Stress effects on the kinetics of hydrogen adsorption in a spherical particle: An analytical model Fernando P. Duda a , Giuseppe Tomassetti b,* a Programa de Engenharia Mec^ anica, COPPE, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil b Universit a di Roma “Tor Vergata”, Dipartimento di Ingegneria Civile e Ingegneria Informatica, Via Politecnico 1, 00169, Italy article info Article history: Received 7 January 2015 Received in revised form 15 July 2015 Accepted 16 July 2015 Available online 10 August 2015 Keywords: Stress-assisted diffusion Nanoparticles Phase transformation Hysteresis Hydrogen storage abstract We consider a two-phase elastic solid subject to diffusion-induced phase transformation by interstitial hydrogen. We derive a simple analytical model to quantify the effect of misfit strain on the kinetic of phase transformation and to calculate the amplitude of the well- know hysteresis cycle observed when a sequence of forward and reverse phase trans- formations takes place. Copyright © 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Introduction Although metal hydrides are considered promising candi- dates for solid-state hydrogen storage, their use for practical applications remains a challenge due to limitation imposed by the slow kinetics of hydrogen uptake and release [1,2]. To overcome this limitation, a great number of approaches have been proposed in the recent years, as, for instance, those based on nanosizing metal hydrides [3,4]. Metallic nanoparticles are characterized by fast hydroge- nation and dehydrogenation kinetics and hence are of partic- ular interest for hydrogen-storage applications. A source of complication in the understanding of the adsorption/release kinetics in these devices is the stress accompanying hydride formation due to the misfit between the metal and the hydride lattice structures. It is well known that the elastic misfits associated to phase transformation give rise to a stress field that may affect considerably phase equilibria in multiphase elastic solids [5,6]. In this respect, of particular importance is the analysis carried out by Schwarz and Kachaturyan [7], who examined a two- phase solid solvent in contact with a reservoir providing so- lute interstitial atoms. Their analysis shows that transformation-induced strain makes it impossible for the two phases to coexist at equilibrium and, moreover, that it is * Corresponding author. E-mail addresses: duda@mecanica.coppe.ufrj.br (F.P. Duda), tomassetti@ing.uniroma2.it (G. Tomassetti). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 40 (2015) 17009 e17016 http://dx.doi.org/10.1016/j.ijhydene.2015.07.088 0360-3199/Copyright © 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.