Comparing laboratory and field samples of lime-cement improved Norwegian clay

acceptedVersio

Orientational mapping of minerals in Pierre shale using X-ray diffraction tensor tomography

Shales have a complex mineralogy with structural features spanning several length scales, making them notoriously difficult to fully understand. Conventional attenuation-based X-ray computed tomography (CT) measures density differences, which, owing to the heterogeneity and sub-resolution features in shales, makes reliable interpretation of shale images a challenging task. CT based on X-ray diffraction (XRD-CT), rather than intensity attenuation, is becoming a well established technique for non-destructive 3D imaging, and is especially suited for heterogeneous and hierarchical materials. XRD patterns contain information about the mineral crystal structure, and crucially also crystallite orientation. Here, we report on the use of orientational imaging using XRD-CT to study crystallite-orientation distributions in a sample of Pierre shale. Diffraction-contrast CT data for a shale sample measured with its bedding-plane normal aligned parallel to a single tomographic axis perpendicular to the incoming X-ray beam are discussed, and the spatial density and orientation distribution of clay minerals in the sample are described. Finally, the scattering properties of highly attenuating inclusions in the shale bulk are studied, which are identified to contain pyrite and clinochlore. A path forward is then outlined for systematically improving the structural description of shales.publishedVersio

Laser recrystallization and inscription of compositional microstructures in crystalline SiGe-core fibres

Glass fibres with silicon cores have emerged as a versatile platform for all-optical processing, sensing and microscale optoelectronic devices. Using SiGe in the core extends the accessible wavelength range and potential optical functionality because the bandgap and optical properties can be tuned by changing the composition. However, silicon and germanium segregate unevenly during non-equilibrium solidification, presenting new fabrication challenges, and requiring detailed studies of the alloy crystallization dynamics in the fibre geometry. We report the fabrication of SiGe-core optical fibres, and the use of CO2 laser irradiation to heat the glass cladding and recrystallize the core, improving optical transmission. We observe the ramifications of the classic models of solidification at the microscale, and demonstrate suppression of constitutional undercooling at high solidification velocities. Tailoring the recrystallization conditions allows formation of long single crystals with uniform composition, as well as fabrication of compositional microstructures, such as gratings, within the fibre core

Tuning and Tracking of Coherent Shear Waves in Molecular Films

We have determined the time-dependent displacement fields in molecular sub-micrometer thin films as response to femtosecond and picosecond laser pulse heating by time-resolved X-ray diffraction. This method allows a direct absolute determination of the molecular displacements induced by electron–phonon interactions, which are crucial for, for example, charge transport in organic electronic devices. We demonstrate that two different modes of coherent shear motion can be photoexcited in a thin film of organic molecules by careful tuning of the laser penetration depth relative to the thickness of the film. The measured response of the organic film to impulse heating is explained by a thermoelastic model and reveals the spatially resolved displacement in the film. Thereby, information about the profile of the energy deposition in the film as well as about the mechanical interaction with the substrate material is obtained

Towards nanoscale 3D imaging of working catalyst nanoparticles, 2014

This proposal is aiming at developing new techniques for studying functional materials such as catalysts at their working conditions. Rational design of catalyst nanomaterials and the ability to identify and observe the active sites while functioning have been highlighted as key barriers for the future design of catalyst materials. While a wide range of techniques are routinely being used to characterise catalyst materials, only a limited few give direct information at reaction conditions relevant to industrial processes (Weckhuysen 2009). Recent advances in methods utilising synchrotron radiation open for unprecedented opportunities to study the electronic and structural properties of nanostructured catalysts and to actually "see" these catalysts working in a realistic environment. In this context, the proposed project is especially targeting methods development for in situ characterization of catalysts, with characterisation of bimetallic core-shell nanoparticles as chosen model system

X-ray computed tomography investigation of dilation of mineral-filled PVC under monotonic loading

The deformation-induced dilation of mineral-filled polyvinyl chloride (PVC) is investigated by means of polychromatic X-ray absorption tomography (XCT). Axisymmetric notched tensile specimens are strained to prescribed elongations using a tensile test apparatus and subsequently scanned by XCT after relaxation. During straining, surface deformations are quantified by digital image correlation (DIC) and contour tracking. The influence of stress triaxiality and strain rate on dilation is investigated by using tensile specimens with three different notch radii, all strained to three deformation levels at two different nominal strain rates. Pronounced reduction of density, corresponding to an increase of volume, is observed for all specimens in the XCT scans, but markedly different relative density distributions are measured for the three geometries. The accuracy of the polychromatic XCT density estimates is evaluated against data obtained with monochromatic synchrotron radiation computed tomography (sr-XCT), and a comparison to surface deformation-based dilation estimates is presented

GPU-Accelerated Visualization of Scattered Point Data

As data sets continue to grow in size, visualization has become a vitally important tool for extracting meaningful knowledge. Scattered point data, which are unordered sets of point coordinates with associated measured values, arise in many contexts, such as scientific experiments, sensor networks, and numerical simulations. In this paper, we present a method for visualizing such scattered point data sets. Our method is based on volume ray casting, and distinguishes itself by operating directly on the unstructured samples, rather than resampling them to form voxels. We estimate the intensity of the volume at points along the rays by interpolation using nearby samples, taking advantage of an octree to facilitate efficient range search. The method has been implemented on multi-core CPUs, GPUs as well as multi-GPU systems. 1 To test our method, actual X-ray diffraction data sets have been used, consisting of up to 240 million data points. We are able to generate images of good quality and achieve interactive frame rates in favorable cases. The GPU implementation (Nvidia Tesla K20) achieves speedups of 8-14 compared with our parallelized CPU version (4-core, hyperthreaded Intel i7 3770K)

High-energy X-ray Tomography for 3D Void Characterization in Au–Sn Solid-Liquid Interdiffusion (SLID) Bonds

Au-Sn SLID bonding is a technique originally developed for harsh environment applications. The technology has recently shown promising results for ultrasound transducer fabrication. Characterizing the spatial and size distributions of voids is crucial for developing a fabrication process that satisfies acoustic requirements. This measurement is traditionally done by optical or electron cross-section microscopy that gives the void distribution in a randomly selected physically cut plane. X-ray micro computed tomography is a powerful tool for non-destructive three-dimensional imaging of void distributions, but is challenging to use in high-density materials like the ones used in ultrasound transducers. We demonstrate that monochromatic, high-energy synchrotron X-ray tomography can give 3D images of such a challenging sample, resolving μm-sized voids in the bondline. The void distribution is highly non-uniform, implying that traditional cross-section microscopy would give different results depending on the plane of sectioning. Computed tomography allows the voids to be parametrized and treated statistically, revealing a wide distribution of void sizes, a tendency to form oblate voids with size-dependent orientation, as well as porous networks

High-energy X-ray Tomography for 3D Void Characterization in Au–Sn Solid-Liquid Interdiffusion (SLID) Bonds

Au-Sn SLID bonding is a technique originally developed for harsh environment applications. The technology has recently shown promising results for ultrasound transducer fabrication. Characterizing the spatial and size distributions of voids is crucial for developing a fabrication process that satisfies acoustic requirements. This measurement is traditionally done by optical or electron cross-section microscopy that gives the void distribution in a randomly selected physically cut plane. X-ray micro computed tomography is a powerful tool for non-destructive three-dimensional imaging of void distributions, but is challenging to use in high-density materials like the ones used in ultrasound transducers. We demonstrate that monochromatic, high-energy synchrotron X-ray tomography can give 3D images of such a challenging sample, resolving μm-sized voids in the bondline. The void distribution is highly non-uniform, implying that traditional cross-section microscopy would give different results depending on the plane of sectioning. Computed tomography allows the voids to be parametrized and treated statistically, revealing a wide distribution of void sizes, a tendency to form oblate voids with size-dependent orientation, as well as porous networks