Search results for "Metals"
showing 10 items of 2013 documents
Modelling of Pe C alloys solidification using the artificial heat source method
1997
Abstract In the paper the numerical solutions concerning the cast iron and also the carbon steel solidification are presented. In order to take into account the non-linearities appearing in differential equations describing the boundary-initial problem considered — a certain algorithm called the artificial heat source method has been used. The examples illustrating the possibilities of proposed method applications have been solved by means of the boundary element method, but the others numerical methods can be also utilized.
Influence of calcination on the structural properties of earth abundant Cu2ZnSnS4
2021
Abstract In the present work, we report on the synthesis of nano-crystalline kesterite copper zinc tin sulfide (CZTS) in powder form and the post-annealing process at high temperatures (calcination), and study their physical properties. We have successfully synthesized CZTS by direct fusion, and the resulting material was crushed to obtain a fine powder. Then, the resulting powder was calcined at high temperatures: 800–1000 ∘C. The calcined samples have been characterized with a number of different structural: X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and optical techniques: photoluminescence (PL), Raman and diffuse reflectance spectr…
Comparative study of air and vacuum annealing atmosphere towards Pt/Ti–W/SiO2 stability
2013
Abstract The thermal stability of Pt/Ti–W/SiO2 system was studied after annealing under air or vacuum in the present work. A Ti–W adhesive film (30 at. % Ti) was deposited on a SiO2 substrate followed by a thicker Pt layer. Depositions were performed using DC magnetron sputtering. The whole as-deposited films are metallic with a columnar growth of platinum deposit which totally wets the substrate. Whatever the atmosphere is, annealing at 500 °C for 12 h does not change the platinum state but modifies the morphology of platinum particles, the lateral average size of which increasing from less than 10 nm up to ca. 75 nm. Besides, a noticeable diffusion of metallic tungsten through Pt film is …
Oxidation of nanocrystalline aluminum by variable charge molecular dynamics
2010
International audience; We investigate the oxidation of nanocrystalline aluminum surfaces using molecular dynamics (MD) simulations with the variable charge model that allows charge dynamically transfer among atoms. The interaction potential between atoms is described by the electrostatic plus (Es+) potential model, which is composed of an embedded atom method potential and an electrostatic term. The simulations were performed from 300 to 750K on polycrystalline samples with a mean grain size of 5 nanometers. We mainly focused on the effect of the temperature parameter on the oxidation kinetic. The results show that, beyond a first linear regime, the kinetics follow a direct logarithmic law…
Growth and characterization of AP-MOCVD iron doped titanium dioxide thin films
1999
Abstract Atmospheric pressure metal organic chemical vapor deposition (AP-MOCVD) was used to prepare iron doped titanium dioxide thin films. Thin films, between 40 and 150 nm thick, were deposited on Si, SiO 2 and Al 2 O 3 substrates using titanium tetra isopropoxide and ferrocene as metal organic precursors. TiO 2 iron doping was achieved in the range of 1–4 at.%. The film morphology and thickness, polycrystalline texture and doping content were studied using respectively scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The influence of growth temperature, deposition time, substrate type and dopant partial pressure were studied. Electr…
Solid state bonding in extrusion and FSW: process mechanics and analogies
2006
Abstract The solid state bonding occurring in extrusion and in friction stir welding (FSW) processes is investigated through FEM models previously developed and validated. In particular, for the AA6082-T6 aluminum alloys, the most relevant field variables have been monitored and compared, such as strain, strain rate, effective stress and pressure. The aim of the research is the development of an effective FSW bonding criterion.
Soft X-ray emission spectroscopy used for the characterization of a-C and CNx thin films
2015
Abstract We present the results of a soft X-ray emission spectroscopy study of a-C and CNx films on a Si(100) substrate. Also for the characterization of the homogeneity in depth of these films electron energy loss spectroscopy measurements with localization better than 4 nm were carried out. In case of CNx films the highest diamond-like modification occurs in the region close to the Si(100) substrate. The film density decreases with increasing distance from the substrate and becomes almost constant in range of thicknesses more than ~ 2 nm.
Local structure in Ga1−xInxSe alloys
2021
Abstract In this work we study the local structure of layered G a 1 − x I n x S e alloys by means of X-ray Absorption. We complement our research with a Raman study. The available alloys have compositions close to the host binaries. The dependence of XANES (X-ray Near Edge Structure) features with synchrotron polarization clearly establishes the substitutional character of the alloying cations. Interstitial atoms, if present, remain under the detection limit of the technique. EXAFS (Extended X-ray Absorption Fine Structure) demonstrates the existence of G a − I n bonds in the alloys. The cation-anion bond-lengths in the alloys remain similar to that of the pure compounds. There is no signif…
SnO2 : Sb - A new material for high-temperature MEMS heater applications: Performance and limitations
2007
MEMS micro heater devices capable of long-term operation at temperatures up to 1000 degrees C are presented. The enhanced long-term stability has been achieved by employing antimony-doped tin oxide (SnO2:Sb) as a substitute for the conventionally used noble metal heater resistors. A detailed investigation of its high-temperature stability reveals that degradation is caused by out-diffusion of Sb impurities from the SnO2 film. (c) 2007 Elsevier B.V. All rights reserved.
Gas sensing properties of multiwall carbon nanotubes decorated with rhodium nanoparticles
2011
International audience; In the present work, multiwalled carbon nanotubes were decorated with rhodium nanoparticles using a colloidal solution in the post-discharge of an RF atmospheric plasma of argon (Ar) or argon/oxygen (Ar:O 2). The properties of these hybrid materials towards the room temperature detection of NO 2 , C 2 H 4 , CO, C 6 H 6 and moisture were investigated and discussed in view of compositional and morphological studies. It was found that the presence of oxygen in the plasma treatment is essential to significantly enhance the gas response of Rh-decorated multiwalled carbon nanotubes and to avoid response saturation even at low gas/vapor concentrations. These desirable effec…