A high performance acetylene gas sensor and its preparation method

Abstract

The present application relates to the technical field of gas-sensitive materials, and in particular to a gas-sensitive material, a gas sensor, a preparation method and application thereof. The gas-sensitive material is made of a semiconductor material SnO2 modified by a bimetallic (metallic Sm and metal Ag), and the Sm2O3-modified SnO2 is prepared by a gel sol method; then, an Ag-containing material is added and mixed and calcined. The gas sensor includes a ceramic tube-based side-heated structure and a gas-sensitive material distributed on the ceramic tube. The gas-sensitive material, gas sensor and preparation method thereof of the present application have higher sensitivity, lower detection limit, lower operating temperature and good selectivity, and can be used for the selective detection of acetylene gas.

Description

Technical Field

[0001] The present application relates to the technical field of gas-sensitive materials, and in particular to a gas-sensitive material, a gas sensor, a preparation method and an application thereof; the application refers to the application of the gas-sensitive material or the gas sensor in the selective detection of acetylene gas. Background Art

[0002] Oil-immersed transformers are crucial equipment in power grids and are of great significance to the safety and stability of power systems. As a key characteristic gas in transformer fault diagnosis, accurately detecting and effectively distinguishing C2H2 from other dissolved gases (H2, CH4, C2H6, C2H4, CO, CO2) is crucial for determining whether a fault has occurred and what type of fault it is. Metal oxide gas sensors offer advantages such as short response time, low cost, and ease of integration, making them suitable for detecting cracked gases in transformer oil. However, cross-sensitivity and insufficient sensitivity have hindered their application. Therefore, developing a metal oxide gas sensor with high selectivity, high sensitivity, and a low detection limit is of great significance.

[0003] SnO2, a commonly used n-type semiconductor metal oxide gas-sensing material, is widely used for detecting various gases due to its universal sensitivity, low production cost, and high stability. However, when multiple gases coexist, especially when multiple hydrocarbon gases with similar composition and structure are present, SnO2 exhibits cross-sensitivity. This means that the target gas C2H2 is easily interfered with by other gases and cannot be accurately identified in practice. Modifying the material to reduce cross-response to interfering gases has always been a key and difficult issue in the field of gas sensing. In addition, according to the "Guidelines for the Analysis and Judgment of Dissolved Gases in Transformer Oil," the cautionary value for C2H2 concentration in transformer oil above 330kV is 1ppm, and the cautionary value for C2H2 concentration in transformer oil below 220kV is 5ppm. Therefore, the issue of how to lower the detection limit of gas-sensing materials is also an urgent issue that needs to be addressed.

[0004] CN 117169292A discloses a semiconductor material SnO2 modified with a bimetallic structure (metallic Sm and metal Pd). However, this material still has the following defects: a detection limit of only 1 ppm, a relatively high price for Pd as a doping element, a complex production process, a MEMS structure, high requirements for the device preparation process, and a low yield rate. Summary of the Invention

[0005] To address the above issues, this application provides the following technical solutions:

[0006] In a first aspect of the present application, a gas-sensitive material is provided, wherein the material is a semiconductor material modified with a bimetal, wherein the bimetal refers to metal Sm and metal Ag, and the semiconductor material includes SnO2;

[0007] The modification refers to preparing Sm2O3-modified SnO2 by a gel sol method, which is recorded as Sm2O3@SnO2; then adding Ag-containing materials and mixing and calcining to prepare Ag-modified Sm2O3@SnO2, which is recorded as Ag@Sm2O3@SnO2.

[0008] A second aspect of the present application relates to a gas sensor, comprising:

[0009] 1) Ceramic tube-based indirectly heated gas sensor, which includes a ceramic tube with gold electrodes at both ends, each gold electrode connected to two Pt wires, a Ni-Cr heating wire, and a hexagonal base;

[0010] 2) The gas-sensitive material of the first aspect is distributed on the ceramic tube of the ceramic tube-based indirectly heated gas sensor and completely covers the surface of the gold electrode; and / or

[0011] 3) Ni-Cr heating wire, the Ni-Cr heating wire should pass through the ceramic tube and the heating part should be completely wrapped by the ceramic tube; and / or

[0012] In a third aspect of the present application, a method for preparing a gas sensor according to any of the above technical solutions is provided, comprising the following steps:

[0013] Provide a ceramic tube-based indirectly heated gas sensor as defined in the above gas sensor;

[0014] Grinding the gas-sensitive material, adding deionized water and mixing, and grinding the resulting mixture to prepare a gas-sensitive slurry;

[0015] Applying the gas-sensitive slurry on the gold electrode of the ceramic tube-based indirectly heated gas sensor so that the gas-sensitive slurry completely covers the surface of the gold electrode;

[0016] After the coating is completed, the mixture is transferred to an infrared lamp for baking.

[0017] In another aspect of the present application, there is provided a use of the gas-sensitive material or gas sensor described above in the selective detection of acetylene gas.

[0018] The gas-sensitive material of the present application is prepared by modifying the semiconductor material SnO2 with specific metal Sm and metal Ag and a suitable modification method to obtain a bimetallic modified semiconductor material. The gas sensor using this material as the gas-sensitive material has significantly improved sensitivity, selectivity and detection limit characteristics, overcoming the defects of traditional semiconductor sensors such as poor selectivity, insufficient sensitivity and high detection limit. It has low cost, can be detected at room temperature, has good response and selectivity to acetylene gas, and has no response to other common gases such as ethylene, carbon monoxide, methane, ethane, carbon dioxide, etc., and can be used for the detection of dissolved gases in transformer oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the XRD pattern of the Ag@Sm2O3@SnO2 material of Example 1 of the present application;

[0020] Figure 2 This is a graph showing the optimal operating temperature of the gas sensor according to Example 3 of the present application;

[0021] Figure 3 The sensitivity test results of the gas sensor of Example 3 of the present application are as follows;

[0022] Figure 4 The response-recovery time test results of the gas sensor of Example 3 of the present application are as follows;

[0023] Figure 5 The selectivity test results of the gas sensor of Example 3 of the present application are as follows;

[0024] Figure 6 Optimal operating temperature curve of the gas sensor of Comparative Example 1;

[0025] Figure 7 The sensitivity test results of the gas sensor of Comparative Example 1 are as follows;

[0026] Figure 8 Response-recovery time test results of the gas sensor of Comparative Example 1;

[0027] Figure 9 The selectivity test results of the gas sensor of Comparative Example 1 are as follows;

[0028] Figure 10 Optimal operating temperature curve of the gas sensor of Comparative Example 2;

[0029] Figure 11 The sensitivity test results of the gas sensor of Comparative Example 2 are as follows;

[0030] Figure 12 Response-recovery time test results of the gas sensor of Comparative Example 2;

[0031] Figure 13 This is the selectivity test result of the gas sensor of Comparative Example 2. DETAILED DESCRIPTION

[0032] the term

[0033] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0034] The terms "and / or", "or / and", and "and / or" used herein include any one of two or more related listed items, and also include any and all combinations of the related listed items, wherein the any and all combinations include any combination of two related listed items, any more related listed items, or all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that in this application, the technical solution undoubtedly includes technical solutions connected by "logical AND" and technical solutions connected by "logical OR". For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, the technical solution of all being connected by "logical OR"), and also includes any and all combinations of A, B, C, and D, that is, the combination of any two or any three of A, B, C, and D, and also includes the four-item combination of A, B, C, and D (that is, the technical solution of all being connected by "logical AND").

[0035] Herein, "preferred", "better", "better", etc. are only used to describe implementation methods or examples with better effects. It should be understood that they do not constitute limitations on the scope of protection of this application.

[0036] In this application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be understood as limiting the scope of protection of this application.

[0037] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0038] In this application, when referring to a numerical interval (i.e., a numerical range), unless otherwise specified, the optional numerical distribution within the above numerical interval is considered continuous and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval refers only to integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0039] Unless otherwise specified, the temperature parameters in this application allow for both constant temperature treatment and temperature fluctuations within a certain temperature range. It should be understood that the constant temperature treatment allows for temperature fluctuations within the accuracy range of instrument control. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are permitted.

[0040] In this application, weight can be mass units known in the chemical industry, such as μg, mg, g, and kg.

[0041] In this application, unless otherwise specified, the size, particle size, and diameter generally refer to the average value.

[0042] In one aspect of the present application, a gas-sensitive material is provided, which is made of a bimetallic-modified semiconductor material, wherein the bimetallic material includes metal Sm and metal Ag, and the semiconductor material includes SnO2; after the SnO2 material is modified with a specific metal, the sensitivity, selectivity and response recovery characteristics are significantly improved, overcoming the defects of traditional semiconductor materials such as poor selectivity, insufficient sensitivity and long response recovery time.

[0043] In some embodiments, the gas-sensitive material is made of a bimetallic modified semiconductor material, wherein the bimetallic refers to metal Sm and metal Ag, and the semiconductor material includes SnO2;

[0044] Modification refers to the preparation of Sm2O3-modified SnO2 by the gel sol method, which is recorded as Sm2O3@SnO2; then Ag-containing materials are added and mixed and calcined to prepare Ag-modified Sm2O3@SnO2, which is recorded as Ag@Sm2O3@SnO2.

[0045] In some embodiments, the steps of preparing Sm2O3-modified SnO2 by a sol-gel method include:

[0046] Take Sm salt and Sn salt and mix them, add solvent to dissolve them, and prepare Sm / Sn salt solution.

[0047] A precipitant is added to a Sm / Sn salt solution to carry out a precipitation reaction, the precipitate is separated and dried, and the dried precipitate is subjected to a first calcination at 500° C. to 700° C. to obtain Sm2O3@SnO2.

[0048] In some embodiments, the preparation conditions for preparing Sm2O3-modified SnO2 using a sol-gel method include at least one of the following:

[0049] 1) The molar ratio of Sn to Sm in the Sm / Sn salt solution is (3.5-4.5):1;

[0050] 2) The precipitation reaction conditions are pH = 8.5-9.5;

[0051] 3) The precipitant is an ammonia solution containing ammonium hydroxide and water in a volume ratio of (0.8-1.2):1;

[0052] 4) separating the precipitate, comprising: filtering to obtain a solid, and washing the solid with deionized water and ethanol;

[0053] 5) The drying temperature is 50°C to 70°C;

[0054] 6) Drying time is 10h~14h;

[0055] 7) The first calcination time is 0.5h to 2h.

[0056] In some embodiments, the step of adding Ag-containing materials and mixing and calcining includes:

[0057] Ag salt, Sm2O3@SnO2 and water were mixed and ultrasonically dispersed to prepare Ag salt / Sm2O3@SnO2 dispersion;

[0058] The liquid of the Ag salt / Sm2O3@SnO2 dispersion was removed, and the obtained solid was subjected to a second calcination at 600°C to 800°C.

[0059] In some embodiments, the preparation conditions for adding the Ag-containing material and mixing and calcining include at least one of the following:

[0060] 1) The Ag salt contains elemental Ag and Sm2O3@SnO2 in a molar weight ratio of 1 mmol: (7.5-8) g;

[0061] 2) The ultrasonic dispersion time is 20 to 50 minutes;

[0062] 3) removing the liquid from the Ag salt / Sm2O3@SnO2 dispersion by drying, wherein the drying temperature is 80°C to 100°C and the drying time is 10 hours to 14 hours;

[0063] 4) The second calcination time is 0.5h to 2h.

[0064] In another aspect of the present application, a gas sensor is provided, which is provided with the gas-sensitive material described above. The gas sensor has good response and selectivity to acetylene gas, a low detection limit, low cost, low detection environment requirements, and is easy to use.

[0065] In some embodiments, the gas sensor comprises:

[0066] 1) Ceramic tube-based indirectly heated gas sensor, which includes a ceramic tube with gold electrodes at both ends, each gold electrode connected to two Pt wires, a Ni-Cr heating wire, and a hexagonal base;

[0067] 2) The aforementioned gas-sensitive material is distributed on the ceramic tube of the ceramic tube-based indirectly heated gas sensor and completely covers the surface of the gold electrode; and / or

[0068] 3) Ni-Cr heating wire, the Ni-Cr heating wire should pass through the ceramic tube and the heating part should be completely wrapped by the ceramic tube; and / or

[0069] In some embodiments, the material of the ceramic tube includes Al2O3, and / or

[0070] The heating wire is a Ni-Cr heating wire; and / or

[0071] In some embodiments, the ceramic tube is 3.9 mm to 4.1 mm long; and / or

[0072] The outer diameter of the ceramic tube is 1.1mm to 1.3mm; and / or

[0073] The distance between the gold electrodes on the ceramic tube is 0.8mm to 1mm; and / or

[0074] The width of the gold electrode on the ceramic tube is 0.5mm to 1mm; and / or

[0075] The distance between the gold electrode and the adjacent end of the ceramic tube is 0.5mm to 2mm; and / or

[0076] The length of the Pt wire connected to the gold electrode is 0.4 mm to 0.8 mm; and / or

[0077] The length of the heating wire is 10 mm to 20 mm; and / or

[0078] The length of the heating wire spiral is 2mm to 4mm; and / or

[0079] The resistance value of the heating wire is 25Ω~35Ω.

[0080] In another aspect of the present application, a method for preparing a gas sensor according to any of the above technical solutions is provided, comprising the following steps:

[0081] Provide a ceramic tube-based indirectly heated gas sensor as defined in the above gas sensor;

[0082] Grinding the gas-sensitive material, adding deionized water and mixing, and grinding the resulting mixture to prepare a gas-sensitive slurry;

[0083] Apply the gas-sensitive slurry on the ceramic tube so that the gas-sensitive slurry completely covers the surface of the gold electrode;

[0084] After coating, transfer to infrared lamp for baking.

[0085] In some embodiments, the method for preparing a gas sensor further comprises the following steps:

[0086] After baking, connect the Pt wires connected to the gold electrodes of the ceramic tube to the designated pins of the indirectly heated hexagonal tube socket.

[0087] Connect both ends of the heating wire to the indirectly heated hexagonal tube holder, and then connect the hexagonal tube holder to the CGS-8 intelligent gas sensitive analysis system.

[0088] Adjust the CGS-8 intelligent gas analysis system to provide a stable current for device aging.

[0089] In another aspect of the present application, there is provided an application of the gas-sensitive material or gas sensor of any of the above technical solutions in low-concentration gas detection.

[0090] In some embodiments, the gas to be measured includes acetylene.

[0091] The gases detected include C2H2.

[0092] In some embodiments, gas detection is directed toward detection of dissolved gases in transformer oil.

[0093] The results of the examples show that a gas sensor made from SnO2 material doped with 3% Sm2O3 and 2% Ag2O has a sensitivity of 27.43 at 180°C. Its detection range for acetylene gas is 0.2-100 ppm, and it does not respond to other common gases produced by transformer oil decomposition (ethylene, carbon monoxide, methane, ethane, carbon dioxide, etc.), demonstrating good selectivity.

[0094] The following are some specific examples.

[0095] For experimental parameters not specified in the following specific examples, reference is made to the guidance given in this application document, and reference may also be made to experimental manuals in the art or other experimental methods known in the art, or to the experimental conditions recommended by the manufacturer.

[0096] The raw materials and reagents involved in the following specific examples can be obtained commercially, or can be prepared by those skilled in the art according to known methods.

[0097] Example 1

[0098] This embodiment provides a specific method for preparing a gas-sensitive material, which specifically includes the following steps:

[0099] (1) Preparation of Sm / Sn salt solution

[0100] Add 40 ml of deionized water, 17.5 g of SnCl4·5H2O, and 0.55 g of SmCl3·6H2O to a beaker. Place the beaker on a thermostatic magnetic stirrer and stir for 30 minutes to prepare a Sm / Sn salt solution as a precursor solution.

[0101] (2) Preparation of Sm2O3@SnO2

[0102] To another beaker, add 20 ml of NH3·H2O and 20 ml of deionized water to prepare an ammonia solution with a volume ratio of NH3·H2O to deionized water of 1:1.

[0103] Using a rubber-tipped pipette, slowly drip ammonia solution into the prepared precursor solution until the pH reaches 9. The solution was washed three times with deionized water and then ethanol, then dried in air at 60°C for 12 hours. After drying, the material was calcined in a tube furnace at 600°C for 1 hour to obtain a SnO2 material modified with Sm2O3 nanoparticles (Sm2O3@SnO2).

[0104] (3) Preparation of Ag@Sm2O3@SnO2

[0105] 15.65g of the above-mentioned material Sm2O3@SnO2 and 0.17g of AgNO3 were added to 40ml of deionized water. The prepared solution was placed in an ultrasonic instrument for 30 minutes and then dried in an air atmosphere at 80℃ for 12 hours. After the material was dried, it was calcined in a tube furnace at 600℃ for 1 hour to obtain a bimetallic SmAg nanoparticle-modified SnO2 material (Ag@Sm2O3@SnO2). The XRD test results of this material are shown as follows: Figure 1 .

[0106] Figure 1 The results show that all samples can be identified as rutile SnO2. The high intensity of the diffraction peak indicates that the crystallinity of the SnO2 samples is good. No diffraction peaks corresponding to Sm3+ and Ag+ were observed in the XRD patterns of the samples, indicating that the doped Sm3+ and Ag+ ions are mainly incorporated into the SnO2 lattice.

[0107] Example 2

[0108] In this embodiment, the Ag@Sm2O3@SnO2 material obtained in Example 1 is used as a gas-sensitive material to prepare a gas sensor. The preparation method is as follows:

[0109] (1) A ceramic tube-based indirectly heated gas sensor is provided, comprising the following structures: 1) a ceramic tube having a length of 4 mm and an outer diameter of 1.2 mm; 2) a Ni-Cr heating wire having a length of 10 mm to 20 mm, a spiral length of 3 mm, and a resistance of 30 Ω, the heating wire serving as a heating element to provide a working temperature for the sensor; 4) a gold electrode having a spacing of 0.9 mm between the gold electrodes, a width of 0.7 mm between the gold electrodes on the ceramic tube, and a spacing of 1 mm between the adjacent ends of the gold electrode and the ceramic tube, for measuring a resistance change of the gas-sensitive material of the sensor; and 3) a Pt wire lead connected to the gold electrode, the Pt wire having a length of 0.4 mm to 0.8 mm, for electrically connecting the gold electrode to the hexagonal tube seat.

[0110] Grind the prepared gas-sensitive material for about 15 minutes, then mix the powder with deionized water in an agate mortar to form a paste. Grind it for another 15 minutes, then use a brush to dip the slurry and evenly apply it on the ceramic tube so that it completely covers the surface of the gold electrode.

[0111] (2) Place the ceramic tube coated with the gas-sensitive material under an infrared lamp and bake for 15 minutes.

[0112] (3) After baking, the Pt wire lead of the gold electrode of the ceramic tube is connected to the indirectly heated hexagonal tube holder, and the two ends of the heating wire of the device are respectively connected to the indirectly heated hexagonal tube holder. The hexagonal tube holder is connected to the CGS-8 intelligent gas sensitive analysis system, and the CGS-8 intelligent gas sensitive analysis system is used to provide the device with a specified current.

[0113] (4) Adjust the current provided by the CGS-8 intelligent gas sensitive analysis system to 90mA.

[0114] (5) The device obtained in step (3) was aged in an air environment at a voltage of 90 mA for 7 days.

[0115] Example 3

[0116] This embodiment uses the gas sensor prepared in Example 2 to detect acetylene and conducts sensor effect evaluation, including:

[0117] (1) Optimum operating temperature

[0118] The gas sensor was tested in acetylene atmosphere at room temperature, and the optimal working voltage curve was as follows: Figure 2As shown, the optimal operating temperature of the sensor for 50ppm acetylene is 180°C; the operating current is 90mA and the power consumption is about 800mW (mainly heating power consumption).

[0119] (2) Sensitivity

[0120] Detect different concentrations of acetylene and obtain resistance-time curves as shown below Figure 3 As shown, according to Figure 3 It can be seen that the detection range of acetylene gas is 0.2-100ppm, which shows that the sensor has a good response to acetylene gas. At an operating temperature of 180℃, the sensitivity to 50ppm acetylene gas reaches 27.43.

[0121] (3) Response-recovery time

[0122] Response time refers to the time required for the sensor signal to rise from zero point to a certain percentage of the ventilation balance point. Recovery time is a parameter that describes how fast the signal recovers when the sensor returns from standard gas to zero point gas. Figure 4 The results show that at an operating temperature of 180°C, the sensor's response recovery times to 50 ppm acetylene gas were 2s and 21s, respectively. When the sensor was removed from the acetylene atmosphere, a 5-second heating pulse at 300°C was applied to the CGS-8 intelligent gas analysis system to accelerate its recovery.

[0123] (4) Selectivity

[0124] The sensitivity of 50ppm C2H4, C2H2, CO, CO2, CH4, C2H6, H2 gas was tested. The test results are as follows: Figure 5 Its sensitivity to 50ppm C2H2 gas reaches 27.43, while the response to the other five gases is very low, reflecting the good selectivity of the sensor.

[0125] As can be seen from the above examples, the gas sensor provided by the present invention has good sensitivity, good response recovery characteristics and selectivity for acetylene gas, and has the characteristics of low power consumption. It effectively improves the low sensitivity and poor selectivity of undoped SnO2 gas sensors.

[0126] Comparative Example 1

[0127] In this comparative example, the Sm2O3@SnO2 material was prepared by the method described in Example 1, and the ceramic tube-based indirectly heated gas sensor was prepared by the method described in Example 2. The difference is that step (3) in Example 1 was omitted, that is, Ag2O doping was not performed.

[0128] This comparative example adopts the method described in Example 2 to prepare a gas sensor and detect acetylene and evaluate the sensor effect, including:

[0129] (1) Optimum operating temperature

[0130] The gas sensor was tested in acetylene atmosphere at room temperature, and the optimal working voltage curve was as follows: Figure 6 As shown in the figure, the optimal working temperature of the sensor for 50ppm acetylene is 220℃.

[0131] (2) Sensitivity

[0132] Detect different concentrations of acetylene and obtain resistance-time curves as shown below Figure 7 As shown, according to Figure 7 It can be seen that the detection range of acetylene gas is 0.5-100ppm, but the response is low below 1ppm. At an operating temperature of 220℃, the sensitivity to 50ppm acetylene gas is only 13.08.

[0133] (3) Response-recovery time

[0134] The single cycle response recovery curve is as follows Figure 8 The results show that the sensor has response recovery times of 4s and 104s to 50ppm acetylene gas at an operating temperature of 220°C, which is much longer than that of Example 3.

[0135] (4) Selectivity

[0136] The sensitivity of 50ppm C2H4, C2H2, CO, CO2, CH4, C2H6, H2 gas was tested. The test results are as follows: Figure 9 The sensitivity to 50ppm C2H2 gas is 13.08, and the sensitivity to ethylene is 2.79. Compared with Example 3, the selectivity is poor.

[0137] It can be seen from the above comparative examples that after omitting the doping of Ag2O material, the sensitivity and selectivity of the gas sensor to acetylene gas are greatly reduced, while the operating temperature and the detection limit are increased, which are not conducive to acetylene detection.

[0138] Comparative Example 2

[0139] In this comparative example, SnO2 material was prepared by the method described in Example 1, except that Ag2O material and Sm2O3 doping were omitted.

[0140] This comparative example adopts the method described in Example 2 to prepare a gas sensor and detect acetylene and evaluate the sensor effect, including:

[0141] (1) Optimum operating temperature

[0142] The gas sensor was tested in acetylene atmosphere at room temperature, and the optimal working voltage curve was as follows: Figure 10 As shown in the figure, the optimal working temperature of the sensor for 50ppm acetylene is 200℃.

[0143] (2) Sensitivity

[0144] Detect different concentrations of acetylene and obtain resistance-time curves such as Figure 11 As shown, according to Figure 11 It can be seen that the detection range of acetylene gas is 0.5-100ppm. When the concentration is below 2ppm, the device has no response to 50ppm acetylene gas and the response is low. At an operating temperature of 200℃, the sensitivity to 50ppm acetylene gas is only 4.75.

[0145] (3) Response-recovery time

[0146] The single cycle response recovery curve is as follows Figure 12 The results show that at an operating temperature of 200°C, the response recovery time of the sensor to 50 ppm acetylene gas is 5s and 183s, respectively, which is much longer than that of Example 3.

[0147] (4) Selectivity

[0148] The sensitivity of 50ppm C2H4, C2H2, CO, CO2, CH4, C2H6, H2 gas was tested. The test results are as follows: Figure 13 Its sensitivity to 50ppm C2H2 gas reaches 4.75, and its sensitivity to ethylene reaches 3.78, with very poor selectivity.

[0149] It can be seen from the above comparative examples that after omitting the doping of both Sm2O3 material and Ag2O material, the sensitivity, response recovery time and selectivity of the gas sensor to acetylene gas are greatly reduced.

[0150] Compared with the technology disclosed in CN 117169292A, the present invention has the following advantages:

[0151] (1) Low detection limit: The detection limit of this invention patent is 0.2ppm, which is less than 1ppm of the previous solution;

[0152] (2) The cost of synthesizing sensitive materials is reduced, and the price of precious metal Ag is lower than that of precious metal Pd;

[0153] (3) This solution adopts a ceramic tube structure, which has a simple preparation process, high yield, easy industrialization and low price.

[0154] All documents mentioned in this application are cited as references in this application, just as each document is cited as reference separately. Unless they conflict with the application purpose and / or technical solution of this application, the cited documents involved in this application are cited in their entirety and for all purposes. When cited documents are involved in this application, the definitions of relevant technical features, terms, nouns, phrases, etc. in the cited documents are also cited. When cited documents are involved in this application, the examples and preferred embodiments of the cited relevant technical features may also be incorporated into this application as references, but are limited to the ability to implement this application. It should be understood that when the cited content conflicts with the description in this application, the present application shall prevail or be adaptively amended according to the description in this application.

[0155] The various technical features of the above-mentioned implementation modes and examples can be combined in any appropriate manner. In order to make the description concise, not all possible combinations of the various technical features in the above-mentioned implementation modes and examples are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of the description in this specification.

[0156] The embodiments described above only express several implementation methods of the present application, but they should not be understood as limiting the scope of the patent application. It should be pointed out that, for those of ordinary skill in the art, without departing from the concept of the present application, several variations and improvements can be made, which all fall within the scope of protection of the present application. In addition, it should be understood that after reading the above-mentioned teaching content of the present application, those skilled in the art can make various changes or modifications to the present application, and the equivalent forms obtained also fall within the scope of protection of the present application. It should also be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the scope of protection of the claims attached to the present application. Therefore, the scope of protection of the patent in this application shall be based on the attached claims, and the description and drawings may be used to explain the contents of the claims.

Claims

1. An acetylene gas-sensitive material, characterized in that: Its material is a semiconductor material modified by a bimetal, wherein the bimetal refers to metal Sm and metal Ag, and the semiconductor material includes SnO2; The modification refers to preparing Sm2O3-modified SnO2 by a gel sol method, which is recorded as Sm2O3@SnO2; then adding Ag-containing materials and mixing and calcining to prepare Ag-modified Sm2O3@SnO2, which is recorded as Ag@Sm2O3@SnO2.

2. The gas-sensitive material according to claim 1, wherein: The steps of preparing Sm2O3-modified SnO2 by the gel sol method include: Take Sm salt and Sn salt and mix them, add solvent to dissolve them, and prepare Sm / Sn salt solution. A precipitant is added to the Sm / Sn salt solution to carry out a precipitation reaction, the precipitate is separated and dried, and the dried precipitate is subjected to a first calcination at 500° C. to 700° C. to obtain the Sm2O3@SnO2.

3. The gas-sensitive material according to claim 2, wherein: The preparation conditions for preparing Sm2O3-modified SnO2 by the gel sol method include at least one of the following: 1) The molar ratio of Sn to Sm in the Sm / Sn salt solution is (30-35):1; 2) The solution condition of the precipitation reaction is pH=8.5-9.5; 3) The precipitant is an ammonia solution containing ammonium hydroxide and water in a volume ratio of (0.8-1.2):1; 4) the step of separating the precipitate comprises: filtering to obtain a solid, and washing the solid with deionized water and ethanol; 5) The drying temperature is 50° C. to 70° C.; 6) The drying time is 10 hours to 14 hours; 7) The first calcination time is 0.5h to 2h.

4. The gas-sensitive material according to claim 1, wherein: The step of adding Ag-containing material and mixing and calcining comprises: Ag salt, the Sm2O3@SnO2 and water are mixed and ultrasonically dispersed to prepare an Ag salt / Sm2O3@SnO2 dispersion; The liquid in the Ag salt / Sm2O3@SnO2 dispersion is removed, and the obtained solid is subjected to a second calcination at 600°C to 800°C.

5. The gas-sensitive material according to claim 4, wherein: The preparation conditions for adding Ag-containing materials and mixing and calcining include at least one of the following: 1) The Ag salt contains elemental Ag and the Sm2O3@SnO2 in a molar weight ratio of 1 mmol: (7.5-8) g; 2) The ultrasonic dispersion time is 20 to 50 minutes; 3) The method of removing the liquid of the Ag salt / Sm2O3@SnO2 dispersion includes drying, the drying temperature is 80°C to 100°C, and the drying time is 10h to 14h; 4) The second calcination time is 0.5h to 2h.

6. A gas sensor, characterized in that: include: 1) Ceramic tube-based bypass heating structure; 2) The gas-sensitive material according to any one of claims 1 to 5, wherein the gas-sensitive material is distributed on the ceramic tube and completely covers the surface of the gold electrode of the ceramic tube.

7. The gas sensor according to claim 6, characterized in that: The gold electrodes at both ends of the ceramic tube are connected to two platinum wire leads respectively; a Ni-Cr heating wire is passed through the ceramic tube, and the platinum wire and the heating wire are welded to the hexagonal base.

8. The method for preparing a gas sensor according to any one of claims 6 to 7, characterized in that: The steps include: Providing a ceramic tube-based indirect heating structure as defined in any one of claims 6 to 7; Grind the gas-sensitive material according to any one of claims 1 to 5, add deionized water and mix, grind the resulting mixture to prepare a gas-sensitive slurry; Applying the gas-sensitive slurry on the ceramic tube so that the gas-sensitive slurry completely covers the surface of the gold electrode of the ceramic tube; After the coating is completed, the coating is transferred to an infrared lamp for baking.

9. The preparation method according to claim 8, characterized in that The following steps are also included: After the baking is completed, the ceramic tube-based indirectly heated gas sensor is connected to an indirectly heated hexagonal tube socket, and the hexagonal tube socket is connected to a CGS-8 intelligent gas sensitive analysis system; The CGS-8 intelligent gas-sensing analysis system is adjusted to stably provide current for device aging.

10. Use of the gas-sensitive material according to any one of claims 1 to 5 or the gas sensor according to any one of claims 6 to 7 in the selective detection of acetylene gas; and / or, the concentration of the acetylene gas is 0.2ppm-100ppm; And / or, the selective detection of acetylene gas includes detection of dissolved gas in transformer oil.

Images