Transformation of Na2O-HfO2-B2O3 glass into a material having interconnected pores

A., M.; Bednarik, J.; Hart, S.; Sch�nberger, H.

doi:10.1007/bf00547965

Cited by 6 publications

(4 citation statements)

References 8 publications

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“…The isomorphic character between the Na 2 HfSi 2 O 7 and the parakeldyshite Na 2 ZrSi 2 O 7 can be explained by close ionic radii for Hf and Zr for the same coordination number [32]. All detail 0,5 0,6 0,7 0,8 0 [18] about the structure of Na 2 HfSi 2 O 7 are currently submitted and reviewed for a formal data deposition into XRD databases.…”

Section: Hafnium Crystallizationmentioning

confidence: 99%

“…Cachia [17] reported a higher conditional solubility at the same temperature, between 1.8 and 2.2 mol% HfO 2 in the same glass by modifying the experimental protocol. In the Na 2 O-B 2 O 3 system, Res [18] observed that increasing the Na 2 O concentration improved the HfO 2 solubility up to 12 mol% HfO 2 at 1400°C for a glass containing 18 mol% Na 2 O. Nevertheless, some dropletlike micro-heterogeneities were revealed by SEM in clear glasses.…”

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confidence: 98%

“…Ellison [20] showed that hafnium solubility decreased in B-free peraluminous melts in the system SiO 2 -Al 2 O 3 -Na 2 O-K 2 O with the SiO 2 content increasing and measured solubility limits lower than 1 mol% HfO 2 in equilibrated liquids at 1400°C. Above the solubility limit, the Hf-bearing crystallized phases were mainly monoclinic hafnia (HfO 2 ) [8,9,18] and occasionally hafnon (HfSiO 4 ) [10,20]. All these authors had melted their glasses under oxidizing conditions, namely in air and in Pt-Rh, ZrO 2 or Al 2 O 3 crucibles.…”

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confidence: 99%

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Hafnium solubility determination in soda-lime aluminosilicate glass

Chevreux

Laplace

Deloule

et al. 2017

Journal of Non-Crystalline Solids

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The solubility of hafnium dioxide (HfO 2 ), used as an uranium surrogate, is measured in glass melts belonging to the CaO-Al 2 O 3 -SiO 2 and Na 2 O-CaO-Al 2 O 3 -SiO 2 systems, under oxidizing and reducing conditions. Two methods have been carried out to determine it and the kinetic factors controlling the HfO 2 dissolution in glass melt have been investigated in order to approach equilibrium. The solubility ranges from 3 to 6.5 mol% HfO 2 in aluminosilicate glasses at temperature between 1250°C and 1400°C, and is not affected by the redox conditions. Conversely, the solubility is modified by the melting temperature and the glass composition. The excess of alkalies or alkaline earths which are not involved in the charge balance of AlO 4 tetrahedrons in the silica network appears to play a significant role. Glass homogeneity is checked by scanning electron microscopy and X-ray diffraction. O 7 are metastable crystals observed in the glass melts. The stability of those crystalline phases mainly depends on the glass composition. KeywordsHafnium oxide, solubility, aluminosilicate glass melt, reducing conditions, crystallization.to optimize the Hf-doped glasses elaboration conditions in order to approach equilibrium. The second objective is to determine hafnium solubility as a function of the melting temperature, the glass composition and the redox conditions. Hafnium crystallization is also investigated. State of the artThe thermodynamic solubility of an element in the glass is the maximum concentration of this element that can be loaded in the glass network at a given temperature. To determine it, two methods are commonly used. The first one consists in gradually increasing the amount the element to incorporate in the glass until a heterogeneous phase appears in the system (crystallization or/and demixing) [12]. The second one is embodied in introducing the desired element in excess in the glass and measuring its concentration in the vitreous matrix [13,14]. That means the saturated glass melt shows lots of heterogeneities. To make a difference between the gradation and the saturation methods, we named the last one the saturation solubility (S S ). The issue of reaching the equilibrium is raised in both cases. To approach equilibrium, the system has to verify several conditions [15], and if not, a conditional solubility (S C ) can be introduced notably for the gradation method [2,10]. This solubility depends on the experimental conditions used by the authors and it may be lower than the thermodynamic solubility for the gradation method or higher for the saturation technique [16]. Most hafnium solubility studies are focused on borosilicate glasses. Lopez measured conditional solubilities in a borosilicate glass as function of the melting temperature [10]. At 1400°C, hafnium conditional solubility was between 1.2 and 1.5 mol% HfO 2 . Cachia [17] reported a higher conditional solubility at the same temperature, between 1.8 and 2.2 mol% HfO 2 in the same glass by modifying the experimental protocol. In the Na 2 O-B 2 O...

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Section: Hafnium Crystallizationmentioning

confidence: 99%

mentioning

confidence: 98%

mentioning

confidence: 99%

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Hafnium solubility determination in soda-lime aluminosilicate glass

Chevreux

Laplace

Deloule

et al. 2017

Journal of Non-Crystalline Solids

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show abstract

“…6 A higher content of HfO 2 in a series of Na 2 O-HfO 2 -B 2 O 3 glasses led to phase separation. 29 Recently, a study of the dissolution of hafnium oxide in peralkaline and peraluminous boroaluminosilicate glasses used for commercial and defense-related nuclear waste reported a maximum solubility of 40 wt% of hafnium oxide. 19 These studies, taken together, suggest that substantial amounts of HfO 2 can be incorporated into RE silicates and that, conversely, modest amounts of REs can stabilize glasses in the hafnia-silica system.…”

Section: Introductionmentioning

confidence: 99%