Structure and Magnetic Properties of Fe<sub>3</sub>O<sub>4</sub>/C Composites Synthesized from Wheat Straw

The porous structure and magnetic properties of nanostructured Fe 3 O 4 /C composites based on wheat straw were investigated in this work. The synthesis was carried out by a one- and two-step method using FeCl 3 and ZnCl 2 as activating agents. X-ray diffraction methods have shown the presence of an additional phase of magnetite Fe 3 O 4 in both synthesized composites, along with the amorphous carbon phase. Magnetic measurements have shown that the composite synthesized in one step has better magnetic properties, in particular, a higher specific saturation magnetisation. However, the samples of the composite synthesized in two steps are characterised by a higher content of micropores and mesopores, which causes an increase in the specific surface area to 884 m 2 /g compared to 405 m 2 /g for the samples synthesized in one step. Based on the dependence of the coercive force on the particle diameter in Fe 3 O 4 dispersions, it was found that the average size of the magnetite particles is ~25 nm for both synthesized magnetoresponsive composites.