Aluminum nanopowder: A substance to be handled with care

Aluminum nanopowders are increasingly used in various areas of research in materials and physical chemistry. Their unconventional properties are still little understood and make their handling sometimes quite hazardous. In this article, we report the case of apparently benign mixtures of Al with sulfuric acid (H2SO4), which violently explode when they are exposed to a flame. The explosions of 100 mg samples were observed by high speed video (60000 fr/s). These experiments have showed a three-step mechanism, in which the primary hydrogen combustion ignites and disperses the nano-Al/H2SO4 paste in clusters with high velocities (similar to 100 m/s). The combustion of the paste increases the hydrogen release and initiates the explosion of the H-2/air mixture, which propagates at high velocities (760-1060 m/s). This effect was not observed with micron-sized Al powders, and it is a good illustration of new hazards with nano-Al. Extreme caution is hence recommended to chemists who handle such materials. (C) 2017 Elsevier B.V. All rights reserved.