Boron Nitride Nanotubes as Templates for Half-Metal Nanowires

We investigate by means of DFT/GGA+U calculations the electronic and structural properties of magnetic nanotubes composed of an iron oxide monolayer and (n,0) Boron Nitride (BN) nanotubes, with n ranging from 6 up to 14. The formation energy per FeO molecule of FeO covered tubes is smaller than the formation energy of small FeO nanoparticles which suggest that the FeO molecules may cover the BN nanotubes rather than to aggregate to form the FeO bulk. We propose a continuous model for the FeO covered BN nanotubes formation energy which predicts that BN tubes with diameter of roughly 13 \AA are the most stable. Unlike carbon nanotubes, the band structure of FeO covered BN nanotubes can not be obtained by slicing the band structure of a FeO layer, the curvature and the interaction with the BN tube is determinant for the electronic behavior of FeO covered tubes. As a result the tubes are semiconductors, intrinsic half-metals or semi-half-metals that can become half-metals charged with either electrons and holes. Such a result may be important in the spintronics context.Comment: 6 pages, 6 figure

Tribocorrosão da liga TI6AL4V em solução salina tamponada com fosfato

The tribocorrosion behavior of Ti6Al4V alloy was investigated in a Phosphate Buffered Saline (PBS) solution by a reciprocating wear, using alumina ball as the counterface material, at different normal forces and sliding velocities. Dry wear experiments were performed in order to compare with the tribocorrosion experiments at open circuit potential and under anodic polarization. Dry wear induced a superior damage on the counterface, forming larger and shallower wear tracks compared with those experiments performed in PBS solution. The anodic current was increased by wear; however the volume of oxidized metal in tribocorrosion experiments correspond to a relative low percentage of the wear track volume

Tribological, electrochemical and tribo-electrochemical characterization of bare and nitrided Ti6Al4V in simulated body fluid solution

Tribological, electrochemical and tribo-electrochemical behaviour of bare and nitrided Ti6Al4V alloy was studied. Scanning Electron Microscopy (SEM), X-ray diffraction and microhardness profile were used to characterize the nitrided Ti6Al4V. The anticorrosive properties of nitrided Ti6Al4V in phosphate buffer saline solution (PBS), simulating the body environment, were evaluated by Electrochemical Impedance Spectroscopy (EIS). Nitriding increased the alloy resistance to corrosion and to dry wear. Resistance to tribocorrosion in PBS at the open circuit potential (OCP) for the nitrided alloy was also significantly increased compared to the bare alloy; nevertheless at an anodic potential this influence became less important

Cell response and corrosion behavior of electrodeposited diamond-like carbon films on nanostructured titanium.

Surface characteristics such as roughness and contact angle of flat and nanostructured titanium samples and diamond-like carbon films (DLC) electrodeposited on the nanostructured samples were evaluated. Also, the mechanical properties and the corrosion resistance of the samples were evaluated in phosphate buffered saline (PBS). Biocompatibility was assessed by analyzing an in vitro cell culture. Nanostructured samples presented better cell biocompatibility. DLC deposited onto nanostructured samples remained with nanostructured morphology, presented high hardness and improved corrosion resistance compared to bare titanium. The DLC films electrodeposited from acetonitrile presented higher corrosion resistance in PBS solution when compared to DLC films deposited from N,N-dimethylformamide