Search results for "pla"
showing 10 items of 51967 documents
Optimization of physicochemical and optical properties of nanocrystalline TiO 2 deposited on porous silicon by metal-organic chemical vapor depositio…
2020
International audience; Titanium dioxide (TiO2) is very employed in solar cells due to its interesting physicochemical and optical properties allowing high device performances. Considering the extension of applications in nanotechnologies, nanocrystalline TiO2 is very promising for nanoscale components. In this work, nanocrystalline TiO2 thin films were successfully deposited on porous silicon (PSi) by metal organic chemical vapor deposition (MOCVD) technique at temperature of 550°C for different periods of times: 5, 10 and 15 min. The objective was to optimize the physicochemical and optical properties of the TiO2/PSi films dedicated for photovoltaic application. The structural, morphologi…
The interdependence of structural and electrical properties in TiO2/TiO/Ti periodic multilayers
2013
International audience; Multilayered structures with 14-50 nm periods composed of titanium and two different titanium oxides, TiO and TiO2, were accurately produced by DC magnetron sputtering using the reactive gas pulsing process. The structure and composition of these periodic TiO2/TiO/Ti stacks were investigated by X-ray diffraction and transmission electronic microscopy techniques. Two crystalline phases, hexagonal close packed Ti and face centred cubic TiO, were identified in the metallic-rich sub-layers, whereas the oxygen-rich ones comprised a mixture of amorphous TiO2 and rutile phase. DC electrical resistivity rho measured for temperatures ranging from 300 to 500 K exhibited a meta…
Variable-charge method applied to study coupled grain boundary migration in the presence of oxygen
2009
International audience; One of the important differences between simulation and experiments in grain boundary (GB)-dominated metallic structures is the lack of impurities such as oxygen in computational samples. A modified variable-charge method [Elsener A, Politano O, Derlet PM, Van Swygenhoven H. Modell Simul Mater Sci Eng 2008;16:025006] based on the Streitz and Mintmire approach [Streitz FH, Mintmire JW. Phys Rev B 1994;50:11996] is used to study coupled GB motion in an Al bicrystal with a [1 1 2] symmetrical tilt GB in the presence of substitutional O, and compared with the stick–slip process identified by Cahn and Mishin [Cahn JW, Mishin Y, Suzuki A. Acta Mater 2006;54:4953]. It is found…
Nanoparticle dispersion in liquid metals by electromagnetically induced acoustic cavitation
2016
Abstract Aim of this study is to investigate experimentally the effect of magnetically induced cavitation applied for the purpose of nanoparticle dispersion in liquid metals. The oscillating magnetic force due to the azimuthal induction currents and the axial magnetic field excites power ultrasound in the sample. If the fields are sufficiently high then it is possible to achieve the acoustic cavitation threshold in liquid metals. Cavitation bubble collapses are known to create microscale jets with a potential to break nanoparticle agglomerates and disperse them. The samples are solidified under the contactless ultrasonic treatment and later analyzed by electron microscopy and energy-dispers…
Effect of Mn doping on the low-temperature synthesis of tricalcium phosphate (TCP) polymorphs
2019
Abstract Effect of Mn doping on the low-temperature synthesis of tricalcium phosphate (TCP) polymorphs was demonstrated in α- and β-TCP polymorphs prepared by wet precipitation method under identical conditions and annealed at 700 °C. Calcium phosphates with Mn doping level in the range from 1 to 5 mol% were studied and the formation of desired polymorph was controlled by varying Mn content in as-prepared precipitates. It was found that increasing Mn content resulted in the formation of β-TCP, while α-TCP was obtained with low Mn doping level, whereas a mixture of two polymorphs was obtained for intermediate Mn concentrations. Moreover, doping with Mn ions allowed the synthesis of β-TCP at …
Reactive Sintering of molybdenum disilicide by Spark Plasma Sintering from mechanically activated powder mixtures: Processing parameters and properti…
2008
Abstract Dense molybdenum disilicide with a nano-organized microstructure was synthesized by mechanical activation, by producing nanostructured agglomerates of a 1:2 mixture of Mo and Si, followed by the synthesis/consolidation in one step using SPS technology. In order to synthesize a dense molybdenum disilicide with a perfectly controlled microstructure, an investigation of the influence of Spark Plasma Sintering processing parameters (temperature, heating rate, mechanical pressure and holding time) on the chemical composition and the microstructure characteristics has been performed. The present work shows also that the so-obtained materials present better oxidation resistance in compari…
Nucleation of GaN nanowires grown by plasma-assisted molecular beam epitaxy: The effect of temperature
2011
Abstract The growth of GaN nanowires by means of plasma assisted molecular beam epitaxy directly on Si(1 1 1) has been investigated as a function of temperature. Statistical analysis of scanning electron microscopy pictures taken for different growth temperatures has revealed that density, diameter, length and length dispersion of nanowires were strongly dependent on temperature. Length dispersion, in particular, was found to be significant at high temperature. These features have been assigned to the different duration of the nucleation process with temperature, namely to the dependence with temperature of the time necessary for the size increase of the three-dimensional precursors up to a…
Evaluation of nano/submicro pores in suspension plasma sprayed YSZ coatings
2019
Abstract Nano-submicro pores could considerably influence the coating performances and thus should be properly designed for the intended applications. However, it is challenging to characterize accurately such small pores in coatings. In this study, YSZ coatings were firstly manufactured by suspension plasma spray (SPS) and the nano-submicro pores in as-prepared coatings were investigated using Ultra-small-angle X-ray scattering (USAXS). Afterwards, a multivariate analysis on the effect of five different process parameters was carried out. The two main results showed that: 1) the nano-submicro pores content in coatings has a negative correlation with suspension mass load and powder size, an…
Quartz resonators for penning traps toward mass spectrometry on the heaviest ions
2020
We report on cyclotron frequency measurements on trapped 206,207Pb+ ions by means of the non-destructive Fourier-transform ion-cyclotron-resonance technique at room temperature. In a proof-of-principle experiment using a quartz crystal instead of a coil as a resonator, we have alternately carried out cyclotron frequency measurements for 206Pb+ and 207Pb+ with the sideband coupling method to obtain 21 cyclotron-frequency ratios with a statistical uncertainty of 6 × 10−7. The mean frequency ratio R¯ deviates by about 2σ from the value deduced from the masses reported in the latest Atomic Mass Evaluation. We anticipate that this shift is due to the ion–ion interaction between the simultaneousl…
HCl gas gettering of low-cost silicon
2013
HCl gas gettering is a cheap and simple technique to reduce transition metal concentrations in silicon. It is attractive especially for low-cost silicon materials like upgraded metallurgical grade (UMG) silicon, which usually contain 3d transition metals in high concentrations. Etching of silicon by HCl gas occurs during HCl gas gettering above a certain onset temperature. The etching rate as well as the gettering efficiency was experimentally determined as a function of the gettering temperature, using UMG silicon wafers. The activation energy of the etching reaction by HCl gas was calculated from the obtained data. The gettering efficiency was determined by analyzing Ni as a representativ…