A spherical NiFe2O4-based phosgene gas sensor and a preparation method thereof

Abstract

The application discloses a kind of based on spherical NiFe2O4 phosgene gas sensor and preparation method thereof.The preparation method includes: S1, using ultrasonic spray method to prepare spherical NiFe2O4 sensitive material;S2, spherical NiFe2O4 sensitive material is mixed with water according to mass ratio (2~6) :1, obtains coating slurry;S3, coating slurry is coated on the surface of ceramic tube substrate, and the sensitive material film is prepared;The surface of ceramic tube substrate has annular electrode, and sensitive material film completely covers annular electrode;S4, using the ceramic tube substrate with sensitive material film is assembled, obtains based on spherical NiFe2O4 phosgene gas sensor.The method provided by the application uses spherical NiFe2O4 as sensitive material, its larger specific surface area can provide more active sites to make gas transmission in material, and then effectively improve the sensitive characteristics of sensor to phosgene.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor technology, specifically relating to a phosgene gas sensor based on spherical NiFe2O4 and its preparation method. Background Technology

[0002] Phosgene is a highly toxic chemical gas. Due to its strong asphyxiating and stealthy nature, it is both an important chemical raw material and a typical chemical warfare agent. Inhalation of even low concentrations can cause irreversible damage to the human body. Exposure to phosgene can lead to pulmonary edema, respiratory failure, and even death. Existing methods for detecting phosgene mainly include chemical colorimetry, electrochemical methods, and spectroscopic methods, but these methods suffer from problems such as insufficient real-time performance, poor portability, and limited environmental adaptability.

[0003] In recent years, gas sensors based on semiconductor oxide materials have gradually become a research hotspot in the field of gas detection due to their high sensitivity, fast response, and strong adaptability. Ferrite materials, in particular, with their spin characteristics and wide bandgap, have become potential materials for the development of phosgene detection sensors due to their unique surface chemical reactivity and excellent gas-sensing performance. NiFe2O4, as a classic ferrite material, possesses the following advantages: high surface activity, excellent stability, and strong electron mobility. However, current research on ferrite materials for phosgene detection is still limited, especially lacking the system development and optimization of high-sensitivity sensors based on NiFe2O4. Therefore, developing a phosgene sensor based on NiFe2O4 can not only compensate for the shortcomings of existing detection technologies but also provide a more efficient solution for industrial safety and battlefield environment monitoring.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a phosgene gas sensor based on spherical NiFe2O4 and its preparation method. The technical problem to be solved by this invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing a phosgene gas sensor based on spherical NiFe2O4, comprising the following steps: S1. Spherical NiFe2O4 sensitive material was prepared by ultrasonic spraying method; S2. The spherical NiFe2O4 sensitive material is mixed with water at a mass ratio of (2~6):1 to obtain a coating slurry; S3. The coating slurry is coated on the surface of the ceramic tube substrate to prepare a sensitive material film; The surface of the ceramic tube substrate has an annular electrode, and the sensitive material film completely covers the annular electrode. S4. Assemble using a ceramic tube substrate with a sensitive material film to obtain a phosgene gas sensor based on spherical NiFe2O4.

[0006] In one embodiment of the present invention, step S1, the preparation of spherical NiFe2O4 sensitive material by ultrasonic spraying includes: S11. Dissolve Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and sodium dodecyl sulfate in water at a mass ratio of (0.5~10): (0.1~10): (0.01~5) to obtain a precursor solution; S12. The precursor solution is sprayed into a quartz tube using an ultrasonic spray method with an inert gas as the carrier gas for a first calcination at a temperature of 200–800°C to obtain precursor powder. S13. The precursor powder is washed, dried, and calcined a second time to obtain spherical NiFe2O4 sensitive material.

[0007] In one embodiment of the present invention, in step S12, the carrier gas is nitrogen; the volumetric flow rate of the carrier gas is 10 to 1000 mL / min.

[0008] In one embodiment of the present invention, in step S13, the washing is performed by sequentially washing with deionized water and ethanol and then centrifuging. The drying temperature is 30–90°C, and the second calcination temperature is 300–500°C.

[0009] In one embodiment of the present invention, step S3, which involves coating the coating slurry onto the surface of a ceramic tube substrate to prepare a sensitive material film, includes: placing the coated ceramic tube substrate under an infrared lamp for baking for 20 to 50 minutes; after the coating slurry has dried, calcining the coated ceramic tube substrate at 300 to 450°C for 2 to 3 hours to form a sensitive material film.

[0010] In one embodiment of the present invention, in step S3, the thickness of the sensitive material film is 5 to 50 μm.

[0011] In one embodiment of the present invention, the ceramic tube base has a length of 4 to 4.5 mm, an outer diameter of 1.2 to 1.5 mm, and an inner diameter of 0.8 to 1.0 mm.

[0012] In one embodiment of the present invention, step S4 includes: placing a nickel-cadmium heating wire with a resistance value of 30 to 40 Ω in the central hole of a ceramic tube substrate with a sensitive material film, and welding it to form a side-heated gas-sensitive element. The side-heated gas-sensitive element is packaged to obtain a phosgene gas sensor based on spherical NiFe2O4.

[0013] Secondly, the present invention provides a phosgene gas sensor based on spherical NiFe2O4, which is obtained by the above-described preparation method.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The method for preparing a phosgene gas sensor based on spherical NiFe2O4 provided by the present invention uses ultrasonic spraying to prepare NiFe2O4 sensitive material into hollow spheres, which have a large specific surface area and can provide more active sites to facilitate gas transport in the material, thereby effectively improving the sensor's sensitivity to phosgene.

[0015] 2. The gas-sensitive material in this invention is synthesized by ultrasonic spraying, which is simple to operate and easy to control; moreover, the raw materials used in the preparation of the gas-sensitive material are all commonly used reagents, resulting in low cost.

[0016] 3. The phosgene gas sensor provided by this invention has a simple process, small size, and wide application in detecting phosgene content in the environment, and is suitable for large-scale production. Furthermore, the NiFe2O4 sensing material can be adapted to ceramic tube substrate process lines, eliminating the need for substrate re-matching and avoiding additional process steps for the phosgene gas sensor.

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for preparing a phosgene gas sensor based on spherical NiFe2O4 according to an embodiment of the present invention; Figure 2 This is a scanning electron microscope (SEM) characterization image of a spherical NiFe2O4 sensitive material provided in an embodiment of the present invention; Figure 3 This is a nitrogen adsorption-desorption curve of a spherical NiFe2O4 sensitive material provided in an embodiment of the present invention; Figure 4 This is an X-ray diffraction pattern of a spherical NiFe2O4 sensitive material provided in an embodiment of the present invention; Figure 5 This is a physical image of a phosgene gas sensor based on spherical NiFe2O4 provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of a spherical NiFe2O4 phosgene gas sensor provided in an embodiment of the present invention; Figure 7This is a dynamic response curve of 50 ppm phosgene based on a spherical NiFe2O4 phosgene gas sensor provided in an embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures: 1-Ceramic tube substrate; 2-Spherical NiFe2O4 sensing material; 3-Ni-Cd heating wire; 4-Ring gold electrode; 5-Platinum lead wire. Detailed Implementation

[0020] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a phosgene gas sensor based on spherical NiFe2O4 and its preparation method according to the present invention.

[0021] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0022] It should be noted that, in this document, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0023] This invention provides a phosgene gas sensor based on spherical NiFe2O4, such as... Figure 6 As shown, the phosgene gas sensor based on spherical NiFe2O4 includes a ceramic tube substrate 1, two annular gold electrodes 4 located on the outer surface of the ceramic tube substrate 1, and each gold electrode connected to a platinum lead 5. A sensitive material film, which is spherical NiFe2O4 sensitive material 2, is present on the outer surface of the ceramic tube substrate 1 and the outer surface of the annular gold electrodes 4. The ceramic tube substrate 1 has a hollow central hole, in which a nickel-cadmium heating wire 3 is disposed.

[0024] like Figure 1 As shown, the method for preparing a phosgene gas sensor based on spherical NiFe2O4 provided by the present invention includes the following steps: S1. Spherical NiFe2O4 sensing material is prepared by ultrasonic spraying. In this preparation method, spherical NiFe2O4 is used as the sensing material. NiFe2O4 has good chemical and thermal stability and can react efficiently with the carbonyl chloride group (–COCl2) in phosgene molecules, thus achieving effective detection of phosgene.

[0025] In some embodiments, the preparation of spherical NiFe2O4 sensitive materials using ultrasonic spraying includes: S11. Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and sodium dodecyl sulfate are dissolved in water at a mass ratio of (0.5–10): (0.1–10): (0.01–5) to obtain a precursor solution. Sodium dodecyl sulfate, acting as an anionic surfactant, regulates surface tension and inhibits particle aggregation during droplet formation and subsequent solvent evaporation.

[0026] For example, the mass ratio of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and sodium dodecyl sulfate can be 0.5:0.1:0.01, or 0.5:1:0.1, or 0.5:10:1, or 0.5:5:5, or 2:2:0.1, or 2:5:1, or 5:0.1:5, or 5:10:0.01, or 10:1:1, or 10:0.1:0.05, or 10:5:5, or 10:10:0.1, etc.

[0027] S12. The precursor solution is sprayed into a quartz tube using an ultrasonic spray method with an inert gas as the carrier gas for the first calcination at a temperature of 200–800°C to obtain precursor powder. In this step, a mixed solution containing nickel source, iron source and morphology guide agent is atomized by high-frequency oscillation and sent to a high-temperature reaction zone by the carrier gas for instantaneous pyrolysis and in-situ oxidation to form ferrite particles with spherical morphology.

[0028] S13. The precursor powder is washed, dried, and calcined a second time to obtain spherical NiFe2O4 sensitive material. In this step, by washing, drying, and calcining the precursor powder a second time, the crystal lattice is fully developed, resulting in spherical NiFe2O4 sensitive material with pure crystal phase and complete morphology.

[0029] Spherical NiFe2O4 was prepared using ultrasonic spraying, such as... Figure 2The image shows a scanning electron microscope (SEM) characterization of the spherical NiFe₂O₄ sensitive material. It can be seen that the synthesized NiFe₂O₄ material is a hollow sphere with wrinkles on its surface. This gives the spherical NiFe₂O₄ a high specific surface area, which is beneficial for improving the sensitivity to phosgene. The large specific surface area also provides abundant active sites, offering an effective channel for gas diffusion. Moreover, the preparation process is simple, easy to control, and inexpensive.

[0030] S2. Mix the spherical NiFe2O4 sensitive material with water at a mass ratio of (2~6):1 to obtain a coating slurry. For example, the mass ratio of the spherical NiFe2O4 sensitive material to water can be 2:1, 3:1, 4:1, 5:1, or 6:1, etc.

[0031] S3. A coating slurry is applied to the surface of a ceramic tube substrate to prepare a sensitive material film. The surface of the ceramic tube substrate has a ring electrode, and the sensitive material film completely covers the ring electrode.

[0032] S4. Assemble a phosgene gas sensor based on spherical NiFe2O4 using a ceramic tube substrate with a sensitive material film. Specifically, a nickel-cadmium heating wire with a resistance of 30-40Ω is placed in the central hole of the ceramic tube substrate with the sensitive material film, and welded to form a side-heated gas sensing element; the side-heated gas sensing element is then packaged to obtain a phosgene gas sensor based on spherical NiFe2O4.

[0033] In one example, in step S12, the carrier gas is nitrogen; the volumetric flow rate of the carrier gas is 10 to 1000 mL / min. The residence time of the precursor solution in the high-temperature zone is adjusted by regulating the volumetric flow rate of the carrier gas within a preset flow rate range.

[0034] In one example, in step S13, washing involves sequentially washing with deionized water and then with ethanol and centrifuging; the drying temperature is 30–90°C; and the second calcination temperature is 300–500°C.

[0035] In one example, step S3 involves coating the surface of a ceramic tube substrate with a coating slurry to prepare the sensitive material film. This includes baking the coated ceramic tube substrate under an infrared lamp for 20–50 minutes, allowing the coating slurry to dry, and then calcining the coated ceramic tube substrate at 300–450°C for 2–3 hours to form the sensitive material film. By adjusting the ratio of the coating slurry and the infrared baking and high-temperature sintering processes, a thin film with a porous structure is formed on the surface of the ceramic tube substrate. The porous structure establishes rapid channels for gas diffusion, allowing phosgene molecules to quickly penetrate into the sensitive film and contact the active sites, shortening the time required for gas exchange and thus improving the sensor's response speed and recovery characteristics at the physical level.

[0036] In one example, in step S3, the thickness of the sensitive material film is 5–50 μm.

[0037] For example, the ceramic tube base has a length of 4 to 4.5 mm, an outer diameter of 1.2 to 1.5 mm, and an inner diameter of 0.8 to 1.0 mm.

[0038] For example, the ceramic tube substrate is an insulating ceramic tube substrate, such as an Al2O3 ceramic tube substrate.

[0039] The following specific embodiments further illustrate the preparation method of the phosgene gas sensor based on spherical NiFe2O4 provided by the present invention.

[0040] Example 1 Step 1: Add 0.58g Ni(NO3)2·6H2O, 1.62g Fe(NO3)3·9H2O and 0.09g sodium dodecyl sulfate to 50ml of deionized water and stir to obtain the precursor solution.

[0041] Step 2: Pour the obtained precursor solution into an ultrasonic sprayer; use nitrogen as the carrier gas with a volumetric flow rate of 500 mL / min; spray the solution into a quartz tube at 600℃ for the first calcination to obtain precursor powder, collect the precursor powder in a conical flask containing deionized water; wash the precursor powder precipitated in the conical flask with deionized water and ethanol by centrifugation; dry the product at 60℃, and then calcine it a second time at 500℃ to obtain spherical NiFe2O4 sensitive material.

[0042] Step 3: Mix the spherical NiFe2O4 sensitive material with water at a mass ratio of 2:1 and grind it to form a paste. Then, take the paste and coat it evenly on the Al2O3 ceramic tube substrate with two ring gold electrodes on the outer surface, so that the NiFe2O4 sensitive material completely covers the ring gold electrodes.

[0043] Step 4: The Al2O3 ceramic tube substrate coated with NiFe2O4 sensing material is baked under infrared light for 30 minutes. After the NiFe2O4 sensing material is dry, the Al2O3 ceramic tube substrate is calcined at 350℃ for 2 hours. Then, a 36Ω nickel-cadmium heating coil is passed through the inside of the Al2O3 ceramic tube substrate as a heating wire. Finally, the above device is welded and packaged according to the general side-heated gas sensing element to obtain a phosgene gas sensor based on spherical NiFe2O4 sensing material.

[0044] Performance testing: 1. For example Figure 2The image shown is a scanning electron microscope (SEM) characterization of the spherical NiFe2O4 sensitive material obtained in step 2 of Example 1. The image reveals that the NiFe2O4 sensitive material synthesized by ultrasonic spraying is spherical with wrinkles on its surface, which helps increase the material's specific surface area.

[0045] 2. For example Figure 3 The figure shows the nitrogen adsorption-desorption curve of the spherical NiFe2O4 sensitive material prepared in step 2 of Example 1. Calculations show that the specific surface area of ​​the prepared NiFe2O4 sensitive material is 16.983 m². 2 / g, pore size distribution: average particle size of 3.8305 nm. These porous NiFe2O4 microspheres with high BET specific surface area and large pore size are beneficial for accelerating gas transfer at surface active sites, thereby improving sensing performance.

[0046] 3. For example Figure 4 The image shown is an X-ray diffraction pattern of the spherical NiFe2O4 sensitive material prepared in step 2 of Example 1. It shows that the sensitive material has high crystallinity and no phase allocated to impurities was detected, proving that the NiFe2O4 sensitive material prepared by the method provided in this invention has high purity.

[0047] 4. For example Figure 5 This is a photograph of the phosgene gas sensor prepared in step 4 of Example 1 connected to the base. Figure 6 This is a schematic diagram of the phosgene gas sensor. As can be seen from the figure, the fabricated sensor has the characteristics of simple structure, small size, and portability.

[0048] 5. Figure 7 This is the dynamic response curve of the spherical NiFe2O4 phosgene gas sensor in Example 1 to 50 ppm phosgene. The figure shows that the sensor has a good response to phosgene and a fast response recovery time, effectively detecting low concentrations of phosgene with high sensitivity.

[0049] The present invention relates to a method for preparing spherical NiFe2O4, which uses ultrasonic spraying to prepare NiFe2O4 sensitive material and fabricate it into a sensor. This method designs a gas sensor that can achieve efficient phosgene detection, which is of great significance for the rapid identification of hazardous chemical components in fields such as industrial safety. It also improves the convenience and timeliness of gas sensor detection of phosgene.

[0050] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a phosgene gas sensor based on spherical NiFe2O4, characterized in that, Includes the following steps: S1. Spherical NiFe2O4 sensitive material was prepared by ultrasonic spraying method; S2. The spherical NiFe2O4 sensitive material is mixed with water at a mass ratio of (2~6):1 to obtain a coating slurry; S3. The coating slurry is coated on the surface of the ceramic tube substrate to prepare a sensitive material film; The surface of the ceramic tube substrate has an annular electrode, and the sensitive material film completely covers the annular electrode. S4. Assemble using a ceramic tube substrate with a sensitive material film to obtain a phosgene gas sensor based on spherical NiFe2O4.

2. The method for preparing a phosgene gas sensor based on spherical NiFe2O4 according to claim 1, characterized in that, In step S1, the preparation of spherical NiFe2O4 sensitive material using ultrasonic spraying includes: S11. Dissolve Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, and sodium dodecyl sulfate in water at a mass ratio of (0.5~10):(0.1~10):(0.01~5) to obtain a precursor solution; S12. The precursor solution is sprayed into a quartz tube using an ultrasonic spray method with an inert gas as the carrier gas for a first calcination at a temperature of 200–800°C to obtain precursor powder. S13. The precursor powder is washed, dried, and calcined a second time to obtain spherical NiFe2O4 sensitive material.

3. The method for preparing a phosgene gas sensor based on spherical NiFe2O4 according to claim 2, characterized in that, In step S12, the carrier gas is nitrogen; the volumetric flow rate of the carrier gas is 10 to 1000 mL / min.

4. The method for preparing a phosgene gas sensor based on spherical NiFe2O4 according to claim 2, characterized in that, In step S13, the washing process involves sequentially washing with deionized water and then with ethanol, followed by centrifugation. The drying temperature is 30–90°C, and the second calcination temperature is 300–500°C.

5. The method for preparing a phosgene gas sensor based on spherical NiFe2O4 according to claim 1, characterized in that, In step S3, the process of coating the coating slurry onto the surface of the ceramic tube substrate to prepare the sensitive material film includes: placing the coated ceramic tube substrate under an infrared lamp for baking for 20 to 50 minutes; after the coating slurry dries, calcining the coated ceramic tube substrate at 300 to 450°C for 2 to 3 hours to form the sensitive material film.

6. The method for preparing a phosgene gas sensor based on spherical NiFe2O4 according to claim 5, characterized in that, In step S3, the thickness of the sensitive material film is 5 to 50 μm.

7. The method for preparing a phosgene gas sensor based on spherical NiFe2O4 according to claim 6, characterized in that, The ceramic tube base has a length of 4–4.5 mm, an outer diameter of 1.2–1.5 mm, and an inner diameter of 0.8–1.0 mm.

8. The method for preparing a phosgene gas sensor based on spherical NiFe2O4 according to claim 1, characterized in that, Step S4 includes: placing a nickel-cadmium heating wire with a resistance of 30 to 40 Ω in the center hole of a ceramic tube substrate with a sensitive material film, and welding it to form a side-heated gas-sensitive element. The side-heated gas-sensitive element is packaged to obtain a phosgene gas sensor based on spherical NiFe2O4.

9. A phosgene gas sensor based on spherical NiFe2O4, characterized in that, It is obtained by the preparation method described in any one of claims 1-8.

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