Negative temperature sensor, preparation method and detection device

Abstract

The present invention discloses a negative temperature sensor, a preparation method and a detection device, wherein the sensor comprises a substrate, a sensing layer, a bonding layer and an electrode layer from bottom to top; wherein the material of the electrode layer comprises one of a conductive metal, a high entropy alloy and a high entropy alloy nitride. The sensor of the present invention is suitable for liquid and gaseous media to be measured. The electrode material used in the present invention is a high entropy alloy, which has a high entropy effect in thermodynamics and a slow diffusion effect in kinetics. Compared with conventional ternary and quaternary nitrides and oxide coatings, it has better high temperature resistance and oxidation resistance. In addition, based on the multi-element characteristics of high entropy alloys, compared with traditional silver electrodes, the acoustic wave transmission performance, ultrasonic signal and piezoelectric constant of the sensor are greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of temperature measurement, and in particular to a negative temperature sensor, a preparation method and a detection device. Background Art

[0002] The aerospace industry is a dominant industry in China. Engines play an important role in the military and civilian fields of aerospace. Safety and reliability are one of the indicators that must be considered in their design and manufacturing. Bolts are the main connection form of the engine rotor system, and their tightening performance is a key factor affecting the rotor connection stiffness, torque transmission capacity, and reliability. However, engines often involve complex working conditions such as a wide temperature range of -60°C to 1500°C, corrosion, and variable loads, which cause the bolts to deviate from the original design, resulting in vibration of the entire engine, bolt breakage, and flying out, causing serious accidents.

[0003] For the rotor bolt connection structure, dynamic measurement of temperature changes is carried out, which is of great significance for early warning of preload loss and improving engine safety and reliability. Traditional temperature measurement technologies such as crystal, optical fiber, and radiation cannot monitor in real time and have poor accuracy. They can only measure the surface temperature of objects, not the internal temperature.

[0004] At present, there is a serious lack of non-destructive measurement methods for the temperature of in-service bolt bodies, especially a lack of high-precision online temperature monitoring technology in the negative temperature range. In this regard, it is urgent to provide corresponding detection devices. Summary of the invention

[0005] In view of the defects of the prior art, the present invention forms ultrasonic sensors and capacitors by depositing piezoelectric layers, dielectric layers or other insulating materials on the surface of substrates such as bolts, and measures changes in ambient temperature by changes in ultrasonic signal amplitude, TOF, capacitance, dielectric constant, resistance and resistivity.

[0006] In order to achieve the above object, the present invention provides a negative temperature sensor, which comprises, from bottom to top, a substrate, a sensing layer, a binding layer and an electrode layer;

[0007] The material of the electrode layer includes one of a metal element, a high entropy alloy, and a high entropy alloy nitride. For example, if the material of the electrode layer is a metal element, it can be Ag, Cu, Cr, Pt, etc., but is not strictly limited.

[0008] Furthermore, the thickness of the electrode layer is 4 to 10 μm;

[0009] The high entropy alloy includes one of AlCrNbSiTiTaY, AlCrNbSiTi, and AlHfNbSiTaTiZr.

[0010] Furthermore, the thickness of the sensing layer is 2 to 18 μm;

[0011] The material of the sensing layer includes one of a piezoelectric material, a dielectric material, and a non-piezoelectric and dielectric insulating material.

[0012] In the present invention, the material of the substrate is not limited, including silicon wafers, copper sheets, glass sheets, alloy materials (including stainless steel, etc.), bolts, etc. At the same time, the material of the sensing layer does not need to be strictly limited. For example, the piezoelectric material can be at least one of LiNbO3, PZT, AlN, AlScN, and ZnO; the dielectric material can be at least one of Al2O3, TiO2, ZrO2, PE, PP, LiNbO3, AlN, AlScN, and ZnO.

[0013] Furthermore, the bonding layer is Cr with a thickness of 50 to 100 nm.

[0014] The present invention also provides a method for preparing a negative temperature sensor, comprising sequentially preparing a sensing layer, a binding layer and an electrode layer on the surface of a substrate;

[0015] Wherein, the material of the electrode layer includes one of a conductive metal, a high entropy alloy, and a high entropy alloy nitride.

[0016] In the present invention, the sensing layer is prepared by an existing magnetron sputtering process, and the parameters used may be: a bias voltage of -5 to -20 V, a radio frequency power of 500 to 1000 W, a total gas pressure of 0.5 to 5 Pa, a deposition temperature of 80 to 250 ° C, a deposition time of 2 h to 10 h, a distance between the target material and the substrate of 2 cm to 7 cm, and when the prepared sensing layer is a nitride, the gases introduced are argon and nitrogen, and the volume ratio of argon to oxygen is 1 / 2 to 5 / 1; when the prepared sensing layer is an oxide, the gases introduced are argon and oxygen, and the volume ratio of argon to oxygen is 1 / 2 to 5 / 1.

[0017] Furthermore, the bonding layer is prepared by arc ion plating in an argon atmosphere, and specific parameters include arc current 80-100A, gas pressure 0.5-2.0Pa, deposition temperature 30-150°C, deposition time 0.5-2min, and target-base distance 60-90mm.

[0018] Furthermore, the electrode layer is prepared by magnetron sputtering in an argon or argon and nitrogen mixture atmosphere, and the specific parameters include RF power 600-900W, gas pressure 1.55-1.95Pa, deposition temperature 30-90°C, deposition time 20-120min, target-base distance 60-90mm, pure argon is used when preparing metal and high-entropy alloy electrode layers, and argon and nitrogen mixture is used when preparing high-entropy alloy nitrides, and the volume ratio of argon to nitrogen is 1 / 2-3 / 1.

[0019] Furthermore, when the electrode layer is prepared by magnetron sputtering, a bias voltage is applied between the substrate with the sensing layer and the bonding layer and the target material for the initial 1.0 to 1.5 min;

[0020] The bias voltage is 30 to 49 V, the current is 1.0 to 2.5 A, and the duty cycle is 40% to 60%. Setting the bias voltage in the early stage of magnetron sputtering can enhance the bonding effect between the electrode layer and the bonding layer.

[0021] The present invention also provides a detection device, comprising the negative temperature sensor mentioned above.

[0022] Furthermore, the detection device also includes a first contact, a second contact, a ground wire, a signal wire, a housing, and a detector, a controller, and a terminal connected in sequence;

[0023] The first contact and the second contact are respectively arranged at the substrate and the electrode layer;

[0024] The housing is used to protect the negative temperature sensor and is provided with a first lead-out hole and a second lead-out hole;

[0025] The ground wire and the signal wire are connected to the first contact and the second contact respectively. The ground wire is connected to the detector and grounded after passing through the first lead-out hole, and the signal wire is connected to the detector after passing through the second lead-out hole.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The sensor of the present invention is suitable for liquid and gaseous media to be measured. The electrode material used in the present invention is a high entropy alloy, which has a high entropy effect in thermodynamics and a slow diffusion effect in kinetics. Compared with conventional ternary and quaternary nitrides and oxide coatings, it has more corrosion resistance, high temperature resistance, and oxidation resistance. In addition, based on the multi-element characteristics of high entropy alloys, compared with traditional silver electrodes, the acoustic wave transmission performance, ultrasonic signal, and piezoelectric constant of the sensor are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 The morphologies of the electrode layers of Examples 1 to 3 are shown, wherein: Figure 1 (a) is the morphology of the electrode layer of Example 1, Figure 1(b) is the morphology of the electrode layer of Example 2, Figure 1 (c) is the morphology of the electrode layer of Example 3;

[0030] Figure 2 The distribution of C and O elements in the electrode layer of Example 3 is shown, wherein: Figure 2 (a) is the C element, Figure 2 (b) is O element;

[0031] Figure 3 The ultrasonic longitudinal wave signal diagrams of Examples 1 to 3 and Comparative Examples 1 to 3 are shown, wherein: Figure 3 (a) is Example 1 and Comparative Example 1, Figure 3 (b) is Example 2 and Comparative Example 2, Figure 3 (c) is Example 3 and Comparative Example 3;

[0032] Figure 4 A schematic diagram showing the structure of the detection device of Example 4 for detecting a medium to be detected;

[0033] Figure 5 A structural schematic diagram showing a connection method of a negative temperature sensor in a detection device of Example 4;

[0034] Figure 6 The detection performance results of the detection device of Example 4 for negative temperatures are shown;

[0035] Figure 7 The performance of the ultrasonic signal of the negative temperature sensor of Example 5 as it changes with temperature is shown;

[0036] Figure 8 The capacitance change of the negative temperature sensor of Example 6 at different temperatures at a measurement frequency of 10 kHz is shown;

[0037] Fig. 9 The dielectric constant and dielectric loss changes of the negative temperature sensor of Example 6 at different temperatures at a measurement frequency of 10 kHz are shown;

[0038] Fig.10 The figure shows the changes in resistance and resistivity of the negative temperature sensor of Example 6 at different temperatures at a measurement frequency of 10 kHz;

[0039] Fig.11 The surface morphology of the electrode layer of the negative temperature sensor of Example 7 before and after salt spray corrosion is shown, wherein: Fig.11 (a) before corrosion, Fig.11 (b) after corrosion;

[0040] Description of reference numerals:

[0041] 1. Substrate; 2. Sensing layer; 3. Binding layer; 4. Electrode layer; 5. First contact; 6. Second contact; 7. Signal line; 8. Ground line; 9. Housing; 10. Detector; 11. Medium to be tested; 12. High and low temperature alternating box; 13. Controller; 14. Terminal. DETAILED DESCRIPTION

[0042] The following will be combined with the specific embodiments of the present invention and the drawings of the specification to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Example 1

[0044] A method for preparing a negative temperature sensor comprises the following steps:

[0045] (1) Using magnetron sputtering, a 12.4 μm thick LiNbO3 was deposited on the surface of the stainless steel plate SS1 to form a sensing layer. The specific parameters included a bias voltage of -10 V, a radio frequency power of 900 W, a deposition temperature of 150 °C, an argon-oxygen ratio of 2 / 1, a total gas pressure of 2.0 Pa, a deposition time of 8 h, and a target-base distance of 5 cm.

[0046] (2) Using arc ion plating, in a pure argon atmosphere, Cr with a thickness of 70 nm was deposited on the surface of the sensing layer to form a bonding layer. The specific parameters included arc current 90 A, gas pressure 1.0 Pa, deposition temperature 60 ° C, deposition time 55 s, and target-base distance 78 mm;

[0047] (3) Using the magnetron sputtering method and AlCrNbSiTiTaY target material, AlCrNbSiTiTaY with a thickness of 6.7 μm was deposited on the surface of the bonding layer in a pure argon atmosphere to form an electrode layer. The specific parameters included RF power of 700 W, gas pressure of 1.55 Pa, deposition temperature of 60 ° C, deposition time of 30 min, and target-substrate distance of 78 mm. At the same time, during the initial 1.0 min of electrode layer deposition, a bias voltage of 40 V, current of 2.1 A, and duty cycle of 50% was applied between the substrate with the sensing layer and the bonding layer and the target material to enhance the bonding effect between the electrode layer and the bonding layer.

[0048] Example 2

[0049] A method for preparing a negative temperature sensor comprises the following steps:

[0050] (1) Using magnetron sputtering, a 12.4 μm thick LiNbO3 was deposited on the surface of the stainless steel plate SS2 to form a sensing layer. The specific parameters included a bias voltage of -10 V, a radio frequency power of 900 W, a deposition temperature of 150 °C, an argon-oxygen ratio of 2 / 1, a total gas pressure of 2.0 Pa, a deposition time of 8 h, and a target-base distance of 5 cm.

[0051] (2) Using arc ion plating, in a pure argon atmosphere, Cr with a thickness of 70 nm was deposited on the surface of the sensing layer to form a bonding layer. The specific parameters included arc current 90 A, gas pressure 1.0 Pa, deposition temperature 60 ° C, deposition time 55 s, and target-base distance 78 mm;

[0052] (3) A magnetron sputtering method was used with a Cr target material to deposit 6.7 μm thick Cr on the surface of the bonding layer in a pure argon atmosphere to form an electrode layer. The specific parameters included RF power of 700 W, gas pressure of 1.55 Pa, deposition temperature of 60 ° C, deposition time of 30 min, and target-substrate distance of 78 mm. At the same time, during the initial 1.0 min of electrode layer deposition, a bias voltage of 51 V, a current of 2.2 A, and a duty cycle of 50% was applied between the substrate with the sensing layer and the bonding layer and the target material to enhance the bonding effect between the electrode layer and the bonding layer.

[0053] Example 3

[0054] A method for preparing a negative temperature sensor comprises the following steps:

[0055] (1) Using magnetron sputtering, a 12.4 μm thick LiNbO3 was deposited on the surface of the stainless steel plate SS3 to form a sensing layer. The specific parameters included a bias voltage of -10 V, a radio frequency power of 900 W, a deposition temperature of 150 °C, an argon-oxygen ratio of 2 / 1, a total gas pressure of 2.0 Pa, a deposition time of 8 h, and a target-base distance of 5 cm.

[0056] (2) Using arc ion plating, in a pure argon atmosphere, Cr with a thickness of 70 nm was deposited on the surface of the sensing layer to form a bonding layer. The specific parameters included arc current 90 A, gas pressure 1.0 Pa, deposition temperature 60 ° C, deposition time 55 s, and target-base distance 78 mm;

[0057] (3) Using the magnetron sputtering method and a Ag target material, in a pure argon atmosphere, Ag with a thickness of 6.7 μm was deposited on the surface of the bonding layer to form an electrode layer. The specific parameters included RF power of 700 W, gas pressure of 1.55 Pa, deposition temperature of 60 ° C, deposition time of 5 min, and target-substrate distance of 78 mm. At the same time, during the initial 1.0 min of electrode layer deposition, a bias voltage of 49 V, a current of 2.2 A, and a duty cycle of 50% was applied between the substrate with the sensing layer and the bonding layer and the target material to enhance the bonding effect between the electrode layer and the bonding layer.

[0058] The morphology of the electrode layers of Examples 1 to 3 was observed using a scanning electron microscope, and the results were as follows: Figure 1 (a)~ Figure 1 (c) Figure 2 (a)~ Figure 2 (b) also shows the distribution of C and O elements in the electrode layer of Example 3. It can be seen that the surface of the AlCrNbSiTiTaY layer is the densest, the Cr layer is the second, and the Ag layer is the most uneven in grain size, sparse and rough. The atomic ratio of Al, Cr, Nb, Si, Ti, Ta, and Y in the AlCrNbSiTiTaY layer is 19:22:21:13:15:5:5. The quality, purity, and elemental composition of the Ag coating are easily affected by the vacuum degree during the preparation process, and carbonization is prone to occur. The coating surface is gray and black. EDS measured that the C and O atomic contents accounted for 10% and 12% respectively.

[0059] Comparative Example 1 to Comparative Example 3

[0060] In order to further determine the influence of the binding layer and the electrode layer prepared by deposition on the sensor performance, in step (1) of the preparation process of Examples 1 to 3, the sensing layer is deposited on the surface of the stainless steel plate, and then silver paste is brushed and dried to obtain an electrode layer with a thickness of 0.1 mm, thereby obtaining a negative temperature sensor. That is, Examples 1 to 3 can be regarded as the sensors of Comparative Examples 1 to 3, after the ultrasonic performance is tested, the silver paste is removed using a cleaning agent such as acetone, ethanol and water, and then the binding layer and the electrode layer are deposited on the LiNbO3 sensing layer in sequence.

[0061] The ultrasonic signals of the embodiment and the corresponding comparative example were tested to evaluate the performance of the sensor. The results are as follows: Figure 3As shown. The ultrasonic longitudinal wave signals of the sensors of Comparative Examples 1 to 3 are 0.3V, 0.45V, and 0.23V, respectively; correspondingly, the ultrasonic longitudinal wave signals of the sensors of Examples 1 to 3 are 3.3V, 1.45V, and 1.6V, respectively, that is, compared with the electrode layer constructed by silver paste, in the presence of a bonding layer, AlCrNbSiTiTaY, Cr, and Ag as electrode layers enhance the ultrasonic longitudinal wave signal by 11 times, 3.2 times, and 7.0 times, respectively, and the measured piezoelectric constants are 2.6pC / N, 2.5pC / V, and 1.0pC / N, respectively. These results also show that AlCrNbSiTiTaY as an electrode material is most conducive to sound wave transmission, and can obtain strong ultrasonic signals and high piezoelectric constants.

[0062] Comparative Example 4

[0063] In order to further determine the effect of the binding layer on the sensor performance, a sensor without a binding layer was prepared. The remaining steps and parameters were the same as in Example 1. As a result, the prepared electrode layer fell off, the ultrasonic signal weakened, and the piezoelectric constant decreased.

[0064] Comparative Example 5

[0065] In order to further determine the effect of bias voltage on sensor performance at the initial stage of electrode layer deposition, the electrode layer was deposited without bias voltage. The remaining steps and parameters were the same as in Example 1. As a result, the prepared electrode layer also showed shedding phenomenon, the ultrasonic signal weakened, and the piezoelectric constant decreased.

[0066] Example 4

[0067] like Figure 4 As shown, a detection device comprises a negative temperature sensor, a first contact 5, a second contact 6, a ground line 8, a signal line 7, a housing 9, and a detector 10, a controller 13 and a terminal 14 connected in sequence. The negative temperature sensor comprises a substrate 1, a sensing layer 2, a bonding layer 3 and an electrode layer 4 from bottom to top, and its preparation method is basically the same as that of Example 1, except that: in step (1), LiNbO3 with a thickness of 14 μm is deposited to form the sensing layer 2, and the specific parameters include a bias voltage of -6 V, a radio frequency power of 900 W, a deposition temperature of 150° C., an argon-oxygen ratio of 6 / 1, a total gas pressure of 2.0 Pa, a deposition time of 8 h, and a target-base distance of 5 cm.

[0068] like Figure 5As shown, the first contact 5 and the second contact 6 are respectively arranged at the substrate 1 and the electrode layer 4; the housing 9 is used to protect the negative temperature sensor and is provided with a first lead-out hole and a second lead-out hole; the ground wire 8 and the signal wire 7 are respectively connected to the first contact 5 and the second contact 6, the ground wire 8 passes through the first lead-out hole and is connected to the detector 10 and grounded, and the signal wire 7 passes through the second lead-out hole and is connected to the detector 10. The housing 9 may be made of epoxy resin, the detector 10 may be a pulse generator or an LCR meter (if it is an acoustic wave sensor, 10 is a pulse generator; if it is a capacitance resistance sensor, 10 is an LCR meter); the terminal 14 may be a mobile phone, a computer or other equipment.

[0069] In order to evaluate the detection performance of the detection device for negative temperatures, Figure 4 As shown in the figure, after setting up the detection device, the negative temperature sensor wrapped in the shell 9 is placed in the medium to be tested 11 in the high and low temperature alternating box 12, and the temperature is set to -60℃, -20℃, 20℃, 60℃, 100℃, and 140℃ in sequence. After the temperature is stable for 30 minutes, the DRP300 pulse generator is used to measure the ultrasonic waveform and signal of the sensor in situ, and the sound time TOF is calculated. The results are shown in Figure 6 The results show that the amplitude of the ultrasonic signal excited by the sensor has almost no change, that is, the prepared sensor has negative temperature stability, but the acoustic time delay phenomenon occurs, which increases from 0.24658μs to 0.25174μs, that is, the substrate expands and contracts due to temperature changes, and the sound wave propagation distance and sound speed change. Therefore, the acoustic time increases with the increase of temperature, and then the ambient temperature can be judged by measuring the ultrasonic acoustic time TOF. The ultrasonic sensor prepared by the present invention has the potential for temperature measurement in the negative temperature domain.

[0070] Example 5

[0071] A method for preparing a negative temperature sensor comprises the following steps:

[0072] (1) A 14 μm thick LiNbO3 sensing layer was deposited on the end surface of a superalloy bolt (M8, Inconel 718, 50 mm in length) by magnetron sputtering. The specific parameters included a bias voltage of -6 V, a radio frequency power of 900 W, a deposition temperature of 150 °C, an argon-oxygen ratio of 6 / 1, a total gas pressure of 2.0 Pa, a deposition time of 8 h, and a target-base distance of 5 cm.

[0073] (2) Using arc ion plating, in a pure argon atmosphere, Cr with a thickness of 70 nm was deposited on the surface of the sensing layer to form a bonding layer. The specific parameters included arc current 90 A, gas pressure 1.0 Pa, deposition temperature 60 ° C, deposition time 55 s, and target-base distance 78 mm;

[0074] (3) Using the magnetron sputtering method and AlCrNbSiTiTaY target material, AlCrNbSiTiTaY with a thickness of 6.7 μm was deposited on the surface of the bonding layer in a pure argon atmosphere to form an electrode layer. The specific parameters included RF power of 700 W, gas pressure of 1.55 Pa, deposition temperature of 60 ° C, deposition time of 30 min, and target-substrate distance of 78 mm. At the same time, during the initial 1.0 min of electrode layer deposition, a bias voltage of 40 V, current of 2.1 A, and duty cycle of 50% was applied between the substrate with the sensing layer and the bonding layer and the target material to enhance the bonding effect between the electrode layer and the bonding layer.

[0075] Then the performance of the ultrasonic signal of the negative temperature sensor of this embodiment changing with temperature was tested. The results are as follows: Figure 7 As shown. It can be seen that when the ambient temperature rises from -60°C to 140°C, the ultrasonic wave excited by the sensor has a sound time delay phenomenon, and the sound time and temperature show a linear relationship. Therefore, the sensor of the present invention can calculate the ambient temperature of the bolt by measuring the ultrasonic sound time TOF and substituting it into the sound time-temperature function, and has excellent negative temperature online measurement potential.

[0076] Example 6

[0077] A method for preparing a negative temperature sensor comprises the following steps:

[0078] (1) Using magnetron sputtering, a 17.87 μm thick LiNbO3 was deposited on the surface of a stainless steel plate to form a sensing layer. The specific parameters included a bias voltage of -6 V, a radio frequency power of 900 W, a deposition temperature of 150 °C, an argon-oxygen ratio of 6 / 1, a total gas pressure of 2.0 Pa, a deposition time of 8 h, and a target-base distance of 3.5 cm.

[0079] (2) Using arc ion plating, in a pure argon atmosphere, Cr with a thickness of 90 nm was deposited on the surface of the sensing layer to form a bonding layer. The specific parameters included arc current 90 A, gas pressure 1.0 Pa, deposition temperature 60 ° C, deposition time 60 s, and target-base distance 78 mm;

[0080] (3) Using the magnetron sputtering method and AlCrNbSiTiTaY target material, a 9.7 μm thick AlCrNbSiTiTaY was deposited on the surface of the bonding layer in a pure argon atmosphere to form an electrode layer. The specific parameters included RF power of 700 W, gas pressure of 1.55 Pa, deposition temperature of 60 ° C, deposition time of 30 min, and target-substrate distance of 73 mm. At the same time, in the initial 1.0 min of electrode layer deposition, a bias voltage of 40 V, current of 2.1 A, and duty cycle of 50% was applied between the substrate with the sensing layer and the bonding layer and the target to enhance the bonding effect between the electrode layer and the bonding layer. The atomic ratio of Al, Cr, Nb, Si, Ti, Ta, and Y in the obtained AlCrNbSiTiTaY layer was 18:23:21:13:15:5:5.

[0081] The dielectric properties of the negative temperature capacitance resistance sensor of this embodiment under temperature changes were then tested. When the measurement frequency was 10kHz, the capacitance changes at negative temperatures of -60℃, -50℃, -20℃, 0℃, and positive temperatures of 10℃, 20℃, and 40℃ were as follows: Figure 8 shown. Fig. 9 The graph shows the changes in dielectric constant and dielectric loss when the measurement frequency is 10 kHz and the temperatures are -60°C, -50°C, -20°C, 0°C, 10°C, 20°C, and 40°C. Fig.10 The graph shows the changes in resistance and resistivity when the measurement frequency is 10 kHz and the temperatures are -60°C, -50°C, -20°C, 0°C, 10°C, 20°C, and 40°C.

[0082] In addition, by changing the measurement frequency to 100 Hz and 1 kHz, it was found that regardless of the measurement frequency, the capacitance, dielectric constant, dielectric loss, resistance, and resistivity of the capacitive sensor all showed a linear relationship with the ambient temperature, and the functional relationship of the respective positive and negative temperature ranges was fitted. Therefore, the measured capacitance, dielectric constant, resistance, and resistivity can be substituted into the function to calculate the ambient temperature. The sensor of the present invention also has excellent potential for online measurement of negative temperatures when the sensing layer is a dielectric material.

[0083] Example 7

[0084] The sensor prepared in Example 1 was placed in a 5% NaCl neutral salt spray environment for continuous corrosion for 100 h, and the surface morphology and element ratio before and after corrosion were measured. Fig.11 , Fig.11 (a) is the morphology of the AlCrNbSiTiTaY electrode layer before corrosion. Fig.11(b) is the morphology of the AlCrNbSiTiTaY electrode layer after corrosion for 100 h. The surface morphology does not change and no corrosion marks are found. EDS measurement shows that the atomic ratios of Al, Cr, Nb, Si, Ti, Ta, and Y in the AlCrNbSiTiTaY coating before corrosion are 19:22:21:13:15:5:5. After corrosion for 100 h, the atomic ratios of Al, Cr, Nb, Si, Ti, Ta, and Y in the AlCrNbSiTiTaY coating are 18:22:22:13:15:5:5. The element composition is stable. It can be seen that the sensor prepared by the present invention has excellent salt spray corrosion resistance.

[0085] Example 8

[0086] A method for preparing a negative temperature sensor is basically the same as that of Example 1, except that in step (3), the magnetron sputtering uses an AlCrNbSiTi target material, that is, the electrode layer material is a high entropy alloy AlCrNbSiTi.

[0087] Example 9

[0088] A method for preparing a negative temperature sensor is basically the same as that of Example 1, except that in step (3), the magnetron sputtering uses an AlHfNbSiTaTiZr target material, that is, the electrode layer material is a high entropy alloy AlHfNbSiTaTiZr.

[0089] Example 10

[0090] A method for preparing a negative temperature sensor is basically the same as that of Example 1, except that in step (3), magnetron sputtering is carried out in an argon and nitrogen atmosphere, and the volume ratio of argon and nitrogen is 1:1, that is, the electrode layer material is a nitride of a high entropy alloy AlCrNbSiTiTaY.

[0091] At temperatures of -60°C, -20°C, 20°C, 60°C, 100°C, and 140°C, the ultrasonic waveforms and signals, capacitance, and resistance of the sensors prepared in Examples 8 to 9 were measured, and the TOF, dielectric constant, and resistivity were calculated. The results also showed that the constructed sensor can determine the ambient temperature by measuring the ultrasonic TOF, capacitance, dielectric constant, resistance, and resistivity.

[0092] At temperatures of -60°C, -20°C, 20°C, 60°C, 100°C, and 140°C, the capacitance and resistance of the sensor prepared in Example 10 were measured, and the dielectric constant and resistivity were calculated. The results also showed that the constructed sensor can determine the ambient temperature by measuring capacitance, dielectric constant, resistance, and resistivity.

[0093] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A negative temperature sensor, characterized in that: From bottom to top, it includes a substrate, a sensing layer, a binding layer and an electrode layer; Wherein, the material of the electrode layer is a high entropy alloy; The high entropy alloy includes one of AlCrNbSiTiTaY, AlCrNbSiTi, and AlHfNbSiTaTiZr; The electrode layer is prepared by magnetron sputtering in an argon atmosphere, and the specific parameters include: RF power 600-900W, gas pressure 1.55-1.95Pa, deposition temperature 30-90°C, deposition time 20-120min, and target-base distance 60-90mm; When preparing the electrode layer by magnetron sputtering, a bias voltage is applied between the substrate with the sensing layer and the bonding layer and the target material during the initial 1.0 to 1.5 min; Among them, the bias voltage is 30~49V, the current is 1.0~2.5A, and the duty cycle is 40%~60%.

2. The negative temperature sensor according to claim 1, characterized in that: The thickness of the electrode layer is 4-10 μm.

3. The negative temperature sensor according to claim 1, characterized in that: The thickness of the sensing layer is 2-18 μm; The material of the sensing layer includes one of a piezoelectric material, a dielectric material, and a non-piezoelectric and dielectric insulating material.

4. The negative temperature sensor according to claim 1, characterized in that: The bonding layer is Cr with a thickness of 50-100 nm.

5. A method for preparing a negative temperature sensor according to any one of claims 1 to 4, characterized in that: The process includes sequentially preparing a sensing layer, a binding layer and an electrode layer on the surface of a substrate; Wherein, the material of the electrode layer is high entropy alloy.

6. The method for preparing a negative temperature sensor according to claim 5, characterized in that: The bonding layer is prepared by arc ion plating in an argon atmosphere, and specific parameters include arc current 80~100A, gas pressure 0.5~2.0Pa, deposition temperature 30~150°C, deposition time 0.5~2min, and target-base distance 60~90mm.

7. A detection device, characterized in that: The negative temperature sensor comprises the negative temperature sensor as described in any one of claims 1 to 4.

8. The detection device according to claim 7, characterized in that: It also includes a first contact, a second contact, a ground wire, a signal wire, a housing, and a detector, a controller, and a terminal connected in sequence; The first contact and the second contact are respectively arranged at the substrate and the electrode layer; The housing is used to protect the negative temperature sensor and is provided with a first lead-out hole and a second lead-out hole; The ground wire and the signal wire are connected to the first contact and the second contact respectively. The ground wire is connected to the detector and grounded after passing through the first lead-out hole, and the signal wire is connected to the detector after passing through the second lead-out hole.

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