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Mineralized hydrogels are increasingly gaining attention as biomaterials for bone regeneration. The most common mineralization strategy has been addition of preformed inorganic particles during hydrogel formation. This maintains injectability. One common form of bone cement is formed by mixing particles of the highly reactive calcium phosphate alpha-tricalcium phosphate (α-TCP) with water to form hydroxyapatite (HA). The calcium ions released during this reaction can be exploited to crosslink anionic, calcium-binding polymers such as the polysaccharide gellan gum (GG) to induce hydrogel formation. In this study, three different amounts of α-TCP particles were added to GG polymer solution to generate novel, injectable hydrogel-inorganic composites. Distribution of the inorganic phase in the hydrogel was studied by high resolution microcomputer tomography (µCT). Gelation occurred within 30 min. α-TCP converted to HA. µCT revealed inhomogeneous distribution of the inorganic phase in the composites. These results demonstrate the potential of the composites as alternatives to traditional α-TCP bone cement and pave the way for incorporation of biologically active substances and in vitro and in vivo testing. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 822-828, 2018., (© 2017 Wiley Periodicals, Inc.)

Synchrotron radiation laminography with X-ray diffraction contrast enables three-dimensional imaging of dislocations in monocrystalline wafers. We outline the principle of the technique, the required experimental conditions, and the reconstruction procedure. The feasibility and the potential of the method are demonstrated by three-dimensional imaging of dislocation loops in an indent-damaged and annealed silicon wafer. [ABSTRACT FROM AUTHOR]

Hard x rays from a synchrotron source are used in this implementation of computed laminography for three-dimensional (3D) imaging of flat, laterally extended objects. Due to outstanding properties of synchrotron light, high spatial resolution down to the micrometer scale can be attained, even for specimens having lateral dimensions of several decimeters. Operating either with a monochromatic or with a white synchrotron beam, the method can be optimized to attain high sensitivity or considerable inspection throughput in synchrotron user and small-batch industrial experiments. The article describes the details of experimental setups, alignment procedures, and the underlying reconstruction principles. Imaging of interconnections in flip-chip and wire-bonded devices illustrates the peculiarities of the method compared to its alternatives and demonstrates the wide application potential for the 3D inspection and quality assessment in microsystem technology. [ABSTRACT FROM AUTHOR]

In-line phase contrast is combined with laminography to image in three dimensions regions of interest in laterally extended flat specimens of weak absorption contrast. The principle of the method and a theoretical description of the imaging process are outlined. The present instrumental implementation enables reconstructing nondestructively the internal structure at different lateral specimen positions with micron resolution. The feasibility and application potential are demonstrated for both phase-contrast and holographic (i.e., using phase retrieval) laminography by the three-dimensional imaging of fuel-cell diffusion layers. [ABSTRACT FROM AUTHOR]

Synchrotron-radiation tomography was used to investigate early foaming stages of aluminium alloys. Monochromatic radiation, high spatial resolution down to the micrometer scale, partial beam coherence, and holographic reconstruction techniques permit the distinction between different foam constituents which are not visible by other volume imaging techniques. In combination with three-dimensional image analysis, the differences in the pore initiation processes in two different aluminium alloys are shown. We find that, in powder compacts made from prealloyed AA6061 alloy powder, pores appear predominantly around the blowing agent particles whereas, in compacts made from a powder blend of Al and Si, pores tend to initiate around Si particles. [ABSTRACT FROM AUTHOR]

Computed laminography with synchrotron radiation is developed and carried out for three-dimensional imaging of flat, laterally extended objects with high spatial resolution. Particular experimental conditions of a stationary synchrotron source have been taken into account by a scanning geometry different from that employed with movable conventional laboratory x-ray sources. Depending on the mechanical precision of the sample manipulation system, high spatial resolution down to the scale of 1 μm can be attained nondestructively, even for objects of large lateral size. Furthermore, high beam intensity and the parallel-beam geometry enables easy use of monochromatic radiation for optimizing contrast and reducing imaging artifacts. Simulations and experiments on a test object demonstrate the feasibility of the method. Application to the inspection of solder joints in a flip-chip bonded device shows the potential for quality assurance of microsystem devices. [ABSTRACT FROM AUTHOR]

Abstract: Tomographic imaging using both laboratory sources and synchrotron radiation (SR) was performed to achieve a multi-scale damage assessment of carbon fibre composites subjected to impact damage, allowing various internal damage modes to be studied in three-dimensions. The focus of this study is the comparison of different tomographic methods, identifying their capabilities and limitations, and their use in a complementary manner for creating an overall 3D damage assessment at both macroscopic and microscopic levels. Overall, microfocus laboratory computed tomography (μCT) offers efficient routine assessment of damage at mesoscopic and macroscopic levels in engineering-scale test coupons and relatively high spatial resolutions on trimmed-down samples; whilst synchrotron radiation computed tomography (SRCT) and computed laminography (SRCL) offer scans with the highest image quality, particularly given the short acquisition times, allowing damage micromechanisms to be studied in detail. [Copyright &y& Elsevier]

Characterization of the microstructure of thermal barrier coatings (TBCs) is essential for assessing coating lifetime and for understanding the damage mechanisms leading to ceramic layer spallation. Recent progress in synchrotron-radiation computed laminography (SRCL) enables imaging of samples that are thin but extended in two dimensions. This study reports on the first results of the 3-D characterization of electron beam–physical vapour deposition TBCs by SRCL. Image analysis was very helpful in investigating the 3-D microstructure obtained and is also described. [ABSTRACT FROM AUTHOR]

Ductile crack initiation and propagation within a naturally aged aluminium alloy sheet has been observed in situ via synchrotron radiation-computed laminography, a technique specifically adapted to three-dimensional imaging of thin objects that are laterally extended. Voids and intermetallic particles, and their subsequent evolution during ductile crack extension at different associated levels of stress triaxiality, were clearly observed within fracture coupons of a reasonable engineering length-scale, overcoming the conventional sample size limitation of computed tomography at high resolutions. [Copyright &y& Elsevier]

Abstract: Computed tomography (CT) is a three-dimensional (3D) imaging method which, for compact or prolate (i.e. rather isotropically extended around the rotation axis) specimens, can yield artefact-free reconstructed cross-sections. Laterally extended specimens like plate-like objects, however, are much less amenable to CT since reliable projection data cannot be acquired from angles where the plate is oriented parallel to the irradiation direction. To overcome this drawback, computed laminography (CL) was introduced recently to imaging set-ups at synchrotron storage rings. Here, we report on the first implementation of computed laminography with neutron radiation, showing measurements that were performed at the ANTARES neutron imaging facility at the FRM II research reactor of Technische Universität München. In general, neutrons are highly interesting probes for imaging since they provide a sensitivity to chemical elements very different from X-rays, yielding complementary information about the specimens investigated. Like for X-ray laminography, we avoid the projection directions where the beam is parallel to the long extensions of the specimen. We accomplish this by tilting of the rotation axis with respect to the transmitted-beam to an angle smaller than 90° (which would be the limiting case of CT) and roughly aligning the specimen''s surface normal parallel to this rotation axis. The principles of neutron laminography are introduced and first test experiments are described. [Copyright &y& Elsevier]

X-ray computed laminography (CL) with synchrotron radiation is used to investigate fracture in carbon fibre–epoxy laminates. CL allows for high-resolution (∼1μm) imaging of laterally extended objects. Whilst artefacts inherent to CL data reduce image quality compared with computed tomography (CT), imaging regions of interest in large planar samples greatly increases the engineering applicability. High-resolution in situ three-dimensional analysis of structural failure is therefore achievable at levels that would be impossible via CT or any other volume-imaging methods. [Copyright &y& Elsevier]