Search results for "Electron backscatter diffraction"
showing 10 items of 44 documents
Low energy nano diffraction (LEND) – A versatile diffraction technique in SEM
2019
Abstract Electron diffraction is a powerful characterization method that is used across different fields and in different instruments. In particular, the power of transmission electron microscopy (TEM) largely relies on the capability to switch between imaging and diffraction mode enabling identification of crystalline phases and in-depth studies of crystal defects, to name only examples. In contrast, while diffraction techniques have found their way into the realm of scanning electron microscopy (SEM) in the form of electron backscatter diffraction and related techniques, on-axis transmission diffraction is still in its infancy. Here we present a simple but versatile setup that enables a ‘…
EBSD, XRD and SRS characterization of a casting Al-7wt%Si alloy processed by equal channel angular extrusion: Dislocation density evaluation
2019
Abstract Aluminum‑silicon (Al Si) alloys of high silicon contents are composite materials; they are used whenever high casting properties are required. They are slightly ductile below 8wt%Si. An increase in ductility can be obtained by refining Si-crystals in elaboration or by a further hot working. In the present work, an Al-7wt%Si alloy was processed by Equal Channel Angular Extrusion (ECAE) at temperatures 20 °C and 160 °C up to three passes. The die was formed by two cylindrical channels with characteristic angles Φ = 110° and Ψ = 0. EBSD, X ray diffraction (XRD) and Strain Rate Sensitivity (SRS) were used to characterize the microstructure and the mechanical properties. High levels of …
Influence of the grain orientation spread on the pitting corrosion resistance of duplex stainless steels using electron backscatter diffraction and c…
2013
Abstract The corrosion behavior of UNS S32202 duplex stainless steel was studied by combining electron backscatter diffraction (EBSD) measurements and critical pitting temperature tests at the microscale. The grain orientation spread (GOS) value was determined in grains of both phases from EBSD data. It was shown that austenitic sites containing extremely small ferrite grains having a GOS value greater than 1.3° were precursor sites for pitting in 4 M NaCl. The critical pitting temperature range was 45–90 °C. All the other sites of both phases remained passive up to 100 °C.
Passive properties of lean duplex stainless steels after long-term ageing in air studied using EBSD, AES, XPS and local electrochemical impedance spe…
2013
Abstract Passivity of duplex stainless steel was studied after long-term ageing in air using local electrochemical impedance spectroscopy, AES, XPS and EBSD. After mechanical polishing, the passive film was homogeneous and had a capacitive behaviour described by the CPE. After long-term ageing, a small thickening was detected and O2−/OH− was significantly higher in the austenite than in the ferrite. Austenite behaved as a blocking electrode whereas two capacitive loops were observed in the ferrite (low value of O2−/OH). The loop at high frequencies was related with the oxygen reduction and the loop at low frequencies was connected with the passive film.
Unusual internal structure of cm-sized coldwater calcite: Weichselian spars in former pools of the Zinnbergschacht Cave (Franconian Alb/SE Germany)
2018
The investigation of the internal structure of calcite crystals is a new focus in speleothem science, especially in the range of crystallization temperatures close to 0°C. Recently found calcite spars from Zinnbergschacht Cave of the Franconian Alb (SE Germany) are ideal for multi-method investigation. The elongated calcites (up to 6 cm in length) with three to six lateral faces and basal triangular faces at the ends are observed in collapse-zones in the cave. 230Th/U-ages of 38.9 ka suggest formation during the periglacial Weichselian, between the Scandinavian and Alpine Glaciations. The δ18O and δ13C values of the calcite spars vary from -11.18 to -16.11‰ V-PDB and from -4.78 to -6.13‰ V-…
Atomic structure solution of the complex quasicrystal approximant Al77Rh15Ru8 from electron diffraction data
2014
The crystal structure of the novel Al77Rh15Ru8phase (which is an approximant of decagonal quasicrystals) was determined using modern direct methods (MDM) applied to automated electron diffraction tomography (ADT) data. The Al77Rh15Ru8E-phase is orthorhombic [Pbma,a= 23.40 (5),b= 16.20 (4) andc= 20.00 (5) Å] and has one of the most complicated intermetallic structures solved solely by electron diffraction methods. Its structural model consists of 78 unique atomic positions in the unit cell (19 Rh/Ru and 59 Al). Precession electron diffraction (PED) patterns and high-resolution electron microscopy (HRTEM) images were used for the validation of the proposed atomic model. The structure of the E…
Ab-initio crystal structure analysis and refinement approaches of oligo p-benzamides based on electron diffraction data.
2012
Ab-initio crystal structure analysis of organic materials from electron diffraction data is presented. The data were collected using the automated electron diffraction tomography (ADT) technique. The structure solution and refinement route is first validated on the basis of the known crystal structure of tri-p-benzamide. The same procedure is then applied to solve the previously unknown crystal structure of tetra-p-benzamide. In the crystal structure of tetra-p-benzamide, an unusual hydrogen-bonding scheme is realised; the hydrogen-bonding scheme is, however, in perfect agreement with solid-state NMR data.
Size-dependent alignment of Fe nanoparticles upon deposition onto W(110)
2010
Using in situ electron diffraction we study the orientation of mass-selected iron nanoparticles upon deposition onto single crystalline W(110) at room temperature. It is found that particles with a diameter below about 4 nm and a kinetic energy $\ensuremath{\le}0.1$ electron volt per atom spontaneously align with respect to the substrate. Larger particles preferentially rest with their (001) and (110) facets parallel to the surface, but do not show further alignment. The data may hint at thermally activated dislocation motions upon the impact on the substrate which are responsible for the observed orientation below 4 nm. By this uniformly oriented monodisperse nanostructures can be prepared…
H-bonding schemes of di- and tri-p-benzamides assessed by a combination of electron diffraction, X-ray powder diffraction and solid-state NMR
2010
The crystal structures of di- and tri-p-benzamides are solved by a combination of single crystal, electron and powder X-ray diffraction. Different hydrogen-bonding schemes observed in the two structures are described and classified. The hydrogen-bonding networks are correlated to complementary data obtained from multinuclear solid-state NMR.
Using Electron Diffraction to Solve the Crystal Structure of a Laked Azo Pigment
2009
The structure of the ζ phase of Pigment Red 53:2 was solved using electron diffraction data. The unit cell determination appeared to be more complicated due to twinning of the crystals. A series of...