Imaging with Neutrons

Elements ◽  
2021 ◽  
Vol 17 (3) ◽  
pp. 189-194
Author(s):  
Gilberto Artioli ◽  
Daniel S. Hussey
Keyword(s):  
Heterogeneous Media ◽  
Imaging Techniques ◽  
Dark Field ◽  
Three Dimensions ◽  
Dark Field Imaging ◽  
Inorganic Composites ◽  
Porous Matrices ◽  
Living Organisms ◽  
Cultural Heritage Objects ◽  
Percolation Processes

By exploiting the penetration, attenuation, and scattering properties of neutrons, images of matter in two or three dimensions reveal information unobtainable using other probes. Despite the limitation in brilliance of neutron sources, several neutron-based imaging techniques are essential to different aspects of modern geoscience. Typical examples include the evaluation of porosity in rocks and sediments, mapping of light elements in solids, noninvasive probing of cultural heritage objects, investigations of thick engineering components, and the exploration of diffusion and percolation processes of fluids within porous matrices, organo-inorganic composites, and living organisms. Techniques under development include simultaneous neutron and X-ray tomography in heterogeneous media, Bragg-edge imaging, and the possibility of porosimetry from dark-field imaging.

Growth of hematite on (0001) and {1102} sapphire substrates

1990 ◽  
Vol 48 (4) ◽  
pp. 376-377
Author(s):  
Lisa A. Tietz ◽  
Scott R. Summerfelt ◽  
C. Barry Carter
Keyword(s):  
Imaging Techniques ◽  
Chemical Vapor ◽  
Interface Energy ◽  
Dark Field ◽  
Cation Sublattice ◽  
Sapphire Substrates ◽  
Dark Field Imaging ◽  
Weak Beam ◽  
Pressure Chemical ◽  
Interface Structures

Defects in thin films are often introduced at the substrate-film interface during the early stages of growth. The interface structures of semiconductor heterojunctions have been extensively studied because of the electrical activity of defects in these materials. Much less attention has been paid to the structure of oxide-oxide heterojunctions. In this study, the structures of the interfaces formed between hematite (α-Fe2O3) and two orientations of sapphire (α-Al2O3) are examined in relationship to the defects introduced into the hematite film. In such heterojunctions, the oxygen sublattice is expected to have a strong influence on the epitaxy; however, defects which involve only the cation sublattice may be introduced at the interface with little increase in interface energy.Oxide heterojunctions were produced by depositing small quantities of hematite directly onto electrontransparent sapphire substrates using low-pressure chemical vapor deposition. Prior to deposition, the ionthinned substrates were chemically cleaned and annealed at 1400°C to give “clean”, crystalline surfaces. Hematite was formed by the reaction of FeCl3 vapor with water vapor at 1150°C and 1-2 Torr. The growth of the hematite and the interface structures formed on (0001) and {102} substrates have been studied by bright-field, strong- and weak-beam dark-field imaging techniques.

scholarly journals Hard X-ray omnidirectional differential phase and dark-field imaging

2021 ◽  
Vol 118 (9) ◽  
pp. e2022319118
Author(s):  
Hongchang Wang ◽  
Kawal Sawhney
Keyword(s):  
Imaging Techniques ◽  
Dark Field ◽  
X Rays ◽  
Contrast Imaging ◽  
X Ray ◽  
Differential Phase ◽  
Dark Field Imaging ◽  
Spiral Path ◽  
Wide Range ◽  
Phase Images

Ever since the discovery of X-rays, tremendous efforts have been made to develop new imaging techniques for unlocking the hidden secrets of our world and enriching our understanding of it. X-ray differential phase contrast imaging, which measures the gradient of a sample’s phase shift, can reveal more detail in a weakly absorbing sample than conventional absorption contrast. However, normally only the gradient’s component in two mutually orthogonal directions is measurable. In this article, omnidirectional differential phase images, which record the gradient of phase shifts in all directions of the imaging plane, are efficiently generated by scanning an easily obtainable, randomly structured modulator along a spiral path. The retrieved amplitude and main orientation images for differential phase yield more information than the existing imaging methods. Importantly, the omnidirectional dark-field images can be simultaneously extracted to study strongly ordered scattering structures. The proposed method can open up new possibilities for studying a wide range of complicated samples composed of both heavy, strongly scattering atoms and light, weakly scattering atoms.

Characterisation of Anisotropic Fibre Orientation in Composites by Means of X-Ray Grating Interferometry Computed Tomography

2015 ◽  
Vol 825-826 ◽  
pp. 868-875 ◽  
Author(s):  
Bernhard Plank ◽  
Christian Hannesschlaeger ◽  
Vincent Revol ◽  
Johann Kastner
Keyword(s):  
Computed Tomography ◽  
Carbon Fibre ◽  
Three Dimensional ◽  
Reference Method ◽  
Dark Field ◽  
Three Dimensions ◽  
Resin Matrix ◽  
Complex Behaviour ◽  
X Ray ◽  
Dark Field Imaging

In this work carbon fibre-reinforced polymer (CFRP) laminates and short glass fibre- reinforced polymers (sGFRP) were investigated by means of X-ray scatter dark field imaging (SDFI) using Talbot-Lau grating interferometer computed tomography. For the characterisation of the laminate structures of CFRP the anisotropic properties of the small angle scattering signal was used to image fibre bundles running in different directions. SDFI allows the visualisation of the weave pattern structure of a carbon fibre bundle in three dimensions, even if the individual fibres cannot be separated or the absorption contrast between the carbon fibres and the epoxy resin matrix is very low. For the investigated sGFRP samples qualitative information about local fibre anisotropies within a specimen were obtained by SDFI. Due to the complex behaviour of fibre alignment during the injection process a clear interpretation of the SDFI signals was difficult. As a reference method, all samples were scanned by means of high resolution cone beam Computed Tomography (µXCT). For the sGFRP the combination of µXCT and appropriate software tools provides local fibre orientations and allows three-dimensional visualisation by colour coding each extracted fibre.

Precipitation and dislocation decoration via extrinsic gettering of Co, Au and Pt by misfit dislocations in Si/Si-2%Ge epitaxy

1989 ◽  
Vol 47 ◽  
pp. 578-579
Author(s):  
D. M. Lee
Keyword(s):  
Imaging Techniques ◽  
Preceding Paper ◽  
Dark Field ◽  
Misfit Dislocations ◽  
Temperature Dependent ◽  
Bright Field ◽  
Dark Field Imaging ◽  
Weak Beam ◽  
Sample Structure ◽  
Field Imaging

Previous work on the gettering activity of a well defined array of buried interfacial misfit dislocations (MDs) showed that the amount of nickel gettered by MD is dominated by the strong temperature-dependent solubility. Precipitation occurs on or in the immediate vicinity of MDs due to nucleation enhancement by strain effects. High temperature 〈1000°C〉 diffusion of gold resulted in the planar colony precipitates on two {111} planes associated with stacking fault formation. In this contribution, we discuss our continuing research pertaining to cobalt, gold (at low temperature), and platinum gettering by MDs which involves studying the nature of dislocation decoration and impurity precipitation in the Si/Si-2%Ge epitaxial system.All the samples used in this study have a buried Si-2%Ge epitaxial layer of ∼ 2 μm thickness.Co, Au and Pt were deliberately diffused into the wafer. The details of the sample structure and preparation are described in a preceding paper. Two-beam bright field and weak-beam dark field imaging techniques were performed on cross-section TEM specimens.

scholarly journals Symmetric Talbot-Lau neutron grating interferometry and incoherent scattering correction for quantitative dark-field imaging

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Youngju Kim ◽  
Jacopo Valsecchi ◽  
Jongyul Kim ◽  
Seung Wook Lee ◽  
Markus Strobl
Keyword(s):  
Imaging Techniques ◽  
Reference Sample ◽  
Dark Field ◽  
Incoherent Scattering ◽  
The Novel ◽  
Contrast Imaging ◽  
Dark Field Imaging ◽  
Novel Approach ◽  
Set Up ◽  
Field Imaging

AbstractWe introduce the application of a symmetric Talbot-Lau neutron grating interferometer which provides a significantly extended autocorrelation length range essential for quantitative dark-field contrast imaging. The highly efficient set-up overcomes the limitation of the conventional Talbot-Lau technique to a severely limited micrometer range as well as the limitation of the other advanced dark-field imaging techniques in the nanometer regime. The novel set-up enables efficient and continuous dark-field contrast imaging providing quantitative small-angle neutron scattering information for structures in a regime from some tens of nanometers to several tens of micrometers. The quantitative analysis enabled in and by such an extended range is demonstrated through application to reference sample systems of the diluted polystyrene particle in aqueous solutions. Here we additionally demonstrate and successfully discuss the correction for incoherent scattering. This correction results to be necessary to achieve meaningful quantitative structural results. Furthermore, we present the measurements, data modelling and analysis of the two distinct kinds of cohesive powders enabled by the novel approach, revealing the significant structural differences of their fractal nature.

Inversion Domain Boundaries in Ain and GaN Thin Films

1998 ◽  
Vol 4 (S2) ◽  
pp. 636-637
Author(s):  
K. Dovidenko ◽  
S. Oktyabrsky ◽  
J. Narayan
Keyword(s):  
Thin Films ◽  
Imaging Techniques ◽  
Chemical Vapor ◽  
Dark Field ◽  
Organic Chemical ◽  
Extended Defects ◽  
Cross Sectional ◽  
Dark Field Imaging ◽  
Aln Film ◽  
Domain Boundaries

High-resolution transmission electron microscopy (HRTEM), multislice image simulation and multiple dark field TEM imaging techniques have been used to investigate the structure of extended defects in AlN and GaN thin films grown on (0001) α-Al2O3 by metal-organic chemical vapor deposition (MOCVD). AlN layers were grown directly on the (0001) sapphire. In the case of GaN thin films, 300-500 Å AlN buffer was deposited first.Cross-sectional TEM revealed the presence of domain boundaries in these Ill-nitride films. In this study we investigated these defects by multiple dark field imaging technique and proved some of them to be IDBs lying in planes. The multiple dark field images of several adjacent domains of AlN film are shown in Fig. 1 (a, b). The images were obtained exactly in [110] zone of AlN using (0002) and (000) reflections.

Tem of Dislocations in Sapphire (α−Al2O3)

1983 ◽  
Vol 31 ◽  
Author(s):  
K.P.D. Lagerlöf ◽  
T.E. Mitchell ◽  
A.H. Heuer
Keyword(s):  
Elevated Temperatures ◽  
Imaging Techniques ◽  
Dark Field ◽  
Separation Distance ◽  
Prism Plane ◽  
Dark Field Imaging ◽  
Weak Beam ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Α Al2o3

ABSTRACTDissociation of both basal and prism plane dislocations in sapphire,α−Al2O3,is common and the partial dislocations can be imaged using conventional transmission electron microscopy and weak beam dark field imaging techniques. At elevated temperatures the dissociation takes place by conservative self-climb, a process involving short range diffusion, whereas at low temperatures the dissociation can occur by glide. Dissociation of a dislocation can in some situations give rise to very strong contrast when using g vectors for which g→.b→=0 for the undissociated dislocation. Those contrast conditions can be used to obtain information about the dislocation morphology and the stacking fault energy of the fault plane through determination of the separation distance.

A Preparation of High Resolution Standards for Electron Microscopy. Part II

1971 ◽  
Vol 29 ◽  
pp. 160-161
Author(s):  
Akira Tanaka ◽  
David F. Harling
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Carbon Black ◽  
Single Crystal ◽  
Dark Field ◽  
Graphitized Carbon Black ◽  
Graphitized Carbon ◽  
Dark Field Imaging ◽  
Crystal Films ◽  
Micro Holes

In the previous paper, the author reported on a technique for preparing vapor-deposited single crystal films as high resolution standards for electron microscopy. The present paper is intended to describe the preparation of several high resolution standards for dark field microscopy and also to mention some results obtained from these studies. Three preparations were used initially: 1.) Graphitized carbon black, 2.) Epitaxially grown particles of different metals prepared by vapor deposition, and 3.) Particles grown epitaxially on the edge of micro-holes formed in a gold single crystal film.The authors successfully obtained dark field micrographs demonstrating the 3.4Å lattice spacing of graphitized carbon black and the Au single crystal (111) lattice of 2.35Å. The latter spacing is especially suitable for dark field imaging because of its preparation, as in 3.), above. After the deposited film of Au (001) orientation is prepared at 400°C the substrate temperature is raised, resulting in the formation of many square micro-holes caused by partial evaporation of the Au film.

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