Thermal stability and reaction properties of Al-CuO system, a mixture of 50-200 nm aluminum nanoparticles passivated by nitrocellulose and 12 nm copper (11) oxide, were investigated with microstructure characterization, differential thermal analysis (DTA), and thermogravimetric analysis (TGA). Transmission electron microscopy observation confirmed that the passivation coating successfully hinders the oxidization. TGA revealed that the passivation shell does not influence the ignition temperature of the thermite reaction. Reaction chemistry of the nano-thermite was elucidated by heating the composite both in inert ambient and vacuum. It was found that the thermite reaction composes of three continuing steps: At 570 degrees C, Al is oxidized into Al(2)O(3) by reacting with CuO, which forms Cu(2)O and produces a significant amount of heat. Subsequently two endothermic reactions occur. Starting at 800 degrees C, alumina reacts with Cu(2)O and forms CuAlO(2). Above this temperature CuAlO(2) will decompose and eventually produce alumina, Cu, and O(2) at 1000 degrees C. Since the nano-thermite reaction pathway differs greatly from bulk thermite reactions, these results are important to develop a nano-thermite platform that can be used for a novel low cost, low temperature, and copper based microjoining and advance IC packaging. (C) 2011 Elsevier Ltd. All rights reserved.
