Transmission Electron Microscopy Selected Area Electron Diffraction Research Articles

Innovative stain-free technique for high-resolution imaging of virus particles via standard transmission electron microscopy

This research presents a groundbreaking approach in virus-related research, addressing challenges in electron microscopy (EM). This imaging technique has been crucial in exploring virus structures; however, traditional methods involve complex sample preparations and the risk of contamination. Herein, we introduce an approach that overcomes these obstacles, enabling high-resolution virus imaging without toxic staining procedures. Focusing on Begomovirus particles, an economically significant plant virus genus, our images confirm their non-enveloped structure and their twin icosahedral symmetry. Our methods involve sample collection, purification, and crystallization, followed by transmission electron microscopy - selected area electron diffraction (TEM-SAED) analysis. Notably, this study achieves 2D and 3D virus imaging through standard TEM, providing a new avenue for virus structure analysis and advancing virus-related research. Remarkable high image quality stemmed from the crystallization process, offering exciting possibilities for improving virus research and diagnosis while eliminating staining limitations.

Novel Focused Ion Beam Liftouts for Spatial Characterization of Spherical Biominerals With Transmission Electron Microscopy.

Focused ion beam (FIB) is frequently used to prepare electron- and X-ray-beam-transparent thin sections of samples, called lamellae. Typically, lamellae are prepared from only a subregion of a sample. In this paper, we present a novel approach for FIB lamella preparation of microscopic samples, wherein the entire cross-section of the whole sample can be investigated. The approach was demonstrated using spherical, porous, and often hollow microprecipitates of biologically precipitated calcium carbonate. The microprecipitate morphology made these biogenic samples more fragile and challenging than materials commonly investigated using FIB lamellae. Our method enables the appropriate orientation of the lamellae required for further electron/X-ray analyses after attachment to the transmission electron microscopy (TEM) grid post and facilitates more secure adhesion onto the grid post. We present evidence of autofluorescence in bacterially precipitated vaterite using this lamella preparation method coupled with TEM selected area diffraction. This innovative approach allows studying biomineralization at the micro to nano scales, which can provide novel insights into bacterial responses to microenvironmental conditions.

A facile mixed complex synthesis method for perovskite oxides toward electrocatalytic oxygen reduction.

The perovskite-type La(0.5+x)Sr(0.5-x)FeO3-δ (x = 0.00, 0.10, 0.20) oxides for the electrocatalytic oxygen reduction reaction (ORR) were synthesized by a facile reaction-EDTA/citric acid mixed complex sol-gel method. The cubic single-phase perovskite structure of the as-prepared oxides is demonstrated using powder X-ray diffraction (XRD). Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy/selected area electron diffraction (TEM-SAED), and X-ray photoelectron spectroscopy (XPS) characterizations were also conducted for the perovskite-type La(0.5+x)Sr(0.5-x)FeO3-δ (x = 0.00, 0.10, 0.20) oxides. Furthermore, the electrochemical ORR properties of the as-prepared oxides in alkaline media were studied, with the oxides exhibiting good electrocatalytic ORR performance.

Preparation, characterization and photocatalytic studies of LaAl0.5Fe0.5O3, LaAl0.5Cr0.5O3 and LaCr0.5Fe0.5O3

Organic dye contaminants which are frequently detected in water bodies have attracted significant attention as they are mostly non-biodegradable. These contaminants pose severe environmental and health risks. In the present work, perovskites of compositions LaAl0.5Fe0.5O3, LaAl0.5Cr0.5O3, LaCr0.5Fe0.5O3 (here after LAFO, LACO and LCFO respectively) were prepared by ethylene glycol assisted gel burning method. The as prepared materials were subjected to powder X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy-selected area electron diffraction (TEM-SAED), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), Raman, UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) techniques for characterization. Rietveld refinement was carried for all the compositions and deduced the unit cell parameters. Bandgap energy was obtained for all the three perovskites from their DRS profiles. The FT-IR and Raman spectra gave characteristic M-O and O-M-O (M = La, Cr, Fe, Al) vibrational modes. The photocatalytic activity of these compounds was examined against the degradation of methylene blue (MB). The participation of transient species in the degradation of MB, mechanism of photodecomposition and stability of the catalyst were also presented.

Repartitioning of co-precipitated Mo(VI) during Fe(II) and S(-II) driven ferrihydrite transformation

Molybdenum is an essential element for most biological systems. Biosynthesis of Mo-enzymes that support global biogeochemical cycles of N, C, and S depends upon bioavailable molybdate (MoO42−). Interactions with Fe(III) (oxyhydr)oxides can limit Mo bioavailability in aerobic environments, while redox-driven mineral transformations can enhance Mo sequestration. Here, we examine Mo repartitioning during Fe(II) and S(-II) driven ferrihydrite transformation under anaerobic conditions. We reacted Mo(VI) co-precipitated 2-line ferrihydrite with Fe(II)(aq) or S(-II)(aq) and monitored geochemical and mineralogical changes over time. Inductively coupled plasma–mass spectrometry (ICP–MS) and synchrotron powder X-ray diffraction (XRD) results revealed rapid Fe(II)(aq) and S(-II)(aq) uptake and limited Mo release during extensive ferrihydrite transformation to goethite [α-FeOOH] and lepidocrocite [γ-FeOOH] in the Fe(II) and S(-II) experiments. Transmission electron microscopy–selected area electron diffraction (TEM-SAED), coupled with Mo LIII-edge and K-edge X-ray absorption near edge structure (XANES) spectroscopy, revealed partial Mo(VI) reduction and precipitation of kamiokite [Fe2MoIV3O8] and sidwillite [MoVIO3‧2H2O] in both experiments. Extended X-ray absorption fine structure (EXAFS) spectroscopy at the Mo K-edge revealed MoO, MoFe and MoMo bonding consistent with kamiokite precipitation in both Fe(II) and S(-II) experiments, and the absence of MoS bonding in the S(-II) experiments. Similar Mo(VI) repartitioning pathways during Fe(II) and S(-II) driven ferrihydrite transformation suggests that: (i) Fe(II) served as the electron donor for ferrihydrite transformation in both experiments, with Fe(II)(aq) likely produced in situ via ferrihydrite sulfidation in the S(-II) experiments; and (ii) co-precipitation inhibited Mo release and limited subsequent interactions S(-II)(aq) during ferrihydrite transformation. Overall, our findings indicate that initial association with FeOx phases can strongly influence Mo sequestration pathways in anaerobic environments.

Synthesis and Characterization of Silver Nanoparticles Using Alginate from the Brown Seaweed Laminaria ochroleuca: Structural Features and Antibacterial Activity

In this study, inexpensive and eco-friendly production of the silver nanoparticles (AgNPs) was explored using Laminaria ochroleuca sodium alginate as stabilizing and reducing agent. The synthesized nanoparticles were characterized by various analytical techniques such as UV–Vis spectroscopy, Energy dispersive X-ray spectrometer (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM), TEM selected area electron diffraction (SAED), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). The synthesis of AgNPs was elucidated by characteristic absorption peaks in the UV–Vis test. The FTIR analysis revealed the involvement of many functional groups in the bioreduction and the stabilization of AgNPs, while TEM images illustrated the spherical shape with maximum particles found in the size range of 10-20 nm. Prominent peaks and silver diffraction rings shown by the XRD spectrum and SAED pattern, respectively, confirmed the crystalline nature (fcc) of the synthesized AgNPs, which were found to be thermally stable based on TGA analysis. The AgNPs exhibited strong antibacterial activity against Gram+ and Gram– bacteria. The synthesized silver nanoparticles using Laminaria ochroleuca sodium alginate revealed interesting properties that could be potentially used for pharmaceutical applications.

Effects of trace ytterbium addition on microstructure, mechanical and thermal properties of hypoeutectic Al–5Ni alloy

Over the past decade, the cast aluminum alloys with excellent mechanical and conductivity properties have emerged as potential materials for thermal management. However, the traditional Al–Si based alloys are difficult to make significant breakthrough in conductivity performance. The hypoeutectic Al–5Ni alloy also possesses sound castability and is expected to be applied in thermal management applications. In this study, the effects of ytterbium (Yb element) at 0–0.5 wt% on the microstructures as well as the electrical/thermal conductivity and mechanical properties of the Al–5Ni alloy were systematically investigated. The experimental results indicate that the addition of Yb at a relatively low amount not only reduces the secondary dendrite arm spacing of the α-Al grains, but also modifies the morphology and distribution of eutectic boundary phase. Moreover, it is found that the dosage of Yb at 0.3 wt% in the Al–5Ni alloy can simultaneously improve the yield strength, ultimate tensile strength and electrical/thermal conductivity. The strengthening and toughening of the Al–5Ni alloy are mainly attributed to the decrease of secondary dendrite arm spacing and the improvement of eutectic phases. The transmission electron microscopy/selected area electron diffraction (TEM/SAED) analysis indicates that the ytterbium in Al–5Ni alloy will form Al3Yb phase, which mainly agglomerates in the Al3Ni phase region. This phase is helpful to decrease the solubility of impurity elements (e.g., Fe and Si) in the α-Al matrix, which is beneficial to electrical/thermal conductivity. The value of this study lays foundation for manufacturing Al–Ni alloys with high thermal conductivity and acceptable mechanical properties.

Synthesis and Characterization of Gold Nanoparticles from Nostoc sp. strain HKAR-2 and their In Vitro Antibacterial, Antifungal, and Antitumor Potentials

In the present study, gold nanoparticles (AuNPs) have been synthesized through biological methods using the cell-free extracts of cyanobacterium Nostoc sp. strain HKAR-2 isolated from the hot spring of India. To determine morphological, structural, and optical properties of green synthesized AuNPs, UV-VIS spectroscopy, FTIR, X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy-selected area electron diffraction (TEM-SAED) were used. Spectroscopic analysis showed the absorbance peak at 540 nm due to the reduction of Au3+ to Au0 by cyanobacterial extract, which indicated surface plasmon resonance (SPR) of the synthesized AuNPs. Characteristic Bragg peaks at (111), (200), (220), and (311) facets of the face center cubic (fcc) confirmed the crystalline nature of AuNPs in the XRD pattern. FTIR results indicated the role of proteins and amino acids in the reduction of Au3+ to Au0 as well as for the stability of AuNPs. Zeta potential confirmed a charge of -2.39Mv on the AuNPs. SEM and TEM results confirmed the large agglomerated shape of AuNPs with sizes ranging between 10-100 nm. Their antibacterial, antifungal and anticancerous properties were also studied against plant bacterial strains, fungal strains, and MCF-7 cells, respectively. AuNPs also showed dose-dependent cytotoxic activity against human breast cancer MCF-7 cells with IC50 of 250 μg/mL.

Thermal stability and mechanical properties of Fe-Cr-Zr alloys developed by mechanical alloying followed by spark plasma sintering

The present work aims to investigate (i) the feasibility of formation of Fe-7Cr-xZr and Fe-15Cr-xZr (x = 0.25, 0.5 and 1 at%) disordered solid solutions by mechanical alloying (MA) and (ii) their thermal stability and mechanical properties of spark plasma sintered (SPSed) samples. Effect of Zr addition on phase evolution in Fe-Cr-Zr alloy and its influence on their thermal stability and mechanical properties (microhardness and compression strength) have been studied in detail. Transmission electron microscopy-selected area diffraction pattern (TEM-SAED) and X-ray diffraction (XRD) phase analysis confirm the formation of complete solid solution after 25 h of MA. Grain size was observed to stabilize significantly within nanometer range after annealing at 600–1200 °C. The SPSed (at 1000 °C) samples showed the best combination of hardness (9.4 GPa) and compressive strength (ultimate compressive strength-2200 MPa and yield strength-1800 MPa) corresponding to an average grain size of<100 nm. This is due to the strengthening mechanisms of grain boundary strengthening (owing to solute segregation and solute drag effect), precipitation hardening (Zener pinning) by Fe2Zr phase and excellent densification achieved by SPS.

Novel bone-mimetic nanohydroxyapatite/collagen porous scaffolds biomimetically mineralized from surface silanized mesoporous nanobioglass/collagen hybrid scaffold: Physicochemical, mechanical and in vivo evaluations.

Bone-mimetic scaffolds are receiving much interest as such scaffolds exhibit excellent biocompatibility and very close mimic to bone structure and composition. Here, novel bone-mimetic nanohydroxyapatite (nHA)/collagen (Col) porous scaffolds (nHA/Col) were prepared from surface silanized mesoporous nanobioglass (NBG)/Col hybrid scaffold by biomimetic mineralization. Surface silanized mesoporous NBG was prepared by ultrasound-assisted sol-gel method and post treatment with 3-aminopropyltriethylsilane (APTS). The surface silanized mesoporous NBG was characterized by transmission electron microscopy (TEM), transmission electron microscopy-selected area electron diffraction (TEM-SAED) and X-ray photoelectron spectroscopy (XPS). The physicochemical/mechanical characterizations of the scaffolds included scanning electron microscopy (SEM) and TEM imaging of micro/nanostructure, energy dispersive X-ray (EDX) analysis of chemical composition, TEM-SAED and X-ray diffraction/Attenuated total Reflectance-Fourier Infrared spectroscopy (XRD/ATR-FTIR) analyses of amorphous-to-crystalline transformations, thermogravimetric/differential scanning calorimetric (TGA/DSC) analyses of thermal behaviour , porosity and dynamic mechanical analyses. The presence of NBG in collagen fibrillar network enabled progressive growth of HA nanocrystals and generation of a novel bone-mimetic hybrid structures while preserving the highly porous structure of collagen scaffold. The crystallinity, crystallite size and crystal morphology of the grown HA nanocrystals were controllable by regulation of the mineralization time. Furthermore, the osteogenic properties of the non-mineralized (NBG/Col) and mineralized (nHA/Col) hybrid porous scaffolds were examined in vivo using critical-sized calvarial bone defect model in rat. Histological and micro-computed tomography (Micro-CT) analyses after 6weeks of implantation revealed that the mineralized scaffolds possess excellent in vivo osteogenic potential compared to the non-mineralized one. Collectively, by using surface silanized mesoporous NBG hybridization with collagen fibrillar network, we successfully introduced a new approach for developing novel bone-mimetic nanohydroxyapatite/collagen hybrid scaffolds that possess significant potential for bone tissue regeneration.

Preparation, magnetic properties, and photocatalytic performance under natural daylight irradiation of Fe3O4-ZnO core/shell nanoparticles designed on reduced GO platelet

Ternary mesoporous nanocomposites of RGO/Fe3O4-ZnO were prepared successfully via hydrothermal technique. Fe3O4-ZnO core/shell nanoparticles were decorated on the surface of reduced graphene oxide platelet to improve charge separation efficiency and magnetic properties. The phase, microstructure and specific surface area of the prepared samples were determined via X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy/selected area electron diffraction (TEM/SAED) and Brunauer–Emmett–Teller (BET) techniques. A vibrating sample magnetometer (VSM) was used for recording the magnetization hysteresis curves. The methylene blue (MB) degradation and photocatalytic activities of prepared catalysts were examined under natural daylight irradiation. The magnetic properties of the RFZ photocatalyst increased compared with the FZ from 12.45emug−1 to 20.18emug−1. The specific surface area (as,BET) for the RFZ compared to the FZ increased from 31.56m2g−1 to 36.05m2g−1. The RFZ photocatalyst, as a result of synergistic effects, indicated an excellent performance for treatment of MB dye. The photocatalytic reactions obeyed pseudo-first-order kinetics and apparent rate constant (kap) of RFZ photocatalyst increased compared to FZ. Furthermore, the RFZ photocatalyst could be recycling using a common magnet besides to the high efficiency of degradation. The repeatability of the photocatalytic activity after 10 cycles was additionally tested and revealed that the RFZ photocatalyst up to 8 cycles showed a small drop in catalysis efficiency. Thus, it was concluded that the RFZ ternary photocatalyst can be an economical multifunctional photocatalyst for the degradation of unsafe compounds in wastewater.

Surfactant-assisted formation of silver titanates as active catalysts for methanol electro-oxidation

Silver nanoparticles successfully incorporated in titanate nanosheets and synthesized hydrothermally via employing cetyltrimethylammonium bromide (CTAB) and triblock copolymer (pluronic F127) assisted templates were thoroughly characterized using transmission electron microscopy-selected area electron diffraction (TEM-SAED), X-ray diffraction, diffuse reflectance UV/visible absorption spectroscopy, N2 sorptiometry, FTIR and Raman spectroscopy. The dispersed Ag nanoparticles of uniform size (2–3nm) were found to contact intimately with titanateF127 nanosheets to show superior crystallinity, wider layer distances and higher surface area and pore volume (SBET=51.1m2g−1,Vp=0.081cm3g−1) than Ag/titanateCTAB (7.2m2g−1, 0.02cm3g−1). This constructed Ag/titanateF127 exhibits markedly improved electrocatalytic (1.4-fold) and photoelectrocatalytic (4.0-fold) activities and stabilities towards methanol oxidation than that of Ag/titanateCTAB; as determined using cyclic voltammetry, linear sweep voltammetry and chronoamperometry. The enhanced activity of Ag/titanateF127 was also attributed to electron transfer across the interface potential of the composite Ag-titanateF127 as well as the delay of charge recombination that has been substantiated not only via exposed Ag but also through the non-decomposed carbon template. This enhanced electron transfer and electronic conductivity was established by impedance spectroscopy, and exhibits the maximum obtained photocurrent density (2.0mAcm−2) under visible light illumination (λ>420nm, 88W). The results revealed that the template F127 had a significant effect not only on enhancing the titanate crystallinity and exhibiting a surface plasmon resonance band; unlike Ag/titanateCTAB, but also in acquiring a high pore volume value and widened layers, which all work towards improving the Ag-titanateF127 durability for methanol oxidation.

Green Synthesis of Gold Nanoparticles using Aqueous Garlic (Allium sativum L.) Extract, and Its Interaction Study with Melamine

Gold nanoparticles (AuNPs) have been successfully prepared by green synthesis method using aqueous extract of garlic with the Latin name of Allium sativum L. (ASL) as a reducing and stabilizing agents. Identification of active compounds in aqueous ASL extract was conducted by phytochemical analysis and Fourier transform infrared (FTIR) spectroscopy, while the synthesized AuNPs were characterized using UV-Vis spectrophotometer and transmission electron microscopy-selected area electron diffraction (TEM-SAED). The AuNPs formation was optimized at aqueous ASL extract concentration of 0.05%, HAuCl4 concentration of 2.0×10-4 M, and pH of 3.6. The optimized AuNPs was characterized using TEM, and has a spherical shape with particle size of 15±3 nm. The particles were also stable up until one month. The synthesized AuNPs has been studied its interaction with melamine, and showed the optimum pH of interaction at 3.6.

Novel Lithium Manganese Silicate with Stable Structure upon Cycling As Positive Electrode for Lithium-Ion Batteries

Lithium manganese silicate Li2MnSiO4 is theoretically one of the most interesting polyanionic material for lithium-ion batteries positive electrode. Its theoretical capacity reaches 333mAh/g thanks to the possible exchange of two lithium ions per formula unit which happens below the organic electrolyte degradation voltage. Indeed, the first lithium ion is calculated to be exchanged at 4.1V vs Li+/Li and the second one at 4.4V [1]. The high energy density combined with the thermal stability of the Si-O bond make Li2MnSiO4 in theory one of the best choice to equip the next generation of electrified transportation [2]. 1st studied in 2006 by Dominko et al. [3], lithium manganese silicate still shows severe limitations. Both its ionic and electronic conductivities are low [4] and Li2MnSiO4 structure cannot accommodate large Li+ extraction without amorphization. Thus, it leads to high polarization and capacity fading during cycling, impeding its practical interest. Despite this trend, manganese-based silicate polyanions are essentially interesting because of their high abundance, low cost and environmental friendliness. Here we propose an unreported manganese silicate material that we recently patented. This new material, usable as a positive electrode for lithium ion batteries, showed remarkable cycling stability. 100 mAh/g were obtained in half-cells versus lithium metal counter-electrode (Figure 1). Ex-situ X-Ray Diffraction showed that the structure was maintained during cycling, demonstrating that the material can accommodate reversible extraction of Li+ ions. To limit particle growth careful attention was paid on the synthesis route. Primary particles of 50 nanometers were obtained by a sol-gel process (Figure 2). Rate capabilities of the material, studied by galvanostatic cycling, will also be presented. Deeper characterization by X-Ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy-Selected Area Electron Diffraction (TEM-SAED) and Differential Scanning Calorimetry (DSC) will be shown to assess the redox process, structure and thermal stability of this material. [1] Arroyo-de Dompablo et al., Electrochem. Commun., 2006, 8, 1292–1298 [2] Andre et al., J. Mater. Chem. A, 2015, 3, 6709–6732 [3] Dominko et al., Electrochem. Commun., 2006, 8, 217–222 [4] Dominko et al., J. Power Sources, 2008, 184, 462–468 Figure 1

Green Method for Synthesis of Gold Nanoparticles Using Polyscias scutellaria Leaf Extract under UV Light and Their Catalytic Activity to Reduce Methylene Blue

The aqueous fraction of Polyscias scutellaria leaf extract (PSE) has been used as a reducing agent and stabilizer in the green synthesis of gold nanoparticles (AuNPs). UV-Vis spectrophotometry, particle size analyzer (PSA), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy-selected area electron diffraction (TEM-SAED), and X-ray diffraction (XRD) were used to characterize AuNPs. The AuNPs have a size of 5–20 nm and have a face centered cubic (fcc) crystal structure and are stable for 21 days. Phenolic compounds, which are secondary metabolites of PSE, act as an active compound to reduce Au3+ ion to Au0, as well as stabilize the AuNPs through their surface interaction with carbonyl and hydroxyl groups of phenols. AuNPs exhibit excellent catalytic activity for the reduction of methylene blue with NaBH4. The reduction of methylene blue using AuNPs catalysts is a pseudo-first-order reaction with a reduction rate constant (kobs) of 0.0223 min−1.

Hydrothermal syntheses of CuO, CuO/Cu2O, Cu2O, Cu2O/Cu and Cu microcrystals using ionic liquids

In this paper, CuO, CuO/Cu2O, Cu2O, Cu2O/Cu and Cu microcrystals were synthesized via a hydrothermal method by mixing Cu(NO3)2·3H2O and NaOH together in the presence of an ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate([BMIM]BF4) or 1-butyl-3-methylimidazolium chloride([BMIM]Cl). The structures and the morphologies of the obtained products were characterized by means of X-ray diffractometer( XRD), field-emission scanning electron microscopy/energy-dispersive spectroscopy(FESEM/EDS), transmission electron microscopy/selected area electron diffraction(TEM/SAED) and Raman spectroscopy. The result of XRD indicates that Cu2O and Cu microcrystals are cubic phase and the Raman spectra confirm the presence of carbon. The results of FESEM and TEM images show Cu2O microcrystals as rule cubes of 2 μm in length and Cu particles of 5 μm in diameter. According to the difference between crystal structures, bi-component and single component products were synthesized by adjusting the reaction conditions. A possible formation mechanism of Cu2O and Cu was proposed in [BMIM]BF4.

Evidence of multimicrometric coherent γ' precipitates in a hot-forged γ-γ' nickel-based superalloy.

This paper demonstrates the existence of large γ' precipitates (several micrometres in diameter) that are coherent with their surrounding matrix grain in a commercial γ-γ' nickel-based superalloy. The use of combined energy dispersive X-ray spectrometry and electron backscattered diffraction (EBSD) analyses allowed for revealing that surprising feature, which was then confirmed by transmission electron microscopy (TEM). Coherency for such large second-phase particles is supported by a very low crystal lattice misfit between the two phases, which was confirmed thanks to X-ray diffractograms and TEM selected area electron diffraction patterns. Dynamic recrystallization of polycrystalline γ-γ' nickel-based superalloys has been extensively studied in terms of mechanisms and kinetics. As in many materials with low stacking fault energy, under forging conditions, the main softening mechanism is discontinuous dynamic recrystallization. This mechanism occurs with preferential nucleation on the grain boundaries of the deformed matrix. The latter is then being consumed by the growth of the newly formed grains of low energy and by nucleation that keeps generating new grains. In the case of sub-solvus forging, large γ' particles usually pin the migrating boundaries and thus limit grain growth to a size which is determined by the distribution of second-phase particles, in good agreement with the Smith-Zener model. Under particular circumstances, the driving force associated with the difference in stored energy between the growing grains and the matrix can be large enough that the pinning forces can be overcome, and some grains can then reach much larger grain sizes. In the latter exceptional case, some intragranular primary γ' particles can be observed, although they are almost exclusively located on grain boundaries and triple junctions otherwise. In both cases, primary precipitates have no special orientation relationship with the surrounding matrix grain(s). This paper demonstrates the existence of high fractions of large γ' precipitate (several micrometres in diameter) that are coherent with their surrounding matrix grain, in a commercial γ-γ' nickel-based superalloy. Such a configuration is very surprising, because there is apparently no reason for the coherency of such particles.

High resolution transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction studies of nanocrystalline manganese borohydride (Mn(BH4)2) after mechano-chemical synthesis and thermal dehydrogenation

Abstract In order to synthesize manganese borohydride, Mn(BH4)2, mechano-chemical activation synthesis (MCAS) of the (2LiBH4 + MnCl2) powder mixture was carried out by ball milling in a magneto ball mill. Both X-ray diffraction and TEM selected area electron diffraction patterns (SAEDPs) clearly confirm the presence of the Mn(BH4)2 and LiCl phases in the synthesized nanocomposite. No other phases were detected. Bright field high-resolution TEM imaging of the synthesized composite powder particles reveals the presence of nanograins consistent with LiCl and Mn(BH4)2 within the powder particles. Their respective grain sizes, estimated as the equivalent circle diameters (ECD) from the high-resolution TEM micrographs with the corrected sample standard deviations, are within the range of 14.1 ± 3.7 nm and 10.0 ± 2.9 nm for LiCl and Mn(BH4)2, respectively. The XRD patterns of the thermally dehydrogenated (Mn(BH4)2 + 2LiCl) nanocomposite do not exhibit any Bragg diffraction peaks belonging to either crystalline Mn or B. In contrast, the SAED patterns and EDS elemental maps provide strong evidence that both Mn and B exist in the dehydrogenated powder as crystalline phases α-Mn and β-B, respectively. The results show that the lack of XRD Bragg diffraction peaks is insufficient evidence that the Mn and B elemental products of Mn(BH4)2 thermolysis can be classified as being amorphous.

Synthesis of ZnO nanoparticles using the cell extract of the cyanobacterium, Anabaena strain L31 and its conjugation with UV-B absorbing compound shinorine

In the present work, we describe a cheap, unexplored and simple procedure for the synthesis of zinc oxide nanoparticles (ZnONPs) using the cell extract of the cyanobacterium, Anabaena strain L31. An attempt was also made to conjugate synthesized ZnONPs with a UV-absorbing water soluble compound shinorine. UV–vis spectroscopy, X-ray diffraction (XRD), Fourier transform infra-red (FTIR) spectroscopy, transmission electron microscopy (TEM) and TEM–selected area electron diffraction (SAED) analyses were made to elucidate the formation and characterization of ZnONPs and ZnONPs-shinorine conjugate. The synthesized ZnONPs were characterized by a sharp peak at 370nm in UV–vis spectrum. TEM images showed the formation of spherical shaped nanoparticles with an average size of 80nm. Results of selective area electron diffraction (SAED) pattern showed a set of rings which suggested uniform shape with hexagonal structure of ZnONPs. XRD spectra confirmed the crystalline structure of particles. Conjugation of ZnONPs with shinorine was successfully achieved at pH 7.0 and 10mM concentration of shinorine. The conjugate showed a zeta potential value of −3.75mV as compared to +30.25mV of ZnONPs. The change in zeta potential value of ZnONPs–shinorine conjugate was attributed to the changes in the surface functionalities after conjugation. The generation of in vivo reactive oxygen species (ROS) by Anabaena strain L31 with treatment of ZnONPs–shinorine conjugate showed approximately 75% less ROS generation as compared to ZnONPs. Properties exhibited by the ZnONPs–shinorine conjugate suggest that it may be used as a potential agent in developing environmental-friendly sunscreen filters of biological origin.

Microalloying of Fe-Cr by using Ultrasonic Irradiation

In this work the formation of Fe-Cr microalloy by ultrasonic irradiation at a frequency of 20 kHz is presented. Two sample series were produced with different ultrasonic irradiation procedures. For the first sample, Fe and Cr powder were each separately brought into the ultrasonic device before they were mixed in 7:1 weight ratio and then together retreated using the ultrasonic method. Secondly, Fe and Cr powder with same weight ratio were mixed and directly ultrasonically irradiated. During the ultrasonic irradiation process both samples were put in a toluene solution of 99%. The formation of the Fe-Cr microstructure in conjunction with ultrasonication time were investigated by using Scanning Electron Microscopy (SEM ), X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). After 40 hours of ultrasonic irradiation the particle sizes of the Fe powder of the first samples became significantly smaller; some particles were also fused together. However, with the exception of smaller-sized particles no fused Cr powders can be found even after 63 hours of ultrasonic irradiation. After both experiments Fe and Cr were mixed and again ultrasonically irradiated for 20 hours. Some particles indicated as Fe-Cr alloys containing 24.34 wt.% Fe and 67.43 wt.% Cr were observed. In the sample produced from the second procedure in which both Fe and Cr powders were irradiated together by an ultrasonic method for 50 hours, some powder particles formed a Fe-Cr microalloy with the composition of 96.27 wt.% Fe and 3.73 wt.% Cr. The XRD analysis revealed that the Fe-Cr alloy from the first samples has a BCC structure with a mass fraction of Fe:Cr:Fe-Cr which is equal to 0.836:0.0294:0.135, while the mass fraction of the Fe-Cr alloy from the second sample series is equal to 0.736:0.0808:0.183, respectively. Analysis of the TEM selected area diffraction patterns (SAED) confirmed that the Fe-Cr microalloy occured originaly from the precursor Fe and Cr particles of size smaller than 2 µm. The Fe-Cr microalloy has been successfully synthesized by using an ultrasonic process.