Preparation of ThSiO4 single crystals by a vapour phase reaction

Kamegashira, Naoki

doi:10.1007/bf00589853

Cited by 5 publications

(2 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Despite the fact that the synthesis of isostructural zircon, − hafnon, , or thorite − has been reported without any difficulty through various experimental protocols, only a few researchers have succeeded in the preparation of coffinite. ,,− Fuchs et al were the first to report the synthesis of USiO 4 , using a precipitation route under hydrothermal conditions ( T = 250 °C, and t = 1 day), starting from a mixture of uranium tetrachloride and Na 2 SiO 3 as a silicon source. Apart from the initial mixture of reactants, this seminal publication already showed the need for several steps of pH regulation and buffering before the performance of the heat treatment, and the inherent difficulties illustrated by a very narrow pH range of formation.…”

Section: Introductionmentioning

confidence: 99%

Coffinite, USiO₄, Is Abundant in Nature: So Why Is It So Difficult To Synthesize?

et al. 2015

View full text Add to dashboard Cite

Coffinite, USiO4, is the second most abundant U(4+) mineral on Earth, and its formation by the alteration of the UO2 in spent nuclear fuel in a geologic repository may control the release of radionuclides to the environment. Despite its abundance in nature, the synthesis and characterization of coffinite have eluded researchers for decades. On the basis of the recent synthesis of USiO4, we can now define the experimental conditions under which coffinite is most efficiently formed. Optimal formation conditions are defined for four parameters: pH, T, heating time, and U/Si molar ratio. The adjustment of pH between 10 and 12 leads probably to the formation of a uranium(IV) hydroxo-silicate complex that acts as a precursor of uranium(IV) silicate colloids and then of coffinite. Moreover, in this pH range, the largest yield of coffinite formation (as compared with those of the two competing byproduct phases, nanometer-scale UO2 and amorphous SiO2) is obtained for 250 °C, 7 days, and 100% excess silica.

show abstract

Section: Introductionmentioning

confidence: 99%

Coffinite, USiO₄, Is Abundant in Nature: So Why Is It So Difficult To Synthesize?

et al. 2015

View full text Add to dashboard Cite

show abstract

“…The natural presence of coffinite was also reported in various uranium ore deposits all around the world. − Nevertheless, very few reliable thermodynamic data related to coffinite formation or solubility are available in the literature, − probably due to the persistent difficulties encountered in the preparation of pure and single-phase USiO 4 samples. Indeed, if a large amount of the literature was dedicated to the synthesis of isostructural zircon, − hafnon, , or thorite, − only a few authors reported the successful preparation of coffinite.…”

Section: Introductionmentioning

confidence: 99%

How To Explain the Difficulties in the Coffinite Synthesis from the Study of Uranothorite?

et al. 2011

View full text Add to dashboard Cite

The preparation of Th(1-x)U(x)SiO(4) uranothorite solid solutions was successfully undertaken under hydrothermal conditions (T = 250 °C). From XRD and EDS characterization, the formation of a complete solid solution between x = 0 (thorite) and x = 0.8 was evidenced. Nevertheless, additional (Th,U)O(2) dioxide and amorphous silica were systematically observed for the highest uranium mole loadings. The influence of kinetics parameters was then studied to avoid the formation of such side products. The variation of the synthesis duration allowed us to point out the initial formation of oxide phases then their evolution to a silicate phase through a dissolution/precipitation process close to that already described as coffinitization. Also, the uranium mole loading initially considered was found to significantly influence the kinetics of reaction, as this latter strongly slows down for x > 0.3. Under these conditions, the difficulties frequently reported in the literature for the synthesis of pure USiO(4) coffinite were assigned to a kinetic hindering associated with the coffinitization reaction.

show abstract

Thorite versus huttonite: stability, electronic properties and X-ray emission spectra from first-principle calculations

Shein

Ivanovskiĭ

2006

Phys Chem Minerals

View full text Add to dashboard Cite

Preparation of ThSiO4 single crystals by a vapour phase reaction

Cited by 5 publications

References 4 publications

Coffinite, USiO₄, Is Abundant in Nature: So Why Is It So Difficult To Synthesize?

Coffinite, USiO₄, Is Abundant in Nature: So Why Is It So Difficult To Synthesize?

How To Explain the Difficulties in the Coffinite Synthesis from the Study of Uranothorite?

Thorite versus huttonite: stability, electronic properties and X-ray emission spectra from first-principle calculations

Contact Info

Product

Resources

About

Preparation of ThSiO4 single crystals by a vapour phase reaction

Cited by 5 publications

References 4 publications

Coffinite, USiO4, Is Abundant in Nature: So Why Is It So Difficult To Synthesize?

Coffinite, USiO4, Is Abundant in Nature: So Why Is It So Difficult To Synthesize?

How To Explain the Difficulties in the Coffinite Synthesis from the Study of Uranothorite?

Thorite versus huttonite: stability, electronic properties and X-ray emission spectra from first-principle calculations

Contact Info

Product

Resources

About

Coffinite, USiO₄, Is Abundant in Nature: So Why Is It So Difficult To Synthesize?

Coffinite, USiO₄, Is Abundant in Nature: So Why Is It So Difficult To Synthesize?