A BN f Method for preparing high-temperature self-reinforced oxidation-resistant coating for BN / SiBN composite matrix

Abstract

The application discloses a preparation method of a high-temperature self-reinforced antioxidation coating for a BN f / SiBN composite substrate, and belongs to the technical field of antioxidation coating of high-temperature oxygen environment composite materials. The method comprises the following steps: dispersing organic silicon oil in an organic solvent, adding a silane coupling agent, and obtaining solution A; dispersing aluminum isopropyl alcohol in an organic solvent, and obtaining solution B; spraying solution A and solution B on a BN f / SiBN composite substrate in a circulating manner, sequentially performing drying and heating treatment on the obtained composite, and obtaining a self-reinforced antioxidation coating. The prepared high-temperature self-reinforced antioxidation coating for the BN f / SiBN composite substrate can be used in the fields of missile radar covers and hypersonic flight, and has excellent high-temperature antioxidation performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oxidation-resistant coating of high-temperature oxygen environment composite material, and particularly relates to a preparation method of high-temperature self-reinforced oxidation-resistant coating for BN f / SiBN composite substrate. BACKGROUND

[0002] The continuous development of contemporary aviation and precision guided weapon technology has generated considerable interest in super-high-temperature composite materials related to various applications such as missile radomes and hypersonic flight. In addition to using materials inherently resistant to high temperatures, oxidation-resistant coating is one of the ways to enhance the high-temperature stability of composite materials. However, the research on oxidation-resistant coating for high-temperature oxygen environment composite materials has been in a state of poor design effect due to the difficulty in matching the coating and the substrate. SUMMARY

[0003] To solve the above technical problems, the present application provides a preparation method of high-temperature self-reinforced oxidation-resistant coating for BN f / SiBN composite substrate. The present application innovatively proposes the design concept of "double-feed proliferation mechanism" for oxidation-resistant film layer, which fully utilizes the interactive reaction mechanism of gas-phase B2O3 generated by the substrate under high-temperature environment and the film layer. When cracks appear in the coating, BN will be oxidized to release B2O3 gas. After contacting with the coating, B2O3 gas will change the state of the coating and make it flow. The flowing coating material will fill the cracks and achieve self-reinforcing effect. Through temperature adjustment control, the film layer can be restored, which can overcome the problem of coating cracks caused by the mismatch of the thermal expansion coefficient of the substrate, and achieve the purpose of high-temperature self-repairing of the film layer. The preparation method is simple, the raw material price is cheap, and it is beneficial to realize large-scale production.

[0004] To achieve the above purpose, the present application provides the following technical scheme:

[0005] A preparation method of high-temperature self-reinforced oxidation-resistant coating for BN f / SiBN composite substrate, comprising the following steps:

[0006] Disperse the organosilicon oil in the organic solvent, add the silane coupling agent to obtain solution A;

[0007] Disperse the aluminum isopropyl alcohol in the organic solvent to obtain solution B;

[0008] Circulating spray solution A and solution B on the BN f / SiBN composite substrate, and sequentially perform drying and heating treatment on the obtained composite to obtain a self-reinforced oxidation-resistant coating.

[0009] Further, the mass ratio of the organosilicon oil to aluminum isopropyl alcohol is 1:1-5:1.

[0010] Furthermore, the silicone oil includes hydrogen-containing silicone oil, methyl silicone oil, methyl hydrogen-containing silicone oil, or diethyl silicone oil; the organic solvent includes ethyl acetate, tetrahydrofuran, or ethanol.

[0011] Furthermore, the number of spray cycles is 4-10.

[0012] Furthermore, the drying parameters are: temperature 50-120℃, time 0.5-30h.

[0013] Furthermore, the parameters for the heating treatment are: heating rate 0.5-20℃ / min, temperature 400-1000℃, and time 5-300min.

[0014] The present invention also provides a BN prepared by the above preparation method. f High-temperature self-reinforcing antioxidant coating for SiBN composite matrix.

[0015] The present invention also provides the BN described above. f Application of high-temperature self-reinforcing antioxidant coatings for SiBN composite substrates in the aerospace field.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects:

[0017] The BN provided by this invention f A method for preparing a high-temperature self-reinforced antioxidant coating on a SiBN composite matrix is ​​presented, exhibiting high stability, strong controllability, simple preparation steps, and readily available and inexpensive raw materials, thus facilitating large-scale production. The prepared BN... f High-temperature self-reinforcing antioxidant coatings for SiBN composite matrices can be used in aerospace fields such as missile radomes and hypersonic flight, exhibiting excellent high-temperature antioxidant properties. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0019] Figure 1 This describes the temperature variation of the B2O3-SiO2 binary oxide system in Example 1 of this invention.

[0020] Figure 2 This describes the dynamic transformation process of the Si-Al-O film at different temperatures in Example 1 of the present invention. Detailed Implementation

[0021] The following detailed description of various exemplary embodiments of the application will not be considered limiting of the application, but rather a description of certain aspects, features and embodiments of the application.

[0022] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Additionally, the use of "including", "comprising", "having" and "with" are not intended to be limiting of the application. It is intended that the specification and examples be considered exemplary only, with the true scope of the application being indicated by the following claims.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. All publications mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. In case of conflict, the content of the present specification will control.

[0024] Various modifications and changes can be made to the specific embodiments of the application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The specification and examples given should be considered exemplary only, with the true scope of the application being indicated by the following claims.

[0025] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional elements or steps.

[0026] The raw materials used in the present application are all purchased from the market. The hydrogen-containing silicone oil (XC202) is purchased from Xingchi Chemical Co., Ltd.; the silane coupling agent (KH550) with a purity of 99% and the aluminum isopropyl alcohol with analytical purity are both purchased from Macklin Reagent; and the ethanol with analytical purity is purchased from National Pharmaceutical Reagent. The SiO 2f The SiO2 matrix is purchased from Shandong Industrial Ceramics Research Institute.

[0027] The BN fThe Si-Al-O oxidation-resistant coating is synthesized on the surface of the SiBN composite substrate by an organic synthesis method. It is found that the oxidation product in the initial oxidation stage of the substrate can continuously generate a new film layer at the damaged part of the oxidation-resistant coating through a gas-phase mass transfer mechanism, so that the oxidation-resistant coating has the ability to repair the surface damage such as puncture, cracking and hollowing caused by the high-temperature oxidation environment, and can bypass the damage of the thermal matching mechanism and completely prevent the protection of oxygen. The application proposes the design concept of the "double-feeding proliferation mechanism" of the oxidation-resistant film layer, that is, even if cracks are generated in the coating during the heating process under the ideal state that the coating completely covers the substrate, the oxidation product generated by the contact between O2 and the surface substrate or fiber at high temperature will immediately react with the coating, promote the coating to flow and cover the cracks, and prevent the further penetration of O2, so as to achieve the purpose of high-temperature oxidation resistance.

[0028] The specific technical scheme is as follows: a BN f The preparation method of the high-temperature self-enhanced oxidation-resistant coating for the SiBN composite substrate comprises the following steps:

[0029] 1) The organosilicon oil is dispersed in an organic solvent, and a silane coupling agent (KH550) is added to obtain solution A; the aluminum isopropoxide is dispersed in an organic solvent to obtain solution B;

[0030] 2) The solutions A and B are circularly sprayed on the BN f composite substrate, and the obtained composite is placed in an oven for drying to remove the organic solvent;

[0031] 3) The composite obtained after drying is treated by heating in an air atmosphere, and the organic matter is cracked and removed to obtain a Si-Al-O system coating, that is, a self-enhanced oxidation-resistant coating.

[0032] In some preferred embodiments of the application, the mass ratio of the organosilicon oil to the aluminum isopropoxide in step 1) is 1:1-5:1, preferably 2:1.

[0033] The organosilicon oil includes hydrogen-containing silicon oil, methyl silicon oil, methyl hydrogen-containing silicon oil or diethyl silicon oil; preferably hydrogen-containing silicon oil.

[0034] The organic solvent includes ethyl acetate, tetrahydrofuran or ethanol, preferably ethyl acetate.

[0035] The silane coupling agent is used to bridge the organosilicon oil and the aluminum isopropoxide, so the silane coupling agent can be added to solution A or solution B. In the following embodiments of the application, the silane coupling agent is added to solution A (i.e., the organosilicon oil). The addition amount of the silane coupling agent is 5% of the mass of the organosilicon oil.

[0036] In step 2) of some preferred embodiments of the present application, the number of cycles of spraying is 4-10, preferably 5. In the spraying process, the solution containing silicone oil is sprayed first, and then the solution containing aluminum isopropanol is sprayed. The cycle of spraying refers to spraying solution A and then spraying solution B, which is one cycle. In the spraying process, the spraying time is 10 s each time, and the spraying distance is 20-30 cm, preferably 25 cm.

[0037] The parameters of the drying are as follows: temperature 50-120℃, time 0.5-30h, preferably drying at 80℃ for 2h.

[0038] The parameters of the temperature rising treatment are as follows: temperature rising rate 0.5-20℃ / min, cracking temperature 400-1000℃, cracking time 5-300min. The preferred parameters are as follows: temperature rising rate 5℃ / min, cracking temperature 700℃, cracking time 60min.

[0039] The BN f The preparation method of the BN / SiBN composite matrix is as follows: weaving BN fibers into a preform, placing the preform into a dipping tank, vacuumizing the dipping tank to a vacuum degree of -0.50Mpa, then immersing the preform into a precursor polysilazane to obtain a BN f / SiBN preform. The obtained BN f / SiBN preform is transferred into an autoclave, high-purity nitrogen is filled into the autoclave to a pressure of 10MPa, the gas inlet valve is closed, and the BN f / SiBN preform is placed into a cracking furnace, heated to 800h, and kept for 3h to obtain a BN f / SiBN matrix.

[0040] The present application is targeted at the BN f / SiBN composite matrix, and the mass transfer of the oxidation product can react with the oxidation-resistant coating, so that the problem of coating cracks caused by the mismatch of the thermal expansion coefficients of the matrix can be solved. The "double-fed film layer" has high designability, different film layer systems can be designed according to different material systems, thereby forming a semi-continuous high-temperature self-film coating design system, which provides a new idea for the high-temperature oxidation-resistant protection of composite materials. Meanwhile, the material preparation method is simple, the raw material price is cheap, and the method is easy to scale up.

[0041] The principle of the present application is as follows: when the coating cracks, BN is oxidized to release B2O3 gas, the B2O3 gas changes the state of the coating after contacting with the coating, so that the coating material flows, the flowing coating material fills the cracks to achieve a self-reinforcing effect, effectively solving the problem of matrix oxidation caused by coating cracks, and protecting the matrix.

[0042] The BN fThe application discloses a high-temperature self-reinforced oxidation-resistant coating for a / SiBN composite matrix.

[0043] The coating has good oxidation-resistant self-repairing properties and can be used in aerospace fields such as missile radomes and hypersonic flight.

[0044] The technical solutions of the application are further described below through examples.

[0045] Example 1

[0046] A BN f A preparation method of the high-temperature self-reinforced oxidation-resistant coating for the / SiBN composite matrix comprises the following steps:

[0047] Step 1) 10g hydrogen-containing silicone oil is dispersed in 50g ethyl acetate, and 5% of the hydrogen-containing silicone oil in mass is added with a silane coupling agent (KH550) to obtain solution A; 5g aluminum isopropoxide is dispersed in 50g ethanol to obtain solution B;

[0048] Step 2) the BN f The solution A is first sprayed on the / SiBN composite matrix, and then the solution B is sprayed, the spraying time of the solution A and the solution B is 10s each time, and the spraying distance is 25cm; the spraying is cycled for 5 times;

[0049] Step 3) the obtained composite is placed in an oven and dried at 80℃ for 2h to dry the organic solvents;

[0050] Step 4) the composite dried in the air is subjected to temperature rising treatment at a temperature rising rate of 5℃ / min, is cracked at 700℃ for 60min to remove the organic matters, and thus a Si-Al-O system coating, namely a self-reinforced oxidation-resistant coating, is obtained.

[0051] Example 2

[0052] The difference from example 1 is that the hydrogen-containing silicone oil in step 1) is replaced with methyl silicone oil.

[0053] Example 3

[0054] The difference from example 1 is that the mass ratio of the silicone oil to the aluminum isopropoxide in step 1) is adjusted to 1:1, that is, the addition amount of the aluminum isopropoxide is 10g.

[0055] Example 4

[0056] The difference from example 1 is that the ethyl acetate in step 1) is replaced with tetrahydrofuran.

[0057] Example 5

[0058] The same as example 1, except that the cracking parameters in step 4) are adjusted to: cracking at 1000℃ for 30min.

[0059] Example 6

[0060] The same as example 1, except that the spraying times in step 2) are adjusted to 10 times.

[0061] Example 7

[0062] The same as example 1, except that the spraying distance in step 2) is adjusted to 30cm.

[0063] Comparative example 1

[0064] The same as example 1, except that the hydrogen-containing silicone oil in step 1) is replaced by sodium silicate. It is found that the hydrogen-containing silicone oil has good film-forming property at low temperature, can completely cover the ceramic substrate, and the hydrogen bond is easy to combine with the silane coupling agent, and the silane coupling agent is easy to combine with aluminum isopropyl alcohol, and easy to form a film; while the sodium silicate has poor combination with the silane coupling agent and aluminum isopropyl alcohol, and has poor film-forming property.

[0065] Comparative example 2

[0066] The same as example 1, except that the ethyl acetate in step 1) is replaced by water. It is found that the hydrogen-containing silicone oil and aluminum isopropyl alcohol are both insoluble in water, and have poor film-forming property.

[0067] Comparative example 3

[0068] The same as example 1, except that the spraying times in step 2) are adjusted to 1 time. It is found that spraying once, the hydrogen-containing silicone oil and aluminum isopropyl alcohol may not be able to completely cover the substrate, and cannot form a film.

[0069] Comparative example 4

[0070] The same as example 1, except that the BN f / SiBN composite substrate is replaced by SiO 2f / SiO2 composite substrate. It is found that the SiO 2f / SiO2 composite substrate has high brittleness at high temperature, and the film layer cannot realize high-temperature self-repair.

[0071] Figure 1The B2O3-SiO2 binary oxide system in Example 1 of the present application changes with temperature; as can be seen from the figure, in the range of 150℃ to 700℃, the film layer changes from an organic continuous film layer to inorganic particles, and when the temperature is increased to 700℃, the inorganic particles on the surface of the material change into an inorganic film layer and are well combined with the interface; in the range of 700℃ to 1150℃, the coating is in an inorganic state, and under this temperature range, the BN fiber and the SiBN matrix have good thermal stability and are not affected by the oxidation reaction; in the range of above 1150℃, part of the oxidation film layer does not match the expansion coefficient of the matrix and cracks are generated, oxygen enters the inside of the matrix along the cracks, the BN fiber is oxidized to generate a gas phase product B2O3, the gas phase B2O3 reacts with the surface Si-Al-O mullite coating in the rising process, enters the coating, and makes the viscosity of the mullite film layer at the crack reduce, and the mullite film layer with reduced viscosity then flows to the fiber defect, gradually repairing and closing the cracks caused by the thermal mismatch mechanism, and reflecting the self-repairing effect.

[0072] Figure 2 The Si-Al-O film layer in Example 1 of the present application changes dynamically at different temperatures. (a) and (b) are scanning cross-sections of the Si-Al-O coating after cracking at 700℃ and combined with the matrix, and it can be seen that the combination between the coating and the matrix is relatively close. (c) and (d) are respectively the surface structure of the coating of the composite material at 1500℃ and the structure of the interaction between the fiber and the coating. As can be seen from (c), the surface coating changes into a molten amorphous state after oxidation treatment. As can be seen from (d), after the chemical reaction of the fiber at the crack of the coating, the gaseous B2O3 reacts with SiO2 in the coating to reduce the viscosity, and the process of flowing to the fiber further illustrates the high-temperature self-reinforcing mechanism of the present application.

[0073] The BN f The BN

[0074] Table 1 Mechanical properties of the material prepared in Example 1 after high-temperature treatment

[0075]

[0076] As can be seen from Table 1, the BN fAfter high temperature heat treatment at 1500℃, the internal structure of the high temperature self-reinforced oxidation resistant coating material for / SiBN composite matrix remains relatively complete, the compressive strength is maintained at 145±5MPa or above, and the bending strength is maintained at 39±2MPa or above. Due to the change of organic silicon oil, organic solvent, spraying period and matrix type, the internal structure of the comparative example remains relatively complete after high temperature heat treatment, but the highest compressive strength is only 83±6MPa, and the highest bending strength is only 32±5MPa. Therefore, the material still has excellent mechanical properties and oxidation resistance after high temperature heat treatment, and at the same time, the material has excellent high temperature resistance.

[0077] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A BN f Method for the production of a high-temperature self-reinforced oxidation-resistant coating for BN The method comprises the following steps: dispersing silicone oil in organic solvent, adding silane coupling agent to obtain solution A; dispersing aluminum isopropyl alcohol in organic solvent to obtain solution B; On BN f Cyclically spray solution A and solution B on the composite substrate of BN / SiBN, and sequentially dry and heat the obtained composite to obtain a self-reinforced antioxidation coating. The mass ratio of the silicone oil to the aluminum isopropyl alcohol is 1:1-5:

1. The parameters of the heating treatment are as follows: temperature increasing rate 0.5-20℃ / min, temperature 400-1000℃, and time 5-300min.

2. The BN of claim 1 f A method for preparing a high-temperature self-reinforced oxidation-resistant coating for a SiBN composite matrix, characterized by, The silicone oil comprises hydrogen-containing silicone oil, methyl silicone oil or diethyl silicone oil; and the organic solvent comprises ethyl acetate, tetrahydrofuran or ethanol.

3. The BN of claim 1 f A method for preparing a high-temperature self-reinforced oxidation-resistant coating for a SiBN composite matrix, characterized by, The number of the cyclic spraying is 4-10 times.

4. The BN of claim 1 f A method for preparing a high-temperature self-reinforced oxidation-resistant coating for a SiBN composite matrix, characterized by, The parameters of the drying are as follows: temperature 50-120℃ and time 0.5-30h.

5. BN produced by the production process according to any one of claims 1 to 4 f High-temperature self-reinforced oxidation-resistant coating for SiBN composite matrix.

6. A BN as claimed in claim 5 f Use of high temperature self-reinforced oxidation resistant coating for SiBN composite matrix in aerospace.

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