Search

The temperature dependent thermal conductivity of In-Sb-Te thin films has been measured by modulated photothermal radiometry in the 20-550 °C range for samples with different Te content. Significant changes with temperature are observed and ascribed to a sequence of structural transformations on the basis of in-situ Raman spectra. The data suggest that the as-deposited material consisting of a mixture of polycrystalline InSb0.8Te0.2and amorphous Te first undergoes a progressive crystallization of the amorphous part, mostly above 300 °C. Further increase in temperature above 460 °C leads, for higher Te content in the alloy, to the formation of crystalline In3SbTe2, intertwined with a less conductive compound, possibly InTe and/or InSb. Upon cooling to room temperature, the initial polycrystalline InSb0.8Te0.2phase is mostly recovered along with other compounds, with a slightly higher thermal conductivity than that of the as deposited material. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

This work addresses the structural quantification of multiphase materials, here nanostructured polymer solid precursors and their micro/nano sized foamed counterparts. It is based on a strategy of contrast/edge enhancement, locally adaptive to image data in digital images of materials. The method allows to binarize straightforwardly the structures (the phases) in TEM and SEM images after edge identification, edge choice, and image virtual reconstruction. A detailed insight is brought into one-step batch supercritical CO 2 foaming of acrylic amorphous PMMA (polymethyl methacrylate) polymers, aided by the nanostructuration of block copolymers (BCP), here MAM (butyl acrylate center block methyl acrylate side blocks). The foaming conditions, i.e., pressure drop rate (PDR) and saturation temperature required for an actual one-step procedure are specified and clarified, whereas previous works, dealing with "one-step procedures", are probably incurring in a two-step procedure. The roles of the BCP content (and size) and saturation temperature are carefully analyzed and further clarified, more comprehensively than in previous literature. Thanks to the analysis of size distributions of foams and foam blend precursors (0.25, 0.5, 10 wt% MAM), bi modality of 10 wt% foams is for example revealed. A discussion of kinetics effects, i.e., evolutions of the effective sample temperature T ef (t), and the effective glass transition temperature T g, ef (t). provides a new insight of "pseudo" one-step VS "real" one-step batch foaming., (© 2024 The Author(s). Small published by Wiley‐VCH GmbH.)

Microbialites are widespread in modern and fossil hypersaline environments, where they provide a unique sedimentary archive. Authigenic mineral precipitation in modern microbialites results from a complex interplay between microbial metabolisms, organic matrices and environmental parameters. Here, we combined mineralogical and microscopic analyses with measurements of metabolic activity in order to characterise the mineralisation of microbial mats forming microbialites in the Great Salt Lake (Utah, USA). Our results show that the mineralisation process takes place in three steps progressing along geochemical gradients produced through microbial activity. First, a poorly crystallized Mg-Si phase precipitates on alveolar extracellular organic matrix due to a rise of the pH in the zone of active oxygenic photosynthesis. Second, aragonite patches nucleate in close proximity to sulfate reduction hotspots, as a result of the degradation of cyanobacteria and extracellular organic matrix mediated by, among others, sulfate reducing bacteria. A final step consists of partial replacement of aragonite by dolomite, possibly in neutral to slightly acidic porewater. This might occur due to dissolution-precipitation reactions when the most recalcitrant part of the organic matrix is degraded. The mineralisation pathways proposed here provide pivotal insight for the interpretation of microbial processes in past hypersaline environments.