The role of aluminum particle size in electrostatic ignition sensitivity of composite energetic materials

Very often unintentional ignition of composite energetic materials (CEM) occurs when static electricity is discharged into the CEM. An interesting finding recently reported showed that for micron particle CEM formulations, only aluminum (Al) combined with copper oxide (CuO) was electrostatic discharge (ESD) ignition sensitive, while commonly used Al combined with molybdenum trioxide (MoO3) was deemed not ESD ignition sensitive. In practice however, nano Al-MoO3 results in frequent unintentional ESD ignition events. This study examines the role of Al particle size on ESD ignition sensitivity and measures electrical conductance for each CEM. Results show that as Al particle size is reduced, electrical conductance increases dramatically as does ESD ignition sensitivity. Overall, electrical conductance is shown to increase linearly with increasing Al surface area to volume ratio and the alumina passivation shell surrounding Al core particles plays a significant role in enhancing ignition sensitivity.