Controllable preparation of magnetic carbon nanocomposites by pyrolysis of organometallic precursors, similar molecular structure but very different morphology, composition and properties

Four cobalt-containing organometallic compounds were synthesized for solid-state pyrolysis (SSP) to study the structure–property relationship between the precursors and the as-synthesized magnetic carbon nanocomposites (MCNs). In this research, the only saturated carbon atom in MC was replaced by a N, O or S atom, to produce precursors MN, MO and MS, respectively. It was found that the crystal phase of cobalt generated upon pyrolysis is dependent on the kind of heteroatom introduced into the precursor: fcc-Co for MC/MN, while the fcc/hcp-Co hybrid for MO/MS. Metal cobalt with different crystal phases has its special catalytic and magnetic properties. Thus, MCNs with very different morphologies, compositions and properties could be prepared by just altering one heteroatom in the precursors upon SSP. Uniform nanotubes were generated from pyrolysis of MC/MN, while nanospheres were generated from MO/MS. The obtained MCNs all show good magnetic properties with Ms ranging from 47.6 to 54.5 emu g−1. Due to the magnetic difference between fcc-Co and hcp-Co, the Ms values of MCNs obtained from MO/MS are slightly lower than those of MC/MN, but the Mr and Hc values of the former are 2 to 5 times higher than those of the latter.