Browsing by Keyword "Silicon"
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Item Decrease of Staphylococcal adhesion on surgical stainless steel after Si ion implantation(2014-08-15) Braceras, Iñigo; Pacha-Olivenza, Miguel A.; Calzado-Martín, Alicia; Multigner, Marta; Vera, Carolina; Broncano, Luis Labajos; Gallardo-Moreno, Amparo M.; González-Carrasco, José Luis; Vilaboa, Nuria; González-Martín, M. Luisa; INGENIERÍA DE SUPERFICIES; Biomateriales316LVM austenitic stainless steel is often the material of choice on temporal musculoskeletal implants and surgical tools as it combines good mechanical properties and acceptable corrosion resistance to the physiologic media, being additionally relatively inexpensive. This study has aimed at improving the resistance to bacterial colonization of this surgical stainless steel, without compromising its biocompatibility and resistance. To achieve this aim, the effect of Si ion implantation on 316LVM has been studied. First, the effect of the ion implantation parameters (50 keV; fluence: 2.5-5 × 10 16 ions/cm 2 ; angle of incidence: 45-90°) has been assessed in terms of depth profiling of chemical composition by XPS and nano-topography evaluation by AFM. The in vitro biocompatibility of the alloy has been evaluated with human mesenchymal stem cells. Finally, bacterial adhesion of Staphylococcus epidermidis and Staphylococcus aureus on these surfaces has been assessed. Reduction of bacterial adhesion on Si implanted 316LVM is dependent on the implantation conditions as well as the features of the bacterial strains, offering a promising implantable biomaterial in terms of biocompatibility, mechanical properties and resistance to bacterial colonization. The effects of surface composition and nano-topography on bacterial adhesion, directly related to ion implantation conditions, are also discussed.Item In vitro corrosion behaviour of surgical 316LVM stainless steel modified by Si+ ion implantation – An electrochemical impedance spectroscopy study(2016-08-15) Galván, J.C.; Larrea, M.T.; Braceras, I.; Multigner, M.; González-Carrasco, J.L.; INGENIERÍA DE SUPERFICIESThis work deals with the surface modification of 316LVM stainless steel by Si+ ion implantation and the in vitro study of its effect on the short-term corrosion behaviour and ion release. In order to achieve a high Si content close to the surface, the experimental set up was designed with different implantation doses, acceleration voltages and angles of incidence. Corrosion tests were carried out by Electrochemical Impedance Spectroscopy (EIS). A special feature of this paper is the evaluation of the EIS data obtained through a critical analysis of the existing equivalent electrical circuits, in order to establish adequate parameters and scientific criteria to propose a classification of the corrosion response of the investigated surfaces. It has been demonstrated that doses of Si+ ion implantation equal to 2.5 × 1016 ion/cm2 and an acceleration voltages of 50 keV enhanced the corrosion protection. In contrast, higher ion-implantation dose (1 × 1017 ion/cm2) and acceleration voltage (80 keV) produced worse results, probably due to the development of strain induced α’-martensite. The quantity of relevant ions (Cr, Fe, Mn, Mo, Ni and Si) released to the medium was determined by an optimized Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) method. It has been shown that a better corrosion resistance is accompanied by a reduction in the amount of ions released.Item Pyrometallurgical Treatment of Apatite Concentrate with the Objective of Rare Earth Element Extraction: Part I(2017-12-01) Sun, Tianming; Kennedy, Mark William; Yurramendi, Lourdes; Aldana, Jose L.; Del Rio, Carmen; Arnout, Sander; Tranell, Gabriella; Aune, Ragnhild E.; VALORIZACIÓN DE RESIDUOSApatite, Ca5(PO4)3F, concentrate from LKAB in Kiruna, Sweden, has been characterized and pyrometallurgically treated using (i) silicon metal and fluxes to extract phosphorus and transition metals at 1600 °C (Part I publication), and (ii) carbon to extract phosphorus without fluxing at temperatures exceeding 1800 °C (Part II publication), with the ultimate objective to recover rare earth elements from the resulting slag/residue phases. A variety of methods (SEM/EDS, EPMA, DTA-TGA, Sessile drop, ICP-MS/OES, and XRD) have been used for the characterization and analysis of both the concentrate and reaction products. Elemental deportment, except for the rare earth metals, is broadly in line with the equilibrium thermodynamic predictions performed using HSC Chemistry®. Phase diagrams were predicted using FactSage® and a custom phosphate database to explain the observed melting/fluxing behaviors.