Continuous synthesis of controlled size carbon-encapsulated iron nanoparticles

Carbon-encapsulated iron nanoparticles were continuously and selectively synthesised in a thermal plasma jet from ethanol (carbon source) and Fe powders with different grain sizes. The grain size of the Fe powder influenced the size distribution of the as-produced carbon encapsulates. The products obtained from large Fe particles (50–78 μm) were comprised of small encapsulates with diameters between 5 and 10 nm. Larger carbon encapsulates with a broad diameter distribution (10–100 nm) were synthesised from the finest Fe particles (18 μm). It was also found that Fe particle size was the most crucial parameter for determining the encapsulation yield. The encapsulation yield was also influenced by the carbon to iron ratio and the thermal conductivity of the plasma gas.

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► A continuous and selective synthesis method of magnetic carbon nanoparticles with controlled size is reported.
► Grain size of the starting Fe powder dictates the diameter of carbon-encapsulated iron nanoparticles.
► The encapsulation yield is controlled by carbon-to-metal ratio.
► The developed method uses green and environmentally friendly feedstocks.