Effect of coumarin concentration on the physical properties of CdO nanostructures

Cataloged from PDF version of article.In this work, nanostructured CdO films with different coumarin contents in the growth solution were fabricated on glass substrates by the SILAR method. The effects of coumarin content in the bath on optical, structural and morphological properties were studied by means of (UV–vis) spectrophotometer, SEM and XRD analysis. The analysis showed that the band gaps, surface morphologies and XRD peak intensities of the CdO films were found to change with coumarin content. A change in the band gap energy can be attributed to the improvement in crystallinity of the samples. XRD analysis showed that, the films have poly-crystalline structures with decent crystallinity levels

Thermal expansion and Vickers hardness measurements on Bi1.6Pb0.4Sr2Ca2-xSmxCu3Oy superconductors

Ozturk, Ozgur/0000-0002-0391-5551WOS: 000239286300004In this work, Bi1.6Pb0.4Sr2Ca2-SmxCu3Oy (x = 0.0000, 0.0005, 0.0010, 0.0050, 0.0100, 0.1000, 0.5000, 1.0000, 1.5000) superconductors were prepared by conventional solid-state reaction method. The effect of the substitution of Sm for Ca in the high-T-c phase Bi-2223 was investigated by DTA, thermal expansion coefficient, Vickers microhardness, XRD and SEM analysis. The lattice constants and volume fractions are estimated from XRD analysis. The thermal expansion coefficient, the microhardness, the volume fraction, and the lattice constants strongly depend on the Sm content of the samples. XRD data show that the high-Tc phase decreases and the low-T-c phase increase as the Sm substitution changes from x = 0.0 to 1.5. The coefficients of thermal expansion (in the range of 30-800 degrees C) of the pure (x = 0.0) and high doped (x = 1.5) samples were 7.90 x 10(-7) and 5.70 x 10-7 degrees C-1, respectively. The results of Vickers hardness measurements varied between 0.254 and 0.623 GPa as increasing the Sm concentration. (c) 2006 Elsevier B.V. All rights reserved

Journal of Physics Conference Series

We investigated the effect of cooling rates on the microstructure and mechanical properties of Bi(1,6)Pb(0,4)Sr(2)Ca(2)Cu(3)Oy superconductors prepared by standard solid state reaction methods. The samples were annealed under identical condition and cooled with different cooling rates. The investigations consisted of Vickers microhardness, SEM and XRD measurements. XRD examination of the samples showed that high percentage of Bi-2212 phase was observed and low-T(c) phase increased with increasing the cooling rates. From SEM analysis, flake-like grains were more pronounced with increasing cooling rates. The indentation load versus diagonal length of the samples under different indentation loads in the range of 0.245-2.940 N were presented. We calculated Vickers hardness, Young's modulus, yield strength, fracture toughness values. These mechanical properties of the samples were found to be load and cooling rate dependent. In addition, we calculated the load independent microhardness, Young's modulus, and yield strength and fracture toughness of the samples using different models. The possible reasons for the observed changes in microstructure and mechanical properties of the samples due to cooling rates were discussed

Effects of thermal oxidation temperature on vacuum evaporated tin dioxide film

WOS: 000301765700013In order to investigate the effect of thermal oxidation temperature on tin dioxide (SnO2), tin dioxide films were obtained on quartz substrates by vacuum evaporation of tin metal. The films were characterized by X-ray diffraction (XRD) analyses, scanning electron microscopy (SEM), temperature dependent electrical resistivity measurement and optical absorption spectroscopy. The SEM images showed that the films are dense, continuous and are composed of nanoparticles and particle sizes are increased after thermal oxidation. From the X-ray measurement results, the films indicated two strong reflection peaks of tetragonal structure in the orientations of (101) and (200) at 20 = 33.8 degrees and 37.95 degrees, respectively. Intensity of the peaks increased with increasing thermal oxidation temperature. We found resistivity values of about 10(-4) Omega-cm. Optical absorption spectra of the films in the UV-Vis spectral range revealed that optical band gap (E-g) value of the films increases with increasing thermal oxidation temperature. (C) 2012 Elsevier Ltd. All rights reserved.Scientific Research Commission of Mustafa Kemal UniversityMustafa Kemal University [1001 M 0115]This work was supported by Scientific Research Commission of Mustafa Kemal University (Project No: 1001 M 0115)

Hardness Behavior of Alumina-Zirconia Nanocomposites Synthesized by Gel Process

The alumina-zirconia composites are one of the relatively good and promising candidates for biomaterials application, due to biocompatibility and their mechanical properties that combines high flexural strength with a high toughness. The aim of the present work is to analyze the mechanical properties of these composites, where zirconia content was varied from 5 to 50 wt%. The citrate gel method, similar to the polymerized complex method, was used to synthesize these ceramics. Scanning electron microscopy, X-ray diffraction and microhardness tests are used to characterize synthesized materials. The examined material exhibits the behaviour of indentation size effect. Modified proportional resistance model are used to analyze the load dependence of the microhardness. X-ray diffraction analysis was used to calculation of the grain size and dislocation density. It is found that hardness is decreased when the zirconia content increases with enlargement of grain size

Mechanical Properties of Nanocrystalline Tetragonal Zirconia Stabilized with CaO, MgO and Y2O3Y_2O_3

The citrate gel method, similar to the polymerized complex method, was used to synthesize homogeneous tetragonal zirconia at 1000°C. Nanocrystalline tetragonal phase has been fully stabilized at wide temperature range with 10 mol.% CaO, MgO, and $Y_2O_3$ addition. Scanning electron microscopy, X-ray diffraction, and microhardness tests are used to characterize synthesized materials. The grain size and dislocation density were calculated from X-ray diffraction data. The examined material exhibits indentation size effect behavior. Results revealed that the Vickers and Knoop microhardness are dependent on indentation test load. Geometrically necessary dislocation model and modified proportional resistance model are used to analyze the load dependence of the microhardness. The highest hardness values were obtained for the samples with CaO addition; however the lowest values were acquired for sample stabilized with $Y_2O_3$ by using both Knoop and Vickers techniques. This situation might be explained using the Hall-Petch relation