Nano-structured energetic materials have been recently proposed as novel energy storage media where the exothermic reaction is the key to control the heat release process. The properties of nano-alloys, which can be engineered not only by the particle size, but also by varying their elemental compositions, are very appealing. This work conducted a comparative experimental study of the exothermic characteristics of two nanomaterials in the air, aluminum nanoparticles (nano-Al) and aluminum-copper nanoalloys (nano-AlCu) based on TGA/DSC studies. The results showed that the general exothermic characteristics of nano-AlCu were very similar to that of nano-Al but the nanoalloy was more reactive. The nano-AlCu was oxidized and ignited at lower temperature, and influenced by the heating rate. An early ignition was found for both nanomaterials, and the eutectic melting of the nano-alloy was believed to be mainly responsible for its early ignition. (C) 2015 Elsevier B.V. All rights reserved.