Papers by Keyword: Structure Properties

Abstract: In this work, the preparation of cadmium telluride (CdTe) nanoparticles by aqueous solution method is presented. The preparation process was performed in the presence of an acidic agent (L-cys) at certain pH value. The x-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) of the prepared samples showed that poly crystalline structure with lowest particle size can be produced by controlling the period of heating process after the preparation step. Accordingly, this parameter can be used carefully to control the surface roughness of nanoscale CdTe samples to serve certain applications requiring some determined values of particle size and surface roughness.

Abstract: Lately, researchers have been considering the miscellaneous in the borophosphate crystalline’s luminescence as one of the important properties in hunt of the new functional material. In this study we discus the structural and luminescence properties of Eu^3+/Dy³⁺ co-doped borophosphate ceramic. A series of ceramic samples based on B₂O₃-(65-)P₂O₅-25MgO-10TeO₂ where (065) mol has successfully been prepared using solid state reaction method and sintered at 900°C. The crystalline phase of the powder samples was characterized using X-ray diffraction pattern. The diffraction patterns analysis indicated that the prepared samples were polycrystalline phase of B(PO₄), Mg(PO₃)₂and Mg(BO₃)(PO₄). The local structure network structure has been investigated using Infrared Spectroscopy using KBr method. The FT-Infrared spectra reveal the presence of B-O-B vibrations, BO₃ and BO₄ bridging oxygen and P-O stretching modes of P-O-P, P=O and PO₄ unit in the ceramics sample. Meanwhile, the luminescence properties of doped sample were measured based on analysis of emission spectra of photoluminescence spectroscopy. The emission peaks of Eu³⁺ doped sample were located at 593 nm, 613 nm, 652 nm, 685 nm due to the assigned transition ⁵D₀-⁷F_J ( J = 1, 2, 3, 4 )_. The Dy³⁺ emission is due to ⁴F_9/2 -⁵H_15/2 and ⁴F_9/2-⁶H_13/2 transition. For Eu^3+/Dy³⁺ co-doped sample consists of peaks belonging to the ⁴F_9/2-⁶H_15/2 (482 nm) and ⁴F_9/2-⁶H_13/2 (573 nm) transition while red emission ⁵D₀-⁷F₂ transitions appears at 611 nm. Improvement in the optical properties due to co-doping may be useful to discover a new highly efficient luminescent material that are very useful in optical devices and solid-state lighting.

Abstract: In this work, cotton was grafted with trifluoroethyl methacrylate (TFEMA) via atom transfer radical polymerization (ATRP) in water aqueous. The appearance of the cotton fabric was characterized with SEM, and SEM of the grafted cotton displayed significant difference from the ungrafted cotton. FT-IR indicated that TFEMA was successfully grafted onto surface of cotton fibers. Surface contact angle test and water repellency rating test showed that the water repellence of the modified cotton fabric were better than the ungrafted cotton fabric. Compared with the ungrafted cotton fabric, the whiteness, air permeability, breaking strength and elongation at break of the grafted cotton fabric decreased slightly. Grafted treatment led to efficient implantation of fluorine atoms on the surface of cotton fabric, this resulted in water repellence without altering the bulk properties of the cotton fabric.

Abstract: Strontium titanate (SrTiO₃) thin film has been deposited on Si (100) substrate using pulsed laser deposition technique. Film deposition was carried out at low temperature (150°C) by maintained the pressure at 10^-4 Torr. Nanometer-thick SrTiO₃ film on Si substrate was characterized using SEM, AFM, XRD, and Raman Spectroscopy. SEM and AFM images show that SrTiO₃ film has growth on Si substrate uniformly. Raman and XRD spectroscopy also support the growth of SrTiO₃ film on Si substrate. Furthermore, to investigate the effect of post-deposition thermal annealing, the samples were annealed up to 900°C. Thermal stability of SrTiO₃/Si structure was studied by mean XRD spectra. The X-Ray Diffraction pattern indicates the crystallinity improvement through atomic arrangements during thermal annealing process.

Abstract: Density Functional Theory method within Generalized Gradient Approximation has been performed to obtain the static lattice parameters, oxygen positional parameter, bond length and bond angle and electronic properties of ideal Dy2Sn2O7 pyrochlore. The results are in excellent agreement with available experimental measurements. DOS of this compound was presented and analyzed. We also notice the presence of the hybridization between oxygen and both Sn and Dy metal.

Abstract: The structure and magnetic properties of fcc-Fe/Cu (100) superlattices have been investigated by the first-principles total energy calculation based on density functional theory (DFT). Through the optimization of the structure of Fe/Cu superlattices, it has been found that the interlayer spacing of Cu layers is contracted while the interlayer spacing of Fe layers is expanded. There are no obviously changes of Fe/Cu interfaces for Fe3Cu3 and Fe3Cu5 models. The layer spacing for Fe3Cu5 changes larger than that of Fe3Cu3 model, which results to a slightly larger magnetic moment of FeCu5 than that of Fe3Cu3 model. We also analyze the density of state near the Fermi surface and calculate spin asymmetry factor of each layer in Fe/Cu systems. Based on the two-current model, we evaluate the magnetoresistance ratio 21.8% for Fe3Cu3 and 22.8 % for Fe3Cu5 system.

Abstract: Lanthanum modified lead zirconate titanate (PLZT) thin films were fabricated on indium doped tin oxide (ITO) - coated glass substrate by sol-gel method. The structure of the films was characterized with XRD and SEM. In the case of PLZT the dielectric function was modelled as a sum of Lorentzian oscillators and found by fitting the transmittance and reflectance spectra measured at normal incidence in the wavelength range of 220-2400 nm. The anomalous behaviour of dielectric function was observed below the absorption edge that was suggested to be due to formation of some defect states. The evolution of the absorption edge as well as dielectric function with film thickness was observed and discussed.