2,736 research outputs found
In situ TEM study of twin boundary migration in sub-micron Be fibers
Deformation twinning in hexagonal crystals is often considered as a way to
palliate the lack of independent slip systems. This mechanism might be either
exacerbated or shut down in small-scale crystals whose mechanical behavior can
significantly deviate from bulk materials. Here, we show that sub-micron
beryllium fibers initially free of dislocation and tensile tested in-situ in a
transmission electron microscope (TEM) deform by a twin thickening. The propagation speed of the twin boundary
seems to be entirely controlled by the nucleation of twinning dislocations
directly from the surface. The shear produced is in agreement with the repeated
lateral motion of twinning dislocations. We demonstrate that the activation
volume () associated with the twin boundary propagation can be retrieved
from the measure of the twin boundary speed as the stress decreases as in a
classical relaxation mechanical test. The value of is comparable to the value expected from surface
nucleation.Comment: 13 pages, 9 figure
Dislocation plasticity in thin metal films
This article describes the current level of understanding of dislocation plasticity in thin
films and small structures in which the film or structure dimension plays an important
role. Experimental observations of the deformation behavior of thin films, including
mechanical testing as well as electron microscopy studies, will be discussed in light of
theoretical models and dislocation simulations. In particular, the potential of applying
strain-gradient plasticity theory to thin-film deformation is discussed. Although the
results of all studies presented follow a âsmaller is strongerâ trend, a clear functional
dependence has not yet been established
Recommended from our members
Simulation and life cycle assessment of algae gasification process in dual fluidized bed gasifiers
We present simulation results for the production of algae-derived syngas using dual fluidized bed (DFB) gasifiers.Part of this work was funded by the Technology Strategy
Board (TSB) grant programme, âCarbon Abatement Technologies,
Phase 2 competition for collaborative R&D and feasibilityâ,
Grant No. TS/J004553. MK acknowledges support by the Singapore National
Research Foundation under its Campus for Research Excellence
And Technological Enterprise (CREATE) program.This is the accepted manuscript. The final version is available at http://pubs.rsc.org/en/Content/ArticleLanding/2015/GC/c4gc01698j#!divAbstract
Saturation of Cs2 Photoassociation in an Optical Dipole Trap
We present studies of strong coupling in single-photon photoassociation of
cesium dimers using an optical dipole trap. A thermodynamic model of the trap
depletion dynamics is employed to extract absolute rate coefficents. From the
dependence of the rate coefficient on the photoassociation laser intensity, we
observe saturation of the photoassociation scattering probability at the
unitarity limit in quantitative agreement with the theoretical model by Bohn
and Julienne [Phys. Rev. A, 60, 414 (1999)]. Also the corresponding power
broadening of the resonance width is measured. We could not observe an
intensity dependent light shift in contrast to findings for lithium and
rubidium, which is attributed to the absence of a p or d-wave shape resonance
in cesium
Atom chip for BEC interferometry
We have fabricated and tested an atom chip that operates as a matter wave interferometer. In this communication we describe the fabrication of the chip by ion-beam milling of gold evaporated onto a silicon substrate. We present data on the quality of the wires, on the current density that can be reached in the wires and on the smoothness of the magnetic traps that are formed. We demonstrate the operation of the interferometer, showing that we can coherently split and recombine a BoseâEinstein condensate with good phase stability
- âŠ