A systematic neutron reflectometry study on hydrogen absorption in thin Mg1-xAlx alloy films Special issue on Neutron Scattering in Canada.

2010 ◽  
Vol 88 (10) ◽  
pp. 723-728 ◽  
Author(s):  
H. Fritzsche ◽  
E. Poirier ◽  
J. Haagsma ◽  
C. Ophus ◽  
E. Luber ◽  
...  
Keyword(s):  
Hydrogen Absorption ◽  
Scattering Length ◽  
Catalyst Layer ◽  
Neutron Reflectometry ◽  
Hydrogen Distribution ◽  
Hydrogen Atoms ◽  
Alloy Films ◽  
Negative Scattering Length ◽  
Insight Into ◽  
Optimum Alloy

In this article, we show how neutron reflectometry (NR) can provide deep insight into the absorption and desorption properties of commercially promising hydrogen storage materials. NR benefits from the large negative scattering length of hydrogen atoms, which changes the reflectivity curve substantially, so that NR can determine not only the total amount of stored hydrogen but also the hydrogen distribution along the film normal, with nanometer resolution. To use NR, the samples must have smooth surfaces, and the film thickness should range between 10 and 200 nm. We performed a systematic study on thin Mg1–xAlx alloy films (x = 0.2, 0.3, 0.4, 0.67) capped with a Pd catalyst layer. Our NR experiments showed that Mg0.7Al0.3 is the optimum alloy composition with the highest amount of stored hydrogen and the lowest desorption temperature. All the thin films expand by about 20% because of hydrogen absorption, and the hydrogen is stored only in the MgAl layer with no hydrogen content in the Pd layer.

BOSE-EINSTEIN CONDENSATION OF ATOMS WITH ATTRACTIVE INTERACTION

1999 ◽  
Vol 13 (05n06) ◽  
pp. 625-631 ◽  
Author(s):  
N. AKHMEDIEV ◽  
M. P. DAS ◽  
A. V. VAGOV
Keyword(s):  
Statistical Physics ◽  
Scattering Length ◽  
Stationary Solutions ◽  
Attractive Potential ◽  
Einstein Condensation ◽  
Pitaevskii Equation ◽  
Bose Einstein Condensation ◽  
Three Body ◽  
Negative Scattering Length ◽  
Bose Einstein

We suggest that crucial effect on Bose-Einstein condensation in systems with attractive potential is three-body interaction. We investigate stationary solutions of the Gross-Pitaevskii equation with negative scattering length and a higher-order stabilising term in presence of an external parabolic potential. Stability properties of the condensate are similar to those for thermodynamic systems in statistical physics which have first order phase transitions. We have shown that there are three possible type of stationary solutions corresponding to stable, metastable and unstable phases. Results are discussed in relation to recently observed 7 Li condensate.

scholarly journals Bose-Einstein Condensation of Confined Atomic Gases at Ultra Low Temperatures

2017 ◽  
Vol 9 (5) ◽  
pp. 96
Author(s):  
M. Serhan
Keyword(s):  
Low Temperatures ◽  
Chemical Potential ◽  
Scattering Length ◽  
Einstein Condensation ◽  
Pitaevskii Equation ◽  
Atomic Gases ◽  
Bose Einstein Condensation ◽  
Gaussian Type ◽  
Negative Scattering Length ◽  
Bose Einstein

In this work I solve the Gross-Pitaevskii equation describing an atomic gas confined in an isotropic harmonic trap by introducing a variational wavefunction of Gaussian type. The chemical potential of the system is calculated and the solutions are discussed in the weakly and strongly interacting regimes. For the attractive system with negative scattering length the maximum number of atoms that can be put in the condensate without collapse begins is calculated.

Coupled Diffusion-Mechanical Model of NiTi Alloys Accounting for Hydrogen Diffusion and Ageing

2020 ◽  
Vol 12 (04) ◽  
pp. 2050039
Author(s):  
Wissem Elkhal Letaief ◽  
Tarek Hassine ◽  
Fehmi Gamaoun ◽  
Riheme Sarraj ◽  
Nabil Ben Kahla
Keyword(s):  
Shape Memory ◽  
Hydrogen Diffusion ◽  
Chemical Potential ◽  
Coupled Model ◽  
Transformation Strain ◽  
Hydrogen Desorption ◽  
Hydrogen Distribution ◽  
Hydrogen Atoms ◽  
Finite Element Software ◽  
Coupled Diffusion

Certain shape memory alloys (SMAs) are considered to be good absorbents of hydrogen atoms (e.g., NiTi). However, upon the absorption of hydrogen atoms, SMAs exhibit deteriorated effects of superelasticity and shape memory mechanisms. In this paper, we have developed a coupled model, based on experimental results, that demonstrates the effects of hydrogen diffusion on NiTi SMAs. The proposed model has been derived thermodynamically while appending the chemical potential of hydrogen to the energy balance law. The effects of hydrogen distribution on the mechanical behavior have been taken into consideration to simulate the ageing effects. Moreover, the model considers the saturation of transformation stress, the preservation of the transformation strain of the hydrogen-induced residual martensite and the recovery of superelasticity after hydrogen desorption. The model has been simulated by means of UMAT and UMATHT subroutines and ABAQUS finite-element software. The numerical results indicate a strong agreement with the experimental ones.

Dependence of the scattering length for hydrogen atoms on effective mass

2009 ◽  
Vol 56 (2) ◽  
pp. 181-188 ◽  
Author(s):  
M. J. Jamieson ◽  
A. S.C. Cheung ◽  
H. Ouerdane
Keyword(s):  
Effective Mass ◽  
Scattering Length ◽  
Hydrogen Atoms

scholarly journals Room-temperature sensing performance of hydrogen using palladium-based film by optical setup

2020 ◽  
Vol 50 (4) ◽  
Author(s):  
_ Yiyun Yao ◽  
Alain J. Corso ◽  
Marco Bazzan ◽  
Enrico Tessarolo ◽  
Zhanshan Wang ◽  
...  
Keyword(s):  
Lattice Constant ◽  
Room Temperature ◽  
Temperature Sensing ◽  
The Other ◽  
Hydrogen Atoms ◽  
Alloy Films ◽  
Sensitivity Loss ◽  
Interstitial Volume ◽  
Pt Alloy ◽  
Sensing Performance

H2 sensing performance of novel Pd–Pt alloy films has been compared with those obtained by using Pd films and H2-reducted PdO films. Two different detecting systems were used to measure the hydrogenation and de-hydrogenation phases with a H2 concentration of both 5% v/v nitrogen and 1% v/v nitrogen at room temperature. The sensitivity loss observed for the Pd–Pt alloy and H2-reducted PdO samples with respect to pure Pd samples can be explained in terms of the reduction in the lattice constant and interstitial volume due to the Pt addition, which determine a decrement of hydrogen atoms penetrating in the films. On the other hand, results show an improvement in time -response for Pd–Pt alloy and H2-reducted PdO films with respect to pure Pd ones, presumably due to the increase of its permeability to H2. Moreover, the sensing measurements repeated after 60 days show that the Pd–Pt alloy films, unlike the Pd-based ones, fully preserve their performances, demonstrating the advantage of the Pt inclusion for stability purposes when the samples are stored upon humidity.

Patterson analysis for layer profile determination by neutron or X-ray reflectometry. II

2014 ◽  
Vol 47 (2) ◽  
pp. 680-683
Author(s):  
Zin Tun
Keyword(s):  
Additional Data ◽  
Scattering Length ◽  
Neutron Reflectometry ◽  
X Rays ◽  
Data Manipulation ◽  
X Ray ◽  
Patterson Function ◽  
Analysis Technique ◽  
Extra Step ◽  
Model Layer

A data analysis technique based on the Patterson function is tested with simulated X-ray reflectometry data. In comparison to the case for neutron reflectometry, additional data manipulation is required because the scattering-length density of materials is generally much higher for X-rays than for neutrons. With this extra step duly performed, the technique yields a model layer profile accurate enough for least-squares refinement.

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