Thermodynamic Criterion for the Stability of Amorphous Intergranular Films in Covalent Materials

Keblinski, Pawel; Phillpot, Simon R.; Wolf, D.; Gleiter, H.

doi:10.1103/physrevlett.77.2965

Cited by 173 publications

(104 citation statements)

References 16 publications

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“…In GBs with comparatively lower energies, e.g. S 7, Y 38X28 123111 CSL GB, the crystalline-like diusion is expected to occur up to I0.9T m [28]. This prediction is in agreement with our recent diusion results of Ge in near S 7 [111] tilt GBs of Al [17] where indeed no curvature in the Arrhenius dependencies was observed in the investigated temperature range 0.56±0.73T m .…”

Section: Temperature Dependence Of Au Gb Diusion In Cu Bicrystalssupporting

confidence: 81%

“…metals indicate a transition from``solid-like'' to``liquid-like'' diusion at elevated temperatures [28]. At high temperatures the GB diusion is characterized by the same universal atomic mobility and by a low activation enthalpy, in comparison to lower temperatures, where the GB diusion is``solid-like'' [28]. The temperature, where this transition occurs, depends on the GB energy of the CSL GB.…”

Section: Temperature Dependence Of Au Gb Diusion In Cu Bicrystalsmentioning

confidence: 99%

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Tracer diffusion of Au and Cu in a series of near Σ=5 (310)[001] symmetrical Cu tilt grain boundaries

et al. 1999

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AbstractÐGrain boundary diusion of Au and Cu was measured in a series of Cu bicrystals with symmetrical near AE 5, Â 36X98 310001 CSL tilt grain boundaries (GBs) using the radiotracer and the serial sectioning technique. The orientations of the bicrystals were very precisely determined with the Kossel technique where all three macroscopic parameters describing the orientations of the grains in the bicrystal were evaluated. The tilt angles ranged from 33.218 to 39.268. The GB diusion of the radiotracers 195 Au and 64 Cu was measured as a function of tilt angle and temperature. In the investigated temperature range 1030±661 K the orientation dependence of both radiotracers shows a characteristic cusp not exactly at but slightly below the ideal AE 5 CSL GB. The Arrhenius parameters, activation enthalpy and frequency factor, determined from lower temperature data adopt a maximum, again slightly before the ideal AE 5 CSL GB. These features are discussed with respect to the accidental small twist and second tilt orientations and the corresponding dislocation network inherent in the investigated real GBs. With increasing temperature a negative deviation from a straight Arrhenius behaviour is observed. This result indicates a certain change in the GB structure in the temperature range above 800 K. #

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Section: Temperature Dependence Of Au Gb Diusion In Cu Bicrystalssupporting

confidence: 81%

Section: Temperature Dependence Of Au Gb Diusion In Cu Bicrystalsmentioning

confidence: 99%

Tracer diffusion of Au and Cu in a series of near Σ=5 (310)[001] symmetrical Cu tilt grain boundaries

et al. 1999

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“…8 Molecular dynamics simulations of silicon grain boundaries have resulted in the conclusion that a confined amorphous equilibrium structure exists in those regions. 9,10 It is expected that in suitably engineered nanostructured materials it should be possible to observe physical properties different from that of their bulk counterparts. Recently, we have shown in nanocomposites comprising copper oxide within a silica gel the electrical conductivity arises due to the presence of an amorphous phase at the boundaries of the nanosized oxide layers.…”

Section: Introductionmentioning

confidence: 99%

Interface controlled electrical and magnetic properties in Fe–Fe3O4–silica gel nanocomposites

Das

Roy

Chen

et al. 2002

Journal of Applied Physics

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Iron nanoparticles with a shell of Fe3O4 phase with a total diameter of 5.3 nm have been grown within a silica gel matrix in the percolative configuration by suitable reduction followed by oxidation treatments. dc electrical resistivity measurements were carried out in the temperature range 80–300 K. The resistivity of the nanocomposites was found to be about 7 orders of magnitude lower than that of the reference gel. The electrical conduction has been explained on the basis of a small polaron hopping mechanism. The activation energy in the case of the composites was calculated from experimental data to be about one-fifth that for the reference sample. An interfacial amorphous phase is believed to cause such reduction in resistivity. The effective dielectric constant of this phase was estimated to be about four times that of the reference glass. Magnetization measurements on these specimens were carried out in the temperature range 5–300 K both in zero field cooled and field cooled states. A peak in the magnetization at ∼120 K was ascribed to an order–disorder (Verwey) transition. Another peak at ∼55 K was explained as arising due to a spin glass like disorder at the interface between the ferromagnetic iron ores and the ferrimagnetic Fe3O4 shell. A loop shift was observed as a result of the spin freezing below this temperature.

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“…In this work we follow the approach of Ref. 24 and model the HEGB structure as an amorphous SiC (a-SiC) because (i) the local environments in HEGBs of covalent materials are known to be similar to amorphous phases 19,20 , and (ii) a bulk a-SiC is computationally more tractable than modeling a full GB structure. A simulation cell is used that is approximately cubic and contains 128 atoms (64 Silicon, and 64 Carbon).…”

Section: Ab-initio Calculationsmentioning

confidence: 99%

“…The high fraction of HEGBs allow them to provide a percolating path for FPs transportation, and HEGBs are one of two GB types that are present in a high enough concentration to form a percolating path (the other GB type is ∑3-GB) 18 . Also, it is often found that disordered (amorphous) materials, which are structurally similar to HEGBs 19,20 , provide a faster transportation pathway for extrinsic defects compared to crystalline materials [21][22][23] . Furthermore, our recent study has suggested that Ag diffusion via HEGB is the dominant path for diffusion in unirradiated SiC 24 .…”

Section: Introductionmentioning

confidence: 99%

Cs diffusion in SiC high-energy grain boundaries

Szlufarska

Morgan

2017

Journal of Applied Physics

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Cesium (Cs) is a radioactive fission product whose release is of concern for Tristructural-Isotropic (TRISO) fuel particles. In this work, Cs diffusion through high energy grain boundaries (HEGBs) of cubic-SiC is studied using an ab-initio based kinetic Monte Carlo (kMC) model. The HEGB environment was modeled as an amorphous SiC (a-SiC), and Cs defect energies were calculated using density functional theory (DFT). From defect energies, it was suggested that the fastest diffusion mechanism as Cs interstitial in an amorphous SiC. The diffusion of Cs interstitial was simulated using a kMC, based on the site and transition state energies sampled from the DFT. The Cs HEGB diffusion exhibited an Arrhenius type diffusion in the range of 1200-1600°C. The comparison between HEGB results and the other studies suggests not only that the GB diffusion dominates the bulk diffusion, but also that the HEGB is one of the fastest grain boundary paths for the Cs diffusion. The diffusion coefficients in HEGB are clearly a few orders of magnitude lower than the reported diffusion coefficients from in-and out-of-pile samples, suggesting that other contributions are responsible, such as a radiation enhanced diffusion.

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Thermodynamic Criterion for the Stability of Amorphous Intergranular Films in Covalent Materials

Cited by 173 publications

References 16 publications

Tracer diffusion of Au and Cu in a series of near Σ=5 (310)[001] symmetrical Cu tilt grain boundaries

Tracer diffusion of Au and Cu in a series of near Σ=5 (310)[001] symmetrical Cu tilt grain boundaries

Interface controlled electrical and magnetic properties in Fe–Fe3O4–silica gel nanocomposites

Cs diffusion in SiC high-energy grain boundaries

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