阅读说明：本技术 一种改性抗氧化复合磷酸盐涂层及其制备方法与应用 (Modified antioxidant composite phosphate coating and preparation method and application thereof ) 是由 罗瑞盈 全华锋 于 2021-09-29 设计创作，主要内容包括：一种改性抗氧化复合磷酸盐涂层及其制备方法与应用,该涂层包括设于复合材料基体表面的偶联层、设于偶联层表面的抗氧化层；偶联层的成分包括钛酸酯偶联剂；抗氧化层的成分包括偏磷酸盐、磷酸盐、硼化物、金属氧化物。复合材料基体材质为纤维增强陶瓷基复合材料或纤维增强碳基复合材料。本发明可有效增强复合材料在湿氧与高温耦合环境下的抗氧化与防腐蚀能力,使复合材料在700℃以上的中低温环境下长期保持性能稳定,且可移植性强,能对多种纤维增强型陶瓷基或碳基复合材料与构件进行抗氧化防护。本发明工艺简单、应用性强,所制备涂层防潮性强、抗热震性能优异,可在水中实现应用,并可对相关复合材料及构件组成的中低温热防护产品进行规模化生产。(A modified antioxidant composite phosphate coating and a preparation method and application thereof, the coating comprises a coupling layer arranged on the surface of a composite material matrix and an antioxidant layer arranged on the surface of the coupling layer; the coupling layer comprises titanate coupling agent; the anti-oxidation layer comprises metaphosphate, phosphate, boride and metal oxide. The matrix material of the composite material is a fiber reinforced ceramic matrix composite material or a fiber reinforced carbon matrix composite material. The invention can effectively enhance the oxidation resistance and the corrosion resistance of the composite material in the environment of coupling the wet oxygen with the high temperature, ensures that the composite material can keep stable performance for a long time in the medium-low temperature environment of more than 700 ℃, has strong transportability, and can carry out oxidation resistance protection on various fiber reinforced ceramic-based or carbon-based composite materials and members. The invention has simple process and strong applicability, and the prepared coating has strong moisture resistance and excellent thermal shock resistance, can be applied in water, and can carry out large-scale production on medium-low temperature thermal protection products consisting of related composite materials and components.)

1. A modified antioxidant composite phosphate coating is characterized in that: the composite material comprises a coupling layer arranged on the surface of a composite material matrix and an anti-oxidation layer arranged on the surface of the coupling layer;

the coupling layer comprises a titanate coupling agent;

the anti-oxidation layer comprises metaphosphate, phosphate, boride and metal oxide.

2. The long-acting waterproof antioxidant composite phosphate coating as claimed in claim 1, wherein: the thickness of the coupling layer is 5-20 mu m; the thickness of the anti-oxidation layer is 40-80 μm.

3. The modified antioxidant composite phosphate coating of claim 1, wherein:

the titanate coupling agent is TMC101, TMC105 or TMC 201;

the metaphosphate is Zn (PO)₃)₂、La(PO₃)₃、Al(PO₃)₃One or more of the following;

the phosphate is AlPO₄、Zn₃(PO₄)₂、NH₄H₂PO₄One or more of the following;

the boride is TiB₂、LaB₆One or more of the following;

the metal oxide is Al₂O₃、ZnO、CaO、Cr₂O₃One or more of the following;

the composite material matrix material is a fiber reinforced ceramic matrix composite material or a fiber reinforced carbon matrix composite material.

4. The modified antioxidant composite phosphate coating of claim 1, wherein: the composite material matrix is made of a silicon carbide fiber reinforced silicon carbide ceramic matrix composite material or a carbon fiber reinforced carbon matrix composite material.

5. The method for preparing the modified antioxidant composite phosphate coating as claimed in any one of claims 1 to 4, wherein the method comprises the following steps: the method comprises the following steps:

s1: preparing a coupling layer on the surface of the composite material matrix by adopting an impregnation method;

s2: and preparing an antioxidation layer on the surface of the coupling layer by adopting a brushing sintering method.

6. The method for preparing the modified antioxidant composite phosphate coating according to claim 5, wherein: the S1 specifically includes the following steps:

carrying out surface polishing and grinding and transition chamfering processing treatment of edges and corners on the composite material substrate;

respectively carrying out surface ultrasonic treatment on the polished and chamfered composite material matrix in acetone, alcohol and deionized water for 60min, and drying in a drying oven at the constant temperature of 110 ℃ for 6 hours;

and (3) putting the dried composite material substrate into a titanate coupling agent for dipping, and then drying and heating until the surface forms a viscous coupling layer without fluidity.

7. The method for preparing the modified antioxidant composite phosphate coating according to claim 5, wherein: the S2 specifically includes the following steps:

metaphosphate according to the mass ratio of powder materials: phosphate salt: boride: metal oxide = (16-30): (6-13): 3-5): 2, respectively weighing each powder material, mixing and grinding to obtain mixed powder material with uniform grinding granularity of 1-10 μm;

adding the ground mixed powder into a paint cup, adding phosphoric acid into the paint cup, and stirring until the mixed powder is uniformly dispersed to form a viscous substance; wherein the mass ratio of the mixed powder to the phosphoric acid is 1 (2-4);

adding alkaline silica sol into the sticky matter, and gently and uniformly stirring until the viscosity is 8-30 mPa & s to obtain phosphate coating slurry; wherein the mass ratio of the mixed powder to the silica sol is 1 (4-8);

uniformly brushing the coating slurry to the surface of the coupling layer in the step S1, and then transferring the coating slurry to a constant-temperature drying box at the temperature of 120 ℃ for drying; taking out the obtained product after drying, cooling, repeatedly brushing coating slurry on the brushing surface, and transferring the obtained product to a constant-temperature drying oven at the temperature of 120 ℃ for drying; and repeating brushing and drying until the thickness of the coating is 40-80 mu m.

8. The method for preparing the modified antioxidant composite phosphate coating according to claim 7, wherein: placing the composite material substrate coated with the phosphate coating in a heat treatment furnace, carrying out heat treatment in a nitrogen environment, and sequentially carrying out a first heating process, a first heat preservation process, a second heating process, a second heat preservation process and a cooling process;

the first temperature rise process comprises the following steps: heating to 200 ℃ at a heating rate of 3 ℃/min;

the first heat preservation process comprises the following steps: keeping the temperature at 200 ℃ for 60 min;

the second temperature rise process comprises the following steps: heating to 700-900 ℃ at a heating rate of 4 ℃/min;

the second heat preservation process comprises the following steps: preserving the heat for 120min at 700-900 ℃;

the cooling process comprises the following steps: cooling to 200 ℃ at a cooling rate of 3 ℃/min.

9. The method for preparing the modified antioxidant composite phosphate coating according to claim 6, wherein: the dipping temperature is 60-80 ℃, and the dipping time is 6-12 hours.

10. The use of the modified antioxidant composite phosphate coating of any one of claims 1 to 4 in the preparation of aerospace and rail transit components.

Technical Field

The invention belongs to the technical field of thermal protection antioxidant coatings, and particularly relates to a long-acting waterproof, moistureproof and antioxidant coating applied to a composite material substrate and a preparation and application method thereof.

Background

The fiber reinforced composite material is a novel high-performance material with the advantages of low density, small thermal expansion coefficient, high specific strength, high specific modulus, large heat capacity, excellent frictional wear performance, good material designability and the like, and is an ideal structural material in the modern aerospace craft and rail transit industries. However, for most of the carbon fibers, carbon interfaces or carbon matrixes in the composite material, when the temperature is higher than 400 ℃, the composite material is oxidized in the air, and the oxidation rate is accelerated along with the increase of the temperature. The oxidation obviously influences the full play of various properties of the composite material and reduces the technical and economic advantages of the application of the composite material. Therefore, improving the oxidation resistance of the composite material is the key to ensure the safe use of the composite material.

For example, the average temperature of normal braking of carbon/carbon aircraft brake materials is generally between 450 and 700 ℃. At present, the carbon/carbon composite material for the brake pair of the airplane in China resists oxidation, a large number of coatings of a P-Si-B system are adopted, and a remarkable effect is achieved. However, the coating system is inconvenient to maintain on site, has insufficient thermal shock resistance, and is difficult to realize the full-life protection of the novel carbon/carbon brake pair for the airplane. As a novel coating, the phosphate coating has relatively simple field maintenance and ideal antioxidant effect, and is a coating for a carbon/carbon composite material brake pair which is worthy of deep research. At present, phosphate coatings are mainly prepared by a brushing method, and researchers try to prepare the phosphate coatings on the basis of SiC coatings by an electrophoresis method. The phosphate coating prepared by using phosphoric acid, phosphate, boride, etc. as raw material by brush coating method is ideal in effect, and after oxidation at 700 deg.C for 30 hr, the minimum mass loss rate is 1.76%, but the coating has insufficient antioxidant capacity at above 700 deg.C. Generally, the oxidation resistance of the coating needs to be improved, and mechanisms such as oxidation resistance and interface combination of the coating need to be studied more deeply.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a modified antioxidant composite phosphate coating and a preparation method and application thereof, so that the antioxidant and anticorrosive capacities of the coating and the composite material in a wet oxygen and high temperature coupling environment are enhanced, and the ceramic matrix or carbon matrix composite material and the components thereof can keep stable comprehensive performance for a long time in a medium-low temperature environment of more than 700 ℃. The invention has simple process, low cost and strong applicability, and the prepared coating has strong moisture resistance, good oxidation resistance and excellent thermal shock resistance, can be used in water, and can carry out large-scale production on medium-low temperature thermal protection products consisting of related composite materials and components.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

in a first aspect, the invention provides a modified antioxidant composite phosphate coating, which comprises a coupling layer arranged on the surface of a composite material matrix and an antioxidant layer arranged on the surface of the coupling layer. The multilayer composite coating is prepared by adopting a painting and sintering process and sequentially comprises a coupling layer and an anti-oxidation layer from inside to outside, wherein the coupling layer is prepared on the surface of the composite material substrate. Wherein the coupling layer comprises a titanate coupling agent; the anti-oxidation layer comprises metaphosphate, phosphate, boride and metal oxide, and is a metaphosphate/phosphate/boride/metal oxide composite system.

In a further embodiment of the invention, in order to improve the adhesive force between the coating and the substrate and further enhance the bonding strength and the permeability of phosphoric acid and groups in the coating to the substrate, firstly, a pyrophosphoric acid type titanate coupling layer is prepared on the surface of the composite substrate by adopting an immersion method, the thickness of the coupling layer is about 5-20 μm, and meanwhile, the drying acceleration can be realized, the baking temperature is reduced, and the baking time is shortened; the composite phosphate oxidation-resistant layer is prepared on the surface of the coupling layer by a coating sintering method, the thickness of the oxidation-resistant layer is about 40-80 mu m, and the oxidation resistance and the water-oxygen corrosion resistance of the easily-oxidized substrate material can be obviously improved.

The titanate coupling agent is TMC101, TMC105 or TMC 201.

The metaphosphate is Zn (PO)₃)₂、La(PO₃)₃、Al(PO₃)₃One or more of them.

The phosphate is AlPO₄、Zn₃(PO₄)₂、NH₄H₂PO₄One or more of them.

The boride is TiB₂、LaB₆One or more of them.

The metal oxide is Al₂O₃、ZnO、CaO、Cr₂O₃One or more of them.

The matrix material of the composite material is a fiber reinforced ceramic matrix composite material or a fiber reinforced carbon matrix composite material.

Preferably, the matrix material of the composite material is a silicon carbide fiber reinforced silicon carbide ceramic matrix composite material or a carbon fiber reinforced carbon matrix composite material.

In a second aspect, the invention provides a preparation method of the modified antioxidant composite phosphate coating, which comprises the following steps: s1: preparing a titanate coupling layer on the surface of the composite material substrate by adopting an impregnation method; s2: and preparing a composite phosphate oxidation-resistant layer on the surface of the coupling layer by adopting a brushing sintering method. Before preparing the buffer layer on the surface of the composite material matrix, chamfering and polishing are preferentially carried out on edges and corners of a sample or a workpiece, and surface ultrasonic treatment is carried out on the matrix by adopting acetone, alcohol and deionized water to remove impurities, fine particles and organic pollutants on the surface of the matrix.

In a further embodiment of the present invention, S1 specifically includes the steps of: carrying out flatness polishing and grinding (to the surface roughness of less than 30 mu m) and transition chamfer angle (less than 3mm) processing treatment on the surface of the composite material matrix sample or the workpiece;

then, respectively carrying out surface ultrasonic cleaning treatment on the composite material matrix sample or the workpiece which is polished and chamfered in acetone, alcohol and deionized water for 60min, and then placing the composite material matrix sample or the workpiece in a drying oven at 110 ℃ for drying for 6 hours at constant temperature;

further, a proper amount of titanate coupling agent is measured, the titanate coupling agent is heated to 60-80 ℃ in a water bath kettle and is kept at a constant temperature, the cleaned and dried composite material sample or workpiece is immersed in the titanate coupling agent (or is coated on the surface of a substrate to be coated) for 6-12 hours, and then the titanate coupling agent is dried at a constant temperature of 140 ℃ until the surface of the titanate coupling agent forms a viscous coupling layer without fluidity; repeating the above dipping process until the thickness of the coupling layer is about 5-20 μm.

In a further embodiment of the present invention, S2 specifically includes the steps of: metaphosphate according to the mass ratio: phosphate salt: boride: weighing various powder materials according to the formula of (16-30): 6-13): 3-5): 2, mixing and grinding to obtain a ceramic mixture with the proportion of mixed powder materials which are uniformly ground and have the granularity of 1-10 mu m; adding the ground mixed powder into a paint cup, slowly adding phosphoric acid with the mass 2-4 times that of the powder, and uniformly stirring the mixed powder and the powder until the mixed powder and the powder are uniformly dispersed to form a sticky matter; and then adding alkaline silica sol which is 4-8 times of the mass of the powder into the sticky matter, and gently and uniformly stirring until the viscosity is 8-30 mPa & s to obtain phosphate coating slurry.

Further, uniformly brushing the coating slurry to the surface of the coupling layer in the step S1, and then transferring the coating slurry to a constant-temperature drying box at the temperature of 120 ℃ for drying; taking out the obtained product after drying, cooling, repeatedly brushing coating slurry on the brushing surface, and transferring the obtained product to a constant-temperature drying oven at the temperature of 120 ℃ for drying; repeatedly brushing and drying until the thickness of the coating is 40-80 mu m; and finally, transferring the mixture into a vacuum furnace for heat treatment.

It should be further noted that, in the heat treatment process, the first temperature rise process, the first heat preservation process, the second temperature rise process, the second heat preservation process and the temperature reduction process are sequentially performed in a nitrogen environment:

the first temperature rise process comprises the following steps: heating to 200 ℃ at a heating rate of 3 ℃/min;

the first heat preservation process comprises the following steps: keeping the temperature at 200 ℃ for 60 min;

the second temperature rise process comprises the following steps: heating to 700-900 ℃ at a heating rate of 4 ℃/min;

the second heat preservation process comprises the following steps: preserving the heat for 120min at 700-900 ℃;

the cooling process comprises the following steps: cooling to 200 ℃ at a cooling rate of 3 ℃/min.

In a third aspect, the invention provides an application of the modified antioxidant composite phosphate coating in preparation of aerospace components and rail transit components.

The technical scheme provided by the invention has the following beneficial effects:

(1) a pyrophosphoric acid type titanate coupling layer is prepared on the surface of a composite material substrate, and a titanate coupling agent is directly coupled with trace carboxyl or hydroxyl adsorbed on the surfaces of fillers such as phosphate/metaphosphate through the chemical action of alkoxy of the titanate coupling agent, so that the penetration depth of coating slurry is increased, the bonding strength of an antioxidant coating and the substrate is enhanced, the coating has better antioxidant performance and longer service life, and the wear resistance and the ageing resistance of a product are improved;

(2) the existence of a large amount of metaphosphate in the oxidation resistant coating is beneficial to reacting with oxygen at low temperature (700-900 ℃) to form corresponding phosphate and a viscous self-healing P-O-P component, and simultaneously, the component is in AlPO₄Can realize stable existence under the balance action, thereby obviously improving the anti-oxidation protection of the coating on the matrix material; while high melting point TiB₂Oxidizing at 900-1000 ℃ to form TiO₂And B₂O₃Flow state B with high temperature self-sealing effect₂O₃The long-acting antioxidation of the coating at 800-1100 ℃ can be realized. Therefore, the invention can provide good oxidation resistance and water-oxygen corrosion resistance in a wide temperature range (middle and low temperature range of 700-1100 ℃);

(3) the invention has simple process, low cost and strong applicability, and the prepared coating has strong moisture resistance, good oxidation resistance and excellent thermal shock resistance, can be used in water, and can carry out large-scale production on medium-low temperature thermal protection products consisting of related composite materials and components.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

FIG. 1 shows the oxidation morphology of a composite phosphate coating prepared in example two of the present invention at 900 ℃;

FIG. 2 is an oxidation curve of the composite phosphate coating prepared in example two of the present invention at 700 deg.C, 900 deg.C and 1100 deg.C;

FIG. 3 is a graph showing the application of the composite phosphate coating prepared in example two of the present invention to a full-scale aircraft brake disc test piece.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.

The experimental procedures in the following examples are conventional unless otherwise specified. The test materials used in the following examples were purchased from a conventional reagent store unless otherwise specified. In the quantitative tests in the following examples, three replicates were set, and the data are the mean or the mean ± standard deviation of the three replicates.

Example one

The preparation method comprises the following steps:

preparing a matrix: cutting 1.0cm multiplied by 1.0cm C/C composite material, and grinding the edge of the edge angle into an arc chamfer by using a grinding stone so as to relieve the stress concentration of the coating at the edge; ultrasonically shaking with acetone, alcohol and deionized water for 60min, respectively, and drying in a drying oven at a constant temperature of 110 deg.C.

Preparation of a coupling layer: measuring a proper amount of titanate coupling agent, heating the titanate coupling agent in a water bath kettle to 60 ℃ for constant temperature, immersing the cleaned and dried composite material sample in TMC101 titanate coupling agent for 8 hours, and then drying the surface titanate coupling agent at 140 ℃ to form a viscous coupling layer without fluidity; the above impregnation procedure was repeated until the coupling layer was about 12 μm thick.

Preparing an anti-oxidation layer: zn (PO) according to the mass ratio₃)₂/La(PO₃)₃/AlPO₄/NH₄H₂PO₄/TiB₂/Al₂O₃Weighing various powder materials according to a formula of 15:15:10:2:4:1:1, mixing and grinding to obtain a ceramic mixture with uniform grinding proportion; adding the ground mixed powder into a paint cup, slowly adding phosphoric acid with the mass 2 times of that of the powder, and uniformly stirring the mixed powder and the powder until the mixed powder and the powder are uniformly dispersed to form a sticky substance; then, the viscous material is addedAdding alkaline silica sol which is 4 times of the mass of the powder, and gently and uniformly stirring until the viscosity is 10mPa & s to obtain phosphate coating slurry. Uniformly brushing the coating slurry to the surface of the coupling layer by using a brush, and then transferring the coating slurry to a constant-temperature drying box at the temperature of 120 ℃ for drying; taking out the obtained product after drying, cooling, repeatedly brushing coating slurry on the brushing surface, and transferring the obtained product to a constant-temperature drying oven at the temperature of 120 ℃ for drying; repeatedly brushing and drying until the thickness of the coating is 60 mu m; and finally, transferring the coating to a vacuum furnace for heat treatment to obtain a coating product. In the heat treatment process, sequentially heating to 200 ℃ at the heating rate of 3 ℃/min in the nitrogen atmosphere; keeping the temperature at 200 ℃ for 60 min; heating to 750 ℃ at the heating rate of 4 ℃/min; keeping the temperature at 750 ℃ for 120 min; cooling to 200 ℃ at a cooling rate of 3 ℃/min.

Example two

The preparation method comprises the following steps:

preparing a matrix: cutting 1.0cm multiplied by 1.0cm C/C composite material, and grinding the edge of the edge angle into an arc chamfer by using a grinding stone so as to relieve the stress concentration of the coating at the edge; ultrasonically shaking with acetone, alcohol and deionized water for 60min, and drying in a drying oven at a constant temperature of 110 deg.C.

Preparation of a coupling layer: measuring a proper amount of titanate coupling agent, heating the titanate coupling agent in a water bath kettle to 60 ℃ for constant temperature, immersing the cleaned and dried composite material sample in TMC201 titanate coupling agent for 12 hours, and then drying the surface titanate coupling agent at 140 ℃ to form a viscous coupling layer without fluidity; the above impregnation procedure was repeated until the coupling layer was about 12 μm thick.

Preparing an anti-oxidation layer: zn (PO) according to the mass ratio₃)₂/La(PO₃)₃/AlPO₄/NH₄H₂PO₄/TiB₂/Al₂O₃Weighing various powder materials according to the formula of 8:8:10:2:4:1:1, mixing and grinding to obtain a ceramic mixture with uniform grinding proportion; adding the ground mixed powder into a paint cup, slowly adding phosphoric acid with the mass 4 times of that of the powder, and uniformly stirring the mixed powder and the powder until the mixed powder and the powder are uniformly dispersed to form a sticky substance; then, the user can use the device to perform the operation,adding alkaline silica sol which is 4 times of the mass of the powder into the sticky matter, and gently and uniformly stirring until the viscosity is 26mPa & s to obtain phosphate coating slurry. Uniformly brushing the coating slurry to the surface of the coupling layer by using a brush, and then transferring the coating slurry to a constant-temperature drying box at the temperature of 120 ℃ for drying; taking out the obtained product after drying, cooling, repeatedly brushing coating slurry on the brushing surface, and transferring the obtained product to a constant-temperature drying oven at the temperature of 120 ℃ for drying; repeating brushing and drying until the thickness of the coating is 80 mu m; and finally, transferring the coating to a vacuum furnace for heat treatment to obtain a coating product. In the heat treatment process, sequentially heating to 200 ℃ at the heating rate of 3 ℃/min in the nitrogen atmosphere; keeping the temperature at 200 ℃ for 60 min; heating to 900 ℃ at the heating rate of 4 ℃/min; keeping the temperature at 900 ℃ for 120 min; cooling to 200 ℃ at a cooling rate of 3 ℃/min.

EXAMPLE III

The preparation method comprises the following steps:

preparing a matrix: cutting 1.0cm multiplied by 1.0cm C/C composite material, and grinding the edge of the edge angle into an arc chamfer by using a grinding stone so as to relieve the stress concentration of the coating at the edge; ultrasonically shaking with acetone, alcohol and deionized water for 60min, respectively, and drying in a drying oven at a constant temperature of 110 deg.C.

Preparation of a coupling layer: measuring a proper amount of titanate coupling agent, heating the titanate coupling agent in a water bath kettle to 60 ℃ for constant temperature, immersing the cleaned and dried composite material sample in TMC201 titanate coupling agent for 12 hours, and then drying the surface titanate coupling agent at 140 ℃ to form a viscous coupling layer without fluidity; the above impregnation procedure was repeated until the coupling layer thickness was about 18 μm.

Preparing an anti-oxidation layer: zn (PO) according to the mass ratio₃)₂/Al(PO₃)₃/AlPO₄/NH₄H₂PO₄/TiB₂/Cr₂O₃Weighing various powder materials according to the formula of 8:13:7:3:5:1:1, mixing and grinding to obtain a ceramic mixture with uniform grinding proportion; adding the ground mixed powder into a paint cup, slowly adding phosphoric acid with the mass equal to 3 times of that of the powder, uniformly stirring the mixed powder and the powder until the mixed powder and the powder are uniformly dispersed to form viscous powderAn agent; then, adding alkaline silica sol which is 4 times of the mass of the powder into the sticky matter, and gently and uniformly stirring until the viscosity is 18mPa & s to obtain phosphate coating slurry. Uniformly brushing the coating slurry to the surface of the coupling layer by using a brush, and then transferring the coating slurry to a constant-temperature drying box at the temperature of 120 ℃ for drying; taking out the obtained product after drying, cooling, repeatedly brushing coating slurry on the brushing surface, and transferring the obtained product to a constant-temperature drying oven at the temperature of 120 ℃ for drying; repeatedly brushing and drying until the thickness of the coating is 60 mu m; and finally, transferring the coating to a vacuum furnace for heat treatment to obtain a coating product. In the heat treatment process, sequentially heating to 200 ℃ at the heating rate of 3 ℃/min in the nitrogen atmosphere; keeping the temperature at 200 ℃ for 60 min; heating to 800 ℃ at the heating rate of 4 ℃/min; keeping the temperature at 800 ℃ for 120 min; cooling to 200 ℃ at a cooling rate of 3 ℃/min.

Example four

The preparation method comprises the following steps:

preparing a matrix: cutting 1.0cm multiplied by 1.0cm C/C composite material, and grinding the edge of the edge angle into an arc chamfer by using a grinding stone so as to relieve the stress concentration of the coating at the edge; ultrasonically shaking with acetone, alcohol and deionized water for 60min, respectively, and drying in a drying oven at a constant temperature of 110 deg.C.

Preparation of a coupling layer: measuring a proper amount of titanate coupling agent, heating the titanate coupling agent in a water bath kettle to 80 ℃ for constant temperature, immersing the cleaned and dried composite material sample in TMC105 titanate coupling agent for 10 hours, and then drying the surface titanate coupling agent at 140 ℃ to form a viscous coupling layer without fluidity; the above impregnation procedure was repeated until the coupling layer thickness was about 15 μm.

Preparing an anti-oxidation layer: according to the mass ratio of Al (PO)₃)₃/La(PO₃)₃/AlPO₄/Zn₃(PO₄)₂/LaB₆Weighing various powder materials according to a formula of 13:10:8:1:4:1:1, mixing and grinding to obtain a ceramic mixture with uniform grinding proportion; adding the ground mixed powder into a paint cup, slowly adding phosphoric acid with the mass equal to 3 times of that of the powder, and uniformly stirring the mixed powder and the powder until the mixed powder and the powder are uniformly dispersed to form a sticky substance; however, the device is not suitable for use in a kitchenAnd then adding alkaline silica sol which is 4 times of the mass of the powder into the sticky matter, and gently and uniformly stirring until the viscosity is 16mPa & s to obtain phosphate coating slurry. Uniformly brushing the coating slurry to the surface of the coupling layer by using a brush, and then transferring the coating slurry to a constant-temperature drying box at the temperature of 120 ℃ for drying; taking out the obtained product after drying, cooling, repeatedly brushing coating slurry on the brushing surface, and transferring the obtained product to a constant-temperature drying oven at the temperature of 120 ℃ for drying; repeating brushing and drying until the thickness of the coating is 40 mu m; and finally, transferring the coating to a vacuum furnace for heat treatment to obtain a coating product. In the heat treatment process, sequentially heating to 200 ℃ at the heating rate of 3 ℃/min in the nitrogen atmosphere; keeping the temperature at 200 ℃ for 60 min; heating to 900 ℃ at the heating rate of 4 ℃/min; keeping the temperature at 900 ℃ for 120 min; cooling to 200 ℃ at a cooling rate of 3 ℃/min.

The composite phosphate coatings prepared in the first to fourth embodiments of the invention were subjected to performance measurement, and the weight loss ratios thereof after oxidation for 100 hours at different temperatures were tested. And (3) testing results: the specific results are shown in table 1 below:

table 1 composite phosphate coating performance test results statistics table

Examples	Weight loss at 700 deg.C (%)	Weight loss at 900 ℃ (%)	Weight loss at 1100 deg.C (%)
				Example one	1.33	11.54	64.65
Example two	-1.75	4.36	34.47
				EXAMPLE III	0.78	9.68	46.87
Example four	3.88	49.63	83.21

It should be noted that, in addition to the cases exemplified in the first to fourth embodiments, other preparation method parameters may be selected.

According to the modified long-acting waterproof antioxidant composite phosphate coating and the preparation method thereof, the boron-containing composite phosphate coating is prepared by preparing the titanate coupling layer on the carbon/carbon composite material in a modified manner, so that the antioxidant and anticorrosive capacities of the coating and the composite material in a wet oxygen and high temperature coupling environment are enhanced, and the ceramic matrix or carbon-based composite material can keep stable comprehensive performance for a long time in a medium-low temperature environment above 700 ℃. The technical scheme provided by the invention has the following advantages: (1) a pyrophosphoric acid type titanate coupling layer is prepared on the surface of a composite material substrate, and a titanate coupling agent is directly coupled with trace carboxyl or hydroxyl adsorbed on the surfaces of fillers such as phosphate/metaphosphate through the chemical action of alkoxy of the titanate coupling agent, so that the penetration depth of coating slurry is increased, the bonding strength of an antioxidant coating and the substrate is enhanced, the coating has better antioxidant performance and longer service life, and the wear resistance and the ageing resistance of a product are improved; (2) the presence of a large amount of metaphosphate in the oxidation resistant coating helps in low temperature conditionsReacting the mixture with oxygen at 700-900 ℃ to form corresponding phosphate and self-healing P with viscous state₂O₅Component (C) in AlPO₄Can realize stable existence under the balance action, thereby obviously improving the anti-oxidation protection of the coating on the matrix material; while high melting point TiB₂Oxidizing at 900-1000 ℃ to form TiO₂And B₂O₃Flow state B with high temperature self-sealing effect₂O₃The long-acting antioxidation of the coating at 800-1100 ℃ can be realized. Therefore, the invention can provide good oxidation resistance and water-oxygen corrosion resistance in a wide temperature range (middle and low temperature range of 700-1100 ℃); (3) the invention has simple process, low cost and strong applicability, and the prepared coating has strong moisture resistance, good oxidation resistance and excellent thermal shock resistance, can be used in water, and can carry out large-scale production on medium-low temperature thermal protection products consisting of related composite materials and components.

It is to be noted that, unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which the invention pertains. Unless specifically stated otherwise, the relative steps, numerical expressions, and values of the components and steps set forth in these embodiments do not limit the scope of the present invention. In all examples shown and described herein, unless otherwise specified, any particular value should be construed as merely illustrative, and not restrictive, and thus other examples of example embodiments may have different values.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention, and all of the technical solutions are covered in the protective scope of the present invention.