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Dedicated machine-learning techniques applied to superresolved HRSTEM images are used to map interstitial atoms with decananometric spatial resolution and picometric precision. This methodology is illustrated with the technologically-relevant case of etched GaN, used for power devices. In general, an average chemical concentration evolution close to a typical erf implantation profile is obtained, in agreement with atomistic simulations.

This contribution shows an unusually high hydrogen storage of multilayer amorphous (A)-crystalline (C) Pd–Si based nanosheets when stacked in the right order. Samples with A/C/A/C/A stacking sequence exhibit 40 and 12 times larger hydrogen sorption than monolithic crystalline and amorphous samples, respectively. The maximum capacitance calculated from the fitting of electrochemical impedance measurements of the same sample is twice larger than that of the conventional polycrystalline Pd films of similar thickness. Five times higher diffusion coefficient calculated from modified Cottrell equation is obtained compared to specimens with C/A/C/A/C stacking. For the A/C/A/C/A multilayers, nanobubbles with diameters of 1–2 nm are homogeneously distributed at Si/SiO 2 interface, and PdH x crystal formation in these regions confirms hydrogen-metal interactions. Furthermore, corrosion-resistant amorphous top layer permits larger amounts of hydrogen ion transfer to inner layers. Thus, hydrogen storage and production can be enhanced by smart design of multilayers targeted for proton exchange membrane electrolysis or fuel cells. [Display omitted] • Ultra-high hydrogen storage in amorphous (A)-crystalline (C) Pd–Si based nanosheets. • Nanobubbles and PdH x crystal formation at metal-Si interface recorded by HR(S)TEM. • Corrosion-resistant amorphous top layer grants hydrogen ion transfer to inner layers. • Modified Cottrell equation yields five times higher diffusion in A/C/A/C/A stacking. • Maximum capacitance of A/C/A/C/A from ECM twice larger than crystal Pd thin film. [ABSTRACT FROM AUTHOR]

Morphological and compositional evolution of omega (ω) precipitates in a model Titanium-20 wt%Vanadium (or 19 at.%V) alloy has been systematically investigated by coupling transmission electron microscopy and atom probe tomography with atomistic ab initio and continuum microelasticity computations. The initial water quenched microstructure comprised of a fine scale distribution of athermal ω precipitates, which form congruently from the β phase via a complete displacive collapse of {222} β planes, that has been rationalized based on DFT computations. Subsequent annealing at 300 °C, over progressively increasing time periods, resulted in isothermal evolution of the ω precipitates, whose morphology changes from ellipsoidal to cuboidal, accompanied with V rejection. The highly V-enriched β matrix consisted of short V V bond lengths, further distorting the bcc lattice, and increasing the β/ω misfit. This facilitates the change in the morphology of omega precipitates from ellipsoidal to cuboidal resulting in a {001} β habit plane for these precipitates. The coupled experimental and computational approach permits rationalizing the evolution of ω precipitate morphology and composition in such high β−ω misfit β-Ti alloys. [ABSTRACT FROM AUTHOR]

The study of metallurgical phase transformations is essential for developing reliable interconnects in thermoelectric devices. PbTe-based devices are used in mid-temperature range applications, with Ni being the most preferred contact metal. Several studies have reported the direct joining of PbTe and Ni through rapid hot-pressing routes. However, the study of equilibrium phase transformations in these processes is complex owing to many external variables (applied pressure, electrical current, and simultaneous sintering of PbTe). Furthermore, the long-term phase transformation behavior of Ni 5 Pb 2 Te 3 and (Ni 3±x Te 2) β 2 phases generated from PbTe/Ni interaction has not been examined. This paper reports the phase decomposition of the high-temperature Ni 5 Pb 2 Te 3 phase in diffusion bonded PbTe/Ni heterointerfaces and presents a general thermodynamic framework to predict such transformations. The phase decomposition is studied through advanced analytical TEM/STEM techniques. The Ni 5 Pb 2 Te 3 phase transforms into monoclinic β 2 and PbTe phases with a lamellae-like arrangement accompanied by the formation of extrinsic stacking faults in the β 2 lamellae. Our work highlights an effective experimental technique (solid-state diffusion bonding) that can be applied to study a metal-contact problem in thermoelectrics and outlines a framework to derive essential thermodynamic data in the absence of any experimental measurements and crystallographic information. [Display omitted] [ABSTRACT FROM AUTHOR]

Ammoxidation of propane to acrylonitrile was examined over a Fe 3 BiO x /SiO 2 sample prepared by thermal decarbonylation of [Et 4 N][Fe 3 (CO) 10 (μ 3 -Bi)] on the surface of mesoporous silica. Catalytic measurements performed at 500 °C showed that this sample yields 49% acrylonitrile selectivity at 36% propane conversion when a 5.5%C 3 H 8 /30%O 2 /11%NH 3 /He balance reaction mixture was used at a GHSV of 1360 h −1 . HRSTEM, EDS, and XPS measurements indicate that mixed Fe 3 BiO 6 oxide particles less than 2 nm in size were formed on the surface of this material under reaction conditions. A Fe/Bi atomic ratio in these particles is approximately 3:1 and the Fe and Bi ions both are in the +3 oxidation state. A Fe-Bi/SiO 2 sample prepared by co-impregnation of individual Fe and Bi salts had very low activity and low selectivity for acrylonitrile formation from propane under similar experimental conditions due to larger sizes of particles formed under reaction conditions and enrichment of their surface with Fe. [ABSTRACT FROM AUTHOR]

The precipitation mechanism of ordered phases in metallic solid solutions has been a long-standing controversy due to the competing roles of chemical clustering (or phase separation) and chemical ordering. In the present study, this controversy has been resolved through the coupled use of aberration-corrected high-resolution scanning transmission electron microscopy and atom probe tomography. The experimental results, obtained at atomic resolution, can only be interpreted satisfactorily on the basis of phase separation via spinodal decomposition followed by chemical ordering. [ABSTRACT FROM AUTHOR]

During high temperature electrical activation of ion-implanted dopant species in SiC, extrinsic dislocation loops are formed on the basal planes of the SiC lattice. Investigations have suggested Si-based loops are caused in accordance with the well-known +1 model. Herein we apply aberration corrected STEM to resolve the atomic structure of these loops. It is shown that the dislocation loops formed during annealing of Al-implanted SiC consist of an extra inserted Si-C bilayer of the (0001) polar sense, which upon insertion into the lattice causes a local extrinsic stacking fault. The +1 model thus needs to be expanded for binary systems. [ABSTRACT FROM AUTHOR]

Abstract: Mixed phase Fe3O4-γ-Fe2O3 (magnetite–maghemite) iron oxide nanoparticles have been fabricated by colloidal routes. HRTEM/HRSTEM images of the nanoparticles show the presence of {111} facets that terminate with enhanced contrast, which is shown to be caused by the presence of additional cations at the edges of the nanoparticles. HRTEM images were taken on a FEI CM200 FEGTEM, a JEOL 3100 with a LaB6 source, and a double aberration corrected JEOL-JEM 2200FS FEGTEM. The enhanced contrast effect was observed on the {111} surface atomic layers resolved using each machine. HRSTEM images, taken on an aberration corrected STEM, resolved enhanced contrast at specific surface sites. Exit wave reconstruction was also carried out on focal series taken on a double aberration corrected JEOL-JEM 2200FS and showed similar highly resolved enhanced contrast at specific surface cation sites. It is apparent that additional cations are occupying the {111} terminating layers of these nanoparticle surfaces. The use of different microscopes and techniques in this paper provides strong evidence that the enhanced contrast is a real effect and not an effect caused by microscope aberrations. [Copyright &y& Elsevier]

This work concerns high Al-containing Ti x Al 1-x N coatings prepared using low pressure-chemical vapour deposition (LP-CVD). The coatings were examined using electron microscopy techniques, such as scanning transmission electron microscopy (STEM), energy dispersive X-ray analysis (EDX) and transmission Kikuchi diffraction (TKD). An intermediate TiN-layer with a 〈211〉 texture consisting of twinned, needle-shaped grains influences the subsequent growth of the TiAlN layer. The TiAlN grains were columnar with a texture of 〈211〉. As the grains grow along 〈111〉, with {001} facets, this led to a tilted pyramid surface morphology. The grains developed an internal periodic epitaxial nanolamella structure. The thicknesses were 2 nm for the low (x = 0.6) and 6 nm for the high (x = 0.9) Al-containing lamellae. The TiAlN layer growth could be described by a "two-wing" model, where two TiAlN grains with a twin-related orientation grow on a twinned TiN grain, where the two TiAlN grains gradually switch sides, making the appearance of two wings of columnar grains. In general, this work shows that it should be possible to control the growth of TiAlN layers by controlling the texture and morphology of an intermediate layer, such as TiN. • High Al-containing Ti 1-x Al x N coatings (x = 0.85) deposited using LP-CVD • Pairs of epitaxially grown TiAlN grains form on top of twinned TiN grains. • 〈112〉 texture of TiAlN grains controlled by ⟨112⟩ texture of underlying TiN layer • Columnar TiAlN grew along ⟨111⟩ with {001} facets, leading to tilted pyramid. • {001} Ti 1-x Al x N facets develop an internal periodic nano-lamella structure. [ABSTRACT FROM AUTHOR]

Quasi-one-dimensional transition metal trichalcogenides (TMTs) feature many valuable properties that make them promising for future downscaled and flexible electronics. However, research efforts on new TMT family members and the mechanical properties of these materials remain insufficient. In this paper, the tensile strength of a new conductive ternary TMT, TaNbSe 6 , is studied by in situ tensile testing using transmission electron microscopy. Our results reveal that the TaNbSe 6 nanobelts have a Young's modulus of 64.8 GPa and yield strength of 9.2 GPa. This outstanding tensile strength results from the novel structure of TaNbSe 6 , in which the Ta and Nb double prisms appear alternately along the c axis. Our work opens a door for exploring other TMTs and expanding mechanical properties for future applications. • We successfully synthesized a new ternary transition metal trichalcogenides, TaNbSe 6. • A novel orderly structure was interpreted from HRSTEM results of the TaNbSe 6 nanobelts. • High tensile yield strength of 9.2 GPa was demonstrated by in situ TEM test for TaNbSe 6 nanobelts. • This high tensile yield strength is explained by the structure and chemical bonding condition. [ABSTRACT FROM AUTHOR]

Abstract: Platinum nanoparticles and nanowires have been synthesized inside zeolite mordenite using a solid-state reduction method. Tetrammine platinum nitrate was introduced into the pores via incipient wetness impregnation and it was reduced using powder sodium borohydride. With this method it was possible to obtain single crystal nanowires along the edges of the zeolite particle. The molar ratio of the reducing agent to platinum atoms was a critical parameter for the formation of either uniform nanoparticles or nanowires. Using a regular aqueous sodium borohydride solution reduction it was not possible to obtain nanowires in this zeolite. To the best of the author''s knowledge this is the first time sodium borohydride in its solid form is used as a reducing agent to form nanostructures and this is also the first time a solid-state method is used to form nanostructures in a zeolite. [Copyright &y& Elsevier]

The microstructure of a René 108 Ni-based superalloy was systematically investigated by X-ray diffraction, light microscopy, energy-dispersive X-ray spectroscopy, and electron microscopy techniques. The material was investment cast in a vacuum and then solution treated (1200 °C-2h) and aged (900 °C-8h). The γ matrix is mainly strengthened by the ordered L12 γ′ phase, with the mean γ/γ′ misfit, δ, +0.6%. The typical dendritic microstructure with considerable microsegregation of the alloying elements is revealed. Dendritic regions consist of secondary and tertiary γ′ precipitates. At the interface of the matrix with secondary γ′ precipitates, nano M5B3 borides are present. In the interdendritic spaces additionally primary γ′ precipitates, MC and nano M23C6 carbides were detected. The γ′ precipitates are enriched in Al, Ta, Ti, and Hf, while channels of the matrix in Cr and Co. The highest summary concentration of γ′-formers occurs in coarse γ′ surrounding MC carbides. Borides M5B3 contain mostly W, Cr and Mo. All of MC carbides are enriched strongly in Hf and Ta, with the concentration relationship between these and other strong carbide formers depending on the precipitate's morphology. The nano M23C6 carbides enriched in Cr have been formed as a consequence of phase transformation MC + γ → M23C6 + γ′ during the ageing treatment. [ABSTRACT FROM AUTHOR]

Microstructural and morphological observations of the surface scale on a high Cr and Ni austenitic heat resistant steel oxidised in water vapour at 700 °C are reported. Analysis of microstructure was carried out by analytical techniques of transmission- and scanning electron microscopy. Investigation of M23C6 nucleated at the interface between matrix and the Z-phase precipitates after exposing to high temperature showed semicoherency between M23C6 and the matrix and no coherency with the Z-phase. Plates developed on the oxide scale surface consist of Cr2O3 crystals separated by amorphous SiO2. [ABSTRACT FROM AUTHOR]

Chemical vapor deposition and growth dynamics of highly anisotropic 2D lateral heterojunctions between pseudo-1D ReS 2 and isotropic WS 2 monolayers are reported for the first time. Constituent ReS 2 and WS 2 layers have vastly different atomic structure, crystallizing in anisotropic 1T' and isotropic 2H phases, respectively. Through high-resolution scanning transmission electron microscopy, electron energy loss spectroscopy, and angle-resolved Raman spectroscopy, this study is able to provide the very first atomic look at intimate interfaces between these dissimilar 2D materials. Surprisingly, the results reveal that ReS 2 lateral heterojunctions to WS 2 produce well-oriented (highly anisotropic) Re-chains perpendicular to WS 2 edges. When vertically stacked, Re-chains orient themselves along the WS 2 zigzag direction, and consequently, Re-chains exhibit six-fold rotation, resulting in loss of macroscopic scale anisotropy. The degree of anisotropy of ReS 2 on WS 2 largely depends on the domain size, and decreases for increasing domain size due to randomization of Re-chains and formation of ReS 2 subdomains. Present work establishes the growth dynamics of atomic junctions between novel anisotropic/isotropic 2D materials, and overall results mark the very first demonstration of control over anisotropy direction, which is a significant leap forward for large-scale nanomanufacturing of anisotropic systems., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)