A microwave absorbing material of nitrogen-doped vanadium oxide and a preparation method thereof

Abstract

The application discloses a kind of nitrogen-doped vanadium oxide microwave absorbing materials and preparation method thereof, first by hydrothermal morphology control process and combining annealing process nitrogen-doped vanadium oxide is synthesized, and its microwave absorption performance is systematically studied.Through adjusting hydrothermal reduction pH value, the complex permittivity of sample can be adjusted.At pH value of 7, by adjusting the thickness of sample, selective absorption of electromagnetic wave can be realized, and at 4.37GHz, the lowest reflection loss can reach 31.57dB.The reflection loss of sample corresponding to thickness in different frequency bands can be less than 10dB, almost covering the entire frequency range.The excellent microwave absorption performance of nitrogen-doped vanadium oxide microwave absorbing material of the application is due to the improvement of conductivity in the dual-phase vanadium oxide after nitrogen doping, good impedance matching and multiple reflection caused by its unique microstructure.The nitrogen-doped vanadium oxide microwave absorbing material can be used as the absorption requirement of different application scenarios, and the corresponding thickness can meet the absorption requirement.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of microwave absorption materials, and particularly relates to a nitrogen-doped vanadium oxide microwave absorption material and a preparation method thereof. BACKGROUND

[0002] In recent years, the field of electromagnetic wave absorption materials has attracted extensive attention due to the driving of the demand for better electromagnetic interference (EMI) shielding, stealth technology and wireless communication systems. Two parameters that determine the electromagnetic wave absorption material are the complex permittivity and the complex permeability. The material mainly with the complex permittivity takes the dipole polarization as the main absorption mode, and is usually only suitable for absorbing high-frequency electromagnetic waves. The material mainly with the complex permeability takes the magnetic dipole interaction, converts the electromagnetic wave into heat energy loss, and is usually only suitable for low frequency, and is limited by its own Curie temperature.

[0003] Vanadium oxide, as a cheap and abundant transition metal oxide on earth, has attracted great interest of researchers due to its excellent optical and electromagnetic properties. The electrons on the V element orbit in vanadium oxide can move along the V-V and V-O chain, which means that vanadium oxide can provide and receive different numbers of electrons, can become an electron pool or an electron transfer medium, and can achieve the result of weakening electromagnetic waves through the relaxation effect of dielectric loss, and may be a potential electromagnetic wave absorption material with excellent effect. In the existing design of microwave absorption materials, it is still an important challenge to achieve wide absorption frequency band and strong absorption performance.

[0004] Based on the above analysis, the present application improves the electron movement efficiency of vanadium oxide by doping nitrogen into vanadium oxide, and controls the microstructure of the precursor to achieve good impedance matching, so that the electromagnetic waves of different wave bands can be selectively absorbed by controlling the thickness of the substrate. SUMMARY

[0005] In view of the above shortcomings, the present application provides a nitrogen-doped vanadium oxide and a preparation method, which is simple to prepare and low in cost, and can realize selective absorption of electromagnetic waves of different wave bands according to the thickness of the scene and functional requirements, and overcome the difficulty of realizing low-frequency absorption and different frequency band absorption of the absorption body mainly with dielectric loss.

[0006] The present application is realized by the following technical solutions:

[0007] The present application first discloses a preparation process of a nitrogen-doped vanadium oxide microwave absorption material, comprising:

[0008] (1) The ammonium metavanadate, guanidine carbonate and glucose are weighed and placed in a marquis mortar for grinding, a mixture obtained is added into a solvent, stirred and uniformly mixed, and heated and kept in a water bath, the pH is adjusted to 7 by adding concentrated hydrochloric acid dropwise, and a first substance is obtained;

[0009] (2) Pour the first substance into the lining of the hydrothermal reactor, place the hydrothermal reactor in an electric constant temperature drying oven for heating and heat preservation, take it out after cooling in the oven, filter and dry it to obtain the precursor.

[0010] (3) The precursor is heated to the reaction temperature in a tube furnace at a rate of 5℃ / min, kept at the temperature, cooled and taken out to obtain a microwave absorbing material of nitrogen-doped vanadium oxide; during the process, a mixed gas is continuously introduced.

[0011] Further, in step (1), the mass ratio of ammonium metavanadate, guanidine carbonate, and glucose is 16:74:10; the solvent includes anhydrous ethanol and deionized water.

[0012] Furthermore, the volume ratio of anhydrous ethanol to deionized water is 3:1.

[0013] Further, the stirring speed in step (1) is 200 r / min and the stirring time is 10 min; the water bath heating and heat preservation temperature is 60℃.

[0014] Furthermore, the heating and heat preservation temperature in step (2) is 180°C, and the heating and heat preservation time is 4 hours.

[0015] Further, the heating and heat preservation temperature in step (3) is 600℃, and the heating and heat preservation time is 3h; the mixed gas is a mixture of ammonia and oxygen.

[0016] Furthermore, the flow rate ratio of ammonia to oxygen is 20:1.

[0017] The present invention also discloses a microwave absorbing material of nitrogen-doped vanadium oxide prepared according to any of the above-described preparation processes.

[0018] The beneficial effects of this invention are as follows:

[0019] The nitrogen-doped vanadium oxide of this invention exhibits excellent microwave absorption performance over a wide frequency range, particularly at pH 7, where selective absorption of electromagnetic waves can be achieved by adjusting the sample thickness, with a minimum reflection loss of 31.57 dB. This invention provides an effective method for modifying microwave performance and has broad application prospects. Attached Figure Description

[0020] Figure 1 Electromagnetic wave absorption performance of the sample in Example 1 of this invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1

[0023] Weigh 1.60 g ammonium metavanadate, 7.40 g aminoguanidine carbonate, and 1.00 g glucose, grind them evenly in a mortar, and then add them to a mixed solution of 38 mL anhydrous ethanol and 12 mL deionized water. After stirring evenly, heat and maintain the temperature in a 60 °C water bath. Adjust the pH of the solution to 7 by adding concentrated hydrochloric acid dropwise, and stir at 200 rpm for 10 minutes. Pour the mixture into the lining of a hydrothermal reactor and react at 180 °C for 4 hours. After cooling, filter and dry the precursor. Heat to 600 °C in a tube furnace at a rate of 5 °C / min, maintain for 3 hours, and then cool to obtain a nitrogen-doped vanadium oxide microwave absorbing material. During the process, a mixture of ammonia and oxygen gas (flow rate ratio 20:1) is continuously introduced. This nitrogen-doped vanadium oxide microwave absorbing material has the ability to selectively absorb electromagnetic waves of 2-18 GHz, and its absorption effect is as follows. Figure 1 As shown in the figure, a reflection value of 10dB represents 99% absorption of electromagnetic waves, and the portion exceeding 10dB is considered effective absorption. The figure shows that the product of different thicknesses has corresponding effective absorption widths in different frequency bands. This means that by adjusting the sample thickness, absorption of electromagnetic waves in different frequency bands can be achieved to meet different application requirements.

[0024] Example 2

[0025] Weigh 2.56 g of ammonium metavanadate, 11.84 g of aminoguanidine carbonate, and 1.60 g of glucose, grind them evenly in a mortar, and then add them to a mixed solution of 60 mL of anhydrous ethanol and 20 mL of deionized water. After stirring evenly, heat and maintain the temperature in a 60 °C water bath. Adjust the pH of the solution to 7 by adding concentrated hydrochloric acid dropwise, and stir at 200 rpm for 10 minutes. Pour the mixture into the lining of a hydrothermal reactor and react at 180 °C for 4 hours. After cooling, filter and dry the precursor. Heat to 600 °C in a tube furnace at a rate of 5 °C / min, hold for 3 hours, and then cool to obtain a nitrogen-doped vanadium oxide microwave absorbing material. During the process, a mixture of ammonia and oxygen gas (flow rate ratio 20:1) is continuously introduced.

Claims

1. A process for preparing a microwave absorbing material of nitrogen-doped vanadium oxide, comprising: (1) Weigh ammonium metavanadate, guanidine carbonate and glucose in a mass ratio of 16:74:10 and grind them thoroughly in an agate mortar. Add the resulting mixture to a solvent and stir until well mixed. The stirring speed is 200 r / min and the stirring time is 10 min. The solvent is anhydrous ethanol and deionized water mixed in a volume ratio of 3:1 and heated to 60 ℃ in a water bath. The pH is adjusted to 7 by adding concentrated hydrochloric acid dropwise to obtain the first substance. (2) Pour the first substance into the lining of the hydrothermal reactor, place the hydrothermal reactor in an electric thermostatic drying oven and heat it to 180 ℃ for 4 h. After cooling in the oven, take it out, filter and dry it to obtain the precursor. (3) The precursor is heated to the reaction temperature in a tube furnace at a rate of 5 °C / min, held at 600 °C for 3 h, and then cooled and taken out to obtain a microwave absorbing material of nitrogen-doped vanadium oxide; during this period, a mixture of ammonia and oxygen is continuously introduced, with a flow ratio of ammonia to oxygen of 20:

1.

2. A microwave absorbing material of nitrogen-doped vanadium oxide prepared by the preparation process according to claim 1.

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