Tungsten Oxide Nanowires As Microwave Absorbing Materials

Tungsten oxide has unique physical properties such as photochromism, electrochromism, thermochromism and gas sensitivity. Its color change can be achieved by changing irradiation wavelength, temperature or applied voltage. Therefore, tungsten oxide can be used in many fields such as sensors, electronic devices and so on. The nature of Yue Yue, its development and research has become a hotspot all over the world.

Some scholars have designed a simultaneous preparation method of tungsten oxide quantum dots and tungsten oxide nanowires. Using one-step hydrothermal method, tungsten oxide quantum dots and nanowires are synthesized by using tungsten hexachloride as tungsten precursor. Tungsten oxide nanowires are synthesized by hydrothermal action, and then tungsten oxide quantum dots are formed by hydrothermal cutting. Tungsten oxide quantum dots and tungsten oxide nanowires can be fabricated simultaneously, reliably and efficiently. The prepared tungsten oxide quantum dots can be used in the conventional applications of quantum dots such as fluorescence imaging and iron ion specific detection. The prepared tungsten oxide nanoparticles can be used as a very good absorbing material.

In order to achieve the above purpose, the concurrent preparation of tungsten oxide quantum dots and tungsten oxide nanowires includes the following steps:

(1)First, 0.0667 g tungsten hexachloride was dissolved in 12 ml absolute ethanol, and golden clarified tungsten hexachloride ethanol solution was obtained after stirring.

(2)Transfer the solution prepared in the step (1) to a Teflon sealed can and put it into a hydrothermal reaction kettle, and heat it for 4-10 hours in a temperature range of 120-220 °C. A hydrothermal solution comprising tungsten oxide quantum dots, tungsten oxide nanowires, an ethanol reactant and water, wherein the ethanol reactant comprises diethyl ether, ethanol, hydrogen chloride and a small amount of water;

(3)When the solution after hydrothermal treatment is naturally reduced to room temperature, the PTFE tank in the hydrothermal reactor is taken out and the solution in the PTFE tank is taken out and put into the centrifugal tube. The centrifugal tube is symmetrically placed in the centrifuge and centrifuged for more than 10 minutes at a speed greater than 10,000 rpm. The centrifugal solution after centrifugation is prepared and separated. The supernatant consists of tungsten oxide quantum dots (TQDs) and ethanol reactants in the supernatant, and the precipitation in the lower layer is tungsten oxide nanowires.

(4)The supernatant of the centrifugal solution prepared in step (3) was dialyzed in a dialysis bag with a molecular weight of 500 for 24 hours, then ether, ethanol and hydrogen chloride were removed by dialysis to produce pure tungsten oxide quantum dot solution.

(5)Take the precipitation in step (3) and wash it with deionized water for 6 times, remove the impurities attached to the surface, then freeze-dry the precipitation below - 20 ℃ for more than 20 hours to prepare tungsten oxide nanowires.

The tungsten oxide nanowires fabricated by the above methods have a diameter of 25-30 nanometers and a length of 0.6-1.6 microns. The maximum aspect ratio of tungsten oxide nanowires can reach 64. Therefore, the anisotropy of tungsten oxide nanowires is improved. When electromagnetic waves are incident on the surface of the nanowires, tungsten oxide nanowires are more advantageous than bulk tungsten oxide materials. Polarization results in better absorbing performance.

The researchers tested the electromagnetic wave absorption properties of tungsten oxide nanowires. When the thickness of the tungsten oxide nanowires absorbing layer was 1.5 mm, the optimum absorbing performance was obtained at 16.7 GHz, and the maximum reflection loss was -40.5 dB. The results show that the tungsten oxide nanowires prepared are good microwave absorbing materials and can be used in electromagnetic masking technology. In the field of field and battle stealth technology, to improve the compatibility of electromagnetic equipment, strengthen the protection of information technology, better protect the health of personnel operating electromagnetic radiation equipment.

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