Study and application status of the nonthermal effects of microwaves in chemistry and materials science - a brief review

Microwaves (MWs) are widely known and used in human life and production activities based on their thermal effects. In contrast, their nonthermal effects are still under debate. Fortunately, the nonthermal effects of MWs have been investigated by an increasing number of researchers and have shown great potential in industrial production. In this review, typical studies that demonstrate the nonthermal effects of MWs in chemistry and materials science are introduced and discussed, and the applications of and the harms that are caused by these effects are summarized to facilitate the safe use of these MW effects. The mechanisms of the nonthermal effects of MWs that have been proposed by researchers with various backgrounds are presented. Because some researchers did not detect nonthermal effects of MWs, four typical relevant studies are identified and introduced. Various types of MW reactors (single-mode and multimode reactors and reactors without a MW cavity) are summarized and compared. Finally, possible directions for future research on the nonthermal effects of MWs are proposed.