A coaxial temperature sensor for radiation pyrometry and a method of making the same

Abstract

The application provides a coaxial temperature sensor for radiation high-temperature measurement and a preparation method thereof, which comprises a sensitive core and a packaging tube, the sensitive core comprises a tungsten-rhenium wire base, an insulating film layer and a positive film layer, the insulating film layer forms a gradient structure on the tungsten-rhenium wire base by a dip-coating method, the gradient structure comprises at least one bottom insulating layer with large porosity and at least two upper insulating layers with high density, the tungsten-rhenium wire base and the positive film layer are respectively connected with metal wires, and the sensitive core is fixed in the packaging tube after being connected with the metal wires. The coaxial temperature sensor detects the thermal radiation energy emitted by a high-temperature object to determine the temperature of the object, and has the advantages of anti-electromagnetic interference, no interference to a flow field, high sensitivity, small size, exquisite and compact structure and the like.

Description

Technical Field

[0001] This invention relates to the technical field of radiation high temperature measurement, and in particular to a coaxial temperature sensor for radiation high temperature measurement and its preparation method. Background Technology

[0002] Accurate temperature measurement is crucial in numerous fields, including industrial production and scientific research. Traditional temperature measurement methods, such as armored thermocouples and resistance temperature detectors (RTDs), 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 sensing elements, leading to shortened element lifespan, decreased accuracy, or even damage. On the other hand, in certain special high-temperature scenarios, such as inside high-temperature furnaces, metal smelting processes, and rocket engine nozzles, contact temperature measurement is difficult to implement. The measuring device cannot directly contact the object being measured, or contact may interfere with the temperature field and physicochemical processes of the object being measured.

[0003] Radiation-based high-temperature measurement 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 calculate the object's temperature. It has the significant advantage of non-contact measurement, enabling temperature measurement without interfering with the temperature field and thermal state of the object being measured. It is suitable for temperature monitoring in high-temperature, long-distance, moving objects, and harsh environments. With the continuous development of optical, detector, and signal processing technologies, the accuracy, response speed, and reliability of radiation-based high-temperature measurement are constantly improving, gradually becoming an indispensable tool in the field of high-temperature measurement. Coaxial temperature sensors can serve as key components for temperature sensing in radiation-based high-temperature measurement. They can be placed in an appropriate location to receive the thermal radiation from the object being measured, causing a change in the temperature of the hot end and generating an electromotive force (EMF) corresponding to the temperature difference. This EMF signal can be acquired by subsequent measurement circuits and data acquisition systems. By measuring and converting the EMF, the temperature change at the hot end can be calculated, thus obtaining the radiation temperature of the object being measured. Traditional coaxial temperature sensors mostly use a nickel-chromium constantan sleeve structure, which suffers from problems such as a low upper temperature limit and large measurement errors due to excessively thick insulation layers. Therefore, there is an urgent need to develop coaxial temperature sensors that can withstand ultra-high temperatures and have high accuracy. Summary of the Invention

[0004] To address the aforementioned technical problems in the existing technology, this invention proposes a coaxial temperature sensor for measuring high-temperature radiation and its fabrication method. This solves the aforementioned technical problems.

[0005] According to a first aspect of the present invention, a coaxial temperature sensor for measuring high-temperature radiation is provided, comprising a sensitive core and a packaged shell. The sensitive core comprises a tungsten-rhenium wire substrate, an insulating thin film layer, and a positive electrode thin film layer. The insulating thin film layer forms a gradient structure on the tungsten-rhenium wire substrate by an dip-coating method. The gradient structure comprises at least one bottom insulating layer with a large porosity and at least two dense upper insulating layers. The tungsten-rhenium wire substrate and the positive electrode thin film layer are respectively connected to metal wires. The sensitive core is fixed in the packaged shell after being connected to the metal wires. The insulating thin film layer is prepared by: 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 multiple times using an dip-coating device to prepare the bottom insulating layer, drying it, and then heat-treating it at high temperature to form a structure with a large porosity; repeating the treatment to prepare the upper insulating layer and making the upper insulating layer dense. By employing the dip-coating method to form a gradient-structured insulating film layer on a tungsten-rhenium wire substrate, consisting of a bottom layer with high porosity and an upper layer with density, the cracking problem caused by the difference in thermal expansion coefficient between the insulating layer and the electrode material at high temperatures is effectively alleviated. This improves the stability and reliability of the sensor in high-temperature environments, ensures the basic structural integrity of the sensor, and enables it to meet the temperature measurement requirements under extreme high-temperature conditions, laying the foundation for subsequent performance improvements.

[0006] In some specific embodiments, the insulating material sol includes hafnium oxide sol or alumina sol, with a solution viscosity ranging from 0.056 to 0.06 Pa·s. The treated tungsten-rhenium wire substrate is immersed in the sol for 3-5 minutes. Using an impregnation and lifting device, the tungsten-rhenium wire substrate is slowly lifted from the sol solution at a speed of 100 μm / s, with 3-5 lifting cycles, to prepare the bottom insulating layer. The bottom insulating layer is dried in a drying oven at 150-200°C for 5 minutes and then heat-treated under vacuum at 1000-1100°C for 20-30 minutes to form a structure with a relatively high porosity. The above steps are repeated, adjusting the solution viscosity to 0.008-0.012 Pa·s, with a lifting speed of 5-10 μm / s and 5-8 lifting cycles, to prepare the top insulating layer, which is then heat-treated under vacuum at 1200-1300°C for 30-40 minutes to make the top insulating layer dense. This setup allows for precise control over the microstructure and performance of the insulating film layer. For example, it enables the formation of a bottom insulating layer with higher porosity to accommodate thermal expansion, while a dense upper insulating layer ensures insulation performance. It also optimizes the bonding effect between the insulating layer and the substrate and positive electrode film layer, further improving the sensor's insulation performance, crack resistance, and overall structural stability at high temperatures. This allows the sensor to maintain good performance even in extreme high-temperature environments, ensuring the accuracy and stability of measurement data.

[0007] In some specific embodiments, the thickness of the bottom insulating layer is 3-5 μm, the thickness of the top insulating layer is 1-2 μm, and the thickness of the positive electrode thin film layer is 10 μm. Defining the thickness ranges of the bottom and top insulating layers and the positive electrode thin film layer allows for precise control of the thickness of the insulating and positive electrode thin film layers, ensuring the performance stability of each layer of the sensor structure. This helps optimize the sensor's electrical and thermal performance, such as ensuring appropriate resistance, capacitance characteristics, thermal conductivity, and insulation effects, thereby improving the sensor's measurement accuracy and sensitivity, enabling accurate measurements across different temperature ranges.

[0008] In some specific embodiments, the positive electrode thin film layer is made of tungsten, and the insulating thin film layer is made of hafnium oxide or aluminum oxide. Specifying tungsten as the positive electrode thin film layer material ensures good conductivity and high-temperature stability, which helps to accurately transmit electrical signals in high-temperature environments. The insulating thin film layer material, including hafnium oxide or aluminum oxide, possesses excellent high-temperature resistance and insulation properties, further enhancing the sensor's insulation performance 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, thus ensuring the accuracy of 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 its high-temperature strength and oxidation resistance, enabling it to better adapt to high-temperature measurement environments. This provides stable support for the insulating layer and the positive electrode thin film layer, ensuring the stability of the overall sensor structure at high temperatures. Simultaneously, it helps improve the sensor's sensitivity and response speed, allowing the sensor to detect temperature changes more quickly and accurately.

[0010] In some specific embodiments, the front end of the sensing core is flush with the front end of the encapsulation shell. The encapsulation shell includes a front sleeve and a rear metal protective tube. The length of the front sleeve is the same as the length of the sensing core. The rear metal protective tube connects to a thermocouple plug, and the end of the metal wire is connected to the inside of the thermocouple plug via a threaded clamp to lead out the signal. This configuration ensures the compactness of the sensor structure, reduces the influence of the external environment on the sensing core, and improves the sensor's anti-interference capability. It also facilitates signal extraction, ensures the stability and accuracy of signal transmission, and is beneficial for the installation and use of the sensor in various complex environments. This improves the sensor's practicality and reliability, enabling 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 fabricating a coaxial temperature sensor based on the dip-coating method is provided, comprising:

[0012] S1: The tungsten rhenium wire substrate is ultrasonically cleaned in a cleaning solution and then dried;

[0013] S2: Prepare the insulating film layer by preparing an insulating material sol. Immerse the tungsten-rhenium wire substrate treated in S1 into the insulating material sol. Use an immersion-pulling device to slowly pull the tungsten-rhenium wire substrate out of the insulating material sol multiple times to prepare the bottom insulating layer. After drying, perform high-temperature heat treatment to form a structure with a large porosity in the bottom insulating layer. Repeat the process to prepare the upper insulating layer and make the upper insulating layer dense.

[0014] S3: Prepare the positive electrode thin film layer, prepare tungsten paste, and immerse the tungsten rhenium wire substrate with the insulating thin film layer prepared in S2 into the tungsten paste. Use an immersion lifting device to slowly lift the tungsten rhenium wire substrate from the tungsten paste, dry it, and then heat-treat it at high temperature to make it uniform and dense, so that the tungsten rhenium wire substrate and the positive electrode thin film layer are bonded through the insulating thin film layer.

[0015] S4: After connecting metal wires to the exposed positive electrode thin film layer and the tungsten rhenium wire substrate, fix them inside the packaging shell.

[0016] In some specific embodiments, the cleaning solution in S1 includes sodium hydroxide, acetone, and anhydrous ethanol. The tungsten rhenium wire substrate is ultrasonically cleaned in sodium hydroxide, acetone, and anhydrous ethanol for 15 minutes each, and then dried. This setup effectively removes oxides, oil, impurities, etc., from the surface of the tungsten rhenium wire substrate, making the substrate surface clean. This enhances the adhesion between the subsequent insulating film layer and positive electrode film layer and the substrate, improves the adhesion between the various layers of the sensor structure, ensures the stability of the sensor structure, and helps improve the overall performance and service life of the sensor. It also makes it less prone to delamination and peeling when working in high-temperature and complex environments, ensuring the accuracy and reliability of measurements.

[0017] In some specific embodiments, the specific parameters of S3 include: immersing the tungsten rhenium wire substrate with the insulating thin film layer prepared in S2 into tungsten slurry for 3-5 minutes; slowly lifting the tungsten rhenium wire substrate from the slurry using an immersion lifting device; drying in a drying oven at 150-200°C for 5 minutes; and then heat-treating under vacuum at 1600°C for 30-40 minutes. This setup ensures the uniformity and density of the positive electrode thin film layer and good bonding with the insulating thin film layer, optimizes the conductivity and high-temperature stability of the positive electrode thin film layer, enables the sensor to accurately convert temperature changes into electrical signals and transmit them effectively, improves the sensor's sensitivity and response speed, ensures stable transmission of electrical signals during high-temperature measurements, and thus improves the accuracy and reliability of temperature measurements.

[0018] In some specific embodiments, S4 specifically includes: fixing the sensitive core inside the front sleeve of the encapsulation shell, connecting the rear metal protective tube of the encapsulation shell to the thermocouple plug via a compression fitting, and connecting the end of the metal wire to the inside of the thermocouple plug via a threaded clamp. This arrangement ensures the robustness of the sensor's internal structure and the smoothness of signal transmission, enhances the sensor's anti-interference capability, prevents external factors from interfering with signal transmission, ensures that the sensor can accurately extract measurement signals in complex environments, improves the overall reliability and practicality of the sensor, and enables it to work stably and accurately measure temperature in various harsh environments.

[0019] This invention proposes a coaxial temperature sensor based on the dip-coating method and its fabrication method. The insulating layer is formed on a tungsten-rhenium wire substrate using the dip-coating method, creating a unique gradient structure comprising at least one bottom insulating layer with high porosity and at least two dense upper insulating layers. This structure effectively solves the problem of cracking of the insulating layer at high temperatures due to the difference in thermal expansion coefficients between the insulating layer and the electrode material. The bottom insulating layer is 3-5 μm thick, and its high porosity provides a buffer space for thermal expansion at high temperatures, preventing cracking caused by thermal stress concentration. The upper insulating layers are 1-2 μm thick, and their 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 is the performance of the insulating layer itself optimized, but the bonding effect between it and the substrate and the positive electrode thin film layer is also enhanced. This enables the sensor to maintain structural stability in extreme high-temperature environments (such as ultra-high temperature gas flow in aerospace engines and extreme high-temperature regions in metallurgical blast furnaces), ensuring the reliability and measurement accuracy of the sensor and greatly improving the stability of the sensor in complex and harsh environments such as high temperature and strong electromagnetic interference. Attached Figure Description

[0020] The accompanying drawings are included to provide a further understanding of the 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 invention. Other embodiments and many anticipated advantages of the embodiments will be readily recognized as they become better understood through reference to the following detailed description. Other features, objects, and advantages of the invention will become more apparent from reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0021] Figure 1 This is a schematic diagram of a coaxial temperature sensor structure based on the dip-lift method according to an embodiment of the invention;

[0022] Figure 2 This is a schematic diagram of the sensitive core of a coaxial temperature sensor based on the impregnation-pulling method according to a specific embodiment of the invention;

[0023] Figure 3 This is a top view of the sensitive core according to a specific embodiment of the invention;

[0024] Figure 4 This is a diagram showing the connection relationship between the sensitive core and the metal wire according to a specific embodiment of the invention;

[0025] Figure 5 This is a diagram of the internal structure of a thermocouple plug according to a specific embodiment of the invention;

[0026] Figure 6 This is a simplified flowchart of a method for fabricating a coaxial temperature sensor based on the dip-coating method according to an embodiment of the invention.

[0027] Figure 7a This is 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;

[0028] Figure 7b This is a comparison test diagram of a coaxial sensor with a gradient insulating layer according to a specific embodiment of the present application and a standard thermocouple. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] Figure 1 A schematic diagram of a coaxial temperature sensor based on an impregnation-pulling method according to an embodiment of the invention is shown, as follows: Figure 1 As shown, the coaxial temperature sensor based on the dip-coating method includes a sensing core and a packaged shell. The sensing core, as the core part of the sensor, includes a tungsten-rhenium wire substrate 1, an insulating thin film layer 2, and a positive electrode thin film layer 3 (e.g., ...). Figure 2 The diagram shows a schematic of the sensitive core of a coaxial temperature sensor based on the dip-coating method according to a specific embodiment of the invention. The insulating film layer 2 is formed into a gradient structure on a tungsten-rhenium wire substrate 1 using the dip-coating method. This gradient structure includes at least one bottom insulating layer 21 with relatively high 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 used as an example, i.e., as shown below). Figure 3The diagram shows a top view of the sensitive core according to a specific embodiment of the invention. This gradient structure effectively mitigates the cracking problem of the insulating layer at high temperatures caused by the difference in thermal expansion coefficients between the insulating layer and the electrode material.

[0032] In a specific embodiment, the bottom insulating layer 21 has a thickness of 3-5 μm, the top insulating layer 22 has a thickness of 1-2 μm, and the total thickness of the insulating thin film layer 2 is 5-8 μm with a length of 80 mm. The positive electrode thin film layer 3 is made of tungsten, with a thickness of 10 μm and a length of 60 mm. Its good conductivity and high-temperature stability help to accurately transmit electrical signals in high-temperature environments. The tungsten-rhenium wire substrate 1 has a tungsten to rhenium ratio of 74:26, a length of 15 cm, and a diameter of 0.5 mm. Metal wires 4 and 5 (e.g., ...) are connected to the tungsten-rhenium wire substrate 1 and the positive electrode thin film layer 3, respectively. Figure 4 The diagram shown illustrates the connection relationship between the sensitive core and the metal wire according to a specific embodiment of the invention. The metal wire material is the same as the material of the connected thermoelectric electrode, ensuring the consistency and stability of signal transmission.

[0033] In one specific embodiment, taking a combination of a bottom insulating layer and two top insulating layers as an example, the bottom insulating layer has a thickness of 4 μm and a distinct void structure with high porosity, effectively accommodating thermal expansion under high-temperature conditions. For instance, 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, preventing cracks caused by thermal stress concentration. This structure, which facilitates thermal expansion buffering, is achieved by heat-treating the bottom insulating layer under vacuum conditions at 1000-1100°C for 20-30 minutes (e.g., heat-treating at 1050°C for 25 minutes). The thicknesses of the upper insulating layers are 0.8 μm and 1.2 μm, respectively. By adjusting the impregnation and pulling process parameters, such as adjusting the solution viscosity to 0.008-0.012 Pa·s (e.g., 0.01 Pa·s), controlling the pulling speed at 5-10 μm / s (e.g., 8 μm / s), and the number of pulling cycles to 5-8 (e.g., 6 times), and then heat-treating under vacuum at 1200-1300℃ for 30-40 minutes (e.g., heat-treating at 1250℃ for 35 minutes), the upper insulating layer is made dense. This dense structure ensures good insulation performance and effectively prevents signal interference.

[0034] In another specific embodiment, taking a combination of two bottom insulating layers and three top insulating layers as an example, the thicknesses of the bottom insulating layers are 2μm and 2.5μm, respectively. The two-layer configuration provides a larger buffer space for thermal expansion. For example, in environments with large temperature cycling variations (from 800℃ to 1600℃), it can better adapt to repeated thermal expansion and contraction of the material, reducing structural damage caused by thermal stress. Through a specific impregnation and pulling process, such as a solution viscosity in the range of 0.056-0.06 Pa·s (e.g., 0.058 Pa·s), a pulling speed of 50-100 μm / s (e.g., 50 μm / s), and 3-5 pulling cycles (e.g., 4 cycles), followed by drying and high-temperature heat treatment, a structure with high porosity is formed. The thicknesses of the top insulating layers are 0.6μm, 0.7μm, and 0.7μm, and the three dense top 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, improving the shielding effect against electromagnetic interference. The maximum porosity of the bottom insulating layer ranges from 20% to 40%, and the density of the upper insulating layer is more than 90% of the theoretical density.

[0035] In a specific embodiment, the sensitive core is fixed inside the encapsulation shell after being connected to the metal wire. The front end of the sensitive core is flush with the front end of the encapsulation shell, ensuring the compactness of the sensor structure, reducing the influence of the external environment on the sensitive core, and improving the sensor's anti-interference capability. The encapsulation shell includes a front sleeve 6 and a rear metal protective tube 7. The length of the front sleeve 6 is the same as the length of the sensitive core, both being 15cm. The rear metal protective 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 threaded clamps (e.g., ...). Figure 5 The diagram shown is an internal structure diagram of a thermocouple plug according to a specific embodiment of the invention. The signal is led out, ensuring the stability and accuracy of signal transmission. This is beneficial for the installation and use of the sensor in various complex environments, improving the practicality and reliability of the sensor, and enabling it to accurately measure temperature and effectively transmit signals in different application scenarios.

[0036] Continue to refer to Figure 6 , Figure 6 A simplified flow chart of a method for fabricating a coaxial temperature sensor based on an impregnation-pulling method according to an embodiment of the invention is shown, as follows: Figure 6 As shown, the preparation method includes the following steps:

[0037] S601: Solution preparation, cleaning of tungsten-rhenium wire.

[0038] In a specific embodiment, the tungsten-rhenium wire substrate 1 is ultrasonically cleaned in a cleaning solution and then 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 effectively removes oil, impurities, and other contaminants from the surface of the tungsten-rhenium wire substrate 1, making the substrate surface clean. This enhances the adhesion between the subsequent insulating film layer 2 and positive electrode film layer 3 and the substrate, improves the adhesion between the various layers of the sensor structure, ensures the stability of the sensor structure, and helps improve the overall performance and service life of the sensor. It also makes it less prone to delamination and peeling when working in high-temperature and complex environments, ensuring the accuracy and reliability of measurements.

[0039] S602: Insulation layer preparation. This includes the preparation of the bottom insulation layer and the preparation of the top insulation layer.

[0040] S603: Curing and sintering of the insulation layer.

[0041] In a specific embodiment, hafnium oxide sol or alumina sol is prepared as the insulating material sol (this embodiment uses hafnium oxide sol as an example). The viscosity of the sol solution is taken in the range of 0.056-0.06 Pa·s (e.g., 0.06 Pa·s). The treated tungsten-rhenium wire substrate 1 is immersed in the sol for 3-5 minutes (e.g., 4 minutes). Using an immersion lifting device, the tungsten-rhenium wire substrate 1 is slowly lifted from the sol solution at a speed of 100 μm / s, and the number of lifting times is 3-5 times (e.g., 4 times) to prepare the bottom insulating layer. After drying the bottom insulating layer in a drying oven at 150-200℃ for 5 minutes, it is heat-treated under vacuum conditions at 1000-1100℃ for 20-30 minutes (e.g., heat-treated under vacuum conditions at 1050℃ for 25 minutes) to form a structure with a large porosity and a thickness of 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), and the number of pulling times to 5-8 (e.g., 6 times), to prepare the upper insulating layer, and heat treat it under vacuum at 1200-1300℃ for 30-40 minutes (e.g., heat treat it under vacuum at 1250℃ 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.

[0042] S604: Tungsten thin film preparation. Prepare tungsten paste, immerse the tungsten rhenium wire substrate 1 with the prepared insulating thin film layer 2 into the tungsten paste for 3-5 minutes (e.g., 4 minutes), and slowly lift the tungsten rhenium wire substrate 1 out of the tungsten paste using an immersion lifting device.

[0043] S605: Tungsten thin film curing and sintering. After drying in a drying oven at 150-200℃ for 5 minutes, heat-treat at 1600℃ under vacuum for 30-40 minutes (e.g., heat-treat at 1600℃ under vacuum for 35 minutes) to make the positive electrode thin film layer 3 uniform and dense and bonded to the insulating thin film layer 2, with a thickness of 10μm and a length of 60mm.

[0044] S606: Connecting metal wires. Metal wires 4 and 5 are connected to the exposed positive electrode thin film layer 3 and the tungsten rhenium wire substrate 1, respectively.

[0045] S607: Packaging. The sensitive core is precisely positioned using a CCD vision system and fixed inside the front sleeve 6 of the packaging shell. High-temperature insulating powder is filled into the relatively large porosity of the sleeve and the sensitive core. The rear metal protective tube 7 of the packaging shell is connected to the thermocouple plug 10 via a compression fitting 8. The ends of the metal wires 4 and 5 are connected to the inside of the thermocouple plug 10 via threaded clamps, completing the sensor assembly.

[0046] Figure 7a This diagram illustrates a comparative test between a coaxial sensor with a normal insulating layer and a standard thermocouple according to a specific embodiment of the present invention; as shown. Figure 7a As shown, coaxial sensors with normal insulation layers (such as No. 101-105) and standard thermocouples (such as No. 106) were tested together in a high-temperature tube furnace. It can be seen that the coaxial sensors with normal insulation layers failed at around 1300℃. Figure 7b This is a comparison test diagram of a coaxial sensor with a gradient insulating layer according to a specific embodiment of the present invention and a standard thermocouple, as shown in the figure. Figure 7b As shown, coaxial sensors (such as No. 201 and 203) with gradient structure insulation layers were tested together with standard thermocouples (such as No. 204) in a high-temperature tube furnace. It can be seen that the insulation layer can remain intact for at least 30 minutes at 1400°C.

[0047] In one specific embodiment, the coaxial temperature sensor of the above-mentioned impregnation-pulling method was tested as follows:

[0048] High-temperature stability testing was conducted by placing the sensor prepared according to this invention in a high-temperature furnace at 1200℃ for 3 hours. The test results showed that the sensor's insulation layer did not crack, the sensitive core structure remained intact, and the measurement accuracy remained within ±1.5% throughout the test. This indicates that the sensor exhibits excellent stability under extreme high-temperature conditions. This is attributed to the gradient structure design of the insulation layer and the precise fabrication process, which effectively mitigates the cracking problem caused by the difference in thermal expansion coefficient between the insulation layer and the electrode material at high temperatures, ensuring reliable operation of the sensor at high temperatures.

[0049] Sensitivity testing was conducted within a temperature range of 100℃-1400℃, with the temperature gradually increased in 100℃ increments, and the change in the sensor's output electromotive force was measured. The test results show that the sensor's sensitivity reaches 20μV / ℃, enabling it to respond quickly and accurately to temperature changes. This is attributed to the material selection and structural design of the positive electrode thin film layer and the insulating layer, which optimizes the sensor's electrical performance, allowing for accurate measurements across different temperature ranges. This meets the requirements of applications demanding high temperature measurement accuracy, such as monitoring minute temperature changes during metal smelting.

[0050] The above description is merely a preferred embodiment of the present invention and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention is not limited to the specific combination of the above-described technical features, but also includes other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in this invention.

Claims

1. A coaxial temperature sensor for measuring high-temperature radiation, characterized in that, The device includes a sensing core and a packaging shell. The sensing core 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 using an dip-coating method. The gradient structure includes at least one bottom insulating layer with high porosity and at least two dense upper insulating layers. The tungsten-rhenium wire substrate and the positive electrode film layer are respectively connected to metal wires. The sensing core is fixed inside the packaging shell after being connected to the metal wires. The insulating film layer is prepared by: preparing an insulating material sol, immersing the pretreated tungsten-rhenium wire substrate in the insulating material sol, and slowly pulling the tungsten-rhenium wire substrate from the insulating material sol multiple times using an dip-coating device to prepare the bottom insulating layer. After drying, high-temperature heat treatment is performed to form a structure with high porosity in the bottom insulating layer. The upper insulating layer is prepared by repeated processing to make the upper insulating layer dense.

2. The coaxial temperature sensor for measuring high-temperature radiation according to claim 1, characterized in that, The insulating material sol includes hafnium oxide sol or alumina sol, and the solution viscosity of the sol is 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. Using the impregnation and lifting device, the tungsten-rhenium wire substrate is slowly lifted from the sol solution at a speed of 100 μm / s, and the lifting is repeated 3-5 times to prepare the bottom insulating layer. The bottom insulating layer is then heated at 150-200℃. After drying in a drying oven for 5 minutes, heat-treat under vacuum at 1000-1100℃ for 20-30 minutes to form a structure with high porosity in the bottom insulating layer; adjust the viscosity of the solution to 0.008-0.012 Pa·s, with a pulling speed of 5-10 μm / s and 5-8 pulling times to prepare the upper insulating layer, and heat-treat under vacuum at 1200-1300℃ for 30-40 minutes to make the upper insulating layer dense.

3. The coaxial temperature sensor for measuring high-temperature radiation according to claim 1, characterized in that, The thickness of the bottom insulating layer is 3-5 μm, the thickness of the top 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 measuring high-temperature radiation according to claim 1, characterized in that, The positive electrode thin film layer is made of tungsten, and the insulating thin film layer is made of hafnium oxide or aluminum oxide.

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

26.

6. The coaxial temperature sensor for measuring high-temperature radiation according to claim 1, characterized in that, The front end of the sensitive core is flush with the front end of the encapsulation shell. The encapsulation shell includes a front sleeve and a rear metal protective tube. The length of the front sleeve is the same as the length of the sensitive core. The rear metal protective 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 clamp to lead out the signal.

7. A method for preparing a coaxial temperature sensor for measuring high-temperature radiation as described in any one of claims 1-6, characterized in that, include: S1: The tungsten rhenium wire substrate is ultrasonically cleaned in a cleaning solution and then dried; S2: Prepare an insulating thin film layer by preparing an insulating material sol. Immerse the tungsten-rhenium wire substrate treated in S1 into the insulating material sol. Slowly pull the tungsten-rhenium wire substrate out of the insulating material sol multiple times using an immersion-pulling device to prepare a bottom insulating layer. After drying, perform high-temperature heat treatment to form a structure with high porosity in the bottom insulating layer. Repeat the process to prepare an upper insulating layer and make the upper insulating layer dense. S3: Prepare a positive electrode thin film layer, prepare a tungsten paste, and immerse the tungsten rhenium wire substrate with the insulating thin film layer prepared in S2 into the tungsten paste. Use an immersion lifting device to slowly lift the tungsten rhenium wire substrate from the tungsten paste, dry it, and then heat-treat it at high temperature to make it uniform and dense, so that the tungsten rhenium wire substrate and the positive electrode thin film layer are bonded through the insulating thin film layer. S4: After connecting metal wires to the exposed positive electrode thin film layer and the tungsten rhenium wire substrate, they are fixed inside the packaging shell.

8. The method for preparing a coaxial temperature sensor for radiation high-temperature measurement 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 sodium hydroxide, acetone and anhydrous ethanol for 15 minutes each and then dried.

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

10. The method for preparing a coaxial temperature sensor for radiation high-temperature measurement according to claim 7, characterized in that, S4 specifically includes: fixing the sensitive core inside the front end sleeve of the encapsulation shell, connecting the rear end metal protective tube of the encapsulation shell to the thermocouple plug through a compression fitting, and connecting the end of the metal wire to the inside of the thermocouple plug through a threaded clamp.

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