Influence of platinum group metal particle aggregation on the rheological behavior of a glass melt

Machado, Norma Maria Pereira; Pereira, Luiz; Neyret, Muriel; Lemaître, Cécile; Marchal, Philippe

doi:10.1016/j.jnucmat.2022.153618

Cited by 8 publications

(6 citation statements)

References 32 publications

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“…While cerianite has a cubic shape, Platinum Group Metal particles have acicular and spherical shapes (RuO 2 needles and PdTe intermetallic spherical beads), and they are frequently found aggregated in small units of about 50 µm, 7 even at high shear. The PGM particles’ strong interactions engender the formation of bigger aggregates (reaching up to 500 µm 13 ) in the melt when submitted to low shear stress. Both the aggregation and the acicular shape of RuO 2 particles are assumed to be responsible for the critical stress and viscosity augmentation observed in PGM‐bearing melts 11 …”

Section: Discussionmentioning

confidence: 99%

“…As well as affecting the rheological properties of the melt, PGM particles can engender changes in electrical conductivity and are prone to settling. 8,13 Nonetheless, the extensive studies carried out in the last decade on the impact of PGM particles on the glass melt physical properties have contributed to a deeper understanding of this particle-melt system and consequently, to better control of the vitrification process.…”

Section: Introductionmentioning

confidence: 99%

“…The high viscosities shown in PGM‐bearing melts at low shear rate regimes are associated with its strong tendency for particle aggregation, which can significantly increase the effective particle volume fraction by trapping the liquid inside its aggregates. As well as affecting the rheological properties of the melt, PGM particles can engender changes in electrical conductivity and are prone to settling 8,13 . Nonetheless, the extensive studies carried out in the last decade on the impact of PGM particles on the glass melt physical properties have contributed to a deeper understanding of this particle‐melt system and consequently, to better control of the vitrification process.…”

Section: Introductionmentioning

confidence: 99%

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Precipitation of cerianite crystals and its effect on the rheology of a simplified nuclear glass melt

Jiusti,

Regnier,

Machado

et al. 2023

Int J of Appl Glass Sci

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In France, high‐activity level wastes resulting from nuclear fission are conditioned in a homogeneous sodium‐aluminoborosilicate glass by high‐temperature vitrification. The tolerance of even a small fraction of crystals could enable an increase in the waste loadings, in addition to promoting process flexibility. If the waste loading were to be increased in French nuclear glass, cerianite (CeO2) crystals could precipitate. In this study, we investigated the cerianite crystallization in a simplified nuclear glass melt at different temperatures, Ce2O3 wt%, and shear conditions. Furthermore, the evolution of the viscosity along with cerianite precipitation was followed. It was found that Ce2O3 is highly soluble in the glass melt, as even for a Ce2O3 wt% as high as 10% wt, the cerianite fraction in dynamic conditions at 1100°C after 8 h of crystallization was less than 1% vol. In addition, shear strongly accelerates cerianite crystallization and a high Ce2O3 content can engender the precipitation of highly branched dendrites. The evolution of the cerianite fraction did not significantly affect the viscosity of the glass melt. Finally, unlike what has been observed in the well‐known platinum group metal (PGM)‐bearing melts, a glass melt containing .8 vol% of cerianite crystals remains Newtonian.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Precipitation of cerianite crystals and its effect on the rheology of a simplified nuclear glass melt

Jiusti,

Regnier,

Machado

et al. 2023

Int J of Appl Glass Sci

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“…9,10 During high-temperature treatment, the viscosity of these systems plays a fundamental role in controlling several phenomena, such as melting, bath-to-glass conversion, particle aggregation, mass transfer, bubble removal, and the quality of the final product. [11][12][13][14][15][16][17][18][19] Glass-ceramic matrices are an alternative way to immobilize nuclear waste because higher amounts of HLWs can be vitrified and these matrices could offer a higher flexibility in the management of various waste streams. In such processes, different physicochemical transformations, such as bubble formation, liquid-liquid phase separation, and/or crystallization may take place.…”

Section: Introductionmentioning

confidence: 99%

“…To achieve this immobilization, the liquid waste is dried, calcined, and fed into a melter together with borosilicate glass frit 9,10 . During high‐temperature treatment, the viscosity of these systems plays a fundamental role in controlling several phenomena, such as melting, bath‐to‐glass conversion, particle aggregation, mass transfer, bubble removal, and the quality of the final product 11–19 …”

Section: Introductionmentioning

confidence: 99%

Rheology of a sodium‐molybdenum borosilicate melt undergoing phase separation

Pereira,

Schuller,

Wadsworth

et al. 2023

Int J of Appl Glass Sci

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During glass production, phase separation can result in the formation of suspended liquid droplets, which can cause changes in the system rheology. In nuclear waste vitrification context, some new glassy matrices may present this phase separation matter, but the mechanisms controlling the viscosity changes have not yet been determined. Here, we measure the viscosity of a sodium‐borosilicate melt containing dissolved MoO3 at different temperatures and subject to different applied shear strain rates. We observe that (i) the viscosity increases sharply as the temperature decreases and (ii) at any constant temperature below 1000°C, the system presents non‐Newtonian response. Using transmission electron microscope observations coupled with viscosity calculations, we interpret the cause of the observed changes as the result of phase separation. We show that the viscosity increase on cooling is in excess of the predicted temperature dependence for a homogeneous melt of the starting composition. The increase is due to the formation of a second phase and is controlled by chemical and structural modifications of the matrix during the loss of the elements that form the droplets. This work provides insights into the rheology of a system composed of two composition sets due to a miscibility gap.

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