Browsing by Subject "Cadmium alloys"

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    Charging/discharging dynamics of CdS and CdSe films under photoillumination using dynamic x-ray photoelectron spectroscopy
    (A I P Publishing LLC, 2010) Sezen, H.; Süzer, Şefik
    Thin films of CdS and CdSe are deposited on HF-cleaned Si O2 /Si substrates containing ∼5 nm thermally grown silicon oxide. x-ray photoelectron spectroscopy (XPS) data of these films are collected in a dynamic mode, which is based on recording the spectrum under modulation with an electrical signal in the form of ±10 V square-wave pulses. Accordingly, all peaks are twined and shifted with respect to the grounded spectrum. The binding energy difference between the twinned peaks of a dielectric system has a strong dependence on the frequency of the electrical stimuli. Therefore, dynamic XPS provides a means to extract additional properties of dielectric materials, such as effective resistance and capacitance. In this work, the authors report a new advancement to the previous method, where they now probe a photodynamic process. For this reason, photoillumination is introduced as an additional form of stimulus and used to investigate the combined optical and electrical response of the photoconductive thin films of CdS and CdSe using dynamic XPS.
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    ItemOpen Access
    Evaluate of braze joint strength and microstructure characterize of titanium-CP with Ag-based filler alloy
    (2012) Ganjeh, E.; Sarkhosh H.; Khorsand H.; Sabet H.; Dehkordi, E.H.; Ghaffari, M.
    This research investigates the influences of brazing parameters (temperature and time) on microstructures and the mechanical properties of commercially pure (CP) titanium sheet when it is brazed with CBS34 (Ag-20Cu-22Zn-24Cd) braze filler foil. Brazing was performed in a conventional atmosphere control furnace. The brazing temperatures and holding times employed in this study were 800-870°C and 10-20min, respectively. The qualities of the brazed joints were evaluated by ultrasonic test and the microstructure and phase constitution of the bonded joints were analyzed by means of metallography, scanning electron microscope (SEM) and X-ray diffraction (XRD). The mechanical properties of brazed joints were evaluated by microhardness and shear tests. The diffusion between Ti, Ag, Cu, Zn and Cd from substrate and braze alloy, developed a strong reaction between each other. A number of intermetallic phases, such as TiCu and Ti2Cu in the Ag-Zn solid solution matrix have been identified especially at 870°C - 20min. Both the brazing temperature and the holding time are critical factors for controlling the microstructure and hence the mechanical properties of the brazed joints. The optimum brazing parameters was achieved at 870°C - 20min. Based on the shear test result, all cracks propagate along the brittle intermetallic compounds like Ti2Cu in the reaction layer which typically are composed of quasi-cleavage (Ag-Zn matrix) and brittle appearance. © 2012 Elsevier Ltd.
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    ItemOpen Access
    Synthesis of stable mesostructured coupled semiconductor thin films: meso-CdS-TiO2 and meso-CdSe-TiO2
    (2010) Okur, H. İ.; Türker, Y.; Dag, Ö.
    Cd(II) ions can be incorporated into the channels of mesostructured titania films, using the evaporation-induced self-assembly (EISA) approach, up to a record high Cd/Ti mole ratio of 25%. The film samples were obtained by spin or dip coating from a mixture of 1-butanol, [Cd(H20)4] (N03)2, HNO3, and Ti(OC4H 9)4 and then aging the samples under 50% humidity at 30 0C (denoted as meso-xCd(II)-y TiO2). The nitrate ions, from nitric acid and cadmium nitrate, play important roles in the assembly process by coordinating as bidentate and bridged ligands to Cd(II) and Ti(IV) sites, respectively, in the mesostructured titania films. The film samples can be reacted under a H 2S (or H2Se) gas atmosphere to produce CdS (or CdSe) on the channel surface and/or pore walls. However, the presence of such a large number of nitrate ions in the film samples also yields an extensive amount of nitric acid upon H2S (or H2Se) reaction, where the nanoparticles are not stable (they undergo decomposition back to metal ion and H2S or H2Se gas). However, this problem can be overcome by further aging the samples at 130 °C for a few hours before H2S (or H2Se) reaction. This step removes about 90% of the nitrate ions, eliminates the nitric acid production step, and stabilizes the CdS nanoparticles on the surface and/or walls of the pores of the coupled semiconductor films, denoted as meso-xCdS-yTiO2. However, the H2Se reaction, additionally, needs to be carried at lower H2Se pressures in an N2 atmosphere to produce stable CdSe nanoparticles on the surface and/or walls of the pores of the films, denoted as meso-xCdSe-.yTiO2. Otherwise, an excessive number of Se8 particles form in the film samples.