Effect of a superhydrophobic coating on the combustion of aluminium and iron oxide nanothermites

There is an interest in broadening the range of applications of nanoenergetic composite materials to include their combustion and energy generation in submerged environments. Currently, their use is primarily limited to gas environments. Oceanic power generation, underwater ordnance, propulsion, metal cutting, and torch technologies are examples of applications that would significantly benefit from nanocomposite energetic materials. Recent research on superhydrophobic coatings has made it possible to coat nanoenergetic samples using a vapor-phase deposition process which significantly reduces the detrimental effects of water entering the composite that can occur during wet-chemistry based superhydrophobic processes. In this work, we discuss the process utilized to produce the superhydrophobic coating on nanoenergetic materials. We then analyze the bubble energy produced and compare this value to other energetic formulations. It was found that the ratio of the bubble energy to the total energy of combustion was an order of magnitude higher for the superhydrophobic coated materials compared to energetic composites containing a hydrophobic binder.

► Al-Fe2O3 thermites were coated with a superhydrophobic coating using a vapor-deposition process.
► Water did not permeate the coated thermites and enabled underwater reaction.
► Water permeates non-coated thermites, quenching the reactions immediately.
► Only nano Al is ignition sensitive enough to ignite and react underwater; micron Al does not.
► Energy produced from submerged reaction is 10× higher than composites with hydrophobic binder.