RESUMEN
Poly(vinylpyrrolidone) (PVP) coated iron nanoparticles which show well-defined core-shell structures have been successfully synthesized in a polar aprotic solvent. In this approach, PVP was employed not as capping agent, but as coating polymer directly applied to the metallic (iron) core nanoparticles. The morphologies, structures, compositions and magnetic properties of the products were investigated by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), SQUID magnetometry and FTIR spectroscopy.
Asunto(s)
Cristalización/métodos , Hierro/química , Nanoestructuras/química , Nanoestructuras/ultraestructura , Nanotecnología/métodos , Povidona/química , Sustancias Macromoleculares/química , Ensayo de Materiales , Conformación Molecular , Tamaño de la Partícula , Solventes/química , Propiedades de SuperficieRESUMEN
A systematic study of the formation of silica-coated magnetite particles via a modified reverse microemulsion approach was investigated by using transmission electron microscopy (TEM), x-ray diffraction (XRD) and a superconducting quantum interference device (SQUID). The results show that the surfactant Igepal CO-520 played an important role in the reaction system, and the thickness of the silica shell could be controlled by the concentration of the reaction agents. The developed ultra-thin silica-coated magnetic particles with a â¼2 nm thin silica shell have a high saturated magnetization around 15 emu g(-1).
RESUMEN
A new sol-gel synthetic route was developed to prepare single-phase phospho-olivines LiMPO4 (M = Fe or Mn), potential cathode materials for the next generation of Li-ion secondary batteries. Triethyl phosphite was used as phosphate organic precursor, with absolute ethanol as solvent. The sol-gel synthesis ensures homogeneity of the precursors at the nanometric scale and improved reactivity, allowing to obtain very small agglomerates and crystal grain size. Several carbon sources were used in order to improve the electrochemical performances of the samples. Galvanostatic cycling tests of the cathodic materials were made on coin cells with Li metal as anode in order to study the influence of the synthesis and the structural-morphological characteristics on the electrochemical performance of the phosphate/C composite.