Isabelle Bardez-giboire - Academia.edu (original) (raw)

Papers by Isabelle Bardez-giboire

Journal of Nuclear Materials, Jul 1, 2023

Journal of Non-Crystalline Solids, 2019

The structural and microstructural properties of both homogeneous and phase separated lanthanum a... more The structural and microstructural properties of both homogeneous and phase separated lanthanum aluminosilicate (La 2 O 3-Al 2 O 3-SiO 2 i.e. LaAS system) glasses were investigated. The microstructural observations and the structural characterization by X-ray Diffraction and by Nuclear Magnetic Resonance have highlighted the role of aluminum to favor a homogeneous vitreous aluminosilicate network by a high-level of Al/Si intermixing. A qualitative and simplified structure description is proposed from 29 Si nuclear magnetic resonance spectra assignment according to Q n (mAl) species by controlling the deviation of chemical parameters. According to this approach, a homogeneous distribution of non-bridging oxygen in the aluminosilicate network and Al-O-Al linkages are considered for homogeneous glasses with high Al/Si atomic ratio. Phase separated samples are characterized by a low Al/Si atomic ratio inducing spinodal or nucleation/growth phase separation according to the depolymerization level. Homogeneity degree of the samples is discussed according to the intermixing level between silicon tetrahedra and aluminum polyhedra as a function of the proportion of Q n and Q n (mAl) species.

npj Materials Degradation, 2018

For the handling of high level nuclear waste (HLW), new glass formulations with a high waste capa... more For the handling of high level nuclear waste (HLW), new glass formulations with a high waste capacity and an enhanced thermal stability, chemical durability, and processability are under consideration. This study focuses on the durability of peraluminous glasses in the SiO 2-Al 2 O 3-B 2 O 3-Na 2 O-CaO-La 2 O 3 system, defined by an excess of Al 3+ ions compared with the network-modifying cations Na + and Ca 2+. To qualify the behavior of such a peraluminous glass in a geological storage situation, its chemical durability was studied in various environments (pure water, groundwater, and alkaline solutions related to a cement environment) and glass alteration regimes (initial rate, residual rate, and resumption of alteration). The alteration solution was characterized by inductively coupled plasma, and the altered glass by scanning electron microscopy, X-ray diffraction and secondary ion mass spectrometry. A comparative study of the chemical durability of these and reference glasses (ISG and SON68) over all timescales highlights the remarkable properties of the former. While their initial dissolution rate is of the same order as the reference glasses, the gel formed under silica saturation conditions is more passivating, making its dissolution rate at least one order of magnitude lower, while its low alkalinity makes it less susceptible to clayey groundwater and highly alkaline solutions.

Journal of Nuclear Materials, 2017

The incorporation and partitioning of americium and trivalent lanthanides were investigated in al... more The incorporation and partitioning of americium and trivalent lanthanides were investigated in aluminoborosilicate glass-ceramics with apatite-like silicate crystals of general formula Ca2(Ln,Am)8(SiO4)6O2. A microstructural and structural study of two glass-ceramics containing Am2O3-La2O3 or Nd2O3-La2O3, respectively, was carried out by XRD, SEM/EDS and EMPA so as to assess a comparison of Lanthanides and Actinides partitioning into apatite crystals and residual glass. Moreover, Raman analyses of residual glasses were performed to compare the role of Am and Nd on the glassy structure. Results put forward that shape, composition, Ln/Am stoichiometry and cell parameters of apatite crystals of both (Am-La) and (Nd-La) glass-ceramics are very close. This paper thus shows similar results for (Am-La) and (Nd-La) glass-ceramics in terms of apatite / glass

Nuclear Science and Engineering, 2006

Abstract New nuclear highly durable glass compositions, able to immobilize a higher concentration... more Abstract New nuclear highly durable glass compositions, able to immobilize a higher concentration of high-level nuclear wastes than current borosilicate nuclear glasses, are being studied. Investigations are performed on rare earth (RE)-rich glasses, known as durable matrices. After a preliminary study on complex and simplified compositions, a basic glass composition was selected and studied (wt%): 51.0 SiO2–8.5 B2O3–12.2 Na2O–4.3 Al2O3–4.8 CaO–3.2 ZrO2–16.0 RE2O3. Chemical durability, physical properties (viscosity, transformation temperature), and crystallization tendency of glasses containing either a mixture of RE (La + Ce + Pr + Nd) or only one RE were studied and compared. The local environment of RE (for RE = Nd) in the glass and its evolution according to Nd2O3 concentration (from 1.3 to 30 wt%) was also studied by coupling characterization methods such as extended X-ray absorption fine structure spectroscopy at the neodymium LIII-edge and optical absorption spectroscopy. 11B, 27Al magic angle spinning-nuclear magnetic resonance, and Raman spectroscopy were also used to study glass structure.

Advanced Materials Research, 2008

The structure of a seven oxide aluminoborosilicate simplified nuclear glass, bearing a high amoun... more The structure of a seven oxide aluminoborosilicate simplified nuclear glass, bearing a high amount of neodymium or lanthanum oxide (16 wt%), alkali and alkaline earth cations is studied. Nd3+ or La3+ are supposed to simulate the trivalent lanthanides and minor actinides present in nuclear wastes. In the studied glass composition, lanthanide ions have a modifying role and are located in highly depolymerized regions of the structure as shown by neodymium optical absorption and EXAFS spectroscopies. Both alkali and alkaline earth cations are present around Nd3+ ions enabling their stabilization in glass structure near non-bridging oxygen atoms (NBOs). We show that both the nature of alkali R+ and alkaline earth R'2+ cations and the K = [R'O]/([R2O]+[R'O]) ratio can greatly influence the structure of the aluminoborosilicate glass network. Three glass series were prepared for which: (i) K ratio was varied from 0 to 0.5 (Na+ and Ca2+ being respectively the only alkali and alka...

Journal of the American Ceramic Society, 2012

Lanthanum and neodymium incorporation in simplified high level waste glasses has been investigate... more Lanthanum and neodymium incorporation in simplified high level waste glasses has been investigated for SiO 2-B 2 O 3-Na 2 O-Al 2 O 3-CaO compositions quenched from 1200°C, for varying La/(La + Nd) (atomic) and increasing rare-earth oxides contents. In this system and beyond the solubility limit, rare-earths (RE) elements are reported to form apatite phases with the general formula Ca 2 RE 8 (SiO 4) 6 O 2. In the current study, speciation of these trivalent RE 3+ cations in both amorphous network and crystal phases was determined from X-ray diffraction, scanning electron microscopy, optical absorption at 10 K, Raman spectroscopy, and electron probe microanalysis. It appeared that RE 2 O 3 solubility was higher for La-rich formulations than for Nd-rich ones and that an increase in the RE oxide content reduces the connectivity of the network building units through formation of non-bridging oxygens at the expense of the oxygen bridges. This depolymerization of the glass network did not affect neodymium environment which consisted in silicate tetrahedra. The composition of the apatite crystals was found to be affected by the La/(La + Nd) of the parent glass and deviation from the ideal composition (Ca 2 RE 8 (SiO 4) 6 O 2) occurred in the neodymium end of the system. It thus appears that both RE 2 O 3 solubility and crystal composition are strongly dependent on the type and crystal chemistry of the RE elements. C. Jantzen-contributing editor Manuscript No. 31058.

Journal of Nuclear Materials, 2006

Glass-ceramics containing neodymium-rich crystalline phases can be obtained by crystallization of... more Glass-ceramics containing neodymium-rich crystalline phases can be obtained by crystallization of silicate glasses (nucleation + crystal growth heat treatments) or by controlled cooling of melts. Such materials could be envisaged as durable matrices for conditioning minor actinides-and Pu-rich nuclear wastes if the partitioning ratio of the wastes between crystalline phase and residual glass is high (principle of double containment barrier). In radioactive waste forms, Nd would be partially substituted by actinides and neutron absorbers (Gd). In this work, two silicate glass compositions leading to efficient nucleation and crystallization of either zirconolite (Ca 1Àx Nd x ZrTi 2Àx Al x O 7 , x < 1) or apatite (Ca 2 Nd 8 Si 6 O 26) in their bulk were studied as potential waste forms. The effect of the method used to prepare glass-ceramics (controlled cooling from the melt or nucleation + crystal growth from the glass) on both the microstructure and the structure of the neodymium-rich crystalline phase was studied. The highest number of zirconolite or apatite crystals in the bulk was obtained using the nucleation + crystal growth method. However, the percentage of neodymium incorporated in zirconolite crystals remained too small to make realistic the use of such materials for the conditioning of actinides in comparison with more durable bulk ceramics.

Journal of Nuclear Materials, 2010

ABSTRACT Because of its high incorporation capacity and of the high thermal neutron capture cross... more ABSTRACT Because of its high incorporation capacity and of the high thermal neutron capture cross-section of hafnium, Hf-zirconolite (CaHfTi2O7) ceramic can be envisaged as a potential waste form for minor actinides (Np, Am, Cm) and plutonium immobilization. In this work, Nd-doped Hf-zirconolite Ca1−xNdxHfTi2−xAlxO7 (x = 0; 0.01 and 0.2) ceramics have been prepared by solid state reaction. Neodymium has been used as trivalent actinide surrogate. The ceramic samples structure has been studied by X-ray diffraction and refined by the Rietveld method. This revealed that Nd3+ ions only enter the Ca site, whereas part of Hf4+ ions substitute titanium into Ti(1) sites and Al3+ ions mainly occupy the Ti(2) split sites and Ti(3) sites of the zirconolite structure. Using various spectroscopic techniques (electron spin resonance, optical absorption and fluorescence), the environment of Nd3+ cations in Hf-zirconolite has been studied and compared with that of Nd3+ cations in Zr-zirconolite (CaZrTi2O7). Different local environments of Nd3+ cations have been detected in Hf-zirconolite that can be attributed to the existence of an important disorder around Nd in the Ca site probably due to the statistical occupancy of the next nearest cationic site of neodymium (a split Ti site) by Ti4+, Al3+ cations and vacancies. No significant differences were observed concerning Nd3+ cations environment and distribution in Hf- and Zr-zirconolite ceramics.

Journal of Non-Crystalline Solids, 2011

The environment of Nd 3+ ions has been studied using optical absorption spectroscopy and EXAFS at... more The environment of Nd 3+ ions has been studied using optical absorption spectroscopy and EXAFS at the Nd L 3-edge, in a series of soda lime aluminoborosilicate glasses with increasing B 2 O 3 content. The proportion of BO 4 units has been determined by 11 B MAS NMR in an equivalent glass series with La 3+ ions replacing the majority of Nd 3+ ions, and complementary information has been obtained by measuring the Nd 3+ decay fluorescence times in these latter glasses. In these glasses with low Al 2 O 3 content, the R′ ratio, with R′ = [Na 2 O exc ] / [B 2 O 3 ] and [Na 2 O exc ] = [Na 2 O] − [Al 2 O 3 ] − [ZrO 2 ], plays a key role in controlling the structural organization and crystallization resistance, in a similar way as the R ratio in the Dell and Bray model of sodium borosilicate glasses. At R′ N 0.5, the Nd 3+ ions are located in a mixed silicate-borate environment and, by slow cooling of the melt, they tend to crystallize within a silicate apatite phase close to the Ca 2 Nd 8 (SiO 4) 6 O 2 composition. At R′ b 0.5, the structural results are compatible with Nd 3+ ions located in a borate-type environment (not excluding Si neighbors), and, by slow cooling of the melt, they segregate with Ca 2+ ions within a Si-depleted separated borosilicate phase.

Journal of Materials Science, 2007

Glass-ceramics containing (Hf,Zr)-zirconolite crystals (nominally CaHf 1Àx Zr x Ti 2 O 7 with 0 x... more Glass-ceramics containing (Hf,Zr)-zirconolite crystals (nominally CaHf 1Àx Zr x Ti 2 O 7 with 0 x 1) were envisaged to immobilize minor actinides and plutonium. Such materials were prepared in this study by controlled crystallization of glasses belonging to the SiO 2-Al 2 O 3-CaO-Na 2 O-TiO 2-HfO 2-ZrO 2-Nd 2 O 3 system. Neodymium was used as trivalent actinides surrogate. The effect of total or partial substitution of ZrO 2 by HfO 2 (neutron poison for fission reactions) on glass crystallization in the bulk and near the surface is presented. It appeared that Hf/Zr substitution had not significant effect on nature, structure, and composition of crystals formed both on glass surface (titanite + anorthite) and in the bulk (zirconolite). This result can be explained by the close properties of Zr 4+ and Hf 4+ ions and by their similar structural role in glass structure. However, strong differences were observed between the nucleation rate I Z of zirconolite crystals in glasses containing only HfO 2 and in glasses containing only ZrO 2. Hf-zirconolite (CaHfTi 2 O 7) crystals were shown to nucleate only very slowly in comparison with Zr-zirconolite (CaZrTi 2 O 7) crystals. Composition changes-by increasing either HfO 2 or Al 2 O 3 concentration or by introducing ZrO 2 in parent glass-were performed to increase I Z in hafnium-rich glasses. The proportion of Nd 3+ ions incorporated in the zirconolite phase was estimated using ESR.

Journal of Materials Science, 2007

Glass-ceramic matrices containing zirconolite (nominally Ca(Zr,Hf)Ti 2 O 7) crystals in their bul... more Glass-ceramic matrices containing zirconolite (nominally Ca(Zr,Hf)Ti 2 O 7) crystals in their bulk that would incorporate high proportions of minor actinides (Np, Am, Cm) or plutonium could be envisaged for their immobilization. Zirconolite-based glass-ceramics can be prepared by controlled crystallization of zirconolite in glasses belonging to SiO 2-Al 2 O 3-CaO-Na 2 O-TiO 2-ZrO 2-HfO 2 system. In this study, neodymium was used as trivalent actinides surrogate. Increasing Al 2 O 3 concentration in glass composition had a strong effect on the nucleation rate I z of zirconolite crystals in the bulk, on the amount of neodymium incorporated in zirconolite phase and on the crystal growth rate of silicate phases (titanite + anorthite) from glass surface. These results could be explained by the existence of competition-in favor of aluminum-between Al 3+ and (Ti 4+ , Zr 4+ , Hf 4+) ions for their association with charge compensators cations to facilitate their incorporation in the glassy network. Differential thermal analysis (DTA) was used to study exothermal effects associated with bulk and surface crystallization. 27 Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectra showed that aluminum enters glasses network predominantly in 4-fold coordination. Neodymium optical absorption and fluorescence spectroscopies showed that the Al 2 O 3 concentration changes performed in this study had not significant effect on Nd 3+ ions environment in glasses.

Nucleation and growth of crystal in an oxide glass was studied in a Si B Al Zr Nd Ca Na O system.... more Nucleation and growth of crystal in an oxide glass was studied in a Si B Al Zr Nd Ca Na O system. The nucleation and growth process were monitored by thermal analysis and isothermal experiments. The effect of the network modifier was studied. Therefore for a Ca rich sample the crystallization is homogeneous in the bulk showing a slow increase of crystallinity as temperature increases. On the other hand, a Na rich sample undergoes several crystallization processes in the bulk or from the surface, leading to bigger crystals. The activation energy of the viscous flow and the glass transition are of same magnitude when that of crystallization is a lot smaller. Early diffusion of element is done with a mechanism different than the configurational rearrangements of the liquid sate. The global density and small size of the crystals within the Ca rich matrix confirmed that it would be a profitable waste form for minor actinides.

MRS Proceedings, 2006

Zirconolite is a candidate host material for conditioning minor tri- and tetra-valent actinides a... more Zirconolite is a candidate host material for conditioning minor tri- and tetra-valent actinides arising from enhanced nuclear spent fuel reprocessing and partitioning, in the case of disposal of the nuclear waste. Its chemical durability has been studied here under charged particle-induced radiolysis (He2+ and proton external beams) to identify the possible effects of water radiolysis on the dissolution rates in pure water and to describe the alteration mechanisms. Two experimental geometries have been used in order to evaluate the influence of the following parameters: solid irradiation, water radiolysis. In the first geometry the beam gets through the sample before stopping at the surface/water interface. In the second one the beam stops before the surface/water interface. Results on the elemental releases due to the enhanced dissolution of the zirconolite surface during charged particle-induced irradiation of water are presented. Under radiolysis, an increase of one order of magn...

Ceramic Transactions, 2010

Glass Physics and Chemistry

Local environments of rare earth ions are studied in a rare earth rich glass (Glass A wt%: 51·0Si... more Local environments of rare earth ions are studied in a rare earth rich glass (Glass A wt%: 51·0SiO 2 –8·5B 2 O 3 – 12·2Na 2 O–4·3Al 2 O 3 –4·8CaO–3·2ZrO 2 –16·0RE 2 O 3 with RE=Nd or La) developed for radioactive waste immobilisation. The aim is to determine the structural environment of rare earths in this glass according to their concentrations, and to study the influence of the peralkaline or peraluminous character of the glass on these environments. To achieve this objective, two series of glasses were prepared from Glass A. The first one contains variable amounts of rare earth oxide (from 0 to 30 wt% RE 2 O 3) and the second one is a series of peralkaline (R>50%) and peraluminous (R<50%) glasses, with R=([Na 2 O]+[CaO]) /([Na 2 O]+[CaO] +[Al 2 O 3 ]) at fixed RE 2 O 3 contents (16 wt%). The coupling of characterisation methods such as EXAFS (extended x-ray absorption fine structure) spectros-copy at the neodymium L III -edge, optical absorption spectroscopy, Raman spectro...

Les actinides mineurs (Np, Am, Cm) sont majoritairement responsables de la radiotoxicité à long t... more Les actinides mineurs (Np, Am, Cm) sont majoritairement responsables de la radiotoxicité à long terme des déchets nucléaires de haute activité. De nouvelles matrices vitrocéramiques à base de zirconolite CaZrTi2O7 ont fait l’objet de plusieurs études dans le cadre d’un confinement spécifique de ces actinides. De récentes recherches ont également été réalisées sur des céramiques et des vitrocéramiques à base de zirconolite CaHfTi2O7, afin d’étudier l’influence du remplacement du zirconium par le hafnium au sein de la phase zirconolite sur la cristallisation du verre. Il s’est avéré possible de synthétiser à la fois les céramiques et les vitrocéramiques voulues, ainsi que des vitrocéramiques mixtes (Zr - Hf). La substitution du zirconium par le hafnium n’a apparemment que peu d’influence sur l’environnement du néodyme (simulant des actinides mineurs) dans la structure zirconolite. Toutefois, répartis au sein d’une matrice vitreuse, les éléments constitutifs de la zirconolite-Hf ont be...

Journal of Non-Crystalline Solids, 2014

Considering the interest of developing new glass matrices able to immobilize higher concentration... more Considering the interest of developing new glass matrices able to immobilize higher concentration of high level nuclear wastes than currently used nuclear borosilicate compositions, glasses containing high rare earth contents are of particular interest. This study focuses on a peraluminous aluminoborosilicate system

Journal of Nuclear Materials, Jul 1, 2023

Journal of Non-Crystalline Solids, 2019

npj Materials Degradation, 2018

Journal of Nuclear Materials, 2017

Nuclear Science and Engineering, 2006

Advanced Materials Research, 2008

Journal of the American Ceramic Society, 2012

Journal of Nuclear Materials, 2006

Journal of Nuclear Materials, 2010

Journal of Non-Crystalline Solids, 2011

Journal of Materials Science, 2007

MRS Proceedings, 2006

Ceramic Transactions, 2010

Glass Physics and Chemistry

Journal of Non-Crystalline Solids, 2014

The reprocessing of nuclear spent fuel generates highly radioactive liquid wastes (HLW) that must... more The reprocessing of nuclear spent fuel generates highly radioactive liquid wastes (HLW) that must be isolated from the biosphere in very durable solid matrices. In the first part of this book (Chapters 1 and 2), generalities are presented on the radionuclides occurring in HLW and on the main characteristics and preparation methods of waste forms (glasses, ceramics, glass-ceramics) for the immobilization of separated or non-separated wastes. In the second part of this book (Chapter 3), the characteristics of two categories of long-lived radionuclides (135Cs and minor actinides: Np, Am, Cm) and the main matrices that have been proposed for their specific immobilization are reviewed. In the third part of this book (Chapter 4), to illustrate previous chapters, several results are presented on ceramic and glass-ceramic matrices developed for the conditioning of Cs (hollandite ceramic) and minor actinides (zirconolite ceramic, zirconolite-based glass-ceramic, apatite-based glass-ceramic) and studied in the laboratory of the authors. For cesium, BaxCsyTi(8-z)MzO16 hollandite ceramics (M: Al3+, Cr3+, Fe3+, Ga3+) prepared by oxide route are characterized by different methods. The effect of M on the single phase character of hollandite and on its capacity to incorporate Cs is studied. External electron irradiation experiments performed on a simple hollandite composition (Ba1.16Ti5.68Al2.32O16) to simulate the effect of -irradiation due to radioactive Cs decay are presented. Structural changes and defects formation are studied by different spectroscopic techniques such as Electron Paramagnetic Resonance (EPR). The stability with temperature of titanium (Ti3+) and oxygen (O2-) paramagnetic defects is studied. For selective immobilization of minor actinides, results concerning both zirconolite ceramic (nominally CaZrTi2O7) and a zirconolite-based glass-ceramic are presented. Rare-earths (mainly neodymium) and Th are used as minor actinide surrogates. Structural and microstructural results concerning the incorporation of Nd3+ ions in Ca1-xNdxZrTi2-xAlxO7 (x  0.6) zirconolite ceramics prepared by oxide route are presented. The local environment of Nd3+ ions in zirconolite ceramic samples is studied by EPR and optical absorption spectroscopy. A zirconolite-based glass-ceramic consisting of small zirconolite crystals homogeneously dispersed in its bulk and prepared by controlled crystallization of a parent glass belonging to the SiO2-Al2O3-CaO-TiO2-ZrO2-Nd2O3 system is studied. The effect of different parameters such as the crystallization temperature on the type of the crystals (bulk + surface), their structure and their microstructure is developed. Glass composition changes are performed in order to increase the amount of zirconolite in the glass-ceramic samples and to incorporate preferentially minor actinide surrogate in the zirconolite crystals (double containment principle). The possibility to prepare rare-earth calcium silicate apatite-based glass-ceramic waste forms (with crystals composition close to Ca2RE8(SiO4)6O2, RE: rare-earth) for the immobilization of actinide-rich nuclear waste solutions is also presented. The last part of this book (Chapter 5) concerns glassy waste forms used or envisaged to immobilize non-separated highly radioactive waste solutions arising from nuclear spent fuel reprocessing. Generalities about the structure and the properties of silicate, borate and borosilicate glasses are presented before developing how fission products and actinides can enter the structure of nuclear glasses. The structural role and the effect on nuclear glass properties of Al2O3 and B2O3 are also developed. Moreover, the relation that may exist between nuclear glasses composition, structure and crystallization tendency during melt cooling is illustrated by several results obtained in the laboratory of the authors on non-radioactive borosilicate nuclear glasses that could be envisaged to immobilize either Mo-rich (crystallization of alkaline or alkaline-earth molybdates) or rare-earth-rich (crystallization of rare-earth silicate apatite) highly radioactive solutions.