MAGNETIC TITANIUM-PILLARED CLAYS (Ti-M-PILC): MAGNETIC STUDIES AND MOSSBAUER SPECTROSCOPY

Pillared clays (PILCs) with magnetic properties are materials with potential for wide application in industry and the environment, but only a few studies of these types of materials have been carried out. The purpose of this study was to advance knowledge of the preparation and magnetic properties of pillared clays by examining in detail a series of magnetic Ti-pillared clays (Ti-M-PILCs). Samples were synthesized at ambient temperature by sodium borohydride reduction of ferrous ions added by ion-exchange to Ti-pillared montmorillonite (Ti-PILCs). The properties of the Ti-M-PILCs were investigated using a superconducting quantum interference device (SQUID) and Mossbauer spectroscopy. Hysteresis, zero-fie Id-cooled (ZFC), and field-cooled (FC) regimes were measured on different precursor materials prepared by calcination of Ti-PILCs at temperatures between 200 and 600 degrees C. Hysteresis loops, recorded between -7 and 7 T in the temperature range 200-300 K, were observed in most samples depending on the preparation of clays. The ZFC/FC measurements were made after heating from 2 to 300 K under an applied magnetic field of 39.8 kA m(-1). The influence of the calcination temperature of the starting Ti-PILCs on the structural and magnetic properties of the Ti-M-PILCs was examined. The presence of two different Fe-alloy distributions was found; a dispersed one for the less-calcined Ti-PILCs and clusters for the more-calcined ones.