Hydrophobically/oleophilically guarded powder metallurgical structures and liquid impregnation for ice mitigation

Icing hazards often pose operational and safety challenges. Various surface and coating approaches have been attempted for ice mitigation purposes, but the durability remains an outstanding issue. Inspired by traditional powder metallurgy and slippery icephobic surfaces, a new strategy for slippery liquid-impregnated porous metallic structure (LIPMS) with gradient porosity was proposed in this study for ice mitigation, by directly impregnating selected liquids into sintered porous copper components with hydrophobic/oleophilic guarding consideration. The results indicated that robust LIPMS with desired porosity were obtained, significantly delaying the icing of surface water droplets, providing good frost resistance in a high humid environment, and demonstrating ultra-low ice adhesion strength (less than 1 kPa). It was confirmed that the hydrophobic/oleophilic guarding design significantly improved icephobic durability, attributing to its role in repelling external water and maintaining internal slippery liquid. To offer a comprehensive understanding of icephobic mechanisms and the potentials of LIPMSs, a concept of ice initiation position was also proposed and theoretically discussed. The pivotal factor of icephobic LIPMS is to maintain the icing initiation position at the unfrozen liquid–liquid interface or inside the homogeneous liquid, thus inhibiting icing and facilitating the ice removal.