COMBUSTION CHARACTERISTICS OF REACTIVE NANOMATERIALS

The combustion ofmetallic particlesis analogous to the combustion of hydrocarbon particles andthe particle burn time can be related to its diametric length. The relationship is called‘d’ law and represented astb=d2. From the physics aspect, many deviations from the established laws at the bulk scale have been reported. As the ignition temperature of energetic nanomaterials is more sensitive to the passivation layer and the external heating conditions, and the burning time of nanomaterials is deviated from the conventional d2 law. Due to the variation of certain parameters such as the particles size distribution, agglomeration, morphology, level of contamination and initial particle size,the correct and precise value of the exponentisdifficult to find. Consequently, there’s no universal law for the burn time and a variant of the dn law is always proposed whose exponent is less than 2 (~ 1.3-1.7).In this research, combustion experiments are performed using a Bunsen burner in a particle-laden methane stream and the relationship of particle burning time with particle diameter is found to be tb ~ d1.2. The combustion process of the various particles is captured using a high speed video camera. The average values of extinction time for Si (720 nm) and Si (1000 nm) are 11.4 ms and 17.2 ms, respectively. It is also observed that the nanoparticles are more reactive than the microsized particles. The average velocity flow fields of the silicon, iron and aluminum particles are also investigated using PIV technique.Before and after the experiments, the particles are characterised using dynamic light scattering (DLS), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM).