Zhuangzhu Luo

A replication strategy for complex micro/nanostructures with superhydrophobicity and superoleophobicity and high contrast adhesion

The present work reports a replication approach to imprint complex micro/nanostructures into polymeric coatings and materials, such as silicone elastomers, polyurethane, ultra-high-molecular-weight polyethylene and polytetrafluoroethylene etc., with applications in engineering. Al and Al2O3 molds with terraced micro/nanostructures were produced using an industrially compatible anodization method. To assist replication, the molds were coated with a water-soluble polymer layer as the sacrificial layer, to reduce the adhesion between replica and mold. Polymeric replicas with complex terraced structures were successfully obtained, which were otherwise impossible to achieve with conventional perfluorinated molds. The as-prepared replicas all exhibited superhydrophobicity without further modification with low-surface-energy coatings. Interestingly, residual hydrophilic sacrificial layer resulted in high water-adhesion without losing superhydrophobicity; these surfaces turned extremely slippery after removal of the residual sacrificial layer. A molecular mechanism is proposed to interpret the contrast adhesion. After being coated with a sticky perfluoroalkyl, containing methacrylate, the surfaces convert to superoleophobicity and low adhesion to a number of oils.

Microstructure evolution and tensile mechanical properties of thixoformed AZ61 magnesium alloy prepared by squeeze casting

Abstract A novel process that combines squeeze casting with partial remelting to obtain AZ61 magnesium alloy with semi-solid microstructures was proposed. In this route, the squeeze casting was used to predeform the magnesium alloy billets to obtain small dendritic structures. During subsequent partial remelting, small dendritic structures transform into globular grains surrounded by liquid films. The results show that the squeeze casting AZ61 alloy after partial remelting produces more ideal, finer semi-solid microstructure compared with as-cast AZ61 alloy treated by the same isothermal holding conditions. Moreover, the mechanical properties of the thixoformed AZ61 alloy prepared by squeeze casting plus partial remelting are better than those of the thixoformed alloy prepared by conventional casting plus partial remelting.