HIT Prepares Tungsten Carbide/Carbon Composites

The researchers of Harbin Institute of Technology (HIT) have obtained a series of tungsten carbide/carbon composites through a simple non-solvent method, which has good and stable microwave absorption performance and excellent corrosion resistance.

Carbides/carbon composites are emerging as a new kind of binary dielectric systems with good microwave absorption performance. Compared with traditional electromagnetic shielding, electromagnetic absorption can realize the effective conversion of electromagnetic energy, which is a more advanced and sustainable electromagnetic pollution protection method. Carbon materials are considered to be an ideal electromagnetic wave absorbing medium due to their stable chemical properties, low density, adjustable dielectric properties and diverse microstructures.

Solvent-free synthesis of ultrafine tungsten carbide nanosheets image

However, a single carbon material generally suffers from poor impedance matching effects. Although common magnetic carbon-based composite materials have good performance, the actual application process is limited by disadvantages such as high density, easy corrosion, uneven composition, and low temperature.

Herein, researchers from HIT obtain a series of tungsten carbide/carbon composites through a simple solvent-free strategy, where the solid mixture of dicyandiamide (DCA) and ammonium metatungstate (AM) is employed as the precursor. Ultrafine cubic WC1-x nanoparticles (3-4 nm) are in situ generated and uniformly dispersed on carbon nanosheets.

This configuration overcomes some disadvantages of conventional carbides/carbon composites and is greatly helpful for electromagnetic dissipation. It is found that the weight ratio of DCA to AM can regulate chemical composition of these composites, while less impact on the average size of WC1-x nanoparticles. With the increase in carbon nanosheets, the relative complex permittivity and dielectric loss ability are constantly enhanced through conductive loss and polarization relaxation.

ultrafine tungsten carbide nanosheets image

The different dielectric properties endow these composites with distinguishable attenuation ability and impedance matching. When DCA/AM weight ratio is 6.0, the optimized composite can produce good microwave absorption performance, whose strongest reflection loss intensity reaches up to - 55.6 dB at 17.5 GHz and qualified absorption bandwidth covers 3.6-18.0 GHz by manipulating the thickness from 1.0 to 5.0 mm. Such a performance is superior to many conventional carbides/carbon composites.

The HIT research team successfully prepared tungsten carbide/carbon composites materials through a simple non-solvent method by using a solid mixture of dicyandiamide and ammonium metatungstate as a precursor, grinding and mixing uniformly, and then pyrolyzing it. The binary dielectric composite material composed of carbide and carbon not only has excellent absorption an effect, but also has stable performance. It has shown good application prospects in the field of electromagnetic absorption, but it is necessary to solve the relatively complicated preparation process of such materials.