Combination Of Scanning Electron Microscopy Research Articles

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.

A highlightedly improved method for isolating and characterizing calcium oxalate crystals from tubercles of Mammillaria schumannii

BackgroundCalcium oxalate (CaOx) is the most prevalent and widespread biomineral in plants and is involved in protective and/or defensive functions against abiotic stress factors. It is, however, expected that this function has an extremely significant contribution to growth processes in plants bearing large amounts of CaOx, such as cacti growing in desert environment.ResultsIn our research, small-sized CaOx crystals (≤ 20 µm) with tetrahedral or spherical shapes were observed to dominate in each epidermal and cortical cell from the tubercles of Mammillaria schumannii, a species from the Cereoideae subfamily, having tubercles (main photosynthetic organs) united with adjacent ones almost into ridges on its stem. Because they have potential significant functions, differential centrifugations after mechanical blending were used to obtain these small-sized CaOx crystals, which extremely tend to adhere to tissue or suspend in solution. And then the combined Scanning Electron Microscope Energy Dispersive System (SEM–EDS) and Raman spectroscopy were further performed to demonstrate that the extracted crystals were mainly CaC2O4·2H2O. Interestingly, spherical druses had 2 obvious abnormal Raman spectroscopy peaks of -CH and -OH at 2947 and 3290 cm−1, respectively, which may be attributed to the occluded organic matrix. The organic matrix was further extracted from spherical crystals, which could be polysaccharide, flavone, or lipid compounds on the basis of Raman spectroscopy bands at 2650, 2720, 2770, and 2958 cm−1.ConclusionsHere we used a highlightedly improved method to effectively isolate small-sized CaOx crystals dominating in the epidermal and cortical cells from tubercles of Mammillaria schumannii, which extremely tended to adhere plant tissues or suspend in isolation solution. And then we further clarified the organic matrix getting involved in the formation of CaOx crystals. This improved method for isolating and characterizing biomineral crystals can be helpful to understand how CaOx crystals in cacti function against harsh environments such as strong light, high and cold temperature, and aridity.

Impact of Solution {Ba2+}:{SO42-} on Charge Evolution of Forming and Growing Barite (BaSO4) Crystals: A ζ-Potential Measurement Investigation.

The impact of solution stoichiometry on formation of BaSO4 (barite) crystals and the development of surface charge was investigated at various predefined stoichiometries (raq = 0.01, 0.1, 1, 10, and 100, where raq = {Ba2+}:{SO42-}). Synthesis experiments and zeta potential (ζ-potential) measurements were conducted at a fixed initial degree of supersaturation (Ωbarite = 1000, where Ωbarite = {Ba2+}{SO42-}/Ksp), at circumneutral pH of ∼6, 0.02 M NaCl, and ambient temperature and pressure. Mixed-mode measurement-phase analysis light scattering (M3-PALS) showed that the particles stayed negative for raq < 1 during barite crystal formation and positive for raq > 1. At raq = 1, two populations with a positive or negative ζ-potential prevailed for ∼2.5 h before a population with a circumneutral ζ-potential (-10 to +10 mV) remained. We relate the observations of particle charge evolution to particle size and morphology evolution under the experimental conditions. Furthermore, we showed that the ζ-potential became more negative when the pH was increased for every raq. In addition, our results demonstrated that the type of monovalent background electrolyte did not influence the ζ-potential of barite crystals significantly, although NaCl showed slightly different behavior compared to KCl and NaNO3. Our results show the important role of surface charge (evolution) during ionic crystal formation under nonstoichiometric conditions. Moreover, our combined scanning electron microscopy and ζ-potential results imply that the surface charge during particle formation can be influenced by solution stoichiometry, besides the pH and ionic strength, and may aid in predicting the fate of barite in environmental settings and in understanding and improving industrial barite (surface chemistry) processes.

Effect of sulfur content on precipitation behaviour of MnS-containing inclusions in X70 pipeline steel

The presence of oxide-MnS complex inclusions is beneficial for the improvement of hydrogen resistance in pipeline steel. The effect of S and Mg contents on the generation mechanism of MnS, MgAl2O4, and MgO inclusions, and the heterogeneous nucleation principle of MnS on the surfaces of MgAl2O4 and MgO were revealed using laboratory experiments, thermodynamic calculations, and density functional theory (DFT) computations. The inclusion characteristics in steel were evaluated by using a Scanning Electron Microscope in combination with an Energy Dispersive Spectrometer (SEM + EDS). It has been found that as the Mg content increased, MgAl2O4 transformed into MgO, which can be well predicted by thermodynamic calculations. It was found that MnS exhibited the ability to nucleate heterogeneously on the surfaces of MgO and MgAl2O4 inclusions. Furthermore, proper S content (approximately 30 ppm) can facilitate the formation of oxide-MnS complex inclusions, excess S content was not desired. The smaller the oxide inclusion, the easier to form wrapped MnS on the oxides. The nucleation ability of MnS and MgAl2O4 was identified by DFT calculations and found that they followed the order of (111)MnS//(111)MgAl2O4>(100)MnS//(100)MgAl2O4>(110)MnS//(110)MgAl2O4. Furthermore, the heterogeneous nucleation ability of MnS and MgO followed in the order of (111)MnS//(111)MgO > (100)MnS//(111)MgO > (100)MnS//(100)MgO. This study provides theoretical evidence supporting the heterogeneous nucleation ability of MnS on the surfaces of MgO and MgAl2O4. Moreover, it helps bridge the disparity between the calculation of MnS and MgO nucleation using the two-dimensional mismatch degree and the experimental findings.

Experimental study on the mechanical behavior of EICP-casein-treated calcareous sand

In order to protect and develop marine resources, it is essential to reinforce the calcareous sand foundation on coral reefs during engineering construction. This study proposes a novel approach that combines enzyme-induced carbonate precipitation (EICP) with casein to solidify calcareous sand, which overcomes the issues of low calcium carbonate crystallization and insufficient cementation strength encountered in the pure EICP method. This study investigated the reinforcement effects and mechanisms of the combined method across various scales. Sonic time testing revealed an initial decline in sample density followed by a gradual increase, with the lowest density observed at 10% casein content. Sample strength depends on casein dosage and curing time. Overall, the trend in sample strength showed an initial decrease followed by a gradual increase, with 10% casein content again resulting in the lowest strength. The measured experimental groups achieved a minimum strength of approximately 1.17 MPa and a maximum strength of around 6.34 MPa. As casein concentration rises, the optimal curing time increases from 12–48 h. Microscopic experiments reveal casein expansion and dissolution in the EICP liquid, explaining UCS value changes with casein dosage and curing time. Combining scanning electron microscopy and microscopic experiments highlights the cementitious material’s vital role in strengthening samples. In conclusion, combining EICP and casein for solidifying calcareous sand is technically feasible and highly effective with significant reinforcement effects.

Diffusion of Alloying Cobalt Oxide (II, III) into Electrical Steel.

This paper aims to reduce power loss in electrical steel by improving its surface resistivity. The proposed approach involves introducing additional alloying elements through diffusion once the steel sheet reaches the desired thickness. Various effective techniques have been suggested and tested to enhance the resistivity of the strip. The method entails creating a paste by combining powdered diffusing elements with specific solutions, which are then applied to the steel's surface. After firing the sample, a successful transfer of certain elements to the steel surface is achieved. The amount and distribution of these elements can be controlled by adjusting the paste composition, modifying the firing parameters, and employing subsequent annealing procedures. This study specifically investigates the effectiveness of incorporating cobalt oxide (II, III) into non-oriented silicon iron to mitigate power loss. The experimental samples consist of non-oriented electrical steels with a composition of 2.4 wt% Si-Fe and dimensions of 0.305 mm × 300 mm × 30 mm. Power loss and permeability measurements are conducted using a single strip tester (SST) within a magnetic field range of 0.5 T to 1.7 T. These measurements are performed using an AC magnetic properties measurement system under controlled sinusoidal conditions at various frequencies. The research explores the impact of cobalt oxide (II, III) addition, observing successful diffusion into the steel through the utilization of a paste based on sodium silicate solution. This treatment results in a significant reduction in power loss in the non-oriented material, with power loss reductions of 14% at 400 Hz and 23% at 1 kHz attributed to the elimination of a porous layer containing a high concentration of the diffusing element. The formation of porosity in the cobalt addition was found to be particularly sensitive to firing temperature near the melting point. The diffusion process was examined through scanning electron microscopy (SEM) in combination with energy-dispersive X-ray spectroscopy (EDS). The results demonstrate improved power losses in the coated samples compared with the uncoated ones. In conclusion, this study establishes that the properties of non-oriented electrical steels can be enhanced through a safer process compared with the methods employed by previous researchers.

Influence of graphene content on the microstructure and properties of GNPs/2024Al composites

In this study, reinforced 2024Al-based composites with different graphene nanoplatelets (GNPs) contents (0 %, 0.25 wt%, 0.5 wt%, 1 wt%, 1.5 wt%) were prepared by the Hot Pressed Sintering process method. The impacts of graphene content on its microstructure, mechanical properties and corrosion resistance were investigated using hardness test, tensile property test and intergranular corrosion property test. Furthermore, the microscopic mechanism was explored by combining scanning electron microscopy (SEM), XRD analysis and electrochemical analysis. It was demonstrated that with the increase of GNPs content, the strengthening effect of the composite showed a trend of increasing and then decreasing, and the best strengthening effect of 0.5 wt% GNPs/2024Al composite was achieved. When the solution and aging was 12 h, the hardness was 161.74 HV0.2 and the tensile strength was 476 MPa. The GNPs could reduce the anti-intergranular corrosion performance of 2024Al. As the content of GNPs increases, the corrosion current density of the composite gradually increases and the anti-corrosion performance gradually decreases.

Competitive role of primary [formula omitted] precipitates and annealing twins on the heterogeneous deformation of a polycrystalline ni-based superalloy: Crystal plasticity modeling and experiments

A crystal plasticity modeling framework is developed and used in combination with experiments for studying the deformation behavior of a polycrystalline Ni-based superalloy. In particular, the monotonic stress-strain response across a range of temperatures and the misorientation development at room temperature are predicted. The model accounts for individual deformation of the matrix and primary γ′ phases, with consideration for the various strengthening mechanisms observed in these alloys. The as-received microstructure has been characterized using Energy Dispersive X-Ray Spectroscopy (EDS) and the concentration of the solute atoms present in the γ and primary γ′ phases obtained from these measurements are used to inform the solute solution strengthening model. Further, the Electron Back Scatter Diffraction (EBSD) microstructures are directly used as inputs for the simulations. The model is first calibrated to the experimental stress-strain response at 293 K and 923 K and then validated by predicting the mechanical response at 523 K and 723 K. Interrupted tensile testing has been performed using a combination of Scanning Electron Microscopy (SEM) and EBSD to study the misorientation developments during deformation. These deformed microstructures are correlated with the simulated EBSD microstructures, in terms of the competitive misorientation developments at grain boundaries, annealing twin boundaries and phase interfaces. Higher misorientation developments were observed at the twin boundaries as compared to the grain boundaries and phase interfaces, indicating a higher propensity of heterogeneous deformation.

Transient melt formation and its effect on conversion phenomena during nuclear waste vitrification – HT‐ESEM analysis

AbstractAlthough the vitrification of nuclear waste has a decades‐long history, numerous opportunities still exist to improve its efficiency and to increase the waste loading in glass. This is especially true for the vitrification of low‐activity waste (LAW), which has been historically treated by other immobilization technologies and is less mature than high‐level waste (HLW) vitrification. In this work, we address one of the least understood phenomena during the conversion of nuclear waste feeds to glass—the formation of molten salt and transient glass‐forming melt. Using high‐temperature environmental scanning electron microscopy (HT‐ESEM) in combination with X‐ray diffraction, thermogravimetry, and evolved gas analysis, we have analyzed the complex chemical reactions and phase transitions as they occur during melting of representative HLW and LAW melter feeds. We evaluated the compositions of amorphous phases and the fractions of salt components, and estimated the fractions of molten salt phases present in the feeds as a function of temperature. We show that the maximum fraction of molten salts is ∼4 % and ∼28 % during HLW and LAW feed melting, respectively, and discuss the possibility of molten salt migration in LAW feeds. We also argue that the presence of significant fractions of molten salt phase can hinder the retention of rhenium (and, hence, radioactive technetium), and discuss how the properties of molten salt phase and transient glass‐forming melt are related to primary foam formation and behavior. Finally, we summarize key unanswered questions requiring further research to increase the understanding of the conversion process and enhance the nuclear waste vitrification efficiency.

High performance all-para-aramid paper prepared by impregnating heterocyclic aramid into poly(p-phenylene terephthalamide) microfiber/nanofiber-based paper

All-para-aramid paper with both excellent mechanical properties and thermal stability is of great significance for the manufacture of specialty honeycomb materials. Herein, a facile method is reported for the preparation of high performance all-para-aramid paper by impregnating heterocyclic aramid (HA) solution into a para-aramid paper (PAP) produced with poly(p-phenylene terephthalamide) (PPTA) short fibers and polymerization-induced para-aramid nanofibers (PANFs). Field emission scanning electron microscopy in combination with microscopic Fourier transform infrared spectroscopy were used to confirm successful coating of HA on paper surface and infiltration of HA inside PAP. Since HA molecules in solution have similar structure to PPTA molecules and much stronger ability to form hydrogen bonds than PPTA fibers, they can effectively act as a binder for both types of PPTA fibers, greatly enhancing the interfacial adhesion between fibers and densifying the paper structure. As a result of these structural changes and also of the excellent mechanical properties of HA itself, the HA-impregnated PAPs (HA/PAPs) exhibit much better mechanical properties than neat PAP. The tensile strength of HA/PAP can be up to 128.5 MPa, 4.8 times that of neat PAP. The internal bond strength of HA/PAP can reach 356.1 J/m2, being 4.5 times that of neat PAP, showing dramatically improved delamination resistance. All-para-aramid HA/PAPs possess intrinsically excellent thermal stability and flame retardancy.

Aging behavior of biodegradable polylactic acid microplastics accelerated by UV/H2O2 processes

The usage of biodegradable plastics is expanding annually due to worldwide plastic limits, resulting in a substantial number of microplastics (MPs) particles formed from biodegradable plastic products entering the aquatic environment. Until now, the environmental behaviors of these plastic product-derived MPs (PPDMPs) have remained unclear. In this work, commercially available polylactic acid (PLA) straws and PLA food bags were used to evaluate the dynamic aging process and environmental behavior of PLA PPDMPs under UV/H2O2 conditions. By combining scanning electron microscopy, two-dimensional (2D) Fourier transform infrared correlation spectroscopy (COS) and X-ray photoelectron spectroscopy, it was determined that the aging process of the PLA PPDMPs was slower than that of pure MPs. The 2D-COS analysis revealed that the response orders for the functional groups on the PLA MPs differed during the aging process. The results demonstrated that the oxygen-containing functional groups of the PLA PPDMPs were the first to react. Subsequently, the –C–H and –C–C− structural responses began, and the polymer backbone was ruptured by the aging process. However, the aging of the pure-PLA MPs started with a brief oxidation process and then breakage of the polymer backbones, followed by continuous oxidation. Moreover, compared to the PLA PPDMPs, the pure-PLA MPs exhibited a greater adsorption capacity, which was increased by 88% after aging, whereas those of the two PPDMPs only increased by 64% and 56%, respectively. This work provides new insights into the behaviors of biodegradable PLA MPs in aquatic environments, which is critical for assessing the environmental risks and management policies for degradable MPs.

Corrosion behavior of magnesium in aqueous sulfate-containing electrolytes

Studies have been conducted on the corrosive behavior of magnesium in aqueous sulfate electrolytes (0.5 mol/L MgSO4; 0.5 mol/L Na2SO4; 0.5 mol/L MgSO4 + 0.5 mol/L Na2SO4).The composition structure and morphology of the surface of the samples were studied using scanning electron microscopy in combination with X-ray spectral microanalysis. The results of the experiments showed the formation of a surface film inhomogeneous in its structure and composition with the main components Mg(OH)2 and MgO. An increase in the exposure time of the electrode in solution led to the formation of microcracks on the main film caused by internal stress because of hydration of magnesium oxide produced during corrosion. The salt composition of the electrolyte determines the morphology and thickness of corrosion films due to differences in the solubility of the products formed during the hydrolysis of magnesium oxide and the kinetics of this process.Applying the methods of scanning electron microscopy X-ray electron analysis gravimetry and voltammetry it has been established that at various stages of magnesium corrosion in different electrolytes the growth rates of corrosion films are determined by the kinetics of magnesium oxide formation its hydration and dissolution followed by crystallization in the form of a brucite phase of loose sediments on the surface.