Diagnostics of carbon-encapsulated iron nanoparticles by laser heating

In this study the laser-induced incandescence (LII) diagnostics has been applied for sizing of carbon-encapsulated iron nanoparticles (CEINs). The carbon covered iron nanoparticles were synthesized by shock waves pyrolysis of the mixtures of Fe(CO)₅ with C₂H₂ or C₆H₆ diluted with argon. Iron nanoparticles were formed in the shock tube behind incident shock waves at the temperatures of 700-1000 K. The pyrolysis of hydrocarbons behind reflected shock waves at the temperatures of 1400-2000 K resulted in formation of carbon shell over iron nanoparticles. At the end of the CEINs formation process, particles were heated by one pulse of Nd:YAG laser operated at wavelength 1064 nm with fluences varied in the range 70- 800 mJ/cm² to collect LII signals. The LII model, which had been used previously for iron and carbon nanoparticles separately, was updated for carbon-encapsulated iron nanoparticles. Additionally, the nanoparticle samples were investigated by a transmission electron microscope (TEM). The iron core size and carbon shell thickness were measured by statistical treatment of microphotographs. The comparison of TEM and LII particle sizing results is discussed.