Gas sensor for non-metallic pipes, method for manufacturing the same, and gas monitoring method.

Abstract

The present invention provides a gas sensor for non-metallic pipes, a method for manufacturing the same, and a gas monitoring method. The method for manufacturing the gas sensor includes: using a dispersion containing MXene nanosheets as a spinning solution and injecting it into a spinning conduit (a sleeve is provided on the outer wall of the spinning conduit, and the temperature of the sleeve gradually decreases along the flow direction of the spinning solution); injecting the spinning solution into a coagulation bath via the spinning conduit; collecting the fibers formed in the coagulation bath, and then obtaining MXene-based gel fibers by at least swelling, freezing with liquid nitrogen, and freeze-drying; and assembling a gas sensor using the MXene-based gel fibers. The gas sensor of the present invention has high sensitivity, can detect gases at low concentrations, and is suitable for monitoring gas permeation through non-metallic pipes.

Description

[Technical Field]

[0001] Technical field This invention relates to a gas sensor for non-metallic pipes, a method for manufacturing the same, and a gas monitoring method, and belongs to the field of gas sensors. [Background technology]

[0002] Background technology Pipeline transportation plays a crucial role in industrial production, with most materials being transported via pipelines. In processes such as oil extraction, gas transport, and wastewater discharge, corrosive media such as CO2, NH3, CH4, and H2S are generated, accelerating the corrosion and aging of metal pipes and posing serious environmental and human safety risks. Therefore, non-metallic pipes are gradually gaining widespread attention due to their superior corrosion resistance, and products are being developed and applied to oilfield pipes, gas pipes, and drainage pipes. As the environment for oil field extraction becomes increasingly harsh, extraction depths increase, and the effects of corrosive media become more pronounced. Furthermore, with the rise in industrialization levels, toxic and harmful gases in urban wastewater processes increase. In these contexts, research and development of non-metallic pipe gas sensors used in the fields of oilfields, gas, and wastewater is of great significance.

[0003] By connecting gas sensors to pipelines, real-time monitoring of hazardous gases in oil extraction and transportation, gas transportation, and wastewater treatment processes can be achieved. This allows for evaluation of the barrier properties of non-metallic pipes, prediction of pipeline service life, monitoring of dynamic changes in corrosive gas content, and further evaluation of safety in oil extraction and transportation, gas transportation, and wastewater treatment processes, providing important guidance for safe production. [Overview of the project] [Problems that the invention aims to solve]

[0004] Currently, to address the challenge of monitoring gas permeation during the use of non-metallic pipes, conventional techniques primarily use 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 vessel with a sealed annular space between it and the sample component for arranging the sample component; a gas source communicating with the inlet of the non-metallic pipe and supplying gas to the sample component; a metering and pressure boosting system located between the gas source and the sample component to adjust the pressure of the gas supplied from the gas source; and a gas detection system located in the metal pressure vessel for detecting gas in the annular space between the metal pressure vessel and the sample component. By filling the inside of the non-metallic pipe and the open area of ​​the annular cavity between the pipe and the outside with gas and maintaining pressure for a long period, leakage detection of the sample can be completed, and the amount of gas permeation in the open area of ​​the annular cavity when pressure is maintained for a long period can be recorded. However, when measuring gas permeation using the differential pressure method, real-time monitoring of gases is difficult, making it impossible to detect abnormal gas conditions in industrial production processes early.

[0005] Two-dimensional transition metal carbon / nitride (MXene) is a novel material that contains many functional groups on its surface, which can function as gas adsorption sites, and thus has the potential to be an excellent gas-sensitive material.

[0006] Liu et al. used a vacuum-assisted layered assembly method to create Ti3C2T xConductive textiles were fabricated by spray-coating MXene and silver nanowires onto a silk fabric substrate, and their applications in electromagnetic shielding, humidity monitoring, and hydrophobicity were also investigated (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. fabricated conductive polyaniline (PANI) / MXene / cotton fabrics (PMCFs) using a highly efficient vacuum filtration-assisted spray coating method and applied them to 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 Electromagnetic Interference Shielding Performances[J]. ACS Appl. Mater. Interfaces 2022, 14, 12703-12712).

[0008] Kim et al., Ti3C2T xThis study investigated the extremely strong signal-to-noise ratio of MXene materials when detecting low concentrations of volatile organic compound gases, revealing their superiority 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 Ti3C2T). x MXene Gas Sensors with Ultrahigh Signal-to-Noise Ratio[J]. ACS Nano 2018, 12, 986-993). This study provides the foundation for theoretical research on MXene as a gas-sensitive material, demonstrating superior performance in gas sensing compared to black phosphorus, molybdenum disulfide, and reduced graphene oxide.

[0009] Conventional research has not yet been conducted on using MXene in non-metallic tube gas sensors, and further improving the gas response sensitivity of MXene-based materials remains one of the research focuses in this field. [Means for solving the problem]

[0010] Summary of the Invention To solve the above technical problems, the present invention aims to provide a gas sensor for non-metallic pipes, a method for manufacturing the same, and a gas monitoring method. The gas sensor of the present invention has high sensitivity, can detect gases at low concentrations, and is suitable for monitoring gas permeation through non-metallic pipes.

[0011] To achieve the above objective, a first aspect of the present invention provides a method for manufacturing a gas sensor for non-metallic pipes, comprising the steps of: using a dispersion containing MXene nanosheets as a spinning solution; injecting the spinning solution into a spinning conduit having a sleeve on its outer wall (the temperature of the sleeve gradually decreases along the flow direction of the spinning solution); injecting the spinning solution into a coagulation bath via the spinning conduit; collecting the fibers formed in the coagulation bath, and then obtaining MXene-based gel fibers by at least swelling, freezing with liquid nitrogen, and freeze-drying; and assembling a gas sensor using the MXene-based gel fibers to obtain a gas sensor for non-metallic pipes.

[0012] According to specific embodiments of the present invention, preferably, the dispersion containing the MXene nanosheet 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 the MXene nanosheet is a dispersion of MXene nanosheets and GO nanosheets, or a dispersion of MXene nanosheets and sodium alginate. Those skilled in the art will understand that when the dispersion is a dispersion of MXene nanosheets, the MXene-based gel fibers are MXene gel fibers; when the dispersion is a dispersion of MXene nanosheets and GO nanosheets, the MXene-based gel fibers are MXene / GO composite gel fibers; and when the dispersion is a dispersion of MXene nanosheets and sodium alginate, the MXene-based gel fibers are MXene / alginate composite gel fibers.

[0013] According to a specific embodiment of the present invention, preferably, the MXene nanosheet is Ti3C2T x Contains MXene nanosheets.

[0014] According to a specific embodiment of the present invention, preferably, the MXene nanosheet is produced by a step of treating a MAX-phase with a mixed solution of LiF and HCl, performing ultrasonic treatment, and then obtaining the MXene nanosheet. Here, the MAX-phase used is preferably a titanium aluminum carbon compound (Ti3AlC2).

[0015] According to a specific embodiment of the present invention, preferably, the concentration of the MXene nanosheet in the dispersion of the MXene nanosheet 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 nanosheet contains dimethyl sulfoxide (DMSO) and / or N,N-dimethylformamide (DMF).

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

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

[0019] In 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 contains water.

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

[0022] In a specific embodiment of the present invention, preferably, the sleeve provided on the outer wall of the spinning conduit is a metal tube, and the gradual decrease in the temperature of the sleeve along the flow direction of the spinning fluid is achieved by installing a cooling source at one end of the sleeve that conducts a cooling amount in the opposite direction to the flow direction of the spinning fluid through the sleeve, so as to ensure that the temperature gradually decreases along the flow direction of the spinning fluid. Specifically, the sleeve may be a copper tube. Furthermore, those skilled in the art will understand that an appropriate gap should exist between the sleeve and the spinning conduit in order to avoid the spinning fluid freezing and solidifying and becoming unable to flow.

[0023] In a specific embodiment of the present invention, preferably, the temperature of the cooling source installed at one end of the sleeve is between -200°C and -100°C. Specifically, the cooling source may be liquid nitrogen (-196°C).

[0024] According to specific embodiments of the present invention, preferably, the coagulation bath includes one or more combinations of ammonium chloride aqueous solution, calcium chloride aqueous solution, aluminum chloride aqueous solution, ammonia water, isopropyl alcohol, ethyl acetate, acetone, acetic acid, n-hexane, dichloromethane, a mixture of dimethyl sulfoxide and acetic acid, and a mixture of isopropyl alcohol and water. More preferably, when the dispersion containing the MXene nanosheet is a dimethyl sulfoxide dispersion of the MXene nanosheet, or a dimethyl sulfoxide dispersion of the MXene nanosheet and GO nanosheet, the coagulation bath is a mixture of dimethyl sulfoxide and acetic acid, and more preferably, the volume ratio of dimethyl sulfoxide to acetic acid in the mixture is 1:3 to 3:1. When the dispersion containing the MXene nanosheet is an N,N-dimethylformamide dispersion of the MXene nanosheet, or an N,N-dimethylformamide dispersion of the MXene nanosheet and GO nanosheet, the coagulation bath is a mixture of isopropyl alcohol and water, and more preferably, the volume ratio of isopropyl alcohol to water in the mixture is 1:2 to 3:1. When the dispersion containing the MXene nanosheet is an aqueous dispersion of the MXene nanosheet and sodium alginate, the coagulation bath is an aqueous solution of ammonium chloride or an aqueous solution of calcium chloride, with a concentration of 0.5 to 1% by mass. In this invention, the spinning solution of MXene or MXene / GO inorganic nanomaterials is dispersed in an organic solvent such as DMSO, preferably a mixture of DMSO and acetic acid, and used as a coagulation bath. DMSO can appropriately slow down the coagulation rate of acetic acid on the fibers, so coagulation in such a weak coagulation bath makes it easier to create a porous structure for the fibers. In this invention, it is preferable to use water as the solvent for the MXene / sodium alginate spinning solution, and it is preferable to form the material in an ion coagulation bath. During the forming process, the polymer alginate can function as a crosslinking agent and can play a role in structural support. Furthermore, in this invention, by controlling the concentration of salts in the ion coagulation bath, it is possible for the fibers to undergo appropriate levels of crosslinking and gelation during the forming process.

[0025] According to a specific embodiment of the present invention, preferably, after collecting the fibers formed in a solidification bath, they are washed, then air-dried, the dried fibers are swelled, the swollen fibers are placed in liquid nitrogen and frozen, 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, after collecting the fibers formed in the coagulation bath, they are 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 even more preferably 2:1.

[0027] According to a specific embodiment of the present invention, preferably, the time for collecting and washing the fibers formed in the coagulation bath and then allowing them to air dry is 0.5 to 1 day.

[0028] According to specific embodiments of the present invention, preferably, a mixture of alcohol and water is used in the swelling, 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 even more preferably 1:1.

[0029] According to a specific embodiment of the present invention, preferably, the time for immersing the dried fibers in a mixture of alcohol and water to cause swelling is 2 to 5 minutes.

[0030] According to a specific embodiment of the present invention, preferably, the time for freezing the swollen fibers in liquid nitrogen is 30 to 60 minutes.

[0031] According to a specific embodiment of the present invention, the freeze-drying temperature is preferably -45°C to -60°C. The freeze-drying can be carried out under vacuum conditions. More preferably, the freeze-drying time is 2 to 4 days.

[0032] According to a specific embodiment of the present invention, the vacuum drying temperature is preferably 40 to 70°C. More preferably, the vacuum drying time is 0.5 to 2 days.

[0033] A second aspect of the present invention provides a non-metallic pipe gas sensor manufactured by the method for manufacturing a non-metallic pipe gas sensor described above, wherein the non-metallic pipe gas sensor includes MXene-based gel fibers.

[0034] According to specific embodiments of the present invention, the non-metallic pipe gas sensor preferably includes an external gas sensor, a wall-mounted gas sensor, or a recessed gas sensor. The external gas sensor is provided on the outside of the non-metallic pipe, the wall-mounted gas sensor is bonded to the outer wall of the non-metallic pipe, and the recessed gas sensor is provided between layers inside the non-metallic pipe. More preferably, the non-metallic pipe gas sensor is an external gas sensor.

[0035] According to a specific embodiment of the present invention, the external gas sensor preferably includes an MXene-based gel fiber sensing element, a sealing cover, a first gas conduit, and a second gas conduit.

[0036] Here, the MXene-based gel fiber sensing element includes one chamber, one substrate, a plurality of the MXene-based gel fibers, and a pair of electrodes, wherein the plurality of the MXene-based gel fibers and the electrodes are all provided on the substrate and arranged within the chamber, the pair of electrodes are connected to the axial ends of the plurality of the MXene-based gel fibers, and the wall of the chamber is provided with a first gas inlet and a first gas outlet. The sealing cover is an annular housing used to seal and cover the portion of the non-metallic tube to be detected, and the sealing cover is provided with a second gas outlet and a second gas inlet. The first gas conduit has one end connected to the second gas outlet and the other end connected to the first gas inlet, and the second gas conduit has one end connected to the first gas outlet and the other end connected to the second gas inlet.

[0037] According to a specific embodiment of the present invention, in the actual application process, after energizing the MXene-based gel fiber sensing element, the change in gas content is converted into a change in electrical resistance, and then a communication connection is established with a computer, thereby enabling real-time monitoring of the environmental gas and / or permeate gas in a non-metallic pipe.

[0038] According to a specific embodiment of the present invention, the MXene-based gel fiber sensing element preferably comprises 2 to 10 parallel-connected MXene-based gel fibers, and more preferably 3 to 6 fibers.

[0039] According to a specific embodiment of the present invention, preferably, the electrode includes one of the following: a copper electrode, a silver electrode, a gold electrode, a platinum electrode, a titanium electrode, a nickel electrode, or an aluminum electrode.

[0040] According to a specific embodiment of the present invention, preferably, the sealing cover includes an upper sealing cover and a lower sealing cover, both of which have a semi-annular housing structure, and the upper sealing cover and the lower sealing cover are connected together to form a circular connection port for penetrating a non-metallic pipe, and a sealed annular space is formed between the connected upper sealing cover and the lower sealing cover and the outer wall of the portion of the non-metallic pipe to be detected.

[0041] In 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.

[0042] According to a specific embodiment of the present invention, preferably, the first gas inlet and the first gas outlet are located at both ends of the MXene-based gel fiber in the axial direction, respectively.

[0043] According to a specific embodiment of the present invention, a gas pump is preferably provided in the first gas conduit.

[0044] According to a specific embodiment of the present invention, the wall-mounted gas sensor preferably includes at least an 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 electrodes, the plurality of the MXene-based gel fibers and the electrodes are all provided on the substrate, and the electrodes are provided at both axial ends of the plurality of the MXene-based gel fibers. The plurality of the MXene-based gel fibers and the electrodes are bonded to the outer wall of a non-metallic tube. More preferably, the wall-mounted gas sensor may further include a sealing cover provided on the outside of the substrate for sealing the MXene-based gel fiber sensing element to the outer wall of the non-metallic tube.

[0045] In a specific embodiment of the present invention, the embedded gas sensor preferably includes an 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 electrodes, all of which are provided on the substrate, and the electrodes are provided at both axial ends of the plurality of the MXene-based gel fibers, and the plurality of the MXene-based gel fibers and the electrodes are bonded to the outer surface of the barrier layer inside the non-metallic tube. Generally, the non-metallic tube is a multilayer composite tube and may include a lining layer, barrier layer, reinforcing layer, etc. from the inside out, but in the present invention, the multilayer composite structure of the non-metallic tube is not particularly limited, and the embedded gas sensor can be installed on the outer surface of the barrier layer.

[0046] According to specific embodiments of the present invention, the external gas sensor can mainly detect permeated gas and / or ambient gas throughout the non-metallic pipe, the wall-mounted gas sensor can mainly detect ambient gas and permeated gas in the non-metallic pipe, and the embedded gas sensor can mainly detect permeated gas in the non-metallic pipe.

[0047] In a specific embodiment of the present invention, preferably, the absolute value of the H2S response value of the non-metallic pipe gas sensor (i.e., |ΔR / R0|) is 3% or more. Here, the method for measuring the absolute value of the H2S response value includes using the non-metallic pipe gas sensor to detect the permeate gas of a non-metallic pipe in which the H2S gas content in the pipeline is 80 to 100 ppm, detecting the change in resistance of the MXene-based gel fiber sensing element using a digital multimeter, and obtaining the absolute value of the H2S response value.

[0048] In a specific embodiment of the present invention, preferably, the absolute value of the CH4 response value of the non-metallic pipe gas sensor (i.e., |ΔR / R0|) is 4% or more. Here, the method for measuring the absolute value of the CH4 response value includes using the non-metallic pipe gas sensor to detect the permeate gas of a non-metallic pipe in which the CH4 gas content in the pipeline is 500 to 600 ppm, detecting the change in resistance of the MXene-based gel fiber sensing element using a digital multimeter, and obtaining the absolute value of the CH4 response value.

[0049] In a specific embodiment of the present invention, preferably, the absolute value of the NH3 response value of the non-metallic pipe gas sensor (i.e., |ΔR / R0|) is 12% or more. Here, the method for measuring the absolute value of the NH3 response value includes using the non-metallic pipe gas sensor to detect the permeate gas of a non-metallic pipe in which the NH3 gas content in the pipeline is 700 ppm, detecting the change in resistance of the MXene-based gel fiber sensing element using a digital multimeter, and obtaining the absolute value of the NH3 response value.

[0050] In a specific embodiment of the present invention, preferably, the absolute value of the H2O response value of the non-metallic pipe gas sensor (i.e., |ΔR / R0|) is 5% or more. Here, the method for measuring the absolute value of the H2O response value includes using the non-metallic pipe gas sensor to detect the permeate gas of a non-metallic pipe in which the H2O gas content in the pipeline is 700 ppm, detecting the change in resistance of the MXene-based gel fiber sensing element with a digital multimeter, and obtaining the absolute value of the H2O response value.

[0051] In a specific embodiment of the present invention, preferably, the absolute value of the CO2 response value of the non-metallic pipe gas sensor (i.e., |ΔR / R0|) is 4% or more. Here, the method for measuring the absolute value of the CO2 response value includes using the non-metallic pipe gas sensor to detect the permeate gas of a non-metallic pipe in which the CO2 gas content in the pipeline is 500 ppm, detecting the change in resistance of the MXene-based gel fiber sensing element with a digital multimeter, and obtaining the absolute value of the CO2 response value.

[0052] In the method for measuring the absolute value of the gas response value described above, ΔR is the resistance change value of the MXene-based gel fiber sensing element, and R0 is the initial resistance value of the MXene-based gel fiber sensing element. Specifically, the non-metallic pipe can be polyethylene (PE), but is not limited thereto, and polypropylene (PP), polyvinylidene fluoride (PVDF), or polyvinyl chloride (PVC) may also be used. The measurement temperature may be room temperature (23±2℃), the measurement pressure may be standard atmospheric pressure (101.325kPa), and the detection gas in the pipeline may be diluted with nitrogen gas. Those skilled in the art will understand that the gas sensor of the present invention is not limited to detecting gases with the above content, nor is the measurement temperature and pressure limited thereto, and that the gas sensor of the present invention has high absolute response values ​​for different gases (including CO2, NH3, CH4, H2S, H2O, or H2, etc.) under multiple measurement conditions (including arbitrary temperature, pressure, humidity, and gas content in the pipeline).

[0053] In this invention, an external gas sensor is preferably used, and a sealed annular space outside the nonmetallic pipe is connected to an MXene-based gel fiber sensing element by a first gas conduit and a second gas conduit. In this way, the permeated gas from the nonmetallic pipe enters the MXene-based gel fiber sensing element via the first gas conduit, and by utilizing the conductive properties of the MXene-based gel fiber to convert changes in gas content into changes in resistance, and transmitting the resistance change signal to a computer, real-time monitoring of the permeated gas from the nonmetallic pipe can be achieved. The signal from the gas sensor of this invention can be transmitted in real time to a monitoring room at the base. For example, one computer can be placed near the gas sensor and another computer can be placed in the monitoring room, thereby allowing observation of data changes at the actual monitoring location and in the monitoring room. At the same time, the gel fibers in the MXene-based gel fiber sensing element are preferably arranged in a parallel connection. In this way, the contact area between the gel fibers and the gas is improved, and the total resistance is reduced, thereby improving the sensitivity of the response. In addition, the gas pump in the first gas conduit is installed so that the gas can flow along a single direction. Furthermore, by providing a second gas outlet and a second gas inlet in the upper and lower sealing covers, respectively, the maximum vertical distance between the second gas outlet and the second gas inlet can be maintained, allowing for more efficient gas flow. In addition, the present invention preferably uses an external gas sensor. This method of easily replacing the MXene-based gel fiber sensing element ensures the long-term use of the gas sensor.

[0054] The present invention provides a gas sensor for non-metallic pipes. The gas sensor includes an MXene-based gel fiber sensing element and is a type of resistive gas sensor. The gas sensor is connected to a non-metallic pipe and uses the conductive properties of the MXene-based gel fiber to convert gas changes into resistive signal changes, thereby intuitively displaying the gas permeation status of the non-metallic pipe and enabling real-time monitoring of gas permeation through the non-metallic pipe.

[0055] In the present invention, MXene is used as a gas-sensitive material. MXene has characteristics such as a two-dimensional layered structure, single-atom thickness, large specific surface area, high conductivity, and adjustable bandgap. Previous research has already demonstrated the use of MXene for gas detection. There are many types of MXene materials, and generally, M n+1 X n T x represents its structure, where the transition metal atom (M) is stacked in a honeycomb-like two-dimensional lattice, carbon and / or nitrogen (X) occupy the octahedral sites of adjacent M layers, and T x represents the end group connected to M, and n usually ranges from 1 to 4 depending on the number of M and X layers. Currently, the most maturely studied MXene material is Ti3C2T x . However, the gas response sensitivity of MXene materials in the prior art needs to be further improved.

[0056] In this invention, MXene-based gel fibers are manufactured using an original low-temperature wet freezing technology. In this invention, a sleeve is provided on the outer wall of the spinning conduit, and as the temperature of the sleeve gradually decreases along the flow direction of the spinning solution, ice crystals that grow regularly in the spinning solution can be formed. These ice crystals can play a role in forming pores during the gel fiber formation process. At the same time, in this invention, a spinning conduit with a length of 0.3 to 1 m and an inner diameter of 0.30 to 1.3 mm is used. This serves as a dimensional limitation. As the spinning solution gradually becomes oriented during the flow process within the spinning conduit, it contributes to improving the orientation of the fiber structure. Furthermore, in this invention, after the hydrogel fibers formed in a coagulation bath are washed and air-dried, they are immersed in a mixture of alcohol and water to swell, then rapidly cooled in a liquid nitrogen environment at -196°C to freeze the hydrogel fibers into a solid state containing ice crystals, and then freeze-dried at -45°C to -60°C. In this process, after the ice crystals sublimate, many voids remain, and the MXene-based gel fibers ultimately obtained have a porous structure due to the regular ice crystal belt structure formed in the spinning solution. Surprisingly, the inventors have found that the MXene-based gel fibers produced by the low-temperature wet freezing technology in this invention have higher gas response sensitivity than MXene-based gel fibers produced by conventional methods, and are suitable for detecting gases such as CO2, NH3, CH4, H2S, H2O, and H2.

[0057] A third aspect of the present invention is: (1) A step to manufacture MXene-based gel fibers, (2) The step of assembling a gas sensor using the MXene-based gel fiber, (3) The steps of detecting the ambient gas and / or permeate gas of the non-metallic pipe using the gas sensor and transmitting the signal obtained by the gas sensor to a computer to realize real-time monitoring of the ambient gas and / or permeate gas of the non-metallic pipe, The present invention provides a gas monitoring method that includes [specific details omitted].

[0058] In a specific embodiment of the present invention, preferably, step (1) includes using a dispersion containing MXene nanosheets as a spinning solution, injecting the spinning solution into a spinning conduit having a sleeve on its outer wall (the temperature of the sleeve gradually decreases along the flow direction of the spinning solution), injecting the spinning solution into a coagulation bath via the spinning conduit, and collecting the fibers formed in the coagulation bath, and then obtaining the MXene-based gel fibers by at least swelling, freezing with liquid nitrogen and freeze-drying.

[0059] In a specific embodiment of the present invention, step (2) preferably includes assembling an external gas sensor, a wall-mounted gas sensor, or an embedded gas sensor using the MXene-based gel fibers. More preferably, an external gas sensor is assembled using the MXene-based gel fibers.

[0060] In a specific embodiment of the present invention, preferably, step (2) includes specifically placing a plurality of MXene-based gel fibers and a pair of electrodes in one chamber, with the pair of electrodes each installed at both axial ends of the plurality of MXene-based gel fibers, a first gas inlet and a first gas outlet provided in the wall of the chamber to obtain an MXene-based gel fiber sensing element, covering the portion of a non-metallic tube to be detected with a sealing cover, the sealing cover being an annular housing and having a second gas outlet and a second gas inlet, connecting the second gas outlet and the first gas inlet with a first gas conduit, and connecting the first gas outlet and the second gas inlet with a second gas conduit to obtain the gas sensor.

[0061] According to specific embodiments of the present invention, preferably, the non-metallic pipe includes one or more types of pipes, such as oil field pipes, gas pipes, and drainage pipes.

[0062] According to a specific embodiment of the present invention, preferably, the gas detected by the gas sensor includes one or a combination of several types of CO2, NH3, CH4, H2S, H2O, and H2.

[0063] The present invention provides a gas sensor for non-metallic pipes, a method for manufacturing the same, and a gas monitoring method. The present invention has at least the following beneficial effects. The gas sensor of the present invention includes MXene-based gel fibers. The MXene-based gel fibers of the present invention are manufactured by low-temperature wet freezing technology, have a porous structure and a large specific surface area, and the length of their monofilaments is adjustable. The low-temperature wet freezing technology of the present invention strengthens the gel structure of the fibers and improves the porosity of the fibers. The MXene-based gel fibers of the present invention have a larger contact area with the gas and higher sensitivity of their gas response. The gas sensor of the present invention has high sensitivity, can detect low concentrations of gas, has strong stability for gas detection, and can be applied in fields such as oil transport, gas transport, and wastewater treatment, and can monitor environmental gases and / or permeate gases in non-metallic pipes in real time. Depending on the placement position of the gas sensor of the present invention, the content of environmental gases and / or permeate gases at different locations in the non-metallic pipe can be detected. The monitoring results of the gas sensor of the present invention can guide the design and development of materials and structures of non-metallic pipes and warn of the risk of gas permeation or leakage in industrial production. The signals from the gas sensor of this invention can be transmitted in real time to a monitoring room at the base, which has significant research implications for realizing the construction of smart oilfields and digital pipelines. [Brief explanation of the drawing]

[0064] [Figure 1] This is a schematic diagram of the structure of the external gas sensor provided in Example 1. [Figure 2] These are scanning electron microscope images of MAX phase Ti3AlC2 and Ti3C2Tx MXene nanosheets in Example 1. [Figure 3] This is a scanning electron microscope image of the cross-sectional pore structure morphology of pure MXene gel fibers in Example 1. [Figure 4] This is a scanning electron microscope image of the cross-sectional pore structure morphology of the MXene / GO composite gel fiber in Example 2. [Figure 5]This is a scanning electron microscope image of the cross-sectional pore structure morphology of pure MXene gel fibers in Comparative Example 1. [Figure 6] This is a scanning electron microscope image of the cross-sectional pore structure morphology of the MXene / GO composite gel fiber in Comparative Example 2. [Modes for carrying out the invention]

[0065] Modes for carrying out the invention In order to more clearly understand the constituent elements, objectives, and beneficial effects of the present invention, the technical proposal of the present invention will be described in detail below, but this should not be understood as limiting the scope of the invention's applicability.

[0066] The raw materials used in the following examples and comparative examples include the following: Titanium aluminum carbon compound (Ti3AlC2, 400 mesh): Purchased from Jilin Yiyi Technology Co., Ltd.

[0067] Lithium fluoride (LiF, 99.99%): Purchased from Shanghai Aladdin. Hydrochloric acid (HCl, 37%): Purchased from Beijing Chemical Factory.

[0068] Dimethyl sulfoxide (DMSO, 99%): Purchased from Tianjin Damao Chemical. N,N-dimethylformamide (DMF, 99%): Purchased from Tianjin Damao Chemical.

[0069] Graphene oxide (GO, sheet layer with a diameter of 8-80 μm in the transverse direction and a thickness of 2 nm or less): Purchased from Hangzhou Gaoxi Technology Co., Ltd.

[0070] Sodium alginate (SA, 1% viscosity 5000 mPa·s): Purchased from Macklin. Acetic acid (AC, 99.9%): Purchased from Tianjin Damao Chemical.

[0071] Ammonium chloride (NH4Cl): Purchased from Tianjin Guangfu. Calcium chloride (CaCl2): Purchased from Tianjin Guangfu. [Examples]

[0072] Example 1 In this embodiment, a gas sensor for non-metallic pipes is provided, which contains MXene-based gel fibers, which are pure MXene gel fibers produced by the low-temperature wet freezing technology of the present invention. The low-temperature wet freezing technology includes at least the following steps: Etching Ti3AlC2 in a constant temperature water bath environment at 35°C using a mixed solution of LiF and HCl (obtained by dissolving 8g of LiF in 100mL of 9M HCl solution); after about 40 hours, ultrasonic peeling in a nitrogen atmosphere for about 1 hour; and finally centrifugation in a centrifuge at a rotation speed of 3500 rpm for 1 hour to obtain a single layer or a small layer of Ti3C2T x A mixture containing MXene nanosheets was obtained. Ti3C2T x MXene nanosheets were centrifuged at high speed, and a 120 mg / mL dispersion was prepared using DMSO as the solvent by solvent displacement. This dispersion was used as the spinning solution, and the spinning solution was injected at a constant rate into a spinning conduit using an injection pump. The spinning conduit had a length of 0.5 m, an inner diameter of 0.80 mm, and an injection rate of 200 μL min. -1The spinning conduit is provided with a sleeve on its outer wall, and an appropriate gap should exist between the sleeve and the spinning conduit. The sleeve is made of copper. Liquid nitrogen is provided at the lower end of the sleeve, along the direction of the spinning fluid flow. In this way, the sleeve conducts cooling from bottom to top (i.e., in the opposite direction to the direction of the spinning fluid flow), causing the temperature of the sleeve to gradually decrease from top to bottom (i.e., in the direction of the spinning fluid flow). The spinning fluid was injected into a coagulation bath through the spinning conduit. The coagulation bath is a mixture of DMSO and acetic acid (where the volume ratio of DMSO to acetic acid is 1:1). The fibers formed in the coagulation bath were collected, washed twice by immersion with a mixture of ethanol and water (where the volume ratio of ethanol to water is 2:1), and then air-dried at room temperature for 0.5 days. The dried fibers were immersed in a mixture of ethanol and water (where the volume ratio of ethanol to water is 1:1) for 2 minutes to swell, then the swollen fibers were placed in liquid nitrogen and frozen for 30 minutes, followed by drying in a freeze-dryer at -57°C for 3 days, and then drying in a vacuum oven at 60°C for 1 day to obtain pure MXene gel fibers.

[0073] The non-metallic pipe gas sensor provided in this embodiment is an external gas sensor and, as shown in Figure 1, includes an MXene-based gel fiber sensing element 1, a sealing cover 2, a first gas conduit 3, a second gas conduit 4, and a gas pump 5.

[0074] Here, the MXene-based gel fiber sensing element 1 includes one chamber 11, one substrate 12, four parallel-connected MXene-based gel fibers 13, and a pair of electrodes 14. The four parallel-connected MXene-based gel fibers 13 and the electrodes 14 are all provided on the substrate 12 and arranged inside the chamber 11. The pair of electrodes 14 are connected to the axial ends of the four parallel-connected MXene-based gel fibers 13, respectively. The wall of the chamber 11 is provided with a first gas inlet 111 and a first gas outlet 112.

[0075] The sealing cover 2 is an annular housing used to seal and cover the portion of the non-metallic tube to be detected. The sealing cover 2 is provided with a second gas outlet 21 and a second gas inlet 22.

[0076] The first gas conduit 3 has one end connected to the second gas outlet 21 and the other end connected to the first gas inlet 111.

[0077] The second gas conduit 4 has one end connected to the first gas outlet 112 and the other end connected to the second gas inlet 22.

[0078] The gas pump 5 is installed in the first gas conduit 3. In this embodiment, both electrodes 14 are copper electrodes.

[0079] In this embodiment, the sealing cover 2 includes an upper sealing cover 23 and a lower sealing cover 24. Both the upper sealing cover 23 and the lower sealing cover 24 have a semi-annular housing structure, and the upper sealing cover 23 and the lower sealing cover 24 are connected together to form a circular connection opening for the non-metallic pipe to pass through. A sealed annular space is then formed between the connected upper sealing cover 23 and lower sealing cover 24 and the outer wall of the portion of the non-metallic pipe to be detected.

[0080] 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.

[0081] In this embodiment, the first gas inlet 111 and the first gas outlet 112 are located at both ends of the MXene-based gel fiber 13 in the axial direction, respectively.

[0082] Figure 1 also shows a digital multimeter and a computer. The digital multimeter converts the gas change signal from the MXene-based gel fiber sensing element 1 into a resistance signal, measures the sensitivity of the gas sensor in this embodiment, inputs the converted signal to the computer, and can be used as a signal converter to realize real-time monitoring of the environmental gas and / or permeate gas in the non-metallic pipe.

[0083] In this embodiment, environmental gases and / or permeated gases in a polyethylene pipeline are monitored. In the actual application process, the MXene-based gel fiber sensing element 1 is placed on the ground near the polyethylene pipeline, and the permeation from the pipeline is introduced to the MXene-based gel fiber sensing element 1 via the first gas conduit 3. The resistance signal of the MXene-based gel fiber sensing element 1 changes as the gas content changes, allowing evaluation of the gas permeation status of the pipeline.

[0084] To measure the sensitivity of the gas sensor in this embodiment, H2S gas diluted with nitrogen gas was introduced into a polyethylene pipeline so that the H2S gas content in the pipeline was 100 ppm. The gas sensor of this embodiment detected the change in the H2S gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the H2S response value was obtained. Under similar conditions, CH4 gas diluted with nitrogen gas was introduced into a polyethylene pipeline so that the CH4 concentration in the pipeline was 600 ppm. The gas sensor of this embodiment detected the change in the CH4 gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the CH4 response value was obtained. The absolute values ​​of the H2S response value and CH4 response value measured in this embodiment are shown in Table 1.

[0085] [Table 1]

[0086] The raw material Ti3AlC2 used in this embodiment and the manufactured Ti3C2T x Scanning electron microscope images of MXene nanosheets are shown in Figure 2, where (a) in Figure 2 is a scanning electron microscope image of MAX phase Ti3AlC2, and (b) in Figure 2 is a scanning electron microscope image of Ti3C2T x This is a scanning electron microscope image of an MXene nanosheet. Figure 3 is a scanning electron microscope image of the cross-sectional pore structure of the pure MXene gel fiber produced in this embodiment.

[0087] Example 2 In this embodiment, a gas sensor for non-metallic pipes is provided, which includes MXene-based gel fibers, which are MXene / GO composite gel fibers manufactured by the low-temperature wet freezing technology of the present invention. The low-temperature wet freezing technology includes at least the following steps: Etching of Ti3AlC2 in a constant temperature water bath environment at 35°C using a mixed solution of LiF and HCl (obtained by dissolving 8g of LiF in 100mL of 9M HCl solution), ultrasonic peeling for approximately 40 hours, further ultrasonic peeling in a nitrogen atmosphere for approximately 1 hour, and finally centrifugation in a centrifuge at a rotation speed of 3500 rpm for 1 hour to obtain a single layer or a small layer of Ti3C2T x A mixture containing MXene nanosheets was obtained. Ti3C2T x MXene nanosheets were centrifuged at high speed and mixed with GO nanosheets by solvent displacement to prepare a dispersion in DMSO with a total concentration of MXene and GO of 100 mg / mL. Here, the mass ratio of MXene nanosheets to GO nanosheets was 3:7. This dispersion was used as the spinning solution, and the spinning solution was injected at a constant rate into a spinning conduit using an injection pump. The spinning conduit had a length of 0.5 m, an inner diameter of 0.80 mm, and an injection rate of 200 μL min. -1The spinning conduit is provided with a sleeve on its outer wall, and an appropriate gap should exist between the sleeve and the spinning conduit. The sleeve is made of copper. Liquid nitrogen is provided at the lower end of the sleeve, along the direction of the spinning fluid flow. In this way, the sleeve conducts cooling from bottom to top (i.e., in the opposite direction to the direction of the spinning fluid flow), causing the temperature of the sleeve to gradually decrease from top to bottom (i.e., in the direction of the spinning fluid flow). The spinning fluid was injected into a coagulation bath through the spinning conduit. The coagulation bath is a mixture of DMSO and acetic acid (where the volume ratio of DMSO to acetic acid is 1:1). The fibers formed in the coagulation bath were collected, washed twice by immersion with a mixture of ethanol and water (where the volume ratio of ethanol to water is 2:1), and then air-dried at room temperature for 0.5 days. The dried fibers were immersed in a mixture of ethanol and water (where the volume ratio of ethanol to water is 1:1) for 2 minutes to swell, and then the swollen fibers were placed in liquid nitrogen and frozen for 30 minutes. After that, they were dried in a freeze-dryer at -57°C for 3 days, and then dried in a vacuum oven at 60°C for 1 day to obtain MXene / GO composite gel fibers.

[0088] The non-metallic pipe gas sensor provided in this embodiment is an external gas sensor, and its structure is the same as that of Embodiment 1.

[0089] To measure the sensitivity of the gas sensor in this embodiment, H2S gas diluted with nitrogen gas was introduced into a polyethylene pipeline so that the H2S gas content in the pipeline was 100 ppm. The gas sensor of this embodiment detected the change in the H2S gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the H2S response value was obtained. Under similar conditions, CH4 gas diluted with nitrogen gas was introduced into a polyethylene pipeline so that the CH4 concentration in the pipeline was 600 ppm. The gas sensor of this embodiment detected the change in the CH4 gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the CH4 response value was obtained. The absolute values ​​of the H2S response value and CH4 response value measured in this embodiment are shown in Table 2.

[0090] [Table 2]

[0091] Figure 4 is a scanning electron microscope image of the cross-sectional pore structure of the MXene / GO composite gel fiber manufactured in this embodiment.

[0092] Example 3 In this embodiment, a gas sensor for non-metallic pipes is provided, which includes MXene-based gel fibers, which are MXene / alginate composite gel fibers produced by the low-temperature wet freezing technology of the present invention. The low-temperature wet freezing technology includes at least the following steps: Etching of Ti3AlC2 in a constant temperature water bath environment at 35°C using a mixed solution of LiF and HCl (obtained by dissolving 8g of LiF in 100mL of 9M HCl solution), ultrasonic peeling for approximately 40 hours, further ultrasonic peeling in a nitrogen atmosphere for approximately 1 hour, and finally centrifugation in a centrifuge at a rotation speed of 3500 rpm for 1 hour to obtain a single layer or a small layer of Ti3C2T x A mixture containing MXene nanosheets was obtained. Ti3C2T xA dispersion was prepared by mixing MXene nanosheets and sodium alginate, with a total concentration of MXene nanosheets and sodium alginate of 90 mg / mL in water as the solvent. Here, the mass ratio of MXene nanosheets to sodium alginate was 9:1. This dispersion was used as the spinning solution, and the spinning solution was injected at a constant rate into a spinning conduit using an injection pump. The spinning conduit had a length of 0.3 m, an inner diameter of 1.3 mm, and an injection rate of 260 μL min. -1 The spinning conduit is provided with a sleeve on its outer wall, and an appropriate gap should exist between the sleeve and the spinning conduit. The sleeve is made of copper. Liquid nitrogen is provided at the lower end of the sleeve, along the direction of the spinning fluid flow. In this way, the sleeve conducts cooling from bottom to top (i.e., in the opposite direction to the direction of the spinning fluid flow), causing the temperature of the sleeve to gradually decrease from top to bottom (i.e., in the direction of the spinning fluid flow). The spinning fluid was injected into a coagulation bath through the spinning conduit. The coagulation bath is an aqueous solution of ammonium chloride with a mass concentration of 1%. The fibers formed in the coagulation bath were collected, immersed and washed twice with a mixture of ethanol and water (where the volume ratio of ethanol to water is 2:1), and then air-dried at room temperature for one day. The dried fibers were immersed in a mixture of ethanol and water (where the volume ratio of ethanol to water is 1:1) for 3 minutes to swell, and then the swollen fibers were placed in liquid nitrogen and frozen for 40 minutes. After that, they were dried in a freeze-dryer at -45°C for 4 days, and then vacuum-dried at 70°C for 1 day to obtain MXene / alginate composite gel fibers.

[0093] The non-metallic pipe gas sensor provided in this embodiment is an external gas sensor, and its structure is the same as that of Embodiment 1.

[0094] To measure the sensitivity of the gas sensor in this embodiment, in this embodiment, NH3 gas diluted with nitrogen gas was introduced into a polyethylene pipeline so that the NH3 gas content in the pipeline was 700 ppm. The gas sensor of this embodiment detected the change in the NH3 gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the response value of NH3 was obtained. Under similar conditions, H2O gas diluted with nitrogen gas was introduced into a polyethylene pipeline so that the H2O concentration in the pipeline was 700 ppm. The gas sensor of this embodiment detected the change in the H2O gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the response value of H2O was obtained. The absolute values ​​of the H2S response value and CH4 response value measured in this embodiment are shown in Table 3.

[0095] [Table 3]

[0096] Example 4 In this example, a gas sensor for non-metallic pipes is provided, which contains MXene-based gel fibers, which are MXene / GO composite gel fibers manufactured by the low-temperature wet freezing technology of the present invention. The method for manufacturing the MXene / GO composite gel fibers is basically the same as in Example 2, but the differences are that the dispersion is a dispersion using DMF as the solvent with a total concentration of MXene and GO of 70 mg / mL (where the mass ratio of MXene nanosheets to GO nanosheets is 1:9), the spinning conduit is 0.8 m long and has an inner diameter of 0.50 mm, and the coagulation bath is a mixture of isopropyl alcohol and water (where the volume ratio of isopropyl alcohol to water is 3:1).

[0097] The non-metallic pipe gas sensor provided in this embodiment is an external gas sensor, and its structure is the same as that of Embodiment 1.

[0098] To measure the sensitivity of the gas sensor in this embodiment, CO2 gas diluted with nitrogen gas was introduced into a polyethylene pipeline so that the CO2 gas content in the pipeline was 500 ppm. The gas sensor of this embodiment detected the change in the CO2 gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the CO2 response value was obtained. Under similar conditions, CH4 gas diluted with nitrogen gas was introduced into a polyethylene pipeline so that the CH4 concentration in the pipeline was 500 ppm. The gas sensor of this embodiment detected the change in the CH4 gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the CH4 response value was obtained. The absolute values ​​of the H2S response value and CH4 response value measured in this embodiment are shown in Table 4.

[0099] [Table 4]

[0100] Example 5 In this embodiment, a gas sensor for non-metallic tubes is provided, which contains MXene-based gel fibers, which are MXene / GO composite gel fibers manufactured by the low-temperature wet freezing technology of the present invention. The method for manufacturing the MXene / GO composite gel fibers is basically the same as in Example 2, but the differences are that the dispersion is a dispersion using DMSO as the solvent with a total concentration of MXene and GO of 160 mg / mL (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.

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

[0102] To measure the sensitivity of the gas sensor in this embodiment, H2S gas diluted with nitrogen gas was introduced into the polyethylene pipeline so that the H2S gas content in the pipeline was 100 ppm. The gas sensor of this embodiment detected the change in the H2S gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the H2S response value was obtained. Under similar conditions, CH4 gas diluted with nitrogen gas was introduced into the polyethylene pipeline so that the CH4 concentration in the pipeline was 600 ppm. The gas sensor of this embodiment detected the change in the CH4 gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the CH4 response value was obtained. The absolute values ​​of the H2S response value and CH4 response value measured in this embodiment are shown in Table 5.

[0103] [Table 5]

[0104] Example 6 In this embodiment, a gas sensor for non-metallic pipes is provided, which contains MXene-based gel fibers, which are MXene / alginate composite gel fibers manufactured by the low-temperature wet freezing technology of the present invention. The method for manufacturing the MXene / alginate composite gel fibers is basically the same as in Example 3, but the differences are that the dispersion is a dispersion of water as the solvent with a total concentration of MXene nanosheets and sodium alginate of 150 mg / mL (where the mass ratio of MXene nanosheets to sodium alginate is 6:4), the spinning conduit is 0.4 m long and has an inner diameter of 0.6 mm, and the coagulation bath is an aqueous calcium chloride solution with a mass concentration of 1%.

[0105] The non-metallic pipe gas sensor provided in this embodiment is an external gas sensor, and its structure is the same as that of Embodiment 1.

[0106] To measure the sensitivity of the gas sensor in this embodiment, H2S gas diluted with nitrogen gas was introduced into the polyethylene pipeline so that the H2S gas content in the pipeline was 100 ppm. The gas sensor of this embodiment detected the change in the H2S gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the H2S response value was obtained. Under similar conditions, CH4 gas diluted with nitrogen gas was introduced into the polyethylene pipeline so that the CH4 concentration in the pipeline was 600 ppm. The gas sensor of this embodiment detected the change in the CH4 gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the CH4 response value was obtained. The absolute values ​​of the H2S response value and CH4 response value measured in this embodiment are shown in Table 6.

[0107] [Table 6]

[0108] Example 7 In this example, a gas sensor for non-metallic tubes is provided, which includes MXene-based gel fibers, which are MXene / alginate composite gel fibers manufactured by the low-temperature wet freezing technology of the present invention. The method for manufacturing the MXene / alginate composite gel fibers is basically the same as in Example 3, but the differences are that the dispersion is a water-based dispersion with a total concentration of MXene nanosheets and sodium alginate of 50 mg / mL (where the mass ratio of MXene nanosheets to sodium alginate is 1:9), the spinning conduit length is 1 m, the inner diameter is 0.6 mm, and the injection rate is 300 μL min -1 The coagulation bath must be a calcium chloride aqueous solution with a mass concentration of 1%.

[0109] The non-metallic pipe gas sensor provided in this embodiment is an external gas sensor, and its structure is the same as that of Embodiment 1.

[0110] To measure the sensitivity of the gas sensor in this embodiment, H2S gas diluted with nitrogen gas was introduced into the polyethylene pipeline so that the H2S gas content in the pipeline was 80 ppm. The gas sensor of this embodiment detected the change in the H2S gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the H2S response value was obtained. Under similar conditions, CH4 gas diluted with nitrogen gas was introduced into the polyethylene pipeline so that the CH4 concentration in the pipeline was 500 ppm. The gas sensor of this embodiment detected the change in the CH4 gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the CH4 response value was obtained. The absolute values ​​of the H2S response value and CH4 response value measured in this embodiment are shown in Table 7.

[0111] [Table 7]

[0112] Example 8 This embodiment provides a gas monitoring method that includes the following steps.

[0113] (1) Manufacturing of MXene-based gel fibers A dispersion containing MXene nanosheets was used as the spinning solution, and the spinning solution was injected into a spinning conduit having a sleeve on its outer wall. The temperature of the sleeve gradually decreased along the flow direction of the spinning solution. The spinning solution was injected into a coagulation bath through the spinning conduit. After collecting the fibers formed in the coagulation bath, the MXene-based gel fibers were obtained by at least swelling, freezing with liquid nitrogen, and freeze-drying.

[0114] (2) Assemble the gas sensor using the MXene-based gel fiber. Specifically, external gas sensors, wall-mounted gas sensors, or embedded gas sensors were assembled using the MXene-based gel fibers.

[0115] (3) By using the gas sensor to detect the ambient gas and / or permeate gas in the non-metallic pipe and transmitting the signal obtained by the gas sensor to a computer, real-time monitoring of the ambient gas and / or permeate gas in the non-metallic pipe is achieved. In this embodiment, the dispersion containing the MXene nanosheet 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 the MXene nanosheet 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 fibers are MXene gel fibers; when the dispersion is a dispersion of MXene nanosheets and GO nanosheets, the MXene-based gel fibers are MXene / GO composite gel fibers; and when the dispersion is a dispersion of MXene nanosheets and sodium alginate, the MXene-based gel fibers are MXene / alginate composite gel fibers.

[0116] In this embodiment, the MXene nanosheet is Ti3C2T x Contains MXene nanosheets. In this example, the MXene nanosheet was produced by treating the MAX phase with a mixed solution of LiF and HCl, followed by sonication, to obtain the MXene nanosheet. Here, the MAX phase used is preferably a titanium aluminum carbon compound (Ti3AlC2).

[0117] In this example, the concentration of MXene nanosheets in the dispersion of MXene nanosheets is 80 to 180 mg / mL, preferably 110 to 150 mg / mL.

[0118] In this embodiment, the solvent in the dispersion of the MXene nanosheets includes dimethyl sulfoxide (DMSO) and / or N,N-dimethylformamide (DMF).

[0119] In this example, the total concentration of MXene nanosheets and GO nanosheets in the dispersion of MXene nanosheets and GO nanosheets is 70 to 160 mg / mL, preferably 100 to 140 mg / mL, and the mass ratio of MXene nanosheets to GO nanosheets is 1:9 to 8:2. Preferably, the thickness of the GO nanosheets is 2 nm or less, and the diameter of the sheet layer in the lateral direction is 8 to 80 μm.

[0120] 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.

[0121] In this embodiment, the length of the spinning conduit is 0.3 to 1 m, and the inner diameter is 0.30 to 1.3 mm. In this embodiment, the sleeve provided on the outer wall of the spinning conduit is a metal tube. The gradual decrease in the temperature of the sleeve along the flow direction of the spinning fluid is achieved by installing a cooling source at one end of the sleeve and conducting the amount of cooling through the sleeve in the direction opposite to the flow direction of the spinning fluid, thereby causing the temperature to gradually decrease along the flow direction of the spinning fluid. Specifically, the sleeve may be a copper tube. Furthermore, those skilled in the art will understand that an appropriate gap should exist between the sleeve and the spinning conduit to prevent the spinning fluid from freezing and solidifying and becoming unable to flow.

[0122] In this embodiment, the temperature of the cooling source installed at one end of the sleeve is between -200°C and -100°C. Specifically, the cooling source may be liquid nitrogen (-196°C).

[0123] In this embodiment, the coagulation bath contains one or more combinations of ammonium chloride aqueous solution, calcium chloride aqueous solution, aluminum chloride aqueous solution, ammonia water, isopropyl alcohol, ethyl acetate, acetone, dimethyl sulfoxide, acetic acid, n-hexane, dichloromethane, a mixture of dimethyl sulfoxide and acetic acid, and a mixture of isopropyl alcohol and water. Preferably, when the dispersion containing the MXene nanosheet is a dimethyl sulfoxide dispersion of the MXene nanosheet, or a dimethyl sulfoxide dispersion of the MXene nanosheet and GO nanosheet, the coagulation bath is a mixture of dimethyl sulfoxide and acetic acid, and more preferably, the volume ratio of dimethyl sulfoxide to acetic acid in the mixture is 1:3 to 3:1. When the dispersion containing the MXene nanosheet is an N,N-dimethylformamide dispersion of the MXene nanosheet, or an N,N-dimethylformamide dispersion of the MXene nanosheet and GO nanosheet, the coagulation bath is a mixture of isopropyl alcohol and water, and more preferably, the volume ratio of isopropyl alcohol to water in the mixture is 1:2 to 3:1. When the dispersion containing the MXene nanosheet is an aqueous dispersion of the MXene nanosheet and sodium alginate, the coagulation bath is an aqueous solution of ammonium chloride or an aqueous solution of calcium chloride, with a mass concentration of 0.5 to 1%.

[0124] In this example, the fibers formed in the coagulation bath were collected, washed, air-dried, swollen, frozen in liquid nitrogen, freeze-dried, and then vacuum-dried to obtain the MXene-based gel fibers.

[0125] In this example, the fibers formed in the coagulation bath were collected and then washed with a mixture of ethanol and water. Preferably, the volume ratio of ethanol to water in the mixture was 1:3 to 3:1, and more preferably 2:1.

[0126] In this example, the time for collecting and washing the fibers formed in the coagulation bath and then allowing them to air dry is 0.5 to 1 day.

[0127] In this embodiment, a mixture of alcohol and water is used in the swelling process, preferably a mixture of ethanol and water, and the volume ratio of ethanol to water in the mixture is 3:4 to 1:3, preferably 1:1.

[0128] In this example, the time for immersing the dried fibers in a mixture of alcohol and water to swell them is 2 to 5 minutes.

[0129] In this example, the time for freezing the swollen fibers in liquid nitrogen is 30 to 60 minutes. In this embodiment, the freeze-drying temperature is between -45°C and -60°C. The freeze-drying can be carried out under vacuum conditions. Preferably, the freeze-drying time is 2 to 4 days.

[0130] In this embodiment, the vacuum drying temperature is 40 to 70°C. Preferably, the vacuum drying time is 0.5 to 2 days.

[0131] In this embodiment, an external gas sensor was assembled using the MXene-based gel fibers. Step (2) specifically includes: placing a plurality of the MXene-based gel fibers and a pair of electrodes in one chamber, with the pair of electrodes each installed at both axial ends of the plurality of the MXene-based gel fibers, and providing a first gas inlet and a first gas outlet in the wall of the chamber to obtain an MXene-based gel fiber sensing element; covering the portion of a non-metallic tube to be detected with a sealing cover, wherein the sealing cover is an annular housing and is provided with a second gas outlet and a second gas inlet; connecting the second gas outlet and the first gas inlet with a first gas conduit; and connecting the first gas outlet and the second gas inlet with a second gas conduit to obtain the gas sensor.

[0132] In this embodiment, the number of MXene-based gel fibers is 2 to 10, preferably 3 to 6. The MXene-based gel fibers are arranged in parallel within the chamber.

[0133] In this embodiment, the electrode includes one of the following: a copper electrode, a silver electrode, a gold electrode, a platinum electrode, a titanium electrode, a nickel electrode, or an aluminum electrode.

[0134] In this embodiment, the sealing cover includes an upper sealing cover and a lower sealing cover. Both the upper and lower sealing covers have a semi-annular housing structure, and the upper and lower sealing covers are connected together to form a circular connection port for penetrating a non-metallic pipe, and a sealed annular space is formed between the connected upper and lower sealing covers and the outer wall of the portion of the non-metallic pipe to be detected.

[0135] In this embodiment, the second gas outlet is provided in the upper sealing cover, and the second gas inlet is provided in the lower sealing cover.

[0136] In this embodiment, the first gas inlet and the first gas outlet are located at both ends of the MXene-based gel fiber in the axial direction, respectively.

[0137] In this embodiment, a gas pump is provided in the first gas conduit. In this embodiment, the non-metallic pipes include one or more types of pipes, such as oil field pipes, gas pipes, and drainage pipes.

[0138] In this embodiment, the gas detected by the gas sensor includes one or a combination of several gases such as CO2, NH3, CH4, H2S, H2O, and H2.

[0139] Comparative Example 1 This comparative example provides a gas sensor for non-metallic pipes containing MXene-based gel fibers, which are pure MXene gel fibers manufactured by conventional wet spinning technology. The manufacturing method of the pure MXene gel fibers in this comparative example includes the following steps: Etching of Ti3AlC2 in a constant temperature water bath environment at 35°C using a mixed solution of LiF and HCl (obtained by dissolving 8g of LiF in 100mL of 9M HCl solution), after about 40 hours, ultrasonic exfoliation in a nitrogen atmosphere for about 1 hour, and finally centrifugation in a centrifuge at a rotation speed of 3500 rpm for 1 hour to obtain a single layer or a small layer of Ti3C2T x A mixture containing MXene nanosheets was obtained. Ti3C2T x MXene nanosheets were centrifuged at high speed, and a 120 mg / mL dispersion was prepared using DMSO as the solvent by solvent displacement. This dispersion was used as the spinning solution, and the spinning solution was injected at a constant rate into the coagulation bath using an injection pump. The injection rate was 200 μL min. -1 The coagulation bath is a mixture of DMSO and acetic acid (where the volume ratio of DMSO to acetic acid is 1:1). The fibers formed in the coagulation bath were collected, washed twice by immersion with a mixture of ethanol and water (where the volume ratio of ethanol to water is 2:1), and then air-dried at room temperature for one day to obtain pure MXene gel fibers.

[0140] The non-metallic pipe gas sensor provided in this comparative example is an external gas sensor, and its structure is the same as that of Example 1.

[0141] To measure the sensitivity of the gas sensor in this comparative example, H2S gas diluted with nitrogen gas was introduced into the polyethylene pipeline so that the H2S gas content in the pipeline was 100 ppm. The gas sensor of this comparative example detected the change in the H2S gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the H2S response value was obtained. Under similar conditions, CH4 gas diluted with nitrogen gas was introduced into the polyethylene pipeline so that the CH4 concentration in the pipeline was 600 ppm. The gas sensor of this comparative example detected the change in the CH4 gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the CH4 response value was obtained. The absolute values ​​of the H2S response value and CH4 response value measured in this comparative example are shown in Table 8.

[0142] [Table 8]

[0143] Figure 5 is a scanning electron microscope image of the cross-sectional pore structure of the pure MXene gel fibers produced in this comparative example.

[0144] Comparative Example 2 This comparative example provides a gas sensor for non-metallic pipes containing MXene-based gel fibers, which are MXene / GO composite gel fibers manufactured by conventional wet spinning technology. The manufacturing method of the MXene / GO composite gel fibers in this comparative example includes the following steps: Etching of Ti3AlC2 in a constant temperature water bath environment at 35°C using a mixed solution of LiF and HCl (obtained by dissolving 8g of LiF in 100mL of 9M HCl solution) for approximately 40 hours, ultrasonic exfoliation for approximately 1 hour in a nitrogen atmosphere, and finally centrifugation at a rotation speed of 3500 rpm for 1 hour to obtain a single layer or a small layer of Ti3C2T x A mixture containing MXene nanosheets was obtained. Ti3C2T xMXene nanosheets were centrifuged at high speed and mixed with GO nanosheets by solvent displacement to prepare a dispersion in DMSO with a total concentration of MXene and GO of 100 mg / mL. Here, the mass ratio of MXene nanosheets to GO nanosheets was 3:7. This dispersion was used as the spinning solution, and the spinning solution was injected at a constant rate into the coagulation bath using an injection pump. The injection rate was 200 μL min. -1 The coagulation bath is a mixture of DMSO and acetic acid (where the volume ratio of DMSO to acetic acid is 1:1). The fibers formed in the coagulation bath are collected, washed twice by immersion with a mixture of ethanol and water (where the volume ratio of ethanol to water is 2:1), and then air-dried at room temperature for one day to obtain MXene / GO composite gel fibers.

[0145] The non-metallic pipe gas sensor provided in this comparative example is an external gas sensor, and its structure is the same as that of Example 1.

[0146] To measure the sensitivity of the gas sensor in this comparative example, H2S gas diluted with nitrogen gas was introduced into the polyethylene pipeline so that the H2S gas content in the pipeline was 100 ppm. The gas sensor of this comparative example detected the change in the H2S gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the H2S response value was obtained. Under similar conditions, CH4 gas diluted with nitrogen gas was introduced into the polyethylene pipeline so that the CH4 concentration in the pipeline was 600 ppm. The gas sensor of this comparative example detected the change in the CH4 gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the CH4 response value was obtained. The absolute values ​​of the H2S response value and CH4 response value measured in this comparative example are shown in Table 9.

[0147] [Table 9]

[0148] Figure 6 is a scanning electron microscope image of the cross-sectional pore structure of the MXene / GO composite gel fiber produced in this comparative example.

[0149] Comparative Example 3 This comparative example provides a gas sensor for non-metallic pipes containing MXene-based gel fibers, which are MXene / GO composite gel fibers manufactured by the low-temperature wet freezing technology of the present invention. The method for manufacturing the MXene / GO composite gel fibers in this comparative example is basically the same as in Example 2, except that the solvent in the dispersion of MXene nanosheets and GO nanosheets in this comparative example is water, and the coagulation bath is an aqueous solution of ammonium chloride with a mass concentration of 1%, while all other steps are the same as in Example 2.

[0150] The non-metallic pipe gas sensor provided in this comparative example is an external gas sensor, and its structure is the same as that of Example 1.

[0151] To measure the sensitivity of the gas sensor in this comparative example, H2S gas diluted with nitrogen gas was introduced into the polyethylene pipeline so that the H2S gas content in the pipeline was 100 ppm. The gas sensor of this comparative example detected the change in the H2S gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the H2S response value was obtained. Under similar conditions, CH4 gas diluted with nitrogen gas was introduced into the polyethylene pipeline so that the CH4 concentration in the pipeline was 600 ppm. The gas sensor of this comparative example detected the change in the CH4 gas content that permeated the pipeline, and the change in resistance of the MXene-based gel fiber sensing element 1 was detected using a digital multimeter, and the CH4 response value was obtained. The absolute values ​​of the H2S response value and CH4 response value measured in this comparative example are shown in Table 10.

[0152] [Table 10]

[0153] As can be seen from the comparison of scanning electron microscope images (Figures 3 and 5) of the pure MXene gel fibers produced in Example 1 and Comparative Example 1, and the comparison of scanning electron microscope images (Figures 4 and 6) of the MXene / GO composite gel fibers produced in Example 2 and Comparative Example 2, in the present invention, the MXene-based gel fibers produced by the low-temperature wet freezing technology have a significantly strengthened gel structure, enhanced porosity, and a larger specific surface area compared to MXene-based gel fibers produced by conventional wet spinning technology. As can be seen from the comparison of the absolute values ​​of the H2S response and CH4 response values ​​(Tables 1 and 8) of Example 1 and Comparative Example 1, and the absolute values ​​of the H2S response and CH4 response values ​​(Tables 2 and 9) of Example 2 and Comparative Example 2, in the present invention, the MXene-based gel fibers produced by the low-temperature wet freezing technology have a clearly improved response value to H2S and CH4 gases compared to MXene-based gel fibers produced by conventional wet spinning technology, thus having higher gas response sensitivity and being able to detect low-concentration gases.

[0154] As can be seen from the comparative data of the MXene / GO composite gel fibers produced in Example 2 and Comparative Example 3 (Tables 2 and 10), in the present invention, the MXene / GO inorganic nanomaterial spinning solution is dispersed in an organic solvent such as DMSO, and a mixture of dimethyl sulfoxide and acetic acid is used as a coagulation bath. By coagulating in such a weak coagulation bath, the fibers are more easily formed into a porous structure. As a result, the MXene / GO composite gel fibers produced in the present invention show a clear improvement in response values ​​to H2S and CH4 gases compared to MXene / GO composite gel fibers produced by ion coagulation bath using water as the solvent.

[0155] As can be seen from the comparison between Example 2 and Example 1, the MXene / GO composite gel fiber of the present invention has higher gas response sensitivity compared to pure MXene gel fiber. GO enhances the mechanical performance of the MXene-based gel fiber and contributes to the gelation of the fiber, resulting in a stronger porous structure. Furthermore, GO itself is gas-responsive, creating a synergistic effect between MXene and GO, which significantly improves the gas response sensitivity of the MXene / GO composite gel fiber of the present invention.

[0156] As described above, the gas sensor of the present invention has high sensitivity, can detect low concentrations of gas, and exhibits strong stability in gas detection, making it applicable in fields such as oil transport, gas transport, and wastewater treatment, and enabling real-time monitoring of environmental gases and / or permeate gases in non-metallic pipes. [Explanation of symbols]

[0157] 1. MXene-based gel fiber sensing element; 2. Sealing cover; 3. First gas conduit; 4. Second gas conduit; 5. Gas pump; 11-Chamber; 12-Substrate; 13-MXene-based gel fiber; 14-Electrode; 111-First gas inlet; 112-First gas outlet; 21 - Second gas outlet; 22 - Second gas inlet; 23 - Upper sealing cover; 24 - Lower sealing cover.

Claims

1. The process involves using a dispersion containing MXene nanosheets as the spinning solution, and injecting the spinning solution into a spinning conduit having a sleeve on its outer wall (the temperature of the sleeve gradually decreases along the flow direction of the spinning solution), The steps include: injecting the spinning solution into the coagulation bath via the spinning conduit; The steps include collecting the fibers formed in the coagulation bath, and then obtaining MXene-based gel fibers by at least swelling, freezing with liquid nitrogen, and freeze-drying, The steps include assembling a gas sensor using the MXene-based gel fiber to obtain a gas sensor for non-metallic pipes, A method for manufacturing a gas sensor for non-metallic pipes, including the method described above.

2. The method for manufacturing a gas sensor for non-metallic pipes according to claim 1, wherein the dispersion containing the MXene nanosheet includes a dispersion of MXene nanosheets, a dispersion of MXene nanosheets and GO nanosheets, or a dispersion of MXene nanosheets and sodium alginate.

3. The aforementioned MXene nanosheet is made of Ti 3 C 2 T x A method for manufacturing a gas sensor for a non-metallic pipe according to claim 1, comprising an MXene nanosheet.

4. The method for manufacturing a gas sensor for non-metallic pipes according to claim 2, wherein the concentration of MXene nanosheets in the dispersion of MXene nanosheets is 80 to 180 mg / mL.

5. The method for manufacturing a gas sensor for non-metallic pipes according to claim 2, wherein the total concentration of MXene nanosheets and GO nanosheets in the dispersion of MXene nanosheets and GO nanosheets is 70 to 160 mg / mL, and the mass ratio of MXene nanosheets to GO nanosheets is 1:9 to 8:

2.

6. The method for manufacturing a gas sensor for non-metallic pipes 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.

7. The method for manufacturing a gas sensor for a non-metallic tube according to claim 1, wherein the spinning conduit has a length of 0.3 to 1 m and an inner diameter of 0.30 to 1.3 mm.

8. The method for manufacturing a gas sensor for a non-metallic tube according to claim 1, wherein the sleeve provided on the outer wall of the spinning conduit is a metal tube, and the gradual decrease in the temperature of the sleeve along the flow direction of the spinning fluid is achieved by installing a cooling source at one end of the sleeve that conducts a cooling amount in the opposite direction to the flow direction of the spinning fluid through the sleeve, such that the temperature of the cooling source is between -200°C and -100°C.

9. The method for manufacturing a gas sensor for non-metallic pipes according to claim 1, wherein the solidification bath comprises one or more combinations of ammonium chloride aqueous solution, calcium chloride aqueous solution, aluminum chloride aqueous solution, ammonia water, isopropyl alcohol, ethyl acetate, acetone, acetic acid, n-hexane, dichloromethane, a mixture of dimethyl sulfoxide and acetic acid, and a mixture of isopropyl alcohol and water.

10. When the dispersion containing the MXene nanosheet is a dimethyl sulfoxide dispersion of the MXene nanosheet, or a dimethyl sulfoxide dispersion of the MXene nanosheet and the GO nanosheet, the coagulation bath is a mixture of dimethyl sulfoxide and acetic acid. When the dispersion containing the MXene nanosheet is an N,N-dimethylformamide dispersion of the MXene nanosheet, or an N,N-dimethylformamide dispersion of the MXene nanosheet and the GO nanosheet, the coagulation bath is a mixture of isopropyl alcohol and water. The method for manufacturing a gas sensor for non-metallic pipes according to claim 9, wherein the dispersion containing the MXene nanosheet is an aqueous dispersion of the MXene nanosheet and sodium alginate, and the coagulation bath is an aqueous solution of ammonium chloride or an aqueous solution of calcium chloride, with a concentration of 0.5 to 1% by mass.

11. A gas sensor for non-metallic pipes manufactured by the method for manufacturing a gas sensor for non-metallic pipes according to any one of claims 1 to 10, wherein the gas sensor for non-metallic pipes contains MXene-based gel fibers.

12. The aforementioned non-metallic pipe gas sensor includes an external gas sensor, a wall-mounted gas sensor, or a built-in gas sensor. The gas sensor for a non-metallic pipe according to claim 11, wherein the external gas sensor is provided on the outside of the non-metallic pipe, the wall-mounted gas sensor is bonded to the outer wall of the non-metallic pipe, and the embedded gas sensor is provided between layers inside the non-metallic pipe.

13. The non-metallic pipe gas sensor according to claim 12, wherein the non-metallic pipe gas sensor is an external gas sensor.

14. The external gas sensor includes an MXene-based gel fiber sensing element, a sealing cover, a first gas conduit, and a second gas conduit. The MXene-based gel fiber sensing element includes one chamber, one substrate, a plurality of the MXene-based gel fibers, and a pair of electrodes, wherein the plurality of the MXene-based gel fibers and the electrodes are all provided on the substrate and arranged within the chamber, the pair of electrodes are connected to the axial ends of the plurality of the MXene-based gel fibers, and the wall of the chamber is provided with a first gas inlet and a first gas outlet. The sealing cover is an annular housing used to seal and cover the portion of the non-metallic tube to be detected, and the sealing cover is provided with a second gas outlet and a second gas inlet. The gas sensor for non-metallic pipes according to claim 13, wherein one end of the first gas conduit is connected to the second gas outlet and the other end is connected to the first gas inlet, and one end of the second gas conduit is connected to the first gas outlet and the other end is connected to the second gas inlet.

15. The gas sensor for non-metallic pipes according to claim 14, wherein the MXene-based gel fiber sensing element includes 2 to 10 MXene-based gel fibers connected in parallel.

16. The nonmetallic pipe gas sensor according to claim 14, wherein the sealing cover includes an upper sealing cover and a lower sealing cover, both of which have a semi-annular housing structure, the upper sealing cover and the lower sealing cover are connected together to form a circular connection port for penetrating a nonmetallic pipe, and a sealed annular space is formed between the connected upper sealing cover and the lower sealing cover and the outer wall of the portion of the nonmetallic pipe to be detected.

17. The gas sensor for non-metallic pipes according to claim 16, wherein the upper sealing cover is provided with the second gas outlet, and the lower sealing cover is provided with the second gas inlet.

18. The gas sensor for non-metallic pipes according to claim 14, wherein the first gas inlet and the first gas outlet are located at both ends in the axial direction of the MXene-based gel fiber, respectively.

19. The wall-mounted gas sensor includes at least an 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 electrodes, the plurality of the MXene-based gel fibers and the electrodes are all provided on the substrate, the electrodes are provided at both axial ends of the plurality of the MXene-based gel fibers, and the plurality of the MXene-based gel fibers and the electrodes are bonded to the outer wall of a non-metallic pipe, as described in claim 12.

20. The embedded gas sensor includes an 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 electrodes, the plurality of the MXene-based gel fibers and the electrodes are all provided on the substrate, the electrodes are provided at both ends in the axial direction of the plurality of the MXene-based gel fibers, and the plurality of the MXene-based gel fibers and the electrodes are bonded to the outer surface of the barrier layer inside the non-metallic pipe, as described in claim 12.

21. (1) A step to manufacture MXene-based gel fibers, (2) The step of assembling a gas sensor using the MXene-based gel fiber, (3) The steps of detecting the ambient gas and / or permeate gas of the non-metallic pipe using the gas sensor and transmitting the signal obtained by the gas sensor to a computer to realize real-time monitoring of the ambient gas and / or permeate gas of the non-metallic pipe, A gas monitoring method, including the following.

22. The gas monitoring method according to claim 21, comprising step (1) using a dispersion containing MXene nanosheets as a spinning solution, injecting the spinning solution into a spinning conduit having a sleeve on its outer wall (the temperature of the sleeve gradually decreases along the flow direction of the spinning solution), injecting the spinning solution into a coagulation bath via the spinning conduit, and collecting the fibers formed in the coagulation bath, and then obtaining the MXene-based gel fibers by at least swelling, freezing with liquid nitrogen and freeze-drying.

23. Step (2) comprises assembling an external gas sensor, a wall-mounted gas sensor, or an embedded gas sensor using the MXene-based gel fibers, the gas monitoring method according to claim 21.

24. The gas monitoring method according to claim 21, wherein the non-metallic pipe includes one or more types of oil field pipes, gas pipes, and drainage pipes.

25. The gas detected by the gas sensor is CO 2 , NH 3 , CH 4 , H 2 S, H 2 O and H 2 The gas monitoring method according to claim 21, comprising one or a combination of plural kinds among them.

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