Synthesis, Structure and Magnetic Properties of Carbon Composites Based on Finely Dispersed Powders of Different Valence Iron Oxides

A method for the synthesizing of carbon composites based on hydrolysis lignin powders and iron oxides (FeO and Fe₂O₃) was proposed in this work. The obtained composites were studied by X-ray diffractometry, adsorption/desorption gas porometry and magnetometry. X-ray phase analysis has revealed the presence of an amorphous carbon phase and crystalline phases of FeO, Fe 3 O 4 , Fe 2 O 3 , and Fe in both types of synthesised composites. The synthesized composites demonstrated significantly higher specific magnetisation values compared to the initial iron oxide powders. For Fe₂O₃ powder, the specific magnetisation was σ s = 6 A·m²/kg, while the saturation specific magnetisation of the composite based on this oxide was σ s = 34 A·m²/kg. For FeO powder, the specific magnetisation was σ s = 28 A·m²/kg, with the composite based on it exhibiting a specific saturation magnetisation of σ s = 40 A·m²/kg. The observed results were explained by the formation of particles with sufficiently high values of specific magnetisation due to thermal reduction of iron oxides in the presence of carbon monoxide, obtained from the pyrolysis of hydrolysed lignin.