Search

Green energy collection is crucial for achieving future net‐zero carbon emissions, with energy harvesting being a key solution. Silicon, a widely used p‐type semiconductor doped with boron ions, is prevalent in modern electronics. However, the impact of lattice boundaries from ion implantation doping on thermoelectric properties remains underexplored. A heavily boron‐doped silicon layer is used to enhance thermoelectric performance. The layers, formed on silicon, exhibit epitaxial crystal structures under all doping conditions using an ion implantation system. Transmission electron microscopy and atom probe tomography reveal that boron interstitial structures create boundaries in the silicon lattice. These boundaries effectively reduce the thermal conductivity of boron‐doped silicon compared to intrinsic silicon. At 372.76 K, the best power factor of the heavily boron‐doped silicon layer is 3.05 mW/m·K2, obtained at an implant dose of 1016 cm−2. This study demonstrates the raised electrical conductivity is induced by effectively substituting silicon with boron atoms, and the reduced thermal conductivity is caused by boron interstitial‐formed boundaries in silicon. These findings highlight the potential of heavily boron‐doped silicon in improving thermoelectric materials and advancing energy‐efficient technologies. [ABSTRACT FROM AUTHOR]

The design of a Cd‐free and wider‐bandgap buffer layer is stringent for future Cu(In,Ga)Se2 (CIGSe) thin‐film solar cell applications. For that, an In2S3 buffer layer alloyed with a limited amount of O (well below 25 mol%) has been proposed as a pertinent alternative solution to CdS or Zn(O,S) buffers. However, the chemical stability of the In2S3/CIGSe heterointerface when O is added is not completely clear. Therefore, in this work, the buffer/absorber interface for a series of sputter‐deposited In2S3 buffers with and without O is investigated. It is found that the solar cell with the highest open‐circuit voltage is obtained for the O‐free In2S3 buffer sputtered at 220 °C. This improved open‐circuit voltage could be explained by the presence of a 20 nm‐thick ordered vacancy compound (OVC) at the absorber surface. A much thinner OVC layer (5 nm) or even the absence of this layer is found for the cell with In2(O0.25S0.75)3 buffer layer where O is inserted. The volume fraction of the OVC layer is directly linked with the magnitude of Cu diffusion from the CIGSe surface into the In2(OxS1−x)3 buffer layer. The O addition strongly reduces the Cu diffusion inside the buffer layer up to complete suppression for very high O contents in the buffer. Finally, it is discussed that the presence of the OVC layer may lower the valence band maximum, thereby forming a hole barrier, suppressing charge carrier recombination at the In2(OxS1−x)3/CIGSe interface, which could result in an increased open‐circuit voltage. [ABSTRACT FROM AUTHOR]

Main‐group chalcogenides show outstanding performance for phase‐change data storage and thermoelectric energy conversion applications. A common denominator for these different property requirements is ascribed to the metavalent bonding (MVB) mechanism. Atom probe tomography (APT) provides a unique way to distinguish MVB from other bonding mechanisms by determining the bond‐breaking behavior. Specifically, an unusually high probability to dislodge several fragments upon one successful laser pulse (probability of multiple events [PME]) is found in metavalently bonded crystalline phase‐change and thermoelectric materials. In contrast, amorphous phase‐change materials and poor thermoelectrics usually show lower PME values. This indicates that the large optical and electrical contrast between the crystalline and amorphous chalcogenides is attributed to a transition of chemical bonding. A strong correlation between high thermoelectric performance and large PME is also established. Besides, APT can investigate structural defects on the subnanometer scale. These characteristics reveal the interdiffusion of elements in interfacial phase‐change materials and revisit its switching mechanism. The complex role of structural defects such as grain boundaries in tuning the thermoelectric properties can also be unraveled by investigating the local composition and bonding mechanism at defects. This review demonstrates that APT is a powerful technique for designing phase‐change and thermoelectric materials. [ABSTRACT FROM AUTHOR]

In the quest for lightweight high‐performance metallic materials in transportation, the limitations of high‐strength Al‐based alloys in high‐temperature (HT) applications have posed a significant challenge. To overcome this long‐standing bottleneck, an innovative design strategy, combining entropy‐driven compositional design and rapid solidification processing, to develop "Al‐based superalloys" with a γ/γ′ duplex microstructure reminiscent of Ni‐based superalloys is presented. By incorporating multirefractory elements (Ti, Zr, Hf, Nb, and Ta) into the alloy design, a high‐volume fraction of thermally stable coherent γ′ phase for strengthening the Al‐rich face‐centered cubic matrix from room temperature (RT) to temperatures close to the melting point is achieved. The developed Al‐based superalloys exhibit exceptional specific yield strength and specific Young's modulus, surpassing aerospace aluminum, cobalt, nickel, and titanium alloys from RT to HT. Moreover, our ultra‐strong alloys demonstrate deformability and exhibit fine‐dimpled fracture behavior. The versatility of our fundamental research on Al‐based superalloys demonstrates their potential and can inspire further research in this field. This work opens new possibilities for the development of next‐generation lightweight alloys with novel microstructures and outstanding mechanical properties. [ABSTRACT FROM AUTHOR]

Understanding crystal characteristics down to the atomistic level increasingly emerges as a crucial insight for creating solid state platforms for qubits with reproducible and homogeneous properties. Here, isotope concentration depth profiles in a SiGe/28Si/SiGe heterostructure are analyzed with atom probe tomography (APT) and time‐of‐flight secondary‐ion mass spectrometry down to their respective limits of isotope concentrations and depth resolution. Spin‐echo dephasing times T2echo=128μs$T_2^\mathbf {echo}=128 \,\umu\mathrm{s}$ and valley energy splittings EVS around 200μeV$200 \,\umu\mathrm{e\mathrm{V}}$ have been observed for single spin qubits in this quantum well (QW) heterostructure, pointing toward the suppression of qubit decoherence through hyperfine interaction with crystal host nuclear spins or via scattering between valley states. The concentration of nuclear spin‐carrying 29Si is 50 ± 20ppm in the 28Si QW. The resolution limits of APT allow to uncover that both the SiGe/28Si and the 28Si/SiGe interfaces of the QW are shaped by epitaxial growth front segregation signatures on a few monolayer scale. A subsequent thermal treatment, representative of the thermal budget experienced by the heterostructure during qubit device processing, broadens the top SiGe/28Si QW interface by about two monolayers, while the width of the bottom 28Si/SiGe interface remains unchanged. Using a tight‐binding model including SiGe alloy disorder, these experimental results suggest that the combination of the slightly thermally broadened top interface and of a minimal Ge concentration of 0.3$0.3$% in the QW, resulting from segregation, is instrumental for the observed large EVS=200μeV$E_\mathrm{VS}=200 \,\umu\mathrm{e\mathrm{V}}$. Minimal Ge additions <1%, which get more likely in thin QWs, will hence support high EVS without compromising coherence times. At the same time, taking thermal treatments during device processing as well as the occurrence of crystal growth characteristics into account seems important for the design of reproducible qubit properties. [ABSTRACT FROM AUTHOR]

Pressureless sintering processing was adopted to fabricate transparent aluminum oxynitride (AlON) ceramics by using magnesium oxide (MgO) as a sintering additive into synthetic single phased aluminum oxynitride powder. Under the condition of adding 0.6 wt% magnesium oxide, the relative density of aluminum oxynitride ceramics increased from 98.67% with no addition to 99.9% after being held at 1800°C for 24 h, coupled by a reducing of average grain size from 190 µm to 130 µm. The optical linear transmittance of the AlON ceramic sample (thickness 1.2 mm) reached 84.2% at the wavelength of 1100 nm. The microstructural characterizations by energy dispersive spectroscopy and atom probe tomography indicated that the doping Mg element was uniformly dispersed inside aluminum oxynitride grains of as‐sintered ceramics. It was demonstrated that magnesium oxide played a key role in inhibiting the movement of grain boundaries, eliminating pores, leading to the fully densification of aluminum oxynitride ceramics. [ABSTRACT FROM AUTHOR]

An atomic‐scale understanding of how electrocatalyst surfaces reconstruct and transform during electrocatalytic reactions is essential for optimizing their activity and longevity. This is particularly important for the oxygen evolution reaction (OER), where dynamic and substantial structural and compositional changes occur during the reaction. Herein, a multimodal method is developed by combining X‐ray fine structure absorption and photoemission spectroscopy, transmission electron microscopy, and atom probe tomography with electrochemical measurements to interrogate the temporal evolution of oxidation states, atom coordination, structure, and composition on Co2MnO4 and CoMn2O4 cubic spinel nanoparticle surfaces upon OER cycling in alkaline media. Co2MnO4 is activated at the onset of OER due to the formation of ≈2 nm Co‐Mn oxyhydroxides with an optimal Co/Mn ratio of ≈3. As OER proceeds, Mn dissolution and redeposition occur for the CoMn oxyhydroxides, extending the OER stability of Co2MnO4. Such dynamic dissolution and redeposition are also observed for CoMn2O4, leading to the formation of less OER‐active Mn‐rich oxides on the nanoparticle surfaces. This study provides mechanistic insights into how dynamic surface reconstruction and transformation affect the activity and stability of mixed CoMn cubic spinels toward OER. [ABSTRACT FROM AUTHOR]

Dopant‐induced microstructure in thermoelectric materials significantly affects thermoelectric properties and offers a potential to break the interdependence between electron and phonon transport properties. However, identifying all‐scale dopant‐induced microstructures and correlating them with thermoelectric properties remain a huge challenge owing to a lack of detailed microstructural characterization encompassing all length scales. Here, the hierarchical boron (B)‐induced microstructures in B‐doped Si80Ge20 alloys with different B concentrations are investigated to determine their precise effects on thermoelectric properties. By adopting a multi‐scale characterization approach, including X‐ray diffraction, scanning and transmission electron microscopy, and atom probe tomography, five distinctive B‐induced phases within Si80Ge20 alloys are identified. These phases exhibit different sizes, compositions, and crystal structures. Furthermore, their configuration is comprehensively determined according to B doping concentrations to elucidate their consequential impact on the unusual changes in carrier concentration, density‐of‐states effective mass, and lattice thermal conductivity. The study provides insights into the intricate relationship between hierarchical dopant‐induced microstructures and thermoelectric properties and highlights the importance of investigating all‐scale microstructures in excessively‐doped systems for determining the precise structure‐property relationships. [ABSTRACT FROM AUTHOR]

Herein, the influence of one‐ and two‐step preageing treatments prior to the artificial ageing step to peak age condition for three different 6xxx alloys, from low to high alloy content, is investigated. Analysis of the preaged conditions using atom probe tomography (APT) reveals a broad distribution of Mg and Si clusters, with some instances of Guinier‐Preston I zones present. Additionally, the high alloyed system exhibits a growth of precipitates toward a needle‐like shaped. These clusters formed during the preageing treatment serve as nucleation sites in the subsequent artificial ageing treatment, leading to an increase in hardness. Microstructural analysis conducted using transmission electron microscopy and APT demonstrates a reduction in the average precipitate length and a more narrow size distribution for T6 condition. This indicates that the preageing treatment results in a decreased portion of already overaged precipitates compared to the direct aged condition. Consequently, the more narrow size distribution of the precipitates leads to more effective hardening of the material, as a higher portion of precipitates is at or close to their optimum size. The investigations highlight the significant influence and positive effect of a preageing treatment at lower temperatures on the subsequent artificial ageing treatment. [ABSTRACT FROM AUTHOR]

To detect hydrogen in materials at the atomic scale, atom probe tomography is now regularly used. In order to avoid cumbersome cryo‐preparation to suppress diffusion, often hydrogen is charged only into the finished specimen. Here, the use of hydrogen gas over electrochemical hydrogen has the advantage that the specimen is not contaminated with an electrolyte. So far, this "charging" has been done in large, expensive systems. Here, we introduce small devices that enable the exposure of atom probe specimens to hydrogen and potentially other gases, using only very small gas volumes. This enables the operation in regular laboratory environments without additional safety measures. These devices can be used to expose the specimen to hydrogen up to 10 bar/90°C. Higher temperatures may be attained with small changes. Validation of the success of charging with these setups is demonstrated through experiments employing deuterium charging of palladium atom probe tips. Research Highlights: Enabling the exposure of atom probe specimens to hydrogen and potentially other gases, using only very small gas volumes.Built setups can be assembled with little money and from freely available parts, making specimen charging much easier.Validation of the success of charging with these setups is demonstrated through experiments employing deuterium charging of palladium atom probe tips. [ABSTRACT FROM AUTHOR]

Herein, the potential of using the thermomechanical treatment ausforming to optimize the microstructure of PH 13‐8 Mo maraging steels is investigated. Of particular interest are the effects on the formation of β‐NiAl precipitates and reverted austenite during subsequent aging. Ausforming experiments at deformation temperatures of 400 and 600 °C and strains of 40% and 70% are conducted using a deformation dilatometer. Afterward, the samples are subjected to aging at temperatures varying from 482 to 593 °C. This is followed by a thorough microstructural characterization ranging from light optical microscopy to X‐Ray diffraction and atom probe tomography. The results demonstrate that ausforming effectively refines the microstructure, resulting in a significant increase in hardness. Moreover, it is revealed that the ausforming parameters have a noticeable influence on the number density of β‐NiAl precipitates and the amount of reverted austenite. A well‐balanced microstructure containing relatively fine precipitates and a high amount of reverted austenite can be achieved by ausforming at 600 °C with 40% strain. Overall, the results prove a promising potential of ausforming for PH 13‐8 Mo maraging steels with regard to tailoring optimized microstructures, which could ultimately benefit the aerospace industry where these alloys are used. [ABSTRACT FROM AUTHOR]

Interactions at high temperatures between thin films and the Si substrate limit materials discovery using combinatorial processing platforms (CPPs). To overcome this, a diffusion and reaction barrier, SiO2, by thermal oxidation of Si tips is developed. The application of this diffusion barrier in CPPs for atomic‐scale investigations of new materials in atom probe tomography is reported. Thermal SiO2 layers (20 and 50 nm thick) are examined as barriers to separate coatings from Si tips. Pt is chosen as it easily forms silicides. CPPs are sequentially annealed in vacuum at 400 °C for 10 h, 600 °C for 2 h, and 800 °C for 2 h. The thermal SiO2 diffusion barrier remains stable and prevents intermixing at least up to 800 °C. Moreover, it provides improved film adhesion as dewetting of Pt on the oxide surface occurred at 800 °C instead of 600 °C without a thermal diffusion barrier. A comprehensive structural and chemical analysis of the Pt film, the thermal SiO2 layer, and their interfaces is performed using scanning and transmission electron microscopy, and atom probe tomography. As a result, the thermal SiO2 forms a stable barrier, even at the lowest thickness of 20 nm, avoiding the formation of Pt silicides, even at 800 °C. [ABSTRACT FROM AUTHOR]

In microalloyed steels, interphase precipitation involves the formation of precipitates at the ferrite/austenite interface during their transformation. The study on interphase precipitation has been ongoing since the 1970s and remains highly relevant today. While this metallurgical approach has been applied in various products of advanced steels, its application to cold‐rolled steels is still absent. This study presents a development of cold‐rolled dual‐phase (DP) steels strengthened by interphase‐precipitated carbides. A CALPHAD‐based approach is established to facilitate austenite to ferrite transformation coupled with interphase precipitation during simulated annealing for cold‐rolled DP steels. Further experimental investigations on the effects of V and Mo optimize the alloy composition, and the corresponding nano/microstructures are validated by transmission electron microscopy (TEM) and atom probe tomography. Besides, this work further addresses the impacts of interfacial segregation and microsegregation bands on the capability of interphase precipitation in the studied steels. In summary, this work charts a new pathway for the development of cold‐rolled DP steels strengthened by interphase‐precipitated carbides, advancing the realm of high‐strength steels. [ABSTRACT FROM AUTHOR]

To achieve the desired microstructural properties, the ongoing development and innovation in new structural steels require novel thermal processing. This study aims to improve the mechanical properties of a commercial spring carbon–silicon steel by tailoring its microstructure through a process involving quenching and partitioning (Q&P) followed by bainitic transformation. A two‐stage Q&P process is proposed to generate a nanoscale dispersion of stable retained austenite and carbides within the tempered martensite and bainite microstructure. The resulting tensile properties demonstrate a yield strength of 1280 MPa, an ultimate tensile strength of 1875 MPa, and a total elongation of 8.03%. These values surpass those of conventional spring 9254 steel, highlighting the effectiveness of the thermal treatment design. Microstructure analysis reveals the presence of tempered martensite, bainite sheaves, nanoscale carbides, and aggregates of retained austenite. Moreover, the resulting body‐centered cubic matrix exhibits minimal lattice tetragonality of ≈1.0051, coupled with stable retained austenite featuring a carbon concentration of ≈3.42 ± 0.5 wt%, resulting in outstanding strength–ductility properties. These findings indicate that the proposed two‐stage Q&P process, followed by bainitic transformation, significantly enhances the mechanical properties of carbon–silicon steels, making it a promising candidate for high‐performance spring applications. [ABSTRACT FROM AUTHOR]

Garnet is a common rock‐forming mineral that occurs in a variety of rock types and over a wide range of pressure (P)–temperature (T) conditions in the Earth's lithosphere. Because garnet is considered a high‐strength mineral stable across an extensive range of conditions (1–25 GPa, <300–2000°C), it is generally accepted that garnets can retain their microstructures and chemical composition during deformation and metamorphism. Therefore, garnet is commonly used as a geothermobarometer and geochronometer to provide P–T and timing constraints on tectonic events. Herein, we study garnet from an eclogite facies mylonite (central Australia) to investigate the mechanisms of element mobility during high‐strain deformation under relatively dry, lower crustal conditions. Electron backscatter diffraction (EBSD) and electron channelling contrast imaging (ECCI) reveal evidence of crystal plasticity associated with brittle deformation in the form of heterogeneous misorientation patterns and low‐angle grain boundaries developed over length scales of 20–50 μm in the rims of garnet porphyroclasts. Atom probe tomography (APT) analysis of a low‐angle grain boundary within a highly strained portion of a clast shows Ca enrichment and Mg depletion along dislocations, whereas APT data along the rim of a mostly undeformed clast reveal a homogeneous distribution of garnet major components in the specimen matrix with the exception of Ca, Fe and Mg enrichment within a healed microfracture. The above‐mentioned results suggest that under relatively dry conditions, crystal plasticity enhances bulk element mobility via pipe diffusion, highlighting the importance of deformation‐induced microstructures on element mobility, with important implications for the robust and reliable use of garnet as a petrological tool. [ABSTRACT FROM AUTHOR]

We investigate the microscopic behaviour of hydrogen‐containing species formed on the surface of III‐N semiconductor samples by the residual hydrogen in the analysis chamber in laser‐assisted atom probe tomography (APT). We analysed AlGaN/GaN heterostructures containing alternate layers with a thickness of about 20 nm. The formation of H‐containing species occurs at field strengths between 22 and 26 V/nm and is independent of the analysed samples. The 3D APT reconstruction makes it possible to map the evolution of the surface behaviour of these species issued by chemical reactions. The results highlight the strong dependence of the relative abundances of hydrides on the surface field during evaporation. The relative abundances of the hydrides decrease when the surface field increases due to the evolution of the tip shape or the different evaporation behaviour of the different layers. [ABSTRACT FROM AUTHOR]

The behavior of catalytic particles depends on their chemical structure and morphology. To reveal this information, the characterization with atom probe tomography has huge potential. Despite progresses and papers proposing various approaches towards the incorporation of particles inside atom probe tips, no single approach has been broadly applicable to date. In this paper, we introduce a workflow that allowed us to prepare atom probe specimens from Ga particles in suspension in the size range of 50 nm up to 2 μm. By combining dielectrophoresis and electrodeposition in a suitable way, we achieve a near‐tip shape geometry, without a time‐consuming FIB lift‐out. This workflow is a simple and quick method to prepare atom probe tips and allows for a high preparation throughput. Also, not using a lift‐out allowed us to use a cryo‐stage, avoiding melting of the Ga particles, while ensuring a mechanical stable atom probe tip. The specimen prepared by this workflow enable a stable measurement and low fracture rates. Research Highlights: Enabling cryo‐preparation of (nano)particles for the atom probe.Characterization of surface and bulk elemental distribution of GaPt model SCALMS. [ABSTRACT FROM AUTHOR]

High‐strength steels are susceptible to H‐induced failure, which is typically caused by the presence of diffusible H in the microstructure. The diffusivity of H in austenitic steels with face‐centered cubic (fcc) crystal structure is slow. The austenitic steels are hence preferred for applications in the hydrogen‐containing atmospheres. However, the fcc structure of austenitic steels is often stabilized by the addition of Ni, Mn, or N, which are relatively expensive alloying elements to use. Austenite can kinetically also be stabilized using C. Herein, an approach is applied to a commercial cold work tool steel, where C is used to fully stabilize the fcc phase. This results in a microstructure consisting of only austenite and M7C3 carbide. An exposure to H by cathodic hydrogen charging exhibits no significant influence on the strength and ductility of the C‐stabilized austenitic steel. While this material is only a prototype based on an existing alloy of different purposes, it shows the potential for low‐cost H‐resistant steels based on C‐stabilized austenite. [ABSTRACT FROM AUTHOR]

Through its capability for 3D mapping of Li at the nanoscale, atom probe tomography (APT) is poised to play a key role in understanding the microstructural degradation of lithium‐ion batteries (LIB) during successive charge‐ and discharge cycles. However, APT application to materials for LIB is plagued by the field induced delithiation (deintercalation) of Li‐ions during the analysis itself that prevents the precise assessment of the Li distribution. Here, we showcase how a thin Cr‐coating, in‐situ formed on APT specimens of NMC811 in the focused‐ion beam (FIB), preserves the sample's integrity and circumvent this deleterious delithiation. Cr‐coated specimens demonstrated remarkable improvements in data quality and virtually eliminated premature specimen failures, allowing for more precise measurements via. improved statistics. Through improved data analysis, we reveal substantial cation fluctuations in commercial grade NMC811, including complete grains of LiMnO. The current methodology stands out for its simplicity and cost‐effectiveness and is a viable approach to prepare battery cathodes and anodes for systematic APT studies. [ABSTRACT FROM AUTHOR]

Solid solution strengthening is a well‐known strengthening mechanism for Al (Mg, Si) alloys. The distribution of solute atoms plays an important role in the enhancement of the mechanical properties. As‐quenched, dilute, Al alloys are analysed by atom probe tomography (APT) and mechanical testing (microhardness, tensile testing) and these data have been employed in order to assess the 3D distribution of solute atoms in the solid solutions. An innovative approach is to abstain from the conventional logic of binary versus ternary alloys in data analysis in favor of a less‐concentrated versus more‐concentrated strategy. This approach enables for the first time that the integration of first‐principles Condon–Morse atomic interaction effects, APT, and mechanical testing, and first principles effects (field, proximity, chemical, and atomic size), which results in a novel empirical singleton‐cluster plot. The plot allows differentiation between singletons, solute clusters, and coclusters as well as between the less‐concentrated and more‐concentrated alloys. The plot also allows determination of the maximal yield strengths from cluster strengthening and from singletons in the absence of clustering. Most critically, this new approach in data analysis allows for the first time the determination of the dmax (maximal distance between solutes in a cluster) based on experimental results. [ABSTRACT FROM AUTHOR]

The metallurgy, mechanical properties, and corrosion of Cu, proposed as the corrosion barrier for Canadian used fuel containers (UFCs) for use in a deep geological repository (DGR), have been studied for decades. Bulk properties have been reported, and the knowledge applied to strengthen the performance of Cu produced by electrodeposition and cold spray. Despite this success, many degradation mechanisms are unclear from bulk testing, which cannot capture nanoscale phenomena driving degradation. This study provides examples using state‐of‐the‐art microscopy to understand mechanisms of Cu degradation, specifically for UFCs. Subtle changes in the electrodeposited Cu microstructure due to oxygen segregation are observed using atom probe tomography (APT). In aggressive sulfide‐containing environments, corrosion of the cold‐sprayed Cu occurs along particle–particle interfaces, likely inherent to the manufacturing process. Microscale tensile testing at particle–particle interfaces confirms brittle cracking in the cold‐sprayed Cu. Although experiments are not consistent with DGR conditions, results do warrant further study on the performance of the cold‐sprayed Cu in particular. [ABSTRACT FROM AUTHOR]

Titanium is commonly used for medical devices, including osseointegrating implants, owing to its biocompatibility and mechanical properties. Nanostructuring titanium implants is known to enhance the healing process by promoting bone growth on the implant surface. Hydroxyapatite nanoparticles, resembling natural bone mineral, have been used to further improve osseointegration. While previous studies have investigated the osseointegration of titanium implants using atom probe tomography, limited research has focused on the attachment of synthetic hydroxyapatite to titanium. Herein, electron microscopy and atom probe tomography are used to reveal the assembly of synthetic hydroxyapatite nanoparticles in the titanium oxide surface. By sputter coating with chromium, a suitable matrix is formed for detailed interfacial analysis. The results demonstrate the diffusion of calcium, phosphorus, and carbon from hydroxyapatite nanoparticles into the titanium oxide surface. [ABSTRACT FROM AUTHOR]

Gas–solid reactions are important for many redox processes that underpin the energy and sustainability transition. The specific case of hydrogen‐based iron oxide reduction is the foundation to render the global steel industry fossil‐free, an essential target as iron production is the largest single industrial emitter of carbon dioxide. This perception of gas–solid reactions has not only been limited by the availability of state‐of‐the‐art techniques which can delve into the structure and chemistry of reacted solids, but one continues to miss an important reaction partner that defines the thermodynamics and kinetics of gas phase reactions: the gas molecules. In this investigation, cryogenic‐atom probe tomography is used to study the quasi in situ evolution of iron oxide in the solid and gas phases of the direct reduction of iron oxide by deuterium gas at 700°C. So far several unknown atomic‐scale characteristics are observed, including, D2 accumulation at the reaction interface; formation of a core (wüstite)‐shell (iron) structure; inbound diffusion of D through the iron layer and partitioning of D among phases and defects; outbound diffusion of oxygen through the wüstite and/or through the iron to the next free available inner/outer surface; and the internal formation of heavy nano‐water droplets at nano‐pores. [ABSTRACT FROM AUTHOR]

The role of β‐CoOOH crystallographic orientations in catalytic activity for the oxygen evolution reaction (OER) remains elusive. We combine correlative electron backscatter diffraction/scanning electrochemical cell microscopy with X‐ray photoelectron spectroscopy, transmission electron microscopy, and atom probe tomography to establish the structure–activity relationships of various faceted β‐CoOOH formed on a Co microelectrode under OER conditions. We reveal that ≈6 nm β‐CoOOH(011‾ ${\bar{1}}$ 0), grown on [1‾21‾ ${\bar{1}2\bar{1}}$ 0]‐oriented Co, exhibits higher OER activity than ≈3 nm β‐CoOOH(101‾ ${\bar{1}}$ 3) or ≈6 nm β‐CoOOH(0006) formed on [022‾1] ${\bar{2}1]}$ ‐ and [0001]‐oriented Co, respectively. This arises from higher amounts of incorporated hydroxyl ions and more easily reducible CoIII−O sites present in β‐CoOOH(011‾ ${\bar{1}}$ 0) than those in the latter two oxyhydroxide facets. Our correlative multimodal approach shows great promise in linking local activity with atomic‐scale details of structure, thickness and composition of active species, which opens opportunities to design pre‐catalysts with preferred defects that promote the formation of the most active OER species. [ABSTRACT FROM AUTHOR]

The standard heat treatment of PH 13-8 Mo maraging steels consists of solution annealing and subsequent aging. Herein, it is investigated how an additional intercritical annealing step prior to aging affects the microstructure, and, consequently, the mechanical properties of a PH 13-8 Mo maraging steel. In situ techniques by means of high-temperature electron backscatter diffraction and high-temperature X-ray diffraction are applied to study the microstructural changes during intercritical annealing and subsequent aging. In addition, highresolution investigation methods, such as transmission electron microscopy and atom probe tomography supplemented by transmission Kikuchi diffraction, are used for an in-depth characterization of the microstructure. The results reveal that a diffusion-controlled martensite to austenite transformation accompanied by partitioning of the substitutional atoms Cr, Ni, and Mo takes place during intercritical annealing. As a result of partitioning during intercritical annealing, an inhomogeneous distribution of Ni remains in the microstructure after the martensitic transformation. Consequently, the formation of reverted austenite is facilitated during subsequent aging due to existing Ni-enriched zones in martensite. Since the fracture toughness is significantly enhanced compared to the standard heat treatment, it is suggested that this improvement is related to the increased phase fraction of reverted austenite. [ABSTRACT FROM AUTHOR]

Herein, a CoCrFeMnNi high‐entropy alloy with reduced Cr content and with the addition of 2 at% C interstitial is processed via high‐pressure torsion (HPT) under 6.5 GPa by three turns at room and cryogenic temperatures. The microstructure is investigated by transmission electron microscopy (TEM) and atom probe tomography (APT). The results indicate that C atoms segregate at the boundaries of the nanograins in the sample processed at room temperature, while the sample processed at cryogenic temperature does not show any notable segregations of carbon. [ABSTRACT FROM AUTHOR]

Many thermoelectric materials benefit from complex microstructures. Grain boundaries (GBs) in nanocrystalline thermoelectrics cause desirable reduction in the thermal conductivity by scattering phonons, but often lead to unwanted loss in the electrical conductivity by scattering charge carriers. Therefore, modifying GBs to suppress their electrical resistivity plays a pivotal role in the enhancement of thermoelectric performance, zT. In this work, different characteristics of GB phases in Ti‐doped NbFeSb half‐Heusler compounds are revealed using a combination of scanning transmission electron microscopy and atom probe tomography. The GB phases adopt a hexagonal close‐packed lattice, which is structurally distinct from the half‐Heusler grains. Enrichment of Fe is found at GBs in Nb0.95Ti0.05FeSb, but accumulation of Ti dopants at GBs in Nb0.80Ti0.20FeSb, correlating to the bad and good electrical conductivity of the respective GBs. Such resistive to conductive GB phase transition opens up new design space to decouple the intertwined electronic and phononic transport in thermoelectric materials. [ABSTRACT FROM AUTHOR]

Perovskite structured transition metal oxides are important technological materials for catalysis and solid oxide fuel cell applications. Their functionality often depends on oxygen diffusivity and mobility through complex oxide heterostructures, which can be significantly impacted by structural and chemical modifications, such as doping. Further, when utilized within electrochemical cells, interfacial reactions with other components (e.g., Ni‐ and Cr‐based alloy electrodes and interconnects) can influence the perovskite's reactivity and ion transport, leading to complex dependencies that are difficult to control in real‐world environments. Here, this work uses isotopic tracers and atom probe tomography to directly visualize oxygen diffusion and transport pathways across perovskite and metal‐perovskite heterostructures, that is, (Ni‐Cr coated) Sr‐doped lanthanum ferrite (La0.5Sr0.5FeO3; LSFO). Annealing in 18O2(g) results in elemental and isotopic redistributions through oxygen exchange (OE) in the LSFO while Ni‐Cr undergoes oxidation via multiple mechanisms and transport pathways. Complementary density functional theory calculations at experimental conditions provide rationale for OE reaction mechanisms and reveal a complex interplay of different thermodynamic and kinetic drivers. These results shed light on the fundamental coupling of defects and oxygen transport in an important class of catalytic materials. [ABSTRACT FROM AUTHOR]

Al‐bearing medium‐Mn low‐density steels possess great potential in the automotive industry because of their excellent mechanical properties based on transformation‐induced plasticity and low specific weight. Reducing the austenite stability against deformation‐induced martensitic transformation enables a high strain‐hardening capacity to be obtained; however, undesirably low stability often results in considerably reduced tensile ductility and brittle fracture. Herein, the brittle fracture that occurs with increasing annealing temperature for a Fe−0.3C–9Mn−5Al (wt%) steel is investigated in relation to Mn segregation at the phase boundaries between ferrite and austenite. The results demonstrate that annealing at 850 and 900 °C leads to ductile fractures with 72% and 95% tensile elongation, respectively, whereas only 25% elongation is achieved for the specimen annealed at 950 °C, exhibiting predominant intergranular facets. 3D atom probe tomography reveals that annealing at 950 °C promotes considerable Mn segregation at the ferrite/austenite phase boundaries with a peak composition of ≈19 at%, which is sufficient to reduce the boundary cohesion for intergranular fracture. Thermodynamic moving boundary simulation reveals that intercritical annealing is not a prerequisite for segregations; however, low‐temperature and prolonged holding should be accompanied, such as the coiling procedures. [ABSTRACT FROM AUTHOR]

Insulating glazings used in products for the building and automotive market consist of flat glass with low‐emissivity (low‐E) coatings. One challenge is to increase the infrared reflectance of the glazing stack while maintaining a high transmittance. This can only be achieved if the chemical interdiffusion between the deposited layers can be controlled and characterized down to the sub‐nanometer level. For that, atom probe tomography (APT) is employed in this work; technique which allows a precise quantification of the chemical interdiffusion in 3D and down to sometimes atomic level. However, the APT specimens prepared using the standard top‐to‐down configuration are prone to systematic fracturing due to strong differences in field evaporation between the layers involved in the glazing stack. The usage of an untypical cross‐section configuration has led to improved yields, but for the latter, artifacts need to be considered and quantified. In particular, the effect of artificial layer intermixing at interfaces due to crossover is studied. It is concluded that Ni diffuses in the Ag layer via grain boundaries already in the as‐deposited state. Hence, this work opens a new perspective in terms of quantification of interdiffusion at early stages, an important finding for low‐E glass applications. [ABSTRACT FROM AUTHOR]

Grain boundaries (GBs) form ubiquitous microstructures in polycrystalline materials which play a significant role in tuning the thermoelectric figure of merit (ZT). However, it is still unknown which types of GB features are beneficial for thermoelectrics due to the challenge of correlating complex GB microstructures with transport properties. Here, it is demonstrated that GB complexions formed by Ga segregation in GeTe‐based alloys can optimize electron and phonon transport simultaneously. The Ga‐rich complexions increase the power factor by reducing the GB resistivity with slightly improved Seebeck coefficients. Simultaneously, they lower the lattice thermal conductivity by strengthening the phonon scattering. In contrast, Ga2Te3 precipitates at GBs act as barriers to scatter both phonons and electrons and are thus unable to improve ZT. Tailoring GBs combined with the beneficial alloying effects of Sb and Pb enables a peak ZT of ≈2.1 at 773 K and an average ZT of 1.3 within 300–723 K for Ge0.78Ga0.01Pb0.1Sb0.07Te. The corresponding thermoelectric device fabricated using 18‐pair p‐n legs shows a power density of 1.29 W cm−2 at a temperature difference of 476 K. This work indicates that GB complexions can be a facile way to optimize electron and phonon transport, further advancing thermoelectric materials. [ABSTRACT FROM AUTHOR]

The operating temperature has a critical impact on the electrical performance of solar cells. It has been shown that the temperature coefficient is not uniform across devices and often varies between different regions due to the inhomogeneous distributions of defects. In this study, temperature‐dependent photoluminescence imaging measurements are used to assess the influence of different processes such as gettering, firing and advanced hydrogenation on the temperature‐dependent electrical performance of cast‐mono silicon wafers. It is found that the height of the wafer within the ingot impacts the response of the temperature coefficient to different fabrication processes. Advanced hydrogenation is found to reduce the temperature sensitivity, more than expected solely from the improvement in implied open‐circuit voltage. Crystallographic defects are found to be the least temperature sensitive regions, indicating that their detrimental impact is reduced at higher operating temperatures. The interesting low temperature sensitivity in the defective regions is further investigated using hyperspectral photoluminescence imaging measurements and atom probe tomography. It is suggested that the reduced sensitivity is due to impurities decorating crystallographic defects. [ABSTRACT FROM AUTHOR]

Solid‐state precipitation can be used to tailor material properties, ranging from ferromagnets and catalysts to mechanical strengthening and energy storage. Thermoelectric properties can be modified by precipitation to enhance phonon scattering while retaining charge‐carrier transmission. Here, unconventional Janus‐type nanoprecipitates are uncovered in Mg3Sb1.5Bi0.5 formed by side‐by‐side Bi‐ and Ge‐rich appendages, in contrast to separate nanoprecipitate formation. These Janus nanoprecipitates result from local comelting of Bi and Ge during sintering, enabling an amorphous‐like lattice thermal conductivity. A precipitate size effect on phonon scattering is observed due to the balance between alloy‐disorder and nanoprecipitate scattering. The thermoelectric figure‐of‐merit ZT reaches 0.6 near room temperature and 1.6 at 773 K. The Janus nanoprecipitation can be introduced into other materials and may act as a general property‐tailoring mechanism. [ABSTRACT FROM AUTHOR]

Herein, the effect of tempering at 200 °C for 20 min on the mechanical properties of a cold‐rolled and intercritical annealed medium Mn steel is investigated in this study. This effect is mainly dependent on the original annealing condition. For the sample annealed at a relatively low temperature (660 °C), the austenite stability of this sample is further improved significantly after tempering. Thus, the transformation‐induced plasticity (TRIP) effect is severely inhibited during deformation, which leads to a decrease in the properties of the sample. By contrast, for the sample possessing suitable austenite fraction (≈30%) and heterostructure, that is, the sample annealed at 680 °C for 10 min, the simultaneously increased strength and ductility are significantly intrigued by tempering treatment. Electron probe microanalysis and 3D atom probe results reveal that C concentration in austenite is increased due to the C repartition during tempering, which leads to the persistent TRIP effect in a broad strain range during tensile deformation. In addition, the heterogeneous‐deformation‐induced stress of the heterostructured sample is found to be obviously intensified by tempering treatment. Thus, an excellent strength plastic synergistic effect with a product of ultimate tensile strength and total elongation of approximately 70 GPa% is obtained in the tempered sample. [ABSTRACT FROM AUTHOR]

Coarse‐grained composites of refractory ceramics and refractory metals are a novel approach for materials at application temperatures up to 1500 °C. Al2O3 and the refractory metals Nb and Ta are suitable candidates for enhanced thermal shock capability, as they show similar thermal expansion. During fabrication, a key aspect to consider is the possible formation of additional phases upon interaction of the constituent phases as well as through reaction with the environment. X‐Ray diffraction (XRD) and investigations of the microstructure with scanning electron microscopy methods unveil Al2O3–Nb composite to form NbO, whereas for Al2O3–Ta the ternary compound aluminum tantalate (AlTaO4) is found. Thermodynamic calculations show that the changing oxygen solubility in Nb accounts for the formation of NbO, and explain the absence of a corresponding niobate (AlNbO4) phase. AlTaO4 is identified as the disordered tetragonal high‐temperature modification. [ABSTRACT FROM AUTHOR]

Understanding the early stages of interactions between oxygen and material surfaces—especially at very high spatial resolutions—is highly beneficial for fields ranging from materials degradation, corrosion, geological sciences, forensics, and catalysis. The ability of in situ atom probe tomography (APT) is demonstrated to track the diffusion of oxygen and metal ions at nanoscale spatial resolution during the early stages of oxidation of a model Fe–Cr–Ni alloy. Using 18O isotope tracers in these in situ APT experiments and complementary ex situ multimodal microscopy, spectroscopy, and computational simulations allows to precisely analyze the kinetics of oxidation and determine that outward cation diffusion to oxide/air interface is the primary mechanism for intragranular oxide growth in this alloy at 300 °C. This unique in situ isotopic tracer APT approach and the insights gained can be highly beneficial for studying early stages of gas–surface reactions in a broad array of materials. [ABSTRACT FROM AUTHOR]

To achieve higher strength and good hardenability and at the same time use the positive effects of thermomechanical controlled processing, the concept of Nb and Ti microalloyed steels is increasingly used for high‐strength low‐alloy (HSLA) steels with higher C contents. Herein, how the addition of Ti affects the grain growth and static recrystallization behavior of a Nb microalloyed HSLA steel with a C content of 0.23 wt% is investigated. For this reason, alloys with varying Ti and constant Nb content are produced and investigated by means of annealing and double‐hit deformation experiments. Atom probe tomography measurements reveal that the Nb concentration in the matrix decreases with increasing Ti content. Therefore, the static recrystallization behavior is steadily inhibited with decreasing Ti content, as more dissolved Nb is available for the formation of strain‐induced NbC precipitates. The annealing experiments show that the combined addition of Ti and Nb is most effective against grain coarsening, regardless of whether the Ti content is 90 or 180 ppm. To use the positive properties of Ti against grain coarsening and Nb to inhibit recrystallization, a middle content must be chosen when alloying Ti to HSLA steels with higher C content. [ABSTRACT FROM AUTHOR]

GeSn on Si has attracted much research interest due to its tunable direct bandgap for mid‐infrared applications. Recently, short‐range order (SRO) in GeSn alloys has been theoretically predicted, which profoundly impacts the band structure. However, characterizing SRO in GeSn is challenging. Guided by physics‐informed Poisson statistical analyses of k‐nearest neighbors (KNN) in atom probe tomography (APT), a new approach is demonstrated here for 3D nanoscale SRO mapping and semi‐quantitative strain mapping in GeSn. For GeSn with ≈14 at. % Sn, the SRO parameters of Sn–Sn 1NN in 10 × 10 × 10 nm3 nanocubes can deviate from that of the random alloys by ±15 %. The relatively large fluctuation of the SRO parameters contributes to band‐edge softening observed optically. Sn–Sn 1NN also tends to be more favored toward the surface, less favored under strain relaxation or tensile strain, while almost independent of local Sn composition. An algorithm based on least square fit of atomic positions further verifies this Poisson‐KNN statistical method. Compared to existing macroscopic spectroscopy or electron microscopy techniques, this new APT statistical analysis uniquely offers 3D SRO mapping at nanoscale resolution in a relatively large volume with millions of atoms. It can also be extended to investigate SRO in other alloy systems. [ABSTRACT FROM AUTHOR]

Binary Fe–Cr alloys are model alloys for ferritic steels proposed as structural materials for future fusion reactors. They are used to investigate the fundamental mechanisms of their degradation induced by heat and irradiation. Fe–Cr presents a miscibility gap, which induces Cr‐rich (α′) regions in an Fe‐rich (α) matrix. As this causes embrittlement, it is crucial to understand this phase decomposition and its role, starting with the heat impact. Fe–Cr alloys with 5−40 wt% Cr were annealed at 500 °C for up to 1008 h. The microstructure was probed by chemical mapping using scanning transmission electron microscopy with energy‐dispersive X‐ray spectroscopy (EDS) and atom probe tomography, and hardness was assessed by Vickers testing. Increasing Cr content increases hardness, and beyond 15 wt% Cr it further increases upon annealing. At 20 wt% Cr, nanoscale globular α′ precipitates appear, while at 40 wt% Cr an α′‐percolating structure develops. In both cases, the α′ core composition reaches slightly more than 80 at% Cr, and hardness doubles. A unified relationship is found between the alloy strength and the α′ structure and it is shown that this type of hardening is a general mechanism for mature systems, independent of the nominal alloy composition. [ABSTRACT FROM AUTHOR]

Silver quantum clusters (Ag QCs) have attracted great attention due to their unique electronic structure and molecule‐like photoluminescence (PL). Applications in catalysis, biology, and optoelectronics have already been realized, however, the understanding of PL mechanism and direct observation of Ag QCs still remain challenging. Here, fully inorganic Ag QCs well stabilized in the borate glass with simultaneous excellent chemical stability, tunable PL emission, and high quantum yield are prepared. And the PL properties of Ag QCs respond drastically to changes of the embedding environment, displaying pronounced fluorescence to phosphorescence (F‐P) switching. Combining the structural and spectral analysis, it is found that the F‐P switching is triggered by the Ag QCs aggregation and [BO3]→[BO4]− conversion of the borate network. Using atom probe tomography enables to quantitatively characterize the evolution of Ag QCs at an atomic level, which reveals that Ag QCs consisting of less than 20 atoms are responsible for the observed PL. [ABSTRACT FROM AUTHOR]

Allvac 718Plus is a derivative of alloy 718 for applications at higher temperatures in rotating and static components of gas turbines. According to literature, various phases as γ, γ′, η, δ, and γ″ can form with so far contradicting results. Herein, the precipitation behavior in different alloy conditions is investigated using transmission electron microscopy and atom probe tomography. The aim is to clarify how local variations in chemical composition alter the sequence of precipitation and type of precipitates that form. Material conditions with a minor volume fraction of η/δ phase and a high fraction of primary γ′ precipitates form γ″ phase due to excess of available Nb. Spherical γ′ precipitates with disc‐shaped γ″ precipitates at γ′ interfaces are observed. During discontinuous coarsening of η/δ plates mainly Nb is consumed which leads to an enrichment of γ′ forming elements and hence the heterogeneous nucleation of γ′ at the η/γ interface. The coexistence of thin η plates embedded in δ phase in grain boundary pinning precipitates could additionally be confirmed. These results show under which conditions certain primary phases form and how the resulting consumption and redistribution of phase promoting elements trigger the formation of other secondary phases. [ABSTRACT FROM AUTHOR]

Atom probe tomography (APT) analysis often produces artifacts in atomic position owing to the difference in evaporation fields in materials. The atomic density profiles of grain boundaries, plate‐shaped low‐field precipitates (cementite), and high‐field precipitates (vanadium carbide) in steels were investigated via two analyses in directions perpendicular and parallel to the boundaries and platelets. Although the perpendicular analysis indicated better quantitative performances in the composition analyses of segregating atoms at the grain boundary and the constituent atoms of the precipitates, an abnormal atomic density was observed around the interfaces of the precipitates. Geometric calculation using a two‐radius model based on the local magnification effect suggested that a spike structure at the front interface and a dip structure at the rear interface for lamellar cementite correspond to an overlap and a gap in the evaporated atoms from the cementite and matrix, respectively. This indicates that even in the perpendicular analysis, the precipitate constituent atoms and matrix atoms mixed in the depth direction. We discuss the origin and impact of the position artifacts in the perpendicular analyses of low‐ and high‐field plate‐shaped precipitates and also discussed the application limits of the model. [ABSTRACT FROM AUTHOR]

Previous investigations revealed that Nb, Ta, and Zr improve the creep properties of fully lamellar titanium aluminides significantly. The enhanced creep properties can originate from different potential effects of the alloying elements. Herein, the elements' partitioning between α2‐Ti3Al and γ‐TiAl and their influence on the lattice parameters of ternary Ti–44Al–5X (X = Nb, Ta, Zr) alloys are investigated in comparison with a binary Ti−44Al alloy by atom probe tomography and high‐energy X‐ray diffraction. Ta partitions nearly equally between α2 and γ, Nb accumulates slightly in γ, and Zr enriches strongly in γ. As all alloying elements have a larger radius than Ti, a stronger partitioning to γ decreases the lattice misfit more. The synchrotron measurements show a clear influence of the alloying elements on the lattice parameters and resulting lattice misfits in γ‐⟨110] and γ‐⟨101] direction as well as the c/a ratio. In accordance with theoretical calculations based on the partitioning behavior, the lattice misfit decreases from Ti–44Al–5Ta over Ti–44Al–5Nb to Ti–44Al–5Zr. The c/a ratio decreases from Ti–44Al–5Nb over Ti–44Al–5Ta to Ti–44Al–5Zr. A correlation between the measured lattice misfits of the ternary Ti−44Al−5X with their primary creep strains is found, as the primary creep strain decreases with decreasing lattice misfit. [ABSTRACT FROM AUTHOR]

Hydrogen passivation is a key industrial technique used to reduce the recombination activity of defects in multicrystalline silicon (mc‐Si). However, not all dislocations and grain boundaries respond well to traditional hydrogen passivation techniques. In order to understand the reasons for these different behaviours, and how superior passivation might be achieved, a method is required for the direct observation of hydrogen at these defects. Here, we present a novel characterisation technique based on a combination of transmission Kikuchi diffraction (TKD), atom probe tomography (APT), and isotopic substitution that enables unambiguous detection and quantification of hydrogen atoms present at crystallographic defects in mc‐Si. [ABSTRACT FROM AUTHOR]

Cu(In,Ga)Se2 thin‐film solar cells have attracted significant research interest in recent decades due to their high efficiency in converting solar energy into electricity for enabling a sustainable future. Although the Cu(In,Ga)Se2 absorber can be grown as a single crystal, its polycrystalline form is dominating the market not only due to its lower costs, but also due to its unexpectedly higher cell efficiency. However, this absorber contains a high fraction of grain boundaries. These are structural defects where deep‐trap states can be localized leading to an increase in recombination activity. This controversy is mirrored in the existing literature studies where two main contradictory believes exist: 1) to be crucial grain boundaries in Cu(In,Ga)Se2 absorber are anomalous, being benign in terms of cell performance, and 2) grain boundaries are regions characterized by an increased recombination activity leading to deteriorated cell performance. Therefore, the present review tackles this issue from a novel perspective unraveling correlations between chemical composition of grain boundaries and their corresponding electronic properties. It is shown that features such as Cu depletion/In enrichment, segregation of 1‐2at.% of alkali dopants, and passivation by a wide‐bandgap or type inversion at grain boundaries are crucial ingredients for low open‐circuit voltage loss and, hence, for superior cell performance. [ABSTRACT FROM AUTHOR]

The effect of surface orientations on the formation of iridium oxide species during the oxygen evolution reaction (OER) remains yet unknown. Herein, we use a needle‐shaped iridium atom probe specimen as a nanosized working electrode to ascertain the role of the surface orientations in the formation of oxide species during OER. At the beginning of electrolysis, the top 2–3 nm of (024), (026), (113), and (115) planes are covered by IrO−OH, which activates all surfaces towards OER. A thick subsurface oxide layer consisting of sub‐stoichiometric Ir−O species is formed on the open (024) planes as OER proceeds. Such metastable Ir−O species are thought to provide an additional contribution to the OER activity. Overall, this study sheds light on the importance of the morphological effects of iridium electrocatalysts for OER. It also provides an innovative approach that can directly reveal surface species on electrocatalysts at atomic scale. [ABSTRACT FROM AUTHOR]

Xenotime (YPO4) is an accessory phase common in low to high‐temperature geological environments. Xenotime is an established geochronometer, though its small size, low modal abundance and textural complexity make it more difficult to analyse with traditional techniques but makes a prime candidate for nanoscale analysis. In this study, we develop an atom probe tomography (APT) protocol to determine the 206Pb/238U and 207Pb/206Pb ages of micro‐scale xenotime crystals with analytical volumes four to six orders of magnitude smaller than typical geochronology techniques. A linear correlation between the 206Pb/238U fractionation and 238UO22+/238UO2+ was used to correct for the atom probe instrument parameters variability between specimens. For 207Pb/206Pb ages, we employed two methods of background correction owing to the 206Pb2+ thermal tail contribution to the 207Pb2+ counts: A constant background correction for the younger (˜ 1000 Ma) Y1 reference material and a variable correction of background for Archaean age reference material xtc to correct for the thermal tail influence. This contribution also proposes strategies for optimisation of xenotime analysis using APT and permits us to explore the various geological problems in the nanoscale realm. This methodology potentially allows determining the age of small xenotime crystals in sedimentary rocks, low metamorphic grade settings and deformation microstructures. [ABSTRACT FROM AUTHOR]

Hydrous phyllosilicate minerals, including the serpentine subgroup, are likely to be major constituents of material that will be bought back to Earth by missions to Mars and to primitive asteroids Ryugu and Bennu. Small quantities (< 60 g) of micrometre‐sized, internally heterogeneous material will be available for study, requiring minimally destructive techniques. Many conventional methods are unsuitable for phyllosilicates as they are typically finely crystalline and electron beam‐sensitive resulting in amorphisation and dehydration. New tools will be required for nanoscale characterisation of these precious extra‐terrestrial samples. Here we test the effectiveness of atom probe tomography (APT) for this purpose. Using lizardite from the Ronda peridotite, Spain, as a terrestrial analogue, we outline an effective analytical protocol to extract nanoscale chemical and structural measurements of phyllosilicates. The potential of APT is demonstrated by the unexpected finding that the Ronda lizardite contains SiO‐rich nanophases, consistent with opaline silica that formed as a by‐product of the serpentinisation of olivine. Our new APT approach unlocks previously unobservable nanominerals and nanostructures within phyllosilicates owing to resolution limitations of more established imaging techniques. APT will provide unique insights into the processes and products of water/rock interaction on Earth, Mars and primitive asteroids. [ABSTRACT FROM AUTHOR]

The alloy design of modern high‐strength low‐alloy (HSLA) steels aims for a well‐balanced combination of high toughness and strength. Using niobium and titanium as microalloying elements together with thermomechanical processing is a common way to obtain a fine‐grained microstructure and therefore enhance the strength and toughness of HSLA steels. Herein, a low‐alloyed steel and a microalloyed HSLA steel are investigated in the as‐rolled condition and by double‐hit experiments using various deformation parameters. Atom probe tomography, scanning transmission electron microscopy inside a scanning electron microscope, transmission kikuchi diffraction, and energy‐dispersive X‐ray spectroscopy are used to investigate the precipitates in the as‐rolled condition and after deformation. It is shown that Nb‐enriched TiN precipitates with an average size of around 15 nm are responsible for grain refinement in the as‐rolled condition. The annealing temperature prior to the rolling process is set below the solution temperature of Nb(C,N). Enhancing the annealing temperature in the double‐hit deformation tests above the solution temperature of Nb(C,N) leads to the precipitation of fine NbC precipitates with a size of around 5 nm. These precipitates are responsible for inhibited static recrystallization behavior. [ABSTRACT FROM AUTHOR]

In order to enable the application of atomic probe tomography combinatorial processing platforms for atomic-scale investigations of phase evolution at elevated temperatures, the pre-sharpened Si tip of 10-20 nm in diameter must be protected against interdiffusion and reaction of the reactive Si with a film of interest by a conformal coating on the Si tip. It is shown that unwanted reactions can be suppressed by introducing a 20-nm-thick intermediate Al2O3 layer grown by atomic layer deposition (ALD). As a representative case, Pt is chosen as a film of interest, as it easily forms silicides. Whereas without the ALD coating diffusion/reactions occur, with the protective film, this is prevented for temperatures up to at least 600°C. The effectiveness of the Al2O3 layer serving as a diffusion barrier is not limited to a sharpened Si tip but works generally for all cases where a Si substrate is used. [ABSTRACT FROM AUTHOR]