Theoretical and Experimental Analyses of the Effects of Composition and Strain on Image Contrast in High-Resolution Transmission Electron Microscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 66-67
Author(s):  
D.F. Sundo ◽  
J.M. Howe
Keyword(s):  
Phase Contrast ◽  
Image Contrast ◽  
X Ray ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Small Defect ◽  
Quantitative Understanding ◽  
Similar Theory ◽  
Substitutional Atom ◽  
Imaging Conditions

Although the effects of composition and strain on amplitude-contrast images in the TEM have been thoroughly developed, similar theory does not exist for phase-contrast images and only a few specific situations have been treated. The purpose of this research is to develop a quantitative understanding of the effects of composition and strain on phase-contrast images and to test this theory experimentally. A simple defect which can cause both a local change in composition and strain is a substitutional atom. Hence, this defect is treated first, with the expectation that results from this analysis can be extended to predict image contrast from larger defects under certain imaging conditions.X-ray scattering theory indicates that diffuse scattering from point defects due to composition and strain is linearly additive. For small defect concentrations, the scattered intensity Sdiff(k) is given by:

scholarly journals Alpha helical surfactant-like peptides self-assemble into pH-dependent nanostructures

Soft Matter ◽  
2021 ◽  
Vol 17 (11) ◽  
pp. 3096-3104
Author(s):  
Valeria Castelletto ◽  
Jani Seitsonen ◽  
Janne Ruokolainen ◽  
Ian W. Hamley
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Small Angle ◽  
Self Assembly ◽  
X Ray ◽  
Cryogenic Transmission Electron Microscopy ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Ph Dependent ◽  
Ray Scattering

A designed surfactant-like peptide is shown, using a combination of cryogenic-transmission electron microscopy and small-angle X-ray scattering, to have remarkable pH-dependent self-assembly properties.

On the selective aerobic oxidation of benzyl alcohol with Pd/Au-nanoparticles in batch and flow

2014 ◽  
Vol 3 (1) ◽  
pp. 99-110 ◽  
Author(s):  
Hannes Alex ◽  
Norbert Steinfeldt ◽  
Klaus Jähnisch ◽  
Matthias Bauer ◽  
Sandra Hübner
Keyword(s):  
Catalytic Activity ◽  
Benzyl Alcohol ◽  
Aerobic Oxidation ◽  
X Ray ◽  
X Ray Scattering ◽  
Oxidation Of Benzyl Alcohol ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
Selective Aerobic Oxidation

AbstractNanoparticles (NP) have specific catalytic properties, which are influenced by parameters like their size, shape, or composition. Bimetallic NPs, composed of two metal elements can show an improved catalytic activity compared to the monometallic NPs. We, herein, report on the selective aerobic oxidation of benzyl alcohol catalyzed by unsupported Pd/Au and Pd NPs at atmospheric pressure. NPs of varying compositions were synthesized and characterized by UV/Vis spectroscopy, transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). The NPs were tested in the model reaction regarding their catalytic activity, stability, and recyclability in batch and continuous procedure. Additionally, in situ extended X-ray absorption fine structure (EXAFS) measurements were performed in order to get insight in the process during NP catalysis.

An X-ray scattering study on inverted Ge–Si huts grown at low temperatures

2004 ◽  
Vol 19 (4) ◽  
pp. 347-351
Author(s):  
J. Xu ◽  
X. S. Wu ◽  
B. Qian ◽  
J. F. Feng ◽  
S. S. Jiang ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Lattice Strain ◽  
Lattice Mismatch ◽  
Grazing Incidence ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Large Lattice ◽  
Scattering Study

Ge–Si inverted huts, which formed at the Si∕Ge interface of Si∕Ge superlattice grown at low temperatures, have been measured by X-ray diffraction, grazing incidence X-ray specular and off-specular reflectivities, and transmission electron microscopy (TEM). The surface of the Si∕Ge superlattice is smooth, and there are no Ge–Si huts appearing on the surface. The roughness of the surfaces is less than 3 Å. Large lattice strain induced by lattice mismatch between Si and Ge is found to be relaxed because of the intermixing of Ge and Si at the Si∕Ge interface.

Analysis of InGaN/GaN single quantum wells by X-ray scattering and transmission electron microscopy

2003 ◽  
Vol 240 (2) ◽  
pp. 297-300 ◽  
Author(s):  
T. M. Smeeton ◽  
M. J. Kappers ◽  
J. S. Barnard ◽  
M. E. Vickers ◽  
C. J. Humphreys
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Wells ◽  
Single Quantum ◽  
X Ray ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Ray Scattering

Determination of the Growth Rate of Hydrothermally Synthesised ZnO2 Crystallites

2017 ◽  
Vol 50 ◽  
pp. 41-47 ◽  
Author(s):  
Martin Egblewogbe ◽  
Garu Gebreyesus ◽  
Samuel A. Atarah
Keyword(s):  
Growth Rate ◽  
Zinc Acetate Dihydrate ◽  
Hydrothermal Process ◽  
Growth Rate Constant ◽  
Acetate Dihydrate ◽  
X Ray ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Zinc Peroxide

Powders consisting of nanoparticles of zinc peroxide were prepared via a simple hydrothermal process using zinc acetate dihydrate and hydrogen peroxide precursors. The size of the crystallites was determined using x-ray powder diffraction. Over a period of 5 hours the crystallite radius increased from 4 nm – 9 nm at a temperature of 68 °C ± 5 °C, with growth rate constant of 0.23 nm3 min−1 calculated using the Lifshitz, Slyozov, and Wagner model. The powders were further characterised with High Resolution Transmission Electron Microscopy, Energy Dispersive X-ray analysis, and Small Angle X-ray Scattering, showing well-crystallised ZnO2 nanoparticles.

X-Ray Scattering Studies of Interfacial Microstructures in Inx, Ga1−x As/GaAs Superlattices

1994 ◽  
Vol 375 ◽  
Author(s):  
Z. H. Ming ◽  
Y. L. Soo ◽  
S. Huang ◽  
Y. H. Kao ◽  
K. Stair ◽  
...  
Keyword(s):  
Quantum Wires ◽  
Large Angle ◽  
Sample Surface ◽  
Lateral Direction ◽  
Direction Parallel ◽  
X Ray ◽  
Periodic Arrays ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Ray Scattering

AbstractInterfacial microstructures in 100-period InxGa1−xAs(15Å)/GaAs(100Å) superlattices grown on GaAs (100) substrates by molecular beam epitaxy were studied by using large angle x-ray scattering techniques. Unusual satellite peaks in the lateral direction parallel to the sample surface were observed in a sample with x = 0.535 grown at 480°C, indicating an in-plane structural ordering. This result is confirmed by high resolution transmission electron microscopy observations that thickness modulation in the InxGa1−xAs layers gives rise to long-range lateral periodic arrays of cluster-like microstructures with spacing on the order of a few hundred Ångstroms. This thickness modulation is found to occur only in [110] direction, thus the material can be viewed as a somewhat disordered array of grown-in parallel quantum wires.

scholarly journals On the Stability of 3C-SiC Single Crystals at High Temperatures

2012 ◽  
Vol 717-720 ◽  
pp. 493-496
Author(s):  
Deborah Dompoint ◽  
Irina G. Galben-Sandulache ◽  
Alexandre Boulle ◽  
Didier Chaussende ◽  
Dominique Eyidi ◽  
...  
Keyword(s):  
Single Crystals ◽  
Volume Fraction ◽  
Diffuse Intensity ◽  
X Ray ◽  
Partial Dislocations ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
The Stability ◽  
Kinetics Of ◽  
Evolution With Time

The 3C-6H polytypic transition in 3C-SiC single crystals is studied by means of diffuse X-ray scattering (DXS) coupled with transmission electron microscopy (TEM). TEM reveals that the partially transformed SiC crystals contain regions of significantly transformed SiC (characterized by a high density of stacking faults) co-existing with regions of pure 3C-SiC. The simulation of the diffuse intensity allows to determine both the volume fraction of transformed material and the transformation level within these regions. It is further shown that the evolution with time and temperature of the transition implies the multiplication and glide of partial dislocations, the kinetics of which are quantified by means of DXS.

White matter imaging of ethanol-fixed rat brain by phase-contrast X-ray computed tomography

2021 ◽  
pp. 028418512110307
Author(s):  
Thet-Thet- Lwin ◽  
Akio Yoneyama ◽  
Shogo Kokubo ◽  
Hiroko Maruyama ◽  
Kazuyuki Hyodo ◽  
...  
Keyword(s):  
White Matter ◽  
Phase Contrast ◽  
Three Dimensional ◽  
Image Contrast ◽  
Cerebral White Matter ◽  
Tissue Fixation ◽  
X Ray ◽  
Density Values ◽  
X Ray Computed ◽  
Formalin Fixed

Background Phase-contrast X-ray computed tomography imaging (PCI) based on crystal X-ray interferometry can detect minute density differences within biological soft tissues without contrast agents. Ethanol fixation yields increased tissue-background density differences due to the dehydrating and delipidifying effects of ethanol. Purpose To obtain high image contrast of cerebral white matter structures in PCI, tissue fixation using ethanol and routinely used formalin have been examined. Material and Methods Ethanol-fixed (EF) (n = 4) and formalin-fixed (FF) (n = 4) rat brains were imaged by crystal X-ray interferometry-based PCI. Tissue staining/microscopy was also performed for histological comparison and myelin density evaluation. Three-dimensional white matter tract images were reconstructed. Results Superior image contrast was obtained in the images of EF brains (EF images) compared to those of formalin-fixed brains (FF images), particularly for white matter structures. Significant density differences between the white matter structures and hippocampus ( P < 0.01)/thalamus ( P < 0.001) were observed in the EF, but not FF, images. Ethanol fixation enhanced the image contrast of white matter tracts by approximately sixfold compared to formalin fixation, and close agreement (r2 = 0.97; P < 0.05) between the density values on the CT images and the myelin density values in histological images was observed for the EF brains. Three-dimensional reconstruction of the white matter tracts was possible from the EF images, but not FF images. Conclusion Ethanol fixation resulted in marked contrast enhancement of cerebral white matter structures in PCI. Thus, high-resolution PCI using ethanol for tissue fixation could be valuable for experimental neurological studies and postmortem neuropathology evaluation.

scholarly journals Structure and Rheology of Polyelectrolyte Complexes in the Presence of a Hydrogen-Bonded Co-Solvent

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1053 ◽  
Author(s):  
Mor Boas ◽  
Gleb Vasilyev ◽  
Rita Vilensky ◽  
Yachin Cohen ◽  
Eyal Zussman
Keyword(s):  
Aqueous Solution ◽  
Network Formation ◽  
Mixed Solvent ◽  
Relative Viscosity ◽  
Degree Of Ionization ◽  
Polyelectrolyte Complexes ◽  
X Ray ◽  
Macromolecular Conformation ◽  
X Ray Scattering ◽  
Transmission Electron

Intermolecular interactions as well as macromolecular conformation affect the rheological and microstructural properties of polyelectrolyte complexes (PECs) solutions. The properties of semi-dilute solutions of weakly charged PECs can be controlled by the degree of ionization and solvent composition. In this work, we examined the effect of ethanol as a co-solvent on PECs composed of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) at low pH. The aqueous PECs solution was turbid, indicating formation of large aggregates, whereas PECs solution in water/ethanol (60:40 w/w) was transparent, implying no aggregation, and demonstrated higher relative viscosity than the aqueous solution, implying pronounced network formation. Imaging PECs solution by transmission electron microscopy (TEM) demonstrated aggregation, whereas the solution prepared with the mixed solvent revealed almost no phase contrast. Small-angle X-ray scattering (SAXS) of PECs in the aqueous solution indicated the presence of aggregates, while PECs in mixed solvent demonstrated a swelled macromolecular conformation with diminished aggregation. PECs with no ionic interactions in the mixed solvent assumes a homogenous network structure, which enables PECs solution processing by electrospinning.

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