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Different long-chain primary alkylamines such as octylamine, dodecylamine, tetradecylamine, hexadecylamine or octadecylamine were used to stabilize Ni-NiO nanoparticles (metal:stabilizer ratio of 1:10) by an organometallic method in organic medium to evaluate their effect on the microstructural and magnetic properties. The Ni-NiO stabilized nanoparticles were characterized by Fourier transformed infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), conventional transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and dynamic light scattering (DLS). The results indicated an adequate stabilization of Ni nanoparticles with the different primary alkylamines. The semi-quantitative analysis suggests that Ni surface composition is a combination of the metallic state with NiO, NiOOH and NiO, but the chain length modified the content and proportion of these compounds. The highest Ni metallic state (57.2 at. %) was obtained with tetradecylamine as stabilizer. The morphology of the samples is similar to a core–shell semi-spherical, but the particle size tends to reduce with the alkyl chain length of primary amines from 20 to 8 nm. The saturation magnetization (Ms) showed important variations depending on the surface composition, for which variable particle size and Ni metallic content were determining factors for the magnetic response. [ABSTRACT FROM AUTHOR]

Ni nanoparticles (NiNPs) were prepared by thermal decomposition of nickel acetylacetonate in the presence of a third generation polypyridylphenylene dendrimer (G3) which acts both as a coordinating ligand due to presence of pyridine groups and as a stabilizing agent due to highly branched architecture. Transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and X‐ray photoelectron spectroscopy (XPS) were used to extensively evaluate structure and morphology of the synthesized NiNPs@G3. The selected area electron diffraction (SAED) allowed us to conclude about fcc structure of NiNPs while STEM EDS analysis demonstrated a formation of core‐shell NiO@Ni NPs. Further, the catalyst was tested in selected Suzuki‐Miyaura cross‐coupling reactions at mild conditions and demonstrated a high efficiency at low Ni loading with negligible content of Ni0 on the NP surface. The functional hyperbranched dendrimer macromolecule provided an excellent stabilization for NiNPs@G3 while allowing an easy access for reactants to catalytic sites. The high activity of the catalyst in the recycling experiments was maintained by the absence of Ni leaching from the NiNPs@G3. [ABSTRACT FROM AUTHOR]

This paper demonstrates a low-temperature solvothermal method of nitrogen-rich covalent organic framework (COF) onions. The atomic structure and the bonding features are revealed by high resolution transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS). The novel COF onion provides potential applications in photocatalysts considering its suitable bandgap value of 2.56 eV. [Display omitted] Achieving hierarchical nanomaterials from a bottom-up approach remains challenging. Here, we report a closed-cage, onion nanostructure of covalent organic framework (COF) obtained through a low-temperature solvothermal synthesis. Atomic resolution transmission electron microscopy revealed the atomic arrangement in this COF onion, in which rich nitrogen was uniformly embedded in the periodic porous graphitic framework. The COF onion structure displayed graphitic features at a 0.33 nm interlayer spacing with Van der Waals interactions predominated between the layers. The onion layers exhibited significant heterogeneity in layer stacking by adopting a combination of different stacking modes. Defects were also found, such as five- or seven-member rings deviating from the perfect hexagonal lattice. These geometrical defects resulted in curving the 2D layers, which may have promoted the formation of onion nanostructures through a layer-by-layer attachment. We constructed a corresponding model that predicts COF onion properties. This novel onion exhibited a bandgap value of 2.56 eV, resembling other carbon-based nanomaterials, suggesting potential applications in sensors, photocatalysts, and nanoelectronics. [ABSTRACT FROM AUTHOR]

Mechanical stirring of bulk Te in N‐methyl‐2‐pyrrolidone (NMP) solution at room temperature resulted in the formation of free‐standing few‐layer (∼1.2–2.8 nm) crystalline ultrathin nanosheets of tellurene with a large lateral thickness (∼1–1.6 μm) as confirmed by atomic force microscopy (AFM). High‐resolution transmission electron microscopy (HRTEM) confirms the presence of α‐ and β‐phases of tellurene. First‐principle density functional theoretical (DFT) based electronic structure calculations demonstrate the indirect band gap of bi‐layer β‐tellurene. The band gap decreases with increasing number of layers in the tellurene nanosheet. [ABSTRACT FROM AUTHOR]

This study aims to clarify the growth process of the β-phase in Al-Mg-Si alloys from the point of view of morphological evolution. The orientation relationship, shape, growth process, misfit value, and interfacial condition between the β-phase and Al matrix were investigated using high-resolution transmission electron microscopy (HR-TEM), focused ion beam (FIB), and optical microscope (OM). In a previous study, the growth process and shape of the β-phase were determined using scanning electron microscopy (SEM). It was proposed that the truncated octahedron (8{111}, 6{100} facets) transforms into a hexahedron (6{100} facets). This study proposes that two new three-dimensional shapes of the β-phase exist between the truncated octahedron and hexahedron, and we identified the {111} β facets at the edges of the β-phase. We proposed the morphology evolution during the growth process of Mg 2 Si crystals and calculated the misfit to understand that the unstable {111} β facet has a higher misfit value compared to the {001} β and {011} β facets. Our observations provide insight into how they influence the behavior of Mg 2 Si crystals, which is crucial for predicting the microstructural evolution of Al-Mg-Si alloys and for designing materials with desired properties. • Investigated the morphology evolution of the β-phase in Al-Mg-Si alloys. • Explored β-phase orientation relationship, shape, and growth process using HR-TEM, FIB, and OM. • Discovered {111} β facets and proposed new three-dimensional shapes for the β-phase. • Calculated misfit values, revealing the instability of the (111) β facet compared to (001) β and (011) β facets. • Contributed to understanding microstructural evolution in Al-Mg-Si alloys and material design. [ABSTRACT FROM AUTHOR]

Pre-stretched strains, 2%, 4%, and 6%, were conducted on the friction-stir-welded dissimilar 2024-to-7075 aluminum alloy joints for strengthening purpose. Tensile tests and microhardness measurements were performed to evaluate the strengthening effect. Transmission electron microscopy and high resolution transmission electron microscopy examinations were employed to characterize precipitates and dislocation structures of the as-welded and pre-stretched joints to elucidate the intrinsic strengthening mechanisms. Results showed that the yield and tensile strengths of the pre-stretched 6% joint respectively increased 147.9 MPa and 31.1 MPa when compared with the as-welded joint. The strain hardening rates of 2024 lower hardness zone (LHZ)-II and 7075 LHZ were higher at the pre-stretched strain rate of 1 mm/min than those of 2 mm/min based on the microhardness area evolution. The yield sequence of the as-welded joint was 2024 LHZ-II, 2024 LHZ-I, 7075 LHZ, stir zone (SZ), and 2024 base material. The appearance of dislocation tangles, dislocation walls, dislocation cells, dislocation pile-ups in the 2024 LHZ-II and 7075 SZ combined with the severe interactions between dislocation structures and precipitates were the dominant strengthening factors. It was very interesting that dislocations provided a diffusion path for Mg atoms and Cu atoms in 2024 LHZ-II during the pre-stretching process. • Pre-stretching was used to strengthen the FSWed dissimilar aluminum alloys joints. • Yield sequence of the FSWed dissimilar aluminum alloys joints was identified. • The strengthened lower hardness zone contributed to the reinforced global joint. • Several kinds of dislocations structures induced by the pre-stretching process. • Dislocations provided a diffusion path for Mg and Cu atoms in 2024 aluminum alloy. [ABSTRACT FROM AUTHOR]

Boron doped diamonds (BDD) with boron concentration above 1019 at./cm3, grown under conditions of high isostatic pressure by the temperature gradient method, were studied by Transmission Electron Microscopy methods, EELS analysis and X-ray diffraction analysis. It was shown that boron is distributed unevenly in the grown crystal. It was found that in places of maximum boron content, interplanar distances d 111 increase from 0.206 to approximately 0.2065 nm. Parallel bands were discovered, the boundaries of which are fragments of the intermediate carbon phase (ICP-phase). Numerous twins along the {111} plane, as well as fragments of rhombohedral 9R phase, were discovered. [Display omitted] [ABSTRACT FROM AUTHOR]

Magnetoplumbite barium hexaferrite (BaFe 11.8 Co 0.2 O 19) is synthesised through sol-gel auto-combustion method under two pH conditions of precursor solutions (acidic i.e. pH < 1 and neutral i.e. pH = 7). The XRD analysis followed by Reitveld refinement indicates the formation of phase pure samples in both cases but the barium hexaferrite obtained from acidic precursor solution has smaller crystallite sizes. The Transmission Electron Microscopy (TEM) analysis followed by High Resolution Transmission Electron Microscopy (HRTEM) confirms a lower particle size of ∼20 nm for barium hexaferrite synthesised from acidic pH precursor solution. The shift in Raman peak (520-540 cm−1) by 20 cm−1, represents the whole structural block and further confirms the differences in the distribution of particle sizes due to the method of synthesis. The magnetic studies display a lower coercive field for the samples with smaller particle sizes. This is due to the crystalline size-induced microstrain that controls the magneto-crystalline anisotropy, shape anisotropy and stress anisotropy. The electromagnetic characterisation confirms broader absorption in the range of 8–18 GHz (X -band) with R L ≤ −7 db for the entire range for the samples with smaller particle sizes. [ABSTRACT FROM AUTHOR]

Herein we report a facile approach for the preparation of a magnetically separable Fe3O4@poly(m‐phenylenediamine)@Cu2O nanocatalyst and its catalytic efficiency in the synthesis of 5‐phenyl‐[1,2,3]triazolo[1,5‐c]quinazolines from (E)‐1‐bromo‐2‐(2‐nitrovinyl)benzenes, aldehydes, and sodium azide under mild reaction condition is described. The morphology, chemical composition, interior structure and magnetic properties of the Fe3O4@PmPDs@Cu2O nanocomposites were studied using powder X‐ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive X‐ray spectroscopy, X‐ray photoelectron microscopy, vibrating sample magnetometer and nitrogen adsorption‐desorption technique. The as‐prepared Fe3O4@PmPDs@Cu2O nanocatalyst was simply recovered using external magnet and reused up to successive six runs with no obvious loss in its catalytic efficiency and structural integrity (confirmed by powder X‐ray diffraction and transmission electron microscopy of recycled nanocatalyst) along with low leaching of copper (2.32 ppm) and iron (0.008 ppm) ions. The present protocol has a broad substrate scope with high yield in shorter reaction time and it does not require any additive or base. Overall, it has better green chemistry metrices like low E‐factor (0.93), process mass intensity (1.93), high reaction mass efficiency (51.9 %) and carbon efficiency (95 %). [ABSTRACT FROM AUTHOR]

Green synthesis of metal oxide nanoparticles (NPs) is a viable alternative methodology because of cost-effective and availability of environmentally friendly templates for desired application, which has attracted the attention of researchers in recent years. In the present study, Co3O4 NPs were synthesized in various volume ratios in the presence of Solanum tuberosum leaf extract as a template. The synthesized Co3O4 NPs were characterized by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), surface area electron diffraction (SAED), UV-Vis diffuse reflectance spectroscopy (UV-DRS), and Fourier transform infrared (FTIR) spectroscopy. XRD analysis found that the average crystalline sizes for the 1 : 2, 1 : 1, and 2 : 1 volume ratios was 25.83, 21.05, and 27.98 nm, respectively. SEM-EDX and TEM analyses suggest that the green-synthesized Co3O4 NPs are spherical in shape without the presence of impurities. The band gap E g values of the 1 : 2, 1 : 1, and 2 : 1 volume ratios of Co3O4 NPs were found to be 1.83, 1.77, and 2.19 eV, respectively. FTIR analysis confirmed the presence of various bioactive ingredients within the leaf extract of Solanum tuberosum. Co3O4 NPs-modified electrodes showed better sensing capability towards ascorbic acid and citric acid due to enhanced electron transfer kinetics. Among three volume ratios (1 : 2, 1 : 1, and 2 : 1) of Co3O4 nanoelectrodes, 1 : 1 and 2 : 1 were identified as the best performing nanoelectrodes. This is possibly due to the high catalytic behavior and the more homogenized surface structure. Co3O4 (1 : 2) nanodrug showed the enhanced antibacterial activity (16 mm) towards S. aureus which is attributed to the formation of enhanced reactive oxygen species (ROS). [ABSTRACT FROM AUTHOR]

To develop wide bandgap materials for solar cells and other optoelectronic devices, undoped hydrogenated silicon oxide (SiOx:H) thin films are prepared by conventional radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method. The variation of carbon dioxide dilution ( Y c ) on optoelectronic and structural properties are studied thoroughly by keeping silane and hydrogen gas flow fixed. Surface morphology of the SiOx:H films have been studied by Field Emission Scanning Electron Microscopy (FESEM) and Atomic Force Microscopy (AFM). Distinct silicon nanocrystallites of average diameter ∼ 3–6 nm embedded uniformly in amorphous SiOx network have been observed in high resolution Transmission Electron Microscopy (HRTEM). From Fourier Transform Infrared spectra (FTIR), it is observed that oxygen content ( C o ) increases initially with Y c and afterwards it decreases. Strong room temperature photoluminescence (PL) peak is obtained for the as-deposited films having lower oxygen content ( C o ). The origin of room temperature PL spectra and its correlation with C o can be explained by quantum confinement effect (QCE) theory. In the current study, undoped hydrogenated silicon oxide (SiOx:H) films were prepared by varying carbon dioxide dilutions with fixed silane and hydrogen gas flow, and a strong room temperature photoluminescence peak is observed for lower value of oxygen content. The microstructural properties of the films have also been studied by AFM, FESEM and HRTEM. In TEM study, a uniform distribution of silicon nanoparticles of average diameter ∼3–6 nm is clearly observed over the amorphous SiOx:H network. [ABSTRACT FROM AUTHOR]

Pyrolytic carbon (PyC) plays a critical role in many applications for its unique properties. In ceramic composite systems, the elastic properties of PyC at the fiber/matrix interface drive toughening mechanisms, enabling structural performance at increased operating temperatures. PyC expresses a wide range of crystallographic texture depending on fabrication parameters. As a result, modelling and optimization requires direct understanding of the texture-property relationships at the relevant length scales. This research leverages high-resolution transmission electron microscopy (HRTEM) to link the PyC microstructure to the elastic response observed via digital image correlation (DIC) during micropillar compression. The HRTEM and DIC results quantitatively resolve a gradient for microstructural texture and Young's modulus respectively, showing that disordered texture increases compressive stiffness normal to the average orientation of the PyC basal planes. The values for modulus ranged from 55 to 150 GPa, which are large compared to most experimental methods, but may be more realistic considering the uniaxial stress state and length scale. The behavior supports findings from numerical homogenization models, suggesting that this advanced technique may provide a path forward for optimization and validation of these nanoscale elasticity models. [Display omitted] [ABSTRACT FROM AUTHOR]

We have discovered Raman peculiarities of sp3-bonded carbon nanoclusters forming ultrahard fullerite synthesized at pressure up to 85 GPa. The nanoclusters differ in the values of bulk modulus B 0 ranging from 580 to 730 GPa. We found that the Raman frequency, corresponding to the C-C stretching mode of the nanoclusters, varies linearly from 1485 to 1640 cm−1, depending on the excitation wavelength used, which ranges from 785 nm to 257 nm. In particular, the nanoclusters with higher B 0 have a higher Raman frequency. We also observed a resonant Raman spectrum when excited at a wavelength of 1064 nm. This showed a plateau from 1400 to 1720 cm−1, covering all Raman band positions of the nanoclusters from 1485 to 1640 cm−1. In addition, two Raman bands at 1285 and 1600 cm−1 appear at the resonance. The presence of several types of carbon sp3-bonded nanoclusters is confirmed by high-resolution transmission electron microscopy. Using moment tensor potentials, a class of machine learning interatomic potentials, we calculated the phonon density of states of the nanoclusters formed during the 3D polymerization of C 60. The presence of high frequency modes in the resonant Raman spectra suggests the existence of bonds with force constants higher than those in a single crystal diamond. In addition, we observed a stiffening effect when analyzing the dependence of the mechanical stiffness on the cluster size, with smaller clusters exhibiting a more rigid structure. [Display omitted] [ABSTRACT FROM AUTHOR]

The origin of hydrogen trapping by the Nb-carbide precipitates in a ferritic steel was studied at the atomic scale with the help of HRTEM (high resolution transmission electron microscopy) and 3D-APT (atom probe tomography). A Nb-added ferritic steel was prepared in the laboratory and subjected to aging after solutionizing treatment to have fine Nb-carbide precipitates in ferrite matrix. The precipitation kinetics were simulated beforehand using TC-Prisma in Thermocalc software. A large number of nanometer-sized Nb-carbide precipitates were observed in the ferrite matrix using TEM. 3D-APT studies on the steel sample electrolytically charged with D (deuterium) showed that the D atoms are trapped more within the precipitates than at the precipitate-matrix interfaces. It has been argued that H atoms occupy the vacant lattice sites on carbon sub-lattice sites in non-stoichiometric NbC 0.83. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, we fabricated white light–emitting phosphors by applying a 350-nm excitation wavelength to Eu 2 O 3 -doped [YBi 0.1 ]VO 4 (red), SrAl 12 O 19 (green), and Sr 3 MgSi 2 O 8 (blue) phosphors. The Eu3+-doped [YBi 0.1 ]VO 4 phosphor was synthesized using a high-temperature solid-state reaction method in an air environment, and the Eu2+-doped SrAl 12 O 19 and Sr 3 MgSi 2 O 8 phosphors were synthesized in a reducing environment. The morphological characteristics, crystal structures, and luminescence performance of the phosphors were investigated using X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), ultra-high-resolution transmission electron microscopy (UHR-TEM), and photoluminescence emission (PL). The white light–emitting phosphor was successfully fabricated at the molar ratio of [Y 0.8 Bi 0.1 Eu 0.1 ]VO 4 :[Sr 0.88 Eu 0.12 ]Al 12 O 19 :[Sr 0.99 Eu 0.01 ] 3 MgSi 2 O 8 phosphors of 1:1.5:1. Its Commission Internationale de l'Eclairage (CIE) chromaticity coordinates were (0.3422, 0.3398), which is close to the coordinates of pure white light at ([0.33, 0.33]). • The Eu 2 O 3 -doped [YBi 0.1 ]VO 4 (R), SrAl 12 O 19 (G), and Sr 3 MgSi 2 O 8 (B) phosphors were development. • The white phosphor was synthesized with molar ratio of R, G, B phosphors. • The CIE close to those of pure white light (0.3422, 0.3398). [ABSTRACT FROM AUTHOR]

Atomic and close-to-atomic scale manufacturing is a new technology that can achieve atomic-level manufacturing precision and functional critical dimension. Here we propose an efficient approach for atomic-scale chemical mechanical polishing (CMP) surface of fine copper utilizing optimized CMP slurry and polishing parameters. The optimal polishing slurry is composed of silica, hydrogen peroxide, aspartic acid, sodium phosphate and deionized water, where abrasive particles of silica nanospheres synthesized are uniformly dispersed. Prior to CMP, copper was precisely lapped by ceria slurry. After CMP, the surface roughness is 0.099 nm with an area of 50 × 50 µm2. Atomic-level flatness surface is acquired. To the best of our knowledge, it is the lowest surface roughness with such a relatively large scanning area, compared with those published previously. High resolution transmission electron microscopy (HRTEM) images of polishing surface further prove that atomic-scale surface roughness is achieved. X-ray photoelectron spectra clarify CMP mechanism that complex oxidation, ionization and chelation are sparked on copper surface and the soft layer is formed. The presented efficient approach for atomic-scale polishing will widen the application fields of copper materials and copper-based components. [Display omitted] [ABSTRACT FROM AUTHOR]

Atomic and close-to-atomic scale manufacturing is a new technology that can achieve atomic-level manufacturing precision and functional critical dimension. Here we propose an efficient approach for atomic-scale chemical mechanical polishing (CMP) surface of fine copper utilizing optimized CMP slurry and polishing parameters. The optimal polishing slurry is composed of silica, hydrogen peroxide, aspartic acid, sodium phosphate and deionized water, where abrasive particles of silica nanospheres synthesized are uniformly dispersed. Prior to CMP, copper was precisely lapped by ceria slurry. After CMP, the surface roughness is 0.099 nm with an area of 50 × 50 µm2. Atomic-level flatness surface is acquired. To the best of our knowledge, it is the lowest surface roughness with such a relatively large scanning area, compared with those published previously. High resolution transmission electron microscopy (HRTEM) images of polishing surface further prove that atomic-scale surface roughness is achieved. X-ray photoelectron spectra clarify CMP mechanism that complex oxidation, ionization and chelation are sparked on copper surface and the soft layer is formed. The presented efficient approach for atomic-scale polishing will widen the application fields of copper materials and copper-based components. [Display omitted] [ABSTRACT FROM AUTHOR]

While bimetallic nanocomposites have demonstrated extraordinary – three to even ten-fold – gains in strength with decreasing layer thickness, their strengths tend to plateau beyond a critical layer thickness. More disappointingly, such increases in strength are almost always accompanied by a decrease in their strains to failure (ductility). In this work we report simultaneous improvements in both strength and mechanical stability of Nb/Mg nanolaminates with decreasing layer thicknesses, a trend seldom reported in nanolaminates consisting of pure metals. Using micro-pillar compression and nanoindentation experiments we show that physical vapor deposited (PVD) Nb/Mg nanolaminates that contain a body center cubic (bcc) Mg pseudomorphic phase demonstrate a >60% increase in strength and a >80% increase in strain to failure over those containing the hexagonal close packed (hcp) Mg phase. Instead of a strength plateau, the hcp-to-bcc phase transition in Mg results in a renewed strengthening regime in the nanolaminate caused by the change to a coherent interface from an incoherent one, along with a concurrent increase in strain-to-failure due to the introduction of a more plastically isotropic bcc material from an anisotropic hcp structure. Using high resolution transmission electron microscopy (HR-TEM) we also demonstrate the presence of a thin layer of bcc Mg at the Nb/Mg interface at larger layer thicknesses when Mg is predominantly hcp. Our results suggest that the increases in strain to failure in the Nb/Mg nanolaminates with decreasing layer thicknesses can be corelated to the approximate volume fraction of the pseudomorphic bcc Mg present in the layers. [Display omitted] [ABSTRACT FROM AUTHOR]

Using common and high resolution transmission electron microscopy (TEM), we study the magnetic and crystal phase structures as well as their evolution in Ni 50 Mn 25 Ga 20 Fe 5 magnetic shape memory material with high Curie point. The particular alloying by Fe and changing thickness of the TEM foil enable us to observe all martensitic phases known in Ni-Mn-Ga Heusler alloy system and their respective transitions simultaneously. Starting from cubic austenite at about 10 nm foil thickness, the structure evolves via peculiar interleaved stripes of austenite and five-layered modulated 10M martensite to pure 10M phase with a low density of stacking faults at 40 nm thickness. With further increasing thickness, the 10M phase transforms gradually to seven-layered modulated 14M martensite with an increased density of stacking faults. Finally, the non-modulated tetragonal NM phase appears within the 14M phase by detwinning of nanotwins forming the modulated phases. High resolution TEM further confirms that nanotwinning and stacking faults are inherent structure features tightly connected with the lattice modulation and intermartensite transformations. Overall, the evolution of average lattice shows the same general trend, an increasing simple shear with (1 1 ¯ 0) shuffling plane, across the whole phase sequence. Additionally, we found large local variation of lattice parameters in all phases, which is is ascribed to strong lattice softening in the vicinity of the martensitic transformation and high density of stacking faults in 14M martensite lattice. • Fe alloying enables complete spectrum of phases in Ni-Mn-Ga-Fe TEM foil. • Martensite structures are formed by regular stacking of (1 1 ¯ 0) basal planes. • Intermartensite transitions occur gradually via irregular faulty stacking. • Lattice softening and faulty stacking cause lattice parameters fluctuation. [ABSTRACT FROM AUTHOR]

Gas atomized Nd-Fe-B powders of several compositions were separated in different size fractions by sieving. These fractions were annealed between 1100 °C and 1150 °C for 24 and 96 h. The oxygen content of the powders was measured before and after annealing for the different size fractions. The oxygen concentration of the powders depends strongly on the particle size and increases significantly during annealing, particularly in the case of small particle sizes. The effect of particle size on the microstructural changes was analyzed in detail, particularly on grain growth, using high resolution scanning electron microscopy and transmission electron microscopy. Electron back scattering diffraction was used to measure grain size. When the particle size rises, the degree of sintering decreases and the higher solid/vapor surface area reduces the mobility of grain boundaries. Oxidation also reduces grain growth rate and its effect is more evident for particles sizes below 45–63 μm and high Nd concentrations. Nb addition leads to the formation of intra- and intergranular precipitates. The size of these Nb-Fe-containing precipitates increases with the particle size for equivalent annealing conditions. At 1150 °C, Nb loses its effect as an inhibitor of grain growth in the particle size fractions larger than 45–63 μm. • Grain size of gas atomized powders increases with particle size from 2 to 10 μm. • Intragranular Nb nanoprecipitation in gas atomized powders was confirmed. • Oxygen (0.1–0.23 wt.%) delays grain growth in small particles (<45–63 μm). • Porosity reduced the mobility of grain boundaries in large particles (>20–63 μm). • Nb loses its effect as inhibitor of grain growth in large particles (>45–63 μm). [ABSTRACT FROM AUTHOR]

• The structural transformation of Y 2 O 3 during high-energy ball milling is investigated. • Complete phase transformation from cubic to monoclinic is achieved after 30 h of milling. • XRD and Rietveld refinement analysis for the quantification of phase fraction, crystallite size and strain. • Transformation mechanism confirmed by HRTEM and EELS analysis. • Transformation sequence is: Yc → Yc + Ym → Ym. • Monoclinic Y 2 O 3 is found to be much finer than its cubic allotrope. [Display omitted] In-depth understanding of the structural transformation mechanism in nanocrystalline yttria (Y 2 O 3) is crucial to design advanced materials satisfying a wide range of technical demands. Present study investigates the structural modification in cubic Y 2 O 3 nanopowders induced by high energy ball-milling as a function of milling duration. Y 2 O 3 nanopowder with an initial crystallite size of 25–50 nm was subjected to high energy ball milling (1000 rpm) for incremental time periods up to 30 h. X-ray diffraction (XRD) and Rietveld analysis were employed to study the phase evolution, crystallite size, and strain at every stages of milling. High Resolution Transmission Electron Microscopy (HR TEM) and Electron Energy Loss Spectroscopy (EELS) is utilized to realize the mechanisms involved in phase transformation. It is observed that as milling duration progresses, the cubic Y 2 O 3 gets refined and gradually transforms to the monoclinic phase. It is also apparent that at finer sizes, the monoclinic phase is preferred over the cubic one. The critical crystallite size for the monoclinic phase to stabilize is observed to be ~ 13 nm. Results show the complete structural modification after 30 h of milling duration. [ABSTRACT FROM AUTHOR]

The schematic illustration shows the role of polymeric films and its thickness in obtaining high quality TEM images. [Display omitted] • Fabrication of polymer modified copper grids for transmission electron microscopy. • Gold nanorods, polymer nanocapsules and nanocapsules incorporating nanorods could be imaged successfully. • Effect of polymer charge, polymer concentration and film thickness on TEM imaging. • Simple and economical way to obtain TEM images of nanomaterials. We report a methodology to functionalize the bare copper grids for high resolution transmission electron microscopy (TEM), by drop casting a thin polymer film instead of carbon film. The polymer coating actively helped in trapping the sample on the top of the mesh, making it available for the imaging. Gold nanorods (AuNRs), poly(allylamine) hydrochloride (PAH)/dextran sulphate (DS) nanocapsules and PAH/DS nanocapsules incorporated with AuNRs, were used as samples on the bare grids, carbon-coated grids and polymer-coated grids. The effect of polymer charge, polymer concentration and film thickness on imaging quality was studied using different polymers such as chitosan, PAH, polystyrene sulfonate, DS and gellan gum. The polymer-coated copper grids showed a comparable performance with the conventional carbon-coated copper grids. Hence, the methodology provides a simple and economical way to obtain high quality TEM images using the bare copper grids. [ABSTRACT FROM AUTHOR]

Nanoporous gold (NPG) is a novel unsupported heterogeneous catalyst intrinsically loaded under stress and strain. Most studies on the correlation between strain and NPG catalytic activity are limited to ex situ chemical analysis and numerical simulations; few studies have investigated the strain evolution in NPG during catalytic reactions. Herein, in situ gas-phase transmission electron microscopy with high spatiotemporal resolution imaging was conducted to study the evolution of strain in the ligaments of the NPG during catalytic methane pyrolysis. The adsorption and desorption of reactant gases and intermediates altered the ligament structure. The release of stress promoted the formation of dislocations and twins; subsequently, the dislocations glided and interacted with twin boundaries. This study elucidates the evolution of strain in catalytic reactions and can facilitate the development of new approaches to tune the catalytic reactivity of heterogeneous catalysts via strain engineering. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • In the cat locus coeruleus, opioid receptors are located in noradrenergic dendrites. • In the cat locus coeruleus, glial profiles express mu and delta opioid receptors. • Plasma membrane expression of mu is significantly higher than delta opioid receptor. The Locus Coeruleus (LC) is a pontine nucleus involved in many physiological processes, including the control of the sleep/wake cycle (SWC). At cellular level, the LC displays a high density of opioid receptors whose activation decreases the activity of LC noradrenergic neurons. Also, microinjections of morphine administered locally in the LC of the cat produce sleep associated with synchronized brain activity in the electroencephalogram (EEG). Even though much of the research on sleep has been done in the cat, the subcellular location of opioid receptors in the LC and their relationship with LC noradrenergic neurons is not known yet in this species. Therefore, we conducted a study to describe the ultrastructural localization of mu-opioid receptors (MOR), delta-opioid receptors (DOR) and tyrosine hydroxylase (TH) in the cat LC using high resolution electron microscopy double-immunocytochemical detection. MOR and DOR were localized mainly in dendrites (45% and 46% of the total number of profiles respectively), many of which were noradrenergic (35% and 53% for MOR and DOR, respectively). TH immunoreactivity was more frequent in dendrites (65% of the total number of profiles), which mostly also expressed opioid receptors (58% and 73% for MOR and DOR, respectively). Because the distribution of MORs and DORs are similar, it is possible that a substantial sub-population of neurons co-express both receptors, which may facilitate the formation of MOR-DOR heterodimers. Moreover, we found differences in the cat subcellular DOR distribution compared with the rat. This opens the possibility to the existence of diverse mechanisms for opioid modulation of LC activity. [ABSTRACT FROM AUTHOR]

The α phase precipitation of β →β'→α in the Ti–13Nb–13Zr alloy has been observed by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The images clearly show that the α phase nucleates at the β′ interface which has a rotation angle with the β matrix. The precipitation of α phase from the β′ phase experiences four steps, each step is similar to the twinning and the symmetric angle successively increases from 57° to 62°, 76° and finally to 90°. The crystallographic relationships between β and β' were also discussed. This study provides guidance in the future for tailoring microstructure of titanium alloys. • A new insight of α phase precipitation in β titanium alloy was discussed. • The precipitation of α phase from the β′ phase experiences four steps. • The rotation angle between the β′ and β was calculated to be 4.6°. [ABSTRACT FROM AUTHOR]

As-produced Cr-coated Optimized ZIRLO™ cladding material fabricated with the cold-spray (CS) deposition process is studied. Cross-sectional electron microscopy, nano-hardness profiling, transmission electron microscopy, transmission Kikuchi diffraction, and atom probe tomography (APT) were performed to investigate the nature of the CS Cr-coating/Optimized ZIRLO™ interface, the microstructure of the coating, and the effects of the deposition on the Zr-substrate microstructure. The former surface of the Zr-substrate was found to have a highly deformed nano-crystalline microstructure, the formation of which was attributed to dynamic recrystallization occurring during coating deposition. This microstructural change, evaluated with electron backscattered diffraction and nano-hardness profiling, appeared to be confined to a depth of a few microns. Through APT analysis, a 10–20 nm thick intermixed bonding region was observed at the interface between coating and substrate. The chemical composition of this region suggests that this layer originated from a highly localized shearing and heating of a thin volume of the outermost former surface of the substrate. The study of the intermixed bonding region's crystalline structure was performed with high resolution transmission electron microscopy and revealed a distorted hexagonal close-packed structure. [ABSTRACT FROM AUTHOR]