Magnetic metal-ceramic nanocomposites obtained from cation-exchanged zeolite by heat treatment in reducing atmosphere

Magnetic nanocomposites are highly demanded on account of their multifarious applications in many technological fields, as they can be easily separated from the media where they are used. Here, we report a smart (and scalable) process to produce magnetic metal-ceramic nanocomposites formed by Ni-0 nanoparticles (5-25 nm) dispersed in an amorphous silica-alumina matrix. Nanocomposites were obtained from Ni2+ exchanged A and X zeolites by means of a two-steps process encompassing: 1) ion exchange of commercial zeolites; 2) thermal treatment (735-750 degrees C) in reducing atmosphere. Obtained nanocomposites were characterized by means of atomic absorption spectrometry, thermal techniques (themogravimetry, differential thermal analysis and temperature programmed reduction), X-rays powder diffraction (with synchrotron source) followed by Rietveld analysis, High Resolution Transmission Electron Microscopy, N-2 adsorption/desorption at - 196 degrees C and magnetic measurements at both room temperature and low temperature. Physico-chemical characterization of the nanocomposites allowed evidencing some of their peculiar properties such as: the different extent of Ni2+ reduction to Ni-0 in nanocomposites obtained from the two zeolites, the dimensions of the resulting metal nanoparticles, the textural and compositional properties of the matrix embedding the Ni-0 nanoparticles. The results of this work show that the properties of the nanocomposites, final product of the process here proposed, can be tailored by a wise choice of the parent zeolite, which markedly affects their morphology, and by properly tuning the thermal treatment conditions, i.e. temperature and time.