Time-resolved laser-induced incandescence on metal nanoparticles: effect of nanoparticle aggregation and sintering

This work examines the excessive absorption and anomalous cooling phenomena reported in laser-induced incandescence measurements on metal nanoparticles by considering the effects of aggregate structure and sintering. Experimental investigations are conducted on iron and molybdenum aerosols, which have different melting points, and thus respond differently to the laser pulse. Although aggregation enhances the absorption cross-section of the nanoparticles and allows for higher peak temperatures, this enhancement does not fully explain the observed excessive absorption. Furthermore, as the aggregates of refractory metals such as molybdenum cool, they may sinter through gradual grain boundary diffusion; this change in structure alters their absorption cross-section, manifesting as a rapid drop in the pyrometric temperature, which could explain the anomalous cooling reported for this metal.