scholarly journals Three-dimensional atomic mapping of ligands on palladium nanoparticles by atom probe tomography

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kyuseon Jang ◽  
Se-Ho Kim ◽  
Hosun Jun ◽  
Chanwon Jung ◽  
Jiwon Yu ◽  
...  
Keyword(s):  
Atom Probe Tomography ◽  
Electrostatic Interactions ◽  
Density Functional ◽  
Imaging Techniques ◽  
Three Dimensional ◽  
Pd Nanoparticles ◽  
Atom Probe ◽  
Atomic Scale ◽  
Colloidal Synthesis ◽  
Spectroscopic Techniques

AbstractCapping ligands are crucial to synthesizing colloidal nanoparticles with functional properties. However, the synergistic effect between different ligands and their distribution on crystallographic surfaces of nanoparticles during colloidal synthesis is still unclear despite powerful spectroscopic techniques, due to a lack of direct imaging techniques. In this study, atom probe tomography is adopted to investigate the three-dimensional atomic-scale distribution of two of the most common types of these ligands, cetrimonium (C19H42N) and halide (Br and Cl) ions, on Pd nanoparticles. The results, validated using density functional theory, demonstrate that the Br anions adsorbed on the nanoparticle surfaces promote the adsorption of the cetrimonium cations through electrostatic interactions, stabilizing the Pd {111} facets. In contrast, the Cl anions are not strongly adsorbed onto the Pd surfaces. The high density of adsorbed cetrimonium cations for Br anion additions results in the formation of multiple-twinned nanoparticles with superior oxidation resistance.

scholarly journals Atom Probe Analysis of Ex Situ Gas-Charged Stable Hydrides

2017 ◽  
Vol 23 (2) ◽  
pp. 307-313 ◽  
Author(s):  
Daniel Haley ◽  
Paul A. J. Bagot ◽  
Michael P. Moody
Keyword(s):  
Atom Probe Tomography ◽  
Three Dimensional ◽  
Atom Probe ◽  
Atomic Scale ◽  
Ex Situ ◽  
Native Oxide ◽  
Probe Analysis ◽  
Atom Probe Tomography Analysis ◽  
Hydrogen Analysis ◽  
Atom Probe Analysis

AbstractIn this work, we report on the atom probe tomography analysis of two metallic hydrides formed by pressurized charging using an ex situ hydrogen charging cell, in the pressure range of 200–500 kPa (2–5 bar). Specifically we report on the deuterium charging of Pd/Rh and V systems. Using this ex situ system, we demonstrate the successful loading and subsequent atom probe analysis of deuterium within a Pd/Rh alloy, and demonstrate that deuterium is likely present within the oxide–metal interface of a native oxide formed on vanadium. Through these experiments, we demonstrate the feasibility of ex situ hydrogen analysis for hydrides via atom probe tomography, and thus a practical route to three-dimensional imaging of hydrogen in hydrides at the atomic scale.

scholarly journals Origins of the hydrogen signal in atom probe tomography: Case studies of alkali and noble metals

2021 ◽  
Author(s):  
Su-Hyun Yoo ◽  
Se-Ho Kim ◽  
Eric Woods ◽  
Baptiste Gault ◽  
Mira Todorova ◽  
...  
Keyword(s):  
Atom Probe Tomography ◽  
Density Functional ◽  
Noble Metals ◽  
Alkali Metals ◽  
Atom Probe ◽  
Operating Conditions ◽  
Atomic Scale ◽  
Three Dimensions ◽  
High Signal ◽  
Specimen Preparation

Abstract Atom Probe Tomography (APT) analysis is being actively used to provide near-atomic-scale information on the composition of complex materials in three-dimensions. In recent years, there has been a surge of interest in the technique to investigate the distribution of hydrogen in metals. However, the presence of hydrogen in the analysis of almost all specimens from nearly all material systems has caused numerous debates as to its origins and impact on the quantitativeness of the measurement. It is often perceived that most H arises from residual gas ionization, therefore affecting primarily materials with a relatively low evaporation field. In this work, we perform systematic investigations to identify the origin of H residuals in APT experiments by combining density-functional theory (DFT) calculations and APT measurements on an alkali and a noble metal, namely Na and Pt, respectively. We report that no H residual is found in Na metal samples, but in Pt, which has a higher evaporation field, a relatively high signal of H is detected. These results contradict the hypothesis of the H signal being due to direct ionization of residual H2 without much interaction with the specimen's surface. Based on DFT, we demonstrate that alkali metals are thermodynamically less likely to be subject to H contamination under APT-operating conditions compared to transition or noble metals. These insights indicate that the detected H-signal is not only from ionization of residual gaseous H2 alone, but is strongly influenced by material-specific physical properties. The origin of H residuals is elucidated by considering different conditions encountered during APT experiments, specifically, specimen-preparation, transportation, and APT-operating conditions by taking thermodynamic and kinetic aspects into account.

scholarly journals Aluminum depletion induced by co-segregation of carbon and boron in a bcc-iron grain boundary

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
A. Ahmadian ◽  
D. Scheiber ◽  
X. Zhou ◽  
B. Gault ◽  
C. H. Liebscher ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Atom Probe Tomography ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Local Variation ◽  
Atom Probe ◽  
Atomic Scale ◽  
Polycrystalline Materials ◽  
Repulsive Interaction ◽  
Structural Units

AbstractThe local variation of grain boundary atomic structure and chemistry caused by segregation of impurities influences the macroscopic properties of polycrystalline materials. Here, the effect of co-segregation of carbon and boron on the depletion of aluminum at a Σ5 (3 1 0 )[0 0 1] tilt grain boundary in a α − Fe-4 at%Al bicrystal is studied by combining atomic resolution scanning transmission electron microscopy, atom probe tomography and density functional theory calculations. The atomic grain boundary structural units mostly resemble kite-type motifs and the structure appears disrupted by atomic scale defects. Atom probe tomography reveals that carbon and boron impurities are co-segregating to the grain boundary reaching levels of >1.5 at%, whereas aluminum is locally depleted by approx. 2 at.%. First-principles calculations indicate that carbon and boron exhibit the strongest segregation tendency and their repulsive interaction with aluminum promotes its depletion from the grain boundary. It is also predicted that substitutional segregation of boron atoms may contribute to local distortions of the kite-type structural units. These results suggest that the co-segregation and interaction of interstitial impurities with substitutional solutes strongly influences grain boundary composition and with this the properties of the interface.

scholarly journals An atomic-scale view at the composition of amyloid-beta fibrils by atom probe tomography

2018 ◽  
Author(s):  
Kristiane A.K. Rusitzka ◽  
Leigh T. Stephenson ◽  
Agnieszka Szczepaniak ◽  
Lothar Gremer ◽  
Dierk Raabe ◽  
...  
Keyword(s):  
Amyloid Beta ◽  
Atom Probe Tomography ◽  
Senile Plaques ◽  
Three Dimensional ◽  
Atom Probe ◽  
Pulse Frequency ◽  
Atomic Scale ◽  
Chemical Information ◽  
Protein Fibrils ◽  
Spectrometry Technique

ABSTRACTAmyloid-beta (Aβ) proteins play an important role in a number of neurodegenerative diseases. Aβ is found in senile plaques in brains of Alzeimer’s disease patients. The 42 residues of the monomer form dimers which stack to fibrils gaining several micrometers in length. Using Aβ fibrils with 13C and 15N marker substitution, we developed an innovative approach to obtain insights to structural and chemical information of the protein. We deposited the modified protein fibrils to pre-sharped aluminium needles with >100-nm apex diameters and, using the position-sensitive mass-to-charge spectrometry technique of atom probe tomography, we acquired the chemically-resolved three dimensional information for every detected ion evaporated in small fragments from the protein. We also discuss the influence of experimental parameters such as pulse energy and pulse frequency of the used Laser beam which lead to differences in the size of the gained fragments, developing the capability of localising metal atom within Aβ plaques.

New Frontiers in Electrocatalyst Characterization – Three Dimensional Atomic-Scale Insights By Atom Probe Tomography

2020 ◽  
Vol MA2020-01 (45) ◽  
pp. 2561-2561
Author(s):  
Kevin Schweinar ◽  
Se-Ho Kim ◽  
Joohyun Lim ◽  
Christina Scheu ◽  
Dierk Raabe ◽  
...  
Keyword(s):  
Atom Probe Tomography ◽  
Three Dimensional ◽  
Atom Probe ◽  
Atomic Scale

Chemical and Structural Characterization of γ/γ′ Interfaces

2012 ◽  
Vol 463-464 ◽  
pp. 20-24
Author(s):  
Kai Zhao
Keyword(s):  
Atom Probe Tomography ◽  
Three Dimensional ◽  
Atom Probe ◽  
Scanning Transmission Electron Microscope ◽  
Atomic Scale ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Nickel Base

More attention has been paid to the interfaces since mechanical properties of nickel-base superalloys are determined to some degree by them. The compositional transition across γ/γ′ interfaces and atomic structure of the interfaces was investigated using three-dimensional atom probe tomography and scanning transmission electron microscope equipped with high-resolution Energy Dispersive X-ray Spectrometry. Results show that no obvious segregation to the interfaces or ledges of the precipitates in the present experimental alloys has been observed. Also, adsorption of a solute to the interface was not observed. The interfaces are not flat as usually thought at an atomic scale. The interfacial thickness is about two atomic layers, i.e. 0.7 nm.

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