Comparative assessment of miscibility and degradability on PET/PLA and PET/chitosan blends

This work reports the synthesis and miscibility of PET/PLA and PET/chitosan blends as well as their degradation in real soil environment (6 months) and in accelerated weathering (1200 h). For this purpose, commercial polyethylene terephthalate (PET) and recycled PET (R-PET) were used as polymer matrixes and extruded with different amounts of polylactic acid (5, 10 and 15 wt-%) or chitosan (1, 2.5 and 5 wt-%) to form filaments. Different characterization techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry/thermogravimetric analysis (DSC/TGA) and scanning electron microscopy (SEM) were used before and after degradation process. The results indicate weak interactions between blend components suggesting secondary bonds by hydrogen bridges or by electrostatic forces. The miscibility of chitosan in both PET matrixes is lower in comparison with PLA; the saturation of PLA into polymer matrixes was reached up to an amount of 10 wt-% whereas longer amounts of 5 wt-% of chitosan become rigid and brittle. The best performance in the miscibility and degradation process was found for PET/chitosan (95/5) which is comparable with commercial bottles of BioPET under similar experimental conditions. © 2014 Elsevier Ltd. All rights reserved

Optimal conditions for the deposition of novel anticorrosive coatings by RF magnetron sputtering for aluminum alloy AA6082

Cerium and lanthanum coatings were deposited on glass, silicon (1 0 0), and aluminum alloy by RF magnetron sputtering in which several experimental conditions such as power, substrate temperature, and deposition time were varied, using pure CeO2 and La2O3 targets. The effect of deposition parameters on the bonding structure, surface morphology and properties against corrosion of rare earth (RE) coatings formed on metallic substrate was reported. The microstructure and chemistry of the thin film were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and X-ray photoelectron spectroscopy (XPS); whereas their use as corrosion resistant coatings was studied in aqueous NaCl solution (3.0 wt%) by using polarization curves. Variations in these properties were observed by increasing the substrate temperature which modifies the crystallinity of the rare earth coatings. XRD and XPS findings indicate that the cerium coatings are composed by CeO2 and a significant quantity of Ce2O3 due to oxygen deficiency in the sputtering chamber, whereas La2O3/La(OH)3 and some La intermetallic compounds are detected in the lanthanum films. Variations in the Ecorr and Icorr were found as a function of the thickness, texture, and morphology of the as-prepared coatings. © 2014 Elsevier B.V. All rights reserved

Rare earth conversion coatings grown on AA6061 aluminum alloys. Corrosion studies

The present work is aimed to investigate the corrosion resistance of rare earth (RE) protective coatings deposited by spontaneous deposition on AA6061 aluminum alloy substrates. Coatings were deposited from water-based Ce(NO3)3 and La(NO3)3 solutions by varying parameters such as rare earth solution concentration, bath temperature and immersion time. The values of the Tafel slopes indicate that the cathodic process is favored by concentration polarization rather than activation polarization. © 2014, Sociedad Química de México

Effect of ZrO2:SiO2 dispersion on the thermal stability, mechanical properties and corrosion behavior of hybrid coatings deposited on carbon steel

In this work we present the development of a nanocomposite material composed by ZrO2:SiO2 (25:75 mol%) nanoparticles in a polyurethane (PU) matrix for corrosion protection of AISI 1018 carbon steel. Specifically, the effect of the pre-dispersion method of ZrO2:SiO2 nanoparticles to reinforce PU coatings in delayed the corrosion and enhance mechanical properties of mild steel, were analyzed by applying two conventional methods: mechanical stirring (1, 3 and 5 h) and sonication (30, 60 and 120 min). The effect of pre-dispersed the ceramic nanoparticles by mechanical stirring and sonication on the mechanical properties and corrosion behavior was analyzed. Sonication improved the dispersion and hardness properties reducing the time of dispersion of the nanoparticles in comparison with mechanical stirring. The EIS results also showed that the hybrid coatings using sonication as method to pre-dispersed the nanoparticles enhanced the dispersion and the degradation resistance of the carbon steel by more than two-order of magnitude as compared to the coated samples with pure polyurethane after 2 h exposure in 3 wt.% NaCl solution. Long-term (20 days) EIS results also confirmed that the hybrid coating synthesized with sonically pre-dispersed particles improved the mechanical properties and degradation resistance in comparison with that observed with coatings using pre-dispersed particles by mechanical stirring, which could be better in service mechanical integrity. © 2014 Elsevier B.V. All rights reserved

Solid solutions of La-doped BiFeO3 obtained by the Pechini method with improvement in their properties

In this work, the synthesis of a series of solid solutions of Bi 1-xLaxFeO3 (BLFO) (0≤x≤ 0.15) obtained by the Pechini method is reported. The effects of lanthanum concentrations on the phase formation, grain size, as well as electric and magnetic properties were studied. The XRD results displayed the single BiFeO3 (BFO) phase for the different employed compositions. Crystal structure and cell parameters were refined by the Rietveld analysis, indicating that the obtained ceramics crystallized in the rhombohedral structure. The slight variation of the cell parameters and density values confirmed the partial substitution of Bi 3+ by La3+ into the perovskite A site like BiFeO 3 structure. Scanning electron microscopy was used to obtain the morphology of the different synthesized compounds, revealing a diminution of the grain sizes during the sintering process, attributed to the increment of La3+ content. Electric impedance spectroscopy (EIS) measurements were performed to evaluate the electric properties, thus showing a notable increase in the permittivity. The effect of incorporating lanthanum into the BFO structure enhanced ferroelectric and ferromagnetic properties. © 2014 Elsevier Ltd and Techna Group S.r.l

Corrosion studies of PPy/Ni organic–inorganic hybrid bilayer coatings on commercial carbon steel

Electrodeposition of polypyrrole (PPy) was achieved on AISI 1018 carbon steel (CS) using a constant potential regime and cyclic voltammetry techniques evaluating different synthesis parameters, in monomer-containing oxalic acid solutions. Thereafter, CS PPy/Ni bilayer films were produced by Ni deposition onto PPy films using a potentiostatic method. The electrochemical performance of PPy/Ni-coated carbon steel systems was investigated in 3.0 wt% NaCl solutions. For this purpose, scanning Kelvin probe (SKP), open-circuit potential (Eocp), polarization curves, and cyclic voltammetry techniques were used. The influence of electro-synthesis method and parameters were analyzed. It was found that the deviation in the Volta potentials is correlated to the interfacial interaction between the PPy/Ni bilayer coating and substrate. Considering both experimental methods to obtain PPy/Ni coatings, a more effective protection against corrosion can be formed when potentiodynamic (cyclic voltammetry) and potentiostatic techniques are combined. © 2014 Springer-Verlag Berlin Heidelber

Improvement of adhesion and barrier properties of biomedical stainless steel by deposition of YSZ coatings using RF magnetron sputtering

The AISI 316L stainless steel (SS) has been widely used in both artificial knee and hip joints in biomedical applications. In the present study, yttria stabilized zirconia (YSZ, ZrO2 + 8% Y2O3) films were deposited on AISI 316L SS by radio-frequency magnetron sputtering using different power densities (50-250 W) and deposition times (30-120 min) from a YSZ target. The crystallographic orientation and surface morphology were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effects of the surface modification on the corrosion performance of AISI 316L SS were evaluated in phosphate buffered saline (PBS) solution using an electrochemical test on both the virgin and coated samples. The YSZ coatings have a (111) preferred orientation during crystal growth along the c-axis for short deposition times (30-60 min), whereas a polycrystalline structure forms during deposition times from 90 to 120 min. The corrosion protective character of the YSZ coatings depends on the crystal size and film thickness. A significant increase in adhesion and corrosion resistance by at least a factor of 46 and a higher breakdown potential were obtained for the deposited coatings at 200 W (120 min). © 2014 Elsevier Inc

Experimental data in support of characterization of the CePO4 dispersion into transparent PMMA/PU IPNs by the sequential route

"This article is focused on the complementary data referring to the article "Dispersion of upconverting nanostructures of CePO4 using rod and semi-spherical morphologies into transparent PMMA/PU IPNs by the sequential route". It contains the XPS data of CePO4, photographs and DSC thermograms of transparent PMMA/PU IPNs as well as with CePO4 dispersed in different wt.%, Confocal laser scanning micrographs, transmission electron microscopy (TEM), optical images of surface, and visual inspection (photographs) before and after aging of hybrid materials.