A quartz fiber composite material with a high-temperature resistant coating and its preparation method

Abstract

The present invention provides a quartz fiber composite material with a high-temperature resistant coating and a preparation method thereof, which relates to the technical field of composite materials. Alumina sol and silica sol are mixed and aged according to the mass ratio of mullite to prepare a composite sol; the quartz fiber composite material is immersed in the composite sol for ultrasonic dip coating and then naturally dried, and this process is repeated several times to obtain an intermediate product; the intermediate product is placed in a muffle furnace for heating and sintering to form a high-temperature ceramic coating on the substrate of the quartz fiber composite material; after cooling, a phosphate coating is further coated on the surface of the high-temperature ceramic coating and heated for curing to obtain a quartz fiber composite material with a high-temperature resistant coating. The present invention forms a high-temperature ceramic coating and a phosphate coating on the surface of the quartz fiber composite material to jointly improve the high-temperature resistance of the composite material, and the high-temperature ceramic coating can seal the pores of the quartz fiber composite material to prevent moisture.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and particularly relates to a quartz fiber composite material with a high-temperature resistant coating and a preparation method thereof. Background Art

[0002] Quartz fiber reinforced quartz ceramic composite material (SiO 2f / SiO2) and quartz fiber reinforced nitride composite material (SiO 2f / Nitride), as materials for radome, not only have excellent thermal and mechanical properties, but also have stable wave transmission properties. However, due to the poor airtightness of fiber composite materials, the porosity is generally 20% - 25%, and most of the pores are through holes, so air and water vapor are likely to penetrate into the internal structure. Air can easily cause rapid heat transfer of the structure and local temperature rise, and water vapor will cause an increase in the dielectric constant and the tangent of the dielectric loss angle of the structure material, resulting in an extremely reduced wave transmission performance, which will ultimately greatly affect the use effect of the structure. Therefore, it is particularly important to prepare a high-temperature resistant sealing coating.

[0003] Using flame spraying and CVD process to deposit ceramic coatings are effective means for densifying the surface of porous ceramics. The flame spraying process has a high treatment temperature (≥1800°C), which not only easily causes a decrease in the mechanical properties of SiO 2f / SiO2 composite materials, but also the thickness of the molten layer is difficult to control; depositing ceramic coatings by CVD process not only has a high treatment temperature (≥1200°C) and a long time (≥10h), resulting in a decrease in the mechanical properties of the material, but also easily penetrates into the material interior, causing non-uniform material composition. Dip coating process is a simple, controllable and low-cost coating preparation technology.

[0004] Existing sealing coatings are divided into inorganic coatings and organic coatings. Organic coatings (such as fluororesin, silicone resin and other polymers) have a low temperature resistance (≤500°C). Inorganic coatings generally have a higher temperature resistance, but often crack and peel off due to the mismatch of the thermal expansion coefficients of the coating and the substrate during heat treatment at a higher temperature. Nano-particle inorganic coatings greatly reduce the heat treatment temperature and have better adhesion to the substrate. Phosphate is an inorganic coating material with excellent functions, such as high-temperature oxidation resistance, corrosion resistance, wear resistance, etc., but directly coating with phosphate coating will corrode quartz fiber composite materials. Summary of the Invention

[0005] The object of the present invention is to provide a quartz fiber composite material with a high-temperature resistant coating and a preparation method thereof, forming a high-temperature ceramic coating and a phosphate coating on the surface of the quartz fiber composite material. The high-temperature ceramic coating and the phosphate coating together constitute a coating capable of withstanding high temperatures, improving the high-temperature resistance of the composite material, and the high-temperature ceramic coating can seal the pores of the quartz fiber composite material to prevent moisture.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A preparation method of a quartz fiber composite material with a high-temperature resistant coating, comprising the following steps:

[0008] 1) Mix and age alumina sol and silica sol according to the mass ratio of mullite 3Al2O3·2SiO2 to prepare a composite sol;

[0009] 2) Immerse the quartz fiber composite material in the composite sol for ultrasonic dip coating, and then air dry naturally. Repeat several times to obtain an intermediate product;

[0010] 3) Put the intermediate product into a muffle furnace for heating and sintering to form a high-temperature ceramic coating on the quartz fiber composite material substrate;

[0011] 4) After cooling, continue to coat a layer of phosphate coating on the surface of the high-temperature ceramic coating, and carry out heating and curing to obtain a quartz fiber composite material with a high-temperature resistant coating.

[0012] Preferably, in step 1), tetraethyl orthosilicate is heated in ethanol, and silica sol is obtained after hydrolysis; aluminum nitrate is stirred in deionized water, and aluminum sol is obtained after hydrolysis.

[0013] Preferably, in step 1), when preparing the composite sol, 2 wt% silica sol and boron gangue are additionally added to reduce the final heat treatment temperature of the coating (i.e., the sintering temperature in step 3), so as to facilitate protecting the fibers from being damaged due to excessive heat treatment temperature.

[0014] Preferably, the ultrasonic dip coating in step 2) is carried out for 60 s.

[0015] Preferably, it is repeated 3 to 5 times in step 2).

[0016] Preferably, the heating and sintering temperature in step 3) is 800 - 850 °C, and the heat preservation duration is 20 - 40 min.

[0017] Preferably, the thickness of the high-temperature ceramic coating in step 3) is 30 - 50 μm.

[0018] Preferably, the heating and curing temperature in step 4) is 150 - 250 °C, and the heat preservation duration is 30 min.

[0019] A quartz fiber composite material with a high-temperature resistant coating is prepared by the above method.

[0020] The beneficial effects achieved by the present invention:

[0021] 1. High-temperature resistance: Due to its high melting point and good thermal stability, the high-temperature ceramic coating can maintain the structural stability in high-temperature environments. Quartz fiber itself has excellent high-temperature resistance. Coupled with the high-temperature ceramic coating and phosphate coating, it can provide an additional thermal barrier. The coating can withstand high temperatures without bulging, cracking or delaminating, thus improving the high-temperature resistance of the basic quartz fiber composite material.

[0022] 2. Sealing and moisture-proof: The quartz fiber composite material itself may have pores, which may absorb moisture. The high-temperature ceramic coating has good hole-sealing properties and can prevent the penetration of moisture and other chemical substances. The test results also show that the coating has excellent moisture-proof performance, and the moisture absorption rate is only 1%-3%, improving the corrosion resistance and biological stability of the composite material.

[0023] 3. Strength and adhesion: Both ceramics and quartz have high hardness and strength. Through the composite sol and heat treatment, the coating has good adhesion to the base material. Their combination will produce a stronger composite material that can withstand thermal shock tests without problems.

[0024] 4. Operability and economy: The sol-gel method is relatively simple to operate and low-cost, without special equipment or complex processes, and has relatively high cost-effectiveness, so it has advantages in industrial production.

[0025] 5. Material optimization: Mullite is a material with very good thermal stability, excellent mechanical properties, and high-temperature and corrosion resistance. Adjusting the chemical composition of the sol to meet the mass ratio of mullite helps to further improve the performance of the composite material.

[0026] 6. Reducing the heat treatment temperature: Adding borax as a sintering aid can reduce the sintering temperature of the ceramic coating, which can reduce the thermal damage to quartz fiber and thus improve the overall performance of the composite material.

[0027] 7. Multiple protection: The combined action of the high-temperature ceramic coating and phosphate coating provides a multiple protection mechanism, with both thermal stability and moisture and corrosion protection properties, making the composite material more suitable for complex and harsh environmental conditions.

[0028] 8. Energy conservation and environmental friendliness: Since the coating improves the durability and lifespan of the material, reduces the replacement and maintenance costs of the material, and also helps to reduce resource consumption and waste generation.

[0029] In summary, the method of the present invention has broad application potential, including but not limited to aerospace, high-temperature engineering, energy systems, and any occasion that requires high-temperature and corrosion-resistant materials. Description of the Drawings

[0030] Figure 1It is a flow chart of a preparation method of a ceramic coating material of the present invention.

[0031] Figure 2 It is an SEM photograph of a high-temperature resistant coating on a ceramic fiber composite substrate. Specific embodiments

[0032] To make the technical features and advantages or technical effects in the above technical solutions of the present invention more obvious and understandable, the following will be described in detail in conjunction with the accompanying drawings.

[0033] Example 1

[0034] The preparation process of the quartz fiber composite material with a high-temperature resistant coating is as Figure 1 shown, and specifically includes the following steps:

[0035] 1) Heat tetraethyl orthosilicate in ethanol, and after hydrolysis, obtain silica sol. Stir aluminum nitrate in deionized water, and after hydrolysis, obtain aluminum sol. Mix and age the alumina sol and silica sol according to the mass ratio of mullite 3Al2O3·2SiO2, and additionally add 2wt% silica sol and boron gangue to prepare a composite sol.

[0036] 2) Immerse the quartz fiber composite material in the composite sol and perform ultrasonic dip coating for 60 s, then air dry naturally, and repeat 3 times to obtain an intermediate product.

[0037] 3) Put the intermediate product into a muffle furnace, heat it up to 800 °C and keep it warm for 30 min to form a high-temperature ceramic coating on the quartz fiber composite substrate, with a thickness of 31 μm.

[0038] 4) After cooling, continue to coat a layer of phosphate coating on the surface of the high-temperature ceramic coating, heat it up to 200 °C and cure for 30 min to obtain the quartz fiber composite material with a high-temperature resistant coating.

[0039] Example 2

[0040] The preparation process of the quartz fiber composite material with a high-temperature resistant coating is as Figure 1 shown, and specifically includes the following steps:

[0041] 1) Heat tetraethyl orthosilicate in ethanol, and after hydrolysis, obtain silica sol. Stir aluminum nitrate in deionized water, and after hydrolysis, obtain aluminum sol. Mix and age the alumina sol and silica sol according to the mass ratio of mullite 3Al2O3·2SiO2, and additionally add 2wt% silica sol and boron gangue to prepare a composite sol.

[0042] 2) Immerse the quartz fiber composite material in the composite sol and perform ultrasonic dip coating for 60 s, then air dry naturally, and repeat 4 times to obtain an intermediate product.

[0043] 3) Put the intermediate product into a muffle furnace, heat it up to 850 °C and sinter for 20 min to form a high-temperature ceramic coating on the quartz fiber composite substrate with a thickness of 48 μm.

[0044] 4) After cooling, continue to coat a layer of phosphate coating on the surface of the high-temperature ceramic coating, heat it up to 250 °C and cure for 30 min to obtain a quartz fiber composite material with a high-temperature resistant coating.

[0045] Example 3

[0046] The preparation process of the quartz fiber composite material with a high-temperature resistant coating is as Figure 1 shown, and specifically includes the following steps:

[0047] 1) Heat tetraethyl orthosilicate in ethanol, and obtain silica sol after hydrolysis. Stir aluminum nitrate in deionized water and obtain aluminum sol after hydrolysis. Mix and age the alumina sol and silica sol according to the mass ratio of mullite 3Al2O3·2SiO2, and additionally add 2 wt% silica sol and boron boride to prepare a composite sol.

[0048] 2) Immerse the quartz fiber composite material into the composite sol and perform ultrasonic dip coating for 60 s, then dry it naturally, repeat 5 times to obtain an intermediate product.

[0049] 3) Put the intermediate product into a muffle furnace, heat it up to 820 °C and sinter for 40 min to form a high-temperature ceramic coating on the quartz fiber composite substrate with a thickness of 37 μm.

[0050] 4) After cooling, continue to coat a layer of phosphate coating on the surface of the high-temperature ceramic coating, heat it up to 150 °C and cure for 30 min to obtain a quartz fiber composite material with a high-temperature resistant coating.

[0051] The test results of the quartz fiber composite material with a high-temperature resistant coating prepared in Example 1 are as follows:

[0052] The thickness of the prepared coating is as Figure 2 shown in the SEM photo, the coating is dense and uniform, and it is measured to be about 40 μm.

[0053] Grind the quartz fiber composite material spline to be flat and perform appropriate roughening treatment, then clean and dry it with alcohol to ensure that there is no residue on the surface of the spline. Then use the following simple and efficient method to test the coating sealing effect and the adhesion between the coating and the substrate.

[0054] Test of the coating sealing effect: First, use a magnifying glass to observe whether there are pores or cracks on the surface morphology of the sample strip with the coating. Secondly, drop ink on the surface of the sample strip and observe whether the ink diffuses and smudges to determine the coating sealing effect. The experimental results show that no smudging and diffusion occurred during the placement of the ink drop on the coating surface, indicating that there are no pores and cracks and the sealing effect is good.

[0055] Test of the adhesion between the coating and the substrate: Directly place the sample strip with the coating into a muffle furnace at 1000 °C and keep it for 5 minutes. Take it out and directly put it into an ice-water bath and keep it for 5 minutes. Take it out and observe whether there are bulges or delamination on the surface of the sample strip. Then repeat this process 3 - 5 times and continue to observe the surface phenomenon. The experimental results show that after repeated thermal shock tests, there are no bulges, cracks or delamination on the surface coating of the sample strip, proving that there is good adhesion between the coating and the substrate.

[0056] Moisture-proof test: The moisture absorption rate of the sample piece with the coating is tested according to the standard of GB / T 5480 - 2017. The moisture absorption rate of the sample piece is tested at 50 °C, 96% humidity for 48 hours. The results show that its moisture absorption rate is 1% - 3%, and the moisture-proof effect is good.

[0057] Although the present invention has been disclosed as above with embodiments, it is not intended to limit the present invention. Any appropriate modification or equivalent replacement of the technical solutions of the present invention by those of ordinary skill in the art shall be covered within the protection scope of the present invention. The protection scope of the present invention shall be subject to that defined by the claims.

Claims

1. A preparation method of a quartz fiber composite material with a high-temperature resistant coating, characterized in that, It includes the following steps: 1) Mix and age alumina sol and silica sol according to the mass ratio of mullite 3Al2O3·2SiO2 to prepare a composite sol; 2) Immerse the quartz fiber composite material in the composite sol for ultrasonic dip coating, and then air dry it. Repeat several times to obtain an intermediate product; 3) Put the intermediate product into a muffle furnace for heating and sintering to form a high-temperature ceramic coating on the quartz fiber composite material substrate; 4) After cooling, continue to coat a layer of phosphate coating on the surface of the high-temperature ceramic coating, and carry out heating and curing to obtain a quartz fiber composite material with a high-temperature resistant coating.

2. The method according to claim 1, characterized in that, In step 1), tetraethyl orthosilicate is heated in ethanol, and silica sol is obtained after hydrolysis; aluminum nitrate is stirred in deionized water, and aluminum sol is obtained after hydrolysis.

3. The method according to claim 1, wherein In step 1), when preparing the composite sol, 2wt% silica sol and boron boride are additionally added.

4. The method according to claim 1, characterized in that, In step 2), the ultrasonic dip coating is carried out for 60 s.

5. The method according to claim 1, wherein In step 2), repeat 3 - 5 times.

6. The method according to claim 1, characterized in that In step 3), the temperature for heating and sintering is 800 - 850 °C, and the heat preservation time is 20 - 40 min.

7. The method according to claim 1, wherein In step 3), the thickness of the high-temperature ceramic coating is 30 - 50 μm.

8. The method according to claim 1, characterized in that, In step 4), the temperature for heating and curing is 150 - 250 °C, and the heat preservation time is 30 min.

9. A quartz fiber composite material with a high-temperature resistant coating, characterized in that, Prepared by the method according to any one of claims 1 - 8.

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