High-temperature platinum thin film temperature sensor based on direct writing molding, preparation method and application

Abstract

The application discloses a high-temperature platinum thin film temperature sensor based on direct writing forming, a preparation method and application, and the sensor comprises a ceramic substrate, a platinum sensitive grid, a precursor ceramic protective layer, a welding spot, a lead wire and a pressing block, the platinum sensitive grid and the precursor ceramic protective layer are sequentially directly written on the ceramic substrate through a Weissberg direct writing forming technology, wherein the raw material components for directly writing the precursor ceramic protective layer comprise 45wt%-55wt% of a SiCN precursor ceramic solution, 25wt%-35wt% of TiB2 powder, 1.2wt%-2wt% of Y2O3 powder and 13.8wt%-23wt% of ZrO2 powder, the precursor ceramic protective layer is covered on the platinum sensitive grid, the lead wire is arranged between the pressing block and the platinum sensitive grid, and the lead wire is electrically connected with the platinum sensitive grid through the welding spot. The sensor has the advantages of high-temperature resistance (50 DEG C to 800 DEG C), small disturbance, good high-temperature stability and the like, and can break through the bottleneck problems of high cost, single material and difficulty in curved surface conforming caused by the platinum thin film temperature sensor prepared by the current silk screen printing and magnetron sputtering process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of temperature sensors, in particular to a high-temperature platinum thin film temperature sensor based on direct writing forming, a preparation method and application. BACKGROUND

[0002] It is one of the world-recognized technical problems to realize real-time monitoring of the high-temperature in-situ temperature of key parts inside an aero-engine and a gas turbine. The platinum thin film temperature sensor is expected to solve the special sensing technology problem in extreme environments such as high temperature due to its small disturbance, high precision, good linearity and strong stability. However, the platinum thin film is easily aggregated and volatilized when directly exposed to a high-temperature environment, which greatly affects the high-temperature stability of the platinum thin film temperature sensor.

[0003] To solve the above problems, various platinum thin film temperature sensors and their preparation methods are provided in the prior art. For example, the Chinese patent application No. CN202110017510.X provides a high-temperature platinum thin film resistance temperature sensor and a preparation method thereof, which uses glass glaze to complete the packaging of the platinum thin film resistance, improves the resistance temperature coefficient and high-temperature (850℃) stability, but the disadvantages are poor low-temperature (250℃-400℃) stability, too thick packaging thickness (100μm-200μm), easy to disturb the flow field of the measured environment, affect the temperature measurement accuracy, and the preparation process of the three-layer packaging structure is complex. For another example, the Chinese patent application No. CN202110812041.0 provides a packaging method of a platinum thin film temperature sensor, which prepares an AlN protective layer on the platinum thin film resistance by a magnetron sputtering method, which can solve the problem of poor high-temperature stability (above 800℃) of the platinum thin film temperature sensor, but it also needs to coat a high-temperature protective glaze layer of hundreds of microns on the AlN protective layer, and the magnetron sputtering process used has a high cost.

[0004] In addition, the existing platinum thin film and its packaging structure are usually prepared by screen printing or magnetron sputtering process, which is difficult to prepare the sensor in-situ on the surface of high-temperature parts with cylindrical / complex curved surface common characteristics. SUMMARY

[0005] In view of the above existing technical problems, the embodiments of the present application provide a high-temperature platinum thin film temperature sensor based on direct writing forming, a preparation method and application to solve the above problems.

[0006] According to a first aspect, the application provides a high-temperature platinum thin film temperature sensor based on direct writing forming, comprising a ceramic substrate, a platinum sensitive grid, a precursor ceramic protective layer, a solder joint, a lead wire and a pressing block, the platinum sensitive grid and the precursor ceramic protective layer are sequentially directly written on the ceramic substrate by a Weissenberg direct writing forming technology, wherein the raw material components for directly writing the precursor ceramic protective layer include: 45wt%-55wt% of SiCN precursor ceramic solution, 25wt%-35wt% of TiB2 powder, 1.2wt%-2wt% of Y2O3 powder and 13.8wt%-23wt% of ZrO2 powder, the precursor ceramic protective layer covers the platinum sensitive grid, the lead wire is arranged between the pressing block and the platinum sensitive grid and is electrically connected to the platinum sensitive grid through the solder joint.

[0007] Preferably, the platinum sensitive grid is provided with four pins, the pins are exposed outside the precursor ceramic protective layer, the solder joint and the lead wire are arranged on each pin respectively, and the lead wire and the pin are fixed through the pressing block and the solder joint.

[0008] Preferably, the pressing block is provided with a slot near the side of the solder joint, the lead wire is in interference fit with the slot and is led out from the slot.

[0009] Preferably, the thickness of the platinum sensitive grid is 3μm-5μm, and the thickness of the precursor ceramic protective layer is 15μm-20μm.

[0010] Preferably, the ceramic substrate is any one of alumina ceramic, aluminum nitride ceramic, silicon nitride ceramic and zirconia ceramic, and the surface of the ceramic substrate includes a plane or a curved surface.

[0011] Preferably, the raw material components of the solder joint include: 35wt%-50wt% of SiCN precursor ceramic solution and 50wt%-65wt% of TiB2 powder.

[0012] Preferably, the lead wire is a platinum wire, and the pressing block is a grooved alumina disc.

[0013] Preferably, the use temperature range of the high-temperature platinum thin film temperature sensor is 50℃-800℃.

[0014] According to a second aspect, the application provides a preparation method of the high-temperature platinum thin film temperature sensor based on direct writing forming described above, comprising the following steps:

[0015] S1: washing and drying the ceramic substrate;

[0016] S2: weigh the platinum slurry raw material, add 2wt%~4wt% of slurry diluent, mix well to obtain a platinum slurry for direct writing, use the Weissenberg direct writing forming technology to directly write platinum sensitive gates on the surface of the ceramic substrate of step S1, the inner diameter of the direct writing needle is 0.25mm~0.4mm, and the direct writing speed is 0.15mm / s~0.3mm / s;

[0017] S3: sinter the platinum sensitive gate of step S2, the sintering conditions are as follows: the temperature is raised from room temperature to 150℃~180℃ at a rate of 5℃ / min~8℃ / min and kept for 10min~20min, then the temperature is continuously raised to 950℃~1000℃ and kept for 20min~30min, and then the temperature is lowered to room temperature at a rate of 5℃ / min~8℃ / min, thereby obtaining a platinum sensitive gate with four pins;

[0018] S4: add 25wt%~35wt% of TiB2 powder, 1.2wt%~2wt% of Y2O3 powder and 13.8wt%~23wt% of ZrO2 powder into 45wt%~55wt% of SiCN precursor ceramic solution, and perform magnetic stirring at a speed of 50r / min~100r / min for 1h~1.5h, thereby obtaining a precursor ceramic protective layer composite solution for direct writing; use the Weissenberg direct writing forming technology to directly write a precursor ceramic protective layer on the surface of the platinum sensitive gate of step S3, and expose the four pins of the platinum sensitive gate, the inner diameter of the direct writing needle is 0.25mm~0.4mm, and the direct writing speed is 0.15mm / s~0.3mm / s;

[0019] S5: pyrolyze the precursor ceramic protective layer of step S4, the pyrolysis conditions are as follows: the temperature is raised from room temperature to 450℃~480℃ at a rate of 4℃ / min~5℃ / min and kept for 1h~1.5h, then the temperature is continuously raised to 800℃~850℃ and kept for 1h~1.5h, and then the temperature is lowered to room temperature at a rate of 4℃ / min~5℃ / min;

[0020] S6: add 50wt%~65wt% of TiB2 powder into 35wt%~50wt% of SiCN precursor ceramic solution, and perform magnetic stirring at a speed of 50r / min~100r / min for 1h~1.5h, thereby obtaining a solder joint composite solution, and coating solder joints on the surfaces of the four pins of the platinum sensitive gate;

[0021] S7: insert the four leads into the slots of the four pressing blocks respectively to form an interference fit, and fix the side with the slots of the pressing block to the solder joints of step S6;

[0022] S8: pyrolyzing the solder joint of step S7, the pyrolysis condition is: heating from room temperature to 800-850 DEG C at a heating rate of 4-5 DEG C / min, and then cooling to room temperature at a cooling rate of 4-5 DEG C / min, so that the four leads of step S7 are electrically connected with the platinum sensitive gate through the solder joint.

[0023] According to a third aspect, the application provides an application of the above-mentioned high-temperature platinum thin film temperature sensor based on direct writing forming in situ temperature monitoring on a curved ceramic bearing.

[0024] Compared with the prior art, the application has the following beneficial effects:

[0025] (1) The high-temperature platinum thin film temperature sensor based on direct writing forming has the advantages of high-temperature resistance, small disturbance and good high-temperature stability, and can work stably at 50 DEG C to 800 DEG C; the total thickness of the platinum sensitive gate and the precursor ceramic protective layer is less than 25 mu m, the high-temperature resistance drift rate (800 DEG C for 1 h) is less than 0.62%, and the linearity is excellent, and the correlation coefficient R 2 reaches 0.99996.

[0026] (2) In the preparation method of the high-temperature platinum thin film temperature sensor based on direct writing forming, the platinum sensitive gate and the precursor ceramic protective layer are both prepared by direct writing forming technology, without mask, and the thickness and uniformity of the thin film are easier to control. Due to the precise deposition of the thin film material, the material loss is small, and the cost is low.

[0027] (3) The high-temperature platinum thin film temperature sensor based on direct writing forming can be prepared in situ and non-destructively on a curved part by a four / five-axis weissenberg direct writing platform, which is expected to break through the bottleneck problems of high cost, single material and difficulty in curved conformal preparation caused by the current screen printing and magnetron sputtering process for preparing thin film temperature sensors. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings are included to provide a further understanding of embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the description, serve to explain the principles of the application. Other embodiments and many of the intended advantages of the embodiments will be readily appreciated as the same becomes better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.

[0029] Figure 1 The structure diagram of the high-temperature platinum thin film temperature sensor based on direct writing forming of the embodiments of the application;

[0030] Figure 2The exploded view of the direct-write precursor based high temperature platinum thin film temperature sensor of the embodiment of the present application;

[0031] Figure 3 The flow chart of the preparation method of the direct-write precursor based high temperature platinum thin film temperature sensor of the embodiment of the present application;

[0032] Figure 4 The high temperature performance test result graph of the direct-write precursor based high temperature platinum thin film temperature sensor of the embodiment of the present application, Figure 4 The (a) is the single round temperature rising and falling test result graph at 50-800℃, the (b) is the temperature-resistance curve fitting result graph, the (c) is the three round temperature-resistance test result graph at 50-800℃, the (d) is the six round temperature curve comparison result graph with K-type thermocouple, the (e) is the high temperature stability test result graph, and the (f) is the high temperature dynamic stability test result graph;

[0033] Figure 5 The micro-morphology characterization and element analysis result graph of the platinum sensitive grid and the protective layer of the high temperature platinum thin film temperature sensor in the embodiment 1 of the present application, Figure 5 The (a) is the EDS line scanning graph of the platinum sensitive grid, the (b) is the SEM magnification graph of the platinum sensitive grid, the (c) is the energy spectrum analysis result graph of the platinum sensitive grid, and the (d) is the SEM result graph of the precursor ceramic protective layer;

[0034] Figure 6 The cross-section morphology characterization and structure schematic diagram of the high temperature platinum thin film temperature sensor in the embodiment 1 of the present application, Figure 6 The (a) is the sensor cross-section SEM result graph, and the (b) is the sensor cross-section structure schematic diagram;

[0035] Figure 7 The sensor structure schematic diagram and test result graph of the sensor without direct-write precursor ceramic protective layer in the comparative example of the present application, Figure 7 The (a) is the sensor structure schematic diagram, and the (b) is the three round temperature-resistance test result graph of the sensor at 50-800℃;

[0036] Figure 8 The structure schematic diagram of the bearing-based high temperature platinum thin film temperature sensor in the embodiment 2 of the present application;

[0037] Figure 9 The three round temperature test result graph of the bearing-based high temperature platinum thin film temperature sensor in the embodiment 2 of the present application;

[0038] The figure mark: 1, ceramic substrate; 2, platinum sensitive grid; 3, precursor ceramic protective layer; 4, solder joint; 5, lead wire; 6, pressing block. DETAILED DESCRIPTION

[0039] The application will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related application, and not to limit the application. In addition, it should be noted that only the parts related to the application are shown in the drawings for ease of description.

[0040] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and embodiments.

[0041] Reference Figure 1 and Figure 2 In the embodiments of the present application, a high-temperature platinum thin film temperature sensor based on direct writing forming is provided, which comprises a ceramic substrate 1, a platinum sensitive grid 2, a precursor ceramic protective layer 3, a solder joint 4, a lead wire 5 and a pressing block 6. The platinum sensitive grid 2 and the precursor ceramic protective layer 3 are sequentially directly written on the ceramic substrate 1 by the Weissenberg direct writing forming technology. The raw material components for directly writing the precursor ceramic protective layer 3 include 45wt%-55wt% of SiCN precursor ceramic solution, 25wt%-35wt% of TiB2 powder, 1.2wt%-2wt% of Y2O3 powder and 13.8wt%-23wt% of ZrO2 powder. The average particle size of the TiB2 powder is 50nm, and the average particle size of the Y2O3 and ZrO2 powders is 30nm-50nm. The precursor ceramic protective layer 3 covers the platinum sensitive grid 2. The lead wire 5 is arranged between the pressing block 6 and the platinum sensitive grid 2 and is electrically connected to the platinum sensitive grid 2 through the solder joint 4. The platinum sensitive grid 2 and the precursor ceramic protective layer 3 are both prepared by the Weissenberg direct writing forming technology, which has the advantages of no need for a mask plate, precise control of the thickness of the sensitive grid and the protective layer, and easy in-situ preparation of the sensor on a curved surface, and has great potential in the application of curved parts. At the same time, compared with the material used in the magnetron sputtering and the blade coating process, the material used in the present application is less, thereby reducing the cost.

[0042] In specific embodiments, the platinum sensitive grid 2 is provided with four pins, the pins are exposed outside the precursor ceramic protective layer 3, the solder joint 4 and the lead wire 5 are arranged on each pin respectively, and the lead wire 5 and the pin are fixed by the pressing block 6 and the solder joint 4. The pressing block 6 is provided with a slot on the side close to the solder joint 4, the lead wire 5 is in interference fit with the slot, and the lead wire 5 is led out from the slot. In order to improve the accuracy of the platinum thin film temperature sensor, a four-wire configuration is adopted to eliminate the influence of the solder joint and the lead wire. Therefore, the solder joint 4, the lead wire 5 and the pressing block 6 on the high-temperature platinum thin film temperature sensor are all four.

[0043] In specific embodiments, the thickness of the platinum sensitive gate 2 is 3-5 μm, and the thickness of the precursor ceramic protective layer 3 is 15-20 μm. Preferably, the thickness of the platinum sensitive gate 2 is 5 μm, the gate line width is 0.4 mm, and the total thickness of the thin film is less than 25 μm. The ceramic substrate 1 is any one of alumina ceramic, aluminum nitride ceramic, silicon nitride ceramic, and zirconia ceramic, and the surface thereof includes a plane or a curved surface. The raw material components of the solder joint include 35-50 wt% of a SiCN precursor ceramic solution and 50-65 wt% of a TiB2 powder. Preferably, the lead wire is a platinum wire, and the press block is a grooved alumina disc. Preferably, the high-temperature platinum thin film temperature sensor has a use temperature range of 50-800 °C and good high-temperature stability.

[0044] Reference Figure 3 The embodiments of the present application provide a preparation method of a high-temperature platinum thin film temperature sensor based on direct writing molding as described above, which comprises the following steps:

[0045] S1: sequentially clean the ceramic substrate 1 with acetone, alcohol, and deionized water by ultrasonic cleaning, and dry the cleaned ceramic substrate 1;

[0046] S2: weigh the platinum slurry raw material, add 2-4 wt% of a slurry diluent, and fully stir and mix to obtain a platinum slurry for direct writing. The platinum sensitive gate 2 is directly written on the surface of the ceramic substrate 1 of step S1 by using the Weissenberg direct writing molding technology, the inner diameter of the direct writing needle is 0.25-0.4 mm, and the direct writing speed is 0.15-0.3 mm / s.

[0047] S3: sinter the platinum sensitive gate 2 of step S2, and the sintering conditions are as follows: the temperature is increased from room temperature to 150-180 °C at a rate of 5-8 °C / min and maintained for 10-20 min, then the temperature is further increased to 950-1000 °C and maintained for 20-30 min, and then the temperature is decreased to room temperature at a rate of 5-8 °C / min, thereby obtaining a platinum sensitive gate 2 with four pins; and thereby reducing the internal defects and internal stress of the platinum thin film, and improving the high-temperature stability of the platinum sensitive gate 2.

[0048] S4: 25wt%-35wt% of TiB2 powder, 1.2wt%-2wt% of Y2O3 powder and 13.8wt%-23wt% of ZrO2 powder are added into 45wt%-55wt% of SiCN precursor ceramic solution, magnetic stirring is carried out, the rotating speed is 50r / min-100r / min, and the time is 1h-1.5h, so as to obtain a direct writing precursor ceramic protective layer 3 composite solution; the Weissenberg direct writing forming technology is adopted to directly write the precursor ceramic protective layer 3 on the upper surface of the platinum sensitive gate 2 in step S3, and four pins of the platinum sensitive gate are exposed, the inner diameter of a direct writing needle is 0.25mm-0.4mm, and the direct writing speed is 0.15mm / s-0.3mm / s.

[0049] S5: the precursor ceramic protective layer 3 in step S4 is pyrolyzed, the pyrolysis condition is that the temperature is increased from room temperature to 450℃-480℃ at a temperature increasing rate of 4℃ / min-5℃ / min, and the temperature is kept for 1h-1.5h, then the temperature is continuously increased to 800℃-850℃ and kept for 1h-1.5h, and then the temperature is decreased to room temperature at a temperature decreasing rate of 4℃ / min-5℃ / min; after high-temperature pyrolysis, the composite protective layer with uniform element distribution is formed.

[0050] S6: 50wt%-65wt% of TiB2 powder is added into 35wt%-50wt% of SiCN precursor ceramic solution, magnetic stirring is carried out, the rotating speed is 50r / min-100r / min, and the time is 1h-1.5h, so as to obtain a solder joint composite solution, and the solder joint 4 is coated on the upper surface of the four pins of the platinum sensitive gate 2 respectively.

[0051] S7: four lead wires 5 are respectively inserted into the slots of the four pressing blocks 6, so as to form an interference fit, and the side with the slot of the pressing block 6 is fixedly connected with the solder joint 4 in step S6.

[0052] S8: the solder joint 4 in step S7 is pyrolyzed, the pyrolysis condition is that the temperature is increased from room temperature to 800℃-850℃ at a temperature increasing rate of 4℃ / min-5℃ / min, and then the temperature is decreased to room temperature at a temperature decreasing rate of 4℃ / min-5℃ / min, so that the four lead wires 5 in step S7 are electrically connected with the platinum sensitive gate 2 through the solder joint 4.

[0053] The embodiment of the application further provides an application of the high-temperature platinum thin film temperature sensor based on the direct writing forming to in-situ temperature monitoring on a curved ceramic bearing.

[0054] The terms used in the application have the meanings generally understood by those of ordinary skill in the art, unless otherwise specified. In order for those skilled in the art to better understand the technical solutions of the application, the application will be further described in detail below with reference to the embodiments.

[0055] In the following examples, various processes and methods that are not described in detail are conventional methods well known in the art. The materials, reagents, devices, instruments, apparatuses, etc. used in the following examples are commercially available unless otherwise stated.

[0056] The present application is further illustrated in the following examples.

[0057] Example 1

[0058] S1: The ceramic substrate 1 was sequentially cleaned with acetone, alcohol and deionized water by ultrasonic cleaning, and the cleaned ceramic substrate 1 was dried;

[0059] S2: The platinum paste raw material was weighed, 3wt% of the paste diluent was added, and the mixture was fully stirred and uniformly mixed to obtain a direct writing platinum paste. The platinum sensitive gate 2 was directly written on the surface of the ceramic substrate 1 of step S1 using the Weissenberg direct writing forming technology, the inner diameter of the direct writing needle was 0.4mm, and the direct writing speed was 0.2mm / s;

[0060] S3: The platinum sensitive gate 2 of step S2 was sintered, and the sintering conditions were as follows: the temperature was raised from room temperature to 150℃ at a rate of 8℃ / min and kept for 10min, then the temperature was raised to 950℃ and kept for 20min, and then the temperature was lowered to room temperature at a rate of 8℃ / min, thereby obtaining a platinum sensitive gate 2 with four pins;

[0061] S4: 30wt% of TiB2 powder, 1.6wt% of Y2O3 powder and 18.4wt% of ZrO2 powder were added to 50wt% of SiCN precursor ceramic solution, and magnetic stirring was performed at a speed of 50r / min for 1h to obtain a direct writing precursor ceramic protective layer 3 composite solution. The precursor ceramic protective layer 3 was directly written on the surface of the platinum sensitive gate 2 of step S3 using the Weissenberg direct writing forming technology, and the four pins of the platinum sensitive gate were exposed, the inner diameter of the direct writing needle was 0.3mm, and the direct writing speed was 0.3mm / s;

[0062] S5: The precursor ceramic protective layer 3 of step S4 was pyrolyzed, and the pyrolysis conditions were as follows: the temperature was raised from room temperature to 450℃ at a rate of 5℃ / min and kept for 1h, then the temperature was raised to 800℃ and kept for 1h, and then the temperature was lowered to room temperature at a rate of 5℃ / min;

[0063] S6: 65wt% of TiB2 powder was added to 35wt% of SiCN precursor ceramic solution, and magnetic stirring was performed at a speed of 50r / min for 1h to obtain a solder joint 4 composite solution, which was coated on the surface of the four pins of the platinum sensitive gate 2;

[0064] S7: Four lead wires 5 were inserted into the slots of four pressing blocks 6 respectively to form an interference fit, and the side with the slot of the pressing block 6 was fixed to the solder joint 4 of step S6.

[0065] S8: pyrolyzing the solder joint 4 of step S7 under the pyrolysis condition of heating from room temperature to 800℃ at a heating rate of 5℃ / min and then cooling to room temperature at a cooling rate of 5℃ / min, so that the four lead wires 5 of step S7 are electrically connected to the platinum sensitive gate 2 through the solder joint 4.

[0066] A high-temperature platinum thin film temperature sensor as shown in Figure 1 and Figure 2 is prepared by the above steps. A data acquisition system and a computer are used to obtain the temperature and resistance signals of the K-type thermocouple and the platinum thin film temperature sensor placed in a tube furnace in real time, so as to test the high-temperature performance of the platinum thin film temperature sensor. The test results are shown in Figure 4 . First, the temperature-resistance variation law of the platinum thin film temperature sensor in a single round of temperature rise and fall from 50℃ to 800℃ is tested. The results are shown in Figure 4 (a). When the temperature is within 50℃ to 800℃, the high-temperature platinum thin film temperature sensor has a temperature rise and fall curve that is relatively coincident, showing a positive resistance temperature coefficient. The single round of temperature-resistance curve of the high-temperature platinum thin film temperature sensor is nonlinearly fitted. The fitting results are shown in Figure 4 (b). The linearity is excellent, and the correlation coefficient R 2 reaches 0.99996.

[0067] In practical applications, the repeatability and high-temperature stability of the high-temperature temperature sensor during temperature cycling are very important. The temperature-resistance variation law of the high-temperature platinum thin film temperature sensor in three rounds from 50℃ to 800℃ is measured. The results are shown in Figure 4 (c). The three rounds of temperature-resistance curves are relatively coincident, indicating that it has good repeatability. By comparison, the upper limit of the temperature measurement in this embodiment is much higher than that of the platinum thin film temperature sensor prepared by the direct writing process reported at present, which has a temperature measurement upper limit of only 500℃. Subsequently, the high-temperature platinum thin film temperature sensor is tested in six rounds of continuous temperature cycling for more than 40 hours, and compared with the K-type thermocouple. The results are shown in Figure 4 (d). It can be clearly seen that the high-temperature platinum thin film temperature sensor has fast response and relatively good dynamic performance.

[0068] The high-temperature stability of the high-temperature platinum thin film temperature sensor is tested, and the resistance drift rate is measured at 500℃, 600℃, 700℃ and 800℃ for 1h respectively. The high-temperature stability test results are shown in Figure 4 (e). The maximum resistance drift rate is only 0.62%, which is better than the polymer precursor ceramic thin film temperature sensor with better oxidation resistance. Finally, the high-temperature dynamic stability of the high-temperature platinum thin film temperature sensor is tested, i.e. four rounds of rapid temperature rise and fall tests are carried out at 500℃ to 600℃, 600℃ to 700℃ and 700℃ to 800℃ respectively. The results are shown in Figure 4(f) shows that the maximum and minimum temperature points of each interval temperature cycle show good consistency, and the maximum resistance change rate is 0.41%. The above test results show that the high-temperature platinum thin film temperature sensor has excellent repeatability and high-temperature stability in the temperature range of 50°C to 800°C.

[0069] The surface micro-morphology of the platinum sensitive grid 2 and the precursor ceramic protective layer 3 is observed and element analyzed by using a scanning electron microscope. The EDS line scanning graph and the SEM magnification graph of the platinum sensitive grid 2 are respectively shown in Figure 5 (a) and 5(b), the porosity of the direct-written platinum sensitive grid 2 is between 16.1% and 19.8%, and the volatilization of the organic solvent in the sintering process is one of the reasons for the generation of the porosity of the platinum sensitive grid 2. In the preparation process of the platinum sensitive grid 2, the existence of appropriate porosity is allowed, and the appropriate porosity will cause the resistance of the platinum sensitive grid 2 to increase, which is helpful to improve the sensitivity of the sensor. The composition of the platinum sensitive grid 2 is analyzed by using a spectrum analyzer, and the result is shown in Figure 5 (c). The atomic composition ratio of C, O and Pt of the platinum sensitive grid 2 is 5.94:2.49:91.57, which shows that the main component of the platinum sensitive grid 2 is platinum, but there is a small amount of impurities. The precursor ceramic protective layer 3 is crucial to the stability improvement of the high-temperature platinum thin film temperature sensor, and the SEM result graph of the precursor ceramic protective layer 3 is shown in Figure 5 (d), the precursor ceramic protective layer 3 has porosity and micro-cracks, which is similar to the typical plasma sprayed YSZ coating morphology. Figure 6 (a) shows the cross-section SEM result graph of the sensor, and the ceramic substrate 1, the platinum sensitive grid 2 and the precursor ceramic protective layer 3 are closely combined with each other. The precursor ceramic protective layer 3 is oxidized after pyrolysis, and the thickness of the oxide layer formed on the surface is about 5.5 μm, and the thickness of the unoxidized part is 13.1 μm. In addition, the thickness of the platinum sensitive grid is about 5 μm, that is, the total thickness of the thin film is less than 25 μm, which can meet the needs of small disturbance and in-situ temperature monitoring of the thin film sensor. The packaging of the platinum thin film temperature sensor by using the precursor ceramic protective layer 3 has the advantage of thin thickness, which can make the temperature measurement of the sensor more accurate, and the response time is shortened, while in the previous research, the packaging thickness of the platinum thin film sensor is often greater than 100 μm.

[0070] The cross-section structure schematic diagram of the sensor is shown in Figure 6(b) shows. The surface TiB2 element of the precursor ceramic protective layer 3 is oxidized to TiO2 and B2O3, and SiCN is oxidized to SiO2, Y2O3 and ZrO2 are stable phases. Therefore, the main components of the surface oxidation layer of the precursor ceramic protective layer 3 are SiO2, B2O3, TiO2, Y2O3 and ZrO2, and the main components of the unoxidized precursor ceramic protective layer 3 are SiCN, TiB2, Y2O3 and ZrO2. Y2O3 and ZrO2 can exist stably at high temperatures, improving the stability and sintering resistance of the precursor ceramic protective layer 3. The glass phase SiO2 and B2O3 have fluidity at high temperatures, which can effectively fill the cracks and pores of the protective layer and prevent further oxidation of the inside, thereby improving the oxidation resistance of the protective layer. In addition, since the precursor ceramic protective layer 3 is prepared based on the liquid phase one-step forming process, it effectively fills the pores of the platinum sensitive grid 2, thereby anchoring the platinum particles to reduce their high-temperature thermal volatilization and agglomeration.

[0071] Comparative Example

[0072] The difference between the comparative example of the present application and example 1 is that the precursor ceramic protective layer 3 is not directly written and pyrolyzed, that is, steps S4 and S5 are not performed, and the rest of the operations are the same as example 1. A high-temperature platinum thin film temperature sensor without a precursor ceramic protective layer 3 is prepared, and its structure is as shown in Figure 7 (a). Its three-round temperature resistance change law at 50-800°C is measured, and the results are shown in Figure 7 (b). The resistance fluctuation is obvious, and the coincidence degree of the three-round temperature resistance curve is low, indicating that the high-temperature platinum thin film temperature sensor without a precursor ceramic protective layer 3 has poor repeatability when measuring temperature. The reason for its poor repeatability is that the platinum sensitive grid 2 is directly exposed to a high-temperature environment, which has problems such as film agglomeration and thermal volatilization, and under the protection of the precursor ceramic protective layer 3, the sensor exhibits excellent stability.

[0073] Example 2

[0074] Reference Figure 8 , example 2 and example 1 use similar sensor structures, the difference is that the ceramic substrate 1 of example 2 can be a silicon nitride bearing with curved surface characteristics, and in addition, when performing step S2, the four pins of the platinum sensitive grid 2 are led to the bearing end face through the five-axis weissenberg direct writing platform. The rest of the operations are the same as example 1. The aviation bearing is one of the most important parts of the aero-engine, and the temperature monitoring of the aviation bearing helps to diagnose the early failure and optimize the structure of the bearing; the existing sensors installed by digging holes, patch type sensors and magnetron sputtering sensors have problems such as difficulty in conforming to curved surfaces and damaging installation. The present application can combine four / five-axis motion platform to prepare platinum thin film temperature sensor in situ and non-destructively on curved surface parts. The multi-round temperature test result graph of the high-temperature platinum thin film temperature sensor based on direct writing in example 2 is as followsFigure 9 The results show that the in-situ temperature monitoring on the surface of the silicon nitride bearing can be achieved from 50 to 800 DEG C. The advantages of the high-temperature platinum thin film temperature sensor prepared based on the direct writing technology are shown, and it is expected to break through the bottleneck problems such as conformal difficulty, single material and high cost caused by the current screen printing and magnetron sputtering process for preparing thin film temperature sensors.

[0075] The specific embodiments of the present application are described above, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0076] In the description of the present application, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "inner", "outer" and the like is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. The word 'comprising' does not exclude the existence or presence of elements or steps not listed in the claims. The word 'a' or 'an' in front of an element does not exclude the existence of multiple such elements. The simple fact that certain measures are recorded in mutually different dependent claims does not indicate that the combination of these measures cannot be used to improve. Any reference signs in the claims should not be interpreted as limiting the scope.

Claims

1. A high-temperature platinum thin-film temperature sensor based on direct-write molding, characterized in that, The system comprises a ceramic substrate, a platinum sensing gate, a precursor ceramic protective layer, solder joints, leads, and a clamping block. The platinum sensing gate and the precursor ceramic protective layer are sequentially direct-written onto the ceramic substrate using Wesenberg direct-write molding technology. The raw material components used for direct-writing the precursor ceramic protective layer include: 45wt%–55wt% SiCN precursor ceramic solution, 25wt%–35wt% TiB2 powder, 1.2wt%–2wt% Y2O3 powder, and 13.8wt%–23wt% ZrO2 powder. The precursor ceramic protective layer covers the substrate. On the platinum sensitive grid, the lead wire is disposed between the pressure block and the platinum sensitive grid, and is electrically connected to the platinum sensitive grid through the solder joint. The platinum sensitive grid has four pins, which are exposed outside the precursor ceramic protective layer. The solder joint and the lead wire are respectively disposed on each pin, and the lead wire and the pin are fixedly connected by the pressure block and the solder joint. The thickness of the platinum sensitive grid is 3μm to 5μm, and the thickness of the precursor ceramic protective layer is 15μm to 20μm. The fabrication method of the high-temperature platinum thin film temperature sensor includes the following steps: S1: Clean and dry the ceramic substrate; S2: Weigh the platinum paste raw material, add 2wt% to 4wt% paste diluent, stir and mix thoroughly to obtain a platinum paste suitable for direct writing, and use the Wesenberg direct writing molding technology to directly write the platinum sensitive grid on the ceramic substrate surface in step S1. The inner diameter of the direct writing needle is 0.25mm to 0.4mm, and the direct writing speed is 0.15mm / s to 0.3mm / s. S3: Sintering the platinum sensing gate from step S2. The sintering conditions are as follows: heating from room temperature to 150℃ to 180℃ at a heating rate of 5℃ / min to 8℃ / min and holding for 10min to 20min, then heating to 950℃ to 1000℃ and holding for 20min to 30min, and then cooling to room temperature at a cooling rate of 5℃ / min to 8℃ / min to obtain a platinum sensing gate with four pins. S4: Add 25wt%–35wt% TiB2 powder, 1.2wt%–2wt% Y2O3 powder, and 13.8wt%–23wt% ZrO2 powder to a 45wt%–55wt% SiCN precursor ceramic solution and magnetically stir at a speed of 50 r / min–100 r / min for 1 h–1.5 h to obtain a precursor ceramic protective layer composite solution suitable for direct writing; use the Weissenberg direct writing molding technology to directly write the precursor ceramic protective layer on the upper surface of the platinum sensitive gate in step S3, exposing the four pins of the platinum sensitive gate. The inner diameter of the direct writing needle is 0.25 mm–0.4 mm, and the direct writing speed is 0.15 mm / s–0.3 mm / s. S5: The precursor ceramic protective layer of pyrolysis step S4, the pyrolysis conditions are as follows: the temperature is raised from room temperature to 450℃~480℃ at a heating rate of 4℃ / min~5℃ / min and held for 1h~1.5h, then the temperature is raised to 800℃~850℃ and held for 1h~1.5h, and then the temperature is lowered to room temperature at a cooling rate of 4℃ / min~5℃ / min. S6: Add 50wt% to 65wt% of TiB2 powder to 35wt% to 50wt% of SiCN precursor ceramic solution, and perform magnetic stirring at a speed of 50 r / min to 100 r / min for 1 h to 1.5 h to obtain a solder joint composite solution. Coat the solder joints on the upper surface of the four pins of the platinum sensitive gate respectively. S7: Insert the four leads into the slots of the four pressure blocks respectively to form an interference fit, and fix the slotted side of the pressure block to the solder joint in step S6. S8: The solder joints in step S7 are pyrolyzed. The pyrolysis conditions are: the temperature is increased from room temperature to 800℃ to 850℃ at a heating rate of 4℃ / min to 5℃ / min, and then cooled to room temperature at a cooling rate of 4℃ / min to 5℃ / min, so that the four leads in step S7 are electrically connected to the platinum sensitive gate through the solder joints.

2. The high-temperature platinum thin-film temperature sensor based on direct-write molding according to claim 1, characterized in that, The pressure block has a slot on the side near the welding point, and the lead wire is interference-fitted with the slot and leads out from the slot.

3. The high-temperature platinum thin-film temperature sensor based on direct-write molding according to claim 1, characterized in that, The ceramic substrate is any one of alumina ceramic, aluminum nitride ceramic, silicon nitride ceramic, and zirconium oxide ceramic, and its surface includes a plane or a curved surface.

4. The high-temperature platinum thin-film temperature sensor based on direct-write molding according to claim 1, characterized in that, The raw material composition of the solder joint includes: 35wt% to 50wt% SiCN precursor ceramic solution and 50wt% to 65wt% TiB2 powder.

5. The high-temperature platinum thin-film temperature sensor based on direct-write molding according to claim 1, characterized in that, The lead wire is a platinum wire, and the pressure block is a grooved alumina disc.

6. The high-temperature platinum thin-film temperature sensor based on direct-write molding according to claim 1, characterized in that, The operating temperature range of the high-temperature platinum thin film temperature sensor is 50°C to 800°C.

7. An application of a high-temperature platinum thin-film temperature sensor based on direct writing molding according to any one of claims 1-6 in in-situ temperature monitoring on curved ceramic bearings.

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