X-ray Diffraction Imaging Techniques Research Articles

Direct atomic-scale confirmation of three-phase storage mechanism in Li4Ti5O12 anodes for room-temperature sodium-ion batteries

Room-temperature sodium-ion batteries attract increasing attention for large-scale energy storage applications in renewable energy and smart grid. However, the development of suitable anode materials remains a challenging issue. Here we demonstrate that the spinel Li4Ti5O12, well-known as a 'zero-strain' anode for lithium-ion batteries, can also store sodium, displaying an average storage voltage of 0.91 V. With an appropriate binder, the Li4Ti5O12 electrode delivers a reversible capacity of 155 mAh g(-1) and presents the best cyclability among all reported oxide-based anode materials. Density functional theory calculations predict a three-phase separation mechanism, 2Li4Ti5O12+6Na(+)+6e(-)↔Li7Ti5O12+Na6LiTi5O12, which has been confirmed through in situ synchrotron X-ray diffraction and advanced scanning transmission electron microscope imaging techniques. The three-phase separation reaction has never been seen in any insertion electrode materials for lithium- or sodium-ion batteries. Furthermore, interfacial structure is clearly resolved at an atomic scale in electrochemically sodiated Li4Ti5O12 for the first time via the advanced electron microscopy.

Coherent x-ray diffraction imaging of paint pigment particles by scanning a phase plate modulator

We have implemented a coherent x-ray diffraction imaging technique that scans a phase plate to modulate wave-fronts of the x-ray beam transmitted by samples. The method was applied to measure a decorative alkyd paint containing iron oxide red pigment particles. By employing an iterative algorithm for wave-front modulation phase retrieval, we obtained an image of the paint sample that shows the distribution of the pigment particles and is consistent with the result obtained from a transmission x-ray microscope. The technique has been experimentally proven to be a feasible coherent x-ray imaging method with about 120 nm spatial resolution and was shown to work well with industrially relevant specimens.

Selective imaging of nano-particle contrast agents by a single-shot x-ray diffraction technique

Iron oxide nano-particles have very different x-ray diffraction properties from tissue. They can be clearly visualized against suppressed tissue background in a single-shot x-ray diffraction imaging technique. This technique is able to acquire both diffraction and absorption images from a single grating-modulated projection image through analysis in the spatial frequency domain. We describe the use of two orthogonal transmission gratings to selectively retain diffraction signal from iron oxide particles that are larger than a threshold size, while eliminating the background signal from soft tissue and bone. This approach should help the tracking of functionalized particles in cell labeling and targeted therapy.

Hard and soft X-ray microscopy and tomography in catalysis: bridging the different time and length scales

X-ray microscopic techniques are excellent and presently emerging techniques for chemical imaging of heterogeneous catalysts. Spatially resolved studies in heterogeneous catalysis require the understanding of both the macro and the microstructure, since both have decisive influence on the final performance of the industrially applied catalysts. A particularly important aspect is the study of the catalysts during their preparation, activation and under operating conditions, where X-rays have an inherent advantage due to their good penetration length especially in the hard X-ray regime. Whereas reaction cell design for hard X-rays is straightforward, recently smart in situ cells have also been reported for the soft X-ray regime. In the first part of the tutorial review, the constraints from a catalysis view are outlined, then the scanning and full-field X-ray microscopy as well as coherent X-ray diffraction imaging techniques are described together with the challenging design of suitable environmental cells. Selected examples demonstrate the application of X-ray microscopy and tomography to monitor structural gradients in catalytic reactors and catalyst preparation with micrometre resolution but also the possibility to follow structural changes in the sub-100 nm regime. Moreover, the potential of the new synchrotron radiation sources with higher brilliance, recent milestones in focusing of hard X-rays as well as spatiotemporal studies are highlighted. The tutorial review concludes with a view on future developments in the field of X-ray microscopy that will have strong impact on the understanding of catalysts in the future and should be combined with in situ electron microscopic studies on the nanoscale and other spectroscopic studies like microRaman, microIR and microUV-vis on the macroscale.

Diffractive Imaging Using Partially Coherent X Rays

The measured spatial coherence characteristics of the illumination used in a diffractive imaging experiment are incorporated in an algorithm that reconstructs the complex transmission function of an object from experimental x-ray diffraction data using 1.4 keV x rays. Conventional coherent diffractive imaging, which assumes full spatial coherence, is a limiting case of our approach. Even in cases in which the deviation from full spatial coherence is small, we demonstrate a significant improvement in the quality of wave field reconstructions. Our formulation is applicable to x-ray and electron diffraction imaging techniques provided that the spatial coherence properties of the illumination are known or can be measured.

Three-Dimensional Characterization of Polycrystalline Materials by Combination of X-ray Diffraction and X-ray Imaging Techniques

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Epitactic growth of a decagonal phase in an Al–Ni–Co alloy film deposited on a (0001) sapphire substrate

Thin films of Al–Ni–Co alloy with an average thickness of 15 nm were produced by means of conventional vacuum deposition technique on (0001) sapphire substrates heated at various test temperatures. The microstructures and textures of the films obtained were thoroughly investigated by atomic force microscopy, X-ray diffraction and transmission electron diffraction and imaging techniques. The diffraction measurements have evidenced that the vacuum deposition of Al72Ni15Co13 alloy on the substrates heated above 400°C allows a homogeneous poly-quasicrystalline film, consisting of the Ni-rich basic decagonal phase to grow. It has been further indicated by in-plane XRD analysis that the film deposited at 550°C contains a considerable amount of the decagonal grains epitaxially grown on the sapphire substrate. Possible epitaxial relations occurring between the deposit and the substrate will be detailed on the basis of results obtained from electron diffraction measurements.

X-ray diffraction imaging of Al2O3 nanoparticles embedded in an amorphous matrix

An experimental “momentum transfer” x-ray diffraction imaging technique is suggested and tested for nondestructive determination of the shape and size of Al2O3 nanoscale particles embedded in an amorphous polymer matrix. An advantage of the proposed technique is that it does not require coherent x rays or a beamstop to block the direct beam. A two-dimensional image of an average Al2O3 nanoparticle has been reconstructed using the Gerchberg–Saxton method, with a spatial resolution of 2.5 nm. The shape of the resulting image yielded the average size of the nanoparticle to be approximately 50 nm, which is in excellent agreement with the expected value.

Alignment of filamentous proteins and associated molecules through confinement in microchannels

A technique has been developed to study the structure and interaction of aligned filamentous proteins by confining them in surface-treated silicon microchannels. The micron-size channels induce the semiflexible biopolymers with comparable or larger persistence lengths than the channel width to naturally align parallel to the channel in solution, which facilitates structural studies by x-ray diffraction and optical imaging techniques. As a model system, we investigated the cross-linking of filamentous actin (F-actin) with the bundling protein α-actinin in the microchannels. Synchrotron x-ray diffraction and fluorescence microscopy were used to confirm that F-actin, when bundled in the device, conforms to the alignment of the channel geometry.

X-ray diffraction microtomography using synchrotron radiation

The X-ray diffraction computed tomography technique is based on the interference phenomena of the coherent scatter. For low-momentum transfer, it is most probable that the scattering interaction will be coherent. A selective discrimination of a given element in a scanned specimen can be realized by fixing the Bragg angle which produces an interference peak and then, to carry out the computed tomography in the standard mode. The image reconstructed exalts the presence of this element with respect to other ones in a sample. This work reports the feasibility of a non-destructive synchrotron radiation X-ray diffraction imaging technique. This research was performed at the X-ray Diffraction beam line of the National Synchrotron Light Laboratory (LNLS) in Brazil. The coherent scattering properties of different tissue and bone substitute materials were evaluated. Furthermore, diffraction patterns of some polycrystalline solids were studied due to industrial and environmental human exposure to these metals. The obtained diffraction patterns form the basis of a selective tomography technique. Preliminary images are presented.

Angle-dispersive diffraction with synchrotron radiation at Laboratório Nacional de Luz Sı́ncrotron (Brazil): potential for use in biomedical imaging

At low angles the scattering of X-rays in the diagnostic energy range (low-momentum transfer), it is probable that the scattering interaction will be coherent. This coherence gives rise to interference effects resulting in X-ray diffraction patterns that are characteristic of the scattering material. The usefulness of coherent scattering is not limited to crystallography. It can provide information about biological material as well. The interatomic and intermolecular co-operative effects which modify the free-atom coherent scattering process are well known for highly ordered structures such as crystalline materials but are important for amorphous solids and liquids where short-range ordering occurs. X-ray diffraction using synchrotron radiation has became a well established technique. This work introduces a non-destructive synchrotron radiation X-ray diffraction imaging technique. The feasibility of the X-ray diffraction computed microtomography using synchrotron radiation has been investigated. This research was carried out at the X-ray diffraction beam line of the National Synchrotron Light Laboratory supported by the National Council for Scientific and Technological Development (LNLS/CNPq) in Brazil. These experimental patterns were carried out with a 500 μm slit in front of the detector and an 11.101 keV beam ( λ=1.117 Å) monochromatic beam from the double crystal monochromator. The diffracted beam was detected by a fast scintillation detector (10 6 counts s −1) designed specifically to meet the needs of high quality X-ray diffraction and synchrotron radiation experiments. The data were recorded at rates of one second per degree of 2 θ (angular steps equal to 0.05±0.01°) and registered by a multichannel analyzer. These experimental data could be used to evaluate the scattering properties of different tissue-substitute (water, lucite, nylon, plastic and polystyrene) and bone-substitute (hydroxyapatite and aluminum) materials. The data are in good agreement with those obtained by other authors, indicating the feasibility of the imaging technique.

A combination of high-resolution X-ray diffractometry and diffraction imaging techniques applied to the study of MOVPE-grown Cd xHg 1−xTe/CdTe on GaAs

We have applied a range of high-resolution X-ray diffractometry and diffraction imaging techniques to study the structural properties of Cd x Hg 1- x Te (CMT) grown epitaxially on GaAs by MOVPE. In this paper we specifically describe three such techniques and evaluate and compare the results from each. Automated double crystal diffractometry with a mapping facility provides information on the quality and uniformity of the layers. 004 rocking curve widths vary from < 70 arc seconds on the best samples to substantially higher values on poorer material. Study of non-uniform layers shows that lattice tilts are a dominant influence on rocking curve widths and large (up to 2°) misorientations between epilayer and substrate (100) planes are found on some samples. These characteristics are further investigated using triple crystal diffractometry. X-ray topography of the layers shows orientation-contrast features which correlate directly with the GaAs substrate dislocation distribution. A number of layers with varying degrees of structural quality have been examined using a combination of the above techniques. Recent results are reported illustrating the value of each technique and we demonstrate how the application of a combination of X-ray diffraction techniques can be a powerful tool for investigating the nature of structural defects in this highly mismatched heteroepitaxial system.