abstract
Composites of lithium ferrite, LiFe5O8 (LFO) particles, dispersed in the biopolymer poly (L-lactic acid) (PLLA) were prepared by solvent casting in concentrations from 0 to 19.5 wt%, which were characterized by thermal analysis (TGA/DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and impedance spectroscopy (IS). As neat PLLA, all obtained composites are semi-crystalline, but the crystallinity decreasing with percentage LFO increase. Moreover, a good dispersion of LFO particles was found, with no interactions with the polymeric matrix. For the lower LFO content (3.5 wt%), dynamical relaxation processes were probed by IS, allowing to disclose subtle differences relative to the neat matrix. Above that concentration, the conductivity dominates and follows the percolation law above a quite low volume concentration of conductive particles (5.45%v/v). Therefore, depending on the LFO content different applications can be envisaged: energy storage for low concentrations and electromagnetic radiation shielding for concentrations above the percolation threshold.
keywords
CONDUCTING POLYMER COMPOSITES; DIELECTRIC-RELAXATION; LITHIUM FERRITE; STRUCTURAL-PROPERTIES; MAGNETIC-PROPERTIES; MOLECULAR MOTIONS; CRYSTALLIZATION; STEREOCOMPLEX; PERCOLATION; BEHAVIOR
subject category
Polymer Science
authors
Teixeira, SS; Gama, N; Cordeiro, T; Barros-Timmons, A; Dionisio, M; Graca, MPF; Costa, LC
our authors
Ana Margarida Madeira Viegas de Barros Timmons
Associate Professor
Nuno Vasco da Costa Gama Batista de Melo
Junior Researcheracknowledgements
This work was developed within the scope of the projects i3N, UIDB/50025/2020 & UIDP/50025/2020, and CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology (FCT)/Ministry of Science, Technology and Higher Education (MCTES).