Study of (010)[101] and (001)[110]/2 dislocations in K-feldspars by HRTEM and modelling

Dislocations in K-feldspars were studied by high resolution transmission electron microscopy (HRTEM) and HRTEM images were further submitted to a filtering in order to improve their interpretation. (010)[101] dislocations appear to be dissociated with (001)[001]/2 planar defect, whereas (001)[110]/2 dislocations are perfect. Structural models of planar defects in (010) and (001) planes were investigated. The energy estimation of these models was performed using the Keating potential. The structural analysis agreed with the experimental result in that dislocations can be dissociated in the (010) plane, whereas they cannot be dissociated in the (001) plane. © 1988 Springer-Verlag

Study of (010)[101] and (001)[110]/2 dislocations in K-feldspars by HRTEM and modelling

Dislocations in K-feldspars were studied by high resolution transmission electron microscopy (HRTEM) and HRTEM images were further submitted to a filtering in order to improve their interpretation. (010)[101] dislocations appear to be dissociated with (001)[001]/2 planar defect, whereas (001)[110]/2 dislocations are perfect. Structural models of planar defects in (010) and (001) planes were investigated. The energy estimation of these models was performed using the Keating potential. The structural analysis agreed with the experimental result in that dislocations can be dissociated in the (010) plane, whereas they cannot be dissociated in the (001) plane. © 1988 Springer-Verlag

Comportement mécanique des sols injectés aux produits chimiques

Le comportement mécanique d'un sable fin consolidé par injection de gels de silicates ou de résines acrylamides est étudié à partir d'essais comprenant : la compression simple avec vitesses de déformation ou de charge contrôlées, la relaxation, le fluage et le fluage sous effet de poinçonnement.La résistance mécanique est liée au facteur temps qui intervient dans le mode de mise sous contraintes et dans la durée d’application des contraintes.L'amplitude et la variation dans le temps de la résistance mécanique sont étroitement liées au dosage interne des différents constituants des produits injectés.Ces notions permettent d'améliorer et de rendre sûr le choix des produits à injecter suivant que le traitement envisagé a un caractère provisoire ou définitif

STUDY OF NUCLEATION PROCESS IN (SiO2, Al2O3, Li2O) GLASSES, BY X-RAY ABSORPTION SPECTROSCOPY AND TRANSMISSION ELECTRON MICROSCOPY

Microscopie électronique (TEM) et spectrométrie d'absorption X (structure fine des seuils et EXAFS) sont utilisées de façon complémentaire pour étudier les toutes premières étapes de la nucléation cristalline dans des verres du système (SiO2-Al2O3-Li2O). La microscopie électronique fine a permis de caractériser les phases cristallines et la taille des cristaux (20-50 Å pour les premiers stades de nucléation, 200-500 Å pour la vitrocéramique finale). La spectrométrie d'absorption X a été réalisée aux seuils des deux éléments nucléants : le titane et le zirconium. Le titane évolue depuis le site de coordinence 4 qu'il occupe dans le verre vers un site de coordinence 6 dans la vitrocéramique. Cela est suivi en particulier par l'analyse du "prépic" au seuil d'absorption K du titane. L'environnement du zirconium reste très désordonné au stade final de la vitrocéramique.TEM and X-ray absorption spectrometry (fine edge structure and EXAFS) are combined to study the earliest stages of crystalline nucleation in glasses of the system (SiO-Al2O3-Li2O). TEM has allowed the characterization of the crystalline phases and the crystal sizes (20-50Å in the first nucleation stages, 200-500Å in the final glass ceramic). X-ray absorption spectrometry has been performed at the K-edge of the two nucleating agents titanium and zirconium. The titanium site changes from a 4-fold coordinated situation in the "green" glass to a 6-fold one in the glass ceramic ; that is directly given by the K-edge prepeak analysis. The zirconium environment remains highly disordered even at the final crystallized stage

Mode de glissement des dislocations (010)[001] dans les feldspaths alcalins. methr et modélisation.

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Influence du recuit sur la structure des couches minces d'or

Changes in film structure during annealing are observed by measuring electrical resistivity variations. It thus appears a re-crystallization stage and a " coagulation " stage. Structures are then investigated by X-rays diffraction method and electron microscopy. The process activation energy may be derived from resistivity data.On suit l'évolution des couches minces au cours de leur recuit par la mesure des variations de la résistance électrique. On distingue ainsi une phase de recristallisation et une phase de « coagulation ». Les structures sont ensuite étudiées par diffraction des rayons X et par microscopie électronique. Des valeurs de la résistance, on peut évaluer l'énergie d'activation du phénomène

CdSxSe1-x nanocrystals grown from solid solution in silicate glass. Structural and interfacial aspects. High resolution transmission electron microscopy and optical absorption spectroscopy

CdS0.4Se0.6 nanocrystals have been formed through nucleation and growth processes during heat treatments at different temperatures (T = 600, 675 and 700°C) and annealing times (t = 1 hour to 8 days). A regime of nucleation and growth seems to occur at T = 600°C. The growth process is dominant at T = 675 and 700°C. The average size of the semiconductor particles ranges between 2 and 15 nm according to the temperature and annealing time. Structural and interfacial aspects of the particles at early stages of the growth are presented here

Phase transitions in Co nanoclusters grown by pulsed laser deposition

The crystalline structure of Co clusters embedded in an amorphous Al2O3 matrix was studied by transmission electron microscopy (TEM) and electron diffraction (TED). In the first stage of the growth a metastable structure (body-centred-cubic) is observed. A face-centred-cubic phase (fcc) is found when the size of the clusters increases (${\rm diameter}> 4$ nm). The hexagonal-close-packed phase arises in the fcc phase by a succession of stacking faults at the largest sizes. The mechanisms of phase transformation have been determined by using high resolution electron microscopy (HREM). The chemical nature of the clusters, in particular the existence of Co-O bonds, was investigated by using electron energy loss spectroscopy (EELS)