Grain Boundaries in Uranium Dioxide: Scanning Electron Microscopy Experiments and Atomistic Simulations

Nerikar, Pankaj; Rudman, Karin; Desai, Tapan; Byler, Darrin D.; Unal, Cetin; McClellan, Kenneth J.; Phillpot, Simon R.; Sinnott, Susan B.; Peralta, Pedro; Uberuaga, Blas P.; Stanek, Christopher R.

doi:10.1111/j.1551-2916.2010.04295.x

Cited by 89 publications

(80 citation statements)

References 33 publications

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“…UO 2 , is the P 9, having a symmetry angle [16] of 38.94°; however, this has also been determined in materials with significantly larger grain sizes. Moreover, as mentioned above, it is not possible to use techniques such as EBSD or OIM to determine the CSL values in such fine-grained materials as those in this study.…”

Section: Grain Growth and Grain Boundary Evolutionmentioning

confidence: 99%

“…As such, it may only be speculated that the dominant CSL is that of the P 9 in this study. Previous studies of the grain boundaries in UO 2 [16,17] have shown that Schottky defects exist at the high-misorientation (asymmetric) grain boundaries, helping to stabilize the system by reducing the energy at the grain boundary. The lower angle grain boundaries and CSL (symmetric) grain boundaries are stabilized by dislocations terminating at the grain boundaries [16,17].…”

Section: Grain Growth and Grain Boundary Evolutionmentioning

confidence: 99%

“…GBs are two-dimensional defects, and can be approximately characterized as low P boundaries, general GBs or misorientated GBs [16]. Here, P refers to the reciprocal density of the coincident site in accordance with the coincident site lattice (CSL) model [17].…”

Section: Introductionmentioning

confidence: 99%

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Irradiation effects on microstructure change in nanocrystalline ceria – Phase, lattice stress, grain size and boundaries

et al. 2012

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Moll, S.; Namavar, F.; and Weber, W.J., "Irradiation effects on microstructure change in nanocrystalline ceria -Phase, lattice stress, grain size and boundaries" (2012 AbstractWith a wide variety of applications in numerous industries, ranging from biomedical to nuclear, ceramics such as ceria are key engineering materials. It is possible to significantly alter the materials functionality and therefore its applications by reducing the grain size to the nanometer size regime, at which point the unique varieties of grain boundaries and associated interfaces begin to dominate the material properties. Nanocrystalline films of cubic ceria deposited onto Si substrates have been irradiated with 3 MeV Au + ions at temperatures of 300 and 400 K to evaluate their response to irradiation. It was observed that the films remained phase stable. Following a slight stress relief stage at low damage levels, the overall lattice is extremely stable up to high irradiation dose of $34 displacements per atom. The grains were also observed to undergo a temperature-dependent grain growth process upon ion irradiation. This is attributed to a defect-driven mechanism in which the diffusion of defects from the collision cascade is critical. Formation of dislocations that terminate and stabilize at symmetric grain boundaries may be the limiting factor in the grain growth and overall energy reduction of the system. Utilizing ion modification, possible improvement of the adhesion of thin films and reduction of the probability of detrimental effects of stress-induced problems are discussed.

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Section: Grain Growth and Grain Boundary Evolutionmentioning

confidence: 99%

Section: Grain Growth and Grain Boundary Evolutionmentioning

confidence: 99%

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Irradiation effects on microstructure change in nanocrystalline ceria – Phase, lattice stress, grain size and boundaries

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“…For example, the pinning of dislocations by implanted helium in aluminum 8 or niobium 9 shows the importance of segregation in determining both enhanced diffusion of atomic species and changes in mechanical properties of the bulk material. Metal-ceramic interfaces, which can be composed of ordered arrays of dislocations, have also been shown to act as energetically favorable nucleation points.…”

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confidence: 99%

Segregation of xenon to dislocations and grain boundaries in uranium dioxide

et al. 2011

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It is well known that Xe, being insoluble in UO 2 , segregates to dislocations and grain boundaries, where bubbles may form resulting in fuel swelling. Less well known is how sensitive this segregation is to the structure of the dislocation or grain boundary. In this work, we employ pair potential calculations to examine Xe segregation to dislocations (edge and screw) and several representative grain boundaries (Σ5 tilt, Σ5 twist and random). Our calculations predict that the segregation trend depends significantly on the type of dislocation or grain boundary. In particular, we find that Xe prefers to segregate strongly to the random boundary as compared to the other two boundaries and to the screw dislocation rather than the edge. Furthermore, we observe that neither the volumetric strain nor the electrostatic potential of a site can be used to predict its segregation characteristics. These differences in segregation characteristics are expected to have important consequences for the retention and release of Xe in nuclear fuels. Finally, our results offer general insights into how atomic structure of extended defects influence species segregation.I. INTRODUCTION Segregation can be understood as the interaction between an isolated zero dimensional defect (in this case, an impurity) and multidimensional defects such as dislocations (1D), grain boundaries (GB) and free surfaces (3D). 11 The driving force for this process is the energy difference (segregation energy) between the isolated impurity in the bulk and that associated with an extended structural defect. If the energy at the structural defect site is lower than in the bulk, the local impurity concentration is higher at the structural defect than in bulk and conversely, if the energy at the defect site is higher than in the bulk, the impurity will remain in the bulk. Segregation phenomena influence many material properties such as ion transport (which has a strong effect, for example on sintering rates), electrical and chemical reactivity and grain growth.2 At higher concentrations, segregating impurities are known to form glassy or ordered phases and can cause structural transformations of the GB. 2,3 In the case of UO 2 nuclear fuel, fission gases such as xenon (Xe) are insoluble in the fuel matrix. 45 Therefore, Xe tends to segregate to dislocations and GBs forming fission gas bubbles. Xe may diffuse along the short circuit paths provided by these two defects and be released into the plenum region between the fuel rod and the cladding. 5 If the gases are released from the fuel, they contribute to the gaseous atmosphere within the fuel pin and the fuel pin internal pressure correspondingly increases; this can contribute to failure of the fuel pin. If these gases are retained inside the fuel, they form bubbles, which lead to swelling of the fuel matrix. Swelling is detrimental to fuel performance as it contributes to fuel-cladding mechanical interaction (FCMI); the resulting stresses can shorten the lifetime of the pin. 7 Swelling and release are compleme...

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“…For details, see Technical Spotlight on page 9. [INL] Work continued on development of a method to account for fuel cracking in engineering-scale analyses by calibrating the cohesive zone model for the fracture of UO 2 …”

Section: Pin-scale Code Developmentmentioning

confidence: 99%

NEAMS Update. Quarterly Report for April - June 2013

Bradley

2013

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Grain Boundaries in Uranium Dioxide: Scanning Electron Microscopy Experiments and Atomistic Simulations

Cited by 89 publications

References 33 publications

Irradiation effects on microstructure change in nanocrystalline ceria – Phase, lattice stress, grain size and boundaries

Irradiation effects on microstructure change in nanocrystalline ceria – Phase, lattice stress, grain size and boundaries

Segregation of xenon to dislocations and grain boundaries in uranium dioxide

NEAMS Update. Quarterly Report for April - June 2013

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