High-temperature-resistant ceramic fiber surface coating and application thereof

Abstract

This invention relates to the field of refractory fiber materials, and more particularly to raw materials comprising, by weight: 30-60 parts magnesium aluminum spinel, 10-30 parts M70 sintered mullite, 5-30 parts silica micropowder, 1-20 parts starch ether, and 0.5-2.0 parts surface-modified reinforcing fiber and 5-20 parts ZrO2 micropowder; wherein the surface-modified reinforcing fiber is pre-oxidized polyacrylonitrile fiber, and its surface is bonded or coated with a layer of silicon-based polymer precursor, wherein the silicon-based polymer precursor is selected from polysiloxane or polycarbosilane. The high-temperature resistant ceramic fiber coating of this application has good thermal insulation performance, strong stability, and excellent resistance to chemical erosion and wind erosion.

Description

Technical Field

[0001] This invention relates to the field of refractory fiber materials, and more particularly to a high-temperature resistant ceramic fiber surface coating and its application. Background Technology

[0002] Refractory fiber coating is a functional slurry specifically designed to protect refractory fiber products (such as ceramic fiber blankets). It uses chopped refractory fibers as reinforcing aggregate, inorganic binders as the bonding matrix, and is formulated with various functional fillers and additives. After application, drying, and curing, a hard, dense ceramic protective coating forms on the fiber surface. It primarily addresses the inherent defects of bare fibers, such as a loose surface that is easily eroded and detached by airflow, and a porous structure that readily absorbs moisture, oil, and corrosive furnace gases (such as K, Na, S, and Cl vapors), thereby preventing fiber loss, contamination, and a decline in thermal insulation performance.

[0003] However, existing fiber coatings still have several drawbacks. First, their commonly used binders (such as water glass and certain phosphates) and some fillers undergo phase transformation, crystallization, or sintering shrinkage under long-term high-temperature environments, leading to coating embrittlement, powdering, or microcracks, thus affecting service life. Second, in environments rich in alkali metal vapors, such as steel plant heating furnaces, SiO2 in the coating easily reacts with K, Na, etc., to form eutectic compounds, thereby compromising structural integrity. Summary of the Invention

[0004] To address the problems mentioned above, this invention provides a high-temperature resistant ceramic fiber coating with good thermal insulation performance, strong stability, and excellent resistance to chemical erosion and wind erosion.

[0005] The solution adopted by the present invention to solve its technical problem is: a high-temperature resistant ceramic fiber surface coating, comprising the following raw materials in parts by weight: 30-60 parts of magnesium aluminum spinel, 10-30 parts of M70 sintered mullite, 5-30 parts of silica micro powder, 1-20 parts of starch ether, and 0.5-2.0 parts of surface-modified reinforcing fiber and 5-20 parts of ZrO2 micro powder; The surface-modified reinforcing fiber is a pre-oxidized polyacrylonitrile fiber, and its surface is bonded or coated with a silicon-based polymer precursor, which is selected from polysiloxane or polycarbosilane.

[0006] Furthermore, the silicon-based polymer precursor layer also contains dispersed nano-ceramic powder, which is at least one of nano-alumina, nano-zirconia, and silicon carbide nanowires, and its mass accounts for 10-50% of the precursor layer mass.

[0007] Furthermore, the ceramic fiber surface coating is one of the following: aluminum-containing type, zirconium-aluminum hybrid type, and zirconium-containing type coating; The aluminum-containing coating contains 52-55 wt% Al2O3, ≥98 wt% Al2O3 + SiO2, and <5 wt% ZrO2. The zirconium-aluminum hybrid coating has an Al2O3 content of 40wt%, a ZrO2 content of 5-7wt%, and an Al2O3 + SiO2 + ZrO2 ≥ 98wt%. The zirconium-containing ceramic fiber coating contains 35 wt% Al2O3, ≥15 wt% ZrO2, and the total content of Al2O3+SiO2+ZrO2 is ≥99.1 wt%.

[0008] Furthermore, the preparation method of the surface-modified reinforcing fiber includes: immersing pre-oxidized polyacrylonitrile fiber in a solution of silicon-based polymer precursor, attaching it to the surface by impregnation, spraying or impregnation-filtration, and then crosslinking and curing it at 180-200°C for 1-2 hours in an inert atmosphere.

[0009] This application also provides a method for preparing a high-temperature resistant ceramic fiber surface coating, characterized by comprising the following steps: S1: Weigh magnesium aluminum spinel, M70 sintered mullite, silica micro powder, and ZrO2 micro powder according to the proportion, and dry mix them to obtain a mixed powder. S2: Dissolve starch ether in water to prepare a binding agent solution; S3: The surface-modified reinforcing fiber is dry-premixed with the mixed powder, and then added to the binder solution for high-speed shear dispersion to obtain a coating slurry.

[0010] In summary, the beneficial effects of the present invention are as follows: 1. The polymer layer on the surface of the surface-modified reinforcing fiber exhibits certain lubricity during the wet mixing stage and has good compatibility with the water-based binder, making it easier for the fiber to disperse evenly in the slurry, effectively preventing fiber agglomeration and ensuring uniform coating composition. Furthermore, the dry premixing process of the fiber with the mixed powder further utilizes the powder particles to isolate the fiber, ensuring a uniform distribution of the reinforcing phase. Starch ether provides slurry plasticity and bonding strength at low temperatures and decomposes during high-temperature service without introducing impurity phases.

[0011] 2. During the low-temperature curing stage, the silicon-based polymer precursor cross-links to form a three-dimensional organic-inorganic hybrid network, which chemically bonds the powder and fiber, solving the problems of easy powdering and cracking of traditional coatings. At the same time, it facilitates the handling and installation of modules in subsequent construction.

[0012] 3. In the high-temperature thermal shock-erosion cycle test, the polymer precursor on the fiber surface is transformed into a ceramic phase that is chemically compatible with the external matrix, such as SiO2 and SiC, which realizes a strong chemical bonding interface between the fiber and the external ceramic matrix. Its reinforcing effect is established and strengthened as the temperature increases, overcoming the inherent defect of high-temperature failure of organic modified layers.

[0013] 4. The polymer precursor on the fiber surface can be transformed into a ceramic phase that is chemically compatible with the external matrix, exhibiting excellent resistance to oxidation and corrosion by molten salt and alkaline vapors. Therefore, the coating's resistance to high-temperature alkaline volatiles, acidic atmospheres, and slag is greatly enhanced, reducing the depth of penetration of harmful media into the coating and fiber matrix, and fundamentally extending the lifespan of the protective matrix in harsh environments.

[0014] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below. Attached Figure Description

[0015] Figure 1 XRF images of ZrO2 in coatings A3, A31, and A32; Figure 2 The following are component analysis diagrams for coatings A1, A2, A3, A4, A5, A6, A31, and A32; part a is a 3D component analysis diagram, part b is a ZrO2 content distribution diagram, part c is a ternary component mapping diagram, and part d is a raw material component radar diagram. Detailed Implementation

[0016] To make the content of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0017] Example 1: Preparation of surface-modified reinforcing fibers Step 1: Prepare pre-oxidized polyacrylonitrile fibers (PANOF, average length 1 mm, diameter 12 μm). Step 2: Preparation of SiO2 precursor coated fibers: Prepare PANOF and methyl polysiloxane (ethanol solution with a solid content of 50 parts). Preparation: Immerse PANOF in the methyl polysiloxane solution, stir for 30 min, filter through a 200-mesh filter, spread evenly, and heat-treat at 180℃ for 1 h.

[0018] Step 3: Fabrication of SiO2 / Al2O3 composite precursor coated fibers: Prepare PANOF, methyl polysiloxane solution (50 parts solids in an ethanol solution), and nano-alumina powder (30 nm). Preparation: Disperse 10 g of nano-alumina powder in 100 g of polysiloxane solution and sonicate for 30 min to obtain a modified solution. Impregnate, filter, and heat-treat at 180℃ for 1 h using the same method. Nano-Al2O3 accounts for 33 wt% of the precursor layer.

[0019] Step 4: Fabrication of SiO2 / ZrO2 composite precursor coated fibers: Prepare PANOF, methyl polysiloxane solution (50 parts solids in an ethanol solution), and nano-zirconia powder (50 nm). Preparation: Disperse 10 g of nano-zirconia powder in 100 g of polysiloxane solution and ultrasonically treat to obtain a modified solution. Impregnate PANOF using the same method, filter, and heat-treat at 180℃ for 1 h to obtain SiO2 / ZrO2 composite precursor coated fibers. The nano-zirconia accounts for approximately 33 parts by mass of the precursor layer.

[0020] Step 5: Fabrication of SiC nanowire composite precursor coated fibers: Prepare PANOF, polycarbosilane (toluene solution, solid content 30 parts), and silicon carbide nanowires (SiC, diameter 50-100 nm, length 5-20 μm). Preparation: Disperse 5 g of SiC nanowires in 100 g of polycarbosilane solution, stir evenly to obtain a modified solution. Impregnate PANOF using the same method, filter, heat treat at 180℃ for 1 h, and then crosslink at 200℃ for 1 h in a nitrogen atmosphere to obtain SiC nanowire composite precursor coated fibers. High-temperature pyrolysis of polycarbosilane mainly degenerates into the SiC phase.

[0021] Step 6: Fabrication of Porous Composite Fibers: Prepare PANOF, methyl polysiloxane solution (50 parts solids in an ethanol solution), and nano-alumina powder (30 nm). Preparation: Disperse 10 g of nano-alumina powder in 100 g of polysiloxane solution, sonicate to obtain a modified solution, add 10 wt% (by solution mass) of polyethylene glycol (PEG, molecular weight 2000) to the modified solution, impregnate PANOF using the same method, filter, and heat-treat at 180℃ for 1 h to obtain porous composite fibers. It should be noted that the porous structure is not formed directly during the 180℃ heat treatment stage, but gradually during subsequent high-temperature treatments (such as coating curing or high-temperature service processes); PEG only acts as a template agent in this stage, and it decomposes and escapes at high temperatures to form the porous structure.

[0022] Example 2: Making Coatings Coating A1 (PANOF, zirconium-aluminum hybrid): Raw materials: 45 parts magnesium aluminum spinel, 18 parts M70 sintered mullite, 18 parts silica micro powder, 5 parts zirconium oxide micro powder, 8 parts starch ether, and 1.4 parts PANOF.

[0023] Preparation method: (1) Dry mixing: After drying magnesium aluminum spinel, M70 sintered mullite, silica micro powder and zirconium oxide micro powder in a dryer at 110°C for 2 hours, they are placed in a three-dimensional mixer and mixed at 30 r / min for 30 minutes to obtain mixed powder.

[0024] (2) Premixing: The mixed powder and PANOF are premixed in a container for 20 minutes to obtain the fiber-powder premix; (3) Slurry preparation: Dissolve starch ether in deionized water to prepare a 10wt% adhesive solution, and stir at 400 r / min for 20 minutes to form an adhesive solution. Add fiber-powder premix, mix at a low speed of 300 r / min for 10 minutes, and then increase the speed to 700 r / min and stir for 25 minutes to form a uniform slurry.

[0025] (4) Degassing: After the slurry has been left to stand for 20 minutes, it is stirred at a low speed of 100 r / min for 5 minutes to degas, thus obtaining coating A1.

[0026] Chemical composition: such as Figure 1 and Figure 2 As shown, XRF analysis revealed that the coating contained 40.0 wt% Al2O3, 6.2 wt% ZrO2, and the total content of Al2O3 + SiO2 + ZrO2 was ≥ 98.0 wt%.

[0027] Coating A2 (Coating containing SiO2 precursor coating fibers): Raw materials: 45 parts magnesium aluminum spinel, 18 parts M70 sintered mullite, 18 parts silica micro powder, 5 parts zirconium oxide micro powder, 8 parts starch ether, and 1.4 parts SiO2 precursor coating fiber.

[0028] Preparation method: (1) Dry mixing: After drying magnesium aluminum spinel, M70 sintered mullite, silica micro powder and zirconium oxide micro powder in a dryer at 110°C for 2 hours, they are placed in a three-dimensional mixer and mixed at 30 r / min for 30 minutes to obtain mixed powder.

[0029] (2) Premixing: The mixed powder and SiO2 precursor coating fiber are premixed in a container for 20 minutes to obtain fiber-powder premix; (3) Slurry preparation: Dissolve starch ether in deionized water to prepare a 10wt% adhesive solution, and stir at 400 r / min for 20 minutes to form an adhesive solution. Add fiber-powder premix, mix at a low speed of 300 r / min for 10 minutes, and then increase the speed to 700 r / min and stir for 25 minutes to form a uniform slurry.

[0030] (4) Degassing: After the slurry has been left to stand for 20 minutes, it is stirred at a low speed of 100 r / min for 5 minutes to degas, thus obtaining coating A2.

[0031] Chemical composition: such as Figure 1 and Figure 2 As shown, XRF analysis revealed that the coating contained 40.0 wt% Al2O3, 6.2 wt% ZrO2, and the total content of Al2O3 + SiO2 + ZrO2 was ≥ 98.0 wt%.

[0032] Coating A3 (containing SiO2 / Al2O3 composite precursor coating fiber): Raw materials: 45 parts magnesium aluminum spinel, 18 parts M70 sintered mullite, 18 parts silica micro powder, 5 parts zirconium oxide micro powder, 8 parts starch ether, and 1.4 parts SiO2 / Al2O3 composite precursor coating fiber.

[0033] Preparation method: (1) Dry mixing: After drying magnesium aluminum spinel, M70 sintered mullite, silica micro powder and zirconium oxide micro powder in a dryer at 110°C for 2 hours, they are placed in a three-dimensional mixer and mixed at 30 r / min for 30 minutes to obtain mixed powder.

[0034] (2) Premixing: The mixed powder and SiO2 / Al2O3 composite precursor coating fiber are premixed in a container for 20 minutes to obtain fiber-powder premix; (3) Slurry preparation: Dissolve starch ether in deionized water to prepare a 10wt% adhesive solution, and stir at 400 r / min for 20 minutes to form an adhesive solution. Add fiber-powder premix, mix at a low speed of 300 r / min for 10 minutes, and then increase the speed to 700 r / min and stir for 25 minutes to form a uniform slurry.

[0035] (4) Degassing: After the slurry has been left to stand for 20 minutes, it is stirred at a low speed of 100 r / min for 5 minutes to degas, thus obtaining coating A3.

[0036] Chemical composition: such as Figure 1 and Figure 2 As shown, XRF analysis revealed that the coating contained 40.0 wt% Al2O3, 6.2 wt% ZrO2, and the total content of Al2O3 + SiO2 + ZrO2 was ≥ 98.0 wt%.

[0037] Coating A4 (containing SiO2 / ZrO2 composite precursor coating fiber): Raw materials: 45 parts magnesium aluminum spinel, 18 parts M70 sintered mullite, 18 parts silica micro powder, 5 parts zirconium micro powder, 8 parts starch ether, and 1.4 parts SiO2 / ZrO2 composite precursor coating fiber.

[0038] Preparation method: (1) Dry mixing: After drying magnesium aluminum spinel, M70 sintered mullite, silica micro powder and zirconium oxide micro powder in a dryer at 110°C for 2 hours, they are placed in a three-dimensional mixer and mixed at 30 r / min for 30 minutes to obtain mixed powder.

[0039] (2) Premixing: The mixed powder and SiO2 / ZrO2 composite precursor coating fiber are premixed in a container for 20 minutes to obtain fiber-powder premix; (3) Slurry preparation: Dissolve starch ether in deionized water to prepare a 10wt% adhesive solution, and stir at 400 r / min for 20 minutes to form an adhesive solution. Add fiber-powder premix, mix at a low speed of 300 r / min for 10 minutes, and then increase the speed to 700 r / min and stir for 25 minutes to form a uniform slurry.

[0040] (4) Degassing: After the slurry has been left to stand for 20 minutes, it is stirred at a low speed of 100 r / min for 5 minutes to degas, thus obtaining coating A4.

[0041] Chemical composition: such as Figure 1 and Figure 2 As shown, XRF analysis revealed that the coating contained 40.0 wt% Al2O3, 6.2 wt% ZrO2, and the total content of Al2O3 + SiO2 + ZrO2 was ≥ 98.0 wt%.

[0042] Coating A5 (containing SiC nanowire composite precursor coating fiber): Raw materials: 45 parts magnesium aluminum spinel, 18 parts M70 sintered mullite, 18 parts silica micro powder, 5 parts zirconium oxide micro powder, 8 parts starch ether, and 1.4 parts SiC nanowire composite precursor coating fiber.

[0043] Preparation method: (1) Dry mixing: After drying magnesium aluminum spinel, M70 sintered mullite, silica micro powder and zirconium oxide micro powder in a dryer at 110°C for 2 hours, they are placed in a three-dimensional mixer and mixed at 30 r / min for 30 minutes to obtain mixed powder.

[0044] (2) Premixing: The mixed powder and SiC nanowire composite precursor coating fiber are premixed in a container for 20 minutes to obtain fiber-powder premix; (3) Slurry preparation: Dissolve starch ether in deionized water to prepare a 10wt% adhesive solution, and stir at 400 r / min for 20 minutes to form an adhesive solution. Add fiber-powder premix, mix at a low speed of 300 r / min for 10 minutes, and then increase the speed to 700 r / min and stir for 25 minutes to form a uniform slurry.

[0045] (4) Degassing: After the slurry has been left to stand for 20 minutes, it is stirred at a low speed of 100 r / min for 5 minutes to degas, thus obtaining coating A5.

[0046] Chemical composition: such as Figure 1 and Figure 2 As shown, XRF analysis revealed that the coating contained 40.0 wt% Al2O3, 6.2 wt% ZrO2, and the total content of Al2O3 + SiO2 + ZrO2 was ≥ 98.0 wt%.

[0047] Coating A6 (containing porous composite fibers): Raw materials: 45 parts magnesium aluminum spinel, 18 parts M70 sintered mullite, 18 parts silica micro powder, 5 parts zirconium oxide micro powder, 8 parts starch ether, and 1.4 parts porous composite fiber.

[0048] Preparation method: (1) Dry mixing: After drying magnesium aluminum spinel, M70 sintered mullite, silica micro powder and zirconium oxide micro powder in a dryer at 110°C for 2 hours, they are placed in a three-dimensional mixer and mixed at 30 r / min for 30 minutes to obtain mixed powder.

[0049] (2) Premixing: The mixed powder and porous composite fiber are premixed in a container for 20 minutes to obtain fiber-powder premix; (3) Slurry preparation: Dissolve starch ether in deionized water to prepare a 10wt% adhesive solution, and stir at 400 r / min for 20 minutes to form an adhesive solution. Add fiber-powder premix, mix at a low speed of 300 r / min for 10 minutes, and then increase the speed to 700 r / min and stir for 25 minutes to form a uniform slurry.

[0050] (4) Degassing: After the slurry has been left to stand for 20 minutes, it is stirred at a low speed of 100 r / min for 5 minutes to degas, thus obtaining coating A6.

[0051] Chemical composition: such as Figure 1 and Figure 2 As shown, XRF analysis revealed that the coating contained 40.0 wt% Al2O3, 6.2 wt% ZrO2, and the total content of Al2O3 + SiO2 + ZrO2 was ≥ 98.0 wt%.

[0052] Coating A31 (containing SiO2 / Al2O3 composite precursor coating fiber): Raw materials: 57.5 parts magnesium aluminum spinel, 12 parts M70 mullite, 18 parts silica micro powder, 12 parts starch ether, 0.5 parts SiO2 / Al2O3 composite coated fiber (without zirconia micro powder).

[0053] Preparation method: (1) Dry mixing: After drying magnesium aluminum spinel, M70 sintered mullite and silica micro powder in a dryer at 110°C for 2 hours, they are placed in a three-dimensional mixer and mixed at 30 r / min for 30 minutes to obtain mixed powder.

[0054] (2) Premixing: The mixed powder and SiO2 / Al2O3 composite precursor coating fiber are premixed in a container for 20 minutes to obtain fiber-powder premix; (3) Slurry preparation: Dissolve starch ether in deionized water to prepare a 10wt% adhesive solution, and stir at 400 r / min for 20 minutes to form an adhesive solution. Add fiber-powder premix, mix at a low speed of 300 r / min for 10 minutes, and then increase the speed to 700 r / min and stir for 25 minutes to form a uniform slurry.

[0055] (4) Degassing: After the slurry has been left to stand for 20 minutes, it is stirred at a low speed of 100 r / min for 5 minutes to degas, thus obtaining coating A31.

[0056] Chemical composition: such as Figure 1 and Figure 2 As shown, XRF analysis revealed that the coating contained 53.5 wt% Al2O3 and ≥ 98.0 wt% Al2O3 + SiO2 + ZrO2.

[0057] Coating A32 (containing SiO2 / Al2O3 composite precursor coating fiber): Raw materials: 30 parts magnesium aluminum spinel, 20 parts M70 mullite, 22 parts silica micro powder, 15 parts zirconium oxide micro powder, 7 parts starch ether, and 2.0 parts SiO2 / Al2O3 composite coated fiber.

[0058] Preparation method: (1) Dry mixing: After drying magnesium aluminum spinel, M70 sintered mullite, silica micro powder and zirconium oxide micro powder in a dryer at 110°C for 2 hours, they are placed in a three-dimensional mixer and mixed at 30 r / min for 30 minutes to obtain mixed powder.

[0059] (2) Premixing: The mixed powder and SiO2 / Al2O3 composite precursor coating fiber are premixed in a container for 20 minutes to obtain fiber-powder premix; (3) Slurry preparation: Dissolve starch ether in deionized water to prepare a 10wt% adhesive solution, and stir at 400 r / min for 20 minutes to form an adhesive solution. Add fiber-powder premix, mix at a low speed of 300 r / min for 10 minutes, and then increase the speed to 700 r / min and stir for 25 minutes to form a uniform slurry.

[0060] (4) Degassing: After the slurry has been left to stand for 20 minutes, it is stirred at a low speed of 100 r / min for 5 minutes to degas, thus obtaining coating A32.

[0061] Chemical composition: such as Figure 1 and Figure 2 As shown, XRF analysis revealed that the coating contained 16.5 wt% ZrO2 and 35.0 wt% Al2O3, with the total content of Al2O3 + SiO2 + ZrO2 ≥ 99.1 wt%.

[0062] Example 3: Comparison of Experimental Performance 1. Comparative test of the comprehensive performance of coatings under the coupled action of high temperature thermal shock and erosion cycle (1) Sample preparation Coatings A1, A2, A3, A4, A5, A6, A31, and A32 were prepared according to the above method, wherein A1-A6 are zirconium-aluminum mixed coatings, A31 is an aluminum-containing coating, and A32 is a zirconium-containing coating. The above coatings were uniformly sprayed onto the surface of a standard zirconium-containing ceramic fiber module (200mm×150mm×40mm) of the same batch, with the coating thickness controlled at 2.0±0.2 mm. After curing at room temperature for 24 hours, the modules were dried at 110℃ for 12 hours to form samples A1, A2, A3, A4, A5, A6, A31, and A32.

[0063] Group B (blank control group): Ceramic fiber modules from the same batch that were not coated with any paint.

[0064] (2) Experimental Procedure and Method The harsh operating conditions in an industrial kiln are simulated, involving intense temperature cycling and alternating chemical erosion. The specific steps are as follows: Step 1: High-temperature resistance to alkaline vapor erosion test. Each group of samples was placed in a dedicated high-temperature furnace. An equal amount of mixed K₂CO₃ and Na₂CO₃ powder (simulating alkaline volatiles) was placed above the samples, with a total addition amount of 1 wt% of the sample mass. The furnace was held at 1750℃ for 24 hours. A trace amount of water vapor (3 vol%) was introduced into the furnace to accelerate the generation and migration of alkaline vapor, with a heating rate of 5℃ / min.

[0065] Step 2: Forced air cooling thermal shock test. The sample is quickly transferred to a room temperature environment. The time interval between removing the sample from 1750°C and starting forced cooling is 30 seconds. Compressed air (wind speed 30 m / s) is used to force-cool the coating surface to below 100°C to complete one thermal shock cycle.

[0066] Step 3: Cyclic Coupling Test. Repeat Steps 1 and 2 of the above experiment to form a complete "high-temperature erosion-forced thermal shock" cycle. Perform a total of 5 cycles.

[0067] (3) Performance testing and evaluation indicators (after the experimental procedure is completed) Peeling rate: The percentage of the total area of ​​coating that has peeled off from the substrate, measured and calculated precisely.

[0068] Crack Grade: Surface cracks are observed and classified into grades 0 to 5 according to their width and density. 0 indicates no corrosion observed; 1 indicates corrosion depth not exceeding 1 mm, crack width not exceeding 1 mm, and powdering or peeling area not exceeding 1 unit; 2 indicates corrosion depth between 1 and 1.5 mm, and crack width between 1 and 1.5 mm; 3 indicates corrosion depth between 1 and 2 mm, crack width between 1 and 2 mm, and powdering or peeling area between 1 and 3 units; 4 indicates corrosion depth between 2 and 2.5 mm, and crack width between 2 and 2.5 mm; 5 indicates corrosion depth greater than 2.5 mm, crack width greater than 2.5 mm, and powdering or peeling area greater than 3 units.

[0069] Alkali penetration depth: measures the depth to which alkaline elements (K, Na) diffuse from the surface into the coating interior and interface.

[0070] Residual strength test: Pull-out adhesion test was performed according to GB / T 5210.

[0071] Thermal conductivity change: measured at a hot surface temperature of 500℃ in accordance with GB / T 10295.

[0072] Assess the stability of its thermal insulation performance.

[0073]

[0074] Note: Thermal conductivity change rate = (thermal conductivity after cycling - initial thermal conductivity) / initial thermal conductivity × 100%. A positive value indicates a decrease in thermal insulation performance. The smaller the thermal conductivity change rate, the more stable the thermal insulation performance. A change rate ≤10% is considered acceptable, and ≤5% is considered excellent.

[0075] As can be seen from the comparison in the table above, all performance indicators of groups A2-A6 are better than those of group A1. Groups A3 (SiO2 / Al2O3) and A4 (SiO2 / ZrO2) are superior to group A2 (pure SiO2) in terms of anti-stripping, anti-permeability and strength retention.

[0076] Both A2 (polysiloxane) and A5 (polycarbosilane) showed good results. Group A5 exhibited superior residual strength, demonstrating the advantage of polycarbosilane-derived SiC phases in terms of high-temperature strength.

[0077] Comparing the test results of A31 (aluminum-containing, ZrO2-free), A3 (zirconium-aluminum hybrid), and A32 (zirconium-containing) coatings, it can be seen that at high temperatures, silica micropowder and other components in the coating will form a silicate liquid phase. For the ZrO2-containing A3 and A32 coatings, zirconium oxide particles (ZrO2) react with SiO2 in these liquid phases to generate zircon (ZrSiO4) or a zirconium-containing glassy phase at the interface, which delays the diffusion and damage of alkali metal ions into the coating interior. At the same time, the volume expansion generated by the tetragonal-to-monoclinic phase transformation of ZrO2 can close microcracks (phase transformation toughening), which works synergistically with the macroscopic toughening mechanism of fiber bridging to gradually consume the crack energy generated by thermal shock, thereby significantly improving the coating's resistance to spalling and cracking. Although A31 (aluminum-containing type) does not contain ZrO2, its high Al2O3 content forms a dense mullite / spinel skeleton. Combined with the fiber bridging effect, it also exhibits good anti-erosion performance (stripping rate 1.8%, alkali penetration depth 90μm), but its thermal shock resistance and alkali penetration resistance are lower than those of A3 and A32 formulations.

[0078] The embodiments described above are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and modifications made by those skilled in the art based on the invention shall fall within the scope of protection of the present invention.

Claims

1. A high-temperature resistant ceramic fiber surface coating, characterized in that, The raw materials include the following parts by weight: 30-60 parts magnesium aluminum spinel, 10-30 parts M70 sintered mullite, 5-30 parts silica micro powder, 1-20 parts starch ether, 0.5-2.0 parts surface-modified reinforcing fiber, and 5-20 parts ZrO2 micro powder. The surface-modified reinforcing fiber is a pre-oxidized polyacrylonitrile fiber, and its surface is bonded or coated with a layer of silicon-based polymer precursor, wherein the silicon-based polymer precursor is selected from polysiloxane or polycarbosilane.

2. The high-temperature resistant ceramic fiber surface coating according to claim 1, characterized in that, The silicon-based polymer precursor also contains dispersed nano-ceramic powder, which is at least one of nano-alumina, nano-zirconia, and silicon carbide nanowires, and the mass of the nano-ceramic powder accounts for 10-50% of the mass of the precursor layer.

3. The high-temperature resistant ceramic fiber surface coating according to claim 1, characterized in that, The ceramic fiber surface coating is one of the following: aluminum-containing type, zirconium-aluminum hybrid type, and zirconium-containing type. The aluminum-containing coating has an Al2O3 content of 52-55 wt%, an Al2O3+SiO2 content of ≥98 wt%, and a ZrO2 content of <5 wt%. The zirconium-aluminum hybrid coating has an Al2O3 content of 40wt%, a ZrO2 content of 5-7wt%, and an Al2O3 + SiO2 + ZrO2 ≥ 98wt%. The zirconium-containing ceramic fiber coating contains 35 wt% Al2O3, ≥15 wt% ZrO2, and the total content of Al2O3+SiO2+ZrO2 is ≥99.1 wt%.

4. A high-temperature resistant ceramic fiber surface coating according to claim 1 or 2, characterized in that, The preparation method of the surface-modified reinforcing fiber includes: immersing pre-oxidized polyacrylonitrile fiber in a solution of silicon-based polymer precursor, attaching it to the surface by impregnation, spraying or impregnation-filtration, and then crosslinking and curing it at 180-200℃ for 1-2 hours in an inert atmosphere.

5. A method for preparing a high-temperature resistant ceramic fiber surface coating as described in any one of claims 1-3, characterized in that, Includes the following steps: S1: Weigh magnesium aluminum spinel, M70 sintered mullite, silica micro powder, and ZrO2 micro powder according to the proportion, and dry mix them to obtain a mixed powder. S2: Dissolve starch ether in water to prepare a binding agent solution; S3: The surface-modified reinforcing fiber is dry-premixed with the mixed powder, and then added to the binder solution for high-speed shear dispersion to obtain a coating slurry.

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