Sequential multiplication of dislocation sources along a crack front revealed by high-voltage electron microscopy and tomography

Tanaka, Masaki; Sadamatsu, Sunao; Liu, Grace S.; Nakamura, Hiromitsu; Higashida, Kenji; Robertson, I. M.

doi:10.1557/jmr.2010.99

Cited by 16 publications

(13 citation statements)

References 22 publications

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“…The test temperature is sufficient for dislocation climb to occur. Dislocation cross slip has been reported to occur near a stress concentrator such as a crack tip at 973 K, 16 although cross slip was not observed often in this study. The expansion of a dislocation loop via climb is discussed next.…”

Section: Resultscontrasting

confidence: 55%

Transition from a punched-out dislocation to a slip dislocation revealed by electron tomography

et al. 2010

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Punched-out dislocations emitted from an octahedral oxide precipitate in single-crystal silicon were investigated using high-voltage electron microscopy and tomography (HVEM-tomography) to understand the mechanism of softening caused by the oxide precipitates. In the present paper, direct evidence of the transition of a punched-out prismatic dislocation loop to a slip dislocation is presented. The punched-out dislocation grows into a large matrix dislocation loop by absorption of interstitial atoms, which were produced during oxide precipitation.

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Section: Resultscontrasting

confidence: 55%

Transition from a punched-out dislocation to a slip dislocation revealed by electron tomography

et al. 2010

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“…Three groups have reported using in-situ TEM at 200 kV to observe hydrogen desorption 15 17 18 . However, conventional TEM with an accelerating voltage of 200 kV has disadvantages including inelastic incident beam interactions with the samples, and the sample dimensions (typically less than 100 nm in thickness) make surface effects more prominent 19 . Recently Mooij and Dam 20 demonstrated in-situ the two dimensional nucleation and growth of single hydride domains of up to several millimeters in diameter by an optical transmission technique (hydrogenography) for thin Mg film.…”

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Evidence of the hydrogen release mechanism in bulk MgH2

Nogita

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Yamamoto

et al. 2015

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Hydrogen has the potential to power much of the modern world with only water as a by-product, but storing hydrogen safely and efficiently in solid form such as magnesium hydride remains a major obstacle. A significant challenge has been the difficulty of proving the hydriding/dehydriding mechanisms and, therefore, the mechanisms have long been the subject of debate. Here we use in situ ultra-high voltage transmission electron microscopy (TEM) to directly verify the mechanisms of the hydride decomposition of bulk MgH2 in Mg-Ni alloys. We find that the hydrogen release mechanism from bulk (2 μm) MgH2 particles is based on the growth of multiple pre-existing Mg crystallites within the MgH2 matrix, present due to the difficulty of fully transforming all Mg during a hydrogenation cycle whereas, in thin samples analogous to nano-powders, dehydriding occurs by a ‘shrinking core' mechanism.

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“…Secondly, conventional TEM with an accelerating voltage of 200 kV–300 kV has disadvantages including inelastic incident beam interactions with the samples, and the sample dimensions (typically less than 100 nm in thickness) make surface effects more prominent10, which becomes particularly important in small samples with a high specific surface area. In this aspect, UHV-TEM is more favorable for determining the mechanism of hydrogen release in real-time.…”

Section: Dehydrogenation Of Mgh2 or Diffusion Of Mg And Kirkendall Vomentioning

confidence: 99%

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Nogita

Tran

Yamamoto

et al. 2017

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Sequential multiplication of dislocation sources along a crack front revealed by high-voltage electron microscopy and tomography

Abstract: Abstract

Cited by 16 publications

References 22 publications

Transition from a punched-out dislocation to a slip dislocation revealed by electron tomography

Transition from a punched-out dislocation to a slip dislocation revealed by electron tomography

Evidence of the hydrogen release mechanism in bulk MgH2

Reply to ‘Comments on “Evidence of the hydrogen release mechanism in bulk MgH2”’

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