High-resolution Transmission Electron Microscopy Results Research Articles

Porous CN@MOF derived N, S-doped hierarchical framework carrying Co3Fe7/Fe0.8Co0.2S heterojunction: An efficient bifunctional cathode catalyst for Zn–air battery

The exploiting of bifunctional transition metal electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is of significance for the commercialization of rechargeable zinc-air batteries (ZABs). Herein, the N and S atoms-doped hierarchical carbon framework hosting the Co3Fe7/Fe0.8Co0.2S heterojunction is synthesized by employing porous g-C3N4 as framework and spacer, and FeCo-ZIF as metal source followed by sulfidation and pyrolysis. The detailed characterization confirms that the porous g-C3N4 plays a crucial role in improving the dispersion of metal nanoparticles. The obtained FeCo-Sx@NSC-900 catalysts exhibit layered accumulation configuration with uniformly distributed metal nanoparticles. Moreover, the typical carbon@metal nanoparticles and heterojunction structure can be observed from the HRTEM (High-Resolution Transmission Electron Microscopy) and HAADF-STEM (high-angle annular dark-field STEM) analysis results. The optimal FeCo-Sx@NSC-900 catalysts deliver exceptional ORR and OER performance with a potential difference between ORR and OER of merely 0.713 V, which is superior to the commercial Pt/C+RuO2 catalysts and other monometallic catalysts. Additionally, the ZAB assembled with the optimal FeCo-Sx@NSC-900 catalysts as cathode affords a good battery performance with high OCV (1.50 V), large power density (172 mW/cm2), good discharge stability, large specific capacity, and long-term charge/discharge stability (>300 cycles).

Facile synthesis of nanosized spinel high entropy oxide (FeCoNiCrMn)3O4 for efficient oxygen evolution reaction

The sluggish reaction kinetics of oxygen evolution reaction (OER) and the high price of noble metal catalysts hinder the wide application of water electrolysis for hydrogen generation. High-entropy oxides (HEOs) with multi-components and high entropy stabilized structures have attracted great research interests due to their efficient and durable performance in electrolytic water splitting reactions. However, the development of efficient HEO electrocatalysts are often hindered by the limited surface exposed active sites because high temperature is usually required to form a high entropy stabilized structure. Herein, a flaky high-entropy oxide with a spinel structure, (FeCoNiCrMn)3O4, was synthesized by using the sacrificial layered carbon template in situ prepared by the volatile reaction between ammonium sulfate and molten glucose. High-resolution TEM results show the as-prepared (FeCoNiCrMn)3O4 flakes are composed of nanosized HEO particles. The nanosized (FeCoNiCrMn)3O4 HEO electrocatalysts exhibit excellent OER activity, with an overpotential of 239 mV at 10 mA/cm2 and a Tafel slope of 52.4 mV/dec. The electrocatalyst has excellent stability. Even at a high current density of 100 mA/cm2, the activity remains unchanged during the stability test for 24 h. The results here shed a new light in the design and fabrication of highly efficient HEO electrocatalysts.

Evolution of carbon nanostructures during coal graphitization: Insights from X-ray diffraction and high-resolution transmission electron microscopy

The evolution of carbon nanostructures during coal graphitization was investigated. The X-ray diffraction (XRD) results showed that amorphous and microcrystalline carbon coexist in anthracite and meta-anthracite, and the latter has a higher proportion of microcrystalline carbon; additionally, semi-graphite and coal-based graphite are mostly composed of crystalline carbon. Coal graphitization starts in anthracite, accompanied by an increase in crystallite size and a decrease in interplanar spacing nonlinearly, especially in semi-graphite, and a large ordered structure is formed in coal-based graphite. The high-resolution transmission electron microscopy (HRTEM) results intuitively reveal the graphitization process by false-colored microphotography, and both the XRD and HRTEM results indicate similar evolution paths. Four types of carbon nanostructures, namely, amorphous, turbostratic, concentric and graphitic-like structures, are identified according to their morphology. Aromatic fringes are arranged randomly in the amorphous structure and are composed of amorphous carbon; local ordering occurs in the turbostratic structure and is commonly observed in anthracite and meta-anthracite. In addition, a concentric structure with hollow pores and parallel annular aromatic fringes was observed, indicating multiple preferred orientations, and the graphitic-like structure was composed of parallel aromatic fringes. Micropores provide the necessary adjustment space for the ordered conversion of carbon nanostructures, and the flattening and merging of micropores may contribute to the enhancement of graphitization.

STRUCTURAL INVESTIGATION OF HETERO-STRUCTURED CORE-SHELL SILVER-SILICA HYBRID AS A POTENTIAL AGRO-SENSOR MATERIAL

Investigation into the novel synthesis and structural properties of Heterostructured core shell Silver-Silica (AgSiO2) Nanohybrid is reported herein, for possible utilization as humidity sensing material in Agricultural post-harvest humidity monitoring system and greenhouse farming. The Heterostructured nanoparticles (Ag and SiO2) were synthesized via a chemical reduction method. Structural characterizations were done using X-ray Diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM), Scanning Electron Microscopy (SEM), UV-Visible spectroscopy, Energy Dispersive X-ray (EDX) spectroscopy and N2 adsorption-desorption techniques. The XRD diffractogram of Ag-SiO2 showed distinct peaks at 2? values of 390, 430, 660 and 790 which was corroborated by the SEM and HRTEM results. EDX convincingly confirmed Ag and SiO2 incorporation into the Ag-SiO2 nanocomposite hetero-structure at 16.7 % and 83.3 % respectively. A Surface Plasmon Resonance absorption peak of 421 nm of Ag was revealed by UV-Visible spectroscopic analysis. An effective and relatively narrow pore size distributions of 3 – 8 nm was revealed by N2 adsorption-desorption for the Ag-SiO2 Nanocomposite. Overall, these properties are promising for effective use as humidity sensing material.

Improvement of the structural, dielectric, ferroelectric, and piezoelectric of PbZr0.52Ti0.48O3 nanopowder features for ultrasonic applications

Smart ferroelectric lead zirconate titanate (PbZr0.52Ti0.48O3) was synthesized in the morphotropic phase boundary by a sol-gel auto-combustion strategy. The as-prepared powder was calcined at three different temperatures, 700, 800, and 900 °C for 3 h, each. The tetragonality of the final product increases with the rise of calcination temperature. Thermal gravimetric analysis and differential thermal gravimetric analysis depicted that complete crystallization of PZT was observed at 400 °C. Structural, vibrational, and microstructure studies were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy investigated for grains and elemental analyses and high-resolution transmission electron microscopy (HR-TEM). Results of XRD and HR-TEM were compatible, showing the formation of nanocrystalline powder with coexisting tetragonal and rhombohedral phases. Rietveld refinement of XRD data was carried out using material analysis using diffraction software in order to obtain the lattice constants. For mechanical and electrical measurements, disks were pressed at 10 MPa. The samples were burned out at 500 °C for 1 h and then 1100 °C for 2 h to obtain more dense disks. The surfaces of the disks were coated with silver paste, followed by burning out for almost an hour. Dielectric and piezoelectric characteristics for the fabricated PZT samples were determined in detail. From these analytical techniques and collected data, one can deduce that the sample annealed at 900 °C can be used as an ultrasonic transducer in various metrological applications.

Ultra-low temperature solid-state synthesis of single-phase SrY2O4 for thermal-barrier-coating applications

Due to the thermal and chemical stability, SrY2O4 has a potential to be utilized as thermal barrier coatings materials. Unfortunately, the relative high synthesis temperature (> 1425 °C) of SrY2O4 leads to high energy consumption limits its industrial production. To address this issue, a novel and easy fabricating approach for single-phased SrY2O4 was explored at ultra-low temperature of 950 °C, in which isopropanol was used to disperse the powder slurry by ball milling. The XRD and high-resolution TEM results demonstrated that the obtained SrY2O4 possesses an anti-spinel orthorhombic crystal structure. In addition, SrY2O4 has good phase stability and high thermal expansion coefficient (11.06 × 10−6 K−1, RT ∼ 1200 °C) at high temperature, which implies that it is a good choice for thermal barrier coatings.

Preparation and analysis of pure and surface modified nanohydroxyapatite derived from eggshells and its in-vitro studies for bone graft applications

The need and significance for quality bone graft substitute increases due to the worldwide increment in the health problems such as osteoporosis, accidental loss and teeth decay etc. Nowadays, nanohydroxyapatite and its polymeric composites are effectively used as bone grafts and dentin. In this work, nanohydroxyapatite (nHAp) and surface-modified nanohydroxyapatite were synthesized through the precipitation method using bio-wastes (eggshells) as a Calcium precursor. The polymers Polyethylene glycol (PEG) and polyvinyl acrylate (PVA) were used as surface modifiers to control the particle size. The prepared samples were analyzed through X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Differential Thermal Analysis (TG-DTA), Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HR-TEM) and X-ray Photoelectronic Spectroscopy (XPS). Also, the samples were subjected to simulated body fluid analysis, antimicrobial and hemolytic assay to analyze the apatite forming ability and hemolytic nature. The XRD, SEM and HR-TEM results show the crystallite and particle sizes are about 41 nm, 57 nm and 66.6 nm (rod-shaped) respectively. While the EDAX spectra show the presence of Calcium, Phosphate, Oxygen and Sodium in the prepared sample. However, the FT-IR spectra confirm the presence of OH, PO43−, and CO32− functional groups in the sample. The thermogram depicts the stability of nHAp/PVA composite is better than nHAp without polymer. This study reports that reprocessing of eggshells to nHAp and its composites paves the way to recover the ecosphere and the obtained value-added product, which may use in making a promising material for bone implants, dental fillers and coatings at low cost.

A combined 3D-atomic/nanoscale comprehension and ab initio computation of iron carbide structures tailored in Q&P steels via Si alloying.

The essences of the quenching and partitioning (Q&P) process are to stabilize the finely divided retained austenite (RA) via carbon (C) partitioning from supersaturated martensite during partitioning. Competitive reactions, i.e., transition carbide precipitation, C segregation, and decomposition of austenite, might take place concurrently during partitioning. In order to maintain the high volume fraction of RA, it is crucial to suppress the carbide precipitation sufficiently. Since silicon (Si) in the cementite θ (Fe3C) is insoluble, alloying Si in adequate concentrations prolongs its precipitation during the partitioning step. Consequently, C partitioning facilitates the desired chemical stabilization of RA. To elucidate the mechanisms of formation of transition η (Fe2C) carbides as well as cementite, θ (Fe3C), besides the transformation of transition carbides to more stable θ during the quenching and partitioning (Q&P) process, samples of 0.4 wt% C steels tailored with different Si contents were extensively characterized for microstructural evolution at different partitioning temperatures (TP) using high resolution transmission electron microscopy (HR-TEM) and three-dimensional atom probe tomography (3D-APT). While 1.5 wt% Si in the steel allowed only the formation of η carbides even at a high TP of 300 °C, reduction in Si content to 0.75 wt% only partially stabilized η carbides, allowing limited η → θ transformation. With 0.25 wt% Si, only θ was present in the microstructure, suggesting a η → θ transition during the early partitioning stage, followed by coarsening due to enhanced growth kinetics at 300 °C. Although η carbides precipitated in martensite under paraequilibrium conditions at 200 °C, θ carbides precipitated under negligible partitioning local equilibrium conditions at 300 °C. Competition with the formation of orthorhombic η and θ precipitation further examined via ab initio (density functional theory, DFT) computation and a similar probability of formation/thermodynamic stability were obtained. With an increase in Si concentration, the cohesive energy decreased when Si atoms occupied C positions, indicating decreasing stability. Overall, the thermodynamic prediction was in accord with the HR-TEM and 3D-APT results.

Microstructural evolution of amorphous nano carbon reinforced TiB2–SiC–B4C composite ceramics derived from absorbent cotton

In this study, amorphous nanocarbon particles were added by the vacuum deposition of absorbent cotton, and TiB 2 –SiC–B 4 C composite ceramics were prepared via vacuum filtration, cold isostatic pressing, and pressureless sintering. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were employed to determine the phase transformation and microstructural evolution of the nanocarbon-reinforced TiB 2 –SiC–B 4 C composites. Based on the high-resolution TEM results, the formation processing of lamellar grains, induced by the presence of parallel nanocarbon particles, was discussed in detail. Furthermore, owing to the optimization of the fracture mode and reinforcement of the nanocarbon particles, the mechanical properties of the composites were found to be significantly improved, that is, the flexural strength and fracture toughness were 585.6 MPa (almost a 39% increase to blank TiB 2 –SiC–B 4 C composite ceramics) and 5.9 MPa m 1/2 (almost a 55% increase), respectively. The introduction of nanocarbon particles via cotton pyrolysis not only reduced the production cost but also solved the problem of nanophase dispersion, providing a novel strategy for the low-cost preparation and improved performance of structural ceramics.

Revealing the Structure and Properties of Polycrystalline Components of the Solid Electrolyte Interface

The formation, structure and composition of the solid-electrolyte interphase (SEI) in lithium batteries have been extensively explored in the prior literature. It is commonly accepted that the SEI consists of two inorganic layer followed by organic layer. However, very little is known about the actual grain boundary (GB) structure of the inorganic layer and the ions transport through it. The present work seeks to understand the structure and stability of the GBs formed between various inorganic components of the SEI and mechanisms of Li diffusion through them. The density functional theory (DFT) calculations supported by the high-resolution transmission electron microscopy (HRTEM) measurements are employed to understand the SEI GB atomic structures and their chemo-mechanical properties.DFT calculations were performed using the Vienna Ab Initio Simulations Package (VASP) code1 employing the generalized-gradient approximation (GGA) using the PBE (Perdew, Burke, and Ernzerhof)2 functional to account for the exchange-correlation effects. The Nudged Elastic Band (NEB) method3 is used for the Li migration barriers calculations as implemented in VASP. To build the GB structures, the Atomistic Tool Kit (ATK)4 “Interface Builder” tool is used, which allows to analyze all possible interphases between two slabs. Cryogenic TEM (Cryo-TEM) images are recorded on a JEOL ARM200CF TEM, equipped with a Gatan Oneview camera operated at 200 kV.The HRTEM measurements revealed the polycrystalline structure of the SEI inorganic layer consisting mainly of LiF, Li2CO3, Li2O and LiOH components. In addition, different surface orientations (e.g., 111, 200, 002, etc.) of the aforementioned components are identified. Based upon the HRTEM results (cf. Fig. 1 left-hand side), the corresponding computational slabs have been built as shown on the right-hand side in Fig. 1. After the optimization of all structures, Li adatom diffusion inside grain and GB and mechanical properties were calculated.For each GB, several Li adatom positions with multi-atom bonding were identified. The activation energy of Li diffusion varies significantly depending upon the slab’s structure and the number of Li adatoms. The NEB calculations also reveal a non-symmetric transition state for all considered structures, which indicates a complex multi-atom hopping mechanism. The calculated elastic properties show the decrease of Young’s modulus with an increase of Li adatoms. Our combined experimental and modeling findings provide valuable insights into developing mitigation strategies towards a better understanding of the SEI components stability and Li migration through the SEI.Figure 1. Identification of grain and GB of the SEI busing HRTEM (left) and the corresponding built DFT slab (right). Lavender spheres denote Li atoms, red spheres are the oxygen atoms, grey spheres represent carbon atoms and green spheres are F atoms. Blue sphere in the GB denotes Li adatom.References G. Kresse, Phys. Rev. B, 59, 1758–1775 (1999).J. P. Perdew, A. Ruzsinszky, G. I. Csonka, O. A. Vydrov, G. E. Scuseria, L. A. Constantin, X. Zhou, K. Burke, Phys. Rev. Lett., 100, 136406 (2007).G. Henkelman, B. P. Uberuaga, H. Jónsson, and G. Henkelman, J. Chem. Phys, 113 9901 (2020). Synopsys QuantumWise A/S, 2017/2. Figure 1

Facile Synthesis and Size Distribution Analysis of Silver Nanoparticles of Fungus Penicillium crustosum, Isolated from Taxus baccata Linn.

The present study was aimed at the synthesis and size distribution analysis of silver nanoparticles (AgNPs), from a fungal endophyte Penicillium crustosum. The fungus was isolated from the needles of Taxus baccata Linn. and identified as Penicillium crustosum by molecular characterization. The fungal extract of P. crustosum was subjected to the synthesis of AgNPs. UV-vis-spectroscopy confirmed the formation of AgNPs by forming the specific peaks at 390-450 nm. The lyophilized AgNPs were subjected to size distribution analysis using tools like X-ray diffraction, energy dispersive spectroscopy (EDS), field emission scanning electron microscopy (FEG-SEM), and high-resolution transmission electron microscopy (HRTEM). The average crystalline size of AgNPs was calculated by Debye-Scherrer’s formula which showed AgNPs of 36.93 nm. These findings substantiated the results of FEG-SEM and HRTEM, where the average size was below 50 nm. Dynamic light scattering results showed Z-average of AgNPs as 352.0 rnm with 0.982 PdI. Zeta potential was -19.1 mV which showed the capacity of formed AgNPs to decline agglomeration. EDS analysis proved that the requisite phase of silver is present in the sample. The present study displayed the potential of P. crustosum as reducing agent which converted silver ions into AgNPs in eco-friendly and cost-effective manner.

Influence of Si doping on the microstructure and hardness of an AlTiSiN coating deposited by low pressure chemical vapor deposition

The effect of Si doping on the microstructure and hardness of an AlTiSiN coating deposited by the low pressure chemical vapor deposition (LPCVD) method was studied in detail using grazing incidence X-ray diffraction (GIXRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and a nanoindenter instrument. The results show that Al0.82Ti0.18N coating exhibits a typical columnar crystal structure, while Al0.88Ti0.09Si0.03N and Al0.82Ti0.08Si0.10N coatings show a fine equiaxed crystal structure. The number of internal substructures (dislocation, stacking fault, etc.) decreased, while the volume fraction of the amorphous structure increased with the increase of Si content. The results of GIXRD and HRTEM show that all AlTiSiN samples mainly consist of fcc AlN phase with a small amount of hcp AlN phase. Furthermore, a small amount of fcc TiN phase can only be observed in Al0.82Ti0.08Si0.10N coating. The hardness of Al0.82Ti0.18N, Al0.88Ti0.09Si0.03N, and Al0.82Ti0.08Si0.10N coatings is 33.0 ± 0.6 GPa, 38.3 ± 1.2 GPa and 27.0 ± 0.8 GPa, respectively. Al0.88Ti0.09Si0.03N coating has obvious potential value for industrial applications.

Improved superelasticity and fatigue resistance in nano-precipitate strengthened Ni50Mn23Ga22Fe4Cu1 microwire

Smart shape memory alloy applied for driving and sensing devices requires reversibility and repeatability. However, the inherent intergranular brittleness of Ni-Mn-Ga shape memory alloy induced poor fracture resistance and insufficient cyclic fatigue life has been the stumbling block for its industrial applications. Here, we develop a dual-phase shape memory microwire with superior large reversible strain and extraordinarily fatigue resistance. The reversible phase transformation can be induced by the stress upon 200 MPa with larger than 10% reversible strain, and at least 104 transformation cycles are stably achieved at room temperature. The High-resolution TEM results show that ~3% content of the uniform precipitates of γ phase is embodied in the austenitic matrix. It acts as a beneficial role to ensure the reproducible transformation stability from the result of In-situ TEM. This study paves the way for designing fatigue resistance long fatigue life shape memory alloys by the synergy of multiphase.

Non-graphitizable resin coating on polyacrylonitrile-based polyHIPE to prepare high surface area graphitic carbon foam and the investigation of its electrochemical performance as an anode of lithium-ion batteries

A novel facile route was proposed for low-temperature stabilization of polyacrylonitrile (PAN)-based polyHIPE polymers to prepare high surface area graphitic carbon foam (CF) under mild carbonization conditions. In this respect, poly(acrylonitrile-co-divinylbenzene) foams with a distinctive microstructure of polyHIPE foams were coated by a non-graphitizable resin to eliminate the complicated and high-temperature stabilization process before pyrolysis. The prepared nanoporous CFs were characterized by different techniques including nitrogen sorption analysis, Raman spectroscopy, scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM). Experimental results revealed that the proposed strategy successfully preserved the foam framework and porosity shape after pyrolysis at 900 °C. The prepared CFs exhibited a high BET specific surface area and a pore volume of 879 m2 g−1 and 0.59 cm3 g−1, respectively. The Raman spectroscopy and HR-TEM results confirmed the successful stabilization and the formation of graphitic domains in the CFs. The obtained CFs when utilized as an anode of Li-ion batteries (LIBs), and showed improved rate capabilities compared to a commercial graphite anode and stable cycle performance up to several hundred cycles. The results revealed the potential applications of the prepared CFs in the batteries specialized for high-power devices.

Luteolin-Fabricated ZnO Nanostructures Showed PLK-1 Mediated Anti-Breast Cancer Activity.

The present work describes a facile and convenient procedure for synthesizing zinc oxide nanoparticles using luteolin isolated from Eclipta alba plant (L-ZnONPs) at room temperature. The formation of as-grown L-ZnONPs was confirmed by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), and selected area electron diffraction (SAED). The Wurtzite structure of ZnO was observed by its hexagonal phases in diffraction patterns. The SEM images revealed the different sizes and morphologies of L-ZnONPs, with diameters between 12 and 25 nm. The HR-TEM result showed that the inter-planar distance between two lattice fringes was 0.262 nm, which coincides with the d-spacing of (002) and (101) lattice planes of the as-obtained material. The anticancer activity of L-ZnONPs against the breast cancer cell line MCF-7 was greater as compared to that of luteolin or ZnO alone. The mechanistic evaluation of such an activity carried out using in silico methods suggested that the anti-breast cancer activity of L-ZnONPs was mediated by polo-like kinase 1 (PLK1) proteins.

Structural anisotropy effect on the nanoscratching of monocrystalline 6H-silicon carbide

Monocrystalline 6H-silicon carbide is a promising material for advanced components and devices; but is also a difficult-to-machine material due to its hardness, brittleness and structural anisotropy. With the aid of large-scale molecular dynamics simulations, this paper comprehensively studied the structural anisotropy effect on the nanoscratching of 6H–SiC. Six typical combinations of scratching plane and direction were selected, namely, (0001)<112‾0>, (0001)<11‾00>, (112‾0)<11‾00>, (112‾0)<0001>, (11‾00)<0001> and (11‾00)<112‾0>. It was found that the scratching-induced deformation morphology, activated dislocations and scratching forces varied significantly under different combinations of scratching conditions due to the strong anisotropy effect of the material. By evaluating the actual depth of cut, elastic recovery, surface roughness and maximum subsurface damage depth, basal plane (0001) along <11‾00> direction was identified as the best combination for conducting nanoscratching on 6H–SiC. Corresponding high-resolution TEM results show that the mechanism revealed by the MD analysis reflects the true deformation of the material.

Photocatalytic and biomedical investigation of green synthesized NiONPs: Toxicities and degradation pathways of Congo red dye

In this study the biomedical and catalytic ability of green synthesized nickel Oxide nanoparticles (NiONPs) was investigated. The extract of medicinal plant Tribulus terrestris were used to synthesized NiONPs. The as-synthesized NiONPs were in nano scale and were characterized with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), High-Resolution Transmission Electron Microscopy (HRTEM), Scanning Electron Microscope (SEM), X-ray photoelectron spectroscopy (XPS) and Energy Dispersive X-ray spectroscopy (EDX). The synthesis of NiONPs was ensured with surface Plasmon resonance (SPR) at 425 nm and the strong EDX. The effect of different concentrations of plant extract on the size of NiONPs was evaluated. The HRTEM results showed particle size between 60 - 90 nm. The study showed that lesser the extract concentration, more spherical and small sized particles were obtained without aggregation. The biological applications of NiONPs were evaluated against different fungal species like Asper gillusflavus, Asper gillusfumigatus, Asper gillusniger and standard medicine Terbinafine. A. niger, A. flavus and A. fumigatus exhibited 57, 63 and 52 % inhibition compared with inhibition of the reference medicine which is 98, 100 and 100%. NiONPs have been shown to be more effective against gram-positive bacteria than gram-negative bacteria like E. Coli 9(±0.7) and S. aureus13 (±0.8). Moreover, antioxidant properties of the as-synthesized NiONPs were evaluated with 2, 2 diphenyl-1-picrylhydrazyl) (DPPH). The catalytic ability of green synthesized of NiONP was investigated for the degradation of Congo red dye (CR) as a hazardous environmentally contaminations in water. The biosynthesized NiONPs were found to be active catalytic for the degradation toxic dyes like CR. the catalytic activity of NiONPs can be explained by its small size compared with balk material. Mechanisms for CR degradation have been proposed. The Ecotoxicity of CR and components derived from dye was investigated with Ecological Structure Activity Relationship (ECOSAR) program.

Structural assessment and irradiation response of La2Zr2O7 pyrochlore: Impact of irradiation temperature and ion fluence

State of the art applications (nuclear waste host, scintillators, piezoelectric, SOFCs, etc.) of isometric pyrochlore, A2B2O7, are very sensitive to the structural assessment upon ion irradiation. In the present study, La2Zr2O7 is irradiated using 1 MeV Xe4+ ions with fluence of 1 × 1013, 5 × 1013, and 1 × 1014 ions/cm2 at ~ 88 K and 300 K. The impact of irradiation temperature and ion fluence on the structural properties of the La2Zr2O7 are investigated using the GIXRD, Raman spectroscopy and high resolution transmission electron microscopy (HR-TEM). The GIXRD and Raman results indicate that the degradation of the crystallinity (i.e., damage/amorphization) are significantly higher with enhanced fluence at ~ 88 K than that of 300 K. The induced lattice strain also increases with an increase of ion fluence and it is more pronounced at ~88 K. The HR-TEM results of the La2Zr2O7 samples exhibit that degradation of the atomic ordering are more pronounced at ~ 88 K. The prominent induced strain and degradation of crystallinity (i.e., damage/amorphization) at ~ 88 K appear to be ion fluence and irradiation temperature-dependent. This study is enlightening the effect of the ion fluence and irradiation temperature on the degradation of crystallinity (i.e., damage/amorphization).

Migration kinetics of twinning disconnections in nanotwinned Cu: An in situ HRTEM deformation study

Growth or annealing twins normally form rectangular shape with abundant incoherent twin boundaries (ITBs), while deformation twins exhibit lenticular shape that composed of serrated coherent twin boundaries (SCTBs). Using in situ high-resolution TEM (HRTEM) deformation technique, here we report the formation-mechanism differences between twinning disconnection (TD) facets/serrations and ITBs. The HRTEM results of nanotwinned Cu manifested the multiple TD facets formation on CTBs by interaction of directional partial dislocations, via migration of TDs along shearing direction. In comparison, periodic 3-layered TDs or ITBs structure were normally formed by annealing or growth process that introduced by spontaneous directionless partial dislocations.

Maghemite-based anode materials for Li-Ion batteries: The role of intentionally incorporated vacancies and cation distribution in electrochemical energy storage

Anode materials for Lithium-Ion Batteries (LIBs) based on Mo- and V-doped maghemite were prepared by the sol-gel route. High-Resolution Transmission Electron Microscopy (HRTEM) showed the formation of isotropic nanoparticles. The X-ray Photoelectron Spectroscopy (XPS) revealed the presence of Fe3+ and Mo6+ or V4+ for Mo- or V-doped samples, respectively. Rietveld refinement of X-ray Diffraction (XRD) patterns revealed the distribution of Mo6+ and V4+ cations and showed increase in vacancies. The crystallite size resulted from Rietveld adjustments was in agreement with the HRTEM results. The Extended X-ray Absorption Fine Structure (EXAFS) showed a shrinkage of Fe–O–Fe linkages which is responsible for the reduction of the maghemite cell parameter which agreed with the structural analysis from XRD. The X-ray Absorption Near Edge Structure (XANES) confirmed XPS analysis that Fe3+ is present. Coin cells were assembled and galvanostatic cycling was implemented at various charge-discharge current densities, cyclic voltammograms of Li-ions insertion/extraction processes were obtained and the Electrochemical Impedance Spectroscopy (EIS) was investigated. An exceptional cyclic stability and storage capacity for the V-doped maghemite was observed for low current density. The Mo-doped maghemite has higher capacity retention at high current densities.