TEM Observations Research Articles

TEM Observation of the Microstructure of Sulfide-Based Solid Electrolytes

TEM Observation of the Microstructure of Sulfide-Based Solid Electrolytes

Enhancing strength-ductility synergy by introducing multilattice defects and heterogeneous structures in CoCrNi-based medium-entropy alloys prepared by powder plasma arc additive manufacturing

In the work, cold rolling and annealing were applied to powder plasma arc additively manufactured (CoCrNi)94Al3Ti3 medium-entropy alloy (MEA) to efficiently attain different types of lattice defects and heterogeneous structures, thereby enhancing the strength of the alloy. Tensile tests show that mechanical properties of the MEA were significantly enhanced after cold rolling and annealing treatments compared to the directly deposited alloys. The microstructure and mechanical properties of cold rolled samples (50 % thickness reduction) annealed at 1073–1273 K for 1 h are compared. It has been shown that the MEAs prepared by additive manufacturing accumulate a large amount of deformation energy within the grains during the cold rolling process. This lead to recrystallized grains first nucleating within the original columnar grains, and efficient recrystallization could be realized. At annealing temperatures ≤1173 K, the recrystallized grain size has not been coarsened, the coarse and fine grains formed a heterogeneous grain structure, leading to significant back stress strengthening. TEM observations at different alloys indicate that the formation and increase in the number of multiple lattice defects (SFs, DTs, and L–C locks) is the main reason for the high work-hardening capacity of the alloy. This investigation demonstrates that the combined approach provides a novel means to fabricate high strength and ductile CoCrNi-based MEAs.

Unexpected pitting inhibition of additively-manufactured austenitic stainless steel by electrochemical hydrogen-charging

Pitting of austenitic stainless steel (SS) is intensified under hydrogen environment, resulting in great uncertainty of safety. However, austenitic SS printed by selective laser melting (SLM) after electrochemical hydrogen-charging manifests an unanticipatedly anti-pitting behavior. Pitting resistance is found in all the SLM samples after H-charging, while the original SLM and all the commercial SS samples are composed of corrosive pits on the surfaces. XRD, EBSD and TEM observations of SLM sample after H-charging reveal that nanotwins and ɛ-phase are newly formed interior of the cellular cells, which inhibit martensite transformation and enhance the formation of Cr oxides in passivation film.

Effects of Copper Content and Thermo-Mechanical Treatment on Microstructure and Mechanical Properties of AlMgSi(Cu) Alloys

This study presents the results of research on the influence of different contents of copper in aluminium alloys based on the 6xxx series on mechanical and structural properties. The investigation started with the alloying, and casting four billet variants with different copper content—0.8% Cu; 2B—1% Cu; 3A—1.2% Cu; and 3B—1.4% Cu. The prepared materials were homogenised and extruded on a 500T horizontal press with two different process temperatures and ram speeds ranging from 1 mm/s to 9 mm/s. After heat treating to the T6 and T5 tempers, their mechanical properties were tested. On this basis, the two most promising alloys 2A and 3B were selected and subjected to further tests. After extrusion and heat treatment of the profiles (to F, T1, T2, T5, and T5510), their mechanical properties were determined to select the preferred process parameters. Finally, a structural test based on crystallographic orientation based on the EBSD technique and TEM observations allowed for the characterisation of grain size, dispersoids, and phase analysis. Bright-field (BF) analysis allowed us to compare the deformed areas for T1, T5, and T5510 temperatures. The results showed significant growth in the mechanical properties of all the subjected alloys, and the best properties were shown for a Cu content of 1.4% with a tensile strength of 460 MPa and an elongation of 16% (T5510 tempering). The structural test showed an average grain size of 18 µm to 23 µm and solid solution decomposition differences for different heat-treating parameters.

Design, Synthesis, and Antifungal Evaluation of Novel Cuminic Acid Derivatives as Potential Laccase Inhibitors.

In search of novel natural product-based fungicides, 49 cuminic acid derivatives were designed, synthesized, and screened for their in vitro antifungal effects toward seven phytopathogenic fungi and oomycetes. Consequently, several derivatives exhibited strong antifungal activities toward Fusarium graminearum, Botryosphaeria dothidea, and Valsa mali. Among them, compound 2b exhibited the most potent antifungal activity toward B. dothidea (EC50 = 0.96 mg/L), more powerful than chlorothalonil. The in vivo assay against B. dothidea found that the protective and curative effects of 2b were comparable to chlorothalonil. Meanwhile, SEM and TEM observations indicated that 2b could ruin the integrity of mycelial morphology and organelles of B. dothidea. Preliminary mechanism research showed that 2b increased the cell membrane permeability and intracellular ROS level, as well as conspicuously decreased the mycelial dry weight and cell wall chitin contents of B. dothidea. The phytotoxicity test revealed that 2b showed good safety on seeds of mung bean and radish. The in vitro laccase inhibitory activity assay and molecular docking study demonstrated that 2b could be a promising laccase inhibitor. This type of cuminic acid hydrazide derivative would provide valuable inspiration for developing novel fungicides against B. dothidea.

Porous Amorphous-Crystalline Heterostructured CoNiP Nanowire Arrays for Enhanced Hydrogen Evolution Performance under Acid-Base Conditions.

A novel porous amorphous-crystalline heterostructured CoNiP nanowire arrays ((a-c)CoNiP/CC) is presented. TEM observations and compositional calculations revealed ≈14.5% of the amorphous regions (a-CoNiP) are interleaved in the crystalline regions (c-(Co3.6Ni0.4)P4), forming massive amorphous-crystalline heterogenous interfaces composed of the same elements. Only 38 and 64mV overpotentials for the (a-c)CoNiP/CC catalyst are required to reach the current density of -10mAcm2 in acid and alkaline electrolyte, respectively, which is very close to the overpotentials (35 and 55mV) of the commercial Pt/C HER catalyst. The theoretical calculation revealed that the (a-c)CoNiP/CC has a completely different enhancement mechanism of HER reaction in acid-base electrolytes. In particular, due to the natural corrosion resistance of the amorphous interface, the HER performance of this catalyst under the high current density condition is much better than that of the Pt/C catalyst either in acidic or in alkaline, suggesting its prospect for commercial applications.

Yolk-shell structured FeS0.5Se0.5@N-doped mesoporous carbon composite as high-performance lithium-ion battery anodes

Transition metal selenides/sulfides are drawing growing attention as promising electrode material for lithium-ion batteries owing to their larger layer spacing and weaker ionic bond compared to transition metal oxides, which are conducive to the intercalation/de-intercalation of Li ions. However, the intrinsic low conductivity and large volume expansion remain a major obstacle for their practical applications. In this work, with the prediction help of the theory model, we design a yolk-shell structure of single-phase ternary FeS0.5Se0.5 and nitrogen-doped mesopore carbon (YS-FeS0.5Se0.5@NMC) via an interfacial co-assembly, followed by one-step selenization and vulcanization. In the composite, single-phase ternary FeS0.5Se0.5 yolk provides more active sites and faster ion/electron transport dynamics than binary Fe2O3, while N-doped mesoporous carbon shell effectively alleviates the large volume expansion of FeS0.5Se0.5, as revealed by in-situ Raman analysis and TEM observation. Meanwhile, the spatial confinement of outer carbon shell also ensures the mechanical stability of the electrode during cycles. These merits endow the YS-FeS0.5Se0.5@NMC anode with a high reversible capacity of 1417mA h/g at 200mA h/g after 120 cycles, and an exceptional rate capability. This work offers an inspired approach for achieving high-performance energy storage electrode materials

Exosomal miR-590-3p derived from bone marrow mesenchymal stem cells promotes osteoblast differentiation and osteogenesis by targeting TGFBR1.

Bone marrow mesenchymal stem cells (BMSCs) have been verified to be essential factors regulating osteogenic functions, which is mainly attributed to their secretion of extracellular vesicles. Exosomes derived from BMSCs (BMSCs-Exo) contribute to osteoblast functions that are critical for improving bone defect. Our current study aims to investigate the molecular mechanism dominated by BMSCs-Exo that affects osteoblast differentiation and osteogenesis. The first step this study validated that BMSCs co-culture enhanced the differentiation ability of osteoblast and promoted bone mineralization, while these tendencies were abolished after GW4869 treatment. Next, the BMSCs-Exo was isolated and identified by TEM observation, insight detection, and western blot analysis. Furthermore, BMSCs-Exo treatment could efficiently promote the differentiation ability and the bone mineralization of osteoblasts, decrease the mRNA levels of Collagen I and Collagen III, and increase the levels of osteogenic proteins, including alkaline phosphatase (ALP), Turning Bone Morphogenetic Protein 2 (BMP2), Bone sialoprofein (BSP), osteocalcin (OCN), and osterix (OSX). However, the abovementioned effects of BMSCs-Exo could be abolished by miR-590-3p silencing. Mechanistic analysis unmasked the negative regulation of miR-590-3p on its downstream target TGFBR1. Finally, the effects of miR-590-3p/TGFBR1 axis on the differentiation and osteogenesis of osteoblasts were validated by rescue assays. In conclusion, the present study demonstrates that exosomal miR-590-3p secreted by BMSCs can induce osteoblast differentiation and osteogenesis.

Preparation and characterization of self-dispersive and reactive carbon black and its application in cotton fabric

This study aims to develop a self-dispersive and reactive carbon black (DRCB) to improve its application in cotton fabric. CB was functionalized with γ-aminopropyl triethoxysilane (KH550) and then grafted with as-synthesized compound to obtain aqueous phase DRCB. FTIR analysis confirmed the successful grafting of as-synthesized compound onto KH550-modified CB surface. The weight grafting of DRCB on DRCB-15 % dyed cotton fabric was approximately 15.18 %, with a half weight grafting time of around 17 min. TEM observation demonstrated that DRCB had a core-shell structure with the mean sizes of 36.02 ± 4.30 nm. Particle size analysis revealed that DRCB had smaller average aggregate size of 110.3 nm and higher zeta potential of −33.7 mV than CB, indicating that DRCB had much better dispersion in aqueous media than CB. Cotton fabric was effectively dyed with DRCB, providing excellent color depth of 60 (K/S value) with dry rubbing and wet rubbing/washing color fastness of Grade 4 and Grade 3, respectively. DRCB dyed cotton fabric exhibited outstanding anti-UV and anti-static properties, with no significant difference in softness and tensile property before and after dyeing. This research proposed a new method to solve nanoparticle agglomeration and prepare textile dyes with excellent self-dispersivity and reactivity.

Structural damage and bubble evolution in SiC-ZrC composite irradiated with 500 keV He-ions at various temperatures

Ceramic composites with high temperature strengths and low neutron cross-sections are promising candidates for core materials in advanced nuclear systems. In present work, SiC-20 vol% ZrC composites were irradiated with 500 keV He-ions at 25, 500 and 800 °C to evaluate the effect of irradiation temperature on the structural damage and bubble evolution in ceramic composites. XRD and Raman spectra analysis give that the irradiation resulted in structural damages of both SiC and ZrC. TEM observations reveal the formation of helium bubbles and defect clusters after irradiation. Moreover, the occurrence of micro-cracks in ZrC grains and amorphization of SiC are observed for the samples irradiated at room temperature. Nanoindentation test showed that there is irradiation induced hardening or softening of the composites which depends on the irradiation temperature or fluence. The correlation between microstructural evolution and mechanical properties response is discussed.

Optimal Arrangements and Local Anisotropy of {100} Guinier-Preston (GP) Zones by Parametric Dislocation Dynamics (PDD) Simulations.

Stress-oriented precipitation and the resulting mechanical anisotropy have been widely studied over the decades. However, the local anisotropy of precipitates with specific orientations has been less thoroughly investigated. This study models the interaction between an edge dislocation source and {100} variants of Guinier-Preston (GP) zones in Al-Cu alloys using the parametric dislocation dynamics (PDD) method. Concentric geometrically necessary dislocation (GND) loops were employed to construct a line integral model for thin platelets. The simulations, conducted with our self-developed code based on Green's function method and Eshelby inclusion theory revealed distinct strengthening behavior along the strong and weak directions for 60° GP zones, demonstrating anisotropic strengthening from the perspective of elastic interactions. Furthermore, the optimal inclined arrangement of the GP zone array was determined through elastic energy calculations, and these results were corroborated by TEM observations.

Facile Preparation of Raspberry-Like SiO2@Polyurea Microspheres with Tunable Wettability and Their Application for Oil-Water Separation.

Raspberry-like microspheres have been widely used as superhydrophobic materials, photonic crystals, drug carriers, etc. Nevertheless, their preparation methods, usually consisting of multiple steps, are generally time- and energy-consuming. Herein raspberry-like SiO2@polyurea microspheres (SiO2@PUM) are readily prepared via a one-step precipitation polymerization of isophorone diisocyanate in a H2O/acetone mixture with the presence of SiO2 particles. The sphere size, surface roughness, and SiO2 content of SiO2@PUM are easily adjustable by varying the experimental conditions. TEM and SEM observations reveal that the final SiO2@PUM exhibits a core-shell structure, with polyurea (PU) in the core and SiO2 particles as the shell. In the process, the SiO2 particles were initially located on the PUM surface as a monolayer. With the reaction proceeding, the monolayer of SiO2 particles became thicker, forming a thicker layer of SiO2 particles on PUM due to the accumulation of SiO2 particles, leading to a multilayer structure of SiO2 particles on the shell of SiO2@PUM. The formation mechanism of the raspberry-like SiO2@PUM was thoroughly discussed and ascribed to electrostatic attraction between the positively charged PU and negatively charged SiO2 particles. Once dried, SiO2@PUM was superhydrophobic and turned hydrophilic if water-wetted. Using a layer of SiO2@PUM, effective separation with good reusability for a variety of oil-water mixtures was achieved regardless of the oil density and types of oil-water emulsions. This work presents a novel protocol for the preparation of raspberry-like microspheres with tunable wettability via a rapid and green process, and the resulting microspheres are highly effective for the separation of diverse types of oil-water mixtures.

NaCl inhibits Geotrichum citri-aurantii growth by inducing lipid droplets accumulation and enhances the biocontrol efficacy of Kloeckera apiculata 34-9

Decays resulting from infections by Geotrichum citri-aurantii cause a significant reduction in citrus postharvest quality and marketable yield. In the present work, 0.8 mol·L−1 NaCl of Generally Recognized as Safe (GRAS) salts were identified to have complete inhibition activity to G. citri-aurantii in vitro and in vivo. An inhibitory mechanism study showed that 0.1 mol·L−1 NaCl changed the expression of six genes (Gci002087, Gci003354, Gci000013, Gci000394, Gci003505 and Gci004433) in target of rapamycin (TOR) pathway, thus inducing a large number of lipid droplets (LDs) accumulation with TEM observations and staining. In vivo, 0.1 mol·L−1 NaCl could raise up the activities of CAT, PAL, PPO and cellulase which hence to strengthen the ability of resistance tolerance of citrus. In addition, NaCl not only accelerated the growth of the biocontrol yeast Kloeckera apiculata strain 34-9, but also increased the expression level of adhesin-encoding genes and biofilm-formation encoding gene (34-9 - 3691). Finally, the storage experiments in 3 months demonstrated that the combination of NaCl and the yeast 34-9 could keep fresh, reduce decay and prolong its shelf-life, thus implying that the combination of biocontrol strain and GRAS salts has been explored as a promising alternative to synthetic fungicides.

Relationship between synthesis conditions and ORR activity of PtCo nanowire/C catalysts for PEFC cathodes

Nanowire (NW) structures have attracted attention as durable catalysts for the oxygen reduction reaction (ORR) due to their resistance to aggregation, unique morphology, and efficient electron conduction. However, NWs often suffer from limited structural stability, and there is a lack of research on their performance in membrane electrode assembly (MEA) studies. In this study, PtCo NW/C catalysts with various amounts of oleylamine (OAm) were prepared, and their oxygen reduction reaction (ORR) activity and durability were investigated by MEA and RDE testing conditions. XRD analysis and TEM observations showed that the prepared PtCo NWs were successfully alloyed,and PtCo NW alloys were observed. CV and LSV results showed that the PtCo NW/C OAm100 catalyst with 2 h of acid treatment had the best ORR activity. The I-V test results demonstrated that the PtCo NW/C OAm100 catalyst with 2 h of acid treatment had higher cell voltage, and cell performance was also excellent. It was found that the ORR activity of PtCo NW was improved by adding the appropriate amount of OAm.

Effect of Pt-Al coating on low-cycle fatigue behavior in a Ni-based single crystal superalloy at 760 °C

The effect of Pt-Al coating on low-cycle fatigue behavior of Ni-based single crystal superalloy at 760 °C was evaluated. The results show that Pt-Al coating does not change the cyclic stress response behavior of the Ni-based single crystal superalloy at 760 °C. Under the total strain amplitude from 0.6 % to 1.2 %, the cyclic stress amplitude value of Pt-Al coating samples is slightly lower than uncoated samples during cyclic deformation at the stable stage under the same applied total strain amplitude, and the fatigue life of Pt-Al coating samples is lower than uncoated ones, with an average fatigue life reduction of about 19.9 %. By the relation curve of comparing the cyclic strain amplitude with the reversals to failure, it is observed that the fatigue ductility coefficient ε′f of the Pt-Al coating sample is higher than the uncoated sample, the fatigue ductility index c and fatigue strength coefficient σ′f are lower than the uncoated sample, but the fatigue strength index b has little difference. It is found that the cyclic strength coefficient K′ and the cyclic strain hardening index n' of the Pt-Al coating sample are lower than the uncoated sample after fitting the curves of the relationship between cyclic stress amplitude and total strain amplitude. In addition, the cyclic stress amplitude of Pt-Al coating sample is slightly lower than uncoated sample under the same applied total strain amplitude. It was found by SEM that the cracks of both uncoated and Pt-Al coating samples initialized near the surface of the samples under low-cycle fatigue loading at 760 °C, and multiple crack sources began to spread into the substrate. It was found by TEM observation that at low strain amplitude (Δεt/2 = 0.6 %), the dislocations in both uncoated and Pt-Al coating samples mainly converged in γ, and a large number of dislocation debris gathered in the γ and dislocation entanglement was generated, while a small number of dislocations were observed to cut into γ'. The γ′ is seriously deformed and slightly rafted at Δεt/2 = 1.2 %, and a few dislocations are also observed in γ'.

Electric current-induced directional slip of dislocation and grain boundary ordering

The evolution of lattice dislocations in metals can be induced by electric current. However, the effect of electric current on the interaction between lattice dislocations and grain boundaries (GBs) remains unclear. Herein, we investigate the evolution of lattice dislocations and grain boundary dislocations (GBDs) induced by electric current in M50 steel via in-situ TEM characterization, density functional theory (DFT) calculations, and molecular dynamics (MD) simulations. Our findings reveal that electric current induces the directional slip of lattice dislocations towards GBs, while the reduction of GB contrast is attributed to the decomposition and reorganization of GBDs. DFT calculations demonstrate that electric current enhances the force on atoms in defect regions. These in-situ TEM observations are well reproduced by MD simulations incorporating electric current, which include a virtual temperature rise at defect regions to reflect the electric current force on defect atoms. Based on these observations, we propose a novel GB accommodation model under electric current. These results provide valuable insights into the mechanisms by which electric current tailors lattice dislocation behavior and enhances GBDs ordering in metallic materials.

The effect of supported metal Species on soot oxidation over PGM/CeO2-ZrO2

Abstract Herein is studied the soot oxidation over platinum group metal oxide/CeO2–ZrO2 (PGM/CZ) catalysts. The ability to capture gas-phase oxygen was in sequence of Ru/CZ > Rh/CZ > Ir/CZ > Pt/CZ > Pd/CZ. A soot oxidation test by TG-DTA showed that Ru/CZ, Rh/CZ, and Ir/CZ are highly active catalysts. It was found that there is a good correlation between the ability to capture gas-phase oxygen and soot oxidation activity. TEM observation revealed that soot oxidation mainly occurs at the interface between soot and CZ surfaces. The Ea values and soot oxidation test using labelled oxygen suggest that highly active catalysts oxidize soot by CZ lattice oxygen. For Ir/CZ, soot oxidation at 270 °C occurred due to the reduction by soot. Ru/CZ and Rh/CZ captured gas-phase oxygen spontaneously below 250 °C, resulting in soot oxidation at 270 °C. H2-TPR results suggest that the reactivity of lattice oxygen in the CZ surface, improved by PGM, is also related to soot oxidation activity. This suggests that the ability to capture gas-phase oxygen and the reactivity of lattice oxygen in the CZ surface determine the soot oxidation activity, and that Ru, Rh, and Ir have the effect of enhancing these properties.

Laser powder bed fusion of Fex(CoCrMnNi)100-x medium-entropy ferrous alloys: Processability, microstructure and dynamic deformation mechanism

In this work, Fex(CoCrMnNi)100-x (x = 40, 60 and 80 at.%) medium-entropy ferrous alloys (MEFAs) were fabricated through laser powder bed fusion (LPBF) of mixed powders composed of FeCoCrNiMn and Fe powders, and the dynamic compressive properties and deformation mechanisms were studied with combination of experiment and molecular dynamics simulation. The results demonstrate that all MEFAs exhibit good processability.The Fe40 and Fe60 samples were predominantly composed of FCC phase with coarse grains, while the Fe80 mainly consisted of BCC phase with a smaller grain size. When subjected to quasi-static and dynamic compression at 3000/s, the yield strengths of Fe40, Fe60 and Fe80 increases by 131, 220 and 256 MPa, respectively, illustrating the positive strain rate sensitivity and influence of Fe on the mechanical properties of MEFAs. Further, both the single-crystal and the polycrystalline models suggested that the incompatibility between the BCC and FCC phases is responsible for the enhancement of strength. Therefore, it is more likely to produce deformation twins, dislocations and thus stress concentration around the BCC phase, which is consistent with the TEM observations.

Nanosheet-assembled porous-wall hollow hydroxyapatite microspheres prepared by a template-free hydrothermal method for pH-responsive drug release

Template residues during the preparation of hydroxyapatite (HA) microspheres with hollow structures limit their biological applications to some extent. In this study, the nanosheet-assembled porous-wall hollow HA microspheres were successfully synthesized by a template-free hydrothermal method. SEM and TEM observations revealed that the prepared hollow HA microspheres were about 3–7 μm in diameter and were composed of an interior cavity and a porous shell assembled by nanosheets (consisting of radial nanorods arranged side-by-side). A possible mechanism for the formation of the hollow HA microspheres was proposed based on the time-gradient experiments. Furthermore, the hollow HA microspheres exhibited excellent vancomycin loading capacity (101.3 mg/g) and pH-responsive release properties. This study provides new inspiration for the design and various applications of hollow materials.

Antifungal mechanism of nanosilver biosynthesized with Trichoderma longibrachiatum and its potential to control muskmelon Fusarium wilt

Fusarium oxysporum (Schl.) f.sp. melonis, which causes muskmelon wilt disease, is a destructive filamentous fungal pathogen, attracting more attention to the search for effective fungicides against this pathogen. In particular, Silver nanoparticles (AgNPs) have strong antimicrobial properties and they are not easy to develop drug resistance, which provides new ideas for the prevention and control of muskmelon Fusarium wilt (MFW). This paper studied the effects of AgNPs on the growth and development of muskmelon, the control efficacy on Fusarium wilt of muskmelon and the antifungal mechanism of AgNPs to F. oxysporum. The results showed that AgNPs could inhibit the growth of F. oxysporum on the PDA and in the PDB medium at 100–200 mg/L and the low concentration of 25 mg/L AgNPs could promote the seed germination and growth of muskmelon seedlings and reduce the incidence of muskmelon Fusarium wilt. Further studies on the antifungal mechanism showed that AgNPs could impair the development, damage cell structure, and interrupt cellular metabolism pathways of this fungus. TEM observation revealed that AgNPs treatment led to damage to the cell wall and membrane and accumulation of vacuoles and vessels, causing the leakage of intracellular contents. AgNPs treatment significantly hampered the growth of mycelia in the PDB medium, even causing a decrease in biomass. Biochemical properties showed that AgNPs treatment stimulated the generation of reactive oxygen species (ROS) in 6 h, subsequently producing malondialdehyde (MDA) and increasing protective enzyme activity. After 6 h, the protective enzyme activity decreased. These results indicated that AgNPs destroy the cell structure and affect the metabolisms, eventually leading to the death of fungus.