TY - JOUR

T1 - The Chemistry, Recrystallization and Thermal Expansion of Brannerite from Akchatau, Kazakhstan

AU - Chen, Ruiqi

AU - Siidra, Oleg I.

AU - Firsova , Vera A.

AU - Arévalo-López, Ángel M.

AU - Colmont, Marie

AU - Bocharov, Vladimir N.

AU - Ugolkov , Valery L.

N1 - Chen, R.; Siidra, O.I.; Firsova, V.A.; Arevalo-Lopez, A.; Colmont, M.; Ugolkov, V.L.; Bocharov, V.N. The Chemistry, Recrystallization and Thermal Expansion of Brannerite from Akchatau, Kazakhstan. Materials 2023, 16, 1719. https://doi.org/10.3390/ma16041719

PY - 2023/2/18

Y1 - 2023/2/18

N2 - Numerous studies expose the potential of brannerite to become a good matrix, concentrating fission products and actinides. Minerals can complement the data collected from the synthetic materials and offer an advantage of a long-time exposure to radiation. Natural metamict brannerite from Akchatau, Kazakhstan, and its annealed sample were studied by EPMA, Raman spectroscopy, TGA, DSC, XRD and HTXRD. The radioactivity of pristine and annealed samples of brannerite was measured. Brannerite from Akchatau is characterized by the absence of significant amounts of REE and yttrium. The studied brannerite regains its structure at a temperature ~650 °C, revealed by the HTXRD and DSC. HTXRD was also performed on the annealed recrystallized brannerite. The thermal expansion for brannerite has been determined for the first time. The brannerite structure expands anisotropically with temperature increase. All the thermal expansion coefficients are positive except for αβ. The decreasing beta parameter indicates a “shear structural deformation“. The angle between the 1st axis of the tensor and the crystallographic a axis decreases with the increase of the temperature. The structure expands mostly in the α11 direction, approaching the bisector of the β angle. Brannerite has a low CTE at room temperature—αv = 16 × 10−6 °C−1, which increases up to 39.4 × 10−6 °C−1 at 1100 °C. In general, the thermal stability of brannerite is comparable to that of the other perspective oxide radioactive waste-immobilizing matrices (e.g., Ln2Zr2O7, CePO4, CaTiO3, CaZrTi2O7). The calculated thermal expansion of brannerite and the understanding of its underlying crystal chemical mechanisms may contribute to the behavior prediction of the material (both metamict and crystalline) at high temperatures.

AB - Numerous studies expose the potential of brannerite to become a good matrix, concentrating fission products and actinides. Minerals can complement the data collected from the synthetic materials and offer an advantage of a long-time exposure to radiation. Natural metamict brannerite from Akchatau, Kazakhstan, and its annealed sample were studied by EPMA, Raman spectroscopy, TGA, DSC, XRD and HTXRD. The radioactivity of pristine and annealed samples of brannerite was measured. Brannerite from Akchatau is characterized by the absence of significant amounts of REE and yttrium. The studied brannerite regains its structure at a temperature ~650 °C, revealed by the HTXRD and DSC. HTXRD was also performed on the annealed recrystallized brannerite. The thermal expansion for brannerite has been determined for the first time. The brannerite structure expands anisotropically with temperature increase. All the thermal expansion coefficients are positive except for αβ. The decreasing beta parameter indicates a “shear structural deformation“. The angle between the 1st axis of the tensor and the crystallographic a axis decreases with the increase of the temperature. The structure expands mostly in the α11 direction, approaching the bisector of the β angle. Brannerite has a low CTE at room temperature—αv = 16 × 10−6 °C−1, which increases up to 39.4 × 10−6 °C−1 at 1100 °C. In general, the thermal stability of brannerite is comparable to that of the other perspective oxide radioactive waste-immobilizing matrices (e.g., Ln2Zr2O7, CePO4, CaTiO3, CaZrTi2O7). The calculated thermal expansion of brannerite and the understanding of its underlying crystal chemical mechanisms may contribute to the behavior prediction of the material (both metamict and crystalline) at high temperatures.

KW - brannerite

KW - metamict minerals

KW - recrystallization of metamict minerals

KW - thermal analysis

KW - thermal expansion

KW - radioactive minerals

KW - matrix for HLW immobilization

UR - https://www.mendeley.com/catalogue/d36c675b-1ae8-3fd8-a801-cfaccaac20f6/

U2 - 10.3390/ma16041719

DO - 10.3390/ma16041719

M3 - Article

C2 - 36837349

VL - 16

JO - Materials

JF - Materials

SN - 1996-1944

IS - 4

M1 - 1719

ER -