Facile cross-linking of CO2-based unsaturated polyethercarbonates with polymercaptanes via thiol–ene click chemistry makes them highly interesting sustainable pre-polymers for material applications as elas-tomers and sealants. CO2-Based... more
Facile cross-linking of CO2-based unsaturated polyethercarbonates with polymercaptanes via thiol–ene click chemistry makes them highly interesting sustainable pre-polymers for material applications as elas-tomers and sealants. CO2-Based unsaturated polyethercarbonates, characterised by a glass transition temperature well below room temperature, were obtained by convenient one-pot synthesis. Terpolymeri-zation of CO2 with propylene oxide and allylglycidylether provided the polyethercarbonates with a defined number of pendant unsaturated bonds along the backbone of the polymer chain. The time-dependent viscoelastic behaviour during cross-linking with pentaerythritol tetrakis(3-mercaptopropionate) revealed faster curing with increasing content of double bonds in the pre-polymer. In parallel, the higher cross-linking density provided access to more rigid elastic materials.
Polyol methods to synthesize nanoparticles and their arrays are firstly described.Magnetic nanoparticles selfassemble under particular conditions into spherical superstructures, like CoNi nanoparticles, or planar structures with hexagonal... more
Polyol methods to synthesize nanoparticles and their arrays are firstly described.Magnetic nanoparticles selfassemble
under particular conditions into spherical superstructures, like CoNi nanoparticles, or planar structures with hexagonal ordering, like FePt nanoparticles.Particles and their arrays are structurally analysed by techniques like TEM, X-ray, etc. Magnetic characterization is firstly performed by VSM magnetomer as a function of the nanoparticles size paying particular attention to the transition from multidomain to single-domain structures.Later on, magnetic exchange coupling effects are discussed including the temperature dependence of magnetic parameters as coercive and exchange bias fields, as well as the influence of field or zero-field cooling processes. Finally, magnetic polymers consisting of magnetic nanoparticles embedded into PVC polymeric matrix are prepared and magnetically analysed.
Monodispersed spherical Co80Ni20 nanoparticles with diameters between 10 and 540 nm have been prepared by boiling liquid reduction of cobalt and nickel salts through a heterogeneous nucleation process (polyol process). All samples exhibit... more
Monodispersed spherical Co80Ni20 nanoparticles with diameters between 10 and 540 nm have been prepared by boiling liquid reduction of cobalt and nickel salts through a heterogeneous nucleation process (polyol process). All samples exhibit a core/shell structure with a ferromagnetic core surrounded by a surface layer consisting of antiferromagnetic oxides and organic matter. The ferromagnetic/antiferromagnetic interface, which arises from the core/shell structure, induces an exchange anisotropy at low temperature when the samples are subjected to a field cooling process or to a zero field cooling process starting from a remanent state. The shift of the hysteresis loops (exchange bias) and the increment of the coercive field are consequences of the presence of this magnetic anisotropy. The effect of the particle size, the temperature and the cooling process on the magnetic behaviour of the samples has been analysed.
Carbon nanotubes (CNTs) have been shown to be a viable conductive additive in Li-Ion batteries [1]. By using CNTs battery life, energy, and power capability can all be improved over carbon black, the traditional conductive additive. A... more
Carbon nanotubes (CNTs) have been shown to be a viable conductive additive in Li-Ion batteries [1]. By using CNTs battery life, energy, and power capability can all be improved over carbon black, the traditional conductive additive. A significantly smaller weight percentage (5% CNTs) is needed to get the same conductivity as 20% carbon black. Many of the previous efforts found that a combination of conductive additives was most advantageous [2]. Unfortunately many of these efforts did not attend to the unique challenge that dispersing nanotubes presents and used non-optimal methods to disperse CNTs (e.g. ball milling) [3,4]. With poor dispersion a stable and resilient conductive network in the cathode is hard to form with CNTs alone. Here we investigate the formation of LiFePO₄ with CNTs using a polyol process synthesis.
Why Carbon Nanotubes? The best batteries have high energy density and can discharge and charge fast and will do so for thousands of cycles. The primary limitation to high current densities in LiFePO4 is the diffusion of lithium in and out of the crystal [4]. Since LiFePO4 is also not particularly conductive the electrode contact should be as near as possible in order to enable the fastest diffusion pathways.
A synthesis method based in the principles of the so-called polyol process has been developed to prepare Co nanocrystals of 5, 8 and 20 nm average diameter. The influence of stabilizers, as oleic and lauric acids, on the morphology and... more
A synthesis method based in the principles of the so-called polyol process has been developed to prepare Co nanocrystals of 5, 8 and 20 nm average diameter. The influence of stabilizers, as oleic and lauric acids, on the morphology and the self-assembled aggregates of the final Co nanocrystals has been analysed, as well as on their magnetic properties. Rather spherical Co nanoparticles were obtained using oleic and lauric acid, respectively, with 8 and 5 nm in diameter and narrow particle size distribution. The lauric acid, having a shorter chain length, seems to be more effective in coating the particles.
