Effect of post weld heat treatment on the microstructure and tensile properties of dissimilar friction stir welded AA 2219 and AA 6061 alloys

In the present work, the effect of post weld heat treatment on the microstructure and mechanical properties of dissimilar friction stir weldments of Al alloys 6061and 2219 (in peak aged T6 temper) was investigated. The survey of microhardness profile in the as-welded samples showed fluctuations across the weld zone and a minimum in the hardness occurred in the heat affected zone (HAZ) of alloy 6061. After a post weld ageing treatment at 165°C for 18h, the hardness was found to increase in weld zone alone and there is no effective improvement in HAZ hardness. On the other hand, a post weld solution treatment at 520°C followed by ageing at 165°C for 18h resulted in significant improvement in hardness across the whole weldment. This is also reflected in the tensile strength of the joint. These results were correlated with microstructures, observed using optical, scanning and transmission electron microscopes.     

Enhanced Solar-Radiation Induced Photocatalytic Activity of Surface-Modified Nanocrystalline Anatase-Titania

Sol-gel derived pure nanocrystalline (~20–30 nm) anatase-titania has been surface-modified by depositing silver(I) oxide and silver (predominantly the former) via UV-reduction process. The pure and surface-modified nanocrystalline anatase-titania have been characterized using different analytical techniques for determining the average nanocrystallite size, phase-contents, surface-chemistry, as well as the absorption and photoluminescence characteristics. It is demonstrated that, the latter exhibits an enhanced solar-radiation induced photocatalytic activity as compared to that of the former as a result of the absorption in the visible-region and enhanced photo-induced e^?/h⁺ life-time, both caused by the surface-deposition of silver(I) oxide and silver.     

Synthesis, electrical and magnetic characterization of core-shell silicon carbo-nitride coated carbon nanotubes

We demonstrate synthesis, electrical and magnetic characterization of silicon carbo-nitride (SiCN) coated multiwalled carbon nanotubes in a core-shell structure. The core formed by a carbon nanotube had a diameter in the range of 10-100 nm. The shell was synthesized by pyrolysis of an SiCN precursor on the surface of carbon nanotubes. Electrical resistivity of an individual composite nanotube was measured to be ~ 2.55 × 10³ Ω cm. The magnetic measurements performed by a superconducting quantum interference device on the composite nanotubes in the temperature range of 5-300 K show a reduced coercive field with increasing temperatures. The monolayer thick coating of an ultra high temperature multifunctional ceramic SiCN makes these composite nanotubes very promising for sensing applications in harsh environments.     

Improved performance of iron-based redox flow batteries using WO3 nanoparticles decorated graphite felt electrode

Iron flow batteries are having tremendous attraction because of their economic feasibility and environmentally favorable electrolytes. Electrode and electrolyte used in iron-based redox flow batteries (IRFBs) have a vital role in the performances of electrochemical energy storage devices. Therefore designing a suitable electrode and optimization of electrolyte composition is highly needed. Graphite is one of the appropriate electrodes used in flow batteries but they have to be modified to improve the electrical performance. Here, for the first time, WO₃ nanoparticles (WONs) were used to modify graphite felt electrode for IRFBs applications. The effect of loading mass per unit cm² of electrochemically active material has been investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (Tafel) studies. The ligand based iron-electrolyte along with anion exchange membrane has been selected for the studies. The performance of the modified graphite felt electrode (3 mg/cm²) assembled in 132 cm² cell results in a peak power density of 53 mW/cm² at 40 mA/cm². This study provides information about the improvement in the electrochemical performance of IRFBs.