Structural investigations of borosilicate glasses containing MoO3 by MAS NMR and Raman spectroscopies

Caurant, Daniel; Majérus, Odile; Fadel, Edward; Quintas, Arnaud; Gervais, Christel; Charpentier, Thibault; Neuville, Daniel R.

doi:10.1016/j.jnucmat.2009.10.059

Cited by 106 publications

(132 citation statements)

References 34 publications

(77 reference statements)

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“…This behavior is similar to alkali molybdates such as Na 2 MoO 4 which are known to be water soluble. Multi-phase waste form composition and processing should be tailored to avoid these secondary phases [26]. …”

Section: Resultsmentioning

confidence: 99%

Single phase melt processed powellite (Ba,Ca)MoO4 for the immobilization of Mo-rich nuclear waste

Brinkman

Fox

Marra

et al. 2013

Journal of Alloys and Compounds

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Crystalline and glass composite materials are currently being investigated for the immobilization of combined High Level Waste (HLW) streams resulting from potential commercial fuel reprocessing scenarios. Several of these potential waste streams contain elevated levels of transition metal elements such as molybdenum (Mo). Molybdenum has limited solubility in typical silicate glasses used for nuclear waste immobilization.Under certain chemical and controlled cooling conditions, a powellite (Ba,Ca)MoO 4 crystalline structure can be formed by reaction with alkaline earth elements. In this study, single phase BaMoO 4 and CaMoO 4 were formed from carbonate and oxide precursors demonstrating the viability of Mo incorporation into glass, crystalline or glass composite materials by a melt and crystallization process. X-ray diffraction, photoluminescence, and Raman spectroscopy indicated a long range ordered crystalline structure. In-situ electron irradiation studies indicated that both CaMoO 4 and BaMoO 4 powellite phases exhibit radiation stability up to 1000 years at anticipated doses with a crystalline to *Manuscript Click here to view linked References amorphous transition observed after 1 X 10 13 Gy. Aqueous durability determined from product consistency tests (PCT) showed low normalized release rates for Ba, Ca, and Mo (<0.05 g/m 2 ).

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Section: Resultsmentioning

confidence: 99%

Single phase melt processed powellite (Ba,Ca)MoO4 for the immobilization of Mo-rich nuclear waste

Brinkman

Fox

Marra

et al. 2013

Journal of Alloys and Compounds

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“…In literature, molybdenum has a compounding effect on phase separation, not only by inducing precipitation of crystalline molybdates at high concentrations, but also by increasing the immiscibility temperature per mol of MoO 3 and lowering the viscosity and glass-transition temperature (T g ) of the melt [20]. It is also found to affect the glassy matrix by increasing network polymerization through a reduction of NBOs [17,23,60].…”

Section: Phase Separationmentioning

confidence: 99%

“…Molybdate formation in particular can be controlled by composition [10,16,17], external heat treatments [12,18,19], redox chemistry [20,21], or by controlled cooling during synthesis [11]. Compositionally, the preferential charge balancing of (BO 4 ) − and (MoO 4 ) 2 − anionic entities by Na + and Ca 2 + cations can determine molybdate speciation and network connectivity [22].…”

Section: Introductionmentioning

confidence: 99%

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Impacts of composition and beta irradiation on phase separation in multiphase amorphous calcium borosilicates

Patel

Boizot

Facq

et al. 2017

Journal of Non-Crystalline Solids

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A B S T R A C TBorosilicate glasses for nuclear waste applications are limited in waste loading by the precipitation of watersoluble molybdates. In order to increase storage efficiency, new compositions are sought out that trap molybdenum in a water-durable CaMoO 4 crystalline phase. Factors affecting CaMoO 4 combination and glass-inglass phase separation in calcium borosilicate systems as a function of changing [MoO 3 ] and [B 2 O 3 ] are examined in this study in order to understand how competition for charge balancers affects phase separation. It further examines the influence of radiation damage on structural modifications using 0.77 to 1.34 GGy of 2.5 MeV electron radiation that replicates inelastic collisions predicted to occur over long-term storage. The resulting microstructure of separated phases and the defect structure were analyzed using electron microscopy, XRD, Raman and EPR spectroscopy prior to and post irradiation. Synthesized calcium borosilicates are observed to form an unusual heterogeneous microstructure composed of three embedded amorphous phases with a solubility limit~2.5 mol% MoO 3. Increasing [B 2 O 3 ] increased the areas of immiscibility and order of (MoO 4 ) 2 − anions, while increasing [MoO 3 ] increased both the phase separation and crystallization temperature resulting in phases closer to metastable equilibrium, and initiated clustered crystallization for [MoO 3 ] > 2.5 mol%. β-irradiation was found to have favorable properties in amorphous systems by creating structural disorder and defect assisted ion migration that thus prevented crystallization. It also increased reticulation in the borosilicate network through 6-membered boroxyl ring and Si ring cleavage to form smaller rings and isolated units. This occurred alongside an increased reduction of Mo 6 + with dose that can be correlated to molybdenum solubility.In compositions with existing CaMoO 4 crystallites, radiation caused a scattering effect, though the crystal content remained unchanged. Therefore β-irradiation can preferentially prevent crystallization in calcium borosilicates for [MoO 3 ] < 2.5 mol%, but has a smaller impact on systems with existing CaMoO 4 crystallites.

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“…Mo predominantly occurs as a hexavalent state Mo 6+ in glasses prepared under oxidising and neutral atmospheres, regardless of glass composition [9][10] with each Mo 6+ cation being coordinated with four oxygens to form a MoO4 2-tetrahedron. The average Mo-O distance range is 1.76-1.78 Å, indicating that Mo 6+ has a high field strength range of 1.89-1.94 Å -2 in glass [6,[10][11][12][13] and thus Mo 6+ cations have a strong ordering effect on surrounding oxygens [14]. Consequently, the MoO4 2-tetrahedra can be easily separated from the silicate glass network.…”

Section: Introductionmentioning

confidence: 99%

MoO3 incorporation in magnesium aluminosilicate glasses

Tan

Ojovan

Hyatt

et al. 2015

Journal of Nuclear Materials

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Structural investigations of borosilicate glasses containing MoO3 by MAS NMR and Raman spectroscopies

Cited by 106 publications

References 34 publications

Single phase melt processed powellite (Ba,Ca)MoO4 for the immobilization of Mo-rich nuclear waste

Single phase melt processed powellite (Ba,Ca)MoO4 for the immobilization of Mo-rich nuclear waste

Impacts of composition and beta irradiation on phase separation in multiphase amorphous calcium borosilicates

MoO3 incorporation in magnesium aluminosilicate glasses

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