Method for improving the bond strength of a surface silicon carbide coating on a graphite substrate and products thereof

Abstract

The application relates to the technical field of semiconductor material preparation, and provides a method for improving the interface bonding strength of a SiC coating on a graphite substrate and a product thereof. The method comprises the following steps: S1, placing a graphite substrate in a carbon nanotube suspension, and forming a carbon nanotube coating layer on the surface of the graphite substrate by adopting an electrophoresis method; S2, placing the graphite substrate treated in the step S1 in a chemical vapor deposition device, vacuumizing the chemical vapor deposition device, and then cleaning the deposition device by using an inert gas; and S3, feeding a mixed gas of a silicon-carbon source gas, a reaction gas and a carrier gas into the chemical vapor deposition device, and depositing a SiC coating on the surface of the carbon nanotube coating layer by adopting a chemical vapor deposition process. The method can increase the interface bonding force between the silicon carbide coating and the graphite substrate, so that the subsequent silicon carbide coating is not prone to peeling off in the use process, and the service life and reliability of the silicon carbide coating material are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor material preparation, and in particular to a method for improving the interface bonding strength of a SiC coating on a graphite substrate and a product thereof. BACKGROUND

[0002] In the field of semiconductors, MOCVD (Metal Organic Chemical Vapor Deposition) technology is used for epitaxial deposition on substrates. Depositing a silicon carbide (SiC) coating on a graphite substrate helps to provide a surface protection with high hardness, corrosion resistance, and high-temperature properties. However, a key problem with traditional silicon carbide coating technology is that the interface bonding strength between the coating and the graphite substrate is not high enough, which can lead to peeling or separation of the SiC coating, thereby affecting the performance and stability of the graphite base. At the same time, due to the inability to accurately control the process of depositing the silicon carbide coating at different temperatures, the product quality cannot be guaranteed. The low production efficiency and lack of effective process control methods result in waste of time and energy during the production process, reducing the overall production efficiency. Therefore, improving the interface bonding strength between the SiC coating and the graphite substrate has become an important technical problem. SUMMARY

[0003] The present application aims to overcome the above-mentioned problems in the prior art and provide a method for improving the bonding strength of a SiC coating on a graphite substrate and a silicon carbide coating material prepared thereby. The method first uses an electrophoresis process to deposit a carbon nanotube (CNT) coating layer on the surface of the graphite substrate, and then uses a chemical vapor deposition process (CVD) to generate a SiC outer coating on the surface of the CNT coating layer. This can increase the interface bonding strength between the silicon carbide coating and the graphite substrate, making the subsequent silicon carbide coating less likely to peel off during use, and improving the service life and reliability of the silicon carbide coating material.

[0004] To achieve the above-mentioned purpose, the first aspect of the present application provides a method for improving the bonding strength of a SiC coating on a graphite substrate, comprising the following steps:

[0005] S1: placing a graphite substrate in a carbon nanotube suspension and using an electrophoresis method to form a carbon nanotube coating layer on the surface of the graphite substrate;

[0006] S2: placing the graphite substrate treated in step S1 in a chemical vapor deposition device, evacuating the chemical vapor deposition device, and then cleaning the deposition device with an inert gas;

[0007] S3: introducing a mixed gas of a silicon-carbon source gas, a reaction gas, and a carrier gas into the chemical vapor deposition device, and using a chemical vapor deposition process to deposit a SiC coating on the surface of the carbon nanotube coating layer.

[0008] The second aspect of the present invention provides a silicon carbide coating material, which is prepared by the method described in the first aspect of the present invention for improving the bonding strength of SiC coating on the surface of a graphite substrate.

[0009] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0010] (1) The method for improving the bonding strength of SiC coating on graphite substrate provided by the present invention can increase the interfacial bonding force between silicon carbide coating and graphite substrate, making the subsequent silicon carbide coating less likely to peel off during use, and improving the service life and reliability of silicon carbide coating material.

[0011] (2) The silicon carbide coating material provided by the present invention has the advantages of strong interfacial bonding, high electrical conductivity and long service life.

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to those ranges or values. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In this document, unless otherwise specified, data ranges include endpoints. Attached Figure Description

[0013] Figure 1 The image shown is an electron microscope image of the silicon carbide coating material. Detailed Implementation

[0014] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0015] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0016] The present application researches and finds that the traditional silicon carbide coating process is often weak in the interface bonding force between the silicon carbide coating and the graphite substrate at a specific temperature during CVD deposition, which may be due to the mismatch of the structural characteristics between the graphite substrate and the silicon carbide coating during the deposition process, resulting in the instability of the interface bonding force, and the silicon carbide is prone to peeling or falling off, the process is difficult to control, and the production demand in a specific environment is limited. At the same time, due to the inability to accurately control the process of depositing the silicon carbide coating at different temperatures, the product quality cannot be stably guaranteed. The production efficiency is low, and there is a lack of effective process control means, resulting in waste of time and energy in the production process, and reducing the overall production efficiency.

[0017] In order to overcome the above problems existing in the prior art, the present application provides the following technical scheme:

[0018] The first aspect of the present application provides a method for improving the bonding strength of a SiC coating on the surface of a graphite substrate, comprising the following steps:

[0019] S1: placing the graphite substrate in a carbon nanotube suspension, and forming a carbon nanotube coating layer on the surface of the graphite substrate by electrophoresis;

[0020] S2: placing the graphite substrate treated in step S1 in a chemical vapor deposition device, vacuumizing the chemical vapor deposition device, and then cleaning the deposition device with an inert gas;

[0021] S3: introducing a mixed gas of a silicon-carbon source gas, a reaction gas and a carrier gas into the chemical vapor deposition device, and depositing a SiC coating on the surface of the carbon nanotube coating layer by a chemical vapor deposition process.

[0022] In the present application, a carbon nanotube (CNT) coating layer is first deposited on the surface of the graphite substrate by electrophoresis, and a good mechanical interlocking and chemical adsorption is formed between the carbon nanotube and the graphite substrate, effectively improving the interface bonding force. Then, a SiC outer coating is generated on the surface of the CNT coating layer by a chemical vapor deposition process (CVD). In the chemical vapor deposition process, the carbon-silicon source penetrates into the microstructure of the porous carbon nanotube at high temperature, and then a carbon nanotube / silicon carbide transition layer and a silicon carbide outer coating are formed on the surface of the CNT coating layer. The carbon nanotube / silicon carbide transition layer can increase the interface bonding force between the silicon carbide coating and the graphite substrate, so that the subsequent silicon carbide coating is not easy to peel off during use, and the service life and reliability of the silicon carbide coating material are improved.

[0023] In some embodiments, the diameter of the carbon nanotube is 8-15 nm, for example, it can be 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm or any point value in the range formed by any two of the above point values.

[0024] In some embodiments, the length of the carbon nanotubes is 30-80 μm, for example, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm or any value within the range defined by any two of the above-mentioned values.

[0025] In the present application, when the diameter and length of the carbon nanotubes are limited within the above-mentioned range, the carbon nanotube coating layer is not too dense due to too small diameter and length of the carbon nanotubes, which is not conducive to the flexibility of the carbon nanotube coating layer and the improvement of the interfacial bonding between the carbon nanotube coating layer and the graphite substrate. Also, the carbon nanotube coating layer has too large network structure pores due to too large diameter and length of the carbon nanotubes, which is also not conducive to the improvement of the interfacial bonding between the carbon nanotube coating layer and the graphite substrate. When the diameter and length of the carbon nanotubes are limited within the above-mentioned range, the interfacial bonding between the carbon nanotube coating layer and the graphite substrate is improved, and thus the interfacial bonding between the SiC coating layer and the graphite substrate is also improved.

[0026] In some embodiments, the thickness of the carbon nanotube coating layer is 25-50 μm, for example, 25 μm, 28 μm, 30 μm, 32 μm, 34 μm, 35 μm, 36 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm or 50 μm. The carbon nanotubes form a continuous coating layer on the surface of the graphite substrate. If the thickness of the carbon nanotube coating layer is too small, the deposition in some areas may not be uniform during the subsequent deposition of the SiC coating layer, which cannot effectively enhance the bonding between the SiC coating layer and the graphite substrate, and the adhesion is insufficient, which leads to easy peeling of the coating layer during use. Moreover, the carbon nanotube coating layer with too small thickness cannot provide sufficient mechanical cushioning effect, which easily leads to the concentration of interfacial thermal stress, and thus causes the cracking or peeling of the coating layer. If the thickness of the carbon nanotube coating layer is too large, the gas transmission is blocked. During the chemical vapor deposition (CVD) process, the too thick carbon nanotube layer limits the permeability of the deposition gas (silicon-carbon source gas, reaction gas, etc.), which leads to the non-uniform deposition of the SiC coating layer, and the deposition rate may be significantly reduced, which increases the process time and cost, and even pores or defects may be formed in some areas. The carbon nanotube coating layer with too large thickness may form a too large stress concentration area at the interface, which may lead to the peeling or delamination of the coating layer, especially under thermal cycling or high temperature conditions.

[0027] In some embodiments, the concentration of the carbon nanotube suspension is 0.03wt.%-0.08wt.%, for example, the concentration can be 0.03wt.%, 0.04wt.%, 0.05wt.%, 0.06wt.%, 0.07wt.%, 0.08wt.% or any point value in the range consisting of any two of the above-mentioned point values. The concentration of the carbon nanotube suspension is the mass concentration, when the concentration of the carbon nanotube suspension is in the above-mentioned range, it can ensure that the carbon nanotubes can be effectively deposited on the surface of the graphite substrate under the action of the electric field, control the thickness of the deposited carbon nanotube coating layer within the protection scope of the present application, and improve the continuity and uniformity of the carbon nanotube coating layer, thereby facilitating the improvement of the interfacial bonding force between the silicon carbide coating and the graphite substrate.

[0028] In some embodiments, the carbon nanotube suspension further comprises a dispersant, and the mass of the dispersant accounts for 15%-25% of the mass of the carbon nanotubes, for example, it can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25% or any point value in the range consisting of any two of the above-mentioned point values. The addition of the dispersant in the carbon nanotube suspension and the limitation of the mass ratio of the dispersant are beneficial to the more uniform dispersion of the carbon nanotube suspension, improve the electrophoretic deposition efficiency, and are beneficial to improving the continuity and uniformity of the carbon nanotube coating layer.

[0029] In some embodiments, the dispersant comprises an aromatic modified non-ionic surfactant, for example, it comprises TNWDIS.

[0030] In some embodiments, in the step S1, the process parameters of the electrophoretic method include: the voltage is 20V-60V, the time is 2min-10min, and the temperature is 20℃-60℃. For example, the voltage can be 20V, 25V, 30V, 35V, 40V, 45V, 50V, 55V, 60V or any point value in the range consisting of any two of the above-mentioned point values; the time can be 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min or any point value in the range consisting of any two of the above-mentioned point values; the temperature can be 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃ or any point value in the range consisting of any two of the above-mentioned point values.

[0031] In the present application, when the process parameters of the electrophoretic method are limited in the above-mentioned range, the carbon nanotube coating layer with better continuity and uniformity can be generated by matching the carbon nanotube suspension with a specific concentration, thereby facilitating the improvement of the interfacial bonding force between the silicon carbide coating and the graphite substrate.

[0032] In some embodiments, the step S1 is further preceded by a pretreatment step of the graphite substrate, for example, a surface treatment method (such as plasma treatment) is used to increase the roughness and activity of the surface of the graphite substrate, so as to enhance the adhesion of the silicon carbide coating and improve the bonding strength of the silicon carbide coating.

[0033] In some embodiments, the step S1 and the step S2 are further followed by a drying step of the graphite substrate: the graphite substrate after the electrophoresis treatment is taken out and placed in a drying oven at 100-150°C for 3-10 hours to obtain a dried graphite CNT-coated body (i.e., the graphite substrate has a carbon nanotube coating layer on the surface).

[0034] In some embodiments, the step S2 further comprises: using a pre-deposited graphite tool to support the graphite substrate after the drying treatment, and then placing it in a chemical vapor deposition device. The pre-deposited graphite tool is a graphite tool with a SiC coating layer deposited on the surface by CVD process, which can avoid the volatilization of impurities from the bare graphite at high temperature, affecting the purity of the silicon carbide coating material; in addition, the position supported by the graphite tool cannot form a SiC outer coating layer during CVD deposition, and the SiC at the supported position of the pre-deposited graphite tool will be embedded into the support point, maintaining the integrity of the silicon carbide coating material product.

[0035] In some embodiments, the process parameters of the chemical vapor deposition in the step S3 include: a deposition temperature of 1100-1400°C, a deposition pressure of 5-20 kPa, and a deposition time of 50-500 min.

[0036] In some embodiments, the deposition temperature can be, for example, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, or any point value in the range consisting of any two of the above-mentioned point values. When the deposition temperature is in the above-mentioned range, the growth of the silicon carbide coating can be promoted, and the silicon carbide coating can be made more dense.

[0037] In some embodiments, the deposition pressure is 5-20 kPa, for example, 5Kpa, 6Kpa, 8Kpa, 10Kpa, 12Kpa, 14Kpa, 16Kpa, 18Kpa, 20Kpa, or any point value in the range consisting of any two of the above-mentioned point values. When the deposition pressure is in the above-mentioned range, the deposition rate can be improved, the quality and uniformity of the SiC coating can be improved, the cost of production can be reduced by avoiding too high deposition pressure, and the density of the SiC coating and the deposition rate can be improved by avoiding too low deposition pressure.

[0038] In some embodiments, the deposition time is 50-500 min, and the deposition time is not strictly limited and can be adjusted according to the thickness of the SiC outer coating layer.

[0039] In some embodiments, the flow ratio of the carbon-silicon source gas to the reaction gas in step S3 is 1:1-1:20, for example, 1:1, 1:2, 1:3, 1:5, 1:7, 1:8, 1:10, 1:12, 1:14, 1:15, 1:16, 1:18, 1:20, or any value within the range defined by any two of the above values. When the flow ratio of the carbon-silicon source gas to the reaction gas is within the above range, a high-quality silicon carbide coating layer is formed by the chemical reaction of the carbon-silicon source gas and the reaction gas, which can increase the density of the silicon carbide outer coating layer and improve the high-temperature resistance, corrosion resistance, mechanical properties, and thermal conductivity of the silicon carbide coating material.

[0040] The flow rate of the carbon-silicon source gas and the flow rate of hydrogen are not limited and can be selected from the flow rate range commonly used in the art.

[0041] In some embodiments, the flow rate of the reaction gas is 0.1 slm-1 slm, for example, 0.1 slm, 0.2 slm, 0.3 slm, 0.4 slm, 0.5 slm, 0.6 slm, 0.7 slm, 0.8 slm, 0.9 slm, 1 slm, or any value within the range defined by any two of the above values.

[0042] In some embodiments, the flow rate of the carrier gas is 50 g / min-150 g / min, for example, 50 g / min, 60 g / min, 80 g / min, 100 g / min, 120 g / min, 150 g / min, or any value within the range defined by any two of the above values.

[0043] In the present application, the "carbon-silicon source gas" refers to a gas that can provide carbon and silicon elements, i.e., a raw material gas that provides a precursor for preparing SiC. The carbon-silicon source gas is not particularly limited and can be selected from a gas compound that can provide carbon and silicon elements and is suitable for preparing a silicon carbide material.

[0044] In some embodiments, the carbon-silicon source gas includes at least one of monosilane, disilane, trisilane, methylchlorosilane, dimethylchlorosilane, or trichloromethylsilane; preferably trichloromethylsilane.

[0045] In some embodiments, the reaction gas includes hydrogen.

[0046] In some embodiments, the carrier gas includes at least one of argon and / or helium, preferably argon.

[0047] The method for improving the bonding strength of the SiC coating on the surface of the graphite substrate provided by the application has a relatively simple electrophoretic deposition process, can be performed at room temperature, and the deposition rate can be flexibly controlled by adjusting parameters such as voltage and time. This adjustability enables the performance requirements of materials in different application scenarios to be met. The process can be performed at a lower temperature and pressure by combining electrophoretic deposition and chemical vapor deposition, thereby reducing energy consumption and material waste, lowering production costs, ensuring full utilization of materials, reducing unnecessary waste generation, and conforming to the trend of green manufacturing.

[0048] The second aspect of the application provides a silicon carbide coating material obtained by the method of the first aspect of the application, which comprises a graphite substrate and a composite coating arranged on the surface of the graphite substrate, and the composite coating comprises a CNT / SiC transition layer and a SiC outer coating.

[0049] As shown in Figure 1 The surface of the silicon carbide coating material comprises a CNT / SiC transition layer and a SiC outer coating. The CNT / SiC transition layer is between the two red dashed lines. The SiC outer coating is above the red dashed line.

[0050] The application first deposits a carbon nanotube (CNT) coating layer on the surface of the graphite substrate by an electrophoretic process, and then generates a CNT / SiC transition layer and a SiC outer coating on the surface of the CNT coating layer by a chemical vapor deposition process (CVD). The CNT / SiC transition layer can increase the interfacial bonding force between the SiC outer coating and the graphite substrate, so that the silicon carbide coating is not easy to peel off during use, thereby improving the service life and reliability of the silicon carbide coating material.

[0051] In addition, carbon nanotubes have high conductivity and high strength characteristics, which can significantly improve the electrical conductivity and structural strength of graphite. The silicon carbide coating material provided by the application has good electrochemical stability and is suitable for applications such as batteries and supercapacitors. Moreover, the strength of carbon nanotubes is several tens of times that of steel, and as a reinforcing material added to the graphite base, it can effectively improve its bending and tensile resistance. In addition, the silicon carbide coating can provide excellent wear resistance and corrosion resistance, ensuring the long-term stability of the silicon carbide coating material in extreme environments, and the silicon carbide coating has good thermal conductivity, which helps heat dissipation and is suitable for high-power electronic devices.

[0052] In some embodiments, the thickness of the CNT / SiC transition layer is 30-50 μm, for example, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm or any value within the range defined by any two of the above values. When the thickness of the CNT / SiC transition layer is within the above range, good mechanical interlocking and chemical adsorption can be formed between the CNT / SiC transition layer and the graphite substrate, effectively improving the interfacial bonding force, which is conducive to improving the interfacial bonding force between the SiC outer coating and the graphite substrate.

[0053] In some embodiments, the thickness of the SiC outer coating is 100-120 μm, for example, 100 μm, 102 μm, 105 μm, 108 μm, 110 μm, 112 μm, 115 μm, 118 μm, 120 μm or any value within the range defined by any two of the above values. When the thickness of the SiC outer coating is within the above range, the wear resistance and corrosion resistance of the silicon carbide coating material can be improved, and the long-term stability of the silicon carbide coating material in extreme environments can be improved.

[0054] In some embodiments, the thickness of the composite coating is 110-160 μm, for example, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm, 150 μm, 155 μm, 160 μm or any value within the range defined by any two of the above values. When the thickness of the composite coating is within the above range based on the thicknesses of the CNT / SiC transition layer and the SiC outer coating, the interfacial bonding force between the composite coating and the graphite substrate can be improved, and the service life and reliability of the silicon carbide coating material can be improved.

[0055] The technical solutions in the embodiments of the present application will be described in detail below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0056] The materials, reagents and the like used in the following examples can be obtained from commercial channels unless otherwise specified.

[0057] The present application will be described in detail below with reference to specific examples, which are used to understand rather than limit the present application.

[0058] Example 1

[0059] (1) Step 1: Commercial CNT aqueous slurry (5 wt.%, solvent is deionized water) was purchased from Chengdu Organic Chemical Co., Ltd. The surfactant used in the CNT aqueous slurry is TNWDIS, the mass of TNWDIS is 20% of the mass of CNT, which is specially used for CNT dispersion. The diameter of CNT is about 10 nm, the length is about 50 μm, the original slurry is diluted with deionized water, and then the mixture is treated with ultrasonic homogenizer for 30 minutes to obtain a 0.05 wt.% uniformly dispersed CNT suspension.

[0060] (2) Step 2: The graphite substrate is placed in the 0.05 wt.% uniformly dispersed CNT suspension for 5 minutes during the electrophoretic deposition (EPD) process, the voltage is 50 V, and the temperature is 30°C; then it is placed in a drying oven at 120°C for 5 hours to obtain a dried graphite CNT coating, and the thickness of the carbon nanotube coating layer is 40 μm.

[0061] (3) Step 3: The dried graphite CNT coating is supported by the graphite tooling after pre-deposition, and then placed in a chemical vapor deposition furnace.

[0062] (4) Step 4: The chemical vapor deposition chamber is evacuated, and then the deposition chamber is purged with inert gas.

[0063] (5) Step 5: When depositing a layer of silicon carbide coating on the surface of the graphite base, the chemical vapor deposition chamber is heated to about 1200°C, and trichloromethylsilane and hydrogen gas are introduced into the chemical vapor deposition chamber, the flow ratio of CH3SiCl3:H2 is 1:10, the hydrogen flow is 0.5 slm, the argon flow is 100 g / min, the deposition pressure is 10 kpa, and the deposition time is 300 min, forming a CNT / SiC transition layer and a SiC outer coating on the surface of the graphite substrate, the thickness of the CNT / SiC transition layer is about 40 μm; the thickness of the SiC outer coating is about 105 μm.

[0064] Example 2 group

[0065] Reference is made to Example 1, except that the conditions of the electrophoretic process are changed:

[0066] Example 2a: The conditions of electrophoretic deposition in Step 2 include: voltage of 20 V, time of 10 min, temperature of 20°C, and the thickness of the carbon nanotube coating layer is 35 μm;

[0067] Example 2b: The conditions of electrophoretic deposition in Step 2 include: voltage of 60 V, time of 2 min, temperature of 60°C, and the thickness of the carbon nanotube coating layer is 25 μm.

[0068] Example 3 group

[0069] Example 1 was followed, except that the diameter and length of the carbon nanotubes were changed:

[0070] Example 3a: CNT diameter of about 15 nm, length of about 80 μm;

[0071] Example 3b: CNT diameter of about 5 nm, length of about 20 μm;

[0072] Example 3c: CNT diameter of about 20 nm, length of about 100 μm.

[0073] Example 4 group

[0074] Example 1 was followed, except that the flow ratio of CH3SiCl3:H2was changed:

[0075] Example 4a: CH3SiCl3:H2flow ratio of 1:1;

[0076] Example 4b: CH3SiCl3:H2flow ratio of 1:20;

[0077] Example 4c: CH3SiCl3:H2flow ratio of 1:0.5;

[0078] Example 4d: CH3SiCl3:H2flow ratio of 1:30.

[0079] Example 5 group

[0080] Example 1 was followed, except that the process parameters of chemical vapor deposition were changed:

[0081] Example 5a: deposition temperature of 1400 °C, deposition pressure of 20 kPa, deposition time of 500 min;

[0082] Example 5b: deposition temperature of 1100 °C, deposition pressure of 5 kPa, deposition time of 50 min;

[0083] Example 5c: deposition temperature of 1000 °C, deposition pressure of 3 kPa, deposition time of 30 min.

[0084] Comparative Example 1

[0085] Example 1 was followed, except that the carbon nanotubes were not electrophoretically coated.

[0086] Comparative Example 2

[0087] Example 1 was followed, except that an equal amount of carbon nanofibers was substituted for the carbon nanotubes.

[0088] Comparative Example 3

[0089] Reference is made to Example 1, except that no chemical vapor deposition is performed.

[0090] The SiC coating materials obtained in the above examples and comparative examples were subjected to relevant performance tests, and the test methods are described as follows:

[0091] (1) The test method for the coating bonding strength of the SiC coating refers to the standard GB / T 31541-2015, and specifically includes the following steps:

[0092] i: Measure the width and thickness of the sample, and place the sample on a clamp with a span of 4 mm;

[0093] ii: Open the software and connect online, select the test method as the bending strength, and set the speed to 0.5 mm / min;

[0094] iii: Input the width and thickness of the sample, and clear all the force, displacement, time, and speed, and click start;

[0095] iv: The bonding strength calculation formula is: In the formula, Rm is the bonding strength, FM is the maximum load, and A is the cross-sectional area.

[0096] (2) Thermal shock performance test

[0097] The SiC product was kept at 400°C for 15 min, and then air-cooled to room temperature. The test was repeated multiple times until cracks appeared on the surface of the SiC product, and the number of cycles was recorded as the thermal shock failure number. The thermal shock performance of the product was evaluated by the number of thermal shock failure numbers. The larger the number of thermal shock failure numbers, the better the thermal shock performance, and the smaller the risk of coating cracking and falling off. The test results are recorded in Table 1.

[0098] (3) Test of electrical conductivity

[0099] Four-probe method to measure the electrical conductivity of SiC coating: Equipment: RTS-9 type double electrical four-probe tester, the measuring probe of the equipment is four equally spaced micro probes, usually with a spacing of 1 mm or less;

[0100] Experimental steps:

[0101] (a) Sample preparation

[0102] Clean the sample: Clean the surface of the sample with anhydrous ethanol or deionized water to ensure that there are no contaminants or dust.

[0103] Select the test area: Ensure that the coating in the test area is uniform to avoid edge effects or defect areas. Measure the coating thickness: Measure the coating thickness t using a 3D profilometer or SEM, and record the data.

[0104] (b) Test setup

[0105] Probe placement: Place the probes on the coating surface with a fixed probe spacing S, ensuring good contact of the probe tips but not piercing the coating.

[0106] Connection circuit: The outer two probes are used to apply a constant current I; the inner two probes are used to measure the voltage V.

[0107] (c) Data collection:

[0108] (d) Data processing

[0109] (e) Result processing: Average the conductivity results of multiple measurement points; if there are obvious outliers, check whether there are defects or poor contact in the corresponding area.

[0110] Table 1

[0111]

[0112]

[0113] As can be seen from Table 1, in the present application, a carbon nanotube (CNT) coating layer is deposited on the surface of the graphite substrate by electrophoresis process, which effectively improves the interfacial bonding force; then a SiC outer coating is generated on the surface of the CNT coating layer by chemical vapor deposition process (CVD), and at high temperature, carbon-silicon source penetrates into the microstructure of the porous carbon nanotube, forming a carbon nanotube / silicon carbide transition layer and a silicon carbide outer coating, the carbon nanotube / silicon carbide transition layer can increase the interfacial bonding force between the silicon carbide coating and the graphite substrate, so that the subsequent silicon carbide coating is not easy to peel off during use, and the thermal shock performance and electrical conductivity of the silicon carbide coating material are improved.

[0114] Among them, the conductivity tested in Comparative Example 3 is higher, which is the conductivity of graphite plus carbon nanotubes.

[0115] It is to be understood that the terminology "including", "containing" or any other variation thereof does not exclude the presence of other elements or steps than those listed in the process, method, article, or apparatus. It is further understood that the steps and elements recited in any of the examples herein can be combined, removed or arranged in various ways without departing from the scope of the application. Further, the features described in relation to one example can be combined with features described in relation to other examples.

[0116] The above description is merely illustrative of the application and does not in any way delimit the scope of the application. Any modification, equivalent replacement or the like made within the spirit and principle of the application shall fall within the scope of the application.

Claims

1. A method of improving the bond strength of a SiC coating on a surface of a graphite substrate, characterized by, The method comprises the following steps: S1: placing a graphite substrate in a carbon nanotube suspension with a concentration of 0.03wt.%-0.08wt.% to form a carbon nanotube coating layer on the surface of the graphite substrate by electrophoresis; In the step S1, the process parameters of the electrophoresis method include: a voltage of 20V-50V, a time of 5min-10min, and a temperature of 20℃-30℃; the carbon nanotube suspension further comprises a dispersing agent, the mass of the dispersing agent accounts for 15%-25% of the mass of the carbon nanotube; the diameter of the carbon nanotube is 8nm-15nm, and the length is 30μm-80μm; the thickness of the carbon nanotube coating layer is 35μm-40μm; S2: placing the graphite substrate treated in the step S1 in a chemical vapor deposition device, vacuumizing the chemical vapor deposition device, and then cleaning the deposition device with an inert gas; S3: introducing a mixed gas of a silicon-carbon source gas, a reaction gas, and a carrier gas into the chemical vapor deposition device to deposit a SiC coating layer on the surface of the carbon nanotube coating layer by chemical vapor deposition; the deposition temperature of the chemical vapor deposition is 1200℃-1400℃; in the step S3, the process parameters of the chemical vapor deposition include: a deposition pressure of 10 kPa-20 kPa and a deposition time of 300min-500min; the flow ratio of the silicon-carbon source gas to the reaction gas is 1:10-1:20; The graphite substrate is a graphite susceptor for MOCVD.

2. The method of claim 1, wherein, The flow of the reaction gas is 0.1slm-1slm.

3. The method of claim 1, wherein, The flow of the carrier gas is 50 g / min-150 g / min.

4. The method of claim 1, wherein, The silicon-carbon source gas comprises at least one of monosilane, disilane, trisilane, methylchlorosilane, dimethylchlorosilane, or trichloromethylsilane; And / or, the reaction gas comprises hydrogen; And / or, the carrier gas comprises at least one of argon and / or helium.

5. The method of claim 1, wherein, The silicon-carbon source gas is trichloromethylsilane.

6. The method of claim 1, wherein, The carrier gas is argon.

7. A SiC coating material obtained by the method of any one of claims 1-6, the SiC coating material comprising a graphite substrate and a composite coating layer disposed on the surface of the graphite substrate, the composite coating layer comprising a CNT / SiC transition layer and a SiC outer coating layer.

8. The silicon carbide coated material of claim 7 wherein, The thickness of the CNT / SiC transition layer is 30μm-50μm; and / or, the thickness of the SiC outer coating layer is 100μm-120μm.

9. The silicon carbide coated material of claim 8 wherein, The thickness of the composite coating layer is 110μm-160μm.

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