A ceramic slurry, a coating for improving corrosion resistance of carbon-carbon composite material, and a method for preparing the same

Abstract

The application relates to the technical field of corrosion prevention of carbon-carbon materials, and specifically discloses a ceramic slurry, a coating for improving the corrosion resistance of carbon-carbon composite materials and a preparation method of the coating. The ceramic slurry comprises the following raw materials in parts by weight: 45-60 parts of kaolin powder, 35-50 parts of bentonite powder, 8-15 parts of silicon carbide powder, 10-30 parts of hafnium carbide composite powder, 260-400 parts of a solvent and 0.4-0.6 parts of a sintering aid; the hafnium carbide composite powder is prepared by sintering raw materials including hafnium carbide powder, zirconium powder and silicon carbide whiskers; the ceramic slurry is obtained by mixing the raw materials; and the ceramic coating is formed on the surface of the carbon-carbon composite material after the ceramic slurry is impregnated on the surface of the carbon-carbon composite material, solvent removal and sintering. The ceramic coating has a compact structure, good fracture toughness and good resistance to silicon vapor corrosion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of corrosion protection of carbon-carbon materials, and more particularly to a ceramic slurry, a coating for improving the corrosion resistance of carbon-carbon composite materials and a preparation method thereof. BACKGROUND

[0002] The carbon / carbon heat shield component in the hot field system of the single crystal furnace has the advantages of light weight, low density, thermal shock resistance and high temperature resistance. However, it is easily eroded by silicon vapor under the condition of hot field and silicon vapor corrosion, and residues fall off, resulting in product failure and reduced shelf life. In order to solve this problem, the current production technology considers adding a dense graphite protective layer to the carbon / carbon heat shield component which is most severely corroded by the single crystal furnace. The solution system adopts a resin material ethanol dissolution system to solidify the graphite powder on the surface of the product, so that the bonding performance of the product is better, and the resin is carbonized and decomposed at high temperature without residual impurities.

[0003] However, the heat shield component in the single crystal furnace is very easy to be eroded by silicon vapor under the condition of hot field and silicon vapor corrosion, and the physical and mechanical properties thereof deteriorate rapidly. The graphite coating still has a falling-off condition.

[0004] In order to solve this problem, coating a ceramic coating on the surface of the carbon-carbon composite material is an effective measure to solve the high-temperature (especially above 1200℃) corrosion resistance of carbon materials. In related technologies, when coating a ceramic coating on the surface of the carbon-carbon composite material, a silicon-containing substance is often added to form silicon carbide with carbon, thereby improving the silicon vapor corrosion resistance of the carbon-carbon composite material.

[0005] However, the above-mentioned scheme still has the problem that although silicon carbide has good silicon vapor corrosion resistance, it also has the problem of low fracture toughness. Therefore, due to the low fracture toughness, the coating also has the problems of cracking and falling off. In addition, the silicon carbide ceramic coating itself also has a pore structure, and its silicon vapor corrosion resistance needs to be improved. SUMMARY

[0006] In order to further improve the silicon vapor corrosion resistance and fracture toughness of the coating, the present application provides a ceramic slurry, a coating for improving the corrosion resistance of carbon-carbon composite materials and a preparation method thereof.

[0007] In a first aspect, the present application provides a ceramic slurry, which adopts the following technical scheme:

[0008] A ceramic slurry comprises the following raw materials by weight:

[0009] Kaolin powder 45-60 parts, bentonite powder 35-50 parts, silicon carbide powder 8-15 parts, hafnium carbide composite powder 10-30 parts, solvent 260-400 parts, sintering aid 0.4-0.6 parts;

[0010] The hafnium carbide composite powder is prepared by sintering raw materials including hafnium carbide powder, zirconium powder and silicon carbide whisker.

[0011] By adopting the technical scheme, the hafnium carbide composite powder is prepared in advance, and the raw materials for preparing the hafnium carbide composite powder include hafnium carbide powder, zirconium powder and silicon carbide whisker. Hafnium carbide itself is a high-temperature-resistant material, but it is still prone to oxidation at a high temperature of 1500 ℃ or above. When hafnium carbide and metal zirconium are mixed and sintered, the metal zirconium diffuses to the (Hf, Zr)C solid solution at the HfC grain boundary to strengthen the grain boundary, reduce the HfC grain size, improve the fracture toughness and densify the ceramic. When hafnium carbide and silicon carbide whisker are mixed and sintered in advance, the silicon carbide whisker has a linear structure and exists in the crystal phase, which can effectively promote crack deflection, bridging and crack arrest between the crystal phases, and the silicon carbide whisker in the form of whisker promotes stress release and inhibits HfC grain growth, thereby achieving the effects of toughening and densification. In addition, the silicon carbide whisker can also form a second phase SiC of the toughened HfC ceramic after sintering. Therefore, the fracture toughness of the material is significantly improved under the cooperation of the dispersion toughening of the metal zirconium, the linear structure toughening of the silicon carbide whisker and the second phase toughening of the silicon carbide. In addition, the reduction of the HfC grain size also effectively realizes the densification of the ceramic, thereby significantly improving the corrosion resistance.

[0012] When the hafnium carbide composite powder is used to prepare a coating, the kaolin powder and the bentonite powder contain a large amount of silicon dioxide, which can react with carbon in the carbon-carbon composite material to generate silicon carbide; meanwhile, when the silicon carbide crystal phase is formed, the aluminum oxide contained therein generates a metal oxide crystal phase. A small amount of added silicon carbide powder can be used as a silicon carbide grain to promote the generation of the silicon carbide crystal phase. After the addition of the hafnium carbide composite powder, the addition of HfC densifies the SiC crystal phase to improve the corrosion resistance of the formed ceramic coating. When the hafnium carbide is sintered, the oxide HfO2 is inevitably generated, that is, the hafnium carbide composite powder itself contains a certain amount of oxide HfO2; when the hafnium carbide composite powder is used to prepare a coating, the HfO2 also reacts with the SiO2 in the kaolin powder and the bentonite powder to generate HfSiO4 with strong oxidation resistance, thereby significantly improving the oxidation resistance of the coating and maintaining the densification characteristics of the coating. In addition, the hafnium carbide composite powder of the present application is a composite ceramic material with a certain crystal phase structure obtained by sintering hafnium carbide, zirconium and silicon carbide in advance. When the composite ceramic material is added as a raw material, it further reacts with other raw materials to further form a new crystal phase structure. The fracture toughness and silicon vapor corrosion resistance of the material prepared from the ceramic material with the crystal phase structure are significantly improved.

[0013] In actual reaction, the ceramic slurry is coated on the surface of the carbon-carbon composite material, and then infiltrates into the surface pores of the carbon-carbon composite material, and the SiO2 in the ceramic slurry reacts with the C in the carbon-carbon composite material to generate SiC. Therefore, the solvent is used to make the ceramic slurry more easily infiltrate into the pores of the carbon-carbon composite material, so that the SiO2 and the C can be in sufficient contact to generate SiC. Another reason for introducing the metal zirconium into the hafnium carbide composite powder is that the melting point of the formed zirconium carbide and the metal zirconium is low, about 1800°C, and after the zirconium carbide and the metal zirconium are melted, the other materials have fluid characteristics, further enter the pores of the carbon-carbon material, so that the ceramic coating formed on the surface of the carbon-carbon material is thicker, and the corrosion resistance of the ceramic coating is improved.

[0014] Optionally, the raw materials for preparing the hafnium carbide composite powder include the following components by weight based on the weight of the hafnium carbide powder:

[0015] The hafnium carbide powder is 100 parts, the zirconium powder is 20-30 parts, and the silicon carbide whisker is 15-25 parts.

[0016] By using the above technical solution, the hafnium carbide composite powder is prepared by using appropriate raw materials and proportions to obtain a densified material with high fracture toughness.

[0017] Optionally, the length of the silicon carbide whisker is 10-50 μm, and the diameter is 100-600 nm.

[0018] Optionally, the zirconium powder and the silicon carbide powder are both nanometer powders.

[0019] By using the above technical solution, the nanometer-level powder is beneficial to make the grain smaller, and the obtained ceramic material is densified, and the fracture toughness and corrosion resistance of the material are improved.

[0020] Optionally, the preparation method of the hafnium carbide composite powder includes the following steps:

[0021] The hafnium carbide powder, the zirconium powder and the silicon carbide whisker are mixed according to the proportions, and then are pressed into a block, and are calcined at 1600-1800°C for 2.5-3.5h to obtain a block;

[0022] The block is crushed to obtain the hafnium carbide composite powder.

[0023] By using the above technical solution, after the raw materials are sintered, a certain crystal phase structure is formed, which is beneficial to improve the fracture toughness and corrosion resistance of the material.

[0024] Optionally, the condition parameters when the block is pressed include that the pressing pressure is 300-400Mpa, and the pressing time is 10-25min.

[0025] Optionally, the sintering aid is selected from any one or more of MgO, La2O3, TiO2 and Y2O3;

[0026] Preferably, the sintering aid consists of MgO, La2O3 and TiO2; the mass ratio of MgO, La2O3 and TiO2 is 4: (2-4): (1-3).

[0027] Optionally, the particle size of the sintering aid is not greater than 20 μm.

[0028] Optionally, the solvent is selected from any one or more of toluene and isopropyl alcohol; preferably, the solvent is a mixture of toluene and isopropyl alcohol; further preferably, the solvent is obtained by mixing toluene and isopropyl alcohol in a volume ratio of 3: (5-9).

[0029] Optionally, the SiO2 in the kaolin powder is ≥ 70 wt%, and the Al2O3 is ≤ 30%; the particle size of the kaolin powder is 15-20 μm.

[0030] The SiO2 in the bentonite powder is ≥ 80 wt%, and the Al2O3 is ≤ 20%; the particle size of the kaolin powder is 17-18 μm.

[0031] In a second aspect, the present application provides a preparation method of the above ceramic slurry, which adopts the following technical scheme:

[0032] A preparation method of the above ceramic slurry, the preparation method comprising the following steps:

[0033] Mixing the kaolin powder, the bentonite powder, the silicon carbide powder, the hafnium carbide composite powder, the solvent and the sintering aid according to the ratio to obtain a mixture, and then ball milling the mixture to obtain the ceramic slurry.

[0034] Optionally, the step of ball milling the mixture to obtain the ceramic slurry further comprises the step of ball milling and crushing the mixture, and the ball milling and crushing conditions include a ball milling speed of 30-50 rpm and a ball milling time of 17-23 h.

[0035] By adopting the above technical scheme, the material mixing is realized in the form of ball milling, and the particle size of the material is further reduced, the specific surface area is increased, more reaction active sites are exposed, the reaction activity is improved, and the ceramic coating is further densified, so that the silicon vapor corrosion resistance and the fracture toughness of the ceramic coating are improved.

[0036] In a third aspect, the present application provides a coating preparation method for improving the corrosion resistance of carbon-carbon composite materials, which adopts the following technical scheme:

[0037] A coating preparation method for improving the corrosion resistance of carbon-carbon composite materials, the coating preparation method comprising the following steps:

[0038] dipping: dipping the carbon-carbon composite material in the ceramic slurry for 1-2 hours to obtain a dipped carbon-carbon composite material;

[0039] solvent removal: heat the dipped carbon-carbon composite material at 450-600°C in an inert gas environment to remove the solvent in the ceramic slurry;

[0040] sintering: heat the dipped carbon-carbon composite material after the solvent removal at 1500-1700°C to synthesize silicon carbide; and then sinter at 2000-2200°C to graphitize the carbon material, i.e. to form the coating on the carbon-carbon composite material.

[0041] By using the above technical solution, the ceramic slurry is fully dipped into the pores of the carbon-carbon composite material to provide a reaction basis for full reaction. The solvent removal is actually to fully remove the solvent to avoid the adverse effects of the solvent on the performance of the ceramic coating. In the sintering process, the heat preservation at 1500-1700°C is used to first generate silicon carbide, and then high-temperature graphitization is used to make the carbon-carbon composite material have high strength and thermal stability, and to remove impurity elements in the material. In addition, the use environment of the product is greater than 1800°C, so higher temperature treatment is required. Finally, a material with high silicon vapor corrosion resistance and fracture toughness is prepared.

[0042] Optionally, in the sintering process, the heat preservation of the dipped carbon-carbon composite material after the solvent removal is performed at 1500-1700°C for 8-12 hours; and the sintering is performed at 2000-2200°C for 65-80 hours.

[0043] Optionally, in the dipping process, the carbon-carbon composite material and the ceramic slurry are placed in an inert gas atmosphere, and a pressure of 0.7-1.2 MPa is applied during the dipping.

[0044] By using the above technical solution, the environmental pressure is applied to promote the ceramic slurry to fully penetrate into the pores of the carbon-carbon composite material, so that the raw materials fully react to form a silicon carbide coating, and a coating with high silicon vapor corrosion resistance and fracture toughness is formed on the surface of the carbon-carbon composite material.

[0045] In a fourth aspect, the present application provides a coating for improving the corrosion resistance of a carbon-carbon composite material, which uses the following technical solution:

[0046] A coating for improving the corrosion resistance of a carbon-carbon composite material is prepared by using the above coating preparation method.

[0047] In summary, the present application has the following beneficial effects:

[0048] 1. Through literature research, it is found that the heat shield material surface can be doped with ceramic material by means of impregnation, plasma spraying, vapor deposition, sol-gel method and other methods, so that a ceramic protective layer is generated on the surface of the carbon-carbon composite material to improve the service life of the heat shield product in the thermal field system. The application adopts wet mixing to prepare ceramic slurry, uses coating method for oxidation resistance treatment, and uses carbon thermal reduction method and pressureless sintering method to sinter silicon carbide coating material.

[0049] 2. The application prepares a hafnium carbide composite powder, which is sintered and crushed from hafnium carbide powder, zirconium powder and silicon carbide whisker; the hafnium carbide composite powder is used to prepare ceramic slurry to react with carbon-carbon composite material, and finally an oxidation-resistant, silicon vapor corrosion-resistant and excellent fracture toughness material is obtained. DETAILED DESCRIPTION

[0050] The application will be further described in detail in combination with examples, and it is particularly pointed out that: in the following examples, the specific conditions are not specified, and the conventional conditions or the conditions recommended by the manufacturer are used, and the raw materials used in the following examples can be obtained from ordinary market sales unless otherwise specified.

[0051] Raw material sources:

[0052] The kaolin powder is purchased from the National Pharmaceutical Group Chemical Reagent Co., Ltd., and the product model is Acros-C21174, and the GAS number is 1332-58-7. The kaolin powder is white, contains SiO2≥70wt%, Al2O3≤30%, the particle size is 15-20μm, and the purity is more than 99wt%. The main component is kaolinite, which belongs to low plasticity soil, is a 1:1 type crystal structure composed of one layer of silicon oxygen tetrahedron and one layer of aluminum oxygen octahedron, and has the chemical composition of Al2O3·2SiO2·2H2O, good plasticity and high adhesion, good acid resistance, good fire resistance and other physical and chemical properties.

[0053] The bentonite powder is purchased from the National Pharmaceutical Group Chemical Reagent Co., Ltd., and the product model is Acros-C44744, and the GAS number is 1302-78-9. The bentonite powder is yellowish white, contains SiO2≥80wt%, Al2O3≤20%, the particle size is 17-18μm, and the purity is more than 99.5wt%. The main component is montmorillonite, which belongs to high plasticity soil, and is a 2:1 crystal structure composed of two silicon oxygen tetrahedrons and one layer of aluminum oxygen octahedron.

[0054] The silicon carbide powder is purchased from the National Pharmaceutical Group Chemical Reagent Co., Ltd., and the product model is Alfa-A13561, and the GAS number is 409-21-2. The silicon carbide powder is light green, the average particle size is 5-10μm, and the purity is more than 99wt%.

[0055] Hafnium carbide powder was purchased from Beijing Deke Island Gold Technology Co., Ltd., product model DK-HfC-001. The hafnium carbide powder was gray-black, with an average particle size of 100 nm, a purity of 99.9wt%, and a hexagonal crystal form.

[0056] Silicon carbide whiskers were purchased from Qinghe County Chaotai Metal Material Co., Ltd., CAS No. 409-21-2, product model SiCW-80 or SiCW-90. Specifically, the silicon carbide whiskers of product model SiCW-80 had a diameter of 200-500 nm and a length of 10-50 μm; specifically, the silicon carbide whiskers of product model SiCW-90 had a diameter of 100-600 nm and a length of 10-50 μm.

[0057] Zirconium powder was purchased from Zhuzhou Runfeng New Material Co., Ltd., CAS No. 7440-67-7, dark gray metal powder, purity ≥ 99.5wt%, particle size 1-3 μm.

[0058] Preparation example of hafnium carbide composite powder

[0059] Preparation example 1

[0060] The preparation raw material of hafnium carbide composite powder was: 300 g of hafnium carbide powder, 60 g of zirconium powder, and 45 g of silicon carbide whiskers; wherein the product model of the silicon carbide whiskers was SiCW-90.

[0061] The preparation method of the hafnium carbide composite powder was: the hafnium carbide powder, the zirconium powder, and the silicon carbide whiskers were mixed according to the ratio, and then pressed into a block under a pressure of 300 MPa for 25 min. Subsequently, the block was placed in a nitrogen atmosphere and calcined at 1600°C for 3.5 h to obtain a block. After the block was crushed to a micro-nano level, the part with a particle size of 500 nm or less was collected by screening, which was the hafnium carbide composite powder.

[0062] Preparation example 2

[0063] The preparation raw material of hafnium carbide composite powder was: 300 g of hafnium carbide powder, 75 g of zirconium powder, and 60 g of silicon carbide whiskers; wherein the product model of the silicon carbide whiskers was SiCW-80.

[0064] The preparation method of the hafnium carbide composite powder was: the hafnium carbide powder, the zirconium powder, and the silicon carbide whiskers were mixed according to the ratio, and then pressed into a block under a pressure of 350 MPa for 20 min. Subsequently, the block was placed in a nitrogen atmosphere and calcined at 1700°C for 3.0 h to obtain a block. After the block was crushed to a micro-nano level, the part with a particle size of 500 nm or less was collected by screening, which was the hafnium carbide composite powder.

[0065] Preparation example 3

[0066] The raw material for preparing the hafnium carbide composite powder is: hafnium carbide powder 300 g, zirconium powder 90 g, and silicon carbide whisker 75 g; wherein the product model of the silicon carbide whisker is SiCW-80.

[0067] The preparation method of the hafnium carbide composite powder is: the hafnium carbide powder, the zirconium powder, and the silicon carbide whisker are uniformly mixed according to the proportion, and then pressed into a block under the pressure of 400 MPa for 10 min; then the block is calcined in a nitrogen atmosphere at 1800 ℃ for 2.5 h to obtain a bulk body. After the bulk body is crushed to the micro-nano level, the part with a particle size of less than 500 nm is collected by screening, and the hafnium carbide composite powder is obtained.

[0068] Preparation Example 4

[0069] The raw material for preparing the hafnium carbide composite powder is: hafnium carbide powder 300 g, zirconium powder 90 g, and silicon carbide whisker 75 g; wherein the product model of the silicon carbide whisker is SiCW-80.

[0070] Preparation Example 5

[0071] The raw material for preparing the hafnium carbide composite powder is: hafnium carbide powder 300 g, zirconium powder 90 g, and silicon carbide whisker 75 g; wherein the product model of the silicon carbide whisker is SiCW-80.

[0072] Preparation Example 6

[0073] The raw material for preparing the hafnium carbide composite powder is: hafnium carbide powder 300 g, zirconium powder 90 g, and silicon carbide whisker 75 g; wherein the product model of the silicon carbide whisker is SiCW-80.

[0074] The preparation method of the hafnium carbide composite powder is: the hafnium carbide powder, the zirconium powder, and the silicon carbide whisker are uniformly mixed according to the proportion, and then pressed into a block under the pressure of 400 MPa for 10 min; then the block is calcined in a nitrogen atmosphere at 1800 ℃ for 2.5 h to obtain a bulk body. After the bulk body is crushed to the micro-nano level, the part with a particle size of less than 500 nm is collected by screening, and the hafnium carbide composite powder is obtained.

[0075] Ceramic slurry example

[0076] Example 1

[0077] A ceramic slurry, the raw material and the proportion of which are:

[0078] Kaolin powder 900 g, bentonite powder 700 g, silicon carbide powder 160 g, hafnium carbide composite powder 200 g, solvent 5200 g, and sintering aid 8 g; wherein the solvent is toluene, the hafnium carbide composite powder is prepared by using the raw material and the method of Preparation Example 1, and the sintering aid is magnesium oxide.

[0079] The preparation method of the ceramic slurry is: the kaolin powder, the bentonite powder, the silicon carbide powder, the hafnium carbide composite powder, the solvent, and the sintering aid are uniformly mixed according to the proportion, and then placed in a 20 L ball mill tank, 20 kg of alumina balls are added, and placed on the ball mill frame, and the rotation speed is set to 30 rpm; after ball milling for 23 h, the ceramic slurry is obtained.

[0080] Example 2

[0081] A ceramic slurry, raw materials and proportions are as follows:

[0082] 1000g of kaolin powder, 900g of bentonite powder, 240g of silicon carbide powder, 400g of hafnium carbide composite powder, 7000g of solvent, and 10g of sintering aid; wherein the solvent is obtained by mixing toluene and isopropyl alcohol at a volume ratio of 3:7, the hafnium carbide composite powder is prepared by using the raw material proportions and method of Preparation Example 2, and the sintering aid is obtained by mixing MgO, La2O3, and TiO2 at a mass ratio of 4:3:2.

[0083] The preparation method of the ceramic slurry is as follows: the kaolin powder, the bentonite powder, the silicon carbide powder, the hafnium carbide composite powder, the solvent, and the sintering aid are mixed uniformly according to the proportions, then placed in a 20L ball mill tank, 20kg of alumina balls are added, placed on a ball mill frame, the rotation speed is set to 40rpm, and the ball milling is performed for 20h to obtain the ceramic slurry.

[0084] Example 3

[0085] A ceramic slurry, raw materials and proportions are as follows:

[0086] 1200g of kaolin powder, 1000g of bentonite powder, 300g of silicon carbide powder, 600g of hafnium carbide composite powder, 8000g of solvent, and 12g of sintering aid; wherein the solvent and the sintering aid are the same as in Example 2, and the hafnium carbide composite powder is prepared by using the raw material proportions and method of Preparation Example 3.

[0087] The preparation method of the ceramic slurry is as follows: the kaolin powder, the bentonite powder, the silicon carbide powder, the hafnium carbide composite powder, the solvent, and the sintering aid are mixed uniformly according to the proportions, then placed in a 20L ball mill tank, 20kg of alumina balls are added, placed on a ball mill frame, the rotation speed is set to 50rpm, and the ball milling is performed for 17h to obtain the ceramic slurry.

[0088] Examples 4-5

[0089] The difference between the following examples and Example 2 is that the amount of hafnium carbide composite powder added in the preparation of the ceramic slurry is different, and the others are the same as in Example 2; the amount of hafnium carbide composite powder added is as follows:

[0090] The amount of hafnium carbide composite powder added in Example 4 is 200g, and the amount of hafnium carbide composite powder added in Example 5 is 600g.

[0091] Comparative Examples

[0092] Comparative Examples 1-3

[0093] The following comparative examples and example 2 differ in that the hafnium carbide composite powder for preparing the ceramic slurry is derived from different preparation examples, and the others are the same as example 2; the source of the hafnium carbide composite powder is as follows:

[0094] The hafnium carbide composite powder in comparative example 1 is prepared by using the raw material ratio and method of preparation example 4, and the hafnium carbide composite powder in comparative example 2 is prepared by using the raw material ratio and method of preparation example 5; the hafnium carbide composite powder in comparative example 3 is prepared by using the raw material ratio and method of preparation example 6.

[0095] Comparative example 4

[0096] The present comparative example and example 2 differ in that the hafnium carbide composite powder is not included in the raw materials of the ceramic slurry, and the others are the same as example 2; the details are as follows:

[0097] A ceramic slurry, whose raw materials and ratio are as follows:

[0098] 1000g of kaolin powder, 900g of bentonite powder, 240g of silicon carbide powder, 7000g of solvent, and 10g of sintering aid; wherein the solvent and sintering aid are the same as in example 2.

[0099] The preparation method of the ceramic slurry is the same as in example 2.

[0100] Coating for improving the corrosion resistance of carbon-carbon composite material

[0101] The carbon-carbon composite material substrate is cut into a block of 4cm x 4cm x 1cm, the surface is washed clean with water and then ultrasonically washed for 10min, and then dried at 110℃ to constant weight for coating the ceramic slurry on the surface to obtain a sample. At the same time, the carbon-carbon composite material is used as a control sample (without coating any slurry) to further illustrate the effect after coating the coating.

[0102] Example 1

[0103] The preparation method of the coating for improving the corrosion resistance of carbon-carbon composite material, the specific steps are as follows:

[0104] Immersion: the treatment is carried out by using the method of liquid immersion, and the specific steps are as follows: the carbon-carbon composite material dried to constant weight obtained above is immersed in the ceramic slurry, then nitrogen gas is filled in the muffle furnace for 10min to ensure that the atmosphere in the muffle furnace is nitrogen; then the carbon-carbon composite material immersed in the ceramic slurry is placed in the muffle furnace together; then a gas pressure of 0.7Mpa is applied, and the immersion is continued at 50℃ for 1h, and the sample is taken out after cooling to obtain the immersed carbon-carbon composite material. The ceramic slurry is prepared by using the formula and method of ceramic slurry example 1.

[0105] Solvent removal: The impregnated carbon-carbon composite material was placed in a muffle furnace filled with nitrogen, heated to 450°C for 6h to remove the solvent in the ceramic slurry by evaporation.

[0106] Sintering: After cooling, the impregnated carbon-carbon composite material after removing the solvent was carefully taken out of the muffle furnace and placed in a high-temperature sintering furnace. The temperature was set to 1500°C and kept for 12h to synthesize silicon carbide; then the temperature was set to 2000°C and sintered for 80h to graphitize the carbon material, finally forming a ceramic coating outside the carbon-carbon composite material.

[0107] Example 2

[0108] The specific steps of the coating preparation method for improving the corrosion resistance of carbon-carbon composite material are as follows:

[0109] Impregnation: The treatment was carried out by liquid phase impregnation, and the specific steps were as follows: the carbon-carbon composite material dried to constant weight obtained above was impregnated in the ceramic slurry, then nitrogen was filled in the muffle furnace for 10min to ensure that the atmosphere in the muffle furnace was nitrogen; then the carbon-carbon composite material impregnated in the ceramic slurry was placed in the muffle furnace together; then 1.0Mpa of air pressure was applied, and the impregnation was continued at 35°C for 1.5h, and the sample was taken out to obtain the impregnated carbon-carbon composite material. The ceramic slurry was prepared by the formula and method of ceramic slurry example 2.

[0110] Solvent removal: The impregnated carbon-carbon composite material was placed in a muffle furnace filled with nitrogen, heated to 500°C for 5h to remove the solvent in the ceramic slurry by evaporation.

[0111] Sintering: After cooling, the impregnated carbon-carbon composite material after removing the solvent was carefully taken out of the muffle furnace and placed in a high-temperature sintering furnace. The temperature was set to 1600°C and kept for 10h to synthesize silicon carbide; then the temperature was set to 2100°C and sintered for 72h to graphitize the carbon material, finally forming a ceramic coating outside the carbon-carbon composite material.

[0112] Example 3

[0113] The specific steps of the coating preparation method for improving the corrosion resistance of carbon-carbon composite material are as follows:

[0114] Impregnation: The treatment was carried out by liquid phase impregnation, and the specific steps were as follows: the carbon-carbon composite material dried to constant weight obtained above was impregnated in the ceramic slurry, then nitrogen was filled in the muffle furnace for 10min to ensure that the atmosphere in the muffle furnace was nitrogen; then the carbon-carbon composite material impregnated in the ceramic slurry was placed in the muffle furnace together; then 1.0Mpa of air pressure was applied, and the impregnation was continued at 35°C for 1.5h, and the sample was taken out to obtain the impregnated carbon-carbon composite material. The ceramic slurry was prepared by the formula and method of ceramic slurry example 2.

[0115] Solvent removal: The impregnated carbon-carbon composite material was placed in a nitrogen-filled muffle furnace, heated to 600°C for 4h to remove the solvent in the ceramic slurry by evaporation.

[0116] Sintering: After cooling, the impregnated carbon-carbon composite material after solvent removal was carefully taken out of the muffle furnace and placed in a high-temperature sintering furnace. The temperature was set to 1700°C and kept for 8h to synthesize silicon carbide; then the temperature was set to 2200°C and sintered for 65h to graphitize the carbon material, and finally a ceramic coating was formed on the outer surface of the carbon-carbon composite material.

[0117] Examples 4-5 and Comparative Examples 1-4

[0118] The following embodiments and Example 2 differ in that the coating that improves the corrosion resistance of the carbon-carbon composite material is prepared from ceramic slurries of different origins; the details are as follows:

[0119] In Example 4, the ceramic slurry is prepared according to the formulation and method of Ceramic Slurry Example 4;

[0120] In Example 5, the ceramic slurry is prepared according to the formulation and method of Ceramic Slurry Example 5;

[0121] In Comparative Example 1, the ceramic slurry is prepared according to the formulation and method of Ceramic Slurry Comparative Example 1;

[0122] In Comparative Example 2, the ceramic slurry is prepared according to the formulation and method of Ceramic Slurry Comparative Example 2;

[0123] In Comparative Example 3, the ceramic slurry is prepared according to the formulation and method of Ceramic Slurry Comparative Example 3;

[0124] In Comparative Example 4, the ceramic slurry is prepared according to the formulation and method of Ceramic Slurry Comparative Example 4.

[0125] Performance testing

[0126] 1. Oxidation resistance testing

[0127] The carbon-carbon composite material coated with a coating on the outer surface obtained by different embodiments (hereinafter referred to as the sample) was placed in a temperature-controlled resistance furnace for the test. The temperature was set to 1000°C, and air was used to provide an oxidation environment; after the sample was oxidized in this environment for 2h, the heating was stopped, and the sample was taken out after cooling to room temperature, weighed, and the oxidation weight loss rate (%) was calculated. At the same time, a control sample was set, which was a pure carbon-carbon composite material without any coating. Among them, the oxidation weight loss rate (%) = (the weight of the sample before oxidation - the weight of the sample after oxidation) / the weight of the sample before oxidation x 100%. The test results of each sample are shown in Table 1.

[0128] Table 1 Oxidation resistance performance of samples obtained by different embodiments

[0129] Embodiment Control sample Example 1 Example 2 Example 3 Example 4 Oxidative weight loss rate (%) 35.21 1.35 0.85 1.58 0.87 Embodiment Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Oxidative weight loss rate (%) 0.54 5.34 8.54 8.03 15.27

[0130] From the data results of Table 1, it can be seen that the oxidation weight loss rate of the sample of the present application is significantly reduced compared with the control sample and the sample of the comparative example, which fully demonstrates that after the ceramic coating of the present application is coated on the carbon-carbon composite material, a dense corrosion-resistant coating can be formed on the carbon-carbon composite material to protect the carbon-carbon composite material and reduce its corrosion damage.

[0131] In addition, by comparing the data of Example 2 and Comparative Example 3, it is found that: the pre-prepared hafnium carbide composite powder is then used for coating preparation, so that the oxidation weight loss rate of the sample is reduced from 8.64% to 0.85%, that is, the sample is oxidized at 1000°C for 2h, and the sample is basically not reduced in weight due to oxidation. The reason may be that the hafnium carbide composite powder is prepared in advance, and the powder is a composite ceramic powder with a specific crystal structure obtained after sintering. After the composite ceramic powder with a specific crystal structure is used to prepare the ceramic coating, it can react with carbon in the carbon-carbon composite material after sintering to form a dense ceramic coating. As can be seen from the results of Comparative Example 4, the addition of hafnium carbide composite powder can significantly improve the oxidation corrosion resistance of the ceramic coating.

[0132] And from the data results of Example 2, Comparative Example 1 and Comparative Example 2, it is found that the addition of zirconium powder and silicon carbide whiskers is necessary when the hafnium carbide composite powder is prepared; otherwise, even if the hafnium carbide composite powder is prepared, the ceramic coating can react with the carbon-carbon composite material to form a ceramic coating, but the effect of the coating on preventing oxidation corrosion is not good.

[0133] 2. Silicon vapor corrosion test

[0134] The carbon-carbon composite material coated with the coating in different embodiments (hereinafter referred to as the sample) is placed in a temperature-controlled resistance furnace for trial in the process of single crystal silicon furnace pulling; the high temperature of 1800°C is treated for 15 days, which is a complete process cycle; then the second process cycle is started. When cracks appear on the sample and / or 10% of the coating falls off, it cannot be used any more; the total processing time when it cannot be used is the service life of the coating. The service life of different samples is counted, and the specific results are shown in Table 2. At a high temperature of 1450°C, the substances in the sample decompose to form a silicon vapor corrosion environment, so the service life obtained by the experiment is the silicon vapor corrosion resistance of the sample: the longer the service life, the stronger the silicon vapor corrosion resistance; the shorter the service life, the shorter the silicon vapor corrosion resistance.

[0135] Table 2 Service life of different samples

[0136]

[0137] From the data results of Table 2, it can be seen that, compared with the sample of the comparative example, the service life of the sample of the present application is significantly prolonged under the silicon vapor corrosion due to the coating of the coating specially prepared in the present application, which reflects the excellent ability of the coating to resist silicon vapor corrosion.

[0138] In addition, by comparing the data of Example 2 and Comparative Example 3, it is found that the service life of the sample is prolonged from 12 months to 22 months by using the hafnium carbide composite powder prepared in advance for coating preparation, which is prolonged by 83%. This result fully demonstrates that the composite ceramic powder with a specific crystal structure obtained by sintering the hafnium carbide composite powder prepared in advance can react with carbon in the carbon-carbon composite material to form a dense ceramic coating after sintering, thereby significantly improving the ability of the coating to resist silicon vapor corrosion.

[0139] Similarly, the data results of Example 2, Comparative Example 1 and Comparative Example 2 show that the addition of zirconium powder and silicon carbide whiskers is necessary when the hafnium carbide composite powder is prepared in advance; otherwise, even if the hafnium carbide composite powder is prepared, the ceramic coating can react with the carbon-carbon composite material to form a ceramic coating, but the ability of the coating to resist silicon vapor corrosion will also be reduced.

[0140] 3. Fracture toughness test

[0141] The fracture toughness was tested according to the provisions of ASTM: 1424-10. When preparing the sample, the initial sample of carbon-carbon composite material was prepared with a size of 130 mm x 15 mm x 6 mm; a total of 4 samples were prepared, which were respectively marked as 1#, 2#, 3# and 4#. 1# was prepared according to the method of Example 2 for improving the corrosion resistance of carbon-carbon composite material; 2# was prepared according to the method of Comparative Example 1 for improving the corrosion resistance of carbon-carbon composite material; 3# was prepared according to the method of Comparative Example 2 for improving the corrosion resistance of carbon-carbon composite material; and 4# was not treated and directly detected. Then, the test was performed according to the above detection method, the loading rate was 0.05 mm / min, and the test span was 18 mm. The specific results are shown in Table 3.

[0142] Table 3 Fracture toughness of different samples

[0143] Embodiment 1# 2# 3# 4# Fracture toughness (Mpa-m 1 / 2 ) 5.43 3.68 3.52 3.02

[0144] From the data results of Table 3, it can be seen that, compared with the 4# sample, the 1# sample coated with the ceramic slurry of the application can significantly improve the fracture toughness. In addition, combined with the detection results of the 2# and 3# samples, it is suggested that the hafnium carbide composite powder in the ceramic slurry should be added with hafnium carbide powder, zirconium powder and silicon carbide whisker at the same time to realize the synergistic toughening effect.

[0145] The specific embodiments are only an explanation of the application, which is not a limitation of the application. Those skilled in the art can make modifications to the embodiments according to the needs after reading the specification, but as long as the modifications are within the scope of the claims of the application, they are protected by the patent law.

Claims

1. A coating preparation method for improving corrosion resistance of carbon-carbon composite material, characterized in that the coating preparation method for improving corrosion resistance of carbon-carbon composite material comprises the following steps: impregnation: impregnating the carbon-carbon composite material in the ceramic slurry for 1-2 hours to obtain the impregnated carbon-carbon composite material; the ceramic slurry comprises the following raw materials by weight: kaolin powder 45-60 parts, bentonite powder 35-50 parts, silicon carbide powder 8-15 parts, hafnium carbide composite powder 10-30 parts, solvent 260-400 parts, sintering aid 0.4-0.6 parts; the hafnium carbide composite powder is prepared by sintering raw materials comprising hafnium carbide powder, zirconium powder and silicon carbide whiskers, the raw materials for preparing the hafnium carbide composite powder comprise the following components by weight based on the weight of the hafnium carbide powder: hafnium carbide powder 100 parts, zirconium powder 20-30 parts, silicon carbide whiskers 15-25 parts; solvent removal: removing the solvent in the ceramic slurry by heat treating the impregnated carbon-carbon composite material at 450-600°C in an inert gas environment; sintering: synthesizing silicon carbide by heat treating the impregnated carbon-carbon composite material after removing the solvent at 1500-1700°C, and then sintering at 2000-2200°C to graphitize the carbon material, i.e. forming the coating on the carbon-carbon composite material. The length of the silicon carbide whiskers is 10-50 μm, and the diameter is 100-600 nm.

2. The method of claim 1, wherein the coating is prepared by a method comprising: (a) applying a first layer of a first material to a surface of a carbon-carbon composite material; (b) applying a second layer of a second material to the first layer; and (c) applying a third layer of a third material to the second layer. The preparation method of the hafnium carbide composite powder comprises the following steps:

3. The method of claim 1, wherein the coating is prepared by a process comprising: (a) applying a first layer of a first coating material to the surface of the carbon-carbon composite; (b) applying a second layer of a second coating material to the first layer; and (c) applying a third layer of a third coating material to the second layer. mixing the hafnium carbide powder, zirconium powder and silicon carbide whiskers according to the ratio, then pressing into a block, and calcining at 1600-1800°C for 2.5-3.5 hours to obtain the block; powdering the block to obtain the hafnium carbide composite powder. The condition parameters when pressing into a block include: pressing pressure of 300-400 MPa, and pressing time of 10-25 minutes.

4. The method of claim 3, wherein the coating is prepared by a method comprising the steps of: (a) preparing a solution of a polymer precursor; (b) applying the solution to a substrate; (c) curing the solution to form a coating; and (d) applying a carbon-containing material to the coating. The sintering aid is selected from any one or more of MgO, La2O3, TiO2 and Y2O3.

5. The method of claim 1, wherein the coating is prepared by a process comprising: (a) applying a first layer of a first coating material to the surface of the carbon-carbon composite; (b) applying a second layer of a second coating material to the first layer; and (c) applying a third layer of a third coating material to the second layer. The sintering aid is composed of MgO, La2O3 and TiO2; the mass ratio of MgO, La2O3 and TiO2 is 4:(2-4):(1-3).

6. The method of claim 1, wherein the coating is prepared by a process comprising: a) providing a carbon / carbon composite material; b) applying a first coating to the carbon / carbon composite material; c) applying a second coating to the first coating; and d) applying a third coating to the second coating. When sintering, the heat treating time of the impregnated carbon-carbon composite material after removing the solvent at 1500-1700°C is 8-12 hours; and the sintering time at 2000-2200°C is 65-80 hours.

7. The method of claim 1, wherein the coating is prepared by a process comprising: (a) applying a first layer of a first coating material to the surface of the carbon-carbon composite; (b) applying a second layer of a second coating material to the first layer; and (c) applying a third layer of a third coating material to the second layer. The coating is prepared by the coating preparation method of claim 1.

8. A coating for improving the corrosion resistance of carbon-carbon composite material, characterized by ​

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