Combination Of Scanning Electron Microscopy Research Articles

A 23-million-year record of morphological evolution within Neotropical grass pollen.

Grass-dominated biomes in South America comprise c. 20 million years of history, yet their evolution and underlying drivers remain poorly understood. Here we apply a novel approach that combines scanning electron microscopy imaging with computational analysis to quantify the morphometrics of grass (Poaceae) pollen micro-ornamentation from the Neotropics since the Early Miocene (23 million years ago). Three spatial-temporal pollen sets were assembled to further elucidate the variation and evolutionary traits of grasses through space and time. Our results reveals that three spatial-temporal pollen groups occupy unique, partially overlapping regions of their exine morphospace. The direction of this shift is consistent over time, progressing towards less dense ornamentation. Interestingly, the extent of the occupied morphospace did not vary significantly. This is the first time that the true morphological variation in Poaceae pollen micro-ornamentation becomes apparent through time. We hypothesize that changes in grass pollen exine since the Early Miocene were driven by evolutionary processes (evolutionary drift and/or directional selection), and potentially migration at the continental scale. The high diversity in pollen micro-ornamentation is likely related to their evolutionary success in the Neogene.

Clay Minerals and Continental‐Scale Remagnetization: A Case Study of South American Neoproterozoic Carbonates

AbstractThe Neoproterozoic carbonate rocks of the Araras Group (Amazon Craton) and the Sete‐Lagoas and Salitre Formations (São Francisco Craton) share a statistically indistinguishable single‐polarity (reversed) characteristic direction. This direction is associated with paleomagnetic poles that do not align with the expected directions for primary detrital remanence. We employ a combination of classical rock magnetic properties and micro imaging/chemical analysis (in thin sections) using synchrotron radiation to examine these remagnetized carbonate rocks. Magnetic data indicate that most samples lack the anomalous hysteresis properties typically associated with carbonate remagnetization (except for distorted loops). Through a combination of Scanning Electron Microscopy with Energy Dispersive X‐ray Spectroscopy (SEM‐EDS), X‐ray Fluorescence (XRF), and X‐ray Absorption Spectroscopy (XAS), we identified subhedral/anhedral magnetite, or spherical grains with a core‐shell structure of magnetite surrounded by maghemite. These grains are within the pseudo‐single domain size range, as do most of the iron sulfides, and are spatially associated with potassium‐bearing aluminosilicates. While fluid percolation and organic matter maturation play a role, smectite‐illitization appears to be crucial for the growth of these phases. X‐ray diffraction analysis, in addition, identifies these silicates as predominantly highly crystalline illite, suggesting exposure to epizone temperatures. These temperatures were likely reached during the final stages of the Gondwana assembly (Cambrian), but remanence was only locked in afterward, in successive cooling events during the Early Middle Ordovician. This is supported by the carbonates' paleomagnetic pole positions compared to Gondwana's apparent polar wander path, and the absence of reversals, contrasting with the high reversal frequency of the Late Ediacaran/Cambrian.

Correlative Raman spectroscopy and electron microscopy identifies glycogen rich deposits correlated with local structural defects in long bones of type IV osteogenesis imperfecta patients

Osteogenesis imperfecta (OI) is a genetic bone disease occurring in approximately 1 in 10,000 births, usually as a result of genetic mutation. OI patients suffer from increased fracture risk and - depending on the severity of the disease - deformation of the limbs, which can even lead to perinatal death.Despite extensive studies, the way in which the genetic mutation is translated into structural and compositional anomalies of the tissue is still an open question. Different observations have been reported, ranging from no structural (or chemical) differences to completely chaotic bone structure and composition.Here, we investigated bone samples from two adolescent OI-IV patients, focusing on the bone structure and chemistry in naturally occurring fractures. The exposed fracture plane allows the investigation of the structure and composition of the weakest bone plane. We do so by combining scanning electron microscopy (SEM) imaging with chemical information from Raman microscopy.The exposed fracture planes show different regions within the same tissue, displaying normal osteonal structures next to disorganized osteons and totally disordered structures, while the collagen mineralization in all cases is similar to that of a healthy bone.In addition, we also detected significant amounts of depositions of glycogen-rich, organic, globules of 250-1000nm in size. These depositions point to a role of cellular disfunction in the disorganization of the collagen in qualitative OI.Overall, our results unite multiple, sometimes contradicting views from the literature on qualitative OI.

Effects of processing parameters on microstructure and mechanical properties of friction stir additive manufactured Al-Zn-Mg-Cu alloy

Abstract A multilayered build was fabricated by friction stir additive manufacturing (FSAM) with different parameters, using 4-mm thick 7A04-T6 aluminum alloy sheets in this study. The parameters effect on the microstructure and mechanical properties of the builds were investigated combined scanning electron microscopy (SEM), transmission electron microscopy (TEM), vickers hardness and tensile tests. Macro-softening phenomenon was observed in the builds. The precipitation and growth of the Mg (Zn, Cu, Al)2 or MgZn2 phase with the effect of the effective thermal cycles during the FSAM process mainly attributed to the formation of the macro-softening. The more effective thermal cycles experienced during the FSAM process, the more Mg (Zn, Cu, Al)2 or MgZn2 phase precipitated and coarsened, resulting in a more pronounced decrease in the mechanical properties of the build. Heat input affected the macro-softening behavior of the build by influencing the degree of dissolution, re-precipitation and coarsening of the precipitates during the FSAM process. Too low or too high heat input resulted in the incomplete dissolution or further precipitation and growth of the precipitates, aggravating the macro-softening phenomenon, and reducing the precipitation strengthening ability of the build. The mechanical properties of the build fabricated at the rotation speed of 700 rpm and travelling speed of 160 mm/min were the best in this study.

Assessing Biofilm at the Bedside: Exploring Reliable Accessible Biofilm Detection Methods.

Biofilm is linked through a variety of mechanisms to the pathogenesis of chronic wounds. However, accurate biofilm detection is challenging, demanding highly specialized and technically complex methods rendering it unapplicable for most clinical settings. This study evaluated promising methods of bedside biofilm localization, fluorescence imaging of wound bacterial loads, and biofilm blotting by comparing their performance against validation scanning electron microscopy (SEM). In this clinical trial, 40 chronic hard-to-heal wounds underwent the following assessments: (1) clinical signs of biofilm (CSB), (2) biofilm blotting, (3) fluorescence imaging for localizing bacterial loads, wound scraping taken for (4) SEM to confirm matrix encased bacteria (biofilm), and (5) PCR (Polymerase Chain Reaction) and NGS (Next Generation Sequencing) to determine absolute bacterial load and species present. We used a combination of SEM and PCR microbiology to calculate the diagnostic accuracy measures of the CSB, biofilm blotting assay, and fluorescence imaging. Study data demonstrate that 62.5% of wounds were identified as biofilm-positive based on SEM and microbiological assessment. By employing this method to determine the gold truth, and thus calculate accuracy measures for all methods, fluorescence imaging demonstrated superior sensitivity (84%) and accuracy (63%) compared to CSB (sensitivity 44% and accuracy 43%) and biofilm blotting (sensitivity 24% and accuracy 40%). Biofilm blotting exhibited the highest specificity (64%), albeit with lower sensitivity and accuracy. Using SEM alone as the validation method slightly altered the results, but all trends held constant. This trial provides the first comparative assessment of bedside methods for wound biofilm detection. We report the diagnostic accuracy measures of these more feasibly implementable methods versus laboratory-based SEM. Fluorescence imaging showed the greatest number of true positives (highest sensitivity), which is clinically relevant and provides assurance that no pathogenic bacteria will be missed. It effectively alerted regions of biofilm at the point-of-care with greater accuracy than standard clinical assessment (CSB) or biofilm blotting paper, providing actionable information that will likely translate into enhanced therapeutic approaches and better patient outcomes.

The Role of Iron Impurities on Nickel Cathodes for Hydrogen Evolution Reaction (HER)

Over the last decades, several studies have reported the effect of traces of iron species on the improvement of the oxygen evolution reaction (OER) kinetics for nickel-based anode materials in alkaline media. [1] However, the effect of iron impurities on the hydrogen evolution reaction (HER) is still a subject to debate. For instance, at low iron concentrations (0.03 – 0.5 ppm) a loss of the HER activity for Ni surface is observed due to the electrochemical deposition of less active Fe. [2,3] Other studies showed less deactivation behavior of the Ni cathode at 3 and 14 ppm iron ion concentration over time. [2,4] This improvement of the lifetime of the Ni electrode in the presence of iron cations is very likely related to the increased surface roughness by Fe electrodeposition and thereby the decrease in the formation of inactive NiH species. [2] Systematic investigations on Fe sputtered Ni surfaces with different coverages showed that ≥ 60% of Fe coverage stabilizes the Ni cathode by preventing hydrogen diffusion through the Ni lattice at constant current density of -100 mA cm-2. [5] Generally, the role of Fe impurities on the HER activity for nickel cathode surface in alkaline environments is still unclear to date.In this work, we comprehensively evaluated the influence of the iron ion concentration on the long-term HER performance for a polycrystalline Ni electrode by using rotating disc electrode (RDE) setup. The changes in HER activity as a function of the iron ion concentration was correlated with resulting surface roughness and layer thickness/coverage of the electrodeposited iron. Highly purified 0.1 M KOH was used as basic electrolyte solution and mixed with iron ion concentrations in the range of <1, 6 and 14 ppm. The initial HER activity on the Ni surface is unchanged irrespective of the iron ion concentration added into the electrolyte. However, at iron ion concentrations of <1 ppm and 6 ppm, the chronopotentiometric (CP) experiments at -10 mA cm-2 for 24 hours show a potential drop of ~70 mV and ~53 mV, respectively, resulting in a deactivation of the Ni surface by forming NiH species. Very interestingly, high iron ion concentrations (e.g. ~14 ppm) lead to an almost constant potential (~ 1 - 7 mV drop) during the CP experiment, by reducing the formation of inactive NiH. The electrochemically treated Ni electrodes were then characterized by X-ray fluorescence spectroscopy (XRF) and scanning electron microscopy in combination of energy dispersive X-ray spectroscopy (SEM-EDX). The SEM micrographs show iron particles electrodeposited uniformly on the polycrystalline Ni surface after the CP experiments with < 1, 6 and 14 ppm of iron ion concentrations in 0.1 M KOH. The analysis of the EDX maps reveals a coverage of 17, 54 and 58 % on the Ni surface at iron ion concentrations of < 1, 6 and 14 ppm, respectively. Obviously, iron ion concentrations of 6 and 14 pm show very similar coverages on the Ni surface, indicating their minor role on the HER activity. We suggest that during the HER the hydrogen bubbles suppress the formation of a dense and complete iron layer on the Ni electrode surface. The spatial distribution and thickness of the electrodeposited Fe particles were also evaluated after 1 h and 24 h of CP experiments with < 1, 6 and 14 ppm iron ion concentrations by using micro-XRF equipped with a polycapillary lens of 20 µm. Thicker iron layers after 24 hours are formed at high iron ion concentrations, preventing the hydrogen diffusion into Ni lattice to form inactive NiH species and to maintain the HER activity over time under alkaline conditions.In summary, we show that traces of iron impurities have a huge impact on the long-term durability of polycrystalline Ni electrodes for HER in alkaline environments. A critical iron ion concentration is required to suppress the formation of inactive NiH species during the HER at -10 mA cm-2 for 24 h and/or to electrodeposite enough iron for maintaining the HER kinetics on the polycrystalline Ni electrodes in alkaline environments.

Mechanical degradation of Longmaxi shale exposed to water-based fluids and supercritical carbon dioxide

Mechanical alterations in shale formations due to exposure to water-based fracturing fluids and supercritical carbon dioxide (ScCO2) significantly affect the performance of shale gas exploration and CO2 geo-sequestration. In this study, a hydrothermal (HT) reaction system was set up to treat Longmaxi shale samples of varying mineralogies (carbonate-, clay-, and quartz-rich) with different fluids, i.e. deionized (DI) water, 2% potassium chloride (KCl) solution, and ScCO2 under HT conditions expected in shale formation. Statistical micro-indentation was conducted to characterize the mechanical property alterations caused by the shale-fluid interactions. An in situ morphological and mineralogical identification technique that combines scanning electron microscopy (SEM) and backscattered electron (BSE) imaging with energy-dispersive X-ray spectroscopy (EDS) was used to analyze the microstructural and mineralogical changes of the treated shale samples. Results show no apparent changes in the Young’s modulus, E, and hardness, H, after treatment with DI water under room temperature (20 °C) and atmospheric pressure for 7 d. In contrast, E and H were decreased by 31.2% and 37.5% at elevated temperature (80 °C) and pressure (8 MPa), respectively. The addition of 2% KCl into DI water mitigated degradation of the mechanical properties. Quartz-rich shale specimens are the least sensitive to the water-based fracturing fluids, followed by the clay-rich and carbonate-rich shale formations. Based on in situ morphological and mineralogical identification, the primary factors for the mechanical degradation induced by water-based fluids include carbonate dissolution, clay swelling, and pyrite oxidation. Slight increases in the measured E and H and compression of porous clay aggregates were observed after treatment with ScCO2. The major factor contributing to the mechanical changes resulting from the exposure to scCO2 appears to be the competition between swelling caused by adsorption and compression of shale matrix.

The Rheological and Structural Properties of Aqueous Graphene Oxide Dispersions: Concentration and pH Dependence.

A modified Hummer's method was used to synthesize aqueous dispersions of graphene oxide (GO). The morphology, chemical structure, and exfoliation state of GO were analyzed by combining scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The structural and rheological properties of the GO dispersions were studied as a function of GO concentration and pH. Increasing the concentration of GO revealed shorter interparticle distances between GO sheets. This induced a transition from fluid to nematic gel-like structures, as observed by polarized optical microscopy (POM). The Herschel-Bulkley model was used to fit the shear thinning curves and to demonstrate the viscoelastic behavior. Both the yield stress and viscoelastic moduli in the linear viscoelastic regime increased. As pH increases, the color of the aqueous GO dispersions becomes darker, the negative values of the zeta potential increase, the distances between the GO sheets decrease as observed by a slight shift of the correlation peak toward higher values of the scattering vector modulus in small-angle X-ray scattering (SAXS), and the rheological properties (yield stress and viscoelastic moduli in the linear viscoelastic region) decrease. These results can be explained by a change in the morphology of GO related to their hydrophilicity. This work presents relationships between rheological and structural properties of GO sheet dispersions, with particular emphasis on the effects of concentration and pH.

Generating open-source 3D phytoplankton models by integrating photogrammetry with scanning electron microscopy.

The community structure and ecological function of marine ecosystems are critically dependent on phytoplankton. However, our understanding of phytoplankton is limited due to the lack of detailed information on their morphology. To address this gap, we developed a framework that combines scanning electron microscopy (SEM) with photogrammetry to create realistic 3D (three-dimensional) models of phytoplankton. The workflow of this framework is demonstrated using two marine algal species, one dinoflagellate Prorocentrum micans and one diatom Halamphora sp. The resulting 3D models are made openly available and allow users to interact with phytoplankton and their complex structures virtually (digitally) and tangibly (3D printing). They also allow for surface area and biovolume calculations of phytoplankton, as well as the exploration of their light scattering properties, which are both important for ecosystem modeling. Additionally, by presenting these models to the public, it bridges the gap between scientific inquiry and education, promoting broader awareness on the importance of phytoplankton.

Combined effect of cathodic potential and calcareous deposits on hydrogen evolution and permeation in Q460 steel

Cathodic protection is widely employed to prevent the corrosion of steel in marine environments. However, an inappropriate cathodic potential may lead to the generation of hydrogen and consequently induce cracking. Therefore, this study investigates the relationships between cathodic deposition potential, calcareous deposits, hydrogen evolution, and hydrogen permeation. Combining scanning electron microscopy, Raman spectroscopy, coupled focused ion beam lithography, and energy dispersive X-ray spectroscopy, it is observed that all calcareous deposits formed in artificial seawater at the potential range of −1.0 to −1.3 VSCE have calcium-rich inner and magnesium-rich outer layers, respectively. The thickness and compactness of each layer of the double-layer deposits vary with the cathodic deposition potential. Combining potentiodynamic polarization, hydrogen permeation experiments, and the morphology of calcareous deposits, we can find that the deposits formed at the cathodic deposition potential of −1.1 VSCE exhibit a thin inner layer and a condensed outer layer, which is effective in balancing hydrogen recombination and absorption, thus, inhibiting hydrogen entry. This study provides guidelines for the cathodic protection of steel materials in marine environments.

Study of the Performance of Emulsified Asphalt Shotcrete in High-Altitude Permafrost Regions

To improve the performance of shotcrete in high-altitude and low-temperature environments, emulsified asphalt shotcrete (EASC), which can be used in negative-temperature environments, was prepared by using low-freezing-point emulsified asphalt, calcium aluminate cement, and sodium pyrophosphate as modified materials. The effect of emulsified asphalt on the performance of shotcrete was investigated through concrete spraying and indoor tests. Then, the modification mechanism of emulsified asphalt with respect to EASC was analyzed by combining scanning electron microscopy images and the pore structure characteristics of EASC. The results showed that in a negative-temperature environment, the incorporation of emulsified asphalt delayed the formation of the peak of the cement hydration exotherm, slowed the rate of the cement hydration exotherm, reduced the thermal perturbation of permafrost by EASC, increased the cohesion of the concrete, improved the bond strength between EASC and permafrost, and reduced the rate of rebound. The mechanical strength of the studied EASC decreased upon increasing the amount of emulsified asphalt in the admixture, and its resistance to cracking gradually improved. A content of less than 5% emulsified asphalt could improve the internal pore structure of EASC, thus improving its durability. Increasing the content of emulsified asphalt affected the hydration process of the cement, and the volume content of the capillary pores and macropores increased, which reduced the durability of the EASC.

Valorizing the potential of saffron petals extract for aluminium corrosion control: An integrated approach involving extraction, experimental and computational analysis

Our study focuses on enhancing the antioxidant potential of saffron petals extract (SPE) as a sustainable corrosion inhibitor for aluminium (Al) in a 3.5% NaCl solution. The phytochemical screening and antioxidant activity are identified. Various investigative methodologies, including experimental techniques such as Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP), were employed to evaluate the effectiveness of this compound in inhibiting corrosion. Computational analysis, involving Density Functional Theory (DFT) and Molecular Dynamics (MD) simulations, were utilized to carry out a Theoretical study on the main constituents of SPE. The surface characteristics and composition of the corroded Al were examined using a combination of Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX) and Fourier Transform Infrared Spectroscopy (FT-IR). The Electrochemical results suggest that the effectiveness of the inhibitor was dependent on its concentration, reaching 95.11% at 500 ppm of SPE. The PDP indicates that mixed inhibition control effectively slowed down the corrosion of Al. Furthermore, the adsorption behaviour of SPE onto Al follows to the Langmuir isotherm model. SEM, EDX and FT-IR analyses further verified significant alterations in the surface morphology and roughness of Al and confirming the successful formation of a protective layer on the Al surface. Ultraviolet-Visible spectroscopy (UV-Vis) reveals evidence of interaction between Al and the SPE molecules. Computational studies substantiated these observations, demonstrating the reactivity and adsorption patterns of the evaluated major bioactive molecules of SPE on the Al surface.

Material representativeness of a polymer matrix doped with nanoparticles as the random speckle pattern for digital volume correlation of fibre-reinforced composites

Combining tomographic imaging with digital volume correlation allows in-situ 3D strain mapping, leading to a quantitative assessment of damage mechanisms and associated material properties in structural materials. Being based on pattern recognition, digital volume correlation is well-suited for materials with intrinsic and stable microstructural heterogeneity, such as certain biological tissues. Unfortunately, conventional polymers and fibre-reinforced polymer composites lack the required heterogeneity. Recently, solutions like doping the polymers with particles have been explored to overcome this limitation. The particles embedded in the polymer matrix provide a random, volumetric speckle pattern, acting as displacement trackers for the digital volume correlation algorithm. However, the particles might influence the mechanical and rheological behaviour of the polymer, which is detrimental in investigations of the composite material properties. This paper investigates the mechanical, mechanistic, and rheological representativeness of an epoxy doped with two types of sub-micrometre particles optimised for digital volume correlation. Since particle dispersion is considered a key driver for representativeness, we simultaneously quantitatively assess the dispersion by combining scanning electron microscopy and X-ray computed tomography.

Correlated IR-SEM-TEM studies of three different grains from Ryugu: From the initial material to post-accretional processes

In order to better constrain the alteration history of the Ryugu parent body, we performed a multi-analytical study combining scanning electron microscopy, transmission electron microscopy and infrared spectroscopy on sections extracted from the three fragments A0064-FO019, A0064-FO021 and C0002-FO019 returned from Ryugu by the Hayabusa2 space mission. The three sections show large differences in terms of structure, mineralogy and infrared signature. Section A0064-FO019 resembles the major Ryugu lithology with the presence of both fine-grained phyllosilicates (fg-phyllos) with embedded nanosulfides and coarse-grained phyllosilicates (cg-phyllos), whereas section C0002-FO019 belongs to the group of the less altered lithologies with the presence of anhydrous minerals embedded in a partially amorphous matrix. Section A0064-FO021 also belongs to this group but shows two different lithologies, a compact amorphous one and a more porous and very fractured one showing the presence of Na-rich phosphate, calcite and olivine. The two less altered lithologies (sections A0064-FO021 and C0002-FO019) show the presence of numerous mineralogical features similar to those observed in cometary interplanetary dust particles, ultra-carbonaceous Antarctic micrometeorites or in the CM Paris meteorite, i.e. amorphous and partially crystallized matrix with GEMS-like ghosts objects, whisker olivine, phosphide, or FeNi metal. This supports an outer solar system origin common with that of cometary material for the Ryugu parent body. Combined with the results of Nakamura et al. (2022b) reporting the presence of a lithology showing the presence of GEMS-like objects, we propose that section C0002-FO019 represents the onset of aqueous alteration of such primitive materials. The cg-phyllos and fg-phyllos of section A0064-FO019, i.e. of the major Ryugu lithology, representing the advanced stage of alteration, exhibit distinctive IR signatures with a higher abundance of oxygen-rich functional groups in the organic matter (OM) from the cg-phyllos. We thus suggest the following chronology of formation and evolution for Ryugu: (1) accretion of highly porous aggregate of GEMS-like units with fine-grained high-temperature anhydrous silicates, (2) onset of alteration with the dissolution of primary nanosulfides and development of amorphous/partially crystallized material in the pores, (3) crystallization of fg-phyllos with a second generation of sulfides, (4) later formation of cg-phyllos devoid of nanosulfides and their associated oxygen-rich OM in a more water-rich environment.

Surface crack treatment of concrete via nano-modified microbial carbonate precipitation

As a new concrete crack patching technology, microbial self-healing slurries offer favourable characteristics including non-pollution, ecological sustainability and good compatibility with concrete. In this paper, a nano-sio2-modified microbial bacteria liquid, combined with sodium alginate and polyvinyl alcohol, was used to prepare a nano-modified microbial self-healing slurry. This slurry was used to coat concrete under negative pressure in order to verify its restoration effect, and the micromorphology of the resulting microbial mineralization products was observed. The results revealed that patching the concrete using the nano-modified microbial slurry significantly improved its permeability, and increased its carbonization resistance by three times in comparison with the control group. Through a combination of Scanning electron microscopy (SEM) and X-ray diffraction (XRD) observation, it was determined that the microbial mineralization reaction products were mainly calcite crystals, which, integrated with the nano-sio2, sodium alginate and polyvinyl alcohol at the microscopic level, filled the internal pores of concrete, thus improving its durability.

The Internal Anatomy and Water Current System of Cambrian Archaeocyaths of South China.

Archaeocyaths are a group of extinct filter feeders that flourished in the early Cambrian period and occupied an important position in the evolution of basal fauna and the early marine ecosystem. However, the detailed morphological and anatomical information of this group are still unclear due to insufficient fossil material and limited experimental analyses. Here, we report exquisitely preserved phosphatized archaeocyathan fossil cups, ca. 515 million years old, from the top of the Shuijingtuo Formation (Series 2, Stage 3) and the Xiannüdong Formation (Series 2, Stage 3) of the Yangtze Platform, South China. Detailed observation of their external morphology via scanning electron microscopy (SEM) and micro-computed tomography (Micro-CT) analysis revealed detailed information of their internal structure. They have a typical double-walled cup, with the perforated inner and outer walls concentrically distributed, but the structure between the two walls differs. The inverted cone-shaped cups have radially distributed septa between the walls. Perforated septa connect the two walls. The low and columnar cups have canals between the two walls, forming the network. These pores and cavities constitute an important component of the water current system (pumping and filtering water with a network of canals and chambers) and influence the process of filtration in the cup. In comparison to traditional thin-section analysis, the combination of SEM and Micro-CT analysis on phosphatized archaeocyaths presented in this study further explored the detailed internal structure and finely reconstructed the microscopic overall morphology and anatomy, which provide important information to help us understand the systematic taxonomy, anatomy, and morphology of archaeocyaths during the Cambrian period.

Study on the mechanical properties and strength formation mechanism of high-volume graphite tailings concrete

Graphite tailings and coal gangue (CG) are solid wastes produced by mines. The large accumulation of surface materials poses great harm globally, and resource utilization is an urgent problem to be solved. In this paper, steel slag (SS), granulated blast furnace slag (GGBS), and fly ash (FA) are used as binder materials. Graphite tailings sand (GTS) is used as a fine aggregate. Using coal gangue and natural gravel as coarse aggregates, high-volume tailings aggregate concrete was prepared by the alkali excitation method. The strength formation mechanism of concrete was analyzed by combining scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetry-differential scanning calorimetry (TG-DSC). The results showed that with increasing tailings replacement rate, the strength of concrete containing natural gravel and coal gangue as coarse aggregates gradually decreased. The strength of coal gangue aggregate concrete is 10-15 MPa lower than that of natural gravel aggregate concrete. The uniaxial compressive failure of GTS concrete is divided into three stages: quasielasticity, stable expansion, and critical stress. A small amount of steel scoria (less than 30 %) can provide a good calcium ion (Ca2+) environment for the hydration reaction. The concrete hydration products are mainly calcium silicate hydrate (C-S-H) gel, sodium aluminosilicate hydrate (N-(A)-S-H) gel, ettringite (AFt), etc., and the formation of calcium silicate hydrate C-S-H gel and N-(A)-S-H gel can inhibit the cracks that proceed by shrinkage deformation and improve the durability of concrete. GTS concrete can reduce carbon emissions and solidify some of the harmful substances of raw materials.

Core-shells particles grown in a tubular reactor: Influence of the seeds nature and MPCVD conditions on boron-doped diamond crystalline quality

A trend in the synthesis of Boron Doped Diamond (BDD) materials resides in increasing surface areas to exalt reactivity at the BDD/electrolyte interface. This can be achieved either by surface structuration of BDD films or conformal growth on 3D substrates. Another strategy considers isolated BDD particles, mainly obtained by milling of BDD layers that can be further deposited on surfaces or embedded in a conductive matrix. Here, we propose an alternative method to obtain boron-doped diamond particles using a core-shell approach, which consists in growing diamond coatings on spherical silica templates seeded with nanodiamonds. We investigated the effects of the nature and the density of diamond seeds as well as growth parameters on the crystalline quality of the coatings. The microstructure and the boron incorporation in the diamond shell was investigated by combining Scanning Electron Microscopy (SEM), UV Raman and X-ray Photoemission Spectroscopy (XPS) investigations. Such characterizations were compared to Scanning TEM (STEM) imaging, Energy Dispersive Spectroscopy (EDS) and Electron energy loss spectroscopy (EELS) performed on thin cross-sections of core-shells prepared by focused ion beam (FIB) milling.

Dynamic Nuclear Polarization from Lithium Metal, a New Method to Study Lithium Batteries

The massive development of portable electronics, electric vehicles, and the increased need for energy storage require higher battery energy density, improved efficiency, and safety. In this context, lithium metal is the ultimate high-energy-density battery anode material. However, its use as an anode material is limited due to the formation of lithium dendrites that could lead to low efficiency and potential safety issues. Therefore, understanding and controlling the formation of lithium dendrites is key to realise lithium metal batteries.Here we show a new approach combining Scanning Electron Microscopy (SEM) and Magic-Angle Spinning Dynamic Nuclear Polarization (MAS DNP) to study the interplay between lithium morphology and interface reactivity. We aim to understand how the Solid-Electrolyte-Interphase (SEI), formed at the surface of lithium metal, affects lithium morphology. 1,2. Whereas the morphology of lithium dendrites can easily be identified using SEM, information about the SEI is more challenging to access. Among the different techniques used to characterize battery material, Nuclear Magnetic Resonance (NMR), has emerged as a powerful method providing information about the chemical composition as well as dynamic properties of a given material, at the atomic scale. Yet, the main limitations of NMR are its low intrinsic sensitivity and lack of selectivity which highly complicate the study of thin interphase as the SEI. In the present work, we use MAS DNP to overcome the low sensitivity of NMR. MAS DNP is based on the transfer of the large electron spin polarization of unpaired electrons to the nuclear spins, leading to the enhancement of the NMR signal intensity. However, the addition of free organic radicals solution to the typical exogenous DNP may alter the nature of the SEI. Furthermore, exogenous DNP is not selective to the interfaces between the lithium metal and the SEI. In this respect, we use the recently developed Lithium metal DNP method which exploits lithium metal's conduction electrons to perform endogenous MAS DNP and achieve one order of magnitude hyperpolarization at room temperature3. In addition to the gain of sensitivity, this technique allows to selectively enhance the chemical species close to the lithium metal providing critical information about the chemical structure of the SEI. This approach, currently under development, provides a powerful tool in research to control and prevent the formation of lithium dendrites which typically result in rapid degradation and potential safety issues. Figure: A) Schematic representation of Lithium dendrites with SEM of lithium dendrites formed on a copper current collector. B) Schematic representation of SEI formed on lithium metal with 7Li MAS DNP spectra recorded with and without microwave irradiation on lithium dendrites

Strategies for revealing deformation and wear mechanisms of polymer composites by combining scanning electron microscopy, energy dispersive x‐ray spectroscopy and cross‐section techniques—Exemplified by glass fiber reinforced poly‐phenylene‐sulphide

AbstractPolymers and polymer composites are frequently used in tribological applications. However, their use is often limited by excessive wear or plastic deformation, therefore research and development aiming to improve the materials is ongoing. Tribological evaluations of polymer composites often study the friction coefficient and wear rate for different types, sizes and amounts of fillers. But rarely are any mechanisms presented. Although polymer materials differ from metals, the techniques typically used for metal components, for example, scanning electron microscopy (SEM) and energy dispersive x‐ray spectroscopy (EDS), can be adapted to polymer materials, to achieve more informative SEM micrographs and EDS analyses. The aim of this article is to present useful analysis strategies, from sample preparation and selection of viewing angles, to selection of instrument settings and detector types. The strategies are exemplified by analysis of poly‐phenylene‐sulphide filled with glass fiber, evaluated against steel in a reciprocating ball‐on‐flat test set‐up. This article takes its starting point with the worn surfaces, and subsequently analyze them using SEM and EDS. A selection of cross section preparation techniques, analysis parameters and microscopy settings are presented and discussed. By combining these techniques and settings, the observation of a strongly modified surface layer, as well as sub‐surface plastic deformation and imbedded wear particles, is facilitated.