• A S ABOUHASWA

      Articles written in Bulletin of Materials Science

    • Crystal structure, optical and electrical characteristics of rutile TiO₂ nanocrystallite-based photoanodes doped with GeO₂

      A S ABOUHASWA A A EL-HAMALAWY Y S RAMMAH

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      The effect of germanium dioxide, GeO₂ doping on dye-sensitized solar cell (DSSC) TiO₂ nanocrystallite photoanodes with composition (TiO₂–(GeO₂)_{$x$} :0 ≤ $x$ ≤ 0.3 wt%) has been studied. The pure sample and GeO₂-doped samples have been synthesized by a conventional solid-state reaction method and analysed by means of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and ultraviolet–visible spectroscopy techniques. The photovoltaic characteristics of the prepared samples have been studied by employing $J–V$ measurements. The pattern of XRD depicted that the dominating phase in the sample with $x$ = 0 is a rutile tetragonal phase with the P4₂/$mnm$ space group. An increase in GeO₂ concentration leads to an appearance and rise of another hexagonal phase structure of α-GeO₂ with the P3₂21 space group. Data obtained from the UV–visible spectroscopy measurements reflect that the optical energy gap ($E$^{optical}) increases with increasing GeO₂ content, while the optical refractive index decreases. $J–V$ photovoltaic characteristics confirm that the DSSCs doped with low-concentration doping, $x$ = 0.05 and 0.1 of GeO₂ have higher values for conversion efficiency (η), fill factor and short circuit current density ($J$_{sc}) compared with samples with high-concentration doping ($x$ = 0.2 and 0.3) of GeO₂. The present results showed that TiO₂–(GeO₂)_{$x$} ($x$ = 0.05 and 0.1 wt%) films are potential candidates for optical filter materials and optoelectrical and photo-conversion energy devices.

    • Effect of WO$_3$ nanoparticle doping on the physical properties of PVC polymer

      A M A HENAISH A S ABOUHASWA

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      Poly(vinyl chloride)/tungsten oxide (PVC/WO$_3$) nanocomposite films were synthesized with different ratio of WO$_3$ content (0, 0.05, 0.1, 0.2 and 0.3 wt%). The sol–gel method was used to prepare WO$_3$ nanoparticles (NPs). X-ray diffraction and scanning electron microscope techniques confirmed that the WO$_3$ NPs were successfully dispersed in a PVC matrix with a single-phase structure. Characteristic absorption bands were observed in infrared spectra for pure PVC and nanocomposites. The morphology of WO$_3$ was observed using transmission electron microscope. The optical energy band gaps ($E_{\rm opt}$; direct and indirect) were estimated by using Tauc’s formula. It was found that the direct band gap energies decreased from 5.15 to 4.53 eV and the indirect bands decreased from 4.8 to 4.1 eV as WO$_3$ doping increased, while the Urbach energy ($E_{\rm u}$) increased as WO$_3$ content increased. It was found that the steepness parameter decreased, which confirms the formation of localized states in the band gap and increasing disorder in PVC polymer samples. The dielectric constant ($\epsilon'$) of the PVC/WO$_3$ nanocomposite films decreased as frequency increased. At a low frequency region, the loss factor ($\epsilon''$) has a high value and then sharply decreased as frequency increased, reaching a frequency independent region at high frequency values. The obtained data are very useful for using the investigated samples (PVC/WO$_3$) as the cores of high frequency transformers with very low dielectric loss.

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    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
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      Posted on July 25, 2019

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