Broadband dielectric spectroscopy of nanocomposites based on PVDF and expanded graphite

International audienceNanocomposites based on poly (vinylidene fluoride) (PVDF) and expanded graphite (EG) were prepared by non-solvent precipitation from solution with different EG concentrations. Films were obtained by compression molding and their structural and dielectric properties studied. From Wide Angle X-ray Scattering (WAXS) experiments, it can be assessed that for all EG concentrations the -crystalline phase of PVDF is the predominant crystalline form. However, for composites with high nanoadditive content, higher than 3 wt.%, the -crystalline phase is also detected. Dielectric spectroscopy results showed that the nanocomposites present both high dielectric constant and electrical conductivity at low percolation threshold

La materia condensada blanda: tu día a día. ¿Acaso no lo sabías?

37 págs. ; XI Semana de la Ciencia Madrid, 2011La materia condensada blanda define los estados de la materia cuyas propiedades no pueden ser descritas como líquidos simples o sólidos.Peer reviewe

Broadband dielectric spectroscopy of nanocomposites based on PVDF and expended graphite

2nd International Conference on Structural Nano Composites (NANOSTRUC 2014); 6 pags.; 4 figs.; Open Access funded by Creative Commons Attribution 3.0 licence.Nanocomposites based on poly (vinylidene fluoride) (PVDF) and expanded graphite (EG) were prepared by non-solvent precipitation from solution with different EG concentrations. Films were obtained by compression molding and their structural and dielectric properties studied. From Wide Angle X-ray Scattering (WAXS) experiments, it can be assessed that for all EG concentrations the -crystalline phase of PVDF is the predominant crystalline form. However, for composites with high nanoadditive content, higher than 3 wt.%, the -crystalline phase is also detected. Dielectric spectroscopy results showed that the nanocomposites present both high dielectric constant and electrical conductivity at low percolation threshold. Published under licence by IOP Publishing LtdThe authors thank the financial support from the Spanish Ministry of Science and Innovation (MICINN), Grant MAT2012-33517 and from the Polish National Science Centre and the Slovak Academy of Sciences in the frame of ERA-NET project APGRAPHEL.Peer Reviewe

Procedimiento de obtención de materiales compuestos como conductores eléctricos

La presente invención se refiere a un procedimiento de obtención de un material compuesto mediante agitación por vibración de una mezcla que comprende polímero y nanomaterial de carbono, al material obtenible por dicho procedimiento y a sus usos como material conductor eléctrico.Peer reviewedConsejo Superior de Investigaciones Científicas (España)A1 Solicitud de patente con informe sobre el estado de la técnic

On the electrical conductivity of PVDF composites with different carbon-based nanoadditives

Composites based on poly(vinylidene fluoride) (PVDF) and different carbon additives, such as carbon nanofibers (CNF), graphite (G), expanded graphite (EG), and single-walled carbon nanotubes (SWCNT) have been prepared by nonsolvent precipitation, from solution, and subsequent melt processing. From a structural point of view, the α-crystal phase is the predominant crystal form in all the nanocomposites. However, those containing CNF, G, and EG at high nanoadditive content present also β-crystal phase. Even though the intrinsic thermal properties of PVDF are hardly affected, the nanoadditives act as nucleating agents for the crystallization. In regard to the electrical properties, all nanocomposites exhibit a percolating behavior. Moreover, the fact that the nanocomposites present both high dc conductivity and high dielectric constant, in a certain nanoadditive concentration range below the percolation threshold, suggests that a tunneling conduction mechanism for charge transport is present. With regard to the ac electrical properties, depending on the morphology of the different additives, the charge transport above percolation threshold can be explained taking into account the anomalous diffusion effect for high nanoadditive content or an intercluster polarization mechanism when the nanoadditive concentration decreases. © 2014 Springer-Verlag.Financial support by MAT2012-33517 from MINECO and by MODELICO (S2009/ESP‐1691) Network from Comunidad de Madrid is gratefully acknowledged. A.S. thanks CSIC and the Fondo Social Europeo (FSE) for cofinancing the JAE-Doc contract.Peer Reviewe

Broadband Dielectric Spectroscopy of Nanocomposites Based on PVDF and Expanded Graphite

International Conference on Structural Nano Composites, Consejo Superior de Investigaciones Científicas (CSIC), Calle de Serrano 123, Madrid, Spain, 20-21 May 2014 ; http://www.ictp.csic.es/ICTP2/es/nanostruc2014Peer Reviewe

Broad-band electrical conductivity of high density polyethylene nanocomposites with carbon nanoadditives: Multiwall carbon nanotubes and carbon nanofibers

A study is presented of the electrical properties of a series of nanocomposites based on high density polyethylene (HDPE) as a matrix and either carbon nanofiber (CNF) or multiwall carbon nanotube (MWCNT) as a nanoadditive. The measurements of the electrical conductivity over a broad-band of frequencies (102 > F/Hz > 109) allow improvement of the description of the electrical properties of polymer nanocomposites based on either carbon nanofibers or carbon nanotubes. Despite the lack of a continuous conducting network between particles at low concentrations, the nanocomposites exhibit a significant dc electrical conductivity due to tunnel conduction. At low nanoadditive concentrations, the frequency dependence of the electrical conductivity is mainly caused by the influence of large polymeric gaps between conducting clusters. As nanoadditive concentration increases, the size of the finitesize cluster tends to increase and the frequency dependence of the conductivity reflects the features of anomalous diffusion in fractal structures, as expected according to percolation theory. A master curve for the electrical conductivity as a function of frequency can be constructed although, for the investigated nanocomposites, this behavior should be contemplated as a working, rather than as a universal, law. © 2008 American Chemical Society.Support from the MCYT (grant MAT2005-01768) UE, Spain,Peer Reviewe