In situ deformation observation via EBSD and EDS during high temperature tensile testing

Tensile testing is the backbone of mechanical characterization for materials science. The possibility to combine mechanical testing with advanced imaging and characterization methods and the option to operate at high temperatures up to 800°C opens a large variety of possibilities for materials research. In this work in situ annealing experiments are shown, where the grain growth is observed via EBSD over the course of the experiment. Different annealing states are achieved and tested after cooling to room temperature. Using the EBSD information, high Schmid factor grains can easily be identified and monitored during the in situ tensile experiment and therefore even the first yielding grains are captured. Further in situ high temperature tensile tests on steel samples up to a temperature of 800 °C are presented. An example of a tested steel specimen is shown in Figure 1. Here, slip band formation is easily observable in BSD contrast. By enabling feature tracking, the chosen region of interest remains in the field of view and is imaged correctly. Please click Download on the upper right corner to see the full abstract

Understanding the agglomerate crystallisation of hexamine through X-ray microscopy and crystallographic modelling

© 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/The detailed molecular-scale mechanism of the growth of organic crystals underpins a diversity of phenomena, such as the isolation and purification of high-quality materials for the pharmaceutical and fine chemical sectors. Recent advances in X-ray Microscopy (XRM) and complementary diffraction contrast tomography (DCT) have enabled the detailed characterisation of the micro-structure of hexamine agglomerates. Detailed XRM analysis of the growth history and micro-structure of such agglomerates reveals a highly orientated epitaxial inter-relationship between their constituent micro-crystallites. This is found to be consistent with a secondary nucleation growth mechanism associated with re-growth at the 3-fold corner sites within the crystals’ dominant {1 1 0} dodecahedral morphology. The agglomeration appears to heal upon further growth as the aligned agglomerated micro-crystals connect and fuse together but, in doing so, pockets of inter-crystallite mother liquor become trapped forming a symmetric pattern of solvent inclusions. The mechanistic origin of this phenomenon is rationalised with respect to historical data together with an analysis of the solid-state chemistry of the compound through the development of a ‘snow flake’ model. The latter draws upon hexamine's propensity for edge growth instabilities with increasing crystal size as well as its tendency for unstable growth at the facet corners along the 〈1 1 1〉 directions, a situation compounded by the lack of growth-promoting dislocations at the centers of the {1 1 0} habit surfaces. The agglomerative mechanism presented here could apply to other high symmetry crystal systems, particularly those whose crystal structures involve centred Bravais lattices and where the dominant inter-molecular interactions are angled towards the facet edges.Peer reviewe

Understanding the evolution of nutritive taste in animals:Insights from biological stoichiometry and nutritional geometry

A major conceptual gap in taste biology is the lack of a general framework for understanding the evolution of different taste modalities among animal species. We turn to two complementary nutritional frameworks, biological stoichiometry theory and nutritional geometry, to develop hypotheses for the evolution of different taste modalities in animals. We describe how the attractive tastes of Na‐, Ca‐, P‐, N‐, and C‐containing compounds are consistent with principles of both frameworks based on their shared focus on nutritional imbalances and consumer homeostasis. Specifically, we suggest that the evolution of multiple nutritive taste modalities can be predicted by identifying individual elements that are typically more concentrated in the tissues of animals than plants. Additionally, we discuss how consumer homeostasis can inform our understanding of why some taste compounds (i.e., Na, Ca, and P salts) can be either attractive or aversive depending on concentration. We also discuss how these complementary frameworks can help to explain the evolutionary history of different taste modalities and improve our understanding of the mechanisms that lead to loss of taste capabilities in some animal lineages. The ideas presented here will stimulate research that bridges the fields of evolutionary biology, sensory biology, and ecology

Inhalation Blend Microstructure:Identifying Metrics to Address Q3 Equivalence using Semi-automated X-Ray Microscopy

Assessing the microstructure of inhalation powder blends is important for assessment of Q3 microstructural equivalence, but it remains a challenge to examine a powder in its pre-actuated state. In this work, we demonstrate a robust, user-independent image analysis workflow for using X-ray Computed Tomography (XCT), allowing the fines-rich phase of different blend formulations to be visualized and quantified. The workflow provides qualitative and quantitative information on formulation microstructure. Qualitatively, differences in XCT-characterized microstructure were consistent with differences in aerosolization behavior of carrier lactose blends with micronized lactose, terbutaline sulfate and fluticasone propionate. Quantitatively, metrics for the local thickness of fines-rich phases were derived that quantify the thicker coating of fluticasone propionate fines around carrier lactose particles in a blend, compared to terbutaline sulfate or micronized lactose, which formed agglomerated regions of fines of lower density and a heterogeneous degree of association with carrier lactose particles. This approach links pre-actuated microstructure of inhalation powder blends with product performance and provides the first steps to the application of XCT to a range of dry powder inhalation products