Carbon-based temperature sensor with wide temperature range and method of manufacturing the same

Abstract

The wide-temperature-range carbon-based temperature sensor provided by the present disclosure comprises: a high-temperature section working unit adopting a wide-bandgap semiconductor ceramic sheet; a medium-low-temperature section working unit adopting a carbon nanotube sensing unit; a first electrode adopting a carbon nanotube film, used for measuring the resistance of the medium-low-temperature section working unit at medium-low temperature and fixing the medium-low-temperature section working unit to the high-temperature section working unit; and a second electrode adopting a carbon nanotube film and insulatedly connected with the first electrode, used for measuring the resistance of the high-temperature section working unit at high temperature. The present disclosure has both wide-temperature-range sensing and miniaturization characteristics, can fully meet the requirements of various application scenarios from low temperature to high temperature, is flexible and convenient to operate, is low in price, and can realize effective sensing under small-size areas and various extreme conditions.

Description

Technical Field

[0001] This disclosure relates to the field of temperature sensor technology, and more specifically to a contact-type, wide-temperature-range carbon-based temperature sensor and its fabrication method. Background Technology

[0002] Currently, high-temperature sensors are divided into two types: contact and non-contact. Contact sensors are represented by thermocouples and temperature-indicating paint, while non-contact sensors are represented by infrared radiation temperature measurement and fiber optic temperature measurement. Both types of temperature measurement methods have their advantages and can meet the temperature measurement needs of different scenarios, but they also have their own limitations.

[0003] Current temperature sensors struggle to simultaneously achieve wide-range temperature sensing and miniaturization. The main problem with non-contact temperature sensors is their limited temperature measurement range, significant susceptibility to actual testing environments, limitation to surface temperature measurement, and high cost. For example, the ROTAMAPII infrared spot thermometer developed by RR in the UK and the FP11 fiber optic pyrometer developed by Land have detection temperatures of 550℃~1400℃ and 600℃~1300℃ respectively, making it difficult to achieve wide-range temperature sensing from low to high temperatures. In practical applications, many objects undergo a cooling process from high temperature to room temperature, in which case these types of temperature detectors cannot achieve effective temperature sensing.

[0004] Regarding contact temperature sensors, taking the Pt / Rh thermocouple developed by OMEGA in the United States as an example, although this product can achieve high-precision temperature sensing at high temperatures, with a maximum detection temperature of 2315℃, the probe size of the thermocouple is too large at high temperatures, exceeding 6 inches, specifically 6 inches to 12 inches, and requires additional cooling and insulation components, limiting its application in temperature measurement of small areas. The Pt-13%Rh / Pt thin-film thermocouple developed by NASA's Lewis Research Center can achieve a smaller unit size, but the temperature measurement range is limited, with a maximum detection temperature of only 1100℃. Summary of the Invention

[0005] This disclosure aims to address at least one of the technical problems existing in the prior art.

[0006] Therefore, this disclosure provides a wide-temperature-range carbon-based temperature sensor and its fabrication method, which combines wide-temperature-range sensing and miniaturization characteristics, can fully meet the needs of various application scenarios from low temperature to high temperature, is flexible and convenient to operate, and is inexpensive. It can achieve effective sensing in small-size areas and under various extreme conditions.

[0007] To achieve the aforementioned objectives, this disclosure employs the following technical solution:

[0008] The first aspect of this disclosure provides a wide-temperature-range carbon-based temperature sensor, comprising:

[0009] The high-temperature operating unit uses a wide-bandgap semiconductor ceramic chip;

[0010] The low-temperature operating unit uses a carbon nanotube sensing unit.

[0011] The first electrode, made of carbon nanotube film, is used to measure the resistance of the low-temperature section working unit at low and medium temperatures and to fix the low-temperature section working unit to the high-temperature section working unit.

[0012] The second electrode, made of carbon nanotube film and insulated from the first electrode, is used to measure the resistance of the high-temperature section working unit at high temperature.

[0013] In some embodiments, the wide bandgap semiconductor ceramic wafer is an aluminum nitride ceramic wafer, a silicon nitride wafer, a silicon carbide wafer, a boron nitride wafer, or a sapphire wafer.

[0014] In some embodiments, the operating temperature range of the high-temperature section working unit is in a temperature range exceeding 900°C.

[0015] In some embodiments, the carbon nanotubes in the carbon nanotube sensing unit are in the form of wires, films, foams, or sponges.

[0016] In some embodiments, the operating temperature range of the medium-low temperature working unit is -60°C to 900°C.

[0017] In some embodiments, the carbon nanotube sensing unit is a structure composed of pure carbon nanotubes continuously spun from an array of super-aligned carbon nanotubes by a dry spinning method, arranged in a preset pattern.

[0018] In some embodiments, the first electrode and the second electrode are both tightly attached to the upper and lower surfaces of the high-temperature section working unit by van der Waals forces, respectively.

[0019] In some embodiments, both the first electrode and the second electrode are thin films composed of multiple layers of pure carbon nanotubes continuously spun from an array of super-aligned carbon nanotubes by dry spinning.

[0020] In some embodiments, the minimum size of the wide-temperature-range carbon-based temperature sensor is on the order of millimeters, and the operating temperature range is -60°C to 1500°C.

[0021] The second aspect of this disclosure provides a method for fabricating a wide-temperature-range carbon-based temperature sensor, comprising:

[0022] Wide-bandgap semiconductor ceramic wafers are fabricated according to the design dimensions and used as high-temperature working units.

[0023] Pure carbon nanotubes continuously spun from an ultra-straight carbon nanotube array using a dry spinning method are arranged in a preset pattern to form a carbon nanotube sensing unit, which is used as a medium-low temperature section working unit and placed on the upper surface of the high temperature section working unit.

[0024] Pure carbon nanotubes continuously spun from an array of super-aligned carbon nanotubes using a dry spinning method are stacked into multiple layers to form a carbon nanotube film, which is then used to form the first and second electrodes according to the designed dimensions.

[0025] The first and second electrodes were immersed in solution A to increase the van der Waals forces between the carbon nanotube film and the wide bandgap semiconductor ceramic sheet.

[0026] The first electrode is attached to the upper surface of the high-temperature section working unit and connected to the low-temperature section working unit. The second electrode is attached to the lower surface of the high-temperature section working unit, and the first electrode and the second electrode are kept insulated to obtain the wide-temperature-range carbon-based temperature sensor.

[0027] The features and beneficial effects of this disclosure are as follows:

[0028] This disclosure uses carbon nanotubes as the core unit of the device, and combines carbon nanotube wires, or carbon nanotube sensing units in any form (such as filtration, spinning, etc.), with aluminum nitride, or any wide bandgap semiconductor ceramic sheet that is insulating at room temperature and conductive at high temperature, to achieve wide temperature sensing of -60℃ to 1500℃ through resistance changes.

[0029] The temperature sensor disclosed herein combines miniaturization with wide-temperature-range sensing at a low cost. Non-contact temperature measurement methods, such as infrared and fiber optic thermometers, cannot achieve such a wide temperature range, severely limiting their application environments. In practical use, if an object needs to undergo temperature changes from low to high temperatures, these types of temperature sensors are unusable. Contact-type Pt / Rh or W / Re thermocouples can achieve high accuracy, but their large probe size prevents temperature measurement of small areas or small objects. The temperature sensor of this disclosure can easily achieve wide-temperature sensing of -60℃ to 1500℃ within a 2mm × 2mm area. Furthermore, currently available temperature sensors are relatively expensive. The temperature sensor of this invention uses inexpensive raw materials and is simple to assemble, giving it a cost advantage over commercially available products. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a temperature sensor based on a carbon nanotube / aluminum nitride structure and a partial cross-section provided in an embodiment of this disclosure;

[0031] Figure 2 yes Figure 1A physical image of the temperature sensor shown.

[0032] Figure 3 yes Figure 1 Optical micrographs of carbon nanotubes and carbon nanotube thin film electrodes in the temperature sensor shown.

[0033] Figure 4 This is a temperature sensing curve of the temperature sensor provided in the embodiments of this disclosure, and a comparison graph of the sensing temperature and the actual temperature measured during actual operation.

[0034] Figure 5 yes Figure 4 The relative error between the temperature sensed by the temperature sensor and the actual temperature at each temperature point. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit this application.

[0036] Conversely, this application covers any alternatives, modifications, equivalent methods, and schemes made within the spirit and scope of this application as defined by the claims. Furthermore, to provide the public with a better understanding of this application, certain specific details are described in detail below. However, this application can be fully understood by those skilled in the art even without these detailed descriptions.

[0037] The structures, proportions, and sizes illustrated in the accompanying drawings are solely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of this application and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, provided they do not affect the effectiveness or purpose of this application, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of this application. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of this application's implementation.

[0038] See Figure 1 , Figure 2 The first aspect of this disclosure provides a wide-temperature-range carbon-based temperature sensor, comprising:

[0039] High-temperature section working unit 1 uses a wide bandgap semiconductor ceramic chip for temperature sensing in the high-temperature section above 900℃.

[0040] The low-temperature range working unit 2 is formed on the upper surface of the high-temperature range working unit 1. It adopts a carbon nanotube sensing unit for temperature sensing in the low-temperature range from -60℃ to 900℃.

[0041] The first electrode 3 is formed on the upper surface of the high-temperature section working unit 1 and connected to the medium-low temperature section working unit 2 to fix the medium-low temperature section working unit 2 to the high-temperature section working unit 1. The first electrode 3 is made of carbon nanotube thin film and is used to measure the resistance of the medium-low temperature section working unit 2 and realize the connection lead with the external circuit.

[0042] The second electrode 4 is formed on the lower surface of the high-temperature section working unit 1 and is insulated from the low-temperature section electrode 3. The second electrode 4 is made of carbon nanotube thin film and is used to measure the resistance of the high-temperature section working unit 1 at high temperatures. The first and second electrodes can be arranged horizontally on the same surface of the wide bandgap semiconductor ceramic sheet, or on the upper and lower sides of the wide bandgap semiconductor ceramic sheet, as long as the first and second electrodes are insulated. In this embodiment, the first and second electrodes are arranged on the upper and lower surfaces of the wide bandgap semiconductor ceramic sheet respectively. This not only facilitates device fabrication, but also measures the resistance through the thickness direction of the wide bandgap semiconductor ceramic sheet, which has the advantages of better control and data analysis than measuring the horizontal resistance by arranging two electrodes on the same side.

[0043] In some embodiments, the wide-bandgap semiconductor ceramic sheet constituting the high-temperature working unit 1 can be made of aluminum nitride ceramic sheet, silicon nitride sheet, silicon carbide sheet, boron nitride sheet, or sapphire sheet, etc., all of which are commercially available products. These materials possess the characteristics of insulation at room temperature and conductivity at high temperatures. The high-temperature working unit 1 avoids the problem of decreased sensing performance caused by the gradual decrease in the resistance of the carbon nanotube sensing unit with temperature change rate above 900°C. Furthermore, the wide-bandgap semiconductor only exhibits a certain degree of conductivity at high temperatures, effectively improving the sensor's temperature measurement range. In addition, these materials generally have high thermal conductivity and low coefficients of thermal expansion, which not only achieves rapid thermal equilibrium and response, meeting the response rate requirements of the temperature sensor, but also maintains the mechanical structural stability of the sensor under thermal shock. Moreover, the high-temperature working unit 1 also serves as the physical support for other components within the temperature sensor provided in this embodiment. The size of the high-temperature working unit 1 determines the size of the temperature sensor in this embodiment. In one embodiment of this application, an aluminum nitride sheet with dimensions of 2mm × 2mm × 0.1mm is used as the high-temperature working unit 1.

[0044] In some embodiments, the carbon nanotube sensing unit constituting the low-temperature range working unit 2 can be a carbon nanotube wire, or a carbon nanotube sensing unit in other forms (such as thin film, foam, sponge, etc.) formed by methods such as filtration and spinning. By observing the change in resistance of the low-temperature range working unit 2 with temperature, temperature sensing can be achieved within a range from low temperature to 900°C. Within the target temperature range, the resistance-temperature relationship of the carbon nanotube wire is monotonically decreasing, which can be used as a basis for temperature sensing. Carbon materials themselves have high-temperature resistance properties. Carbon nanomaterials maintain high-temperature stability while also possessing the advantages of miniaturization and integrability. Moreover, the conductivity of carbon materials changes accordingly with temperature. Carbon nanotube wire bundles have the advantages of being easy to process and composite, making them suitable as the core working unit of temperature sensor devices. In one embodiment of this application, the low-temperature working unit 2 uses carbon nanotubes with a length of 2 mm and a diameter of approximately 30 μm, which are composed of super-aligned carbon nanotube arrays (SACNTs). Specifically, pure carbon nanotube yarns are continuously spun from the SACNT array using existing dry spinning methods, and then carbon nanotubes of appropriate lengths are obtained by laser cutting or direct cutting. An optical micrograph of the carbon nanotubes in this embodiment is shown below. Figure 3 As shown.

[0045] In some embodiments, the first electrode 3 and the second electrode 4 formed on the upper and lower surfaces of the high-temperature section working unit 1 are both made of carbon nanotube thin films. The resistance of the low-temperature section working unit 2 is measured through the first electrode 3, and the resistance of the high-temperature section working unit 1 is measured through the second electrode 4. The carbon nanotube thin film electrode can not only be tightly bonded to the high-temperature section working unit 1 through van der Waals forces, and have carbon-carbon contact with each working unit to avoid the influence of contact resistance, but also has low resistance itself, ensuring the accuracy of resistance measurement. Similar to the method for preparing carbon nanotube wires, the carbon nanotube film in this embodiment is a multilayer carbon nanotube film composed of an array of super-aligned carbon nanotubes. It serves as a flexible electrode, and its preparation method is similar to dry spinning. The extracted carbon nanotubes are stacked in multiple layers to obtain a flexible carbon nanotube film with good conductivity. The carbon nanotube film is then immersed in solution A (which can be a solution that wets carbon nanotubes, such as ethanol, isopropanol, n-butanol, or terpineol) to increase the van der Waals force between the carbon nanotube film and the wide-bandgap semiconductor ceramic sheet, ensuring the strength and stability between them, thereby fixing the carbon nanotube wires to the upper surface of the wide-bandgap semiconductor ceramic sheet. A carbon nanotube film is prepared on the lower surface of the wide-bandgap semiconductor ceramic sheet using the same method as the second electrode 4, used for testing the resistance of the wide-bandgap semiconductor ceramic sheet at high temperatures. Simultaneously, high-temperature resistant carbon materials such as graphite rods and graphite sheets are used as electrodes for external circuit leads, forming a complete testing system. In this embodiment, the size of the first electrode 3 is 0.5 mm × 1 mm, and the size of the second electrode 4 is 1 mm × 2 mm.

[0046] In practical operation, the carbon nanotube sensing unit is responsible for temperature sensing in the range of -60℃ to 900℃, while the wide-bandgap semiconductor ceramic sheet is responsible for temperature sensing in the range of 900℃ to 1500℃. Near 900℃, both sensing units can work together. After obtaining the sensing temperature and corresponding error through calibration formulas, the two units can be compared, and the unit with the smaller error is selected as the final sensing basis to reduce sensing error. For each working unit, the resistance value of each unit at different temperatures is first calibrated. Fitting the calibrated resistance data yields the resistance-temperature relationship curve formula. In actual use, the measured resistance value of the working unit is substituted into the resistance-temperature formula to obtain the measured temperature. In this embodiment, the resistance R-temperature T relationship obtained from the high-temperature section working unit 1 is R(Ω)=exp(37275 / (T / K)-12.59); the resistance R-temperature T relationship obtained from the fitting of the medium-low temperature section working unit 2 is: R(Ω)=415.62139-0.39246(T / ℃)+1.95504E-4(T / ℃) 2 The resistance-temperature sensing curve and error test results of the temperature sensor provided in this embodiment are as follows: Figure 4 and Figure 5 As shown. Within a wide temperature range of -60℃ to 1500℃, the devices provided in the embodiments of this disclosure can all achieve effective temperature sensing, and the sensing error is less than 3%.

[0047] This disclosure also provides a method for preparing the above-mentioned temperature sensor, including the following steps:

[0048] First, two working units, carbon nanotube wires and a wide-bandgap semiconductor ceramic sheet, are obtained and processed to suitable dimensions using laser cutting and slicing. Then, a carbon nanotube thin-film electrode is fabricated by overlapping and laying multiple layers of extracted carbon nanotubes to obtain a flexible carbon nanotube thin film with good conductivity. After soaking in a solution such as ethanol, the carbon nanotube wires are attached to the wide-bandgap semiconductor ceramic sheet using the carbon nanotube thin film. The two are bonded together by van der Waals forces, exhibiting a certain strength and stability. A carbon nanotube thin-film electrode is fabricated on the other side of the semiconductor ceramic sheet using the same method, serving as the testing electrode for the resistance of an aluminum nitride sheet at high temperatures, thus obtaining the temperature sensor device of this invention.

[0049] Compared to other temperature sensing solutions in the same field, the innovation of this disclosure lies in the use of high-temperature resistant and highly maneuverable carbon nanotubes as the core sensing unit and electrode. The van der Waals forces between carbon nanotubes allow them to be arbitrarily bundled and laid into films, facilitating integration and composite with various other materials, thus combining the advantages of miniaturization and integrability. Based on this, carbon nanotube wires are composited with a wide-bandgap aluminum nitride ceramic sheet that exhibits significant resistance changes at high temperatures. This achieves wide-temperature sensing ranging from -60℃ to 1500℃ within a core size of only 2mm × 2mm × 0.1mm, with sensing errors all within 3%. The temperature sensor provided by this disclosure combines miniaturization with a wide temperature sensing range of -60℃ to 1500℃, offering high sensing accuracy and low cost, demonstrating significant advantages over products in the same field.

[0050] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0051] Although embodiments of this disclosure have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this disclosure, the scope of which is defined by the claims and their equivalents.

Claims

1. A wide-temperature-range carbon-based temperature sensor, characterized in that, include: The high-temperature operating unit uses a wide-bandgap semiconductor ceramic chip; The low-temperature operating unit uses a carbon nanotube sensing unit. The first electrode, made of carbon nanotube film, is used to measure the resistance of the low-temperature section working unit at low and medium temperatures and to fix the low-temperature section working unit to the high-temperature section working unit. The second electrode, made of a carbon nanotube film and insulated from the first electrode, is used to measure the resistance of the high-temperature section working unit at high temperature. Both the first electrode and the second electrode are tightly attached to the upper and lower surfaces of the high-temperature section working unit by van der Waals forces, respectively. Both the first electrode and the second electrode are thin films composed of multiple layers of pure carbon nanotubes continuously spun from an array of super-aligned carbon nanotubes by dry spinning.

2. The wide-temperature-range carbon-based temperature sensor according to claim 1, characterized in that, The wide bandgap semiconductor ceramic wafer is made of aluminum nitride, silicon nitride, silicon carbide, boron nitride, or sapphire.

3. The wide-temperature-range carbon-based temperature sensor according to claim 1, characterized in that, The operating temperature range of the high-temperature section working unit exceeds 900°C.

4. The wide-temperature-range carbon-based temperature sensor according to claim 1, characterized in that, The carbon nanotubes in the carbon nanotube sensing unit are in the form of wires, thin films, foams, or sponges.

5. The wide-temperature-range carbon-based temperature sensor according to claim 1, characterized in that, The operating temperature range of the medium and low temperature section working unit is -60℃ to 900℃.

6. The wide-temperature-range carbon-based temperature sensor according to claim 1, characterized in that, The carbon nanotube sensing unit is a structure composed of pure carbon nanotubes continuously spun from an array of super-aligned carbon nanotubes using a dry spinning method, arranged in a preset pattern.

7. The wide-temperature-range carbon-based temperature sensor according to any one of claims 1 to 6, characterized in that, The minimum size of the wide-temperature-range carbon-based temperature sensor is on the order of millimeters, and its operating temperature range is -60℃ to 1500℃.

8. A method for fabricating a wide-temperature-range carbon-based temperature sensor, characterized in that, Includes the following steps: Wide-bandgap semiconductor ceramic wafers are fabricated according to the design dimensions and used as high-temperature working units. Pure carbon nanotubes continuously spun from an array of super-aligned carbon nanotubes using a dry spinning method are arranged in a preset pattern to form a carbon nanotube sensing unit, which is used as a working unit in the medium and low temperature range and placed on the upper surface of the working unit in the high temperature range. Pure carbon nanotubes continuously spun from an array of super-aligned carbon nanotubes using a dry spinning method are stacked into multiple layers to form a carbon nanotube film, which is then used to form the first and second electrodes according to the designed dimensions. The first and second electrodes were immersed in solution A to increase the van der Waals forces between the carbon nanotube film and the wide bandgap semiconductor ceramic sheet. The first electrode is attached to the upper surface of the high-temperature section working unit and connected to the low-temperature section working unit. The second electrode is attached to the lower surface of the high-temperature section working unit, and the first electrode and the second electrode are kept insulated to obtain the wide-temperature-range carbon-based temperature sensor.

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