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•Al graded Mg-Al thin films were synthesized via combinatorial magnetron sputtering.•Al graded Mg-Al thin films were analyzed via in-situ electrochemistry.•The Mg-Al solid solution ...corrosion resistance increases with the Al concentration.•Exceeding cAl ∼ 4 wt% causes a distinct anodic current density decrease.•Exceeding cAl ∼ 4 wt% causes a predominant cathodic partial reaction on the surface.
The effect of varying Al concentrations on the electrochemical corrosion resistance of binary Mg-Al solid solutions thin films under alkaline immersion conditions was investigated via a combination of in-situ flow-cell, scanning vibrating electrode technique and microscopy analysis. These spatially resolving characterization techniques are employed along the Al concentration gradient of the combinatorically grown thin films enabling efficient screening of the Al concentration dependent electrochemical corrosion behaviour. The analysis revealed an increasing corrosion resistance with increasing Al concentration, as a consequence of Al induced hydroxide reinforcement. Specifically, the addition of >4 wt.% Al decreases the corrosion current density in the range of 70–90 % compared to pure Mg.
The temperature-dependent composition and phase formation during the physical vapor deposition (PVD) of Mg-Ca thin films is modeled using a CALPHAD-based approach. Considering the Mg and Ca ...sublimation fluxes calculated based on the vapor pressure obtained by employing thermochemical equilibrium calculations, the experimentally observed synthesis-temperature trends in the thin-film composition and phase formation were reproduced. The model is a significant step towards understanding how synthesis parameters control composition and, therefore, phase formation in the PVD of metals with high vapor pressures.
Impurities can be incorporated during thin film deposition, but also can originate from atmosphere exposure. As impurities can strongly affect the composition-structure-property relations in ...magnetron sputter deposited thin films, it is important to distinguish between both incorporation channels. Therefore, the impurity incorporation by atmosphere exposure into sputtered Mg, Al, and Ca thin films is systematically studied by a variation of the deposition temperatures and atmosphere exposure times. Deposition temperature variation results in morphological modifications explained by considering surface and bulk diffusion as well as grain boundary motion and evaporation. The film morphologies exhibiting the lowest oxygen concentrations, as measured by energy dispersive X-ray spectroscopy, are obtained at a homologous temperature of 0.4 for both Mg and Al thin films. For Ca, preventing atmosphere exposure is essential to hinder impurity incorporation: By comparing the impurity concentration in Al-capped and uncapped thin films, it is demonstrated that Ca thin films are locally protected by Al-capping, while Mg (and Al) form native passivation layers. Furthermore, it can be learned that the capping (or self-passivation) efficiency in terms of hindering further oxidation of the films in atmosphere is strongly dependent on the underlying morphology, which in turn is defined by the growth temperature.
Tissue engineering is a promising approach in repairing damaged tissues. During the last few years, magnetic nanoparticles have been of great interest in this field of study due to their controlled ...responsive characteristics in specific external magnetic fields. In this study, after synthesizing iron oxide (magnetite) nanoparticles through a reverse coprecipitation method, silk fibroin/chitosan-based magnetic scaffolds were prepared using different amounts of magnetite nanoparticles (0, 0.5, 1 and 2%) by freeze-casting method. The physicochemical activity of the scaffolds was monitored in phosphate-buffered saline (PBS) solution to determine the biodegradation and swelling behaviors. The stability of the magnetite nanoparticles in the fabricated scaffolds was determined by atomic absorption spectroscopy (AAS). Moreover, the cellular activity of the magnetic scaffolds was examined under a static magnetic field. The results showed that the lamellar structured scaffolds having MNPs in the walls could not affect the final structure and deteriorate the biological characteristics of the scaffolds, while the ability of magnetic responsivity was added to the scaffolds. This study warrants further pre-clinical and clinical evaluations.
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•Based on TEM micrograph and Rietveld refinement the particle size of MNPs was approximately 12nm.•The water absorption of silk scaffolds increases by the addition of chitosan content.•Addition of 0.5wt% MNPs led to decrease in scaffolds degradation and number of living cells.•By increasing the MNPs from 0.5 to 1 and 2, the degradation rate and living cells increased.•In scaffolds with 2wt% MNPs cell attachment is slightly better than those of 0.5wt%.
Nanocrystalline Mg was sputter deposited onto an Ar ion etched Si {100} substrate. Despite an ∼6 nm amorphous layer found at the interface, the Mg thin film exhibits a sharp basal-plane texture ...enabled by surface energy minimization. The columnar grains have abundant 〈0001〉 tilt grain boundaries in between, most of which are symmetric with various misorientation angles. Up to ∼20° tilt angle, they are composed of arrays of equally-spaced edge dislocations. Ga atoms were introduced from focused ion beam milling and found to segregate at grain boundaries and preferentially decorate the dislocation cores. Most symmetric grain boundaries are type-1, whose boundary planes have smaller dihedral angles with {21&cmb.macr;1&cmb.macr;0} rather than {101&cmb.macr;0}. Atomistic simulations further demonstrate that type-2 grain boundaries, having boundary planes at smaller dihedral angles with {101&cmb.macr;0}, are composed of denser dislocation arrays and hence have higher formation energy than their type-1 counterparts. The finding correlates well with the dominance of type-1 grain boundaries observed in the Mg thin film.
In a textured Mg thin film, two types of 〈0001〉 tilt grain boundaries are identified by electron microscopy and atomistic simulation. Coincidence site lattice and dislocation models are applied to study boundaries in hexagonal close-packed crystals.
The temperature-dependent composition and phase formation during physical vapor deposition (PVD) of Mg-Ca thin films is modelled using a CALPHAD-based approach. Considering the Mg and Ca sublimation ...fluxes calculated based on the vapor pressure obtained by employing equilibrium thermochemical calculations, experimentally observed synthesis temperature trends in thin film composition and phase formation are reproduced. The model is a significant step towards understanding how synthesis parameters control composition and thereby phase formation in PVD of metals with high vapor pressures.
