Ultrathin Zirconia Passivation and Stabilization of Aluminum Nanoparticles for Energetic Nanomaterials via Atomic Layer Deposition

The stability of aluminum (Al) nanoparticles is a key issue that determines the energy performance of solid fuels, Al-based green propellants, and fuel cells. The surface native oxide shell (Al2O3), nevertheless, cannot stabilize Al nanoparticles under hot water conditions. Herein, we report a passivation method utilizing an ultrathin zirconia (ZrO2) coating via atomic layer deposition, where a sub-nanometer coating layer could completely prevent the reactions between Al nanoparticles and hot water (80 °C). The weight percentage of metallic Al for ultrathin ZrO2 coated Al nanoparticles can reach 82.2 wt %, which is close to that of original Al nanoparticles with Al2O3 native oxide (88 wt %). The metallic Al’s weight has been kept at 93.4% for the ultrathin ZrO2 coated Al nanoparticles compared to the original Al nanoparticles. As a comparison, the Al2O3 coated Al nanoparticles result in the oxidation failure in 60 °C water. The proposed passivation mechanism is attributed to ZrO2 coating’s structural stability and the enhanced hydrophobicity to water. The ultrathin ZrO2 passivation offers a valuable tool for enhancing the stability of Al nanoparticles and thereby enables their potential applications in energy field.