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  • "Understanding the evolution of mechanical properties under irradiation in nuclear glasses via experiments."
  • M. Barlet, J.-M. Delaye, D. Bonamy and C. L. Rountree
    , In 13th International Conference on Fracture. Beijing, China (June 16-21, 2013)
BibTeX:
@conference{Barlet2013,
  author = {M. Barlet and J.-M. Delaye and D. Bonamy and C. L. Rountree},
  title = {Understanding the evolution of mechanical properties under irradiation in nuclear glasses via experiments.},
  booktitle = {13th International Conference on Fracture},
  year = {2013},
  url = {http://www.gruppofrattura.it/ocs/index.php/ICF/icf13/paper/download/11521/10900}
}
Abstract: Abstract This paper's focus is the failure and hardness properties of pure amorphous silica (Corning 7980®) after β-irradiation at different doses (0-2 GGy). Crack propagation takes place in the SCC\ regime (10-7-10-10 m.s-1) and Vickers indentation techniques probe the hardness properties of the samples. Irradiation is found to create point defects which mainly include E’ centers, Non-Bridging Oxygen Hole Centers and Peroxy Radicals. β-irradiation herein invokes minor changes in the structure. A small effect of β-irradiation on SCC\ and hardness variations cannot be eliminated, despite minute variations in the SCC\ and the hardness properties.
BibTeX:
@article{Barlet2014,
  author = {M. Barlet and J-M. Delaye and M. Gennisson and R. Caraballo and B. Boizot and D. Bonamy and C.L. Rountree},
  title = {Influence of Electronic Irradiation on Failure and Hardness Properties of Pure Silica Glasses },
  journal = {Procedia Materials Science },
  year = {2014},
  volume = {7},
  number = {0},
  pages = {286 - 293},
  note = {2nd International Summer School on Nuclear Glass Wasteform: Structure, Properties and Long-Term Behavior, SumGLASS 2013 },
  url = {http://www.sciencedirect.com/science/article/pii/S2211812814010803},
  doi = {10.1016/j.mspro.2014.10.037}
}
  • "Antiferromagnetic long-range spin ordering in Fe- and NiFe2-doped BaTiO3 multiferroic layers"
  • A. Barbier, T. Aghavnian, V. Badjeck, C. Mocuta, D. Stanescu, H. Magnan, C. L. Rountree, R. Belkhou, P. Ohresser and N. Jedrecy
    Physical Review B. 91(3):035417 (January, 2015)
Abstract: We report on the Fe doping and on the comparative Ni-Fe codoping with composition close to NiFe2 of fully oxidized BaTiO3 layers (similar to 20 nm) elaborated by atomic oxygen plasma assisted molecular beam epitaxy; specifically any role of oxygen vacancies can be excluded in our films. Additionally to the classical in situ laboratory tools, the films were thoroughly characterized by synchrotron radiation x-ray diffraction and x-ray absorption spectroscopy. For purely Fe-doped layers, the native tetragonal perovskite structure evolves rapidly toward cubiclike up to 5% doping level above which the crystalline order disappears. On the contrary, low codoping levels (similar to 5% NiFe2) fairly improve the thin film crystalline structure and surface smoothness; high levels (similar to 27 lead to more crystallographically disordered films, although the tetragonal structure is preserved. Synchrotron radiation magnetic dichroic measurements reveal that metal clustering does not occur, that the Fe valence evolves from Fe2+ for low Fe doping levels to Fe3+ for high doping levels, and that the introduction of Ni favors the occurrence of the Fe2+ valence in the films. For the lower codoping levels it seems that Fe2+ substitutes Ba2+, whereas Ni2+ always substitutes Ti4+. Ferromagnetic long-range ordering can be excluded with great sensitivity in all samples as deduced from our x-ray magnetic absorption circular dichroic measurements. On the contrary, our linear dichroic x-ray absorption results support antiferromagnetic long-range ordering while piezoforce microscopy gives evidence of a robust ferroelectric long-range ordering showing that our films are excellent candidates for magnetic exchange coupled multiferroic applications.
BibTeX:
@article{Barbier2015,
  author = {Barbier, A. and Aghavnian, T. and Badjeck, V. and Mocuta, C. and Stanescu, D. and Magnan, H. and Rountree, C. L. and Belkhou, R. and Ohresser, P. and Jedrecy, N.},
  title = {Antiferromagnetic long-range spin ordering in Fe- and NiFe2-doped BaTiO3 multiferroic layers},
  journal = {Physical Review B},
  year = {2015},
  volume = {91},
  number = {3},
  pages = {035417},
  doi = {10.1103/PhysRevB.91.035417}
}
  • "Hardness and toughness of sodium borosilicate glasses via Vickers's indentations"
  • M. Barlet, J.-M. Delaye, T. Charpentier, M. Gennisson, D. Bonamy, T. Rouxel and C. L. Rountree
    Journal of Non-crystalline Solids. 417:66-79 (June, 2015)
Abstract: This study investigates the mechanical response of sodium borosilicate (SBN) glasses as a function of their chemical composition. Vickers's indentation tests provide an estimate of the material hardness (H-V) and indentation fracture toughness (K-C(VIF)) plus the amount of densification/shear flow processes. Sodium content significantly impacts the glass behavior under a sharp indenter. Low sodium glasses maintain high connected networks and low Poisson's ratios (nu). This entails significant densification processes during deformation. Conversely, glasses with high sodium content, i.e. large nu, partake in a more depolymerized network favoring deformation by shear flow. As a consequence, indentation patterns differ depending on the processes occurring. Densification processes appear to hinder the formation of half-penny median-radial cracks. Increasing nu favors shear flow and residual stresses enhance the development of half-penny median-radial cracks. Hence, K-C(VIF) decreases linearly with nu. (C) 2015 Elsevier B.V. All rights reserved.
BibTeX:
@article{Barlet2015,
  author = {Barlet, Marina and Delaye, Jean-Marc and Charpentier, Thibault and Gennisson, Mickael and Bonamy, Daniel and Rouxel, Tanguy and Rountree, Cindy L.},
  title = {Hardness and toughness of sodium borosilicate glasses via Vickers's indentations},
  journal = {Journal of Non-crystalline Solids},
  year = {2015},
  volume = {417},
  pages = {66--79},
  doi = {10.1016/j.jnoncrysol.2015.02.005}
}
  • "Local electronic structure and photoelectrochemical activity of partial chemically etched Ti-doped hematite"
  • M. Rioult, R. Belkhou, H. Magnan, D. Stanescu, S. Stanescu, F. Maccherozzi, C. Rountree and A. Barbier
    Surface Science. 641:310-313 (November, 2015)
Abstract: The direct conversion of solar light into chemical energy or fuel through photoelectrochemical water splitting is promising as a clean hydrogen production solution. Ti-doped hematite (Ti:alpha-Fe2O3) is a potential key photoanode material, which despite its optimal band gap, excellent chemical stability, abundance, non-toxicity and low cost, still has to be improved. Here we give,evidence of a drastic improvement of the water splitting performances of Ti-doped hematite photoanodes upon a HCl wet-etching. In addition to the topography investigation by atomic force microscopy, a detailed determination of the local electronic structure has been carried out in order to understand the phenomenon and to provide new insights in the understanding of solar water splitting. Using synchrotron radiation based spectromicroscopy (X-PEEM), we investigated the X-ray absorption spectral features at the L-3 Fe edge of the as grown surface and of the wet-etched surface on the very same sample thanks to patterning. We show that HCl wet etching leads to substantial surface modifications of the oxide layer including increased roughness and chemical reduction (presence of Fe2+) without changing the band gap. We demonstrate that these changes are profitable and correlated to the drastic changes of the photocatalytic activity. (C) 2015 Elsevier B.V. All rights reserved.
BibTeX:
@article{Rioult2015a,
  author = {Rioult, Maxime and Belkhou, Rachid and Magnan, Helene and Stanescu, Dana and Stanescu, Stefan and Maccherozzi, Francesco and Rountree, Cindy and Barbier, Antoine},
  title = {Local electronic structure and photoelectrochemical activity of partial chemically etched Ti-doped hematite},
  journal = {Surface Science},
  year = {2015},
  volume = {641},
  pages = {310--313},
  doi = {10.1016/j.susc.2015.01.002}
}
  • "From network depolymerization to stress corrosion cracking in sodium-borosilicate glasses: Effect of the chemical composition"
  • M. Barlet, J.-M. Delaye, B. Boizot, D. Bonamy, R. Caraballo, S. Peuget and C. L. Rountree
    Journal of Non-crystalline Solids. 450:174-184 (October, 2016)
Abstract: The study herein examines how chemical composition impacts sub-critical stress corrosion cracking (SCC) in sodium borosilicate glasses. The crack speed versus stress intensity factor (v vs. K-I) curves were obtained for seven ternary SiO2-Na2O-B2O3 (SBN) glasses of selected chemical compositions. Na2O plays an interesting role in the SCC behavior. First, increasing the Na2O concentration yields an increase in the environmental limit (K-e). Second, increasing the Na2O concentration affects how fast SCC occurs as K-I increases (i.e. the slope in region I SCC). This second effect is highly nonlinear: it is insignificant for Na2O <20% but it becomes increasingly important above 20 when sodium acts as a network modifier. Raman spectroscopy and Molecular Dynamics (MD) simulations aid in revealing the structural variations which arise from increasing concentrations of Na2O. Na2O causes the relative proportions of the different chemical bonds accessible in SBN glasses to vary. For this series of glasses, the Si-O-Si bond does not dominate the SCC properties. SCC variations originate in the mesoscale structure where sodium ions act as network modifiers on both the silica and borate units, thus yielding a partial depolymerization (i.e. a decrease in the reticulation level) of the network. This second effect reveals itself to be the one responsible for the SCC chemical dependency. Poissons ratio increases approximately linearly with increasing Na2O concentration, and thus, it is also not simply proportional to the slope in region I SCC. Partial depolymerization of the glass provides a novel prospective on the controlling factors in the sub-critical crack growth. (C) 2016 Elsevier B.V. All rights reserved.
BibTeX:
@article{Barlet2016,
  author = {Barlet, Marina and Delaye, Jean-Marc and Boizot, Bruno and Bonamy, Daniel and Caraballo, Richard and Peuget, Sylvain and Rountree, Cindy L.},
  title = {From network depolymerization to stress corrosion cracking in sodium-borosilicate glasses: Effect of the chemical composition},
  journal = {Journal of Non-crystalline Solids},
  year = {2016},
  volume = {450},
  pages = {174--184},
  doi = {10.1016/j.jnoncrysol.2016.07.017}
}
  • "Low energy electron imaging of domains and domain walls in magnesium-doped lithium niobate"
  • G. F. Nataf, P. Grysan, M. Guennou, J. Kreisel, D. Martinotti, C. L. Rountree, C. Mathieu and N. Barrett
    Scientific Reports. 6:33098 (September, 2016)
Abstract: The understanding of domain structures, specifically domain walls, currently attracts a significant attention in the field of (multi)-ferroic materials. In this article, we analyze contrast formation in full field electron microscopy applied to domains and domain walls in the uniaxial ferroelectric lithium niobate, which presents a large 3.8 eV band gap and for which conductive domain walls have been reported. We show that the transition from Mirror Electron Microscopy (MEM - electrons reflected) to Low Energy Electron Microscopy (LEEM - electrons backscattered) gives rise to a robust contrast between domains with upwards (P-up) and downwards (P-down) polarization, and provides a measure of the difference in surface potential between the domains. We demonstrate that out-of-focus conditions of imaging produce contrast inversion, due to image distortion induced by charged surfaces, and also carry information on the polarization direction in the domains. Finally, we show that the intensity profile at domain walls provides experimental evidence for a local stray, lateral electric field.
BibTeX:
@article{Nataf2016,
  author = {Nataf, G. F. and Grysan, P. and Guennou, M. and Kreisel, J. and Martinotti, D. and Rountree, C. L. and Mathieu, C. and Barrett, N.},
  title = {Low energy electron imaging of domains and domain walls in magnesium-doped lithium niobate},
  journal = {Scientific Reports},
  year = {2016},
  volume = {6},
  pages = {33098},
  doi = {10.1038/srep33098}
}
  • "Adsorbate Screening of Surface Charge of Microscopic Ferroelectric Domains in Sol-Gel PbZr0.2Ti0.8O3 Thin Films"
  • O. Copie, N. Chevalier, G. L. Rhun, C. L. Rountree, D. Martinotti, S. Gonzalez, C. Mathieu, O. Renault and N. Barrett
    ACS Applied Materials & Interfaces. 9(34):29311-29317 (2017)
BibTeX:
@article{Copie2017,
  author = {O. Copie and N. Chevalier and G. Le Rhun and C. L. Rountree and D. Martinotti and S. Gonzalez and C. Mathieu and O. Renault and N. Barrett},
  title = {Adsorbate Screening of Surface Charge of Microscopic Ferroelectric Domains in Sol-Gel PbZr0.2Ti0.8O3 Thin Films},
  journal = {ACS Applied Materials & Interfaces},
  year = {2017},
  volume = {9},
  number = {34},
  pages = {29311-29317},
  note = {PMID: 28776367},
  url = {http://dx.doi.org/10.1021/acsami.7b08925},
  doi = {10.1021/acsami.7b08925}
}
  • "Roughness of oxide glass sub-critical fracture surfaces"
  • G. Pallares, F.Lechenault, M. George, E. Bouchaud, C. Ottina, C. L. Rountree and M. Ciccotti
    Journal of the American Ceramic Society. (2017)
BibTeX:
@article{Pallares2017,
  author = {G. Pallares and F.Lechenault and M. George and E. Bouchaud and C. Ottina and C. L. Rountree and M. Ciccotti},
  title = {Roughness of oxide glass sub-critical fracture surfaces},
  journal = {Journal of the American Ceramic Society},
  year = {2017},
  doi = {10.1111/jace.15262}
}
  • "Recent progress to understand stress corrosion cracking in sodium borosilicate glasses: linking the chemical composition to structural, physical and fracture properties"
  • C. L. Rountree
    Journal of Physics D: Applied Physics. 50:34 (2017)
BibTeX:
@article{Rountree2017,
  author = {C. L. Rountree},
  title = {Recent progress to understand stress corrosion cracking in sodium borosilicate glasses: linking the chemical composition to structural, physical and fracture properties},
  journal = {Journal of Physics D: Applied Physics},
  year = {2017},
  volume = {50},
  pages = {34},
  url = {http://iopscience.iop.org/article/10.1088/1361-6463/aa7a8b/meta},
  doi = {10.1088/1361-6463/aa7a8b}
}
 

Maj : 04/12/2017 (2790)

 

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