High voltage cathodes for Na-ion batteries: Na3V2O2x(PO4)2F3-2x system

254 p : il, graf. col.

Microwave Resonant and Zero-Field Absorption Study of Doped Magnetite Prepared by a Co-Precipitation Method

Fe3O4 and ZnxFe3-xO4 pure and doped magnetite magnetic nanoparticles (NPs) were prepared in aqueous solution (Series A) or in a water-ethyl alcohol mixture (Series B) by the co-precipitation method. Only one ferromagnetic resonance line was observed in all cases under consideration indicating that the materials are magnetically uniform. The shortfall in the resonance fields from 3.27 kOe (for the frequency of 9.5 GHz) expected for spheres can be understood taking into account the dipolar forces, magnetoelasticity, or magnetocrystalline anisotropy. All samples show non-zero low field absorption. For Series A samples the grain size decreases with an increase of the Zn content. In this case zero field absorption does not correlate with the changes of the grain size. For Series B samples the grain size and zero field absorption behavior correlate with each other. The highest zero-field absorption corresponded to 0.2 zinc concentration in both A and B series. High zero-field absorption of Fe3O4 ferrite magnetic NPs can be interesting for biomedical applications.

Geochemical characterization of the fire-fountain fed deposits of Las Herrerias volcano (Campo de Calatrava Volcanic Field, Ciudad Real)

The Las Herrerias volcano (Bolanos de Calatrava, Campo de Calatrava Volcanic Field) is characterized by the great amount and variety of fire-fountain fed deposits. All these deposits are compositionally similar, being constituted by magnesium-rich (MgO = 11.58-4.19%), aluminium-poor (Al2O3 = 9.64-10.99%) highly sodic (Na2O = 2.24-3.81%) melanephelinites, with high contents in rare earth-elements (10x-200x chondrite), particularly in light-rare earth elements with respect to the heavy ones [(La/Lu)(N) = 32-35]. Contrary to the equivalent melanephelinites of this volcanic field, the relatively low contents in Ni (233-286 ppm), Cr (393-520 ppm) and magnesium number (Mg* = 45-54) indicate that these rocks do not correspond with primary melts. On the other hand, the variable distribution of clinopyroxene in the magma during eruption would be responsible for the slight compositional differences observed in the studied samples. Finally, we argue that these fire fountains were developed in a continental intraplate setting.