Atomic scale investigation of silicon nanowires and nanoclusters

In this study, we have performed nanoscale characterization of Si-clusters and Si-nanowires with a laser-assisted tomographic atom probe. Intrinsic and p-type silicon nanowires (SiNWs) are elaborated by chemical vapor deposition method using gold as catalyst, silane as silicon precursor, and diborane as dopant reactant. The concentration and distribution of impurity (gold) and dopant (boron) in SiNW are investigated and discussed. Silicon nanoclusters are produced by thermal annealing of silicon-rich silicon oxide and silica multilayers. In this process, atom probe tomography (APT) provides accurate information on the silicon nanoparticles and the chemistry of the nanolayers

Etude de la segregation intra et intergranulaire de solutes par sonde atomique tomographique et microscopie electronique en transmission

Segregation is a general expression which describe the accumulation of atoms near defects of a material. Tomographic atom probe has been used to analyze, at a nanometric scale, the distribution of atoms near linear and planar defects.Boron atoms are added in small amount in Fe-40Al alloy (B2 ordered structure) to improve the mechanical resistance at ambient temperature. The spatial distribution of boron atoms in the grain of Fe-40Al alloy show a segregation to antiphase boundaries and stacking faults. A Cottrell atmosphere has been visualized for the first time at a nanometric scale. The enrichment of boron at the dislocation core is correlated with a depletion of aluminium atoms. We speculate that boron atoms substitute to aluminium atoms. This segregation of boron atoms within the grain of a Fe-40Al alloy seems to be responsible for the stabilisation of a new microstructure.A transmission electron microscope and a tomographic atom probe have been used to find a relation between the structure and the chemistry of a grain boundary. The experimental support of this work is a nickel base superalloy N18. Boron, molybdenium and chromium atoms segregate to the grain boundaries. This study show us that “random” grain boundaries are the most enriched in boron atoms. When this intergranular enrichment reach and is well above five atoms per square nanometer, a gamma disordered region of two nanometer in thickness separate always the gamma prime precipitates and the grain boundary plane.In a grain boundary plane, atoms are arranged in a way of parallelepipedal cells. Such a repartition might be the result of the particular structure of this grain boundary which is slightly misoriented to a position of coincidence.La ségrégation est une expression générale qui décrit un rassemblement d’atomes autour des défauts d’un matériau. La sonde atomique tomographique a été utilisée pour analyser à une échelle nanométrique la répartition des atomes prés de défauts linéaires et plans.Le bore est ajouté en quantité infinitésimale dans l’alliage Fe-40Al (structure ordonnée B2) pour augmenter sa résistance mécanique à température ambiante. La répartition spatiale des atomes de bore dans les grains de l’alliage Fe-40Al montre que ces atomes ségrégent sur les parois d’antiphase et les fautes d’empilements. L’image d’une atmosphère de Cottrell a été visualisée pour la première fois à une échelle nanométrique. L’enrichissement en bore au cœur de la dislocation s’accompagne d’un appauvrissement en aluminium. Le bore se substituerait aux atomes d’aluminium. Cette ségrégation de bore sur les défauts de l’alliage Fe-40Al semble responsable de la stabilisation d’une nouvelle microstructure.L’utilisation conjointe de la microscopie électronique en transmission et de la sonde atomique a permis d’étudier sur plusieurs joints de grains, la relation entre leur chimie et leur structure. Un superalliage à base de nickel N18 dopé au bore constitue le support expérimental de cette étude. Le bore, le molybdène et le chrome ségrègent aux joints. Mais ces analyses démontrent que les joints dits « généraux » sont les plus riches en bore. Quand cet enrichissement en bore atteint et dépasse 5 atomes par nanomètre carré, une zone désordonnée gamma de deux nanomètres d’épaisseur sépare toujours les précipités ordonnés gamma prime et le plan du joint.Dans le plan d’un joint de grains, des atomes ségrégés forment des cellules parallélépipédiques. Cette répartition semble provenir de la position légèrement désorientée par rapport à une position de coïncidence, de ce joint

Etude de la segregation intra et intergranulaire de solutes par sonde atomique tomographique et microscopie electronique en transmission

Segregation is a general expression which describe the accumulation of atoms near defects of a material. Tomographic atom probe has been used to analyze, at a nanometric scale, the distribution of atoms near linear and planar defects.Boron atoms are added in small amount in Fe-40Al alloy (B2 ordered structure) to improve the mechanical resistance at ambient temperature. The spatial distribution of boron atoms in the grain of Fe-40Al alloy show a segregation to antiphase boundaries and stacking faults. A Cottrell atmosphere has been visualized for the first time at a nanometric scale. The enrichment of boron at the dislocation core is correlated with a depletion of aluminium atoms. We speculate that boron atoms substitute to aluminium atoms. This segregation of boron atoms within the grain of a Fe-40Al alloy seems to be responsible for the stabilisation of a new microstructure.A transmission electron microscope and a tomographic atom probe have been used to find a relation between the structure and the chemistry of a grain boundary. The experimental support of this work is a nickel base superalloy N18. Boron, molybdenium and chromium atoms segregate to the grain boundaries. This study show us that “random” grain boundaries are the most enriched in boron atoms. When this intergranular enrichment reach and is well above five atoms per square nanometer, a gamma disordered region of two nanometer in thickness separate always the gamma prime precipitates and the grain boundary plane.In a grain boundary plane, atoms are arranged in a way of parallelepipedal cells. Such a repartition might be the result of the particular structure of this grain boundary which is slightly misoriented to a position of coincidence.La ségrégation est une expression générale qui décrit un rassemblement d’atomes autour des défauts d’un matériau. La sonde atomique tomographique a été utilisée pour analyser à une échelle nanométrique la répartition des atomes prés de défauts linéaires et plans.Le bore est ajouté en quantité infinitésimale dans l’alliage Fe-40Al (structure ordonnée B2) pour augmenter sa résistance mécanique à température ambiante. La répartition spatiale des atomes de bore dans les grains de l’alliage Fe-40Al montre que ces atomes ségrégent sur les parois d’antiphase et les fautes d’empilements. L’image d’une atmosphère de Cottrell a été visualisée pour la première fois à une échelle nanométrique. L’enrichissement en bore au cœur de la dislocation s’accompagne d’un appauvrissement en aluminium. Le bore se substituerait aux atomes d’aluminium. Cette ségrégation de bore sur les défauts de l’alliage Fe-40Al semble responsable de la stabilisation d’une nouvelle microstructure.L’utilisation conjointe de la microscopie électronique en transmission et de la sonde atomique a permis d’étudier sur plusieurs joints de grains, la relation entre leur chimie et leur structure. Un superalliage à base de nickel N18 dopé au bore constitue le support expérimental de cette étude. Le bore, le molybdène et le chrome ségrègent aux joints. Mais ces analyses démontrent que les joints dits « généraux » sont les plus riches en bore. Quand cet enrichissement en bore atteint et dépasse 5 atomes par nanomètre carré, une zone désordonnée gamma de deux nanomètres d’épaisseur sépare toujours les précipités ordonnés gamma prime et le plan du joint.Dans le plan d’un joint de grains, des atomes ségrégés forment des cellules parallélépipédiques. Cette répartition semble provenir de la position légèrement désorientée par rapport à une position de coïncidence, de ce joint

ETUDE DE LA SEGREGATION INTRA ET INTERGRANULAIRE DE SOLUTES PAR SONDE ATOMIQUE TOMOGRAPHIQUE ET MICROSCOPIE ELECTRONIQUE EN TRANSMISSION

ROUEN-BU Sciences (764512102) / SudocROUEN-BU Sciences Madrillet (765752101) / SudocSudocFranceF

Suzuki effect on \0 0 1\ stacking faults in boron-doped FeAl intermetallics

International audienceThree dimensional atom probe (3DAP) investigations of boron doped (400 ppm) FeAl40Ni3.8 samples aged at 400 °C for 1800 h, combined with electron microscopy observations, reveal that \001\ planar faults are boron enriched and aluminium depleted. The structure of such high energy defect is discussed and is thought to be stabilised by the segregation of boron. \textcopyright 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Suzuki effect on \0 0 1\ stacking faults in boron-doped FeAl intermetallics

International audienceThree dimensional atom probe (3DAP) investigations of boron doped (400 ppm) FeAl40Ni3.8 samples aged at 400 °C for 1800 h, combined with electron microscopy observations, reveal that \001\ planar faults are boron enriched and aluminium depleted. The structure of such high energy defect is discussed and is thought to be stabilised by the segregation of boron. \textcopyright 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Experimental simulation of spallation elements production in a 9Cr-1Mo martensitic steel 3D atom probe characterisation

International audienceThe irradiation damage in the target window of a demonstrator of an Accelerator Driven System (ADS) consists of atomic displacements (dpa) and spallation element production that will affect the in-service properties of the structural material of the target. The atomic displacements (about 100 dpa/year) will promote the formation of point defect clusters, dislocation loops and the precipitation of various phases that contribute to hardening and embrittlement of the structural material. As an example, the Ca and Ti production should harden the material via precipitation, in parallel to embrittlement due to P and S segregation. The purpose of this work was to simulate the spallation element loading, via ion implantation (using the IRMA implanter at CSNSM) and to study at the atomic scale, with the 3D atom probe, their evolution in the 9Cr-1Mo reference martensitic steel. In order to realize this, specific experiments, performed at 300°C, were carried out using low energy ions (Ca, Ti or S) implanted in the extremely small atom probe specimens (needles of 100 nanometers thickness)

Experimental simulation of spallation elements production in a 9Cr-1Mo martensitic steel 3D atom probe characterisation

International audienceThe irradiation damage in the target window of a demonstrator of an Accelerator Driven System (ADS) consists of atomic displacements (dpa) and spallation element production that will affect the in-service properties of the structural material of the target. The atomic displacements (about 100 dpa/year) will promote the formation of point defect clusters, dislocation loops and the precipitation of various phases that contribute to hardening and embrittlement of the structural material. As an example, the Ca and Ti production should harden the material via precipitation, in parallel to embrittlement due to P and S segregation. The purpose of this work was to simulate the spallation element loading, via ion implantation (using the IRMA implanter at CSNSM) and to study at the atomic scale, with the 3D atom probe, their evolution in the 9Cr-1Mo reference martensitic steel. In order to realize this, specific experiments, performed at 300°C, were carried out using low energy ions (Ca, Ti or S) implanted in the extremely small atom probe specimens (needles of 100 nanometers thickness)

Approches croisées de l’analyse de discours pour l’accompagnement du changement organisationnel : sémantique et statistique lexicale

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