Band 3, Heft 1

Polarization data characterize the corrosion behavior of a metal giving a quick estimate of corrosion current density icorr and corrosion potential Ecorr. These two characteristics determine the corrosion rate and position of the metal in galvanic series. The chosen system for the study is steel (SS304) in NaCl solution. In these studies, icorr and Ecorr of Butler-Volmer equation are obtained by fitting the full expression to experimental current vs potential data unlike the graphical method using Tafelslopes. MATLAB optimization tool box is utilized for this purpose. The novel optimization technique is explained for determining Ecorr and icorr

Durability is a major issue and has been the growing focus of research for the commercialization of polymer electrolyte fuel cells (PEFCs). Corrosion of carbon support is a key parameter as it triggers the Pt catalyst degradation and affects cell performance, which in turn affects the longevity of the cells. Herein, we describe a hybrid composite support of TiO 2 -nanowires and Multiwalled carbon nanotubes (MWCNTs) that offers resistance to corrosion under stressful operating conditions. Titania nanowireswhich have been shown to be more efficient and catalytically active than spherically shaped TiO 2 . TiO 2 -MWCNT composites are prepared through a hydrothermal method, followed by Pt deposition using a polyol method. Crystal structure, morphology, and oxidation state are examined through various characterization techniques. Electrochemical performance of TiO2-nanowire/MWCNT composite-supported Pt at various ratios of TiO 2 /MWCNT is assessed in PEFCs. Pt on support with optimum composition of TiO 2 -nanowires to MWCNTs exhibits fuel cell performance superior to Pt onMWCNTs. Accelerated stress testing (AST) between 1 and 1.5 V reveals that the designed catalyst on nanocomposite support possesses superior electrochemical activity and shows only 16% loss in catalytic activity in relation to 35% for Pt/MWCNTs even after 6000 potential cycles. Subsequently, the samples were characterized after AST to correlate the loss in fuel cell performance

Aluminum oxide films on SS 304 deposited by DC reactive magnetron sputtering technique were studied with respect to the composition of the sputter gas (Ar:O 2 ), gas pressure, substrate temperature, current etc. to achieve good insulating films with high corrosion resistance. The films were characterized by XRD and SEM techniques. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements were made under static conditions in order to evaluate the corrosion performance of the alumina-coated SS 304 for various immersion durations in 0.5 M and 1 M NaCl solution. Alumina-coated SS 304 has low corrosion value of 0.4550 and 1.1090MPY for 24 h immersion time in both solutions. The impedance plots for the alumina coated SS 304 in 1 M NaCl solution at different durations are slightly different to when compared to its immersion in 0.5 M NaCl solutions and are composed of two depressed semi circles. For the alumina coated film, the impedance spectrum decreased, when immersion time increased.

To enhance the energy density and power performance of supercapacitors, the rational design and synthesis of active electrode materials with hierarchical mesoporous structure is highly desired. In the present work, fabrication of high-performance hierarchical mesoporous WO 3 -MnO 2 composite nanostructures on carbon cloth substrate via a facile hydrothermal method is reported. By varying the content of MnO2 in the composite, different WO 3 -MnO 2 composite thin films are obtained. The formation of composite is confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. The Brunauer-Emmett-Teller (BET) analysis reveals maximum specific surface area of 153 m 2 g −1 . The optimized WO 3 -MnO 2 composite electrode demonstrates remarkable electrochemical performance with high specific capacitance of 657 F g −1 at a scan rate of 5 mV s −1 and superior longterm cycling stability (92% capacity retention over 2000 CV cycles). Furthermore, symmetric flexible solid-state supercapacitor based on WO 3 -MnO 2 electrodes has been fabricated. The device exhibits good electrochemical performance with maximum specific capacitance of 78 F g −1 at a scan rate of 5 mV s −1 and specific energy of 10.8 Wh kg −1 at a specific power of 0.65 kW kg −1 . The improved electrochemical performance could be ascribed to the unique combination of multivalence WO 3 and MnO 2 nanostructures and synergistic effect between them

Ce 0.8 Gd 0.2 O 2−δ (GDC) and Ce 0.8 Sm 0.2 O 2−δ (SDC) nanocrystalline materials are prepared by a solid state reaction method. The synthesized nano crystalline solid solutions have cubic fluorite structure as evident from XRD patterns. The materials are qualitatively analyzed by FTIR. The morphology, size and shape of grains etc. are identified from the SEM images. The grain size of GDC is smaller than that of SDC. The better morphology is obtained for GDC. Hence, this is electrically characterized. The activation energy is calculated from the slope of Arrhenius plot (showing variation of conductivity with temperature).