C. Barrera-Solano

Size and surface effects in the magnetic properties of maghemite and magnetite coated nanoparticles

An increasing number of promising applications for future technology is arising from size constraints in nanoparticles (NPs) and from the chemical manipulation of their surfaces. In this work, we analyse the finite-size and surface effects on polyacrylic acid-coated Fe3O4 NPs and oleic acid-coated γ-Fe2O3 NPs by studying their magnetization curves at different temperatures. The measured thermal dependence of the saturation magnetization is no longer explained by the typical T3/2 Bloch law, yielding higher values than those expected for its exponent. When incorporated in polymeric matrixes to form magnetic transparent nanocomposites, the oleic acid-coated γ-Fe2O3 NPs also deviate from Bloch’s law, but following the opposite trend observed in free coated NPs.

Obtaining and sintering yttria stabilized zirconia (YSZ) powders from alkoxides

Amorphous zirconia ceramics powders containing 3 and 6 mol% yttria were prepared by controlled hydrolysis of alkoxides. Characterization of these powders was carried away by Thermal Analysis, X-ray Diffraction, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX™). The calcination temperature was optimized for compaction at a temperature ranging from 500–800°C. 3% molar YSZ powders from alkoxide, that attained 98% of the theoretical bulk density, showed the best behaviour.