A hydrogen sensor based on modified polyimide fiber weaving and a preparation method thereof

Abstract

The application relates to the technical field of hydrogen gas sensors, and particularly discloses a hydrogen sensor based on modified polyimide fiber spinning and a preparation method thereof, which comprises a base cloth, the base cloth is formed by spinning mixed fiber yarn and non-conductive fiber, the mixed fiber yarn comprises modified polyimide fiber, and the preparation method of the modified polyimide fiber comprises the following steps: A1 taking fiber silk, soaking the fiber silk in a polyimide precursor solution, then sequentially performing heat curing treatment, UV modification treatment, and then performing heat treatment to obtain polyimide fiber silk; and A2 adopting an evaporation process to deposit a palladium film with a thickness of 10-200 nm on the surface of the polyimide fiber silk to obtain modified polyimide fiber. The polyimide fiber is used as an initial raw material, the polyimide fiber is modified, copper wires and non-conductive fibers are introduced, and specific position arrangement and weft and warp spinning are performed, so that an arrayed hydrogen gas sensor with the characteristics of flexibility and free curved surface can be formed.

Description

Technical Field

[0001] This invention relates to the field of hydrogen sensor technology, and more specifically, to a hydrogen sensor based on modified polyimide fiber textiles and its preparation method. Background Technology

[0002] Hydrogen is an important industrial raw material, widely used in chemical, electronics, metallurgy, food, aerospace, and other industrial and scientific research fields. In recent years, significant progress has been made in hydrogen energy development and utilization technologies, represented by photocatalytic water splitting and hydrogen fuel cells. The widespread adoption of hydrogen fuel cell vehicles and portable devices has led to a surge in demand for hydrogen storage. However, the development of hydrogen sensing technology lags behind, significantly hindering the popularization of hydrogen energy. Hydrogen sensing technology is mainly applied to hydrogen sensors, which require high sensitivity, short response time, high selectivity, high stability, miniaturization, low power consumption, and low cost in practical applications.

[0003] For example, patent CN116660330A discloses a flexible wearable hydrogen peroxide sensor based on silk fiber and its construction method. A certain amount of degummed silk fiber bundles are activated, and then, under light-shielded conditions, the activated silk fiber bundles are successively irradiated with ultraviolet light of different powers in a photosensitizer to obtain silk fiber bundles with in-situ Prussian blue deposition. This in-situ deposition is repeated multiple times to obtain controllable multilayer PB-deposited silk fibers. The PB@ASF fibers are then fixed on a working electrode to obtain a PB@ASF fiber sensor. This fiber sensor is combined with traditional textiles to process PB@ASF strands, strips, and flexible sensing fabrics, resulting in a hydrogen sensor that exhibits significant responsiveness to hydrogen peroxide, ultra-high sensitivity at low concentrations, and high wash resistance.

[0004] However, most existing hydrogen sensors, such as those mentioned above, are unable to achieve large-scale real-time monitoring of leaks in hydrogen transmission pipelines and hydrogen transport tanks, resulting in an inability to promptly and accurately detect abnormal situations such as hydrogen leaks. Summary of the Invention

[0005] The purpose of this invention is to solve the problem that existing hydrogen sensors are unable to achieve large-scale real-time monitoring of leaks in hydrogen transmission pipelines and hydrogen transport tanks.

[0006] This invention is achieved through the following technical solution:

[0007] This invention provides a hydrogen sensor based on modified polyimide fiber textiles, comprising a base fabric made by weaving a mixture of fiber yarns and non-conductive fibers.

[0008] The method for preparing the hydrogen sensor based on modified polyimide fiber textile provided by the present invention includes the following steps:

[0009] (1) First, take carbon fiber filaments, polish them smooth with Cu, Ag, Al, etc. to obtain conductive fibers, then wash away the oxide layer with dilute hydrochloric acid, wash with water, acetone and ethanol in sequence to remove acid, and then blow dry with nitrogen to obtain the treated fiber filaments; immerse the treated fiber filaments in 8-20% mass concentration polyimide precursor solution for about 10 minutes to make the surface of the fiber filaments uniformly coated with a layer of polyimide; then perform heat curing treatment at a high temperature of about 200-350℃ for about 30 minutes, and then perform UV modification. Use dual-wavelength simultaneous irradiation mode, select 185nm wavelength ultraviolet light for irradiation, and the UV modification photoexcitation intensity is 180mJ / cm 2 The process involves directly breaking the low-energy CN and CC bonds in the PI molecular chain; 254nm assisted oxidation causes the broken molecular chain to form volatile polar fragments. Both methods synergistically improve etching efficiency, allowing for targeted chain breakage. Irradiation time of 10-15 min allows for precise control of the subsequent groove depth to 5-10 nm. Then, heat treatment is performed in a high-purity nitrogen atmosphere (N2 purity ≥99.999%), with the gas flow rate controlled at 50-80 sccm and the heating rate at 3-5℃ / min, holding at 220-250℃ for 30-60 min. This evaporates and removes the broken small molecules while preventing localized oxidation of the copper core and coating cracking. Finally, the material is naturally cooled to room temperature to avoid rapid cooling that could cause surface structure collapse, resulting in grooves with a depth of 5-10 nm on the surface, yielding polyimide fiber filaments.

[0010] (2) Fix the polyimide fiber filaments onto a rotatable carrier in the vacuum chamber and evacuate to 10°C. -5 Up to 10 -6 Pa is used to remove air impurities; then, using an electron beam evaporation source, palladium (Pd) raw material is loaded and heated to above 1554℃ to evaporate it into gaseous atoms or molecules. The evaporation rate is adjusted to 0.05-0.2 nm / s, the substrate temperature is maintained at 80-150℃, and the rotation speed of the polyimide fiber on the carrier is controlled at 5-10 rpm for palladium deposition, depositing a palladium film with a thickness of 10-200 nm. Pd undergoes a hydrogenation reaction under the action of hydrogen, causing the palladium film to expand in volume, and the fibers come into contact with each other, reducing the resistance and giving it semiconductor properties. After deposition, a vacuum environment is maintained, and the mixture is cooled to room temperature. Finally, it is annealed at 150-200℃ for 20-40 min under a nitrogen atmosphere to obtain modified polyimide fibers, such as... Figure 1 The figure shown is a schematic diagram of the cross-sectional structure of polyimide fibers with Pd uniformly covered on the surface in this invention.

[0011] (3) Select copper wire with a diameter of 8-15μm, install it and modified polyimide fiber monofilament on the pay-off frame of the twisting machine, and ensure smooth unwinding so that the fiber passes through the precision tensioner and yarn guide device, and adjust and maintain the tension at a constant and uniform value to ensure that the yarn structure is uniform and defect-free. Converge multiple fibers at one point and twist them through a high-speed rotating spindle. The twist is precisely controlled by the ratio of spindle speed and traction speed. Heat treat the twisted yarn at a specific temperature and tension to permanently lock the twist structure, prevent untwisting, improve the yarn dimensional stability and mechanical properties, and transform the high-performance modified polyimide fiber monofilament into a structurally stable and strong mixed fiber yarn. The mixed fiber yarn is twisted by mixing copper wire with modified polyimide fiber monofilament and used as a signal transmission line on the base fabric.

[0012] A hydrogen sensor is obtained by taking mixed fiber yarns and non-conductive fibers and performing fiber spinning using a plain weave spinning process.

[0013] The 8-15μm copper wire selected in this invention has excellent flexibility, which can be smoothly woven with modified polyimide fibers to form a stable and soft sensing fabric. The resistance is low enough to effectively transmit the Pd resistance change signal with minimal self-noise. Moreover, copper wire products of this diameter are mature, easy to obtain and process.

[0014] Specifically, in fiber spinning, various methods can be used to blend and spin mixed fiber yarns with non-conductive fibers.

[0015] For example: Figure 2 As shown, multiple mixed fiber yarns and non-conductive fibers are used, with the mixed fiber yarns as wefts and the non-conductive fibers as warp yarns, to perform warp and weft weaving. After weaving, the weft yarns corresponding to the non-conductive fibers are cut to form transversely independent response unit structures, thus obtaining a hydrogen sensor.

[0016] For example: Figure 3 As shown, mixed fiber yarns are used as warp yarns, and a non-conductive fiber is added after every two mixed fiber yarns in the warp yarns to form a warp and weft weaving. Then, the transverse mixed fiber yarns in front of each non-conductive fiber are cut to form an independent sensing area. At the beginning and end of every two warp mixed fiber yarns, signal transmission lines are formed by screen printing with silver paste or copper powder for electrical signal transmission.

[0017] For example: Figure 4As shown, two mixed fiber yarns are first used for warp and weft weaving; a non-conductive fiber is used as the third warp, and copper or silver fiber is used to form an array unit; then three mixed fiber yarns and one non-conductive fiber are added as warp, and one copper or silver fiber is used as weft, forming a 3×3 signal sensing area. This process is repeated to obtain a sensing area of ​​sufficient size. To ensure the formation and stability of the above arrangement structure, flexible flat cable (FFC) or FPC connectors can be used on the signal transmission line to lead to the detection circuit.

[0018] The technical solution of the present invention has the following beneficial effects:

[0019] The hydrogen sensor proposed in this invention, based on modified polyimide fiber textiles, loads palladium material sensitive to hydrogen onto polyimide fiber yarns through a special process. The modified yarns are then processed into an array of hydrogen sensors, which combine flexibility and freeform surface characteristics. The arraying of sensitive materials is achieved through textile technology, breaking through the limitations of the rigid structure of traditional sensors. It can be widely used for leakage monitoring in large-scale devices such as hydrogen storage and hydrogen transportation pipelines, and has advantages such as high sensitivity, fast response, and customizable structure. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the cross-sectional structure of polyimide fibers with Pd uniformly covered on the surface in this invention.

[0021] Figure 2 This is a top view of the hydrogen sensor in Example 1;

[0022] Figure 3 This is a top view of the hydrogen sensor in Example 2;

[0023] Figure 4 This is a top view of the hydrogen sensor in Example 3;

[0024] Figure 5 This is a schematic diagram of the structure of the multi-twist modified polyimide fiber in this invention. Figure 5 (Left) is a schematic cross-sectional view of the modified polyimide fiber after twisting. Figure 5 (Right) is a side view of the modified polyimide fiber after it has been wound into a spiral fiber. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, they are performed according to conventional conditions or conditions recommended by the manufacturer; where the manufacturers of the instruments, equipment, reagents, or raw materials used are not specified, they are all conventional products that can be purchased commercially.

[0026] In the specific manufacturing process, the upper and lower base fabrics are positioned opposite each other, and the signal transmission lines and fluff tufts are symmetrically positioned to them. The specific dimensions and arrangement of the signal transmission lines and fluff tufts need to be calculated and controlled according to the following standards.

[0027] like Figure 5 As shown, where Figure 5 (Left) is a schematic cross-sectional view of the modified polyimide fiber after twisting. The modified polyimide fiber with a diameter of D1 and loaded with Pd is shown in the diagram. Figure 5 The fibers are tightly packed together in a twisted manner as shown on the left, where the area within the red triangle is designated as S1, and the area occupied by the fibers within this area is designated as S2.

[0028] (1);

[0029] (2);

[0030] (3);

[0031] The lateral area S3 of a single fiber per unit length is (4);

[0032] S3 is the lateral surface area of ​​a single fiber, which reflects the effective area of ​​a single fiber filament that can adsorb hydrogen gas before spinning.

[0033] A single fiber is wound at an angle θ into a helical fiber with a diameter of D2 and a twisted length of L1, such as... Figure 5 (Right) is a side view of the modified polyimide fiber wound into a spiral fiber. The height h of one winding and the required fiber length L2 are as follows:

[0034] (5);

[0035] (6);

[0036] The required total fiber length L3 is (7);

[0037] If the total number of fibers used for twisting is n, then the total area S4 occupied by the fibers is (8);

[0038] The cross-sectional area S5 of the twist is (9);

[0039] but (10) or (11).

[0040] Ignoring the area at both ends of the fiber, the effective area for hydrogen adsorption on a twisted thread is:

[0041] (12).

[0042] If a detection unit is woven from N of the above-mentioned twisted threads into a warp and weft structure, then the area S7 occupied by the detection unit can be obtained as follows: (13);

[0043] The effective area S of the detection unit per unit area that can adsorb hydrogen gas is:

[0044] (14).

[0045] Based on the above experiments and calculations, by changing the processing conditions, the effective area S of hydrogen adsorption per unit area of ​​the hydrogen sensor based on modified polyimide fiber textiles was calculated under different conditions. The results are shown in Table 1 below:

[0046] Table 1. Experimental results of the effective area S of adsorbable hydrogen for different stereo hydrogen sensor samples.

[0047]

[0048] As can be seen from the experimental results in Table 1 above, the hydrogen sensor based on modified polyimide fiber textile proposed in this invention has a high effective area for H2 adsorption, and the detector sensitivity and response time can be greatly improved.

[0049] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hydrogen sensor based on modified polyimide fiber textile, characterized in that, Includes a base fabric, which is woven from a mixture of fiber yarns and non-conductive fibers; The mixed fiber yarn comprises modified polyimide fibers and copper wire. The preparation method of the mixed fiber yarn involves mixing and twisting the modified polyimide fibers and copper wire, followed by heat treatment to obtain the mixed fiber yarn. The preparation method of the modified polyimide fibers includes the following steps: A1 Take fiber filaments, immerse them in polyimide precursor solution, and then perform thermosetting treatment, UV modification treatment, and then heat treatment to obtain polyimide fiber filaments. A2 uses a vapor deposition process to deposit a palladium film with a thickness of 10-200 nm onto the surface of polyimide fibers to obtain modified polyimide fibers; UV modification treatment: Using a dual-wavelength simultaneous irradiation mode, ultraviolet light with wavelengths of 185nm and 254nm is used to etch the surface of polyimide fibers, forming grooves with a depth of 5-10nm on the surface of polyimide fibers.

2. The hydrogen sensor based on modified polyimide fiber textile according to claim 1, characterized in that, In step A2, at 10 -5 Up to 10 -6 The vapor deposition process is carried out under a vacuum of Pa.

3. The hydrogen sensor based on modified polyimide fiber textile according to claim 2, characterized in that, The specific processing steps of the vapor deposition process are as follows: Palladium raw material was heated to above 1554℃ using an electron beam evaporation source, the arraying rate was adjusted to 0.05-0.2 nm / s, the substrate temperature was maintained at 80-150℃, and the rotation speed of the polyimide fiber on the carrier was controlled at 5-10 rpm for palladium deposition.

4. The hydrogen sensor based on modified polyimide fiber textile according to claim 3, characterized in that, After deposition, maintain a vacuum environment, cool to room temperature, and finally anneal at 150-200℃ for 20-40 minutes under a nitrogen atmosphere.

5. The hydrogen sensor based on modified polyimide fiber textile according to claim 1, characterized in that, The diameter of the copper wire is 8-15 μm.

6. A method for preparing a hydrogen sensor based on modified polyimide fiber textile as described in any one of claims 1 to 5, characterized in that, Includes the following steps: The method for preparing the mixed fiber yarn described in S1 is to mix and twist modified polyimide fibers with copper wire, and then perform heat treatment to obtain the mixed fiber yarn. S2 Take the mixed fiber yarn prepared in step S1, and then take non-conductive fibers, each as warp and weft, and make the hydrogen sensor by warp and weft weaving.

7. The method for preparing a hydrogen sensor based on modified polyimide fiber textiles according to claim 6, characterized in that, In step S2, after the warp and weft spinning is completed, the warp or weft yarns are cut to form an independent sensing area by spinning adjacent mixed fiber yarns.

8. The method for preparing a hydrogen sensor based on modified polyimide fiber textile according to claim 7, characterized in that, The ends of the mixed fiber yarn are screen-printed with silver paste or copper powder to form signal transmission lines.

9. The method for preparing a hydrogen sensor based on modified polyimide fiber textile according to claim 8, characterized in that, The end of the signal transmission line is led out to the detection circuit via a flexible flat cable or an FPC connector.

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