Hydrogenation rate limiting step, diffusion and thermal conductivity in cold rolled magnesium hydride

Lang, Julien; Eagles, Mitch; Conradi, Mark S.; Huot, Jacques

doi:10.1016/j.jallcom.2013.08.126

Cited by 38 publications

(15 citation statements)

References 6 publications

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“…By cold rolling, the particle size is reduced and defects are generated which contribute positively to the effectivity of microwave heating. Concerning the positive effect of cold rolling on hydrogen desorption, similar behavior has been observed for the conventional heating of cold rolled hydride powders [31,39,40]. This behavior has been attributed to the decrease in crystallite size and crystal defects generated during rolling which could act as fast diffusion paths and heterogeneous nucleating sites for diffusional phase transformations.…”

Section: X-ray Diffraction: Microwave Irradiation Effectssupporting

confidence: 66%

Effect of Cold Rolling on the Hydrogen Desorption Behavior of Binary Metal Hydride Powders under Microwave Irradiation

Dupim

Santos

Huot

2015

Metals

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In this paper we report that cold rolling could drastically improve hydrogen desorption kinetics under microwave irradiation. Samples of metal hydride powders (TiH2, ZrH2, and MgH2) in as-received conditions and after cold rolling were microwave irradiated in a vacuum using a simple experimental setup. After irradiation, the samples were characterized by X-ray diffraction in other to evaluate the effectiveness of microwave heating. The diffraction patterns indicated that only MgH2 could be fully decomposed (dehydrided) in the as received state. TiH2 was only partially decomposed while no decomposition was observed for ZrH2. However, cold rolling the hydride powders prior to microwave heating led to a significant improvement of hydride decomposition, resulting in the complete dehydriding of TiH2 and extensive dehydriding of ZrH2. These results clearly indicated the positive effects of cold rolling on the microwave assisted desorption of the investigated binary hydrides.

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Section: X-ray Diffraction: Microwave Irradiation Effectssupporting

confidence: 66%

Effect of Cold Rolling on the Hydrogen Desorption Behavior of Binary Metal Hydride Powders under Microwave Irradiation

Dupim

Santos

Huot

2015

Metals

Self Cite

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“…Good reviews describing kinetic models have already been published [43][44][45][47][48][49][50] . The classical model designation 45 , as well as a more identifiable designation, adopted before by Lang et al 51 , are given in Table 1.…”

Section: (De)hydrogenation Measurementsmentioning

confidence: 99%

“…The best-fitted model indicates the most probable limiting step. A widespread and most straightforward procedure to find this out 51,52 is to arrange the model equations by leaving, on the left side, a function of the reacted fraction α, which ranges from 0 (at the beginning of reaction) to 1 (maximum attained sample capacity). The right side of all equations is kt: where k is the reaction constant and t is the reaction time.…”

Section: (De)hydrogenation Measurementsmentioning

confidence: 99%

Hydrogen Absorption/Desorption Behavior of a Cold-Rolled TiFe Intermetallic Compound

et al. 2021

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The (de)hydrogenation properties of a TiFe intermetallic compound (IMC) alloy activated by cold rolling inside a glovebox at ambient temperature were investigated by kinetic measurements, x-ray powder diffraction (XRD), and transmission electron microscopy (TEM). Rate-limiting steps were identified by testing kinetic models on hydrogen absorption and desorption curves. To prevent surface poisoning during air exposure, the TiFe IMC was also cold rolled with polytetrafluoroethylene (PTFE) and ultra-high molecular weight polyethylene (UHMWPE). The addition of either PTFE or UHMWPE to nanostructured TiFe by cold rolling did not produce a polymer-metal composite with O 2 poisoning resistance, regardless of the polymer-mixing way adopted. This occurred because large surfaces of the particles were not adequately coated with polymer. The results identify challenges to the TiFe IMC polymer-covered material that must be overcome before a methodology can significantly contribute to the formation of nanostructured TiFe-polymer composites with enhanced hydrogen storage properties. The diffusion-controlled reactions in the cold-rolled TiFe IMC without polymer were prevalent in all cases, as predicted by the Jander three-dimensional diffusion model. The main contribution of this work regards estimation of the amount of hydrogen released, which was 0.60% after 6 min and reproducible for the three subsequent cycles.

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“…The rate limiting step can be determined from the best fit between the experimental data and the proposed models. This method of analysis is detailed in several reaction kinetic publications [11,47] and the mathematical models are given in Table 2. There are three single particle models that can describe kinetic reaction behaviour: surface reaction [48], Johnson-Mehl-A vrami (JMA) [3][4][5] and Carter-Valensi/Contracting Volume (CV) [8,49] models.…”

Section: Desorption Reaction Kineticsmentioning

confidence: 99%

“…(iii) Normalised data, a (dividing final amount desorbed experimentally after 24 h by the maximum possible hydrogen capacity, 5 wt.%). Table 3 Expanded set of reaction kinetic model equations [47].…”

Section: Desorption Reaction Kineticsmentioning

confidence: 99%

Reaction kinetic behaviour with relation to crystallite/grain size dependency in the Mg–Si–H system

et al. 2015

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a b s t r a c tAn empirical understanding of the relationship between crystallite size and reaction kinetics for the dehydrogenation of MgH 2 in the presence of Si was determined. MgH 2 was combined with Si under different conditions to obtain varying crystallite sizes of both reactants. Thermal analysis and isothermal desorption were undertaken to obtain reaction kinetic information and therefore determine activation energies as well as the rate limiting step for each of the different crystallite sizes. It was found that there is a strong correlation between crystallite size and activation energy for the growth of the Mg 2 Si phase, however, any correlation between the nucleation (of Mg 2 Si) activation energy was less evident. Direct measurements of kinetic behaviour from a manometric Sieverts apparatus showed that initial reaction kinetics were fastest when MgH 2 was mixed with Si nanoparticles, however, this sample was not able to fully desorb. Data from the Sieverts measurements were then used with well-known theoretical models to determine the rate limiting step of the reaction. The three dimensional Carter-Valensi (or contracting volume) diffusion model could be used to describe the rate limiting step for most of the reactions. These results have led to a proposed mechanism for the formation of Mg 2 Si during the decomposition reaction.

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Hydrogenation rate limiting step, diffusion and thermal conductivity in cold rolled magnesium hydride

Cited by 38 publications

References 6 publications

Effect of Cold Rolling on the Hydrogen Desorption Behavior of Binary Metal Hydride Powders under Microwave Irradiation

Effect of Cold Rolling on the Hydrogen Desorption Behavior of Binary Metal Hydride Powders under Microwave Irradiation

Hydrogen Absorption/Desorption Behavior of a Cold-Rolled TiFe Intermetallic Compound

Reaction kinetic behaviour with relation to crystallite/grain size dependency in the Mg–Si–H system

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