Chitosan-coated iron oxide nanoparticles obtained by laser pyrolysis

The structural and magnetic properties of iron oxide nanoparticles (NPs) synthesized by laser pyrolysis, as well as their chitosan-stabilized aqueous suspensions were studied in regards to the ratio between O2 and Ar. During the synthesis, the flow of Fe(CO)5 precursor vapors and C2H4 sensitizer molecules was kept constant, while the ratio between O2 and Ar in the reactive mixture was increased (1:4, 1:2, 1:1, and 2:1). The formation of small particles (under 4 nm in size) was observed at lower O2 concentrations, whereas their mean crystallite size increased to ∼14 nm for those formed from the richest O2 content, which also induced the formation of particles with the highest magnetization saturation (101.4 emu/g). Maghemite and/or magnetite phases were identified as the main components in all samples, while a small amount of α iron/iron carbides presence was detected with the exception of sample obtained at 1:1 O2 to Ar ratio. The formation of these minor phases reveals the interplay between oxidative and reductive processes which depend on O2 content and C2H4 reactivity at different temperatures. After chitosan loading, all aqueous suspensions presented excellent stability (zeta potential values over 76 mV). Moreover, the samples stabilized using low polymer concentration (0.05 g/l) displayed relatively low hydrodynamic sizes (110–125 nm)

Multifunctional composites and nanocomposites with applications in the aerospace industry

Polymer nanocomposites (PNCs) ,namely, nanoparticles dispersed in a polymer matrix, have garnered academic and industrial interest since 1990.This is due to the very attractive properties of nanostructurated fillers, as carbon nanotubes, laser synthesized nanocarbon and layered silicates; PNCs do not expand the performance space of traditional filled polymers, but introduce new properties, low volume additions (1÷5 %) of nanoparticles such as carbon nanotubes and montmorillonite providing properties and enhancements comparable to those achieved by conventional loadings (15-40%) of traditional fillers [1].Most important, tough, are value –added such as reduced permeability, flame retardant, increased resistance to oxidation and ablation. Also, the effect of carbon nanotubes on grain boundary sliding in zirconia policrystals as re- reentry shield, or thermal barrier [2]represents a matter of interest.Multifunctional composites are materials with carbon fibre or glass fibre as reinforcing networking in nanoaditivated polymer matrix.In aerospace technique these may be antistatic, antilightning, anti radar protectors, as paints, laminates and as sandwich structure. Though the most important application of nanocomposites is their usability in the engineered structural composites.The work presents a partial synthesis of researches performed in this field by the consortium INCAS, INFLPR, ICECHIM, Ovidius University within the CEEX Programme 2005

Oriented carbon nanostructures grown by hot-filaments plasma-enhanced CVD from self-assembled Co-based catalyst on Si substrates

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Titanium dioxide nanoparticles prepared by laser pyrolysis : synthesis and photocatalytic properties

TiO2 nanoparticles were synthesized via the laser pyrolysis of titanium tetrachloride-based gas-phase mixtures. In the obtained nanopowders, a mixture of anatase and rutile phases with mean particle size of about 14 nm was identified. Using the thermal heated laser nanopowders, mechanically stable films were produced by immobilizing titania nanopowders on glass substrates (the doctor blading method followed by compression). The photocatalytic activity of the prepared films was tested by the degradation of 4-chlorophenol in an aqueous solution under UV-illumination. By referring to known commercial samples (Degussa P25) similarly prepared, higher photocatalytic efficiency was found for the laser-prepared samples