Flexible SiC composite film with in-situ pressure monitoring function and preparation method thereof

Abstract

The invention discloses a flexible SiC composite film with an in-situ pressure monitoring function and a preparation method thereof, and belongs to the technical field of flexible composite films. The invention discloses a flexible SiC composite film with an in-situ pressure monitoring function. The flexible SiC composite film comprises a flexible SiC piezoelectric layer, an electroluminescent layer and a temperature-resistant packaging layer which are arranged in sequence, the flexible SiC piezoelectric layer is formed by compounding SiC particles and a polymer matrix; the electroluminescent layer is filled with a luminescent material; and the temperature-resistant packaging layer comprises a modified polytetrafluoroethylene layer and a SiO2 aerogel layer connected with the electroluminescent layer. According to the composite film, the piezoelectric layer formed by compounding SiC particles and a high-temperature polymer matrix is adopted, a double-layer temperature-resistant packaging structure composed of SiO2 aerogel and modified polytetrafluoroethylene is combined, and the composite film can stably work in a medium-high temperature environment to a certain degree, has excellent flexibility and can be pasted on the surface of a complex curved surface structural part in a shape follow-up mode.

Description

Technical Field

[0001] The invention relates to the technical field of flexible composite films, and in particular to a flexible SiC composite film with an in-situ pressure monitoring function and a preparation method thereof. Background Art

[0002] Most existing pressure sensors are based on the principles of resistance strain, capacitance or piezoelectricity, and rely on wire connections or embedded electrodes to transmit electrical signals. They have significant limitations in high temperature, strong vibration or complex curved surface applications. For example, although traditional piezoelectric ceramic sensors (such as PZT) are highly sensitive, they are brittle and have poor flexibility, making it difficult to fit curved surface structures, and are prone to depolarization at high temperatures; while metal strain gauges can adapt to a certain temperature range, they require complex wiring and are susceptible to electromagnetic interference. In recent years, flexible sensor technology has gradually developed, but its temperature resistance is generally insufficient. Some studies have attempted to improve temperature resistance through packaging materials, but a single packaging layer is difficult to take into account both thermal insulation and mechanical protection functions, and the increased surface roughness at high temperatures can easily introduce noise. Summary of the invention

[0003] The object of the present invention is to provide a flexible SiC composite film with in-situ pressure monitoring function and a preparation method thereof, so as to solve the technical problems of complex wiring and insufficient temperature resistance of pressure sensors in the prior art.

[0004] To achieve the above object, in one embodiment of the present invention, there is provided a flexible SiC composite film with an in-situ pressure monitoring function, comprising a flexible SiC piezoelectric layer, an electroluminescent layer and a temperature-resistant packaging layer arranged in sequence; The flexible SiC piezoelectric layer is made of SiC particles and a polymer matrix; The electroluminescent layer is filled with a light-emitting material; The heat-resistant packaging layer comprises a modified polytetrafluoroethylene layer and a SiO2 aerogel layer connected with the electroluminescent layer.

[0005] In one preferred embodiment of the present invention, the thickness of the flexible SiC piezoelectric layer is 80 μm-150 μm, and the piezoelectric coefficient d 33 It is 15pC / N-25pC / N.

[0006] In one of the preferred solutions of the present invention, the mass ratio of SiC particles to polymer matrix is ​​5:5-7:3, and the particle size of SiC particles is 50nm-200nm.

[0007] In one of the preferred embodiments of the present invention, the polymer matrix includes any one of polysilazane, polyimide and polyetheretherketone.

[0008] In one of the preferred embodiments of the present invention, the thickness of the electroluminescent layer is 20 μm-50 μm.

[0009] In one of the preferred solutions of the present invention, the luminescent material is copper-doped zinc sulfide or chromium-doped yttrium aluminum garnet.

[0010] In one of the preferred solutions of the present invention, the particle size of copper-doped zinc sulfide is 1 μm-3 μm, and the particle size of chromium-doped yttrium aluminum garnet is 3 μm-5 μm.

[0011] In one of the preferred solutions of the present invention, the thickness of the SiO2 aerogel layer is 40 μm-100 μm, and the thermal conductivity is lower than 0.02 W / (m·K).

[0012] The present invention also discloses a method for preparing a flexible SiC composite film with an in-situ pressure monitoring function, comprising the following steps: The SiC particles and the polymer matrix prepolymer are composited to prepare a flexible SiC piezoelectric layer; depositing an electroluminescent layer on the flexible SiC piezoelectric layer; A temperature-resistant encapsulation layer is sprayed on the electroluminescent layer to obtain a flexible SiC composite film with an in-situ pressure monitoring function; The electroluminescent layer is prepared by mixing a luminescent material, silica gel and a scattering agent, and the temperature-resistant packaging layer comprises a SiO2 aerogel layer and a modified polytetrafluoroethylene layer.

[0013] One of the preferred solutions of the present invention is to prepare a flexible SiC piezoelectric layer by compounding SiC particles and a polymer matrix prepolymer, comprising: Mixing SiC particles, a polymer matrix prepolymer and a solvent to obtain a slurry; Applying the slurry on a substrate for step curing; The step-cured film is then polarized to obtain a flexible SiC piezoelectric layer.

[0014] One of the preferred schemes of the present invention is to mix SiC particles, a polymer matrix prepolymer and a solvent to obtain a slurry, including: calculating the mass of the polymer prepolymer according to the mass ratio of the SiC particles and the polymer matrix, adding a solvent to the SiC particles and the polymer prepolymer to adjust the solid content of the material to 25%-45%, and dispersing to obtain a slurry.

[0015] In one of the preferred embodiments of the present invention, the polymer matrix prepolymer includes any one of polysilazane prepolymer, polyimide prepolymer and polyetheretherketone prepolymer, and the solvent includes any one of nitrogen methyl pyrrolidone, xylene, acetone, hexane and cyclohexane.

[0016] One of the preferred schemes of the present invention is to coat the slurry on the substrate for step curing, including: coating the slurry on the substrate by tape casting, with a wet film thickness of 150μm-300μm, preheating at 110℃-130℃ for 0.5h-1.5h after coating, and heating to 200℃-250℃ and maintaining for 1h-2h after preheating.

[0017] One of the preferred schemes of the present invention is that the thin film after step curing is subjected to polarization treatment to obtain a flexible SiC piezoelectric layer, including: applying a DC polarization electric field of 6kV / mm-10kV / mm to the thin film after step curing, and subjecting it to constant temperature polarization treatment at 100℃-120℃ for 0.5h-1.5h to obtain a flexible SiC piezoelectric layer.

[0018] One of the preferred schemes of the present invention is to deposit an electroluminescent layer on a flexible SiC piezoelectric layer, comprising: mixing a luminescent material and silica gel in a mass ratio of 1:2-3, adding a scattering agent in a ratio of 0.5%-1% of the mass of the luminescent material, stirring and mixing to obtain a slurry, depositing the obtained slurry on the surface of the flexible SiC piezoelectric layer, and performing UV curing after the deposition is completed.

[0019] In one of the preferred solutions of the present invention, the luminescent material is copper-doped zinc sulfide or chromium-doped yttrium aluminum garnet, and the scattering agent includes any one of TiO2, SiO2, BaSO4 and CaCO3.

[0020] One of the preferred solutions of the present invention is to spray a temperature-resistant encapsulation layer on the electroluminescent layer to obtain a flexible SiC composite film with an in-situ pressure monitoring function, comprising: Using tetraethyl orthosilicate as a precursor, SiO2 sol is prepared by a sol-gel method, and the prepared sol is dip-coated on the electroluminescent layer, and dried to obtain a SiO2 aerogel layer; The modified polytetrafluoroethylene suspension is sprayed onto the surface of the SiO2 aerogel layer, and a flexible SiC composite film with an in-situ pressure monitoring function is obtained after drying and heating.

[0021] In summary, the beneficial effects of the present invention are: 1. The flexible SiC composite film with in-situ pressure monitoring function of the present invention forms a flexible SiC piezoelectric layer by compounding nano-SiC particles with a high-temperature polymer matrix. It generates charges under pressure and stimulates the luminescent material in the adjacent electroluminescent layer to emit light. The light intensity distribution directly reflects the pressure. It is further combined with a double-layer heat-resistant packaging layer structure composed of SiO2 aerogel and modified polytetrafluoroethylene to block heat flow and reduce surface roughness, ensuring stability and anti-interference ability in high-temperature environments, and solving the problems of complex wiring and insufficient temperature resistance of traditional sensors.

[0022] 2. The electroluminescent layer of the flexible SiC composite film with in-situ pressure monitoring function of the present invention selects ZnS:Cu (copper-doped zinc sulfide) or YAG:Cr (chromium-doped yttrium aluminum garnet) material according to the operating temperature, and combines TiO2 scattering agent to improve luminescence uniformity.

[0023] 3. The flexible SiC composite film with in-situ pressure monitoring function of the present invention integrates a flexible SiC piezoelectric layer, an electroluminescent layer and a temperature-resistant packaging layer into one. By combining the piezoelectric effect with the electroluminescent technology, it can realize in-situ pressure monitoring in a high-temperature environment. It also has excellent flexibility and can be adhered to the surface of complex curved structural parts. It is suitable for real-time pressure monitoring in medium, high temperature and high pressure scenarios such as aerospace and industrial equipment.

[0024] 4. The high temperature and anti-interference ability of the flexible SiC composite film with in-situ pressure monitoring function of the present invention is achieved through a double-layer temperature-resistant packaging structure composed of SiO2 aerogel and modified polytetrafluoroethylene, so that the film can work stably for a long time at a high temperature of 400°C, and has low surface roughness, which effectively reduces the noise caused by airflow disturbance and significantly improves the monitoring accuracy under high temperature and high pressure environment.

[0025] 5. The flexible SiC composite film with in-situ pressure monitoring function of the present invention utilizes the piezoelectric effect to directly convert the pressure signal into a light intensity distribution density signal, thereby realizing wireless optical signal output without the need for wires or electrode connections, thus simplifying the complex wiring problems of traditional sensors and avoiding the influence of electromagnetic interference on signal transmission.

[0026] 6. The flexible SiC composite film with in-situ pressure monitoring function of the present invention has high flexibility through the composite design of the flexible SiC piezoelectric layer and the high-temperature resistant polymer matrix, which can closely fit complex curved structures (such as aircraft engine blades), thereby expanding its application scenarios on curved components.

[0027] 7. The flexible SiC composite film with in-situ pressure monitoring function of the present invention realizes sensitive detection of tiny pressures through the piezoelectric properties of nano-SiC particles combined with the uniform scattering of electroluminescent materials, and provides real-time feedback through changes in light intensity to meet dynamic monitoring needs.

[0028] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by implementing the present invention. The purpose and other advantages of the present invention can be described by the effects described in the description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of a flexible SiC composite film with in-situ pressure monitoring function in an embodiment of the present invention; Figure 2 Schematic diagram of the structure of a flexible SiC composite film with in-situ pressure monitoring function in an embodiment of the present invention; Figure 3 The flowchart is a method for preparing a flexible SiC composite film with an in-situ pressure monitoring function in an embodiment of the present invention.

[0030] Among them, 1-flexible SiC piezoelectric layer, 2-electroluminescent layer, 3-heat-resistant packaging layer, 4-SiO2 aerogel layer, 5-modified polytetrafluoroethylene layer. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0033] like Figure 1 As shown, the present invention discloses a flexible SiC composite film with in-situ pressure monitoring function, such as Figure 2 As shown, it comprises a flexible SiC piezoelectric layer 1, an electroluminescent layer 2 and a temperature-resistant packaging layer 3 arranged in sequence, wherein the thickness of the flexible SiC piezoelectric layer 1 is 80 μm-150 μm, and the piezoelectric coefficient d 33 is 15pC / N-25pC / N, and the thickness of the electroluminescent layer 2 is 20μm-50μm; The flexible SiC piezoelectric layer 1 is composited with SiC particles and a polymer matrix, and the mass ratio of SiC particles to the polymer matrix is ​​5:5-7:3; wherein the SiC particles are nano-SiC particles with a particle size of 50nm-200nm, and the polymer matrix is ​​a high-temperature resistant polymer matrix, which is a polymer material having certain high-temperature resistance and being able to maintain flexibility at an appropriate high temperature, including any one of polysilazane, polyimide and polyetheretherketone; The general formula of polysilazane is [-Si(CH3)2-NH-] n or [-Si(CH2=CH)2-NH-] n, Companies that sell organic polysilazanes on the market include Hangzhou Qingci New Material Technology Co., Ltd. (product models: vinyl polysilazane TC-P11, methyl polysilazane TC-P01A, TC-L11, TC-P05, etc.), Merck KGaA, Germany (product models: Durazane® 1000 series, etc.); The electroluminescent layer 2 is filled with a luminescent material, which is selected according to the target temperature. The luminescent material is copper-doped zinc sulfide (ZnS:Cu) or chromium-doped yttrium aluminum garnet (YAG:Cr). The particle size of copper-doped zinc sulfide is 1 μm-3 μm, and the particle size of chromium-doped yttrium aluminum garnet is 3 μm-5 μm. The heat-resistant packaging layer 3 includes a modified polytetrafluoroethylene layer 5 and a SiO2 aerogel layer 4 connected to the electroluminescent layer 2. The thickness of the SiO2 aerogel layer 4 is 40 μm-100 μm, and the thermal conductivity is lower than 0.02 W / (m·K). The SiO2 aerogel layer 4 can block the influence of high-temperature heat flow on the internal functional layer. The modified polytetrafluoroethylene layer 5 can still maintain a surface roughness of less than 0.5 μm after being continuously heated at 400° C. for 10 hours, thereby avoiding additional noise caused by airflow disturbance.

[0034] The flexible SiC composite film with in-situ pressure monitoring function of the present invention integrates a flexible SiC piezoelectric layer 1, an electroluminescent layer 2 and a heat-resistant packaging layer 3 into one. The flexible SiC piezoelectric layer 1 is formed by compounding nano-SiC particles with a high-temperature polymer matrix. Charges are generated under pressure to stimulate the luminescent material in the adjacent electroluminescent layer 2 to emit light. The light intensity distribution directly reflects the pressure. The double-layer heat-resistant packaging layer 3 structure composed of SiO2 aerogel and modified polytetrafluoroethylene is further combined to block heat flow and reduce surface roughness, thereby ensuring stability and anti-interference ability in high-temperature environments.

[0035] The present invention also discloses a method for preparing a flexible SiC composite film with an in-situ pressure monitoring function, such as Figure 3 As shown, the following steps are included: Step (1): preparing a flexible SiC piezoelectric layer 1 by compounding SiC particles and a polymer matrix prepolymer; Step (2): depositing an electroluminescent layer 2 on the flexible SiC piezoelectric layer 1; Step (3): spraying a temperature-resistant encapsulation layer 3 on the electroluminescent layer 2 to obtain a flexible SiC composite film with an in-situ pressure monitoring function; The electroluminescent layer 2 is prepared by mixing a luminescent material, silica gel and a scattering agent, and the temperature-resistant encapsulation layer 3 includes a SiO2 aerogel layer 4 and a modified polytetrafluoroethylene layer 5, wherein the silica gel is a high-temperature resistant silica gel; Wherein, step (1) of preparing a flexible SiC piezoelectric layer 1 by compounding SiC particles and a polymer matrix prepolymer comprises: Step (101): mixing SiC particles, a polymer matrix prepolymer and a solvent to obtain a slurry; specifically, the mass of the polymer prepolymer is calculated according to a mass ratio of SiC particles to polymer matrix of 5:5-7:3, nano SiC particles with a particle size of 50nm-200nm and the polymer matrix prepolymer are mixed, and after mixing, a solvent is added to adjust the solid content of the material to 25%-40%, and then the material is treated in an ultrasonic disperser at a power of 500W for 30 minutes to obtain a uniformly dispersed slurry, wherein the polymer matrix prepolymer includes any one of polysilazane prepolymer, polyimide prepolymer and polyetheretherketone prepolymer, and the polysilazane prepolymer is a type of inorganic or organic-inorganic hybrid polymer with Si-N bonds as the main chain, which is in an intermediate state of incomplete cross-linking and can be further cured or cracked to form functional materials such as ceramics and coatings; wherein the solvent includes any one of nitrogen methyl pyrrolidone, xylene, acetone, hexane and cyclohexane; Step (102): coating the slurry on a substrate for step curing; specifically, coating the slurry obtained in step (101) on a glass substrate with a surface treated with silane by a tape casting process, with a wet film thickness of 150 μm-300 μm, and then transferring to a vacuum drying oven for step curing, wherein the step curing is as follows: first preheating at 110° C.-130° C. for 0.5 h-1.5 h to volatilize the solvent, and then heating to 200° C.-250° C. and maintaining for 1 h-2 h to complete polymer cross-linking; Step (103): The step-cured thin film is subjected to polarization treatment to obtain a flexible SiC piezoelectric layer 1; specifically, the thin film cured in step (102) is subjected to a DC polarization electric field of 6 kV / mm-10 kV / mm in a silicone oil bath, and is subjected to constant temperature polarization treatment at 100°C-120°C for 0.5h-1.5h, so that the internal polarization direction of the SiC particles is oriented along the direction of the external electric field, and finally a flexible SiC piezoelectric layer 1 with a thickness of 80 μm-150 μm and a piezoelectric coefficient d 33 A flexible SiC piezoelectric layer 1 of 15pC / N-25pC / N; Step (2) depositing an electroluminescent layer 2 on the flexible SiC piezoelectric layer 1 comprises: selecting a luminescent material according to a target operating temperature: for application scenarios below 400°C, copper-doped zinc sulfide (ZnS:Cu) powder with a particle size of 1 μm-3 μm is used; for high-temperature conditions above 400°C, chromium-doped yttrium aluminum garnet (YAG:Cr) powder with a particle size of 3 μm-5 μm is used; The luminescent material and silica gel are mixed in a mass ratio of 1:2-3, and a scattering agent is added according to 0.5wt%-1wt% of the mass of the luminescent material. After mixing for 10min-20min at a planetary mixer with a speed of 1500r / min-2000r / min, a uniform slurry is formed. The slurry is uniformly deposited on the surface of the flexible SiC piezoelectric layer 1 by an electrostatic spraying process at a spraying voltage of 25kV-40kV and a substrate temperature of 70℃-90℃. The single spraying thickness is controlled to be about 10μm, and the spraying is repeated 2 to 5 times. The total thickness is controlled to reach 20μm-50μm as needed, and then UV curing is performed in a nitrogen atmosphere with a wavelength of 365nm and an intensity of 50mW / cm 2 -60mW / cm 2 The silica gel is irradiated with an ultraviolet light source for 5 minutes to 8 minutes to crosslink and solidify; wherein the scattering agent includes any one of TiO2, SiO2, BaSO4 and CaCO3; Step (3) spraying a heat-resistant encapsulation layer 3 on the electroluminescent layer 2 to obtain a flexible SiC composite film with an in-situ pressure monitoring function, comprising: Step (301): using tetraethyl orthosilicate as a precursor, preparing SiO2 sol by a sol-gel method, and dip-coating the prepared sol on the electroluminescent layer, and drying to obtain a SiO2 aerogel layer; specifically: preparing a SiO2 precursor solution by a sol-gel method, using tetraethyl orthosilicate as a silicon source and ethanol as a solvent, the volume ratio of the two being 1:5-1:10, adding hydrochloric acid with a volume concentration of 0.01M-0.1M as a catalyst to promote a hydrolysis reaction to form a sol, forming a film on the surface of the electroluminescent layer 2 by a dip-coating method, and completing the transformation of the gel into the SiO2 aerogel by an ultraviolet-assisted low-temperature heat treatment process, while avoiding thermal damage to the SiC piezoelectric layer and the electroluminescent layer 2 during the preparation process, to obtain a SiO2 aerogel layer 4; Step (302): spraying the modified polytetrafluoroethylene suspension onto the surface of the SiO2 aerogel layer 4, and obtaining a flexible SiC composite film with an in-situ pressure monitoring function after drying and heating; specifically, spraying a polytetrafluoroethylene suspension with a solid content of 20%-30% (adding 15wt% of Fe3O4 to modify the polytetrafluoroethylene for temperature resistance) onto the surface of the SiO2 aerogel layer 4 by a spraying process, using an air pressure spraying method with a spraying pressure of 0.4MPa-0.7MPa, a spraying distance of about 20cm, and drying for 10min-15min under ventilation conditions after spraying to completely evaporate the solvent, and then heating in a muffle furnace at 200℃-250℃ for 15min-30min to form a dense composite layer and cooling with the furnace to obtain a flexible SiC composite film with an in-situ pressure monitoring function; preferably, the pressure needs to be gradually reduced during the spraying of the polytetrafluoroethylene suspension to optimize the uniformity of the coating.

[0036] Example 1: Aircraft engine blade surface pressure monitoring Step 1: Preparation of flexible SiC piezoelectric layer 1 SiC nanoparticles with a particle size of 100 nm were mixed with polysilazane prepolymer at a ratio of 7:3, and nitrogen methyl pyrrolidone was added to adjust the solid content to 30%. After ultrasonic dispersion, the film was cast to a wet film thickness of 200 μm. After preheating at 120°C for 1 h and cross-linking and curing at 250°C for 2 h, a polarizing electric field of 8 kV / mm was applied in a silicone oil bath at 100°C to obtain a piezoelectric film with a thickness of 100 μm. Step 2: Deposition of electroluminescent layer 2 YAG:Cr powder (particle size 4μm) was selected and mixed with high temperature resistant silica gel at a ratio of 1:3, 0.5wt% TiO2 was added, and then electrostatically sprayed on the surface of the piezoelectric layer at a spraying voltage of 30kV, a substrate temperature of 80℃, and a total thickness of 40μm. After UV curing, a uniform luminous layer was formed; Step 3: Packaging A 50 μm thick SiO2 aerogel was prepared on the surface of the light-emitting layer by a sol-gel method, and then a modified polytetrafluoroethylene coating was sprayed and heated at 250°C for 20 min to form a dense outer layer.

[0037] The film is attached to the surface of an aircraft engine blade. After airflow is applied to the blade to generate pressure, the light intensity of the luminous layer increases with the pressure. The light signal is collected by external optical equipment to achieve in-situ monitoring of the dynamic pressure of the blade.

[0038] Example 2: Monitoring of air flow pressure distribution on a car body Step 1: Flexible SiC piezoelectric layer preparation SiC nanoparticles with a particle size of 150 nm were mixed with polyimide prepolymer in a mass ratio of 6:4, and xylene was used as a solvent to adjust the solid content to 35%. The wet film thickness after tape casting was 250 μm. After preheating at 110 ° C for 1 h and cross-linking and curing at 250 ° C for 2 h, the film piezoelectric coefficient d was finally obtained using a polarization electric field strength of 10 kV / mm. 33 22pC / N; Step 2: Preparation of electroluminescent layer YAG:Cr powder (particle size 5μm) was selected and mixed with high temperature resistant silica gel in a mass ratio of 1:2, and 0.8wt% TiO2 scattering agent was added. Then, it was electrostatically sprayed on the surface of the piezoelectric layer. The spraying voltage was 35kV, the substrate temperature was 80℃, and the total thickness was 50μm. After UV curing, a uniform luminous layer was obtained. Step 3: Preparation of heat-resistant encapsulation layer A 40 μm thick SiO2 aerogel was prepared on the surface of the light-emitting layer by a sol-gel method, and then a modified polytetrafluoroethylene coating was sprayed and heated at 250°C for 25 min to form a dense outer layer.

[0039] The film is attached to the complex curved surfaces of the car body (such as the arc of the door and the edges of the hood) to monitor the airflow pressure distribution in real time during the aerodynamic analysis of the car body shape, achieving no-blind-angle monitoring. The applicable temperature range is from room temperature to 200°C.

[0040] Comparative example: Single-layer heat-resistant packaging without SiO2 aerogel Step 1: Flexible SiC piezoelectric layer preparation The parameters are the same as those in Example 2, and the piezoelectric coefficient d 33 21pC / N; Step 2: Preparation of electroluminescent layer The parameters are the same as those in Example 2; Step 3: Encapsulation layer preparation Only a single layer of modified polytetrafluoroethylene coating was used without adding a SiO2 aerogel layer. The surface roughness of the polytetrafluoroethylene coating was 0.8 μm after being heated at 250°C.

[0041] The composite films prepared in Example 2 and the comparative example were tested for surface roughness, thermal conductivity, maximum temperature rise inside the film under the same airflow conditions, and luminescence response stability. The test results are shown in Table 1: Table 1: Test results of composite films prepared in Example 2 and Comparative Example

[0042] It can be seen from Table 1 that the temperature-resistant packaging layer in the comparative example does not include the SiO2 aerogel layer, resulting in a significant increase in the surface roughness of the film. Due to the lack of the heat insulation effect of the SiO2 aerogel layer, the thermal conductivity increases. Under the same airflow conditions, the maximum temperature rise on the inner side of the film increases by 115°C, which is not conducive to the high-temperature and long-term operation of the film. At the same time, it significantly affects the stability of the luminous signal, causing the light intensity signal fluctuation to increase from 5% to 30%, affecting the determination of the effective signal.

[0043] In summary, the flexible SiC composite film with in-situ pressure monitoring function of the present invention can work stably in a medium to high temperature environment to a certain extent, and has excellent flexibility. It can be adhered to the surface of complex curved structural parts in a conformal manner, and is suitable for real-time pressure monitoring in medium to high temperature and high pressure scenarios such as aerospace and industrial equipment.

[0044] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering and technical personnel in the field should all fall within the protection scope of the claims of the present invention.

Claims

1. A flexible SiC composite film with in-situ pressure monitoring function, characterized in that: It includes a flexible SiC piezoelectric layer, an electroluminescent layer and a temperature-resistant packaging layer arranged in sequence; The flexible SiC piezoelectric layer is composited with SiC particles and a polymer matrix; The electroluminescent layer is filled with a luminescent material; The temperature-resistant packaging layer comprises a modified polytetrafluoroethylene layer and a SiO2 aerogel layer connected to the electroluminescent layer.

2. The flexible SiC composite film with in-situ pressure monitoring function according to claim 1, characterized in that: The thickness of the flexible SiC piezoelectric layer is 80 μm-150 μm, and the piezoelectric coefficient d 33 It is 15pC / N-25pC / N.

3. The flexible SiC composite film with in-situ pressure monitoring function according to claim 1 or 2, characterized in that: The mass ratio of the SiC particles to the polymer matrix is ​​5:5-7:3, and the particle size of the SiC particles is 50nm-200nm.

4. The flexible SiC composite film with in-situ pressure monitoring function according to claim 3, characterized in that: The polymer matrix includes any one of polysilazane, polyimide and polyetheretherketone.

5. The flexible SiC composite film with in-situ pressure monitoring function according to claim 1, characterized in that: The thickness of the electroluminescent layer is 20 μm-50 μm.

6. The flexible SiC composite film with in-situ pressure monitoring function according to claim 1, characterized in that: The luminescent material is copper-doped zinc sulfide or chromium-doped yttrium aluminum garnet.

7. The flexible SiC composite film with in-situ pressure monitoring function according to claim 6, characterized in that: The particle size of the copper-doped zinc sulfide is 1 μm-3 μm, and the particle size of the chromium-doped yttrium aluminum garnet is 3 μm-5 μm.

8. The flexible SiC composite film with in-situ pressure monitoring function according to claim 1, characterized in that: The thickness of the SiO2 aerogel layer is 40 μm-100 μm, and the thermal conductivity is lower than 0.02 W / (m·K).

9. A method for preparing a flexible SiC composite film with in-situ pressure monitoring function, characterized in that: The following steps are involved: The SiC particles and the polymer matrix prepolymer are composited to prepare a flexible SiC piezoelectric layer; depositing an electroluminescent layer on the flexible SiC piezoelectric layer; A temperature-resistant encapsulation layer is sprayed on the electroluminescent layer to obtain a flexible SiC composite film with an in-situ pressure monitoring function; The electroluminescent layer is prepared by mixing a luminescent material, silica gel and a scattering agent, and the temperature-resistant packaging layer comprises a SiO2 aerogel layer and a modified polytetrafluoroethylene layer.

10. The method for preparing a flexible SiC composite film with in-situ pressure monitoring function according to claim 9, characterized in that: The method of preparing a flexible SiC piezoelectric layer by compounding SiC particles and a polymer matrix prepolymer comprises: Mixing SiC particles, a polymer matrix prepolymer and a solvent to obtain a slurry; Applying the slurry on a substrate for step curing; The step-cured film is then polarized to obtain a flexible SiC piezoelectric layer.

11. The method for preparing a flexible SiC composite film with in-situ pressure monitoring function according to claim 10, characterized in that: The SiC particles, the polymer matrix prepolymer and the solvent are mixed to obtain a slurry, including: calculating the mass of the polymer prepolymer according to the mass ratio of the SiC particles and the polymer matrix, adding the solvent after mixing the SiC particles and the polymer prepolymer to adjust the solid content of the material to 25%-45%, and dispersing to obtain the slurry.

12. The method for preparing a flexible SiC composite film with in-situ pressure monitoring function according to any one of claims 10 or 11, characterized in that: The polymer matrix prepolymer includes any one of polysilazane prepolymer, polyimide prepolymer and polyetheretherketone prepolymer, and the solvent includes any one of nitrogen methyl pyrrolidone, xylene, acetone, hexane and cyclohexane.

13. The method for preparing a flexible SiC composite film with in-situ pressure monitoring function according to claim 10, characterized in that: The step curing of coating the slurry on the substrate includes: coating the slurry on the substrate by tape casting, with a wet film thickness of 150 μm-300 μm, preheating at 110° C.-130° C. for 0.5 h-1.5 h after coating, and heating to 200° C.-250° C. and maintaining for 1 h-2 h after preheating.

14. The method for preparing a flexible SiC composite film with an in-situ pressure monitoring function according to claim 10, characterized in that: The step-cured film is subjected to polarization treatment to obtain a flexible SiC piezoelectric layer, including: applying a DC polarization electric field of 6kV / mm-10kV / mm to the step-cured film, and subjecting the film to constant temperature polarization treatment at 100°C-120°C for 0.5h-1.5h to obtain a flexible SiC piezoelectric layer.

15. The method for preparing a flexible SiC composite film with in-situ pressure monitoring function according to claim 9, characterized in that: The method of depositing an electroluminescent layer on the flexible SiC piezoelectric layer comprises: mixing a luminescent material and silica gel at a mass ratio of 1:2-3, adding a scattering agent at 0.5%-1% of the mass of the luminescent material, stirring and mixing to obtain a slurry, depositing the obtained slurry on the surface of the flexible SiC piezoelectric layer, and performing ultraviolet curing after the deposition is completed.

16. The method for preparing a flexible SiC composite film with in-situ pressure monitoring function according to claim 15, characterized in that: The luminescent material is copper-doped zinc sulfide or chromium-doped yttrium aluminum garnet, and the scattering agent includes any one of TiO2, SiO2, BaSO4 and CaCO3.

17. The method for preparing a flexible SiC composite film with an in-situ pressure monitoring function according to claim 9, characterized in that: The method of spraying a temperature-resistant encapsulation layer on the electroluminescent layer to obtain a flexible SiC composite film with an in-situ pressure monitoring function comprises: Using tetraethyl orthosilicate as a precursor, SiO2 sol is prepared by a sol-gel method, and the prepared sol is dip-coated on the electroluminescent layer, and dried to obtain a SiO2 aerogel layer; The modified polytetrafluoroethylene suspension is sprayed onto the surface of the SiO2 aerogel layer, and a flexible SiC composite film with an in-situ pressure monitoring function is obtained after drying and heating.

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