Synthesis and Characterization of Nanocomposites of Fe Nanoparticles and   Activated Carbon
  We have synthesized the bulk form of the superparamagnetic nanocomposites of Fe nanoparticles and activated carbon. Here highly porous feature of activated carbon and magnetic properties of Fe nanoparticles were combined together to form the nanocomposites by mechanical mixing of different proportion of both of them. These nanocomposites are characterized by various characterization techniques like X-ray diffraction (XRD), transmission electron microscopy (TEM), magnetization measurement and M\"ossbauer spectroscopy. The observed XRD patterns have shown most intense peaks at 2{\theta} = 44.8 degree, which correspond to the (110) plane of the pure Fe in body centered cubic phase. Average particles sizes obtained by TEM imaging are in the range of 20 nm, which are below the required limit for Fe nanoparticles to be in superparamagnetic phase. The superparamagnetic nature of the nanocomposites together with trace amount of the ferromagnetic phase was confirmed by magnetization measurements and M\"ossbauer spectroscopy. Particles size calculated by the Langavin function fitting of the magnetization vs magnetic field curves are in qualitatively good agreement with the size obtained from TEM imaging. 
Satyendra Prakash Pal and P. Sen
cond-mat.mes-hall cond-mat.mtrl-sci