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Mechanisms relating to growth and/or compositional modification of zircon occur at the atomic scale. For felsic igneous systems, processes responsible for growth patterns in zircon have previously remained elusive as the volume of material needed to analyze these compositional features using traditional in-situ methods is considerably larger than the typical sub-micron scale distribution of trace elements. To illuminate some of these driving forces, we characterize and quantify minor and trace element concentrations in igneous zircon grains by combining methods of cathodoluminescence (CL) imaging, electron microprobe microanalysis (EMPA) elemental maps for Hf, Y, Yb and U or Th, and atom probe tomography (APT). We focus on igneous zircon from the Chon Aike Silicic Large Igneous Province (Patagonia) that provide novel insights into (1) dissolution and re-crystallization during crustal anatexis, (2) crystallization to produce oscillatory zonation patterns that are typical of igneous zircons, and (3) the incorporation of trace element impurities (e.g., P, Be, and Al) at the nanoscale. Significantly, these APT volumes provide nanoscale sampling of boundaries between oscillatory growth zones in an igneous zircon to reveal compositional zoning of Y and, to a lesser extent P, which appear as high-angle, planar features. These concentration boundaries measured on the order of 10 to 12 nm are difficult to reconcile with proposed mechanisms for generating fine-scaled oscillations. Lastly, we fit diffusional profiles to measured Y concentrations to provide an estimate on the maximum timescales of zircon growth prior to eruption, as a function of the temperature at which diffusion occurred. When combined with known pressure-temperature-time paths for the magmatic system considered, these extremely short diffusion profiles that are resolvable by APT provide a powerful method to constrain timescales of crystal growth. [ABSTRACT FROM AUTHOR]

At temperatures above about 600 °C, alkali feldspar forms a continuous solid solution between the Na and K end members. Towards lower temperatures a miscibility gap opens, and alkali feldspar of intermediate composition exsolves, forming an intergrowth of relatively more Na-rich and K-rich lamellae. During exsolution, the crystal structure usually remains coherent across the lamellar interfaces, a feature that may be preserved over geological times. Due to the compositional dependence of the lattice parameters, coherent intergrowth requires that the lamellae are elastically strained. The associated elastic strain energy counteracts exsolution, and the solvus delimiting the misciblity gap for coherent intergrowth lies below the solvus for strain free phase equilibria. To determine the coherent solvus, homogeneous gem quality alkali feldspar of intermediate composition was annealed at conditions falling into the two-phase region of the phase diagram. Thereby a coherent intergrowth of approximately 10–20 nanometers wide lamellae was produced. Lamellar compositions were determined with atom probe tomography defining points on the coherent solvus. In parallel, the coherent solvus was calculated using a thermodynamic mixing model calibrated on the same alkali feldspar as used for the exsolution experiments and accounting for the elastic strain energy associated with coherent lamellar intergrwoth. The experimentally determined and the calculated coherent solvus are in excellent agreement indicating that phase equilibria in coherent lamellar intergrowth of alkali feldspar are adequately described, providing a sound basis for the interpretation of phase relations in coherently exsolved alkali feldspar. [ABSTRACT FROM AUTHOR]

This work aims at understanding the formation of a beneficial thin continuous aluminum (Al)-rich interfacial layer with uniform distribution of fine equiaxed Fe-Al crystals formed at the substrate/coating interface during the initial stages of interfacial reactions as well as hindrance of Fe dissolution in Zn layer as soon as copper (Cu) pre-coated high-strength steel substrate is immersed into the molten zinc (Zn) bath containing 0.2 wt.% Al. Pre-coated Cu does not allow the immediate interaction and interdiffusion of Fe and Zn because of the positive heat of mixing between Fe and Cu. As the Cu dissolves in liquid Zn, counter-diffusion of Al and Zn toward the steel interface allows Fe to react with Al and Zn forming the thin Fe-Al inhibition layer with finer equiaxed grains. Moreover, dissolved Cu in the Zn layer would also prevent Fe diffusion in Zn in the time span during dipping, which is beneficial. Atom probe tomography (APT) analysis at the substrate/coating interface location reveals the presence of 56.22 ± 1.36 at.% Al, 35.01 ± 1.31 at.% Fe, 6.33 ± 0.66 at.% Zn, and 0.032 ± 0.01 at.% Cu, similar to the intermetallic compound of Fe2Al(5-x)Znx, as well Cu in the Zn layer supporting the above reasoning. [ABSTRACT FROM AUTHOR]

In this work, hardness and micro- and nano-structure of W–10Cr–0.5Y alloy, which is a promising material for fusion reactors, before and after irradiation with Fe ions with an energy of 5.6 MeV at 500°C were studied. Nanoindentation for hardness measurement and transmission electron microscopy and atom probe tomography for structural changes were used. A formation of Cr clusters with the concentration of Cr in clusters of 52 ± 2 and 77 ± 3 at % for radiation doses of 1 and 10 displacement per atom (dpa), respectively, was detected. An increase in the hardness with increasing the irradiation dose from 1 to 10 dpa was found, which correlates with the increase in the Cr concentration in clusters. [ABSTRACT FROM AUTHOR]

The mechanical property and microstructures of the 15-5PH stainless steel aged at 500 °C for different times have been studied in detail by using transmission electron microscopy and atom probe tomography. The precipitation-hardening effect is significant during aging and the peak hardness occurs at 2 h, but prolonged aging decreases the hardness significantly. The peak hardness is attributed to the formation of a large number of Cu-rich precipitates of 3-6 nm in diameter, with the Ni and Mn atoms segregating around the Cu-rich precipitates and forming a core–shell structure. The over-aging process increases the size of Cu-rich precipitates and causes Si and Nb atoms to segregate to the vicinity of Ni and Mn atoms, forming Nb-rich and NbN-rich particles. The formation of various phase precipitates, including possible G-phase particles, and their effects on mechanical property are discussed. [ABSTRACT FROM AUTHOR]

An analysis of results obtained from studying the granulable the granulable nickel-based superalloy VV751P with the Ni–15Co–12Cr–0.7V–0.3C–0.9W–2.7Mo–3.4Ti–2.0Nb–8.3Al–0.02Hf–0.008B composition (at %) by atom probe tomography has been performed. Details of the formation of clusters that are 2–5 nm in size consisting of Cr, Co, and Mo atoms within γ'-phase particles are considered; the width of the transition layer between contacting γ- and γ'-phase particles has been determined. [ABSTRACT FROM AUTHOR]

The characterization of the nanostructure of modern oxide dispersion strengthened steels requires a comprehensive analysis using complementary techniques. In this work, the methods of small-angle X-ray scattering, transmission electron microscopy and atom probe tomography have been applied to several oxide dispersion strengthened steels. Comparison of the obtained results allows the most correct characterization of inclusion types and their number in the studied materials. It is shown that most of the studied steels contain oxide inclusions and nanosized clusters enriched in O and Y, as well as V, Ti, Al, and Zr, depending on the initial steel composition. Transmission electron microscopy and atom probe tomography provide detailed information about the inclusion types, and small-angle X-ray scattering gives the most accurate estimation of the average density of inclusions in large volumes of material. The importance of the correct determination of the inclusion types for hardening calculations is shown, the results of such calculations are compared with microhardness measurements. The calculated values of hardness for the studied steels are in the range 2.7–4.3 GPa, which is well confirmed by microhardness measurements. [ABSTRACT FROM AUTHOR]

The microstructural properties and strengthening mechanisms in precipitation strengthening Corrax stainless steel manufactured by laser powder bed fusion have been investigated. The as-printed sample initially contains a fully martensitic microstructure. However, aging heat treatment triggered the formation of austenite laths between the martensitic structure. Despite having softer reverted austenite, Corrax showed excellent hardness and strength due to the formation of Ni- and Al-rich, spherical precipitates (with an average size of 4.27 ± 1.20 nm). The atom probe tomography analysis reveals that Cr, Mo and Si are segregated in the Fe-based martensitic matrix, while the Mn diffused to the Al- and Ni-rich precipitates. [ABSTRACT FROM AUTHOR]

We report a combination of experimental results with density functional theory (DFT) calculations to understand electronic structure of indium tin oxide and molybdenum disulfide (ITO–MoS2) interface. Our results indicate ITO and MoS2 conform an n-type Schottky barrier of c.a. − 1.0 eV due to orbital interactions; formation of an ohmic contact is caused by semiconducting and metal behavior of ITO as a function of crystal plane orientation. ITO introduces energy levels around the Fermi level in all interface models in the Γ-Μ-Κ-Γ path. The resulted Van der Waals interface and the values of Schottky barrier height enhance electron carrier injection. [ABSTRACT FROM AUTHOR]

Results of the study of the chemical composition of contacting γ- and γ'-phase particles in a granular heat-resistant nickel alloy (HNA) VV751P (Ni–15Co–12Cr–0.7V–0.3C–0.9W–2.7Mo–3.4Ti–2.0Nb–8.3Al–0.02Hf–0.008B, at %) by atom probe tomography are analyzed. Experimental and literature data on the preferential location of alloying elements in γ- and γ'-phase particles in different heat-resistant nickel alloys are considered. A criterion for the characterization of each of elements based on the ratio K = Еv/r2 (where Еv is the number of valence electrons and r is the atomic radius of an element) is suggested. It is shown that the higher the K value, the more probable the enrichment of γ-phase particles in this element and the higher the degree of such an enriching. The lower the K value, the more probable the enrichment of γ'‑phase particles in this element and the higher the degree of such an enriching. The effect of γ- and γ'-forming elements in heat-resistant nickel alloys and other factors on the stability of the γ- and γ' phases, mechanical characteristics of disc heat-resistant nickel alloys at room temperature, and long-term strength at operating temperatures is discussed. [ABSTRACT FROM AUTHOR]

Bimetallic nanoparticles are often superior candidates for a wide range of technological and biomedical applications owing to their enhanced catalytic, optical, and magnetic properties, which are often better than their monometallic counterparts. Most of their properties strongly depend on their chemical composition, crystallographic structure, and phase distribution. However, little is known of how their crystal structure, on the nanoscale, transforms over time at elevated temperatures, even though this knowledge is highly relevant in case nanoparticles are used in, e.g., high-temperature catalysis. Au-Fe is a promising bimetallic system where the low-cost and magnetic Fe is combined with catalytically active and plasmonic Au. Here, we report on the in situ temporal evolution of the crystalline ordering in Au-Fe nanoparticles, obtained from a modern laser ablation in liquids synthesis. Our in-depth analysis, complemented by dedicated atomistic simulations, includes a detailed structural characterization by X-ray diffraction and transmission electron microscopy as well as atom probe tomography to reveal elemental distributions down to a single atom resolution. We show that the Au-Fe nanoparticles initially exhibit highly complex internal nested nanostructures with a wide range of compositions, phase distributions, and size-depended microstrains. The elevated temperature induces a diffusion-controlled recrystallization and phase merging, resulting in the formation of a single face-centered-cubic ultrastructure in contact with a body-centered cubic phase, which demonstrates the metastability of these structures. Uncovering these unique nanostructures with nested features could be highly attractive from a fundamental viewpoint as they could give further insights into the nanoparticle formation mechanism under non-equilibrium conditions. Furthermore, the in situ evaluation of the crystal structure changes upon heating is potentially relevant for high-temperature process utilization of bimetallic nanoparticles, e.g., during catalysis. [ABSTRACT FROM AUTHOR]

Data collected with an atom probe tomograph allow to reconstruct 3D atom maps of chemical element atoms with high accuracy. Due to the permanent improvement of AP installations, new 3D reconstruction procedures are required. This work proposes an improved approach for atom probe data reconstruction which uses dynamic parameters and a calibration based on the material density. [ABSTRACT FROM AUTHOR]

Analysis of mechanical testing and microstructural investigations of the irradiated VVER-440 reactor pressure vessel (RPV) metal before and after annealing carried out in the frameworks of the international project "PRIMAVERA" is presented. The role of chemical elements (Cu and P) was studied in relation to irradiation embrittlement of the VVER-440 RPV weld metal in the initial state, after recovery annealing and after post-annealing irradiation. It was shown that under primary irradiation, copper atoms formed small clusters (size ~1‒2 nm) which also include P, Si and Mn atoms. Phosphorus atoms also segregated on copper clusters, dislocations, grain boundaries, and additionally formed phosphorus clusters and atmospheres. Under thermal annealing at 475°C, the irradiation-induced copper-enriched and phosphorus clusters partially dissolved, increasing the copper concentration in the annealed metal, which was significantly lower compared to the unirradiated material. Since most copper atoms after annealing were not contained in the ferritic matrix but in precipitates, the contribution of copper atoms to an increase in the ductile-to-brittle transition temperature under re-irradiation was minimized and so hardening and embrittlement after subsequent post-annealing irradiation were lower than under primary irradiation. [ABSTRACT FROM AUTHOR]

Glassy melt inclusions are unique geological repositories that preserve evidence of the formation and evolution of mantle and crustal-derived magmas. However, the mechanisms responsible for their preservation in slowly cooled crustal rocks remain contentious, in some part due to their small size (commonly < 10 µm) and the technical difficulty in quantifying composition and microstructures. In this work, time-of-flight secondary ion mass spectrometry, transmission electron microscopy and atom probe tomography are used to characterize glassy melt inclusions found in peritectic garnets of a migmatite from the Spanish Betic Cordillera. The glassy melt inclusions coexist in a close spatial relationship with partially to totally crystallized melt inclusions (nanogranitoids). Analyses of the glassy inclusions show a heterogeneous, patchy distribution of Na and K within the glass and along inclusion walls. Nanoscale spherical domains of Al, Fe, K, Na, Cl and Li are also found systematically distributed at inclusion edges, and are interpreted to represent pre-nucleation clusters. The location and compositional similarity of these clusters with micas and feldspars in nanogranitoids indicate that the glassy inclusions represent former nanogranitoids "captured" at an earlier stage of crystallization, suggesting a likely common origin for both the glassy inclusions and nanogranitoids. A comparison between the composition of melt inclusions with previously published data reveals that preserved glassy inclusions contain significant less H2O (av. 2.72 wt%) than nanogranitoids (average of 6.91 wt%). This suggests the low-H2O content representing a further impediment to crystallization, along with the very small volume of these cavities, favouring the coexistence of glassy inclusions and nanogranitoids. In contrast, crystal nucleation is enhanced in more hydrous melts, where H2O reduces melt viscosity and promotes diffusion. [ABSTRACT FROM AUTHOR]

The geometry and composition of deformation-related low-angle boundaries in naturally deformed olivine were characterized by electron backscattered diffraction (EBSD) and atom probe tomography (APT). EBSD data show the presence of discrete low-angle tilt boundaries, which formed by subgrain rotation recrystallisation associated with the (100)[001] slip system during fluid-catalysed metamorphism and deformation. APT analyses of these interfaces show the preferential segregation of olivine-derived trace elements (Ca, Al, Ti, P, Mn, Fe, Na and Co) to the low-angle boundaries. Boundaries with < 2° show marked enrichment associated with the presence of multiple, non-parallel dislocation types. However, at larger disorientation angles (> 2°), the interfaces become more ordered and linear enrichment of trace elements coincides with the orientation of dislocations inferred from the EBSD data. These boundaries show a systematic increase of trace element concentration with disorientation angle. Olivine-derived trace elements segregated to the low-angle boundaries are interpreted to be captured and travel with dislocations as they migrate to the subgrain boundary interfaces. However, the presence of exotic trace elements Cl and H, also enriched in the low-angle boundaries, likely reflect the contribution of an external fluid source during the fluid-present deformation. The observed compositional segregation of trace elements has significant implications for the deformation and transformation of olivine at mantle depth, the interpretation of geophysical data and the redistribution of elements deep in the Earth. The observation that similar features are widely recognised in manufactured materials, indicates that the segregation of trace elements to mineral interfaces is likely to be widespread. [ABSTRACT FROM AUTHOR]

Rigorous electrostatic modeling of the specimen electrode environment is required to better understand the fundamental processes of atom probe tomography (APT) and guide the analysis of APT data. We have developed a simulation tool that self-consistently solves the nonlinear electrostatic Poisson equation along with the mobile charge carrier concentrations and provides a detailed picture of the electrostatic environment of APT specimen tips. We consider cases of metals, semiconductors, and dielectrics. Traditionally in APT, and regardless of specimen composition, the apex electric field E apex has been approximated by the relation E apex = S V / (k r) , which was originally derived for sharp, metallic conductors; we refer to this equation as the "K-factor approximation". Here, SV is tip-electrode bias, r is the radius of curvature of the tip apex, and k is a dimensionless fitting parameter with 1.5 < k < 8.5 . As expected, our Poisson solver agrees well with the k-factor approximation for metal tips; it also agrees remarkably well for semiconductor tips-regardless of the semiconductor doping level. We ascribe this finding to the fact that even if a semiconductor tip is fully depleted of majority carriers under the typical SV conditions used in APT, an inversion layer will appear at the apex surface. The inversion forms a thin, conducting layer that screens the interior of the tip, thus mimicking metallic behavior at the apex surface. By contrast, we find that the k-factor approximation yields a very poor representation of the electrostatics of a purely dielectric tip. We put our numerical results into further context with a brief discussion of our own separate work and the results of other publications. [ABSTRACT FROM AUTHOR]

Hydrogen embrittlement of Ti6Al4V alloy was investigated under electrochemical cathodic hydrogen charging. Advanced surface treatment and material characterisation, laser shock peening (LSP) or laser peening (LP), atom probe tomography, slow strain rate tensile (SSRT) test, and XRD residual stress are employed for analysis. Results obtained exposed the opportunity to implement surface treatment for controlling hydrogen embrittlement. Induced grain refinement and compressive residual stress restrict the hydrogen uptake in Ti6Al4Valloy. Furthermore, APT results gave wt. % of TiH (titanium hydride) in laser peened hydrogen charged and untreated hydrogen-charged specimens. Thus, it is concluded that compressive stress induced by laser peening process controlled uptake of hydrogen by Ti6Al4V alloy. [ABSTRACT FROM AUTHOR]

The interaction of trace elements, fluids and crystal defects plays a vital role in a crystalline material's response to an applied stress. Fluid inclusions are typically known to facilitate crystal-plastic deformation in minerals. Herein we discuss a model of fluid hardening, whereby dislocations are pinned at fluid inclusions during crystal-plastic deformation, initiating pipe diffusion of trace elements from the fluid inclusions into crystal defects that leads to their stabilization and local hardening. We derive this hypothesis from atom probe tomography data of naturally deformed pyrite, combined with electron backscatter diffraction mapping, electron channelling contrast imaging and scanning transmission electron microscopy. The 2D and 3D micro- to nanoscale structural and chemical data reveal nanoscale fluid inclusions enriched in As, O, Na and K that are linked by As-enriched dislocations. Our efforts advance the understanding of the interplay between nanostructures and impurities during relatively low temperature deformation, which yields insight into the larger scale mass transfer processes on Earth. [ABSTRACT FROM AUTHOR]

The paper reports the results of the ion irradiation impact on a monocrystalline tungsten alloy, W–6Re. This material is considered for use in the design of fusion reactors. Irradiation was carried out in order to simulate radiation effects and analyze the radiation resistance of the fusion reactor material. Specimens were irradiated with 5.6 MeV Fe ions at 500°C up to a maximum damage dose of 8 dpa. Microstructure of W–6Re was analyzed before and after irradiation. It is shown with transmission electron microscopy that the formation of structural defects, dislocation loops with sizes of 2–15 nm and a number density of 1.2 × 1023 m–3 occurs as a result of irradiation. Detailed analysis by atomic probe tomography microscope revealed the decomposition of the solid solution with the formation of nanoscale segregations enriched in rhenium by 18 at %. The radiation-induced hardening of the irradiated layer is determined by nanoindentation. The strength increment was 1.6 GPa. [ABSTRACT FROM AUTHOR]

In this paper, the results of study of the AlCoCrFeNi high-entropy alloy by means of atom probe tomography are presented. Two phases were found, one enriched in Fe and Cr and the other enriched in Ni and Al. Owing to the complex surface morphology and spatial configuration of the phases, they were analyzed by various statistical methods. The Fe–Cr phase has a honeycomb structure that contains Co particles with the characteristic size of ~10 nm. The enrichment of the cell boundaries in Fe and Cr atoms reaches 50 at %. In turn, the Al–Ni phase is enriched in each of these elements up to 30 at % and contains nanoscale precipitates of Fe and Cr atoms. The volume density of these clusters is ~5 × 1022 cm–3. [ABSTRACT FROM AUTHOR]

We report a unique in situ instrument development effort dedicated to studying gas/solid interactions relevant to heterogeneous catalysis and early stages of oxidation of materials via atom probe tomography and microscopy (APM). An in situ reactor cell, similar in concept to other reports, has been developed to expose nanoscale volumes of material to reactive gas environments, in which temperature, pressure, and gas chemistry are well controlled. We demonstrate that the combination of this reactor cell with APM techniques can aid in building a better mechanistic understanding of resultant composition and surface and subsurface structure changes accompanying gas/surface reactions in metal and metal alloy systems through a series of case studies: O2/Rh, O2/Co, and O2/Zircaloy-4. In addition, the basis of a novel operando mode of analysis within an atom probe instrument is also reported. The work presented here supports the implementation of APM techniques dedicated to atomic to near-atomically resolved gas/surface interaction studies of materials broadly relevant to heterogeneous catalysis and oxidation. [ABSTRACT FROM AUTHOR]

Atom probe tomography (APT) with high sensitivity and spatial resolution was applied to study the elemental distributions in spheroidal graphite in ductile iron. A specimen of quenched ductile iron with some graphite nodules in direct contact with liquid phase was used in this study to understand the role of alloying elements in spheroidal graphite formation. Compositional analysis was performed at the graphite/matrix interface and graphite/nuclei interface using APT and EDX (energy-dispersive X-ray). Distributions of various alloying elements at interfaces were obtained. Compositional gradients were observed at both the graphite/liquid interface and the graphite/nuclei interface. The spheroidal graphite nuclei were differentiated as the complex compound made of oxide, nitride and sulfide. The graphite–nuclei interface was shown to be semi-coherent/incoherent using the transmission electron microscopy, with a high density of crystallographic defects and high curvatures in the graphite basal planes growing off the nuclei. Intercalation of large nodulizing elements within and in between the graphite basal planes may account for the spherical morphology of the graphite in ductile irons. [ABSTRACT FROM AUTHOR]

The precipitation of a suitable amount of Cu phase is the key to the antibacterial performance of Cu-containing antibacterial stainless steel. In order to study the precipitation behavior of Cu in ferritic stainless steel, the nucleation rate–temperature curve and phase transition kinetics curve of the Cu-rich phase were calculated theoretically. The distribution, size, and composition of Cu precipitates were characterized, and the distributions of Ni and Mn in the Cu precipitates at different annealing times were also analyzed by atom probe tomography and transmission electron microscopy. The crystal structure of the Cu precipitates was observed by high-resolution electron microscopy. With an increase in annealing temperature, the nucleation rate decreases and the time for nucleation of Cu precipitates increases monotonously. Accordingly, the size of the Cu-rich phase increases, and the number density decreases with increasing annealing time. Moreover, the contents of Ni and Mn gradually increase, and the Ni and Mn atoms aggregate on the surface of the Cu-rich phase. When the steel is annealed for 60 s, the Cu precipitate in the ferrite matrix exhibits a 9R structure with multiple twins. [ABSTRACT FROM AUTHOR]

We used atom probe tomography to complement electron microscopy for the investigation of spinodal decomposition in alkali feldspar. To this end, gem-quality alkali feldspar of intermediate composition with a mole fraction of a K = 0.43 of the K end-member was prepared from Madagascar orthoclase by ion-exchange with (NaK)Cl molten salt. During subsequent annealing at 550 ∘ C and close to ambient pressure the ion-exchanged orthoclase unmixed producing a coherent lamellar intergrowth of Na-rich and K-rich lamellae. The chemical separation was completed, and equilibrium Na–K partitioning between the different lamellae was attained within four days, which was followed by microstructural coarsening. After annealing for 4 days, the wavelength of the lamellar microstructure was ≈ 17 nm and it increased to ≈ 30 nm after annealing for 16 days. The observed equilibrium compositions of the Na-rich and K-rich lamellae are in reasonable agreement with an earlier experimental determination of the coherent solvus. The excess energy associated with compositional gradients at the lamellar interfaces was quantified from the initial wavelength of the lamellar microstructure and the lamellar compositions as obtained from atom probe tomography using the Cahn–Hilliard theory. The capability of atom probe tomography to deliver quantitative chemical compositions at nm resolution opens new perspectives for studying the early stages of exsolution. In particular, it helps to shed light on the phase relations in nm scaled coherent intergrowth. [ABSTRACT FROM AUTHOR]

Zircon microcrystals are found in many planetary crustal rocks and nanoscale research on grains from well-characterized impact environments on Earth provide a baseline for reconstructing extreme shock and thermal histories elsewhere. However, using zircon to date large impact events can be challenging given that shock-related isotopic re-setting of U–Pb ratios, when measured at micrometre scale, is often incomplete and difficult to interpret as the underlying Pb migration mechanisms are unclear. To better understand shocked zircon U–Pb systematics, we performed atom probe tomography and electron microscopy with the previous SIMS analyses of two shock metamorphosed Mesoarchean zircon grains from deep (≥ 15 km) beneath the centre of the 2.020 Ga giant Vredefort impact structure. We find evidence of two types of impact-related nanoscale Pb mobility. In one grain, clustering has produced ~ 10 nm diameter bodies of radiogenic Pb, unsupported by U and co-located with Al, with an average 207Pb/206Pb ratio of ~ 0.50 (n = 4); the value extant in the grain at the time of impact. Conversely, nearby nanodomains exhibit randomly distributed radiogenic Pb, U and Al and yield 206Pb/238U dates consistent with 100% loss of pre-impact radiogenic Pb atoms during shock metamorphic processes. Notably, domains with multiple Pb clusters occur within micrometres of domains that experienced 100% Pb loss, precluding a uniform radial pattern of thermally-driven Pb diffusion at the grain scale. These cases of broadly coeval clustering and outward Pb mobility during geologically instantaneous shock metamorphism point to unusually rapid, multi-path diffusion processes within sub-micrometre volumes which, when averaged, yield normally discordant U–Pb dates. The isolation of spatially variable styles of Pb retention and loss at nanoscale amidst classical grain-scale shock microstructures shows promise for recognizing and resolving bombardment histories in planetary crusts using zircon. [ABSTRACT FROM AUTHOR]

Atom probe tomography (ATP) is a technique that has actively been developed in recent years. This method allows one to investigate three-dimensional distributions of chemical elements in various materials with atomic spatial resolution. The raw APT data reconstruction algorithm uses the geometry of evaporated ion trajectories. However, the basic algorithm uses the approximation of rectilinear trajectories of ions moving from the specimen to the detector. In this study, we present the main approaches to adapting and optimizing the basic APT data reconstruction algorithm concerning the mass reconstruction procedure. Methods for taking into account the nonlinear distortions of ion trajectories due to the wide-angle detection system and other features of ion detection in atom probe tomography are demonstrated. Using a titanium alloy (Ti—5Al—2.7Mo—2Zr), we demonstrate that the consideration of the above effects in the reconstruction of ATP data makes it possible to increase the mass resolution, m/Δm50%, of the main peaks of the mass spectrum to 600 and above. In general, the set of performed procedures allows one to achieve a high accuracy of the positioning of the peaks up to 0.01 amu and ensures a significant (more than tenfold) increase in the mass resolution for mass spectrum peaks that are distant from the main peaks. [ABSTRACT FROM AUTHOR]

The study is devoted to the methodology of simulation experiments for the analysis of radiation damage of structural materials of nuclear power plants by irradiation with heavy ions and subsequent analysis with use of the ultramicroscopy and nanoindentation methods. Details of the irradiation experiments in the TIPr accelerator (Institute for Theoretical and Experimental Physics) with ion energy of 101 keV/nucleon are given. Current approaches to the analysis of radiation-induced changes in the structural phase state of samples irradiated with ions with use of transmission electron microscopy and atom probe tomography are demonstrated. Models for the evaluation of radiation hardening based on microscopic changes, as well as the capabilities of the nanoindentation method for direct measurement of the hardening of a specimen layer irradiated by ions, are considered. [ABSTRACT FROM AUTHOR]

High chromium ferritic steels are being used as construction materials for interconnects in solid oxide electrolysis cells (SOEC). Addition of niobium in the range of a few tenths of a percent is suitable for increasing the high-temperature creep strength of this type of ferritic steel. In the present work, the high-temperature isothermal oxidation behavior of a niobium containing ferritic steel at 800 °C was investigated in Ar–4%H2–4%H2O gas simulating the service environment in an SOEC (cathode side) and compared with that of a Nb-free counterpart alloy. Gravimetric data were correlated with the results from microstructural analyses using, among others, scanning and transmission electron microscopy as well as glow discharge optical emission spectroscopy. Atom probe tomography was used for obtaining atomic-scale insight into the segregation processes in external oxides and their interfaces. The oxidation rate was substantially higher for the Nb-containing than for the Nb-free alloy. Both alloys formed double-layered oxide scales consisting of inner chromia and outer MnCr2O4 spinel. Additionally, a thin layer of rutile-type Nb(Ti,Cr)O2 oxide of 200–300 nm thickness was observed at the scale–alloy interface in the Nb-containing steel. Nb addition to the alloy led to its segregation at chromia grain boundaries which affected the diffusion of Cr and other solute species such as Ti, Mn and Si. [ABSTRACT FROM AUTHOR]

Specimens of ChS-139 steel (0.2 С–12 Cr–Ni–Mo–W–Nb–V–N–B) were irradiated up to 6 displacements per atom (dpa) with Fe ions at 250, 300, and 400°C. The radiation-induced clusters and Cottrell atmospheres enriched in Ni, Si, and Mn were revealed in irradiated samples by atom probe tomography. The typical sizes of the radiation-induced clusters were about 2–7 nm, and their number density was about (2–20) × 1023 m–3. It was shown that the highest irradiation temperature (400°C) is compliant with the lowest enrichment of clusters in Ni, Si, and Mn as well as with the largest average size of clusters (~5 nm) and the least number density (~2 × 1023 m–3). A noticeable decrease in the number density of radiation-induced clusters with an increase in the damage dose to 4 dpa at 300°C was found. At the same time, it was shown that the Cr–V–Nb–N clusters found in the initial state dissolve with the increase in the irradiation dose at all considered temperatures. The value of detected radiation-induced effects is indicative of their significant role in the low temperature radiation embrittlement of ChS-139 steel. [ABSTRACT FROM AUTHOR]

Model γ-NiCrAl alloys with and without titanium were oxidized for short times up to 32 h at 1000 °C and subsequently characterized by scanning electron microscopy, transmission electron microscopy, and atom probe tomography in order to clarify the role of Ti on the oxidation behavior of alumina-forming nickel alloys. At the longer oxidation times, Ti was found to have no significant effect on the major protective oxide phases formed and overall scale and individual oxide layer thicknesses. Ti was observed to segregate to interfaces within the scale and form a Ti-rich oxide at the scale surface over time. At the shortest oxidation times before a continuous Al2O3 layer formed, the Ti-containing alloys exhibited thicker Cr2O3 layers, suggesting that Ti accelerates Cr2O3 growth kinetics. Additionally, oxide nodules resulting from fast oxidation of TiN particles were observed on the Ti-containing alloys. These may be linked to increased spalling propensity of Ti-containing alloys. [ABSTRACT FROM AUTHOR]

GaAs1−xBix has been grown by solid-source molecular beam epitaxy using varying substrate rotation rates. Changes in local bismuth saturation were studied by varying the Bi/Ga pressure ratio across the wafer. Films were grown on both GaAs and InGaAs buffer layers with varying indium content to change the strain conditions of the bismide layer and the out-of-plane growth rate. All samples demonstrated vertical composition modulations with a period of ∼ 4 nm that tracked with the rate of growth per substrate rotation cycle. The thermal stability of these composition modulations was shown to behave similarly to bulk GaAsBi. Bismide composition modulations are attributed to the low growth temperature and the varying Bi/Ga pressure ratio across the sample rather than the varying V/III ratio. [ABSTRACT FROM AUTHOR]

Low-temperature radiation hardening of prospective structural steel Eurofer 97 as the material for the first wall of the DEMO fusion reactor is studied in this work. Specimens of Eurofer 97 steel were irradiated with Fe ions up to 10 dpa at temperatures of 250, 300 and 400°C. Irradiated samples were studied by transmission electron microscopy and atom probe tomography. TEM study of irradiated samples showed preferential formation of dislocation loops at all temperatures of irradiation. Pair-correlation function analysis detected the initial stage of matrix solid solution decomposition of Eurofer 97 steel only at the temperature of 400°C. Detected microscopic changes and calculated hardening in the framework of the DBH (dispersed barrier hardening) model have shown that formation of dislocation loops is the main origin of low temperature radiation hardening of Eurofer 97 under irradiation with Fe ions with fluence up to 10 dpa. [ABSTRACT FROM AUTHOR]

Bimetallic alloys are increasingly used in heterogeneous catalysis because the synergistic effects between the two metals may create more efficient catalysts. As an example, a dilute amount of Ag within an Au catalyst allows to obtain a low temperature activity together with a large selectivity for selective oxidation reactions. In this context, we present a systematic study of segregations occurring on Au-8.8 at.% Ag samples by atom probe tomography (APT). The samples are prepared as sharp tips representing a single nanoparticle of catalyst. The segregation behaviours are studied by exposing the catalyst to unreactive (Ar), oxidative (O2 and N2O) and reductive (H2) atmospheres at different temperature (323, 373 and 473 K). With a dedicated reaction-cell mounted on the APT system, the exposure conditions are close to the operating conditions of applied formulations of the catalyst. The segregation lead to important surface composition changes, e.g. from Au91.2-Ag8.8 to Ag84-Au16. The obtained results highlight the presence of different Ag segregation behaviours due to surface diffusion after O2 exposure, and due to bulk diffusion after N2O exposure: the different dissociation properties of these two gases explain the different segregation behaviour. Gold segregation was also identified after sample treatments in H2 gas. These results are promising for the engineering of catalysts since it would be possible to design the surface composition by applying different treatments to the sample, therefore allowing a better control on the activity and selectivity of such designed catalysts.Graphical Abstract: [ABSTRACT FROM AUTHOR]

The need for a sustainable energy supply in the face of depleting oil reserves has reignited the importance of Fischer-Tropsch (FT) synthesis technology. Presently, the FT process is practiced at the industrial scale to predominately produce synthetic diesel-type fuels and lubricants. More recently, the possibility of hydrogenating CO toward oxygenates, and not just hydrocarbons, has been explored. We have developed a series of CoCuMn and CoMnK catalysts prepared via the oxalate co-precipitation route that are capable of forming oxygenates with desirable selectivity. Upon H2-assisted thermal decomposition of the resultant mixed metal Co1Cu1Mn1 oxalates, catalysts naturally exhibited a cobalt core-copper shell configuration with Mn5O8 dispersed throughout the catalyst nanoparticle as determined via Atom Probe Tomography (APT). We suggest structural changes are induced by the CO and H2 reactants to form the catalytically active phase under real-time reaction conditions as demonstrated by corroborative Density Functional Theory calculations and experimental evidence. APT studies also show that a Co4Mn1K0.1 catalyst post reaction contained a cobalt carbide phase as determined from a Co/C ratio of 2/1. Manganese and potassium were found only in the outermost part of the particle. Both catalysts were found to contain the presence of a Mn5O8 oxidic phase before and post reaction which we attribute to the high activity toward oxygenates of these two catalysts. [ABSTRACT FROM AUTHOR]

We study the possibilities of the chemical analysis of materials with determination of the positions of individual atoms of various chemical elements in a sample using an APPLE-3D atom probe tomograph with femtosecond-laser assisted evaporation, developed at the Institute of Theoretical and Experimental Physics of the National Research Center “Kurchatov Institute.” The results of investigations of ferritic-martensitic steels and an aluminum alloy are presented; the characterization and visualization of features with a size on the order of 10 nm are demonstrated. [ABSTRACT FROM AUTHOR]

The oxidation response and microstructural evolution of an Inconel 625 alloy exhaust manifold exposed to an automobile racing environment has been examined using a range of advanced electron microscopy-based techniques, atom probe tomography and high-sensitivity laser ablation mass spectrometry. The dynamic, corrosive gas conditions result in accelerated oxidation, with the inner exhaust surface also heavily contaminated by multiple species including Zn, P, K and Na. Nb carbides and Ti nitrides identified in stock control samples evolve into mixed (Ti, Nb)N species during exposure, decorated by smaller Mo, Si-rich precipitates. The exposed alloy component therefore reveals unique surface and subsurface features following in-service use. [ABSTRACT FROM AUTHOR]

The chemical element distributions and the fine structure were studied using atom probe tomography in ChS-139 steel (Fe-12Cr-Nb-Mo-W-V-N-B) after conventional heat treatment (normalizing at 1190°C for 25 s and subsequent tempering at 720°C for 2 h) and after subsequent Fe ion irradiation at room temperature up to the damage doses of 8 and 16 displacements per atom (dpa). A large number of nanosized clusters (~1023 m−3) enriched in chromium, vanadium, nitrogen, and niobium were found throughout the Ch-139 steel after conventional heat treatment. The chemical element distribution in the M23C6 carbide, Nb2(C, N) and M6(C, N) carbonitride phases, pre-precipitates of M6X carbide phases, and the Cottrell atmosphere were studied. The changes in the cluster composition and sizes resulting from irradiation at room temperature were found. An increase in the cluster sizes upon irradiation was accompanied by a reduction in the concentrations of chromium, vanadium, nitrogen, and niobium. [ABSTRACT FROM AUTHOR]

Atom probe tomography (APT) analysis with a femtosecond laser is one of the most promising techniques to characterize local variations of chemical distribution in materials with subnanometer spatial resolution. In this study, the effect of APT analysis conditions on the accuracy of data recovery for chromium steels and Fe-Cr alloys is investigated. Dependences of mass resolving power and the detected composition of chromium as a function of laser power, specimen geometry, and evaporation rate are presented. [ABSTRACT FROM AUTHOR]

It is widely accepted that the growth of protective α-AlO scales on Ni-based alloys is governed by the inward diffusion of oxygen through the oxide grain boundaries (GB). However, there is also some outward diffusion of metal ions to the surface, but it is difficult to quantify. In this work we apply atomic force microscopy, scanning electron microscopy and transmission electron microscopy to investigate the outward flux of Al, which manifests as the growth of small ridges along the alumina GBs after the removal of the outermost oxide layer by mechanical polishing or focused ion beam techniques followed by additional oxidation. As a model alumina-former, NiAl with Hf and Zr additions was investigated. In comparison to Zr, Hf was found to reduce the outward Al diffusion. This outward diffusion was six orders of magnitude smaller than the O inward diffusion. [ABSTRACT FROM AUTHOR]

The atom probe tomography of the nanostructure evolution in ODS Eurofer, ODS 13.5Cr, and ODS 13.5Cr-0.3Ti steels under heavy ion irradiation at 300 and 573 K is performed. The samples were irradiated by 5.6 MeV Fe ions and 4.8 MeV Ti ions to a fluence of ~10 cm. It is shown that the number of nanoclusters increases by a factor of 2-3 after irradiation. The chemical composition of the clusters in the steels changes after irradiation at 300 K, whereas the chemical composition of the clusters in the 13.5Cr-0.3Ti ODS steel remains the same after irradiation at 573 K. [ABSTRACT FROM AUTHOR]

Ni-Cr-Mo low alloy steels are being considered as alternative materials to replace the Mn-Mo-Ni low alloy steels used in reactor pressure vessels in nuclear power plants, because of their higher strength and toughness. However, the neutron irradiation occurring during reactor operation causes degradation of Ni-Cr-Mo low alloy steel. In this study, irradiation-induced clusters in a Ni-Cr-Mo model alloy irradiated in the High-flux advanced neutron application reactor (HANARO) research reactor were investigated via Atom probe tomography (APT). The irradiated specimens showed irradiation-induced hardening and embrittlement. The neutron irradiation caused Si clustering, and these spherical clusters were homogeneously distributed within the matrix. Ni was also clustered at the Si clusters. However, the other elements did not clearly exhibit clustering behavior. Si and Ni atoms were also located at the dislocations. To quantify the nano-sized clusters, a method based on the Density-based spatial clustering of applications with noise (DBSCAN) algorithm was implemented. The total number of clusters was calculated to be ~7 × 10 n/nm and the average cluster radius was less than 2 nm. The APT approach was demonstrated to be well suited for discovering the irradiation defect structures. [ABSTRACT FROM AUTHOR]

We report on the oxidation behavior of AlN/CrN multilayers at 900 °C, deposited by radio frequency magnetron sputtering. It is shown that oxidation in this system is controlled by diffusion of Cr towards the surface and formation of CrO. Cr diffusion is found to mainly occur along grain boundaries. Thus, coherent cubic AlN/CrN multilayer regions with coarse columnar grain structures are found to be oxidation resistant, whereas regions decomposed into hexagonal AlN/cubic CrN are prone to oxidation. [ABSTRACT FROM AUTHOR]

We address the competitive precipitation and coprecipitation of three types of secondary phases, i.e., Cu-rich precipitates (CRPs), reverted austenite (RA), and alloyed carbide, in a high-strength low-alloy steel with austenite reversion treatment at 675 °C by using electron back-scatter diffraction, transmission electron microscopy, and atom probe tomography. There is a strong competitive diffusion of Ni and Cu participating in austenite reversion and Cu precipitation with the fact that no CRPs are detected in and around the RA. Meanwhile, there is also a strong competitive diffusion of austenite stabilizing element Ni and carbide-forming elements Cr and Mo into the pre-existing C-rich zone, leading to the formation of nonequilibrium alloyed carbide deviating from the stoichiometric composition. On the other hand, the alloyed carbide and CRPs provide constituent elements for each other and make the coprecipitation thermodynamically favorable. The knowledge on the interactive formation of these three features provides versatile access to tailor the distributional morphology of CRPs, RA, and alloyed carbide via a multistage heat treatment and thus realize their beneficial effect on strength and toughness. [ABSTRACT FROM AUTHOR]

Atom probe tomography and transmission electron microscopy are used to analyze magnetron-sputtered MoS2 films containing Ti and Au/Sb2O3 as a model system for tribological coatings. Transmission electron microscopy characterization showed that the Ti–MoS2 film is dense and featureless whereas Sb2O3/Au–MoS2 film is less dense and have columnar morphology. Three-dimensional atom probe reconstructions revealed that the Ti–MoS2 films have a homogeneous composition and contain about 15 at.% Ti, which is uniformly distributed throughout the MoS2 matrix without any evidence of Ti precipitation. Sb2O3/Au–MoS2 films also showed homogeneous distribution of Sb2O3 throughout the MoS2 matrix and the presence of Au-rich precipitates. The complementary techniques of atom probe tomography and transmission electron microscopy indicate that Ti and Sb2O3 incorporation in the deposition of MoS2 produces amorphous microstructures, whereas the addition of Au forms nano-sized and well-dispersed precipitates. [ABSTRACT FROM PUBLISHER]

Environmental control during transfer between instruments is required for samples sensitive to air or thermal exposure to prevent morphological or chemical changes prior to analysis. Atom probe tomography is a rapidly expanding technique for three-dimensional structural and chemical analysis, but commercial instruments remain limited to loading specimens under ambient conditions. In this study, we describe a multifunctional environmental transfer hub allowing controlled cryogenic or room-temperature transfer of specimens under atmospheric or vacuum pressure conditions between an atom probe and other instruments or reaction chambers. The utility of the environmental transfer hub is demonstrated through the acquisition of previously unavailable mass spectral analysis of an intact organic molecule made possible via controlled cryogenic transfer into the atom probe using the hub. The ability to prepare and transfer specimens in precise environments promises a means to access new science across many disciplines from untainted samples and allow downstream time-resolved in situ atom probe studies. [ABSTRACT FROM AUTHOR]

The enhancement of the performance of advanced nitride-based optoelectronic devices requires the fine tuning of their composition, which has to be determined with a high accuracy and at the nanometer scale. For that purpose, we have evaluated and compared energy dispersive X-ray spectroscopy (EDX) in a scanning transmission electron microscope (STEM) and atom probe tomography (APT) in terms of composition analysis of AlGaN/GaN multilayers. Both techniques give comparable results with a composition accuracy better than 0.6 % even for layers as thin as 3 nm. In case of EDX, we show the relevance of correcting the X-ray absorption by simultaneous determination of the mass thickness and chemical composition at each point of the analysis. Limitations of both techniques are discussed when applied to specimens with different geometries or compositions. [ABSTRACT FROM AUTHOR]

Considered in the article, α'-phase growth and coagulation stages under 500°С thermal aging of Fe-22% Cr binary alloy have been investigated on the atomic scale level, with atom probe tomography being applied. α'-phase appearing precipitates are shown to be separated in space. In addition, after 100-hour thermal aging the nucleation stage evolves into the growth and coagulation stage of α'-phase precipitates, with their number density being decreased simultaneously. Deviation of time dependences from Lifshitz-Slezov theory is revealed in Fe-22% Cr supersaturated solid solution alloy. [ABSTRACT FROM AUTHOR]

An Fe–0.26C–1.96Si–2Mn with 0.31Mo (wt%) steel was subjected to a novel thermomechanical processing route to produce fine ferrite with different volume fractions, bainite, and retained austenite. Two types of fine ferrites were found to be: (i) formed along prior austenite grain boundaries, and (ii) formed intragranularly in the interior of austenite grains. An increase in the volume fraction of fine ferrite led to the preferential formation of blocky retained austenite with low stability, and to a decrease in the volume fraction of bainite with stable layers of retained austenite. The difference in the morphology of the bainitic ferrite and the retained austenite after different isothermal ferrite times was found to be responsible for the deterioration of the mechanical properties. The segregation of Mn, Mo, and C at distances of 2–2.5 nm from the ferrite and retained austenite/martensite interface on the retained austenite/martensite site was observed after 2700 s of isothermal hold. It was suggested that the segregation occurred during the austenite-to-ferrite transformation, and that this would decrease the interface mobility, which affects the austenite-to-ferrite transformation and ferrite grain size. [ABSTRACT FROM AUTHOR]

The initial stage of phase separation of binary Fe-22 at % Cr alloy during thermal aging at 500°C is studied at the atomic-scale level by atom probe tomography. Upon the behavior analysis of pair-correlation function of chromium atoms, long-range correlations typical of spinodal decomposition are observed at short aging times, which disappear 25 h after aging. The analysis of 3D atomic maps shows that Cr-rich regions form at the initial steps of decomposition, where the chromium concentration increases with an increase in the aging time. At the aging time of ~100 h, the chromium concentration in the center of these regions reaches 80 at %, which corresponds to the α' phase. [ABSTRACT FROM AUTHOR]

The characterization of ZnO nanowires is crucial for developing nanostructured devices together with related compounds and alloys with an atomic-scale regime. This study describes the effects of laser energy on the atom probe tomography analysis of a single ZnO nanowire with a high aspect ratio, diameters of 80?100 nm and lengths of 10 µm. We observed both an asymmetrical evolution in the apex morphology and the compositional nonuniformities of Zn and O ions with respect to the laser energies ranging from 5 to 40 nJ. When the higher laser illumination exposed to the ZnO nanowires, non-uniform field strength becomes noticeable especially at the laser incident side of the samples. Moreover, we measured the charge state ratios of Zn and Zn ions as a function of the applied laser energies. Our results proved important for accurate quantitative characterization and better interpretation for the laser-pulsed atom probe tomography of ZnO-based devices. [ABSTRACT FROM AUTHOR]