scholarly journals Vacancy-controlled ultrastable nanoclusters in nanostructured ferritic alloys

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Z. W. Zhang ◽  
L. Yao ◽  
X.-L. Wang ◽  
M. K. Miller
Keyword(s):  
Atom Probe Tomography ◽  
State Of The Art ◽  
Atom Probe ◽  
High Dose ◽  
Ferritic Alloy ◽  
Ferritic Alloys ◽  
New Class ◽  
O Vacancy ◽  
Dose Radiation

Abstract A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. Here we report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using a combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters.

Towards Radiation Tolerant Nanostructured Ferritic Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 23-28 ◽  
Author(s):  
Michael K. Miller ◽  
David T. Hoelzer ◽  
Kaye F. Russell
Keyword(s):  
Atom Probe Tomography ◽  
Isothermal Annealing ◽  
Extreme Environments ◽  
Atom Probe ◽  
Extrusion Process ◽  
Ferritic Alloys ◽  
New Class ◽  
Significant Difference ◽  
Radiation Tolerant ◽  
Yttria Powder

The high temperature and irradiation response of a new class of nanostructured ferritic alloys have been investigated by atom probe tomography. These materials are candidate materials for use in the extreme environments that will be present in the next generation of power generating systems. Atom probe tomography has revealed that the yttria powder is forced into solid solution during the mechanical alloying process andsubsequently 2-nm-diameter Ti-, Y- and O-enriched nanoclusters are formedduring the extrusion process. These nanoclusters have been shown to be remarkably stable during isothermal annealing treatments up to 0.92 of the melting temperature and during proton irradiation up to 3 displacements per atom. No significant difference in sizes, compositions and number densities of the nanoclusters was also observed between the unirradiated and proton irradiated conditions. The grain boundaries were found to have high number densities of nanoclusters as well as chromium and tungsten segregation which pin the grain boundary to minimize creep and grain growth.

A new approach to atomic level characterization of grain boundaries by atom probe tomography

2014 ◽  
Vol 1645 ◽  
Author(s):  
L. Yao ◽  
M. K. Miller
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Atom Probe Tomography ◽  
Ion Irradiation ◽  
Atom Probe ◽  
Heavy Ion ◽  
Solute Segregation ◽  
Full Description ◽  
High Dose ◽  
Ferritic Alloy

ABSTRACTA novel atom probe tomography (APT) method has been developed that enables a full description of the orientation relationship between individual grains to be determined together with estimates of the extents of solute segregation for all elements over the surface of the grain boundary with 1 nm by 1 nm spatial resolution. This approach also enables variations in the solute excess for the elements with the habit plane and curvature of the grain boundary to be evaluated. The method has been applied to a mechanically-alloyed nanostructured ferritic alloy (NFA) after high dose heavy ion irradiation. The innovative high-resolution two-dimensional mapping of the solute segregation across the surface of grain boundaries in the NFA clearly demonstrates that the distributions of chromium and tungsten are not uniform across the grain boundaries, and the distributions correlate with changes in its local curvature and the position of the grain boundary precipitates. These features pin the grain boundary against grain growth and provide the stability for excellent creep properties.

scholarly journals Nanoscale Perspectives of Metal Degradation via In Situ Atom Probe Tomography

2020 ◽  
Vol 63 (15-18) ◽  
pp. 1606-1622 ◽  
Author(s):  
Sten V. Lambeets ◽  
Elizabeth J. Kautz ◽  
Mark G. Wirth ◽  
Graham J. Orren ◽  
Arun Devaraj ◽  
...  
Keyword(s):  
Heterogeneous Catalysis ◽  
Instrument Development ◽  
Atom Probe Tomography ◽  
Atom Probe ◽  
Development Effort ◽  
Subsurface Structure ◽  
Structure Changes ◽  
Reactor Cell ◽  
Reactive Gas

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

scholarly journals An in-situ approach for preparing atom probe tomography specimens by xenon plasma-focussed ion beam

2019 ◽  
Vol 202 ◽  
pp. 121-127 ◽  
Author(s):  
J.E. Halpin ◽  
R.W.H. Webster ◽  
H. Gardner ◽  
M.P. Moody ◽  
P.A.J. Bagot ◽  
...  
Keyword(s):  
Atom Probe Tomography ◽  
Ion Beam ◽  
Atom Probe ◽  
Focussed Ion Beam

scholarly journals In-situ and In-operando Cobalt Oxidation Studied by Atom Probe Tomography

2020 ◽  
Vol 26 (S2) ◽  
pp. 1872-1873
Author(s):  
Sten Lambeets ◽  
Mark Wirth ◽  
Graham Orren ◽  
Norbert Kruse ◽  
Daniel Perea
Keyword(s):  
Atom Probe Tomography ◽  
Atom Probe ◽  
Cobalt Oxidation ◽  
In Operando

Electron Beam-Induced Deposition for Atom Probe Tomography Specimen Capping Layers

2016 ◽  
Vol 23 (2) ◽  
pp. 321-328 ◽  
Author(s):  
David R. Diercks ◽  
Brian P. Gorman ◽  
Johannes J. L. Mulders
Keyword(s):  
Electron Beam ◽  
Atom Probe Tomography ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Atom Probe ◽  
Near Surface ◽  
Surface Features ◽  
Dicobalt Octacarbonyl ◽  
Electron Beam Induced Deposition

AbstractSix precursors were evaluated for use as in situ electron beam-induced deposition capping layers in the preparation of atom probe tomography specimens with a focus on near-surface features where some of the deposition is retained at the specimen apex. Specimens were prepared by deposition of each precursor onto silicon posts and shaped into sub-70-nm radii needles using a focused ion beam. The utility of the depositions was assessed using several criteria including composition and uniformity, evaporation behavior and evaporation fields, and depth of Ga+ ion penetration. Atom probe analyses through depositions of methyl cyclopentadienyl platinum trimethyl, palladium hexafluoroacetylacetonate, and dimethyl-gold-acetylacetonate [Me2Au(acac)] were all found to result in tip fracture at voltages exceeding 3 kV. Examination of the deposition using Me2Au(acac) plus flowing O2 was inconclusive due to evaporation of surface silicon from below the deposition under all analysis conditions. Dicobalt octacarbonyl [Co2(CO)8] and diiron nonacarbonyl [Fe2(CO)9] depositions were found to be effective as in situ capping materials for the silicon specimens. Their very different evaporation fields [36 V/nm for Co2(CO)8 and 21 V/nm for Fe2(CO)9] provide options for achieving reasonably close matching of the evaporation field between the capping material and many materials of interest.

New Atom Probe Tomography Reconstruction Algorithm for Multilayered Samples: Beyond the Hemispherical Constraint

2017 ◽  
Vol 23 (2) ◽  
pp. 247-254 ◽  
Author(s):  
Nicolas Rolland ◽  
François Vurpillot ◽  
Sébastien Duguay ◽  
Baishakhi Mazumder ◽  
James S. Speck ◽  
...  
Keyword(s):  
Experimental Data ◽  
Atom Probe Tomography ◽  
State Of The Art ◽  
Reconstruction Algorithm ◽  
Atom Probe ◽  
Field Evaporation ◽  
Standard State ◽  
Reconstruction Methods ◽  
Tomography Reconstruction ◽  
Specimen Shape

AbstractAccuracy of atom probe tomography measurements is strongly degraded by the presence of phases that have different evaporation fields. In particular, when there are perpendicular interfaces to the tip axis in the specimen, layers thicknesses are systematically biased and the resolution is degraded near the interfaces. Based on an analytical model of field evaporated emitter end-form, a new algorithm dedicated to the 3D reconstruction of multilayered samples was developed. Simulations of field evaporation of bilayer were performed to evaluate the effectiveness of the new algorithm. Compared to the standard state-of-the-art reconstruction methods, the present approach provides much more accurate analyzed volume, and the resolution is clearly improved near the interface. The ability of the algorithm to handle experimental data was also demonstrated. It is shown that the standard algorithm applied to the same data can commit an error on the layers thicknesses up to a factor 2. This new method is not constrained by the classical hemispherical specimen shape assumption.

Martensite to austenite reversion in a high-Mn steel: Partitioning-dependent two-stage kinetics revealed by atom probe tomography, in-situ magnetic measurements and simulation

2019 ◽  
Vol 166 ◽  
pp. 178-191 ◽  
Author(s):  
I.R. Souza Filho ◽  
A. Kwiatkowski da Silva ◽  
M.J.R. Sandim ◽  
D. Ponge ◽  
B. Gault ◽  
...  
Keyword(s):  
Atom Probe Tomography ◽  
Magnetic Measurements ◽  
Atom Probe ◽  
Two Stage ◽  
Mn Steel

In-situ observation of non-hemispherical tip shape formation during laser-assisted atom probe tomography

2011 ◽  
Vol 109 (10) ◽  
pp. 104909 ◽  
Author(s):  
S. Koelling ◽  
N. Innocenti ◽  
A. Schulze ◽  
M. Gilbert ◽  
A. K. Kambham ◽  
...  
Keyword(s):  
Atom Probe Tomography ◽  
Atom Probe ◽  
In Situ Observation ◽  
Shape Formation

The Application of the OPTICS Algorithm to Cluster Analysis in Atom Probe Tomography Data

2019 ◽  
Vol 25 (2) ◽  
pp. 338-348 ◽  
Author(s):  
Jing Wang ◽  
Daniel K. Schreiber ◽  
Nathan Bailey ◽  
Peter Hosemann ◽  
Mychailo B. Toloczko
Keyword(s):  
Cluster Analysis ◽  
Atom Probe Tomography ◽  
Spatial Clustering ◽  
Atom Probe ◽  
Atomic Density ◽  
Scale Model ◽  
Small Scale ◽  
Physical Parameters ◽  
Structure Property ◽  
Ferritic Alloy

AbstractAtom probe tomography (APT) is a powerful technique to characterize buried three-dimensional nanostructures in a variety of materials. Accurate characterization of those nanometer-scale clusters and precipitates is of great scientific significance to understand the structure–property relationships and the microstructural evolution. The current widely used cluster analysis method, a variant of the density-based spatial clustering of applications with noise algorithm, can only accurately extract clusters of the same atomic density, neglecting several experimental realities, such as density variations within and between clusters and the nonuniformity of the atomic density in the APT reconstruction itself (e.g., crystallographic poles and other field evaporation artifacts). This clustering method relies heavily on multiple input parameters, but ideal selection of those parameters is challenging and oftentimes ambiguous. In this study, we utilize a well-known cluster analysis algorithm, called ordering points to identify the clustering structures, and an automatic cluster extraction algorithm to analyze clusters of varying atomic density in APT data. This approach requires only one free parameter, and other inputs can be estimated or bounded based on physical parameters, such as the lattice parameter and solute concentration. The effectiveness of this method is demonstrated by application to several small-scale model datasets and a real APT dataset obtained from an oxide-dispersion strengthened ferritic alloy specimen.

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