elemental concentration in atmospheric particulate matter estimation of nanoparticle contribution

Atmospheric nanoparticles (NPs) are often contained in aggregates or included in larger particles. We show that some of these structures can be crushed in water media by the application of ultrasounds, leading to a suspension of insoluble NPs. The contribution of these NPs to the total elemental concentration is evaluated as the difference between the inductively coupled plasma (ICP-MS) analysis before and after the elution of the suspension from an ion exchange cartridge. Total elemental content in PM can be therefore fractionated into three contributions - soluble species, solid NPs released from larger structures, insoluble particles - that may likely have different health and environmental effects. The method was applied to both Certified Material NIST 1649a and size-segregated atmospheric PM samples collected by a 13-stage impactor. The results indicate that alkaline and alkaline earth metals are found in the suspension only as watersoluble species, also when they are contained in the fine fraction of PM. Instead, a significant fraction of most elements typically emitted from combustion sources (Pb, Sb, Sn, Cd, V and As) is present in fine PM as insoluble nanoparticles that are easily dispersed in water under ultrasound application

Effect of annealing on structure and superconducting properties in Fe(Se,Te)

Abstract In this paper, the effect of post synthesis annealing treatments on a Fe(Se,Te) polycrystalline material is evaluated and discussed. The samples have been obtained via melting route. The material has been subjected to a high-temperature annealing treatment, carried out for 45 h at 680 °C. The role of the cooling step was investigated comparing samples obtained after a controlled cooling or after quenching in liquid nitrogen. From a morpho-structural point of view, the annealing treatment improves homogeneity, with respect to pristine samples, and influences secondary phase precipitate morphology. Regarding superconducting properties, a key role of the cooling procedure is assessed: controlled cooling leads in fact to a significant improvement of high field behaviour with respect to the melted material, while quenched samples are characterized by a worsening of the superconducting properties. Despite the overall worsening, however, the quenched samples show evidence of the presence of superconducting phases characterized by a remarkably high critical temperature (Tc > 18 K), observed for these materials only in films or under pressure

Effect of oxygen contamination on densification of Fe(Se,Te)

Abstract The optimization of sintering behaviour of iron chalcogenides superconducting materials is mandatory to enhance their critical current density, in order to pursuit their application in the production of superconducting wires. In this context it has been investigated here the effect of oxygen contamination on the material densification, considering the issues related to industrial oxygen-free isolated production lines. Our results show that the densification process is negatively affected by oxygen contamination. However, despite the difference in density, all sintered samples are characterized by similar structural and morphological features, and show comparable electrical and magnetic properties, with low critical current densities (Jc<103 A/cm2). These results suggest that densification is not the key limiting factor in these conditions, and that grain boundary or misorientation factors may play a greater role in limiting the performance of sintered iron chalcogenides superconductors