Lucangelo Dimesso

LiFePO4 – 3D carbon nanofiber composites as cathode materials for Li-ions batteries

The characterization of carbon nanofiber 3D nonwovens, prepared by electrospinning process, coated with olivine structured lithium iron phosphate is reported. The LiFePO4 as cathode material for lithium ion batteries was prepared by a Pechini-assisted reversed polyol process. The coating has been successfully performed on carbon nanofiber 3D nonwovens by soaking in aqueous solution containing lithium, iron salts and phosphates at 70 °C for 2−4 h. After drying-out, the composites were annealed at 600 °C for 5 h under nitrogen. The surface investigation of the prepared composites showed a uniform coating of the carbon nonwoven nanofibers as well as the formation of cauliflower-like crystalline structures which are uniformly distributed all over the surface area of the carbon nanofibers. The electrochemical measurements on the composites showed good performances delivering a discharge specific capacity of 156 mAhg− 1 at a discharging rate of C/25 and 152 mAhg− 1 at a discharging rate of C/10 at room temperature.

STRUCTURE AND MAGNETORESISTANCE EFFECT IN GRANULAR AG-NI ALLOYS PREPARED BY GAS FLOW CONDENSATION TECHNIQUE

Giant magnetoresistance (GMR) effect in heterogeneous granular Ag–Ni alloys, prepared by utilizing coevaporation of the metals in continuous He flow, is reported. The average grain size, determined from x-ray diffraction (XRD) data, increases from 11 to 28 nm with increasing He pressure. The transmission electron microscope analysis revealed the presence of Ag and Ni isolated grains which give rise to coalescence. The nitrogen adsorption measurements show a decrease of the surface area with increasing pressure confirming the XRD data. Electrical measurements revealed a GMR effect as large as 7%, at room temperature and a magnetic field H=1 T, on the specimen prepared with a final pressure of 800 Pa.