Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine
Absorption of microwaves by various materials is accompanied by heating of varying degree [1]. The purpose of this work is to study the dependence of the heating temperature of briquetted SiC powders on the microwave radiation time and power. Study of the influence of time from 1 min. up to 3 min. and power from 350 W to 700 W on the heating temperature of the investigated powder materials was carried out due to the absorption of microwave radiation with a frequency of 2.45 GHz . Six samples of silicon carbide synthesized under different conditions were used: 1 – synthesized from electrode graphite and Si; 2 – synthesized from petroleum coke and SiO₂; 3 – synthesized from thermally expanded graphite (TEG) and Si; 4 –ground ceramics infiltrated TEG by Si at 2000°С; 5 – synthesized from TEG and Si and purified in HF; 6 – ground reaction-bonded silicon and boron carbide (SiC-B₄C-Si). The weak dependence of the heating temperature on the time of microwave action at a power of 350 W for samples 1, 2 and 4 is due to the presence of crystalline silicon in the compositions of synthesized silicon carbide powders. The monotonous increase in the heating temperature of samples 3.5 and 6 from the time of microwave exposure is evidence of their high dielectric properties in a wide temperature range. An increase in temperature over 950°C during of 3 minutes is a main evidence of cubic modification silicon carbide in the form of a solid solution of carbon in silicon carbide. Dissolved carbon in the form of planar carbon clusters with sp3 hybridization of atoms leads to an increase in dielectric properties. The phase composition of sample 6 is characterized by the presence mainly of hexagonal 4H-SiC, as well as crystalline silicon. However, the presence of silicon does not affect microwave absorption. A monotonous increase in temperature up to 750°C is observed during 3 minutes.
