Characterisation of a Complex CaZr0.9Ce0.1Ti2O7 Glass–Ceramic Produced by Hot Isostatic Pressing

Wilkins, Malin C. J. Dixon Dixon; Gausse, Clémence; Townsend, Luke T.; Gardner, Laura J.; Corkhill, Claire L.

doi:10.3390/ceramics5040074

Cited by 4 publications

(3 citation statements)

References 28 publications

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“…As re-oxidation from sputtered O atoms 53 prevents complete reduction at short times 48,50,53,55,56 , the absence of a u‴ Ce 4+ peak (916.7 eV) and v(Ce 3+ ) approaching unity after 30 s 3 keV and 80 s 200 eV sputtering, respectively, are consistent with a bulk v(Ce 3+ ) near unity. This is attributable to the HIP canister imposing reducing synthesis conditions [57][58][59] , consistent with significant v(Ce 3+ ) for HIP-synthesised zirconolites, often alongside secondary-phase perovskite 29,60,61 . Indeed, Ce 3+ is preferentially incorporated into perovskite through ionic radii considerations 9,13,43 .…”

Section: Perovskite As a Minor Phasementioning

confidence: 64%

Undetected perovskite phase interference with zirconolite dissolution measurements

Goût,

Mir,

Fairclough

et al. 2024

npj Mater Degrad

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Zirconolite ceramics present a chemically durable host matrix for waste actinides, but zirconolite dissolution rates reported in the literature often vary significantly. Here, the release of Ca and Al from a hot isostatically pressed zirconolite (Ca0.8Zr0.9Ce0.3Ti1.6Al0.4O7.0) was shown to be predominantly driven by preferential dissolution of minor perovskite and alumina phases. Both phases were undetectable by XRD, and the perovskite was difficult to detect by SEM-EDS. Whilst the zirconolite phase exhibited no signs of alteration, dissolution of the perovskite proceeded congruently without forming a hydrated altered layer or diffusion of protons into the solid that would be indicative of an ion-exchange mechanism. The weak temperature dependence of dissolution (40, 90 and 150 °C) showed that kinetics were limited by transport and a mixed transport-surface controlled reaction for Ca and Al, respectively. A significant H2O-D2O isotope effect on dissolution was observed for Ca but not for Al at all temperatures. The former was consistent with an abated rate of hydrolysis in the absence of a contribution from diffusion, whilst the latter could be attributed to differences in the activated complex for Ca and Al release through hydrolysis. These results demonstrate the role of a secondary phase perovskite in the dissolution kinetics of zirconolite even when perovskite occurs at low concentration and evades detection by bulk techniques such as XRD. This study provides a potential explanation of variations in zirconolite ceramic dissolution rates present in the literature and provides a null result to tests of an incongruent Ca release mechanism from zirconolite.

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Section: Perovskite As a Minor Phasementioning

confidence: 64%

Undetected perovskite phase interference with zirconolite dissolution measurements

Goût,

Mir,

Fairclough

et al. 2024

npj Mater Degrad

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“…From a mixture of 70% CaZr 0.9 Ce 0.1 Ti 2 O 7 and 30% albite glass NaAlSi 3 O 8 , a GCM was obtained by the HIP method to study the interaction of the matrix with a canister [212]. The pellets were heat treated for 4 h at 1250 • C in an atmosphere of Ar and 5% H 2 /95% N 2 .…”

Section: Glass Crystalline Materials (Gcm) With Zirconolite Crystalli...mentioning

confidence: 99%

Zirconolite Matrices for the Immobilization of REE–Actinide Wastes

et al. 2023

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The structural and chemical properties of zirconolite (ideally CaZrTi2O7) as a host phase for separated REE–actinide-rich wastes are considered. Detailed analysis of both natural and synthetic zirconolite-structured phases confirms that a selection of zirconolite polytype structures may be obtained, determined by the provenance, crystal chemistry, and/or synthesis route. The production of zirconolite ceramic and glass–ceramic composites at an industrial scale appears most feasible by cold pressing and sintering (CPS), pressure-assisted sintering techniques such as hot isostatic pressing (HIP), or a melt crystallization route. Moreover, we discuss the synthesis of zirconolite glass ceramics by the crystallization of B–Si–Ca–Zr–Ti glasses containing actinides in conditions of increased temperatures relevant to deep borehole disposal (DBD).

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“…For example, post-sintering treatment by HIP is applied to eliminate residual porosity during production of transparent ceramic parts. This technique is mainly used for engineered ceramics requiring optimum properties for high-performance applications, such as glass–ceramic nuclear wasteforms [ 30 , 32 , 33 ].…”

Section: Introductionmentioning

confidence: 99%

Non-Destructive Examination for Cavitation Resistance of Talc-Based Refractories with Different Zeolite Types Intended for Protective Coatings

et al. 2023

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In many industrial processes that include fluid flow, cavitation erosion of different engineering structures (pumps, turbines, water levels, valves, etc.) during their operation is expected. Metallic, ceramic, and composite materials are usual candidates considered for application in such extreme conditions. In this study, the idea is to synthesize refractory ceramic material based on talc with the addition of zeolite for utilization as protective coatings in cavitating conditions. Two talc-based refractories with zeolites from two Serbian deposits were produced. The behaviors of the samples in simulated cavitation conditions were examined by an advanced non-destructive methodology consisting of monitoring mass loss and surface degradation using image analysis compiled with principal component analysis (PCA), interior degradation by ultrasonic measurements, and the microstructure by a scanning electron microscope (SEM). Lower mass loss, surface degradation level, and modeled strength decrease indicated better cavitation resistance of the sample with Igros zeolite, whereby measured strength values validated the model. For the chosen critical strength, the critical cavitation period as well as critical morphological descriptors, Area and Diameter (max and min), were determined. A Young’s elasticity modulus decrease indicated that surface damage influence progressed towards interior of the material. It can be concluded that the proposed methodology approach is efficient and reliable in predicting the materials’ service life in extreme conditions.

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Characterisation of a Complex CaZr0.9Ce0.1Ti2O7 Glass–Ceramic Produced by Hot Isostatic Pressing

Cited by 4 publications

References 28 publications

Undetected perovskite phase interference with zirconolite dissolution measurements

Undetected perovskite phase interference with zirconolite dissolution measurements

Zirconolite Matrices for the Immobilization of REE–Actinide Wastes

Non-Destructive Examination for Cavitation Resistance of Talc-Based Refractories with Different Zeolite Types Intended for Protective Coatings

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