Composite binder and high-entropy coating flexible thermal insulation material using the same

Abstract

The present application relates to a kind of composite binder and high entropy coating flexible thermal insulation material using it, belong to high entropy ceramic coating thermal insulation material technical field.The composite binder is formed by silicon sol and aluminum dihydrogen phosphate composite;The flexible thermal insulation material is formed by high entropy ceramic coating and flexible matrix by the composite binder closely combined.Formed by the composite binder of the present application, the high entropy thermal insulation coating attached to the surface of flexible matrix, can be bent with flexible matrix, and coating surface does not appear crack, has very high thermal insulation performance and can protect flexible matrix from being burnt through by flame.

Description

Technical Field

[0001] This invention relates to a composite binder and a high-entropy coating flexible thermal insulation material using the same, belonging to the technical field of high-entropy ceramic coating thermal insulation materials. Background Technology

[0002] In aerospace, electronics, and automotive industries, numerous pipelines, curved surfaces, joints, and irregular components operate in high-temperature environments for extended periods. There is an urgent need for flexible thermal insulation materials that can tightly conform to these complex and irregularly shaped surfaces to achieve uniform thermal protection without any blind spots. Traditional rigid thermal insulation materials (such as ceramic fiber boards and aerogel felt) are inflexible and fragile, making them difficult to effectively cover in such scenarios and prone to creating gaps that pose safety hazards. Therefore, the development of thermal insulation materials that combine excellent high-temperature resistance with high flexibility has become an urgent requirement.

[0003] Existing flexible thermal insulation materials are mainly achieved through the following technical approaches: Firstly, fabrics based on organic polymer coatings such as silicone resins have excellent flexibility and adhesion, but their organic matrix will undergo thermal oxidation and decomposition in environments exceeding 400 ℃, leading to coating failure and failing to meet the requirements of medium and high temperature applications. Secondly, flexible heat insulation felt made of inorganic fibers such as alumina and zirconium oxide is soft in itself, but it is mostly loose and porous with no dense protective layer on the surface. It has problems such as low tensile strength, easy to generate dust, and inability to effectively block the erosion of high-temperature airflow. Thirdly, inorganic adhesives (such as silicates and phosphates) are combined with inorganic thermal insulation fillers and coated onto the surface of fiber fabrics. Theoretically, this technology can achieve both high-temperature resistance and surface protection. However, in practical applications, it has encountered core technical obstacles: traditional inorganic adhesives (such as water glass and pure aluminum dihydrogen phosphate) are inherently brittle and have high curing shrinkage rates. The resulting coatings are prone to cracking or peeling when bent, and they have poor compatibility with the smooth, chemically inert organic or carbon fiber matrix, making it impossible to simultaneously meet the requirements of high bonding strength and high flexibility.

[0004] To further improve the high-temperature resistance and thermal insulation capabilities of flexible thermal insulation materials, researchers have recently begun to incorporate low thermal conductivity ceramic materials such as high-entropy ceramics, rare-earth zirconates, and rare-earth cerates as functional thermal insulation fillers into flexible thermal insulation coatings. High-entropy ceramics, due to their high-entropy stabilization effect, lattice distortion effect, and hysteresis diffusion effect, exhibit excellent high-temperature phase stability, low thermal conductivity, and good anti-sintering properties, showing promising application prospects in the field of ultra-high temperature thermal protection. Using high-entropy ceramics as thermal insulation fillers to prepare flexible high-entropy coatings can significantly improve the high-temperature resistance and thermal insulation performance of the materials. However, high-entropy ceramics themselves lack adhesive properties; their stable adhesion to flexible substrates mainly depends on the adhesive system. Existing inorganic adhesives struggle to balance high-temperature adhesion and flexibility, easily leading to cracks due to curing shrinkage and thermal stress, resulting in high-entropy filler detachment, coating powdering, and interface failure, thus limiting the practical application of high-entropy coated flexible thermal insulation materials.

[0005] Therefore, developing a composite binder that combines high-temperature stability, high interfacial bonding strength, and good flexibility, and using this composite binder to construct high-entropy coated flexible thermal insulation materials, so that they can maintain good structural integrity, interfacial bonding performance, and thermal insulation performance under high-temperature environments and repeated bending conditions, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] To overcome the shortcomings of the existing technology, the present invention aims to provide a composite binder and a high-entropy coating flexible thermal insulation material using the same. The high-entropy thermal insulation coating prepared by the composite binder and attached to the surface of a flexible substrate can be bent together with the flexible substrate without cracking on the coating surface. It has extremely high thermal insulation performance and can protect the substrate from being burned through by flame.

[0007] To achieve the objectives of this invention, the following technical solutions are provided.

[0008] A composite adhesive, said composite adhesive being composed of silica sol and aluminum dihydrogen phosphate.

[0009] Preferably, based on the mass of the composite binder as 100%, the mass fraction of aluminum dihydrogen phosphate is 14% to 25%, and the mass fraction of silica sol is 75% to 86%.

[0010] Preferably, the silica sol is a neutral silica sol with a pH value of 7 to 8 (neutral), a SiO2 mass fraction of 29% to 30%, and an average particle size of 10 nm to 13 nm.

[0011] A high-entropy coated flexible thermal insulation material using the composite adhesive described in this invention, wherein the flexible thermal insulation material is formed by tightly bonding a high-entropy ceramic coating to a flexible substrate through the composite adhesive.

[0012] Preferably, the high-entropy ceramic is a high-entropy titanate with the chemical composition (La). 0.3 K 0.1 Ca 0.2 Sr 0.2 Ba 0.2 TiO3.

[0013] Preferably, the flexible matrix is ​​a flexible fiber fabric; more preferably, the flexible fiber fabric is one of carbon fiber fabric, pre-oxidized fiber fabric, and basalt fiber fabric; most preferably, the flexible matrix is ​​oxidized polyacrylonitrile fabric (OPAN) with an areal density of 280 g / m³. 2 ~ 480 g / m 2 .

[0014] Preferably, the thickness of the high-entropy ceramic coating is 100 μm to 150 μm.

[0015] A method for preparing a high-entropy coated flexible thermal insulation material using the composite binder described in this invention, comprising the following steps: (1) Immerse the flexible substrate in the mixed solution to allow the mixed solution to fully penetrate the flexible substrate, and then dry it to obtain the pretreated flexible substrate; In step (1): The mixed solution is a mixture of silica sol and anhydrous ethanol. More preferably, the mass ratio of silica sol to ethanol is 15-20:5-10. The preferred soaking time is 2 hours to 3 hours; The preferred drying temperature is 60 ℃ ~ 80 ℃; the drying time is 1 h ~ 2 h.

[0016] (2) Mix high-entropy ceramic powder, composite binder, dispersant and defoamer, and ball mill to obtain heat insulation slurry; In step (2): The dispersant is ammonium polyacrylate; The defoamer is n-octanol; Preferably, the high-entropy ceramic powder has a particle size of 100 nm to 10 μm; Preferably, based on the total mass of the high-entropy ceramic powder and the composite binder as 100%, the mass fraction of the high-entropy ceramic powder as filler is 17% to 25%, and the mass fraction of the composite binder is 75% to 83%. The amount of dispersant used is 1% to 2% of the total mass of the high-entropy ceramic powder and composite binder; The amount of defoamer used is 0.1% to 0.3% of the total mass of the high-entropy ceramic powder and composite binder; Preferably, the ball milling time is 2 h to 4 h.

[0017] (3) The heat insulation slurry is sprayed onto the surface of the pretreated flexible substrate. After the heat insulation slurry dries and cures, a high-entropy coating is formed on the surface of the flexible substrate, thus preparing a high-entropy coating flexible heat insulation material using the composite binder described in this invention. In step (3): Preferably, the spraying method is air spraying; more preferably, the air spraying conditions are: spraying distance of 15 cm to 20 cm, spraying pressure of 0.4 MPa to 0.5 MPa, and spraying times of 4 to 6 times.

[0018] Beneficial effects (1) The present invention provides a composite adhesive, wherein the composite adhesive is constructed by combining silica sol and aluminum dihydrogen phosphate to obtain an inorganic composite adhesive system with both flexibility and high-temperature bonding performance; wherein, silica sol can improve the wettability and film continuity of the composite adhesive and form a continuous inorganic network during the curing process; aluminum dihydrogen phosphate can improve the high-temperature bonding strength; the two are combined to form a stable cross-linked structure, which overcomes the defects of existing single silica sol being easy to pulverize at high temperature and having insufficient bonding strength, as well as the defects of single aluminum dihydrogen phosphate being brittle and easy to crack when bent, and achieves a synergistic improvement in high-temperature stability, bonding strength and flexibility.

[0019] (2) The present invention provides a high-entropy coating flexible thermal insulation material using the composite adhesive described in the present invention. The material integrates three seemingly contradictory core functions on a flexible substrate: ultra-high temperature thermal insulation, all-inorganic non-flammability and high flexibility and conformability. This creates a new type of pure inorganic flexible thermal insulation material that can fit tightly to complex high-temperature components like "skin". The resulting flexible thermal insulation material can keep the coating back temperature stable at about 600°C under continuous heating with a flame of 1000°C to 1200°C. It also has good room temperature bending performance and excellent ultra-high temperature thermal insulation performance, flexibility and conformability. It can be widely used in the thermal protection of complex irregular curved surfaces in aerospace, electronic equipment and automotive industries.

[0020] (3) The present invention provides a method for preparing a high-entropy coating flexible thermal insulation material using the composite binder described in the present invention. In the method, a mixture of silica sol and anhydrous ethanol is used to pretreat the flexible substrate. This allows the silica sol to penetrate into the gaps of the flexible substrate and fill the surface pores, improving the wettability and surface condition of the substrate surface. This enables the composite binder to spread evenly and form a tighter interface bond with the flexible substrate, thereby improving the adhesion strength between the coating and the flexible substrate and reducing the risk of coating cracking, peeling and interface failure during high temperature or repeated bending.

[0021] (4) The present invention provides a method for preparing a high-entropy coated flexible thermal insulation material using the composite binder described in the present invention. In the method, the high-entropy ceramic particles are firmly bonded to the surface of a flexible substrate using a composite binder. The composite binder can not only improve the dispersion uniformity of the high-entropy ceramic particles on the substrate surface, but also enhance the bonding force between particles and between particles and the substrate, so that the obtained thermal insulation coating has good structural integrity and can maintain a stable thermal insulation layer structure under high temperature environment and bending conditions, thereby improving the service reliability of the flexible thermal insulation material.

[0022] (5) The present invention provides a method for preparing a high-entropy coated flexible thermal insulation material using the composite binder described in the present invention. In the method, high-entropy titanate is used as thermal insulation filler and combined with the composite binder described in the present invention to form a flexible ceramic thermal insulation coating. High-entropy titanate has excellent high-temperature phase stability and low thermal conductivity. Under the action of the composite binder, it can be uniformly dispersed in the coating to form a stable thermal insulation layer, so that the obtained flexible thermal insulation material has high temperature resistance, thermal insulation performance and flexibility, which can meet the high temperature protection requirements of complex curved surfaces and irregularly shaped components. Attached Figure Description

[0023] Figure 1 The image shows the SEM image of the surface microstructure of the high-entropy coated flexible thermal insulation material prepared in Example 1. Figure 2 The figure shows the flexibility test results of the high-entropy coated flexible thermal insulation material prepared in Example 1; Figure 3 The graph shows the test results of the thermal insulation performance of the high-entropy coated flexible thermal insulation material prepared in Example 1; Figure 4 This is a SEM image of the surface microstructure of the high-entropy coated flexible thermal insulation material prepared in Example 2; Figure 5 The figure shows the flexibility test results of the high-entropy coated flexible thermal insulation material prepared in Example 2; Figure 6 The graph shows the test results of the thermal insulation performance of the high-entropy coated flexible thermal insulation material prepared in Example 2; Figure 7 This is a SEM image of the surface microstructure of the high-entropy coated flexible thermal insulation material prepared in Example 3; Figure 8 The figure shows the flexibility test results of the high-entropy coated flexible thermal insulation material prepared in Example 3; Figure 9 The graph shows the test results of the thermal insulation performance of the high-entropy coated flexible thermal insulation material prepared in Example 3. Detailed Implementation

[0024] In the following embodiments: The silica sol is a neutral silica sol with a pH of 7 to 8, a SiO2 mass fraction of 30%, and an average particle size of 10 nm to 13 nm. High-entropy ceramics are high-entropy titanates, and their chemical composition is (La... 0.3 K 0.1 Ca 0.2 Sr 0.2 Ba 0.2 TiO3; The particle size of high-entropy ceramic powder is 100 nm ~ 10 μm; The dispersant is ammonium polyacrylate; The defoamer is n-octanol.

[0025] The performance of the high-entropy coated flexible thermal insulation material prepared in the examples and comparative examples was tested as follows: (1) Microscopic morphology The microstructure of the coating surface and cross-section of the material was observed using a German ZEISS GeminiSEM 360 field emission scanning electron microscope. (2) Flexibility test According to the bending test method for flexible thermal insulation materials in the standard QJ 990.7–1986 of the Ministry of Aerospace Industry of China, the material was subjected to 180° inward bending, outward bending and S-shaped bending tests. (3) Thermal insulation performance test Butane spray gun was used as heat source to heat the material under the same flame height and spray distance. The flame temperature was about 1200 ℃. K-type thermocouple and YOSEEN6800-NA infrared thermal imager provided by Gewu Yongxin Company were used to record the temperature changes of the material's fire-exposed and unfired surfaces, respectively. (4) Interface integration performance According to the national standard GB / T 5210-2006, the pull-out method is used to evaluate the interfacial bonding performance between high-entropy coatings and flexible substrates.

[0026] Example 1 A composite adhesive, wherein the composite adhesive is composed of silica sol and aluminum dihydrogen phosphate, as detailed below: Weigh 25 g of silica sol and 5 g of aluminum dihydrogen phosphate (ADP), and stir magnetically for 15 min at room temperature until homogeneous to obtain a composite adhesive.

[0027] A method for preparing a high-entropy coated flexible thermal insulation material using the composite binder described in this embodiment, the method comprising the following steps: (1) Cut oxidized polyacrylonitrile fabric (OPAN) with a surface density of 350 g / m² into 70 mm × 70 mm samples as flexible substrates; weigh 15 g of silica sol and mix with 7.5 g of anhydrous ethanol, stir in a magnetic stirrer for 15 min to obtain a mixed solution. The flexible matrix was completely immersed in the mixed solution and immersed at room temperature for 2 hours to allow the mixed solution to fully penetrate into the fiber gaps of the flexible matrix. Then it was placed in a 60 ℃ forced-air drying oven for 2 hours to obtain the pretreated flexible matrix. (2) Add high-entropy ceramic powder to the composite binder, then add dispersant and defoamer and mix. Ball mill in a ball mill for 2 h to uniformly disperse the high-entropy ceramic powder in the composite binder to obtain heat insulation slurry; Based on the total mass of high-entropy ceramic powder and composite binder being 100%, the mass fraction of high-entropy ceramic powder as filler is 20%, and the mass fraction of composite binder is 80%; the amount of dispersant is 1% of the total mass of high-entropy ceramic powder and composite binder; and the amount of defoamer is 0.1% of the total mass of high-entropy ceramic powder and composite binder. (3) The heat insulation slurry was sprayed onto the surface of the pretreated flexible substrate by air spraying. The air spraying conditions were: spraying distance of 15 cm, spraying pressure of 0.5 MPa, and spraying times of 6 times. After each spraying, the slurry was allowed to level naturally. After all the spraying was completed, the slurry was dried in an 80 ℃ drying oven for 2 h. After the slurry was cured, a high-entropy coating was formed on the surface of the flexible substrate. The coating thickness was about 120 μm. A high-entropy coating flexible heat insulation material using the composite binder described in this embodiment was prepared.

[0028] The performance of the high-entropy coated flexible thermal insulation material prepared in this embodiment was tested as follows: (1) Microscopic morphology Using a butane spray gun as a heat source, the high-entropy coated flexible thermal insulation material was heated by flame under the same flame height and spray distance conditions. The flame temperature was about 1200 ℃. After the spray gun was continuously burned for 120 seconds, a scanning electron microscope was taken. Scanning electron microscopy (SEM) results of high-entropy coated flexible thermal insulation materials before and after high-temperature burning are as follows: Figure 1 As shown, Figure 1 The left image shows the high-entropy coated flexible insulation material before burning, and the right image shows the high-entropy coated flexible insulation material after burning. The results show that the high-entropy coating can continuously cover the surface of the flexible substrate, and the high-entropy ceramic particles are uniformly dispersed. After calcination, the cracks in the high-entropy coating further shrink, concentrating only in some areas, indicating that high-temperature calcination did not destroy the continuous and dense bonding layer formed between the high-entropy coating and the flexible substrate. Furthermore, the composite binder liquefied and flowed after high-temperature calcination, repairing some of the cracks. The concentrated small cracks exist to release thermal stress. After the silica sol pretreatment in step (1) of the preparation method, the pores between the fibers of the flexible substrate were effectively filled, and the high-entropy coating was tightly bonded to the flexible substrate. After calcination, no obvious interface delamination was observed. This indicates that the silica sol pretreatment enhanced the bonding performance of the high-entropy coating and improved the integrity of the coating.

[0029] (2) Flexibility test like Figure 2 As shown, Figure 2 The left image shows the bent surface of the high-entropy coated flexible thermal insulation material before heat treatment, and the right image shows the bent surface of the high-entropy coated flexible thermal insulation material after heat treatment. According to the aerospace industry standard QJ 990.7-1986, when the bending diameter is 9 mm, the coating does not crack or peel off significantly. Test results show that the material can be bent to a diameter of 9 mm at room temperature without significant cracking or peeling of the coating. After heat treatment at 1200 ℃, a bending test was conducted again, and only a small number of dispersed microcracks were observed. No through cracks or interface peeling were observed, indicating that the material has good bending performance and interface stability.

[0030] (3) Thermal insulation performance test The results are as follows Figure 3 As shown, Figure 3 The left image in the figure shows the flexible substrate in this embodiment, and the right image shows the high-entropy coated flexible thermal insulation material. After the flexible substrate and the high-entropy coated flexible insulation material were continuously burned with a butane torch for 120 seconds, the flexible substrate was burned through by the flame in about 120 seconds, while the high-entropy coated flexible insulation material remained intact after being heated for 300 seconds without burning through. After being heated by the flame for 120 seconds, the temperature of the unexposed surface was about 424 °C lower than that of the flexible substrate. After being heated for 300 seconds, the temperature difference between the exposed surface and the unexposed surface remained at about 377 °C, indicating that the high-entropy coated flexible insulation material has excellent fire resistance and heat insulation performance.

[0031] (4) Interface integration performance Test results show that the composite adhesive can significantly improve the bonding strength between the coating and the flexible substrate. After bending and high-temperature treatment, the coating is still firmly attached to the substrate surface, and no obvious peeling or powdering phenomenon occurs. This indicates that the composite adhesive described in this invention can effectively improve the service reliability of flexible thermal insulation materials.

[0032] Therefore, it can be seen that the high-entropy coated flexible thermal insulation material prepared in this embodiment is formed by the close bonding of a high-entropy ceramic coating and a flexible substrate through the composite adhesive.

[0033] Example 2 A composite adhesive, wherein the composite adhesive is composed of silica sol and aluminum dihydrogen phosphate, as detailed below: Weigh 30 g of silica sol and 5 g of aluminum dihydrogen phosphate, and stir magnetically for 15 min at room temperature to obtain a composite binder.

[0034] A method for preparing a high-entropy coated flexible thermal insulation material using the composite binder described in this embodiment, the method comprising the following steps: (1) The areal density is 280 g / m 2 Oxidized polyacrylonitrile fabric (OPAN) was cut into 70 mm × 70 mm samples as flexible substrates; 20 g of silica sol was weighed and mixed with 5 g of anhydrous ethanol, and stirred in a magnetic stirrer for 15 min to obtain a mixed solution. The flexible matrix was completely immersed in the mixed solution and immersed at room temperature for 3 hours to allow the mixed solution to fully penetrate into the fiber gaps of the flexible matrix. Then, it was placed in an 80 ℃ forced-air drying oven for 1 hour to obtain the pretreated flexible matrix. (2) Add high-entropy ceramic powder to the composite binder, then add dispersant and defoamer and mix. Ball mill in a ball mill for 4 h to uniformly disperse the high-entropy ceramic powder in the composite binder to obtain heat insulation slurry; Based on the total mass of high-entropy ceramic powder and composite binder as 100%, the mass fraction of high-entropy ceramic powder as filler is 17%, and the mass fraction of composite binder is 83%; the amount of dispersant is 2% of the total mass of high-entropy ceramic powder and composite binder; and the amount of defoamer is 0.3% of the total mass of high-entropy ceramic powder and composite binder. (3) The heat insulation slurry was sprayed onto the surface of the pretreated flexible substrate by air spraying. The air spraying conditions were: spraying distance of 20 cm, spraying pressure of 0.4 MPa, and spraying times of 4 times. After each spraying, the slurry was allowed to level naturally. After all the spraying was completed, the slurry was dried in an 80 ℃ drying oven for 2 h. After the slurry was cured, a high-entropy coating was formed on the surface of the flexible substrate. The coating thickness was about 100 μm. A high-entropy coating flexible heat insulation material using the composite binder described in this embodiment was prepared.

[0035] The performance of the high-entropy coated flexible thermal insulation material prepared in this embodiment was tested as follows: (1) Microscopic morphology Using a butane spray gun as a heat source, the high-entropy coated flexible thermal insulation material was heated by flame under the same flame height and spray distance conditions. The flame temperature was about 1200 ℃, and the image was taken by scanning electron microscopy after the spray gun was continuously burned for 120 seconds.

[0036] Scanning electron microscopy (SEM) results of high-entropy coated flexible thermal insulation materials before and after high-temperature burning are as follows: Figure 4 As shown, Figure 4 The left image shows the high-entropy coated flexible insulation material before burning, and the right image shows the high-entropy coated flexible insulation material after burning.

[0037] The results show that the high-entropy coating can continuously cover the surface of the flexible substrate, and the high-entropy ceramic particles are uniformly dispersed. After calcination, the cracks in the high-entropy coating are further reduced and concentrated only in some areas, indicating that high-temperature calcination did not destroy the continuous and dense bonding layer formed between the high-entropy coating and the flexible substrate. Furthermore, the composite binder liquefied and flowed after high-temperature calcination, repairing some of the cracks. The small cracks that were concentrated were there to release thermal stress. After the silica sol pretreatment in step (1) of the preparation method, the pores between the fibers of the flexible substrate were effectively filled, and the high-entropy coating was tightly bonded to the flexible substrate. After calcination, no obvious interface delamination was observed. This indicates that the silica sol pretreatment enhanced the bonding performance of the high-entropy coating and improved its integrity. Since the aluminum dihydrogen phosphate content in this embodiment is relatively lower than that in Example 1, the cross-linking network strength formed by the composite binder is reduced. After high-temperature burning, a small number of shrinkage cracks appear in local areas, indicating that the structural stability of the high-entropy coating after high-temperature burning in this embodiment is slightly lower than that in Example 1, but it is still a significant improvement compared to the prior art.

[0038] (2) Flexibility test like Figure 5 As shown, Figure 5 The left image shows the bent surface of the high-entropy coated flexible thermal insulation material before heat treatment, and the right image shows the bent surface of the high-entropy coated flexible thermal insulation material after heat treatment. According to the aerospace industry standard QJ 990.7-1986, when the bending diameter is 9 mm, the coating does not crack or peel off significantly. Test results show that the material can be bent to a diameter of 9 mm at room temperature, and the high-entropy coating does not show obvious cracking or peeling, exhibiting good flexibility. After heat treatment at 1200 ℃, a bending test was conducted again, and local cracks further expanded, but no overall peeling occurred, indicating that the low content of aluminum dihydrogen phosphate can maintain good flexibility, but the high temperature structural stability is slightly lower than that of Example 1.

[0039] (3) Thermal insulation performance test like Figure 6 The image shows the result of burning the high-entropy coated flexible thermal insulation material; The high-entropy coated flexible thermal insulation material was continuously ignited with a butane torch. After 300 seconds of continuous heating, no burn-through occurred, indicating good fire resistance and thermal insulation performance. However, due to the low aluminum dihydrogen phosphate content, the inorganic bonding phase formed during high-temperature sintering was relatively insufficient, and the temperature of the unexposed surface was slightly higher than that of Example 1, indicating that its thermal insulation performance was slightly lower than that of Example 1.

[0040] (4) Interface integration performance Test results show that silica sol pretreatment can effectively improve interfacial bonding strength, and the coating did not significantly peel off during bending. However, due to the low aluminum dihydrogen phosphate content in the composite binder, the interfacial bonding strength after high-temperature treatment was slightly lower than that in Example 1.

[0041] Therefore, it can be seen that the high-entropy coated flexible thermal insulation material prepared in this embodiment is formed by the close bonding of a high-entropy ceramic coating and a flexible substrate through the composite adhesive.

[0042] Example 3 A composite adhesive, wherein the composite adhesive is composed of silica sol and aluminum dihydrogen phosphate, as detailed below: Weigh 15 g of silica sol and 5 g of aluminum dihydrogen phosphate, and stir magnetically for 15 min at room temperature to obtain a composite binder.

[0043] A method for preparing a high-entropy coated flexible thermal insulation material using the composite binder described in this embodiment, the method comprising the following steps: (1) The surface density is 480 g / m 2 Oxidized polyacrylonitrile fabric (OPAN) was cut into 70 mm × 70 mm samples as flexible substrates; 18 g of silica sol was weighed and mixed with 10 g of anhydrous ethanol, and stirred in a magnetic stirrer for 15 min to obtain a mixed solution. The flexible matrix was completely immersed in the mixed solution and immersed at room temperature for 2.5 h to allow the mixed solution to fully penetrate into the interfibers of the flexible matrix. Then it was placed in a 70 ℃ forced-air drying oven for 1.5 h to obtain the pretreated flexible matrix. (2) Add high-entropy ceramic powder to the composite binder, then add dispersant and defoamer and mix. Ball mill for 3 h to uniformly disperse the high-entropy ceramic powder in the composite binder to obtain heat insulation slurry. Based on the total mass of high-entropy ceramic powder and composite binder as 100%, the mass fraction of high-entropy ceramic powder as filler is 25%, and the mass fraction of composite binder is 75%; the amount of dispersant is 1.5% of the total mass of high-entropy ceramic powder and composite binder; and the amount of defoamer is 0.2% of the total mass of high-entropy ceramic powder and composite binder. (3) The heat insulation slurry was sprayed onto the surface of the pretreated flexible substrate by air spraying. The air spraying conditions were: spraying distance of 18 cm, spraying pressure of 0.5 MPa, and spraying times of 5 times. After each spraying, the slurry was allowed to level naturally. After all the spraying was completed, the slurry was dried in an 80 ℃ drying oven for 2 h. After the slurry was cured, a high-entropy coating was formed on the surface of the flexible substrate. The coating thickness was about 150 μm. A high-entropy coating flexible heat insulation material using the composite binder described in this embodiment was prepared.

[0044] The performance of the high-entropy coated flexible thermal insulation material prepared in this embodiment was tested as follows: (1) Microscopic morphology Using a butane spray gun as a heat source, the high-entropy coated flexible thermal insulation material was heated by flame under the same flame height and spray distance conditions. The flame temperature was about 1200 ℃. After the spray gun was continuously burned for 120 seconds, a scanning electron microscope was taken. Scanning electron microscopy (SEM) results of high-entropy coated flexible thermal insulation materials before and after high-temperature burning are as follows: Figure 7 As shown, Figure 7 The left image shows the high-entropy coated flexible insulation material before burning, and the right image shows the high-entropy coated flexible insulation material after burning. The results show that the high-entropy coating can continuously cover the surface of the flexible substrate, and the high-entropy ceramic particles are uniformly dispersed. After calcination, the cracks in the high-entropy coating are further reduced and concentrated only in some areas, indicating that high-temperature calcination did not destroy the continuous and dense bonding layer formed between the high-entropy coating and the flexible substrate. Furthermore, the composite binder liquefied and flowed after high-temperature calcination, repairing some of the cracks. The small cracks that were concentrated were there to release thermal stress. After the silica sol pretreatment in step (1) of the preparation method, the pores between the fibers of the flexible substrate were effectively filled, and the high-entropy coating was tightly bonded to the flexible substrate. After calcination, no obvious interface delamination was observed. This indicates that the silica sol pretreatment enhanced the bonding performance of the high-entropy coating and improved its integrity. In this embodiment, the aluminum dihydrogen phosphate content is relatively higher than that in Example 1, further enhancing the high-temperature bonding ability of the composite binder and resulting in better overall continuity of the high-entropy coating. However, due to the increased proportion of inorganic bonding phase, volume shrinkage and thermal stress increase during curing, leading to a small number of microcracks on the surface of the high-entropy coating, with a few cracks observed in localized areas. After high-temperature burning, the cracks slightly expanded, but the high-entropy coating as a whole remained bonded to the substrate without significant delamination. The effect is slightly worse than that in Example 1, but still represents a significant improvement over existing technologies.

[0045] (2) Flexibility test like Figure 8 As shown, Figure 8The left image shows the bent surface of the high-entropy coated flexible thermal insulation material before heat treatment, and the right image shows the bent surface of the high-entropy coated flexible thermal insulation material after heat treatment. According to the Ministry of Aerospace Industry standard QJ 990.7-1986, when the bending diameter is 9 mm, the coating does not crack or peel off significantly. Test results show that the high-entropy coating can bend with the flexible substrate at room temperature. However, with the increase of aluminum dihydrogen phosphate content, the rigidity of the high-entropy coating increases, and the number of cracks generated during bending is greater than in Example 1. After heat treatment at 1200 °C, bending was performed again, and the number of cracks increased further, but the high-entropy coating still maintained a continuous coverage on the substrate surface without large-area peeling.

[0046] (3) Thermal insulation performance test The results are as follows Figure 9 The image shows the result of burning the high-entropy coated flexible thermal insulation material; The high-entropy coated flexible thermal insulation material was continuously burned with a butane torch. After 300 seconds of continuous heating, no burn-through occurred, demonstrating good fire resistance and thermal insulation performance. Due to the high aluminum dihydrogen phosphate content, more inorganic bonding phases were formed at high temperatures, allowing the high-entropy coating to maintain good overall structural stability. However, due to the increase in cracks, the local thermal insulation performance decreased slightly, and its overall thermal insulation effect was not significantly improved compared to Example 1.

[0047] (4) Interface integration performance Test results show that silica sol pretreatment effectively improves interfacial bonding strength, and the coating did not significantly peel off during bending. The composite binder has a high aluminum dihydrogen phosphate content, which is beneficial for improving the high-entropy coating's high-temperature bonding ability, allowing it to maintain good adhesion even after high-temperature treatment. However, due to the increased rigidity of the high-entropy coating, it is more prone to cracking during repeated bending, resulting in lower overall flexibility compared to Example 1.

[0048] Therefore, it can be seen that the high-entropy coated flexible thermal insulation material prepared in this embodiment is formed by the high-entropy ceramic coating and the flexible substrate being tightly bonded together by the composite adhesive.

[0049] In summary, Examples 1-3 demonstrate that, within the scope defined by this invention, the composite binder can achieve stable film formation of high-entropy ceramic coatings on flexible substrates, imparting excellent high-temperature resistance and thermal insulation properties to the material. Specifically, when the mass fraction of aluminum dihydrogen phosphate is 17%, the composite binder achieves a good balance between flexibility and high-temperature bonding performance, resulting in a coating with fewer cracks, strong interfacial bonding, and optimal overall performance. When the mass fraction of aluminum dihydrogen phosphate decreases to 14%, the high-temperature structural stability decreases. When its mass fraction increases to 25%, although the high-temperature bonding ability is enhanced, the increased curing shrinkage and thermal stress lead to more coating cracks and a decrease in flexibility. Therefore, the technical solution of Example 1 is the most preferred embodiment of this invention.

[0050] Comparative Example 1 An adhesive, wherein the adhesive is silica sol.

[0051] A method for preparing a high-entropy coated flexible thermal insulation material using the binder described in this comparative example, wherein the method is the same as the preparation method in Example 1 except for the binder.

[0052] The performance of the high-entropy coated flexible thermal insulation material prepared in this comparative example was tested as follows: (1) Microscopic morphology Test results show that the high-entropy coating on the obtained high-entropy flexible thermal insulation material can continuously cover the surface of the flexible substrate, but after heat treatment at 1200 ℃, the high-entropy coating shrinks significantly, and local areas show powdering and crack propagation. (2) Flexibility test Test results show that the high-entropy coated flexible thermal insulation material has a certain degree of flexibility at room temperature, but the coating is prone to local peeling after high-temperature treatment. (3) Thermal insulation performance test Test results show that the high-entropy coated flexible thermal insulation material has a certain thermal insulation capacity, but the integrity of the coating decreases under continuous high temperature, and the temperature of the unexposed surface is higher than that of Example 1.

[0053] The results of this comparative example demonstrate that using silica sol alone as a binder results in insufficient high-temperature structural stability and interfacial bonding ability of high-entropy coated flexible thermal insulation materials.

[0054] Comparative Example 2 An adhesive, wherein the adhesive is aluminum dihydrogen phosphate.

[0055] A method for preparing a high-entropy coated flexible thermal insulation material using the binder described in this comparative example, wherein the method is the same as the preparation method in Example 1 except for the binder.

[0056] The performance of the high-entropy coated flexible thermal insulation material prepared in this comparative example was tested as follows: (1) Microscopic morphology Test results show that the high-entropy coating on the obtained high-entropy flexible thermal insulation material can form a continuous covering layer, but many through cracks are generated during the drying process. (2) Flexibility test Test results show that obvious cracks can be observed on the high-entropy coating when it is bent at room temperature, and local peeling occurs in some areas; after heat treatment at 1200 ℃, the cracks further expand and the flexibility is significantly reduced. (3) Thermal insulation performance test Test results show that the high-entropy coating has good high-temperature resistance, but due to the large number of cracks, local heat is easily transferred along the cracks, and the overall heat insulation performance is lower than that of Example 1.

[0057] This comparative example illustrates that while using aluminum dihydrogen phosphate alone can improve high-temperature bonding performance, the high-entropy coating is relatively brittle, which is not conducive to the long-term service of flexible thermal insulation materials.

[0058] Comparative Example 3 A composite adhesive, the same as the composite adhesive in Example 1.

[0059] A method for preparing a high-entropy coated flexible thermal insulation material using the composite binder described in this comparative example, wherein step (1) of the preparation method in Example 1 is omitted, and the remaining steps are the same as in Example 1.

[0060] The performance of the high-entropy coated flexible thermal insulation material prepared in this comparative example was tested as follows: (1) Microscopic morphology Test results show that the high-entropy coating on the high-entropy flexible thermal insulation material has uneven thickness due to the large pores between the flexible matrix fibers and the penetration of some slurry into the fabric, resulting in holes and interface defects in some areas. (2) Flexibility test Test results show that the high-entropy coated flexible thermal insulation material exhibits interface cracking in local areas during bending, and local delamination occurs between the high-entropy coating and the substrate. (3) Thermal insulation performance test Test results show that, due to the reduced thickness of the effective heat insulation layer on the surface, the temperature on the unexposed side is higher than that in Example 1. This indicates that silica sol pretreatment can improve the wettability and interfacial state of the flexible substrate surface, enhance the bonding ability between the high-entropy coating and the substrate, and facilitate the formation of a continuous and uniform thermal insulation layer.

[0061] Table 1. Overall performance comparison of the embodiments and comparative examples

[0062] Table 2 Performance test results of the examples and comparative examples

Claims

1. A composite adhesive, characterized in that: The composite adhesive is composed of silica sol and aluminum dihydrogen phosphate.

2. The composite adhesive according to claim 1, characterized in that: Based on the mass of the composite binder as 100%, the mass fraction of aluminum dihydrogen phosphate is 14% to 25%, and the mass fraction of silica sol is 75% to 86%; the silica sol is a neutral silica sol.

3. A high-entropy coated flexible thermal insulation material using the composite binder as described in claim 1 or 2, characterized in that: The flexible thermal insulation material is formed by tightly bonding a high-entropy ceramic coating to a flexible substrate through the composite adhesive.

4. The high-entropy coated flexible thermal insulation material according to claim 3, characterized in that: The chemical composition of high-entropy ceramics is (La) 0.3 K 0.1 Ca 0.2 Sr 0.2 Ba 0.2 TiO3; the flexible matrix is ​​a flexible fiber fabric.

5. A high-entropy coated flexible thermal insulation material according to any one of claims 3 or 4, characterized in that: Flexible fiber fabric is one of carbon fiber fabric, pre-oxidized fiber fabric and basalt fiber fabric.

6. The high-entropy coated flexible thermal insulation material according to claim 5, characterized in that: The flexible substrate is oxidized polyacrylonitrile fabric with an areal density of 280 g / m². 2 ~ 480 g / m 2 .

7. The high-entropy coated flexible thermal insulation material according to claim 3, characterized in that: The thickness of the high-entropy ceramic coating is 100 μm ~ 150 μm.

8. A method for preparing a high-entropy coated flexible thermal insulation material as described in any one of claims 3 to 7, characterized in that: (1) Immerse the flexible substrate in the mixed solution to allow the mixed solution to fully penetrate the flexible substrate, and then dry it to obtain the pretreated flexible substrate; The mixed solution is a mixture of silica sol and anhydrous ethanol; (2) Mix high-entropy ceramic powder, composite binder, dispersant and defoamer, and ball mill to obtain heat insulation slurry; (3) The heat insulation slurry is sprayed onto the surface of the pretreated flexible substrate. After the heat insulation slurry dries and cures, a high-entropy coating is formed on the surface of the flexible substrate, thus preparing a high-entropy coating flexible heat insulation material using a composite binder.

9. The method for preparing a high-entropy coated flexible thermal insulation material according to claim 8, characterized in that: In step (1), the mass ratio of silica sol to ethanol is 15~20:5~10; In step (2), the high-entropy ceramic powder has a particle size of 100 nm ~ 10 μm, the dispersant is ammonium polyacrylate, and the defoamer is n-octanol; Based on the total mass of high-entropy ceramic powder and composite binder as 100%, the mass fraction of high-entropy ceramic powder is 17%~25%, and the mass fraction of composite binder is 75%~83%. The amount of dispersant used is 1% to 2% of the total mass of the high-entropy ceramic powder and composite binder; The amount of defoamer used is 0.1% to 0.3% of the total mass of the high-entropy ceramic powder and composite binder; In step (3), the spraying method is air spraying.

10. The method for preparing a high-entropy coated flexible thermal insulation material according to claim 8, characterized in that: In step (1), the soaking time is 2h ~ 3h; the drying temperature is 60℃ ~ 80℃, and the drying time is 1h ~ 2h; In step (2), the ball milling time is 2 h ~ 4 h; In step (3), the air spraying conditions are as follows: spraying distance is 15 cm ~ 20 cm, spraying pressure is 0.4 MPa ~ 0.5 MPa, and the number of sprays is 4 ~ 6.

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