Search results for "Meta"

Modeling self-sustaining waves of exothermic dissolution in nanometric Ni-Al multilayers

2016

Abstract The self-sustained propagating reaction occurring in nanometric metallic multilayers was studied by means of molecular dynamics (MD) and numerical modeling. We focused on the phenomenon of the exothermic dissolution of one metallic reactant into the less refractory one, such as Ni into liquid Al. The exothermic character is directly related to a negative enthalpy of mixing. An analytical model based on the diffusion-limited dissolution [1] coupled with heat transfer was derived to account for the main aspects of the process. Together, several microscopic simulations were carried out. The first series were set up to obtain all the parameters governing the process, including the heat…

Pressure-induced insulator-to-metal transition in α-SnWO4

2016

In-situ high-pressure W L1 and L3 edges x-ray absorption and mid-infrared spectroscopies complemented by first-principles calculations suggest the existence of pressure- induced insulator-to-metal transition in α-SnWO4 in the range of 5-7 GPa. Its origin is explained by a symmetrization of metal-oxygen octahedra due to a strong interaction of Sn 5s, W 5d and O 2p states along the b-axis direction, leading to a collapse of the band gap.

Silicon Surface Passivation by ALD-Ga2O3: Thermal vs. Plasma-Enhanced Atomic Layer Deposition

2020

Silicon surface passivation by gallium oxide (Ga2O3) thin films deposited by thermal- and plasma-enhanced atomic layer deposition (ALD) over a broad temperature range from 75 °C to 350 °C is investigated. In addition, the role of oxidant (O3 or O-plasma) pulse lengths insufficient for saturated ALD-growth is studied. The material properties are analyzed including the quantification of the incorporated hydrogen. We find that oxidant dose pulses insufficient for saturation provide for both ALD methods generally better surface passivation. Furthermore, different Si surface pretreatments are compared (HF-last, chemically grown oxide, and thermal tunnel oxide). In contrast to previous reports, t…

Metallurgical Strategies for the Joining of Titanium Alloys with Steels

2018

MeV-energy Xe ion-induced damage in LiF: The contribution of electronic and nuclear stopping mechanisms

2016

The contribution of electronic and nuclear damage mechanisms in the modification of structure and micromechanical properties of LiF crystals irradiated with 52, 224, and 450 MeV Xe ions at fluences 1010–1014 ions cm−2 has been studied. The ion-induced formation of dislocations and hardening in LiF at fluences above 1010 ions cm−2 has been observed. The depth profiles of nanoindentation show a joint contribution of electronic excitation and nuclear (impact) mechanisms to the ion-induced hardening. The electronic excitation mechanism dominates in the major part of the ion range while the impact mechanism prevails in a narrow zone at the end of the ion range. The efficiency of hardening produc…

Tuning of interfacial perpendicular magnetic anisotropy and domain structures in magnetic thin film multilayers

2019

We investigate the magnetic domain structures and the perpendicular magnetic anisotropy (PMA) arising in CoFeB films interfaced with selected heavy metal (HM) layers with large spin Hall angles in HM/CoFeB/MgO (HM = W, Pt, Pd, W x Ta1−x ) stacks as a function of CoFeB thickness and composition for both as-deposited and annealed materials stacks. The coercivity and the anisotropy fields of annealed material stacks are higher than for the as-deposited stacks due to crystallisation of the ferromagnetic layer. Generally a critical thickness of MgO > 1 nm provides adequate oxide formation at the top interface as a requirement for the generation of PMA. We demonstrate that in stacks with Pt as th…

2020

Recent experiments have demonstrated the formation of free-standing Au monolayers by exposing the Au–Ag alloy to electron beam irradiation. Inspired by this discovery, we used semi-empirical effective medium theory simulations to investigate monolayer formation in 30 different binary metal alloys composed of late d-series metals such as Ni, Cu, Pd, Ag, Pt, and Au. In qualitative agreement with the experiment, we find that the beam energy required to dealloy Ag atoms from the Au–Ag alloy is smaller than the energy required to break the dealloyed Au monolayer. Our simulations suggest that a similar method could also be used to form Au monolayers from the Au–Cu alloy and Pt monolayers from Pt–…

Explosive crystallization in amorphous CuTi thin films: a molecular dynamics study

2019

Abstract Molecular dynamic simulation was used to study mechanism of self-propagating waves of explosive crystallization (devitrification) in the CuTi metallic glass. Processes in thin rectangular samples composed of one to two million atoms were simulated and compared with experimental data. It was shown that the nucleation of primary crystalline clusters occurs homogeneously due to spontaneous fluctuations of atomic structure; the clusters not

ABSOLUTE THERMOELECTRIC POWER OF Pb–Sn ALLOYS

2011

International audience; In this work, absolute thermoelectric power (ATP) of Pb, Sn, Pb-20 wt.% Sn, Pb-40 wt.% Sn, Pb-60 wt.% Sn, Pb-80 wt.% Sn are measured. Measurements are performed in a temperature gradient furnace from 20 degrees C to 500 degrees C, for both solid and liquid states. Temperatures are measured with T-type copper-constantan thermocouples, while voltage signal between copper electrodes of those thermocouples is recorded in order to calculate ATP of the sample metal.

The effects of thermal treatment on structural, morphological and optical properties of electrochemically deposited Bi2S3 thin films

2017

Abstract Thin films of bismuth sulfide (Bi 2 S 3 ) have been electrochemically deposited on indium–doped tin oxide substrates from aqueous solutions of Bi(NO 3 ) 3 , ethylene diamine tetraacetic acid (EDTA) and Na 2 S 2 O 3 . The structural properties of the films were characterized using X–ray diffraction and high–resolution transmission electron microscopy analyses. The film crystallizes in an orthorhombic structure of Bi 2 S 3 along with metallic bismuth. Thermal annealing of the prepared film in sulfur atmosphere improves its crystallinity and cohesion. The band gap values of the deposited film before and after annealing at 400 °C were found to be 1.28 and 1.33 eV, respectively.