David Amantia

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.

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.

O2 selective membranes based on a dextrin-nanosponge (NS) in a PVDF-HFP polymer matrix for Li–air cells

A novel oxygen selective highly hydrophobic membrane is prepared by non-solvent induced phase separation in which a dextrin-based nanosponge is incorporated into a poly(vinylidene fluoride co-hexafluoropropylene) (PVDF-HFP) matrix. The membrane presents high capability to entrap moisture from air as well as good hydrophobic behaviour. The membrane was assembled in a pouch type Li-air cell, which was cycled in a galvanostatic mode at curtailed capacity, in air with 17% relative humidity (RH). Owing to the protection of the membrane, the Li-air cell was able to discharge and re-charge for approximately 145 cycles, which correspond to about 1450 h of cell operation.