Particle size and oxide shell effects on microwave-induced heating of copper powder compacts

Microwave heating of metallic powders is strongly influenced by particle size, surface oxidation, and electromagnetic coupling, yet the relative contributions of these effects remain incompletely understood. In this study, copper powder compacts with systematically varied particle sizes were exposed to microwave radiation under identical experimental conditions, and the resulting thermal response was monitored using infrared thermography. Smaller particle sizes exhibited significantly enhanced microwave-induced heating compared to larger particles, which increasingly approached bulk-like behaviour. Microstructural and phase characterization revealed size-dependent oxide formation that contributed to differences in thermal response. A simplified heat-transfer model incorporating effective emissivity and convective losses was used to interpret steady-state temperature trends, providing qualitative insight into relative microwave-to-thermal energy conversion across particle sizes. The results demonstrate that copper powder heating under microwave exposure is governed by a combination of particle size, oxide shell effects, and heat dissipation mechanisms, highlighting the importance of microstructural scale in microwave processing of metallic powders.