Preparation method and application of WO3 nano-wall gas-sensitive material
By using tungsten hexachloride and 1-dodecyl-3-methylpyridine bromide on the surface of ceramic tubes, the WO3 nanowall film was solved, and the problem of uneven material coverage and limited calcination temperature was achieved. It has high gas-sensitive performance and low cost WO3 nanowall film gas-sensitive components, suitable for real-time monitoring of hydrazine.
Patent Information
- Application Number
- CN202411347126.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-26
- Publication Date
- 2024-12-13
AI Technical Summary
In the prior art, when constructing WO3 nanomaterials, solvent heat treatment leads to uneven coverage of the material, limited calcination temperature, affects gas-sensitive performance, and the process is complex and time-consuming.
Tungsten hexachloride (WCl6) and 1-dodecyl-3-methylpyridine bromide as reaction raw materials and surfactant, WO3 nanowall film was constructed in situ on the surface of ceramic tubes by solvothermal method, simplifying the process and Reduce costs.
It achieves uniform coverage and high gas-sensitive properties of WO3 nanowall film, is low in cost, has an operating temperature as low as 70℃, and has high selectivity and sensitivity to hydrazine (N2H4), which is suitable for mass production.
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Abstract
Description
Technical Field
[0001] The invention relates to a preparation method of a WO3 nano wall and application of the WO3 nano wall as a gas sensitive material. Background Art
[0002] Hydrazine (N2H4) is a typical volatile nitrogen compound (VNCs) with a high heat of combustion and can be used as a rocket fuel. At the same time, hydrazine is also an excellent reducing agent that can remove oxygen from hot water heating systems and reduce the occurrence of pipeline corrosion. In the pharmaceutical industry, hydrazine is also used to produce anti-tuberculosis and anti-diabetic drugs. In the pesticide industry, hydrazine is the main component of herbicides, plant growth regulators, fungicides and insecticides. In the plastics and rubber industries, hydrazine is used to synthesize plastic foaming agents, antioxidants, polymer cross-linking agents and chain extenders. Although hydrazine has a wide range of applications in various fields, its toxicity and potential risks during use cannot be ignored. First, hydrazine has a strong irritating effect on the skin and eyes. Inhaling excessive hydrazine vapor can seriously damage human liver tissue, and can also reduce blood sugar and blood dehydration, thereby causing anemia. In addition, hydrazine can instantly burn or explode when it encounters an open flame. Therefore, it is crucial to effectively monitor the content of hydrazine vapor in the air during the use of hydrazine or hydrazine-containing products to improve production safety.
[0003] WO3 is an important transition metal oxide. Recent studies have found that WO3 nanomaterials with different morphologies have obvious sensitivity to volatile nitrogen-containing compounds (VNCs), especially WO3 materials with nanosheets or nanoflowers with two-dimensional structures as basic building units. The sensitivity of VNCs is particularly outstanding. However, in the process of using the above materials to construct sensors, the prepared sensitive materials must be mixed with solvents such as ethanol or pinene alcohol to form a slurry, and then applied to the substrate of the device such as ceramic tubes or interdigitated electrodes to form a thick film sensitive layer. After application, the device needs to be calcined twice to remove the solvent in the slurry. If ethanol is used as a solvent to prepare the slurry in this process, the thick film sensitive layer will crack and loosen after the ethanol dries. Using pinene alcohol, a high-boiling point organic reagent, as a solvent to prepare the slurry will cause secondary growth or recrystallization of the material during the secondary calcination process, thereby affecting the gas sensing performance. In addition, since it is difficult to achieve uniform coverage by manual application, the thick film sensitive layer will have accumulation or overlap of materials, and the underlying material is difficult to contact the gas to be measured and cannot participate in the gas sensing process, thereby greatly reducing the active surface area of the material. In order to prevent the above problems from occurring, it is an ideal solution to construct the material in situ on the surface of a ceramic tube or an interdigitated electrode substrate to form a homogeneous thin film sensitive layer.
[0004] At present, the method of in-situ construction of a two-dimensional WO3 sensitive material on the surface of a ceramic tube generally uses sodium tungstate (Na2WO4), citric acid (C6H8O7) and hydrochloric acid (HCl) as the main reaction raw materials, forms a tungstate precursor through the action of strong acid and sodium tungstate, and deposits the above precursor on the surface of the ceramic tube by chemical deposition, and obtains a WO3 sensitive layer through subsequent calcination.
[0005] The existing technology of in-situ construction of two-dimensional nanosheets has the following obvious disadvantages:
[0006] 1. There are many reactants involved in the reaction system, and the system is complex and poorly controllable. 2. Chemical deposition during the reaction process takes a long time, which is time-consuming and labor-intensive. 3. Since the in-situ construction process is achieved by chemical deposition at low temperature, the precursor material constructed on the surface of the substrate is relatively loose. In order to convert the precursor into WO3, calcination treatment is required. The increase in calcination temperature will cause the loose material to collapse. Therefore, the synthetic material of this method can only be calcined within a lower temperature range (150-400°C). Changes in calcination temperature will directly affect the surface chemical state, phase composition and crystallinity of the calcined product, thereby affecting the sensitive properties of the material. The narrow calcination temperature range is not conducive to obtaining sensitive materials with excellent gas sensing properties. Summary of the invention
[0007] The purpose of the present invention is to provide a method for in-situ construction of WO3 nano-wall on the surface of a ceramic tube by a solvent thermal method using tungsten hexachloride (WCl6) as a reaction raw material and 1-dodecyl-3-methylpyridinium bromide as a surfactant. At the same time, the ceramic tube covered with the WO3 nano-wall thin film sensitive layer is constructed into a resistive gas sensor. The sensor constructed by this method not only has high selectivity and sensitivity to hydrazine (N2H4), but also has a simple synthesis process and low cost.
[0008] The WO3 nano-wall material of the present invention is synthesized by the following method:
[0009] 1. Add 1-dodecyl-3-methylpyridinium bromide to n-butanol and ultrasonicate it. After it is completely dissolved, add WCl6 to the solution and stir it magnetically until WCl6 is fully dissolved.
[0010] 2. Transfer the above solution into a hydrothermal reactor of appropriate volume, immerse the ceramic tube in the above solution, and perform a solvent thermal reaction. After the reaction is completed, cool the reactor naturally to room temperature and take out the ceramic tube. Wash the ceramic tube with anhydrous ethanol and ultrapure water several times, and obtain a ceramic tube covered with a nano-wall morphology precursor after vacuum drying.
[0011] 3. The ceramic tube covered with the precursor is calcined in an air atmosphere, and the precursor on the surface of the ceramic tube is converted into a WO3 nano-wall film sensitive layer.
[0012] The method for making the gas sensor of the present invention is as follows:
[0013] A heating wire was inserted into the ceramic tube covered with the WO3 nano-wall film sensitive layer, and the ceramic tube was welded as a whole on a small hexagonal base to form a gas sensor, which was then aged at 150°C for three days.
[0014] The obvious benefit of the present invention is that it discloses a method for preparing a WO3 nano-wall thin film sensitive layer in situ on the surface of a ceramic tube and constructing it into a gas-sensitive element. This method opens up a new idea for real-time monitoring of volatile nitrogen-containing compounds (VNCs). At the same time, this method solves the problems of the inability to achieve complete homogeneity of artificial coatings, overlapping and accumulation of sensitive materials, and low effective active surface in the process of making gas-sensitive elements. The product structure of the present invention is stable, the morphology is uniform, the synthesis method is simple, and the cost is low. The WO3 nano-wall thin film sensitive layer constructed in situ on the surface of the ceramic tube is in close contact with the ceramic tube, the coverage is uniform, and it exhibits excellent gas-sensitive performance for N2H4, and the optimal operating temperature is as low as 70 °C. At this operating temperature, the sensitivity of the sensitive element to N2H4 with a concentration of 100 ppm is as high as 266. The synthesis and post-treatment methods of this method are simple, the product is easy to separate, and it is suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.
[0016] Figure 1 The scanning electron microscope images are of the uncalcined precursor of the present invention and the WO3 nano-wall obtained at a calcination temperature of 400-600°C.
[0017] Figure 2 The XRD spectrum of the WO3 nano-wall obtained at a calcination temperature of 400-600°C in the present invention.
[0018] Figure 3 This is the response-recovery curve of WO3 nanowall to different concentrations of N2H4 at 70 ℃.
[0019] Figure 4 This is the linear response relationship of WO3 nanowall to 10-100 ppm N2H4 at 70 ℃. DETAILED DESCRIPTION
[0020] Dissolve 0.045-0.089 g of 1-dodecyl-3-methylpyridinium bromide in 25-35 mL of n-butanol and perform ultrasonic treatment until it is completely dissolved to obtain a colorless transparent solution.
[0021] Dissolve 0.15-0.40 g WCl6 in the above solution and stir magnetically until it is fully dissolved to obtain a yellow solution.
[0022] Transfer the yellow solution into a hydrothermal kettle, immerse the ceramic tube in the solution, react at 140-180°C for 20-50 min, cool naturally to room temperature, take out the ceramic tube and wash it with anhydrous ethanol and ultrapure water respectively, and then vacuum dry it at 60-80°C for 8-12 h.
[0023] The dried ceramic is calcined in air at 400-600°C. The scanning electron microscopy images of WO3 nanowalls obtained at different calcination temperatures are shown in Figure 1 As shown in the figure, the product is a nanowall composed of a large number of two-dimensional nanosheets with a thickness of 20 to 40 nm. The product morphology can still be maintained after calcination at 400, 500 and 600 °C.
[0024] XRD spectra of products calcined at different temperatures (see Figure 2 ) It can be seen that all diffraction peaks in the XRD spectrum of the nanowall product are consistent with the spectrum of the standard XRD card JCPDS: 83-0951, indicating that the product is pure phase WO3.
[0025] In order to obtain the gas-sensing performance of the prepared WO3 nano-wall, a heating wire is inserted into the middle of a ceramic tube covered with a WO3 nano-wall thin film sensitive layer, and the heating wire is welded together with the ceramic tube as a whole to a small hexagonal base to form a gas-sensitive element.
[0026] The gas sensing performance test is as follows:
[0027] The gas sensing performance test was conducted using the static gas distribution method. First, a glass container with a volume of 10 L was evacuated, and then a certain amount of N2H4 liquid was injected into the glass container and air was introduced from the bottom of the container. The N2H4 liquid was completely gasified while the air pressure inside and outside the bottle was balanced with air. After the gas sensor achieved a stable resistance in the air, the gas sensor was inserted into the glass container containing N2H4 gas, and the element was taken out when the resistance of the gas sensor stabilized again.
[0028] During the test, the response value R of the gas sensor is given by the formula R = R a / R g Among them, R a Indicates the stable resistance value of the gas sensor in the air, R g It indicates the resistance value of the gas sensor in a certain concentration of N2H4 gas. The response time and recovery time correspond to the resistance value of the gas sensor placed in N2H4 gas from R a Change to R a -90%(R a -R g ) and the resistance after removal from N2H4 gas is determined by R g Change to R g +90%(Ra -R g ) time required.
[0029] Depend on Figure 3 It can be seen that the WO3 nano-wall film sensor obtained by calcining at 500℃ has a good fast response characteristic to N2H4 gas with a concentration of 10-100 ppm at an operating temperature of 70℃. Its response time to 100 ppm N2H4 is only 17 s, and the gas sensor has a good linear relationship within the detection range (fitting coefficient R 2 =0.9930).
Claims
1. A method for preparing WO3 nano-wall material is as follows: (1) Dissolve 1-dodecyl-3-methylpyridinium bromide in 25-35 mL n-butanol and ultrasonicate for 10-30 min until it is completely dissolved to obtain a colorless transparent solution. Add WCl6 to the above solution and stir magnetically for 30-60 min until it is fully dissolved to obtain a yellow solution; (2) Transfer the yellow solution into a hydrothermal reactor, immerse the ceramic tube in the solution, react at 140-180°C for 20-50 min, cool naturally to room temperature, take out the ceramic tube and wash it with anhydrous ethanol and ultrapure water respectively, and then vacuum dry it at 60-80°C for 8-12 h; (3) The dried ceramic tube is calcined at 400-600°C in an air atmosphere.
2. The method for preparing the WO3 nano-wall according to claim 1, characterized in that In step (1), 0.045-0.089 g of 1-dodecyl-3-methylpyridinium bromide was dissolved in 25-35 mL of n-butanol.
3. The method for preparing the WO3 nano-wall according to claim 1, characterized in that In step (1), 0.15 ~ 0.40 g WCl6 was dissolved in 25 ~ 35 mL n-butanol.
4. The method for preparing the WO3 nano-wall according to claim 1, characterized in that Step (1) Magnetic stirring for 30 to 60 minutes.
5. The method for preparing the WO3 nano-wall according to claim 1, characterized in that In step (2), the ceramic tube is reacted at 140-180°C for 20-50 min.
6. The method for preparing the WO3 nano-wall according to claim 1, characterized in that In step (2), the ceramic tube is placed in a vacuum dryer at 60 to 80 °C for 8 to 12 hours.
7. The method for preparing the WO3 nano-wall according to claim 1, characterized in that In step (3), the ceramic tube is placed in an air atmosphere and calcined at 400-600°C.