Search

Studded tyres made of tungsten carbide cobalt (WC-Co) are in the Northern countries commonly used during the winter time. Tungsten (W)-containing nano- and micron-sized particles have been detected close to busy roads in several European countries. Other typical traffic wear particles consist of copper (Cu). The aims of this study were to investigate particle stability and transformation/dissolution properties of nanoparticles (NPs) of WC-Co compared with NPs of tungsten carbide (WC), cobalt (Co), and Cu. Their physicochemical characteristics (primarily surface oxide and charge) are compared with their extent of sedimentation and metal release in synthetic surface water (SW) with and without two different model organic molecules, 2,3- and 3,4-dihydroxybenzoic acid (DHBA) mimicking certain sorption sites of humic substances, for time periods up to 22 days. The WC-Co NPs possessed a higher electrochemical and chemical reactivity in SW with and without DHBA molecules as compared with NPs of WC, Co, and Cu. Co was completely released from the WC-Co NPs within a few hours of exposure, although it remained adsorbed/bonded to the particle surface and enabled the adsorption of negatively charged DHBA molecules, in contrast with the WC NPs (no adsorption of DHBA). The DHBA molecules were found to rapidly adsorb on the Co and Cu NPs. The sedimentation of the WC and WC-Co NPs was not influenced by the presence of the 2,3- or 3,4-DHBA molecules. A slight influence (slower sedimentation) was observed for the Co NPs, and a strong influence (slower sedimentation) was observed for the Cu NPs in SW with 2,3-DHBA compared with SW alone. The extent of metal release increased in the order: WC < Cu < Co < WC-Co NPs. All NPs released more than 1 wt-% of their metal total mass. The release from the Cu NPs was most influenced by the presence of DHBA molecules. [ABSTRACT FROM AUTHOR]

NM's potential to induce adverse effects in humans or the environment is being addressed in numerous research projects, and methods and tools for NM hazard identification and risk assessment are advancing. This article describes how integrated approaches for the testing and assessment of NMs can ensure the safety of nanomaterials, while adhering to the 3Rs principle. [ABSTRACT FROM AUTHOR]

Abstract: We present here the first experimental evidence of a significant enhancement in the thermoelectric properties of networks containing bismuth nanotubes and nanowires fabricated via aqueous chemical routes. The as-prepared samples revealed two dominant morphologies: double wall nanotubes with 4–6nm diameter and nanowires of 15–30nm diameters. Transport measurements in the range 15–300K were performed on cold pressed pellets which contained these bismuth nanostructures. We find that the cold pressed networks of nanostructured bismuth exhibit a non-metallic behavior, the corresponding room temperature resistivities vary from ∼0.54 to 5.8mΩ-cm, depending on the detailed nanomorphology. The measured thermal conductivity for the networks of bismuth nanotubes and nanowires is almost 5 times lower compared to bismuth powder at room temperature. The observed improvement in the thermoelectric performance has been attributed to the reduced lattice thermal conductivity of nanostructured bismuth networks via interface scattering. [Copyright &y& Elsevier]