Effect of alloying magnesium with chromium and vanadium on hydrogenation kinetics studied with neutron reflectometry

Kalisvaart, Peter; Luber, Erik J.; Fritzsche, H.; Mitlin, David

doi:10.1039/c0cc05501h

Cited by 23 publications

(22 citation statements)

References 16 publications

(15 reference statements)

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“…A similar situation takes place in Mg/Ta/Pd films. Recent experiments on thick Mg films [32], Mg/Ti multilayers [33] and thin Mg films [34] by means of profilometry, X-ray and Neutron reflectometry, respectively, show a thickness increase of about 30%, which is very similar to the expansion in magnesium hydride bulk. Thus, the volume strain in Mg/Ta/Pd films, ε ν , resembles Mg bulk upon hydrogen loading as well.…”

Section: Hysteresis Behavior and Stress-strain Analysis Of Mg/ta/pd Tmentioning

confidence: 79%

Thermodynamic Properties, Hysteresis Behavior and Stress-Strain Analysis of MgH2 Thin Films, Studied over a Wide Temperature Range

2012

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Using hydrogenography, we investigate the thermodynamic parameters and hysteresis behavior in Mg thin films capped by Ta/Pd, in a temperature range from 333 K to 545 K. The enthalpy and entropy of hydride decomposition, ∆H des = −78.3 kJ/molH 2 , ∆S des = −136.1 J/K molH 2 , estimated from the Van't Hoff analysis, are in good agreement with bulk results, while the absorption thermodynamics, ∆H abs = −61.6 kJ/molH 2 , ∆S abs = −110.9 J/K molH 2 , appear to be substantially affected by the clamping of the film to the substrate. The clamping is negligible at high temperatures, T > 523 K, while at lower temperatures, T < 393 K, it is considerable. The hysteresis at room temperature in Mg/Ta/Pd films increases by a factor of 16 as compared to MgH 2 bulk. The hysteresis increases even further in Mg/Pd films, most likely due to the formation of a Mg-Pd alloy at the Mg/Pd interface. The stress-strain analysis of the Mg/Ta/Pd films at 300-333 K proves that the increase of the hysteresis occurs due to additional mechanical work during the (de-)hydrogenation cycle. With a proper temperature correction, our stress-strain analysis quantitatively and qualitatively explains the hysteresis behavior in thin films, as compared to bulk, over the whole temperature range. OPEN ACCESSCrystals 2012, 2 711

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Section: Hysteresis Behavior and Stress-strain Analysis Of Mg/ta/pd Tmentioning

confidence: 79%

Thermodynamic Properties, Hysteresis Behavior and Stress-Strain Analysis of MgH2 Thin Films, Studied over a Wide Temperature Range

2012

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“…[19][20][21][22][23][24][25][26][27][28][29][30] This ability is empowered by the high contrast between hydrogen isotopes (hydrogen and deuterium) which can be used to precisely probe, non-destructively, the amount of hydrogen penetrating into the metal and any surface films. The fact that NR can be carried out in situ by applying a controlled electrochemical condition adds a new dimension to the study of hydrogen transport through the oxide and metal films, and of their corrosion resistance.…”

Section: 8-13mentioning

confidence: 99%

Hydrogen Absorption into Titanium under Cathodic Polarization: An In-Situ Neutron Reflectometry and EIS Study

Vezvaie¹,

Noël

Tun³

et al. 2013

J. Electrochem. Soc.

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Hydrogen (deuterium) absorption into sputter-coated titanium (Ti) film electrodes during cathodic polarization in heavy water (D 2 O) was monitored using in-situ neutron reflectometry (NR) and electrochemical impedance spectroscopy (EIS). The scattering length density (SLD) of Ti metal increased with increasing cathodic polarization, due to the penetration of deuterium through the surface oxide and into the underlying metal. The rate of D absorption estimated from the NR data showed a pattern with four distinctive regions separated by potential boundaries between −0.35 and −0.4 V SCE and around ∼−0.6 V SCE . EIS results support division of the behavior into these potential ranges. Hydrogen absorption by Ti was observed at potentials <∼−0.35 V SCE , where the capacitance and resistance of the TiO 2 layer dramatically changed. At this point, the D content of the film quickly achieved a level of ∼900 ppm by weight (atom ratio D:Ti ∼ 0.04). Decreased absorption kinetics were observed over the potential region from ∼−0.40 V SCE to −0.6 V SCE , indicating that D absorption was controlled either by a diffusion process through the TiO 2 layer or by the formation of blocking hydrides at the Ti/TiO 2 interface, at the base of the defective locations in the oxide through which the hydrogen was entering. Significant increases in the current density and SLD of the Ti film at potentials more negative than −0.6 V SCE were assigned to widespread hydrogen absorption and TiH x growth within the metal. These observations are consistent with hydrogen ingress through the oxide film, probably via weak points containing electronic defects and disorder, such as grain boundaries and triple points, at potentials as mild as ∼−0.4 V SCE , and with hydrogen penetration through continuous, intact oxide via the previously published redox transformation mechanism, at potentials more negative than −0.6 V SCE . Titanium corrosion processes are often accompanied by hydrogen production. For example, 80% or more of the crevice corrosion process on Ti is driven by the reduction of protons inside the crevice:This leads to the absorption of atomic hydrogen, and can result in extensive hydride formation. 1,2 Cathodic polarization and galvanic coupling with active metals can also cause hydrogen evolution on the Ti surface and hydrogen penetration into the bulk metal. Since hydrogen absorption into Ti structures can lead to their failure by brittle cracking, once the hydrogen concentration achieves a critical level, 3 safe operation of such structures requires a detailed knowledge of the mechanism of hydrogen entry into Ti so that exposure conditions that put the structure at risk of hydrogen-induced cracking can be avoided. A number of studies have been done on the physicochemical properties of Ti/H systems, as well as on hydrogen-induced cracking of Ti.3,4 Here we explore the role of the electrochemical potential in determining whether adsorbed hydrogen atoms generated by water reduction can penetrate the native oxide on Ti.The surface oxide layer play...

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“…Later, Munter et al showed how deuterium absorption could be monitored in-situ during loading experiments on thin Pd films 9,10 . More recently, a series of studies has been published by Fritzche et al, showing how NR can be used to investigate the thermodynamics of hydrogen uptake process in Pd-capped metal alloy films [11][12][13][14][15] . NR has also proved an efficient way to characterize deviations in the hydrogen stoichiometry in very thin interface layers 9,16 , and can be used to determine inter-diffusion of elements at the interfaces of metal hydride films 11,12 .…”

mentioning

confidence: 99%

“…D has a positive coherent scattering length for neutrons, and thereby contributes to an increase in the SLD as opposed to H. If two sets of samples are prepared in the same way but one with H the other with D, the difference in SLD can give an accurate estimation of the H/D content of the sample. Similarly, NR has been used to study loading/unloading of H in metallic films, where the SLD prior to and post-loading is compared in order to estimate the H concentration 9,11,13,15,20,21 .…”

mentioning

confidence: 99%

Surface oxide on thin films of yttrium hydride studied by neutron reflectometry

Mongstad

Platzer‐Björkman

Mæhlen

et al. 2012

Applied Physics Letters

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The applicability of standard methods for compositional analysis is limited for H-containing films. Neutron reflectometry is a powerful, non-destructive method that is especially suitable for these systems due to the large negative scattering length of H. In this work we demonstrate how neutron reflectometry can be used to investigate thin films of yttrium hydride. Neutron reflectometry gives a strong contrast between the film and the surface oxide layer, enabling us to estimate the oxide thickness and oxygen penetration depths. A surface oxide layer of 5-10 nm thickness was found for unprotected yttrium hydride films.

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Effect of alloying magnesium with chromium and vanadium on hydrogenation kinetics studied with neutron reflectometry

Cited by 23 publications

References 16 publications

Thermodynamic Properties, Hysteresis Behavior and Stress-Strain Analysis of MgH2 Thin Films, Studied over a Wide Temperature Range

Thermodynamic Properties, Hysteresis Behavior and Stress-Strain Analysis of MgH2 Thin Films, Studied over a Wide Temperature Range

Hydrogen Absorption into Titanium under Cathodic Polarization: An In-Situ Neutron Reflectometry and EIS Study

Surface oxide on thin films of yttrium hydride studied by neutron reflectometry

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