A porcelainizable high-temperature resistant coating and a preparation method thereof

Abstract

The application belongs to the technical field of coating preparation, and provides a porcelainizable high-temperature-resistant coating and a preparation method thereof. A core-shell polysiloxane resin solution is prepared first, then ZrB2 / SiC composite particles are prepared, and a reaction shell layer is constructed by using dravite, pseudo-boehmite, colloidal silicon dioxide, boric acid, the core-shell polysiloxane resin solution and an ethanol aqueous solution, and is coated on the surface of the composite particles to form core-shell microspheres. Then, the core-shell polysiloxane resin solution, a coupling agent, butyl titanate and fumed silicon dioxide are compounded to prepare a coating slurry. Through the synergistic design of the resin core-shell structure and the reaction-type core-shell microspheres, the coating layer is porcelainized at a low temperature and forms a dense and stable protective layer in a super-high-temperature environment, and the construction film-forming property and the service protective property are considered, and the coating is suitable for the surface protection of a matrix under high-temperature oxidation, ablation and thermal shock conditions.

Description

Technical Field

[0001] This invention belongs to the field of coating preparation technology, and relates to a ceramic-type high-temperature resistant coating and its preparation method. Background Technology

[0002] Ultra-high temperature resistant coatings are mainly used for surface protection of graphite, carbon-based composites, silicon carbide ceramics, and other high-temperature resistant substrates. Under high-temperature oxidation, thermal shock, and ablation erosion conditions, these materials are prone to surface oxidation and weight loss, structural loosening, crack propagation, and localized spalling, leading to decreased mechanical properties, reduced dimensional stability, and shortened service life. Existing high-temperature resistant coatings often employ a compounding approach using organosilicon resins, inorganic fillers, and glass phase additives. This involves forming a ceramicized layer upon heating to improve the substrate's oxidation and ablation resistance. While this technology offers some workability and film-forming properties, it still has several shortcomings. Firstly, some systems struggle to form a continuous and dense ceramicized layer at lower temperatures, resulting in coatings with numerous pores, loose structure, and insufficient shielding ability in the initial stages of heating, failing to provide effective protection for the substrate. On the other hand, although some systems can improve low-temperature vitrification performance by introducing low-melting phases, they are prone to softening, cracking, bubbling or even failure at higher temperatures due to excessive liquid phase, excessive fluidity or insufficient structural stability. It is difficult to achieve both rapid low-temperature vitrification and long-term stable protection at ultra-high temperatures.

[0003] Furthermore, while commonly used ultra-high temperature ceramic fillers in existing technologies possess high melting points and certain oxidation resistance, simply dispersing them in a resin matrix through mixing often results in insufficient interfacial bonding, limited particle synergy, and discontinuous phase evolution paths at high temperatures. This makes it difficult for the coating to form a continuous protective structure from the surface to the interior during thermal exposure. Especially when the temperature continues to rise or undergoes repeated thermal shocks, the thermal expansion mismatch between different components within the coating, uneven local oxidation reactions, and delayed densification processes can all further induce cracks and spalling, affecting the protective effect. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a ceramic-like high-temperature resistant coating and its preparation method. By constructing a core-shell polyborosiloxane resin liquid and preparing composite core-shell microspheres with a reactive shell, and synergistically compounding them with other components, a coating system with both construction film-forming properties and high-temperature reactivity is formed. After being heated, the coating can gradually form a continuous and dense protective layer, thereby meeting the needs of actual production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a ceramic-compatible high-temperature resistant coating, the method comprising:

[0007] S1, phenyltriethoxysilane, the first part of xylene and sulfuric acid are mixed, deionized water is added dropwise to react, triethylamine is added, then the second part of xylene is added and the temperature is raised to distill off the ethanol, boric acid is added and isobutanol is reacted to obtain the core-shell polyborosiloxane resin liquid.

[0008] S2, ZrB2 powder, α-SiC powder, anhydrous ethanol and polyvinylpyrrolidone are mixed and ball-milled to obtain a slurry, and the slurry is spray-granulated to obtain ZrB2 / SiC composite particles.

[0009] S3, andalusite, pseudoboehmite, colloidal silica, boric acid, core-shell polyborosilicate resin liquid and ethanol aqueous solution are mixed and dispersed to obtain a reaction shell slurry. ZrB2 / SiC composite particles are placed in a granulator and sprayed into the reaction shell slurry to obtain ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres.

[0010] S4. A core-shell polyborosiloxane resin liquid, ZrB2 / SiC@andalusite-aluminosilicate boron shell core-shell microspheres, γ-aminopropyltriethoxysilane, tetrabutyl titanate, fumed silica and xylene / isobutanol mixture are mixed and ground to obtain a ceramic-compatible high-temperature resistant coating slurry.

[0011] The preparation method specifically includes:

[0012] S1, phenyltriethoxysilane, the first part of xylene and sulfuric acid are mixed, and deionized water is added dropwise. After the addition is completed, the reaction is stirred for 8-12 hours. Then triethylamine is added, followed by the second part of xylene and the temperature is raised to 90-100℃ to distill off the byproduct ethanol. After 20-30 minutes, boric acid and isobutanol are added, and the reaction is continued at 100-115℃ for 2-4 hours. Then the reaction is carried out under reduced pressure to obtain a core-shell polyborosiloxane resin solution.

[0013] S2, ZrB2 powder, α-SiC powder, anhydrous ethanol and polyvinylpyrrolidone are added to a ball mill jar and ball milled for 4-6 hours to obtain a slurry. The slurry is then spray-granulated to obtain ZrB2 / SiC composite particles.

[0014] S3, andalusite, boehmite, colloidal silica, boric acid, core-shell polyborosilicate resin liquid and ethanol aqueous solution are mixed and dispersed to obtain a reaction shell slurry. ZrB2 / SiC composite particles are placed in a granulator, and the reaction shell slurry is sprayed into the particles while they are rolling and then dried to obtain ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres.

[0015] S4. A core-shell polyborosiloxane resin liquid, ZrB2 / SiC@andalusite-aluminosilicate boron shell core-shell microspheres, γ-aminopropyltriethoxysilane, tetrabutyl titanate, fumed silica and xylene / isobutanol mixture are mixed and ground to obtain a ceramic-compatible high-temperature resistant coating slurry.

[0016] In the preparation of core-shell polyborosiloxane resin solution, phenyltriethoxysilane first undergoes acid-catalyzed hydrolysis, with ethoxy groups gradually being replaced by hydroxyl groups to form Si–OH-containing intermediates. Subsequently, dehydration condensation occurs between Si–OH groups, and dealcoholization condensation occurs between Si–OH groups and residual ethoxy groups, gradually forming a polysiloxane structure with Si–O–Si as the main chain. After the addition of triethylamine, the acidity of the system decreases, and polycondensation continues, with the already formed polysiloxane segments remaining as a continuous phase. The subsequently added boric acid mainly reacts with the residual Si–OH and the surface sites where further condensation can occur, generating Si–O–B bonds. Since the boron source is introduced after the pre-polymerization of polysiloxane, the boron-containing structure is mainly distributed on the periphery of the existing polysiloxane network, and the resulting resin solution exhibits a structural state in which a polysiloxane core and a Si–O–B-containing outer layer coexist. During the subsequent heating process, the organic side groups of the resin gradually decompose, while the inorganic framework composed of Si–O–Si and Si–O–B is retained and continues to condense, and the resin phase changes from an organic continuous phase to an inorganic continuous phase.

[0017] Upon heating, the boehmite in the reaction shell slurry first dehydrates and dehydroxylates, transforming into an activated alumina mesophase. The colloidal silica particles, originally bearing Si–OH sites, continue to condense upon heating, forming a Si–O–Si network. The Al–OH sites on the activated alumina surface condense upon contact with the Si–OH sites on the silica surface, forming Al–O–Si bonds. Boric acid gradually dehydrates upon heating, forming a boron-oxygen structure containing B–O bonds, which then enters the glassy phase surrounding the aluminum-silicon-oxygen framework. The addition of core-shell polyborosiloxane resin to the shell slurry provides a binder phase containing Si–O–Si and Si–O–B during the initial drying and heating stages, allowing andalusite, boehmite, and colloidal silica to form a continuous coating layer.

[0018] Upon heating, andalusite gradually transforms into mullite, releasing a SiO2-rich glassy phase. This process is accompanied by rearrangement of the original aluminum-silicon-oxygen structure and localized liquid phase precipitation. As the andalusite particle size decreases, the reaction interface area increases, shortening the pathway for mullite transformation within the particles, and allowing the SiO2-rich glass to migrate more easily from the particle interior to the interparticle spaces. The active alumina derived from boehmite in the shell comes into contact with this SiO2-rich glass, further generating a new mullite phase. Upon heating, the shell sequentially exhibits aluminum-oxygen framework formation, andalusite mullification, SiO2-rich glass precipitation, and secondary mullite formation. The previously open channels between particles are filled with SiO2-rich glass, and some of the liquid phase reacts with the aluminum source to transform into a solid phase, resulting in continuous changes in the porosity and phase composition of the shell.

[0019] Within the composite core particles, ZrB2 and α-SiC exist as composite particles. External oxygen diffuses inward through the shell, first reaching ZrB2 and SiC near the particle surface. ZrB2 oxidation produces ZrO2 and B2O3, while SiC oxidation produces SiO2. Upon contact with SiO2, B2O3 forms a borosilicate liquid phase, which can flow and enter the pores and interparticle spaces within the oxide layer. The oxidized ZrO2 remains in situ, forming a solid framework. As oxidation continues, an oxide layer gradually forms on the outer side of the core particles, composed of both liquid borosilicate and solid ZrO2. The liquid phase, located between the solid particles, alters the path of further inward diffusion of oxygen; the solid particles restrict the complete loss of the liquid phase, keeping it confined to the outer region of the particles. The SiO2 formed by SiC oxidation increases the SiO2 content in the borosilicate liquid phase, causing a gradual shift in the liquid phase composition from a B2O3-rich side to a SiO2-rich side.

[0020] As the temperature continues to rise, B2O3 in the oxide layer gradually volatilizes, increasing the proportion of SiO2 in the residual liquid phase. The already formed ZrO2 reacts with SiO2 upon contact, forming ZrSiO4. This reaction occurs at the interface between the ZrO2 particles and the SiO2-rich region, with the generated ZrSiO4 located between the original solid particles and the glassy phase. The oxide layer surrounding the core particles further develops into a structure where ZrO2, ZrSiO4, and SiO2-rich glass coexist. The glassy phase fills the interparticle gaps, with ZrO2 and ZrSiO4 forming the solid-phase support. Incompletely oxidized ZrB2 and SiC are located further inward. During the heating process, a single core-shell microsphere forms a layered structure consisting of an outer reaction shell, a transitional oxide layer, and an inner unreacted core.

[0021] When γ-aminopropyltriethoxysilane is added to the coating slurry, the ethoxy group first undergoes hydrolysis to generate Si–OH, which then condenses with Si–OH on the surface of colloidal silica in the shell layer, pseudoboehmite, or residual surface sites after dehydroxylation, forming Si–O–Si or Si–O–Al bonds. One end of the coupling agent is fixed to the surface of the inorganic particles, while the organic group at the other end faces the resin phase. When the core-shell polyborosiloxane in the resin solution spreads on the particle surface, a continuous transition layer is formed between the particle surface and the resin phase. Butyl titanate undergoes alcoholysis and hydrolysis in the slurry to form Ti–OH-containing intermediates, which then condense with Si–OH to form Ti–O–Si bonds, with some intermediates forming Ti–O–Ti bonds. The Si–OH on the surface of the fumed silica particles comes into contact with each other in the solvent system and forms reversible bonds, establishing spatial connections between particles, allowing the high-density core-shell microspheres to remain dispersed when stationary.

[0022] After the coating is formed, the solvent evaporates, and the Si–OH and Si–OEt in the resin solution continue to condense, forming more Si–O–Si connections between the coupling layer on the particle surface and the resin phase. The initial curing stage results in a core-shell microsphere structure with a continuous resin phase. Upon heating, the organic side groups in the continuous resin phase decompose, leaving the residual inorganic framework between the particles, and the original continuous resin phase transforms into an inorganic connecting phase. Since each core-shell microsphere already has a pre-existing andalusite-alumina-silicon-boron reaction shell, the first change after heat treatment begins is in the shell of each individual particle. The SiO2-rich glass and alumina-silicon-oxygen phases in the shell first locally seal the pores around the particles, then expand to adjacent particles. The connections between particles are initially provided by the inorganic Si–O–Si / Si–O–B network after resin inorganization, and are subsequently further strengthened by the glassy and mullite phases generated by the shell reaction.

[0023] Under sustained high temperatures, andalusite transformation and glass phase precipitation occur earlier near the outer surface, with pores initially filled by the SiO2-rich phase. Near the core particles, the borosilicate liquid phase generated from the oxidation of ZrB2 and SiC continues to replenish the surface. The SiO2-rich glass provided by the outer shell exchanges composition with the borosilicate liquid phase obtained from the core oxidation upon contact. Al2O3 in the shell continuously reacts with the outer SiO2-rich glass to form mullite; therefore, the shell does not remain in the glassy state but undergoes a continuous process of glass filling and solid-phase precipitation. ZrO2 in the core oxide layer contacts the outer glass phase, further forming ZrSiO4.

[0024] The chemical mechanism of this invention follows the path of "resin inorganicization—shell layer reaction densification—core core oxidation and stabilization." The core-shell polyborosiloxane resin first undergoes hydrolysis and condensation to form a Si–O–Si / Si–O–B network, which transforms from an organic continuous phase to an inorganic connecting phase upon heating. The reaction shell, composed of andalusite, boehmite, colloidal silica, and boric acid, undergoes sequential dehydroxylation, condensation, mullite formation, and SiO2-rich glass precipitation during heating, achieving outer layer densification through interstitial glass phase filling and secondary mullite formation. The ZrB2 / SiC composite core oxidizes at higher temperatures to generate ZrO2, SiO2, borosilicate, and ZrSiO4, with the corresponding liquid and solid phases jointly forming the inner barrier structure. Thus, a multi-layered protective structure is gradually established within the coating, primarily composed of a Si–O–Si / Si–O–B framework, a mullite / SiO2-rich phase, and a ZrO2 / ZrSiO4 / borosilicate phase.

[0025] As a preferred embodiment of the present invention, in S1, the mass ratio of phenyltriethoxysilane, the first part xylene, sulfuric acid, deionized water, triethylamine, the second part xylene, boric acid, and isobutanol is (80-90):(10-15):(0.08-0.15):(6-8):(0.1-0.3):(10-15):(8-12):(5-8), for example, it can be (80, 81, 82, 83, 84, 85, 86, 87, 88, 89 or 90):(10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5 or 15):(0.08, 0.087, 0.094, 0.101, 0.108, 0.115, 0.122, 0.129, 0.136, 0.1). 43 or 0.15): (6.0, 6.2, 6.4, 6.6, 6.8, 7.0, 7.2, 7.4, 7.6, 7.8 or 8.0): (0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, 0.28 or 0.3): (10, 10.5, 11, 11.5, 12, 12.5, 13, 1 3.5, 14, 14.5 or 15: (8, 8.4, 8.8, 9.2, 9.6, 10.0, 10.4, 10.8, 11.2, 11.6 or 12): (5, 5.3, 5.6, 5.9, 6.2, 6.5, 6.8, 7.1, 7.4, 7.7 or 8), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0026] In some optional embodiments, the sulfuric acid is concentrated sulfuric acid with a mass fraction of 98 wt.%.

[0027] In a preferred embodiment of the present invention, in S2, the mass ratio of ZrB2 powder, α-SiC powder, anhydrous ethanol, and polyvinylpyrrolidone is (42-48):(18-22):(25-30):(0.8-1.2), for example, it can be (42, 42.6, 43.2, 43.8, 44.4, 45, 45.6, 46.2, 46.8, 47.4 or 48):(18, 18.4, 18.8, 19.2, 19...). 6, 20.0, 20.4, 20.8, 21.2, 21.6 or 22: (25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5 or 30): (0.8, 0.84, 0.88, 0.92, 0.96, 1.0, 1.04, 1.08, 1.12, 1.16 or 1.2), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0028] In some optional embodiments, the D50 of the ZrB2 powder is 1-3 μm, for example, it can be 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm or 3.0 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0029] In some optional embodiments, the D50 of the α-SiC powder is 0.8-1.5 μm, for example, it can be 0.8 μm, 0.87 μm, 0.94 μm, 1.01 μm, 1.08 μm, 1.15 μm, 1.22 μm, 1.29 μm, 1.36 μm, 1.43 μm or 1.5 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0030] In some optional embodiments, the inlet air temperature of the spray granulation is 150-170°C and the outlet air temperature is 75-90°C. For example, the inlet air temperature can be (150, 152, 154, 156, 158, 160, 162, 164, 166, 168 or 170)°C and the outlet air temperature can be (75, 76.5, 78, 79.5, 81, 82.5, 84, 85.5, 87, 88.5 or 90)°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] As a preferred embodiment of the present invention, in S3, the mass ratio of andalusite, boehmite, colloidal silica, boric acid, core-shell polyborosiloxane resin solution, ethanol aqueous solution, and ZrB2 / SiC composite particles is (14-18):(4-6):(12-16):(3-5):(2-4):(20-30):(60-65), for example, it can be (14, 14.4, 14.8, 15.2, 15.6, 16.0, 16.4, 16.8, 17.2, 17.6 or 18):(4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8 or 6.0):(12, 12.4, 12.8). 13.2, 13.6, 14.0, 14.4, 14.8, 15.2, 15.6 or 16: (3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8 or 5.0): (2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8 or 4.0): (20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30): (60, 60.5, 61, 61.5, 62, 62.5, 63, 63.5, 64, 64.5 or 65), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0032] In some alternative embodiments, the D50 of the andalusite is 2-5 μm, for example, it can be 2.0 μm, 2.3 μm, 2.6 μm, 2.9 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4.1 μm, 4.4 μm, 4.7 μm or 5.0 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0033] In some optional embodiments, the mass fraction of SiO2 in the colloidal silica is 25-30 wt.%, for example, it can be 25 wt.%, 25.5 wt.%, 26 wt.%, 26.5 wt.%, 27 wt.%, 27.5 wt.%, 28 wt.%, 28.5 wt.%, 29 wt.%, 29.5 wt.%, or 30 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0034] In some optional embodiments, the mass ratio of anhydrous ethanol to deionized water in the aqueous ethanol solution is 4:1.

[0035] As a preferred technical solution of the present invention, in S4, the mass ratio of the core-shell polyborosiloxane resin liquid, ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres, γ-aminopropyltriethoxysilane, tetrabutyl titanate, fumed silica and xylene / isobutanol mixture is (30-36):(55-65):(0.5-1):(0.3-0.8):(0.8-1.5):(10-18), for example, it can be (30, 30.6, 31.2, 31.8, 32.4, 33.0, 33.6, 34.2, 34.8, 35.4 or 36):(55, 56, 57, 58, 59, 60, 61, 62, 63, 64 or 65): (0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 or 1.0): (0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75 or 0.8): (0.8, 0.87, 0.94, 1.01, 1.08, 1.15, 1.22, 1.29, 1.36, 1.43 or 1.5): (10, 10.8, 11.6, 12.4, 13.2, 14, 14.8, 15.6, 16.4, 17.2 or 18), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0036] In some optional embodiments, the mass ratio of xylene to isobutanol in the xylene / isobutanol mixture is 3:1.

[0037] In some optional embodiments, the fineness of the ceramicizable high-temperature resistant coating slurry is no greater than 35 μm.

[0038] Secondly, the present invention provides a ceramicizable high-temperature resistant coating prepared by the preparation method described in the first aspect.

[0039] Compared with existing technologies, the beneficial effects of this invention are as follows: Through the synergistic design of core-shell polyborosiloxane resin liquid and reactive core-shell microspheres, this invention enables the coating to gradually transform from an organic continuous phase to an inorganic continuous phase during heating, forming a continuous protective framework within the coating. The reactive shell layer composed of andalusite, pseudoboehmite, colloidal silica, and boric acid undergoes mullite formation, glassy phase precipitation, and interstitial densification during heating. The ZrB2 / SiC composite particles further generate stable oxidation products and barrier phases, thereby constructing a continuously evolving protective structure from the outside in. This effectively improves the coating's oxidation resistance, ablation resistance, thermal shock resistance, adhesion stability, and long-term service reliability. Attached Figure Description

[0040] Figure 1This is a photograph of the cured ceramic-resistant high-temperature coating provided in Embodiment 1 of the present invention. Detailed Implementation

[0041] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0042] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0043] Example 1

[0044] This embodiment provides a ceramicizable high-temperature resistant coating and its preparation method, which specifically includes the following steps:

[0045] S1, phenyltriethoxysilane, a first portion of xylene, and 98 wt.% sulfuric acid were mixed, and deionized water was added dropwise. After the addition was complete, the mixture was stirred and reacted for 8 hours. Then, triethylamine was added, followed by a second portion of xylene, and the temperature was raised to 90°C to distill off the byproduct ethanol. After 30 minutes, boric acid and isobutanol were added, and the mixture was reacted at 100°C for 4 hours. Then, the mixture was distilled under reduced pressure at 0.03 MPa for 1 hour to obtain a core-shell polyborosiloxane resin solution. The mass ratio of phenyltriethoxysilane, a first portion of xylene, sulfuric acid, deionized water, triethylamine, a second portion of xylene, boric acid, and isobutanol was 80:15:0.08:8:0.1:15:8:8.

[0046] S2, ZrB2 powder with a D50 of 1 μm, α-SiC powder with a D50 of 1.5 μm, anhydrous ethanol and polyvinylpyrrolidone are added to a ball mill jar and ball-milled for 4 hours to obtain a slurry. The slurry is then spray-granulated to obtain ZrB2 / SiC composite particles. The mass ratio of ZrB2 powder, α-SiC powder, anhydrous ethanol and polyvinylpyrrolidone is 42:22:25:1.2. The inlet air temperature of the spray granulation is 150℃ and the outlet air temperature is 90℃.

[0047] S3, andalusite (D50: 2 μm), boehmite, colloidal silica (SiO2 mass fraction: 25 wt.%), boric acid, core-shell polyborosiloxane resin solution, and ethanol aqueous solution are mixed and dispersed to obtain a reaction shell slurry. ZrB2 / SiC composite particles are placed in a granulator, sprayed into the reaction shell slurry while the particles are rolling, and dried to obtain ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres. The mass ratio of andalusite, boehmite, colloidal silica, boric acid, core-shell polyborosiloxane resin solution, ethanol aqueous solution, and ZrB2 / SiC composite particles is 14:6:12:5:2:30:60, and the mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution is 4:1.

[0048] S4, a core-shell polyborosiloxane resin liquid, ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres, γ-aminopropyltriethoxysilane, tetrabutyl titanate, fumed silica, and xylene / isobutanol mixture are mixed and ground to a fine consistency. The mass ratio of the core-shell polyborosiloxane resin liquid, ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres, γ-aminopropyltriethoxysilane, tetrabutyl titanate, fumed silica, and xylene / isobutanol mixture is 30:65:0.5:0.8:0.8:18, and the mass ratio of xylene to isobutanol in the xylene / isobutanol mixture is 3:1, to obtain a ceramic-compatible high-temperature resistant coating slurry with a fineness of no more than 35μm.

[0049] Figure 1 This is a photograph of the cured ceramic-resistant high-temperature coating slurry prepared in this embodiment.

[0050] Example 2

[0051] This embodiment provides a ceramicizable high-temperature resistant coating and its preparation method, which specifically includes the following steps:

[0052] S1, phenyltriethoxysilane, a first portion of xylene, and 98 wt.% sulfuric acid were mixed, and deionized water was added dropwise. After the addition was complete, the mixture was stirred and reacted for 12 h. Triethylamine was then added, followed by a second portion of xylene, and the mixture was heated to 100 °C to distill off the byproduct ethanol. After 20 min, boric acid and isobutanol were added, and the mixture was reacted at 115 °C for 2 h. Then, the mixture was distilled under reduced pressure at 0.05 MPa for 0.5 h to obtain a core-shell polyborosiloxane resin solution. The mass ratio of phenyltriethoxysilane, a first portion of xylene, sulfuric acid, deionized water, triethylamine, a second portion of xylene, boric acid, and isobutanol was 90:10:0.15:6:0.3:10:12:5.

[0053] S2, ZrB2 powder with a D50 of 3 μm, α-SiC powder with a D50 of 0.8 μm, anhydrous ethanol and polyvinylpyrrolidone are added to a ball mill jar and ball-milled for 6 hours to obtain a slurry. The slurry is then spray-granulated to obtain ZrB2 / SiC composite particles. The mass ratio of ZrB2 powder, α-SiC powder, anhydrous ethanol and polyvinylpyrrolidone is 48:18:30:0.8. The inlet air temperature of the spray granulation is 170℃ and the outlet air temperature is 75℃.

[0054] S3, andalusite (D50: 5 μm), boehmite, colloidal silica (SiO2 mass fraction: 30 wt.%), boric acid, core-shell polyborosiloxane resin solution, and ethanol aqueous solution are mixed and dispersed to obtain a reaction shell slurry. ZrB2 / SiC composite particles are placed in a granulator, sprayed into the reaction shell slurry while the particles are rolling, and dried to obtain ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres. The mass ratio of andalusite, boehmite, colloidal silica, boric acid, core-shell polyborosiloxane resin solution, ethanol aqueous solution, and ZrB2 / SiC composite particles is 18:4:16:3:4:20:65, and the mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution is 4:1.

[0055] S4, a core-shell polyborosiloxane resin liquid, ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres, γ-aminopropyltriethoxysilane, tetrabutyl titanate, fumed silica, and xylene / isobutanol mixture are mixed and ground to a fine consistency. The mass ratio of the core-shell polyborosiloxane resin liquid, ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres, γ-aminopropyltriethoxysilane, tetrabutyl titanate, fumed silica, and xylene / isobutanol mixture is 36:55:1:0.3:1.5:10, and the mass ratio of xylene to isobutanol in the xylene / isobutanol mixture is 3:1, to obtain a ceramic-compatible high-temperature resistant coating slurry with a fineness of no more than 35μm.

[0056] Example 3

[0057] This embodiment provides a ceramicizable high-temperature resistant coating and its preparation method, which specifically includes the following steps:

[0058] S1, phenyltriethoxysilane, a first portion of xylene, and 98 wt.% sulfuric acid were mixed, and deionized water was added dropwise. After the addition was complete, the mixture was stirred and reacted for 10 h. Triethylamine was then added, followed by a second portion of xylene, and the temperature was raised to 95 °C to distill off the byproduct ethanol. After 25 min, boric acid and isobutanol were added, and the mixture was reacted at 110 °C for 3 h. Then, the mixture was distilled under reduced pressure at 0.04 MPa for 0.6 h to obtain a core-shell polyborosiloxane resin solution. The mass ratio of phenyltriethoxysilane, a first portion of xylene, sulfuric acid, deionized water, triethylamine, a second portion of xylene, boric acid, and isobutanol was 85:12:0.12:7:0.2:12:10:6.

[0059] S2, ZrB2 powder with a D50 of 2μm, α-SiC powder with a D50 of 1.2μm, anhydrous ethanol and polyvinylpyrrolidone are added to a ball mill jar and ball-milled for 5 hours to obtain a slurry. The slurry is then spray-granulated to obtain ZrB2 / SiC composite particles. The mass ratio of ZrB2 powder, α-SiC powder, anhydrous ethanol and polyvinylpyrrolidone is 45:20:28:1.0. The inlet air temperature of the spray granulation is 160℃ and the outlet air temperature is 80℃.

[0060] S3, andalusite with a D50 of 3.5 μm, boehmite, colloidal silica with a SiO2 mass fraction of 28 wt.%, boric acid, core-shell polyborosiloxane resin solution, and ethanol aqueous solution are mixed and dispersed to obtain a reaction shell slurry. ZrB2 / SiC composite particles are placed in a granulator, sprayed into the reaction shell slurry while the particles are rolling, and dried to obtain ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres. The mass ratio of andalusite, boehmite, colloidal silica, boric acid, core-shell polyborosiloxane resin solution, ethanol aqueous solution, and ZrB2 / SiC composite particles is 16:5:14:4:3:25:62, and the mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution is 4:1.

[0061] S4, the core-shell polyborosiloxane resin liquid, ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres, γ-aminopropyltriethoxysilane, tetrabutyl titanate, fumed silica, and xylene / isobutanol mixture are mixed and ground into fine particles. The mass ratio of the core-shell polyborosiloxane resin liquid, ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres, γ-aminopropyltriethoxysilane, tetrabutyl titanate, fumed silica, and xylene / isobutanol mixture is 33:60:0.8:0.5:1.2:14, and the mass ratio of xylene to isobutanol in the xylene / isobutanol mixture is 3:1, to obtain a ceramic-compatible high-temperature resistant coating slurry with a fineness of no more than 35μm.

[0062] Example 4

[0063] This embodiment provides a ceramicizable high-temperature resistant coating and its preparation method, which specifically includes the following steps:

[0064] S1, phenyltriethoxysilane, a first portion of xylene, and 98 wt.% sulfuric acid were mixed, and deionized water was added dropwise. After the addition was complete, the mixture was stirred and reacted for 9 hours. Then, triethylamine was added, followed by a second portion of xylene, and the mixture was heated to 98°C to distill off the byproduct ethanol. After 28 minutes, boric acid and isobutanol were added, and the mixture was reacted at 105°C for 3.5 hours. Then, the mixture was distilled under reduced pressure at 0.04 MPa for 0.7 hours to obtain a core-shell polyborosiloxane resin solution. The mass ratio of phenyltriethoxysilane, a first portion of xylene, sulfuric acid, deionized water, triethylamine, a second portion of xylene, boric acid, and isobutanol was 88:13:0.10:7.5:0.15:13:9:7.

[0065] S2, ZrB2 powder with a D50 of 1.5 μm, α-SiC powder with a D50 of 1.0 μm, anhydrous ethanol and polyvinylpyrrolidone are added to a ball mill jar and ball-milled for 4.5 h to obtain a slurry. The slurry is then spray-granulated to obtain ZrB2 / SiC composite particles. The mass ratio of ZrB2 powder, α-SiC powder, anhydrous ethanol and polyvinylpyrrolidone is 46:19:26:1.1. The inlet air temperature of the spray granulation is 155℃ and the outlet air temperature is 85℃.

[0066] S3, andalusite (D50: 4 μm), boehmite, colloidal silica (SiO2 mass fraction: 26 wt.%), boric acid, core-shell polyborosiloxane resin solution, and ethanol aqueous solution are mixed and dispersed to obtain a reaction shell slurry. ZrB2 / SiC composite particles are placed in a granulator, sprayed into the reaction shell slurry while the particles are rolling, and dried to obtain ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres. The mass ratio of andalusite, boehmite, colloidal silica, boric acid, core-shell polyborosiloxane resin solution, ethanol aqueous solution, and ZrB2 / SiC composite particles is 15:5.5:13:4.5:2.5:22:63, and the mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution is 4:1.

[0067] S4, the core-shell polyborosiloxane resin liquid, ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres, γ-aminopropyltriethoxysilane, tetrabutyl titanate, fumed silica, and xylene / isobutanol mixture are mixed and ground into fine particles. The mass ratio of the core-shell polyborosiloxane resin liquid, ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres, γ-aminopropyltriethoxysilane, tetrabutyl titanate, fumed silica, and xylene / isobutanol mixture is 35:58:0.6:0.6:1.0:12, and the mass ratio of xylene to isobutanol in the xylene / isobutanol mixture is 3:1, to obtain a ceramic-compatible high-temperature resistant coating slurry with a fineness of no more than 35μm.

[0068] Comparative Example 1

[0069] This embodiment provides a ceramicizable high-temperature resistant coating and its preparation method. The difference between this embodiment and Embodiment 1 is that, in S1, the core-shell polyborosiloxane resin liquid obtained by stepwise polycondensation is not used. Instead, a common polyborosiloxane resin liquid obtained by one-time co-condensation of phenyltriethoxysilane and boric acid is used. In S3 and S4, the common polyborosiloxane resin liquid is used accordingly. Other process parameters and operating conditions are exactly the same as in Embodiment 1.

[0070] Comparative Example 2

[0071] This embodiment provides a ceramicizable high-temperature resistant coating and its preparation method. The difference between this embodiment and Embodiment 1 is that in S3, the ZrB2 / SiC composite particles are not coated with a andalusite-aluminum-silicon-boron reaction shell, and in S4, the ZrB2 / SiC composite particles are directly mixed with other components and ground into a fine powder. Other process parameters and operating conditions are exactly the same as in Embodiment 1.

[0072] Comparative Example 3

[0073] This embodiment provides a ceramicizable high-temperature resistant coating and its preparation method. The difference between this embodiment and Embodiment 1 is that the ZrB2 / SiC composite particles in S2 are replaced with only α-SiC particles, and ZrB2 is not added. In S3 and S4, α-SiC particles or their coating products are used respectively. Other process parameters and operating conditions are exactly the same as in Embodiment 1.

[0074] Curing steps: Spray the coating slurry onto the substrate surface, control the single-coat wet film thickness to be 150μm, and dry at 70℃ for 25min after each coat. Repeat the application for 3 coats. After coating, keep the coating at 135℃ for 45min, 200℃ for 0.7h, and 260℃ for 1.5h to complete the curing. Then, raise the temperature to 700℃ and keep it at 70min using a programmed temperature increase method to perform pre-ceramization treatment on the coating, and obtain a cured and pre-ceramized coating.

[0075] Performance testing: Adhesion testing method is ASTM D4541; low-temperature vitrification microhardness testing method is ASTM C1327; high-temperature static oxidation testing method is ISO 20509:2003, with the evaluation index being mass change per unit area, in mg / cm³. 2 The oxy-acetylene ablation test method was ASTM E285-08(2020), and the evaluation index was the linear ablation rate, in mm / s. The test results of the ceramicizable high-temperature resistant coatings of Examples 1-4 and Comparative Examples 1-3 are shown in Table 1.

[0076] Table 1. Test results of ceramic-type high-temperature resistant coatings from Examples 1-4 and Comparative Examples 1-3

[0077]

[0078] As shown in Table 1, compared with Example 1, Comparative Example 1 showed decreased adhesion, decreased microhardness, increased change in mass per unit area, and increased linear ablation rate; Comparative Example 2 showed decreased adhesion, decreased microhardness, increased change in mass per unit area, and increased linear ablation rate; and Comparative Example 3 showed decreased adhesion, decreased microhardness, increased change in mass per unit area, and increased linear ablation rate.

[0079] This is because Comparative Example 1 uses ordinary polyborosiloxane resin liquid, where the distribution of the polysiloxane core and boron-containing outer layer in the resin is unclear. Upon heating, the formation process of the continuous Si–O–Si / Si–O–B framework weakens, and the integrity of the transition layer and inorganic connection phase on the particle surface decreases. Therefore, adhesion, microhardness after low-temperature porcelainization, and subsequent oxidation and ablation resistance are all reduced. Comparative Example 2 lacks a andalusite-aluminosilicate-boron reaction shell. The outer surface of the particles lacks the initial dehydroxylation, condensation, mullite formation, and SiO2-rich glass precipitation process. In the initial stage of heating, it is difficult to form a continuous and dense outer layer, resulting in insufficient bridging and interstitial filling between particles, decreased microhardness, and easier propagation of cracks and pores during high-temperature oxidation and ablation. After removing ZrB2 in Comparative Example 3, the core can only generate SiO2 by SiC oxidation at high temperatures. The lack of an oxide barrier layer composed of ZrO2, ZrSiO4 and boron-containing liquid phase means that although the shell can still provide initial densification, its subsequent high-temperature stabilization and oxygen barrier capabilities are weakened, resulting in an increase in the change in mass per unit area and the linear ablation rate.

[0080] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a ceramic-like high-temperature resistant coating, characterized in that, The preparation method includes: S1, phenyltriethoxysilane, the first part of xylene and sulfuric acid are mixed, deionized water is added dropwise to react, triethylamine is added, then the second part of xylene is added and the temperature is raised to distill off the ethanol, boric acid is added and isobutanol is reacted to obtain the core-shell polyborosiloxane resin liquid. S2, ZrB2 powder, α-SiC powder, anhydrous ethanol and polyvinylpyrrolidone are mixed and ball-milled to obtain a slurry, and the slurry is spray-granulated to obtain ZrB2 / SiC composite particles. S3, andalusite, pseudoboehmite, colloidal silica, boric acid, core-shell polyborosilicate resin liquid and ethanol aqueous solution are mixed and dispersed to obtain a reaction shell slurry. ZrB2 / SiC composite particles are placed in a granulator and sprayed into the reaction shell slurry to obtain ZrB2 / SiC@andalusite-aluminum-silicon-boron shell core-shell microspheres. S4. A core-shell polyborosiloxane resin liquid, ZrB2 / SiC@andalusite-aluminosilicate boron shell core-shell microspheres, γ-aminopropyltriethoxysilane, tetrabutyl titanate, fumed silica and xylene / isobutanol mixture are mixed and ground to obtain a ceramic-compatible high-temperature resistant coating slurry.

2. The method for preparing a ceramic-like high-temperature resistant coating according to claim 1, characterized in that, In S1: The mass ratio of the phenyltriethoxysilane, the first part xylene, sulfuric acid, deionized water, triethylamine, the second part xylene, boric acid and isobutanol is (80-90):(10-15):(0.08-0.15):(6-8):(0.1-0.3):(10-15):(8-12):(5-8).

3. The method for preparing a ceramic-like high-temperature resistant coating according to claim 1, characterized in that, In S2: The mass ratio of ZrB2 powder, α-SiC powder, anhydrous ethanol and polyvinylpyrrolidone is (42-48):(18-22):(25-30):(0.8-1.2).

4. The method for preparing a ceramic-like high-temperature resistant coating according to claim 1, characterized in that, In S2: The D50 of the ZrB2 powder is 1-3 μm; The α-SiC powder has a D50 of 0.8-1.5 μm.

5. The method for preparing a ceramic-like high-temperature resistant coating according to claim 1, characterized in that, In S2: The inlet air temperature of the spray granulation is 150-170℃ and the outlet air temperature is 75-90℃.

6. The method for preparing a ceramic-like high-temperature resistant coating according to claim 1, characterized in that, In S3: The mass ratio of andalusite, pseudoboehmite, colloidal silica, boric acid, core-shell polyborosiloxane resin solution, ethanol aqueous solution and ZrB2 / SiC composite particles is (14-18):(4-6):(12-16):(3-5):(2-4):(20-30):(60-65).

7. The method for preparing a ceramic-like high-temperature resistant coating according to claim 1, characterized in that, In S4: The mass ratio of the core-shell polyborosiloxane resin liquid, ZrB2 / SiC@andalusite-aluminosilicate boron shell core-shell microspheres, γ-aminopropyltriethoxysilane, tetrabutyl titanate, fumed silica and xylene / isobutanol mixture is (30-36):(55-65):(0.5-1):(0.3-0.8):(0.8-1.5):(10-18).

8. The method for preparing a ceramic-like high-temperature resistant coating according to claim 1, characterized in that, In S4: The mass ratio of xylene to isobutanol in the xylene / isobutanol mixture is 3:

1.

9. The method for preparing a ceramic-like high-temperature resistant coating according to claim 1, characterized in that, In S4: The fineness of the ceramic-like high-temperature resistant coating slurry is no greater than 35μm.

10. A ceramic-like high-temperature resistant coating, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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