Polymer precursor ceramic membrane thermocouple and method of making same

Abstract

The present application relates to a kind of polymer precursor ceramic film thermocouple and its manufacturing method, thermocouple includes A electrode and B electrode, it is made on electric insulating coating, then lead is connected with welding spot, to output electric signal, manufacturing method is as follows: polysilazane solution and indium tin oxide (tin content 10% mass fraction) nano powder are mixed according to certain proportion to prepare A electrode, polysilazane solution and indium tin oxide (tin content 5% mass fraction) nano powder are mixed according to certain proportion to prepare B electrode, after screen printing, thin film A electrode line, B electrode line is obtained in electric insulating coating, and after solidification, it is placed in tube furnace, with 1 ℃ / min heating rate to 450 ℃, keep warm 1 hour;Again with 2.5 ℃ / min heating rate to 1000 ℃, keep warm 1 hour;Finally with 2.5 ℃ / min cooling rate to room temperature, finally, platinum wire is connected to two electrodes with welding spot, to output electric signal.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of ceramic thin film temperature sensors, and particularly relates to a polymer precursor ceramic thin film thermocouple and a manufacturing method thereof. BACKGROUND

[0002] An aero-engine blade is in an extreme environment of high temperature and high pressure for a long time, and is thus easily damaged, thereby affecting the health of the entire turbine engine. A large number of studies have shown that temperature is one of the main factors causing the damage of the engine blade. Therefore, it is required to accurately measure the temperature of the surface of the turbine blade. Only by accurately monitoring the temperature of the surface of the turbine blade in real time, can the damage of the engine blade due to excessively high temperature be effectively prevented.

[0003] A thermocouple is a widely used temperature measuring sensor, has a wide test temperature range, and is low in cost, high in precision and simple to use. Compared with a traditional filament thermocouple, a thin film thermocouple has higher test precision and faster response speed, and does not affect the flow field of the blade surface. A metal alloy thin film thermocouple has good thermoelectric response, but has limited high-temperature resistance and cannot be used for temperature measurement on the engine blade.

[0004] In the 1960s, a scholar proposed using a polymer precursor conversion method to prepare an advanced ceramic material. The ceramic is called polymer precursor ceramic, and is obtained by directly pyrolyzing a polymer precursor. The precursor is generally a polymer liquid, and can have specific properties through molecular design. The types of the precursor are various, and the materials can be selected from a plurality of materials. After solidification, cross-linking and pyrolysis, the precursor becomes a ceramic material.

[0005] Polymer precursor ceramics are widely researched and applied, and mainly include micro-electro-mechanical systems, high-temperature sensors, porous ceramics, energy storage materials, ceramic matrix composites and other fields. The polymer precursor ceramic has a temperature resistance of 1400 DEG C or above, and simultaneously has excellent high-temperature electrical properties, high-temperature creep resistance and high-temperature impact resistance.

[0006] Research on the preparation of temperature sensors by using polymer precursor ceramics mainly focuses on block temperature sensors, which are mainly contact type wired active and non-contact type wireless passive temperature sensors. Since a thin film temperature sensor has the advantages of small size, no disturbance to the flow field, high test precision and fast response, polymer precursor ceramic sensor thinning has become a trend. However, the temperature resistance of the temperature resistance type thin film sensor prepared by using the polymer precursor ceramic is low, the precision is poor, and there is great limitation. SUMMARY

[0007] The present application aims to provide a polymer precursor ceramic thin film thermocouple and a manufacturing method thereof to overcome the deficiencies of the prior art, fill the blank of using polymer precursor ceramics to prepare thermocouples, and solve the problem of difficult temperature detection of hot components such as engine blades. The technical scheme is as follows:

[0008] A polymer precursor ceramic thin film thermocouple for monitoring the temperature of the surface of a hot component comprises an A electrode and a B electrode, and the A electrode and the B electrode meet and overlap at one end to form a hot junction;

[0009] The A electrode and the B electrode are respectively provided with a solder joint at the end away from the hot junction, and a lead wire is connected for signal output;

[0010] The A electrode and the B electrode are respectively made of a polysilazane solution and indium tin oxide nano powder mixed in a certain proportion.

[0011] Optionally, the mass fraction of the polysilazane solution is 20% to 80%, and the mass fraction of the indium tin oxide nano powder is 80% to 20%.

[0012] Optionally, the A electrode and the B electrode are respectively made of 20% mass fraction of polysilazane solution and 80% mass fraction of indium tin oxide nano powder;

[0013] The tin content of the indium tin oxide nano powder in the A electrode mixture is 10% by mass;

[0014] The tin content of the indium tin oxide nano powder in the B electrode mixture is 5% by mass.

[0015] Optionally, the average particle size of the indium tin oxide nano powder is 20nm to 20µm.

[0016] Optionally, the solder joint is made of sintering of conductive paste, and the conductive paste is silver paste or platinum paste or silver palladium paste;

[0017] The lead wire is in a filament structure, and the lead wire is a platinum wire with a diameter of 0.2um.

[0018] Optionally, the thickness of the A electrode and the B electrode is less than 100um;

[0019] The width of the A electrode and the B electrode is 400um to 550um.

[0020] A manufacturing method of a polymer precursor ceramic thin film thermocouple comprises a mixed slurry a for manufacturing an A electrode and a mixed slurry b for manufacturing a B electrode;

[0021] The manufacturing steps are as follows:

[0022] (1) The mixed slurry a and the mixed slurry b are magnetically stirred at room temperature for 120 minutes;

[0023] (2) respectively screen printing mixed slurry a and mixed slurry b on the surface of the hot component to form A electrode lines and B electrode lines, and standing at room temperature for six hours or heating at 100℃ for half an hour to solidify;

[0024] (3) placing the hot component for preparing A electrode and B electrode in a tube furnace, heating to 450℃ at a heating rate of 1℃ / min, keeping for 1 hour; then heating to 1000℃ at a heating rate of 2.5℃ / min, keeping for 1 hour; finally, cooling to room temperature at a cooling rate of 2.5℃ / min and taking out;

[0025] (4) preparing a welding point at the end point of A electrode and B electrode, and then sintering at 800℃ for 10 minutes in a tube furnace.

[0026] Optionally, the hot component is a conductive component, and an electrically insulating coating is prepared on the surface of the hot component, and the step (2) is performed on the electrically insulating coating.

[0027] Optionally, the electrically insulating coating is an insulating material such as alumina or silicon carbide.

[0028] The thickness of the electrically insulating coating is 1 um - 100 um.

[0029] Optionally, one end of the A electrode and the B electrode is overlapped to form a hot node, and the end of the A electrode and the B electrode away from the hot node is provided as a welding point.

[0030] In summary, the present application includes the following beneficial effects:

[0031] 1. The present application provides a thin film thermocouple obtained by uniformly mixing a polymer precursor ceramic solution and a ceramic powder and then pyrolyzing at high temperature, which can withstand a temperature of 1400℃ or above, and has excellent high-temperature electrical properties, high-temperature creep resistance and high-temperature impact resistance.

[0032] 2. The thin film thermocouple prepared by using a polymer precursor ceramic is used for temperature measurement of engine blades, which can realize the detection of engine blade temperature in a high-temperature and high-pressure environment, solve the problem of difficulty in temperature detection on hot component blades, effectively prevent the hot component blades from being damaged due to excessive temperature, and ensure the healthy operation of the hot component. The hot component mainly includes high-temperature components in the fields of aeroengines, gas turbines, nuclear power devices and industrial chemical engineering.

[0033] 3. The thin film thermocouple prepared in the present application as a polymer precursor ceramic temperature sensor has the advantages of small volume, no interference to the flow field, high testing precision and fast response, and can adapt to high-temperature measurement in harsh environments, which is conducive to measuring small area surfaces and areas with rapid temperature changes. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a structural schematic diagram of the application of the polymer precursor ceramic thin film thermocouple in the heat component in the embodiment;

[0035] Figure 2 is a schematic diagram of the overall shape of the specific implementation of the polymer precursor ceramic thin film thermocouple on the engine blade in the embodiment;

[0036] Figure 3 is a schematic diagram of the structure of the engine blade root welding point and the lead wire in the embodiment;

[0037] Figure 4 is a schematic diagram of the cycle test of the polymer precursor ceramic thin film thermocouple in the embodiment;

[0038] Figure 5 is a signal output diagram of the cycle test of the polymer precursor ceramic thin film thermocouple in the embodiment.

[0039] Explanation of reference numerals: 1, insulating coating; 2, hot node; 3, A electrode; 4, B electrode; 5, lead wire; 6, welding point. DETAILED DESCRIPTION

[0040] The following will be described in detail in combination with the accompanying drawings. Figures 1-5 The application will be further described in detail.

[0041] The embodiment of the application discloses a polymer precursor ceramic thin film thermocouple and a manufacturing method thereof. The structure of the polymer precursor ceramic thin film thermocouple comprises an A electrode 3 and a B electrode 4. The thermocouple of the application is mainly used in the detection of heat components, which refers to some high-temperature parts and devices, such as high-temperature components in the fields of aero-engines, gas turbines, nuclear power devices and industrial chemical engineering, etc. Figure 1 The A electrode 3 and the B electrode 4 are prepared on the surface of the heat component. One end of the A electrode 3 and the B electrode 4 is overlapped to form a hot node. The other end of the A electrode 3 and the B electrode 4 is respectively provided with a welding point for connecting a lead wire to output a signal.

[0042] The application mainly takes the engine blade as an example, but the application of the thermocouple is not limited to the engine blade. Any heat component applying the thermocouple for temperature detection belongs to the parameters that can be modified by the person skilled in the art according to different use scenarios, which belongs to a simple replacement under the technical concept of the embodiment.

[0043] Taking the engine blade as an example, as shown in FIG. 1, the A electrode 3 and the B electrode 4 are prepared on the surface of the engine blade. One end of the A electrode 3 and the B electrode 4 is overlapped to form a hot node 2. The other end of the A electrode 3 and the B electrode 4 is respectively provided with a welding point 6 for connecting a lead wire 5 to output a signal. Figure 2An electrically insulating coating 1, i.e. an insulating layer, is laid on the surface of the engine blade, and then a polymer precursor ceramic thin film thermocouple is prepared on the insulating layer, with an A electrode 3 and a B electrode 4 oppositely arranged and both extending from the surface of the engine blade to the blade root and extending to the blade root, and the A electrode 3 and the B electrode 4 intersect and overlap at one end on the surface of the engine blade to form a hot junction 2, and the A electrode 3 and the B electrode 4 are connected to a lead wire 5 at the other end away from the hot junction 2, i.e. at the blade root, for outputting an electric signal of the thermocouple, and the solder joint 6 and the lead wire 5 are welded together as shown in Figure 3 .

[0044] The hot junction 2 is a temperature measuring point of the polymer precursor ceramic thin film thermocouple, and is used to measure the temperature at the point on the surface of the engine blade, and the polymer precursor ceramic thin film thermocouple is connected to the relevant detection equipment through the lead wire 5 and outputs an electric potential signal through the lead wire 5.

[0045] The solder joint 6 of the present application is made of conductive paste sintering, and the conductive paste is silver paste or platinum paste or silver palladium paste, preferably conductive silver paste, and high-temperature silver paste is used for making, sintering at 800℃ for 10 minutes, and is used for connecting the lead wire 5 and the solder joint 6, which is not easy to fall off after solidification. The lead wire 5 is in a wire-like structure, and a platinum wire with a diameter of 0.2um can be selected for outputting a signal and connecting the relevant detection equipment to output an electric potential signal.

[0046] The polymer precursor ceramic thin film thermocouple of the present application is mainly prepared by using polymer precursor ceramic, which is a ceramic obtained directly by pyrolyzing a polymer precursor. The precursor is generally a polymer liquid, which can have specific properties through molecular design, and there are many types of materials that can be selected. After solidification, crosslinking and pyrolysis, it becomes a ceramic material. Crosslinking and pyrolysis are processes of decarburization and dehydrogenation, and part of the chemical bonds are broken to produce NH3, H2, CH4 and other gases, with a volume shrinkage of more than 50%, so it is relatively easy to break. Generally, the method of using particulate filler is used to offset the volume shrinkage. The pyrolysis temperature is lower than 800℃, close to the insulator, and the electrical conductivity is very large at 1400℃, and the same can be added to the particulate filler to regulate the performance.

[0047] Therefore, the polymer precursor ceramic thin film thermocouple of the present application is mainly prepared by mixing polysilazane solution and indium tin oxide nano powder in a certain proportion. The mass fraction of the polysilazane solution can be selected to be 20%~80%, and the mass fraction of the indium tin oxide nano powder can be selected to be 80%~20%, and the average particle size of the indium tin oxide nano powder is 20nm~20µm. The polymer precursor ceramic prepared by mixing the polysilazane solution and the indium tin oxide nano powder has high temperature resistance, which can be as high as more than 1400℃, and at the same time has excellent high temperature electrical properties, high temperature creep resistance and high temperature impact resistance.

[0048] The polymer precursor ceramic preparation process is more, including spin coating, dip coating, micro-molding, screen printing, electrojet printing and the like, the preparation process is simple, low cost, and the ceramic temperature is low, so as to provide a preparation method of polymer precursor ceramic thin film thermocouple.

[0049] The polymer precursor ceramic thin film thermocouple is prepared as follows:

[0050] (1) The mixed slurry a of the A electrode 3 and the mixed slurry b of the B electrode 4 are magnetically stirred at room temperature for 120 minutes.

[0051] (2) An electrically insulating coating 1 is coated on the surface of the engine blade (if the prepared hot part is an insulator, it does not conduct electricity, and no electrically insulating coating 1 is needed, and the next step is directly performed);

[0052] (3) The mixed slurry a and the mixed slurry b are screen printed on the electrically insulating coating 1 to form A electrode 3 lines and B electrode 4 lines, and are left to stand at room temperature for six hours or are heated on a heating table at 100℃ for half an hour to solidify;

[0053] (4) The engine blade for preparing the A electrode 3 and the B electrode 4 is placed in a tube furnace, and is heated at a heating rate of 1℃ / min to 450℃, and is kept at this temperature for 1 hour; then is heated at a heating rate of 2.5℃ / min to 1000℃, and is kept at this temperature for 1 hour; finally is cooled at a cooling rate of 2.5℃ / min to room temperature and is taken out;

[0054] (5) The soldering points 6 are prepared at the end points of the A electrode 3 and the B electrode 4, and then are sintered at 800℃ for 10 minutes in the tube furnace.

[0055] The electrically insulating coating 1, i.e. the insulating layer, mainly adopts an insulating block of alumina or silicon carbide, and the thickness of the electrically insulating coating 1 is 1um-100um.

[0056] The mixed ratio of the mixed slurry a is: 20% mass fraction of polysilazane solution and 80% mass fraction of indium tin oxide (wherein the tin content is 10% mass fraction) nano powder are mixed, and are magnetically stirred at room temperature for 120 minutes, and are used for preparing the A electrode 3.

[0057] The mixed ratio of the mixed slurry b is: 20% mass fraction of polysilazane solution and 80% mass fraction of indium tin oxide (wherein the tin content is 5% mass fraction) nano powder are mixed, and are magnetically stirred at room temperature for 120 minutes, and are used for preparing the B electrode 4.

[0058] The line width of the cured A electrode 3 and B electrode 4 obtained by screen printing is 400 um - 550 um, and the thickness is less than 100 um. Alternatively, the line width of the A electrode 3 and B electrode 4 is about 500 um, and the thickness is about 10 um, and the two have an intersection and overlap heat node 2 on the surface of the blade, and extend to the blade root through the surface of the blade and the edge plate respectively.

[0059] After the preparation, the polymer precursor ceramic thin film thermocouple is subjected to a cycle test from room temperature to 900℃, and the schematic diagram of the test system is shown in Figure 4 The hot junction end of the thin film thermocouple is placed in a high temperature furnace, and a standard S-type thermocouple is placed above the hot junction to synchronously measure the temperature at the hot junction. The cold junction of the thermocouple is placed on a water cooling table, and a K-type thermocouple is placed at the same level of the cold junction to synchronously measure the temperature at the cold end. The voltage output of the thermocouple, the temperatures at the cold and hot junctions measured by the two thermocouples are synchronously acquired by a multifunctional data acquisition system. The signal output of the polymer precursor ceramic thin film thermocouple is shown in Figure 5 The data points are fitted by a cubic term, and it can be known that the repetition characteristics of the three times of temperature rising and falling cycles are very good, the output is very stable, the maximum output voltage is 12.3 mV, and the Seebeck coefficient is about 15.1 uV / ℃.

[0060] The above are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, therefore: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A polymer precursor ceramic thin film thermocouple for monitoring the temperature of a hot component surface, characterized in that ;It comprises an A electrode and a B electrode, one end of the A electrode and the B electrode intersect and overlap to form a thermal node; The A electrode and the B electrode are respectively provided with a welding point at the end away from the thermal node, and the welding point is connected with a lead wire for outputting a signal; The A electrode and the B electrode are respectively made of a polysilazane solution and indium tin oxide nano powder mixed in a certain proportion; the mass fraction of the polysilazane solution is 20% to 80%, and the mass fraction of the indium tin oxide nano powder is 80% to 20%; the average particle size of the indium tin oxide nano powder is 20 nm to 20 µm; The A electrode and the B electrode are respectively made of 20% mass fraction of polysilazane solution and 80% mass fraction of indium tin oxide nano powder; the tin content of the indium tin oxide nano powder in the A electrode mixture is 10% mass fraction; the tin content of the indium tin oxide nano powder in the B electrode mixture is 5% mass fraction.

2. The polymer precursor ceramic thin film thermocouple of claim 1, wherein: The welding point is made of sintering of conductive paste, and the conductive paste is silver paste or platinum paste or silver palladium paste; The lead wire is in a filamentous structure, and the lead wire is a platinum wire with a diameter of 0.2 um.

3. The polymer precursor ceramic thin film thermocouple of claim 1, wherein: The thickness of the A electrode and the B electrode is less than 100 um; The width of the A electrode and the B electrode is 400 um to 550 um.

4. A method of fabricating a polymer precursor ceramic thin film thermocouple, comprising: It comprises a mixed slurry a for making the A electrode and a mixed slurry b for making the B electrode; the mixed slurry a is made of 20% mass fraction of polysilazane solution and 80% mass fraction of indium tin oxide nano powder, and the tin content of the indium tin oxide nano powder in the mixture is 10% mass fraction; the mixed slurry b is made of 20% mass fraction of polysilazane solution and 80% mass fraction of indium tin oxide nano powder, and the tin content of the indium tin oxide nano powder in the mixture is 5% mass fraction; The manufacturing steps are as follows: (1) The mixed slurry a and the mixed slurry b are magnetically stirred at room temperature for 120 minutes; (2) The mixed slurry a and the mixed slurry b are respectively screen printed on the surface of the thermal component to form A electrode lines and B electrode lines, and are left to stand at room temperature for six hours or are heated on a heating table at 100℃ for half an hour to solidify; (3) The thermal component provided with the A electrode and the B electrode is placed in a tube furnace, heated to 450℃ at a heating rate of 1℃ / min, kept for 1 hour, then heated to 1000℃ at a heating rate of 2.5℃ / min, kept for 1 hour, and finally cooled to room temperature at a cooling rate of 2.5℃ / min and taken out; (4) The welding points are prepared at the end points of the A electrode and the B electrode, and then sintered in the tube furnace at 800℃ for 10 minutes.

5. The method of claim 4, wherein the method further comprises: The thermal component is a conductive component, and an electrically insulating coating is prepared on the surface of the thermal component, and the step (2) is performed on the electrically insulating coating.

6. The method of claim 5, wherein the method further comprises: The electrically insulating coating is an alumina or silicon carbide insulating material; The thickness of the electrically insulating coating is 1 um to 100 um.

7. The method of claim 4, wherein the method further comprises: One end of the A electrode and the B electrode intersects and overlaps to form a thermal node, and the end of the A electrode and the B electrode away from the thermal node is provided with a welding point.

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