A magnetic field enhanced molybdate ethanol sensing system

Abstract

The present invention relates to the technical field of ethanol sensing, and in particular to a magnetic field-enhanced molybdate ethanol sensing system. The system comprises a pipeline, an air inlet, an air outlet, and a gas-sensitive element. The air inlet and the air outlet are respectively arranged at two ends of the pipeline. The gas-sensitive element is arranged in the pipeline. The gas-sensitive element comprises a substrate, a heating coil, a heating electrode, an interdigital electrode, a measuring electrode, and molybdate. The heating coil, the heating electrode, the interdigital electrode, and the measuring electrode are placed on the substrate. The two ends of the heating coil are connected to the heating electrodes, the interdigital electrodes are connected to the measuring electrodes, and the molybdate is placed on the interdigital electrodes. In addition, the magnetic field-enhanced molybdate ethanol sensing system of the present invention further comprises a first coil. When energized, the first coil generates an alternating magnetic field that acts on the molybdate, causing the molybdate to generate micro-vibrations and a micro-airflow near the molybdate, so that the molybdate is quickly coated in an oxidizing gas or a reducing gas, thereby shortening response and recovery time and improving the efficiency of ethanol gas sensing.

Description

Technical Field

[0001] The present invention relates to the technical field of ethanol sensing, in particular to a magnetic field enhanced molybdate ethanol sensing system. Background Art

[0002] Gas sensors utilize various chemical reactions or physical mechanisms to convert information such as gas type, composition, and concentration into a visual electrical signal output. Gas sensors have been widely used in everyday life. For example, detecting combustible gases can prevent numerous accidents. In industrial production, gas sensors are used in the semiconductor industry and various chemical industries. The development of more sensitive and efficient gas sensors is of profound significance to the healthy development of industrial society.

[0003] Among many gases, the sensing and detection of ethanol is of great significance. Ethanol is widely used in industry, agriculture, and food production. As a flammable substance, ethanol gas, at certain concentrations, can cause fires. Therefore, sensing and monitoring ethanol gas is crucial. Common ethanol sensors include semiconductor gas sensors and electrochemical sensors. Semiconductor gas sensors have attracted widespread attention and application due to their high reliability, low cost, and minimal maintenance.

[0004] Metal molybdates have excellent catalytic properties and have received widespread attention in ethanol gas detection. In particular, iron molybdate, as a member of the A-MoO4 binary metal oxide system, is a particularly effective catalyst, exhibiting high sensitivity in ethanol gas detection. Reference is made to Enhanced low-temperature gas-sensing performance of Fe2(MoO4)3layered microplates, Journal of Material Science: Material Electron, Vol. 33, pp. 10880-10889, 2022. In the practical application of gas sensors, in addition to sensitivity, response and recovery time are also important performance indicators. Shortening response and recovery time can achieve highly efficient gas sensing. Therefore, exploring new technologies to shorten response and recovery time is of great significance. Summary of the Invention

[0005] In order to solve the above problems, that is, to shorten the response and recovery time of the ethanol gas sensor, the present invention provides a magnetic field-enhanced molybdate ethanol sensing system, comprising a pipeline, an air inlet, an air outlet, and a gas sensitive element, wherein the air inlet and the air outlet are respectively arranged at both ends of the pipeline, and the gas sensitive element is arranged in the pipeline. The gas sensitive element comprises a substrate, a heating coil, a heating electrode, an interdigital electrode, a measuring electrode, and molybdate, wherein the heating coil, the heating electrode, the interdigital electrode, and the measuring electrode are placed on the substrate, the two ends of the heating coil are connected to the heating electrodes, the interdigital electrodes are connected to the measuring electrodes, and the molybdate is placed on the interdigital electrodes; in addition, the magnetic field-enhanced molybdate ethanol sensing system of the present invention also comprises a first coil, which generates an alternating magnetic field to act on the molybdate when energized.

[0006] The core idea of ​​the present invention is to use the first coil to generate an alternating magnetic field. The alternating magnetic field acts on molybdate. Due to the magnetism of molybdate, the molybdate produces micro-vibrations, and a micro-airflow is generated near the molybdate, so that the molybdate is quickly coated in the oxidizing gas or the reducing gas, shortening the response and recovery time and improving the efficiency of ethanol gas sensing.

[0007] Furthermore, the molybdate is iron molybdate.

[0008] Furthermore, the molybdate is iron molybdate microspheres composed of nanosheets.

[0009] Furthermore, iron molybdate microspheres composed of nanosheets are prepared by a hydrothermal method.

[0010] Furthermore, the hydrothermal method is to react in a polytetrafluoroethylene reactor at a reaction temperature of 170 degrees Celsius and a reaction time of 12 hours.

[0011] Furthermore, the first coil is fixed on the upper side of the gas sensor on the inner wall of the pipeline. Preferably, the first coil is annular.

[0012] Furthermore, the substrate is aluminum oxide, the heating coil is annular, the interdigital electrodes are placed inside the heating coil, and the outer side of the interdigital electrodes is annular.

[0013] Furthermore, the distance between the fingers of the interdigital electrode is greater than 0.2 mm and less than 0.5 mm, and the diameter of the heating electrode is greater than 4 mm and less than 6 mm.

[0014] Furthermore, the device further comprises a second coil, which is fixed to the outer wall of the pipe below the gas sensor and generates an alternating magnetic field to act on the gas sensor when energized.

[0015] Furthermore, the first coil and the second coil are connected in series.

[0016] Beneficial effects of the present invention:

[0017] (1) The present invention utilizes a first coil to generate an alternating magnetic field, which acts on magnetic molybdate, causing the molybdate to generate micro-vibrations and micro-airflows near the molybdate, so that both oxidizing gas and reducing gas can be quickly coated on the molybdate and react with the molybdate, which not only shortens the recovery time, but also shortens the response time, thereby improving the efficiency of gas sensing.

[0018] (2) The present invention utilizes iron molybdate microspheres as semiconductor sensing materials, and the iron molybdate microspheres are composed of loosely arranged nanosheets; the nanosheets not only increase the specific surface area of ​​the iron molybdate microspheres and the degree of bonding with the gas, thereby improving the gas detection sensitivity; but also, under the action of an alternating magnetic field, these nanosheets can also generate micro-vibrations, changing the atmosphere around the nanosheets, which is conducive to further shortening the response and recovery time.

[0019] (3) In the present invention, the first coil, the second coil, and the interdigitated electrodes are all annular, which is conducive to generating a stronger magnetic field at the molybdate, causing the molybdate to produce stronger micro-vibrations and generating stronger micro-airflow near the molybdate, so that both the oxidizing gas and the reducing gas can react quickly with the molybdate, further shortening the response and recovery time.

[0020] (4) The present invention utilizes the series connection of the first coil and the second coil to confine the magnetic field between the first coil and the second coil, thereby enhancing the magnetic field at the molybdate, strengthening the micro-vibration of the molybdate, accelerating the micro-airflow near the molybdate, and further shortening the response and recovery time.

[0021] Based on the above effects, the present invention has good application prospects in the field of ethanol sensing technology.

[0022] The present invention will be described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of a magnetic field enhanced molybdate ethanol sensing system.

[0024] Figure 2 It is a schematic diagram of a gas sensor.

[0025] Figure 3 This is a scanning electron microscope image of iron molybdate microspheres composed of nanosheets.

[0026] Figure 4 This is a schematic diagram of another magnetic field enhanced molybdate ethanol sensing system.

[0027] In the figure: 1, pipeline; 2, air inlet; 3, air outlet; 4, gas sensor; 5, first coil; 6, second coil; 41, heating coil; 42, heating electrode; 43, interdigital electrode; 44, measuring electrode. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of this application more clear, the application is further described in detail below with reference to the accompanying drawings and examples.

[0029] The present invention provides a magnetic field enhanced molybdate ethanol sensing system, such as Figure 1 As shown, it includes a pipe 1, an air inlet 2, an air outlet 3, and a gas sensor 4. The air inlet 2 and the air outlet 3 are respectively arranged at both ends of the pipe 1, and the air inlet 2 and the air outlet 3 are used to input and output air and formaldehyde gas. The gas sensor 4 is arranged in the pipe 1. The shape of the pipe 1 is not limited, but in order to facilitate the arrangement of the first coil 5 and the second coil 6 later, preferably, the pipe 1 has a horizontal bottom surface and a horizontal top surface. In addition to the base, as shown in FIG. Figure 2As shown, the gas sensor 4 also includes a heating coil 41, a heating electrode 42, interdigital electrodes 43, a measuring electrode 44, and molybdate. The substrate is made of aluminum oxide (aluminum oxide ceramic). The length of the substrate is greater than 20 mm and less than 40 mm; the width is greater than 5 mm and less than 7 mm; and the thickness is greater than 0.5 mm and less than 1 mm. The substrate is adhered to the inner bottom surface of the pipe 1 to prevent the gas sensor 4 from moving under the influence of gas. The heating coil 41, heating electrode 42, interdigital electrodes 43, and measuring electrode 44 are placed on the substrate. The ends of the heating coil 41 are connected to the heating electrode 42, and the interdigital electrodes 43 are connected to the measuring electrode 44. The heating coil 41, heating electrode 42, interdigital electrodes 43, and measuring electrode 44 are all platinum electrodes. Platinum is not easily oxidized at high temperatures and has good chemical stability. The molybdate is placed on the interdigital electrodes 43. The heating coil 41 is annular, and the interdigital electrodes 42 are placed inside the heating coil 41. The outer surface of the interdigital electrodes 43 is also annular. The distance between the interdigital electrodes 43 is greater than 0.2 mm and less than 0.5 mm; the diameter of the heating coil 41 is greater than 4 mm and less than 6 mm. The interdigital electrodes 43 and the measuring electrode 44 are used to measure the change in the resistance of the molybdate. The heating electrodes 42 and the heating coil 41 generate heat through resistance, which is then transferred to the molybdate, allowing the molybdate to perform gas sensing at a suitable temperature. Furthermore, the magnetic field-enhanced molybdate ethanol sensing system of the present invention also includes a first coil 5, which is annular and fixed to the inner wall of the pipe 1 above the gas sensor 4. The first coil 5 is connected to an external AC circuit. When energized, it generates an alternating magnetic field that acts on the molybdate. Positioning the first coil 5 on the inner wall of the pipe 1 generates a stronger magnetic field at the gas sensor 4. Alternatively, the first coil 5 can be positioned outside the pipe 1 for a simpler structure. In this case, the pipe 1 wall can be made of a non-magnetic material.

[0030] During application, an alternating current flows through the first coil 5 to generate an alternating magnetic field at the gas sensor 4 ; at the same time, a direct current flows through the heating coil 41 to generate heat to heat the molybdate on the interdigital electrode 43 ; the resistance change of the molybdate is measured by the measuring electrode 44 .

[0031] The core idea of ​​the present invention is to use the first coil 5 to generate an alternating magnetic field. The alternating magnetic field acts on molybdate. Since molybdate is magnetic, under the action of the alternating magnetic field, the molybdate produces micro-vibrations, and a micro-airflow is generated near the molybdate, so that the molybdate is quickly coated in the oxidizing gas or the reducing gas and reacts with the molybdate, thereby accelerating the process of the oxidation reaction and the reduction reaction, shortening the response and recovery time, and improving the efficiency of ethanol gas sensing.

[0032] Preferably, the molybdate is iron molybdate. Iron molybdate has two main crystal systems: orthorhombic and monoclinic. The orthorhombic iron molybdate exhibits a metastable phase that transforms to a monoclinic stable phase at 537K. Iron molybdate has strong catalytic properties. Related literature indicates that iron molybdate has important applications in the field of ethanol sensing.

[0033] Preferably, the present invention uses iron molybdate microspheres as the sensitive material. Figure 3 As shown in FIG, iron molybdate is an iron molybdate microsphere composed of nanosheets, and the nanosheets radiate outward from the center. The iron molybdate microspheres are prepared by a hydrothermal method, and the core steps are: (1) (NH3)6Mo7O 24 ·4H2O is added to deionized water and fully dissolved; Fe(NO3)3·9H2O is also added to deionized water and dissolved repeatedly; (2) Fe(NO3)3 solution is slowly added to Fe(NO3)3 solution, and stirring is continued to obtain a yellow suspension; (3) A pH meter is placed in the yellow suspension obtained in the previous step, and concentrated ammonia and water are diluted in a ratio of 1:4, and then the dilute ammonia is slowly dripped into the solution with a rubber-tipped dropper, and the pH value of the solution is observed until the pH value of the solution is adjusted to 3; (4) The obtained yellow-brown suspension is poured into a polytetrafluoroethylene reactor and reacted at a constant temperature of 170℃ for 12 hours, and then naturally cooled to room temperature; (5) After filtration, ethanol and deionized water washing, the final product is obtained on filter paper, and the final product is placed in a vacuum drying oven at a temperature of 80℃ and dried for 12 hours, and finally a yellow-brown Fe2(MoO4)3 powder is obtained, and its SEM image is as follows Figure 3 The nanosheets in the iron molybdate microspheres not only increase the specific surface area of ​​the iron molybdate microspheres and improve the degree of gas bonding, thereby improving gas detection sensitivity; but also, under the action of an alternating magnetic field, these nanosheets can also produce micro-vibrations, changing the atmosphere around the nanosheets, which helps to further shorten the response and recovery time.

[0034] Iron molybdate is an n-type semiconductor whose resistance depends primarily on electrons, which are the primary charge carriers. In air, oxygen molecules in the air bind to oxygen vacancies on the surface of iron molybdate. The oxygen molecules capture free electrons in the conduction band of the iron molybdate and ionize into chemically adsorbed oxygen ions. This reduces the electron concentration in the space charge region on the surface of the iron molybdate, forming an electron barrier or electron depletion layer, resulting in the high resistance of iron molybdate in air (denoted as Ra). In ethanol, ethanol molecules react with the chemically adsorbed oxygen anions, releasing the electrons captured by the oxygen molecules back into the conduction band of the iron molybdate, causing the resistance of the iron molybdate to decrease (denoted as Rg). The ratio of Ra to Rg is recorded as sensitivity S, that is, S = Ra / Rg.

[0035] Preferably, the magnetic field-enhanced molybdate ethanol sensing system of the present invention further includes a second coil 6, which is fixed to the outer wall of the pipe 1 below the gas sensor 4. When energized, the second coil 6 generates an alternating magnetic field that acts on the gas sensor 4. The second coil 6 is annular in shape. The second coil 6 is also connected to an external AC circuit, generating an alternating magnetic field at the gas sensor 4. This alternating magnetic field also acts on the iron molybdate microspheres, causing them to produce stronger microvibrations and generating stronger microairflow near the microspheres, further shortening response and recovery times and improving sensing efficiency.

[0036] Preferably, the first coil 5 and the second coil 6 are connected in series, and the strong magnetic field is confined between the first coil 5 and the second coil 6, that is, the position where the gas sensor 4 is located, so that the iron molybdate microspheres produce stronger micro-vibrations, further shortening the response and recovery time.

[0037] In addition, the first coil 5, the second coil 6, and the interdigitated electrode 43 in the present invention are all annular, which is conducive to generating a stronger magnetic field at the molybdate, causing the molybdate to produce stronger micro-vibrations and generating stronger micro-airflow near the molybdate, so that both the oxidizing gas and the reducing gas can react quickly with the molybdate, further shortening the response and recovery time.

[0038] In summary, the present invention provides a magnetic field-enhanced molybdate ethanol sensing system, comprising a pipeline 1, an air inlet 2, an air outlet 3, and a gas sensitive element 4, wherein the air inlet 2 and the air outlet 3 are respectively arranged at both ends of the pipeline 1, and the gas sensitive element 4 is arranged in the pipeline 1, and the gas sensitive element 4 comprises a substrate, a heating coil 41, a heating electrode 42, an interdigitated electrode 43, a measuring electrode 44, and molybdate, wherein the heating coil 41, the heating electrode 42, the interdigitated electrode 43, and the measuring electrode 44 are placed on the substrate, the two ends of the heating coil 41 are connected to the heating electrode 42, the interdigitated electrode 43 is connected to the measuring electrode 44, and the molybdate is placed on the interdigitated electrode 43; in addition, the magnetic field-enhanced molybdate ethanol sensing system of the present invention also comprises a first coil 5, which generates an alternating magnetic field when energized to act on the molybdate, causing the molybdate to generate micro-vibrations and a micro-airflow near the molybdate, so that the molybdate is quickly coated in the oxidizing gas or the reducing gas, shortening the response and recovery time, and improving the efficiency of ethanol gas sensing. The inventive concept proposed in the present invention can not only improve the efficiency of ethanol gas sensing, but also has guiding significance for improving the efficiency of other gas sensing, and has good application prospects in the field of gas sensing technology.

[0039] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A magnetic field enhanced molybdate ethanol sensing system, comprising a pipeline, an air inlet, an air outlet, and a gas sensor, wherein the air inlet and the air outlet are respectively arranged at both ends of the pipeline, the gas sensor is arranged in the pipeline, the gas sensor comprises a substrate, a heating coil, a heating electrode, an interdigital electrode, a measuring electrode, and a molybdate, wherein the heating coil, the heating electrode, the interdigital electrode, and the measuring electrode are placed on the substrate, the two ends of the heating coil are connected to the heating electrodes, the interdigital electrodes are connected to the measuring electrodes, and the molybdate is placed on the interdigital electrodes, characterized in that: It also includes a first coil, which generates an alternating magnetic field to act on the molybdate when energized. The molybdate is iron molybdate microspheres composed of nanosheets, and the nanosheets radiate outward from the center. The iron molybdate microspheres are prepared by a hydrothermal method.

2. The magnetic field-enhanced molybdate ethanol sensing system according to claim 1, wherein: The hydrothermal method is to react in a polytetrafluoroethylene reactor at a reaction temperature of 170 degrees Celsius and a reaction time of 12 hours.

3. The magnetic field-enhanced molybdate ethanol sensing system according to claim 1, wherein: The first coil is fixed on the upper side of the gas sensor on the inner wall of the pipeline.

4. The magnetic field-enhanced molybdate ethanol sensing system according to claim 1, wherein: The substrate is aluminum oxide, the heating coil is annular, the interdigital electrodes are placed in the heating coil, and the outer side of the interdigital electrodes is annular.

5. The magnetic field-enhanced molybdate ethanol sensing system according to claim 4, characterized in that: The distance between the interdigital electrodes is greater than 0.2 mm and less than 0.5 mm, and the diameter of the heating electrode is greater than 4 mm and less than 6 mm.

6. The magnetic field-enhanced molybdate ethanol sensing system according to any one of claims 1 to 5, characterized in that: The device further comprises a second coil, which is fixed on the outer wall of the pipe and below the gas sensor. When the second coil is energized, it generates an alternating magnetic field to act on the gas sensor.

7. The magnetic field-enhanced molybdate ethanol sensing system according to claim 6, wherein: The first coil and the second coil are connected in series.

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