Leah Lavery

Diffraction Contrast Tomography in the Laboratory – Applications and Future Directions

LabDCT derives 3D crystallographic information via diffraction contrast tomography (DCT) within a commercial laboratory X-ray microscope (ZEISS Xradia 520 Versa) that uses a synchrotron-style detection system for tomography. The establishment of DCT into a laboratory setting opens the way for routine, non-destructive, time-evolution studies of grain structure over meaningful sample volumes. The combination of grain information with microstructural features such as cracks, porosity, and inclusions, all derived non-destructively in 3D, enables materials characterization of damage, deformation, and growth mechanisms. Here, we introduce LabDCT and demonstrate its capabilities through a selection of materials science

Application of X-ray microtomography for the characterisation of hollow polymer-stabilised spray dried amorphous dispersion particles

The aim of this study was to investigate the capability of X-ray microtomography to obtain information relating to powder characteristics such as wall thickness and solid volume fraction for hollow, polymer-stabilised spray dried dispersion (SDD) particles. SDDs of varying particle properties, with respect to shell wall thickness and degree of particle collapse, were utilised to assess the capability of the approach. The results demonstrate that the approach can provide insight into the morphological characteristics of these hollow particles, and thereby a means to understand/predict the processability and performance characteristics of the bulk material. Quantitative assessments of particle wall thickness, particle/void volume and thereby solid volume fraction were also demonstrated to be achievable. The analysis was also shown to be able to qualitatively assess the impact of the drying rate on the morphological nature of the particle surfaces, thus providing further insight into the final particle shape. The approach demonstrated a practical means to access potentially important particle characteristics for SDD materials which, in addition to the standard bulk powder measurements such as particle size and bulk density, may enable a better understanding of such materials, and their impact on downstream processability and dosage form performance.

Fusing Multi-scale and Multi-modal 3D Imaging and Characterization

Three-dimensional X-ray microscopy (XRM) has emerged as a powerful interior imaging technique that obtains information from a range of materials under a variety of conditions and environments. Recently, laboratory-based X-ray microscopes have demonstrated tomographic datasets with resolution down to 50 nm for investigation across a great span of sample dimensions from the nanoscale to the mesoscale. [1-3] It has been used to study a wide spectrum of materials from carbonate rocks to murine brains, including hierarchical structured materials. [4] This talk will present the current state of the art in laboratory X-ray microscopy at various length scales and multi-modal capabilities for XRM-SEM combined image visualization, transformation, manipulation, and analysis using commercial software package from Object Research Systems (ORS).

Nondestructive Materials Characterization in 3D by Laboratory Diffraction Contrast Tomography – Applications and Future Directions

The majority of metallic and ceramic engineering materials of interest are polycrystalline. The properties of these materials can be significantly affected by behaviour at the length scale of the crystalline grain structure. The ability to characterise this crystallographic microstructure, non-destructively and in threedimensions, is thus a powerful tool for understanding many facets of materials performance.

Recent Advancements in 3D X-ray Microscopes for Additive Manufacturing

Three-dimensional X-ray microscopy (XRM) is a powerful sub-surface imaging technique that reveals tomography of three-dimensional microstructure from a range of materials, non-destructively. The nondestructive nature of X-rays has made the technique widely appealing, with the potential for characterizing sample changes in “4D,” delivering 3D microstructural information on physically the same sample over time, as a function of sequential processing conditions or experimental treatments. This has led to a new generation of functional studies with applications and is in a state of rapid expansion [1]. Recently, laboratory-based X-ray sources have been coupled with high resolution X-ray focusing and detection optics from synchrotron-based systems to acquire tomographic datasets with resolution down to 50 nm across a great span of sample dimensions [2]. Additionally, the technique of laboratory based X-ray diffraction contrast tomography has recently become available; allowing the nondestructive routine characterization of 3D crystallographic information on polycrystalline materials in a commercial laboratory X-ray microscope (ZEISS Xradia 520 Versa). Known as laboratory diffraction contrast tomography (LabDCT), this imaging modality will open the way for routine, nondestructive studies of time-evolution of grain structure to complement destructive electron backscatter diffraction (EBSD) end-point characterization. This talk will explore both the implementation of optics in nanoscale and sub-micron laboratory XRM architectures and review in detail several leading applications examples for the field of additive manufacturing including the ability to track changes, in grain size and orientation, over time, e.g. ‘4D’ time lapse studies using LabDCT. XRM for tomography using a laboratory source was used to characterize porosity in additive process control study for various steel input materials and Ti-6Al-4V built with Arcam SEBM. For additional process and material qualification using LabDCT, an example of this capability was used to follow the sintering of copper particles through a series of time-lapsed DCT measurements. XRM tomographic data provides multiscale imaging and visualization for a wide variety of AM materials, even creation of accurate 3D-printed models in biomimetic studies [4-5]. XRM can provide accurate 3D internal structural information critical to aid computational design of next-generation materials.

3D Mapping Grain Morphology and Grain Orientations by Laboratory Diffraction Contrast Tomography

Recent developments in laboratory-based diffraction contrast tomography (LabDCT) has shown its capability to non-destructively map the 3D morphology and crystallographic orientation in the bulk of a polycrystalline sample. Here we introduce the methodology behind this novel imaging modality and provide examples of use cases taking advantages of the ability to characterise grain microstructures, nondestructively and in three-dimensions and thereby opening the path to 4D studies of materials evolution.

Detection of Osteogenesis in Explanted Synthetic Hydroxyapatite-Silicone Orbital Implants Using 3D X-Ray Microscopy

Hydroxyapatite orbital implants are widely used in the treatment of post-nucleation socket syndrome. The porous hydroxyapatite serves as a matrix for vascular tissue ingrowth. We investigate the degree of fibro-vascular tissue integration and the presence of osteogenesis within the porous hydroxyapatite part of the orbital implants. For comprehensive imaging, all implants were prepared using a grinding technique that allows light microscopy, backscattered electron imaging and 3D X-ray microscopy on undecalcified specimen.

Non-destructive, Multi-scale 3D Fractographic Analysis of a Carbon Fiber Composite Hockey Stick after Compressive Failure

Composite materials are present in many areas of daily life. From bicycle frames and automotive components to aerospace and industrial applications, composites are widely employed to produce tough materials that make the best use of the constituent material properties. However, fractures and failures occur in a variety of modes stemming from extreme and varied loads that are a natural consequence of the material service conditions (such as tension, compression, or bending modes). Understanding the fracture mechanics is critical to future improvements of the material design.

3D Crystallographic Imaging Using Laboratory-Based Diffraction Contrast Tomography (DCT)

Traditional X-ray tomography has, for some time, operated under a single absorption-based contrast mechanism. However, in recent years X-ray imaging has experienced a dramatic increase in the range of accessible imaging modalities – extending the classical absorption contrast with e.g. phase contrast, dark-field contrast, fluorescence, diffraction contrast, etc. Common for almost all such new imaging modalities are that they were developed at synchrotron facilities, and then – for some – have since been implemented on laboratory X-ray systems. [1,2]

3D X-ray Microscopy: A New High Resolution Tomographic Technology for Biological Specimens

A new field of 3D X-ray Microscopy (XRM) has emerged bringing dramatic resolution and contrast improvements to X-ray tomographic imaging of biological specimens for correlative studies and hierarchical structure investigations of hard and soft tissue. An X-ray microscope uses an X-ray source rather than a visible light source to view the internal structure of opaque specimens. Analogous to computed tomography (CT) a specimen can be imaged without physical sectioning and a complete 3D view of the object is generated. Yet X-ray microscopes provide superior spatial resolution down to the nanoscale and tunable phase contrast to image nature’s vast diversity from cells to entire organisms ex vivo up to tens of centimeters in size. Light microscopy and immunostaining techniques have become essential practice for biological and biomedical research providing functional information on the distribution of gene products such as proteins and ribonucleic acids from primarily 2D images. More recent developments, such as Light Sheet Fluorescence Microscopy (LSFM), have provided an attractive option for developmental biology and other research when observing millimeter-sized live specimens in 3D due to an optical architecture that enables fast acquisition with low phototoxicity [1]. Despite the revolutionary advancements of light microscopy, visible light has physical penetration limits due to specimen thickness or opacity. Microcomputed tomography (microCT), an alternative technique capable of producing full 3D images, uses multiple X-ray projections to reconstruct a 3D representation of an object. MicroCT has been highly useful for large objects such as the human body in vivo and applications requiring resolution no greater than ~5-10 µm. However, demand is growing for applications that require 3D imaging with high resolution (single micron and below) and high contrast for hard and soft tissue as well as cell-level information. Laboratory XRM, which emerged in the past decade from the foundations of synchrotron-based X-ray imaging technology, produces direct 3D tomographic information from opaque specimens with resolutions well into the sub-micron range, even achieving 10’s of nm resolution for certain architectures and applications [2]. This presentation will cover 3D XRM technique, followed by a survey of recent application areas for XRM within the life sciences where it acts as a complementary and correlative bridge between the contrast and resolution standards set by light and electron microscopy. By integrating an imaging detector with sufficiently small and tunable pixel size coupled to optimized scintillation materials, the standard trade-off of sample size versus resolution found in conventional laboratory microCT are improved with XRM. High total system spatial resolution may be maintained while reducing the dependence on geometric penumbra. This, in turn, reduces the dependence of resolution on geometric magnification, relaxing restrictions on sample placement relative to the source and source spot size [3]. By employing such a geometry, samples of considerable size (tens of centimeters for low density objects) may be imaged in 3D with high resolution. In addition, as a result of small effective detector pixel dimensions and tunable detector and source positions, propagation