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Hetherly, J.; Martinez, E.; Di, Z.F.; Nastasi, M.; Caro, A. |
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Helium bubble precipitation at dislocation networks |
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Journal Article |
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2011 |
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Scripta Materialia |
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In Press |
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Uncorrected Proof |
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Modeling; Precipitation; Grain boundary structure; He bubbles |
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We report on a study of nanoscale He bubble precipitation and growth at a twist grain boundary in two face-centered cubic materials. Experimentally, the twist boundary in Au captures all the He in the sample, forming equal-sized bubbles at the dislocation intersection junctions. Simulations in Cu reveal a complex structure of the interface and different He pressure in the interface bubbles compared to bulk, providing an explanation for the high efficiency of the boundary to capture all the He in the sample. |
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1359-6462 |
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NU @ karnesky @ |
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11267 |
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Martinez, E.; Ronsheim, P.; Barnes, J.-P.; Rochat, N.; Py, M.; Hatzistergos, M.; Renault, O.; Silly, M.; Sirotti, F.; Bertin, F.; Gambacorti, N. |
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Lanthanum diffusion in the TiN/LaOx/HfSiO/SiO2/Si stack |
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Journal Article |
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2011 |
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Microelectronic Engineering |
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Proceedings of the 17th Biennial International Insulating Films on Semiconductor Conference, 17th Bi |
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88 |
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7 |
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1349-1352 |
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Metal/high-k stack; TiN; HfSiO; La; Interfacial dipole; Threshold voltage tuning; ToF-SIMS; Apt; Atr-Ftir; S-Xps |
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Band edge Complementary Metal Oxide Semiconductor (CMOS) devices are obtained by insertion of a thin LaOx layer between the high-k (HfSiO) and metal gate (TiN). High temperature post deposition anneal induces Lanthanum diffusion across the HfSiO towards the SiO2 interfacial layer, as shown by Time of Flight Secondary Ions Mass Spectroscopy (ToF-SIMS) and Atom Probe Tomography (APT). Fourier Transform Infrared Spectroscopy in Attenuated Total Reflexion mode (ATR-FTIR) shows the formation of La-O-Si bonds at the high-k/SiO2 interface. Soft X-ray Photoelectron Spectroscopy (S-XPS) is performed after partial removal of the TiN gate. Results confirm La diffusion and changes in the La chemical environment. |
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0167-9317 |
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NU @ karnesky @ |
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11170 |
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Martinez, E.; Fu, C.-C.; Levesque, M.; Nastar, M.; Soisson, F. |
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Simulations of decomposition kinetics of Fe-Cr solid solutions during thermal aging |
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Journal Article |
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2011 |
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Solid State Phenomena |
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172-174 |
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1016 |
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cond-mat.mtrl-sci; cond-mat.stat-mech; physics.comp-ph |
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The decomposition of Fe-Cr solid solutions during thermal aging is modeled by Atomistic Kinetic Monte Carlo (AKMC) simulations, using a rigid lattice approximation with composition dependant pair interactions that can reproduce the change of sign of the mixing energy with the alloy composition. The interactions are fitted on ab initio mixing energies and on the experimental phase diagram, as well as on the migration barriers in iron and chromium rich phases. Simulated kinetics is compared with 3D atom probe and neutron scattering experiments. |
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arXiv:1102.1091v1; 6 pages, 5 figures, PTM 2010 |
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NU @ karnesky @ |
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11018 |
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Tang, Fengzai; Gault, Baptiste; Ringer, Simon P.; Martin, Phil; Bendavid, Avi; Cairney, Julie M. |
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Microstructural investigation of Ti-Si-N hard coatings |
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Journal Article |
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2010 |
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Scripta Materialia |
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63 |
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2 |
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192-195 |
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Titanium silicon nitride; Pulsed laser atom probe (PLAP); Nanostructure; Nanocomposite |
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The microstructures of nanostructured Ti-Si-N hard coatings were investigated by transmission electron microscopy and pulsed laser atom probe. C and O impurities were detected. No evidence of increased Si levels at the grain boundaries was found, suggesting that Si is either in the form of a layer too thin to be detected using the techniques employed or in the form of a solid solution of SiN clusters. |
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1359-6462 |
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NU @ karnesky @ |
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10856 |
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Wu, Ling-Mei; Seyring, Martin; Rettenmayr, Markus; Wang, Wen-Hsiung |
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Characterization of precipitate evolution in an artificially aged Al-Zn-Mg-Sc-Zr alloy |
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Journal Article |
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2010 |
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Materials Science and Engineering: A |
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527 |
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1068-1073 |
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Al-Zn-Mg-Sc-Zr alloy; age hardening; precipitation; transmission electron microscopy (TEM) |
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The precipitates of an age hardenable Al-Zn-Mg-Sc-Zr alloy aged at 140 °C have been studied by transmission electron microscopy (TEM). The results are interpreted in terms of structural transformations that involve two types of Guinier-Preston (GP) zones (I and II), the metastable [eta]’ hardening precipitate and the stable phase [eta]-phase (MgZn2). At early stages of ageing, the GPI zones act as nucleation sites for the plate-like [eta]’ phase which precipitates on the 111Al plane. The transformation from [eta]’ to [eta] occurs gradually at longer ageing times. The [eta] particles mainly consist of [eta]1 and [eta]2 phase, with small amounts of [eta]4 type and minor quantities of [eta]’ type structures. Furthermore, while a fine dispersion of coherent Al3(Sc,Zr) precipitates is known to have a beneficial effect on the strengthening of the alloy, the formation of GPII zones is suppressed in the presence of zirconium that leads to a reduction in the amount of [eta]’ formed during subsequent ageing. |
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0921-5093 |
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NU @ karnesky @ Wu2009 |
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10688 |
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Martin, G. |
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A diffuse interface model for the interfacial transfer coefficient |
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Journal Article |
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2005 |
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Acta Materialia |
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53 |
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9 |
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2629-2632 |
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Diffusion; Interfaces; Alloys; Kinetics; Phase field models; Theory |
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Based on an extension to non-equilibrium problems, of Cahn's interface layer thermodynamics, we demonstrate that the matrix of transfer coefficients across a coherent interface between two phases, [alpha] and [beta], can be viewed as a correction to the Onsager's matrix of mobility coefficients along the continuous concentration profile. The latter coefficients are defined along the equilibrium concentration profile in the interfacial layer and in the [alpha]- and [beta]-phases. Combining the above definition with that of solute interfacial excess, we can define transfer coefficients relative to two components chosen arbitrarily, the values of which are intrinsic properties of the interfacial layer, independent of its precise location and thickness. |
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NU @ p-kolli @ |
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9702 |
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Brechet, Yves; Martin, Georges |
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Nucleation problems in metallurgy of the solid state: recent developments and open questions |
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Journal Article |
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2006 |
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Comptes Rendus Physique |
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7 |
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9-10 |
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959-976 |
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Coherent precipitation; Recrystallisation; Precipitation coherente; Recristallisation |
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Nucleation processes play a key role in the microstructure evolution of metallic alloys during thermomechanical treatments. These processes can involve phase transformations (such as precipitation) and structural instabilities (such as recrystallisation). Although the word `nucleation' is used in both cases, the situation is profoundly different for precipitation and for recrystallisation on which this article is focussed. In the case of precipitation, species are conserved and the underlying physics is stochastic fluctuations, allowing the apparition of critical germs of the new phase. In the case of recrystallisation, the underlying physical phenomenon is the progressive growth of subgrain structures leading to an unstable configuration, allowing a dislocation free grain to grow at the expense of a dislocated one. The two cases require different types of modelling which are presented in the article. To cite this article: Y. Brechet, G. Martin, C. R. Physique 7 (2006). |
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NU @ karnesky @ |
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9593 |
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Mao, Zugang; Sudbrack, Chantal K.; Yoon, Kevin E.; Martin, Georges; Seidman, David N. |
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The mechanism of morphogenesis in a phase separating concentrated multi-component alloy |
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Journal Article |
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2007 |
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Nature Materials |
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6 |
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3 |
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210-216 |
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What determines the morphology of a decomposing alloy? Besides the well
established effect of the nucleation barrier, we demonstrate that, in a concentrated
multi-component Ni(Al,Cr) alloy, the details of the diffusion mechanism affect
strongly the kinetic pathway of precipitation. Our argument is based on the
combined use of atomic-scale observations, employing 3-dimensional atom-probe
tomography (3-D APT), lattice kinetic Monte Carlo simulations, and the theory of
diffusion. By an optimized choice of thermodynamic and kinetic parameters we first
reproduce the 3-D APT observations, in particular the early stage transient
occurrence of coagulated precipitates. We then modify the kinetic correlations
among the atomic fluxes in the simulation, without altering the thermodynamic
driving force for phase separation, by changing the vacancy-solute interactions,
resulting in a suppression of coagulation. Such changes can only be quantitatively
accounted for with nonzero values for the off-diagonal terms of the Onsager matrix,
at variance with classical models. |
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NU @ karnesky @ |
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1885 |
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Martin, Georges |
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Curriculum Vitae Georges Martin |
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Miscellaneous |
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2021 |
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2021 Curriculum Vitae Georges Martin |
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NU @ isheim @ |
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11562 |
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Mao, Zugang; Booth-Morrison, Christopher; Sudbrack, Chantal K.; Martin, Georges; Seidman, David N. |
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Kinetic pathways for phase separation: An atomic-scale study in Ni–Al–Cr alloys |
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Journal Article |
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2011 |
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Acta Materialia |
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60 |
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4 |
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1871-1888 |
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Nickel-based superalloys; Kinetic pathways; Atom probe tomography; Lattice kinetic Monte Carlo; Nanostructures |
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The kinetic pathways involved in the formation of [gamma]'(L12 structure)-precipitates during aging of concentrated Ni–Al–Cr alloys at 873 K, for three distinct alloy compositions, are studied experimentally by atom probe tomography, and computationally with lattice kinetic Monte Carlo (LKMC) simulations using parameters deduced from first-principles calculations of cohesive energies, and from experimental diffusion data. It is found that the compositional evolution of the [gamma]'-precipitate phase does not follow the predictions of a classical mean-field model for coarsening of precipitates in ternary alloys. LKMC simulations reveal that long-range vacancy–solute binding plays a key role during the early stages of [gamma]'-precipitation. With the aid of Monte Carlo techniques using the parameters employed in the LKMC simulations, we compute the diffusion matrix in the terminal solid-solutions and demonstrate that key features of the observed kinetic pathways are the result of kinetic couplings among the diffusional fluxes. The latter are controlled by the long-range vacancy–solute binding energies. It is concluded that, because it neglects flux couplings, the classical mean-field approach to phase separation for a ternary alloy, despite its many qualitatively correct predictions, fails to describe quantitatively the true kinetic pathways that lead to phase separation in concentrated metallic alloys. |
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1359-6454 |
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NU @ karnesky @ |
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11306 |
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