Pseudo-oxide metal carbodiimides: Application in thermite reactions

Well-known thermite reactions, which are strong exothermic reactions typically between a metal and an oxide, offer diverse important applications, such as the synthesis and processing of materials, detonators, and propulsion. A fascinating family of nitrogen-containing analog solid-state metal carbodiimides, with the general formula Mx(NCN)y considered to be pseudo-chalcogenide or even pseudo-oxide, have drawn much attention owing to their unique physico-chemical properties. Herein, metal carbodiimides such as CuNCN are investigated as novel oxidizers for thermite reactions. We studied the Al/CuNCN thermite reaction, including thermal transformation, energy release and combustion performance, by means of complementary techniques, such as thermogravimetric-mass spectrometry (TGA-MS), differential scanning calorimetry (DSC), pressure evolution measurements and high-speed cameras. Compared to conventional Al/CuO thermite, the novel Al/CuNCN thermite system not only exhibited a strong combustion phenomenon with large energy release but also generated gases such as N2 and (CN)2. Additionally, the burning flame of Al/CuNCN presented a mushroom-cloud shape and was accompanied by a large number of hot spots due to the unique combustion characteristics of blasting and gas production. Even more encouraging was that the Al/CuNCN system was able to prepare AlN materials following a self-propagating route within one second. This work sheds light on the novel application of CuNCN in thermite reactions and potential routes to prepare gas generator and AlN.