Organic mixed ionic–electronic conductors (OMIECs) are an emerging family of materials crucial in the development of flexible, bio-, and optoelectronics. In electrochromic polymers, the cyclic redox ...reaction is associated with a mechanical breathing strain, which deforms the OMIECs and degrades the device reliability. We set forth an in situ nanoindentation approach to measure the breathing strain of a poly(3,4-propylenedioxythiophene) (PProDOT) thin film in a customized liquid cell during electrochromic cycles. A breathing volumetric strain of 12–25% is persistent in different sets of electrolytes of various solvents, salts, and salt molarities. The electrochemical conditioning, intermittence time, and cyclic protocol have minor effects on the mechanical response of PProDOT. The mechanical behavior and anion diffusivity measurement further infer the redox kinetics. Heavily cycled PProDOT films show reduced volumetric strain and accumulated mechanical damage of channel cracks and dysfunctional regions of slow and inhomogeneous electrochromic switching. This work is a systematic characterization of mechanical deformation and damage in a model OMIEC and informs the mechanical reliability of organic electrochromic devices.
It is known, that under constrained tensile deformation the mechanical response and the failure behavior of rubber vulcanizates reveal unlikely features. Due to multiaxial stress concentrations, the ...formation of internal cracks can be initiated.
For the first time, fundamental investigations on unfilled styrene-butadiene-rubber pancake specimens were performed. Via in situ dilatometry and X-ray microtomography experiments, the damage process under constrained tensile deformation is studied and discussed. Although cavitation has been often discussed for filler reinforced rubber vulcanizates, the results of this study demonstrate how it occurs also in unfilled rubbers. In fact, the stronger the geometrical constraints are, the higher is the number of small cavities. However, the integral cavity volume is not affected. Moreover, micrographs of fracture surfaces indicate that cavitation is controlled by an omnidirectional growth of radial side-cracks. Finally, an energy-based approach to describe the cavitation onset criterion initiating the damaging process is presented to revise Gent's theory.
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•In situ experiments to explore the formation and growth of cavities.•Often suspected, cavitation is monitored in unfilled rubber vulcanizates.•The cavitation process is controlled by confinements – also under uniaxial tension.•Cavity growth is driven by omnidirectional propagation of side-cracks.
In situ synchrotron small‐angle X‐ray scattering (SAXS) is a powerful tool for studying dynamic processes during material preparation and application. The processing and analysis of large data sets ...generated from in situ X‐ray scattering experiments are often tedious and time consuming. However, data processing software for in situ experiments is relatively rare, especially for grazing‐incidence small‐angle X‐ray scattering (GISAXS). This article presents an open‐source software suite (SGTools) to perform data processing and analysis for SAXS and GISAXS experiments. The processing modules in this software include (i) raw data calibration and background correction; (ii) data reduction by multiple methods; (iii) animation generation and intensity mapping for in situ X‐ray scattering experiments; and (iv) further data analysis for the sample with an order degree and interface correlation. This article provides the main features and framework of SGTools. The workflow of the software is also elucidated to allow users to develop new features. Three examples are demonstrated to illustrate the use of SGTools for dealing with SAXS and GISAXS data. Finally, the limitations and future features of the software are also discussed.
Data processing and analysis tools are presented that are suitable for the large data sets generated from in situ small‐angle X‐ray scattering experiments.
•In situ heating transmission electron microscopy was used to study Au nanoparticles.•Their apparent thermal stability is influenced by the electron beam affecting the ligands.•Sample treatments can ...influence these ligands and thus also the apparent thermal stability.•Plasma cleaning can make them more stable, activated carbon can make them less stable.
In situ TEM is a valuable technique to offer novel insights in the behavior of nanomaterials under various conditions. However, interpretation of in situ experiments is not straightforward since the electron beam can impact the outcome of such measurements. For example, ligands surrounding metal nanoparticles transform into a protective carbon layer upon electron beam irradiation and may impact the apparent thermal stability during in situ heating experiments. In this work, we explore the effect of different treatments typically proposed to remove such ligands. We found that plasma treatment prior to heating experiments for Au nanorods and nanostars increased the apparent thermal stability of the nanoparticles, while an activated carbon treatment resulted in a decrease of the observed thermal stability. Treatment with HCl barely changed the experimental outcome. These results demonstrate the importance of carefully selecting pre-treatments procedures during in situ heating experiments.
Main conclusion
Open-Top Chambers should be more used in tropical ecosystems to study climate change effects in plants as they are still insufficient to extract plant response patterns in these ...ecosystems.
Understanding flora response to climate change (CC) is critical for predicting future ecosystem dynamics. Open-Top Chambers (OTCs) have been widely used to study the effects of CC on plants and are very popular in temperate ecosystems but are still underused in tropical regions. In this systematic review, we aimed to discuss the use of OTCs in the study of the effects of different agents of climate change on tropical flora by presenting scientometric data, discussing the technical aspects of its use and enumerating some observations on plant response patterns to climatic alterations in the tropics. Our analysis indicated that the bottleneck in choosing an OTC shape is not strictly related to its purpose or the type of parameter modulated; instead, passive or active approaches seem to be a more sensitive point. The common critical point in using this technique in warmer regions is overheating and decoupling, but it can be overcome with simple adaptations and extra features. The most frequently parameter modulated was CO
2
, followed by O
3
and temperature. The plant families with more representatives in the studies analyzed were Fabaceae, Myrtaceae, and Poaceae, and the most represented biome was tropical and subtropical moist broadleaf forests. In conclusion, OTCs are a valuable and feasible tool to study CC effects on various tropical ecosystems, regardless of structure, active/passive approach, or other technical features. One of the primary advantages of this methodology is its applicability for in situ use, eliminating the need for plant transplantation. We encourage studies using OTC experimental design for plant conservation in the tropics.
The purpose of this paper is to (i) review field data on stress‐induced permeability changes in fractured rock; (ii) describe estimation of fractured rock stress‐permeability relationships through ...model calibration against such field data; and (iii) discuss observations of temperature and chemically mediated fracture closure and its effect on fractured rock permeability. The field data that are reviewed include in situ block experiments, excavation‐induced changes in permeability around tunnels, borehole injection experiments, depth (and stress) dependent permeability, and permeability changes associated with a large‐scale rock‐mass heating experiment. Data show how the stress‐permeability relationship of fractured rock very much depends on local in situ conditions, such as fracture shear offset and fracture infilling by mineral precipitation. Field and laboratory experiments involving temperature have shown significant temperature‐driven fracture closure even under constant stress. Such temperature‐driven fracture closure has been described as thermal overclosure and relates to better fitting of opposing fracture surfaces at high temperatures, or is attributed to chemically mediated fracture closure related to pressure solution (and compaction) of stressed fracture surface asperities. Back‐calculated stress‐permeability relationships from field data may implicitly account for such effects, but the relative contribution of purely thermal‐mechanical and chemically mediated changes is difficult to isolate. Therefore, it is concluded that further laboratory and in situ experiments are needed to increase the knowledge of the true mechanisms behind thermally driven fracture closure, and to further assess the importance of chemical‐mechanical coupling for the long‐term evolution of fractured rock permeability.
This paper reviews stress‐induced permeability changes in fractured rock observed from field data, including effects of temperature and chemically mediated fracture closure. While the stress‐permeability relationship of a rock mass might be bounded from site specific field investigations, it is concluded that further laboratory and in situ experiments are needed to increase the knowledge of the true mechanisms underlying thermally driven fracture closure, and to further assess chemical‐mechanical coupling effects on the long‐term evolution of fractured rock permeability.
Utilizing two-dimensional material as a model catalyst, the reconstruction behavior of rocksalt CoO during oxygen evolution reaction was revealed by in situ X-ray absorption spectroscopy.
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The reconstruction during oxygen evolution reaction (OER) significantly affects the electronic and local geometry structure of metal sites in electrocatalyst. Compared with well-investigated cobalt-based materials, the reconstruction of rocksalt CoO with purely Co2+ in octahedral (Oh) coordination has not been revealed in detail. Herein, monolayer CoO supported on reduced graphene oxide (rGO) was synthesized via a one-pot hydrothermal strategy with calcinating in Ar atmosphere. The structure evolution of two-dimension (2D) CoO/rGO during OER was revealed by in situ X-ray absorption spectroscopy (XAS). The transition from CoO toward Co3O4 already occurred at open circuit potential, further enhanced at 1.23 V (vs. RHE). The CoOx(OH)y was determined as the active phase at 1.53 V, displaying a tetrahedral Co coordination defective spinel Co3O4 with the Co-O shell that featured the (oxy)hydroxide, not the standard CoOOH. After OER, the irreversible transition from CoO to Co3O4 was observed. In contrast, in situ Raman spectra revealed a reversible amorphization process on Co3O4/rGO under operation conditions. Furthermore, this study indicated that the reconstruction behavior could be more effectively revealed by XAS using 2D materials.
•We reviewed the recent progress of various in situ testing rigs compatible with both laboratory and synchrotron radiation X-ray facilities.•Taking metallic alloys and composites as model materials, ...we demonstrate the unique advantages of in situ X-ray three-dimensional tomography in unveiling complex failure mechanisms.•We also discuss the ongoing direction of in situ multi-scale visualization and characterization in advanced materials and structures.
Damage evolution characterization and performance evaluation under realistic conditions are essential to ensure reliable operation of critical safety components. However, previous studies focus on the surface detection because of very limited penetration capacity of nondestructive testing facilities. Here, we review the recent progress of material damage mechanism by various in situ testing rigs that are compatible with laboratory and synchrotron radiation X-ray facilities. Then, taking metallic alloys and composites as model materials, we demonstrate the unique advantages of in situ X-ray three-dimensional tomography in unveiling complex failure mechanisms, quantifying crack growth driving forces and crack closure phenomena, and elucidating the strengthening/degrading effects from microstructure and environment on structural material degradation. Finally, we also discuss the ongoing direction of in situ multi-scale visualization and characterization with the development of advanced high-energy X-ray facilities, the improvement of in situ devices and sample environments, the demand of high-throughput tests, and the processing and application of massive test data.
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There are numerous studies measuring the rate and extent of bioturbation worldwide, however, information on mixing rates in the deep ocean, especially in the polar regions, are extremely scarce. The ...present study presents mixing rates and mixed layer depths for the deep seafloor at the LTER (Long-Term Ecological Research) observatory HAUSGARTEN in Fram Strait, Arctic Ocean. Two stations at similar water depths (HG-IV at 2492 m, and S3 at 2391 m) but different distances to the ice edge (approx. 65 km and 115 km, respectively) were chosen to carry out long-term in situ bioturbation experiments (2 and 4 years, respectively), using luminophores as a tracer. Enhanced bioturbation at the northern site, located closer to the high productive Marginal Ice Zone (MIZ) and thus expected to receive higher amounts of settling organic matter thereby supporting a richer benthic community, could not be confirmed. Instead, biodiffusion-like mixing rates (Db) at the experimental sites showed no significant differences (0.26 ± 0.27 SD cm−2 y−1 at station HG-IV; 0.28 ± 0.40 SD cm−2 y−1 at station S3). Moreover, mixed layer depths (L) at the two sites were almost identical; mixing of surface sediments occurred down to approx. 6–7 cm sediment depth. Indications for a non-local transport of sediment particles from the surface to deeper parts of the sediment, resulting in higher values for the Non-Local Index (NLI), could only be found for the central HAUSGARTEN site HG-IV. Differences in macro- and megafauna communities at the two experimental sites might be responsible for subsurface maxima in luminophore distribution and slightly (non-significantly) higher NLI values at this site (5.37 ± 3.35 SD at station HG-IV; 3.26 ± 1.82 SD at station S3). Temporal variations in benthic activities should have been levelled out in the multi-year experiments, thus providing reliable baseline data for the deep Fram Strait.
•Experimental approach to assess bioturbation rates at the LTER observatory HAUSGARTEN.•ROVs used to conduct the experiments in situ to avoid artefacts in deep-water studies.•First bioturbation experiments at great water depths using luminophores as tracers.•Results include biodiffusion-like mixing rates, non-local transport and mixing depths.•Meio-, macro-, megafauna quantified to relate bioturbation rates to their creators.
Wandering spiders climb vertically and walk upside‐down on rough and smooth surfaces using a nanostructured attachment system on their feet. The spiders are assumed to adhere by intermolecular van ...der Waals forces between the adhesive structures and the substrate. The adhesive elements are arranged highly ordered on the hierarchically structured attachment hair (setae). While walking, it has been suggested that the spiders apply a shear force on their legs to increase friction. However, the detailed mechanical behavior of the hair's structures during attachment and detachment remains unknown. Here, gradients of the mechanical properties of the attachment hair on different length scales that have evolved to support attachment, stabilize adhesion in contact, and withstand high stress at detachment, examined by in situ experiments, are shown. Shearing helps to self‐align the adhesive elements with the substrate. The study is anticipated to contribute to the development of optimized artificial dry adhesives.
Nanostructured adhesive hair on the feet of spiders is responsible for strong adhesion, enabling the animals to walk upside down. Using scanning nanofocus X‐ray scattering under force control, the mechanism of alignment and consequently intimate contact, leading to adhesion of the nanostructures to a surface, is examined. The results show excellent adaptation of the biological structures for their specific function.
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