Wireless high-temperature strain sensor based on alumina ceramics

Abstract

The invention belongs to the technical field of sensors, and particularly relates to an aluminum oxide ceramic-based wireless high-temperature strain sensor, which comprises an upper-layer metal structure, an aluminum oxide substrate and a lower-layer metal structure, the upper-layer metal structure is arranged on the upper surface of the aluminum oxide substrate, and the lower-layer metal structure is arranged on the lower surface of the aluminum oxide substrate. According to the invention, the size of the sensor is accurately optimized, so that the strain sensitivity of the sensor is ensured. The high-temperature sensor is excited through the coplanar waveguide antenna. According to the invention, remote signal monitoring is realized by adopting a microwave scattering technology, the problem that a traditional wired sensing transmission line is damaged at a high temperature is solved, and strain measurement with a measuring range of + / -400 [mu] epsilon in a range of 25-800 DEG C is realized by utilizing high-temperature-resistant ceramic (Al2O3 ceramic).

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and particularly relates to a wireless high-temperature strain sensor based on alumina ceramics. Background Art

[0002] Traditional strain monitoring means often have difficulty adapting to high-temperature environments. For example, contact sensors are easily damaged due to high temperatures, and their wiring is complex and difficult to maintain. Wireless high-temperature strain sensors, on the other hand, overcome these drawbacks. They can achieve real-time data acquisition and transmission without wiring through wireless transmission technology. Wireless passive sensing technology has unparalleled advantages in obtaining temperature parameters in harsh environments, which has attracted the attention of researchers. Wireless passive temperature measurement technologies mainly include four types: based on surface acoustic wave (SAW) technology, sensitive capacitance-inductance type (LC) resonant mutual inductance coupling technology, optical fiber technology, and microwave backscattering technology.

[0003] SAW sensors have advantages such as simple structure, small size, and long transmission distance, but they have the problem that the substrate material is unstable at high temperatures, so the test signal is easily interfered by the environment; LC resonant mutual inductance coupling technology obtains energy through electromagnetic induction and is suitable for short-distance wireless transmission, but LC resonant mutual inductance coupling technology has weak anti-interference ability in complex electromagnetic environments; optical fiber technology has advantages such as high precision, anti-electromagnetic interference, and long-distance transmission, but the installation and maintenance costs of optical fiber sensors are relatively high, and the optical fiber itself is relatively fragile and easily damaged physically. Summary of the Invention

[0004] In view of the technical problems existing in the above-mentioned traditional sensors, the present invention provides a wireless high-temperature strain sensor based on alumina ceramics.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A wireless high-temperature strain sensor based on alumina ceramics includes an upper metal structure, an alumina substrate, and a lower metal structure. The upper metal structure is disposed on the upper surface of the alumina substrate, and the lower metal structure is disposed on the lower surface of the alumina substrate.

[0007] The upper metal structure and the lower metal structure have the same structure, and both the upper metal structure and the lower metal structure include two symmetrically arranged resonant cavities.

[0008] The distance between the two resonant cavities is 1 mm, the thickness is 0.02 mm, and the conductivity is 9.52×106 S / m.

[0009] The thickness of the alumina substrate is 1.3 mm; the materials of the upper metal structure and the lower metal structure are both platinum, the thickness is 0.02 mm, and the width is 2.5 mm.

[0010] The distance between the upper metal structure and the lower metal structure from the edge of the alumina substrate in the X direction is 0.5 mm, and the distance in the Y direction from the edge of the alumina substrate is 2 mm.

[0011] It further includes an interrogation antenna, and the interrogation antenna is arranged above the upper metal structure.

[0012] The interrogation antenna includes a dielectric substrate, a ground plane, a microstrip transmission line, and a rectangular radiation patch. The ground plane, the microstrip transmission line, and the rectangular radiation patch are all arranged on the upper surface of the dielectric substrate. The ground plane is arranged on both sides of the microstrip transmission line, and the microstrip transmission line is connected to the rectangular radiation patch.

[0013] The size of the dielectric substrate is 120 mm * 20 mm * 0.6 mm, the size of the rectangular radiation patch is 17 mm * 19.5 mm, the size of the microstrip transmission line is 1 mm * 98 mm, the distance between the ground plane and the microstrip transmission line is 0.9 mm, and the distance between the ground plane and the rectangular radiation patch is 5 mm.

[0014] The ground plane, the microstrip transmission line, and the rectangular radiation patch are all made of platinum metal paste, and their thicknesses are all 20 μm.

[0015] A preparation method of a wireless high-temperature strain sensor based on alumina ceramics includes the following steps:

[0016] S1. Al 2 O 3 The substrate is made from a green ceramic sheet through hole punching and positioning, isostatic pressing, and cutting to become a ceramic sheet with regular shape.

[0017] S2. Sinter the fabricated ceramic sheet in a muffle furnace to harden it; the specific sintering process is to raise the temperature to 850 °C at a rate of 10 °C / min and then keep it warm for 120 min, and then naturally cool it to room temperature.

[0018] S3. Using the screen printing process, print the metal structure on the upper and lower surfaces of the alumina substrate with platinum metal paste, and its thickness is 20 μm; the screen printing process can directly prepare a patterned metal layer on the substrate layer, and also includes the metal structure of the coplanar waveguide antenna.

[0019] S4. Put the printed sensor into a holding furnace and keep it warm at 90 °C for about 20 min and then take it out to prevent the just-printed platinum paste from flowing on the surface layer of the alumina substrate.

[0020] S5. Prepare the designed coplanar waveguide antenna in the same steps.

[0021] S6. Put the held sensor and the antenna sample into the muffle furnace and conduct high-temperature firing again.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] Through precise optimization of the sensor size, the present invention ensures its sensitivity to strain. The high-temperature sensor is excited by a coplanar waveguide antenna. The present invention uses microwave scattering technology to achieve long-distance signal monitoring, solves the problem of damage to traditional wired sensing transmission lines at high temperatures, and uses high-temperature resistant ceramics (Al 2 O 3 ceramics) to achieve strain measurement with a range of ±400 με in the temperature range of 25°C - 800°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained according to the provided drawings.

[0025] The structures, ratios, sizes, etc. shown in this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they do not have a substantial technical meaning. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present invention.

[0026] Figure 1 The top view of a wireless high-temperature strain sensor based on alumina ceramic provided by an embodiment of the present invention;

[0027] Figure 2 The side view of a wireless high-temperature strain sensor based on alumina ceramic provided by an embodiment of the present invention;

[0028] Figure 3 The schematic structural diagram of the interrogation antenna in an embodiment of the present invention;

[0029] Figure 4 The schematic cooperation diagram of the high-temperature sensor and the interrogation antenna in an embodiment of the present invention;

[0030] Figure 5 The schematic data diagram of the actual temperature test of the present invention at normal temperature of 25°C and 800°C;

[0031] Figure 6 The fitting diagram of the relationship between the resonance frequency and the temperature of the present invention at different temperatures.

[0032] Wherein: 1 is the upper metal structure, 101 is the resonant cavity, 2 is the alumina substrate, 3 is the lower metal structure, 4 is the interrogation antenna, 401 is the dielectric substrate, 402 is the ground plane, 403 is the microstrip transmission line, and 404 is the rectangular radiation patch. Specific embodiments

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. These descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention; based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0034] The following will further describe in detail the specific embodiments of the present invention in conjunction with the drawings and embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0035] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0036] The embodiment of the present invention provides a wireless high-temperature strain sensor based on alumina ceramics, including a sensor body and a coplanar waveguide antenna for reading sensor signals, as Figure 1 、 Figure 2 shown. The sensor includes an alumina substrate 2 and an upper metal structure 1 and a lower metal structure 3 located above and below the alumina substrate 2.

[0037] Specifically, in this embodiment, the alumina substrate 2 is alumina with a length and width of 20 mm and a thickness of 1.3 mm, its relative dielectric constant is 9.9, and the dielectric loss is 0.0001; the materials of the upper metal structure 1 and the lower metal structure 3 on the upper and lower surfaces of the alumina substrate 2 are metal platinum paste materials, and their thickness is 20 μm.

[0038] Specifically, a preparation method of a wireless high-temperature strain sensor based on alumina ceramics in this embodiment includes the following steps:

[0039] S1. The alumina substrate 2 is made from green ceramic wafers. After punching for positioning, isostatic pressing, and cutting, it becomes a ceramic wafer with regular shape.

[0040] S2. Sinter the fabricated ceramic wafer in a muffle furnace to harden it. The specific sintering process is to raise the temperature to 850 °C at a rate of 10 °C / min and hold for 120 min, and then naturally cool to room temperature.

[0041] S3. Using the screen printing process, print the metal structure on the upper and lower surfaces of the alumina substrate 2 with platinum metal paste, and its thickness is 20 μm. The screen printing process can directly prepare a patterned metal layer on the substrate layer, and also includes the metal structure of the coplanar waveguide antenna.

[0042] S4. Put the printed sensor into a holding furnace and hold at 90 °C for about 20 min and then take it out. The purpose of this is to prevent the just-printed platinum paste from flowing on the surface layer of the substrate.

[0043] S5. Prepare the designed coplanar waveguide antenna in the same steps.

[0044] S6. Put the held sensor and antenna samples into the muffle furnace and conduct high-temperature firing again.

[0045] Specifically, in this embodiment, as Figure 3 shown, the size of the dielectric substrate 401 is 20 mm * 120 mm * 0.6 mm, the size of the rectangular radiation patch 404 is 17 mm * 19.5 mm, the size of the microstrip transmission line 403 is 1 mm * 98 mm, the distance between the ground plane 402 of the interrogation antenna 4 and the microstrip transmission line 403 is 0.9 mm, and the distance between the ground plane 402 and the rectangular radiation patch 404 is 5 mm.

[0046] Specifically, in this embodiment, the rectangular radiation patch 404, the microstrip transmission line 403, and the ground plane 402 use platinum metal paste, and its thickness is 20 μm.

[0047] Figure 4 is a schematic diagram of the cooperation between the high-temperature sensor and the interrogation antenna 4 in the embodiment of the present invention. The rectangular radiation patch 404 of the interrogation antenna 4 is arranged above the sensor. The radius of the sensor is 20 mm × 20 mm, and the length of the interrogation antenna 4 is 120 mm.

[0048] Figure 5 is the result diagram of the temperature test experiment of the embodiment of the present invention. The temperature test of the present invention starts from room temperature 25 °C, and then gradually conducts heating tests, and the temperature is raised to a maximum of 800 °C. The resonance frequency of the sensor gradually decreases as the temperature increases. The strain of the sensor ranges from compression to tension, and the resonance frequency gradually increases. Figure 6The vertical coordinate S11 is the self - reflection coefficient of the interrogation antenna 4, and Frequency is the resonant frequency. As Figure 6 shown in (a), the resonant frequency of the sensor at 25 °C is 3.79625 GHz; as Figure 6 shown in (b), the resonant frequency of the sensor at 800 °C is 3.67620 GHz.

[0049] Figure 6 Data processing and analysis were carried out for the embodiments of the present invention. By extracting the resonant frequency of the wave - trough points from the directly measured curves, the change curve of the sensor's resonant frequency from 25 °C to 800 °C was finally obtained. The resonant frequency decreases as the temperature increases, and the variation law of this phenomenon is consistent with the theory. From the analysis of the test data, it can be seen that the resonant frequency of the sensor changes approximately linearly at different temperatures. Among them, the sensitivity of the sensor at 25 °C is 3.585 KHz / με, and the sensitivity at 800 °C high temperature is 4.025 KHz / με. The fitting curve is as Figure 6 shown, and the corresponding strain - resonant frequency relationship formula is as follows, where y is the strain value in με and x is the resonant frequency in GHz.

[0050] Figure 6 (a) is the fitting curve at room temperature of 25 °C, and its expression is:

[0051] y = 2.787×10 ― 5 x ― 1.03×10 ― 6

[0052] Figure 6 (b) is the fitting curve at room temperature of 800 °C, and its expression is:

[0053] y = 2.468×10 ― 5 x ― 1.31×10 ― 6

[0054] The above data shows that the high - temperature sensor of the present invention can achieve strain measurement with a range of ±400 με in the range of 25 °C - 800 °C, and has good linear characteristics and high sensitivity, expanding the application of traditional sensors in a multi - metal environment.

[0055] In summary, the present invention provides a wireless high - temperature strain sensor based on alumina ceramics. By precisely optimizing the size of the sensor, its sensitivity to strain is ensured. The high - temperature sensor is excited by a coplanar waveguide antenna. The present invention uses microwave scattering technology to achieve remote signal monitoring, solving the problem of damage to traditional wired sensing transmission lines at high temperatures; using high - temperature - resistant ceramics (Al2 O 3 The strain measurement with a range of ±400 με within the temperature range of 25°C - 800°C is achieved by using (ceramics).

[0056] The above only elaborates on the preferred embodiments of the present invention in detail. However, the present invention is not limited to the above embodiments. Within the knowledge scope of those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention, and all such changes should be included within the protection scope of the present invention.

Claims

1. A wireless high temperature strain sensor based on alumina ceramics, characterized in that: The invention comprises an upper metal structure (1), an aluminum oxide substrate (2) and a lower metal structure (3), wherein the upper metal structure (1) is arranged on the upper surface of the aluminum oxide substrate (2), and the lower metal structure (3) is arranged on the lower surface of the aluminum oxide substrate (2).

2. The wireless high-temperature strain sensor based on alumina ceramics according to claim 1, characterized in that: The upper metal structure (1) and the lower metal structure (3) have the same structure, and both the upper metal structure (1) and the lower metal structure (3) include two symmetrically arranged resonant cavities (101).

3. The wireless high temperature strain sensor based on alumina ceramics according to claim 2, characterized in that: The distance between the two resonant cavities (101) is 1 mm, the thickness is 0.02 mm, and the electrical conductivity is 9.52×106 S / m.

4. The wireless high-temperature strain sensor based on alumina ceramics according to claim 1, characterized in that: The thickness of the aluminum oxide substrate (2) is 1.3 mm; the materials of the upper metal structure (1) and the lower metal structure (3) are both platinum, with a thickness of 0.02 mm and a width of 2.5 mm.

5. The wireless high-temperature strain sensor based on alumina ceramics according to claim 1, characterized in that: The upper metal structure (1) and the lower metal structure (3) are 0.5 mm away from the edge of the aluminum oxide substrate (2) in the X direction, and 2 mm away from the edge of the aluminum oxide substrate (2) in the Y direction.

6. The wireless high-temperature strain sensor based on alumina ceramics according to claim 1, characterized in that: It also comprises an interrogation antenna (4), wherein the interrogation antenna (4) is arranged above the upper metal structure (1).

7. The wireless high-temperature strain sensor based on alumina ceramics according to claim 6, characterized in that: The interrogation antenna (4) comprises a dielectric substrate (401), a ground plate (402), a microstrip transmission line (403) and a rectangular radiation patch (404); the ground plate (402), the microstrip transmission line (403) and the rectangular radiation patch (404) are all arranged on the upper surface of the dielectric substrate (401); the ground plate (402) is arranged on both sides of the microstrip transmission line (403); and the microstrip transmission line (403) is connected to the rectangular radiation patch (404).

8. The wireless high-temperature strain sensor based on alumina ceramics according to claim 7, characterized in that: The size of the dielectric substrate (401) is 120 mm*20 mm*0.6 mm, the size of the rectangular radiation patch (404) is 17 mm*19.5 mm, the size of the microstrip transmission line (403) is 1 mm*98 mm, the distance between the ground plate (402) and the microstrip transmission line (403) is 0.9 mm, and the distance between the ground plate (402) and the rectangular radiation patch (404) is 5 mm.

9. The wireless high-temperature strain sensor based on alumina ceramics according to claim 7, characterized in that: The ground plate (402), the microstrip transmission line (403) and the rectangular radiation patch (404) are all made of metal platinum slurry, and the thickness of each of them is 20 um.

10. A method for preparing a wireless high-temperature strain sensor based on alumina ceramics according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1, Al2O3 substrate is made of raw ceramic sheets through punching, isostatic pressing and cutting to become ceramic sheets with regular shapes; S2, sintering the produced ceramic piece in a muffle furnace to harden it; The specific sintering process is to raise the temperature to 850℃ at a rate of 10℃ / min, keep it at that temperature for 120min, and then naturally drop to room temperature; S3, using a screen printing process, printing a metal structure on the upper and lower surfaces of the alumina substrate (2) using a metal platinum slurry, with a thickness of 20 um; The screen printing process can directly prepare a patterned metal layer on the substrate layer, including the metal structure of the coplanar waveguide antenna; S4, placing the printed sensor in a heat preservation furnace at 90° C. for about 20 minutes and then taking it out to prevent the newly printed platinum paste from flowing on the surface of the alumina substrate (2); S5. Prepare the designed coplanar waveguide antenna in the same steps; S6. Place the insulated sensor and antenna samples into the muffle furnace for high-temperature firing again.

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