IN-SITU SYNTHESIS OF FERRITES IN CELLULOSICS

Superparamagnetic cellulosic fibers were prepared by synthesizing ferrites by an in situ method. Five cycles of the reaction were performed on the following four substrates: sodium carboxymethylcellulose lap pulp (Na-CMC), calcium alginate fibers, continuous filament rayon tire cord, and sulfonated thermomechanical wood pulp (TMP). Vibrating sample magnetometry showed that the sulfonated TMP exhibited the highest saturation magnetization (approximately 25 J/T/kg of sample after five cycles of reaction). TEM micrographs of sections of sulfonated TMP fibers showed that the largest concentration of ferrites (approximately 100 angstrom in size) were arranged at the external fiber surfaces. The micrographs also showed ferrites of less than 20 angstrom in size, dispersed across the fiber cell wall. Electron diffraction indicated that the major components of the oxides were gamma-Fe2O3 (needles) and Fe3O4 (disks). Room-temperature Mossbauer spectra of the sulfonated TMP, after the in situ reaction, indicated the presence of small superparamagnetic ferrites for the first and second cycle samples. A ferrimagnetic component was observed for the third cycle sample and predominated in the fourth and fifth cycle samples as a result of larger ferrite grains being formed both on the surface and inside the lumen of the pulp fibers.