Influence of Si nanoparticles on the electrochemical behavior of organic coatings on carbon steel in chloride environment

Scanning electrochemical microscopy (SECM) is an excellent technique to detect electrochemical processes with high spatial resolution. In this work, the effect of silicon (Si) nanoparticles on the corrosion protection performance of epoxy-coated steel was examined by electrochemical impedance spectroscopy (EIS) and SECM analysis. The EIS was performed in continuous immersion in 0.1?M NaCl_(aq) solution. The addition of Si nanoparticles increased the coating film resistance (R _f) and the charge transfer resistance (R _ct) of coated steel. SECM mapping and line scan analysis was performed in order to estimate the coating performance with Si nanoparticles in 0.1?M NaCl_(aq) solution. SECM results indicated that the tip current at ?0.70?V was decreased by the addition of Si nanoparticles in epoxy film. These results suggested that the dissolved oxygen (DO) was consumed by anodic dissolution of Si nanoparticles. Surface analysis showed that the Si was enriched at the scratched region of the coated steel after a corrosion test. From these results, Si was dissolved as Si ⁿ⁺ and transferred to the scratched area, and then consumed the DO in the solution. Thus, the anodic dissolution of Fe at the scratched area was suppressed by the Si nanoparticles, which implies the sacrificial effect of Si from the coating against the steel corrosion. Hence, it was concluded that the Si nanoparticles had a beneficial effect on enhancing the corrosion resistance of the coated steel.     

Collective cell guidance by cooperative intercellular forces

Cells comprising a tissue migrate as part of a collective. How collective processes are coordinated over large multi-cellular assemblies has remained unclear, however, because mechanical stresses exerted at cell-cell junctions have not been accessible experimentally. We report here maps of these stresses within and between cells comprising a monolayer. Within the cell sheet there arise unanticipated fluctuations of mechanical stress that are severe, emerge spontaneously, and ripple across the monolayer. Within that stress landscape, local cellular migrations follow local orientations of maximal principal stress. Migrations of both endothelial and epithelial monolayers conform to this behaviour, as do breast cancer cell lines before but not after the epithelial-mesenchymal transition. Collective migration in these diverse systems is seen to be governed by a simple but unifying physiological principle: neighbouring cells join forces to transmit appreciable normal stress across the cell-cell junction, but migrate along orientations of minimal intercellular shear stress.     

Highly transparent and organosoluble polyimides derived from 2,2′‐disubstituted‐4,4′‐oxydianilines

Polypyrrole (PPy) and Polypyrrole‐ZnO (PPy‐ZnO) nanocomposites were electrodeposited on mild steel and its corrosion protection ability was studied by Tafel and Impedance techniques in 3.5% NaCl solution. Pure Polypyrrole film was not found to protect the mild steel perfectly but the coating with nano‐sized ZnO (PPy‐ZnO) has dramatically increased the corrosion resistance of mild steel. Electrochemical Impedance Spectroscopy (EIS) measurements indicated that the coating resistance (R_coat) and corrosion resistance (R_corr) values for the PPy‐ZnO nanocomposite coating was much higher than that of pure PPy coated electrode. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of shallow and deep cryogenic treatment on the residual state of stress of 4140 steel

The present research work studies the effect of cryogenic treatment on the residual stress state in 4140 steel. Two kinds of cryogenic treatment, namely shallow (SCT, −80 °C × 5 h) and deep cryogenic treatment (DCT, −196 °C × 24 h) were carried out between quenching and tempering in conventional heat treatment process. The results evidenced an increase in the compressive residual stress in steel are subjected to cryogenic treatment before tempering. X-ray diffractometry revealed that residual stresses are relieved during tempering, according to the redistribution of carbon in martensite and the precipitation of transition carbides. While conventional heat treatment (CHT) and shallow cryogenic treatment (SCT) promote a tensile state of residual stress, DCT shows a compressive residual stress.     

Cycle synthesis and optimization of a VSA process for postcombustion CO2 capture

A systematic analysis of several vacuum swing adsorption (VSA) cycles with Zeochem zeolite 13X as the adsorbent to capture CO₂ from dry, flue gas containing 15% CO₂ in N₂ is reported. Full optimization of the analyzed VSA cycles using genetic algorithm has been performed to obtain purity‐recovery and energy‐productivity Pareto fronts. These cycles are assessed for their ability to produce high‐purity CO₂ at high recovery. Configurations satisfying 90% purity‐recovery constraints are ranked according to their energy‐productivity Pareto fronts. It is shown that a 4‐step VSA cycle with light product pressurization gives the minimum energy penalty of 131 kWh/tonne CO₂ captured at a productivity of 0.57 mol CO₂/m³ adsorbent/s. The minimum energy consumption required to achieve 95 and 97% purities, both at 90% recoveries, are 154 and 186 kWh/tonne CO₂ captured, respectively. For the proposed cycle, it is shown that significant increase in productivity can be achieved with a marginal increase in energy consumption. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4735–4748, 2013     

Ionic conduction in poly(vinyl chloride)/poly(ethyl methacrylate)-based polymer blend electrolytes complexed with different lithium salts

Poly(vinyl chloride)/poly(ethyl methacrylate)-based polymer blend electrolytes comprising propylene carbonate as a plasticizer and a lithium salt LiX (X = BF₄⁻, ClO₄⁻, CF₃SO₃⁻) are prepared by a solvent casting technique. The electrolytes are subjected to characterization by ionic conductivity, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetic/differential thermal analysis. The electrolytes that contain LiBF₄ exhibit maximum conductivity and are thermally stable up to 254 °C.     

Desalination by solar-powered reverse osmosis in a remote area of the Sultanate of Oman

The Ministry of Water Resources successfully conducted an experimental study on the use of solar power to desalinate brackish ground water at their Heelat ar Rakah camp, a remote location some 900 km south of Muscat, the capital of Oman. The system comprises components for pre-treatment of pumped well water to separate hydrogen sulphide, acid dosing to correct the pH, cartridge filtration, a solar powered reverse osmosis unit, and a reject-water evaporation pond. The solar powered system comprises a 23.2 m² solar photovoltaic generator with a peak capacity of 3250 W_p, a boost charge battery of 200 Ah at 48 VDC, a charge controller, a sine-wave inverter of 3000 VA with an output of 230 V, 50 Hz, and necessary controls and instrumentation. The design water output of 5 m³/day during 5 h (of each day) was achieved, with the output sometimes exceeding 7.5 m³/day. The average cost of production is estimated at US$6.52/m³ over the 20-year lifetime of the equipment. The study has demonstrated that solar-powered reverse osmosis systems are particularly appropriate to remote locations that have limited or no access to supply services such as fuel, power or potable water.     

Characterization of plasticized PMMA-LiBF4 based solid polymer electrolytes

Polymer electrolyte films prepared from poly(methyl methacrylate) and LiBF₄ with different concentrations of plasticizer (DBP) are described. The formation of polymer-salt complex has been confirmed by FTIR spectral studies. The temperature dependence of conductivity of polymer films seems to obey the VTF relation. Values of conductivities of the polymer complexes are presented and discussed.     

Effect of ZrO2 on conductivity of PVC-PMMA-LiBF4-DBP polymer electrolytes

The preparation and characterization of composite polymer electrolytes of PVC-PMMA-LiBF₄-DBP for different concentrations of ZrO₂ have been investigated. FTIR studies indicate complex formation between the polymers, salt and plasticizer. The electrical conductivity values measured by a.c. impedance spectroscopy is found to depend upon the ZrO₂ concentration. The temperature dependence of the conductivity of the polymer films seems to obey the VTF relation. The conductivity values are presented and results discussed.     

Development and Initial Validation of Sustainable Construction Safety and Health Rating System

This paper presents a study to develop and validate a sustainable construction safety and health (SCSH) rating system. The rating system provides an opportunity to rate projects based on the importance given to construction worker safety and health and the degree of implementation of safety and health elements. A Delphi survey using an expert panel of 12 experienced safety and health professionals representing different sectors of the construction industry was employed to develop the SCSH rating system. The study resulted in a rating system consisting of a total of 50 safety and health elements organized into 13 categories. Each category contains safety and health elements which carry credits based on their effectiveness in preventing construction worker injuries and illnesses. The rating system was initially validated based on data from 25 construction projects and found to accurately represent the safety performance of large projects. The SCSH rating system can be used as an effective tool to develop and plan construction safety and health programs and evaluate the potential safety performance of construction projects.