| 1. |
- Abrikosov, I. A., et al.
(författare)
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Multiscale approach to theoretical simulations of materials for nuclear energy applications : Fe-Cr and Zr-based alloys
- 2013
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Ingår i: Advances in materials for nuclear energy. - : Materials Research Society. - 9781605114910 ; , s. 3-14
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Konferensbidrag (refereegranskat)abstract
- We review basic ideas behind state-of-the-art techniques for first-principles theoretical simulations of the phase stabilities and properties of alloys. We concentrate on methods that allow for an efficient treatment of compositional and thermal disorder effects. In particular, we present novel approach to evaluate free energy for strongly anharmonic systems. Theoretical tools are then employed in studies of two materials systems relevant for nuclear energy applications: Fe-Cr and Zr-based alloys. In particular, we investigate the effect of hydrostatic pressure and multicomponent alloying on the mixing enthalpy of Fe-Cr alloys, and show that in the ferromagnetic state both of them reduce the alloy stability at low Cr concentration. For Zr-Nb alloys, we demonstrate how microscopic parameters calculated from first-principles can be used in higher-level models.
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| 2. |
- Allali, Naoual, et al.
(författare)
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Electrocatalytic effect towards NADH induced by HiPco single-walled carbon nanotubes covalently functionalized by ferrocene derivatives
- 2013
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Ingår i: 2012 MRS Fall Meeting. - : Cambridge University Press.
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Konferensbidrag (refereegranskat)abstract
- The present work reports the covalent functionalization of single-walled carbon nanotubes (SWCNTs) by ferrocene derivatives with polyethyleneglycol linkers. A very clean initial sample was chosen to avoid any residual catalyst and carbon impurities. Functionalized SWCNTs (f-CNTs) are deposited on the surface of a glassy carbon electrode (GCE) and this modified electrode is used for oxidizing the cofactor NADH (dihydronicotinamide adenine dinucleotide) in the presence of diaphorase. A clear electrocatalytic effect is evidenced, which can only be attributed to the f-CNTs.
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| 3. |
- Allali, Naoual, et al.
(författare)
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Few-wall carbon nanotubes covalently functionalized by ferrocene groups for bioelectrochemical devices
- 2012
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Ingår i: MRS Online Proceedings Library. - : Cambridge University Press. - 9781605114286
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Konferensbidrag (refereegranskat)abstract
- The present work reports the covalent functionalization of few-wall CNTs (FWCNTs) by ferrocene derivatives to i) improve their dispersion efficiency in water and ii) to graft electroactive chemical groups on their side-walls in order to promote electron transfer to biomolecules. The functionalized CNTs (f-CNTs) are used to modify a glassy carbon electrode and this modified electrode is used for oxidizing the cofactor NADH (dihydronicotinamide adenine dinucleotide).
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| 4. |
- Andersson, Henrik C. M., et al.
(författare)
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Creep testing of thick-wall copper electron beam and friction stir welds
- 2004
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Ingår i: Materials Research Society Symposium Proceedings. - 0272-9172 .- 1946-4274. - 1558997741 ; 824, s. 51-56
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Tidskriftsartikel (refereegranskat)abstract
- Thick section copper canisters are planned to be used as a corrosion protection of nuclear waste disposal containers for long term underground deposal in Sweden. The copper canisters will have the top and possibly the bottom lid welded to the canister walls using electron beam or friction stir welding. Due to the high external hydrostatic pressure and the relatively high temperature of the waste during the first one hundred years the copper will creep. The creep process will close the manufacturing gap between the cast iron container and the copper canister. The creep ductility must be sufficient to avoid cracking of the weld. Specimens cut from the friction stir welds and the electron beam welds have been creep tested at temperatures ranging from 75 to 175 degreesC. Cross-weld specimens were used for both friction stir and electron beam welds. Weld metal, heat affected zone and base metal were also studied for friction stir welds. The results for the electron beam welds show that the main creep deformation is concentrated to the weld metal where the failure takes place. Weld metal and most cross-weld tests of friction stir weld material show similar creep lives and ductility as base metal tests. Ductility at rupture was found to exceed 30% for friction stir weld specimens, and the Norton power law exponent was determined to be between 30 and 50.
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| 5. |
- André, Magnus, et al.
(författare)
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Determining sorption coefficients in intact rock using an electrical potential gradient as a driving force for migration
- 2006
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Ingår i: Scientific Basis for Nuclear Waste Management XXIX. - WARRENDALE, PA : MATERIALS RESEARCH SOCIETY. - 1558998896 ; , s. 975-982
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Konferensbidrag (refereegranskat)abstract
- The transport of radionuclides in indigenous rock is greatly affected by the sorption of cations in the porous rock matrix. For the determination of sorption coefficients, batch experiments have traditionally been used. For these experiments, the rock sample is crushed into fine particles to reduce the experimental time. However, this procedure increases the specific surface area of the sample and the new surfaces created could have different sorption qualities than the naturally occurring surfaces, which may impair the results of sorption coefficient determinations. A new method for determining sorption coefficients in intact rock is being developed, using electromigration as a means to speed up the transport process, thereby allowing for faster equilibration between the rock sample and the tracer solution. Here, we report results from preliminary experiments, using cesium as a sorbing tracer, showing a consistent difference between sorption coefficients obtained using electromigration methods on intact rock samples and traditional batch experiments on crushed samples.
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| 6. |
- Bader, Thomas K., 1980-, et al.
(författare)
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From lignin to spruce : Poromechanical upscaling of wood strength
- 2011
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Ingår i: 2010 MRS Fall Meeting. - Warrendale, Pennsylvania, USA : Materials Research Society. - 9781605112787 ; , s. 75-80
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Wood strength is highly anisotropic, due to the inherent structural hierarchy of the material. In the framework of a combined random-periodic multiscale poro-micromechanics model, we here translate compositional information throughout this hierarchy into the resulting anisotropic strength at the softwood level, based on “universal” elastic properties of cellulose, hemicelluloses, and lignin, and on the shear strength of the latter elementary constituent. Therefore, derivation of the elastic energy in a piece (representative volume element – RVE) of softwood, stemming from homogeneous macroscopic strains prescribed in terms of displacements at the boundary of the RVE and from pressure exerted by water filling the nanoporous space between the hemicelluloses-lignin network within the cell walls, with respect to the shear stiffness of lignin, yields higher order strains in the lignin phase, approximating micro-stress peaks leading to local lignin failure. Relating this (quasi-brittle) failure to overall softwood failure (or strictly speaking, elastic limit of softwood) results in a macroscopic microstructure-dependent failure criterion for softwood. The latter satisfactorily predicts the biaxial strength of spruce at various loading angles with respect to the grain direction. The model also predicts the experimentally well-established fact that uniaxial tensile and compressive strengths, as well as the shear strength of wood, depend quasi-linearly on the cell water content, but highly nonlinearly on the lumen porosity.
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| 7. |
- Biswas, Anis, et al.
(författare)
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The effect of oxygen partial pressure during deposition in the magnetic properties of ZnO thin film
- 2011
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Ingår i: Mater Res Soc Symp Proc. - : Springer Science and Business Media LLC. - 9781605112695 ; , s. 117-122
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Konferensbidrag (refereegranskat)abstract
- We have studied the magnetic properties of 100 nm thick ZnO thin films prepared by magnetron sputtering in different oxygen partial pressures (ratio of oxygen pressure to total pressure in deposition chamber, P Oxy). Only the films fabricated at P Oxy below ∼ 0.5 show room temperature ferromagnetism. The saturation magnetization at room temperature is initially found to increase as P Oxy increases and reaches maximum value of ∼ 5 emu/gm at P Oxy ∼ 0.3 and then starts to decrease and becomes diamagnetic for P Oxy > 0.5. From small angle XRD study of structural properties of the films, we find that the lattice stress developed in the film along c-axis also exhibits a similar behavior with the variation of P Oxy. Thus, both the room temperature ferromagnetism and lattice stress appear to originate from the intrinsic defects present in the sample.
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| 8. |
- Boosalis, Alexander, et al.
(författare)
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Spectroscopic Mapping Ellipsometry of Graphene Grown on 3C SiC
- 2012
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Ingår i: MRS Proceedings Volume 1407. - : Springer Science and Business Media LLC. ; , s. aa20-43
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Konferensbidrag (refereegranskat)abstract
- Spectroscopic mapping ellipsometry measurements in the visible spectrum (1.25 to 5.35 eV) are performed to determine the lateral variations of epitaxial graphene properties as grown on 3C SiC. Data taken in the visible spectrum is sensitive to both the Drude absorption of free charge carriers and the characteristic exciton enhanced van Hove singularity at 5 eV. Subsequent analysis with simple oscillator models allows the determination of physical parameters such as free charge carrier scattering time and local graphene thickness with a lateral resolution of 50 microns.
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| 9. |
- Butorin, S. M., et al.
(författare)
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Resonant inelastic soft X-ray scattering studies of U(VI) reduction on iron surfaces
- 2004
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Ingår i: Materials Research Society Symposium Proceedings. - 0272-9172 .- 1946-4274. ; 807:Scientific Basis for Nuclear Waste Management XXVII, s. 113-118
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Tidskriftsartikel (refereegranskat)abstract
- The authors report on the spectroscopic anal. of several samples relevant to the processes governing the behavior of oxidized U species in groundwater solns. under anoxic conditions. Both Fe samples with different times of exposure to the U(IV) soln. and Fe metal-soln. interfaces in the liq. cell ex-situ and in-situ, resp. Resonant inelastic soft x-ray scattering is sensitive to the chem. state of U. The measurements were performed at a no. of energies of the primary photon beam across the U 5d absorption edge. The results unambiguously indicate the redn. of U(VI) to U(IV) on the Fe surface. [on SciFinder(R)]
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| 10. |
- Cera, E., et al.
(författare)
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Modelling experimental results on radiolytic processes at the spent fuel water interface. II. Radionuclides release
- 2006
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Ingår i: Mater Res Soc Symp Proc. - : Springer Science and Business Media LLC. - 1558998896 - 9781558998896 ; , s. 537-546
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Konferensbidrag (refereegranskat)abstract
- Experimental and modelling efforts in the last decade in the frame of nuclear waste management field have been focused on studying the role of the UO2 surfaces in poising the redox state of solid/water systems as well as the radionuclides release behaviour. For this purpose, an experimental programme was developed consisting on dissolution experiments with PWR spent fuel fragments in an anoxic environment and by using different solution compositions. Some of the collected data has been previously published [1], specifically those data concerning radiolysis products and dissolution of the matrix. The results and the modelling tasks indicated an overall balance of the generated radiolytic species and that uranium dissolution was controlled by the oxidation of the spent fuel matrix in 10mM bicarbonate solutions while in the tests carried out at lower or without carbonate concentrations uranium in the aqueous phase was governed by the precipitation of schoepite. This paper is the continuation of a series accounting for the data and modelling work related to investigating the release behaviour of minor radionuclides from the spent fuel. Uranium concentrations as a function of time showed an initial increase until reaching a steady stale, indicating a matrix dissolution control. The same behaviour is observed for neptunium, caesium, strontium, technetium and molybdenum indicating a congruent release of these elements with the major component of the fuel matrix. On the other hand, no clear tendency is observed for plutonium data where additional solubility limiting mechanisms may apply. Kinetic modelling of the trace elements: caesium, strontium, technetium and molybdenum is based on the congruent release of these elements with the major component of the fuel matrix. Rate constants have been determined. Kinetic modelling of neptunium data took also into account the. subsequent precipitation as Np(IV) hydroxide. Finally, measured Pu concentrations may be explained by the precipitation of Pu(IV) and/or Pu(III) solid phases.
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