The influence of structure on thermal behavior of reactive Al-Ni powder mixtures formed by ball milling

Ball milling (BM) was used to produce reactive Al-Ni powder mixtures that exhibit self-propagating exothermic reactions (SPER) for nano-micro heater applications. Powders with an Al-Ni molar ratio of 1:3 were milled, cold pressed into pellets and ignited using a heat source. The structural and thermal properties of the pellets were characterized before and after ignition using X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The reaction characteristics of the pellets were evaluated using an infrared camera during ignition experiments. Pellet microstructures show that the BM technique created nanoscale lamellar structures, with dimensions diminishing with increasing milling time. Pellets milled longer than 16 h exhibited SPER. Flame velocity increased with pellet density.