Effect of the Delay in Time Between Cooling and Aging in Heat-Treated Cast Aluminum Alloys

The mechanical properties of cast aluminum alloys can be affected by the delay in time involved between the stages of rapid cooling after solubilization (quenching) and aging. This effect was studied on samples from three different Al-Si alloys that were cast with a wide range of microstructures. It was found that the parameter that exerts the highest influence on the mechanical properties is the degree of microstructural refining, which is referred to dendrite arm spacing, as a finer structure enhances the strength and ductility. It was found that the yield strength and total elongation, and to a lesser extend the ultimate tensile strength, are affected by the delay in time. The material that was treated to the peak-aged condition was found to be more susceptible to the reduction in mechanical properties with the increase in the delay in time.     

Hierarchical reinforcement of polyurethane-based composites with inorganic micro- and nanoplatelets

Hierarchically reinforced structures are widespread in nature but less common among man-made materials. In this paper, we show that polyurethane-based thermoplastic polymers can be hierarchically reinforced with laponite nanoplatelets and alumina microplatelets to reach strength and elastic modulus that are, respectively, 7- and 29-fold higher than that of the pure polymer matrix (91.7 MPa and 6.97 GPa, respectively). We find that the selective reinforcement of the polyurethane hard domains with laponite nanoplatelets is key to keep the polymer matrix sufficiently ductile for the incorporation of high concentrations of alumina microplatelets. Effective reinforcement of the polymer with microplatelets of different surface chemistries was only possible after annealing the composite at 130 °C to promote strong bonding at the oxide/polymer interface. Large-area composite films and bulk parts exhibiting good alignment of alumina microplatelets were obtained through conventional tape-casting. The concept of hierarchical reinforcement demonstrated here can be explored to obtain composite materials covering a wide range of mechanical properties using only a few reinforcing building blocks within the same polymer matrix.     

Effect of the metallic substrate and zinc layer on the atmospheric corrosion resistance of phosphatized and painted electrogalvanized steels

In this work, the influence of the metallic substrate and zinc layer on the atmospheric corrosion resistance of phosphatized and painted electrogalvanized steels was evaluated. For this purpose two types of electrogalvanized steels were used, one with drawing quality carbon steel as metallic substrate, and the other one with a substrate of Ni–Cu–Cr added carbon steel. The corrosion resistance was determined by accelerated and non‐accelerated corrosion tests, using cyclic test chambers and field tests in industrial and marine atmosphere. The mean corrosion advance and the maximum corrosion penetration of samples were measured using image analysis techniques. The study showed that the substrate and zinc layer mass play a decisive role on the atmospheric corrosion resistance of the phosphatized and painted electrogalvanized steels. It was also verified that it is possible to use smaller zinc layer masses without compromising the corrosion resistance of the material, provided that the metallic substrate has characteristics of atmospheric corrosion resistance, thus contributing to the improvement of the zinc coated steels.     

Data‐driven bounded‐error fault detection

In this paper, a new data‐driven fault‐detection method is proposed. This method is based on a new nonparametric system identification approach, which constitutes the principal contribution to this work. The fault‐detection method is a parametric model‐free approach that can be applied to nonlinear systems that work at various operating points. Not only can the fault‐detection process be applied to the steady state of each operating point, but it can also be applied to the transient state resulting from a change in the operating point. In order to detect faults, the proposed method uses an interval predictor based on bounded‐error techniques. The utilization of techniques based on bounded error enables system uncertainties to be included in an explicit way. This in turn leads to the possibility of obtaining interval predictions of the behaviour of the system, which include information on the reliability of the prediction itself. In order to show the effectiveness of the fault‐detection method, two examples are presented: in the form of a simulated process (counter‐flow shell‐and‐tube heat‐exchanger system) and an example of a real application (two‐tanks system). A comparison with two fault‐detection methods has also been included. Copyright © 2013 John Wiley & Sons, Ltd.     

Influence of nitriding on corrosion resistance of martensitic X17CrNi16‐2 stainless steel

Nitriding increases surface hardness and improves wear resistance of stainless steels. However, nitriding can sometimes reduce their corrosion resistance. In this paper, the influence of nitriding on the corrosion resistance of martensitic stainless steel was investigated. Plasma nitriding at 440 °C and 525 °C and salt bath nitrocarburizing were carried out on X17CrNi16‐2 stainless steel. Microhardness profiles of the obtained nitrided layers were examined. Phase composition analysis and quantitative depth profile analysis of the nitrided layers were preformed by X‐ray diffraction (XRD) and glow‐discharge optical emission spectrometry (GD‐OES), respectively. Corrosion behaviour was evaluated by immersion test in 1% HCl, salt spray test in 5% NaCl and electrochemical corrosion tests in 3.5% NaCl aqueous solution. Results show that salt bath nitrocarburizing, as well as plasma nitriding at low temperature, increased microhardness without significantly reducing corrosion resistance. Plasma nitriding at a higher temperature increased the corrosion tendency of the X17CrNi16‐2 steel.     

Co‐optimization of SnS absorber and Zn(O,S) buffer materials for improved solar cells

Thin‐film solar cells consisting of earth‐abundant and non‐toxic materials were made from pulsed chemical vapor deposition (pulsed‐CVD) of SnS as the p‐type absorber layer and atomic layer deposition (ALD) of Zn(O,S) as the n‐type buffer layer. The effects of deposition temperature and annealing conditions of the SnS absorber layer were studied for solar cells with a structure of Mo/SnS/Zn(O,S)/ZnO/ITO. Solar cells were further optimized by varying the stoichiometry of Zn(O,S) and the annealing conditions of SnS. Post‐deposition annealing in pure hydrogen sulfide improved crystallinity and increased the carrier mobility by one order of magnitude, and a power conversion efficiency up to 2.9% was achieved. Copyright © 2014 John Wiley & Sons, Ltd.     

Isomerization of lactose over natural sepiolite

Sepiolite (a hydrated magnesium silicate) was investigated as a catalyst for the isomerization of lactose. Factors such as temperature, concentration and time were studied. The main reaction product was lactulose; small amounts of epilactose, galactose, tagatose and 3-deoxypentulose were also formed. Product distribution indicated that the reaction routes were isomerization of the disaccharide followed by degradation of lactulose.     

Biological Implications of a Stroke Therapy Based in Neuroglobin Hyaluronate Nanoparticles. Neuroprotective Role and Molecular Bases

Exogenous neuroprotective protein neuroglobin (Ngb) cannot cross the blood–brain barrier. To overcome this difficulty, we synthesized hyaluronate nanoparticles (NPs), able to deliver Ngb into the brain in an animal model of stroke (MCAO). These NPs effectively reached neurons, and were microscopically identified after 24 h of reperfusion. Compared to MCAO non-treated animals, those treated with Ngb-NPs showed survival rates up to 50% higher, and better neurological scores. Tissue damage improved with the treatment, but no changes in the infarct volume or in the oxidative/nitrosative values were detected. A proteomics approach (p-value < 0.02; fold change = 0.05) in the infarcted areas showed a total of 219 proteins that significantly changed their expression after stroke and treatment with Ngb-NPs. Of special interest, are proteins such as FBXO7 and NTRK2, which were downexpressed in stroke, but overexpressed after treatment with Ngb-NPs; and ATX2L, which was overexpressed only under the effect of Ngb. Interestingly, the proteins affected by the treatment with Ngb were involved in mitochondrial function and cell death, endocytosis, protein metabolism, cytoskeletal remodeling, or synaptic function, and in regenerative processes, such as dendritogenesis, neuritogenesis, or sinaptogenesis. Consequently, our pharmaceutical preparation may open new therapeutic scopes for stroke and possibly for other neurodegenerative pathologies.     

Cold Atmospheric Plasma Apoptotic and Oxidative Effects on MCF7 and HCC1806 Human Breast Cancer Cells

Breast cancer (BC) is a malignant neoplasia with the highest incidence and mortality rates in women worldwide. Currently, therapies include surgery, radiotherapy, and chemotherapy, including targeted therapies in some cases. However, treatments are often associated with serious adverse effects. Looking for new options in BC treatment, we evaluated the therapeutic potential of cold atmospheric plasma (CAP) in two cell lines (MCF7 and HCC1806) with distinct histological features. Apoptosis seemed to be the most prevalent type of death, as corroborated by several biochemical features, including phosphatidylserine exposure, the disruption of mitochondrial membrane potential, an increase in BAX/BCL2 ratio and procaspase 3 loss. Moreover, the accumulation of cells in the G2/M phase of the cell cycle points to the loss of replication ability and decreased survival. Despite reported toxic concentrations of peroxides in culture media exposed to plasma, intracellular peroxide concentration was overall decreased accompanying a reduction in GSH levels shortly after plasma exposure in both cell lines. In HCC1806, elevated nitric oxide (NO) concentration accompanied by reduced superoxide levels suggests that these cells are capable of converting plasma-derived nitrites into NO that competes with superoxide dismutase (SOD) for superoxide to form peroxinitrite. The concomitant inhibition of the antioxidative activity of cells during CAP treatment, particularly the inhibition of cytochrome c oxidase with sodium azide, synergistically increased plasma toxicity. Thus, this in vitro research enlightens the therapeutic potential of CAP in the treatment of breast cancer, elucidating its possible mechanisms of action.