Gas sensor for non-metal pipe and gas monitoring method

Abstract

The invention provides a gas sensor for a non-metal pipe and a gas monitoring method. The gas sensor comprises MXene-based gel fibers and is prepared through the following steps that dispersion liquid containing MXene nanosheets serves as spinning liquid, the spinning liquid is injected into a spinning guide pipe, a sleeve is arranged on the outer wall of the spinning guide pipe, and the temperature of the sleeve is gradually reduced in the flowing direction of the spinning liquid; injecting the spinning solution into a coagulating bath through a spinning guide pipe; and collecting the fiber formed in the coagulating bath, and at least performing swelling, liquid nitrogen freezing and freeze drying to obtain the MXene-based gel fiber. According to the gas monitoring method, the gas sensor is used for monitoring environment gas and / or permeable gas of the non-metal pipe. The gas sensor provided by the invention is high in sensitivity, can detect low-concentration gas, and is suitable for monitoring gas permeation of a non-metal pipe.

Description

Technical Field

[0001] The invention relates to a gas sensor for a non-metallic pipe and a gas monitoring method, belonging to the technical field of gas sensors. Background Art

[0002] Pipeline transportation plays an important role in industrial production, and most media are transported through pipelines. CO is generated in the process of oil field exploitation, gas transportation and sewage discharge. 2 NH 3 , CH 4 , H 2 Corrosive media such as S will cause metal pipes to corrode and age, seriously affecting the environment and human safety. Therefore, non-metallic pipes have gradually attracted widespread attention due to their good corrosion resistance, and products have been developed for use in oilfield pipes, gas pipes and drainage pipes. As the oilfield mining environment becomes increasingly harsh, the mining depth increases, the impact of corrosive media becomes more obvious, and the toxic and harmful gases in the urban drainage process increase due to the increase in industrialization, the research and development of non-metallic pipe gas sensors for oilfields, gas and drainage fields is of great significance.

[0003] Connecting gas sensors to pipelines can achieve real-time monitoring of dangerous gases during oil extraction and transportation, gas transmission and drainage, thereby evaluating the barrier properties of non-metallic pipes, predicting the service life of pipelines, and monitoring the dynamic changes in corrosive gas content. In turn, the safety of oil extraction and transportation, gas transmission and drainage can be evaluated, which has important guiding significance for safe production.

[0004] At present, in order to solve the problem of monitoring gas permeation during the use of non-metallic pipes, the existing technology mainly uses the differential pressure method to measure gas permeation. CN215894320U discloses a full-size gas permeation detection device for non-metallic composite pipes. The device includes: a metal pressure autoclave for placing a test sample assembly, and a closed annular space is set between the metal pressure autoclave and the test sample assembly; a gas source, which is connected to the inlet of the non-metallic pipe and is used to provide gas to the test sample assembly; a metering booster system, which is arranged between the gas source and the test sample assembly, and is used to adjust the gas pressure output by the gas source; a gas detection system, which is arranged on the metal pressure autoclave, and is used to detect the gas in the annular space between the metal pressure autoclave and the test sample assembly. By inflating the inside of the non-metallic pipe and the annular space between the pipe and the outer cavity, and under long-term pressure maintenance, the test sample leakage detection is completed, and the gas permeation amount of the annular space under long-term pressure maintenance is recorded. However, it is not easy to realize real-time monitoring of gas by using the differential pressure method to measure gas permeation, and it is impossible to give an early warning of abnormal gas conditions in industrial production processes.

[0005] Two-dimensional transition metal carbon / nitride (MXene) is an emerging material with rich functional groups on its surface, which can serve as sites for gas adsorption and has excellent prospects as a gas-sensing material.

[0006] Liu et al. used the vacuum-assisted layer-by-layer assembly method to 3 C 2 T x MXene and silver nanowires were sprayed on silk fabric substrates to prepare conductive fabrics, and their applications in electromagnetic shielding, humidity monitoring and hydrophobicity were studied (Liu-Xin Liu, Wei Chen, Hao-Bin Zhang, Qi-Wei Wang, Fanglan Guan, Zhong-Zhen Yu. Flexible and multifunctional silk textiles with biomimetic leaf-like MXene / silver nanowire nanostructures for electromagnetic interference shielding, humidity monitoring, and self-derived hydrophobicity[J]. Advanced Functional Materials, 2019, 29, 1905197).

[0007] Li et al. used a high-efficiency vacuum filtration-assisted spraying method to prepare conductive polyaniline (PANI) / MXene / cotton fabrics (PMCFs) for acid / alkali responsive and tunable EMI shielding applications (Dan-Yang Li, Liu-Xin Liu, Qi-Wei Wang, Hao-Bin Zhang, Wei Chen, Guang Yin, and Zhong-Zhen Yu. Functional Polyaniline / MXene / Cotton Fabrics with Acid / Alkali Responsive and Tunable ElectromagneticInterference Shielding Performances[J]. ACS Appl. Mater. Interfaces 2022, 14, 12703-12712).

[0008] Kim et al. studied Ti 3 C 2 T xMXene materials have a superb signal-to-noise ratio when detecting low-concentration volatile organic compound gases, revealing their advantages in the field of gas sensing (Seon Joon Kim, Hyeong-Jun Koh, Chang E. Ren, Ohmin Kwon, Kathleen Maleski, Soo-Yeon Cho, Babak Anasori, Choong-Ki Kim, Yang-Kyu Choi, Jihan Kim, Yury Gogotsi, and Hee-Tae Jung. Metallic Ti 3 C 2 T x MXeneGas Sensors with Ultrahigh Signal-to-Noise Ratio[J].ACS Nano 2018,12,986-993). This study provides a theoretical basis for MXene as a gas-sensitive material, and compared with black scale, molybdenum disulfide and reduced graphene oxide, MXene shows better performance advantages in gas sensing.

[0009] The existing technology has not yet studied the application of MXene in non-metallic tube gas sensors, and further improving the gas response sensitivity of MXene-based materials remains one of the research hotspots in this field. Summary of the invention

[0010] To solve the above technical problems, the purpose of the present invention is to provide a gas sensor and a gas monitoring method for non-metallic pipes. The gas sensor provided by the present invention has high sensitivity and can detect low-concentration gas, and is suitable for monitoring gas permeation of non-metallic pipes.

[0011] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a gas sensor for a non-metallic tube, which includes a MXene-based gel fiber, and the MXene-based gel fiber is prepared by at least the following steps: using a dispersion containing MXene nanosheets as a spinning solution, injecting the spinning solution into a spinning tube, the outer wall of the spinning tube is provided with a sleeve, and the temperature of the sleeve gradually decreases along the flow direction of the spinning solution; the spinning solution is injected into a coagulation bath through the spinning tube; and the fibers formed in the coagulation bath are collected and at least swollen, liquid nitrogen frozen and freeze-dried to obtain the MXene-based gel fiber.

[0012] According to a specific embodiment of the present invention, preferably, the dispersion containing MXene nanosheets includes a dispersion of MXene nanosheets, a dispersion of MXene nanosheets and GO (graphene oxide) nanosheets, or a dispersion of MXene nanosheets and sodium alginate. More preferably, the dispersion containing MXene nanosheets is a dispersion of MXene nanosheets and GO nanosheets or a dispersion of MXene nanosheets and sodium alginate. It can be understood by those skilled in the art that when the dispersion is a dispersion of MXene nanosheets, the MXene-based gel fiber is a MXene gel fiber; when the dispersion is a dispersion of MXene nanosheets and GO nanosheets, the MXene-based gel fiber is a MXene / GO composite gel fiber; when the dispersion is a dispersion of MXene nanosheets and sodium alginate, the MXene-based gel fiber is a MXene / alginate composite gel fiber.

[0013] According to a specific embodiment of the present invention, preferably, the MXene nanosheets include Ti 3 C 2 T x MXene nanosheets.

[0014] According to a specific embodiment of the present invention, preferably, the MXene nanosheet is prepared by the following steps: treating the MAX phase with a mixed solution of LiF and HCl, and obtaining the MXene nanosheet after ultrasonic treatment. The MAX phase used is preferably a titanium aluminum carbon compound (Ti 3 AlC 2 ).

[0015] According to a specific embodiment of the present invention, preferably, the concentration of the MXene nanosheets in the dispersion of the MXene nanosheets is 80 to 180 mg / mL, more preferably 110 to 150 mg / mL.

[0016] According to a specific embodiment of the present invention, preferably, the solvent in the dispersion of the MXene nanosheets includes dimethyl sulfoxide (DMSO) and / or N,N-dimethylformamide (DMF).

[0017] According to a specific embodiment of the present invention, preferably, the total concentration of MXene nanosheets and GO nanosheets in the dispersion of MXene nanosheets and GO nanosheets is 70-160 mg / mL, more preferably 100-140 mg / mL, and the mass ratio of MXene nanosheets to GO nanosheets is 1:9-8:2. More preferably, the thickness of the GO nanosheet is less than 2 nm, and the transverse diameter of the sheet is 8-80 μm. Among them, the transverse diameter of the sheet of the GO nanosheet generally refers to the maximum value of the straight-line distance between any two points on the nanosheet.

[0018] According to a specific embodiment of the present invention, preferably, the solvent in the dispersion of the MXene nanosheets and GO nanosheets comprises dimethyl sulfoxide and / or N,N-dimethylformamide.

[0019] According to a specific embodiment of the present invention, preferably, the total concentration of MXene nanosheets and sodium alginate in the dispersion of MXene nanosheets and sodium alginate is 50 to 150 mg / mL, more preferably 80 to 130 mg / mL, and the mass ratio of MXene nanosheets to sodium alginate is 1:9 to 9:1.

[0020] According to a specific embodiment of the present invention, preferably, the solvent in the dispersion of MXene nanosheets and sodium alginate includes water.

[0021] According to a specific embodiment of the present invention, preferably, the spinning conduit has a length of 0.3 to 1 m and an inner diameter of 0.30 to 1.3 mm.

[0022] According to a specific embodiment of the present invention, preferably, the sleeve provided on the outer wall of the spinning duct is a metal tube, and the temperature of the sleeve is gradually reduced along the flow direction of the spinning solution by the following method: a cold source is provided at one end of the sleeve, so that the sleeve conducts cold energy in the opposite direction of the flow direction of the spinning solution, so that the temperature is gradually reduced along the flow direction of the spinning solution. Specifically, the sleeve can be a copper tube. Specifically, the spinning duct and the sleeve can be arranged vertically, and the cold source is provided at the lower end of the sleeve, so that the sleeve conducts cold energy from bottom to top, so that the temperature is gradually reduced from top to bottom. In addition, it can be understood by those skilled in the art that there should be an appropriate gap between the sleeve and the spinning duct to prevent the spinning solution from freezing and solidifying and being unable to flow.

[0023] According to a specific embodiment of the present invention, preferably, the temperature of the cold source provided at the lower end of the sleeve is -200° C. to -100° C. Specifically, the cold source may be liquid nitrogen (-196° C.).

[0024] According to a specific embodiment of the present invention, preferably, the coagulation bath comprises one or a combination of aqueous ammonium chloride solution, aqueous calcium chloride solution, aqueous aluminum chloride solution, aqueous ammonia, isopropanol, ethyl acetate, acetone, acetic acid, n-hexane, dichloromethane, a mixed solution of dimethyl sulfoxide and acetic acid, and a mixed solution of isopropanol and water. More preferably, when the dispersion containing MXene nanosheets is a dimethyl sulfoxide dispersion of MXene nanosheets, or a dimethyl sulfoxide dispersion of MXene nanosheets and GO nanosheets, the coagulation bath is a mixture of dimethyl sulfoxide and acetic acid, and further preferably, the volume ratio of dimethyl sulfoxide to acetic acid in the mixture is 1:3 to 3:1; when the dispersion containing MXene nanosheets is an N,N-dimethylformamide dispersion of MXene nanosheets, or an N,N-dimethylformamide dispersion of MXene nanosheets and GO nanosheets, the coagulation bath is a mixture of isopropanol and water, and further preferably, the volume ratio of isopropanol to water in the mixture is 1:2 to 3:1; when the dispersion containing MXene nanosheets is an aqueous dispersion of MXene nanosheets and sodium alginate, the coagulation bath is an aqueous solution of ammonium chloride or an aqueous solution of calcium chloride, and its mass concentration is 0.5 to 1%. For the spinning solution of MXene or MXene / GO inorganic nanomaterials, the present invention preferably uses an organic solvent such as DMSO for dispersion, and preferably uses a mixture of DMSO and acetic acid as a coagulation bath. DMSO can appropriately slow down the coagulation rate of acetic acid on the fiber, and coagulation in such a weak coagulation bath makes it easier for the fiber to present a porous structure. For MXene / sodium alginate spinning solution, the present invention preferably uses water as a solvent, and preferably forms it in an ion coagulation bath. During the forming process, the polymer alginate can be used as a crosslinking agent and can also play a structural support role; at the same time, the present invention controls the concentration of salts in the ion coagulation bath, which can make the fiber undergo an appropriate degree of crosslinking and gelation during the forming process.

[0025] According to a specific embodiment of the present invention, preferably, the fibers formed in the coagulation bath are collected and washed, and then naturally dried, the dried fibers are swollen, the swollen fibers are placed in liquid nitrogen for freezing, and then freeze-dried, and then vacuum dried to obtain the MXene-based gel fibers.

[0026] According to a specific embodiment of the present invention, preferably, the fibers formed in the coagulation bath are collected and washed with a mixture of ethanol and water. More preferably, the volume ratio of ethanol to water in the mixture is 1:3 to 3:1, and further preferably 2:1.

[0027] According to a specific embodiment of the present invention, preferably, the time for naturally drying the fibers formed in the coagulation bath after being collected and washed is 0.5 to 1 day.

[0028] According to a specific embodiment of the present invention, preferably, the swelling adopts a mixture of alcohol and water, more preferably a mixture of ethanol and water, and the volume ratio of ethanol to water in the mixture is 3:4 to 1:3, and more preferably 1:1.

[0029] According to a specific embodiment of the present invention, preferably, the dried fiber is immersed in a mixture of alcohol and water for swelling for 2 to 5 minutes. According to a specific embodiment of the present invention, preferably, the swollen fiber is placed in liquid nitrogen for freezing for 30 to 60 minutes.

[0030] According to a specific embodiment of the present invention, preferably, the freeze drying temperature is -45°C to -60°C. The freeze drying can be performed under vacuum conditions. More preferably, the freeze drying time is 2 to 4 days.

[0031] According to a specific embodiment of the present invention, preferably, the vacuum drying temperature is 40 to 70° C. More preferably, the vacuum drying time is 0.5 to 2 days.

[0032] According to a specific embodiment of the present invention, preferably, the gas sensor for non-metallic tubes includes an external gas sensor, a wall-attached gas sensor or an embedded gas sensor; the external gas sensor is arranged outside the non-metallic tube, the wall-attached gas sensor is attached to the outer wall of the non-metallic tube, and the embedded gas sensor is arranged between layers in the non-metallic tube. More preferably, the gas sensor for non-metallic tubes is an external gas sensor.

[0033] According to a specific embodiment of the present invention, preferably, the wall-attached gas sensor at least includes a MXene-based gel fiber sensing element; the MXene-based gel fiber sensing element includes a substrate, a plurality of the MXene-based gel fibers, and an electrode, the plurality of the MXene-based gel fibers and the electrode are both arranged on the substrate, and the electrode is arranged at both ends of the axial direction of the plurality of the MXene-based gel fibers; the plurality of the MXene-based gel fibers and the electrode are attached to the outer wall of the non-metallic tube. More preferably, the wall-attached gas sensor may also include a sealing cover, the sealing cover is arranged on the outer side of the substrate, and is used to seal the MXene-based gel fiber sensing element to the outer wall of the non-metallic tube.

[0034] According to a specific embodiment of the present invention, preferably, the embedded gas sensor includes a MXene-based gel fiber sensing element; the MXene-based gel fiber sensing element includes a substrate, a plurality of the MXene-based gel fibers and an electrode, the plurality of the MXene-based gel fibers and the electrode are arranged on the substrate, and the electrode is arranged at both ends of the axial direction of the plurality of the MXene-based gel fibers; the plurality of the MXene-based gel fibers and the electrode are attached to the outer surface of the barrier layer in the non-metallic tube. Generally speaking, the non-metallic tube is a multi-layer composite tube, which may include an inner lining layer, a barrier layer, a reinforcement layer, etc. from the inside to the outside. The present invention does not impose special restrictions on the multi-layer composite structure of the non-metallic tube, and only arranges the embedded gas sensor on the outer surface of the barrier layer.

[0035] According to a specific embodiment of the present invention, preferably, the external gas sensor comprises: a MXene-based gel fiber sensing element, a sealing cover, a first air duct and a second air duct;

[0036] The MXene-based gel fiber sensing element comprises a chamber, a substrate, a plurality of the MXene-based gel fibers, and a pair of electrodes. The plurality of the MXene-based gel fibers and the electrodes are arranged on the substrate and placed in the chamber, and the pair of electrodes are respectively connected to the two ends of the axial direction of the plurality of the MXene-based gel fibers; the chamber wall of the chamber is provided with a first gas inlet and a first gas outlet;

[0037] The sealing cover is an annular shell, which is used to seal and cover the part of the non-metallic pipe to be inspected; the sealing cover is provided with a second gas outlet and a second gas inlet;

[0038] One end of the first gas duct is connected to the second gas outlet, and the other end is connected to the first gas inlet; one end of the second gas duct is connected to the first gas outlet, and the other end is connected to the second gas inlet.

[0039] According to a specific embodiment of the present invention, in actual application, after the MXene-based gel fiber sensing element is energized, it converts changes in gas content into changes in resistance, and can be connected to a computer for communication, thereby realizing real-time monitoring of the ambient gas and / or permeating gas of the non-metallic pipe.

[0040] According to a specific embodiment of the present invention, preferably, the MXene-based gel fiber sensing element includes 2 to 10 MXene-based gel fibers connected in parallel, and more preferably 3 to 6 MXene-based gel fibers.

[0041] According to a specific embodiment of the present invention, preferably, the electrode includes one of a copper electrode, a silver electrode, a gold electrode, a platinum electrode, a titanium electrode, a nickel electrode or an aluminum electrode.

[0042] According to a specific embodiment of the present invention, preferably, the sealing cover includes an upper sealing cover and a lower sealing cover, and the upper sealing cover and the lower sealing cover are both semi-annular shell structures. The upper sealing cover and the lower sealing cover are coupled and connected to form a circular connecting port, and the circular connecting port is used to allow the non-metallic pipe to pass through, and after the upper sealing cover and the lower sealing cover are coupled and connected, a closed annular space is formed between the outer wall of the non-metallic pipe portion to be inspected.

[0043] According to a specific embodiment of the present invention, preferably, the upper sealing cover is provided with the second gas outlet, and the lower sealing cover is provided with the second gas inlet.

[0044] According to a specific embodiment of the present invention, preferably, the first gas inlet and the first gas outlet are respectively located at two ends of the axial direction of the MXene-based gel fiber.

[0045] According to a specific embodiment of the present invention, preferably, a gas pump is provided on the first air duct.

[0046] According to a specific embodiment of the present invention, the external gas sensor can mainly detect the permeation gas of the entire non-metallic tube, the wall-attached gas sensor can mainly detect the ambient gas and permeation gas of the non-metallic tube, and the embedded gas sensor can mainly detect the permeation gas of the non-metallic tube.

[0047] The present invention preferably adopts an external gas sensor, and the closed annular space outside the non-metallic tube is connected to the MXene-based gel fiber sensing element through the first air duct and the second air duct. The permeated gas of the non-metallic tube enters the MXene-based gel fiber sensing element through the first air duct, and the change of gas content is converted into a change of resistance by using the conductive properties of the MXene-based gel fiber. The resistance change signal is transmitted to the computer to realize the real-time monitoring of the permeated gas of the non-metallic tube. The signal of the gas sensor of the present invention can be transmitted to the monitoring room of the base in real time. For example, a computer can be set near the gas sensor, and a computer can also be set in the monitoring room. In this way, data changes can be observed at the actual monitoring position and the monitoring room. At the same time, the gel fibers in the MXene-based gel fiber sensing element are preferably arranged in parallel, which can increase the contact area between the gel fibers and the gas, reduce the total resistance, and thus improve the sensitivity of the response. In addition, the setting of the gas pump on the first air duct allows the gas to flow in a single direction. Moreover, by respectively arranging the second gas outlet and the second gas inlet on the upper sealing cover and the lower sealing cover, the maximum vertical distance between the second gas outlet and the second gas inlet is maintained, which can make the gas flow more fully. In addition, the present invention preferably adopts an external gas sensor, which can ensure the long-term use of the gas sensor by conveniently replacing the MXene-based gel fiber sensing element.

[0048] The present invention provides a gas sensor for a non-metallic pipe. The gas sensor includes a MXene-based gel fiber sensing element and is a resistive gas sensor. The gas sensor is connected to the non-metallic pipe and utilizes the conductive properties of the MXene-based gel fiber to convert gas changes into resistance signal changes, which can intuitively display the gas permeation of the non-metallic pipe and monitor the gas permeation of the non-metallic pipe in real time.

[0049] The present invention uses MXene as a gas-sensitive material. MXene has two-dimensional layered structure, single-atom thickness, large specific surface area, high conductivity, adjustable band gap and other characteristics. Studies have confirmed that MXene can be used for gas detection. n+1 X n T x represents its structure, in which transition metal atoms (M) are stacked into a honeycomb two-dimensional lattice; carbon and / or nitrogen (X) occupy the octahedral sites of adjacent M layers; T x It represents the end group connected to M, and n varies from 1 to 4 according to the number of M and X layers. Currently, the most mature MXene material is Ti 3 C 2 T x However, the gas response sensitivity of MXene materials in the prior art needs to be further improved.

[0050] The present invention creatively adopts low-temperature wet freezing technology to prepare MXene-based gel fibers. The present invention is provided with a sleeve on the outer wall of the spinning conduit, and the temperature of the sleeve is gradually reduced along the flow direction of the spinning solution, so that ice crystals that grow in an orderly manner can be formed in the spinning solution, and these ice crystals can play a role in pore formation during the formation of the gel fiber. At the same time, the present invention uses a spinning conduit with a length of 0.3 to 1m and an inner diameter of 0.30 to 1.3mm, which plays a role in size limitation. The spinning solution will gradually be oriented during the flow process in the spinning conduit, which is beneficial to improve the orientation of the fiber structure. In addition, the present invention washes and naturally dries the hydrogel fiber formed in the coagulation bath, then immerses it in a mixed solution of alcohol and water for swelling, and then quenches it in a liquid nitrogen environment at -196°C, so that the hydrogel fiber is frozen into a solid state containing ice crystals, and then freezes and dries at -45°C to -60°C. During the process of freeze drying, the ice crystals sublimate and leave numerous gaps. Thanks to the ordered ice crystal band structure formed in the spinning solution, the MXene-based gel fiber finally obtained has a more regular pore structure. The inventors of this case surprisingly found that the MXene-based gel fiber prepared by the low-temperature wet freezing technology of the present invention has a higher gas response sensitivity than the MXene-based gel fiber prepared by the method in the prior art, and is suitable for detecting CO 2 NH 3 , CH 4 , H 2 S.H. 2 O and H 2 And other gases.

[0051] A second aspect of the present invention provides a gas monitoring method, which comprises the following steps: using the above-mentioned gas sensor for non-metallic pipes to monitor the ambient gas and / or permeated gas of the non-metallic pipe.

[0052] According to a specific embodiment of the present invention, preferably, the non-metallic pipe includes one or a combination of oilfield pipes, gas pipes, drainage pipes and the like.

[0053] According to a specific embodiment of the present invention, preferably, the gas detected by the gas sensor includes CO 2 NH 3 , CH 4 , H 2 S.H. 2 O and H 2 One or a combination of the above.

[0054] According to a specific embodiment of the present invention, preferably, the gas monitoring method comprises the following steps:

[0055] (1) Preparation of MXene-based gel fibers;

[0056] (2) assembling a gas sensor using the MXene-based gel fiber;

[0057] (3) The gas sensor is used to detect the ambient gas and / or permeated gas of the non-metallic pipe, and the signal obtained by the gas sensor is transmitted to a computer to achieve real-time monitoring of the ambient gas and / or permeated gas of the non-metallic pipe.

[0058] In summary, the present invention provides a gas sensor and a gas monitoring method for non-metallic pipes. The technical solution of the present invention has at least the following beneficial effects: the gas sensor of the present invention includes a MXene-based gel fiber, which is prepared by low-temperature wet freezing technology, has a relatively regular porous structure and a large specific surface area, and its monofilament length is adjustable. The low-temperature wet freezing technology of the present invention enhances the gel structure of the fiber and improves the porosity of the fiber. The contact area between the MXene-based gel fiber of the present invention and the gas is larger, and the sensitivity of its gas response is higher. The gas sensor of the present invention has high sensitivity, can detect low-concentration gas, and has strong stability in gas detection. It is applied to the fields of oil transportation, gas transportation, drainage, etc., and can monitor the environmental gas and / or permeated gas of non-metallic pipes in real time. According to the different setting positions of the gas sensor of the present invention, the content of environmental gas and / or permeated gas at different positions of the non-metallic pipe can be detected. According to the monitoring results of the gas sensor of the present invention, the design and development of materials and structures of non-metallic pipes can be guided, and the danger of gas penetration or leakage in industrial production can be warned. The signal of the gas sensor of the present invention can be transmitted to the monitoring room of the base in real time, which has important research significance for realizing the construction of smart oil fields and digital pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a schematic diagram of the structure of the external gas sensor provided in Example 1.

[0060] Figure 2 is the MAX phase Ti in Example 1 3 AlC 2 and Ti 3 C 2 T x Scanning electron microscope image of MXene nanosheets.

[0061] Figure 3 This is a scanning electron microscope photograph of the cross-sectional pore structure morphology of the pure MXene gel fiber in Example 1.

[0062] Figure 4 This is a scanning electron microscope photograph of the cross-sectional pore structure morphology of the MXene / GO composite gel fiber in Example 2.

[0063] Figure 5 This is a scanning electron microscope photograph of the cross-sectional pore structure morphology of the pure MXene gel fiber in Comparative Example 1.

[0064] Figure 6 This is a scanning electron microscope photograph of the cross-sectional pore structure morphology of the MXene / GO composite gel fiber in Comparative Example 2.

[0065] Description of Figure Numbers:

[0066] 1-MXene-based gel fiber sensing element; 2-sealing cover; 3-first air duct; 4-second air duct; 5-gas pump;

[0067] 11-chamber; 12-substrate; 13-MXene-based gel fiber; 14-electrode; 111-first gas inlet; 112-first gas outlet;

[0068] 21 - second gas outlet; 22 - second gas inlet; 23 - upper sealing cover; 24 - lower sealing cover. DETAILED DESCRIPTION

[0069] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0070] The raw materials used in the following examples and comparative examples include:

[0071] Titanium aluminum carbon compound (Ti 3 AlC 2 , 400 mesh): purchased from Jilin Yiyi Technology Co., Ltd.

[0072] Lithium fluoride (LiF, 99.99%): purchased from Shanghai Aladdin.

[0073] Hydrochloric acid (HCl, 37%): purchased from Beijing Chemical Plant.

[0074] Dimethyl sulfoxide (DMSO, 99%): purchased from Tianjin Damao Chemical.

[0075] N,N-Dimethylformamide (DMF, 99%): purchased from Tianjin Damao Chemical.

[0076] Graphene oxide (GO, lateral diameter of the sheet is 8 to 80 μm, thickness is less than 2 nm): purchased from Hangzhou Gaoxin Technology Co., Ltd.

[0077] Sodium alginate (SA, 1% viscosity 5000 mPa·s): purchased from McLean.

[0078] Acetic acid (AC, 99.9%): purchased from Tianjin Damao Chemical.

[0079] Ammonium chloride (NH 4 Cl): Purchased from Tianjin Guangfu.

[0080] Calcium chloride (CaCl 2 ): Purchased from Guangfu, Tianjin.

[0081] Example 1

[0082] This embodiment provides a gas sensor for a non-metallic tube, which includes a MXene-based gel fiber, wherein the MXene-based gel fiber is a pure MXene gel fiber prepared by the low-temperature wet freezing technology of the present invention. The low-temperature wet freezing technology at least comprises the following steps: using a mixed solution of LiF and HCl (which is obtained by dissolving 8g of LiF in 100mL of a 9M HCl solution) to freeze Ti in a constant temperature water bath environment at 35°C. 3 AlC 2 Etching was performed for about 40 hours, followed by ultrasonic stripping in a nitrogen atmosphere for about 1 hour, and finally centrifugation was performed at 3500 rpm for 1 hour to obtain a single layer or a few layers of Ti 3 C 2 T x Mixture of MXene nanosheets; Ti 3 C 2 T x The MXene nanosheets were centrifuged at high speed and prepared into a 120 mg / mL dispersion with DMSO as solvent by solvent replacement method; the dispersion was used as spinning solution, and the spinning solution was uniformly injected into a vertical spinning tube through an injection pump. The spinning tube had a length of 0.5 m, an inner diameter of 0.80 mm, and an injection speed of 200 μL min -1 The outer wall of the spinning tube is provided with a sleeve, and there should be an appropriate gap between the sleeve and the spinning tube. The sleeve is a copper tube, and liquid nitrogen is provided at the lower end of the sleeve. The sleeve conducts cold from bottom to top, so that the temperature of the sleeve gradually decreases from top to bottom; the spinning solution is injected into the coagulation bath through the spinning tube, and the coagulation bath is a mixture of DMSO and acetic acid (wherein the volume ratio of DMSO and acetic acid is 1:1); the fiber formed in the coagulation bath is collected, and is soaked and washed twice with a mixture of ethanol and water (wherein the volume ratio of ethanol and water is 2:1), and then naturally dried for 0.5 day at room temperature; the dried fiber is immersed in a mixture of ethanol and water (wherein the volume ratio of ethanol and water is 1:1) for swelling for 2 minutes, and then the swollen fiber is placed in liquid nitrogen for freezing for 30 minutes, and then placed in a freeze dryer at -57°C for drying for 3 days, and then dried in a vacuum oven at 60°C for 1 day to obtain pure MXene gel fiber.

[0083] The gas sensor for non-metallic pipes provided in this embodiment is an external gas sensor, such as Figure 1 As shown, it includes: a MXene-based gel fiber sensing element 1, a sealing cover 2, a first air guide tube 3, a second air guide tube 4 and a gas pump 5;

[0084] The MXene-based gel fiber sensing element 1 comprises a chamber 11, a substrate 12, four parallel MXene-based gel fibers 13, and a pair of electrodes 14. The four parallel MXene-based gel fibers 13 and the electrodes 14 are arranged on the substrate 12 and placed in the chamber 11. The pair of electrodes 14 are respectively connected to the two ends of the axial direction of the four parallel MXene-based gel fibers 13. The chamber wall of the chamber 11 is provided with a first gas inlet 111 and a first gas outlet 112.

[0085] The sealing cover 2 is an annular shell, which is used to seal and cover the part of the non-metallic tube to be inspected; the sealing cover 2 is provided with a second gas outlet 21 and a second gas inlet 22;

[0086] One end of the first gas duct 3 is connected to the second gas outlet 21, and the other end is connected to the first gas inlet 111;

[0087] One end of the second gas duct 4 is connected to the first gas outlet 112 , and the other end is connected to the second gas inlet 22 ;

[0088] The gas pump 5 is disposed on the first gas pipe 3 .

[0089] In this embodiment, the pair of electrodes 14 are both copper electrodes.

[0090] In this embodiment, the sealing cover 2 includes an upper sealing cover 23 and a lower sealing cover 24. The upper sealing cover 23 and the lower sealing cover 24 are both semi-annular shell structures. The upper sealing cover 23 and the lower sealing cover 24 are connected to form a circular connecting port, which is used to allow the non-metallic pipe to pass through. After the upper sealing cover 23 and the lower sealing cover 24 are connected to each other, a closed annular space is formed between the outer wall of the non-metallic pipe portion to be inspected.

[0091] In this embodiment, the upper sealing cover 23 is provided with a second gas outlet 21 , and the lower sealing cover 24 is provided with a second gas inlet 22 .

[0092] In this embodiment, the first gas inlet 111 and the first gas outlet 112 are respectively located at two ends of the axial direction of the MXene-based gel fiber 13 .

[0093] Figure 1A digital multimeter and a computer are also shown. The digital multimeter can be used as a signal converter to convert the gas change signal of the MXene-based gel fiber sensing element 1 into a resistance signal, thereby testing the sensitivity of the gas sensor of this embodiment, and inputting the converted signal into a computer to realize real-time monitoring of the ambient gas and / or permeated gas of the non-metallic pipe.

[0094] This embodiment monitors the ambient gas and / or permeated gas of the polyethylene pipeline. In actual application, the MXene-based gel fiber sensing element 1 can be placed on the ground near the polyethylene pipeline, and the permeation of the pipeline is introduced into the MXene-based gel fiber sensing element 1 through the first air guide tube 3. The change in gas content causes the resistance signal of the MXene-based gel fiber sensing element 1 to change, so as to evaluate the gas permeability of the pipeline.

[0095] In order to test the sensitivity of the gas sensor of this embodiment, H2 diluted with nitrogen was introduced into the polyethylene pipe. 2 S gas, H in pipeline 2 The S gas content is 100 ppm. The gas sensor of this embodiment is used to detect the H permeated in the pipeline. 2 The content of S gas changes, and the resistance change of MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain H 2 Under the same conditions, nitrogen-diluted CH 4 Gas, CH in pipeline 4 The concentration is 600 ppm. The gas sensor of this embodiment is used to detect the CH 4 The content of the gas changes, and the resistance change of the MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain CH 4 The response value of H measured in this embodiment 2 S response value and CH 4 The absolute values ​​of the responses are shown in Table 1.

[0096] Table 1 Absolute values ​​of gas response of pure MXene gel fibers prepared by low-temperature wet freezing technology

[0097] <![CDATA[|ΔR / R 0 |(%,H 2 S)]]> <![CDATA[|ΔR / R 0 |(%,CH 4 )]]> Example 1 3.5 4.6

[0098] The raw material Ti used in this embodiment 3 AlC 2 and prepared Ti 3 C 2 T x Scanning electron microscope images of MXene nanosheets Figure 2 As shown, Figure 2 (a) is the MAX phase Ti3 AlC 2 Scanning electron microscope photo of Figure 2 (b) in the figure is Ti 3 C 2 T x Scanning electron microscope image of MXene nanosheets. Figure 3 This is a scanning electron microscope photograph of the cross-sectional pore structure morphology of the pure MXene gel fiber prepared in this example.

[0099] Example 2

[0100] This embodiment provides a gas sensor for a non-metallic tube, which includes a MXene-based gel fiber, wherein the MXene-based gel fiber is a MXene / GO composite gel fiber prepared by the low-temperature wet freezing technology of the present invention. The low-temperature wet freezing technology at least comprises the following steps: using a mixed solution of LiF and HCl (which is obtained by dissolving 8g of LiF in 100mL of a 9M HCl solution) to freeze Ti in a constant temperature water bath at 35°C. 3 AlC 2 Etching was performed for about 40 hours, followed by ultrasonic stripping in a nitrogen atmosphere for about 1 hour, and finally centrifugation was performed at 3500 rpm for 1 hour to obtain a single layer or a few layers of Ti 3 C 2 T x Mixture of MXene nanosheets; Ti 3 C 2 T x The MXene nanosheets were centrifuged at high speed and mixed with GO nanosheets by solvent replacement method to prepare a dispersion solution with a total concentration of MXene and GO of 100 mg / mL in DMSO as solvent, wherein the mass ratio of MXene nanosheets to GO nanosheets was 3:7; the dispersion solution was used as a spinning solution, and the spinning solution was uniformly injected into a vertically arranged spinning tube through an injection pump, wherein the spinning tube had a length of 0.5 m, an inner diameter of 0.80 mm, and an injection speed of 200 μL min -1The outer wall of the spinning tube is provided with a sleeve, and there should be an appropriate gap between the sleeve and the spinning tube. The sleeve is a copper tube, and liquid nitrogen is provided at the lower end of the sleeve. The sleeve conducts cold from bottom to top, so that the temperature of the sleeve gradually decreases from top to bottom; the spinning solution is injected into the coagulation bath through the spinning tube, and the coagulation bath is a mixture of DMSO and acetic acid (wherein the volume ratio of DMSO and acetic acid is 1:1); the fiber formed in the coagulation bath is collected, and is soaked and washed twice with a mixture of ethanol and water (wherein the volume ratio of ethanol and water is 2:1), and then naturally dried for 0.5 day at room temperature; the dried fiber is immersed in a mixture of ethanol and water (wherein the volume ratio of ethanol and water is 1:1) for swelling for 2 minutes, and then the swollen fiber is placed in liquid nitrogen for freezing for 30 minutes, and then placed in a freeze dryer at -57°C for drying for 3 days, and then dried in a vacuum oven at 60°C for 1 day to obtain MXene / GO composite gel fiber.

[0101] The gas sensor for non-metallic tubes provided in this embodiment is an external gas sensor, and its structure is the same as that of Embodiment 1.

[0102] In order to test the sensitivity of the gas sensor of this embodiment, H2 diluted with nitrogen was introduced into the polyethylene pipe. 2 S gas, H in pipeline 2 The S gas content is 100 ppm. The gas sensor of this embodiment is used to detect the H permeated in the pipeline. 2 The content of S gas changes, and the resistance change of MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain H 2 Under the same conditions, nitrogen-diluted CH 4 Gas, CH in pipeline 4 The concentration is 600 ppm. The gas sensor of this embodiment is used to detect the CH 4 The content of the gas changes, and the resistance change of the MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain CH 4 The response value of H measured in this embodiment 2 S response value and CH 4 The absolute values ​​of the responses are shown in Table 2.

[0103] Table 2 Absolute values ​​of gas response of MXene / GO composite gel fibers prepared by low-temperature wet freezing technology

[0104] <![CDATA[|ΔR / R 0 |(%,H 2 S)]]> <![CDATA[|ΔR / R 0 |(%,CH 4 )]]> Example 2 4.8 6.4

[0105] Figure 4 This is a scanning electron microscope photograph of the cross-sectional pore structure morphology of the MXene / GO composite gel fiber prepared in this example.

[0106] Example 3

[0107] The present embodiment provides a gas sensor for a non-metallic tube, which includes a MXene-based gel fiber, wherein the MXene-based gel fiber is a MXene / alginate composite gel fiber prepared by the low-temperature wet freezing technology of the present invention. The low-temperature wet freezing technology at least comprises the following steps: using a mixed solution of LiF and HCl (which is obtained by dissolving 8g of LiF in 100mL of a 9M HCl solution) to freeze Ti in a constant temperature water bath environment at 35°C. 3 AlC 2 Etching was performed for about 40 hours, followed by ultrasonic stripping in a nitrogen atmosphere for about 1 hour, and finally centrifugation was performed at 3500 rpm for 1 hour to obtain a single layer or a few layers of Ti 3 C 2 T x Mixture of MXene nanosheets; Ti 3 C 2 T x MXene nanosheets and sodium alginate are mixed to prepare a dispersion liquid with a total concentration of MXene nanosheets and sodium alginate of 90 mg / mL in water as a solvent, wherein the mass ratio of MXene nanosheets to sodium alginate is 9:1; the dispersion liquid is used as a spinning solution, and the spinning solution is uniformly injected into a vertically arranged spinning tube through an injection pump, wherein the spinning tube has a length of 0.3 m, an inner diameter of 1.3 mm, and an injection speed of 260 μL min -1 The outer wall of the spinning tube is provided with a sleeve, and there should be an appropriate gap between the sleeve and the spinning tube. The sleeve is a copper tube, and liquid nitrogen is provided at the lower end of the sleeve. The sleeve conducts cold from bottom to top, so that the temperature of the sleeve gradually decreases from top to bottom; the spinning solution is injected into a coagulation bath through the spinning tube, and the coagulation bath is an ammonium chloride aqueous solution with a mass concentration of 1%; the fiber formed in the coagulation bath is collected, and is soaked and washed twice with a mixed solution of ethanol and water (wherein the volume ratio of ethanol to water is 2:1), and then naturally dried at room temperature for 1 day; the dried fiber is immersed in a mixed solution of ethanol and water (wherein the volume ratio of ethanol to water is 1:1) for swelling for 3 minutes, and then the swollen fiber is placed in liquid nitrogen for freezing for 40 minutes, and then placed in a freeze dryer at -45°C for drying for 4 days, and then vacuum dried at 70°C for 1 day to obtain MXene / alginate composite gel fiber.

[0108] The gas sensor for non-metallic tubes provided in this embodiment is an external gas sensor, and its structure is the same as that of Embodiment 1.

[0109] In order to test the sensitivity of the gas sensor of this embodiment, NH 2 diluted with nitrogen was introduced into the polyethylene pipe. 3 Gas, NH in pipeline 3 The gas content is 700 ppm. The gas sensor of this embodiment is used to detect the NH 3 The content of the gas changes, and the resistance change of the MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain the NH 3 Under the same conditions, nitrogen-diluted H 2 O gas, H in pipeline 2 The O concentration is 700 ppm. The gas sensor of this embodiment is used to detect the H 2 The content of O gas changes, and the resistance change of MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain H 2 The response value of H O measured in this embodiment 2 S response value and CH 4 The absolute values ​​of the responses are shown in Table 3.

[0110] Table 3 Absolute values ​​of gas response of MXene / alginate composite gel fibers prepared by low-temperature wet freezing technology

[0111] <![CDATA[|ΔR / R 0 |(%,NH 3 )]]> <![CDATA[|ΔR / R 0 |(%,H 2 O)]]> Example 3 12.8 5.2

[0112] Example 4

[0113] This embodiment provides a gas sensor for a non-metallic tube, which includes a MXene-based gel fiber, which is a MXene / GO composite gel fiber prepared by the low-temperature wet freezing technology of the present invention. The preparation method of the MXene / GO composite gel fiber is basically the same as that of Example 2, except that: the dispersion liquid is a dispersion liquid with a total concentration of MXene and GO of 70 mg / mL using DMF as a solvent, wherein the mass ratio of MXene nanosheets to GO nanosheets is 1:9; the length of the spinning duct is 0.8 m and the inner diameter is 0.50 mm; and the coagulation bath is a mixture of isopropanol and water (wherein the volume ratio of isopropanol to water is 3:1).

[0114] The gas sensor for non-metallic tubes provided in this embodiment is an external gas sensor, and its structure is the same as that of Embodiment 1.

[0115] In order to test the sensitivity of the gas sensor of this embodiment, CO diluted with nitrogen was introduced into the polyethylene pipe. 2 Gas, CO in pipeline 2 The gas content is 500ppm. The gas sensor of this embodiment is used to detect the CO permeation in the pipeline.2 The content of the gas changes, and the resistance change of the MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain the CO 2 Under the same conditions, nitrogen-diluted CH 4 Gas, CH in pipeline 4 The concentration is 500 ppm. The gas sensor of this embodiment is used to detect the CH 4 The content of the gas changes, and the resistance change of the MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain CH 4 The response value of H measured in this embodiment 2 S response value and CH 4 The absolute values ​​of the responses are shown in Table 4.

[0116] Table 4 Absolute values ​​of gas response of MXene / GO composite gel fibers prepared by low-temperature wet freezing technology

[0117] <![CDATA[|ΔR / R 0 |(%,CO 2 )]]> <![CDATA[|ΔR / R 0 |(%,CH 4 )]]> Example 4 4.2 4.8

[0118] Example 5

[0119] This embodiment provides a gas sensor for a non-metallic tube, which includes a MXene-based gel fiber, which is a MXene / GO composite gel fiber prepared by the low-temperature wet freezing technology of the present invention. The preparation method of the MXene / GO composite gel fiber is basically the same as that of Example 2, except that: the dispersion liquid is a dispersion liquid with a total concentration of MXene and GO of 160 mg / mL using DMSO as a solvent, wherein the mass ratio of MXene nanosheets to GO nanosheets is 8:2; the length of the spinning conduit is 0.3 m and the inner diameter is 0.60 mm.

[0120] The gas sensor for non-metallic tubes provided in this embodiment is an external gas sensor, and its structure is the same as that of Embodiment 1.

[0121] In order to test the sensitivity of the gas sensor of this embodiment, H2 diluted with nitrogen was introduced into the polyethylene pipe. 2 S gas, H in pipeline 2 The S gas content is 100 ppm. The gas sensor of this embodiment is used to detect the H permeated in the pipeline. 2 The content of S gas changes, and the resistance change of MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain H 2 Under the same conditions, nitrogen-diluted CH 4 Gas, CH in pipeline 4The concentration is 600 ppm. The gas sensor of this embodiment is used to detect the CH 4 The content of the gas changes, and the resistance change of the MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain CH 4 The response value of H measured in this embodiment 2 S response value and CH 4 The absolute values ​​of the responses are shown in Table 5.

[0122] Table 5 Absolute values ​​of gas response of MXene / GO composite gel fibers prepared by low-temperature wet freezing technology

[0123] <![CDATA[|ΔR / R 0 |(%,H 2 S)]]> <![CDATA[|ΔR / R 0 |(%,CH 4 )]]> Example 5 5.1 6.8

[0124] Example 6

[0125] The present embodiment provides a gas sensor for a non-metallic tube, which includes a MXene-based gel fiber, which is a MXene / alginate composite gel fiber prepared by the low-temperature wet freezing technology of the present invention. The preparation method of the MXene / alginate composite gel fiber is basically the same as that of Example 3, except that: the dispersion liquid is a dispersion liquid with a total concentration of MXene nanosheets and sodium alginate of 150 mg / mL in water as a solvent, wherein the mass ratio of MXene nanosheets to sodium alginate is 6:4; the length of the spinning duct is 0.4 m and the inner diameter is 0.6 mm; the coagulation bath is a calcium chloride aqueous solution with a mass concentration of 1%.

[0126] The gas sensor for non-metallic tubes provided in this embodiment is an external gas sensor, and its structure is the same as that of Embodiment 1.

[0127] In order to test the sensitivity of the gas sensor of this embodiment, H2 diluted with nitrogen was introduced into the polyethylene pipe. 2 S gas, H in pipeline 2 The S gas content is 100 ppm. The gas sensor of this embodiment is used to detect the H permeated in the pipeline. 2 The content of S gas changes, and the resistance change of MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain H 2 Under the same conditions, nitrogen-diluted CH 4 Gas, CH in pipeline 4 The concentration is 600 ppm. The gas sensor of this embodiment is used to detect the CH 4 The content of the gas changes, and the resistance change of the MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain CH 4 The response value of H measured in this embodiment2 S response value and CH 4 The absolute values ​​of the responses are shown in Table 6.

[0128] Table 6 Absolute values ​​of gas response of MXene / alginate composite gel fibers prepared by low-temperature wet freezing technology

[0129] <![CDATA[|ΔR / R 0 |(%,H 2 S)]]> <![CDATA[|ΔR / R 0 |(%,CH 4 )]]> Example 6 3.8 5.5

[0130] Example 7

[0131] This embodiment provides a gas sensor for a non-metallic tube, which includes a MXene-based gel fiber, which is a MXene / alginate composite gel fiber prepared by the low-temperature wet freezing technology of the present invention. The preparation method of the MXene / alginate composite gel fiber is basically the same as that of Example 3, except that: the dispersion liquid is a dispersion liquid with a total concentration of MXene nanosheets and sodium alginate of 50 mg / mL in water as a solvent, wherein the mass ratio of MXene nanosheets to sodium alginate is 1:9; the length of the spinning tube is 1m, the inner diameter is 0.6mm, and the injection speed is 300μLmin -1 ; The coagulation bath is a calcium chloride aqueous solution with a mass concentration of 1%.

[0132] The gas sensor for non-metallic tubes provided in this embodiment is an external gas sensor, and its structure is the same as that of Embodiment 1.

[0133] In order to test the sensitivity of the gas sensor of this embodiment, H2 diluted with nitrogen was introduced into the polyethylene pipe. 2 S gas, H in pipeline 2 The S gas content is 80 ppm. The gas sensor of this embodiment is used to detect the H permeated in the pipeline. 2 The content of S gas changes, and the resistance change of MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain H 2 Under the same conditions, nitrogen-diluted CH 4 Gas, CH in pipeline 4 The concentration is 500 ppm. The gas sensor of this embodiment is used to detect the CH 4 The content of the gas changes, and the resistance change of the MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain CH 4 The response value of H measured in this embodiment 2 S response value and CH 4 The absolute values ​​of the responses are shown in Table 7.

[0134] Table 7 Absolute values ​​of gas response of MXene / alginate composite gel fibers prepared by low-temperature wet freezing technology

[0135] <![CDATA[|ΔR / R 0 |(%,H 2 S)]]> <![CDATA[|ΔR / R 0 |(%,CH 4 )]]> Example 7 3.1 4.3

[0136] Example 8

[0137] This embodiment provides a gas monitoring method, which includes the following steps:

[0138] (1) Preparation of MXene-based gel fibers

[0139] A dispersion containing MXene nanosheets is used as a spinning solution, and the spinning solution is injected into a vertically arranged spinning tube, the outer wall of the spinning tube is provided with a sleeve, and the temperature of the sleeve gradually decreases along the flow direction of the spinning solution; the spinning solution is injected into a coagulation bath through the spinning tube; the fibers formed in the coagulation bath are collected and washed, and then naturally dried, the dried fibers are immersed in a mixed solution of alcohol and water for swelling, the swollen fibers are placed in liquid nitrogen for freezing, and then freeze-dried, and then vacuum dried to obtain the MXene-based gel fiber;

[0140] (2) Assembling a gas sensor using the MXene-based gel fiber

[0141] A plurality of the MXene-based gel fibers and a pair of electrodes are placed in a chamber, wherein the pair of electrodes are respectively arranged at the two ends of the axial direction of the plurality of the MXene-based gel fibers, and the chamber wall of the chamber is provided with a first gas inlet and a first gas outlet, thereby obtaining a MXene-based gel fiber sensing element; the portion of the non-metallic tube to be detected is covered with a sealing cover, wherein the sealing cover is an annular shell and is provided with a second gas outlet and a second gas inlet; the second gas outlet and the first gas inlet are connected through a first gas duct; the first gas outlet and the second gas inlet are connected through a second gas duct, thereby obtaining the gas sensor;

[0142] (3) The gas sensor is used to detect the ambient gas and / or permeated gas of the non-metallic pipe, and the signal obtained by the gas sensor is transmitted to a computer to achieve real-time monitoring of the ambient gas and / or permeated gas of the non-metallic pipe.

[0143] In this embodiment, the dispersion containing MXene nanosheets includes a dispersion of MXene nanosheets, a dispersion of MXene nanosheets and GO nanosheets, or a dispersion of MXene nanosheets and sodium alginate. Preferably, the dispersion containing MXene nanosheets is a dispersion of MXene nanosheets and GO nanosheets or a dispersion of MXene nanosheets and sodium alginate. When the dispersion is a dispersion of MXene nanosheets, the MXene-based gel fiber is a MXene gel fiber; when the dispersion is a dispersion of MXene nanosheets and GO nanosheets, the MXene-based gel fiber is a MXene / GO composite gel fiber; when the dispersion is a dispersion of MXene nanosheets and sodium alginate, the MXene-based gel fiber is a MXene / alginate composite gel fiber.

[0144] In this embodiment, the MXene nanosheets include Ti 3 C 2 T x MXene nanosheets.

[0145] In this embodiment, the MXene nanosheets are prepared by the following steps: treating the MAX phase with a mixed solution of LiF and HCl, and then ultrasonically treating the MAX phase to obtain the MXene nanosheets. 3 AlC 2 ).

[0146] In this embodiment, the concentration of the MXene nanosheets in the dispersion of the MXene nanosheets is 80 to 180 mg / mL, preferably 110 to 150 mg / mL.

[0147] In this embodiment, the solvent in the dispersion of the MXene nanosheets includes dimethyl sulfoxide (DMSO) and / or N,N-dimethylformamide (DMF).

[0148] In this embodiment, the total concentration of MXene nanosheets and GO nanosheets in the dispersion of MXene nanosheets and GO nanosheets is 70-160 mg / mL, preferably 100-140 mg / mL, and the mass ratio of MXene nanosheets to GO nanosheets is 1:9-8:2. Preferably, the thickness of the GO nanosheet is less than 2 nm, and the transverse diameter of the sheet is 8-80 μm.

[0149] In this embodiment, the total concentration of MXene nanosheets and sodium alginate in the dispersion of MXene nanosheets and sodium alginate is 50 to 150 mg / mL, preferably 80 to 130 mg / mL, and the mass ratio of MXene nanosheets to sodium alginate is 1:9 to 9:1.

[0150] In this embodiment, the spinning tube has a length of 0.3 to 1 m and an inner diameter of 0.30 to 1.3 mm.

[0151] In this embodiment, the sleeve provided on the outer wall of the spinning duct is a metal tube, and the temperature of the sleeve is gradually reduced along the flow direction of the spinning solution by the following method: a cold source is provided at one end of the sleeve, so that the sleeve conducts cold energy in the opposite direction of the flow direction of the spinning solution, so that the temperature is gradually reduced along the flow direction of the spinning solution. Specifically, the sleeve can be a copper tube. Specifically, the spinning duct and the sleeve can be arranged vertically, and the cold source is provided at the lower end of the sleeve, so that the sleeve conducts cold energy from bottom to top, so that the temperature is gradually reduced from top to bottom. In addition, it can be understood by those skilled in the art that there should be an appropriate gap between the sleeve and the spinning duct to prevent the spinning solution from freezing and solidifying and being unable to flow.

[0152] In this embodiment, the temperature of the cold source arranged at the lower end of the sleeve is -200° C. to -100° C. Specifically, the cold source is liquid nitrogen (-196° C.).

[0153] In this embodiment, the coagulation bath includes one or a combination of aqueous ammonium chloride solution, aqueous calcium chloride solution, aqueous aluminum chloride solution, ammonia water, isopropanol, ethyl acetate, acetone, dimethyl sulfoxide, acetic acid, n-hexane, dichloromethane, a mixture of dimethyl sulfoxide and acetic acid, and a mixture of isopropanol and water. Preferably, when the dispersion containing MXene nanosheets is a dimethyl sulfoxide dispersion of MXene nanosheets, or a dimethyl sulfoxide dispersion of MXene nanosheets and GO nanosheets, the coagulation bath is a mixture of dimethyl sulfoxide and acetic acid, and further preferably, the volume ratio of dimethyl sulfoxide to acetic acid in the mixture is 1:3 to 3:1; when the dispersion containing MXene nanosheets is an N,N-dimethylformamide dispersion of MXene nanosheets, or an N,N-dimethylformamide dispersion of MXene nanosheets and GO nanosheets, the coagulation bath is a mixture of isopropanol and water, and further preferably, the volume ratio of isopropanol to water in the mixture is 1:2 to 3:1; when the dispersion containing MXene nanosheets is an aqueous dispersion of MXene nanosheets and sodium alginate, the coagulation bath is an aqueous ammonium chloride solution or an aqueous calcium chloride solution, and its mass concentration is 0.5 to 1%.

[0154] In this embodiment, the fibers formed in the coagulation bath are collected and washed with a mixture of ethanol and water. Preferably, the volume ratio of ethanol to water in the mixture is 1:3 to 3:1, more preferably 2:1.

[0155] In this embodiment, the fibers formed in the coagulation bath are collected and washed and then naturally dried for 0.5 to 1 day.

[0156] In this embodiment, the dried fiber is immersed in a mixture of alcohol and water for swelling for 2 to 5 minutes.

[0157] In this embodiment, the mixed solution of alcohol and water used for swelling includes a mixed solution of ethanol and water, and the volume ratio of ethanol to water in the mixed solution is 3:4 to 1:3, preferably 1:1.

[0158] In this embodiment, the swollen fiber is placed in liquid nitrogen for freezing for 30 to 60 minutes.

[0159] In this embodiment, the freeze drying temperature is -45°C to -60°C. The freeze drying can be performed under vacuum conditions. Preferably, the freeze drying time is 2 to 4 days.

[0160] In this embodiment, the vacuum drying temperature is 40-70° C. Preferably, the vacuum drying time is 0.5-2 days.

[0161] In this embodiment, the number of the plurality of MXene-based gel fibers is 2 to 10, preferably 3 to 6, and the plurality of MXene-based gel fibers are arranged in parallel in the chamber.

[0162] In this embodiment, the electrode includes one of a copper electrode, a silver electrode, a gold electrode, a platinum electrode, a titanium electrode, a nickel electrode or an aluminum electrode.

[0163] In this embodiment, the sealing cover includes an upper sealing cover and a lower sealing cover, and the upper sealing cover and the lower sealing cover are both semi-annular shell structures. The upper sealing cover and the lower sealing cover are coupled and connected to form a circular connecting port, and the circular connecting port is used to allow non-metallic pipes to pass through. After the upper sealing cover and the lower sealing cover are coupled and connected, a closed annular space is formed between the outer wall of the non-metallic pipe portion to be inspected.

[0164] In this embodiment, the second gas outlet is disposed on the upper sealing cover, and the second gas inlet is disposed on the lower sealing cover.

[0165] In this embodiment, the first gas inlet and the first gas outlet are respectively located at two ends of the axial direction of the MXene-based gel fiber.

[0166] In this embodiment, a gas pump is provided on the first air duct.

[0167] In this embodiment, the non-metallic pipe includes one or a combination of oilfield pipes, gas pipes, and drainage pipes.

[0168] In this embodiment, the gas detected by the gas sensor includes CO 2 NH 3 , CH 4 , H 2 S.H. 2 O and H 2 One or a combination of the above.

[0169] Comparative Example 1

[0170] This comparative example provides a gas sensor for a non-metallic tube, which includes a MXene-based gel fiber, wherein the MXene-based gel fiber is a pure MXene gel fiber prepared by conventional wet spinning technology. The preparation method of the pure MXene gel fiber in this comparative example comprises the following steps: using a mixed solution of LiF and HCl (which is obtained by dissolving 8g of LiF in 100mL of 9M HCl solution) to treat Ti in a constant temperature water bath environment at 35°C. 3 AlC 2 Etching was performed for about 40 hours, followed by ultrasonic stripping in a nitrogen atmosphere for about 1 hour, and finally centrifugation was performed at 3500 rpm for 1 hour to obtain a single layer or a few layers of Ti 3 C 2 T x Mixture of MXene nanosheets; Ti 3 C 2 T x The MXene nanosheets were centrifuged at high speed and prepared into a 120 mg / mL dispersion with DMSO as solvent by solvent replacement method. The dispersion was used as spinning solution, and the spinning solution was uniformly injected into the coagulation bath through an injection pump at an injection speed of 200 μL min -1 The coagulation bath is a mixture of DMSO and acetic acid (wherein the volume ratio of DMSO to acetic acid is 1:1); the fibers formed in the coagulation bath are collected, and are soaked and washed twice with a mixture of ethanol and water (wherein the volume ratio of ethanol to water is 2:1), and then naturally dried at room temperature for 1 day to obtain pure MXene gel fibers.

[0171] The gas sensor for non-metallic tubes provided in this comparative example is an external gas sensor, and its structure is the same as that of Example 1.

[0172] In order to test the sensitivity of the gas sensor of this comparative example, H2 diluted with nitrogen was introduced into the polyethylene pipe. 2 S gas, H in pipeline 2The S gas content is 100ppm. The gas sensor of this comparative example is used to detect the H 2 The content of S gas changes, and the resistance change of MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain H 2 Under the same conditions, nitrogen-diluted CH 4 Gas, CH in pipeline 4 The concentration is 600ppm. The gas sensor of this comparative example is used to detect the CH 4 The content of the gas changes, and the resistance change of the MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain CH 4 The response value of H measured in this comparative example 2 S response value and CH 4 The absolute values ​​of the responses are shown in Table 8.

[0173] Table 8 Absolute values ​​of gas response of pure MXene gel fibers prepared by conventional wet spinning technology

[0174] <![CDATA[|ΔR / R 0 |(%,H 2 S)]]> <![CDATA[|ΔR / R 0 |(%,CH 4 )]]> Comparative Example 1 1.9 2.6

[0175] Figure 5 This is a scanning electron microscope photograph of the cross-sectional pore structure morphology of the pure MXene gel fiber prepared in this comparative example.

[0176] Comparative Example 2

[0177] The present comparative example provides a gas sensor for a non-metallic tube, which includes a MXene-based gel fiber, wherein the MXene-based gel fiber is a MXene / GO composite gel fiber prepared by conventional wet spinning technology. The preparation method of the MXene / GO composite gel fiber of the present comparative example comprises the following steps: using a mixed solution of LiF and HCl (which is obtained by dissolving 8g LiF in 100mL 9M HCl solution) to treat Ti in a constant temperature water bath environment at 35°C. 3 AlC 2 Etching was performed for about 40 hours, followed by ultrasonic stripping in a nitrogen atmosphere for about 1 hour, and finally centrifugation was performed at 3500 rpm for 1 hour to obtain a single layer or a few layers of Ti 3 C 2 T x Mixture of MXene nanosheets; Ti 3 C 2 T xThe MXene nanosheets were centrifuged at high speed and mixed with GO nanosheets by solvent replacement method to prepare a dispersion solution with a total concentration of MXene and GO of 100 mg / mL in DMSO as solvent, wherein the mass ratio of MXene nanosheets to GO nanosheets was 3:7; the dispersion solution was used as a spinning solution, and the spinning solution was uniformly injected into a coagulation bath through an injection pump at an injection speed of 200 μL min -1 The coagulation bath is a mixture of DMSO and acetic acid (wherein the volume ratio of DMSO to acetic acid is 1:1); the fibers formed in the coagulation bath are collected, and are soaked and washed twice with a mixture of ethanol and water (wherein the volume ratio of ethanol to water is 2:1), and then naturally dried at room temperature for 1 day to obtain MXene / GO composite gel fibers.

[0178] The gas sensor for non-metallic tubes provided in this comparative example is an external gas sensor, and its structure is the same as that of Example 1.

[0179] In order to test the sensitivity of the gas sensor of this comparative example, H2 diluted with nitrogen was introduced into the polyethylene pipe. 2 S gas, H in pipeline 2 The S gas content is 100ppm. The gas sensor of this comparative example is used to detect the H 2 The content of S gas changes, and the resistance change of MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain H 2 Under the same conditions, nitrogen-diluted CH 4 Gas, CH in pipeline 4 The concentration is 600ppm. The gas sensor of this comparative example is used to detect the CH 4 The content of the gas changes, and the resistance change of the MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain CH 4 The response value of H measured in this comparative example 2 S response value and CH 4 The absolute values ​​of the responses are shown in Table 9.

[0180] Table 9 Absolute values ​​of gas response of MXene / GO composite gel fibers prepared by conventional wet spinning technology

[0181] <![CDATA[|ΔR / R 0 |(%,H 2 S)]]> <![CDATA[|ΔR / R 0 |(%,CH 4 )]]> Comparative Example 2 2.3 3.1

[0182] Figure 6 This is a scanning electron microscope photograph of the cross-sectional pore structure morphology of the MXene / GO composite gel fiber prepared in this comparative example.

[0183] Comparative Example 3

[0184] This comparative example provides a gas sensor for a non-metallic tube, which includes a MXene-based gel fiber, which is a MXene / GO composite gel fiber prepared by the low-temperature wet freezing technology of the present invention. The preparation method of the MXene / GO composite gel fiber in this comparative example is basically the same as that in Example 2, except that: the solvent in the dispersion of the MXene nanosheets and GO nanosheets in this comparative example is water, and the coagulation bath is an ammonium chloride aqueous solution with a mass concentration of 1%, and the remaining steps are the same as those in Example 2.

[0185] The gas sensor for non-metallic tubes provided in this comparative example is an external gas sensor, and its structure is the same as that of Example 1.

[0186] In order to test the sensitivity of the gas sensor of this comparative example, H2 diluted with nitrogen was introduced into the polyethylene pipe. 2 S gas, H in pipeline 2 The S gas content is 100ppm. The gas sensor of this comparative example is used to detect the H 2 The content of S gas changes, and the resistance change of MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain H 2 Under the same conditions, nitrogen-diluted CH 4 Gas, CH in pipeline 4 The concentration is 600ppm. The gas sensor of this comparative example is used to detect the CH 4 The content of the gas changes, and the resistance change of the MXene-based gel fiber sensing element 1 is detected by a digital multimeter to obtain CH 4 The response value of H measured in this comparative example 2 S response value and CH 4 The absolute values ​​of the responses are shown in Table 10.

[0187] Table 10 Absolute values ​​of gas response of MXene / GO composite gel fibers prepared by low-temperature wet freezing technology and ion coagulation bath

[0188] <![CDATA[|ΔR / R 0 |(%,H 2 S)]]> <![CDATA[|ΔR / R 0 |(%,CH 4 )]]> Comparative Example 3 3.4 4.7

[0189] Scanning electron microscope photos of pure MXene gel fibers prepared in Example 1 and Comparative Example 1 ( Figure 3 and Figure 5 ) and scanning electron microscope photos of MXene / GO composite gel fibers prepared in Example 2 and Comparative Example 2 ( Figure 4 and Figure 6), it can be seen that the MXene-based gel fiber prepared by the low-temperature wet freezing technology of the present invention has a significantly enhanced gel structure, improved porosity, a more regular pore structure and a large specific surface area compared to the MXene-based gel fiber prepared by the conventional wet spinning technology. 2 S response value and CH 4 The absolute values ​​of the response values ​​(Table 1 and Table 8) and the H values ​​of Example 2 and Comparative Example 2 are shown in Table 1. 2 S response value and CH 4 From the comparison of the absolute values ​​of the response values ​​(Table 2 and Table 9), it can be seen that the MXene-based gel fiber prepared by the low-temperature wet freezing technology of the present invention has a higher response to H than the MXene-based gel fiber prepared by the conventional wet spinning technology. 2 S and CH 4 The gas response value is significantly improved, so it has higher gas response sensitivity and can detect low-concentration gases.

[0190] From the comparative data of the MXene / GO composite gel fibers prepared in Example 2 and Comparative Example 3 (Table 2 and Table 10), it can be seen that the present invention uses an organic solvent such as DMSO to disperse the spinning solution of the MXene / GO inorganic nanomaterial, and uses a mixed solution of dimethyl sulfoxide and acetic acid as a coagulation bath. Coagulation in such a weak coagulation bath is more likely to make the fiber present a porous structure. Therefore, the MXene / GO composite gel fiber prepared in the present invention is more sensitive to H than the MXene / GO composite gel fiber prepared by using water as a solvent and using an ion coagulation bath. 2 S and CH 4 The response value of the gas is significantly improved.

[0191] By comparing Example 2 with Example 1, it can be seen that the MXene / GO composite gel fiber of the present invention has a higher gas response sensitivity than the pure MXene gel fiber. GO enhances the mechanical properties of the MXene-based gel fiber and helps the fiber gelation, making the porous structure more solid. At the same time, GO itself also has gas responsiveness. A synergistic effect is generated between MXene and GO, which significantly improves the gas response sensitivity of the MXene / GO composite gel fiber of the present invention.

[0192] In summary, the gas sensor of the present invention has high sensitivity, can detect low-concentration gases, and has strong stability in gas detection. It is used in the fields of oil transportation, gas transportation, drainage, etc., and can monitor the environmental gas and / or permeated gas of non-metallic pipes in real time.

Claims

1. A gas sensor for a non-metallic tube, comprising a MXene-based gel fiber, wherein the MXene-based gel fiber is prepared by at least the following steps: using a dispersion containing MXene nanosheets as a spinning solution, injecting the spinning solution into a spinning tube, wherein the outer wall of the spinning tube is provided with a sleeve, and the temperature of the sleeve gradually decreases along the flow direction of the spinning solution; injecting the spinning solution into a coagulation bath through the spinning tube; collecting the fibers formed in the coagulation bath and subjecting them to at least swelling, liquid nitrogen freezing and freeze drying to obtain the MXene-based gel fiber.

2. The gas sensor for non-metallic pipe according to claim 1, wherein: The dispersion containing MXene nanosheets includes a dispersion of MXene nanosheets, a dispersion of MXene nanosheets and GO nanosheets, or a dispersion of MXene nanosheets and sodium alginate; Preferably, the dispersion containing MXene nanosheets is a dispersion of MXene nanosheets and GO nanosheets or a dispersion of MXene nanosheets and sodium alginate.

3. The gas sensor for non-metallic pipe according to claim 1, wherein: The MXene nanosheets include Ti3C2T x MXene nanosheets.

4. The gas sensor for non-metallic pipe according to claim 2, wherein: The concentration of the MXene nanosheets in the dispersion of the MXene nanosheets is 80 to 180 mg / mL; Preferably, the solvent in the dispersion of the MXene nanosheets includes dimethyl sulfoxide and / or N,N-dimethylformamide.

5. The gas sensor for non-metallic pipe according to claim 2, wherein: The total concentration of the MXene nanosheets and the GO nanosheets in the dispersion of the MXene nanosheets and the GO nanosheets is 70 to 160 mg / mL, and the mass ratio of the MXene nanosheets to the GO nanosheets is 1:9 to 8:2; Preferably, the solvent in the dispersion of the MXene nanosheets and GO nanosheets comprises dimethyl sulfoxide and / or N,N-dimethylformamide.

6. The gas sensor for non-metallic pipe according to claim 2, wherein: The total concentration of MXene nanosheets and sodium alginate in the dispersion of MXene nanosheets and sodium alginate is 50 to 150 mg / mL, and the mass ratio of MXene nanosheets to sodium alginate is 1:9 to 9:1; Preferably, the solvent in the dispersion of MXene nanosheets and sodium alginate comprises water.

7. The gas sensor for non-metallic pipe according to claim 1, wherein: The spinning tube has a length of 0.3 to 1 m and an inner diameter of 0.30 to 1.3 mm; Preferably, the sleeve arranged on the outer wall of the spinning tube is a metal tube, and the temperature of the sleeve is gradually reduced along the flow direction of the spinning solution by the following method: a cold source is arranged at one end of the sleeve, so that the sleeve conducts cold energy in the direction opposite to the flow direction of the spinning solution, thereby achieving a gradual reduction in temperature along the flow direction of the spinning solution; more preferably, the temperature of the cold source is between -200°C and -100°C.

8. The gas sensor for non-metallic pipe according to claim 1, wherein: The coagulation bath comprises one or a combination of an aqueous solution of ammonium chloride, an aqueous solution of calcium chloride, an aqueous solution of aluminum chloride, aqueous ammonia, isopropanol, ethyl acetate, acetone, acetic acid, n-hexane, dichloromethane, a mixed solution of dimethyl sulfoxide and acetic acid, and a mixed solution of isopropanol and water; Preferably, when the dispersion containing MXene nanosheets is a dimethyl sulfoxide dispersion of MXene nanosheets, or a dimethyl sulfoxide dispersion of MXene nanosheets and GO nanosheets, the coagulation bath is a mixture of dimethyl sulfoxide and acetic acid; When the dispersion containing MXene nanosheets is an N,N-dimethylformamide dispersion of MXene nanosheets, or an N,N-dimethylformamide dispersion of MXene nanosheets and GO nanosheets, the coagulation bath is a mixture of isopropanol and water; When the dispersion containing MXene nanosheets is an aqueous dispersion of MXene nanosheets and sodium alginate, the coagulation bath is an aqueous solution of ammonium chloride or an aqueous solution of calcium chloride, and the mass concentration thereof is 0.5-1%.

9. The gas sensor for non-metallic pipe according to claim 1, wherein: The swelling is performed using a mixture of alcohol and water; preferably a mixture of ethanol and water, wherein the volume ratio of ethanol to water in the mixture is 3:4 to 1:3; Preferably, the freeze-drying temperature is -45°C to -60°C.

10. The gas sensor for non-metallic pipe according to claim 1, wherein: The gas sensor for the non-metallic tube includes an external gas sensor, a wall-attached gas sensor or an embedded gas sensor; the external gas sensor is arranged outside the non-metallic tube, the wall-attached gas sensor is attached to the outer wall of the non-metallic tube, and the embedded gas sensor is arranged between layers in the non-metallic tube; Preferably, the gas sensor for the non-metallic tube is an external gas sensor.

11. The gas sensor for non-metallic pipe according to claim 10, wherein: The external gas sensor comprises: a MXene-based gel fiber sensing element, a sealing cover, a first air duct and a second air duct; The MXene-based gel fiber sensing element comprises a chamber, a substrate, a plurality of the MXene-based gel fibers, and a pair of electrodes. The plurality of the MXene-based gel fibers and the electrodes are arranged on the substrate and placed in the chamber, and the pair of electrodes are respectively connected to the two ends of the axial direction of the plurality of the MXene-based gel fibers; the chamber wall of the chamber is provided with a first gas inlet and a first gas outlet; The sealing cover is an annular shell, which is used to seal and cover the part of the non-metallic pipe to be inspected; the sealing cover is provided with a second gas outlet and a second gas inlet; One end of the first gas duct is connected to the second gas outlet, and the other end is connected to the first gas inlet; one end of the second gas duct is connected to the first gas outlet, and the other end is connected to the second gas inlet.

12. The gas sensor for non-metallic pipe according to claim 11, wherein: The MXene-based gel fiber sensing element includes 2 to 10 MXene-based gel fibers connected in parallel, preferably 3 to 6.

13. The gas sensor for non-metallic pipe according to claim 11, wherein: The sealing cover comprises an upper sealing cover and a lower sealing cover, both of which are semi-annular shell structures, and the upper sealing cover and the lower sealing cover are connected to form a circular connection port, and the circular connection port is used for non-metallic pipes to pass through, and after the upper sealing cover and the lower sealing cover are connected to form a closed annular space with the outer wall of the non-metallic pipe to be detected; Preferably, the upper sealing cover is provided with the second gas outlet, and the lower sealing cover is provided with the second gas inlet.

14. The gas sensor for non-metallic pipe according to claim 11, wherein: The first gas inlet and the first gas outlet are respectively located at two ends of the axial direction of the MXene-based gel fiber.

15. The gas sensor for non-metallic pipe according to claim 11, wherein: A gas pump is arranged on the first air guide tube.

16. A gas monitoring method comprising the following steps: The gas sensor for non-metallic pipes according to any one of claims 1 to 15 is used to monitor the ambient gas and / or the permeated gas of the non-metallic pipes; Preferably, the non-metallic pipe includes one or a combination of oilfield pipe, gas pipe and drainage pipe; Preferably, the gas detected by the gas sensor includes one or a combination of CO2, NH3, CH4, H2S, H2O and H2.

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