Nano-film resistance type three-dimensional hydrogen sensor and preparation method thereof

Abstract

The invention relates to the technical field of spinning and sensing. In order to solve the problems that an existing hydrogen sensor is poor in selectivity, prone to being affected by common gas such as methane, large in system error and low in detection sensitivity, the invention particularly discloses a nano-film resistance type three-dimensional hydrogen sensor and a preparation method thereof. A plurality of signal transmission lines are arranged between the upper base cloth and the lower base cloth, the tail end of each signal transmission line is connected with a fluff cluster piece, and the fluff cluster pieces sequentially penetrate through the upper base cloth and the lower base cloth; the raw material of the villus tufting piece comprises modified polyimide fibers with the surface loaded with a palladium-gold material, the thickness of the palladium-gold material is 5-12 nm, and the villus gap of the villus tufting piece is smaller than or equal to 5 nm. By performing specific selection, modification treatment and the like on a fluff cluster piece material and combining a textile process, array arrangement of sensitive materials is realized, the limitation of a rigid structure of a traditional hydrogen sensor is broken through, and the sensor has the advantages of high sensitivity, quick response, customizable structure and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of textiles and sensing technology, in particular to a three-dimensional hydrogen sensor of nanometer film resistance type and a preparation method thereof. BACKGROUND

[0002] Hydrogen sensors have the performance advantages of high sensitivity, short response time, high selectivity, high stability, miniaturization, low power consumption and low cost. With the development of hydrogen sensing technology, hydrogen sensors have also gradually developed. The existing hydrogen sensors on the market mainly include four categories: electrochemical type, catalytic combustion type, metal oxide resistance type and thermal conduction type.

[0003] For example, the patent with publication number CN116660330A discloses a silk fiber-based flexible wearable hydrogen peroxide sensor and a construction method thereof. A certain amount of degummed silk fiber bundle is activated, then the activated silk fiber bundle is irradiated with different power ultraviolet light in a photosensitizer under light protection to obtain a silk fiber bundle with in-situ deposited Prussian blue. The silk fiber with adjustable multi-layer PB deposition is obtained by cyclic in-situ deposition. The PB@ASF fiber is fixed on the working electrode to obtain a PB@ASF fiber sensor. The fiber sensor is combined with traditional textiles to process PB@ASF strands, belts and flexible sensing fabrics to obtain a hydrogen sensor with obvious responsiveness to hydrogen peroxide, high sensitivity at low concentration and high washing resistance.

[0004] However, the existing hydrogen sensors of the above-mentioned types all have a common performance defect, i.e. poor selectivity, strong response to common gases such as carbon monoxide, methane, acetylene and ethanol, serious false reporting problem, large system error and low detection sensitivity. In addition, most of the existing hydrogen sensors are only single component design, which cannot detect the source of gas leakage and cannot implement online full coverage monitoring. SUMMARY

[0005] The present application aims to solve the problems of poor selectivity of existing hydrogen sensors, easy influence by common gases such as carbon monoxide, methane, acetylene and ethanol, large system error and low detection sensitivity.

[0006] The present application is realized by the following technical solutions: The present application provides a three-dimensional hydrogen sensor of nanometer film resistance type, which adopts palladium gold (Pd) material with strong selectivity and sensitivity to hydrogen. The Pd material is loaded on the surface of the yarn through a specific process, and the yarn is made into an array hydrogen sensor by using the flannel textile technology. Since Pd will undergo hydrogenation reaction under the action of hydrogen, the volume of the Pd-loaded film material will expand, the flannels will contact each other, and the resistance will decrease, thereby feeding back the signal of hydrogen concentration, etc.

[0007] In this invention, the three-dimensional hydrogen sensor includes an upper base fabric and a lower base fabric stacked together. A plurality of signal transmission lines are disposed between the upper base fabric and the lower base fabric. Each signal transmission line has a tuft of fibers connected to its end. The tuft of fibers passes sequentially through the upper base fabric and the lower base fabric, as shown in the diagram. Figure 2 As shown, the upper and lower base fabrics provide a substrate for the fluff cluster, maximizing the specific surface area per unit area of ​​Pd. Among these, Figure 2 The specific arrangement and shape of the signal transmission lines and fluff clusters in the present invention are only an example, but the three-dimensional hydrogen sensor proposed in this invention can use signal transmission lines and fluff clusters arranged in any standard array. (one) like Figure 1 The diagram shown is a top view of the three-dimensional hydrogen sensor of this invention. Figure 1 The red part in the diagram represents the signal transmission line, which is mainly composed of nanowires made of conductive materials such as copper (Cu), gold (Au), or silver (Ag). Its main function is to serve as the electrode of the three-dimensional hydrogen sensor. The signal transmission line is located on the surfaces of the upper and lower base fabrics that are far apart from each other. The nanowires in the signal transmission line are woven into a sheet material with the non-conductive fibers in the upper or lower base fabric through warp and weft.

[0009] In this invention, the signal transmission line serves as the electrode of the three-dimensional hydrogen sensor. Conductive silver paste or copper foil, etc., are arranged on the back side of the upper or lower base fabric using screen printing technology. (Structure reference...) Figure 2 . (two) Figure 1 The yellow portion is a pile tuft, made from modified polyimide fibers with Pd loaded on the surface, obtained through weaving. Figure 1 The fluff tuft shown is square, but the three-dimensional hydrogen sensor proposed in this invention can adopt any shape, and is not limited to or protected only by square fluff tufts.

[0011] The preparation process of modified polyimide fiber is as follows: first, polyamic acid (PAA) is spun into PAA precursor fiber; then, it is converted into polyimide fiber through imidization treatment; then, the structure is modified through UV modification and heat treatment to increase the specific surface area of ​​polyimide fiber, thus obtaining modified polyimide fiber. Grooves of 5-12nm are formed on its surface to increase the adhesion of palladium nanoparticles and reduce palladium consumption.

[0012] Specifically, modified polyimide fibers can be prepared using the following methods: Method 1: Install an ultrasonic vibrator on the nozzle of the electrospinning device, start the injection pump and high voltage to spin the fibers, and simultaneously start the ultrasonic vibrator to make the nozzle vibrate at high frequency and small amplitude. At this time, the wavy PAA precursor fibers formed are collected on the receiving device, and then high temperature setting is performed to convert polyamic acid into polyimide and permanently fix the wavy groove structure to obtain modified polyimide fibers with uniform and regular grooves on the surface.

[0013] Method 2: At a molar ratio of 1:1, polyamine monomers (e.g., 4,4'-diaminodiphenyl ether, ODA) and dianhydride monomers (e.g., pyromellitic dianhydride, PMDA) are added to N,N-dimethylacetamide (DMAc) or N-methylpyrrolidone (NMP) solvent. The mixture is reacted at 0-30℃ for 8-12 hours under a nitrogen atmosphere to obtain a PAA solution. Then, at a molar ratio of 8-9:1-2, the PAA solution is thoroughly mixed with polyethylene glycol (PEG), degassed, and filtered. The mixture is then passed through a multi-channel composite spinneret with an outer pore size of 0.03-0.07 mm at 25-50℃, with a spinneret ratio of 4-6 and a coagulation bath containing a water / DMAc mixture with a volume ratio of 7:3, to obtain PAA precursor fibers. Then, using solvents such as toluene, the mixture is treated at 30-50℃ for 3-5 hours to dissolve and remove the PEG marine phase components, allowing the PAA conductive phase / core layer dispersed therein to form independent ultrafine fibers. Subsequently, the decomposed PAA ultrafine fiber bundles are pre-stretched 1.2-1.5 times at 60-80℃, followed by a gradient thermal imidization process, i.e., heating at a rate of 5-10℃ / min, holding at 80-120℃ for 1 hour, 150-180℃ for 1-1.5 hours, 250-300℃ for 1-2 hours, and 300-350℃ under nitrogen protection for 0.5 hours to carry out imidization conversion, finally obtaining polyimide fibers with a diameter of 0.08-0.12μm.

[0014] Furthermore, UV modification refers to using strong ultraviolet light, such as short-wavelength excimer lamps, to irradiate fibers in an air atmosphere to remove impurities and break weak chemical bonds, side chains, and low molecular weight fragments on the fiber surface.

[0015] Heat treatment refers to the structural shaping, deep purification, and pore fixation of fibers. It involves heat treatment of fibers under programmed temperature rise and tension control in an inert or controlled oxidizing atmosphere. Heat treatment can remove impurities, completely decompose and evaporate volatile impurities such as degradation fragments and residual solvents generated by UV modification, achieve structural recombination, and complete the imidization of molecular chains. In the resulting grooves, the step difference between the protrusions and depressions is between 5-12 nm.

[0016] In the pile component, modified polyimide fiber is uniformly loaded with Pd material with a thickness of 5-12nm on the surface of the modified polyimide fiber through processes such as vapor deposition, thereby controlling the pile gap of the pile component to be within 5nm.

[0017] Specifically, the vapor deposition process is as follows: First, the modified polyimide fiber is fixed on a rotatable support, placed in a vacuum chamber, and evacuated to 10°C. -3 Pa is above 10 Pa; then the palladium source is heated, and after the palladium source evaporates, palladium atoms are deposited on the rotating fiber surface to form a nanofilm. After cooling, the nanofilm is removed to obtain a modified polyimide fiber with Pd loaded on the surface.

[0018] By using textile processes, modified polyimide fibers loaded with Pd can be made into fleece-based fabric materials. The specific textile manufacturing methods are as follows: like Figure 3 The diagram shows a schematic planar representation of the fabric structure of the pile fabric. The upper base fabric warp (outer warp) is controlled by the upper shed drive mechanism (first heald frame), responsible for forming the shed of the upper fabric; the lower base fabric warp (inner warp) is controlled by the lower shed drive mechanism (second heald frame), responsible for forming the shed of the lower fabric; the pile warp (pile warp) connecting the upper and lower layers is equipped with a separate auxiliary heald frame. The ground weave, the lower layer feed weave, and the upper layer lifting weave are all non-conductive fiber weaves. All four types of pile warp are composed of Pd-loaded modified polyimide fibers. The blank areas in the diagram represent polyimide fibers without Pd loading, which serve to separate the hydrogen sensor array units.

[0019] Furthermore, such as Figure 4 This is a schematic diagram of the cross-sections of four different warp types. Figure 4 The arrows indicate modified polyimide fibers loaded with Pd, which need to be cut after being woven into a fleece fabric to form the basic unit of a single sensor. This three-ply-one-press weaving method not only secures the fleece ends but also simplifies the weaving process.

[0020] The technical solution of the present invention has the following beneficial effects: The nano-thin film resistive three-dimensional hydrogen sensor proposed in this invention combines the characteristics of flexibility and freeform surface. The sensitive material is arrayed through textile technology, which breaks through the rigid structure limitation of traditional hydrogen sensors. It can be widely used for leakage monitoring of large hydrogen source devices such as hydrogen storage and hydrogen transportation pipelines. It has the advantages of high sensitivity, fast response and customizable structure. Attached Figure Description

[0021] Figure 1 This is a top view of the three-dimensional hydrogen sensor in this invention. Figure 2 This is a schematic diagram of the cross-sectional structure of the three-dimensional hydrogen sensor in this invention; Figure 3 This is a schematic planar diagram of the structure of the fleece textile in this invention; Figure 4 This is a cross-sectional schematic diagram of the four types of pile warp weaving in this invention. Figure 5 This is a schematic diagram of the structure of the multi-twist modified polyimide fiber in this invention; Figure 6 This is a schematic diagram of the detection unit in this invention. Detailed Implementation

[0022] 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.

[0023] 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.

[0024] like Figure 5 As shown, modified polyimide fibers with a diameter of D1 loaded with Pd are used, according to... 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. (1); (2); (3); The lateral area S3 of a single fiber per unit length is (4); The purpose of using S3 to represent the lateral surface area of ​​a single fiber is to indicate the area of ​​a single fiber that can adsorb hydrogen gas before spinning.

[0025] A single fiber is wound at an angle θ into a helical fiber with a diameter of D2 and a twisted length of L1, as shown in the structure. Figure 5 As shown on the right, the height h of the fiber winding for one turn and the required fiber length L2 are respectively: (5); (6); The required total fiber length L3 is (7); If the total number of fibers used for twisting is n, then the total area S4 occupied by the fibers is (8); The cross-sectional area S5 of the twist is (9); but (10) or (11).

[0026] Ignoring the area at both ends of the fiber, the effective area for hydrogen adsorption on a twisted thread is: (12).

[0027] like Figure 6 The image shows the final detection unit, consisting of the red portion of the warp and weft structure and the blue portion of a twisted yarn. Assuming the diameter of the yarn used in the warp and weft structure is D3, the area S7 of one detection unit is: (13); The effective area S per unit area that can adsorb hydrogen gas is: (14).

[0028] Based on the above experiments and calculations, by changing the processing conditions, the effective area S of the three-dimensional hydrogen sensor per unit area that can adsorb hydrogen was calculated under different conditions. The results are shown in Table 1 below: Table 1. Experimental results of the effective area S of adsorbable hydrogen for different stereo hydrogen sensor samples.

[0029] As can be seen from the experimental results in Table 1 above, the nanofilm resistive stereo hydrogen sensor proposed in this invention has high detector sensitivity and a significantly improved response time.

[0030] 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 nanofilm resistive three-dimensional hydrogen sensor, characterized in that, It includes an upper base fabric and a lower base fabric stacked together, and a plurality of signal transmission lines are provided between the upper base fabric and the lower base fabric. Each signal transmission line is connected to a pile tuft at its end, and the pile tuft is arranged to pass through the upper base fabric and the lower base fabric in sequence. The raw material of the fluff tuft includes modified polyimide fibers with palladium material loaded on the surface, and the thickness of the palladium material is 5-12nm, and the fluff gap of the fluff tuft is ≤5nm.

2. The nanofilm resistive three-dimensional hydrogen sensor according to claim 1, characterized in that, The preparation process of the modified polyimide fiber is as follows: first, polyamic acid is spun into PAA precursor fiber, then imidized to convert it into polyimide fiber, and then UV modified and heat treated to obtain modified polyimide fiber with grooves formed on the surface. The step difference between the protrusion and depression of the groove is 5-12nm.

3. The nanofilm resistive stereo hydrogen sensor according to claim 2, characterized in that, A nano-palladium film can be deposited on the surface of the modified polyimide fiber using a vapor deposition process, resulting in modified polyimide fiber with palladium-loaded material on its surface.

4. The nanofilm resistive stereo hydrogen sensor according to claim 1, characterized in that, The pile tufts are fabricated using a double-layer napping method, the specific process of which is as follows: The upper base fabric warp yarns are controlled by the upper shed drive mechanism to form the shed of the upper fabric; the lower base fabric warp yarns are controlled by the lower shed drive mechanism to form the shed of the lower fabric; the pile warp yarns connecting the upper and lower layers are separately equipped with an auxiliary shed drive mechanism. The pile warp and the outer warp yarn form the upper layer, while the pile warp and the inner warp yarn form the lower layer.

5. The nanofilm resistive stereo hydrogen sensor according to claim 4, characterized in that, Non-conductive fibers are used to inject into the lower and upper layers of the structure, and the modified polyimide fibers with palladium material loaded on the surface are surrounded by array units of polyimide fibers.

6. The nanofilm resistive stereo hydrogen sensor according to claim 1, characterized in that, The fluff cluster is a single unit or multiple units arranged in an array, and each fluff cluster is connected to the end of one of the signal transmission lines.

7. The nanofilm resistive stereo hydrogen sensor according to claim 1, characterized in that, The signal transmission line is composed of nanowires made of one or more materials selected from copper, gold, or silver. Both the upper and lower base fabrics are made of non-conductive fibers, and the nanowires in the signal transmission line and the non-conductive fibers in the upper or lower base fabric are woven into a sheet material through warp and weft.

8. A method for fabricating a nanofilm resistive stereo hydrogen sensor as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1 First, polyamic acid is spun into PAA precursor fibers, which are then imidized to produce polyimide fibers. Then, UV modification and heat treatment are performed to obtain modified polyimide fibers with Pd loaded on the surface. The modified polyimide fibers with Pd loaded on the surface are spun into a fleece base material to obtain fleece tufts. S2 Take an upper base fabric and a lower base fabric, thread a signal transmission line between the upper base fabric and the lower base fabric, and connect a fluff tuft to the end of the signal transmission line; weave the nanofibers of the signal transmission line and non-conductive fibers into a sheet, and integrate the modified polyimide fiber with Pd loaded on the surface, the signal transmission line and the fluff tuft to obtain the nano-thin film resistive three-dimensional hydrogen sensor.

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