A high-temperature-resistant thin film temperature sensor manufactured in-situ by laser without packaging and a preparation method thereof

Abstract

The application discloses a laser in-situ manufactured packaging-free high-temperature-resistant thin film temperature sensor and a preparation method thereof. High-temperature insulating material is used as a substrate, a temperature-sensitive thin film precursor layer is formed on the surface of the substrate by coating a titanium boride-based precursor ink, and after solidification, laser sintering is performed to realize conduction between titanium boride microparticles and nanometer particles, so that a temperature-sensitive layer with excellent conductive performance is obtained, and meanwhile, a glass phase silicon borate formed by laser-induced passivation compensates for defects of the titanium boride microparticles and nanometer particles, so that the oxidation resistance under high temperature is achieved, a laser sintering and passivation process flow of titanium boride and silicon carbide mixed ink from 'powder-liquid-solid state-functionality' transformation is realized, and the laser sintering and passivation process flow is successfully applied to high-temperature temperature sensing. Compared with the prior art, the application can realize rapid in-situ preparation of the sensor based on laser one-step processing technology, and can accurately process required patterns.

Description

Technical Field

[0001] This invention belongs to the field of extreme environment sensor technology, and relates to an unencapsulated high-temperature resistant thin-film temperature sensor manufactured in situ by laser and its preparation method. Background Technology

[0002] Many industrial sectors, such as aerospace, power generation, metallurgy, and chemicals, often involve production environments with extreme high temperatures. In these environments, temperature monitoring is crucial for ensuring the safe operation of systems. Temperature sensors provide accurate temperature data, helping to prevent overheating-related accidents, protect equipment from damage, and thus increase overall system safety. They also help optimize production processes, improve energy efficiency, reduce energy waste, lower emissions of harmful substances, and enhance environmental performance.

[0003] Under these conditions, conventional temperature sensors cannot function properly, thus requiring specially designed high-temperature resistant temperature sensors to ensure accurate process monitoring and control. Currently, temperature sensors used in extreme high-temperature environments mainly include thermocouples, infrared sensors, and fiber optic temperature sensors. However, they all have drawbacks such as being unable to conformally attach, requiring specialized subsequent circuitry, being complex to install, and potentially affecting the operation of the monitored device.

[0004] High-temperature resistant thin-film temperature sensors have advantages such as strong adaptability, in-situ fabrication on the substrate to be monitored, high precision, fast response, and easy integration. Currently, most high-temperature resistant thin-film temperature sensors are based on precious metals such as platinum and sintered ceramics, which have high cost, complex preparation process, long preparation time, and require an antioxidant protective layer. Platinum-based thermal resistance thin-film temperature sensors (a high-temperature platinum thin-film resistance temperature sensor and its preparation method, application number 202110017510.X) are expensive and have low sensitivity, limiting their application in high-precision applications. Indium tin oxide-indium oxide thin-film thermocouples (a method for preparing a crystal plane-preferred orientation indium tin oxide-indium oxide thin-film thermocouple, application number 202110423427.2) have better performance, but they cannot overcome the problem of requiring cold junction compensation and dedicated post-processing circuits. Polymer-converted ceramic precursor-based thin-film temperature sensors (a method for preparing a polymer precursor high-temperature ceramic thin-film sensor, application number 202310860565.6) have excellent performance and low cost, but their preparation usually requires long-term high-temperature pyrolysis in a high-temperature furnace, which is time-consuming, energy-intensive, and requires encapsulation protection. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a laser-manufactured, unencapsulated, high-temperature resistant thin-film temperature sensor and its preparation method. This high-temperature resistant thin-film temperature sensor is prepared by laser one-step sintering and induced passivation. It features a more convenient processing method, extremely fast processing speed, lower cost, and a wider measurement range.

[0006] The objective of this invention can be achieved by adopting the following technical solution:

[0007] A laser-manufactured, unencapsulated, high-temperature resistant thin-film temperature sensor includes a high-temperature substrate, a sensitive film, a connecting layer, lead wires, and a connection protection layer. The sensitive film is fabricated on the high-temperature substrate and is formed by laser sintering and induced passivation of titanium boride-based precursor ink to create a titanium boride conductive path protected by glassy borosilicate for oxidation resistance. Laser sintering enables conduction between titanium boride micro- and nano-particles in the precursor ink, while laser-induced passivation forms glassy borosilicate, protecting the titanium boride conductive path from oxidation. The high-temperature substrate is an insulating ceramic such as alumina ceramic or silicon carbide ceramic. The sensitive film has negative temperature-sensitive properties. The connecting layer is located on the sensitive film at the required lead wire locations to connect the lead wires. The connection protection layer covers the connecting layer to suppress breakage failure caused by the thermal expansion difference between the connecting layer and the sensitive film. The connecting layer is a high-temperature resistant paste such as silver paste or silver-palladium paste. The lead wires are located between the connecting layer and the connection protection layer and are used to extract the electrical signal from the sensitive film. The lead wires are made of precious metals such as platinum wire.

[0008] Another objective of this invention is to provide a method for fabricating a laser-manufactured, unencapsulated, high-temperature resistant thin-film temperature sensor, comprising the following steps:

[0009] Step 1: Prepare the precursor ink. The appropriate amount of solvent to add can be selected according to the different film-forming methods to be used in the subsequent process, so as to achieve the appropriate ink concentration.

[0010] Step 2: High-temperature substrate pretreatment. Appropriate cleaning and drying methods can be selected for different high-temperature substrates to remove impurities from their surface.

[0011] Step 3: Preparation of precursor thin film. The appropriate film-forming technology and parameters can be selected according to the concentration of the ink to be prepared.

[0012] Step 4: Using laser direct writing technology on a high-temperature substrate, sensitive films with specified patterns are precisely processed by adjusting parameters for precursor films of different thicknesses.

[0013] Step 5: Apply the bonding layer and fix the lead wire to ensure good connection with the sensitive film in Step 4;

[0014] Step 6: Prepare a bonding protective layer by drop-coating the precursor ink onto the bonding layer of the sample obtained in Step 5.

[0015] Further, the precursor ink preparation described in step 1, wherein the precursor ink is composed of titanium boride powder, silicon carbide powder, isopropanol, glycerol, and polyvinylpyrrolidone, is prepared by adding titanium boride powder and silicon carbide powder in portions to a functional solvent obtained by mixing isopropanol, glycerol, and polyvinylpyrrolidone, and then dispersing by ultrasonication; wherein the ratio of titanium boride powder, silicon carbide powder, polyvinylpyrrolidone, glycerol, and isopropanol is 2.8–3.2 g: 0.4–0.8 g: 0.4–0.5 g: 0.2–0.4 g: 4–6 mL, the particle size of titanium boride powder is preferably 1–3 μm, and the particle size of silicon carbide is preferably 0.5–0.7 μm. According to a specific embodiment of the present invention, the specific preparation steps can be as follows:

[0016] (1) Weigh 0.446g of polyvinylpyrrolidone and 0.3g of glycerin using a microbalance and place them in a reagent bottle;

[0017] (2) Use a pipette to measure 5 ml of isopropanol and inject it into the reagent bottle of (1);

[0018] (3) Add the magnetic rotor and stir on the magnetic stirring table for 1 hour (1000 rpm, 60 degrees Celsius);

[0019] (4) Add 1g of titanium diboride and 0.2g of silicon carbide to the solvent that has been completely clarified after stirring;

[0020] (5) Disperse in an ultrasonic cell disruptor for 2 minutes;

[0021] (6) Repeat (4) and (5) three times.

[0022] Furthermore, the high-temperature substrate mentioned in step 2 can be alumina ceramic, silicon carbide ceramic, or other high-temperature resistant and insulating substrates.

[0023] Furthermore, the high-temperature substrate pretreatment includes ultrasonic alcohol cleaning, ultrasonic water cleaning, and drying. According to a specific embodiment of the present invention, the specific steps can be as follows:

[0024] (1) Place the alumina ceramic substrate in alcohol and sonicate for 2 minutes;

[0025] (2) Then place the alumina ceramic substrate in deionized water and sonicate for 2 minutes;

[0026] (3) Finally, the alumina ceramics were dried in a vacuum drying oven at 60 degrees Celsius.

[0027] Furthermore, the precursor film preparation method described in step 3 can be used to prepare the film on a high-temperature substrate by spin coating, or by any coating method such as drop coating, blade coating, dispensing, direct ink writing (DIW), screen printing, etc. Different methods require different viscosity of the precursor ink, which can be achieved by adjusting the amount of isopropanol and glycerol added.

[0028] Furthermore, the specific steps for preparing thin films on high-temperature substrates using spin coating, according to a specific embodiment of the present invention, can be as follows:

[0029] (1) Place the high-temperature substrate treated in step 2 into a spin coater, turn on the air pump to draw a vacuum, and achieve adsorption and fixation of the high-temperature substrate.

[0030] (2) Drop a small amount of precursor ink onto the center of the high-temperature substrate and spin coat for 3 seconds at a spin coating speed of 400 rpm;

[0031] (3) Fill in the areas on the high-temperature substrate that the ink did not reach, and then drop 2-3 ml of precursor ink into the center of the high-temperature substrate and spin coat at a spin coating speed of 500 rpm for 15 seconds;

[0032] (4) Remove the high-temperature substrate after spin coating and place it on a heating table to dry at 60 degrees Celsius for 5 minutes.

[0033] Furthermore, the laser direct writing described in step 4 involves using laser-integrated technology on a high-temperature substrate. This utilizes the photothermal effect and photochemical reaction of the laser to sinter the precursor ink coating onto the high-temperature substrate according to a designed pattern, inducing passivation to form titanium boride with glassy silicon borate protection, thus obtaining a temperature-sensitive thin film. According to a specific embodiment of the present invention, the specific steps of the laser direct writing technology can be as follows:

[0034] (1) Use AutoCAD software to draw the pattern to be processed and import it into the laser control software;

[0035] (2) Using an energy density of 6.4 J / mm 2 A continuous green light at 532nm is used to rapidly sinter the precursor to form a temperature-sensitive thin film.

[0036] Furthermore, the connecting layer mentioned in step 5 is a high-temperature resistant conductive paste, such as silver paste or silver-palladium paste, and the lead wire is a high-temperature resistant precious metal wire, such as platinum wire. The connection between the sensitive film, the connecting layer, and the lead wire involves fixing the lead wire by coating a precursor ink onto the required position of the sensitive film, pressing the lead wire with alumina ceramic, and maintaining it at 80-150 degrees Celsius for 1 hour to cure the connecting layer and achieve electrical conductivity between the sensitive film and the lead wire. According to a specific embodiment of the present invention, the specific steps can be as follows:

[0037] (1) Embed a platinum wire with a diameter of 0.2 mm into a D3*1 mm alumina ceramic sheet with a 0.25 mm diameter groove;

[0038] (2) Apply 02H-1805 silver-palladium paste by hand to both ends of the sensitive film as a bonding layer;

[0039] (3) Press the alumina ceramic embedded with platinum wire onto the connecting layer, press a 50g weight on the ceramic, and dry the whole device at 130 degrees Celsius for 1 hour to solidify the connecting layer, so that electrical conduction is formed between the sensitive film and the lead wire.

[0040] Furthermore, the purpose of the connecting protective layer in step 6 is to suppress breakage between the connecting layer and the sensitive film due to the difference in thermal expansion coefficients. According to a specific embodiment of the present invention, the specific steps can be as follows:

[0041] (1) Drop a small amount of precursor ink onto the bonding layer;

[0042] (2) Heat and dry on a heating table (80 degrees Celsius) for 10 minutes.

[0043] The beneficial technical effects of this invention are:

[0044] 1. The sensor of the present invention can be conformally fabricated in situ on the insulating component to be tested. Compared with thermocouples, fiber optic temperature sensors, etc., it does not require installation or dedicated post-processing circuits.

[0045] 2. The sensor of this invention has a thin-film structure with a sensitive film thickness of less than 100 micrometers, which has almost no impact on the normal operation of the component to be detected (such as aero-engine, turbine blade, etc.).

[0046] 3. The sensor ink raw materials of this invention are mainly based on titanium boride and silicon carbide powder, which are cheaper than precious metals such as platinum.

[0047] 4. The sensor of this invention can detect temperatures from room temperature to 950 degrees Celsius, and has excellent cyclicity in detection from room temperature to 800 degrees Celsius. It can be used for more than 20 hours at a high temperature of 800 degrees Celsius.

[0048] 5. The sensor fabrication process of this invention is simple and the fabrication time is short. Compared with traditional high-temperature sintering ceramic technology (usually more than 5 hours, and some require a special gas atmosphere), the laser rapid sintering used in this invention can achieve conductive connection and temperature sensitivity of the precursor film within two minutes (in air). Attached Figure Description

[0049] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the structure of an embodiment of the thermal resistance type high temperature resistant thin film temperature sensor of the present invention, wherein a is a schematic diagram of the sensor structure and b is a schematic diagram of the sensor structure.

[0051] Figure 2 This is a flowchart illustrating the fabrication process of a thermally resistive high-temperature thin-film temperature sensor according to the present invention.

[0052] Figure 3 This invention provides a testing platform for a thermal resistance-type high-temperature resistant thin-film temperature sensor.

[0053] Figure 4 This is a processing result diagram of the temperature-sensitive layer in the thermal resistance type high-temperature resistant thin-film temperature sensor of the present invention;

[0054] Figure 5 This is a processing result diagram of laser patterning in some specific embodiments of the present invention;

[0055] Figure 6 This is a SEM micrograph of the thermal resistance type high temperature resistant thin film temperature sensor of the present invention, where a is before high temperature test and b is after high temperature test, and the scale bar is 10 micrometers.

[0056] Figure 7 These are Raman characterization images of the thermal resistance type high-temperature resistant thin-film temperature sensor of the present invention before and after testing;

[0057] Figure 8 These are XPS characterization images of the thermal resistance type high-temperature resistant thin-film temperature sensor of this invention before and after testing.

[0058] Figure 9 This is the FTIR characterization diagram of the thermal resistance type high temperature resistant thin film temperature sensor of the present invention;

[0059] Figure 10 These are sheet resistance contour plots of films with different ink ratios and different laser processing energy densities after high-temperature testing according to the present invention.

[0060] Figure 11 This is a calibration diagram of the thermal performance of the sensitive layer of the thermally resistive high-temperature thin-film temperature sensor of the present invention. Figure 12 This is a hysteresis curve of the thermal resistance type high temperature resistant thin film temperature sensor of the present invention in the range of 100-800 degrees Celsius;

[0061] Figure 13 This is a repeatability test pattern of the thermal resistance type high temperature resistant thin film temperature sensor of the present invention at 100-800 degrees Celsius.

[0062] Figure 14 This is a long-term stability test diagram of the thermal resistance type high-temperature resistant thin-film temperature sensor of the present invention at 800 degrees Celsius.

[0063] Figure 15 This is a temperature gradient test diagram of the thermal resistance type high temperature resistant thin film temperature sensor of the present invention;

[0064] Figure 16 This is a temperature-sensitive characteristic diagram of the connecting layer, substrate, and original ink of the thermal resistance type high-temperature resistant thin-film temperature sensor of the present invention.

[0065] Figure 17 This is a test diagram of the adhesion force of the thermal resistance type high temperature resistant thin film temperature sensor of the present invention;

[0066] Figure 18 This is the response diagram of the thermal resistance type high-temperature resistant thin-film temperature sensor of the present invention to a transient flame;

[0067] Figure 19 These are wear and vibration characterization diagrams of the thermal resistance type high-temperature resistant thin-film temperature sensor of this invention;

[0068] In the diagram: A1, high-temperature substrate; A2, sensitive film; A3, connecting layer; A4, lead wire; A5, connecting protective layer. Detailed Implementation

[0069] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0070] The high-temperature sensor of this invention utilizes the thermal resistance characteristics of semiconductors. As temperature increases, the migration speed of charge carriers and holes in the semiconductor increases, macroscopically manifested as a decrease in bulk resistance. During the fabrication of the sensitive thin film, the instantaneous high temperature of a laser is utilized. The addition of silicon carbide further enhances the photothermal conversion of the laser, thus enabling the sintering of the thin film precursor in an extremely short time. Laser sintering, while forming the conductive pathway of the thin film, also promotes the formation of silicon borate, improving the oxidation resistance of the sensitive thin film at high temperatures.

[0071] A laser-manufactured, unencapsulated, high-temperature resistant thin-film temperature sensor, such as... Figure 1 As shown, this is a thermal resistance temperature sensor, comprising an insulating high-temperature substrate A1, a sensitive film A2, a connecting layer A3, lead wires A4, and a connecting protective layer A5. The sensitive film A2 is prepared on the high-temperature substrate A1 by laser sintering. The high-temperature substrate A1 is an insulating ceramic such as alumina ceramic or silicon carbide ceramic. The sensitive film A2 has negative temperature sensitivity. The connecting protective layer A5 covers the connecting layer A3 to suppress fracture failure caused by the difference in thermal expansion between the connecting layer A3 and the sensitive film A2. The connecting layer A3 is a high-temperature resistant paste such as silver paste or silver-palladium paste. The lead wire A4 is located between the connecting layer A3 and the connecting protective layer A5 and is used to lead out the electrical signal of the sensitive film A2. The lead wire A4 is a precious metal wire such as platinum wire.

[0072] According to a specific embodiment of the present invention, a method for fabricating an unencapsulated high-temperature resistant thin-film temperature sensor using laser in-situ manufacturing is provided, comprising the following steps:

[0073] Step 1: Weigh 0.446g of polyvinylpyrrolidone and 0.3g of glycerol into a reagent bottle using a microbalance. Use a pipette to measure 5ml of isopropanol and inject it into the reagent bottle. Add a magnetic rotor to the reagent bottle and stir on a magnetic stirring table for 1 hour (set to 1000 rpm, 60 degrees Celsius) to obtain the functional solvent.

[0074] Step 2: Weigh 1g of titanium boride powder with a particle size of 1-3 micrometers and 0.2g of silicon carbide powder with a particle size of 0.5-0.7 micrometers using a microbalance, add them to the functional solvent prepared in Step 1, and disperse in an ultrasonic cell disruptor for two minutes to obtain a uniformly dispersed ink. Repeat Step 2 a total of 3 times to obtain the precursor ink;

[0075] Step 3: Select 96α-alumina ceramic with an application temperature of 300-1700 degrees Celsius as the high-temperature substrate, and pretreat the high-temperature substrate by placing the alumina ceramic substrate in alcohol and sonicating for 2 minutes; then placing the alumina ceramic substrate in deionized water and sonicating for 2 minutes; finally, place the alumina ceramic in a vacuum drying oven and dry at 60 degrees Celsius.

[0076] Step 4: Precursor film preparation. Place the cleaned high-temperature substrate in a spin coater, turn on the air pump to create a vacuum, and achieve adsorption and fixation of the high-temperature substrate. Drop a small amount of precursor ink onto the center of the high-temperature substrate and spin coat at 400 rpm for 3 seconds to achieve initial coating of the precursor ink on the high-temperature substrate. For areas on the high-temperature substrate where the ink was not spin-coated, use a pipette to apply a small amount of ink for repair, then drop 2-3 ml of precursor ink onto the center of the high-temperature substrate and spin coat at 500 rpm for 15 seconds. Remove the spin-coated high-temperature substrate and place it on a heating stage to dry at 60 degrees Celsius for 5 minutes to complete the preparation of the precursor film.

[0077] Step 5: Draw the pattern to be processed using AutoCAD software and import it into the laser control software Ezcard; use an energy density of 6.4 J / mm². 2 A 532nm continuous green light is used to rapidly sinter the precursor to form a temperature-sensitive thin film. During the laser treatment, silicon carbide acts as a photothermal converter to realize the laser-to-thermal conversion. The precursor film densifies under rapid heating conditions, forming a conductive path. At the same time, the instantaneous ultra-high temperature induces partial oxidation of silicon carbide and titanium boride, generating silicon borate, which encapsulates the conductive path of titanium boride, effectively preventing further oxygen intrusion and improving oxidation resistance at high temperatures.

[0078] Step 6: Hand-apply 02H-1805 silver-palladium paste to both ends of the sensitive film as a bonding layer; embed a 0.2mm diameter platinum wire into a D3*1mm alumina ceramic sheet with a 0.25mm diameter groove; press the alumina ceramic with the platinum wire embedded onto the bonding layer, press a 50g weight on the ceramic, and dry the entire device at 130 degrees Celsius for 1 hour to solidify the bonding layer, so that electrical conductivity is formed between the sensitive film and the lead wire;

[0079] Step 7: Drop a small amount of precursor ink onto the bonding layer from Step 6 and heat it on a heated platform (80 degrees Celsius) for 10 minutes to dry.

[0080] Step 8: Prepare control group films, except for the different mass ratios of titanium boride and silicon carbide in Step 2 (control group: 10:0, 10:1, 10:4, 10:6), and different laser processing energy densities (0 J / mm). 2 2.58J / mm 2 9.04 J / mm 2 The remaining steps are the same.

[0081] In this example, the thickness and pattern of the sensitive film, connecting layer, and connecting protective layer can be adjusted as needed. Preferably, the thickness of the sensitive film is 10–50 micrometers, the thickness of the connecting layer is 10–30 micrometers, and the thickness of the connecting protective layer is 20–100 micrometers.

[0082] According to a specific example of the present invention, the preparation process is as follows: Figure 2 As shown.

[0083] Testing platform such as Figure 3 As shown. The test platform includes a tubular furnace, commercial type K thermocouples, a Keysight data acquisition device, and a laptop computer. Signals from the prototype and the commercial type K thermocouples are read by the Keysight data acquisition device and transmitted to the computer for visualization.

[0084] Two examples of the temperature-sensitive thin film in the thermal resistance type high-temperature thin film temperature sensor of this invention have the following shapes: Figure 4 As shown in the figure, C1 is the high-temperature substrate, and C2 is the sensitive thin film. This further demonstrates the patterning capability of laser manufacturing in this invention, such as... Figure 5 As shown.

[0085] The scanning electron microscope (SEM) image of the thermal resistance type high-temperature resistant thin-film temperature sensor in this example is as follows: Figure 6 As shown, the SEM image reveals that sensitive films prepared with different laser energy densities exhibit different morphologies before and after prolonged exposure to high temperatures. From... Figure 6 The microscopic images show 6.46 J / mm. 2 The sensitive thin film prepared by laser energy density retains excellent surface morphology even at high temperatures, without defects such as cracks, pores, or fissures. However, too low a laser energy density leads to significant surface oxidation, while too high a density causes surface cracking. The preferred laser energy density is 4–7 J / mm². 2 532nm green light.

[0086] The Raman characterization of the thermal resistance-type high-temperature resistant thin-film temperature sensor in this example is as follows: Figure 7 As shown, the upper curve represents the film before the high-temperature test, and the lower curve represents the film after the high-temperature test. The Raman characterization demonstrates that the main material of the film remains TiB2 before and after the high-temperature test. TiB2 is a component of the conductive path in the film, and the fact that this material remained almost unchanged before and after the high-temperature test proves that the film possesses high-temperature stability.

[0087] The XPS characterization of the thermal resistance-type high-temperature resistant thin-film temperature sensor in this example is as follows: Figure 8 As shown, the XPS characterization revealed that the B element in the film exists in the form of [BO4] rather than in the form of boron oxide [BO3], indicating the formation of silicon borate.

[0088] The FTIR characterization of the thermal resistance-type high-temperature resistant thin-film temperature sensor in this example is as follows: Figure 9 As shown, the FTIR characterization revealed various bonds present in the thin film, with 920.8 cm⁻¹ being the most prominent. -1 and 783.4cm-1 All of these studies prove the existence of silicon borate.

[0089] The sheet resistance contour plot of the control group film after high-temperature testing is shown below. Figure 10 As shown in the contour map, the film prepared with ink without added silicon carbide becomes insulating at high temperature and completely oxidizes and fails because an effective silicon borate protective phase cannot be formed in this film.

[0090] The thermal resistance type high-temperature resistant thin-film temperature sensor in this example has the following thermal layer thermal sensitivity performance: Figure 11 As shown, the sensitivity can be fitted according to the Steinhart-hart equation. The specific fitting formula is as follows:

[0091] 1 / T = 0.00125 + 1.1023 × 10 -4 lnR+1.73711×10 -6 (lnR) 3 In the fitting formula, T is the temperature to be detected in Kelvin, and R is the output resistance of the thermal resistance type high-temperature thin-film temperature sensor in this example in ohms.

[0092] The temperature test hysteresis curve of the thermal resistance type high-temperature resistant thin-film temperature sensor in this example is as follows: Figure 12 As shown, the hysteresis curve is divided into six cycles: a temperature increase of 100-800 degrees Celsius and a temperature decrease of 800-100 degrees Celsius. It exhibits excellent stability. The resistance fluctuation during the first temperature increase is due to the flow of borosilicate acid filling the pores in the laser-processed film during this process.

[0093] The temperature cycling detection curve of the thermal resistance type high-temperature resistant thin-film temperature sensor in this example is as follows: Figure 13 As shown, the temperature cycle consists of a heating of 100-800 degrees Celsius and a cooling of 800-100 degrees Celsius, which is repeated four to five times.

[0094] The high-temperature stability of the thermal resistance type high-temperature resistant thin-film temperature sensor in this example is as follows: Figure 14 As shown, the high-temperature stability test involves placing the sensor at 800 degrees Celsius for more than 20 hours without failure.

[0095] This example demonstrates a temperature gradient test using a thermal resistance-type high-temperature resistant thin-film temperature sensor. Figure 15 As shown, the temperature gradient test involves placing the sensor at 100 degrees Celsius intervals for 30 minutes between 0 and 800 degrees Celsius to test its stability.

[0096] In this example, the thermal resistance type high-temperature resistant thin-film temperature sensor exhibits the following temperature-sensitive characteristics in its connecting layer, substrate, and original ink: Figure 16As shown, the temperature-sensitive properties of the connecting layer in the example are negligible compared to the sensitive film, and the substrate and the original ink in the example can be considered as insulation.

[0097] This example demonstrates the adhesion test of the sensitive film of a thermal resistance-type high-temperature thin-film temperature sensor. Figure 17 As shown, the resistance of the sensitive film hardly changes after being peeled off with 3M tape 30 times and subjected to ultrasonic damage for 10 minutes.

[0098] The transient response test of the thermal resistance type high-temperature resistant thin-film temperature sensor in this example is as follows: Figure 18 As shown, the sensor can respond quickly under a flame torch.

[0099] This example demonstrates the wear and vibration resistance tests of a thermal resistance-type high-temperature thin-film temperature sensor. Figure 19 As shown, the resistance of the sensor hardly changes under sandpaper abrasion and vibration.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A high temperature resistant thin film temperature sensor fabricated by laser in-situ without packaging, characterized in that, The sensor comprises a high-temperature substrate (1), a sensitive film (2), a connecting layer (3), a connecting protective layer (4) and a lead wire (5), the sensitive film (2) is prepared on the high-temperature substrate (1) and is formed by laser sintering and induced passivation of a titanium boride-based precursor ink to form a titanium boride conductive path protected by glass-phase silicon borate oxidation, the connecting layer (3) is arranged on the sensitive film (2) and is used for connecting the lead wire (5), the connecting protective layer (4) is arranged on the connecting layer (3) and is used for inhibiting the fracture failure caused by the thermal expansion difference between the connecting layer (3) and the sensitive film (2), the lead wire (5) is arranged between the connecting layer (3) and the connecting protective layer (4) and is used for leading out the electric signal of the sensitive film (2), and the sensor is a thermal resistance type temperature sensor; the precursor ink is composed of titanium boride powder, silicon carbide powder, isopropyl alcohol, glycerol and polyvinylpyrrolidone, and the laser is a 532 nm continuous green light.

2. The high temperature resistant thin film temperature sensor of claim 1, wherein, The thickness of the sensitive film is 1-100 microns.

3. The high temperature thin film temperature sensor of claim 1, wherein, The high-temperature substrate is an insulating material, the connecting layer is a high-temperature resistant conductive paste, and the lead wire is a high-temperature resistant conductive wire.

4. The high temperature resistant thin film temperature sensor of claim 3, wherein, The insulating material comprises alumina ceramic or silicon carbide ceramic; the high-temperature resistant conductive paste comprises silver paste or silver-palladium paste; and the high-temperature resistant conductive wire comprises platinum wire.

5. The high temperature thin film temperature sensor of claim 1, wherein, The connecting protective layer is prepared by using the precursor ink.

6. A method of making a high temperature resistant thin film temperature sensor as claimed in any one of claims 1 to 5 characterised in that, The preparation steps comprise: Step 1: preparing a precursor ink; Step 2: high-temperature substrate pretreatment; Step 3: precursor film preparation; Step 4: laser sintering to prepare a sensitive film; Step 5: coating a connecting layer and fixing a lead wire to make the lead wire well connected with the sensitive film; Step 6: using the precursor ink to drop coat the connecting layer of the sample obtained in step 5 to prepare a connecting protective layer.

7. The method of claim 6, wherein the high temperature resistant thin film temperature sensor is prepared by the steps of: The precursor ink in step 1 is composed of titanium boride powder, silicon carbide powder, isopropyl alcohol, glycerol and polyvinylpyrrolidone and is prepared by adding the titanium boride powder and the silicon carbide powder into a functional solvent obtained by mixing isopropyl alcohol, glycerol and polyvinylpyrrolidone in batches and ultrasonic dispersion; wherein the amount ratio of the titanium boride powder, the silicon carbide powder, the polyvinylpyrrolidone, the glycerol, the isopropyl alcohol is 2.8-3.2 g:0.4-0.8 g:0.4-0.5 g:0.2-0.4 g:4-6 mL, the particle size of the titanium boride powder is 1-3 microns, and the particle size of the silicon carbide is 0.5-0.7 microns.

8. The method of claim 6, wherein the high temperature resistant thin film temperature sensor is prepared by the steps of: The high-temperature substrate pretreatment in step 2 is ultrasonic alcohol cleaning, ultrasonic water cleaning and drying, and the precursor film preparation method in step 3 is to make the precursor ink uniformly cover the surface of the high-temperature substrate by any coating method and to obtain a uniform precursor film after drying on a heating table.

9. The method of claim 6, wherein the temperature sensor is a high temperature thin film temperature sensor. The laser sintering to prepare a sensitive film in step 4 is to sinter the precursor ink coating on the high-temperature substrate according to a designed pattern by using the photo-thermal effect and photo-chemical reaction of laser to induce passivation and form glass-phase silicon borate envelope titanium boride and obtain a sensitive film.

10. The method for preparing a high-temperature resistant thin-film temperature sensor according to claim 6, characterized in that, The fixed lead-out wire described in step 5 is fixed by coating a precursor ink on a desired position of the sensitive thin film, pressing the lead-out wire on the coated position, and curing the connection layer by covering alumina ceramic thereon and maintaining at 80-150 degrees Celsius for 1 hour to achieve electrical conduction between the sensitive thin film and the lead-out wire.

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