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

Abstract

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 M_C was replaced by a N, O or S atom, to produce precursors M_N, M_O and M_S, 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 M_C/M_N, while the fcc/hcp-Co hybrid for M_O/M_S. 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 M_C/M_N, while nanospheres were generated from M_O/M_S. The obtained MCNs all show good magnetic properties with M_s ranging from 47.6 to 54.5 emu g⁻¹. Due to the magnetic difference between fcc-Co and hcp-Co, the M_s values of MCNs obtained from M_O/M_S are slightly lower than those of M_C/M_N, but the M_r and H_c values of the former are 2 to 5 times higher than those of the latter.