Hydrazine gas-sensitive sensor based on sea urchin-shaped ZnO / SiC nano composite material and preparation method of hydrazine gas-sensitive sensor

Abstract

The invention relates to a hydrazine gas sensor based on a sea urchin-shaped ZnO / SiC nano composite material and a preparation method of the hydrazine gas sensor, and belongs to the technical field of semiconductor gas sensors. Aiming at the problems that the existing hydrazine detection technology is complex in equipment and poor in real-time performance and the traditional ZnO sensor is low in selectivity, insufficient in stability and the like, the ZnO / SiC nano composite material is synthesized by adopting a solvothermal method through a triple cooperation strategy of morphology regulation and control, heterostructure construction and defect engineering. The material takes cubic silicon carbide (3C-SiC) as a core, zinc oxide grows on the surface to form an urchin-shaped nano structure, and a material system is optimized by controlling the addition amount of SiC. The sensing performance is innovatively improved through the synergistic effect of a three-dimensional mesoporous diffusion channel, n-n heterojunction interface charge separation and oxygen vacancy mediated surface activation. The response value of the prepared sensor to 50ppm hydrazine at 160 DEG C can reach 45, the response / recovery time is only 22s / 13s, the lower detection limit is as low as 1ppm, and the sensor has excellent selectivity and long-term stability of more than 30 days. Compared with a traditional ZnO sensor, the prepared sensor is low in raw material cost, high in sensitivity and low in working temperature. The invention provides a new material solution for developing portable hydrazine detection equipment with high sensitivity and quick response, and is suitable for the fields of aerospace fuel monitoring, chemical safety early warning and the like.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology and relates to a hydrazine gas sensor based on sea urchin-shaped ZnO / SiC nanocomposite material and its preparation method. Background Technology

[0002] Hydrazine (N₂H₄) is an important chemical substance, also known as hydrazine, a colorless, oily liquid with a pungent odor similar to ammonia. Hydrazine has a wide range of uses, primarily as fuel for rockets and jet engines, and also as a deoxygenating agent for high-pressure boiler feedwater. In the pharmaceutical industry, hydrazine is used to synthesize drugs such as aminourea, isoniazid, and furacilin. In addition, hydrazine is used in crystal silver plating, metallizing plastics and glass, and as a foaming agent, antioxidant, and reducing agent.

[0003] With the acceleration of industrialization and urbanization, the volatility of hydrazine leads to an extremely high risk of leakage, necessitating the development of highly sensitive real-time detection technologies. Current methods for detecting hydrazine mainly include fluorescent probe methods, chromatography / mass spectrometry, electrochemical spectrophotometry, and rapid detection strip methods. While these methods offer high accuracy, they suffer from limitations such as expensive equipment, complex operation, and difficulty in real-time monitoring, making it challenging to achieve real-time monitoring of hydrazine in specific locations. Therefore, developing a portable sensor capable of rapid real-time detection of hydrazine is of significant practical importance.

[0004] As is well known, semiconductor gas sensors exhibit significant advantages in the field of gas detection due to their unique working principle and material properties. At a certain temperature, oxygen molecules (O2) in the air are adsorbed onto the semiconductor surface (such as SnO2, ZnO, etc.). This is achieved by capturing free electrons in the semiconductor's conduction band, forming chemically adsorbed oxygen ions (O2). - O - O 2- At this point, an electron depletion layer forms on the semiconductor surface, increasing resistance. When a reducing gas (such as N₂H₄) comes into contact with the semiconductor surface, it reacts with the adsorbed oxygen. The electrons released in the reaction return to the semiconductor conduction band, reducing the thickness of the depletion layer and causing a change in resistance. The change in resistance (ΔR) is positively correlated with the gas concentration; the gas concentration can be inferred by measuring the resistance value. This type of sensor has a wider detection limit and offers advantages such as higher sensitivity, faster response / recovery time, higher stability, reliable repeatability, ease of operation, and integration into portable devices.

[0005] This invention directly captures gaseous hydrazine based on changes in resistance signal, without the need for complex pretreatment. In contrast, the MnFePBA-Ag-CNTs electrochemical sensor disclosed in CN201310446406 relies on liquid-phase catalytic oxidation, the zirconium-based MOF fluorescent probe disclosed in CN202311600508 requires UV excitation and defect-state fluorescence recovery, the HPQ-IM solid-state fluorescent probe disclosed in CN202410611988 is limited by anti-diffusion imaging mode, and the cellulose-based naphthalenediimide probe disclosed in CN202411844435 is prone to swelling in organic solvents, all of which fail to achieve real-time gaseous monitoring. This invention achieves high-performance detection of hydrazine through an innovative sea urchin-like ZnO / SiC nanocomposite material. To achieve real-time monitoring of hydrazine in specific environments, this invention employs a triple synergistic strategy of morphology control, heterostructure construction, and defect engineering, using a solvothermal method to synthesize the sea urchin-like ZnO / SiC nanocomposite material, meeting the requirements for hydrazine detection. Summary of the Invention

[0006] This invention addresses the shortcomings of existing hydrazine detection technologies, such as expensive equipment, complex operation, and difficulty in real-time monitoring, by proposing a hydrazine gas sensor based on sea urchin-shaped ZnO / SiC nanocomposite materials and its preparation method.

[0007] The technical solution of the present invention is as follows:

[0008] A hydrazine gas sensor based on urchin-shaped ZnO / SiC nanocomposite material, the gas sensor comprising an Al2O3 ceramic tube with two Au electrodes on its surface, each Au electrode having two Pt pins soldered to a sensor base, a Ni-Cr wire passing through the inside of the Al2O3 ceramic tube and soldered to the sensor base, and the surface of the Al2O3 ceramic tube being coated with urchin-shaped ZnO / SiC nanocomposite material.

[0009] Preferably, the coating thickness of the urchin-shaped ZnO / SiC nanocomposite material is 10-20 μm.

[0010] Preferably, the urchin-like ZnO / SiC nanocomposite material comprises 3C-SiC particles and ZnO nanowires grown on the outside of the 3C-SiC particles.

[0011] Preferably, the average particle size of the 3C-SiC particles is 50 nm.

[0012] Preferably, the preparation method of the sea urchin-like ZnO / SiC nanocomposite material includes the following steps:

[0013] S1. Solution preparation: First, prepare 60 mL of 50 vol% ethanol solution, then add polyethylene glycol and stir to dissolve.

[0014] S2. Adding raw materials: After adding SiC powder to the solution, ultrasonically treat for 30 minutes, then add zinc nitrate hexahydrate, potassium citrate and urea to the solution, and continue heating and stirring for 1 hour.

[0015] S3, Solventothermic method: The solution is transferred to a 100mL high-pressure reactor, kept at a temperature in an oven for a period of time, and then the precipitated particles are collected by centrifugation;

[0016] S4. Annealing: The precipitated particles are washed several times with ethanol and deionized water, dried, and then annealed in a muffle furnace to obtain the sea urchin-shaped ZnO / SiC nanocomposite material.

[0017] Preferably, the amount of polyethylene glycol used is 2-8 mg; more preferably, the amount of polyethylene glycol used is 5 mg.

[0018] Preferably, the number average molecular weight of the polyethylene glycol is 8000.

[0019] Preferably, the heating and stirring temperature of the raw materials is 60°C;

[0020] Preferably, heating and stirring can be carried out using a water bath.

[0021] Preferably, the synthesis temperature of the solvothermal method is 120-160℃ and the synthesis time is 16-24h; more preferably, the synthesis temperature of the solvothermal method is 140℃ and the synthesis time is 20h.

[0022] Preferably, the centrifugal collection speed is 5000-8000 r / min; more preferably, the centrifugal collection speed is 6000 r / min.

[0023] Preferably, the annealing time is 0.5-2 hours and the annealing temperature is 450-550°C; more preferably, the annealing time is 1 hour and the annealing temperature is 500°C.

[0024] Preferably, annealing is performed at 500°C for 1 hour with a heating rate of 5°C / min.

[0025] This invention also provides a hydrazine gas-sensitive sensor based on sea urchin-shaped ZnO / SiC nanocomposite material, the preparation method of which includes the following steps:

[0026] S1. Add ethanol to the sea urchin-shaped ZnO / SiC nanocomposite material and grind it into a paste to obtain a ZnO / SiC nanocomposite material paste.

[0027] S2. Apply the ZnO / SiC nanocomposite paste to the surface of the Al2O3 ceramic tube;

[0028] S3. Solder the Pt pin onto the sensor base;

[0029] S4. Pass the Ni-Cr wire through the inside of the Al2O3 ceramic tube and weld the Ni-Cr wires at both ends to the sensor base;

[0030] S5. Install the welded sensor components onto the gas-sensitive test plate and age them on the aging table to obtain the hydrazine gas-sensitive sensor.

[0031] Preferably, the aging time is 22-26 hours and the aging temperature is 180-220°C; more preferably, the aging time can be 26 hours at 180°C, 24 hours at 200°C, or 22 hours at 220°C, but is not limited thereto.

[0032] ZnO is an n-type wide-bandgap semiconductor (E g ZnO (with a voltage of 3.37 eV) exhibits excellent surface reactivity in gas sensing due to its abundant surface active sites. However, pure ZnO sensors, besides requiring operation in specific environments, also suffer from poor selectivity and the need for temperature compensation. Strategies to optimize material performance through heterojunctions or composite structures have attracted considerable attention. ZnO, as a representative metal oxide semiconductor material, possesses significant polarization characteristics and strong electronic correlation. At the interface, the breaking of symmetry enhances the coupling of its charge, spin, orbital, and lattice degrees of freedom, potentially leading to a richer array of physical phenomena than pure ZnO. Therefore, heterojunctioning ZnO with other materials may effectively improve its gas-sensing performance.

[0033] Cubic silicon carbide (3C-SiC) possesses excellent chemical inertness, high electron mobility, high thermal conductivity, and good chemical stability. Furthermore, it exhibits good lattice compatibility with ZnO, enhancing interfacial charge separation and improving sensitivity. The high thermal stability and chemical inertness of 3C-SiC effectively compensate for the shortcomings of pure ZnO, such as grain agglomeration and structural instability in high-temperature or humid environments, significantly extending sensor lifespan. The resulting heterojunction interface optimizes electron transport paths and minimizes drastic changes in interfacial barrier height during gas adsorption.

[0034] When the sensor is exposed to air, oxygen molecules are adsorbed onto the surface of the ZnO material and capture electrons from the ZnO conduction band to form oxygen anions (O2). - O - O 2-The ZnO surface becomes a surface acceptor state due to electron loss in the conduction band. This creates a high-barrier electron depletion region, hindering electron movement between grains. Once the chemisorption process reaches equilibrium, the resistance of ZnO remains constant. When the sensor is exposed to an N₂H₄ atmosphere, N₂H₄ molecules are chemisorbed onto the ZnO surface, reacting with oxygen anions to oxidize them. This causes more free electrons to migrate to the conduction band. Consequently, the thickness of the electron depletion layer decreases, the carrier density increases, and the resistance of ZnO decreases until equilibrium is reached. During this process, not only are free electrons released, but nitrogen and water are also generated. Then, as the gas flows, the target gas gradually separates from the ZnO and returns to the air, restoring the resistance to its original state. The gas sensing characteristics of the material are also related to surface chemical reactions and gas diffusion. When the temperature is below 150℃, surface chemical reactions play a dominant role. Adsorbed oxygen can only capture a small number of electrons to form O₂. - Therefore, the larger the specific surface area of ​​a material, the more active sites it has, and the higher its sensitivity. When the temperature is above 150℃ and below 300℃, the combined effect of surface chemical reactions and gas diffusion allows O2 to... - Further capture of electrons to form O - When the temperature exceeds 300℃, O - It will continue to capture electrons, forming O 2- In this case, the larger the pore size and porosity of the material, the more favorable the gas diffusion and the stronger the gas sensitivity.

[0035] This invention grows ZnO nanowires on the surface of 3C-SiC particles and prepares sea urchin-like ZnO / SiC nanocomposites through a triple synergistic strategy of morphology control, heterostructure construction, and defect engineering.

[0036] This invention studies the hydrazine sensing performance, providing new ideas for the design of high-performance hydrazine sensors, and also innovatively applies ZnO / SiC composite materials to gas sensors.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) In this invention, ZnO nanowires are grown on the surface of 3C-SiC particles by a solvothermal method, and the length of ZnO nanowires in the sea urchin-shaped ZnO / SiC nanocomposite material is controllable.

[0039] (2) The present invention uses sea urchin-shaped ZnO / SiC nanocomposite material as gas-sensitive material for detecting hydrazine. The test temperature range is 100-180℃, and the response value to 50ppm hydrazine at 160℃ reaches 45.

[0040] (3) Due to the formation of the sea urchin-like structure, the specific surface area of ​​the gas-sensitive material in this invention is as high as 22.54 m².2 / g provides more active sites for gas adsorption.

[0041] (4) In this invention, ZnO / SiC forms an n-type heterojunction, and electrons are transferred from SiC (work function 5.0eV) to ZnO (5.2eV), which increases the thickness of the depletion layer and can enhance the redox reaction on the material surface.

[0042] (5) The sea urchin-like ZnO / SiC nanocomposite material of this invention contains abundant oxygen vacancies, which can promote the adsorption of oxygen molecules into reactive oxygen species (O2). - O - O 2- This accelerates the oxidation reaction with hydrazine. Attached Figure Description

[0043] Figure 1 This is a scanning electron microscope image of the sea urchin-like ZnO / SiC nanocomposite material of the present invention;

[0044] Figure 2 This is the X-ray diffraction pattern of the sea urchin-like ZnO / SiC nanocomposite material of the present invention;

[0045] Figure 3 The nitrogen adsorption-desorption isotherm and pore size distribution of the sea urchin-like ZnO / SiC nanocomposite material of this invention are shown below.

[0046] Figure 4 The response of a hydrazine gas sensor based on sea urchin-shaped ZnO / SiC nanocomposite material to 50 ppm hydrazine at 100-180℃ is shown.

[0047] Figure 5 The response curves of a hydrazine gas sensor based on sea urchin-shaped ZnO / SiC nanocomposite material to 1-100 ppm hydrazine at 160 °C are shown.

[0048] Figure 6 The dynamic response recovery curve of a hydrazine gas sensor based on sea urchin-shaped ZnO / SiC nanocomposite material to 50 ppm hydrazine at 160 °C is shown.

[0049] Figure 7 The selective response of a hydrazine gas sensor based on sea urchin-shaped ZnO / SiC nanocomposite material to 50 ppm of various gases / vapors at 160 °C;

[0050] Figure 8 To assess the repeatability of a hydrazine gas sensor based on urchin-shaped ZnO / SiC nanocomposite material for detecting 50 ppm hydrazine at 160 °C;

[0051] Figure 9 The long-term stability of the ZnO / SiC-2 gas sensor against 50ppm hydrazine at 160℃ was determined. Detailed Implementation

[0052] To better understand the present invention, the following embodiments further illustrate the content of the invention, but the scope of protection of the present invention is not limited to the following embodiments. Numerous specific details are set forth in the following description to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details.

[0053] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0054] Unless otherwise specified, all raw materials are derived from commercially available products and do not contain any unspecified components other than unavoidable impurities.

[0055] The zinc nitrate hexahydrate used in this embodiment of the invention is a commercially available product with a purity > 99.0%.

[0056] The potassium citrate used in this embodiment of the invention is a commercially available product with a purity > 99.5%.

[0057] The urea used in this embodiment of the invention is a commercially available product with a purity > 99.0%.

[0058] The silicon carbide used in the embodiments of the present invention is a commercially available product with a purity >99.5%.

[0059] The anhydrous ethanol used in the embodiments of this invention is a commercially available product with analytical purity.

[0060] The Al2O3 ceramic tube, Ni-Cr heating wire, sensor base, aging table, and gas-sensitive element testing system used in this embodiment of the invention were all provided by Winsen Electronics Technology Co., Ltd.

[0061] In this embodiment of the invention, the resistance of the gas-sensitive element in air and in the target are respectively denoted as R. a and R g The response of the sensor can be defined as R. a / R g The response / recovery time of a sensor is defined as the time it takes for the resistance value to change from its initial value to 90% of its stable value.

[0062] Example 1: Preparation of ZnO / SiC-0 gas-sensitive material

[0063] 60 mL of 50 vol% ethanol solution was measured, and 5 mg of polyethylene glycol was added and stirred to dissolve. The prepared solution was ultrasonically treated for 0.5 h. Then, 1.2 g of zinc nitrate hexahydrate, 0.2 g of potassium citrate, and 1 g of urea were added. The mixture was heated and stirred in a water bath at 60 °C. After heating, the suspension was transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner and kept at 140 °C for 20 h. Subsequently, the white precipitate was collected by centrifugation at 6000 r / min and washed several times with ethanol and deionized water. After drying, the precipitate was calcined in a muffle furnace at 500 °C for 1 h at a heating rate of 5 °C / min to obtain the ZnO / SiC-0 gas-sensitive material.

[0064] The scanning electron microscope image of the gas-sensitive material prepared in this embodiment is shown below. Figure 1 As shown in a1 and a2, the X-ray diffraction patterns are as follows: Figure 2 The ZnO / SiC-0 curve is shown in the figure. The nitrogen adsorption-desorption isotherm and pore size distribution diagram are shown in the figure. Figure 3 As shown in 'a'.

[0065] Example 2: Fabrication and Testing of ZnO / SiC-0 Gas Sensor

[0066] The ZnO / SiC-0 gas-sensitive material prepared in Example 1 was added to ethanol and ground into a paste to obtain a paste. The paste was then coated on the surface of an Al2O3 ceramic tube. Subsequently, Pt pins were soldered to the sensor base, and Ni-Cr wires were passed through the inside of the Al2O3 ceramic tube. The Ni-Cr wires at both ends were soldered to the sensor base. Finally, the soldered sensor was installed on a gas-sensitive test plate and aged on an aging table at 180°C for 26 hours to obtain the ZnO / SiC-0 gas sensor.

[0067] The prepared sensor is inserted into the circuit board and placed in the closed gas chamber of the gas-sensitive testing system. The required amount of target gas is added according to the static gas distribution principle. The temperature is controlled by heating the Ni-Cr wire. The test parameters are calculated by measuring the voltage and resistance changes on the load resistor.

[0068] Example 3: Preparation of ZnO / SiC-1 gas-sensitive material

[0069] 60 mL of 50 vol% ethanol solution was measured, and 5 mg of polyethylene glycol was added and stirred to dissolve. After dissolution, 5 mg of 3C-SiC powder (50 nm) was added. The prepared solution was ultrasonically treated for 0.5 h. Then, 1.2 g of zinc nitrate hexahydrate, 0.2 g of potassium citrate, and 1 g of urea were added. The mixture was heated and stirred at 60 °C in a water bath. After the reaction, the suspension was transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner and kept at 140 °C for 20 h. Subsequently, the white precipitate was collected by centrifugation at 6000 r / min and washed several times with ethanol and deionized water. After drying, the precipitate was calcined in a muffle furnace at 500 °C for 1 h at a heating rate of 5 °C / min to obtain the ZnO / SiC-1 gas-sensitive material.

[0070] The scanning electron microscope image of the gas-sensitive material prepared in this embodiment is shown below. Figure 1 As shown in b1 and b2, the X-ray diffraction patterns are as follows: Figure 2 The ZnO / SiC-1 curve is shown in the figure. The nitrogen adsorption-desorption isotherm and pore size distribution diagram are shown in the figure. Figure 3 As shown in b in the figure.

[0071] Example 4: Fabrication and Testing of ZnO / SiC-1 Gas Sensor

[0072] The ZnO / SiC-1 gas-sensitive material prepared in Example 3 was added to ethanol and ground into a paste to obtain a paste. The paste was then coated on the surface of an Al2O3 ceramic tube. Subsequently, Pt pins were soldered to the sensor base, and Ni-Cr wires were passed through the inside of the Al2O3 ceramic tube. The Ni-Cr wires at both ends were soldered to the sensor base. Finally, the soldered sensor was installed on a gas-sensitive test plate and aged on an aging table at 180°C for 26 hours to obtain the ZnO / SiC-1 gas-sensitive sensor.

[0073] The prepared sensor is inserted into the circuit board and placed in the closed gas chamber of the gas-sensitive testing system. The required amount of target gas is added according to the static gas distribution principle. The temperature is controlled by heating the Ni-Cr wire. The test parameters are calculated by measuring the voltage and resistance changes on the load resistor.

[0074] Example 5: Preparation of ZnO / SiC-2 gas-sensitive materials

[0075] 60 mL of 50 vol% ethanol solution was measured, and 5 mg of polyethylene glycol was added and stirred to dissolve. After dissolution, 10 mg of 3C-SiC powder (50 nm) was added. The prepared solution was ultrasonically treated for 0.5 h. Then, 1.2 g of zinc nitrate hexahydrate, 0.2 g of potassium citrate, and 1 g of urea were added. The mixture was heated and stirred at 60 °C in a water bath. After the reaction, the suspension was transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner and kept at 140 °C for 20 h. Subsequently, the white precipitate was collected by centrifugation at 6000 r / min and washed several times with ethanol and deionized water. After drying, the precipitate was calcined in a muffle furnace at 500 °C for 1 h at a heating rate of 5 °C / min to obtain the ZnO / SiC-2 gas-sensitive material.

[0076] The scanning electron microscope image of the gas-sensitive material prepared in this embodiment is shown below. Figure 1 As shown in c1 and c2, the X-ray diffraction pattern is as follows: Figure 2 The ZnO / SiC-2 curve is shown in the figure. The nitrogen adsorption-desorption isotherm and pore size distribution diagram are shown in the figure. Figure 3 As shown in c in the figure.

[0077] Example 6: Fabrication and Testing of ZnO / SiC-2 Gas Sensor

[0078] The ZnO / SiC-2 gas-sensitive material prepared in Example 5 was added to ethanol and ground into a paste to obtain a paste. The paste was then coated on the surface of an Al2O3 ceramic tube. Subsequently, Pt pins were soldered to the sensor base, and Ni-Cr wires were passed through the inside of the Al2O3 ceramic tube. The Ni-Cr wires at both ends were soldered to the sensor base. Finally, the soldered sensor was installed on a gas-sensitive test plate and aged on an aging table at 180°C for 26 hours to obtain the ZnO / SiC-2 gas sensor.

[0079] The prepared sensor is inserted into the circuit board and placed in the closed gas chamber of the gas-sensitive testing system. The required amount of target gas is added according to the static gas distribution principle. The temperature is controlled by heating the Ni-Cr wire. The test parameters are calculated by measuring the voltage and resistance changes on the load resistor.

[0080] Example 7: Preparation of ZnO / SiC-3 gas-sensitive material

[0081] 60 mL of 50 vol% ethanol solution was measured, and 5 mg of polyethylene glycol was added and stirred to dissolve. After dissolution, 15 mg of 3C-SiC powder (50 nm) was added. The prepared solution was ultrasonically treated for 0.5 h. Then, 1.2 g of zinc nitrate hexahydrate, 0.2 g of potassium citrate, and 1 g of urea were added. The mixture was heated and stirred at 60 °C in a water bath. After the reaction, the suspension was transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner and kept at 140 °C for 20 h. Subsequently, the white precipitate was collected by centrifugation at 6000 r / min and washed several times with ethanol and deionized water. After drying, the precipitate was calcined in a muffle furnace at 500 °C for 1 h at a heating rate of 5 °C / min to obtain the ZnO / SiC-3 gas-sensitive material.

[0082] The scanning electron microscope image of the gas-sensitive material prepared in this embodiment is shown below. Figure 1 As shown in d1 and d2, the X-ray diffraction pattern is as follows: Figure 2 The ZnO / SiC-3 curve is shown in the figure. The nitrogen adsorption-desorption isotherm and pore size distribution diagram are shown in the figure. Figure 3 As shown in d.

[0083] Example 8: Fabrication and Testing of ZnO / SiC-3 Gas Sensor

[0084] The ZnO / SiC-3 gas-sensitive material prepared in Example 7 was added to ethanol and ground into a paste to obtain a paste. The paste was then coated on the surface of an Al2O3 ceramic tube. Subsequently, Pt pins were soldered to the sensor base, and Ni-Cr wires were passed through the inside of the Al2O3 ceramic tube. The Ni-Cr wires at both ends were soldered to the sensor base. Finally, the soldered sensor was installed on a gas-sensitive test plate and aged on an aging bench at 180°C for 26 hours to obtain the ZnO / SiC-3 gas sensor.

[0085] The prepared sensor is inserted into the circuit board and placed in the closed gas chamber of the gas-sensitive testing system. The required amount of target gas is added according to the static gas distribution principle. The temperature is controlled by heating the Ni-Cr wire. The test parameters are calculated by measuring the voltage and resistance changes on the load resistor.

[0086] Example 9:

[0087] The gas sensors prepared in Examples 2, 4, 6, and 8 were applied to the detection of hydrazine. The specific steps were as follows: Within an operating temperature range of 100-180°C, these four sensors were switched between a 50 ppm hydrazine atmosphere and dry air. The transient resistance curves of hydrazine at each different operating temperature were tested. Each switching lasted for 3 minutes. The response value (R0) at each temperature was recorded and calculated. a / R g).

[0088] Figure 4 The response values ​​of four hydrazine gas sensors to 50 ppm hydrazine at 100-180℃ are shown. The response values ​​to hydrazine vary at different temperatures. In the following examples, 160℃ is selected as the detection temperature because it has a better response / recovery time.

[0089] Example 10:

[0090] The gas sensors prepared in Examples 2, 4, 6, and 8 were applied to the detection of hydrazine. The specific steps were as follows: At an operating temperature of 160°C, the four sensors were switched between 1-100 ppm hydrazine atmospheres and dry air. The transient resistance curves of hydrazine at each different operating temperature were tested. Each switching lasted for 3 minutes. The response value (R0) at each gas concentration was recorded and calculated. a / R g ).

[0091] Figure 5 The response curves of four hydrazine gas sensors to 1-100 ppm hydrazine at 160℃ are shown. The response values ​​to hydrazine are different at different concentrations. Obviously, the response values ​​of the four sensors also increase with the increase of concentration. Among them, the ZnO / SiC-2 gas sensor prepared in Example 6 has the best effect and has a high response to hydrazine as low as 1 ppm.

[0092] Example 11:

[0093] The gas sensors prepared in Examples 2, 4, 6 and 8 were applied to the detection of hydrazine. The specific steps were as follows: at an operating temperature of 160°C, the four sensors were tested by switching back and forth between a 50ppm hydrazine atmosphere and dry air, and the dynamic response / recovery curves were recorded.

[0094] Figure 6 The figures show the dynamic response recovery curves of four hydrazine gas sensors at 160°C to 50 ppm hydrazine. In this invention, the prepared gas sensors all have good response recovery times, which meet the requirements for real-time detection of hydrazine.

[0095] Example 12:

[0096] The gas sensors prepared in Examples 2, 4, 6, and 8 were applied to the detection of hydrazine. The specific steps were as follows: at an operating temperature of 160°C, the four sensors were switched between atmospheres of 50 ppm hydrazine, nitric oxide, aniline, hydrogen, nitrogen dioxide, and formaldehyde, and dry air. Tests were performed on each gas, and the response value (R0) for each gas was recorded. a / R g ).

[0097] Figure 7 The selective responses of four hydrazine gas sensors to 50 ppm of various gases / vapors at 160 °C were shown. For different gases, the four sensors exhibited excellent selectivity for hydrazine, with the ZnO / SiC-2 gas sensor prepared in Example 6 showing the best performance.

[0098] Example 13:

[0099] The gas sensors prepared in Examples 2, 4, 6 and 8 were applied to the detection of hydrazine. The specific steps were as follows: at an operating temperature of 160°C, the four sensors were tested by switching back and forth between a 50 ppm hydrazine atmosphere and dry air several times, and the repeatability curves for hydrazine were recorded.

[0100] Figure 8 The repeatability curves of four hydrazine gas sensors at 160°C for 50 ppm hydrazine are shown. In this invention, the prepared gas sensors all have good repeatability and meet the requirements for repeated detection of hydrazine.

[0101] Example 14:

[0102] The ZnO / SiC-2 gas sensor prepared in Example 6 was applied to the detection of hydrazine. The specific steps were as follows: at an operating temperature of 160°C, the gas sensor prepared in Example 6 was switched back and forth between a 50ppm hydrazine atmosphere and dry air. The test was carried out every 5 days, and the stability response curve to hydrazine was recorded over 30 days.

[0103] Figure 9 The image shows the long-term stability response curve of the ZnO / SiC-2 gas sensor prepared in Example 6 to 50 ppm hydrazine at 160 °C. In this invention, the ZnO / SiC-2 gas sensor prepared in Example 6 has good stability, and the response does not fluctuate significantly within a 30-day span, meeting the requirements for long-term detection of hydrazine.

[0104] Furthermore, those skilled in the art should understand that although many problems exist in the prior art, each embodiment or technical solution of the present invention can be improved in only one or a few aspects, without necessarily solving all the technical problems listed in the prior art or the background art simultaneously. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as a limitation on that claim.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hydrazine gas sensor based on urchin-shaped ZnO / SiC nanocomposite material, the gas sensor comprising an Al2O3 ceramic tube with two Au electrodes on its surface, each Au electrode having two Pt leads soldered to a sensor base, and a Ni-Cr wire threaded inside the Al2O3 ceramic tube and soldered to the sensor base, characterized in that: The surface of the Al2O3 ceramic tube is coated with an urchin-shaped ZnO / SiC nanocomposite material.

2. The urchin-like ZnO / SiC nanocomposite material according to claim 1, characterized in that: The urchin-like ZnO / SiC nanocomposite material comprises 3C-SiC particles and ZnO nanowires grown on the outside of the 3C-SiC particles.

3. The urchin-like ZnO / SiC nanocomposite material according to claim 2, characterized in that, The preparation method includes the following steps: S1. Solution preparation: First, prepare 60 mL of 50 vol% ethanol solution, then add polyethylene glycol and stir to dissolve. S2. Adding raw materials: After adding SiC powder to the solution, ultrasonically treat for 30 minutes, then add zinc nitrate hexahydrate, potassium citrate and urea to the solution, and continue heating and stirring for 1 hour. S3, Solventothermic method: The solution is transferred to a 100mL high-pressure reactor, kept at a temperature in an oven for a period of time, and the precipitated particles are collected by centrifugation. S4. Annealing: The precipitated particles are washed several times with ethanol and deionized water, dried, and then annealed in a muffle furnace to obtain the sea urchin-shaped ZnO / SiC nanocomposite material.

4. The method for preparing the urchin-like ZnO / SiC nanocomposite material according to claim 3, characterized in that: The amount of polyethylene glycol used is 2-8 mg.

5. The method for preparing the urchin-like ZnO / SiC nanocomposite material according to claim 3, characterized in that: The number-average molecular weight of the polyethylene glycol is 8000.

6. The method for preparing the urchin-like ZnO / SiC nanocomposite material according to claim 3, characterized in that: The raw material is heated at 60°C for 0.5-1 hour; Preferably, heating and stirring can be carried out using a water bath.

7. The method for preparing the urchin-like ZnO / SiC nanocomposite material according to claim 3, characterized in that: The synthesis temperature of the solvothermal method is 120-160℃.

8. The method for preparing the urchin-like ZnO / SiC nanocomposite material according to claim 3, characterized in that: The synthesis time for the solvothermal method is 16-24 hours.

9. The method for preparing the urchin-like ZnO / SiC nanocomposite material according to claim 3, characterized in that: The centrifugal collection speed is 5000-8000 r / min.

10. The method for preparing the urchin-like ZnO / SiC nanocomposite material according to claim 3, characterized in that: The annealing time is 0.5-2 hours, and the annealing temperature is 450-550℃. Preferably, annealing is performed at 450-550℃ for 0.5-2h with a heating rate of 5℃ / min.

11. The hydrazine gas sensor based on urchin-shaped ZnO / SiC nanocomposite material according to claim 1, characterized in that, The preparation method includes the following steps: S1. Add ethanol to the sea urchin-shaped ZnO / SiC nanocomposite material prepared according to claim 3 and grind it into a paste to obtain a ZnO / SiC nanocomposite material paste. S2. Apply the ZnO / SiC nanocomposite paste to the surface of the Al2O3 ceramic tube; S3. Solder the Pt pin onto the sensor base; S4. Pass the Ni-Cr wire through the inside of the Al2O3 ceramic tube and weld the Ni-Cr wires at both ends to the sensor base; S5. Install the welded sensor components onto the gas-sensitive test plate and age them on the aging table to obtain the hydrazine gas-sensitive sensor.

12. The method for preparing a gas sensor according to claim 11, characterized in that: The aging time is 22-26 hours, and the aging temperature is 180-220℃.

13. The method for preparing a gas sensor according to claim 11, characterized in that: The ceramic tube is coated with a sensitive material film 10-20 μm thick.

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