Navegando por Autor "Pereira, Rafael Santiago Floriani"
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Artigo Effect of laser surface texturing on primary stability and surface properties of zirconia implants(Elsevier, 2017-12-01) Nascimento, Rubens Maribondo do; Moura, Filipe Samuel; Pereira, Rafael Santiago Floriani; Buciumeanu, Mihaela; Carvalho, Oscar; Bartolomeu, Flávio; Silva, Filipe SamuelThe aim of this study was to investigate the influence of different laser surface texturing parameters on static and dynamic coefficient of friction values of Yttria-tetragonal zirconia polycrystals (3Y-TZP) against bone to assess the primary stability of implants. The ability of the textures to promote osseointegration, as measured by wettability, and eventual changes in roughness, due to possible aging during sterilization, were also assessed. 3Y-TZP disks were divided into four groups: as sintered sample, sandblasting and etching treatment, laser irradiation using two output power of 0.9 and 1.8 W. The friction tests were carried out by using a pin-on-plate configuration, being the pins the 3Y-TZP disks and the plates the bone. The surfaces were inspected by SEM/ EDS and by surface roughness profilometer. Wettability characteristics were also evaluated by drop contact angle, and aging was assessed, after laser treatments, by XRD analysis. Results demonstrate that with laser surface texturing of zirconia it is possible to combine better wettability, better aging performance, and better primary stability, as compared to traditional - Sand blasting and Etching treatments. Thus, it is shown that the laser irradiation technique is a promising alternative to conventional sandblasting and etching proceduresArtigo Effects of laser fluence and liquid media on preparation of small Ag nanoparticles by laser ablation in liquid(Elsevier, 2017-12-01) Nascimento, Rubens Maribondo do; Moura, Caroline Gomes; Pereira, Rafael Santiago Floriani; Andritschky, Martin; Lopes, Augusto Luís Barros; Grilo, João Paulo de Freitas; Silva, Filipe SamuelThis study aims to assess a method for preparation of small and highly stable Ag nanoparticles by nanosecond laser ablation in liquid. Effect of liquid medium and laser fluence on the size, morphology and structure of produced nanoparticles has been studied experimentally. Pulses of a Nd:YAG laser of 1064 nm wavelength at 35 ns pulse width at different fluences were employed to irradiate the silver target in different environments (water, ethanol and acetone). The UV-Visible absorption spectra of nanoparticles exhibit surface plasmon resonance absorption peak in the UV region. STEM and TEM micrographs were used to evaluate the size and shape of nanoparticles. The stability of silver colloids in terms of oxidation at different liquid media was analyzed by SAED patterns. The results showed that characteristics of Ag nanoparticles and their production rate were strongly influenced by varying laser fluence and liquid medium. Particles from 2 to 80 nm of diameter were produced using different conditions and no oxidation was found in ethanol and acetone media. This work puts in evidence a promising approach to produce small nanoparticles by using high laser fluence energyArtigo Laser printing of micro-electronic communication systems for smart implants applications(Elsevier, 2020-08) Nascimento, Rubens Maribondo do; Moura, Caroline Gomes; Magalhães, Vitor H.; Pereira, Rafael Santiago Floriani; Carvalho, Oscar; Cerqueira, Maria de Fátima; Gonçalves, Luis Miguel V.; Silva, Filipe SamuelEndow the implant with intrinsic communication system between sensors and actuators or between implant and patient is a key factor for its long-term success. The capacity of early diagnosis of failures and the ability to remedy them are necessary to minimize expensive complications and reducing revision procedures. Ti6Al4V is the most used titanium alloy for implant’s fabrication. In this sense, this work presents a promising approach to print communication systems by using laser technology, aiming integrate the smart components on titanium implants. Laser has been employed as a versatile tool to modify the surface in different ways, such as texturing, oxidizing and sintering. Silver wires have been printed on Ti6Al4V surface in order to conduct electrical current. To minimize current loss for the substrate, titanium oxide layer has been produced by different methods (laser and anodization). Laser sintering (LS) has been also compared to a conventional method (Hot-pressing- HP) to consolidate the silver powder into the cavities. In comparison to the conventional techniques, laser demonstrated to be a competitive approach to oxidizing the surface and also for consolidating the micro-wires on Ti6Al4V surface. Consequently, the micro-wires printed by laser approach presented satisfactory results in terms of electrical resistance, actuating as the conductor path for electrical current, with values of 0.0131 Ω, which is similar to the resistance of the wire printed in an insulator substrate