Preparation method of antioxidant carbon-carbon composite material applying multilayer coatingTechnical Field
The invention relates to the technical field of carbon composite materials, in particular to a preparation method of an antioxidant carbon-carbon composite material with a multilayer coating.
Background
The Carbon/Carbon composite material (Carbon-Carbon composite materials) exhibits excellent heat resistance, specific strength, thermal shock resistance at a high temperature of 2000 ℃ or higher, and strength is enhanced with an increase in temperature. However, the high temperature rigidity of these carbon/carbon composites is limited to Non-oxidizing (Non-oxidizing) atmospheres, oxidation and degradation phenomena occur from 400 ℃ under oxidizing atmospheres, and the materials are difficult to apply at high temperatures due to high temperature surface chemical reactions or mechanical friction. In order to overcome the limitations of carbon/carbon composites in terms of heat resistance, oxidation resistance and wear resistance at high temperatures, it is becoming increasingly important to develop new materials and coating technologies that can improve surface properties.
Currently, research is being conducted in both mainly developed countries and domestically, with ultra-high temperature ceramics (Ultra high temperature ceramics, UHTC) coated on the surface of carbon/carbon composites, which are resistant even at ultra-high temperatures above 2000 ℃. In the method for coating the carbon composite material by using the ultra-high temperature ceramic (UHTC), a Silicon Carbide (SiC) coating method has the advantages of excellent oxidation resistance, lower thermal expansion coefficient, low process cost and the like, and can be used as a good choice for preventing the oxidation of the carbon composite material.
In the prior art, methods of silicon carbide coating are plasma spraying, chemical Vapor Deposition (CVD), slurry sintering, chemical Vapor Reaction (CVR), and the like. However, when the chemical gas phase reaction is carried out at a temperature of 2173K or above, coarse silicon carbide particles are formed, and the generated silicon carbide coating has the defect of interlayer peeling phenomenon; in view of this, a method for preparing an antioxidant carbon-carbon composite material using a multilayer coating is proposed.
Disclosure of Invention
The invention aims to provide a preparation method of an antioxidant carbon-carbon composite material with a multilayer coating, which aims to solve the problems in the background technology.
In order to achieve the above purpose, the present invention provides the following technical solutions: a method for preparing an antioxidant carbon-carbon composite material by using a multilayer coating, comprising the following steps:
Step S1, preparing a carbon/carbon composite material;
s2, performing first silicon carbide coating treatment on the surface of the carbon/carbon composite material by using a chemical gas phase reaction method to prepare a primary material;
and step S3, performing a second coating treatment on the primary material in the step S2 by a chemical vapor deposition mode.
The silicon carbide coating with oxidation resistance is formed by adopting a composite multiple coating method. And coating a layer of silicon carbide on the surface of the carbon composite material by a chemical vapor reaction method to form silicon carbide with a bimodal morphology, thereby improving the surface roughness and forming a larger specific surface area.
Optionally, the step S1 further includes: and filling a carbon source mixture in a carbon fiber preform and performing heat treatment to prepare the carbon/carbon composite material, wherein the carbon fiber preform is prepared from PAN-based carbon fibers, pitch-based carbon fibers and rayon-based carbon fibers.
Optionally, the carbon fiber preform is densified and graphitized by a liquid phase impregnation or chemical vapor infiltration process;
The liquid impregnation method is to impregnate a carbon fiber preform with resins such as asphalt, phenolic resin, furan resin, epoxy resin and the like as carbon sources, and then pyrolyze the resins;
The chemical vapor infiltration method is to inject hydrocarbon gases such as methane, propane, butane and the like as carbon sources into a reactor equipped with a carbon fiber preform, and pyrolyze at a temperature of 800-1100 ℃ to produce a carbon/carbon composite material. And (3) performing secondary coating on the carbon composite material by using a chemical vapor deposition method. A compact and thick silicon carbide coating is formed on the basis of the primary coating, the oxidation resistance of the carbon/carbon composite material is improved by the multi-coating process, and excellent heat resistance can be kept even in a high-temperature extreme environment of more than 2000 ℃, so that the service life of the carbon/carbon composite material is prolonged.
Optionally, in the step S2, carbon on the surface of the carbon/carbon composite material is used as a carbon source, and a thermal decomposition reaction is performed with the SiO2 silicon-based material, so as to form a silicon carbide coating, and the reaction process is as follows:
The reaction temperature of the reaction is 2000-2500 ℃.
Optionally, the thickness of the silicon carbide coating in the step S2 is 10-100 mu m, and the chemical vapor reaction time is 10-30 hours.
Optionally, the step S3 further includes:
The methyltrichlorosilane gas and hydrogen were supplied to the reaction chamber together with the primary coated carbon/carbon composite material at 1250 c by means of chemical vapor deposition to react, keeping the methyltrichlorosilane gas flow rate at 6.7cc/min and the total reaction time at 24h.
Alternatively, the concentration ratio of hydrogen to methyltrichlorosilane is 7.5%.
Optionally, the reaction temperature of the chemical vapor deposition is 1100-1500 ℃.
Optionally, the deposition reaction in the step S3 may form a silicon carbide coating with a thickness of 10-300 μm.
Compared with the prior art, the invention provides a preparation method of an antioxidant carbon-carbon composite material applying a multilayer coating, which has the following beneficial effects:
The preparation method of the antioxidant carbon-carbon composite material with the multilayer coating adopts a composite multiple coating method to form the silicon carbide coating with oxidation resistance. And coating a layer of silicon carbide on the surface of the carbon composite material by a chemical vapor reaction method to form silicon carbide with a bimodal morphology, thereby improving the surface roughness and forming a larger specific surface area. Then, the carbon composite material is coated with a second coating by chemical vapor deposition. A compact and thick silicon carbide coating is formed on the basis of the primary coating, the oxidation resistance of the carbon/carbon composite material is improved by the multi-coating process, and excellent heat resistance can be kept even in a high-temperature extreme environment of more than 2000 ℃, so that the service life of the carbon/carbon composite material is prolonged.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in fig. 1, the present invention provides a technical solution: the preparation method of the antioxidant carbon-carbon composite material with the multilayer coating comprises the following steps:
Step S1, preparing a carbon/carbon composite material, where step S1 further includes: carbon source mixture is filled in a carbon fiber preform and is subjected to heat treatment to densify the carbon source mixture, so that a carbon/carbon composite material is prepared, the carbon fiber preform is made of PAN-based carbon fibers, pitch-based carbon fibers and rayon-based carbon fibers, and the carbon fiber preform is formed by molding the carbon fibers into a certain shape.
Notably, the carbon fiber preform is densified and graphitized by a liquid phase impregnation or chemical vapor infiltration process (CVI). The liquid impregnation method is to impregnate a carbon fiber preform with resins such as pitch, phenolic resin, furan resin, epoxy resin, etc. as a carbon source, and then pyrolyze the resins. In the liquid impregnation method, it is preferable to use, as the carbon source, pitch having high carbon yield, low viscosity, and excellent wettability, and the pitch selected is isotropic pitch, mesophase pitch, or a mixture thereof. In the chemical vapor infiltration method, hydrocarbon gas such as methane, propane, butane, etc. is injected as a carbon source into a reactor equipped with a carbon fiber preform, and pyrolyzed at a temperature of 800 to 1100 ℃ to produce a carbon/carbon composite material. And the density of the composite material can be increased by multiple densification processes. After the densification treatment, the carbon fiber preform is subjected to the next graphitization treatment within the temperature range of 1500-2500 ℃.
And S2, performing first silicon carbide coating treatment on the surface of the carbon/carbon composite material by using a chemical gas phase reaction method to prepare a primary material.
Carbon on the surface of the carbon/carbon composite material is used as a carbon source, and the thermal decomposition reaction is carried out on the carbon/carbon composite material and the SiO2 silicon-based material, so that a silicon carbide coating is formed, and the reaction process is as follows:
In order to coat enough silicon carbide on the surface of carbon/carbon composite materials and form particles of varying thickness, the reaction temperature is 2000-2500 ℃. If the temperature for chemical vapor reaction (CVR) is 2000 ° C or lower, a uniformly shaped silicon carbide coating will be formed, thereby suppressing the formation of coarse particles. If the operating temperature is 2500 ℃ or higher, the high temperature may cause the deposited silicon carbide coating to melt, making it difficult to form a silicon carbide coating; if the process time is less than 10 hours, the reaction time is short and the reaction is not sufficiently performed, and it is difficult to form a silicon carbide coating. If the process time exceeds 30 hours, the formed coating is thicker, which increases the risk of defects and reduces the mechanical strength of the finished material.
In addition, the thickness of the silicon carbide coating in the step S2 is 10-100 mu m, and the chemical gas phase reaction time is 10-30 hours.
And step S3, performing a second coating treatment on the primary material in the step S2 by a chemical vapor deposition mode.
Methyl Trichlorosilane (MTS) gas and hydrogen (H2) were supplied to the reaction chamber at 1250 ℃ together with the primary coated carbon/carbon composite material by means of chemical vapor deposition to react, maintaining a flow rate of Methyl Trichlorosilane (MTS) gas of 6.7cc/min and a total reaction time of 24 hours. The ratio of hydrogen (H2） to Methyltrichlorosilane (MTS) is 7.5%) the reaction temperature of chemical vapor deposition is 1100-1500 ℃, and silicon carbide coating is difficult to obtain when the process temperature is lower than 1100 ℃, on the contrary, if the process temperature exceeds 1500 ℃, the activation of chemical substances can permeate into the carbon/carbon composite material, and is not deposited on the silicon carbide coating.
The deposition reaction can form a silicon carbide coating with the thickness of 10-300 mu m, and if the coating is thinner and the thickness is smaller than 10 mu m, the protection effect is reduced; if the thickness of the silicon carbide coating is more than 300 mu m, the formed coating is too thick, but peeling phenomenon can occur due to flame and the like, so that the silicon carbide coating falls off, and the heat resistance of the carbon/carbon composite material is reduced.
As an application of the present embodiment: the silicon carbide coating with oxidation resistance is formed by adopting a composite multiple coating method. More specifically, a layer of silicon carbide is coated on the surface of the carbon composite material by a chemical vapor reaction method to form silicon carbide with a bimodal morphology, so that the surface roughness is improved, and a larger specific surface area is formed. Then, the carbon composite material is coated with a second coating by chemical vapor deposition. A compact and thick silicon carbide coating is formed on the basis of the primary coating, the oxidation resistance of the carbon/carbon composite material is improved by the multi-coating process, and excellent heat resistance can be kept even in a high-temperature extreme environment of more than 2000 ℃, so that the service life of the carbon/carbon composite material is prolonged.
The foregoing invention has been generally described in great detail, but it will be apparent to those skilled in the art that modifications and improvements can be made thereto. Accordingly, it is intended to cover modifications or improvements within the spirit of the inventive concepts.