Conducting carbon/polymer composites as a catalyst support for proton exchange membrane fuel cells

Carbon/poly(3,4‐ethylene dioxythiophene) (C/PEDOT) composites are synthesized by in situ chemical oxidative polymerization of EDOT monomer on carbon black in order to decrease carbon corrosion that occurred in carbon‐supported catalysts used in proton exchange membrane fuel cell. The effects of different dopants including polystyrene sulfonic acid, p‐toluenesulfonic acid and camphorsulfonic acid with the addition of ethylene glycol or dimethyl sulfoxide on the properties of the composites are investigated. The synthesized composites are characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, surface area analysis and scanning electron microscope. Electrical conductivity is determined by using the four‐point probe technique. Electrochemical oxidation characteristics of the synthesized C/PEDOT composites are investigated by cyclic voltammetry by applying 1.2 V for 24 h. The composite prepared at 25 °C with p‐toluenesulfonic acid and ethylene glycol shows the best carbon corrosion resistance. Platinum‐supported catalyst by using this composite was prepared using microwave irradiation technique, and it was seen that the prepared catalyst did not significantly lose its hydrogen oxidation and oxygen reduction reaction activities after electrochemical oxidation. Copyright © 2013 John Wiley & Sons, Ltd.     

The morphology and corrosion resistance of electrodeposited Co‐TiO2 nanocomposite coatings

Co‐TiO₂ nanocomposite coatings with various contents of TiO₂ nanoparticles were prepared by electrodeposition in Co sulfate plating bath containing TiO₂ nanoparticles. The influence of the TiO₂ nanoparticles concentration in the bath, of the current density and of sodium dodecyle sulfate (SDS) as anionic surfactant on the morphology, composition, texture, roughness, and microhardness of the coatings was investigated. The morphology and composition of coatings were studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The phase structure of coatings was analyzed by X‐ray diffraction (XRD). The results showed that the maximum codeposition of TiO₂ nanoparticles in Co matrix was around 4.5 vol% obtained in 60 g/L TiO₂ in the bath, 30 mA/cm² and 0.15 g/L SDS. The microhardness of coatings was increased up to 504 Hv by increasing TiO₂ concentration in the bath to 60 g/L TiO₂. The electrochemistry tests including potentiodynamic polarization and impedance spectroscopy revealed that by addition of TiO₂ into Co matrix, the corrosion current density, polarization resistance, and charge transfer resistance of Co‐TiO₂ coating were increased compared with Co coating.     

The effect of Acetobacter sp. and a sulfate-reducing bacterial consortium from ethanol fuel environments on fatigue crack propagation in pipeline and storage tank steels

This paper evaluates the effects of microbiologically influenced corrosion (MIC) on fatigue-crack growth of candidate materials useful in expanding bio-ethanol usage, including a storage-tank steel (ASTM A36) and two pipeline steels (API 5L X52 and X70). The microbiological species sampled and cultivated from an ethanol fuel production stream are responsible for both acetic acid and hydrogen sulfide production that lead to significant increases in fatigue-crack growth rate across a wide range of stress-intensity-factor amplitudes (ΔK). The mechanism for increased fatigue damage is hydrogen uptake through adsorption into the steel, which embrittles material ahead of the growing fatigue crack.     

Thermal expansion behavior,microhardness and electrochemical corrosion resistance properties of Au52Cu27Ag17–x(NiZn0.5)x alloys

The thermal expansion behavior, microhardness and electrochemical corrosion resistance of Au₅₂Cu₂₇Ag_17–x(NiZn_0.5)_x (x=0, 6 and 12) alloys were investigated by dilatometer (DIL), microhardness tester, electrochemical workstation, X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). With increasing x, the relative length expansion and DIL maximum temperature T_{l m} (i.e., thermal stability) of the alloys increase in thermal expansion measurements, which can be explained by the change of the atomic binding energy, mismatch entropy together with phase transformation. With the increase of x, the microhardness can be improved, but the corrosion resistance decreases; in addition, the anodic peak current densities of polarization curves decrease, which are related closely with the solid solution degree and dissolution of Ag, Ni and Zn alloying elements in Cl⁻-containing solution.     

Preparation of the Sb-containing purple conversion coating on brass

A new chemical method for preparing a purple conversion coating on brass was developed. The effect of antimonous oxide concentration and temperature on color and corrosion resistance of the conversion coating, and the change of electric potential with time on coating forming process were studied. The optimum technological conditions were 10?g/L antimonous oxide, 20?g/L copper acetate, 200?mL/L hydrochloric acid at 65°C for 3?min. Results of electrochemical and dropping experiments showed that the brass with purple conversion coating presents better corrosion resistance than bare brass. The scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) results showed that the conversion coating mainly comprising copper and antimony was uniform and compact.     

Effects of environmental factors on corrosion behavior of aluminum

Aluminum, used as a material for heat exchangers in air conditioners, often has problems of leakage of refrigerant on the Al surface due to corrosion. The problems originate from pitting corrosion of the Al in an external environment. To understand corrosion problems, it is necessary to study the corrosion behavior of Al in various environments. In this study, the effects of environmental factors on the corrosion behavior of Al were studied by the surface analysis and electrochemical testing in 3.5 wt% NaCl solutions, with changes of dissolved oxygen, temperature, and concentration of Cl⁻ and S ions. Among the external environmental factors, the presence of oxygen and the increase of Cl⁻ ion concentration do not significantly affect the corrosion potential of Al, leading to an increase of only 1.1 and 6 times, respectively. There was a significant decrease in the corrosion resistance of Al, approximately 40 and 800 times, respectively, with the increase of concentration of S and temperature.