Monte Carlo simulation of a LSC based on stacked layers of fiber arrays with core-coating different absorbing properties.

In this work, a Monte Carlo ray-tracing model for the simulation and optimization of a fiber Luminescent Solar Concentrator (LSC) based on stacked layers of fiber arrays is developed and validated. The fiber LSC efficiency improvements are compared against a conventional planar LSC. We developed a new model to analyze the performance of different configurations of bulk-doped fibers and fibers constituted by a doped coating and a passive core. These configurations are analyzed also varying fiber packing geometry diameters, and length. Due to the exceptionally low absorption coefficient of the silica fibers (αwg ≈ 10-4 cm-1), concentration factors of up to 1.9 are predicted when dimensions are scaled over 1 m2, which improve more than twice the maximum concentration factor ever reported. These results serve as a preliminary theoretical study for the future development of a new LSC design based on flexible silica micro-fibers coated with Si-QDs doped poly(lauryl methacrylate) (PLMA) layers.

Laser-assisted production of spherical TiO2 nanoparticles in water.

TiO(2) nanoparticles with controllable average diameter have been obtained by laser ablation in water. A monomode ytterbium doped fiber laser (YDFL) was used to ablate a metallic titanium target placed in deionized water. The resulting colloidal solutions were subjected to laser radiation to study the resizing effect. The crystalline phases, morphology and optical properties of the obtained nanoparticles were characterized by means of transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), x-ray energy dispersive spectroscopy (EDS) and UV-vis absorption spectroscopy. The colloidal suspensions produced consisting of titanium dioxide crystalline nanoparticles show almost perfect spherical shape with diameters ranging from 3 to 40 nm. The nanoparticles are polycrystalline and exhibit anatase as well as rutile phases.

Continuous fiberizing by laser melting (Cofiblas): Production of highly flexible glass nanofibers with effectively unlimited length.

The development of nanofibers is expected to foster the creation of outstanding lightweight nanocomposites and flexible and transparent composites for applications such as optoelectronics. However, the reduced length of existing nanofibers and nanotubes limits mechanical strengthening and effective manufacturing. Here, we present an innovative method that produces glass nanofibers with lengths that are, effectively, unlimited by the process. The method uses a combination of a high-power laser with a supersonic gas jet. We describe the experimental setup and the physical processes involved, and, with the aid of a mathematical simulation, identify and discuss the key parameters which determine its distinctive features and feasibility. This method enabled the production of virtually unlimited long, solid, and nonporous glass nanofibers that display outstanding flexibility and could be separately arranged and weaved.

Three-dimensional bioactive glass implants fabricated by rapid prototyping based on CO(2) laser cladding.

Three-dimensional bioactive glass implants were produced by rapid prototyping based on laser cladding without using moulds. CO(2) laser radiation was employed to melt 45S5 and S520 bioactive glass particles and to deposit the material layer by layer following a desired geometry. Controlled thermal input and cooling rate by fine tuning of the processing parameters allowed the production of crack-free fully dense implants. Microstructural characterization revealed chemical composition stability, but crystallization during processing was extensive when 45S5 bioactive glass was used. Improved results were obtained using the S520 bioactive glass, which showed limited surface crystallization due to an expanded sintering window (the difference between the glass transition temperature and crystallization onset temperature). Ion release from the S520 implants in Tris buffer was similar to that of amorphous 45S5 bioactive glass prepared by casting in graphite moulds. Laser processed S520 scaffolds were not cytotoxic in vitro when osteoblast-like MC3T3-E1 cells were cultured with the dissolution products of the glasses; and the MC3T3-E1 cells attached and spread well when cultured on the surface of the materials.

Laser cladding of bioactive glass coatings.

Laser cladding by powder injection has been used to produce bioactive glass coatings on titanium alloy (Ti6Al4V) substrates. Bioactive glass compositions alternative to 45S5 Bioglass were demonstrated to exhibit a gradual wetting angle-temperature evolution and therefore a more homogeneous deposition of the coating over the substrate was achieved. Among the different compositions studied, the S520 bioactive glass showed smoother wetting angle-temperature behavior and was successfully used as precursor material to produce bioactive coatings. Coatings processed using a Nd:YAG laser presented calcium silicate crystallization at the surface, with a uniform composition along the coating cross-section, and no significant dilution of the titanium alloy was observed. These coatings maintain similar bioactivity to that of the precursor material as demonstrated by immersion in simulated body fluid.