture for compression molding to obtain a oriented carbon fiber preform; and performing vacuum pressure infiltration treatment using molten aluminum or molten aluminum alloy to obtain the continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material. This invention achieves interface structure optimization, thorough aluminum infiltration, and continuous thermally conductive network construction through ultra-short-time gas-phase in-situ reaction, oriented preform molding, and vacuum pressure infiltration processes. The resulting aluminum-based composite material possesses high thermal conductivity, low thermal expansion, and high mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of metal matrix composites, specifically to a continuous SiC interface layer carbon fiber aluminum matrix high thermal conductivity composite material and its preparation method. Background Technology

[0002] With the rapid development of 5G communication, high-performance computing chips, new energy vehicles, and aerospace equipment towards high power density, miniaturization, and lightweighting, efficient thermal management has become a key bottleneck restricting system reliability and service life. The requirements for heat dissipation materials in the electronic packaging field are becoming increasingly stringent: on the one hand, they need to have high thermal conductivity to quickly dissipate heat from the chip; on the other hand, they need to have a low coefficient of thermal expansion that matches semiconductor materials (silicon approximately 4.2 ppm / K, gallium arsenide approximately 5.9 ppm / K) to avoid packaging failure due to thermal cycling stress. Aluminum-based thermal management composite materials, with their low density (2.7 g / cm³), offer a solution. 3 With its high thermal conductivity (approximately 1 / 3 that of copper), high thermal conductivity (pure aluminum is approximately 237 W / (m·K)), and good processing performance, aluminum is considered an ideal lightweight solution to replace traditional high-density copper-based heat dissipation.

[0003] Mesophase pitch-based carbon fibers, due to their highly oriented graphite microcrystalline structure arranged along the fiber axis, exhibit near-non-scattering axial phonon conduction with high efficiency, achieving an axial thermal conductivity of 300–1000 W / (m·K). Furthermore, they possess extremely low thermal expansion coefficients (-1–2 ppm / K), combining low density with high specific modulus, making them ideal reinforcements for lightweight, high-thermal-conductivity, and low-thermal-expansion aluminum-based composites. However, the composite of mesophase pitch-based carbon fibers with an aluminum matrix faces three major technical challenges: First, extremely poor interfacial wettability. The carbon fiber surface is chemically inert, resulting in a large wetting angle (>90°) with molten aluminum. This makes it difficult for molten aluminum to spontaneously penetrate the fiber bundle gaps, leading to high porosity and insufficient interfacial physical contact in the composite material, resulting in extremely high interfacial thermal resistance and severely limiting thermal conductivity. Second, harmful interfacial reactions are difficult to suppress. During high-temperature composite processes, carbon fibers and the aluminum matrix are prone to interfacial reactions, generating a brittle Al₄C₃ phase. This phase not only has poor thermal conductivity, but also forms stress concentration sources at the interface, significantly deteriorating the mechanical strength and long-term service reliability of the composite material. Thirdly, fiber dispersion and orientation control are difficult. Carbon fibers are prone to agglomeration in the matrix, making it difficult to achieve uniform dispersion; at the same time, fiber orientation directly affects the anisotropic characteristics of thermal conductivity. Without effective means of controlling the directional arrangement, the advantage of the ultra-high axial thermal conductivity of the fibers cannot be fully utilized.

[0004] To address the aforementioned issues, several solutions have been proposed in existing technologies. For example, electroless copper plating can be used to metallize the surface of carbon fibers, but this process is complex, costly, and the interface compatibility between copper and aluminum still needs improvement. A SiC coating can be obtained by coating a SiC precursor onto the fiber surface using the sol-gel method followed by high-temperature heat treatment, but this method is time-consuming, coating uniformity is difficult to guarantee, and repeated heat treatments can easily damage the fiber structure. While chemical vapor deposition (CVD) (such as patent CN119663251A) can deposit a SiC interface layer on the carbon fiber surface, CVD equipment is expensive, deposition rates are low, and the process cycle is long (several hours to over ten hours). Furthermore, it requires an organosilicon source (such as CH3SiCl3), and the reaction process generates corrosive exhaust gases, making it unsuitable for large-scale production.

[0005] Therefore, there is an urgent need to develop a preparation method that can efficiently construct a continuous and dense SiC interface layer in an ultra-short time, maintain the structural integrity of carbon fibers, and simultaneously achieve fiber orientation and full infiltration of aluminum liquid, so as to achieve a synergistic improvement in the thermal conductivity, mechanical properties and thermal expansion properties of mesophase pitch-based carbon fiber reinforced aluminum matrix composites. Summary of the Invention

[0006] In view of the technical problems existing in the background art, the present invention provides a continuous SiC interface layer carbon fiber aluminum matrix high thermal conductivity composite material and its preparation method, aiming to solve the technical problems of poor wettability of the interface between mesophase pitch-based carbon fiber and aluminum matrix, difficulty in suppressing harmful interface reactions, difficulty in controlling fiber dispersion and orientation, and poor thermal conductivity, mechanical and thermal expansion properties of aluminum matrix composite materials caused by the long reaction time and easy damage to fiber structure in the existing SiC coating preparation method.

[0007] In a first aspect, the present invention provides a method for preparing a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material, comprising the following steps: S1. Pre-treatment of mesophase pitch-based carbon fibers by graphitization to obtain carbon fiber bundles. S2. Place the carbon fiber bundle above the silicon source powder, without direct contact between the carbon fiber bundle and the silicon source powder, and carry out the heating reaction under negative pressure and inert atmosphere to obtain modified carbon fiber bundle containing a continuous SiC interface layer; the heating reaction conditions are: 1400~1600℃ for 1~2 minutes; the silicon source powder is a mixture of silicon powder and silicon dioxide powder. S3. The modified carbon fiber bundles are placed in a volume-adjustable fixture and compressed to obtain a oriented carbon fiber preform. S4. Vacuum pressure impregnation of carbon fiber preforms is performed using molten aluminum or molten aluminum alloy, and after cooling, a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material is obtained.

[0008] Preferably, in step S1, the graphitization pretreatment specifically involves: graphitizing the mesophase pitch-based carbon fiber at a temperature of 2500~3000℃ and then cutting it to a fixed length.

[0009] Preferably, in step S1, the axial thermal conductivity of the mesophase pitch-based continuous carbon fiber is ≥900 W / (m·K).

[0010] Preferably, in step S2, the molar ratio of silicon powder to silicon dioxide is 1:1.

[0011] Preferably, in step S2, the negative pressure is a vacuum degree <10 Pa; the inert atmosphere is argon or nitrogen; and the heating rate of the heating reaction is 5~10℃ / min.

[0012] Preferably, in step S3, the volume fraction of modified carbon fiber in the carbon fiber preform is 20 vol.%~60 vol.%.

[0013] Preferably, in step S3, the volume fraction of modified carbon fiber in the carbon fiber preform is 40 vol.%~60 vol.%.

[0014] Preferably, in step S4, the conditions for vacuum pressure impregnation are: temperature of 720~780℃, pressure of 5~15MPa, and heat and pressure holding for 2~10 minutes.

[0015] Preferably, in step S4, the aluminum alloy includes 6063 aluminum alloy.

[0016] In a second aspect, the present invention provides a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material, which is prepared by the preparation method described in the first aspect.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a method for preparing a continuous SiC interface layer carbon fiber aluminum matrix high thermal conductivity composite material. Through an in-situ SiO gas-phase reaction process, a continuous and dense SiC interface layer is constructed on the carbon fiber surface in an ultra-short time while maintaining the integrity of the carbon fiber graphite structure. This effectively solves the problems of poor interfacial wettability between carbon fibers and the aluminum matrix and the formation of harmful Al4C3 phase. Furthermore, by compressing carbon fiber bundles to construct oriented carbon fiber preforms and using a vacuum pressure impregnation process, highly oriented continuous thermally conductive skeletons are formed within the aluminum matrix composite material. Through the synergistic control of these three core processes, the interface structure, fiber orientation, and aluminum liquid impregnation state are simultaneously optimized. The continuous SiC interface layer carbon fiber aluminum matrix high thermal conductivity composite material prepared by the method of this invention possesses high axial thermal conductivity, low coefficient of thermal expansion, and excellent mechanical properties. Attached Figure Description

[0018] Figure 1This is a schematic diagram of the process flow for the preparation method of the continuous SiC interface layer carbon fiber aluminum matrix high thermal conductivity composite material in Embodiment 1 of the present invention. Figure 2 These are scanning electron microscope images of the modified carbon fiber bundles in Examples 2, 2, and 3 of the present invention, where (a) series is Example 2, (b) series is Comparative Example 2, and (c) is Comparative Example 3. Figure 3 The images are scanning electron microscope (SEM) images of the cross sections of aluminum-based composite materials prepared under different gas-phase in-situ reaction times according to the present invention, wherein (a) series is Comparative Example 1, (b) series is Example 2, (c) series is Comparative Example 2, and (d) series is Comparative Example 3. Figure 4 Scanning electron microscope (SEM) images of cross sections of aluminum matrix composites prepared with different fiber volume fractions, wherein (a) series is Example 4, (b) series is Example 2, (c) series is Example 3, and (d) series is Example 1; Figure 5 The XRD patterns of the modified carbon fiber bundles in Examples 2, 2, and 3 of this invention are shown. Detailed Implementation

[0019] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0020] To address the technical problems of poor interfacial wettability between mesophase pitch-based carbon fibers and aluminum matrices, difficulty in suppressing harmful interfacial reactions, challenges in controlling fiber dispersion and orientation, and the long reaction time and easy damage to fiber structure in existing SiC coating preparation methods, resulting in poor thermal conductivity, mechanical properties, and thermal expansion properties of aluminum-based composite materials, this invention provides a continuous SiC interfacial layer carbon fiber aluminum-based high thermal conductivity composite material and its preparation method. Specifically, a continuous and dense SiC interfacial layer is efficiently constructed by ultra-short-time in-situ SiO gas-phase reaction while maintaining the integrity of the carbon fiber-graphite structure. Combined with the synergistic control of the volume fraction of oriented carbon fiber preforms and the vacuum pressure impregnation process, interface structure optimization, sufficient aluminum liquid impregnation, and the construction of a continuous thermally conductive network are achieved.

[0021] In a first aspect, embodiments of the present invention provide a method for preparing a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material, comprising the following steps: S1. Pre-treatment of mesophase pitch-based carbon fibers by graphitization to obtain carbon fiber bundles. S2. Place the carbon fiber bundle above the silicon source powder, without direct contact between the carbon fiber bundle and the silicon source powder, and carry out the heating reaction under negative pressure and inert atmosphere to obtain modified carbon fiber bundle containing a continuous SiC interface layer; the heating reaction conditions are: 1400~1600℃ for 1~2 minutes; the silicon source powder is a mixture of silicon powder and silicon dioxide powder. S3. The modified carbon fiber bundles are placed in a volume-adjustable fixture and compressed to obtain a oriented carbon fiber preform. S4. Vacuum pressure impregnation of carbon fiber preforms is performed using molten aluminum or molten aluminum alloy, and after cooling, a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material is obtained.

[0022] In the technical solution of this invention embodiment, the present invention efficiently constructs a continuous and dense SiC interface layer by ultra-short time (1~2 minutes) SiO gas phase in-situ reaction, while maintaining the integrity of the carbon fiber graphite structure. This effectively solves the problem of fiber structure damage caused by excessively long reaction time in traditional methods. At the same time, the SiC interface layer significantly improves the wettability of aluminum liquid on carbon fibers, ensuring the quality of interface bonding. The continuous SiC interface layer, as a physical and chemical dual barrier layer, inhibits the formation of brittle Al4C3 phase from the root. By combining the synergistic control of directional preform molding and vacuum pressure impregnation process, the interface structure is optimized, the aluminum liquid is fully impregnated, and a continuous thermally conductive network is constructed. The final aluminum-based composite material has excellent thermal conductivity, mechanical properties, and low thermal expansion properties.

[0023] The principle of constructing a continuous and dense SiC interface layer through ultrashort-time in-situ SiO vapor-phase reaction is as follows: At high temperatures, silicon powder undergoes a silicothermic reduction reaction with silicon dioxide to generate gaseous silicon monoxide (SiO): Si(s) + SiO2(s) = 2SiO(g). The generated SiO gas diffuses to the surface of carbon fibers and undergoes a gas-solid in-situ reaction with the active carbon atoms on the carbon fiber surface: SiO(g) + 2C(s) = SiC(s) + CO(g), forming a continuous and dense SiC interface layer in situ on the carbon fiber surface. Within the temperature range of 1400~1600℃, the generation rate of SiO gas is extremely high, and the partial pressure of SiO gas rapidly reaches a supersaturated state, achieving explosive nucleation at the active sites on the carbon fiber surface. At the same time, due to the highly oriented graphite microcrystalline structure on the carbon fiber surface, the active carbon atoms are densely distributed at the edge sites, providing sufficient reaction sites for the adsorption and reaction of SiO gas. Under the aforementioned temperature conditions, the growth rate of the reaction (SiO + 2C → SiC + CO) can reach 0.2~0.5 μm / min, thus forming a continuous and dense SiC interface layer of 0.2~1 μm within 1~2 minutes. Compared to the reaction time of several hours to more than ten hours in the existing CVD method, the efficiency is improved by more than two orders of magnitude. More importantly, this ultra-short-time high-temperature treatment can avoid significant thermal damage to the carbon fiber graphite structure, ensuring the inherent high thermal conductivity of the fiber.

[0024] Furthermore, in some embodiments, in step S1, the graphitization pretreatment specifically involves: graphitizing the mesophase pitch-based carbon fiber at a temperature of 2500~3000℃ and then cutting it to a fixed length.

[0025] In the technical solution of this invention, graphitization pretreatment can improve the orientation degree of carbon fiber microcrystals, enhance its intrinsic thermal conductivity, and expose more active sites, providing a highly reactive surface for subsequent in-situ SiO vapor-phase reaction and promoting uniform nucleation and dense growth of the SiC interface layer. Simultaneously, cutting the fibers to a fixed length facilitates subsequent directional alignment and compression molding in the fixture. This invention does not impose a specific limitation on the cutting length, which can be adjusted according to the fixture specifications; a cutting length of 5-10 cm is recommended.

[0026] Furthermore, in some embodiments, in step S1, the axial thermal conductivity of the mesophase pitch-based continuous carbon fiber is ≥900 W / (m·K).

[0027] Furthermore, in some embodiments, in step S2, the molar ratio of silicon powder to silicon dioxide is 1:1.

[0028] Furthermore, in some embodiments, in step S2, the negative pressure is a vacuum of <10 Pa; the inert atmosphere is argon or nitrogen; and the heating rate of the heating reaction is 5~10℃ / min.

[0029] Furthermore, in some embodiments, in step S3, the volume fraction of modified carbon fiber in the carbon fiber preform is 20 vol.% to 60 vol.%.

[0030] In the technical solution of this invention, the volume fraction of modified carbon fiber in the carbon fiber preform directly affects the thermal conductivity, thermal expansion behavior, and mechanical properties of the composite material. When the volume fraction is too low, the fiber spacing is large, making it difficult to form an effective continuous thermally conductive network. Conversely, when the volume fraction is too high, the fiber packing density is too high, making it difficult for the molten aluminum to fully fill the fiber gaps, easily leading to porosity defects, which in turn affect the thermal conductivity and mechanical properties. Through extensive experiments, this invention has found that within the range of 20–60 vol.%, as the volume fraction increases, the axial thermal conductivity increases, the coefficient of thermal expansion continuously decreases, and the flexural strength increases simultaneously. Among these, 40–60 vol.% is the preferred range for synergistic performance optimization, achieving the optimal match between thermal conductivity, mechanical properties, and low thermal expansion performance.

[0031] In this invention, the adjustable clamp in step S3 is not specifically limited, as long as it can achieve the compression molding of carbon fiber bundles and precise control of their packing density. In some embodiments of this invention, the adjustable clamp is a clamp structure composed of upper and lower graphite plates and four corner connecting bolts. The height of the inner cavity is controlled by adjusting the tightness of the bolts, thereby controlling the carbon fiber volume fraction of the carbon fiber preform in real time.

[0032] Furthermore, in some embodiments, in step S3, the volume fraction of modified carbon fiber in the carbon fiber preform is 40 vol.% to 60 vol.%.

[0033] Furthermore, in some embodiments, in step S4, the conditions for vacuum pressure impregnation are: temperature of 720~780℃, pressure of 5~15 MPa, and holding at temperature and pressure for 2~10 minutes.

[0034] Furthermore, in some embodiments, in step S4, the aluminum alloy includes 6063 aluminum alloy.

[0035] Secondly, embodiments of the present invention provide a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material, which is prepared by the preparation method described in the first aspect.

[0036] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0037] Example 1 Figure 1 The schematic diagram shows the process flow for preparing a continuous SiC interface layer carbon fiber aluminum matrix high thermal conductivity composite material. (See attached diagram.) Figure 1 A method for preparing a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material, the specific steps of which are as follows: (1) After the mesophase pitch-based carbon fiber is graphitized at 3000 ℃ (single filament diameter 10 μm, axial thermal conductivity ≥900 W / (m·K)), it is cut to a length of 8 cm to obtain the pretreated carbon fiber bundle.

[0038] (2) Construction of a continuous SiC interface layer by ultrashort-time gas-phase in-situ reaction: The pretreated carbon fiber bundles were placed on the upper part of a graphite crucible (about 3-5 cm from the bottom); a mixture of silicon powder and silica powder (molar ratio 1:1, total mass about 50 g) was placed at the bottom of the crucible. The crucible was placed in a vacuum tube furnace, and after evacuation to a vacuum degree <10 Pa, argon gas (flow rate 100 mL / min) was introduced for protection. The temperature was increased to 1500℃ at 10℃ / min, held for 1 minute, and then naturally cooled to obtain modified carbon fiber bundles containing a continuous SiC interface layer. The obtained carbon fiber surface was uniformly coated with a grayish-white continuous SiC interface layer. SEM observation showed that the interface layer was continuous, dense, and crack-free. XRD analysis confirmed that the interface layer was of the β-SiC crystal form and had no other impurity phases.

[0039] (3) Construction and volume fraction control of oriented carbon fiber preforms: Modified carbon fiber bundles containing a continuous SiC interface layer are uniformly laid in a graphite plate fixture, which consists of an upper graphite plate, a lower graphite plate, and four corner connecting bolts. The fiber bundle accumulation volume is compressed by tightening the bolts, and the volume of the fixture cavity and the fiber mass are measured in real time. The fiber volume fraction is calculated to the target value of 60 vol.%, resulting in an oriented carbon fiber preform.

[0040] (4) Preparation of composite materials by vacuum pressure infiltration: The graphite plate fixture containing the preform is placed in a graphite mold, and the graphite mold is placed in a vacuum pressure infiltration furnace. 6063 aluminum alloy is heated to 750°C in an independent crucible until completely melted. After preheating the graphite mold to 750°C, the molten aluminum is poured into the mold cavity, and a pressure of 10 MPa is quickly applied and held for 5 minutes. After the pressure holding is completed, the pressure is released, and the furnace is cooled to room temperature. The aluminum-based composite material is then demolded to obtain the composite material.

[0041] Example 2 The difference between this embodiment and embodiment 1 is that the fiber volume fraction in step (3) is 30 vol.%, and the parameters of the other steps are the same as those in embodiment 1.

[0042] Example 3 The difference between this embodiment and embodiment 1 is that the fiber volume fraction in step (3) is 40 vol.%, and the parameters of the other steps are the same as those in embodiment 1.

[0043] Example 4 The difference between this embodiment and embodiment 1 is that the fiber volume fraction in step (3) is 20 vol.%, and the parameters of the other steps are the same as those in embodiment 1.

[0044] Comparative Example 1 The difference between this comparative example and Example 2 is that it uses mesophase pitch-based carbon fibers without SiC interface layer treatment, and the fiber volume fraction is adjusted to 30 vol.% using a graphite plate clamp for direct vacuum pressure impregnation of aluminum; the specific steps are as follows: (1) The graphitized pretreated mesophase pitch-based carbon fiber bundles are evenly laid in a graphite plate clamp. The clamp consists of an upper graphite plate, a lower graphite plate, and four corner connecting bolts. The fiber bundle accumulation volume is compressed by tightening the bolts. The volume of the clamp cavity and the fiber mass are measured in real time. The fiber volume fraction is calculated to the target value of 30 vol.%, and a directional carbon fiber preform is obtained.

[0045] (2) Preparation of composite materials by vacuum pressure infiltration: The graphite plate fixture containing the preform is placed in a graphite mold, and the graphite mold is placed in a vacuum pressure infiltration furnace. 6063 aluminum alloy is heated to 750°C in an independent crucible until completely melted. After preheating the graphite mold to 750°C, the molten aluminum is poured into the mold cavity, and a pressure of 10 MPa is quickly applied and held for 5 minutes. After the pressure holding is completed, the pressure is released, and the furnace is cooled to room temperature. The aluminum-based composite material is then demolded to obtain the composite material.

[0046] Comparative Example 2 The difference between this comparative example and Example 2 is that the holding time at 1500°C during the in-situ gas phase reaction in step (2) is adjusted to 15 minutes, while the other process parameters are the same as in Example 1.

[0047] Comparative Example 3 The difference between this comparative example and Example 2 is that the holding time at 1500℃ during the in-situ gas phase reaction in step (2) is adjusted to 30 minutes, while the other process parameters are the same as in Example 1.

[0048] Performance testing The performance of the aluminum-based composite materials prepared in each embodiment and comparative example was tested using the following methods: thermal conductivity was determined by laser scintillation (LFA 457), coefficient of thermal expansion (CTE) was determined by thermomechanical analyzer (DIL 402C), flexural strength was determined by universal testing machine, and density was determined by Archimedes' drainage method.

[0049] The test results are shown in Table 1 below.

[0050] Table 1

[0051] Figure 2 These are scanning electron microscope (SEM) images of the modified carbon fiber bundles in Examples 2, 2, and 3 of this invention, where (a) series represents Example 2, (b) series represents Comparative Example 2, and (c) series represents Comparative Example 3. In Example 2, the in-situ gas-phase reaction was carried out for 1 minute. SEM observation showed that the SiC interface layer of the obtained modified carbon fiber bundles was continuous, dense, and uniformly coated on the fiber surface. In Comparative Example 2, the in-situ gas-phase reaction was carried out for 15 minutes. SEM observation showed that the SiC interface layer of the obtained modified carbon fiber bundles was continuous but significantly thicker (approximately 1.75 μm), with cracks appearing on some fiber surfaces, indicating damage to the internal structure of the fibers. In Comparative Example 2, the in-situ gas-phase reaction was carried out for 30 minutes. SEM observation showed that the SiC interface layer of the obtained modified carbon fiber bundles had penetrated into the fiber interior, with cracks appearing in the fibers, indicating damage to the internal structure.

[0052] Figure 3 These are scanning electron microscope (SEM) images of the cross-sections of aluminum-based composite materials prepared under different gas-phase in-situ reaction times according to the present invention. Series (a) represents Comparative Example 1, series (b) represents Example 2, series (c) represents Comparative Example 2, and series (d) represents Comparative Example 3. In Comparative Example 1, the carbon fibers were not modified with a SiC interface layer. SEM observation showed gaps at the interface of the resulting aluminum-based composite material. In Example 2, a continuous SiC interface layer was constructed from carbon fibers through an ultra-short-time gas-phase in-situ reaction. SEM observation showed that the carbon fiber / aluminum interface of the resulting aluminum-based composite material was tightly bonded. In Comparative Example 2, the SiC interface layer formed by the carbon fibers after a 15-minute gas-phase in-situ reaction was relatively thick, and some fiber structures were damaged. SEM observation showed local gaps at the carbon fiber / aluminum interface of the resulting aluminum-based composite material. In Comparative Example 3, the SiC layer formed by the carbon fibers after a 30-minute gas-phase in-situ reaction was excessively thick. SEM observation showed that aluminum penetrated into the fiber interior, and the fiber structure was damaged.

[0053] Figure 4 These are scanning electron microscope (SEM) images of the cross-sections of aluminum-based composite materials prepared with different fiber volume fractions according to the present invention, wherein (a) series is Example 4, (b) series is Example 2, (c) series is Example 3, and (d) series is Example 1. Figure 4It can be seen that the fiber arrangement in the composite material becomes more compact with the increase of carbon fiber volume fraction. In Example 4 (20 vol.%), the fiber distribution in the matrix is ​​relatively sparse and there is local segregation, with a significant increase in fiber spacing, and the aluminum matrix dominates. In contrast, in Example 1 (60 vol.%), the fiber arrangement is highly dense and uniformly oriented, forming a continuous and interconnected thermally conductive network. At the same time, at this high volume fraction, the molten aluminum can fully fill the fiber gaps, the interface bonding is tight, and no obvious pores or macroscopic defects were found, resulting in optimal composite material density.

[0054] Figure 5 The XRD patterns of the modified carbon fiber bundles in Examples 2, 2, and 3 of this invention are shown. The XRD results show that the SiC on the surface of the modified carbon fiber obtained by the in-situ gas-phase reaction in Example 2 for 1 min is of the β-SiC crystal form and there are no other impurity phases. However, in Comparative Examples 2 and 3, as the in-situ gas-phase reaction holding time is extended, the SiC diffraction peak intensity is significantly enhanced, while the relative intensity of the C(002) diffraction peak of the carbon fiber body structure is significantly weakened and the peak shape is broadened. This indicates that the long-term high-temperature reaction leads to a sharp increase in the thickness of the SiC interface layer and seriously damages the graphite ordered structure of the fiber body, resulting in fiber damage.

[0055] Analysis of the data in Table 1 shows that the aluminum-based composite material prepared in the embodiments of the present invention has high thermal conductivity, high mechanical properties, and low thermal expansion. Furthermore, with the increase of fiber volume fraction, the axial thermal conductivity continuously increases, the coefficient of thermal expansion significantly decreases, and the flexural strength increases simultaneously. 40~60 vol.% is the preferred range, achieving the optimal match between thermal conductivity, mechanical properties, and thermal expansion properties. The gas-phase in-situ reaction method used in this invention can grow a continuous, dense, and uniformly thick SiC coating on the carbon fiber surface in a very short time. With the extension of the holding time, the coating thickness continuously increases. In Comparative Example 2, the coating further thickened after 15 minutes of holding; in Comparative Example 3, the holding time was extended to 30 minutes, resulting in an excessively thick coating. The prolonged high-temperature silicon infiltration reaction severely damaged the fiber structure, significantly degrading the original high thermal conductivity, high strength, and high modulus properties of the carbon fiber. Therefore, the present invention, by controlling the holding time to 1~2 minutes, can form a continuous and dense SiC interface layer on the fiber surface while effectively protecting the integrity of the fiber structure, representing the optimal time window for balancing interface modification and fiber performance preservation.

[0056] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A method for preparing a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material, characterized in that, Includes the following steps: S1. Pre-treatment of mesophase pitch-based carbon fibers by graphitization to obtain carbon fiber bundles. S2. The carbon fiber bundle is placed above the silicon source powder, and the carbon fiber bundle and the silicon source powder are not in direct contact. The heating reaction is carried out under negative pressure and inert atmosphere to obtain modified carbon fiber bundle containing a continuous SiC interface layer. The heating reaction conditions are: 1400~1600℃ for 1~2 minutes. The silicon source powder is a mixture of silicon powder and silicon dioxide powder. S3. The modified carbon fiber bundle is placed in a volume-adjustable fixture and compressed to obtain a directional carbon fiber preform. S4. Vacuum pressure impregnation treatment is performed on the carbon fiber preform using molten aluminum or molten aluminum alloy, and after cooling, the continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material is obtained.

2. The method for preparing a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material according to claim 1, characterized in that, In step S1, the graphitization pretreatment specifically involves graphitizing the mesophase pitch-based carbon fiber at a temperature of 2500~3000℃ and then cutting it to a fixed length.

3. The method for preparing a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material according to claim 1, characterized in that, In step S1, the axial thermal conductivity of the mesophase pitch-based continuous carbon fiber is ≥900 W / (m·K).

4. The method for preparing a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material according to claim 1, characterized in that, In step S2, the molar ratio of silicon powder to silicon dioxide is 1:

1.

5. The method for preparing a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material according to claim 1, characterized in that, In step S2, the negative pressure is a vacuum degree <10 Pa; And / or, the inert atmosphere is argon or nitrogen; And / or, the heating rate of the heating reaction is 5~10℃ / min.

6. The method for preparing a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material according to claim 1, characterized in that, In step S3, the volume fraction of modified carbon fiber in the carbon fiber preform is 20 vol.%~60 vol.%.

7. The method for preparing a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material according to claim 6, characterized in that, The volume fraction of modified carbon fiber in the carbon fiber preform is 40 vol.%~60 vol.%.

8. The method for preparing a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material according to claim 1, characterized in that, In step S4, the conditions for the vacuum pressure impregnation treatment are: temperature of 720~780℃, pressure of 5~15 MPa, and heat and pressure holding for 2~10 minutes.

9. The method for preparing a continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material according to claim 1, characterized in that, In step S4, the aluminum alloy includes 6063 aluminum alloy.

10. A continuous SiC interface layer carbon fiber aluminum-based high thermal conductivity composite material, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 9.

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