Silicon is a promising anode material for lithium-ion batteries due to its enormous theoretical energy density. Fracture during electrochemical cycling has limited the practical viability of silicon electrodes, but recent studies indicate that fracture can be prevented by taking advantage of lithiation-induced plasticity. In this paper, we provide experimental insight into the nature of plasticity in amorphous LixSi thin films. To do so, we vary the rate of lithiation of amorphous silicon thin films and simultaneously measure stresses.
We successfully synthesized a family of alginate/polyacrylamide hydrogels using various multivalent cations. These hydrogels exhibit exceptional mechanical properties. In particular, we found that the hydrogels cross-linked by trivalent cations are much stronger than those cross-linked by divalent cations. We demonstrate stretchability and toughness of the hydrogels by inﬂating a hydrogel sheet
Hydrogels that undergo a volume phase transition in response to an
external stimulus are of great interest because of their possible use as
actuator materials. The performance of an actuator material is normally
characterized by its force–stroke curve, but little is known about the
force–stroke behavior of hydrogels. We use the theory of the ideal
elastomeric gel to predict the force–stroke curves of a
temperature-sensitive hydrogel and introduce an experimental method for
measuring the curve. The technique is applied to PNIPAm hydrogels with
low cross-link densities. The maximum force generated by the hydrogel
increases with increasing cross-link density, while the maximum stroke
Dielectric elastomers are capable of large voltage-induced deformation, but achieving
such large deformation in practice has been a major challenge due to electromechanical
instability and electric breakdown. The complex nonlinear behavior suggests an important
opportunity: electromechanical instability can be harnessed to achieve giant voltage-induced
In a novel design of lithium-ion batteries, hollow electrode particles coated with stiff shells are used to mitigate mechanical and chemical degradation.In particular, silicon anodes of such core-shell nanostructures have been cycled thousands of times with little capacity fading.To reduce weight and to facilitate lithium diffusion, the shell should be thin.However, to avert fracture and debonding from the core, the shell must be sufficiently thick.
Dielectric elastomer transducers are often subject to large tensile stretches and are susceptible to rupture. Here we carry out an experimental study of the rupture behavior of membranes of an acrylic dielectric elastomer (VHB 4905). Pure-shear test specimens are used to measure force-displacement curves, using samples with and without pre-cracks. We find that introducing a pre-crack into a membrane drastically reduces the stretch at rupture. Furthermore, we measure the stretch at rupture and fracture energy using samples of different heights at various stretch-rates. The stretch at rupture is found to decrease with sample height, and the fracture energy is found to increase with stretch-rate.
This paper has appeared in the Journal of Applied Physics and can be downloaded from:
A combination of experiment and theory shows that dielectric elastomers exhibit complex interplay of nonlinear processes. Membranes of a dielectric elastomer are prepared in various states of prestretches by using rigid clamps and mechanical forces.