Growth and characterization of carbon nanotubes on FeSi substrates via chemical vapor deposition: influence of synthesis parameters and magnetic properties

FeSi powders were investigated as a dual-function substrate–catalyst for carbon nanotube (CNT) synthesis via chemical vapor deposition (CVD), offering an alternative to conventional transition metal catalysts deposited on inert oxide supports. Unlike Fe, Co, or Ni nanoparticles on SiO₂ or Al₂O₃, which require separate deposition steps and often suffer from aggregation, FeSi provides an in-situ source of catalytically active Fe atoms within a thermally stable silicide matrix. Multi-walled CNTs were synthesized at 800 ºC using ethylene (C₂H₄) at flow rates of 400–1000 sccm. SEM and TEM analyses revealed CNT diameters ranging from 33.55 to 48.55 nm, with the number of walls estimated at 34 ± 6. Raman spectroscopy showed IG/ID ratios of 1.11–1.29, indicating good graphitic quality with low defect density. Magnetic measurements at 10 K and 300 K confirmed superparamagnetic behavior with zero coercivity, attributed to nanoscale Fe-containing particles encapsulated within the CNT structure. The saturation magnetization decreased from ~ 20 emu/g (pristine FeSi) to ~ 9–15 emu/g (CNT-FeSi composites) due to carbon mass dilution. This work demonstrates that FeSi powders can serve as an effective substrate–catalyst system for CNT growth, eliminating the need for external catalyst deposition while providing in-situ generated superparamagnetic properties.