Triple Band Dual Polarized CPW-Fed Planar Monopole Antenna

Wireless Personal Communications - This article presents a novel, simple and planar design of a CPW-fed tri-band and dual polarized monopole antenna. The proposed structure includes inverted...     

Austenite reversion in 18% Ni maraging steel and its weldments

In the heat-treated condition, 18% Ni maraging steels have a microstructure of aged martensite and essentially no austenite. However, austenite can form if the material is overaged. This has been termed as austenite reversion, a subject which has received much attention, because it importantly influences properties and performance of the steel. Reversion of austenite in fusion zones of weld joints in these steels has also been widely studied. Because of microsegregation, austenite reversion in the fusion zone is accelerated. Reverted austenite in the fusion zone strongly influences the performance of the weld joints. The present review critically analyses the published work on austenite reversion and its effects on properties and performance, covering both base metal and weld joints.     

Nanostructured SrTiO3 thin films sensitized by Cu2O for photoelectrochemical hydrogen generation

We prepared nanostructured thin films of pristine SrTiO₃, Cu₂O and SrTiO₃/Cu₂O heterojunction with varying the thickness of Cu₂O. SrTiO₃ and Cu₂O thin films were deposited on ITO (Sn:In₂O₃) glass substrate using sol–gel spin-coating technique and spray pyrolysis method respectively. Samples were characterized using XRD (X-ray diffractometry), SEM (Scanning electron microscopy), and UV–Visible absorption spectroscopy. Nanostructured thin films of pristine SrTiO₃, Cu₂O and SrTiO₃/Cu₂O heterojunction systems were used as photoelectrode in the Photoelectrochemical (PEC) cell for water splitting reaction. Maximum photocurrent density value of 2.44 mA cm⁻² at 0.95 V/SCE were observed for SrTiO₃/Cu₂O heterojunction photoelectrode with 454 nm thickness, which was approximately 34 times higher than pristine SrTiO₃ thin film. Increased photocurrent density observed for the heterojunction can be attributed to the improved conductivity and better separation of the photogenerated charge carriers at the SrTiO₃/Cu₂O interface.     

CdSe quantum dots sensitized nanoporous hematite for photoelectrochemical generation of hydrogen

A novel system of CdSe quantum dots (QDs) sensitized porous hematite (α-Fe₂O₃) films has been investigated as a potential photoelectrode for hydrogen generation via photoelectrochemical (PEC) splitting of water. Before sensitization, nanoporous hematite thin films were prepared by spray pyrolysis. Characterizations for crystalline phase formation, crystallite size, absorption spectra, and flatband potential were carried out to analyze PEC data. Loading time of sensitizer to hematite thin films was found to be crucial in affecting its PEC properties. Film having sensitizer loading time as 42 h exhibited best photocurrent density of 550 μA cm⁻² at 1.0 V versus SCE. Current study, for the first time, explores the possibility of using low band gap QDs sensitization on a low band gap film, hematite in PEC splitting of water.     

Naturally occurring neem gum: An unprecedented green resource for bioelectrochemical flexible energy storage device

Naturally available neem tree gum consisting of bioelectrolyte and bioelectrode was fabricated for flexible energy storage device. Structural morphology, thermal stability, porosity and surface area of as prepared bioelectrode were characterized thoroughly by using scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) isotherm respectively. The bioelectrolyte conductivity was optimized under various concentrations of lithium ion salts and temperatures through electrochemical impedance spectroscopy (EIS). A flexible supercapacitor (SCs) was fabricated by using bioelectrodes and electrolyte and tested for its electrochemical properties. The supercapacitor displayed specific capacitance of 640 Fg^-1 and 200 Fg^-1 at a current density 0.5 Ag^-1 and 1.0 V operating potential window. The energy device has also demonstrated large operational window (2.0 V) and shown 102 Fg^-1 at a current density of 1.0 Ag^-1. The novelty of the present work lies in the simplified, cost-effective procedure for preparation of biomaterials, their remarkably high stability under strong mechanical bent and long-term charging-discharging cycles of the fabricated device.     

Catalytic effect of carbon nanostructures on the hydrogen storage properties of MgH2–NaAlH4 composite

The present investigation describes the hydrogen storage properties of 2:1 molar ratio of MgH₂–NaAlH₄ composite. De/rehydrogenation study reveals that MgH₂–NaAlH₄ composite offers beneficial hydrogen storage characteristics as compared to pristine NaAlH₄ and MgH₂. To investigate the effect of carbon nanostructures (CNS) on the de/rehydrogenation behavior of MgH₂–NaAlH₄ composite, we have employed 2 wt.% CNS namely, single wall carbon nanotubes (SWCNT) and graphene nano sheets (GNS). It is found that the hydrogen storage behavior of composite gets improved by the addition of 2 wt.% CNS. In particular, catalytic effect of GNS + SWCNT improves the hydrogen storage behavior and cyclability of the composite. De/rehydrogenation experiments performed up to six cycles show loss of 1.50 wt.% and 0.84 wt.% hydrogen capacity in MgH₂–NaAlH₄ catalyzed with 2 wt.% SWCNT and 2 wt.% GNS respectively. On the other hand, the loss of hydrogen capacity after six rehydrogenation cycles in GNS + SWCNT (1.5 + 0.5) wt.% catalyzed MgH₂–NaAlH₄ is diminished to 0.45 wt.%.     

F.E.T. mixer with the drain l.o. injection

Performance of a 6/4 GHz frequency convertor showed conversion gains up to 4.7 dB with 3.9 dB noise figure. On cooling to 200 K, a gain increase of 2.4 dB and a noise-figure decrease of 1.8 dB were measured.