Coaxial temperature sensor for radiation thermometry and preparation method thereof

Abstract

The invention provides a coaxial temperature sensor for radiation thermometry and a preparation method thereof, the coaxial temperature sensor comprises a sensitive core body and a packaging tube shell, the sensitive core body comprises a tungsten-rhenium wire substrate, an insulating film layer and a positive electrode film layer, the insulating film layer forms a gradient structure on the tungsten-rhenium wire substrate through a dip-coating method, and the positive electrode film layer forms a negative electrode structure on the tungsten-rhenium wire substrate. The gradient structure comprises at least one bottom insulating layer with larger porosity and at least two compact upper insulating layers, the tungsten-rhenium wire substrate and the positive electrode film layer are respectively connected with metal wires, and the sensitive core body is connected with the metal wires and then fixed in the packaging tube shell. The coaxial temperature sensor determines the temperature of an object by detecting thermal radiation energy emitted by the high-temperature object, and has the advantages of electromagnetic interference resistance, no interference to a flow field, high sensitivity, small size, exquisite and compact structure and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of radiation high temperature measurement, in particular to a coaxial temperature sensor used for radiation high temperature measurement and a preparation method thereof. Background Art

[0002] Accurate temperature measurement is crucial in many fields such as industrial production and scientific research. Traditional temperature measurement methods such as armored thermocouple temperature measurement and thermal resistor temperature measurement face many challenges when measuring high temperatures, especially ultra-high temperatures exceeding 1800°C. On the one hand, high temperature environments can cause severe thermal shock and chemical corrosion to contact temperature measuring components, resulting in shortened component life, reduced accuracy, and even damage. On the other hand, in some special high-temperature scenarios, such as inside high-temperature furnaces, metal smelting processes, and rocket engine nozzles, contact temperature measurement is difficult to implement, and the measuring device cannot directly contact the object being measured, or the contact will interfere with the temperature field and physical and chemical processes of the measured object.

[0003] Radiation pyrometry is based on the principle of thermal radiation. It detects the thermal radiation energy emitted by the object being measured and uses specific radiation laws to infer the temperature of the object. It has the significant advantage of non-contact measurement. It can measure temperature without interfering with the temperature field and thermal state of the object being measured. It is suitable for temperature monitoring at high temperature, long distance, moving objects and in harsh environments. With the continuous development of optical technology, detector technology and signal processing technology, the accuracy, response speed and reliability of radiation pyrometry are also continuously improving, and it has gradually become an indispensable and important means in the field of high temperature measurement. The coaxial temperature sensor can be used as a key component of temperature perception in radiation pyrometry. It can be placed in an appropriate position to receive the thermal radiation of the object being measured, so that the temperature of the hot end changes and generates an electromotive force corresponding to the temperature difference. This electromotive force signal can be obtained by the subsequent measurement circuit and data acquisition system. By measuring and converting the electromotive force, the temperature change of the hot end can be inferred, and then the radiation temperature of the object being measured can be obtained. Most traditional coaxial temperature sensors use a nickel-chromium-constantan sleeve structure, which has problems such as low upper temperature measurement limit and large measurement error caused by too thick insulation layer. Therefore, it is urgent to develop a coaxial temperature sensor with ultra-high temperature resistance and high accuracy. Summary of the invention

[0004] In order to solve the above technical problems existing in the prior art, the present invention proposes a coaxial temperature sensor for radiation high temperature measurement and a preparation method thereof, which solves the above technical problems.

[0005] According to a first aspect of the present invention, a coaxial temperature sensor for radiation high temperature measurement is proposed, comprising a sensitive core and a packaging tube shell, wherein the sensitive core comprises a tungsten-rhenium wire substrate, an insulating film layer and a positive electrode film layer, wherein the insulating film layer forms a gradient structure on the tungsten-rhenium wire substrate by an immersion-pulling method, wherein the gradient structure comprises at least one bottom insulating layer with a large porosity and at least two dense upper insulating layers, wherein the tungsten-rhenium wire substrate and the positive electrode film layer are respectively connected with metal wires, wherein the sensitive core is fixed in the packaging tube shell after being connected with the metal wires, and wherein the insulating film layer is prepared by the following method: preparing an insulating material sol, immersing the pretreated tungsten-rhenium wire substrate in the insulating material sol, slowly pulling the tungsten-rhenium wire substrate from the insulating material sol for multiple times by an immersion-pulling device, preparing a bottom insulating layer, drying and then subjecting the bottom insulating layer to a high-temperature heat treatment so that the bottom insulating layer forms a structure with a large porosity; repeating the treatment to prepare an upper insulating layer, and making the upper insulating layer dense. By adopting the immersion pulling method to form a gradient structure insulating film layer on the tungsten-rhenium wire substrate, including a bottom layer with a large porosity and an upper layer with a dense structure, the cracking problem of the insulating layer caused by the difference in thermal expansion coefficient and electrode material at high temperature is effectively alleviated, the stability and reliability of the sensor in high temperature environment are improved, and the basic structural integrity of the sensor is ensured, so that it can adapt to the temperature measurement needs under extreme high temperature conditions, laying the foundation for subsequent performance improvement.

[0006] In some specific embodiments, the insulating material sol includes hafnium oxide sol or aluminum oxide sol, and the solution viscosity of the sol is within the range of 0.056-0.06 Pa·s. The treated tungsten-rhenium wire substrate is immersed in the sol for 3-5 minutes, and the tungsten-rhenium wire substrate is slowly lifted from the sol solution at a speed of 100 μm / s using an immersion pulling device. The pulling times are 3-5 times to prepare a bottom insulating layer. The bottom insulating layer is dried in a drying oven at 150-200°C for 5 minutes and then heat-treated at 1000-1100°C under vacuum conditions for 20-30 minutes to form a structure with a larger porosity in the bottom insulating layer; repeat the above steps, adjust the solution viscosity to 0.008-0.012 Pa·s, the pulling speed is 5-10 μm / s, the pulling times are 5-8 times, prepare an upper insulating layer, and heat-treat at 1200-1300°C under vacuum conditions for 30-40 minutes to make the upper insulating layer dense. With this setting, the microstructure and properties of the insulating film layer can be precisely controlled. For example, a bottom insulating layer with a larger porosity is formed to accommodate thermal expansion, and a dense upper insulating layer is formed to ensure insulation performance. The bonding effect between the insulating layer and the substrate and the positive electrode film layer is optimized, and the insulation performance, crack resistance and overall structural stability of the sensor at high temperatures are further improved, so that the sensor can still maintain good performance in extremely high temperature environments, ensuring the accuracy and stability of the measurement data.

[0007] In some specific embodiments, the thickness of the bottom insulating layer is 3-5 μm, the thickness of the upper insulating layer is 1-2 μm, and the thickness of the positive electrode thin film layer is 10 μm. The thickness ranges of the bottom insulating layer, the upper insulating layer, and the positive electrode thin film layer are clearly defined, so that the thickness of the insulating layer and the positive electrode thin film layer can be accurately controlled, ensuring the performance stability of each layer structure of the sensor, and helping to optimize the electrical and thermal properties of the sensor, such as ensuring appropriate resistance and capacitance characteristics as well as heat conduction and insulation effects, thereby improving the measurement accuracy and sensitivity of the sensor, so that it can accurately measure in different temperature ranges.

[0008] In some specific embodiments, the material of the positive electrode thin film layer is tungsten, and the material of the insulating thin film layer includes hafnium oxide or aluminum oxide. Limiting the material of the positive electrode thin film layer to tungsten ensures good electrical conductivity and high-temperature stability, which helps to accurately transmit electrical signals in high-temperature environments; the material of the insulating thin film layer includes hafnium oxide or aluminum oxide, which has excellent high-temperature resistance and insulation properties, further enhancing the insulation performance of the sensor at high temperatures, preventing signal interference, and improving the reliability of the sensor in complex environments such as extreme high temperatures and strong electromagnetic interference, ensuring the accuracy of the measurement data.

[0009] In some specific embodiments, the ratio of tungsten to rhenium in the tungsten-rhenium wire substrate is 74:26. ​​The physical and chemical properties of the substrate are optimized, such as improving the high temperature strength and oxidation resistance of the substrate, so that it can better adapt to the high temperature measurement environment, provide stable support for the insulating layer and the positive electrode film layer, ensure the stability of the overall structure of the sensor at high temperature, and help improve the sensitivity and response speed of the sensor, so that the sensor can sense temperature changes more quickly and accurately.

[0010] In some specific embodiments, the front end of the sensitive core is flush with the front end of the packaging tube shell, and the packaging tube shell includes a front tube sleeve and a rear metal protection tube, the length of the front tube sleeve is the same as the length of the sensitive core, the rear metal protection tube is connected to the thermocouple plug, and the end of the metal wire is connected to the inside of the thermocouple plug through a threaded pressing piece to lead out the signal. This setting ensures the compactness of the sensor structure, reduces the impact of the external environment on the sensitive core, and improves the anti-interference ability of the sensor; it facilitates the extraction of signals, ensures the stability and accuracy of signal transmission, is conducive to the installation and use of the sensor in various complex environments, improves the practicality and reliability of the sensor, and enables it to accurately measure temperature and effectively transmit signals in different application scenarios.

[0011] According to a second aspect of the present invention, a method for preparing a coaxial temperature sensor based on an immersion-pulling method is proposed, comprising: S1: ultrasonically cleaning the tungsten-rhenium wire substrate in a cleaning solution and drying it; S2: preparing an insulating film layer, preparing an insulating material sol, immersing the tungsten-rhenium wire substrate treated by S1 into the insulating material sol, slowly pulling the tungsten-rhenium wire substrate from the insulating material sol multiple times by an immersion pulling device, preparing a bottom insulating layer, drying and then performing a high-temperature heat treatment to form a structure with a large porosity in the bottom insulating layer; repeating the process to prepare an upper insulating layer, and making the upper insulating layer dense; S3: preparing a positive electrode thin film layer, preparing a tungsten slurry, and immersing the tungsten-rhenium wire substrate with the insulating thin film layer prepared in S2 into the tungsten slurry for wetting, slowly lifting the tungsten-rhenium wire substrate from the tungsten slurry by an immersion and pulling device, drying it, and subjecting it to high-temperature heat treatment to make it uniform and dense, so that the tungsten-rhenium wire substrate and the positive electrode thin film layer are bonded via the insulating thin film layer; S4: Connect metal wires to the exposed positive electrode film layer and the tungsten-rhenium wire substrate respectively and then fix them in a packaging tube shell.

[0012] In some specific embodiments, the cleaning solution in S1 includes sodium hydroxide, acetone and anhydrous ethanol, and the tungsten-rhenium wire substrate is ultrasonically cleaned in sodium hydroxide, acetone and anhydrous ethanol for 15 minutes each and then dried. This setting can effectively remove oxides, oil stains, impurities, etc. on the surface of the tungsten-rhenium wire substrate, make the substrate surface clean, enhance the bonding force between the subsequent insulating film layer and the positive electrode film layer and the substrate, improve the adhesion between the various layers of the sensor structure, ensure the stability of the sensor structure, help improve the overall performance and service life of the sensor, and make it less prone to stratification and shedding when working in high temperature and complex environments, ensuring the accuracy and reliability of the measurement.

[0013] In some specific embodiments, the specific parameters of S3 include: immersing the tungsten-rhenium wire substrate prepared with the insulating film layer in S2 into the tungsten slurry for 3-5 minutes, slowly lifting the tungsten-rhenium wire substrate from the tungsten slurry by an immersion and pulling device, drying in a drying oven at 150-200°C for 5 minutes, and then heat treating at 1600°C under vacuum conditions for 30-40 minutes. With this setting, the uniform density of the positive electrode film layer and the good bonding with the insulating film layer are ensured, the conductivity and high-temperature stability of the positive electrode film layer are optimized, so that the sensor can accurately convert temperature changes into electrical signals and effectively transmit them, thereby improving the sensitivity and response speed of the sensor, ensuring the stable transmission of electrical signals during high-temperature measurement, and thus improving the accuracy and reliability of temperature measurement.

[0014] In some specific embodiments, S4 specifically includes: fixing the sensitive core in the front end sleeve of the packaging tube shell, connecting the rear end metal protection tube of the packaging tube shell to the thermocouple plug through a ferrule joint, and connecting the end of the metal wire to the inside of the thermocouple plug through a threaded pressing piece. This setting ensures the stability of the internal structure of the sensor and the smoothness of signal transmission, enhances the anti-interference ability of the sensor, prevents external factors from interfering with signal transmission, ensures that the sensor can accurately lead out the measurement signal in a complex environment, improves the overall reliability and practicality of the sensor, and enables it to work stably and accurately measure temperature in various harsh environments.

[0015] The present invention proposes a coaxial temperature sensor based on the immersion pulling method and a preparation method thereof. The insulation layer adopts the immersion pulling method to form a unique gradient structure on the tungsten-rhenium wire substrate, which includes at least one bottom insulation layer with a larger porosity and at least two dense upper insulation layers. This structure effectively solves the problem that the insulation layer is prone to cracking at high temperatures due to the difference in thermal expansion coefficient and electrode materials. The thickness of the bottom insulation layer is 3-5μm, and its larger porosity structure can provide a buffer space for thermal expansion at high temperatures, avoiding cracking caused by thermal stress concentration; the thickness of the upper insulation layer is 1-2μm, and the dense structure ensures excellent insulation performance and prevents signal interference. By precisely controlling the structure and preparation process of the insulating layer, such as solution viscosity, pulling speed, number of times, and heat treatment conditions, not only the performance of the insulating layer itself is optimized, but also the bonding effect between it and the substrate and the positive electrode film layer is enhanced, so that the sensor can maintain structural stability in extreme high temperature environments (such as ultra-high temperature gas flow in aerospace engines, extremely high temperature areas in metallurgical blast furnaces, etc.), ensuring the reliability and measurement accuracy of the sensor, and greatly improving the stability of the sensor when working in complex and harsh environments such as high temperature and strong electromagnetic interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate the embodiments and together with the description are used to explain the principles of the present invention. Other embodiments and many of the expected advantages of the embodiments will be readily appreciated as they become better understood by reference to the following detailed description. Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of the non-limiting embodiments made with reference to the following drawings: Figure 1 It is a schematic structural diagram of a coaxial temperature sensor based on an immersion-pulling method according to an embodiment of the invention; Figure 2 It is a structural schematic diagram of a sensitive core of a coaxial temperature sensor based on an immersion-pulling method according to a specific embodiment of the invention; Figure 3is a top view of a sensitive core according to a specific embodiment of the invention; Figure 4 is a diagram showing the connection relationship between a sensitive core and a metal wire according to a specific embodiment of the invention; Figure 5 It is a diagram of the internal structure of a thermocouple plug according to a specific embodiment of the invention; Figure 6 It is a simplified flow chart of a method for preparing a coaxial temperature sensor based on an immersion pulling method according to an embodiment of the invention; Figure 7a This is a comparison test diagram of a coaxial sensor with a normal insulation layer and a standard thermocouple according to a specific embodiment of the present invention; Figure 7b This is a comparison test diagram of the coaxial sensor of the gradient insulation layer of the present application and a standard thermocouple according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0018] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0019] Figure 1 FIG. 4 shows a schematic structural diagram of a coaxial temperature sensor based on an immersion-pulling method according to an embodiment of the invention, as shown in FIG. Figure 1 As shown, the coaxial temperature sensor based on the immersion pulling method includes a sensitive core and a packaging tube shell, wherein the sensitive core is the core part of the sensor, including a tungsten-rhenium wire substrate 1, an insulating film layer 2 and a positive electrode film layer 3 (such as Figure 2 FIG. 1 is a schematic diagram showing a structure of a sensitive core of a coaxial temperature sensor based on an immersion pulling method according to a specific embodiment of the invention. The insulating film layer 2 forms a gradient structure on a tungsten-rhenium wire substrate 1 by an immersion pulling method. The gradient structure includes at least one bottom insulating layer 21 with a relatively large porosity and at least two dense upper insulating layers 22 (in this embodiment, one bottom insulating layer 21 and two upper insulating layers 22 are taken as an example, that is, Figure 3 1 shows a top view of a sensitive core according to a specific embodiment of the invention). The gradient structure effectively alleviates the cracking problem of the insulating layer at high temperature caused by the difference in thermal expansion coefficient and electrode material.

[0020] In a specific embodiment, the bottom insulating layer 21 has a thickness of 3-5 μm, the upper insulating layer 22 has a thickness of 1-2 μm, and the total thickness of the insulating film layer 2 is 5-8 μm and the length is 80 mm. The positive electrode film layer 3 is made of tungsten, has a thickness of 10 μm and a length of 60 mm. Its good electrical conductivity and high temperature stability help to accurately transmit electrical signals in a high temperature environment. The ratio of tungsten to rhenium elements in the tungsten-rhenium wire substrate 1 is 74:26, the length is 15 cm, and the diameter is 0.5 mm. The tungsten-rhenium wire substrate 1 and the positive electrode film layer 3 are respectively connected with metal wires 4 and 5 (such as Figure 4 ), the material of the metal wire is the same as the material of the connected thermode, ensuring the consistency and stability of signal transmission.

[0021] In a specific embodiment, taking a bottom insulating layer and two upper insulating layers as an example, the bottom insulating layer is 4 μm thick, has a distinct void structure, and has a large porosity, which can effectively accommodate thermal expansion in a high temperature environment. For example, when the sensor is rapidly heated from room temperature to 2500°C, the voids in the bottom insulating layer provide sufficient space for material expansion to avoid cracks caused by thermal stress concentration. By heat treatment at 1000-1100°C under vacuum conditions for 20-30 minutes (such as heat treatment at 1050°C for 25 minutes), the bottom insulating layer is formed into such a structure that is conducive to thermal expansion buffering. The thickness of the upper insulating layer is 0.8μm and 1.2μm respectively. By adjusting the immersion and pulling process parameters, such as adjusting the solution viscosity to 0.008-0.012Pa·s (such as 0.01Pa·s), controlling the pulling speed at 5-10μm / s (such as 8μm / s), pulling times 5-8 times (such as 6 times), and heat treatment at 1200-1300℃ vacuum conditions for 30-40 minutes (such as 1250℃ heat treatment for 35 minutes), the upper insulating layer is made dense. This dense structure ensures good insulation performance and effectively prevents signal interference.

[0022] In another specific embodiment, taking the combination of two bottom insulating layers and three upper insulating layers as an example, the thickness of the bottom insulating layer is 2μm and 2.5μm respectively, and the two-layer setting provides a larger thermal expansion buffer space. For example, in an environment with a large temperature cycle change (from 800°C to 1600°C), it can better adapt to the repeated thermal expansion and contraction of the material and reduce structural damage caused by thermal stress. Through a specific immersion and pulling process, such as a solution viscosity in the range of 0.056-0.06Pa·s (such as 0.058Pa·s), a pulling speed of 50-100μm / s (such as 50μm / s), and a pulling number of 3-5 times (such as 4 times), and after drying and high-temperature heat treatment, a structure with a larger porosity is formed. The thickness of the upper insulating layer is 0.6μm, 0.7μm and 0.7μm, and the three dense upper insulating layers further enhance the insulation performance. By optimizing the parameters during the impregnation and pulling process, the microstructure of the upper insulating layer is made more dense and uniform, which improves the shielding effect of electromagnetic interference. The maximum porosity of the above-mentioned bottom insulating layer ranges from 20% to 40%, and the density of the upper insulating layer is more than 90% of the theoretical density.

[0023] In a specific embodiment, the sensitive core is connected to the metal wire and fixed in the packaging tube shell. The front end of the sensitive core is flush with the front end of the packaging tube shell, which ensures the compactness of the sensor structure, reduces the impact of the external environment on the sensitive core, and improves the anti-interference ability of the sensor. The packaging tube shell includes a front tube sleeve 6 and a rear metal protection tube 7. The length of the front tube sleeve 6 is the same as that of the sensitive core, both of which are 15 cm. The rear metal protection tube 7 is connected to the thermocouple plug 10. The ends of the metal wires 4 and 5 are connected to the inside of the thermocouple plug 10 through a threaded pressing piece (such as Figure 5 The internal structure diagram of the thermocouple plug according to a specific embodiment of the invention is shown), and the signal is led out, which ensures the stability and accuracy of signal transmission, is conducive to the installation and use of the sensor in various complex environments, improves the practicality and reliability of the sensor, and enables it to accurately measure temperature and effectively transmit signals in different application scenarios.

[0024] Continue to refer Figure 6 , Figure 6 A simplified flow chart of a method for preparing a coaxial temperature sensor based on an immersion-pulling method according to an embodiment of the invention is shown, as shown in FIG. Figure 6 As shown, the preparation method comprises the following steps: S601: Solution preparation, tungsten-rhenium wire cleaning.

[0025] In a specific embodiment, the tungsten-rhenium wire substrate 1 is ultrasonically cleaned in a cleaning solution and dried. The cleaning solution includes sodium hydroxide, acetone and anhydrous ethanol. The tungsten-rhenium wire substrate 1 is ultrasonically cleaned in sodium hydroxide, acetone and anhydrous ethanol for 15 minutes each and then dried. This step can effectively remove oil stains, impurities, etc. on the surface of the tungsten-rhenium wire substrate 1, clean the surface of the substrate, enhance the bonding force between the subsequent insulating film layer 2 and the positive electrode film layer 3 and the substrate, improve the adhesion between the various layers of the sensor structure, ensure the stability of the sensor structure, and help improve the overall performance and service life of the sensor, so that it is not easy to have problems such as delamination and falling off when working in high temperature and complex environments, and ensure the accuracy and reliability of the measurement.

[0026] S602: Preparation of insulation layer, including preparation of bottom insulation layer and upper insulation layer.

[0027] S603: Insulation layer curing and sintering.

[0028] In a specific embodiment, hafnium oxide sol or aluminum oxide sol is configured as an insulating material sol (the present embodiment takes hafnium oxide sol as an example), the solution viscosity of the sol is taken in the range of 0.056-0.06 Pa·s (such as 0.06 Pa·s), the treated tungsten rhenium wire substrate 1 is immersed in the sol for 3-5 minutes (such as 4 minutes), and the tungsten rhenium wire substrate 1 is slowly lifted from the sol solution at a speed of 100 μm / s using an immersion pulling device, and the number of pulling times is 3-5 times (such as 4 times) to prepare a bottom insulating layer. After the bottom insulating layer is dried in a drying oven at 150-200°C for 5 minutes, it is heat-treated at 1000-1100°C under vacuum conditions for 20-30 minutes (such as heat-treated at 1050°C under vacuum conditions for 25 minutes), so that the bottom insulating layer forms a structure with a large porosity, and its thickness reaches 4 μm. Repeat the above steps, adjust the solution viscosity to 0.008-0.012 Pa·s (e.g., 0.012 Pa·s), the pulling speed to 5-10 μm / s (e.g., 10 μm / s), the pulling times to 5-8 times (e.g., 6 times), prepare the upper insulating layer, and heat treat it at 1200-1300°C under vacuum conditions for 30-40 minutes (e.g., heat treat it at 1250°C under vacuum conditions for 35 minutes) to make the upper insulating layer dense and the thickness of the upper insulating layer reaches 2 μm, thereby forming an insulating film layer 2 with a total thickness of 8 μm.

[0029] S604: Preparation of tungsten thin film: Prepare tungsten slurry, immerse the tungsten-rhenium wire substrate 1 prepared with the insulating thin film layer 2 into the tungsten slurry for 3-5 minutes (eg, 4 minutes), and slowly lift the tungsten-rhenium wire substrate 1 from the tungsten slurry by an immersion and pulling device.

[0030] S605: Tungsten film solidification and sintering. After drying in a drying oven at 150-200°C for 5 minutes, heat treatment is performed at 1600°C under vacuum conditions for 30-40 minutes (e.g., heat treatment at 1600°C under vacuum conditions for 35 minutes) to make the positive electrode film layer 3 uniform and dense and bonded to the insulating film layer 2, with a thickness of 10μm and a length of 60mm.

[0031] S606: Connecting metal wires: Connect metal wires 4 and 5 to the exposed positive electrode thin film layer 3 and the tungsten-rhenium wire substrate 1 respectively.

[0032] S607: Packaging. Use the CCD vision system to accurately position the sensitive core, fix the sensitive core in the front sleeve 6 of the packaging shell, and fill the high-temperature insulating powder in the larger porosity of the sleeve and the sensitive core. The rear metal protection tube 7 of the packaging shell is connected to the thermocouple plug 10 through the ferrule joint 8, and the ends of the metal wires 4 and 5 are connected to the inside of the thermocouple plug 10 through the threaded pressing sheet to complete the assembly of the sensor.

[0033] Figure 7a FIG. 4 shows a comparison test diagram of a coaxial sensor with a normal insulating layer and a standard thermocouple according to a specific embodiment of the present invention; Figure 7a As shown, the coaxial sensors with normal structural insulation layers (such as No. 101-105) and the standard thermocouples (such as No. 106) were placed in a high-temperature tube furnace for testing. It can be seen that the coaxial sensors with normal structural insulation layers failed at around 1300°C. Figure 7b : is a comparison test diagram of the coaxial sensor of the gradient insulation layer of the present application and the standard thermocouple according to a specific embodiment of the present invention, such as Figure 7b As shown, the coaxial sensors (such as No. 201 and 203) prepared with gradient structure insulation layer and the standard thermocouple (such as No. 204) were placed in a high-temperature tube furnace for testing. It can be seen that the insulation layer can last for at least 30 minutes without failure in an environment of 1400°C.

[0034] In a specific embodiment, the following test was conducted on the coaxial temperature sensor of the immersion pulling method: In the high temperature stability test, the sensor prepared by the present invention was placed in a high temperature furnace, the temperature was set to 1200°C, and it was continuously operated for 3 hours. The test results showed that the insulating layer of the sensor did not crack, the sensitive core structure remained intact, and the measurement accuracy was maintained within ±1.5% during the entire test process, indicating that the sensor has excellent stability in extreme high temperature environments. This is due to the gradient structure design of the insulating layer and the precise preparation process, which effectively alleviated the cracking problem of the insulating layer at high temperatures caused by the difference in thermal expansion coefficient and electrode materials, and ensured the reliable operation of the sensor at high temperatures.

[0035] Sensitivity test, within the temperature range of 100℃-1400℃, gradually change the temperature at intervals of 100℃, and measure the change in the output electromotive force of the sensor. The test results show that the sensitivity of the sensor reaches 20μV / ℃, and it can respond to temperature changes quickly and accurately. This is due to the material selection and structural design of the positive film layer and the insulating layer, which optimizes the electrical performance of the sensor, allowing the sensor to accurately measure in different temperature ranges, meeting the application scenarios with high requirements for temperature measurement accuracy, such as monitoring of subtle temperature changes during metal smelting.

[0036] The above description is only a preferred embodiment of the present invention and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present invention is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present invention (but not limited to) to form a technical solution.

Claims

1. A coaxial temperature sensor for radiative pyrometry, characterized in that The invention comprises a sensitive core and a packaging tube shell, wherein the sensitive core comprises a tungsten-rhenium wire substrate, an insulating film layer and a positive electrode film layer, wherein the insulating film layer forms a gradient structure on the tungsten-rhenium wire substrate by an immersion-pulling method, wherein the gradient structure comprises at least one bottom insulating layer with a larger porosity and at least two dense upper insulating layers, wherein the tungsten-rhenium wire substrate and the positive electrode film layer are respectively connected with metal wires, and the sensitive core is fixed in the packaging tube shell after being connected with the metal wires; the insulating film layer is prepared by the following method: an insulating material sol is prepared, the pretreated tungsten-rhenium wire substrate is immersed in the insulating material sol, the tungsten-rhenium wire substrate is slowly pulled from the insulating material sol for multiple times by an immersion-pulling device to prepare a bottom insulating layer, and the bottom insulating layer is formed into a structure with a larger porosity by high-temperature heat treatment after drying; and an upper insulating layer is prepared by repeated treatment, and the upper insulating layer is made dense.

2. The coaxial temperature sensor for radiation pyrometry according to claim 1, characterized in that The insulating material sol includes hafnium oxide sol or aluminum oxide sol, the solution viscosity of the sol is taken in the range of 0.056-0.06 Pa·s, the treated tungsten-rhenium wire substrate is immersed in the sol for 3-5 minutes, and the tungsten-rhenium wire substrate is slowly lifted from the sol solution at a speed of 100 μm / s by using the immersion and pulling equipment, and the pulling times are 3-5 times to prepare the bottom insulating layer, and the bottom insulating layer is heated at 150-200°C. After drying in a drying oven for 5 minutes, heat treatment is performed at 1000-1100°C under vacuum conditions for 20-30 minutes to form a structure with larger porosity in the bottom insulating layer; the solution viscosity is adjusted to 0.008-0.012 Pa·s, the pulling speed is 5-10 μm / s, the pulling times are 5-8 times, the upper insulating layer is prepared, and heat treatment is performed at 1200-1300°C under vacuum conditions for 30-40 minutes to make the upper insulating layer dense.

3. The coaxial temperature sensor for radiation pyrometry according to claim 1, characterized in that The thickness of the bottom insulating layer is 3-5 μm, the thickness of the upper insulating layer is 1-2 μm, and the thickness of the positive electrode thin film layer is 10 μm.

4. The coaxial temperature sensor for radiation pyrometry according to claim 1, characterized in that The material of the positive electrode thin film layer is tungsten, and the material of the insulating thin film layer includes hafnium oxide or aluminum oxide.

5. The coaxial temperature sensor for radiation pyrometry according to claim 1, characterized in that The ratio of tungsten to rhenium elements in the tungsten-rhenium wire substrate is 74:

26.

6. The coaxial temperature sensor for radiation pyrometry according to claim 1, characterized in that The front end of the sensitive core is flush with the front end of the packaging tube shell. The packaging tube shell includes a front end tube sleeve and a rear end metal protection tube. The length of the front end tube sleeve is the same as the length of the sensitive core. The rear end metal protection tube is connected to a thermocouple plug. The end of the metal wire is connected to the inside of the thermocouple plug through a threaded pressing sheet to lead out the signal.

7. A method for preparing a coaxial temperature sensor for radiation pyrometry according to any one of claims 1 to 6, characterized in that: include: S1: ultrasonically cleaning the tungsten-rhenium wire substrate in a cleaning solution and drying it; S2: preparing an insulating film layer, preparing an insulating material sol, immersing the tungsten-rhenium wire substrate treated in S1 into the insulating material sol, slowly pulling the tungsten-rhenium wire substrate from the insulating material sol for multiple times by an immersion pulling device, preparing a bottom insulating layer, drying and then subjecting the bottom insulating layer to a high-temperature heat treatment so that the bottom insulating layer forms a structure with a large porosity; repeating the process to prepare an upper insulating layer, and making the upper insulating layer dense; S3: preparing a positive electrode thin film layer, preparing a tungsten slurry, and immersing the tungsten-rhenium wire substrate with the insulating thin film layer prepared in S2 into the tungsten slurry for wetting, slowly lifting the tungsten-rhenium wire substrate from the tungsten slurry by an immersion and pulling device, drying and subjecting the substrate to high-temperature heat treatment to make it uniform and dense, so that the tungsten-rhenium wire substrate and the positive electrode thin film layer are bonded via the insulating thin film layer; S4: Connecting metal wires to the exposed positive electrode thin film layer and the tungsten-rhenium wire substrate respectively and then fixing them in the packaging tube shell.

8. The method for preparing a coaxial temperature sensor for radiation pyrometry according to claim 7, characterized in that: The cleaning solution in S1 includes sodium hydroxide, acetone and anhydrous ethanol. The tungsten-rhenium wire substrate is ultrasonically cleaned in the sodium hydroxide, acetone and anhydrous ethanol for 15 minutes respectively and then dried.

9. The method for preparing a coaxial temperature sensor for radiation pyrometry according to claim 7, characterized in that: The specific parameters of S3 include: immersing the tungsten-rhenium wire substrate prepared with the insulating film layer in S2 into tungsten slurry for 3-5 minutes, slowly lifting the tungsten-rhenium wire substrate from the tungsten slurry by an immersion pulling device, drying it in a drying oven at 150-200°C for 5 minutes, and then heat treating it at 1600°C under vacuum conditions for 30-40 minutes.

10. The method for preparing a coaxial temperature sensor for radiation pyrometry according to claim 7, characterized in that: The S4 specifically includes: fixing the sensitive core in the front end sleeve of the packaging tube shell, connecting the rear end metal protection tube of the packaging tube shell to the thermocouple plug through a ferrule joint, and connecting the end of the metal wire to the inside of the thermocouple plug through a threaded pressing piece.

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