Method for improving bonding strength of SiC coating on surface of graphite substrate and product thereof

Abstract

The invention relates to the technical field of semiconductor material preparation, and provides a method for improving the interface bonding strength of a SiC coating on the surface of a graphite base material and a product thereof. The method comprises the following steps: S1, placing a graphite base material in a carbon nanotube suspension, and forming a carbon nanotube coating layer on the surface of the graphite base material by adopting an electrophoresis method; s2, the graphite base material treated in the step S1 is placed in chemical vapor deposition equipment, the chemical vapor deposition equipment is vacuumized, and then the deposition equipment is cleaned with inert gas; and S3, mixed gas of silicon carbon source gas, reaction gas and carrier gas is introduced into chemical vapor deposition equipment, and the SiC coating is deposited on the surface of the carbon nanotube coating layer by adopting a chemical vapor deposition process. According to the method, the interface bonding force between the silicon carbide coating and the graphite substrate can be increased, so that the subsequent silicon carbide coating is not easy to peel off in the use process, and the service life and the reliability of the silicon carbide coating material are improved.

Description

Technical Field

[0001] The present invention 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 surface and a product thereof. Background Art

[0002] In the semiconductor field, MOCVD (Metal Organic Chemical Vapor Deposition) technology performs epitaxial deposition on the substrate, and depositing silicon carbide (SiC) coating on the graphite substrate helps to provide surface protection with high hardness, corrosion resistance and high temperature characteristics. However, there is a key problem with traditional silicon carbide coating technology, that is, the interface bonding force between the coating and the graphite substrate is not high enough, which will cause the 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 silicon carbide coating at different temperatures, the product quality cannot be stably guaranteed. The low production efficiency and the lack of effective process control means lead to a waste of time and energy in the production process, which reduces the overall production efficiency. Therefore, improving the interface bonding force between the SiC coating and the graphite substrate has become an important technical issue. Summary of the invention

[0003] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and provide a method for improving the bonding strength of SiC coating on the surface of graphite substrate and the silicon carbide coating material prepared therefrom. The method first uses an electrophoresis process to deposit a carbon nanotube (CNT) coating layer on the surface of the graphite substrate, and then generates a SiC outer coating on the surface of the CNT coating layer by a chemical vapor deposition process (CVD), which can increase the interface bonding strength between the silicon carbide coating and the graphite substrate, so that the subsequent silicon carbide coating is not easy to peel off during use, thereby improving the service life and reliability of the silicon carbide coating material.

[0004] In order to achieve the above object, the first aspect of the present invention provides a method for improving the bonding strength of a SiC coating on a graphite substrate surface, comprising the following steps:

[0005] 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 an electrophoresis method;

[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 depositing a SiC coating on the surface of the carbon nanotube coating layer by a chemical vapor deposition process.

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

[0009] The present invention adopts the above technical solution to achieve the following beneficial effects:

[0010] (1) The method for improving the bonding strength of the SiC coating on the surface of the graphite substrate provided by the present invention 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, thereby improving the service life and reliability of the silicon carbide coating material;

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

[0012] The endpoints and any values ​​of the range disclosed in this article are not limited to the precise range or value, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article. Herein, in the absence of special instructions, data ranges include endpoints. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Shown is an electron microscope image of silicon carbide coating material. DETAILED DESCRIPTION

[0014] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

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

[0016] The present invention has found that the traditional silicon carbide coating process performs CVD deposition at a specific temperature, which often leads to a weak interface bonding force between the silicon carbide coating and the graphite substrate. This 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 peeling or shedding phenomenon is prone to occur. The process is difficult to control, which limits the production demand in a specific environment. 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, which leads to a waste of time and energy in the production process, reducing the overall production efficiency.

[0017] In order to overcome the above problems existing in the prior art, the present invention proposes the following technical solutions:

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

[0019] 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 an electrophoresis method;

[0020] 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;

[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 invention, a carbon nanotube (CNT) coating layer is first deposited on the surface of a graphite substrate by an electrophoresis process, and good mechanical intercalation and chemical adsorption are formed between the carbon nanotubes and the graphite substrate, thereby effectively improving the interface bonding strength; then a SiC outer coating is generated on the surface of the CNT coating layer by a chemical vapor deposition process (CVD), in which a carbon silicon source penetrates into the microstructure of the porous carbon nanotubes 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, and the carbon nanotube / silicon carbide transition layer can increase the interface bonding strength between the silicon carbide coating and the graphite substrate, so that the subsequent silicon carbide coating is not easy to peel off during use, thereby improving the service life and reliability of the silicon carbide coating material.

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

[0024] In some embodiments, the length of the carbon nanotubes is 30 μm-80 μm, for example, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm or any point value in the range consisting of any two of the above points.

[0025] In the present invention, when the diameter and length of the carbon nanotubes are further limited within the above range, it is possible to avoid the carbon nanotubes having too small a diameter and too small a length, which results in the carbon nanotube coating being too dense, which is not conducive to exerting the flexibility of the carbon nanotube coating and improving the interface bonding strength between the carbon nanotube coating and the graphite substrate; it is also possible to avoid the carbon nanotubes having too large a diameter and too large a length, which results in the network structure pores of the carbon nanotube coating being too large, which is also not conducive to improving the interface bonding strength between the carbon nanotube coating and the graphite substrate; when the diameter and length of the carbon nanotubes are limited within the above range, the interface bonding strength between the carbon nanotube coating and the graphite substrate can be improved, thereby increasing the interface bonding strength between the silicon carbide coating and the graphite substrate.

[0026] In some embodiments, the thickness of the carbon nanotube coating is 25 μm-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, 50 μm. The carbon nanotubes form a continuous covering layer on the surface of the graphite substrate. If the thickness of the carbon nanotube coating is too small, it may cause uneven deposition in some areas during the subsequent deposition of the SiC coating, and the combination of the SiC coating and the graphite substrate cannot be effectively enhanced. The adhesion is insufficient, resulting in easy peeling of the coating during use; and the thickness of the carbon nanotube coating is too small to provide sufficient mechanical buffering, which easily leads to concentration of thermal stress at the interface, thereby causing cracking or peeling of the coating. If the thickness of the carbon nanotube coating is too large, gas transmission will be blocked: During the chemical vapor deposition (CVD) process, an overly thick carbon nanotube layer will limit the permeability of the deposition gas (silicon carbon source gas, reaction gas, etc.), resulting in uneven deposition of the SiC coating. The deposition rate may be significantly reduced, increasing the process time and cost, and may even form pores or defects in local areas; If the thickness of the carbon nanotube coating is too large, an excessively large stress concentration area may be formed at the interface, especially under thermal cycling or high temperature conditions, and this stress may cause peeling or delamination of the coating.

[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 of the above two 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 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, and the thickness of the deposited carbon nanotube coating layer is controlled within the protection scope of the present invention, which can improve the continuity and uniformity of the carbon nanotube coating layer, thereby facilitating the improvement of the interface bonding force between the silicon carbide coating and the graphite substrate.

[0028] In some embodiments, the carbon nanotube suspension further includes a dispersant, the mass of which accounts for 15%-25% of the mass of the carbon nanotubes, for example, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25% or any point value in the range of any two of the above point values. Adding a dispersant to the carbon nanotube suspension and limiting the mass proportion of the dispersant are conducive to more uniform dispersion of the carbon nanotube suspension, improving the efficiency of electrophoretic deposition, and improving the continuity and uniformity of the carbon nanotube coating layer.

[0029] In some embodiments, the dispersant includes an aromatic modified nonionic surfactant, for example, including TNWDIS.

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

[0031] In the present invention, when the process parameters of the electrophoresis method are limited to the above range, a carbon nanotube suspension with a specific concentration can generate a carbon nanotube coating layer with better continuity and uniformity, which is beneficial to improving the interface bonding strength between the silicon carbide coating and the graphite substrate.

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

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

[0034] In some embodiments, step S2 further includes: using a pre-deposited graphite fixture to support the dried graphite substrate, and then placing it in a chemical vapor deposition device. The pre-deposited graphite fixture is to deposit a SiC coating on the surface of the graphite fixture using a CVD process, which can prevent the exposed graphite from volatile impurities at high temperatures and affect the purity of the silicon carbide coating material; in addition, the position supported by the graphite fixture cannot form a SiC outer coating during CVD deposition. When the pre-deposited graphite fixture is used, the SiC at the supporting position will be embedded in the supporting point to maintain the integrity of the silicon carbide coating material product.

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

[0036] In some embodiments, the deposition temperature may be, for example, 1000° C., 1100° C., 1200° C., 1300° C., 1400° C., or any point value in a range consisting of any two of the above points. When the deposition temperature is within the above range, the growth of the silicon carbide coating may be promoted, making the silicon carbide coating more dense.

[0037] In some embodiments, the deposition pressure is 5kPa-20kPa, for example, 5KPa, 6KPa, 8KPa, 10KPa, 12KPa, 14KPa, 16KPa, 18KPa, 20KPa or any point value in the range formed by any two of the above points. When the deposition pressure is within the above range, the deposition rate can be increased, the quality and uniformity of the SiC coating can be improved, and the high production cost caused by excessive deposition pressure can be avoided, while the low density of the SiC coating and the slow deposition rate caused by too low deposition pressure can be avoided.

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

[0039] In some embodiments, in step S3, the flow ratio of the carbon silicon source gas to the reaction gas is 1:1 to 1:20, and the flow ratio can be, 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 point value in the range of any two of the above point 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 is formed by the chemical reaction of the carbon silicon source gas and the reaction gas, which can increase the compactness of the silicon carbide outer coating and improve the high temperature resistance, corrosion resistance, mechanical properties and thermal conductivity of the silicon carbide coating material.

[0040] The flow rates of the carbon silicon source gas and the hydrogen gas are not limited, and the flow rate ranges conventionally used in the art can be selected.

[0041] In some embodiments, the flow rate of the reaction gas is 0.1slm-1slm, for example, it can be 0.1slm, 0.2slm, 0.3slm, 0.4slm, 0.5slm, 0.6slm, 0.7slm, 0.8slm, 0.9slm, 1slm or any point value in the range consisting of any two of the above points.

[0042] In some embodiments, the flow rate of the carrier gas is 50 g / min-150 g / min, for example, it can be 50 g / min, 60 g / min, 80 g / min, 100 g / min, 120 g / min, 150 g / min or any point value in the range consisting of any two of the above point values.

[0043] In the present invention, the "carbon silicon source gas" refers to a gas that can provide carbon and silicon elements, that is, a raw material gas for preparing a precursor of SiC. There is no particular limitation on the carbon silicon source gas, and any gas compound commonly used in the art that can provide carbon and silicon elements and is suitable for preparing silicon carbide materials can be selected.

[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 present invention has a relatively simple electrophoretic deposition process, which can be performed at room temperature, and the deposition rate can be flexibly controlled by adjusting parameters such as voltage and time. This adjustability can meet the material performance requirements in different application scenarios. The process can be performed at a lower temperature and pressure by combining electrophoretic deposition and chemical vapor deposition, which reduces energy consumption and material waste, reduces production costs, ensures full utilization of materials, reduces unnecessary waste generation, and conforms to the trend of green manufacturing.

[0048] The second aspect of the present invention provides a silicon carbide coating material obtained by the method described in the first aspect of the present invention, wherein the silicon carbide coating material includes a graphite substrate and a composite coating arranged on the surface of the graphite substrate, and the composite coating includes a CNT / SiC transition layer and a SiC outer coating.

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

[0050] The present invention firstly deposits a carbon nanotube (CNT) coating layer on the surface of a graphite substrate by an electrophoresis process, and then generates a CNT / SiC transition layer and a SiC outer coating layer on the surface of the CNT coating layer by a chemical vapor deposition process (CVD). The CNT / SiC transition layer can increase the interface bonding force between the SiC outer coating layer 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 electrical 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 present invention has good electrochemical stability and is suitable for applications such as batteries and supercapacitors. Moreover, the strength of carbon nanotubes is dozens of times that of steel. When added to the graphite base as a reinforcing material, it can effectively improve its ability to resist bending and stretching. 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 to dissipate heat and is suitable for high-power electronic devices.

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

[0053] In some embodiments, the thickness of the SiC outer coating is 100 μm-120 μm, for example, 100 μm, 102 μm, 105 μm, 108 μm, 110 μm, 112 μm, 115 μm, 118 μm, 120 μm, or any point value in the range of any two of the above points. 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 μm-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 point value in the range of any two of the above points. On the basis of defining the thickness of the CNT / SiC transition layer and the SiC outer coating, when the thickness of the composite coating is further defined in the above range, the interface bonding force between the composite coating and the graphite substrate is comprehensively improved, and the service life and reliability of the silicon carbide coating material are improved.

[0055] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0057] The present invention is described in detail below in conjunction with specific embodiments, which are used to understand but not to limit the present invention.

[0058] Example 1

[0059] (1) Step 1: Commercial CNT aqueous slurry (5wt.%, 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, and it is specifically used for CNT dispersion. The CNT diameter is about 10nm and the length is about 50μm. The original slurry is diluted with deionized water, and then the mixture is ultrasonically treated for 30 minutes using an ultrasonic homogenizer to obtain a 0.05wt.% uniformly dispersed CNT suspension.

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

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

[0062] (4) Step 4: Evacuate the chemical vapor deposition chamber and then purge the deposition chamber with an inert gas.

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

[0064] Example 2 Group

[0065] The same method is carried out as in Example 1, except that the conditions of the electrophoresis process are changed:

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

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

[0068] Example 3 Group

[0069] The method is carried out in accordance with Example 1, except that the diameter and length of the carbon nanotubes are changed:

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

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

[0072] Example 3c: The CNT diameter is about 20 nm and the length is about 100 μm.

[0073] Example 4 Group

[0074] The same procedure is carried out as in Example 1, except that the flow ratio of CH3SiCl3:H2 is changed:

[0075] Example 4a: The flow ratio of CH3SiCl3:H2 is 1:1;

[0076] Example 4b: The flow ratio of CH3SiCl3:H2 is 1:20;

[0077] Example 4c: The flow ratio of CH3SiCl3:H2 is 1:0.5;

[0078] Example 4d: The flow ratio of CH3SiCl3:H2 is 1:30.

[0079] Example 5 Group

[0080] The process is carried out with reference to Example 1, except that the process parameters of chemical vapor deposition are changed:

[0081] Example 5a: The deposition temperature is 1400° C., the deposition pressure is 20 kPa, and the deposition time is 500 min;

[0082] Example 5b: The deposition temperature is 1100° C., the deposition pressure is 5 kPa, and the deposition time is 50 min;

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

[0084] Comparative Example 1

[0085] The process is carried out in accordance with Example 1, except that the electrophoresis coating of carbon nanotubes is not performed.

[0086] Comparative Example 2

[0087] The same method is carried out as in Example 1, except that an equal amount of carbon nanofibers replaces the carbon nanotubes.

[0088] Comparative Example 3

[0089] The same process is carried out as in Example 1, except that chemical vapor deposition is not performed.

[0090] The silicon carbide 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 bonding strength of SiC coating refers to GB / T 31541-2015 standard, which specifically includes the following steps:

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

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

[0094] iii: Input the width and thickness of the sample, reset the force, displacement, time and speed to zero, and click Start;

[0095] iv: Bond strength calculation formula: Where: Rm—bonding strength; FM—maximum load; A—cross-sectional area.

[0096] (2) Thermal shock performance test

[0097] The silicon carbide product was kept at 400°C for 15 minutes and then air-cooled. The test was repeated for multiple cycles until cracks appeared on the surface of the silicon carbide product. The number of cycles was recorded as the number of thermal shock failures. The thermal shock performance of the product was evaluated by the number of thermal shock failures. The greater the number of thermal shock failures, the better the thermal shock performance and the smaller the risk of cracking and falling off of the coating. The test results are recorded in Table 1.

[0098] (3) Conductivity test

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

[0100] Experimental steps:

[0101] (a) Sample preparation

[0102] Clean the sample: Use anhydrous ethanol or deionized water to clean the sample surface to ensure there is no contaminant or dust.

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

[0104] (b) Test setup

[0105] Probe placement: Place the probe on the coating surface with the probe spacing S fixed, ensuring that the probe tip has good contact but cannot pierce the coating;

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

[0107] (c) Data collection:

[0108] (d) Data processing

[0109] (e) Result processing: Take the average value of the conductivity results of multiple measurement points; if there are obvious abnormal values, check whether the corresponding area has defects or poor contact.

[0110] Table 1

[0111]

[0112]

[0113] As can be seen from Table 1, in the present invention, a carbon nanotube (CNT) coating layer is deposited on the surface of the graphite substrate by an electrophoresis process, thereby 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), and the carbon silicon source penetrates into the microstructure of the porous carbon nanotubes at high temperature to form a carbon nanotube / silicon carbide transition layer and a silicon carbide outer coating. 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, thereby improving the thermal shock resistance and electrical conductivity of the silicon carbide coating material.

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

[0115] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0116] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for improving the bonding strength of a SiC coating on a graphite substrate, characterized in that: The following steps are involved: 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 an electrophoresis method; 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; 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.

2. The method according to claim 1, characterized in that The carbon nanotubes have a diameter of 8nm-15nm and a length of 30μm-80μm; And / or, the carbon nanotube coating layer has a thickness of 25 μm-50 μm.

3. The method according to claim 1, characterized in that The concentration of the carbon nanotube suspension is 0.03wt.%-0.08wt.%; Preferably, 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.

4. The method according to claim 1, characterized in that: In step S1, the process parameters of the electrophoresis method include: voltage of 20V-60V, time of 2min-10min, and temperature of 20°C-60°C.

5. The method according to any one of claims 1 to 4, characterized in that: In the step S3, the process parameters of chemical vapor deposition include: deposition temperature of 1100° C.-1400° C., deposition pressure of 5 kPa-20 kPa, and deposition time of 50 min-500 min.

6. The method according to any one of claims 1 to 4, characterized in that: In the step S3, the flow ratio of the carbon silicon source gas to the reaction gas is 1:1 to 1:

20.

7. The method according to any one of claims 1 to 4, characterized in that: The flow rate of the reaction gas is 0.1slm-1slm; Preferably, the flow rate of the carrier gas is 50 g / min-150 g / min.

8. The method according to any one of claims 1 to 4, characterized in that: The carbon silicon source gas includes at least one of monosilane, disilane, trisilane, methylchlorosilane, dimethylchlorosilane or trichloromethylsilane; preferably trichloromethylsilane; and / or, the reaction gas comprises hydrogen; And / or, the carrier gas comprises at least one of argon and / or helium, preferably argon.

9. A silicon carbide coating material obtained by the method according to any one of claims 1 to 8, wherein the silicon carbide coating material comprises a graphite substrate and a composite coating arranged on the surface of the graphite substrate, wherein the composite coating comprises a CNT / SiC transition layer and a SiC outer coating.

10. The silicon carbide coating material according to claim 9, characterized in that: The thickness of the CNT / SiC transition layer is 30 μm-50 μm; and / or the thickness of the SiC outer coating is 100 μm-120 μm; Preferably, the composite coating has a thickness of 110 μm-160 μm.

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