A curved surface conformal wireless passive thermal flow sensor and its preparation method

Abstract

The present invention proposes a curved conformal wireless passive heat flow sensor and its preparation method, belonging to the field of high-temperature sensor technology. The heat flow sensor comprises a metal wire, a silicon carbide substrate, a sensitive layer, and a thermal resistance layer, arranged in order from bottom to top. The sensitive layer comprises a thermopile, an inductor, a capacitor, and a microstrip antenna, all made of metal using an ink direct writing process. One end of the thermopile is connected to the capacitor, and the microstrip antenna and inductor are connected to the other end of the thermopile. The thermal resistance layer has at least one opening to expose the thermopile's hot junction. The metal wire connects the inductor and capacitor to form a resonant circuit. The heat flow sensor of the present invention is flexible as a whole, capable of adaptively conforming to the surface of curved components, and possesses high-temperature resistance. It achieves wireless passive transmission of heat flow signals and solves the problems of difficult lead wire connection and easy breakage in high-temperature and high-rotation environments.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature sensors, and in particular to a curved surface conformal wireless passive heat flow sensor and a preparation method thereof. Background Art

[0002] Thermal flow testing of high-temperature, high-rotation, and curved components in aerospace, specialty metallurgy, energy, and power generation sectors places higher demands on high-temperature wireless passive thermal flow sensors. Aircraft engine combustion chamber wall temperatures exceed 1200°C, with heat flux densities reaching 3MW / m². Meeting these demands for high-temperature resistance, surface conformality, and wireless passive performance has become a major bottleneck hindering the development of these sectors.

[0003] In recent years, thermal flow sensor technology has made some progress, and types such as silicon-based sensors, flexible sensors and rigid sensors have emerged.

[0004] During the development of this invention, the inventors discovered at least the following issues with existing technologies: Silicon-based sensors fail at temperatures above 300°C due to the failure of the PN junction, making them incapable of high-temperature measurement. While flexible sensors, using materials like PDMS (dimethylsiloxane) and carbon nanotubes, can adapt to curved surfaces, their temperature limits are generally below 600°C, making metal leads susceptible to melting and signal transmission interruption. Rigid sensors struggle to adhere to complex curved surfaces, leading to measurement errors. Furthermore, existing heat flow sensors often rely on wired power and data transmission, making them difficult to operate stably around rotating components. This creates a technical bottleneck for in-situ monitoring of heat flow parameters in applications such as aircraft engines and specialty metallurgical rollers. Summary of the Invention

[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0006] To this end, the purpose of the present invention is to propose a curved conformal wireless passive thermal flow sensor and a preparation method thereof, which can adapt to high temperature and high-speed rotation environments and does not rely on wired power supply.

[0007] To achieve the above-mentioned object, the first aspect of the present invention provides a curved conformal wireless passive heat flow sensor, comprising a metal wire, a silicon carbide substrate, a sensitive layer and a thermal resistance layer arranged in sequence from bottom to top;

[0008] The sensitive layer includes a thermopile, an inductor, a capacitor, and a microstrip antenna, all of which are made of metal using an ink direct writing process. One end of the thermopile is connected to the capacitor, and the microstrip antenna and the inductor are connected to the other end of the thermopile. The thermal resistance layer has at least one opening to expose the hot junction of the thermopile. The metal wire connects the inductor and the capacitor to form a resonant circuit.

[0009] The thermopile is used to generate a voltage signal corresponding to the heat flow temperature; the resonant circuit is used to modulate the voltage signal into a high-frequency signal; and the microstrip antenna is used to transmit the high-frequency signal outward in the form of radio waves.

[0010] According to the beneficial effects of the curved conformal wireless passive thermal flow sensor of the present invention: the curved conformal wireless passive thermal flow sensor of the present invention is prepared based on a flexible silicon carbide substrate, and is combined with a thermopile, inductor, capacitor, microstrip antenna and metal wire made by an ink direct writing process. The thermal flow sensor as a whole is still flexible, can adaptively fit the surface of the curved component, and has high temperature resistance. In addition, the inductor, capacitor and metal wire constitute a resonant circuit, which modulates the thermal flow signal into a high-frequency signal and realizes long-distance transmission through a microstrip antenna without the need for wired power supply, thereby realizing wireless passive transmission of the thermal flow signal and solving the problem of difficult lead wires and easy breakage of leads in high temperature and high rotation environments.

[0011] According to one embodiment of the present invention, the thermopile includes multiple pairs of thermocouples connected end to end, wherein each pair of thermocouples includes a first electrode and a second electrode connected to each other, the first electrode is made of platinum, and the second electrode is made of platinum-rhodium.

[0012] According to one embodiment of the present invention, the cross-section of the silicon carbide substrate is a quadrilateral, the thermopile is arranged around three sides of the silicon carbide substrate, the microstrip antenna is arranged on the remaining side of the silicon carbide substrate, and the thermopile and the microstrip antenna surround the inductor and the capacitor.

[0013] A second aspect of the present invention provides a method for preparing a curved surface conformal wireless passive thermal flow sensor, comprising:

[0014] providing a silicon carbide substrate;

[0015] The first electrode of the thermopile is prepared on the surface of the silicon carbide substrate by an ink direct writing process;

[0016] The second electrode in the thermopile is prepared on the surface of the silicon carbide substrate by an ink direct writing process;

[0017] Resonant circuits and microstrip antennas were fabricated on the surface of silicon carbide substrates using an ink direct writing process.

[0018] A thermal resistance layer is formed on the front surface of the silicon carbide substrate.

[0019] The beneficial effects of the preparation method of the curved conformal wireless passive thermal flow sensor according to the present invention are as follows: the thermal flow sensor is prepared based on a flexible silicon carbide substrate, and is combined with a thermopile, a resonant circuit and a microstrip antenna made by an ink direct writing process. The thermal flow sensor as a whole is still flexible, can adaptively fit the surface of a curved component, and has high temperature resistance. In addition, the resonant circuit can modulate the thermal flow signal into a high-frequency signal and transmit it over long distances through a microstrip antenna without the need for wired power supply, thereby realizing wireless passive transmission of the thermal flow signal and solving the problem of difficult lead wires and easy breakage of leads in high temperature and high rotation environments.

[0020] According to one embodiment of the present invention, providing a silicon carbide substrate includes:

[0021] The silicon carbide substrate was prepared by chemical vapor deposition.

[0022] According to one embodiment of the present invention, preparing the first electrode in the thermopile on the surface of the silicon carbide substrate by the ink direct writing process includes:

[0023] Platinum metal slurry is deposited on the front of the silicon carbide substrate through a nozzle, heated for pre-solidification, and sintered to form a dense platinum metal film. The silicon carbide substrate with platinum metal is annealed to obtain the first electrode of the thermopile.

[0024] According to one embodiment of the present invention, preparing the second electrode in the thermopile on the surface of the silicon carbide substrate by the ink direct writing process includes:

[0025] Platinum-rhodium metal slurry is deposited on the front of the silicon carbide substrate through a nozzle, heated for pre-solidification, and sintered to form a dense platinum-rhodium metal film. The silicon carbide substrate with platinum-rhodium metal is annealed to obtain the second electrode of the thermopile.

[0026] According to one embodiment of the present invention, the preparation of a resonant circuit and a microstrip antenna on the surface of a silicon carbide substrate by an ink direct writing process includes:

[0027] Platinum-rhodium metal slurry is deposited on the front surface of a silicon carbide substrate through a nozzle, pre-cured by heating, and sintered to form a dense platinum-rhodium metal film. The silicon carbide substrate with platinum-rhodium metal is annealed to obtain an inductor, a capacitor, and a microstrip antenna, wherein the capacitor is connected to one end of the thermopile, and the inductor and the microstrip antenna are connected to the other end of the thermopile;

[0028] The silicon carbide substrate in the area where the capacitor and inductor are located is perforated, and platinum-rhodium metal slurry is deposited on the back of the silicon carbide substrate through a nozzle. It is heated for pre-curing and sintered to form a dense platinum-rhodium metal film. The silicon carbide substrate with platinum-rhodium metal is annealed to obtain metal wires. The metal wires are used to connect the capacitor and inductor together through the perforations to form a resonant circuit.

[0029] According to one embodiment of the present invention, the step of forming a thermal resistance layer on the front surface of the silicon carbide substrate includes:

[0030] A pulsed laser deposition process is used to deposit a thermal resistance layer on the front surface of the silicon carbide substrate. The material of the thermal resistance layer is aluminum oxide.

[0031] According to an embodiment of the present invention, the method further includes performing an annealing process, wherein the thermal resistance layer has an opening, and the opening is used to expose the hot junction of the thermopile.

[0032] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference numerals are used throughout the accompanying drawings to denote the same components.

[0034] Figure 1 4 is a cross-sectional schematic diagram of a curved conformal wireless passive thermal flow sensor proposed in one embodiment of the present invention.

[0035] Figure 2 Schematic diagram of the decomposed structure of a curved conformal wireless passive thermal flow sensor proposed in one embodiment of the present invention.

[0036] Figure 3 1 is a front view of a silicon carbide substrate of a curved conformal wireless passive thermal flow sensor according to an embodiment of the present invention.

[0037] Figure 4 yes Figure 3 Schematic diagram of the back.

[0038] Figure 5 The figure is a schematic diagram showing the connection between the sensitive layer and the metal wire of the curved conformal wireless passive heat flow sensor proposed in one embodiment of the present invention.

[0039] Figure 6 Schematic diagram of the principle of a curved surface conformal wireless passive heat flow sensor proposed in one embodiment of the present invention.

[0040] Figure 7 This is a flow chart of a method for preparing a curved conformal wireless passive thermal flow sensor according to an embodiment of the present invention.

[0041] Figure 8 The figure is a schematic diagram of a process flow for preparing a curved conformal wireless passive thermal flow sensor according to an embodiment of the present invention.

[0042] Figure 9This is a graph showing the temperature resistance limit test results of a curved conformal wireless passive heat flux sensor according to an embodiment of the present invention.

[0043] Figure 10 1 is a graph showing the heat flow and output voltage test results of a curved conformal wireless passive heat flow sensor according to an embodiment of the present invention.

[0044] Figure 11 This is a graph showing the dynamic response time test results of a curved conformal wireless passive thermal flow sensor according to an embodiment of the present invention.

[0045] Description of reference numerals:

[0046] 10 - metal wire, 20 - silicon carbide substrate, 30 - sensitive layer, 40 - thermal resistance layer, 31 - first electrode, 32 - second electrode, 33 - microstrip antenna, 34 - resonant circuit, 35 - thermopile, 41 - opening, 341 - inductor, 342 - capacitor. DETAILED DESCRIPTION

[0047] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention. On the contrary, the embodiments of the present invention include all variations, modifications, and equivalents that fall within the spirit and scope of the appended claims.

[0048] Refer to the following Figures 1 to 6 , describing a curved conformal wireless passive thermal flow sensor according to an embodiment of the present invention.

[0049] Combine Figures 1 to 5 As shown, the curved conformal wireless passive thermal flow sensor according to an embodiment of the present invention includes a metal wire 10, a silicon carbide substrate 20, a sensitive layer 30 and a thermal resistance layer 40 arranged in sequence from bottom to top.

[0050] Sensitive layer 30 includes a thermopile 35, an inductor 341, a capacitor 342, and a microstrip antenna 33, all made of metal using an ink direct writing process. One end of thermopile 35 is connected to capacitor 342, while the other end of microstrip antenna 33 and inductor 341 are connected to thermopile 35. The thermal resistance layer 40 has at least one opening 41 to expose the hot junction of thermopile 35. Metal wire 10 connects inductor 341 and capacitor 342 to form a resonant circuit 34.

[0051] The thermopile 35 is used to generate a voltage signal corresponding to the heat flow temperature, the resonant circuit 34 is used to modulate the voltage signal into a high-frequency signal, and the microstrip antenna 33 is used to transmit the high-frequency signal outward in the form of radio waves.

[0052] The silicon carbide substrate 20 is made of silicon carbide ceramic fiber, which is a flexible material with advantages such as high thermal conductivity and low thermal expansion coefficient. The size and shape of the silicon carbide substrate 20 are set according to actual needs and are not limited to this. For example, the thickness of the silicon carbide substrate 20 is 50-200μm. The ink direct writing process is a technology that directly deposits metal materials in liquid or semi-solid state. The thermopile 35 is formed by multiple pairs of thermocouples connected in series. The thermocouple is made of two different metal materials, and the specific material is selected according to actual needs. For example, high-temperature resistant materials such as platinum and platinum rhodium can be used. The inductor 341, capacitor 342, and microstrip antenna 33 are all made of high-temperature resistant metal. The specific type of inductor 341 is set according to actual needs, for example, the inductor 341 is spiral-shaped, and the specific type of capacitor 342 is set according to actual needs, for example, the capacitor 342 is a cross-finger capacitor. The specific type of microstrip antenna 33 is set according to actual needs, for example, the microstrip antenna 33 is square wave-shaped and can transmit traveling waves. The metal wire 10 is also made of high temperature resistant metal material, such as platinum-rhodium.

[0053] like Figure 6 As shown, the conformal wireless passive heat flow sensor of an embodiment of the present invention operates as follows: When a perpendicular heat flow passes through the heat flow sensor, a temperature difference forms between the hot and cold junctions of the thermopile, generating a voltage signal across the thermopile. The resonant circuit 34 modulates the voltage signal into a high-frequency signal, and the microstrip antenna 33 transmits the high-frequency signal as radio waves. A remote monitoring operator can use a network analyzer to receive the radio waves containing temperature information and convert them into temperature values, enabling remote monitoring.

[0054] According to the curved conformal wireless passive thermal flow sensor of the embodiment of the present invention, it is prepared based on a flexible silicon carbide substrate, and is combined with a thermopile, inductor, capacitor, microstrip antenna and metal wire made by an ink direct writing process. The thermal flow sensor as a whole is still flexible, can adaptively fit the surface of the curved component, and has the characteristic of high temperature resistance. In addition, the inductor, capacitor and metal wire constitute a resonant circuit, which modulates the thermal flow signal into a high-frequency signal and realizes long-distance transmission through the microstrip antenna without the need for wired power supply, thereby realizing wireless passive transmission of the thermal flow signal and solving the problem of difficult lead wires and easy breakage of leads in high temperature and high rotation environments.

[0055] like Figure 3As shown, the thermopile 35 includes a plurality of pairs of thermocouples connected end to end, wherein one pair of thermocouples includes a first electrode 31 and a second electrode 32 connected to each other, the first electrode 31 is made of platinum, and the second electrode 32 is made of platinum rhodium. Thermocouples are based on the Seebeck effect. When the junctions of two different metals are at different temperatures, an electromotive force is generated, thereby measuring the temperature difference. The number of logarithms of the thermocouples is set according to the actual measurement temperature needs, and there is no restriction on this. The first electrode 31 and the second electrode 32 are connected end to end, and the specific type is set according to actual needs, and there is no restriction on this. For example, the first electrode 31 and the second electrode 32 are both L-shaped to adapt to a specific spatial layout. It should be noted that, Figure 3 The quadrilateral backing is only for the purpose of better displaying graphics such as thermocouples and does not exist physically.

[0056] The thermal resistance layer 40 can play an isolating role, reducing the interference and damage of the thermopile from the external environment. The thermal resistance layer 40 covers the remaining area of ​​the silicon carbide substrate 20 except the thermopile hot junction. The thermal resistance layer 40 can be made of aluminum oxide. The thermopile junction covered by the thermal resistance layer 40 is the cold junction, and the exposed junction is the hot junction. Figure 2 As shown, since the thermopiles are distributed on three sides of the silicon carbide substrate 20, the number of openings 41 on the thermal resistance layer 40 is also 3. In one example, the line width of the first electrode 31 and the second electrode 32 is 20-50 μm, the spacing is 100-200 μm, and the thermal resistance layer thickness is about 10-50 μm.

[0057] In one example, the cross-section of the silicon carbide substrate 20 is quadrilateral, with the thermopile 35 arranged around three sides of the silicon carbide substrate 20 and the microstrip antenna 33 located on the remaining side. The thermopile 35 and microstrip antenna 33 surround the inductor 341 and capacitor 342. This layout maximizes space utilization, enabling a compact design, while also effectively collecting heat and improving the signal transmission performance of the microstrip antenna.

[0058] Combine Figures 1 to 8 As shown, the embodiment of the present invention also provides a method for preparing the curved surface conformal wireless passive heat flow sensor used in the above embodiment. The method includes the following steps:

[0059] Step S102: providing a silicon carbide substrate.

[0060] In this embodiment, the silicon carbide substrate can be manufactured by physical vapor transport, chemical vapor deposition, or the like.

[0061] Step S104 , preparing the first electrode of the thermopile on the surface of the silicon carbide substrate by an ink direct writing process.

[0062] In this embodiment, the material of the first electrode is platinum (Pt) metal.

[0063] Step S106 , preparing the second electrode in the thermopile on the surface of the silicon carbide substrate by an ink direct writing process.

[0064] In this embodiment, the material of the second electrode is platinum-rhodium (Pt-Rh) metal. A plurality of second electrodes are connected end to end with the first electrode to form a thermopile.

[0065] Step S108 , preparing a resonant circuit and a microstrip antenna on the surface of the silicon carbide substrate by an ink direct writing process.

[0066] In this embodiment, the resonant circuit includes capacitors, inductors, and metal wires. The capacitors and inductors are located on the front side of the silicon carbide substrate, while the metal wires are located on the back side to prevent interference between the metal wires and the capacitors and inductors. The capacitors, inductors, and microstrip antenna are all made of platinum-rhodium (Pt-Rh) metal.

[0067] Step S110 , forming a thermal resistance layer on the front surface of the silicon carbide substrate.

[0068] In this embodiment, the thermal resistance layer is made of aluminum oxide. As a ceramic material, aluminum oxide has good insulation, high melting point, excellent chemical stability, and relatively low thermal conductivity.

[0069] According to the preparation method of the curved conformal wireless passive thermal flow sensor of an embodiment of the present invention, the thermal flow sensor is prepared based on a flexible silicon carbide substrate, and is combined with a thermopile, a resonant circuit and a microstrip antenna made by an ink direct writing process. The thermal flow sensor as a whole is still flexible, can adaptively fit the surface of the curved component, and has high temperature resistance. In addition, the resonant circuit can modulate the thermal flow signal into a high-frequency signal and realize long-distance transmission through the microstrip antenna without the need for wired power supply, thereby realizing wireless passive transmission of the thermal flow signal and solving the problem of difficult lead wires and easy breakage of leads in high temperature and high rotation environments.

[0070] In some embodiments, step S102 of providing a silicon carbide substrate includes:

[0071] The silicon carbide substrate was prepared by chemical vapor deposition.

[0072] The specific implementation method is as follows: in this embodiment, graphite material is selected and cleaned to ensure the purity of the deposition surface; a gas containing silicon and carbon elements is transported to the reaction chamber through a transportation system; the temperature of the reaction chamber is controlled to about 1200-1600°C and a relatively high gas pressure is maintained, and the gas flow rate is adjusted to create an environment suitable for the growth of silicon carbide; the carbon source gas and the silicon source gas are pyrolyzed or reacted in the reaction chamber to generate silicon carbide and deposited on the surface of the substrate. During pyrolysis, the carbon source gas decomposes carbon atoms to react with the silicon source gas; by controlling the reaction conditions and deposition time, the thickness, crystallinity, orientation and other properties of the silicon carbide film can be regulated; after the deposition is completed, the reaction chamber is slowly cooled, and then the substrate with the silicon carbide deposited is removed.

[0073] In some embodiments, step S104 of preparing the first electrode of the thermopile on the surface of the silicon carbide substrate by an ink direct writing process includes:

[0074] Platinum metal slurry is deposited on the front of the silicon carbide substrate through a nozzle, heated for pre-solidification, and sintered to form a dense platinum metal film. The silicon carbide substrate with platinum metal is annealed to obtain the first electrode of the thermopile.

[0075] The pre-curing temperature is 150°C for 10 minutes, and the sintering temperature is controlled between 900-1350°C to ensure the formation of a dense metal film.

[0076] In some embodiments, step S106 of preparing the second electrode of the thermopile on the surface of the silicon carbide substrate by an ink direct writing process includes:

[0077] Platinum-rhodium metal slurry is deposited on the front of the silicon carbide substrate through a nozzle, heated for pre-solidification, and sintered to form a dense platinum-rhodium metal film. The silicon carbide substrate with platinum-rhodium metal is annealed to obtain the second electrode of the thermopile.

[0078] The pre-curing temperature is 150°C for 10 minutes. The sintering temperature is controlled between 900°C and 1350°C to ensure the formation of a dense metal film. The resulting square thermopile film consists of a first electrode and a second electrode spaced apart and connected in an S-shaped pattern. The junction between adjacent metals forms the thermopile node.

[0079] In some embodiments, step S108 of preparing a resonant circuit and a microstrip antenna on the surface of a silicon carbide substrate by an ink direct writing process includes:

[0080] Platinum-rhodium metal slurry is deposited on the front surface of a silicon carbide substrate through a nozzle, pre-cured by heating, and sintered to form a dense platinum-rhodium metal film. The silicon carbide substrate with platinum-rhodium metal is annealed to obtain an inductor, a capacitor, and a microstrip antenna, wherein the capacitor is connected to one end of the thermopile, and the inductor and the microstrip antenna are connected to the other end of the thermopile;

[0081] The silicon carbide substrate in the area where the capacitor and inductor are located is perforated, and platinum-rhodium metal slurry is deposited on the back of the silicon carbide substrate through a nozzle. It is heated for pre-curing and sintered to form a dense platinum-rhodium metal film. The silicon carbide substrate with platinum-rhodium metal is annealed to obtain metal wires. The metal wires are used to connect the capacitor and inductor together through the perforations to form a resonant circuit.

[0082] The pre-curing temperature is 150°C for 10 minutes. The sintering temperature is controlled between 900°C and 1350°C to ensure the formation of a dense metal film. The perforations can be formed using laser irradiation or reactive ion etching.

[0083] In some embodiments, step S110 of forming a thermal resistance layer on the front surface of the silicon carbide substrate includes:

[0084] A pulsed laser deposition process is used to deposit a thermal resistance layer on the front surface of the silicon carbide substrate. The material of the thermal resistance layer is aluminum oxide.

[0085] The pulsed laser deposition process deposits the aluminum oxide thermal resistor layer as follows: an aluminum oxide target is mounted on a rotatable target holder. The silicon carbide substrate is ultrasonically cleaned in deionized water, alcohol, and acetone for 5 minutes each, dried with nitrogen, and then mounted on a sample stage. Before deposition, the aluminum oxide target surface is pre-sputtered with a low-energy laser for 3 minutes to remove the oxide layer and contaminants. During deposition, the oxygen flow is precisely controlled by a needle valve, and the chamber pressure is adjusted to a range of 0.01–1 Pa. The laser energy density is approximately 1 J / cm², and the deposition rate is approximately 0.5 nm / pulse. The deposition rate is monitored online using a quartz crystal microbalance (QCM), and the thermal resistor layer thickness is precisely controlled by accumulating pulses. After deposition, the thermal resistor layer film is annealed in a two-zone tube furnace at 400°C for 30 minutes under argon atmosphere to ensure high density and stability.

[0086] The method for preparing a curved conformal wireless passive thermal flow sensor further includes step S112 of performing an annealing treatment, wherein the thermal resistance layer has an opening, and the opening is used to expose the hot junction of the thermopile.

[0087] After the above steps, a finished curved surface conformal wireless passive thermal flow sensor can be obtained.

[0088] The following performance tests were performed on the finished curved conformal wireless passive thermal flow sensor obtained according to the above method:

[0089] Place the finished heat flow sensor in a thermal environment with a muffle furnace as the core heat source, set the muffle furnace temperature from room temperature to 1200℃, and record the temperature and voltage data.

[0090] Figure 9 This is the complete data of the temperature resistance limit test. It can be seen that as the temperature of the heat flux sensor rises to 1200℃, the output thermoelectric potential also rises without any jump or drop.

[0091] Figure 10 This is the fitting curve of the output voltage of the thin film heat flux sensor and the heat flux density recorded by the standard heat flux meter. It can be seen that the output voltage and heat flux density are distributed in a quadratic curve.

[0092] In order to evaluate the dynamic performance of the thin film heat flow sensor, a response time test was conducted. Figure 11The output voltage of the heat flow sensor is recorded when a step heat flow is applied. The response time is calculated as the time required for the output voltage to reach 90% of its steady-state value, which is 1.09 s. The recovery time is defined as the time it takes for the output to drop to 90% of the steady-state value, which is calculated to be 1.18 s.

[0093] The high-temperature-resistant curved surface conformal wireless passive heat flow sensor based on silicon carbide prepared by the method of the embodiment of the present invention utilizes thin film technology and radio frequency technology and has the following advantages:

[0094] 1. By regulating the film thickness gradient, the chemical vapor deposition parameters such as precursor flow rate and annealing temperature are optimized to control the growth direction of silicon carbide grains, reduce stress concentration at grain boundaries, establish a dynamic correlation model between interfacial stress transfer and crack initiation, and inhibit the propagation of high-temperature oxidation cracks.

[0095] 2. The entire thermal flow sensor is made based on a flexible silicon carbide substrate. By making the silicon carbide substrate flexible and directly printing the metal layer using an ink direct writing process, the sensor can be adaptively bonded to the surface of curved components. In practical applications, it can be bonded to aircraft turbine blades.

[0096] 3. A highly sensitive thermopile was prepared using platinum and platinum-rhodium, two metal materials with a large difference in Seebeck coefficient, which solved the problem of low sensitivity of traditional thin-film thermopile heat flow sensors.

[0097] 4. The LC resonant circuit is used to modulate the heat flow signal into a high-frequency signal and transmit it over long distances through a microstrip antenna, realizing wireless passive transmission of the heat flow signal and solving the problem of difficult lead wires and easy lead wire breakage in high temperature and high rotation environments.

[0098] 5. The heat flow sensor prepared in the embodiment of the present invention has the advantages of flexibility, high sensitivity, and long-distance transmission. These advantages make the heat flow sensor more reliable and stable when used in harsh environments such as high temperature and high rotation.

[0099] It should be noted that, in the description of the present invention, the terms "first," "second," etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0100] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0101] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0102] In the description of the present invention, the terms "left", "right", "front", "rear", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0103] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may be performed out of the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention pertain.

[0104] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0105] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A curved surface conformal wireless passive thermal flow sensor, characterized in that: The invention comprises a metal wire (10), a silicon carbide substrate (20), a sensitive layer (30) and a thermal resistance layer (40) arranged in sequence from bottom to top, The sensitive layer (30) includes a thermopile (35), an inductor (341), a capacitor (342), and a microstrip antenna (33), all of which are made of metal using an ink direct writing process. One end of the thermopile (35) is connected to the capacitor (342), and the microstrip antenna (33) and the inductor (341) are connected to the other end of the thermopile (35). The thermal resistance layer (40) has at least one opening (41) to expose the hot junction of the thermopile (35). The metal wire (10) connects the inductor (341) and the capacitor (342) to form a resonant circuit (34). The thermopile (35) includes a plurality of pairs of thermocouples connected end to end, wherein each pair of thermocouples includes a first electrode (31) and a second electrode (32) connected to each other, the first electrode (31) is made of platinum, and the second electrode (32) is made of platinum-rhodium; the silicon carbide substrate (20) is made of silicon carbide ceramic fiber, and the cross-section of the silicon carbide substrate (20) is a quadrilateral; the thermopile (35) is arranged around three sides of the silicon carbide substrate (20), and the microstrip antenna (33) is arranged on the remaining side of the silicon carbide substrate (20); the thermopile (35) and the microstrip antenna (33) surround the inductor (341) and the capacitor (342); The thermopile (35) is used to generate a voltage signal corresponding to the heat flow temperature; the resonant circuit (34) is used to modulate the voltage signal into a high-frequency signal; and the microstrip antenna (33) is used to propagate the high-frequency signal outward in the form of radio waves.

2. A method for preparing the curved surface conformal wireless passive thermal flow sensor according to claim 1, characterized in that: include: providing a silicon carbide substrate; The first electrode of the thermopile is prepared on the surface of the silicon carbide substrate by an ink direct writing process; The second electrode in the thermopile is prepared on the surface of the silicon carbide substrate by an ink direct writing process; Resonant circuits and microstrip antennas were fabricated on the surface of silicon carbide substrates using an ink direct writing process. A thermal resistance layer is formed on the front surface of the silicon carbide substrate.

3. The method for preparing a curved surface conformal wireless passive thermal flow sensor according to claim 2, characterized in that: Providing a silicon carbide substrate comprises: The silicon carbide substrate was prepared by chemical vapor deposition.

4. The method for preparing a curved surface conformal wireless passive thermal flow sensor according to claim 2, characterized in that: The method of preparing the first electrode in the thermopile on the surface of the silicon carbide substrate by the ink direct writing process comprises: Platinum metal slurry is deposited on the front of the silicon carbide substrate through a nozzle, heated for pre-solidification, and sintered to form a dense platinum metal film. The silicon carbide substrate with platinum metal is annealed to obtain the first electrode of the thermopile.

5. The method for preparing a curved surface conformal wireless passive thermal flow sensor according to claim 2, characterized in that: The method of preparing the second electrode in the thermopile on the surface of the silicon carbide substrate by the ink direct writing process comprises: Platinum-rhodium metal slurry is deposited on the front of the silicon carbide substrate through a nozzle, heated for pre-solidification, and sintered to form a dense platinum-rhodium metal film. The silicon carbide substrate with platinum-rhodium metal is annealed to obtain the second electrode of the thermopile.

6. The method for preparing a curved surface conformal wireless passive thermal flow sensor according to claim 2, characterized in that: The method of preparing a resonant circuit and a microstrip antenna on the surface of a silicon carbide substrate by an ink direct writing process comprises: Platinum-rhodium metal slurry is deposited on the front surface of a silicon carbide substrate through a nozzle, pre-cured by heating, and sintered to form a dense platinum-rhodium metal film. The silicon carbide substrate with platinum-rhodium metal is annealed to obtain an inductor, a capacitor, and a microstrip antenna, wherein the capacitor is connected to one end of the thermopile, and the inductor and the microstrip antenna are connected to the other end of the thermopile; The silicon carbide substrate in the area where the capacitor and inductor are located is perforated, and platinum-rhodium metal slurry is deposited on the back of the silicon carbide substrate through a nozzle. It is heated for pre-curing and sintered to form a dense platinum-rhodium metal film. The silicon carbide substrate with platinum-rhodium metal is annealed to obtain metal wires. The metal wires are used to connect the capacitor and inductor together through the perforations to form a resonant circuit.

7. The method for preparing a curved surface conformal wireless passive thermal flow sensor according to claim 2, characterized in that: The step of forming a thermal resistance layer on the front surface of the silicon carbide substrate comprises: A pulsed laser deposition process is used to deposit a thermal resistance layer on the front surface of the silicon carbide substrate. The material of the thermal resistance layer is aluminum oxide.

8. The method for preparing a curved surface conformal wireless passive thermal flow sensor according to claim 7, characterized in that: The method further includes performing an annealing process, wherein the thermal resistance layer has an opening, and the opening is used to expose the hot junction of the thermopile.

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