Preferential Orientation Of Plane Research Articles

Vertical nanostructures thin films of CdS and CdTe using low temperatures GLAD

This research develops a distinct method for obtaining of thin films of CdS and CdTe with vertical nanostructure morphology grown at low temperatures on the substrate of about 100 °C, were obtained by RF sputtering and sublimation from a vapor effusion source, respectively, both methods were combined with the glancing angle deposition technique. The CdS thin film exhibited a hexagonal structure with preferential plane orientation (002) under compressive stress and a crystallite size of approximately 45 nm. The CdTe film showed a cubic Zinc-Blende structure with an expansive lattice of the unit cell and with preferential plane orientation (111). The size of the crystallites in CdTe was approximately 56 nm. Scanning electron microscopy showed porous nanocolumn structures with vertical nanorods with a width of approximately 16 nm for the CdS and 80 nm for the CdTe, respectively with thicknesses of approximately 335 nm for the CdS and 1330 nm for the CdTe. Using open-source software ImageJ obtained a porosity measurement of approximately 10.4% for CdS and 9.4% for CdTe, respectively. The bandgap energy of the CdS and CdTe thin films was 2.47 eV and 2.51 eV, respectively. The refractive index was 2.5 for CdS and 3.5 for CdTe, respectively. The Urbach energy of the CdS and CdTe was 146 meV and 62 meV respectively. Our results are optimal for possible applications in photovoltaic devices, especially in solar cells and flexible solar cells.

A facile microwave synthesis of rGO, ZrO2 and rGO–ZrO2 nanocomposite and their room temperature gas sensing properties

Microwave irradiation technique provides a simple and quick synthesis route for nanomaterials at controlled experimental conditions. In this view, nanostructures of rGO, ZrO2, and rGO–ZrO2 composite were synthesized using microwave synthesis technique. Herein, we experimented the preparation of rGO using optimized conditions using convection mode at 373 K in a commercial microwave oven. Structural properties revealed the formation of mixed phases of the orthorhombic and rhombohedral crystal structure of ZrO2. The preferential plane orientation was found to be in c-axis (002) for rGO–ZrO2 nanocomposite, which revealed the predominance of rGO in the nanocomposite. Morphology of the prepared nanostructures exhibited agglomerated sheets, denser nanograins and randomly aggregated nanosheets for rGO, ZrO2, and mixed nanocomposite respectively. Room temperature gas sensing properties of the prepared nanostructures were investigated and reported. rGO showed responses of 5.3 and 5.2 towards 200 ppm of trimethylamine (TMA) and methanol. ZrO2 nanostructure showed a response of 35 towards 200 ppm of ammonia with response–recovery times of 91 and 6 s.

Formic acid electrooxidation on carbon supported platinum catalyst with preferential plane orientation

Pt-based nanocatalysts supported on Vulcan XC-72R carbon, were prepared by water-in-oil microemulsion method, with addition of various amounts of HCl in the water phase. Polyethileneglycoldodecylether (BRIJ 30) was used as a surfactant, which influenced the Pt surface structure, along with HCl. Catalysts prepared with addition of 0, 15, 25 and 35 % of HCl during the synthesis, were electrochemically characterised in 0,5 M H2SO4 using cyclic voltammetry and CO oxidation. Formic acid electrooxidation was examined on all investigated catalysts, in terms of their electrocatalytic activity and stability. Platinum loading on carbon support was examined by Thermogravimetric analysis. Catalysts showed different features in hydrogen region, and slight differences in formic acid oxidation mechanisms.

Physical and chemical effects of CeF 3 compact in sliding against Hastelloy C in temperature to 700°C

The dependence of friction coefficient vs. temperature of Hastelloy C/CeF 3 compact was studied in the paper. The wear debris was studied by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Findings indicated that CeF 3 had physical and chemical effects in sliding at evaluated temperatures. The physical effects were known as preferential orientation, degree of crystallization and plastic deformation. The preferential orientation of plane (002) had a positive effect on friction reduction. The friction coefficients were low as the degrees of crystallization were high. The chemical effect was known as oxidation. The difference between static and sliding conditions was that the starting temperature of the former was higher than that of the latter. The cause was the temperature difference between the sliding surface and environment caused by frictional action. The oxidation of CeF 3 compact had a negative effect on its lubricity below 700°C since CeO 2 showed poor lubricity within the range of these temperatures. At 700°C, CeO 2 exhibited good friction-reducing, transferring and film-forming properties, which means the oxidation above 700°C may have a beneficial effect on friction reduction.

Thermal properties and tribological characteristics of CeF 3 compact

By studying the oxidation behavior of CeF 3 in air, a CeF 3 compact was prepared on a substrate and the structure is characterized in the paper. Effects of temperature, load and velocity on the sliding friction behavior of the compact were studied on a pin-on-disk tribometer. Findings indicated that the CeF 3 compact provided low friction in sliding against Hastelloy C between 400°C and 700°C at high velocity and low load. Analysis results suggested that preferential orientation of plane (002) and the oxidation of CeF 3 are the two factors that affect the friction-reducing property of CeF 3. Furthermore, the transfer film provided by CeF 3 compact provided Hastelloy C with minimized wear rate over the evaluated temperatures. All these suggested that CeF 3 can be used as solid lubricant for use from 400°C to 700°C.