Temperature influence on the properties of carbon-encapsulated iron nanoparticles forming in pyrolysis of gaseous precursors

In the present study the carbon-encapsulated iron nanoparticles were synthesized by shock waves pyrolysis of the Fe(CO)₅ vapor in the mixture with C₂H₂ or C₆H₆ diluted by argon. The iron nanoparticles were formed behind incident shock waves at the temperatures of 600–1200 K. The pyrolysis of hydrocarbons behind the reflected shock waves at the temperatures of 1100–2500 K resulted in carbon shell formation over iron nanoparticles. The mean particle sizes measured by transmission electron microscopy were found to be 3.5–5 nm and 7–10 nm for the samples formed in the mixtures with presence of acetylene and benzene correspondingly. The extinction measurements of condensed phase growth and laser-induced incandescence measurements of particle sizes were used as in-situ diagnostics. The dependences of particle volume fraction and final particle size on temperature of pyrolysis and kind of hydrocarbon are presented and discussed.