A review of microwave-metal discharge interaction:Mechanism,regulation,and application for synthesis of nanomaterials

Placing metals within microwave ovens has been generally viewed as a dangerous practice because of occurrence of violent discharge,but in recent years such discharge phenomenon has attracted increasing attention and has enabled a variety of exciting applications.In this work,we provide a comprehensive review of fundamental understanding of microwave-metal discharge interaction and its state-of-the-art application for nanomaterials synthesis.We introduce the microscopic interaction between different categories of materials and the electric and magnetic field of microwaves.For microwave-metal interaction,we highlight its size-dependence and point out the influence of the oxide layer on the surface of metals.We discuss the required conditions for occurrence of discharge,microscopic formation mechanism,and characteristic features of microwave-metal discharge processes.Through analyzing the influence from the microwave input,discharging metals,and surrounding discharging media,we discuss the strategy for systematical regulation of the discharge process.We describe the applications of the microwave-metal discharge for facile synthesis of various functional nanomaterials including core-shell carbon/metal,metal oxides,metal chalcogenides,intermetallic compounds,metallic nanoparticles and metallic compounds,and organic compounds.Finally,the challenges in precise characterization and dynamic regulation of the discharge process as well as exciting application opportunities are discussed.