Experimental Study of Microwave-Induced Discharge and Mechanism Analysis Based on Spectrum Acquisition

When conductor or semiconductor materials are exposed to microwave radiation in different atmospheres (Ar, He, N
₂
, and O
₂
+N
₂
) intense discharge phenomena are observed. The discharge phenomena, generated when strips of the metals Fe, Al, and Zn or particles of the semiconductor SiC are irradiated with microwaves, are characterized experimentally using spectrum acquisition and analysis. Filamentary discharge is observed in an Ar atmosphere while spark discharge is observed in He, N
₂
, and O
₂
+N
₂
atmospheres. The spectral lines of the discharges are concentrated mainly in the visible region, but there are also peaks in the ultraviolet region. The nature of the discharge and the specific details of the spectra are influenced by: 1) the target metal or semiconductor used; 2) the atmosphere; and 3) the microwave field characteristics. The spectra always consist of two parts: one corresponding to the target metal or semiconductor irradiated by the microwaves and the other due to the formation of the high-energy excitation states of atoms, molecules, and ions induced in the gaseous atmosphere. The microwave-induced discharge and the corresponding luminous and plasma effects have potential uses as energy sources in many applications including chemical or photocatalytic enhancement of reactions and the destruction of volatile organic compounds for which preliminary results are encouraging.