Tubular zinc ferrite nano material as well as preparation method and application thereof

Abstract

The invention discloses a tubular zinc ferrite nano material as well as a preparation method and application thereof, the preparation method comprises the following steps: mixing melamine and aluminum, reacting for 0.5-4 hours at the high temperature of 900-1500 DEG C under the protection of inert gas, soaking the obtained reactant in an inorganic acid solution for 2-24 hours, washing and drying to obtain a nitrogen-doped bamboo-like carbon fiber tube material; dispersing the nitrogen-doped bamboo-like carbon fiber tube material, a zinc salt and an iron salt in an aqueous solution, uniformly stirring, pre-freezing the mixture at the bottom of a refrigerator, then carrying out vacuum freeze drying, and finally carrying out heating reaction in an air atmosphere at 300-700 DEG C for 0.5-5 hours to obtain the tubular zinc ferrite nano material, as a sensitive layer material of a gas sensor, the material has the advantages of good selectivity, high sensitivity, good stability, rapid response and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of nanomaterials, and particularly relates to a tubular zinc ferrite nanomaterial and a preparation method and application thereof. Background Art

[0002] To build a harmonious, beautiful, safe, and happy world, the detection of trace amounts of toxic, harmful, flammable, and explosive gases in industry and homes is gaining increasing attention. Compared to other technologies and methods (such as colorimetry and chromatography), gas sensors are recognized as a potential tool for addressing this problem due to their simple operation and low cost. The adsorption and desorption of volatile organic compounds (VOCs) such as toluene, benzene, ethanol, ether, and propane induce changes in the electrical conductivity of metal oxide semiconductor materials. Gas sensors based on metal oxide semiconductors have been developed for over 50 years and play a key role in the gas sensor family. Gas sensors based on various metal oxide semiconductors, such as ZnO, In2O3, NiO, and SnO2, have been widely studied and applied in real life due to their small size, low cost, and simple sensing methods.

[0003] However, in the unremitting pursuit of excellent sensing performance such as high sensitivity, high selectivity and high stability, binary oxide semiconductors have gradually been studied. By precisely controlling the particle size, shape and micro / nanostructure of these materials, their gas sensing performance can be effectively improved. However, due to their inherent physical and chemical properties, single-component metal oxide semiconductors are difficult to achieve satisfactory sensing performance, especially in terms of sensitivity and selectivity. In order to achieve higher sensing performance, the latest research progress of metal oxide semiconductors has turned to the construction of nanocomposites based on metal oxide semiconductors. Compared with single metal oxide semiconductors, metal oxide semiconductor nanocomposites benefit from the synergistic effect between different components and are considered to be easier to obtain better gas sensing performance.

[0004] Zinc ferrite (ZnFe2O4) is a common spinel ferrite in which the transition metal cation Zn 2+ Doped (Fe 2+ Fe 3+ ZnFe2O4, a typical n-type binary metal oxide semiconductor, has attracted widespread attention as a gas sensing material due to its superior gas sensing performance compared to single metal oxide semiconductors. Manipulating the morphology, microstructure, and specific surface area of ​​ZnFe2O4 sensitive materials to promote gas transport within the sensitive membrane and increase the number of active catalytic sites is key to improving sensor sensitivity. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a tubular zinc ferrite nanomaterial and a preparation method thereof. A nitrogen-doped bamboo-shaped carbon fiber tube material is prepared by high-temperature decomposition, catalytic growth and acid treatment, and then the tubular zinc ferrite nanomaterial is prepared by in-situ compounding and calcination.

[0006] The present invention also provides an application of the tubular zinc ferrite nanomaterial in a gas sensor. The tubular zinc ferrite nanomaterial of the present invention is used as a sensitive material of the gas sensor, which has excellent properties such as good selection, high sensitivity, good stability, and fast response.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for preparing a tubular zinc ferrite nanomaterial, the method comprising the following steps:

[0009] (1) Melamine and aluminum are mixed and reacted at a high temperature of 900 to 1500° C. for 0.5 to 4 hours under the protection of an inert gas. The resulting reactant is soaked in an inorganic acid solution for 2 to 24 hours, washed, and dried to obtain a nitrogen-doped bamboo-shaped carbon fiber tube material;

[0010] (2) The nitrogen-doped bamboo-shaped carbon fiber tube material, zinc salt and iron salt are dispersed in an aqueous solution and stirred evenly. The mixture is first pre-frozen at the bottom of a freezer, then vacuum freeze-dried, and finally heated at 300-700°C in an air atmosphere for 0.5-5 hours to obtain a tubular zinc ferrite nanomaterial.

[0011] In step (1), the usage ratio of melamine to aluminum is 20 g: (0.1-0.5) g.

[0012] In step (1), the inorganic acid is at least one of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid, and the concentration of the solution is 1-8 mol / L, preferably 2-3 mol / L; the soaking temperature is 5-80°C, preferably 25-50°C for 6-8 hours.

[0013] In step (1), the high temperature reaction is preferably carried out at 1100-1200° C. for 2-3 hours.

[0014] In step (1), the inert atmosphere is nitrogen or argon.

[0015] In step (2), the mass ratio of the nitrogen-doped bamboo-shaped carbon fiber tube material to the zinc salt is 0.05:(0.17-1.53), and the molar ratio of the zinc salt to the iron salt is 1:2.

[0016] The mass ratio of the nitrogen-doped bamboo-shaped carbon fiber tube material, the zinc salt, and the iron salt is preferably 0.05:(0.51-1.53):(1.37-4.11).

[0017] In step (2), the zinc salt is one or more of zinc nitrate, zinc chloride, zinc sulfate and zinc acetate, preferably zinc chloride and zinc acetate.

[0018] In step (2), the iron salt is one or more of ferric nitrate, ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate and ammonium ferrous sulfate, preferably ferric chloride and ferrous chloride.

[0019] In step (2), the temperature of the freeze-drying cold trap is -60°C and the vacuum degree is 0.1 to 1.0 Pa.

[0020] In step (2), the vacuum freeze-drying time is 24 to 72 hours, preferably 36 to 48 hours.

[0021] In step (2), the reaction is preferably heated at 400-500° C. for 2-3 hours.

[0022] The present invention also provides an application of the tubular zinc ferrite nanomaterial in a gas sensor. Using the tubular zinc ferrite nanomaterial as the sensitive layer material of the gas sensor has the advantages of good selection, high sensitivity, good stability, and fast response.

[0023] The present invention provides a method for preparing a tubular zinc ferrite nanomaterial. First, a multi-layered, bamboo-shaped, nitrogen-doped carbon fiber tube is synthesized using high-temperature catalysis with melamine as a carbon source and aluminum as a catalyst. Following acid treatment, the carbon fiber tube is then mixed with an iron salt and a zinc salt in water in a specific proportion. During freezing, the iron and zinc salts precipitate from the solution and evenly adhere to the surface of the carbon fiber tube. Freeze-drying allows the iron and zinc salts to be evenly loaded onto the surface of the carbon fiber tube. After high-temperature calcination, the hollow tubular zinc ferrite nanomaterial is successfully obtained.

[0024] The chemical reaction formula involved in the above reaction process is expressed as follows:

[0025] C3H6N6→3C+3N2↑+3H2↑

[0026] 2Fe(NO3)3·9H2O+Zn(NO3)2·6H2O→ZnFe2O4+8NO2↑+24H2O↑+2O2↑

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) The prepared tubular zinc ferrite nanomaterial has high purity and uniform tubular morphology and size;

[0029] (2) The prepared tubular zinc ferrite nanomaterial has good stability and high temperature resistance;

[0030] (3) The prepared tubular zinc ferrite nanomaterial has a large specific surface area, which allows the detection gas to be fully adsorbed on the inner and outer surfaces of the material, accelerating gas transmission and improving sensitivity;

[0031] (4) The prepared tubular zinc ferrite nanomaterial is used as a semiconductor gas sensor, which has the advantages of high sensitivity, fast response and high stability;

[0032] (5) The preparation process is simple and easy to operate, with low requirements for experimental instruments and equipment. The raw materials are easy to obtain and the cost is low, and batch production can be carried out. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is an SEM image of the nitrogen-doped bamboo-shaped carbon fiber tube prepared in Example 1;

[0034] Figure 2 This is the XRD pattern of the nitrogen-doped bamboo-shaped carbon fiber tube prepared in Example 1;

[0035] Figure 3 This is an SEM image of the tubular zinc ferrite nanomaterial prepared in Example 1;

[0036] Figure 4 This is an SEM image of the tubular zinc ferrite nanomaterial prepared in Example 2;

[0037] Figure 5 This is an SEM image of the nitrogen-doped bamboo-shaped carbon fiber tube material prepared in Example 3;

[0038] Figure 6 This is an SEM image of the tubular zinc ferrite nanomaterial prepared in Example 3;

[0039] Figure 7 TEM image of the tubular zinc ferrite nanomaterial prepared in Example 3;

[0040] Figure 8 This is the XRD pattern of the tubular zinc ferrite nanomaterial prepared in Example 3;

[0041] Figure 9 This is an SEM image of the tubular zinc ferrite nanomaterial prepared in Example 4;

[0042] Figure 10 This is an SEM image of the tubular zinc ferrite nanomaterial prepared in Example 5;

[0043] Figure 11 The carbon nanotube material prepared using the iron sheet as the catalyst in Comparative Example 1;

[0044] Figure 12 The carbon nanotube material prepared using the cobalt sheet as the catalyst in Comparative Example 1;

[0045] Figure 13The carbon nanotube material prepared using the nickel sheet as a catalyst in Comparative Example 1;

[0046] Figure 14 This is the response graph of the tubular zinc ferrite nanomaterial prepared in Example 3 to eight organic vapors (100 ppm) at a working temperature of 240°C;

[0047] Figure 15 This is a response-recovery curve of the tubular zinc ferrite nanomaterial prepared in Example 3 to 100 ppm acetone at a working temperature of 240°C. DETAILED DESCRIPTION

[0048] The present invention is described in detail below with reference to the embodiments.

[0049] Example 1

[0050] A method for preparing a tubular zinc ferrite nanomaterial, comprising the following steps:

[0051] (1) 20.0 g of melamine and 0.1 g of aluminum sheet were placed in a high-temperature tube furnace and reacted at 1500 ° C for 0.5 hours under a nitrogen atmosphere. Then, they were immersed in 60 mL of 1.0 mol / L sulfuric acid solution and reacted for 24 hours. After washing with deionized water and drying, nitrogen-doped bamboo-like carbon fiber tube materials were obtained. The SEM image of the prepared nitrogen-doped bamboo-like carbon fiber tube is shown in FIG. Figure 1 Its XRD pattern is shown as Figure 2 As shown;

[0052] (2) 0.05g nitrogen-doped bamboo-shaped carbon fiber tube material, 0.17g zinc nitrate hexahydrate and 0.46g ferric nitrate nonahydrate were dispersed in 10mL deionized water. The mixture was first pre-frozen at -56°C at the bottom of the freezer for 1 hour, and then placed in a vacuum freeze dryer with a cold trap temperature of -60°C and a vacuum degree of 0.1Pa for 24 hours. Finally, the sample was placed in a muffle furnace and reacted at 300°C in an air atmosphere for 5 hours to obtain tubular zinc ferrite nanomaterials. The SEM image of the product is shown in Figure 2. Figure 3 As shown in the figure, it can be seen that the tubular zinc ferrite nanomaterial is a hollow structure.

[0053] Example 2

[0054] A method for preparing a tubular zinc ferrite nanomaterial, comprising the following steps:

[0055] (1) 20.0 g of melamine and 0.2 g of aluminum sheet were placed in a high-temperature tube furnace and reacted at 1400°C for 0.7 hours under a nitrogen atmosphere. The mixture was then immersed in 60 mL of a 2 mol / L hydrochloric acid solution and reacted for 8 hours. The mixture was then washed with deionized water and dried to obtain a nitrogen-doped bamboo-like carbon fiber tube material.

[0056] (2) 0.05g nitrogen-doped bamboo-shaped carbon fiber tube material, 0.26g zinc nitrate hexahydrate and 0.69g ferric nitrate nonahydrate were dispersed in 10mL deionized water. The mixture was first pre-frozen at -56°C at the bottom of the freezer for 1 hour, and then placed in a vacuum freeze dryer with a cold trap temperature of -60°C and a vacuum degree of 0.1Pa for 36 hours. Finally, the sample was placed in a muffle furnace and reacted at 400°C in an air atmosphere for 3 hours to obtain tubular zinc ferrite nanomaterials. The SEM image of the product is shown in FIG. Figure 4 As shown in the figure, it can be seen that the tubular zinc ferrite nanomaterial is a hollow structure.

[0057] Example 3

[0058] A method for preparing a tubular zinc ferrite nanomaterial, comprising the following steps:

[0059] (1) 20.0 g of melamine and 0.3 g of aluminum sheet were placed in a high-temperature tube furnace and reacted at 1200 ° C for 1 hour under a nitrogen atmosphere. Then, they were immersed in 60 mL of 3 mol / L sulfuric acid solution and reacted for 6 hours. After washing with deionized water and drying, nitrogen-doped bamboo-like carbon fiber tube materials were obtained. The SEM image of the prepared nitrogen-doped bamboo-like carbon fiber tube is shown in FIG. Figure 6 As shown;

[0060] (2) 0.05g nitrogen-doped bamboo-shaped carbon fiber tube material, 0.51g zinc nitrate hexahydrate and 1.37g ferric nitrate nonahydrate were dispersed in 10mL deionized water. The mixture was first pre-frozen at -56°C at the bottom of the freezer for 1 hour, and then placed in a vacuum freeze dryer with a cold trap temperature of -60°C and a vacuum degree of 0.1Pa for 48 hours. Finally, the sample was placed in a muffle furnace and reacted at 500°C in an air atmosphere for 2 hours to obtain tubular zinc ferrite nanomaterials. The SEM image of the product is shown in Figure 2. Figure 5 As shown in the TEM image Figure 6 As shown in the figure, it can be seen that the tubular zinc ferrite nanomaterial is a hollow structure; the XRD pattern of the product is as follows Figure 7 As shown, the characteristic diffraction peak of zinc ferrite can be seen from the figure.

[0061] Example 4

[0062] A method for preparing a tubular zinc ferrite nanomaterial, comprising the following steps:

[0063] (1) 20.0 g of melamine and 0.4 g of aluminum sheet were placed in a high-temperature tube furnace and reacted at 1100°C for 2 hours under a nitrogen atmosphere. The mixture was then immersed in 60 mL of a 6 mol / L nitric acid solution and reacted for 4 hours. The mixture was then washed with deionized water and dried to obtain a nitrogen-doped bamboo-like carbon fiber tube material.

[0064] (2) 0.05g nitrogen-doped bamboo-shaped carbon fiber tube material, 1.02g zinc nitrate hexahydrate and 2.74g ferric nitrate nonahydrate were dispersed in 10mL deionized water. The mixture was first pre-frozen at -56℃ at the bottom of the freezer for 1 hour, and then placed in a vacuum freeze dryer with a cold trap temperature of -60℃ and a vacuum degree of 0.1Pa for 60 hours. Finally, the sample was placed in a muffle furnace and reacted at 600℃ in an air atmosphere for 1h to obtain tubular zinc ferrite nanomaterials. The SEM image of the product is shown in Figure 2. Figure 9 As shown in the figure, it can be seen that the tubular zinc ferrite nanomaterial is a hollow structure.

[0065] Example 5

[0066] A method for preparing a tubular zinc ferrite nanomaterial, comprising the following steps:

[0067] (1) 20.0 g of melamine and 0.5 g of aluminum sheet were placed in a high-temperature tube furnace and reacted at 900°C for 4 hours under a nitrogen atmosphere. The mixture was then immersed in 60 mL of 8 mol / L phosphoric acid solution and reacted for 2 hours. The mixture was washed with deionized water and dried to obtain a nitrogen-doped bamboo-like carbon fiber tube material.

[0068] (2) 0.05g nitrogen-doped bamboo-shaped carbon fiber tube material, 1.53g zinc nitrate hexahydrate and 4.11g ferric nitrate nonahydrate were dispersed in 10mL deionized water. The mixture was first pre-frozen at -56℃ at the bottom of the freezer for 1 hour, and then placed in a vacuum freeze dryer with a cold trap temperature of -60℃ and a vacuum degree of 0.1Pa for 72 hours. Finally, the sample was placed in a muffle furnace and reacted at 700℃ in an air atmosphere for 0.5 hours to obtain tubular zinc ferrite nanomaterials. The SEM image of the product is shown in Figure 2. Figure 10 As shown in the figure, it can be seen that the tubular zinc ferrite nanomaterial is a hollow structure.

[0069] Comparative Example 1

[0070] 20.0g of melamine and 0.5g of iron sheet, nickel sheet or cobalt sheet were placed in a high temperature tube furnace and reacted at 1100℃ for 4 hours under nitrogen atmosphere. Then, they were immersed in 60mL of 5.0mol / L sulfuric acid solution and reacted at 80℃ for 2 hours. After washing with deionized water and drying, nitrogen-doped carbon nanotube material was obtained, and its SEM image is shown as follows: Figure 11-13 As shown in the figure, it can be seen that the diameter of the nanotubes is small, there is no bamboo-like shape, and the thickness is uneven.

[0071] Application Example 1

[0072] Application of tubular zinc ferrite nanomaterials in gas sensors

[0073] 0.05 g of the final tubular zinc ferrite nanomaterial obtained in Example 3 was placed in a centrifuge tube, 0.5 mL of ethanol was added, and ultrasonic dispersion was performed. 100 μL of the solution was then pipetted onto the surface of an alumina tube with a gold electrode. The solution was then dried at 60°C for 2 hours and then treated at 300°C for 2 hours. A small Ni-Cr alloy coil was inserted into the ceramic tube as a heater to maintain the operating temperature of the gas sensor. To improve the long-term stability of the sensor, the sensor was aged at 240°C for 48 hours.

[0074] The sensor is placed in a test chamber and the resistance change of the sensor's sensitive membrane at an operating temperature of 240°C is monitored using an electrochemical workstation. The test gas is then injected into the test chamber and the test gas is exhausted after the sensor response value stabilizes. The sensor's response sensitivity to the test gas is defined as: S = R a / R g (reducing gas), R a is the resistance of the sensor in air, R g Is the resistance of the sensor in the gas to be tested. In this test system, the response sensitivity of the sensor to the test gas can also be calculated using the following formula: S = I air / I gas ,I air and I gas The response time and recovery time are the time required for the sensor output current to reach 90% of the stable value after sample injection or removal of the test gas.

[0075] At an operating temperature of 240°C, the sensor's response sensitivity to eight organic vapors (100 ppm) is as follows: Figure 14 As shown. Figure 14 It can be seen that the sensor has a good sensitive response to organic vapors such as 100ppm ethanol, acetone and formaldehyde at an operating temperature of 240℃. Figure 15 This is the real-time response and recovery curve of the zinc ferrite tube gas sensor to 100ppm acetone vapor. Figure 15 It can be seen that the response time and recovery time of the sensor to 100 ppm acetone vapor are approximately 11 s and 14.5 s, respectively.

[0076] The sensor has a good sensitivity response to organic vapors such as ethanol and formaldehyde, and the response and recovery time are short. This is mainly because the tubular morphology of zinc ferrite provides abundant active sites and transmission channels for the rapid adsorption and diffusion of gas molecules.

[0077] The detailed description of a tubular zinc ferrite nanomaterial, its preparation method, and application with reference to the above-mentioned embodiments is illustrative rather than restrictive. Several embodiments may be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a tubular zinc ferrite nanomaterial, characterized in that: The preparation method comprises the following steps: (1) Melamine and aluminum are mixed and reacted at a high temperature of 900 to 1500° C. for 0.5 to 4 hours under the protection of an inert gas. The resulting reactant is soaked in an inorganic acid solution for 2 to 24 hours, washed, and dried to obtain a nitrogen-doped bamboo-shaped carbon fiber tube material; (2) The nitrogen-doped bamboo-shaped carbon fiber tube material, zinc salt and iron salt are dispersed in an aqueous solution and stirred evenly. The mixture is first pre-frozen at the bottom of a freezer, then vacuum freeze-dried, and finally heated at 300-700°C in an air atmosphere for 0.5-5 hours to obtain a tubular zinc ferrite nanomaterial.

2. The preparation method according to claim 1, characterized in that In step (1), the usage ratio of melamine to aluminum is 20g:(0.1-0.5)g.

3. The preparation method according to claim 1, characterized in that In step (1), the inorganic acid is one or more of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid, and the concentration of the solution is 1 to 8 mol / L.

4. The preparation method according to claim 1, characterized in that In step (2), the mass ratio of the nitrogen-doped bamboo-shaped carbon fiber tube material to the zinc salt is 0.05:(0.17-1.53), and the molar ratio of the zinc salt to the iron salt is 1:

2.

5. The preparation method according to claim 1, characterized in that In step (2), the zinc salt is one or more of zinc nitrate, zinc chloride, zinc sulfate and zinc acetate.

6. The preparation method according to claim 1, characterized in that In step (2), the iron salt is one or more of ferric nitrate, ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate and ferrous ammonium sulfate.

7. The preparation method according to claim 1, characterized in that In step (2), the cold trap temperature of the freeze dryer is -60°C and the vacuum degree is 0.1 to 1.0 Pa.

8. The preparation method according to claim 1, characterized in that In step (2), the freeze-drying time is 24 to 72 hours.

9. The tubular zinc ferrite nanomaterial prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the tubular zinc ferrite nanomaterial according to claim 9 in a gas sensor.

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