Silicon carbide nanowire-diamond interpenetrating composite film and preparation method thereof

Abstract

The invention belongs to the technical field of diamond materials, and particularly relates to a silicon carbide nanowire-diamond interpenetrating composite film and a preparation method thereof. The preparation method comprises the following steps: sequentially depositing a carbon film and a nickel film on the surface of a silicon substrate, and carrying out annealing treatment to grow a silicon carbide nanowire in situ on the silicon substrate; then putting the silicon substrate on which the silicon carbide nanowires grow into a nano-diamond suspension for ultrasonic treatment, so that nano-diamond particles are adsorbed on the surfaces of the silicon carbide nanowires; and carrying out chemical vapor deposition on diamond by utilizing microwave plasma, so that pores of the silicon carbide nanowire network skeleton are filled with the diamond, and a three-dimensional network structure in which the silicon carbide nanowires and the diamond are mutually penetrated is formed. The silicon carbide nanowire-diamond interpenetrating composite film prepared by the preparation method disclosed by the invention has excellent heat-conducting property and good toughness while keeping high hardness.

Description

Technical Field

[0001] This invention belongs to the field of diamond material technology, specifically relating to a silicon carbide nanowire-diamond interpenetrating composite film and its preparation method. Background Technology

[0002] Single-crystal diamond, as the hardest and most thermally conductive material known in nature, has been widely used in ultra-precision machining tools and high-efficiency heat sinks. Silicon carbide thin films, with their excellent thermal conductivity and chemical stability, are often used as wear-resistant coatings or semiconductor substrates. To improve the oxidation resistance of diamond tools and the wettability of solder, studies have been conducted on depositing silicon carbide thin films on diamond surfaces. However, these films are mostly dense planar structures with limited adhesion to the diamond substrate and are inherently brittle, easily developing and propagating cracks under complex stress, leading to structural failure. Therefore, it is difficult to simultaneously achieve high toughness and high thermal conductivity.

[0003] On the other hand, combining metal or ceramic matrices (such as aluminum or resin) with silicon carbide to improve its mechanical and thermal properties is also a common approach. However, these matrix materials themselves have low thermal conductivity and hardness. Although they can improve some toughness or wear resistance, they are difficult to meet the requirements of extreme heat dissipation and high wear resistance scenarios. At the same time, the silicon carbide reinforcing phase is often randomly distributed in the matrix, resulting in anisotropic properties, and the interfacial bonding strength is not easy to control, further limiting its application in the field of heat dissipation materials.

[0004] In recent years, silicon carbide nanowires and diamond nanocoatings have attracted attention due to their outstanding mechanical, thermal, and field emission properties, and their combination is considered a feasible direction for achieving high-performance composite structures. However, silicon carbide nanowires are usually grown on inexpensive substrates such as silicon, making them difficult to use directly for high-performance system integration; diamond nanocoatings suffer from low nucleation density and poor adhesion on non-diamond substrates. Existing studies mostly employ simple stacked composite structures, but due to the low thermal conductivity of the substrates and the mismatch between the substrates and the thermal expansion of the materials, the interfacial thermal resistance is high, the overall thermal management performance is only slightly improved, and interfacial delamination or overall failure easily occurs during thermal cycling.

[0005] In summary, existing technologies often focus on optimizing a single performance characteristic, making it difficult to synergistically achieve multiple objectives such as high hardness and high toughness, high thermal conductivity and high interfacial stability. Therefore, this invention proposes an innovative structural design aimed at achieving a good combination of silicon carbide nanowires and diamond nanocoatings, strengthening interfacial bonding and improving toughness. This significantly improves the thermal management efficiency and long-term service stability of the composite structure, overcoming the delamination problem commonly found in previous combinations, and ultimately obtaining a composite material with both high thermal conductivity and good toughness. Summary of the Invention

[0006] The primary objective of this invention is to provide a method for preparing silicon carbide nanowire-diamond interpenetrating composite films.

[0007] The second objective of this invention is to provide a silicon carbide nanowire-diamond interpenetrating composite film obtained by the above preparation method, which maintains high hardness while also possessing excellent thermal conductivity and good toughness.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a silicon carbide nanowire-diamond interpenetrating composite film includes the following steps: (1) Carbon film and nickel film are deposited sequentially on the surface of silicon substrate, and silicon carbide nanowires are grown in situ on the silicon substrate after annealing. (2) The silicon substrate with silicon carbide nanowires grown in step (1) is placed in a nanodiamond suspension for ultrasonic treatment, so that nanodiamond particles are adsorbed on the surface of the silicon carbide nanowires. (3) Place the sample processed in step (2) in a plasma chemical vapor deposition apparatus, introduce hydrogen and carbon source, and deposit diamond under the conditions of microwave power 3000-5000W, temperature 900℃ and cavity pressure 1-2 kPa, so that the diamond fills the pores of the silicon carbide nanowire network skeleton and forms a three-dimensional network structure in which silicon carbide nanowires and diamonds interpenetrate each other.

[0009] Furthermore, the carbon film and nickel film deposited in step (1) are achieved by magnetron sputtering, wherein the sputtering current for depositing the carbon film is 150-180 mA and the time is 10-20 min, and the sputtering current for depositing the nickel film is 170-200 mA and the time is 10-20 min.

[0010] This invention requires pre-sputtering before magnetron sputtering. The pre-sputtering operation is as follows: adjust the RF current to 100 mA, wait for ignition, and then perform pre-sputtering for 10 min.

[0011] Furthermore, the annealing treatment in step (1) is performed at a temperature of 1000-1100 ℃ for 50-60 min.

[0012] Further, in step (2), the concentration of the nanodiamond suspension is 1-5 g / L; the particle size of the nanodiamond is 5-10 nm; and the power of the ultrasonic treatment is 40-50 W, and the time is 5-6 min.

[0013] The present invention involves immersing a silicon substrate with silicon carbide nanowires in a diamond suspension and sonicating it. The purpose is to allow a layer of nanodiamond particles to be physically adsorbed on the surface of the silicon carbide nanowires as a "seed layer" to provide diamond nucleation sites, while removing any possible amorphous carbon layers.

[0014] Furthermore, the time for depositing diamond in step (3) is 40-50 min.

[0015] Furthermore, the carbon source mentioned in step (3) is any one of methane, acetone or graphite.

[0016] Furthermore, the molar ratio of carbon source to hydrogen in step (3) is 1%-8%.

[0017] A silicon carbide nanowire-diamond interpenetrating composite film, prepared by the above method, includes a silicon carbide nanowire network framework and a continuous diamond phase filling the pores of the framework, wherein the silicon carbide nanowires and diamond interpenetrate to form a three-dimensional interpenetrating network structure.

[0018] The beneficial technical effects of this invention are as follows: The silicon carbide nanowire and diamond composite material prepared by this invention possesses an interpenetrating structure, exhibiting extremely high mechanical strength, good thermal conductivity, and ideal toughness. This invention combines the advantages of diamond and silicon carbide nanowires to construct an interpenetrating composite material, demonstrating superior comprehensive performance: when microcracks develop in the diamond film, the cracks deflect, bypass, and branch upon encountering the high-strength, high-elasticity SiC nanowires during propagation, effectively dissipating energy and reducing crack propagation; simultaneously, the nanowires can bridge cracks and buffer stress, significantly improving the material's fracture toughness, impact resistance, and fatigue resistance, achieving a synergy of high hardness and high toughness. In terms of thermal management, the three-dimensional interpenetrating thermal network formed by the two materials can efficiently diffuse and dissipate localized heat, while the uniform interpenetrating structure makes the overall thermal expansion coefficient of the material more uniform. Combined with the elastic strain adjustment capability of silicon carbide nanowires, this ensures reliable thermal matching when connected to semiconductor chips. Furthermore, the interface between the two materials remains thermodynamically stable at high temperatures, and the transferable design further enhances the interfacial stability and practical potential of this composite film. Attached Figure Description

[0019] Figure 1 This is a scanning electron microscope image of the silicon carbide nanowires obtained in step (1) of Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the silicon carbide nanowire-diamond interpenetrating composite film prepared in Example 1 of the present invention. Figure 3 This is a scanning electron microscope image of a common diamond film. Detailed Implementation

[0020] The following is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all reagents or instruments used are conventional products obtained through commercial channels.

[0021] (I) Implementation Examples Example 1 Example 1 provides a method for preparing a silicon carbide nanowire-diamond interpenetrating composite film, comprising the following steps: (1) The silicon substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 15 min each to remove organic matter and particulate contaminants. After drying in a nitrogen atmosphere, it was placed in a clean petri dish for later use. The silicon substrate was placed in a vacuum chamber with the carbon target as a substrate, so that the silicon substrate was directly below the carbon target. The target-substrate distance was adjusted to 6.5 cm. The vacuum chamber door was closed and the vacuum was drawn. The radio frequency current was adjusted to 100 mA. After observing the ignition, the substrate was pre-sputtered for 10 min. Then the current was adjusted to 160 mA and the substrate was deposited for 15 min to obtain a carbon-deposited silicon substrate. The carbon target was replaced with a nickel target. The carbon-deposited silicon substrate was used as a substrate. After pre-sputtering according to the above steps, the current was adjusted to 180 mA and the substrate was deposited for 15 min to obtain a coated silicon substrate. The coated silicon substrate was annealed at 1000 °C for 60 min in an argon atmosphere. After cooling, it was ultrasonically cleaned in a 1 mol / L hydrochloric acid ethanol solution (50 W) to obtain a silicon substrate with silicon carbide nanowires grown on it. (2) Diamond particles with an average particle size of about 10 nm were added to water to obtain a diamond suspension with a concentration of 3 g / L. Then, a silicon substrate with silicon carbide nanowires was immersed in the diamond suspension and sonicated at a power of 50 W for 5 min to adsorb nanodiamond particles on the surface of silicon carbide nanowires. After drying, a composite substrate was obtained. (3) Place the composite substrate in the MPCVD chamber and evacuate to <1.0×10⁻⁶. -3 Pa, then high-purity hydrogen gas was introduced, and the pressure inside the cavity was stabilized at 2 kPa by adjusting the throttle valve. The composite substrate was heated to 900 °C using 4000 W microwave power, and a mixture of methane and hydrogen gas (with methane accounting for 5% of the molar ratio) was introduced at this temperature and deposited for 45 min to obtain a silicon carbide nanowire-diamond interpenetrating composite film.

[0022] This embodiment also provides a silicon carbide nanowire-diamond interpenetrating composite film prepared by the above method.

[0023] Example 2 Example 2 provides a method for preparing a silicon carbide nanowire-diamond interpenetrating composite film, comprising the following steps: (1) The silicon substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 15 min each to remove organic matter and particulate contaminants. After drying in a nitrogen atmosphere, it was placed in a clean petri dish for later use. The silicon substrate was placed in a vacuum chamber with the carbon target as the substrate, so that the silicon substrate was directly below the carbon target. The target-substrate distance was adjusted to 6 cm. The vacuum chamber door was closed and the vacuum was drawn. The radio frequency current was adjusted to 100 mA. After observing the ignition, the substrate was pre-sputtered for 8 min. Then the current was adjusted to 180 mA and the substrate was deposited for 10 min to obtain a carbon-deposited silicon substrate. The carbon target was replaced with a nickel target. The carbon-deposited silicon substrate was used as the substrate. After completing the pre-sputtering according to the above steps, the current was adjusted to 200 mA and the substrate was deposited for 10 min to obtain a coated silicon substrate. The coated silicon substrate was annealed at 1000 °C for 50 min in an argon atmosphere and ultrasonically cleaned in a 1 mol / L hydrochloric acid ethanol solution (50 W) to obtain a silicon substrate with silicon carbide nanowires grown on it. (2) Diamond particles with an average particle size of about 5 nm were added to water to obtain a diamond suspension with a concentration of 1 g / L. Then, a silicon substrate with silicon carbide nanowires was immersed in the diamond suspension and sonicated at a power of 40 W for 6 min to adsorb nanodiamond particles on the surface of silicon carbide nanowires. After drying, a composite substrate was obtained. (3) Place the composite substrate in the MPCVD chamber and evacuate to <1.0×10⁻⁶. -3 Pa, then high-purity hydrogen gas is introduced, and the pressure inside the cavity is stabilized at 1 kPa by adjusting the throttle valve. The composite substrate is heated to 900 °C using 3000 W microwave power, and a mixture of methane and hydrogen gas (of which methane accounts for 5% by volume) is introduced at this temperature and deposited for 40 min to obtain a silicon carbide nanowire-diamond interpenetrating composite film.

[0024] This embodiment also provides a silicon carbide nanowire-diamond interpenetrating composite film prepared by the above method.

[0025] Example 3 Example 3 provides a method for preparing a silicon carbide nanowire-diamond interpenetrating composite film, comprising the following steps: (1) The silicon substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 15 min each to remove organic matter and particulate contaminants. After drying in a nitrogen atmosphere, it was placed in a clean petri dish for later use. The silicon substrate was placed in a vacuum chamber with the carbon target as a substrate, so that the silicon substrate was directly below the carbon target. The target-substrate distance was adjusted to 7 cm. The vacuum chamber door was closed and the vacuum was drawn. The radio frequency current was adjusted to 100 mA. After observing the ignition, the substrate was pre-sputtered for 8 min. Then the current was adjusted to 150 mA and the substrate was deposited for 20 min to obtain a carbon-deposited silicon substrate. The carbon target was replaced with a nickel target. The carbon-deposited silicon substrate was used as a substrate. After pre-sputtering according to the above steps, the current was adjusted to 170 mA and the substrate was deposited for 20 min to obtain a coated silicon substrate. The coated silicon substrate was annealed at 1100 °C for 60 min in an argon atmosphere. After cooling, it was ultrasonically cleaned in a 1 mol / L hydrochloric acid ethanol solution (50 W) to obtain a silicon substrate with silicon carbide nanowires grown on it. (2) Diamond particles with an average particle size of about 10 nm were added to water to obtain a diamond suspension with a concentration of 5 g / L. Then, a silicon substrate with silicon carbide nanowires was immersed in the diamond suspension and sonicated at a power of 50 W for 5 min to adsorb nanodiamond particles on the surface of silicon carbide nanowires. After drying, a composite substrate was obtained. (3) Place the composite substrate in the MPCVD chamber and evacuate to <1.0×10⁻⁶. -3 Pa, then high-purity hydrogen gas is introduced, and the pressure inside the cavity is stabilized at 2 kPa by adjusting the throttle valve. The composite substrate is heated to 1000 ℃ using 5000 W microwave power, and a mixture of methane and hydrogen gas (with methane accounting for 3% of the molar ratio) is introduced at this temperature and deposited for 50 min to obtain silicon carbide nanowire-diamond interpenetrating composite film.

[0026] This embodiment also provides a silicon carbide nanowire-diamond interpenetrating composite film prepared by the above method.

[0027] (III) Comparative Example Comparative Example 1 The preparation process of Comparative Example 1 is basically the same as that of Example 1, except that step (1) in Example 1 is omitted and commercially available silicon carbide nanowires are used instead of in-situ grown silicon carbide nanowires.

[0028] Comparative Example 2 The preparation process of Comparative Example 2 is basically the same as that of Example 1, except that step (2) in Example 1 is omitted, that is, the treatment of nanodiamond seed layer is omitted.

[0029] Comparative Example 3 The preparation process of Comparative Example 3 is basically the same as that of Example 1, except that the microwave power in step (3) of Example 1 is set to 1500 W.

[0030] Comparative Example 4 The preparation process of Comparative Example 4 is basically the same as that of Example 1, except that the pressure inside the cavity in step (3) of Example 1 is set to 8 kPa.

[0031] Comparative Example 5 The preparation process of Comparative Example 5 is basically the same as that of Example 1, except that the molar ratio of carbon source to hydrogen in step (3) of Example 1 is set to 10%.

[0032] (III) Structural characterization and performance testing Structural characterization The product of Example 1 was subjected to SEM testing, and the scanning electron microscope image of the silicon carbide nanowires obtained in step (1) is shown below. Figure 1 As shown, the scanning electron microscope image of the composite thin film obtained in step (3) is as follows. Figure 2 As shown. From Figure 1-2 As can be seen, diamond fills the pores of the silicon carbide nanowire network framework, forming a three-dimensional network structure in which silicon carbide nanowires and diamond interpenetrate. Furthermore, for comparison, this invention also performed SEM tests on ordinary diamond films, and the scanning electron microscope images are shown below. Figure 3 As shown.

[0033] Performance testing The composite films prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to the following performance tests: Thermal conductivity test: The transient thermal reflection method was used to heat the surface of the thin film with a laser pulse of 15 J and a pulse width of 10 ms. The surface temperature decay curve over time was recorded by a detector with a sampling frequency of 200 kHz. The thermal conductivity of the thin film was obtained by fitting and calculation. The test results are shown in Table 1.

[0034] Hardness: The hardness of the material was calculated by using a diamond indenter to press into the sample surface with extremely high precision and continuously recording the load-displacement curve. The test results are shown in Table 1.

[0035] Toughness: In the nanoindenter, a cubic diamond indenter was used. The loading rate was set to 0.5 mN / s and the load was gradually increased until the material produced a sufficiently long and clear crack. The load was held for 5-10 s to reduce the influence of material creep on the measurement. Finally, the length of the crack was measured and the fracture toughness was calculated by combining the elastic modulus and hardness. The test results are shown in Table 1.

[0036] Fatigue resistance: Cyclic loading nanoindentation was performed using a diamond cubic indenter at a frequency of 10 Hz under loads of 5 / 10 / 20 mN. The indentation depth was monitored in real time as the number of cycles increased. A sudden change in depth indicated fatigue failure of the film, and the number of cycles at this point was recorded. The test results are shown in Table 1.

[0037] Thermal cycling life: Temperature change test chamber + Raman spectroscopy. The sample was placed in a high and low temperature cycling test chamber, and a harsh temperature change range (40-150 ℃) and number of cycles (≥1000 cycles) were set. During the cycling process, the shift of the characteristic peaks of diamond and SiC was monitored using Raman spectroscopy to calculate the change in residual stress. When the residual stress changed abruptly, the number of cycles was recorded. The test results are shown in Table 1.

[0038] Impact resistance: Nanoscale impact testing utilizes a nanomechanical testing system to subject the sample surface to three levels of load: 5 / 10 / 20 mN, at frequencies of 10 Hz and 50 Hz. The maximum number of cycles is 1 × 10⁻⁶. 6 The damage depth and volume change of the material under repeated impacts were recorded, and the impact resistance was calculated. The test results are shown in Table 1.

[0039] Table 1. Test results of composite films prepared in Examples 1-3 and Comparative Examples 1-5 As shown in Table 1, the composite films prepared in Examples 1-3 of the present invention maintain high hardness while also possessing excellent thermal conductivity and good toughness.

[0040] Compared to Example 1, Comparative Example 1 omits step 1 and uses commercially available silicon carbide nanowires instead of in-situ grown silicon carbide nanowires. The mechanical properties and thermal conductivity of the resulting composite film are significantly reduced, indicating that the silicon carbide nanowire network structure formed by in-situ growth is superior to commercially available products.

[0041] Comparative Example 2 omitted the nanodiamond seed layer treatment step in Example 1, resulting in a change in the diamond film formation process and a decrease in thermal conductivity. This demonstrates that the nanodiamond seed layer treatment can promote the formation of continuous diamond films and serves as a bridge between the "substrate" and "film deposition." This invention pre-lays a diamond phase on a heterogeneous substrate using physical means, simplifying the complex "heterogeneous nucleation" into a relatively easy "homogeneous growth," which is a key method to ensure the formation of high-density, uniform, and robust diamond films.

[0042] Comparative Examples 3-6, with adjustments to the MPCVD process parameters, showed varying degrees of decrease in the mechanical properties and thermal conductivity of the prepared composite films. This indicates that only by using the preparation process parameters of this invention can diamond-silicon carbide nanowire composite films with interpenetrating structures be prepared. Using process parameters deviating from those of this application, it is impossible to prepare silicon carbide nanowire-diamond interpenetrating composite films or interpenetrating composite films with ideal performance. Specifically, low microwave power leads to unstable thermal stress changes, excessive deposition pressure causes uneven plasma distribution, and excessive methane concentration intensifies secondary nucleation or causes amorphous carbon precipitation. These three key parameters all affect the formation of the composite film, thus affecting its performance. Therefore, after adjusting the MPCVD process parameters in Comparative Examples 3-6, both the mechanical and thermal properties decreased to varying degrees.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A method for preparing a silicon carbide nanowire-diamond interpenetrating composite thin film, characterized in that, Includes the following steps: (1) Carbon film and nickel film are deposited sequentially on the surface of silicon substrate, and silicon carbide nanowires are grown in situ on silicon substrate after annealing. (2) The silicon substrate with silicon carbide nanowires grown in step (1) is placed in a nanodiamond suspension for ultrasonic treatment, so that nanodiamond particles are adsorbed on the surface of the silicon carbide nanowires. (3) Place the sample processed in step (2) in a plasma chemical vapor deposition device, introduce hydrogen and carbon source, and deposit diamond under the conditions of microwave power of 3000-5000W, temperature of 900-1000℃ and cavity pressure of 1-2 kPa, so that the diamond fills the pores of the silicon carbide nanowire network skeleton and forms a three-dimensional network structure in which silicon carbide nanowires and diamonds interpenetrate each other.

2. The method for preparing silicon carbide nanowire-diamond interpenetrating composite thin films according to claim 1, characterized in that, In step (1), the carbon film and nickel film are deposited using a magnetron sputtering process. The sputtering current for depositing the carbon film is 150-180 mA and the time is 10-20 min. The sputtering current for depositing the nickel film is 170-200 mA and the time is 10-20 min.

3. The method for preparing silicon carbide nanowire-diamond interpenetrating composite thin films according to claim 1, characterized in that, The annealing process in step (1) is performed at a temperature of 1000-1100 ℃ for 50-60 min.

4. The method for preparing silicon carbide nanowire-diamond interpenetrating composite thin films according to claim 1, characterized in that, The concentration of the nanodiamond suspension in step (2) is 1-5 g / L; the particle size of the nanodiamond is 5-10 nm; the power of the ultrasonic treatment is 40-50 W and the time is 5-6 min.

5. The method for preparing a silicon carbide nanowire-diamond interpenetrating composite film according to claim 1, characterized in that, The time for depositing diamond in step (3) is 40-50 min.

6. The method for preparing a silicon carbide nanowire-diamond interpenetrating composite thin film according to claim 1, characterized in that, The carbon source mentioned in step (3) is any one of methane, acetone or graphite.

7. The method for preparing silicon carbide nanowire-diamond interpenetrating composite thin films according to claim 1, characterized in that, The molar ratio of carbon source to hydrogen in step (3) is 1%-8%.

8. A silicon carbide nanowire-diamond interpenetrating composite film, characterized in that, The method described in any one of claims 1-7 is used to prepare a silicon carbide nanowire network framework and a continuous diamond phase filling the pores of the framework, wherein the silicon carbide nanowires and diamond interpenetrate to form a three-dimensional interpenetrating network structure.

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