A novel approach for the synthesis of iron carbide nanostructures using spark plasma sintering

• Published in: Journal of magnetism and magnetic materials 2020-09, Vol.510, p.166935, Article 166935
• Main Authors: Kalyan Kamal, S.S., Hemanth Kumar, B., Siva Santosh, S., Vimala, J., Majumdar, Bhaskar, Ghosal, P., Durai, L.
• Format: Article
• Language: English
• Subjects: Carbon; Cementite; Decomposition; Ferric nitrate; Iron carbides; Iron oxides; Magnetic properties; Nanoparticles; Plasma sintering; Process parameters; Reaction mechanisms; Reaction time; Spark plasma sintering; Synthesis; Thermal decomposition; Time constant
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2020.166935

•A greener route than chemical routes for synthesis of Fe3C nanoparticles is reported.•In situ decomposition, reduction and carbide formation from ferric nitrate is reported.•Minimum temperature of 900 °C is required for formation of Fe3C NPs in SPS.•Fe3C NPs with Ms of 138.16 emu/g and coercivity of 475.20 Oe were obtained.•Temperature and reaction time play a crucial role on the formation of Fe3C NPs. In this paper we report a facile and economical route for the synthesis of nano structured iron carbide (Fe3C). An in situ thermal decomposition of ferric nitrate salt coated on free carbon in spark plasma sintering (SPS) equipment was employed. The effect of process parameters on the formation of Fe3C and the associated magnetic properties are discussed in detail. A set of experiments were carried out at temperatures ranging between 600 and 900 °C, by keeping the pressure and reaction time constant at 60 MPa and 2 min respectively. The reaction mechanism of formation of Fe3C nanoparticles (NPs) was investigated using X-ray diffraction (XRD) studies and it reveals that the nitrate salt decomposes to Fe3O4, which subsequently convert to Fe at 800 °C through carbothermal reduction. These Fe atoms subsequently react with graphitic carbon and convert to Fe3C at 900 °C. The average size of the Fe3C nanoparticles obtained through this route is 25 nm. The effect of C:Fe ratio reveals that up to 1:2 ratio the reaction parameters of 900 °C, 60 MPa and 2 min reaction time is sufficient for the formation of Fe3C NPs. However, for 1:3 ratio the reaction time in SPS has to be increased to 15 min for the formation of Fe3C NPs. This shows that a longer time is required for the complete reaction of C and Fe atoms as the Fe content in the sample increases.