A treating solution for an oxidation-preventing coating and a method for preparing an oxidation-preventing coating
By using an organic compound treatment solution to form a complex salt coating, the problem of high-temperature oxidation of carbon/carbon composite materials was solved, achieving stable anti-oxidation effect and substrate protection at high temperatures.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAMEN SINOMA HANGTE TECH CO LTD
- Filing Date
- 2024-06-28
- Publication Date
- 2026-06-26
AI Technical Summary
Existing carbon/carbon composite materials are prone to oxidation at high temperatures, and traditional anti-oxidation coatings react with the substrate at high temperatures, resulting in unstable protective effects.
A treatment solution containing organic compounds, including tetraethyl silicate, tetrabutyl titanate, aluminum isopropoxide, tributyl borate, and a weak alkaline solution, is used to form a complex salt coating by sintering. This avoids the solubility problems of inorganic salts/oxides and ensures the uniformity and penetration of the coating into the substrate.
The resulting coating is stable at high temperatures, does not react with the substrate, maintains the substrate's dimensions and assemblability, has excellent anti-oxidation properties, and achieves a residual weight rate of 98.16%, making it suitable for a variety of harsh environments.
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Figure CN118580696B_ABST
Abstract
Description
Technical Field
[0001] This disclosure belongs to the technical field of anti-oxidation coating materials, and relates to a treatment liquid for anti-oxidation coatings and a method for preparing anti-oxidation coatings. Background Technology
[0002] Carbon / carbon composites (CC composites or carbon-carbon composite materials) are carbon matrix composites reinforced with carbon fibers and their fabrics, characterized by low density (<2.0 g / cm³). 3 With its advantages of high strength, high specific modulus, high thermal conductivity, low coefficient of expansion, good friction performance, good thermal shock resistance, and high dimensional stability, it is one of the few alternative materials for applications above 1650℃, and its highest theoretical temperature is as high as 2600℃. Therefore, it is considered one of the most promising high-temperature materials.
[0003] Carbon / carbon composites undergo severe oxidation at temperatures above 600℃, leading to increased porosity and decreased strength. Based on relevant data, it is estimated that at 600℃, the weight loss rate is approximately 20% per hour, and after just one hour, the material strength drops to about one-tenth of its original value.
[0004] Therefore, anti-oxidation treatment is of paramount importance for carbon / carbon composite materials. Currently, commonly used anti-oxidation coatings can be broadly classified into three types based on their chemical composition: ① silicate-based, ② phosphate-based, and ③ borate-based. Silicate and phosphate coatings have the widest range of applications, both domestically and internationally. For example, phosphate coatings are used on carbon brake discs in aircraft and Formula 1 racing, while silicate coatings are used on some carbon / carbon crucibles. Phosphate coating technology is relatively mature and can provide good protection below 1000℃. However, at higher temperatures, phosphates react with the carbon elements in the substrate, losing their protective effect. Silicate coatings can withstand even higher temperatures, reaching approximately 1500℃, but as the temperature continues to rise, the problem of reaction with the substrate still arises. Summary of the Invention
[0005] This disclosure provides a treatment liquid for anti-oxidation coatings and a method for preparing anti-oxidation coatings, which can effectively solve the above-mentioned problems.
[0006] This disclosure is implemented as follows:
[0007] This disclosure provides a treatment solution for an anti-oxidation coating, the treatment solution comprising:
[0008] The first processing solution comprises: tetraethyl silicate, tetrabutyl titanate, aluminum isopropoxide, tributyl borate, and an organic solvent.
[0009] The second treatment solution comprises a weak alkali and deionized water.
[0010] Furthermore, this disclosure provides a method for preparing an anti-oxidation coating, the method comprising:
[0011] Tetraethyl silicate, tetrabutyl titanate, aluminum isopropoxide, and tributyl borate are dissolved in an organic solvent and mixed evenly to obtain the first treatment solution.
[0012] The first treatment liquid is evenly applied to the surface of the substrate and left to stand until the first treatment liquid is completely absorbed by the substrate to obtain the first substrate, wherein the substrate is a carbon / carbon composite material.
[0013] The second treatment liquid is evenly applied to the surface of the first substrate and left to stand until the second treatment liquid is completely absorbed by the first substrate to obtain the second substrate. The second treatment liquid is a weak alkaline solution.
[0014] The second substrate is placed in a sintering furnace, and a protective gas is introduced into the sintering furnace to maintain the protective gas atmosphere. The temperature is raised to 850-950°C for sintering. After natural cooling, the anti-oxidation coating is obtained.
[0015] The beneficial effects of this disclosure are:
[0016] This disclosure provides a treatment liquid for anti-oxidation coatings, wherein the raw material of the first treatment liquid is an organic compound, replacing the inorganic salts / oxides in traditional methods. The raw material is miscible in any proportion in an organic solvent, thereby enabling the first treatment liquid to uniformly cover the substrate surface. This overcomes the problem that inorganic salts / oxides have limited solubility in solvents, resulting in poor uniformity of the treatment liquid and poor coating consistency.
[0017] Furthermore, both the first and second treatment solutions used are liquids with low surface tension and good permeability, which can penetrate deep into the substrate. Moreover, the coating formed after sintering does not change the size of the substrate and can maintain the original assemblability of the substrate. This has particularly obvious advantages in applications such as assemblies and harsh environments.
[0018] This disclosure provides a method for preparing an anti-oxidation coating. The prepared coating does not exhibit disintegration or powdering after oxidation testing, and the residual weight rate can reach 98.16%. The coating can effectively enable the substrate to obtain excellent high-temperature resistance and anti-oxidation properties. Attached Figure Description
[0019] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 This is a photograph of the sample with an anti-oxidation coating prepared in Example 1 after an anti-oxidation test;
[0021] Figure 2 This is a photograph of the sample with an anti-oxidation coating prepared in Comparative Example 1 after an anti-oxidation test.
[0022] Figure 3 This is a photograph of the sample with the anti-oxidation coating prepared in Comparative Example 2 after an anti-oxidation test. Detailed Implementation
[0023] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure. Therefore, the following detailed description of the embodiments of this disclosure provided in the accompanying drawings is not intended to limit the scope of the claimed disclosure, but merely represents selected embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.
[0024] This disclosure discloses a treatment solution for an anti-oxidation coating, the treatment solution comprising:
[0025] The first processing solution comprises: tetraethyl silicate, tetrabutyl titanate, aluminum isopropoxide, tributyl borate, and an organic solvent.
[0026] The raw materials of the first treatment liquid in this embodiment are all liquid organic ester components. Compared with traditional inorganic salt / oxide raw materials, they can be mixed in any proportion in organic solvents. Compared with the anti-oxidation coating prepared by traditional inorganic raw materials, it effectively solves the problem of unstable protective effect caused by uneven composition.
[0027] Furthermore, the ratio of each component in the raw materials can be adjusted based on the experimental results.
[0028] In some embodiments, the mass ratio of tetraethyl silicate, tetrabutyl titanate, aluminum isopropoxide, and tributyl borate is (6-10):(1-3):(4-6):1.
[0029] In some embodiments, the organic solvent is ethyl acetoacetate.
[0030] Ethyl acetoacetate was chosen as the organic solvent, as it has good solubility for each component in the organic raw materials. The reagent is harmless to humans and the substrate and is readily available.
[0031] The first treatment solution, prepared from raw materials and organic solvents, exhibits excellent fluidity, enabling it to uniformly cover the substrate surface. Surface damage such as scratches and abrasions does not affect the protective effect. Furthermore, the first treatment solution penetrates deep into the internal pores of carbon / carbon composite materials, and after sintering, it achieves protective effects without affecting the material's shape and dimensions, offering greater versatility and applicability to various harsh environments. Simultaneously, it does not alter assemblability, making its application in assemblies particularly advantageous.
[0032] The second treatment solution comprises a weak alkali and deionized water.
[0033] The role of a weak alkaline solution is to provide an alkaline environment to promote the hydrolysis of organic esters in the raw materials, converting them into inorganic salts and oxides.
[0034] In some embodiments, the second treatment solution is an aqueous solution of ammonium bicarbonate with a mass fraction of 10%.
[0035] Ammonium bicarbonate aqueous solution is preferred because it leaves no residue after heating, avoiding the introduction of other metal ions such as sodium bicarbonate and sodium hydroxide, which could damage the complex salt structure of the anti-oxidation coating.
[0036] In principle, toxic or irritating reagents should not be used, such as ammonia.
[0037] In some embodiments, the ammonium bicarbonate is of analytical grade or higher.
[0038] Ammonium bicarbonate must be of AR grade or higher. It cannot be replaced by fertilizer-grade ammonium bicarbonate because fertilizer-grade ammonium bicarbonate often contains small amounts of stabilizers, phosphates, etc., to improve fertilizer stability and enhance fertilizer efficiency. However, these additives will destroy the effective components of the anti-oxidation coating, causing it to fail. Therefore, high-purity ammonium bicarbonate must be selected.
[0039] This disclosure provides a method for preparing an anti-oxidation coating, the method comprising:
[0040] Tetraethyl silicate, tetrabutyl titanate, aluminum isopropoxide, and tributyl borate are dissolved in an organic solvent and mixed evenly to obtain the first treatment solution.
[0041] The first treatment liquid is evenly applied to the surface of the substrate and left to stand until the first treatment liquid is completely absorbed by the substrate to obtain the first substrate, wherein the substrate is a carbon / carbon composite material.
[0042] The second treatment liquid is evenly applied to the surface of the first substrate and left to stand until the second treatment liquid is completely absorbed by the first substrate to obtain the second substrate. The second treatment liquid is a weak alkaline solution.
[0043] In some embodiments, uniformly covering the substrate surface with the first treatment liquid includes: uniformly spraying the first treatment liquid onto the substrate surface, or immersing the substrate in the first treatment liquid.
[0044] The second treatment liquid is uniformly applied to the surface of the first substrate, including: uniformly spraying the second treatment liquid onto the surface of the first substrate, or immersing the first substrate in the second treatment liquid.
[0045] The first and second treatment solutions can be applied by spraying or immersion to achieve surface coverage, thus avoiding errors caused by human operation.
[0046] The second substrate is placed in a sintering furnace, and a protective gas is introduced into the sintering furnace to maintain the protective gas atmosphere. The temperature is raised to 850-950°C for sintering. After natural cooling, the anti-oxidation coating is obtained.
[0047] In some embodiments, the second substrate is placed in a sintering furnace, the furnace is filled with a protective gas, the protective gas atmosphere is maintained, and the temperature is raised to 850–950°C for sintering, including:
[0048] The second substrate is placed in a sintering furnace, a vacuum is drawn, and the temperature is raised to 180-220°C to allow the organic solvent and solvent water to evaporate and the ammonium bicarbonate to decompose. The evaporated and decomposed gases are then removed to avoid affecting the sintering process.
[0049] Then, a protective gas is introduced into the sintering furnace to maintain the protective gas atmosphere, and the temperature is raised to 850-950℃ for sintering.
[0050] The protective gas should be a gas that does not chemically react with the raw materials and substrates, such as rare gases like helium, neon, argon, krypton, and xenon, or mixtures thereof. For example, carbon dioxide should not be selected.
[0051] The protective gas should not be a gas that decomposes at high temperatures to avoid environmental pollution. For example, nitrogen should not be chosen.
[0052] Considering cost and difficulty in obtaining it, argon is generally chosen.
[0053] When the raw materials may react at higher temperatures, introducing a protective gas can save costs.
[0054] The coating raw materials are sintered to form complex salts, which are more chemically stable than single silicates, phosphates and borates. They can withstand higher temperatures and do not react with the substrate, thus providing better anti-oxidation effects.
[0055] The materials and reagents used in the embodiments of this disclosure are as follows: high-purity carbon / carbon composite preform (20mm*20mm*10mm), tetraethyl silicate (AR), tetrabutyl titanate (AR), aluminum isopropoxide (AR), tributyl borate (AR), ethyl acetoacetate (AR), ammonium bicarbonate (AR), deionized water, and high-purity argon (99.999%).
[0056] Example 1
[0057] A method for preparing an anti-oxidation coating, the method comprising:
[0058] Step 1: Prepare the first treatment solution: Mix the coating raw materials tetraethyl silicate, tetrabutyl titanate, aluminum isopropoxide and tributyl borate in a mass ratio of 8:2:5:1, add an equal volume of ethyl acetoacetate to dissolve, mix evenly to obtain the first treatment solution.
[0059] Step 2: Prepare the second treatment solution: Dissolve ammonium bicarbonate in deionized water to obtain an ammonium bicarbonate aqueous solution as the second treatment solution. The mass fraction of ammonium bicarbonate is 10%.
[0060] Step 3: In a closed spraying chamber, the first treatment solution is evenly sprayed onto the surface of the high-purity carbon / carbon composite preform. After spraying, allow it to stand for 10 minutes to allow the spray solution to be fully absorbed by the preform.
[0061] Step four: Evenly spray the second treatment liquid onto the surface of the blank treated in step three. After spraying, let it stand for 30 minutes to allow the sprayed liquid to be fully absorbed by the blank.
[0062] Step 5: Place the billet processed in Step 4 into the sintering furnace, and use a vacuum pump to evacuate the furnace until the pressure inside is less than 500 Pa, and then heat it to 200 °C.
[0063] Step six: After reaching 200℃, turn off the vacuum pump and fill the furnace with argon gas for protection. Maintain an argon atmosphere inside the furnace, raise the temperature to 900℃, and hold for 2 hours, then allow it to cool naturally to room temperature.
[0064] Comparative Example 1
[0065] An anti-oxidation coating was prepared on the same preform as in Example 1 using a commercially available silicate anti-oxidation coating liquid. The specific steps included:
[0066] According to the instructions, after brushing the protective coating liquid onto the surface of the billet, place it in a sintering furnace and sinter at 500°C for 4 hours under an argon atmosphere, then allow it to cool naturally to room temperature.
[0067] Comparative Example 2
[0068] An anti-oxidation coating was prepared on the same preform as in Example 1 using a commercially available phosphate anti-oxidation coating solution. The specific steps included:
[0069] According to the instructions, after brushing the protective coating liquid onto the surface of the billet, place it in the sintering furnace and sinter at 630℃ for 2 hours under an argon atmosphere, then allow it to cool naturally to room temperature.
[0070] Comparative Example 3
[0071] The same preform as in Example 1 was used directly, without an anti-oxidation coating.
[0072] Test case
[0073] Weigh and record the mass of the sintered green bodies obtained in Example 1 and Comparative Examples 1-2, as well as the mass of the green body without anti-oxidation coating in Comparative Example 3.
[0074] The four samples were then placed in a muffle furnace and sintered at 700°C for 8 hours to conduct an antioxidant test. After sintering, the samples were allowed to cool naturally to room temperature.
[0075] Weigh the samples again and calculate the residual weight percentage.
[0076] The morphologies of the samples in Example 1 and Comparative Examples 1-2 after antioxidant tests are as follows: Figure 1-3 As shown.
[0077] As can be seen from the figure, the sample of Example 1 remained unchanged after the anti-oxidation test, without disintegration or powdering, and maintained high strength. The residual weight rate, calculated based on the sample mass before and after the anti-oxidation test, was 98.16%, indicating that the anti-oxidation coating was highly effective and significantly superior to Comparative Examples 1-2.
[0078] The sample in Comparative Example 1 showed significant powdering and brittleness after the antioxidant test, with obvious shape changes and the substrate losing its strength. The calculated residual weight rate was 46%, indicating that the coating reacted with the substrate, resulting in a loss of protective effect.
[0079] The sample in Comparative Example 2 was severely oxidized after the anti-oxidation test, almost disappearing completely and leaving huge void defects. The calculated residual weight was 73%, indicating poor compositional uniformity of the coating, resulting in inconsistent protective effects.
[0080] The sample in Comparative Example 3 was completely oxidized and disappeared after the antioxidant test.
[0081] The anti-oxidation coating prepared in Example 1 effectively isolates the substrate from the external environment, effectively protecting the substrate and overcoming the drawbacks of anti-oxidation coating products prepared by existing methods. At the same time, the preparation method is simple and suitable for large-scale industrial production, which can reduce the production difficulty of anti-oxidation coating products.
[0082] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.
Claims
1. A method for preparing an anti-oxidation coating, characterized in that, The preparation method includes: Tetraethyl silicate, tetrabutyl titanate, aluminum isopropoxide, and tributyl borate are dissolved in an organic solvent and mixed evenly to obtain a first treatment solution. The mass ratio of tetraethyl silicate, tetrabutyl titanate, aluminum isopropoxide, and tributyl borate is (6-10):(1-3):(4-6):
1. The organic solvent is ethyl acetoacetate. The first treatment liquid is evenly applied to the surface of the substrate and left to stand until the first treatment liquid is completely absorbed by the substrate to obtain the first substrate, wherein the substrate is a carbon / carbon composite material. The second treatment solution is evenly applied to the surface of the first substrate and left to stand until the second treatment solution is completely absorbed by the first substrate to obtain the second substrate. The second treatment solution is an aqueous solution of ammonium bicarbonate with a mass fraction of 10%, and the ammonium bicarbonate is of analytical grade or higher. The second substrate is placed in a sintering furnace, and a protective gas is introduced into the sintering furnace to maintain the protective gas atmosphere. The temperature is raised to 850~950℃ for sintering. After natural cooling, the anti-oxidation coating is obtained.
2. The preparation method according to claim 1, characterized in that, The protective gas is one or a mixture of helium, neon, argon, krypton, and xenon.
3. The preparation method according to claim 1, characterized in that, The second substrate is placed in a sintering furnace, which is then filled with a protective gas. The protective gas atmosphere is maintained, and the temperature is raised to 850-950°C for sintering, including: The second substrate is placed in a sintering furnace, a vacuum is drawn, and the temperature is raised to 180~220℃. Then, a protective gas is introduced into the sintering furnace, and the protective gas atmosphere is maintained. The temperature is raised to 850~950℃ for sintering.
4. The preparation method according to claim 1, characterized in that, The first treatment liquid is uniformly applied to the surface of the substrate, including: uniformly spraying the first treatment liquid onto the surface of the substrate, or immersing the substrate in the first treatment liquid. The second treatment liquid is uniformly applied to the surface of the first substrate, including: uniformly spraying the second treatment liquid onto the surface of the first substrate, or immersing the first substrate in the second treatment liquid.