A silicon carbide whisker toughened ceramic coating and method of making and use thereof

Abstract

The application belongs to the technical field of ceramic coating, and particularly relates to a silicon carbide whisker toughened ceramic coating and a preparation method and application thereof. The silicon carbide whisker toughened ceramic coating provided by the application is provided with a SiC transition layer in which SiC whiskers are inserted between a ceramic layer and a substrate, the SiC whiskers can be inserted to the surface of the substrate and the surface of the ceramic layer, thereby improving the bonding force between the ceramic layer and the substrate, the transition layer itself is uniformly distributed, the influence caused by the difference in the thermal expansion coefficient between the substrate and the ceramic layer can be relieved, the ceramic layer and the substrate are closely linked, and the problem that the traditional ceramic outer coating and the substrate are insufficient in bonding capacity and are prone to falling off is solved. The ceramic outer protective layer provided by the application with the SiC transition layer (containing SiC whiskers) can have a close bonding force at an ultra-high temperature, has high fracture toughness, and is not prone to falling off.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic coating, and particularly relates to a silicon carbide whisker toughened ceramic coating and a preparation method and application thereof. BACKGROUND

[0002] With the gradually harsh requirements for the use of thermal protection materials of supersonic aircraft, the ceramic materials are required to resist ablation at 2000-3000 DEG C and have certain strength to ensure service life. The leading edge and tail of the supersonic aircraft usually suffers from the erosion of hot gas flow at 2200-3000 DEG C, and therefore it is necessary to improve the temperature resistance and ablation limit temperature of the ceramic materials.

[0003] At present, the superhigh-temperature thermal protection layer is mainly composed of carbide ceramic and composite ceramic system. The carbide ceramic material (such as silicon carbide, zirconium carbide and hafnium carbide ceramic) has high melting point, high hardness, high wear resistance and high chemical stability, but its fracture toughness is low, and the bonding force between the ceramic material and the substrate is insufficient, which is easy to fall off, thereby limiting the further application. SUMMARY

[0004] Therefore, the application aims to provide a silicon carbide whisker toughened ceramic coating and a preparation method and application thereof. The ceramic coating provided by the application has high fracture toughness and high bonding force with the substrate, and is not easy to fall off.

[0005] In order to achieve the above-mentioned purpose, the application provides the following technical scheme:

[0006] The application provides a silicon carbide whisker toughened ceramic coating, which comprises a silicon carbide transition layer covering the surface of a substrate and a ceramic layer covering the surface of the silicon carbide transition layer.

[0007] The silicon carbide transition layer comprises a metal distributed on the surface of the substrate, a silicon carbide base layer covering the metal, and silicon carbide whiskers formed based on the metal, and part of the silicon carbide whiskers penetrate the surface of the silicon carbide transition layer.

[0008] Preferably, the composition of the ceramic layer comprises a main component and a secondary component; the main component is HfC; and the secondary component comprises at least two of HfB2, SiC and HfSi2.

[0009] Preferably, the diameter of the silicon carbide whisker is 10 nm-2 microns.

[0010] The application further provides a preparation method of the silicon carbide whisker toughened ceramic coating.

[0011] The substrate is immersed in an organic solvent containing a metal-based catalyst to obtain a substrate covered with a metal-based catalyst.

[0012] placing the substrate coated with the metal-based catalyst into a carbon and silicon containing investment material, and performing first sintering under a first protective gas to obtain a substrate coated with a silicon carbide transition layer;

[0013] mixing raw materials corresponding to the components of the ceramic layer and hydrogen-containing silicone oil, and performing second sintering under a second protective gas after the ceramic slurry is coated on the surface of the silicon carbide transition layer to obtain a ceramic coating layer toughened by silicon carbide whiskers.

[0014] Preferably, the carbon and silicon containing investment material comprises Si powder and activated carbon; and the mass ratio of the Si powder and the activated carbon is (10-50):(5-30).

[0015] Preferably, the metal-based catalyst is a metal nickel-based catalyst.

[0016] Preferably, the temperature of the first sintering is 1100-1600℃, and the holding time is 1-2h.

[0017] Preferably, the temperature of the second sintering is 1100-1600℃, and the holding time is 1-2h.

[0018] Preferably, the mass concentration of the metal-based catalyst in the organic solvent containing the metal-based catalyst is 1-5%.

[0019] The application further provides application of the ceramic coating layer toughened by silicon carbide whiskers to a thermal protection material of a supersonic aircraft.

[0020] The application provides a ceramic coating layer toughened by silicon carbide whiskers, which comprises a silicon carbide transition layer coated on the surface of a substrate and a ceramic layer coated on the surface of the silicon carbide transition layer; the silicon carbide transition layer comprises metal distributed on the surface of the substrate, a silicon carbide base layer covering the metal, and silicon carbide whiskers formed based on the metal, and part of the silicon carbide whiskers penetrates into the surface of the silicon carbide transition layer.

[0021] The ceramic coating provided by the present application is provided with a SiC transition layer with SiC whiskers penetrating between the ceramic layer and the substrate, the SiC whiskers can penetrate between the interface of the substrate and the transition layer and the interface of the transition layer and the surface of the ceramic layer, the binding force between the ceramic layer and the substrate is improved through the effects of pull-out, crack deflection and crack bridging, moreover, the transition layer is uniformly distributed, the difference of the thermal expansion coefficient between the substrate and the ceramic layer is too large, the expansion coefficient of the transition layer is intermediate, the influence caused by the difference of the thermal expansion coefficient between the substrate and the ceramic layer is relieved, the ceramic layer and the substrate are closely linked, and the problem of the insufficient binding capacity and easy falling off of the traditional ceramic outer coating and the substrate is solved. The ceramic outer protective layer with the SiC transition layer (containing SiC whiskers) provided by the present application can have a close binding force at super-high temperature, high fracture toughness and is not easy to fall off.

[0022] In addition, the ceramic layer of the present application takes high-melting-point HfC as the main component, takes HfB2, HfC and HfSi2 as the secondary component, and takes the ceramic layer with hafnium carbide as the main phase and the SiC transition layer with SiC whiskers, the ceramic coating formed by the ceramic layer and the SiC transition layer can not only resist the erosion of super-high-temperature hot gas flow of 2500-3000 DEG C and has excellent ablation resistance, but also has strong binding strength between the ceramic coating and the substrate, and can solve the problem that the melting point of the ceramic main phase in the traditional super-high-temperature ceramic-based thermal protection coating is low, resulting in short service life under the super-high-temperature environment above 2000-2500 DEG C. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The XRD change graph of the ceramic coating sample with SiC whisker toughening prepared for example 1 before and after ablation at 2000 DEG C under hydrogen-oxygen flame;

[0024] Figure 2 The morphology graph of the ceramic coating with SiC whisker toughening prepared for example 1;

[0025] Figure 3 The SEM graph of the ceramic coating with SiC whisker toughening prepared for example 1;

[0026] Figure 4 The morphology graph of the ceramic coating with SiC whisker toughening prepared for example 1 after ablation at 2000 DEG C under H2-O2 flame;

[0027] Figure 5 The SEM graph of the ceramic coating without SiC whisker toughening prepared for comparative example 1 after ablation at 2000 DEG C under H2-O2 flame;

[0028] Figure 6 The morphology graph of the ceramic coating without SiC whisker toughening prepared for comparative example 1 after ablation at 2000 DEG C under H2-O2 flame. DETAILED DESCRIPTION

[0029] The present application provides a silicon carbide whisker toughened ceramic coating, comprising a silicon carbide transition layer covering the surface of a substrate and a ceramic layer covering the surface of the silicon carbide transition layer.

[0030] The silicon carbide transition layer comprises a metal distributed on the surface of the substrate, a silicon carbide base layer covering the metal and silicon carbide whiskers formed based on the metal, part of the silicon carbide whiskers penetrating the surface of the silicon carbide transition layer.

[0031] The present application provides a silicon carbide whisker toughened ceramic coating, comprising a silicon carbide transition layer covering the surface of a substrate and a ceramic layer covering the surface of the silicon carbide transition layer.

[0032] In the present application, the diameter of the silicon carbide whisker is preferably 10 nm to 2 μm, more preferably 100 nm to 500 nm; the mass percentage of the silicon carbide whisker in the silicon carbide transition layer is preferably 0.1 to 5%, more preferably 0.2 to 1%.

[0033] In the present application, the thickness of the silicon carbide transition layer is preferably 10 nm to 1 μm, more preferably 50 nm to 100 nm.

[0034] In the present application, the ceramic layer preferably comprises a main component and a secondary component; the main component is preferably HfC; the secondary component preferably comprises at least two of HfB2, SiC and HfSi2, more preferably HfB2 and SiC; the thickness of the ceramic layer is preferably 50 nm to 2 μm, more preferably 100 nm to 1 μm.

[0035] The ceramic layer of the application mainly comprises high-melting-point HfC, and secondarily comprises HfB2, HfC and HfSi2, and the ceramic coating formed by the ceramic layer and the silicon carbide transition layer containing silicon carbide whiskers can not only resist the erosion of super-high-temperature hot gas flow of 2500-3000 DEG C and has excellent ablation resistance, but also has strong bonding strength between the ceramic coating and the substrate, thus solving the problem of short service life of the ceramic main phase in the traditional super-high-temperature ceramic-based thermal protection coating under the super-high-temperature environment above 2000-2500 DEG C.

[0036] The application further provides a preparation method of the silicon carbide whisker toughened ceramic coating.

[0037] The substrate is immersed in the organic solvent containing the metal-based catalyst to obtain the substrate coated with the metal-based catalyst.

[0038] The substrate coated with the metal-based catalyst is placed in the embedding material containing carbon and silicon, and first sintering is performed under a first protective gas to obtain the substrate coated with the silicon carbide transition layer.

[0039] The raw materials corresponding to the components of the ceramic layer and the hydrogen-containing silicone oil are mixed, the obtained ceramic slurry is coated on the surface of the silicon carbide transition layer, and second sintering is performed under a second protective gas to obtain the silicon carbide whisker toughened ceramic coating.

[0040] Unless otherwise specified, the application does not have special requirements for the source of the raw materials used for preparation, and commercially available goods known to those skilled in the art can be used.

[0041] In the application, the substrate is immersed in the organic solvent containing the metal-based catalyst to obtain the substrate coated with the metal-based catalyst.

[0042] In the application, the substrate is preferably a C / C composite material, and the density of the substrate is preferably 0.8-1.9 g / cm 3 , and more preferably 1-1.5 g / cm 3 .

[0043] In the application, the metal-based catalyst is a metal nickel-based catalyst, and the metal nickel-based catalyst preferably comprises a catalyst whose first sintering product is nickel or nickel oxide, and more preferably comprises acetylacetone nickel, nickel nitrate, nickel amino acid, nickel or nickel oxide; the organic solvent is preferably tetrahydrofuran; and the mass concentration of the metal-based catalyst in the organic solvent containing the metal-based catalyst is preferably 1-5%, and more preferably 2-3%. The application uses the metal-based catalyst as a nucleating agent for in-situ growth of SiC whiskers during preparation, including but not limited to a series of pyrolysis products such as acetylacetone nickel, nickel nitrate, nickel amino acid, and nickel oxide or nickel salt.

[0044] In the present application, the impregnation time is preferably 10-30 min, more preferably 15-25 min.

[0045] After the impregnation is completed, the present application preferably dries the impregnated substrate to obtain a substrate coated with a metal-based catalyst. In the present application, the drying is preferably baking; the drying temperature is preferably 50-100℃, more preferably 60-80℃; and the drying time is preferably 10-60 min, more preferably 15-60 min.

[0046] After the substrate coated with a metal-based catalyst is obtained, the present application places the substrate coated with a metal-based catalyst in a carbon and silicon-containing investment material and performs first sintering under a first protective gas to obtain a substrate coated with a silicon carbide transition layer on the surface.

[0047] In the present application, the carbon and silicon-containing investment material preferably comprises Si powder and activated carbon; and the mass ratio of the Si powder and activated carbon is preferably (10-50):(5-30), more preferably (20-50):(10-20).

[0048] In the present application, the first protective gas is preferably argon; the purity of the argon is preferably 98-99.9%, more preferably 99.5-99.9%; the first sintering temperature is preferably 1100-1600℃, more preferably 1200-1500℃, and the holding time is preferably 1-2h, more preferably 1.5-1.8h; and the heating rate for heating to the first sintering temperature is preferably 5-10℃ / min, more preferably 5-8℃ / min.

[0049] After the first sintering is completed, the present application preferably further comprises: after the first sintering product is cooled to room temperature, sequentially performing cleaning and drying; the cooling is preferably natural cooling; the cleaning is preferably performed using ethanol; the drying temperature is preferably 50-100℃, more preferably 60-80℃; and the drying time is preferably 10-30 min, more preferably 15-25 min.

[0050] The present application mixes raw materials corresponding to the components of the ceramic layer and hydrogen-containing silicone oil to obtain a ceramic slurry.

[0051] In the present application, the raw material corresponding to the component of the ceramic layer preferably comprises, in mass fraction, HfC powder 60-90 parts, HfB2 powder 0-20 parts, SiC powder 0-10 parts, and HfSi2 powder 0-20 parts, and at least two of the HfB2 powder, SiC powder, and HfSi2 powder are not 0 parts, and more preferably comprises HfC powder 70-80 parts, HfB2 powder 5-15 parts, SiC powder 5-10 parts, and HfSi2 powder 0-5 parts; the particle size of the HfC powder, HfB2 powder, SiC powder, and HfSi2 powder is independently preferably ≤30 μm, and more preferably 20-30 μm.

[0052] In the present application, the raw material corresponding to the component of the ceramic layer preferably further comprises an additive; the additive preferably comprises one or more of polyvinyl butyral (PVB), SiC whiskers, and carbon fiber composite material, and more preferably SiC whiskers; the carbon fiber composite material and SiC whiskers are purchased from Shanghai Xu Tian New Material Technology Co., Ltd., and polyvinyl butyral (PVB) is purchased from the National Medicine Reagent Network, and the purity is chemical purity. In the present application, the mass of the polyvinyl butyral (PVB) is preferably 0-1% of the mass of the raw material corresponding to the component of the ceramic layer, and more preferably 0.5-0.7%; the mass of the SiC whiskers is preferably 0-1% of the mass of the raw material corresponding to the component of the ceramic layer, and more preferably 0.5-0.7%; the diameter of the SiC whiskers is preferably 10 nm-2 μm, and more preferably 100 nm-1 μm; the mass of the carbon fiber composite material is preferably 0-1% of the mass of the raw material corresponding to the component of the ceramic layer, and more preferably 0.5-0.7%.

[0053] In the present application, the hydrogen content in the hydrogen-containing silicone oil (H-PSO) is preferably 0.1-1.6%, and more preferably 0.5-1%. The hydrogen-containing silicone oil functions as a dispersant

[0054] In the present application, the mass ratio of the raw material corresponding to the component of the ceramic layer and the hydrogen-containing silicone oil is preferably (1-2):1, and more preferably (1-1.5):1.

[0055] The present application does not have special limitations on the process of mixing the raw material corresponding to the component of the ceramic layer and the hydrogen-containing silicone oil in the present application, and a mixing process known in the art can be used to uniformly mix the materials.

[0056] Before mixing the raw materials corresponding to the components of the ceramic layer and the hydrogen-containing silicone oil, the application preferably further comprises: ball milling the raw materials corresponding to the components of the ceramic layer; the ball milling is preferably wet ball milling; the ball-to-material ratio of the ball milling is preferably 1:(20-50), more preferably 1:(20-30); the rotation speed of the ball milling is preferably 100-200 rpm, more preferably 120-150 rpm; the ball milling time is preferably 1-12 h, more preferably 2-6 h; the solvent used in the wet ball milling is preferably ethanol; the mass ratio of the raw materials corresponding to the components of the ceramic layer to ethanol is preferably (1-4):1, more preferably (1-1.5):1.

[0057] The application uniformly disperses the raw materials of the ceramic layer through ball milling.

[0058] After obtaining the ceramic slurry and the substrate with the silicon carbide transition layer, the application coats the ceramic slurry on the surface of the silicon carbide transition layer, and then performs second sintering under a second protective gas to obtain a ceramic coating toughened by silicon carbide whiskers.

[0059] In the application, the ceramic slurry is preferably coated on the surface of the silicon carbide transition layer; the thickness of the ceramic slurry on the surface of the silicon carbide transition layer is preferably 0.5-3 mm, more preferably 1-2 mm.

[0060] After coating the ceramic slurry on the surface of the silicon carbide transition layer, the application preferably further comprises: drying; the drying is preferably oven drying; the drying temperature is preferably 100-200°C, more preferably 120-180°C; the drying time is preferably 1-3 h, more preferably 1-2 h.

[0061] In the application, the second protective gas is preferably argon; the purity of the argon is preferably 98-99.9%, more preferably 99.5-99.9%; the second sintering temperature is preferably 1100-1600°C, more preferably 1300-1500°C; the holding time is preferably 1-2 h, more preferably 1-1.5 h; the heating rate for heating to the second sintering temperature is preferably 5-10°C / min, more preferably 6-8°C / min.

[0062] In the application, the application further provides an application of the ceramic coating toughened by silicon carbide whiskers in the above technical solution or prepared by the preparation method in the above technical solution in a thermal protection material of a supersonic aircraft.

[0063] The application of the ceramic coating toughened by silicon carbide whiskers in the thermal protection material of the supersonic aircraft is not particularly limited in the application, and the application mode known in the art can be used.

[0064] The technical solutions in the present application will be clearly and completely described below with reference to the embodiments in the present application, but they should not be understood as limitations to the protection scope of the present application.

[0065] Example 1

[0066] Si powder and activated carbon with a mass ratio of 50:10 were weighed, and acetylacetone nickel was dissolved in tetrahydrofuran, and the mass concentration of acetylacetone nickel in the solution was 5%; the Si powder and activated carbon were mixed uniformly to obtain an investment material, and a C / C composite material substrate with a density of 1.41 g / cm 3 After the C / C composite material substrate was immersed in the tetrahydrofuran solution containing acetylacetone nickel for 20 min, the C / C composite material substrate was taken out and dried at 80℃ for 1 h, and then was placed in the investment material of Si powder and activated carbon and was placed in a tube furnace, and was heated to 1600℃ at a rate of 5℃ / min under the protection of argon gas (with a purity of 99%) and was kept for 2 h for first sintering, and was naturally cooled to room temperature, and was cleaned with ethanol and was dried at 80℃ for 15 min, to obtain a C / C composite material with a silicon carbide whisker interpenetrated in-situ silicon carbide transition layer on the surface;

[0067] HfC 75 parts, HfB2 10 parts, SiC 10 parts and HfSi2 5 parts with a particle size of ≤30 μm were mixed according to weight, and ethanol (the mass ratio of raw materials to ethanol was 4:1) was added for wet ball milling, the ball-to-material ratio was 1:20, the ball milling speed was 150 rpm, and the ball milling time was 2 h; the obtained raw materials corresponding to the composition of the ceramic layer were mixed uniformly with hydrogen-containing silicone oil (H-PSO, with a hydrogen content of 1%) at a mass ratio of 1:1 to obtain a ceramic slurry; the obtained ceramic slurry was coated on the surface of the silicon carbide transition layer with a thickness of 2 mm, and was dried at 100℃ for 1 h, and then the dried sample was placed in a tube furnace, and was heated to 1600℃ at a rate of 5℃ / min under the protection of argon gas (with a purity of 99%) and was kept for 2 h for second sintering, to obtain a silicon carbide whisker toughened ceramic coating.

[0068] Example 2

[0069] The difference from example 1 is that:

[0070] (1) the silicon carbide transition layer raw material is Si powder and activated carbon with a mass ratio of 40:10, the mass concentration of acetylacetone nickel in the tetrahydrofuran solution containing acetylacetone nickel is 4%, and the first sintering is heated to 1500℃ at a rate of 5℃ / min and kept for 2 h;

[0071] (2) The raw material corresponding to the composition of the ceramic layer is HfC 70 parts, HfB2 10 parts, SiC 10 parts, and HfSi2 10 parts by weight. The raw material corresponding to the composition of the ceramic layer is mixed with hydrogen-containing silicone oil (H-PSO) at a mass ratio of 1.2:1 to obtain a ceramic slurry. The second sintering is to heat to 1500°C at a rate of 5°C / min and then keep for 2h.

[0072] Example 3

[0073] The difference from Example 1 is that:

[0074] (1) The raw material of the silicon carbide transition layer is Si powder and activated carbon with a mass ratio of 30:10. The mass concentration of acetylacetone nickel in the acetylacetone nickel-containing tetrahydrofuran solution is 3%. The first sintering is to heat to 1400°C at a rate of 5°C / min and then keep for 2h.

[0075] (2) The raw material corresponding to the composition of the ceramic layer is HfC 80 parts, HfB2 25 parts, SiC 5 parts, and HfSi2 10 parts by weight. The raw material corresponding to the composition of the ceramic layer is mixed with hydrogen-containing silicone oil (H-PSO) at a mass ratio of 1.2:1 to obtain a ceramic slurry. The second sintering is to heat to 1500°C at a rate of 5°C / min and then keep for 2h.

[0076] Example 4

[0077] The difference from Example 1 is that:

[0078] (1) The raw material of the silicon carbide transition layer is Si powder and activated carbon with a mass ratio of 20:10. The mass concentration of acetylacetone nickel in the acetylacetone nickel-containing tetrahydrofuran solution is 2%. The first sintering is to heat to 1200°C at a rate of 5°C / min and then keep for 2h.

[0079] (2) The raw material corresponding to the composition of the ceramic layer is HfC 75 parts, HfB2 25 parts, SiC 5 parts, and HfSi2 20 parts by weight. The raw material corresponding to the composition of the ceramic layer is mixed with hydrogen-containing silicone oil (H-PSO) at a mass ratio of 1.2:1 to obtain a ceramic slurry. The second sintering is to heat to 1200°C at a rate of 5°C / min and then keep for 2h.

[0080] Example 5

[0081] The difference from Example 1 is that:

[0082] (1) The raw material of the silicon carbide transition layer is Si powder and activated carbon with a mass ratio of 10:10. The mass concentration of acetylacetone nickel in the acetylacetone nickel-containing tetrahydrofuran solution is 2%. The first sintering is to heat to 1100°C at a rate of 5°C / min and then keep for 2h.

[0083] (2) The raw materials corresponding to the composition of the ceramic layer are HfC 77.5 parts, HfB25 parts, SiC 5 parts, and HfSi22.5 parts by weight. The raw materials corresponding to the composition of the ceramic layer are mixed with hydrogen-containing silicone oil (H-PSO) at a mass ratio of 2:1 to obtain a ceramic slurry. The second sintering is to heat to 1100°C at a rate of 5°C / min and keep for 2h.

[0084] Example 6

[0085] The difference from Example 1 is that:

[0086] (1) The mass ratio of HfC, HfB2, SiC, and HfSi2 in the raw materials corresponding to the composition of the ceramic layer is 70:5:5:20. An additive is added to the raw materials, and the additive includes PVB (chemical pure, National Medicine Reagent Network), SiC whisker (diameter of 1 μm, Shanghai Xu Tian New Material Technology Co., Ltd.), and carbon fiber composite material (Shanghai Xu Tian New Material Technology Co., Ltd.) accounting for 0.5%, 0.5%, and 1% of the total mass of the raw materials, respectively. The raw materials and the additive are mixed uniformly, and then ethanol (the mass ratio of the raw materials to ethanol is 4:1) is added for wet ball milling;

[0087] (2) The second sintering is to heat to 1400°C at a rate of 5°C / min and keep for 1h, and then heat to 1600°C at a rate of 5°C / min and keep for 1h.

[0088] The mass ablation rate of the obtained ceramic layer ablated at 2500°C for 5min under hydrogen-oxygen flame is -0.23mg / s, the hardness is 2100HV, and the compressive strength is 203.62kN / cm 2 .

[0089] Example 7

[0090] The difference from Example 1 is that:

[0091] (1) The mass ratio of HfC, HfB2, SiC, and HfSi2 in the raw materials corresponding to the composition of the ceramic layer is 77.5:15:5:2.5. An additive is added to the raw materials, and the additive includes PVB (chemical pure, National Medicine Reagent Network), SiC whisker (diameter of 1 μm, Shanghai Xu Tian New Material Technology Co., Ltd.), and carbon fiber composite material (Shanghai Xu Tian New Material Technology Co., Ltd.) accounting for 0.5%, 1%, and 1% of the total mass of the raw materials, respectively. The raw materials and the additive are mixed uniformly, and then ethanol (the mass ratio of the raw materials to ethanol is 4:1) is added for wet ball milling;

[0092] (2) The second sintering is to heat to 1400°C at a rate of 5°C / min and keep for 1h, and then heat to 1600°C at a rate of 5°C / min and keep for 1h.

[0093] The obtained ceramic layer exhibited a mass ablation rate of -0.53 mg / s after being ablated in an oxyhydrogen flame at 2500 °C for 5 min, a hardness of 1400 HV, and a compressive strength of 193.12 kN / cm². 2 .

[0094] Comparative Example 1

[0095] Weigh out silicon powder and activated carbon in a mass ratio of 50:10, mix them evenly to obtain an encapsulating material with a density of 1.41 g / cm³. 3 The C / C composite material was placed in an embedding material of silicon powder and activated carbon and placed in a tube furnace. Under the protection of argon gas (purity of 99%), the temperature was increased to 1600°C at 5°C / min and held for 2 hours for the first sintering. After natural cooling to room temperature, it was cleaned with ethanol and dried at 80°C for 15 minutes to obtain a C / C composite material with a silicon carbide transition layer on the surface. The difference from Example 1 is that there are no in-situ generated silicon carbide whiskers in the silicon carbide transition layer.

[0096] Subsequently, 75 parts of HfC, 10 parts of HfB2, 10 parts of SiC, and 25 parts of HfSi were weighed and mixed. Ethanol was added (the mass ratio of raw materials to ethanol was 4:1) and wet ball milling was performed. The raw materials corresponding to the composition of the ceramic layer were mixed with hydrogen-containing silicone oil (H-PSO) at a mass ratio of 1:1 to obtain a ceramic slurry. The obtained ceramic slurry was coated onto the surface of the silicon carbide transition layer and dried at 100°C for 1 hour. Then, the dried sample was placed in a tube furnace and heated to 1600°C at 5°C / min under argon gas (purity of 99%) protection. The temperature was then maintained for 2 hours for a second sintering to obtain a ceramic coating without silicon carbide whisker toughening.

[0097] Performance testing

[0098] (1) Figure 1 XRD pattern of the silicon carbide whisker-toughened ceramic coating sample prepared in Example 1 before and after ablation at 2000℃ in an oxyhydrogen flame for 120s.

[0099] Depend on Figure 1 It can be seen that, in Example 1, the central region of the silicon carbide whisker-toughened ceramic coating sample was mainly composed of HfC and HfB2 before ablation, and became mainly composed of HfO2 after H2-O2 ablation. The phase change in the edge region of the sample before and after ablation was minimal; the main components were HfC and HfB2 before ablation and remained HfC and HfB2 after ablation. This demonstrates that the silicon carbide whisker-toughened ceramic coating has a certain protective effect at high temperatures.

[0100] (2) Figure 2 The image shows the morphology of the silicon carbide whisker-toughened ceramic coating prepared in Example 1.

[0101] Depend on Figure 2It can be seen that the surface of the ceramic coating sample prepared in Example 1 is smooth and dense, and no cracking or peeling phenomenon occurs. The SiC whisker-penetrated SiC transition layer effectively fixes the outer ceramic layer on the substrate.

[0102] (3) Figure 3 SEM images of the SiC whisker-toughened ceramic coating prepared in Example 1, wherein (a) is the cross-sectional morphology of the coating structure, (b) is the interface morphology of the SiC transition layer, and (c) is the enlarged morphology of the SiC transition layer penetrated by in-situ grown SiC whiskers.

[0103] From Figure 3 It can be seen from (a) that the bottom layer is a SiC transition layer tightly coated with SiC whiskers on the C / C composite material, and a ceramic layer mainly composed of HfC-HfB2-SiC-HfSi2 is connected to the surface of the transition layer. Figure 3 It can be seen from (b) that the SiC whiskers are penetrated between the C / C substrate and the SiC transition layer interface, and the in-situ grown SiC whiskers are also penetrated between the HfC-HfB2-SiC-HfSi2 outer ceramic layer and the transition layer.

[0104] (4) Figure 4 Morphology of the SiC whisker-toughened ceramic coating prepared in Example 1 after ablation for 120 s under H2-O2 flame at 2000°C.

[0105] From Figure 4 It can be seen that after the sample in Example 1 is ablated for 120 s under H2-O2 flame at 2000°C, the surface coating is oxidized to form an oxide layer, and no cracking phenomenon occurs on the surface of the oxide layer. This is because the in-situ generated SiC whiskers penetrated between the SiC transition layer and the ceramic outer layer fix the HfO2 generated by the oxidation of HfC and HfB2 in the ceramic outer layer on the surface of the coating.

[0106] (5) Figure 5 SEM image of the ceramic coating without SiC whisker toughening prepared in Comparative Example 1 after ablation for 120 s under H2-O2 flame at 2000°C.

[0107] From Figure 5 It can be seen that in Comparative Example 1, the interface between the outer HfC and HfB2 and the C / C composite substrate can be clearly seen, and there is a gap at the interface. This is because the in-situ grown SiC whiskers are not penetrated, and there is a clear gap between the oxides generated by the ablation of the SiC transition layer and the ceramic outer layer, resulting in a loose connection of the coating structure, and the oxide layer will fall off, leading to a decrease in the thermal protection performance of the coating.

[0108] (6) Figure 6The image shows the morphology of the silicon carbide whisker-free ceramic coating prepared for Comparative Example 1 after ablation at 2000℃ in an H2-O2 flame for 120s.

[0109] Depend on Figure 6 It can be seen that, in Comparative Example 1, the oxide layer formed after the oxidation of the outer HfC and HfB2 layers of the sample lacks the interpenetration effect of the whiskers in the SiC transition layer where SiC whiskers are interpenetrated in situ. Consequently, the outer HfO2 oxide layer is extremely prone to detachment and cracking. Therefore, the SiC transition layer with interpenetrated SiC whiskers can effectively improve the thermal protection performance of the coating.

[0110] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A silicon carbide whisker toughened ceramic coating, characterized by, It includes a silicon carbide transition layer covering the surface of the substrate and a ceramic layer covering the surface of the silicon carbide transition layer; The silicon carbide transition layer includes a metal distributed on the surface of the substrate, a silicon carbide base layer covering the metal, and silicon carbide whiskers formed with the metal as the base point, with some silicon carbide whiskers penetrating the surface of the silicon carbide transition layer. The diameter of the silicon carbide whiskers is 100nm~500nm; The silicon carbide transition layer contains 0.1% to 5% silicon carbide whiskers by mass. The thickness of the silicon carbide transition layer is 50 nm to 100 nm. The method for preparing the silicon carbide whisker-toughened ceramic coating includes the following steps: The substrate is impregnated in an organic solvent containing a metal-based catalyst to obtain a substrate coated with a metal-based catalyst. The substrate coated with the metal-based catalyst was placed in a carbon and silicon-containing embedding material and subjected to a first sintering under a first protective gas to obtain a substrate with a silicon carbide transition layer on its surface. The raw materials corresponding to the composition of the ceramic layer are mixed with hydrogen-containing silicone oil. The resulting ceramic slurry is then coated on the surface of the silicon carbide transition layer and subjected to a second sintering under a second protective gas to obtain a silicon carbide whisker-toughened ceramic coating. By mass parts, the raw materials corresponding to the composition of the ceramic layer include: 70-80 parts of HfC powder, 5-15 parts of HfB2 powder, 5-10 parts of SiC powder, and 0-5 parts of HfSi2 powder. The metal-based catalyst is a nickel-based catalyst; the nickel-based catalyst is nickel acetylacetone, nickel nitrate, amino acid nickel, nickel, or nickel oxide; the mass concentration of the metal-based catalyst in the organic solvent containing the metal-based catalyst is 1-5%; The first sintering temperature is 1200~1600℃, and the holding time is 1~2h.

2. The method of claim 1 wherein the silicon carbide whisker toughened ceramic coating is prepared by the steps of: Includes the following steps: The substrate is impregnated in an organic solvent containing a metal-based catalyst to obtain a substrate coated with a metal-based catalyst. The substrate coated with the metal-based catalyst was placed in a carbon and silicon-containing embedding material and subjected to a first sintering under a first protective gas to obtain a substrate with a silicon carbide transition layer on its surface. The raw materials corresponding to the composition of the ceramic layer are mixed with hydrogen-containing silicone oil. The resulting ceramic slurry is then coated on the surface of the silicon carbide transition layer and subjected to a second sintering under a second protective gas to obtain a silicon carbide whisker-toughened ceramic coating. By mass, the raw materials corresponding to the composition of the ceramic layer include: 70-80 parts of HfC powder, 5-15 parts of HfB2 powder, 5-10 parts of SiC powder, and 0-5 parts of HfSi2 powder; The metal-based catalyst is a nickel-based catalyst; the nickel-based catalyst is nickel acetylacetone, nickel nitrate, amino acid nickel, nickel, or nickel oxide; the mass concentration of the metal-based catalyst in the organic solvent containing the metal-based catalyst is 1-5%; The first sintering temperature is 1200~1600℃, and the holding time is 1~2h.

3. The preparation method according to claim 2, characterized in that, The carbon and silicon-containing encapsulating material includes Si powder and activated carbon; the mass ratio of Si powder to activated carbon is (10~50):(5~30).

4. The preparation method according to claim 2, characterized in that, The second sintering temperature is 1100~1600℃, and the holding time is 1~2h.

5. Use of the silicon carbide whisker toughened ceramic coating according to claim 1 or of the silicon carbide whisker toughened ceramic coating produced by the method according to any one of claims 2 to 4 as a thermal protection material for a hypersonic aircraft.

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