Transmission Electron Microscopy Investigations Research Articles

Multiscale Regulation of Ordered PtCu Intermetallic Electrocatalyst for Highly Durable Oxygen Reduction Reaction.

Transforming the Pt-M alloy into an ordered intermetallic is an effective strategy to improve the electrocatalytic activity and stability toward the oxygen reduction reaction (ORR). However, the synthesis of nanosized intermetallics remains challenging. Herein, we report an efficient ORR electrocatalyst, consisting of a monodisperse nanosized PtCu intermetallic on hollow mesoporous carbon spheres (HMCS). As predicted by theoretical calculations, PtCu intermetallics exhibit beneficial electronic structure, with a low theoretical overpotential of 0.33 V and enhanced Cu stability. Resulting from the multiscale modulation of catalyst structure, the O-PtCu/HMCS catalyst delivers a high mass activity of 2.73 A cm-2Pt at 0.9 V and remarkable stability. Identical location transmission electron microscopy (IL-TEM) investigations demonstrate that the rate of carbon corrosion is alleviated on HMCS, which contributes to the long-term durability. This work provides a promising design strategy for an ORR electrocatalyst, and the IL-TEM investigations offer new perspectives for the performance enhancement mechanism.

Ultra-high dilutions analysis: Exploring the effects of potentization by electron microscopy, Raman spectroscopy and deep learning

The subject of ultrahigh dilutions has been under continuous debate over the years, mainly because the possibilities to analyze such diluted solutions are limited. In this context, transmission electron microscopy (TEM) investigations were conducted to evaluate the morphological characteristics of ethanol- and water-based highly diluted solutions of gold; three levels of potentization (6C, 30C, and 200C) were examined for each type of solution. Moreover, Raman spectroscopy and deep learning (DL) algorithms were employed for the analysis of the three potentization levels of purified water, unpurified water, and purified water-based gold solutions. Three batches were assessed for each considered category, and the ability to discriminate between all investigated classes, between the potencies within each group or between the classes within the same level of potentization were presented and discussed in correlation with the TEM findings. Distinct forms of organization were revealed by TEM for the three levels of potentization, while the gated recurrent unit (GRU) model showed great accuracy (88 %) for discriminating all classes, over 90 % accuracy for distinguishing the samples within each group and over 95 % accuracy for classification within the same level of potentization if unpretreated Raman spectra were used. Thus, this suite of methods (TEM-EDX and Raman spectroscopy in combination with DL) can be successfully used for the characterization and differentiation of highly diluted solutions resulting after potentization treatment. Furthermore, considering the results obtained from the discrimination study involving all 11 classes and a data augmentation approach, the spectral segmentation method can be seen as a valuable strategy for increasing the model prediction accuracy.

Complementary metalloporphyrin-based nanostructure decorated with silver nanoparticles for photocatalytic degradation of organic dyes

A hybrid composite photocatalyst, SA-T@Ag, was fabricated by the photoreduction of silver salts in the presence of nanomaterials composed of self-assembled complementary porphyrin triad SA-T. We confirmed the formation of SA-T@Ag from SA-T using various spectroscopic techniques, including X-ray diffraction (XRD), infrared (IR) spectroscopy, UV–visible spectroscopy, and fluorescence spectroscopy. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) investigations revealed that a substantial amount of silver nanoparticles (AgNPs) were deposited on the surface of SA-T and that the microstructure of SA-T was intact during photoreduction. The formation of AgNPs on the surface of SA-T reduced the band gap energy (Eg) of SA-T@Ag compared to that of SA-T. This not only improves its light-harvesting properties but also delays the recombination of photogenerated electron-hole pairs, which promotes more reactivity under visible light irradiation and improves the efficiency of polluted dye degradation. These photophysical properties are reflected in the degradation of methylene blue (MB) dye under visible light irradiation. The first-order degradation rate constant of MB dye within 45 min of visible light irradiation is much higher for SA-T@Ag (0.081 min−1) than SA-T (0.028 min−1). This report is of great importance in the field of environmental remediation and provides new opportunities for designing porphyrin-based photocatalytic systems as alternatives to conventional photocatalysts.

A transmission electron microscopy investigation suggests that telocytes, skeletal muscles, myoblasts, and stem cells in common carp (Cyprinus carpio) respond to salinity challenges

BackgroundTelocytes are modified interstitial cells that communicate with other types of cells, including stem cells. Stemness properties render them more susceptible to environmental conditions. The current morphological investigation examined the reactions of telocytes to salt stress in relation to stem cells and myoblasts. The common carp are subjected to salinity levels of 0.2, 6, and 10 ppt. The gill samples were preserved and prepared for TEM.ResultsThe present study observed that telocytes undergo morphological change and exhibit enhanced secretory activities in response to changes in salinity. TEM can identify typical telocytes. This research gives evidence for the communication of telocytes with stem cells, myoblasts, and skeletal muscles. Telocytes surround stem cells. Telopodes made planar contact with the cell membrane of the stem cell. Telocytes and their telopodes surrounded the skeletal myoblast. These findings show that telocytes may act as nurse cells for skeletal stem cells and myoblasts, which undergo fibrillogenesis. Not only telocytes undergo morphological alternations, but also skeletal muscles become hypertrophied, which receive telocyte secretory vesicles in intercellular compartments.ConclusionIn conclusion, the activation of telocytes is what causes stress adaptation. They might act as important players in intercellular communication between cells. It is also possible that reciprocal interaction occurs between telocytes and other cells to adapt to changing environmental conditions.

Nanostructured Coatings Based on Graphene Oxide for the Management of Periprosthetic Infections.

To modulate the bioactivity and boost the therapeutic outcome of implantable metallic devices, biodegradable coatings based on polylactide (PLA) and graphene oxide nanosheets (nGOs) loaded with Zinforo™ (Zin) have been proposed in this study as innovative alternatives for the local management of biofilm-associated periprosthetic infections. Using a modified Hummers protocol, high-purity and ultra-thin nGOs have been obtained, as evidenced by X-ray diffraction (XRD) and transmission electron microscopy (TEM) investigations. The matrix-assisted pulsed laser evaporation (MAPLE) technique has been successfully employed to obtain the PLA-nGO-Zin coatings. The stoichiometric and uniform transfer was revealed by infrared microscopy (IRM) and scanning electron microscopy (SEM) studies. In vitro evaluation, performed on fresh blood samples, has shown the excellent hemocompatibility of PLA-nGO-Zin-coated samples (with a hemolytic index of 1.15%), together with their anti-inflammatory ability. Moreover, the PLA-nGO-Zin coatings significantly inhibited the development of mature bacterial biofilms, inducing important anti-biofilm efficiency in the as-coated samples. The herein-reported results evidence the promising potential of PLA-nGO-Zin coatings to be used for the biocompatible and antimicrobial surface modification of metallic implants.

Dislocation structure evolution during room temperature dwell loading of a Ti-6Al-4 V alloy

The current work examines the evolution of the dislocation structure, within both the α and β phases, of a Ti-6Al-4 V alloy subjected to room temperature dwell loading performed at about 96% of the macroscopic yield stress level for several durations, as part of a synchrotron in-situ deformation experiment. The obtained findings represent a vital contribution to creating a scientific basis for improving lifing predictions for aero-propulsion components. The dislocation configuration, type and density were examined post-mortem using transmission electron microscopy (TEM). Despite the relatively low applied stress level, well-developed dislocation structures were already formed within the α phase at a dwell duration of 10 min and changed only modestly up to 60 min. The plastic deformation of the above phase took place solely via dislocation slip. To facilitate a comparison between different dwell durations, the TEM investigation focused on the regions oriented for the prismatic glide that represented the main deformation mode due to the starting crystallographic texture. After deformation, the regions oriented for the prismatic slip contained planar slip bands largely consisting of dislocations of a screw type. There was rather limited interaction between different bands, as the dislocation arrays passed through the slip band intersections with only minor difficulty. The screw-type dislocations seemed to preferentially form during straining. Dislocation Burgers vectors experimentally determined within the β phase occasionally departed from the Schmid rule and such dislocations typically showed a prevalent screw component. Some deformation banding and {112} 〈111〉 − type mechanical twin formation were locally detected within the β phase.

High-Resolution Characterization of Enamel Remineralization Using Time-of-Flight Secondary Ion Mass Spectrometry and Electron Microscopy

Introduction: The aim of this in vitro study was to assess the suitability of high-resolution time-of-flight secondary ion mass spectrometry (ToF-SIMS) for visualizing cross-sectional changes in human enamel microstructure and chemical composition during treatment and remineralization cycling of artificially generated caries lesions underneath an artificial plaque. Methods: Treatments consisted of exposure to twice daily toothpaste/water slurries prepared from 0, 1,100, and 5,000 μg/g fluoride (F) NaF/silica toothpastes. In addition, treatments with slurries prepared from 1,100 μg/g F SnF2/silica toothpastes were done using 44Ca in the remineralization solution to allow for differentiation of newly formed mineral and exploration of incorporated metal dopants using ToF-SIMS. Complementary microhardness, scanning electron microscopy, and high-resolution transmission electron microscopy (HR-TEM) investigations were performed on enamel cross sections. Results: HR-TEM was used for the first time to determine the change in crystallinity during remineralization revealing distinct microstructural zones within one lesion. Chemical mapping using ToF-SIMS demonstrated that the distribution of F, while observed primarily in the new mineral phase, was widespread throughout the lesion with 44Ca substantially limited to the remineralizing mineral. Both penetrated the inter-rod spaces of the sound enamel illustrating how acid damage propagates into the native mineral as the caries lesion deepens. HR-TEM examination revealed different regions within the lesion characterized by distinct micro- and ultrastructures. Importantly, HR-TEM revealed a return of crystallinity following remineralization. F dose-response observations verified the ability of these high-resolution techniques to differentiate remineralization efficacy. Conclusion: The collective results provided new insights such as the visualization of F or calcium penetration pathways, as well as new tools to study the caries process.

Hydrophobic polymer nano hybrid ternary composite electrode for nanomolar tracing of Cd2+ ions

AbstractIn the present study, we reported the successful synthesis of a ternary nano hybrid polymer composite system obtained by solution casting. Composing carbon nanotubes (CNTs) and molybdenum disulfide (MoS2) in ethylene vinyl acetate (EVA) derived ECM ternary electrode. It demonstrated an excellent electrochemical sensor performance and a more efficient supercapacitor. Chemical structure of hybrid electrode Fourier transform Infrared Spectroscopy (FTIR) illustrated the CS and CN stretching with MoS2 and CNT new bands (at 1368 and 1032 cm−1). FE‐SEM and Atomic force microscopy (AFM) 3D topographic image identified the decreased rough morphology of the hybrid electrode. Whereas contact angle measurements revealed the enhanced wettability of electrode system. Microporous nature of the hybrid electrode was observed through SEM investigation. Transmission electron microscopy (TEM) revealed the nano hybrid entity in a hybrid electrode system. XRD and TEM investigation confirmed semicrystalline phase of the hybrid electrode system due to the presence of MoS2. D band, G bands, E12g and A1g vibrational modes in Raman spectroscopy revealed the occupied hybrid filler CNTs and MoS2. An electroactive site for the Cd2+ ion sensor was confirmed by the ECM/PGE hybrid electrode. It comply the desirable sensor qualities, such as excellent selectivity, reproducibility and repeatability with a high accuracy and lower detection limit of 15 nM. Additionally, the ECM/PGE electrode demonstrated a capacitive nature with an aerial capacitance of 73 μF/cm2 at an applied current density of 3 μA/cm2. Furthermore, it exhibited a power density of 44 mW/cm2 and an energy density of 148 μWh/cm2 over a wide potential range of 1 V.

Ultrastructural and morphological studies on variables affecting Escherichia coli with selected commercial antibiotics

BackgroundMany studies reported the effects of antibiotic exposure on E. coli bacterial growth and cell modification. However, scarce descriptive information on ultrastructural effects upon exposure of commercial antibiotics. MethodsThis study described the morphological and ultrastructural alterations caused by selected antibiotics (amoxicillin-clavulanate, ceftriaxone, polymyxin B, colistin, gentamicin, and amikacin) that targeted cell wall, plasma membrane, and cytoplasmic density, and also proteins synthesis. We determined extracellular morphological changes of exposure through scanning electron microscopy (FESEM) and intracellular activities through transmission electron microscopy (TEM) investigation. ResultsFESEM and TEM micrograph of E. coli exposed with selected antibiotics shows ultrastructural changes in beta-lactam class (amoxicillin-clavulanate, ceftriaxone) elongated the cells as the cell wall was altered as it inhibits bacterial cell wall synthesis, polymyxin class (polymyxin B, colistin) had plasmid and curli-fimbriae as it breaking down the plasma/cytoplasmic membrane, and aminoglycoside class (gentamicin, and amikacin) reduced ribosome concentration as it inhibits bacterial protein synthesis by binding to 30 s ribosomes. ConclusionMorphological and ultrastructural alterations of E. coli’s mechanism of actions were translated and depicted. This study could be reference for characterization studies for morphological and ultrastructural of E. coli upon exposure to antimicrobial agents.

Atomic-scale investigation of γ-Ga2O3 deposited on MgAl2O4 and its relationship with β-Ga2O3

Nominally phase-pure γ-Ga2O3 was deposited on (100) MgAl2O4 within a narrow temperature window centered at ∼470 °C using metal-organic chemical vapor deposition. The film deposited at 440 °C exhibited either poor crystallization or an amorphous structure; the film grown at 500 °C contained both β-Ga2O3 and γ-Ga2O3. A nominally phase-pure β-Ga2O3 film was obtained at 530 °C. Atomic-resolution scanning transmission electron microscopy (STEM) investigations of the γ-Ga2O3 film grown at 470 °C revealed a high density of antiphase boundaries. A planar defect model developed for γ-Al2O3 was extended to explain the stacking sequences of the Ga sublattice observed in the STEM images of γ-Ga2O3. The presence of the 180° rotational domains and 90° rotational domains of β-Ga2O3 inclusions within the γ-Ga2O3 matrix is discussed within the context of a comprehensive investigation of the epitaxial relationship between those two phases in the as-grown film at 470 °C and the same film annealed at 600 °C. The results led to the hypotheses that (i) incorporation of certain dopants, including Si, Ge, Sn, Mg, Al, and Sc, into β-Ga2O3 locally stabilizes the “γ-phase” and (ii) the site preference(s) for these dopants promotes the formation of “γ-phase” and/or γ-Ga2O3 solid solutions. However, in the absence of such dopants, pure γ-Ga2O3 remains the least stable Ga2O3 polymorph, as indicated by its very narrow growth window, lower growth temperatures relative to other Ga2O3 polymorphs, and the largest calculated difference in Helmholtz free energy per formula unit between γ-Ga2O3 and β-Ga2O3 than all other polymorphs.

Electron beam-induced demetallation of Fe, Co, Ni, Cu, Zn, Pd, and Pt metalloporphyrins: insights in e-beam chemistry and metal cluster formations.

Electron beams are versatile tools for nanoscale fabrication processes, however, the underlying e-beam chemistry remains in its infancy. Through operando transmission electron microscopy investigations, we elucidate a redox-driven cargo release of individual metal atoms triggered by electron beams. The chosen organic delivery molecule, tetraphenylporphyrin (TPP), proves highly versatile, forming complexes with nearly all metals from the periodic table and being easily processed in solution. A comprehensive cinematographic analysis of the dynamics of single metal atoms confirms the nearly instantaneous ejection of complexed metal atoms under an 80 kV electron beam, underscoring the system's broad versatility. Providing mechanistic insights, we employ density functional theory to support the proposed reductive demetallation pathway facilitated by secondary electrons, contributing novel perspectives to electron beam-mediated chemical reaction mechanisms. Lastly, our findings demonstrate that all seven metals investigated form nanoclusters once ejected from TPP, highlighting the method's potential for studying and developing sustainable single-atom and nanocluster catalysts.

In-depth insight into the structural properties of nanoparticulate NiO for CO sensing

The outstanding properties exhibited by the p-type NiO nanostructures can be greatly affected by morpho-structural and defect characteristics with constructive or competing effects. We have conducted an in-depth study on NiO nanoparticles obtained by hydrothermal synthesis and submitted to various thermal treatments, to monitor the evolution of their structural properties and the effect of the thermal history on their CO sensing. Correlated electron paramagnetic resonance and analytical transmission electron microscopy investigations evidenced an amount of up to 1 % metallic nickel clusters close to surface in the NiO nanoparticles calcined at 400 °C and 500 °C for 8 h. Subsequent annealing in vacuum and in air of the sample calcined at 400 °C resulted in different size distributions and morphology of the NiO nanoparticles and an increase/decrease of the nickel phase, respectively. Comparative CO sensing tests on the two pristine samples and on the sample calcined at 400 °C and further annealed in air at 500 °C for 2 h showed an increase in the baseline resistance of the later due to the decrease of free charge carriers induced by the dissolution of the nickel clusters. The overall CO sensing results show a strong dependence on the samples thermal history.

Highly Stable and Active Ru Clusters Supported on Boron Carbon Nitride for Acidic Water Oxidation

In recent years, metal oxides, such as IrO2, have been widely used in proton exchange membrane water electrolysis (PEMWE) because of their excellent catalytic activity and long-term stability [1]. However the high price and scarcity of these catalysts were not enough to meet the requirements of PEMWE [2]. Therefore, it is significant to explore novel electrochemically active, stable, and low-cost catalysts.In this paper, a uniformly dispersed Ru confined on boron carbon nitride support was synthesized and studied. The surface chemical states of Ru were tuned by the interaction between Ru and the active N in boron carbon nitrogen (BCN), forming a highly stable Ru-N bond. Benefiting from a graphene-like structure, the BCN-0.5Ru catalyst exhibited greater conductivity than RuO2. The strong interaction between Ru and the BCN support also allowed for accelerated charge transfer at the electrode interface.Transmission electron microscopy (TEM) investigations revealed that Ru clusters were uniformly dispersed on BCN (Figure 1a), and the particle size distributions (Figure 1b) showed that the Ru clusters possessed an average particle size of 4 nm. It suggests that the Ru nanoclusters on the BCN support had small particle sizes and a narrow particle size distribution. These results demonstrated that the BCN support helped disperse the Ru metal nanoclusters more homogeneously than what occurred when RuO2 was prepared via direct RuCl3 annealing. The electrochemical performance of oxygen evolution reaction (OER) for BCN-xRu catalysts in O2-saturated 0.5 M H2SO4 solution was evaluated. The BCN-0.5Ru catalyst demonstrates a low overpotential of 164 mV at a current density of 10 mA cm–2 and remains stable for 12 h in acidic electrolyte (Figure 1c). In contrast, RuO2 without any support fails in only 1 h (Figure 1c). We propose that the surface chemical states of Ru supported by BCN may play an important role in enhancing stability. This study provides insights into designing and synthesizing high-performance electrocatalysts for acidic OER.

Cold sintering of BaZr0.8Y0.2O3-ẟ ceramics: Phase formation and grain boundary properties

Electrochemical devices based on the proton conducting ceramic BaZrO3 have shown their immense potential for efficient energy conversion and gas separation processes at intermediate temperatures. A major drawback of this material class is the inevitably high sintering temperature, which is necessary to reach sufficient densities for gas tightness. Recently, cold sintering has been applied to densify BaZrO3 – BaCeO3 solid solutions at low temperatures using a partial dissolution of the Ce-rich phase. Here, we apply the method to BaZr0.8Y0.2O3-ẟ (BZY20), which is a Ce-free proton conducting ceramic. We show that densification by cold sintering is viable at temperatures between 150 °C and 250 °C under uniaxial pressures of 400 MPa and deionized water as a sintering aid. The dissolution of yttrium from BZY20 during cold sintering acts as the trigger for densification at low temperatures but forms Y(OH)3 as an instable side product. Therefore, we developed a two-step cold sintering process that adds an additional thermal treatment between 900 and 1100 °C directly after the cold sintering process to enable electrochemical characterization and transmission electron microscopy investigations.

Insight into grain boundaries with reduced liquid metal embrittlement susceptibility in a boron-added 3rd generation advanced high strength steel

The addition of boron to the advanced high-strength steels (AHSS) enhances grain boundary cohesion and can play a significant role in intergranular degradation phenomena such as Zn-assisted liquid metal embrittlement (LME). The objective of this study is to reveal a thorough understanding of the effect of B on LME behaviour, where the welding test results indicated substantial improvement even at relatively low B concentration. Here, we adopted the strategy of identifying LME-sensitive grain boundaries, followed by characterizing grain boundary chemistry. EBSD measurements and prior austenite grain (PAG) reconstruction provided strong evidence of intergranular LME crack propagation via PAGBs. Further transmission electron microscopy and energy dispersive X-ray spectroscopy investigations demonstrated an asymmetric Mn profile along the PAGB in B-free steel. Therefore, we propose that B addition and consequently, lower grain boundary energy appears to prevent Mn segregation. Based on our observation, we conclude that B seems to have the similar desired effect on Zn diffusion along the PAGBs and eventually mitigates Zn-assisted LME.

Quantitative study on the microstructural evolution and dimensional stability mechanism of 2024 Al alloy during long-term thermal cycling

During the start-stop process of high-precision instruments in service, the critical materials of instruments undergo thermal cycling, resulting in changes in microstructure and dimension. In this paper, the evolution and coupling effects of dislocations and precipitates within 2024 Al alloy during 500 cycles were investigated, and their influence on the dimensional change was quantitatively characterized and decoupling analyzed. Transmission Electron Microscopy (TEM)/aberration-corrected scanning TEM (CS-TEM), X-ray diffraction (XRD), and Three-Dimensional Atom Probe Tomography (3D-APT) were used for microstructural evolution analysis and quantitative statistics. The dislocation density increased from 3.32 × 1014 m−2 to 5.75 × 1014 m−2 after 500 cycles, which accelerated elemental diffusion and provided nucleation sites of precipitates, contributing to an increase in the number density of the S'/S phase from 1.04 × 1024 m−3 to 1.41 × 1024 m−3. Based on the quantitative statistics of precipitate types and corresponding volume fractions, the dimensional change induced by precipitate evolution was −1.25 × 10−4. The dimensional change caused by the free volume introduced by dislocation density was 3.32 × 10−6. Comparing these values with the experimental value of −1.94 × 10−4, it is clear that the precipitate evolution is the main factor that triggers the dimensional change.

In Situ TEM/STEM Investigation of Crystallization in Y3Al5O12:Ce at High Temperatures Inside a Transmission Electron Microscope.

Y3Al5O12:Ce (YAG:Ce) phosphors are extensively used in the field of white light-emitting diodes (LEDs) due to their efficient luminescent properties. To optimize the performance of YAG:Ce phosphors, a comprehensive understanding of their synthesis and structural evolution is essential. This paper presents a direct in situ transmission electron microscopy (TEM) /scanning TEM (STEM) investigation on the transformation process of a precursor comprising nanocrystalline CeO2 dispersed in an amorphous Y-Al oxide matrix into crystalline YAG:Ce particles. The study reveals that nanocrystalline CeO2 particles dissolve completely in the Y-Al oxide matrix at a temperature above 900 °C, while YAlO3 (YAP)-type crystalline particles with Al2O3 phase in grain boundaries are observed above 1000 °C. Finally, YAG:Ce-type crystalline particles are formed above 1180 °C. Atomic-resolution energy-dispersive X-ray spectroscopy (EDS) elemental mapping demonstrates that the doped cerium (Ce) atoms occupy the same atomic sites as yttrium (Y). Photoluminescence measurements validate the efficient luminescent properties of the obtained YAG:Ce phosphor.

Dielectric, conductivity properties, elastic moduli, and gamma-ray attenuation abilities: A wide-ranging investigation into Molybdenum added ferrite nanoparticles

The auto combustion technique was employed to synthesis magnesium nano ferrite (MgMoxFe2-xO4). The impact of Mo-doped on the crystal’s structural, morphological, and elastic properties were inspected by applying x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy techniques. Pursuant to the XRD analysis, all samples have a cubic structure with single-phase. The average crystallite size was identified to be in the nanometer range confirmed by SEM and TEM investigations. FTIR data was implemented to assign the force constants of the octahedral and tetrahedral sites. Elastic moduli including the Poisson ratio, Young’s modulus, bulk modulus, and rigidity modulus have been estimated. The division of elastic moduli for all synthesized concentrations was interpreted using binding forces between ions of the cubic lattice spinel. Over and above, the AC conductivity (σ AC) and dielectric properties and their frequency dependence were investigated for the nano ferrites samples as a function of dopant Mo content and temperature. Finally, the radiation shielding capacities of the proposed samples against gamma and fast neutron radiation have been assessed. The findings reveal that the higher the Mo content, the lower the value of the mass attenuation coefficient. There is no significant diversity between the obtained mass attenuation coefficients for the nano and the micro. Among the samples investigated in this study, the highest Mo concentration sample had the largest fast neutron removal cross-section.

Room‐Temperature Synthesis of a Compositionally Complex Rare‐Earth Carbonate Hydroxide and its Conversion into a Bixbyite‐Type High‐Entropy Sesquioxide

AbstractIn the present work, the solvent‐deficient synthesis of the high‐entropy rare‐earth carbonate hydroxide RE(CO3)(OH) (RE=La, Ce, Pr, Nd, Sm, and Gd) and its thermal conversion into bixbyite‐type sesquioxide RE2O3 are reported for the first time. The high‐entropy rare earth carbonate hydroxide was prepared via mechanochemical reaction of the corresponding metal nitrate hydrates with ammonium hydrogen carbonate followed by the removal of the NH4NO3 by‐product. Calcination of the carbonate hydroxide precursor in ambient atmosphere at temperatures in the range from 500 to 1000 °C led to the high‐entropy rare earth sesquioxide which exhibited a bixbyite‐type structure ( ) independent of the calcination temperature. Transmission electron microscopy (TEM) investigation revealed the homogeneous distribution of all six rare earth cations in the high‐entropy sesquioxide lattice, however, with some compositional variation between individual grains. The bixbyite‐type structure may be considered as the result of heavy doping of the fluorite‐type CeO2 lattice with the other rare earth cations, which leads to a high concentration of oxygen vacancies, as revealed by electron diffraction and Raman spectroscopy data. The solvent‐deficient synthesis method used in the present study is considered as a valuable, straightforward and easily up‐scalable method to synthesize compositionally complex oxide ceramics.

TEM investigation of helium bubble evolution in tungsten and ZrC-strengthened tungsten at 800 and 1000°C under 40keV He+ irradiation

Helium-induced defect nucleation and accumulation in polycrystalline W and W0.5 wt%ZrC (W0.5ZrC) were studied in-situ using the transmission electron microscopy (TEM) combined with 40 keV He+ irradiation at 800 and 1000°С at the maximum damage level of 1 dpa. Radiation-induced dislocation loops were not observed in the current study. W0.5ZrC was found to be less susceptible to irradiation damage in terms of helium bubble formation and growth, especially at lower temperature (800 °C) when vacancies were less mobile. The ZrC particles present in the W matrix pin the forming helium bubbles via interaction between C atom and neighbouring W atom at vacancies. This reduces the capability of helium to trap a vacancy which is required to form the bubble core and, as a consequence, delays, the bubble nucleation.At 1000 °C, significant bubble growth occurred in both materials and all the present bubbles transitioned from spherical to faceted shape, whereas at 800 °C, the faceted helium bubble population was dominated in W.