Laurent Aubouy

Improved power factor of polyaniline nanocomposites with exfoliated graphene nanoplatelets (GNPs)

In this work, exfoliated graphene nanoplatelets (GNPs)/polyaniline (PANI) nanocomposites have been prepared by sequential processing comprising: (i) a first aniline oxidative polymerization step under acidic conditions and (ii) mechanical blending with GNPs at different percentages. Thermoelectric pellets of the hybrid materials have been obtained at suitable circular geometry by means of cold pressing. Thermoelectric parameters have been determined at room temperature (electrical conductivity, Seebeck coefficient and thermal conductivity). Thermoelectric measurements show a drastic enhancement in both electrical conductivity and Seebeck coefficient with the addition of GNPs. A respectable maximum power factor value of 14 μW m−1 K−2 is reached for hybrid materials charged at 50 wt% GNP content, evidencing a 1000-fold enhancement with respect to the raw PANI polymer. The measured thermal conductivity is in the range of 0.5 W m−1 K−1 for pure PANI to 3.3 W m−1 K−1 for 50 wt% GNP content, which matches the parallel thermal resistor model for this nanocomposite.

Electrospun carbon nanofiber membranes for filtration of nanoparticles from water

Nowadays, hundreds of consumer products contain metal and metal oxide nanoparticles (NP); this increases the probability of such particles to be released to natural waters generating a potential risk to human health and the environment. This paper presents the development of efficient carboneous nanofibrous membranes for NP filtration from aqueous solutions. Free-standing carbon nanofiber (CNF) mats with different fiber size distribution ranging from 126 to 554 nm in diameter were produced by electrospinning of polyacrylonitrile (PAN) precursor solution followed by thermal treatment. Moreover, tetraethoxyorthosilicate was added to provide flexibility and increase the specific surface area of the CNF. The resulting membranes are bendable and mechanically strong enough to withstand filtration under pressure or vacuum. The experimental results of filtration revealed that the fabricated membranes could efficiently reject nanoparticles of different types (Au, Ag, and TiO2) and size (from 10 to 100 nm in diameter) from aqueous solutions. It is worth mentioning that the removal of Ag NP with diameters as small as 10 nm was close to 100% with an extremely high flux of 47620 Lm-2 h-1 bar-1.

Influence of Nanomaterial Compatibilization Strategies on Polyamide Nanocomposites Properties and Nanomaterial Release during the Use Phase

The incorporation of small amounts of nanofillers in polymeric matrices has enabled new applications in several industrial sectors. The nanofiller dispersion can be improved by modifying the nanomaterial (NM) surface or predispersing the NMs to enhance compatibility. This study evaluates the effect of these compatibilization strategies on migration/release of the nanofiller and transformation of polyamide-6 (PA6), a thermoplastic polymer widely used in industry during simulated outdoors use. Two nanocomposites (NCs) containing SiO2 nanoparticles (NPs) with different surface properties and two multiwalled carbon nanotube (MWCNT) NCs obtained by different addition methods were produced and characterized, before and after accelerated wet aging conditions. Octyl-modified SiO2 NPs, though initially more aggregated than uncoated SiO2 NPs, reduced PA6 hydrolysis and, consequently, NM release. Although no clear differences in dispersion were observed between the two types of MWCNT NCs (masterbatch vs direct addition) after manufacture, the use of the MWCNT masterbatch reduced PA6 degradation during aging, preventing MWCNT accumulation on the surface and further release or potential exposure by direct contact. The amounts of NM released were lower for MWCNTs (36 and 108 mg/m(2)) than for SiO2 NPs (167 and 730 mg/m(2)), being lower in those samples where the NC was designed to improve the nanofiller-matrix interaction. Hence, this study shows that optimal compatibilization between NM and matrix can improve NC performance, reducing polymer degradation and exposure and/or release of the nanofiller.

Electrospun Pd-doped mesoporous carbon nano fibres as catalysts for rechargeable Li–O2 batteries

Mesoporous carbon nanofibres doped with palladium nanoparticles (Pd CNFs) are synthesized by electrospinning with subsequent thermal treatment processes and used as electro-catalysts at the oxygen cathode of Li–O2 batteries. FESEM images show that the spherical Pd nanoparticles (NPs) are homogeneously dispersed on the surface of CNFs and X-ray diffraction (XRD) measurements display a fcc structure of Pd. The surface area of the nanocomposite CNFs is greatly increased with the incorporation of the metal NPs up to 600 m2 g−1 and the presence of the metal promotes graphitization of the carbon. Addition of the N-[(aminoethyl)aminopropyl]trimethoxysilane additive in the precursor solution for electrospinning allows the reduction of the Pd NPs particles size, preserving the highly mesoporous N-doped large surface area and graphitic-nitrogen groups of the carbon nanofibres. Incorporating with a Pd/CNFs catalysed cathode, the Li–O2 battery shows a very low voltage gap of 0.48 V vs. Li+/Li between the terminal discharge and charge voltages, as the recharge occurs at a potential underneath 4.0 V vs. Li+/Li for about 90 cycles at the curtailed capacity of 200 mA h g−1. The low recharge voltage can relieve parasitic reactions due to the decomposition of electrolyte and favour a longer cycle life.