Grain boundary complexions in silicon carbide

Cancino‐Trejo, Félix; Navarro‐Solís, David J.; López‐Honorato, Eddie; Rabone, Jeremy; Walker, Ross C.; Salomon, Romelia

doi:10.1111/jace.15300

Cited by 14 publications

(9 citation statements)

References 21 publications

(60 reference statements)

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“…In many instances, grain boundary complexion transitions can be used to enhance the processing, properties, and performance of engineering materials. In Table , we provide a summary of recent applications and examples of complexion transitions, some of which can be considered as examples of grain boundary complexion engineering (GBCE). The idea of engineering grain boundaries to enhance the bulk properties of engineering materials is not new.…”

Section: Introductionmentioning

confidence: 99%

Review of grain boundary complexion engineering: Know your boundaries

et al. 2018

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Grain boundary structure-property relationships influence bulk performance and, therefore, are an important criterion in materials design. Materials scientists can generate different grain boundary structures by changes in temperature, pressure, and chemical potential because interfaces attain their own equilibrium states, known as complexions. Complexions undergo first-order transitions by changes in thermodynamic variables, which results in discontinuous changes in properties.Grain boundary complexion engineering is introduced in this paper as a method for controlling complexion transitions to improve material performance. This International Conference on Sintering 2017 lecture describes the tools for grain boundary complexion engineering: complexion equilibrium and time-temperaturetransformation (TTT) diagrams. These tools can be implemented in processing design to tailor grain boundary properties, including grain boundary mobility.While impactful, these diagrams are often limited in scope because they are currently empirically derived. This article discusses how measurement techniques can be combined with data analytical methods to build mechanistically derived complexion equilibrium and TTT diagrams.

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Section: Introductionmentioning

confidence: 99%

Review of grain boundary complexion engineering: Know your boundaries

et al. 2018

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“…38,42 Increased C activity in SiC is typically associated with C deposits or inclusions, C-rich grain boundaries, and C-saturated grains, [39][40][41] and the presence of C-rich grain boundaries has been reported in the SiC layer of TRISO particles. 43 However, C-rich grain boundaries have not been observed in the samples included in this work. Nanocrystalline regions possess a greater density of grain boundaries than the other ultrafine-grained areas in the SiC layer of TRISO particles, meaning that the likelihood of a Crich grain boundary being present is increased.…”

Section: The Nature Of Crystalline Sio 2 Nodulesmentioning

confidence: 84%

“…Localized regions with increased C activity are also known to accelerate oxidation and facilitate the formation of pores in SiO 2 scales 38,42 . Increased C activity in SiC is typically associated with C deposits or inclusions, C‐rich grain boundaries, and C‐saturated grains, 39–41 and the presence of C‐rich grain boundaries has been reported in the SiC layer of TRISO particles 43 . However, C‐rich grain boundaries have not been observed in the samples included in this work.…”

Section: Discussionmentioning

confidence: 99%

High‐temperature oxidation behavior of the SiC layer of TRISO particles in low‐pressure oxygen

et al. 2023

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Surrogate tristructural-isotropic (TRISO)-coated fuel particles were oxidized in 0.2 kPa O 2 at 1200-1600 • C to examine the behavior of the SiC layer and understand the mechanisms. The thickness and microstructure of the resultant SiO 2 layers were analyzed using scanning electron microscopy, focused ion beam, and transmission electron microscopy. The majority of the surface comprised smooth, amorphous SiO 2 with a constant thickness indicative of passive oxidation. The apparent activation energy for oxide growth was 188 ± 8 kJ/mol and consistent across all temperatures in 0.2 kPa O 2 . The relationship between activation energy and oxidation mechanism is discussed. Raised nodules of porous, crystalline SiO 2 were dispersed across the surface, suggesting that active oxidation and redeposition occurred in those locations. These nodules were correlated with clusters of nanocrystalline SiC grains, which may facilitate active oxidation.These findings suggest that microstructural inhomogeneities such as irregular grain size influence the oxidation response of the SiC layer of TRISO particles and may influence their accident tolerance.

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“…[7][8][9][10] Recently, Cancino et al identified three types of Dillon-Harmer grain-boundary complexions 11 in SiC and suggested that the complex diffusion behavior of fission products could be explained through the existence of grain-boundary complexions and complexion transitions. 12 Therefore, in this work, we studied the effect of Pd on the microstructure of SiC. We observed for the first time that Pd can induce important changes in composition in SiC at the grain boundaries.…”

Section: Introductionmentioning

confidence: 98%

“…Among these coatings, SiC is considered the most important as it retains most of the metallic fission products and provides the mechanical strength to the particle. 12 Therefore, in this work, we studied the effect of Pd on the microstructure of SiC. [4][5][6] Furthermore, it has been suggested that Pd can enhance the diffusion of other relevant fission products such as Ag 110m (a strong γ-ray emitter), however, it is still unclear how Pd could enhance such diffusion since the original theory suggesting the formation of a solid solution has not been corroborated experimentally, since Pd and Ag have been observed to diffuse separately.…”

Section: Introductionmentioning

confidence: 99%

Effect of palladium on the microstructure and grain boundary complexions in SiC

2019

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One of the main challenges in the study of TRISO (Tristructural Isotropic) coated fuel particles is the understanding of the diffusion of fission products through SiC. Among the elements produced inside the uranium kernel, it has been suggested that Pd might enhance the diffusion of other fission products. In this work, we have studied the interaction between Pd and SiC. We have observed that as Pd diffuses it can change the chemical composition and microstructure of SiC. Electron Backscattered Diffraction (EBSD) analysis showed that Pd increased the amount of high angle grain boundaries from 47% to 59%. Furthermore, we have observed that as Pd diffused, it changed the composition of SiC by leaving a trail of excess carbon at the grain boundary. This change in localized chemical composition and microstructure suggests a grain boundary complexion transition induced by Pd and a new way in which Pd can lead to faster diffusion routes for other fission products.

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Grain boundary complexions in silicon carbide

Cited by 14 publications

References 21 publications

Review of grain boundary complexion engineering: Know your boundaries

Review of grain boundary complexion engineering: Know your boundaries

High‐temperature oxidation behavior of the SiC layer of TRISO particles in low‐pressure oxygen

Effect of palladium on the microstructure and grain boundary complexions in SiC

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