Publications
391 results found
Kim S-H, Shin K, Zhou X, et al., 2023, Atom probe analysis of BaTiO3 enabled by metallic shielding, Scripta Materialia, Vol: 229, Pages: 1-5, ISSN: 1359-6462
Atom probe tomography has been raising in prominence as a microscopy and microanalysis technique to gain sub-nanoscale information from technologically-relevant materials. However, the analysis of some functional ceramics, particularly perovskites, has remained challenging with extremely low yield and success rate. This seems particularly problematic for materials with high piezoelectric activity, which may be difficult to express at the low temperatures necessary for satisfactory atom probe analysis. Here, we demonstrate the analysis of commercial BaTiO3 particles embedded in a metallic matrix. Density-functional theory shows that a metallic coating prevents charge penetration of the electrostatic field, and thereby suppresses the associated volume change linked to the piezoelectric effect.
Khanchandani H, Rolli R, Schneider H-C, et al., 2023, Hydrogen embrittlement of twinning-induced plasticity steels: Contribution of segregation to twin boundaries, SCRIPTA MATERIALIA, Vol: 225, ISSN: 1359-6462
Sasidhar KN, Khanchandani H, Zhang S, et al., 2023, Understanding the protective ability of the native oxide on an Fe-13 at% Cr alloy at the atomic scale: A combined atom probe and electron microscopy study, CORROSION SCIENCE, Vol: 211, ISSN: 0010-938X
Wang S, Douglas JO, Lovell E, et al., 2023, Near-atomic scale chemical analysis of interfaces in a La(Fe,Mn,Si)13-based magnetocaloric material, Scripta Materialia, Vol: 224, Pages: 1-6, ISSN: 1359-6462
La(Fe,Mn,Si)13-based magnetocaloric materials are one of the most promising material families for the realisation of near-room temperature magnetic refrigeration. The functional and mechanical properties of these materials crucially depend on their chemistry, which is difficult to control at interfaces between microstructural units. Atom probe tomography was employed to reveal the local elemental distribution at the α-Fe/1:13 phase boundary and the 1:13/1:13 grain boundary. Strong Mn segregation (and Fe depletion) at the α-Fe/1:13 phase boundary suggests the potential effect of phase boundary area on the Curie temperature of the material. A local off-1:13 stoichiometry layer at the 1:13/1:13 grain boundary may adversely affect the magnetocaloric performance. Routes to mitigate the negative effects of interfaces on the functional and mechanical performance of these materials are discussed, in order to achieve durable and efficient operation of magnetic cooling devices.
Katnagallu S, Freysoldt C, Gault B, et al., 2023, Ab initio vacancy formation energies and kinetics at metal surfaces under high electric field, Physical Review B, Vol: 107, ISSN: 2469-9950
Recording field ion microscope images under field-evaporating conditions and subsequently reconstructing the underlying atomic configuration, called three-dimensional field ion microscopy (3D-FIM), is one of the few techniques capable of resolving crystalline defects at an atomic scale. However, the quantification of the observed vacancies and their origins are still a matter of debate. It was suggested that high electrostatic fields (1-5 V/Å) used in 3D-FIM could introduce artifact vacancies. To investigate such effects, we used density functional theory simulations. Stepped nickel and platinum surfaces with kinks were modeled in the repeated-slab approach with a (971) surface orientation. An electrostatic field of up to 4 V/Å was introduced on one side of the slab using the generalized dipole correction. Contrary to what was proposed, we show that the formation of vacancies on the electrified metal surface is more difficult compared to a field-free case. We also find that the electrostatic field can introduce kinetic barriers to a potential "vacancy annihilation"mechanism. We rationalize these findings by comparing to insights from field evaporation models.
Dubosq R, Woods E, Gault B, et al., 2023, Electron microscope loading and in situ nanoindentation of water ice at cryogenic temperatures., PLoS One, Vol: 18
Interest in the technique of low temperature environmental nanoindentation has gained momentum in recent years. Low temperature indentation apparatuses can, for instance, be used for systematic measurements of the mechanical properties of ice in the laboratory, in order to accurately determine the inputs for the constitutive equations describing the rheologic behaviour of natural ice (i.e., the Glen flow law). These properties are essential to predict the movement of glaciers and ice sheets over time as a response to a changing climate. Herein, we introduce a new experimental setup and protocol for electron microscope loading and in situ nanoindentation of water ice. Preliminary testing on pure water ice yield elastic modulus and hardness measurements of 4.1 GPa and 176 MPa, respectively, which fall within the range of previously published values. Our approach demonstrates the potential of low temperature, in situ, instrumented nanoindentation of ice under controlled conditions in the SEM, opening the possibility for investigating individual structural elements and systematic studies across species and concentration of impurities to refine to constitutive equations for natural ice.
Zhu Y, Heo TW, Rodriguez JN, et al., 2022, Hydriding of titanium: Recent trends and perspectives in advanced characterization and multiscale modeling, CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE, Vol: 26, ISSN: 1359-0286
Singh MPP, Kim S-H, Zhou X, et al., 2022, Near-Atomic-Scale Evolution of the Surface Chemistry in Li[Ni,Mn,Co]O-2 Cathode for Li-Ion Batteries Stored in Air, ADVANCED ENERGY AND SUSTAINABILITY RESEARCH, ISSN: 2699-9412
Kim S-H, Stephenson LT, da Silva AK, et al., 2022, Phase separation and anomalous shape transformation in frozen microscale eutectic indium, MATERIALIA, Vol: 26, ISSN: 2589-1529
Saksena A, Kubacka D, Gault B, et al., 2022, The effect of gamma matrix channel width on the compositional evolution in a multi-component nickel-based superalloy, SCRIPTA MATERIALIA, Vol: 219, ISSN: 1359-6462
Kim S-H, Dong K, Zhao H, et al., 2022, Understanding the degradation of a model si anode in a li-ion battery at the atomic scale., Journal of Physical Chemistry Letters, Vol: 36, Pages: 8416-8421, ISSN: 1948-7185
To advance the understanding of the degradation of the liquid electrolyte and Si electrode, and their interface, we exploit the latest developments in cryo-atom probe tomography. We evidence Si anode corrosion from the decomposition of the Li salt before charge-discharge cycles even begin. Volume shrinkage during delithiation leads to the development of nanograins from recrystallization in regions left amorphous by the lithiation. The newly created grain boundaries facilitate pulverization of nanoscale Si fragments, and one is found floating in the electrolyte. P is segregated to these grain boundaries, which confirms the decomposition of the electrolyte. As structural defects are bound to assist the nucleation of Li-rich phases in subsequent lithiations and accelerate the electrolyte's decomposition, these insights into the developed nanoscale microstructure interacting with the electrolyte contribute to understanding the self-catalyzed/accelerated degradation Si anodes and can inform new battery designs unaffected by these life-limiting factors.
Wu Y, Skokov KP, Schafer L, et al., 2022, A comparative study of Nd (15) Fe B-78 ( 7) and Nd (15) Co 78 B (7) systems: phase formations and coercivity mechanisms, ACTA MATERIALIA, Vol: 240, ISSN: 1359-6454
Gomell L, Tsai S-P, Roscher M, et al., 2022, In situ nitriding of Fe2VAl during laser surface remelting to manipulate microstructure and crystalline defects, PHYSICAL REVIEW MATERIALS, Vol: 6, ISSN: 2475-9953
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- Citations: 1
Gomell L, Tsai S-P, Roscher M, et al., 2022, <i>In situ</i> nitriding of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Fe</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>VAl</mml:mi></mml:mrow></mml:math> during laser surface remelting to manipulate microstructure and crystalline defects, Physical Review Materials, Vol: 6
Gault B, Schweinar K, Zhang S, et al., 2022, Correlating atom probe tomography with x-ray and electron spectroscopies to understand microstructure-activity relationships in electrocatalysts, MRS BULLETIN, Vol: 47, Pages: 718-726, ISSN: 0883-7694
Han L, Maccari F, Souza Filho IR, et al., 2022, A mechanically strong and ductile soft magnet with extremely low coercivity, NATURE, Vol: 608, Pages: 310-316, ISSN: 0028-0836
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- Citations: 7
Sun Z, Ma Y, Ponge D, et al., 2022, Thermodynamics-guided alloy and process design for additive manufacturing, NATURE COMMUNICATIONS, Vol: 13
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- Citations: 7
López Freixes M, Zhou X, Zhao H, et al., 2022, Revisiting stress-corrosion cracking and hydrogen embrittlement in 7xxx-Al alloys at the near-atomic-scale., Nat Commun, Vol: 13
The high-strength 7xxx series aluminium alloys can fulfil the need for light, high strength materials necessary to reduce carbon-emissions, and are extensively used in aerospace for weight reduction purposes. However, as all major high-strength materials, these alloys can be sensitive to stress-corrosion cracking (SCC) through anodic dissolution and hydrogen embrittlement (HE). Here, we study at the near-atomic-scale the intra- and inter-granular microstructure ahead and in the wake of a propagating SCC crack. Moving away from model alloys and non-industry standard tests, we perform a double cantilever beam (DCB) crack growth test on an engineering 7xxx Al-alloy. H is found segregated to planar arrays of dislocations and to grain boundaries that we can associate to the combined effects of hydrogen-enhanced localised plasticity (HELP) and hydrogen-enhanced decohesion (HEDE) mechanisms. We report on a Mg-rich amorphous hydroxide on the corroded crack surface and evidence of Mg-related diffusional processes leading to dissolution of the strengthening η-phase precipitates ahead of the crack.
Xu Y, Toda H, Shimizu K, et al., 2022, Suppressed hydrogen embrittlement of high-strength Al alloys by Mn-rich intermetallic compound particles, ACTA MATERIALIA, Vol: 236, ISSN: 1359-6454
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- Citations: 4
Wang S, Gavalda-Diaz O, Luo T, et al., 2022, The effect of hydrogen on the multiscale mechanical behaviour of a La(Fe,Mn,Si)13-based magnetocaloric material, Journal of Alloys and Compounds, Vol: 906, Pages: 1-10, ISSN: 0925-8388
Magnetocaloric cooling offers the potential to improve the efficiency of refrigeration devices and hence cut the significant CO2 emissions associated with cooling processes. A critical issue in deployment of this technology is the mechanical degradation of the magnetocaloric material during processing and operation, leading to limited service-life. The mechanical properties of hydrogenated La(Fe,Mn,Si)13-based magnetocaloric material are studied using macroscale bending tests of polycrystalline specimens and in situ micropillar compression tests of single crystal specimens. The impact of hydrogenation on the mechanical properties are quantified. Understanding of the deformation/failure mechanisms is aided by characterization with transmission electron microscopy and atom probe tomography to reveal the arrangement of hydrogen atoms in the crystal lattice. Results indicate that the intrinsic strength of this material is ~3-6 GPa and is dependent on the crystal orientation. Single crystals under compressive load exhibit shearing along specific crystallographic planes. Hydrogen deteriorates the strength of La(Fe,Mn,Si)13 through promotion of transgranular fracture. The weakening effect of hydrogen on single crystals is anisotropic; it is significant upon shearing parallel to the {111} crystallographic planes but is negligible when the shear plane is {001}-oriented. APT analysis suggests that this is associated with the close arrangement of hydrogen atoms on {222} planes.
Kim S-H, Yoo S-H, Shin S, et al., 2022, Controlled Doping of Electrocatalysts through Engineering Impurities, ADVANCED MATERIALS, Vol: 34, ISSN: 0935-9648
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- Citations: 3
Dubosq R, Schneider DA, Zhou X, et al., 2022, Bubbles and atom clusters in rock melts: A chicken and egg problem, JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH, Vol: 428, ISSN: 0377-0273
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- Citations: 1
Raabe D, Ponge D, Uggowitzer PJ, et al., 2022, Making sustainable aluminum by recycling scrap: The science of "dirty " alloys, PROGRESS IN MATERIALS SCIENCE, Vol: 128, ISSN: 0079-6425
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- Citations: 11
Tan Q, Yan Z, Wang H, et al., 2022, The role of β pockets resulting from Fe impurities in hydride formation in titanium, Scripta Materialia, Vol: 213, Pages: 114640-114640, ISSN: 1359-6462
The corrosion potential of commercially pure titanium in NaCl solutions is dramatically affected by trace Fe additions, which cause the appearance of submicron pockets of β phase at grain boundary triple points. Furthermore, the low solubility of hydrogen in hexagonal close-packed α-Ti makes titanium alloys prone to subsequent hydride-associated failures due to stress corrosion cracking. We analyzed α-α and α-β sections of the abutting grain boundary of a β pocket in a Grade 2 CP-Ti, and the α-β phase boundary. Fe and H partition to β and segregate at the grain boundary, but no segregation is seen at the α-β phase boundary. In contrast, a significant Ni (>1 at%) accumulation is observed at the α-β phase boundary. We propose that the β-pockets act as hydrogen traps and facilitate the nucleation and growth of hydrides along grain boundaries in CP-Ti.
da Silva AK, Souza Filho IR, Lu W, et al., 2022, A sustainable ultra-high strength Fe18Mn3Ti maraging steel through controlled solute segregation and alpha-Mn nanoprecipitation, NATURE COMMUNICATIONS, Vol: 13
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- Citations: 5
Ma Y, Filho IRS, Bai Y, et al., 2022, Hierarchical nature of hydrogen-based direct reduction of iron oxides, SCRIPTA MATERIALIA, Vol: 213, ISSN: 1359-6462
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- Citations: 4
Joseph S, Kontis P, Chang Y, et al., 2022, A cracking oxygen story: a new view of stress corrosion cracking in titanium alloys, Acta Materialia, Vol: 227, Pages: 117687-117687, ISSN: 1359-6454
Titanium alloys can suffer from halide-associated stress corrosion cracking at elevated temperatures e.g., in jet engines, where chlorides and Ti-oxide promote the cracking of water vapour in the gas stream, depositing embrittling species at the crack tip. Here we report, using isotopically-labelled experiments, that crack tips in an industrial Ti-6Al-2Sn-4Zr-6Mo alloy are strongly enriched (>5 at.%) in oxygen from the water vapour, far greater than the amounts (0.25 at.%) required to embrittle the material. Surprisingly, relatively little hydrogen (deuterium) is measured, despite careful preparation and analysis. Therefore, we suggest that a combined effect of O and H leads to cracking, with O playing a vital role, since it is well-known to cause embrittlement of the alloy. In contrast it appears that in α + β Ti alloys, it may be that H may drain away into the bulk owing to its high solubility in β-Ti, rather than being retained in the stress field of the crack tip. Therefore, whilst hydrides may form on the fracture surface, hydrogen ingress might not be the only plausible mechanism of embrittlement of the underlying matrix. This possibility challenges decades of understanding of stress-corrosion cracking as being related solely to the hydrogen enhanced localised plasticity (HELP) mechanism, which explains why H-doped Ti alloys are embrittled. This would change the perspective on stress corrosion embrittlement away from a focus purely on hydrogen to also consider the ingress of O originating from the water vapour, insights critical for designing corrosion resistant materials.
Poplawsky JD, Pillai R, Ren Q-Q, et al., 2022, Measuring oxygen solubility in Ni grains and boundaries after oxidation using atom probe tomography, SCRIPTA MATERIALIA, Vol: 210, ISSN: 1359-6462
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- Citations: 1
Varanasi RS, Gault B, Ponge D, 2022, Effect of Nb micro-alloying on austenite nucleation and growth in a medium manganese steel during intercritical annealing, ACTA MATERIALIA, Vol: 229, ISSN: 1359-6454
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- Citations: 4
Liu C, Lu W, Xia W, et al., 2022, Massive interstitial solid solution alloys achieve near-theoretical strength, NATURE COMMUNICATIONS, Vol: 13
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- Citations: 10
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