Publications
439 results found
Lilensten L, Antonov S, Gault B, et al., 2021, Enhanced creep performance in a polycrystalline superalloy driven by atomic-scale phase transformation along planar faults, ACTA MATERIALIA, Vol: 202, Pages: 232-242, ISSN: 1359-6454
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- Citations: 22
Garner A, Euesden R, Yao Y, et al., 2021, Multiscale analysis of grain boundary microstructure in high strength 7xxx Al alloys, ACTA MATERIALIA, Vol: 202, Pages: 190-210, ISSN: 1359-6454
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- Citations: 37
Khanchandani H, Kim S-H, Varanasi RS, et al., 2021, Hydrogen and deuterium charging of lifted-out specimens for atom probe tomography., Open Res Eur, Vol: 1
Hydrogen embrittlement can cause a dramatic deterioration of the mechanical properties of high-strength metallic materials. Despite decades of experimental and modelling studies, the exact underlying mechanisms behind hydrogen embrittlement remain elusive. To unlock understanding of the mechanism and thereby help mitigate the influence of hydrogen and the associated embrittlement, it is essential to examine the interactions of hydrogen with structural defects such as grain boundaries, dislocations and stacking faults. Atom probe tomography (APT) can, in principle, analyse hydrogen located specifically at such microstructural features but faces strong challenges when it comes to charging specimens with hydrogen or deuterium. Here, we describe three different workflows enabling hydrogen/deuterium charging of site-specific APT specimens: namely cathodic, plasma and gas charging. All the experiments in the current study have been performed on a model twinning induced plasticity steel alloy. We discuss in detail the caveats of the different approaches in order to help future research efforts and facilitate further studies of hydrogen in metals. Our study demonstrates successful cathodic and gas charging, with the latter being more promising for the analysis of the high-strength steels at the core of our work.
Ye X, Yan F, Schaefer L, et al., 2020, Magnetoelectric tuning of pinning-type permanent magnets through atomic-scale engineering of grain boundaries, Advanced Materials, Vol: 33, Pages: 1-7, ISSN: 0935-9648
Pinning-type magnets with high coercivity at high temperatures are at the core of thriving clean-energy technologies. Among these, Sm2Co17-based magnets are excellent candidates owing to their high-temperature stability. However, despite intensive efforts to optimize the intragranular microstructure, the coercivity currently only reaches 20–30% of the theoretical limits. Here, the roles of the grain-interior nanostructure and the grain boundaries in controlling coercivity are disentangled by an emerging magnetoelectric approach. Through hydrogen charging/discharging by applying voltages of only ≈1 V, the coercivity is reversibly tuned by an unprecedented value of ≈1.3 T. In situ magneto-structural characterization and atomic-scale tracking of hydrogen atoms reveal that the segregation of hydrogen atoms at the grain boundaries, rather than the change of the crystal structure, dominates the reversible and substantial change of coercivity. Hydrogen reduces the local magnetocrystalline anisotropy and facilitates the magnetization reversal starting from the grain boundaries. This study opens a way to achieve the giant magnetoelectric effect in permanent magnets by engineering grain boundaries with hydrogen atoms. Furthermore, it reveals the so far neglected critical role of grain boundaries in the conventional magnetization-switching paradigm of pinning-type magnets, suggesting a critical reconsideration of engineering strategies to overcome the coercivity limits.
Kamachali RD, da Silva AK, McEniry E, et al., 2020, Segregation-assisted spinodal and transient spinodal phase separation at grain boundaries, NPJ COMPUTATIONAL MATERIALS, Vol: 6
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- Citations: 27
El-Zoka AA, Kim S-H, Deville S, et al., 2020, Enabling near-atomic-scale analysis of frozen water, Science Advances, Vol: 6, Pages: 1-11, ISSN: 2375-2548
Transmission electron microscopy went through a revolution enabling routine cryo-imaging of biological and (bio)chemical systems, in liquid form. Yet, these approaches typically lack advanced analytical capabilities. Here, we used atom probe tomography to analyze frozen liquids in three dimensions with subnanometer resolution. We introduce a specimen preparation strategy using nanoporous gold. We report data on 2- to 3-μm-thick layers of ice formed from both high-purity deuterated water and a solution of 50 mM NaCl in high-purity deuterated water. The analysis of the gold-ice interface reveals a substantial increase in the solute concentrations across the interface. We explore a range of experimental parameters to show that atom probe analyses of bulk aqueous specimens come with their own challenges and discuss physical processes that produce the observed phenomena. Our study demonstrates the viability of using frozen water as a carrier for near-atomic–scale analysis of objects in solution by atom probe tomography.
Nadarajah R, Tahir S, Landers J, et al., 2020, Controlling the oxidation of magnetic and electrically conductive solid-solution iron-rhodium nanoparticles synthesized by laser ablation in liquids, Nanomaterials, Vol: 10, Pages: 1-16, ISSN: 2079-4991
This study focuses on the synthesis of FeRh nanoparticles via pulsed laser ablation in liquid and on controlling the oxidation of the synthesized nanoparticles. Formation of monomodal γ-FeRh nanoparticles was confirmed by transmission electron microscopy (TEM) and their composition confirmed by atom probe tomography (APT). For these particles, three major contributors to oxidation were analysed: (1) dissolved oxygen in the organic solvents, (2) the bound oxygen in the solvent and (3) oxygen in the atmosphere above the solvent. The decrease of oxidation for optimized ablation conditions was confirmed through energy-dispersive X-ray (EDX) and Mössbauer spectroscopy. Furthermore, the time dependence of oxidation was monitored for dried FeRh nanoparticles powders using ferromagnetic resonance spectroscopy (FMR). By magnetophoretic separation, B2-FeRh nanoparticles could be extracted from the solution and characteristic differences of nanostrand formation between γ-FeRh and B2-FeRh nanoparticles were observed.
Rousseau L, Normand A, Morgado FF, et al., 2020, Dynamic Effects in Voltage Pulsed Atom Probe, MICROSCOPY AND MICROANALYSIS, Vol: 26, Pages: 1133-1146, ISSN: 1431-9276
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- Citations: 4
Edmondson PD, Gault B, Gilbert MR, 2020, An atom probe tomography and inventory calculation examination of second phase precipitates in neutron irradiated single crystal tungsten, NUCLEAR FUSION, Vol: 60, ISSN: 0029-5515
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- Citations: 14
Kasian O, Schweinar K, Gault B, 2020, (Invited) From Atomic-Scale Understanding to Design of Advanced Electrocatalyst Materials, ECS Meeting Abstracts, Vol: MA2020-02, Pages: 3154-3154
<jats:p> Increasing concerns regarding the environmental impact of power generation and the reduction of carbon emissions have become a major motivation for the use of sustainable electrical power. In this perspective, renewable energy sources are expected to take up an important part of electric energy produced in the near future. Since renewable sources such as wind and solar are intermittent in nature, their increased installation will result in either excessive or insufficient power generation at times. A large variety of concepts for using this surplus power is currently under development.</jats:p> <jats:p>Acidic water electrolysis is an attractive environmentally-safe solution for the conversion and storage of excess electricity into hydrogen and oxygen. The large scale application of water electrolysis systems is currently hindered by low efficiency and instability of catalysts during long term operation [1]. This is especially crucial for the anodic oxygen evolution reaction (OER) which catalyzed by Iridium based alloys and oxides making the issues related to efficiency of catalyst utilization and durability even more critical. The development of catalyst materials with superior performance demands a deep understanding of the OER itself as well as electrocatalysts degradation mechanisms. Although a large number of possible OER mechanisms have been proposed [2], the topic remains a subject of intensive debates across the scientific literature, since the intermediates and their possible interrelations are in most cases unknown. Additional challenges in mechanistic studies are related to the changes in the composition of the catalyst and its degradation triggered by OER. Though the existence of experimental correlation between the structure, activity of OER catalyst and its dissolution was numerously reported and discussed [2,3], reports addressing all these aspects in one study are rare. This indicates that further research ef
Schonhobel AM, Madugundo R, Barandiaran JM, et al., 2020, Nanocrystalline Sm-based 1:12 magnets, ACTA MATERIALIA, Vol: 200, Pages: 652-658, ISSN: 1359-6454
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- Citations: 21
Raabe D, Sun B, Kwiatkowski Da Silva A, et al., 2020, Current Challenges and Opportunities in Microstructure-Related Properties of Advanced High-Strength Steels, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, Vol: 51, Pages: 5517-5586, ISSN: 1073-5623
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- Citations: 85
Massey CR, Hoelzer DT, Unocic KA, et al., 2020, Extensive nanoprecipitate morphology transformation in a nanostructured ferritic alloy due to extreme thermomechanical processing, ACTA MATERIALIA, Vol: 200, Pages: 922-931, ISSN: 1359-6454
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- Citations: 8
Dubosq R, Gault B, Hatzoglou C, et al., 2020, Analysis of nanoscale fluid inclusions in geomaterials by atom probe tomography: Experiments and numerical simulations, ULTRAMICROSCOPY, Vol: 218, ISSN: 0304-3991
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- Citations: 8
Zhao H, Gault B, Ponge D, et al., 2020, Reversion and re-aging of a peak aged Al-Zn-Mg-Cu alloy, SCRIPTA MATERIALIA, Vol: 188, Pages: 269-273, ISSN: 1359-6462
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- Citations: 27
Zhang S, Ahmet I, Kim S-H, et al., 2020, Different photostability of BiVO₄ in near-pH-neutral electrolytes, ACS Applied Energy Materials, Vol: 3, Pages: 9523-9527, ISSN: 2574-0962
Photoelectrochemical water splitting is a promising route to produce hydrogen from solar energy. However, corrosion of photoelectrodes remains a fundamental challenge for their implementation. Here, we reveal different dissolution behaviors of BiVO4 photoanode in pH-buffered borate, phosphate, and citrate (hole-scavenger) electrolytes, studied in operando employing an illuminated scanning flow cell. We demonstrate that decrease in photocurrents alone does not reflect the degradation of photoelectrodes. Changes in dissolution rates correlate to the evolution of surface chemistry and morphology. The correlative measurements on both sides of the liquid-semiconductor junction provide quantitative comparison and mechanistic insights into the degradation processes.
Schwarz T, Lomuscio A, Siebentritt S, et al., 2020, On the chemistry of grain boundaries in CuInS<inf>2</inf> films, Nano Energy, Vol: 76, ISSN: 2211-2855
We conducted correlated transmission Kikuchi diffraction and atom probe tomography measurements to investigate the relationship between the structure and chemistry of grain boundaries in Cu-rich and Cu-poor sulfide chalcopyrite CuInS2 thin-films. We detect different elemental redistributions at random high-angle grain boundaries, Σ9 twin boundaries and stacking faults in the Cu-rich and Cu-poor film but no chemical fluctuations at Σ3 twin boundaries. For the Cu-rich CuInS2 thin-film, our atom probe tomography analyses reveal Cu enrichment as well as In and S depletion at random grain boundaries, Σ9 twin boundaries and stacking faults. Hence, we may observe a ‘Cu on In’ scenario, which is accompanied by co-segregation of Na and C. In contrast, for the Cu-poor CuInS2 thin-film, our analyses show Cu depletion and In enrichment at random grain boundaries and at the vast majority of stacking faults. For S we do not observe a clear trend. Therefore, for the Cu-poor CuInS2 thin-film we may observe a ‘In on Cu’ scenario, which is accompanied by co-segregation of Na, K and O at the random grain boundaries but not at stacking faults. The amount of impurity segregation varies from one grain boundary to another in both thin-films.
He J, Scholz F, Horst OM, et al., 2020, On the Re segregation at the low angle grain boundary in a single crystal Ni-base superalloy (vol 185, pg 88, 2020), SCRIPTA MATERIALIA, Vol: 187, Pages: 309-309, ISSN: 1359-6462
Harding I, Mouton I, Gault B, et al., 2020, Microstructural Evolution in an Fe-10Ni-0.1C Steel During Heat Treatment and High Strain-Rate Deformation, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, Vol: 51, Pages: 5056-5076, ISSN: 1073-5623
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- Citations: 3
Katnagallu S, Wu G, Singh SP, et al., 2020, Nanoglass-Nanocrystal Composite-a Novel Material Class for Enhanced Strength-Plasticity Synergy, SMALL, Vol: 16, ISSN: 1613-6810
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- Citations: 8
Kini AR, Maischner D, Weisheit A, et al., 2020, In-situ synthesis via laser metal deposition of a lean Cu-3.4Cr-0.6Nb (at%) conductive alloy hardened by Cr nano-scale precipitates and by Laves phase micro-particles, ACTA MATERIALIA, Vol: 197, Pages: 330-340, ISSN: 1359-6454
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- Citations: 20
Stueckler M, Krenn H, Kuernsteiner P, et al., 2020, Intermixing of Fe and Cu on the atomic scale by high-pressure torsion as revealed by DC- and AC-SQUID susceptometry and atom probe tomography, ACTA MATERIALIA, Vol: 196, Pages: 210-219, ISSN: 1359-6454
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- Citations: 11
Antonov S, Zheng Y, Sosa JM, et al., 2020, Plasticity assisted redistribution of solutes leading to topological inversion during creep of superalloys, SCRIPTA MATERIALIA, Vol: 186, Pages: 287-292, ISSN: 1359-6462
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- Citations: 21
Gomell L, Katnagallu S, Diack-Rasselio A, et al., 2020, Chemical segregation and precipitation at anti-phase boundaries in thermoelectric Heusler-Fe<sub>2</sub>VA1, SCRIPTA MATERIALIA, Vol: 186, Pages: 370-374, ISSN: 1359-6462
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- Citations: 8
Antonov S, Li B, Gault B, et al., 2020, The effect of solute segregation to deformation twin boundaries on the electrical resistivity of a single-phase superalloy, SCRIPTA MATERIALIA, Vol: 186, Pages: 208-212, ISSN: 1359-6462
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- Citations: 10
Serrano-Sánchez F, Luo T, Yu J, et al., 2020, Thermoelectric properties of n-type half-Heusler NbCoSn with heavy-element Pt substitution, Journal of Materials Chemistry A, Vol: 8, Pages: 14822-14828, ISSN: 2050-7488
Half-Heusler compounds with a valence electron count of 18, including ZrNiSn, ZrCoSb, and NbFeSb, are good thermoelectric materials owing to favorable electronic structures. Previous computational studies had predicted a high electrical power factor in another half-Heusler compound NbCoSn, but it has not been extensively investigated experimentally. Herein, the synthesis, structural characterization, and thermoelectric properties of the heavy-element Pt-substituted NbCoSn compounds are reported. Pt is found to be an effective substitute enabling the optimization of electrical power factor and simultaneously leading to a strong point defect scattering of phonons and the suppression of lattice thermal conductivity. Post-annealing significantly improves the carrier mobility, which is ascribed to the decreased grain boundary scattering of electrons. As a result, a maximum power factor of ∼3.4 mW m-1 K-2 is obtained at 600 K. In conjunction with the reduced lattice thermal conductivity, a maximum figure of merit zT of ∼0.6 is achieved at 773 K for the post-annealed NbCo0.95Pt0.05Sn, an increase of 100% compared to that of NbCoSn. This work highlights the important roles that the dopant element and microstructure play in the thermoelectric properties of half-Heusler compounds.
Sohn SS, Kim DG, Jo YH, et al., 2020, High-rate superplasticity in an equiatomic medium-entropy VCoNi alloy enabled through dynamic recrystallization of a duplex microstructure of ordered phases, ACTA MATERIALIA, Vol: 194, Pages: 106-117, ISSN: 1359-6454
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- Citations: 45
Wu G, Balachandran S, Gault B, et al., 2020, Crystal-Glass High-Entropy Nanocomposites with Near Theoretical Compressive Strength and Large Deformability, ADVANCED MATERIALS, Vol: 32, ISSN: 0935-9648
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- Citations: 56
He J, Scholz F, Horst OM, et al., 2020, On the rhenium segregation at the low angle grain boundary in a single crystal Ni-base superalloy, SCRIPTA MATERIALIA, Vol: 185, Pages: 88-93, ISSN: 1359-6462
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- Citations: 21
Schweinar K, Gault B, Mouton I, et al., 2020, Lattice oxygen exchange in rutile IrO2during the oxygen evolution reaction, Journal of Physical Chemistry Letters, Vol: 11, Pages: 5008-5014, ISSN: 1948-7185
The development of efficient acidic water electrolyzers relies on understanding dynamic changes of the Ir-based catalytic surfaces during the oxygen evolution reaction (OER). Such changes include degradation, oxidation, and amorphization processes, each of which somehow affects the material’s catalytic performance and durability. Some mechanisms involve the release of oxygen atoms from the oxide’s lattice, the extent of which is determined by the structure of the catalyst. While the stability of hydrous Ir oxides suffers from the active participation of lattice oxygen atoms in the OER, rutile IrO2 is more stable and the lattice oxygen involvement is still under debate due to the insufficient sensitivity of commonly used online electrochemical mass spectrometry. Here, we revisit the case of rutile IrO2 at the atomic scale by a combination of isotope labeling and atom probe tomography and reveal the exchange of oxygen atoms between the oxide lattice and water. Our approach enables direct visualization of the electrochemically active volume of the catalysts and allows for the estimation of an oxygen exchange rate during the OER that is discussed in view of surface restructuring and subsequent degradation. Our work presents an unprecedented opportunity to quantitatively assess the exchange of surface species during an electrochemical reaction, relevant for the optimization of the long-term stability of catalytic systems.
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