CuO/Mg/fluorocarbon sandwich-structure superhydrophobic nanoenergetic composite with anti-humidity property

Sandwich-structure superhydrophobic CuO/Mg/fluorocarbon nanoenergetic composite is prepared on the silicon substrate. An adhesion layer of Cu₂O is sputtered on the clean silicon substrate. Cu thin film is then deposited on it by E-beam evaporation. Nanostructured CuO is formed by thermal oxidation of Cu thin film. Mg and fluorocarbon layers are then deposited sequentially by thermal evaporation and sputtering, respectively. The nanostructured energetic composite is characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Accelerated aging test is performed in a temperature and humidity chamber (35°C, 95% relative humidity) and the heat-release characteristics are studied in detail by differential scanning calorimetry. It is found that Mg layer obtains the nano-texture from CuO and engenders superhydrophobicity after being coated with a fluorocarbon layer. Both the fluorocarbon coating and the CuO layer react with Mg intermediate layer but in different temperature ranges. Thus, the respective heat release can be adjusted almost independently. Because of the superhydrophobicity, CuO/Mg/fluorocarbon maintains about 82% chemical energy after 240h exposure. The nanoenergetic composite holds more than 50% of the original energy after 6h underwater storage. Superhydrophobic MoO₃/Mg/fluorocarbon and MoO₃/Al/fluorocarbon are also successfully prepared to prove the generality of this new design concept.