ZnO / siC nano-heterojunction high-temperature ethanol gas sensor and preparation method thereof

Abstract

The application belongs to the technical field of sensors and relates to a ZnO / SiC nano-heterojunction high-temperature ethanol gas-sensitive sensor and a preparation method thereof. ZnO nanoparticles are in-situ grown on the surface of SiC nanowires through a hydrothermal method, and the agglomeration degree of the ZnO nanoparticles of the ZnO / SiC nano-heterojunction is controllable. The ZnO / SiC nano-heterostructure with a ZnO nanoparticle growth time of 300-1200 min is used as a gas-sensitive material of a high-temperature ethanol sensor, and the responsivity of the ZnO / SiC nano-heterostructure is obviously higher than that of a high-temperature gas-sensitive sensor prepared by using single ZnO nanoparticles and single SiC monocrystal nanowires, and the responsivity is relatively high.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology and relates to a ZnO / SiC nanostructure high-temperature ethanol gas sensor and its preparation method. Background Technology

[0002] Sensor technology is one of the key technologies for measuring modernization. Advances in silicon, micromachining, VLSI technology, and materials preparation and property research have further highlighted the importance of sensors. Among various sensors, gas sensors are devices that can convert and output the types and concentrations of gases invisible to the naked eye as visual signals. With the proposal and development of major national science and technology projects, the requirements for high-temperature and high-pressure resistant, lightweight, small-size, and radiation-resistant gas sensors are becoming increasingly stringent.

[0003] As is well known, the most widely used semiconductor gas sensors are silicon-based field emission sensors. However, due to the narrow bandgap of silicon semiconductors, self-heating and leakage current under high temperature and high power conditions limit their maximum operating temperature to only 250℃, which cannot meet the requirements for high-temperature applications. Researchers have discovered that the bulk resistance of metal oxide semiconductors changes after gas adsorption, showing potential for gas detection. In 1962, Taguchi first developed a gas sensor based on SnO2 material, and subsequently, metal oxide gas sensors with different crystal forms and morphologies were developed. Currently, reported metal oxide semiconductor materials include SnO2, TiO2, ZnO, WO3, V2O5, In2O3, NiO, and some binary oxides. However, oxide-based semiconductor gas sensors face two main problems in application: first, oxides have poor thermal conductivity, and "hot spots" easily form on the surface under high temperature conditions, weakening their adsorption capacity for target gases; second, oxides can undergo chemical reactions in certain corrosive and high-humidity environments, leading to performance instability. To address the stability issues of semiconductors in harsh high-temperature environments, researchers have begun to focus their attention on wide-bandgap semiconductors.

[0004] Silicon carbide (SiC) is currently the most promising third-generation wide-bandgap semiconductor material, possessing wide bandgap, high electron drift velocity, high thermal conductivity, high electron mobility, high breakdown voltage, and excellent mechanical properties and chemical stability. It offers significant advantages for devices used in harsh environments such as high temperature, high frequency, and high radiation, making it an ideal material for developing highly sensitive and stable high-temperature gas sensors. Currently, numerous studies both domestically and internationally have reported on the gas-sensing properties of low-dimensional SiC nanostructures, such as the humidity response of SiC nanowires and the response of Pt@SiC nanowires to hydrogen. However, the response coefficients of pure SiC or doped SiC remain relatively small, failing to meet the requirements for higher sensitivity.

[0005] Chinese patent application document (CN111564549A) discloses a SiC / ZnO nanoheterojunction pressure sensor and its fabrication method. It mainly utilizes the coupling of the piezoresistive properties of SiC and the piezoelectric properties of ZnO to obtain a higher current response. However, after testing, it was found that its gas response was not ideal. Summary of the Invention

[0006] To address the shortcomings of the prior art, this invention aims to provide a ZnO / SiC nanoheterojunction gas sensor and its preparation method. First, single-crystal SiC nanowires are prepared via organic precursor pyrolysis. Then, ZnO nanoparticles are grown in situ on the surface of the single-crystal SiC nanowires using a hydrothermal method, thus realizing the preparation of the ZnO / SiC nanoheterojunction. The constructed gas sensor exhibits higher sensitivity to ethanol at high temperatures.

[0007] One objective of this invention can be achieved through the following technical solutions:

[0008] A ZnO / SiC nanoheterojunction high-temperature ethanol gas sensor, the gas sensor comprising a ceramic tube with gold electrodes, a heating wire, a insert, and a functional unit loaded on the ceramic tube, wherein the functional unit is a ZnO / SiC nanoheterojunction.

[0009] Preferably, the ZnO / SiC nanoheterojunction includes SiC single-crystal nanowires and ZnO nanoparticles grown on the surface of the SiC single-crystal nanowires.

[0010] The surface of SiC single-crystal nanowires is coated with ZnO nanoparticles, which effectively couple the high gas sensitivity of ZnO nanoparticles with the high thermal conductivity and high electron mobility of SiC single-crystal nanowires.

[0011] When the sensor is exposed to air, the gas-sensitive material adsorbs oxygen molecules from the air. These oxygen molecules capture the conduction band electrons of the gas-sensitive material, converting them into oxygen populations (O2). - O 2- O2 -Because electrons are trapped in the gas-sensitive material, the electron concentration decreases, forming an electron depletion layer on its surface, leading to an increase in sensor resistance. When the sensor is exposed to a reducing atmosphere (electron acceptor), the target gas reacts with the oxygen population and then releases the trapped electrons back into the gas-sensitive material. The increased electron concentration lowers the sensor resistance, demonstrating a response to the target gas. When encountering an oxidizing gas (electron acceptor), more electrons are trapped by the adsorbed gas, further reducing the sensor's conductivity and increasing resistance. First, because ZnO nanoparticles are grown in situ on SiC single-crystal nanowires, ZnO nanoparticle aggregation is effectively reduced, increasing reactive sites and improving gas-sensing performance. Second, ethanol and oxygen molecule adsorption are exothermic reactions. At higher operating temperatures, a large amount of heat energy accumulates on the surface of the gas-sensitive material, causing target gas molecules and oxygen populations to move towards desorption, resulting in decreased sensor sensitivity at high temperatures. SiC single-crystal nanowires have good thermal conductivity, which can disperse some of the heat energy on the ZnO surface. At the same time, the high electron mobility of SiC can accelerate electron transport, all of which contribute to improving the high-temperature gas-sensing performance of the sensor. In addition, the ZnO nanoparticles and SiC single-crystal nanowires form a heterojunction with a barrier height difference of ~0.2 eV, allowing electrons to migrate from the SiC conduction band to the ZnO conduction band, resulting in electron enrichment on the ZnO surface and expanding the electron depletion layer, which further enhances the gas-sensing performance. For these reasons, the ZnO / SiC nanoheterojunction ethanol high-temperature sensor exhibits excellent performance.

[0012] The SiC single-crystal nanowires used to construct the ZnO / SiC nanoheterojunction in this invention can be selected from one or more of the following: undoped SiC nanowires, N-doped SiC nanowires, and P-doped SiC nanowires.

[0013] Preferably, the SiC nanowires of the present invention are undoped SiC single-crystal nanowires.

[0014] Preferably, the SiC single-crystal nanowires have a diameter of 100-600 nm and a length of 10-60 μm.

[0015] This invention also provides a method for preparing the above-mentioned ZnO / SiC nanostructure high-temperature ethanol gas sensor, the method comprising the following steps:

[0016] S1. Preparation of ZnO / SiC nanoheterojunction: SiC single crystal nanowires are dispersed in NaOH solution, and then centrifuged and washed to obtain hydroxylated SiC single crystal nanowires;

[0017] Hydroxylated SiC single-crystal nanowires were placed in a hydrothermal reaction system, and zinc nitrate hexahydrate, water and triethanolamine were used as precursors for growing ZnO nanoparticles. ZnO was grown on the surface of the SiC nanowires, thereby obtaining a ZnO / SiC nanoheterojunction.

[0018] S2. Gas sensor construction: ZnO / SiC nanoheterojunction and deionized water are ground and uniformly coated on a ceramic tube. After drying and aging, the gas sensor is installed in a metal oxide gas-sensitive testing system.

[0019] Preferably, the method for preparing the SiC single-crystal nanowires includes the following steps:

[0020] S1. Place the liquid polysilazane into a graphite crucible;

[0021] S2. Place the carbon paper substrate loaded with catalyst on top of the graphite crucible;

[0022] S3. Place the graphite crucible in the atmosphere sintering furnace. First, evacuate the atmosphere sintering furnace to 1-5 Pa, and then introduce a protective atmosphere. Sinter the SiC single crystal nanowires under the protective atmosphere.

[0023] Preferably, the hydrothermal growth time of the ZnO nanoparticles is 300-1200 min.

[0024] In-situ growth of ZnO nanoparticles on the surface of SiC single-crystal nanowires leverages the synergistic effect of the two materials to improve the high-temperature gas-sensing performance of ZnO / SiC nanoheterojunctions. The growth status of the ZnO nanoparticles on the SiC nanowire surface is crucial. When the hydrothermal growth time of ZnO nanoparticles is within the range of 300-1200 min, the ZnO / SiC nanoheterojunction exhibits superior high-temperature gas-sensing response compared to either ZnO nanoparticles alone or SiC single-crystal nanowires alone.

[0025] Further preferably, the growth time of the ZnO nanoparticles is 660-780 min. The morphology and distribution of the ZnO nanoparticles within this time range result in a superior high-temperature gas-sensitive response for the ZnO / SiC nanoheterostructure.

[0026] Preferably, the hydrothermal reaction temperature is 80-150℃.

[0027] The molar ratio of SiC single-crystal nanowires to zinc nitrate hexahydrate is 1:(8-9).

[0028] Preferably, the aging treatment temperature is 380-450℃ and the time is 45-55h.

[0029] Preferably, the preparation method of the above-mentioned ZnO / SiC nanostructure high-temperature ethanol sensor specifically includes the following steps:

[0030] The catalyst supported on the carbon paper substrate is preferably one or more of the following: cobalt nitrate, nickel nitrate, ferric nitrate, and nickel sulfate.

[0031] Further preferably, the catalyst is cobalt nitrate. A carbon paper substrate is immersed in a 0.02-0.08 mol / L Co(NO3)2 ethanol solution and air-dried to obtain a carbon paper substrate loaded with Co(NO3)2.

[0032] In the method for preparing SiC single-crystal nanowires, high-purity argon is used as the protective atmosphere. The temperature is first rapidly increased from room temperature to 1400-1500℃ at a rate of 20-30℃ / min, then further increased to 1550-1600℃ at a rate of 3-7℃ / min, followed by cooling at a rate of 15-25℃ / min, and finally furnace cooled to room temperature to obtain SiC single-crystal nanowires.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) In this invention, ZnO nanoparticles are grown in situ on the surface of SiC nanowires by hydrothermal method, and the degree of aggregation of ZnO nanoparticles in ZnO / SiC nanoheterostructure is controllable.

[0035] (2) ZnO / SiC nanoheterojunction is used as the functional unit of high temperature ethanol sensor. The test temperature range is 275-505℃, and the best responsivity of 25.4 appears at 464℃, which can realize high temperature and high sensitivity detection.

[0036] (3) In this invention, ZnO / SiC nano heterostructure with a growth time of 300-1200 min is used as the gas-sensitive material of high-temperature ethanol sensor. The responsivity of ZnO / SiC nano heterostructure is significantly higher than that of high-temperature gas-sensitive sensor prepared by single ZnO nanoparticle and single SiC single crystal nanowire, and has a higher responsivity. Attached Figure Description

[0037] Figure 1 This is a scanning electron microscope (SEM) image of the ZnO / SiC nanoheterostructure prepared in Example 1 of the present invention.

[0038] Figure 2 The images show transmission electron microscopy (TEM) and selected area electron diffraction (SAED) patterns of the ZnO / SiC nanoheterostructure prepared in Example 1 of this invention.

[0039] Figure 3 The images show X-ray diffraction (XRD) patterns of the ZnO / SiC nanoheterojunction prepared in Example 1 of the present invention, the pure ZnO prepared in Comparative Example 1, and the pure SiC nanowires prepared in Comparative Example 2.

[0040] Figure 4 This is a schematic diagram of the gas sensor structure of the ZnO / SiC nanoheterojunction prepared in Example 1 of the present invention, the pure ZnO prepared in Comparative Example 1, and the pure SiC nanowire prepared in Comparative Example 2.

[0041] Figure 5 The graph shows the response of the ZnO / SiC nanoheterojunction gas sensor prepared in Example 1 of this invention to 100 ppm ethanol at different operating temperatures.

[0042] Figure 6 The response / recovery curve of the ZnO / SiC nanoheterojunction gas sensor prepared in Example 1 of the present invention to 100 ppm ethanol at 464 °C;

[0043] Figure 7 The ZnO / SiC nanoheterojunction gas sensor prepared in Example 1 of this invention exhibits a cyclic response curve to 100 ppm ethanol at 464 °C.

[0044] Figure 8 This is a comparison chart of the gas response of the ZnO / SiC nanoheterojunction gas sensor prepared in Example 1 of the present invention to 100ppm acetone, ethanol, DMF, hydrogen and ammonia at 464℃.

[0045] Figure 9 This is a scanning electron microscope (SEM) image of the pure ZnO prepared in Comparative Example 1 of the present invention.

[0046] Figure 10 The graph shows the response of the pure ZnO gas sensor prepared in Comparative Example 1 of this invention to 100 ppm ethanol at different operating temperatures.

[0047] Figure 11 This is a comparison chart showing the gas response of the pure ZnO gas sensor prepared in Comparative Example 1 of the present invention to 100 ppm acetone, ethanol, DMF, hydrogen and ammonia at 464 °C.

[0048] Figure 12 This is a scanning electron microscope (SEM) image of the pure SiC nanowires prepared in Comparative Example 2 of this invention.

[0049] Figure 13 The images show transmission electron microscopy (TEM) and selected area electron diffraction (SAED) patterns of the pure SiC nanowires prepared in Comparative Example 2 of this invention.

[0050] Figure 14 The graph shows the response of the pure SiC nanowire gas sensor prepared in Comparative Example 2 of this invention to 100 ppm ethanol at different operating temperatures.

[0051] Figure 15 This is a comparison chart showing the gas response of the pure SiC nanowire gas sensor prepared in Comparative Example 2 of the present invention to 100 ppm acetone, ethanol, DMF, hydrogen and ammonia at 464 °C.

[0052] Figure 16 This is a scanning electron microscope (SEM) image of the ZnO / SiC nanoheterojunction gas sensor prepared in Comparative Example 3 of this invention. Detailed Implementation

[0053] The technical solution of the present invention will be further described and illustrated below with reference to specific embodiments and accompanying drawings. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used in the art, and the methods used in the embodiments are all conventional methods in the art.

[0054] Example 1:

[0055] The ZnO / SiC nanoheterojunction gas sensor of this embodiment 1 includes a metal oxide gas sensing system, a insert, an alumina ceramic with a gold electrode, a heating wire, and a ZnO / SiC nanoheterojunction as a functional unit for a high-temperature ethanol sensor.

[0056] The fabrication method of the ZnO / SiC nanostructure gas sensor includes the following steps:

[0057] (1) Preparation of SiC single-crystal nanowires:

[0058] Weigh 300 mg of polysilazane liquid and place it at the bottom of a graphite crucible. Cut a 5 × 5 cm (length × width) piece of carbon paper and immerse it in a 0.05 mol / L Co(NO3)2 ethanol solution. After 5 min, remove it and let it air dry. Place the carbon paper substrate loaded with the catalyst Co(NO3)2 on top of the graphite crucible, and place the graphite crucible in a graphite resistance heating atmosphere sintering furnace. First, evacuate the atmosphere sintering furnace to 3 Pa, and then fill it with high-purity argon as a protective atmosphere. First, rapidly heat the furnace from room temperature to 1450 °C at a rate of 30 °C / min, then continue heating at a rate of 5 °C / min to 1550 °C, and then cool it down at a rate of 20 °C / min. Finally, furnace cool to room temperature to obtain SiC single-crystal nanowires.

[0059] (2) Preparation of ZnO / SiC nanoheterostructures:

[0060] SiC single-crystal nanowires were dispersed in a 5M NaOH solution and subjected to alkali treatment for 36 hours. The precipitate was then obtained by centrifugation and washed three times with deionized water to obtain hydroxylated SiC single-crystal nanowires. 1.67 mmol of zinc nitrate hexahydrate and 0.2 mmol of silicon carbide nanowires were mixed in 20 mL of deionized water. While stirring continuously at room temperature, 5 mL of triethanolamine was slowly added to the solution. The resulting mixture was magnetically stirred for 30 min at room temperature, then transferred to a 50 mL high-pressure reactor and reacted at 120 °C for 12 hours. After natural cooling to room temperature, the mixture was centrifuged. The precipitate was washed three times with water and ethanol, and finally dried in an 80 °C drying oven to prepare a ZnO / SiC nanoheterojunction.

[0061] Figure 1 (a) and (b) are SEM characterization images of the ZnO / SiC nanoheterostructure sample prepared in this example. It can be seen that ZnO nanoparticles are attached to SiC nanowires, which effectively reduces the aggregation of ZnO nanoparticles. The length of the ZnO / SiC nanoheterostructure can reach tens of micrometers, and the size is relatively uniform. Figure 2 (a) is a TEM image of the ZnO / SiC nanoheterostructure, clearly showing that ZnO and SiC are tightly connected to form a layered heterostructure. Figure 2 (b) The high-resolution transmission electron microscopy (HRTEM) image shows that the SiC single-crystal nanowires grow along the

[111] direction. Figure 3 The XRD pattern of the ZnO / SiC nanoheterostructure shows that, after removing the substrate, the prepared material is a composite material of wurtzite ZnO and 3C-SiC with high crystallinity.

[0062] (3) Construction of ZnO / SiC nanostructure gas sensor:

[0063] A gas-sensitive material of ZnO / SiC nanoheterostructure was coated onto an alumina ceramic tube with a gold electrode to construct... Figure 4 The ZnO / SiC nanostructured ethanol gas sensor shown is illustrated. Figure 5 The graph shows the response of a gas sensor with ZnO / SiC nanoheterojunction as the functional unit to 100 ppm ethanol at different operating temperatures. The graph shows that the response first increases and then decreases with increasing temperature, with the optimal operating temperature being 464℃ and the highest response being 25.4. Figure 6 The figure shows the response / recovery curves of the gas sensor with ZnO / SiC nanoheterojunction as the functional unit at 464°C to 100 ppm ethanol. The figure indicates that the response time and recovery time of the gas sensor with ZnO / SiC nanoheterojunction as the functional unit at 464°C to 100 ppm ethanol are 19 s and 49 s, respectively. Figure 7The graph shows the cyclic response curve of the gas sensor, which uses the ZnO / SiC nanoheterojunction prepared in Example 1 of this invention as a functional unit, to 100 ppm ethanol at 464 °C. The graph shows that the sensor has good cycling performance. Figure 8 This is a comparison chart of the gas response of the ZnO / SiC nano-heterojunction gas sensor prepared in Example 1 of the present invention to 100ppm acetone, ethanol, DMF, hydrogen and ammonia at 464℃. The chart shows that the ZnO / SiC nano-heterojunction gas sensor has good gas selectivity for ethanol.

[0064] Comparative Example 1:

[0065] The only difference between Comparative Example 1 and Example 1 is that the gas sensor functional unit of Comparative Example 1 is ZnO nanoparticles, which are used to compare the effect of constructing ZnO / SiC nanoheterojunctions on gas sensing performance.

[0066] Figure 8 The image shows the SEM characterization of the pure ZnO prepared in Comparative Example 1. It can be seen that the pure ZnO is composed of a large number of oxide particles aggregated into spheres with a diameter of approximately 0.5-3 μm. Figure 3 The XRD pattern of pure ZnO in Comparative Example 1 is shown. After removing the substrate, the results indicate that the prepared pure ZnO is hexagonal wurtzite with high crystallinity. Figure 10 The graph shows the response of the gas sensor with pure ZnO as the functional unit in Comparative Example 1 to 100 ppm ethanol at different operating temperatures. The graph shows that, at the same ethanol concentration, the response first increases and then decreases with increasing temperature. The optimal operating temperature is 464℃, and the highest response is 10.4, which is significantly lower than that in Example 1. Figure 11 The graph shows a comparison of the gas response of the ZnO nanoheterojunction gas sensor prepared in Comparative Example 1 to 100 ppm acetone, ethanol, DMF, hydrogen, and ammonia at 464 °C. The graph indicates that the pure ZnO gas sensor has a high response to both ethanol and acetone, but its gas selectivity is significantly worse than that of Example 1. This demonstrates that constructing ZnO / SiC nanoheterojunctions as functional units can improve the gas-sensing performance of gas sensors.

[0067] Comparative Example 2:

[0068] The only difference between Comparative Example 2 and Example 1 is that the gas sensor functional unit of Comparative Example 2 is a pure SiC nanowire, used to compare the effect of constructing a ZnO / SiC nanoheterojunction on gas sensing performance.

[0069] Figure 12 The image shows the SEM characterization of the pure SiC single-crystal nanowires prepared in Comparative Example 2. It can be seen that the diameter of the pure SiC nanowires is 100-600 nm. Figure 13(a) is a TEM image of pure SiC nanowires in Comparative Example 2. Figure 13 (b) is the selected area electron diffraction (SAED) pattern of pure SiC nanowires in Comparative Example 2. The pure SiC in the figure is a single crystal nanowire grown along the

[111] direction. Figure 3 The XRD pattern of pure SiC nanowires in Comparative Example 2 is shown. After removing the substrate, the results indicate that the prepared pure SiC nanowires are 3C-SiC, i.e., β-SiC, and have good crystallinity. Figure 14 The graph shows the response of the gas sensor using pure SiC nanowires as the functional unit in Comparative Example 2 to 100 ppm ethanol at different operating temperatures. It can be clearly observed that the response of the pure SiC nanowires in Comparative Example 2 is significantly lower than that in Example 1. Figure 15 The graph shows a comparison of the gas reactivity of the pure SiC nanowire gas sensor prepared in Comparative Example 2 at 464 °C for 100 ppm of acetone, ethanol, DMF, hydrogen, and ammonia. The graph indicates that the pure SiC nanowire gas sensor exhibits similar reactivity to these five organic gases, but its gas selectivity is significantly worse than that of Example 1. This demonstrates that constructing ZnO / SiC nanoheterojunctions as functional units can improve the gas-sensing performance of the gas sensor.

[0070] Comparative Example 3:

[0071] The difference between Comparative Example 3 and Example 1 is that the gas sensor functional unit of Comparative Example 3 is a ZnO / SiC nanoheterojunction, wherein the ZnO / SiC nanoheterojunction includes SiC single crystal nanowires and a ZnO nanolayer grown on the surface of the SiC single crystal nanowires, which is used to compare the effect of constructing a ZnO / SiC nanoheterojunction on gas sensing performance.

[0072] Specifically, SiC single-crystal nanowires were dispersed in a 5M NaOH solution and subjected to alkali treatment for 36 hours. The precipitate was then obtained by centrifugation and washed three times with deionized water to obtain hydroxylated SiC single-crystal nanowires. 0.42 mmol of zinc nitrate hexahydrate and 0.2 mmol of silicon carbide nanowires were mixed in 20 ml of deionized water. While stirring continuously at room temperature, 1.25 ml of triethanolamine was slowly added to the solution. The resulting mixture was magnetically stirred at room temperature for 30 min, then transferred to a 50 ml high-pressure reactor and reacted at 120 °C for 12 hours. After natural cooling to room temperature, the mixture was centrifuged. The precipitate was washed three times with water and ethanol, and finally dried in an 80 °C drying oven to prepare a ZnO / SiC nanoheterojunction. Figure 16 As can be seen, in the SiC single-crystal nanowires prepared in Comparative Example 3 and the ZnO nanolayers grown on the surface of the SiC single-crystal nanowires, most of the SiC is exposed, and the amount of ZnO growth is low, which leads to a significant reduction in their sensitivity to gas response.

[0073] The embodiments described herein cover any points not exhaustively within the scope of the technical claims of this invention, as well as new technical solutions formed by equivalent substitutions of one or more technical features in the embodiments. These are all within the scope of the claims of this invention. Furthermore, in all listed or unlisted embodiments of this invention, each parameter in the same embodiment merely represents an instance (i.e., a feasible solution) of its technical solution, and there is no strict coordination or limitation relationship between the parameters. The parameters can be substituted for each other without violating axioms and the claims of this invention, unless otherwise stated.

[0074] The technical means disclosed in this invention are not limited to those described above, but also include technical solutions composed of any combination of the above technical features. The above descriptions are specific embodiments of this invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

[0075] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A ZnO / SiC nanostructured high-temperature ethanol gas sensor, characterized in that, The gas sensor includes a ceramic tube with a gold electrode, a heating wire, a insert, and a functional unit loaded on the ceramic tube. The functional unit is a ZnO / SiC nanoheterojunction. The sensor fabrication method includes the following steps: S1. Preparation of ZnO / SiC nanoheterojunction: SiC single crystal nanowires are dispersed in NaOH solution, and then centrifuged and washed to obtain hydroxylated SiC single crystal nanowires; Hydroxylated SiC single-crystal nanowires were placed in a hydrothermal reaction system, and zinc nitrate hexahydrate, water and triethanolamine were used as precursors for growing ZnO nanoparticles. ZnO was grown on the surface of the SiC nanowires, thereby obtaining a ZnO / SiC nanoheterojunction. S2. Gas sensor construction: ZnO / SiC nanoheterojunctions are ground with water and uniformly coated onto a ceramic tube. After drying and aging, they are then installed in a metal oxide gas-sensitive testing system to construct a gas sensor. The hydrothermal growth time of the ZnO nanoparticles is 660-780 min; The hydrothermal reaction temperature is 80-150℃; The method for preparing the SiC single-crystal nanowires includes the following steps: S1. Place the liquid polysilazane into a graphite crucible; S2. Place the carbon paper substrate loaded with catalyst on top of the graphite crucible; S3. Place the graphite crucible in an atmosphere sintering furnace. First, evacuate the atmosphere sintering furnace to 1-5 Pa, then introduce a high-purity Ar protective atmosphere. Sinter under the protective atmosphere to obtain SiC nanowires.

2. The high-temperature ethanol gas sensor according to claim 1, characterized in that, The ZnO / SiC nanoheterojunction includes SiC single-crystal nanowires and ZnO nanoparticles grown on the surface of the SiC single-crystal nanowires.

3. The high-temperature ethanol gas sensor according to claim 2, characterized in that, The SiC single-crystal nanowires are one or more of undoped SiC nanowires, N-doped SiC nanowires, and P-doped SiC nanowires.

4. The high-temperature ethanol gas sensor according to claim 2, characterized in that, The SiC single-crystal nanowires have a diameter of 100-600 nm and a length of 10-60 μm.

5. The high-temperature ethanol gas sensor according to claim 1, characterized in that, The aging treatment temperature is 380-450℃, and the time is 45-55h.

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