Ignition of nickel coated aluminum agglomerates using shock tube

Abstract

Al is used as additives for solid propellants due to its high energy density. However, Al is difficult to ignite since it is covered with a protective oxide film having a high melting point. One method suggested to solve this problem is surface coating with other metal particles. Thus, in this study, Al particles were coated with Ni nanoparticles by a simple spray drying technique. The coating process was carried out by varying the weight percent of Ni to Al particles. The crystalline structure of Ni-coated Al particles was retained without any intermetallic or additional phase formation, as identified by XRD. SEM and EDS results show uniform and continuous coating of Ni-nanoparticles on the surface of 10 µm Al particles was formed when the sample was prepared using an equal weight percentage ratio of Ni and Al. When the ratio of Ni to Al was decreased, the Ni-nanoparticles only partly covered the surface of the Al particles. The presence of elements was confirmed from the XPS analysis with strong surface interaction between Ni nanoparticles and Al particles. Ni-coated Al particles in an air atmosphere showed higher exothermic energy than pure Al particles. Ignition performance of Ni-coated Al particles obtained from a shock tube experiment at high temperature demonstrated the significant decrease in ignition delay time as the Ni content in the sample increased.