Taher Ghrib

Synthesis and characterization of ZnO/ZnS core/shell nanowires

ZnO nanowires of approximately 3 µm length and 200 nm diameter are prepared and implanted vertically on substrate glass which is coated with thin layer of ITO which is too covered with bulk ZnO thin layer via electrodeposition process by cyclic voltammetrychronoamperometry and with a chemical process that is described later; we have synthesized a ZnS nanolayer. ZnO/ZnS core/shell nanowires are formed by ZnO nanowires core surrounded by a very thin layer of porous ZnS shell principally constituted with a crystal which is about 15-20 nm in diameter. In the method, ZnS nanoparticles were prepared by reaction of ZnO nanowires with Na2S in aqueous solution at low temperature and also we have discussed the growth mechanism of ZnO/ZnS nanowires. The morphology, structure, and composition of the obtained nanostructures were obtained by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). For the structure, SEM and XRD measurements indicated that the as-grown ZnO nanowires microscale was of hexagonal wurtzite phase with a high crystalline quality, and TEM shows that the ZnS is uniformly distributed on the surface of the ZnO nanowires.

Microstructural and Thermal Properties of Porous Aluminum Filled with Nanocrystalline Silicon

In this work, the structural, thermal and optical properties of porous aluminum thin film carried out with various intensities of the anodization current in sulfuric acid. The obtained pores at the surface are filled by nanocrystalline silicon (nc-Si) thin films deposited by plasma enhancement chemical vapor deposition (PECVD), which the role is to improving its optical absorption and thermal properties. The prepared sample is an assembly of three different media such as Al sample/ Porous aluminum layer filled with silicon (PAS)/ nanocrystallite silicon layer (nc-Si). The effect of anodization current on the microstructure of porous aluminium and the effect of the deposited silicon layer were systematically studied by atomic force microscopy (AFM), X-ray diffraction (XRD) and Raman spectroscopy. The thermal properties such as the thermal conductivity (K) and thermal diffusivity (D) were determined by the photo-thermal deflection (PTD) technique, which is a non-destructive technique. Based on this full characterization, it is demonstrated that the thermal and optical characteristics of this films are directly correlated to their microstructural properties.

Thermal and Structural Study of Mono- and Multi-Layered Thin Films Composed of CuAlS2 Chalcogenide

Thin films constituted of CuAlS2 nanoparticles deposited with various deposition velocities in single and multilayers onto silicon Si(111) substrates by thermal evaporation have been studied by lifting their structural and thermal properties. Thermal properties of Si(111) and Si(111)/CuAlS2 structures are determined by using the photothermal deflection technique by comparing experimental and theoretical signals. We succeed in extracting the thermal conductivity, the thermal diffusivity, and the electron free mean path of these deposited chalcogenide layers. For the multilayers, the obtained values of the thermal conductivity are in good agreement with the theoretical data.

High Thermoelectric Figure of Merit of Ag 8 SnS 6 Component Prepared by Electrodeposition Technique

A new thermoelectric material Ag8SnS6, with ultra-low thermal conductivity in thin film shape, is prepared on indium tin oxide coated glass (ITO) substrates using a chemical process via the electrodeposition technique. The structural, thermal and electrical properties are studied and presented in detail, which demonstrate that the material is of semiconductor type, orthorhombic structure, with a band gap in the order of 1.56 eV and a free carrier concentration of 1.46 × 1017 cm−3. The thermal conductivity, thermal diffusivity, thermal conduction mode, Seebeck coefficient and electrical conductivity are determined using the photo-thermal deflection technique combined with the Boltzmann transport theory and Cahills model, showing that the Ag8SnS6 material has a low thermal conductivity of 3.8 Wm−1K−1, high electrical conductivity of 2.4 × 105 Sm−1, Seebeck coefficient of − 180 μVK−1 and a power factor of 6.9 mWK−2m−1, implying that it is more efficient than those obtained in recently experimental investigations for thermoelectric devices.

Effect of Annealing Process on Porous Aluminium Filled with Graphite

Thermal properties of porous thin films formed by anodization of thin aluminum films in sulfuric acid. The obtained pores at the surface are filled by sprayed graphite which the role is to improving its optical and thermal absorption giving a structure of an assembly of three different media such as graphite/(Porous aluminium layer filled with graphite)/(Al sample). The realized structure is annealed in temperature range varying from the room temperature to 650∫C for various durations. Thermal properties of the realized structure was studied by Photothermal Deflection (PTD) Technique and correlated to the microstructure evolution. It was found that this structure is characterised by thermal conductivity which, conversely to thermal diffusivity, increases with the heating duration and temperature in the furnace and can be used in solar energy field.

Correlation between Thermal and Mechanical Properties of the 10NiCr11

In this work we have studied the effect of the carburizing duration on the evolution of the thermal and mechanical properties of the 10NiCr11 steel. The thermal properties are determined by the photothermal deflection technique and it was shown that the thermal conductivity as well as the thermal diffusivity decrease with the carbon fraction in the steel unlike the Vickers hardness which increases. From this study we have established an empiric mathematical formula between Vickers hardness, the thermal properties, and the carburizing duration which permit to deduce the Vickers hardness value without needing to measure it.