iMechanica - surface tension
https://imechanica.org/taxonomy/term/5490
enEffects of surface tension and electrochemical reactions in Li-ion battery electrode nanoparticles
https://imechanica.org/node/20446
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/7849">lithium-ion batteries</a></div><div class="field-item odd"><a href="/taxonomy/term/5490">surface tension</a></div><div class="field-item even"><a href="/taxonomy/term/11369">reaction kinetics</a></div><div class="field-item odd"><a href="/taxonomy/term/11370">stress-enhanced diffusion</a></div><div class="field-item even"><a href="/taxonomy/term/6751">Nanoparticle</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>The size- and shape-dependency of the chemo-mechanical behavior of spherical and ellipsoidal nanoparticles in Li-ion battery electrodes are investigated by a stress-assisted diffusion model and 3D finite element simulations. The model features surface tension, a direct coupling between diffusion and elasticity, concentration-dependent diffusivity, and a Butler-Volmer relation for the description of electrochemical reactions that is modified to account for mechanical effects. Simulation results on spherical particles reveal that surface tension causes additional pressure fields in the particles, shifting the stress state towards the compressive regime. This provides mechanical stabilization, allowing, in principle, for higher charge/discharge rates. However, due to this pressure the attainable lithiation for a given potential difference is reduced during insertion, whereas a higher amount of ions is given off during extraction. Ellipsoidal particles with an aspect ratio deviating from that of a sphere with the same volume expose a larger surface area to the intercalation reactions. Consequently, they exhibit accelerated (dis)charge rates. However, due to the enhanced pressure in regions with high curvature, the accessible capacity of ellipsoidal particles is less than that of spherical particles.</p>
<p><span>Link: </span><a id="ddDoi" class="S_C_ddDoi" href="http://dx.doi.org/10.1016/j.jpowsour.2016.09.085" target="doilink">http://dx.doi.org/10.1016/j.jpowsour.2016.09.085</a></p>
</div></div></div>Wed, 12 Oct 2016 13:00:31 +0000Peter Stein20446 at https://imechanica.orghttps://imechanica.org/node/20446#commentshttps://imechanica.org/crss/node/20446Journal Club Theme of February 2013: Surface energy and mechanical instabilities in soft materials
https://imechanica.org/node/14119
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/3950">soft materials</a></div><div class="field-item odd"><a href="/taxonomy/term/5490">surface tension</a></div><div class="field-item even"><a href="/taxonomy/term/8405">creases</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p align="justify">
When a material is soft or the size of the material is small, the effect of surface energy on its deformation can be significant.The importance of surface energy on the deformation of a structure could be evaluated by the magnitude of a dimensionless number, called elastocapillary number: γ/μL, where γ is surface energy density, μ is shear modulus and L is the characteristic length of the structure. Many intriguing phenomena of surface energy induced deformation of even instabilities have been observed in different experiments. In this journal club, I want to initiate a discussion on how surface energy may affect mechanical instabilites in soft materials. In the following, I would like to use our recent work as exmaples. Any thoughts and comments on this topic are welcome.
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<p align="justify">
Recently, we have studied the influence of surface energy on the creasing instability of an elastomer under uniaxial compression. In experiments we found that creases form by nucleation at preexisting defects and grow by channeling across the surface of the film. Surface energy provides a nucleation barrier and also resists channeling for finite values of the elastocapillary number. While the heterogeneous nucleation makes it difficult to characterize the critical strain for nucleation, the condition for channeling is well characterized and depends on the elastocapillary number. We further show that adhesion, rather than plastic deformation, is responsible for the dramatic hysteresis between the first and subsequent cycles of compression.
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<p align="justify">
Our paper can be found in the following link. Some experimental videos have been put in the supplemental materials.
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<p>
<a href="http://prl.aps.org/abstract/PRL/v109/i3/e038001">Surface energy as a barrier to creasing of elastomer films: An elastic analogy to classical nucleation</a>
</p>
<p>
Another paper of us illustrates the influence of surface tension and streching limit of polymers on the snap-through instabilities of a cavity inside an elastomer. The link is given in the following.
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<p>
<a href="http://www.mit.edu/~shqcai/9.pdf">Snap-through expansion of a gas bubble in an elastomer</a>
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</div></div></div>Fri, 01 Feb 2013 06:36:22 +0000Cai Shengqiang14119 at https://imechanica.orghttps://imechanica.org/node/14119#commentshttps://imechanica.org/crss/node/14119Capturing wetting angles in transient simulations of fluids
https://imechanica.org/node/8753
<div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Dear all,<br />
I'm trying to simulate the transient behavior of a fluid and I'm finding it very difficult to capture the wetting angle.<br />
To begin with, I only considering the idealized case. </p>
<p>The common approach is to apply the pressure load<br /><cite>p = 2 H γ</cite><br />
where <cite>p</cite> is the pressure (normal traction) on the surface, <cite>H</cite> is the Gaussian curvature of the surface, and <cite>γ</cite> is the surface energy<br />
This load will of course always yield the same equilibrium shape for a viscous fluid, regardless of the value of <cite>γ</cite>.</p>
<p>Now, comparing with <a href="http://en.wikipedia.org/wiki/Wetting#Simplification_to_planar_geometry.2C_Young.27s_relation">Young's relation</a>, where one obtains a balance containing surface energies for every interface.<br />
This equation is only valid for equilibrium, but even if I were to apply<br /><cite>p = 2 H γ</cite><br />
for each interface, the solid flat surface would still have zero curvature, <cite>H=0</cite>, thus resulting in zero pressure anyway, <cite>p=0</cite>.</p>
<p>I have seen some work, which more or less forces the wetting angle to a certain predetermined parameter (i.e. treating it as a material parameter), but then again, in that case only the equilibrium state would be correct.</p>
<p>This leads to my current predicament. What am i missing? Where should the surface energies for the other interfaces come into play?<br />
I would love to hear someone else's input on this.</p>
</div></div></div><div class="field field-name-taxonomy-forums field-type-taxonomy-term-reference field-label-above"><div class="field-label">Forums: </div><div class="field-items"><div class="field-item even"><a href="/forum/109">Ask iMechanica</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-above"><div class="field-label">Free Tags: </div><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/217">surface energy</a></div><div class="field-item odd"><a href="/taxonomy/term/846">FEM</a></div><div class="field-item even"><a href="/taxonomy/term/5488">wetting angle</a></div><div class="field-item odd"><a href="/taxonomy/term/5489">contact angle</a></div><div class="field-item even"><a href="/taxonomy/term/5490">surface tension</a></div></div></div>Mon, 23 Aug 2010 22:14:23 +0000Mikael Öhman8753 at https://imechanica.orghttps://imechanica.org/node/8753#commentshttps://imechanica.org/crss/node/8753