A high-temperature resistant stealth composite material and its preparation method

Abstract

This invention relates to a high-temperature resistant stealth composite material and its preparation method. The preparation method includes: mixing a fiber-absorbing agent with chopped quartz fibers in different proportions to form electromagnetic films with different dielectric constants using a wet papermaking process; stacking the prepared electromagnetic films with quartz fiber cloth and quartz mesh, and then needle-punching them to obtain a quartz preform containing the electromagnetic film; pretreating the quartz preform to remove the sizing agent; placing the quartz preform (with the sizing agent removed) into a molding fixture, evacuating it under vacuum for 1-2 hours, adding concentrated silica sol to the fixture, continuing to evacuate under vacuum for 1-2 hours, then applying an external pressure of 2-4 MPa within the fixture, holding the pressure for 6-36 hours, and then heating to cure the silica sol; finally, drying and sintering the cured quartz preform to obtain the high-temperature resistant stealth composite material. The high-temperature resistant stealth composite material prepared by this invention possesses excellent high-temperature mechanical properties while achieving integrated structural stealth.

Description

Technical Field

[0001] This invention belongs to the field of ceramic composite materials technology, specifically relating to a high-temperature resistant stealth composite material and its preparation method. Background Technology

[0002] With the development of radar detection, tracking and identification technologies and the continuous increase in aircraft flight speed, high-temperature resistant stealth composite materials have become an important research direction in the field of aircraft development.

[0003] For magnetic loss materials, demagnetization occurs at high temperatures, leading to a significant decrease in high-temperature absorption performance and rendering them unusable. Therefore, absorbing materials that can effectively operate at high temperatures are generally electrical loss materials. Existing coating-type high-temperature absorbing materials are commonly used absorption methods, but they are limited by thickness constraints and electrical loss mechanisms, resulting in drawbacks such as narrow stealth bandwidth, high weight, large thickness, simple absorption mechanism, low dielectric loss capability, and susceptibility to damage at high temperatures. These shortcomings severely restrict the development of lightweight and convenient stealth absorbing materials. Furthermore, stealth components of aircraft face complex service environments with high temperatures, high strength, and high vibration, placing stringent requirements on the temperature resistance and mechanical properties of components. Therefore, it is necessary to develop a high-temperature resistant stealth composite material with good mechanical properties and broadband absorption to solve these problems. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention adopts a multi-layer absorbing structure design and prepares a high-temperature stealth composite material by embedding absorbing electromagnetic materials in a quartz preform. The ceramic matrix composite material prepared by this method has excellent high-temperature mechanical properties and can achieve integrated structural stealth.

[0005] In a first aspect, the present invention provides a method for preparing a high-temperature resistant stealth composite material, specifically including the following steps:

[0006] Step S1: Prepare an electromagnetic membrane by mixing fiber absorbing agent with short-cut quartz fibers and forming an electromagnetic membrane (absorbing membrane) through a wet papermaking process.

[0007] Step S2: The prepared electromagnetic film is stacked and arranged with quartz fiber cloth and quartz mesh in a certain order, and needle-punched to a certain thickness to prepare a quartz preform containing electromagnetic film.

[0008] Step S3: Remove the wetting agent from the quartz preform;

[0009] Step S4: Place the quartz preform after removing the impregnating agent into the molding fixture, evacuate for 1-2 hours, add concentrated silica sol to the fixture at a controlled rate, continue evacuating for 1-2 hours, then apply an external pressure of 2-4 MPa in the fixture, maintain the pressure for 6-36 hours, and then heat to cure the silica sol.

[0010] Step S5: Remove the cured quartz fiber preform from the tooling, dry and sinter it to obtain a high-temperature resistant stealth composite material.

[0011] Furthermore, it also includes step S6: repeating steps S4 and S5 according to the technical specifications of the required product, and finally obtaining the high-temperature resistant stealth composite material.

[0012] Further, in step S1, the fiber absorbing agent is mixed with short-cut quartz fibers in different proportions to form electromagnetic films with different dielectric constants through a wet papermaking process.

[0013] Furthermore, the fiber absorbent in step S1 can be tungsten (W) chopped fibers coated with silica (SiO2), and the diameter of the W chopped fibers is 10 to 100 μm.

[0014] Furthermore, the layered arrangement in step S2 can be one layer of quartz fiber cloth + one layer of quartz mesh + one layer of electromagnetic film, or two layers of quartz fiber cloth + one layer of quartz mesh + one layer of electromagnetic film. The arrangement method can be adjusted according to the stealth requirements and product thickness, and the density of the preform can be controlled between 0.2 and 0.75 g / cm³. 3 .

[0015] Further, in step S3, the prepared quartz preform is placed in a cleaning fixture, pretreated with water or acetone to remove the wetting agent, and then dried.

[0016] Further, in step S3, the pretreatment method of the preform is to boil the preform in acetone at 60°C for 36-48 hours, then replace it with new acetone and continue boiling for 12-24 hours, and finally air-dry it in an explosion-proof room for 3-4 days; or boil it in ultrapure water at 60°C for 24-96 hours, changing the water every 2-4 hours, and after boiling, the preform is dried by stepwise temperature increase, drying at 40°C, 60°C, 80°C, 100°C and 120°C for 1-3 hours respectively.

[0017] Furthermore, the density of the concentrated silica sol used in step S4 is 1.20–1.38 g / cm³. 3 The particle size of the silica sol should not exceed 200 nm, the viscosity should not exceed 10 mPa / s, the addition rate of the silica sol should be controlled at 0.5 to 3 L / min, the curing temperature should be 50 to 95 ℃, and the curing time should be determined according to the curing temperature. The lower the curing temperature, the shorter the curing time.

[0018] Furthermore, the drying process in step S5 is a stepped drying process, with holding temperatures at 50℃, 80℃, 100℃, 120℃, 150℃, 200℃ and 250℃ for 1 to 3 hours respectively; the highest sintering temperature in the sintering process is 600 to 850℃, and the holding time is not less than 30 minutes and not more than 2 hours.

[0019] Furthermore, the number of repetitions of steps S4 and S5 in step S6 is determined by the product's required technical specifications. Lower density and mechanical property requirements result in fewer repetitions, while higher requirements lead to more repetitions. Generally, the product's density range can be controlled between 0.6 and 1.6 g / cm³. 3 Inside.

[0020] Secondly, the present invention provides a high-temperature resistant stealth composite material prepared by the above method.

[0021] The beneficial effects achieved by this invention are as follows:

[0022] (1) The high-temperature stealth composite material prepared by the present invention can maintain a certain mechanical strength at 1000℃ and can achieve wave absorption stealth of the composite material in the range of 2 to 18 GHz; the fiber absorber in the present invention is tungsten short-cut fiber with silicon dioxide coating. The W fiber has high electrical conductivity and can dissipate electromagnetic wave energy through electrical loss to achieve wave absorption. The silicon dioxide on the outer surface can ensure that the W fiber does not oxidize and lose conductivity at high temperature, thereby achieving high-temperature stealth effect.

[0023] (2) This invention can prepare silica sol with densities ranging from 0.6 to 1.6 g / cm³ by curing silica sol of different concentrations and by multiple composite curing processes. 3 Ceramic matrix composites can achieve a match between the designed performance of ceramic matrix composites and the composite process. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below through specific embodiments.

[0025] Example 1

[0026] Low density 0.75~0.8g / cm³ 3 The preparation method of the high-temperature resistant microwave absorbing plate includes the following steps:

[0027] 1) A microwave absorbing film is made by mixing 10μm tungsten (W) short-cut fibers coated with silicon dioxide (SiO2) with short-cut quartz fibers and then using a wet papermaking process.

[0028] 2) The prepared electromagnetic membrane, quartz fiber cloth, and quartz mesh are arranged in a layered sequence of one layer of quartz fiber cloth + one layer of mesh + one layer of electromagnetic membrane, and then needle-punched to form a size of 350×350×15mm and a density of 0.35g / cm³. 3 Quartz preforms;

[0029] 3) Boil the quartz preform in 60℃ acetone for 36 hours, then replace with new acetone and continue boiling for 12 hours, then air dry in an explosion-proof room for 4 days.

[0030] 4) Place the dried quartz preform into the molding fixture, close the mold, and vacuum for 1 hour to achieve a density of 1.25 g / cm³. 3 The silica sol was injected into the tooling and a pressure of 3.6 MPa was applied and held for 24 hours, followed by curing at 90°C for 96 hours.

[0031] 5) Demolding, drying the quartz plate, and sintering at 800℃ for 1 hour to prepare a high-temperature resistant microwave absorbing plate.

[0032] The density of the prepared plate is 0.74 g / cm³. 3 At 1000℃, its tensile strength is 11.1MPa, normal compressive strength is 74.6MPa, flexural strength is 16.0MPa, and reflectivity is ≤-3dB (2GHz≤frequency≤4GHz) and ≤-5dB (4GHz<frequency≤18GHz), achieving integrated structural wave absorption.

[0033] Example 2

[0034] High density 1.5~1.6g / cm³ 3 The preparation method of the high-temperature resistant microwave absorbing plate includes the following steps:

[0035] 1) 10μm, 20μm and 50μm tungsten (W) short fibers coated with silicon dioxide (SiO2) were mixed with short quartz fibers and three microwave absorbing films with different dielectric constants were made by wet papermaking process.

[0036] 2) The three types of electromagnetic films prepared are arranged with quartz fiber cloth and quartz mesh in a layered sequence of one layer of quartz fiber + one layer of mesh + one layer of electromagnetic film, and then needle-punched to form a size of 350×350×11mm and a density of 0.67g / cm³. 3 Quartz preforms;

[0037] 3) Boil the quartz preform in 60℃ water for 48 hours, changing the water every 2 hours, and then dry it at 40℃, 60℃, 80℃, 100℃ and 120℃ for 2 hours respectively;

[0038] 4) Place the dried quartz preform into the molding fixture, close the mold, and vacuum for 1 hour to achieve a density of 1.36 g / cm³. 3 The silica sol was injected into the tooling and a pressure of 3.6 MPa was applied. The pressure was maintained for 24 hours, and then cured at 80°C for 48 hours.

[0039] 5) Demold, dry the quartz plate, and sinter at 800℃ for 1 hour.

[0040] 6) Repeat steps 4) and 5) three times, using silica sol concentrations of 1.36, 1.32, and 1.30 g / cm³ for the last three times. 3 The curing temperatures were 80℃, 85℃, and 90℃, and the curing times were 48, 60, and 72 hours, respectively. The final product was a quartz composite material plate.

[0041] The density of the prepared plate is 1.52 g / cm³. 3 At 1000℃, its tensile strength is 37.6MPa, normal compressive strength is 179MPa, flexural strength is 25.3MPa, and reflectivity is ≤-5dB (2GHz≤frequency≤4GHz) and ≤-10dB (4GHz<frequency≤18GHz). Under certain mechanical strength, it has good wave absorption performance.

[0042] Example 3

[0043] Density is 1.1–1.15 g / cm³ 3 The method for preparing a high-temperature resistant microwave absorbing plate includes the following steps:

[0044] 1) A microwave absorbing film is made by mixing 20μm tungsten (W) short-cut fibers coated with silicon dioxide (SiO2) with short-cut quartz fibers and then using a wet papermaking process.

[0045] 2) The prepared electromagnetic membrane, quartz cloth layer, and quartz mesh are arranged in a stacking sequence of one layer of quartz fiber cloth + one layer of mesh + one layer of electromagnetic membrane, and then needle-punched to form a size of 350×350×5mm and a density of 0.50g / cm³. 3 Quartz preforms;

[0046] 3) Boil the quartz preform in 60℃ water for 24 hours, changing the water every 2 hours, and then dry it at 40℃, 60℃, 80℃, 100℃ and 120℃ for 2 hours respectively.

[0047] 4) Place the dried quartz preform into the molding fixture, close the mold, and vacuum for 1 hour to achieve a density of 1.25 g / cm³. 3 The silica sol was injected into the tooling and a pressure of 3.6 MPa was applied. The pressure was maintained for 12 hours, and then cured at 90°C for 96 hours.

[0048] 5) Demold, dry the quartz plate, and sinter at 800℃ for 1 hour.

[0049] 6) Repeat steps 4) and 5) once, using a silica sol concentration of 1.36 g / cm³. 3 The curing temperature was 80℃, and the curing time was 48 hours. The final product was a quartz composite material plate.

[0050] The density of the prepared plate is 1.12 g / cm³. 3 At 1000℃, its tensile strength is 26.4MPa, normal compressive strength is 90.5MPa, flexural strength is 18.3MPa, and reflectivity is ≤-3dB (2GHz≤frequency≤4GHz) and ≤-5dB (4GHz<frequency≤18GHz). Under certain mechanical strength, it has good wave absorption performance.

[0051] Example 4

[0052] Its density is 1.2–1.3 g / cm³. 3 The method for preparing a high-temperature resistant microwave absorbing plate includes the following steps:

[0053] 1) 10μm and 20μm tungsten (W) short fibers coated with silicon dioxide (SiO2) were mixed with short quartz fibers and microwave absorbing films with different dielectric constants were made by wet papermaking process.

[0054] 2) The prepared electromagnetic membrane, quartz cloth layer, and quartz mesh are arranged in a stacking sequence of one layer of quartz fiber cloth + one layer of mesh + one layer of electromagnetic membrane, and then needle-punched to form a size of 300×300×12mm and a density of 0.35g / cm³. 3 Quartz preforms;

[0055] 3) Boil the quartz preform in 60℃ water for 24 hours, changing the water every 2 hours, and then dry it at 40℃, 60℃, 80℃, 100℃ and 120℃ for 2 hours respectively.

[0056] 4) Place the dried quartz preform into the molding fixture, close the mold, and vacuum for 1 hour to achieve a density of 1.25 g / cm³. 3 The silica sol was injected into the tooling and a pressure of 3.6 MPa was applied. The pressure was maintained for 12 hours, and then cured at 90°C for 96 hours.

[0057] 5) Demold, dry the quartz plate, and sinter at 800℃ for 1 hour.

[0058] 6) Repeat steps 4) and 5) three times, using the same silica sol concentration and curing process as in steps 4) and 5). The final product is a quartz composite material plate.

[0059] The density of the prepared plate is 1.28 g / cm³. 3 At 1000℃, its tensile strength is 28.3MPa, normal compressive strength is 176MPa, flexural strength is 20.3MPa, and reflectivity is ≤-5dB (2GHz≤frequency≤4GHz) and ≤-8dB (4GHz<frequency≤18GHz). Under certain mechanical strength, it has good wave absorption performance.

[0060] The specific embodiments of the present invention disclosed above are intended to help understand the content of the present invention and to implement it accordingly. Those skilled in the art will understand that various substitutions, changes, and modifications are possible without departing from the spirit and scope of the present invention. The present invention should not be limited to the content disclosed in the embodiments of this specification; the scope of protection of the present invention is defined by the claims.

Claims

1. A method for preparing a high-temperature resistant stealth composite material, characterized in that, Includes the following steps: A fiber absorbing agent is mixed with short-cut quartz fibers and an electromagnetic film is formed by a wet papermaking process; the fiber absorbing agent is tungsten short-cut fibers coated with silica, and the diameter of the tungsten short-cut fibers is 10~100μm. The prepared electromagnetic membrane is stacked with quartz fiber cloth and quartz mesh, and then needle-punched to obtain a quartz preform containing the electromagnetic membrane; the stacked arrangement is one layer of quartz fiber cloth + one layer of quartz mesh + one layer of electromagnetic membrane, or two layers of quartz fiber cloth + one layer of quartz mesh + one layer of electromagnetic membrane. The quartz preform is pretreated to remove the impregnating agent. Place the quartz preform after removing the wetting agent into the molding fixture, vacuum for 1-2 hours, add concentrated silica sol into the fixture, continue vacuuming for 1-2 hours, then apply an external pressure of 2-4 MPa into the fixture, hold the pressure for 6-36 hours, and then heat to cure the silica sol. The solidified quartz preform is dried and sintered to obtain a high-temperature resistant stealth composite material. The high-temperature resistant stealth composite material has wave-absorbing stealth function in the range of 2~18GHz at 1000℃.

2. The method according to claim 1, characterized in that, The process of mixing the fiber absorbing agent with chopped quartz fibers involves mixing the fiber absorbing agent and chopped quartz fibers in different proportions, and then forming electromagnetic films with different dielectric constants through a wet papermaking process.

3. The method according to claim 1, characterized in that, The density of the quartz preform is controlled between 0.2 and 0.75 g / cm³. 3 .

4. The method according to claim 1, characterized in that, The pretreatment of the quartz preform includes: placing the prepared quartz preform into a cleaning fixture, pretreating it with water or acetone to remove the wetting agent, and then drying it.

5. The method according to claim 4, characterized in that, The pretreatment of the quartz preform includes: boiling the preform in acetone at 60°C for 36-48 hours, then replacing with new acetone and continuing to boil for 12-24 hours, and finally air-drying in an explosion-proof room for 3-4 days; or boiling in ultrapure water at 60°C for 24-96 hours, changing the water every 2-4 hours, and then drying the preform by stepwise temperature increase at 40°C, 60°C, 80°C, 100°C and 120°C for 1-3 hours respectively.

6. The method according to claim 1, characterized in that, The density of the concentrated silica sol is 1.20~1.38 g / cm³. 3 The particle size of the silica sol is no greater than 200 nm, the viscosity is no more than 10 mPa / s, the addition rate of the silica sol is controlled at 0.5~3 L / min, and the curing temperature is 50~95℃.

7. The method according to claim 1, characterized in that, The drying process is a stepped drying process, with temperature holding at 50℃, 80℃, 100℃, 120℃, 150℃, 200℃ and 250℃ for 1 to 3 hours respectively; the highest sintering temperature during the sintering process is 600~850℃, and the holding time is not less than 30 minutes and not more than 2 hours.

8. The method according to claim 1, characterized in that, The process involves repeatedly adding silica sol, heating and curing the silica sol, and drying and sintering the cured quartz preform according to the required product specifications to obtain the final high-temperature resistant stealth composite material. The density of the high-temperature resistant stealth composite material is 0.6~1.6 g / cm³. 3 .

9. The high-temperature resistant stealth composite material prepared by the method according to any one of claims 1 to 8.