Papers by Author: T. Hansen

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Authors: H. Sitepu, J.P. Wright, T. Hansen, Daniel Chateigner, Heinz Günter Brokmeier, Clemens Ritter, Takaomi Ohba
Abstract: The crystal structure of R-phase in Ti50.75.Ni47.75.Fe1.50 shape memory alloy (SMA) has been studied at a temperature of (290 ± 7) K on cooling by combined synchrotron and neutron powder diffraction using Rietveld refinement with generalized spherical harmonic (GSH) description for preferred orientation (PO). The results showed that (i) no significant improvement in the crystallographic RWP-factor was found when the inversion center was removed from the 3 P model, suggesting that the space group was indeed 3 P and not lower symmetry 3 P neither m P31 and (ii) the refined atomic parameters were converging only when the 3 P space group was used in the refinement.
255
Authors: Abdelilah Benmarouane, T. Hansen, Pierre Millet, Alain Lodini
Abstract: The basic principles behind human tissue response to artificial surface implantation may be developed under its biological aspect, it is necessary for a medical use to study the mechanical limits of every biomaterials to predict the tissue and the body's response according to the composition, the structure and the design of a biomedical material. To promote a stable and functional direct connection between bone and implant, titanium implants can be coated with materials based on calcium phosphate ceramics such as hydroxyapatite (HAp)(Ca10(P04)6(OH)2). The preferred orientation of HAp crystallites at the interface bone-implant in sheep tibia bones has been measured with the neutron 2-axis diffractometer D20 at the Institut Max von Laue-Paul Langevin (ILL), extracted 60 days after implantation. The implant has two faces, one coated and one non-coated with plasma-sprayed HAp (80 .m). We probed the samples with a spatial resolution of 0.5 mm started from the interface in order to inspect the reorganisation of the HAp crystallite’s distribution after implantation.
612
Authors: Abdelilah Benmarouane, T. Hansen, Pierre Millet, Alain Lodini
951
Authors: Abdelilah Benmarouane, Helene Citterio-Bigot, T. Hansen, Pierre Millet, Alain Lodini
Abstract: In recent years, nanostructured coatings by Plasma Thermal Spraying (PTS) attracted intense interest due to their enhanced mechanical properties as hardness, strength and ductility. The aim of this study was to evaluate the influence of coating the implant by nanohydroxyaptite, n-HAp, Ca10 (PO4)6(OH)2. The results obtained with n-HAp will also compared with the implant coated with HAp. Bone is a composite material in which are associated a mineral phase in the form of crystals of HAp and an organic matrix constituted by collagen. The c-axes of HAp and the collagen fibers are preferentially oriented in the direction of the stresses that the bones need to withstand. At the interface implant-bone, the new bone reconstituted after implantation must have the same proprieties of the original bone in order to have good fixation with the implant. Therefore, it is necessary to study the mechanical properties of this new bone crystals reconstituted at the interface with the implants coated with n-HAp and HAp by neutrons diffraction on D20 at ILL.
163
Authors: I. Golosovsky, V. Dvornikov, T. Hansen, A. Fokin, E. Koroleva, L. Korotkov, A. Naberezhnov, M. Tovar
Abstract: Combined neutron diffraction, dielectric and conductivity measurements of NaNO2 embedded into porous glasses with average pore diameter 7 nm are performed in the ferroelectric and paraelectric phases. The temperature interval of existence of a volume premelted state in this confined material is determined. It is shown that the observed earlier giant growth of dielectric constant above TC can be attributed with an appearance of ionic conductivity due to jumping diffusion (or hopping) of constituent ions. These data are in a good agreement with experimental results of our earlier measurements of temperature evolution of structure of this nanocomposite material.
221
Authors: Abdelilah Benmarouane, Helene Citterio-Bigot, Guillaume Geandier, T. Hansen, Pierre Millet, Alain Lodini
Abstract: The quantitative evaluation of the preferential orientation of crystallites by the synchrotron and neutron diffraction techniques during regeneration at the interface with implant gives a good prediction of the mechanical properties of the bone. During the process of bone healing after implantation, the speed and quality of regeneration is affected by the nature of the implant surface. Titanium alloy (Ti-Al-4V) is currently coating with the hydroxyapatite (HAp), Ca10(PO4)6 (OH)2, in order to obtain a stable and functional direct connection between bone and implant. At the interface implant-bone, the new bone reconstituted after implantation must have the same mechanical properties of bone in order to accept the implant. Therefore, it is necessary to study by means of two non destructive techniques: neutron diffraction and synchrotron radiation, the crystal growth and texture of this new bone crystals reconstituted at the interface.
748
Authors: I. Popa, Sophie Rivoirard, Daniel Chateigner, T. Hansen, Daniel Fruchart
Abstract: In this study, a hot forging process is applied to Nd-Fe-V as cast alloys in order to develop both the microstructure and the crystallographic texture appropriate for permanent magnet properties. A neutron diffraction texture analysis is used to account for the extrinsic magnetic anisotropy: the stabilisation of the Nd(Fe,V)12 hard magnetic phase has been achieved during forging but its extrinsic anisotropy level remains low. Attempts to understand this phenomenon are made through a discussion on the Nd-Fe-V alloy rheological and mechanical behaviour and a comparison with Nd-Fe-B permanent magnets.
1389
Authors: A. Benmarouane, T. Hansen, Pierre Millet, Alain Lodini
Abstract: The preferred orientation of hydroxyapatite Ca10(PO4)6(OH)2 (HAp) crystallites at the interface bone-implant in sheep tibia bones has been measured with the neutron 2-axis diffractometer D20 at the Institut Max von Laue-Paul Langevin, extracted 60 days after implantation. The implant has two faces, one coated and one non-coated with plasma-sprayed HAp (80 µm). We probed the samples with a spatial resolution of 0.5 mm started from the interface in order to inspect the reorganisation of the HAp crystallite distribution after implantation.
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