ABSTRACT
Present commercial titanium alloy implants have an elastic modulus higher than 100 GPa, whereas that of the cortical bone is much smaller (17−28 GPa). This elastic modulus mismatch produces a stress shielding effect and the resorption of the bone surrounding the implant. In the present work, a <100> fiber texture is developed in ß type Ti-42Nb (wt%) alloy ingots generated by laser-directed energy deposition (LDED) in order to achieve anisotropic mechanical properties. In addition, we demonstrate that laser-deposited ß type Ti-42Nb alloy ingots with an intense <100> fiber texture exhibit a very low elastic modulus in the building direction (Ez < 50 GPa) and high yield (σ0.2z > 700 MPa) and tensile (UTSz > 700 MPa) strengths. Laser-deposited Ti-42Nb alloy enhances the osteoinductive effect, promoting the adhesion, proliferation, and spreading of human osteoblast-like cells. Hence, we propose that laser-deposited ß type Ti-42Nb alloy is a potentially promising candidate for the manufacturing of pioneering biomedical implants with a very low elastic modulus that can suppress stress shielding.
ABSTRACT
Antibiotic resistance is a leading cause of death worldwide. In this paper, we explore new alternatives in the treatment of infections. Noble metal nanoparticles could help to mitigate this problem. In this work, palladium nanoparticles were synthesized by laser ablation in order to explore their antimicrobial capacity. To obtain palladium nanoparticles, a palladium plate immersed in water, or methanol, was ablated, using two pulsed lasers that emit radiation with wavelengths of 532 nm and 1064 nm, respectively. Pure Pd-NPs with crystalline microstructure and rounded shape were obtained. The nanoparticles' size is more homogeneous if the laser wavelength is 532 nm, and it decreases when methanol is used as solvent, reaching mean diameters smaller than 6 nm. With the objective of studying antimicrobial activity against Staphylococcus aureus, the Pd-NPs were immobilized on the surface of titanium discs. The release of palladium ions was recorded during the first seven days, and the cytotoxicity of the immobilized NPs was also tested with L929 mouse fibroblast cell line. Palladium nanoparticles synthesized by means of the infrared laser in methanol showed a strong inhibitory effect on S. aureus and good cytocompatibility, with no toxic effect on fibroblast cells.
ABSTRACT
Laser-directed energy deposition (LDED) is an additive manufacturing (AM) technology which can be an alternative to the traditional subtractive milling process for the obtention of porcelain-fused-to-metal (PFM) prosthesis. Still, the adhesion performance of the veneering ceramics for this material has been not studied yet. The main objective of this study is to perform a systematic comparison of the adhesion performance of Co-Cr-W metal frameworks obtained through LDED and conventional milling techniques. Comparison includes microstructural, superficial, and adhesion analysis. Co-Cr manufactured via LDED technique presents similar behavior (p < 0.05) in comparison to the material obtained via milling techniques, and its performance was validated with the veneering ceramics and veneering composites currently employed in the dental industry.
ABSTRACT
Slate is a natural rock usually used in roofs, façades, and for tiling. In spite of this broad use, the production process of slate tiles requires substantial improvements. An important quantity of slate from the quarry is wasted during the manufacturing of the final product. Furthermore, processes are not automatized and the production lead times can be considerably shortened. Therefore, new processing methods to increase productivity, reduce costs and to provide added value to the final slate product are required. Drilling is an important part of these manufacturing processes. Conventional drilling processes usually cause the breaking of the slate tiles; then, even a higher quantity of material is wasted. To overcome these problems, lasers emerge as a feasible tool to produce holes in this material, since mechanical stresses are not induced on the workpiece. In this work, we have studied the CO2 laser microdrilling of slate tiles. We used a Design of Experiments (DOE) methodology to determine the influence of the laser processing parameters on the hole quality. This work demonstrates the capability of a CO2 laser to produce holes in slate with less than 100 microns in diameter, avoiding any fracture, and with a processing time of less than 50 ms per hole. Finally, this process demonstrates the viability of the production of high-density micron-sized holes in a slate tile for water draining purposes.
