Mechanical and structural properties of radiation-damaged allanite-(Ce) and the effects of thermal annealing

Reissner, Claudia E.; Bismayer, U.; Kern, Daniel; Reissner, M.; Park, Sulgiye; Zhang, Jiaming; Ewing, Rodney C.; Shelyug, Anna; Navrotsky, Alexandra; Paulmann, Carsten; Škoda, Radek; Groat, Lee A.; Pöllmann, Herbert; Beirau, Tobias

doi:10.1007/s00269-019-01051-z

Cited by 15 publications

(6 citation statements)

References 49 publications

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“…An overall comparable (but in the investigated temperature region less pronounced) recrystallization related mechanical hardening has been revealed for the U and/or Th containing radiation-damaged minerals allanite [(Ca)(REE)(Al) 2 (Fe 2 + )[SiO 4 ][Si 2 O 7 ]O(OH)] [65] and at higher temperatures also titanite (CaTiSiO 5 ) [66] . Although, initial me-chanical softening, as found in titanite [66 , 67] , has not been observed in pyrochlore.…”

Section: Effect Of Thermal Annealingmentioning

confidence: 61%

Mechanical and Structural Response of Radiation-Damaged Pyrochlore to Thermal Annealing

Reissner

Roddatis²,

Bismayer³

et al. 2020

SSRN Journal

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Nanoindentation has been employed to probe the mechanical properties [indentation hardness ( H ) and elastic modulus ( E )] of radiation-damaged pyrochlore before and after step-wise thermal annealing up to 900 K. Three natural U and/or Th containing samples with increasing degree of disorder have been investigated (i.e., Panda Hill: 1.8 wt% ThO 2 , maximum life-time alpha-decay event dose ~1.6 × 10 18 -decay g − 1 ; Blue River: 11.9 wt% UO 2 , maximum life-time alpha-decay event dose ~115.4 × 10 18 -decay g − 1 ; and Miass: 7.2 wt% ThO 2 , maximum life-time alpha-decay event dose ~23.1 × 10 18 -decay g − 1 ). Complementary investigations by photoluminescence and Raman spectroscopy and in-situ annealing transmission electron microscopy (TEM) allowed us to follow the structural evolution. Therefore, a comprehensive understanding of the thermally induced structural reorganization process was obtained. Recrystallization has found to start above 500 K in the pyrochlores. Due to the increasing structural order a general hardening of the mechanical properties was observed. Miass pyrochlore (highest degree of structural damage of the investigated samples) reaches a polycrystalline state after annealing. While lesser damaged, but also highly disordered Blue River pyrochlore (containing small preserved crystalline domains) has found to transform into a single crystal. The recrystallization of both pyrochlore samples was followed by in-situ TEM at 800 and 750 K, respectively.

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Section: Effect Of Thermal Annealingmentioning

confidence: 61%

Mechanical and Structural Response of Radiation-Damaged Pyrochlore to Thermal Annealing

Reissner

Roddatis²,

Bismayer³

et al. 2020

SSRN Journal

Self Cite

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“…The loss of structural O-H as shown in the IR results leads to the breakdown of the structure, and the widening of FWHM Bragg peaks is proof of the degradation of the crystal structure that has caused the internal and surface cracking. Internal and surface cracking after stepwise annealing from 527-727 °C caused by heterogeneous recrystallization and hydrogen loss was also observed by Reissner et al (2019).…”

Section: Surface Topographymentioning

confidence: 79%

Heating Effects in the Structure of Non-metamict Allanite-(La) from Palawan, Philippines

Dingle¹,

Jecong²,

Olivares³

et al. 2021

Philipp J Sci

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Allanite is one of the most common sources of rare-earth elements (REEs) and contains significant amounts of thorium (Th) and uranium (U). The presence of radioactive Th and U nuclides in the mineral exposes it to long-term radiation. Like other natural minerals containing Th and U, allanite can be used as a natural analog to understand the long-term radiation effects in high-level nuclear waste (HLW) matrices. Allanite group mineral is generally found in the amorphous phase due to structural damage induced by self-irradiation. In this work, crystalline allanite-(La) samples collected in San Vicente, Palawan, Philippines – having a low absorbed -dose of ~ 1014 α-decays/ mg – were heated at 450, 650, and 850 °C to study the response of non-metamict allanite to heating at elevated temperatures, particularly at the early stages of exposure to alpha-particle radiation. An increase in structural order was observed upon heating to 450 and 650 °C, which is exhibited by a decrease in the unit cell volume by 1.6% and a decrease of the full width at half maximum (FWHM) of selected Bragg planes. It was evident that certain Bragg planes respond differently to the annealing temperatures with preferential reorientation. After annealing at 850 °C, however, the loss of OH bonds was observed in the infrared (IR) spectra, and the broadening of Bragg peaks was seen in the x-ray diffraction (XRD) patterns, suggesting an onset of structural degradation. Surface cracks are also seen in the scanning electron microscope (SEM) images. The study shows that the non-metamict allanite-(La) mineral structure responds to heating similarly to that of metamict ones reported in the literature. This study will provide data on the properties of allanite as part of the ongoing studies on radiation damage in silicate matrices.

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“…2 in spectra for the unannealed sample and those annealed at lower temperatures results from the metamictization process. In untreated allanite-(Ce) specimens with various degrees of metamictization, the ratio of ΣFe 2+ to ΣFe varied from 0.40 to 0.73 [31,32]. For a sample of fully metamict allanite, heating in atmospheric air at 1000 K causes only partial oxidation of Fe 2+ to Fe 3+ [32].…”

Section: Changes In Fe 2+ Componentsmentioning

confidence: 99%

57Fe Mössbauer Spectroscopy and X-ray Diffraction of Annealed Highly Metamict Perrierite: Activation Energy and Recrystallization Processes

Malczewski,

Grabias,

Dziurowicz

et al. 2023

Minerals

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This paper presents the results of 57Fe Mössbauer spectroscopy and X-ray diffraction analysis of highly metamict perrierite (REE,Ca,Th)4(Fe2+,Mg)2(Ti,Fe3+)3Si4O22 after annealing in argon from 673 to 1273 K for one hour. Radioactive elements in metamict minerals damage crystal structure on geologic time scales primarily due to recoil nuclei from α-decay of 238U, 232Th, 235U, and their daughter products. Metamict minerals are widely used in geochronology and can serve as natural analogs for the study of radiation effects in high-level nuclear waste. Analyses were performed on fragments of a perrierite sample collected from granitoids near Amherst, Virginia (USA). Electron microprobe and gamma-ray spectrometry recorded Fe concentrations of 4.7 wt.% and Th and U concentrations of 0.64 and 0.06 wt.%, respectively. The calculated total absorbed α-dose was 7.8 × 1015 α-decay mg−1. The Mössbauer spectrum of the untreated sample can be fitted to two Fe2+ and two Fe3+ doublets in octahedral coordination with a relative ΣFe2+/ΣFe of 0.63. For samples annealed at 1173 K and 1273 K, spectra show a decrease in the total contribution of Fe2+ to 0.58 due to dehydroxylation associated with the simultaneous oxidation of post-metamict Fe2+ to Fe3+. In the examined perrierite, Fe2+ occurs in structural positions B and C(1). The broad, predominant Fe3+ doublet observed in the spectrum of the unannealed sample splits into two components at 973 K interpreted to represented positions C(1) and C(2) in the perrierite structure. The Mössbauer spectra show a prominent decrease in the width of the high-energy absorption peak representing Fe2+ components with increasing temperature. The variation in the width of this peak versus the annealing temperature seems to be an indicator of thermally induced recrystallization. Based on the exponential dependence of the derivative function of the parameter with the inverse temperature and using an Arrhenius plot, an activation energy (EA) of 0.73 eV was determined for thermally-induced recrystallization. Corresponding XRD data show progressive recrystallization with increasing annealing temperature. The XRD pattern of the fragment annealed at 1273 K indicates that highly metamict perrierite recrystallized to the pre-metamict state that can be indexed to the C2/m space group.

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Mechanical and structural properties of radiation-damaged allanite-(Ce) and the effects of thermal annealing

Cited by 15 publications

References 49 publications

Mechanical and Structural Response of Radiation-Damaged Pyrochlore to Thermal Annealing

Mechanical and Structural Response of Radiation-Damaged Pyrochlore to Thermal Annealing

Heating Effects in the Structure of Non-metamict Allanite-(La) from Palawan, Philippines

57Fe Mössbauer Spectroscopy and X-ray Diffraction of Annealed Highly Metamict Perrierite: Activation Energy and Recrystallization Processes

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