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Summary: Non‐invasive imaging techniques like X‐ray computed tomography have become very popular in zoology, as they allow for simultaneous imaging of the internal and external morphology of organisms. Nevertheless, the effect of different staining approaches required for this method on samples lacking mineralized tissues, such as soft‐bodied invertebrates, remains understudied. Herein, we used synchrotron radiation‐based X‐ray micro‐computed tomography to compare the effects of commonly used contrasting approaches on onychophorans – soft‐bodied invertebrates important for studying animal evolution. Representatives of Euperipatoides rowelli were stained with osmium tetroxide (vapour or solution), ruthenium red, phosphotungstic acid, or iodine. Unstained specimens were imaged using both standard attenuation‐based and differential phase‐contrast setups to simulate analyses with museum material. Our comparative qualitative analyses of several tissue types demonstrate that osmium tetroxide provides the best overall tissue contrast in onychophorans, whereas the remaining staining agents rather favour the visualisation of specific tissues and/or structures. Quantitative analyses using signal‐to‐noise ratio measurements show that the level of image noise may vary according to the staining agent and scanning medium selected. Furthermore, box‐and‐whisker plots revealed substantial overlap in grey values among structures in all datasets, suggesting that a combination of semiautomatic and manual segmentation of structures is required for comprehensive 3D reconstructions of Onychophora, irrespective of the approach selected. Our results show that X‐ray micro‐computed tomography is a promising technique for studying onychophorans and, despite the benefits and disadvantages of different staining agents for specific tissues/structures, this method retrieves informative data that may eventually help address evolutionary questions long associated with Onychophora. [ABSTRACT FROM AUTHOR]

The influence of second phase fine powders on solid state sintering was investigated in situ by synchrotron radiation X-ray computed tomography (SR-CT). The evolutions of microstructure during sintering of pure SiO powders and SiO powders mixed with SiN powders were observed from reconstructed SR-CT images. Typical sintering parameters, which determine mechanical properties, were extracted from the experimental data, and the effects of the second phase powders were quantitatively analyzed. The experimental results showed that with second phase powders, 1) the specific surface area decreases more efficiently; 2) pore shape evolution is accelerated; 3) sintering necks grow faster and 4) densification process is notably accelerated. It was indicated that the SiN fine powders enhanced the sintering of the original SiO powders rather than hindering the process. A qualitative explanation based on the experimental results and existing powder sintering theory is provided. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present the in-situ investigation on microstructure evolution of metal powders during microwave sintering by using synchrotron radiation X-ray computed tomography (SR-CT) technique. Through the experimental reconstructed images, sequential 2-D and 3-D microstructure evolution phenomena of the same grains set were clearly observed, such as the rearrangement and migration of particles, the formation and growth of sintering neck, and the removal of large initial differences in surface curvature. Moreover, anomalous sintering neck growth kinetics mechanisms (log(x/a)−log (t)) during microwave sintering process were revealed and compared with the conventional sintering experiment, the reasons for these phenomena may be the “non-thermal effects”. [Copyright &y& Elsevier]