Thermally induced dislocation loops in polycrystalline ice

Liu, Fuping; Baker, Ian; Dudley, Michael

doi:10.1080/01418619508242953

Cited by 33 publications

(5 citation statements)

References 13 publications

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“…Most observed dislocations in ice so far have one of the three equivalent 1/3 < 2110 > Burgers vectors and are constrained to glide in the basal plane (0001) owing to their tendency to dissociate into partial dislocations (Higashi, 1988;Hondoh, 2000). Rare 1/3 < 2110 > dislocations have been observed to glide on prismatic planes by X-ray diffraction in low strain conditions where very few dislocations were activated (Shearwood and Withworth, 1989), and when crystals were oriented to minimize the resolved shear stress in the basal plane (Liu and Baker, 1995). Indirect evidence of double cross-slip of basal dislocations was obtained from X-ray diffraction observations on single crystal deformed in torsion (Montagnat et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Non-basal dislocations should be accounted for in simulating ice mass flow

Chauve

Montagnat

Piazolo

et al. 2017

Earth and Planetary Science Letters

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International audiencePrediction of ice mass flow and associated dynamics is pivotal at a time of climate change. Ice flow is dominantly accommodated by the motion of crystal defects – the dislocations. In the specific case of ice, their observation is not always accessible by means of the classical tools such as X-ray diffraction or transmission electron microscopy (TEM). Part of the dislocation population, the geometrically necessary dislocations (GNDs) can nevertheless be constrained using crystal orientation measurements via electron backscattering diffraction (EBSD) associated with appropriate analyses based on the Nye (1950) approach. The present study uses the Weighted Burgers Vectors, a reduced formulation of the Nye theory that enables the characterization of GNDs. Applied to ice, this method documents, for the first time, the presence of dislocations with non-basal or Burgers vectors. These or dislocations represent up to of the GNDs observed in laboratory-deformed ice samples. Our findings offer a more complex and comprehensive picture of the key plasticity processes responsible for polycrystalline ice creep and provide better constraints on the constitutive mechanical laws implemented in ice sheet flow models used to predict the response of Earth ice masses to climate change

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Section: Introductionmentioning

confidence: 99%

Non-basal dislocations should be accounted for in simulating ice mass flow

Chauve

Montagnat

Piazolo

et al. 2017

Earth and Planetary Science Letters

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“…The growth of ice crystals and the general preparation of specimens have been described in detail elsewhere. − Notched sheet tensile specimens with (0001) perpendicular to the loading direction were produced as described elsewhere . In this orientation, the shear stresses on all slip planes from the far stress field are zero.…”

Section: Methodsmentioning

confidence: 99%

Temperature Dependence of Dislocations in Notched Ice Crystals

Hu¹,

Baker²,

Dudley³

1997

J. Phys. Chem. B

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“…For an interstitial loop, the 0002 diffraction vector drawn from the center of the loop would pass through the double image. Reproduced from Liu et al (1995a) with permission of the publisher. See http://www.tandf.co.uk.…”

Section: Conventional X-ray Topographymentioning

confidence: 98%

“…Liu and co-workers (Jia et al, 1996;Liu et al, 1992bLiu et al, , 1993Liu et al, , 1995a are the only researchers to have used SWBXT to study polycrystalline ice. They used in-situ straining to demonstrate that grain boundary regions always deform before the grain interiors.…”

Section: Synchrotron X-ray Topographymentioning

confidence: 99%

“…Later, Liu et al (1992a), using synchrotron white-beam X-ray topography (SWBXT), described below, showed that a loop-free zone is present next to grain boundaries in quenched polycrystalline ice because the interstitials migrate to the grain boundaries rather than condensing to form loops. Liu et al (1995a) also devised a straightforward method for determining whether a faulted loop on the basal plane was of interstitial or vacancy character. The method is based on determining whether the [0002] vector drawn from the center of the loop passes through a single image of the bounding dislocation (vacancy loop) or through a double image (interstitial loop) (Fig.…”

Section: Conventional X-ray Topographymentioning

confidence: 99%

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Imaging dislocations in ice

Baker

2003

Microscopy Res & Technique

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Three techniques have been used to study dislocations in ice: etch pitting-replication, transmission electron microscopy, and X-ray topography (XT). It is shown that, because ice is a weak absorber of X-rays and can be produced with a low dislocation density, allowing relatively thick specimens to be studied, the most useful technique is XT. The observations that have been made with conventional XT are briefly outlined. However, the introduction of high-intensity synchrotron radiation, with its concomitant short exposure times, showed that images obtained through conventional XT observations were of dislocations that had undergone recovery. The important dynamic observations and measurements that have been made using synchrotron X-ray topography are presented. Dynamic synchrotron X-ray topography observations of ice single crystals undergoing deformation in situ have shown that slip mainly occurs by the movement of screw and 60 degrees (1/3) [1120] dislocations on the basal plane, although non-basal slip by edge dislocations can also occur. The operation of Frank-Read and other dislocation multiplication sources have been clearly demonstrated and dislocation velocities have been measured. In contrast, in polycrystals, dislocation generation occurred at grain boundaries where there are stress concentrations before lattice dislocation generation mechanisms operate. Faulted dislocation loops have been determined to be mainly interstitial in both polycrystals and single crystals.

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Thermally induced dislocation loops in polycrystalline ice

Cited by 33 publications

References 13 publications

Non-basal dislocations should be accounted for in simulating ice mass flow

Non-basal dislocations should be accounted for in simulating ice mass flow

Temperature Dependence of Dislocations in Notched Ice Crystals

Imaging dislocations in ice

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