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A Brief Overview of Atom Probe Tomography Research
Gault, Baptiste Korean Society of Microscopy 2016 Applied microscopy Vol.46 No.3
Atom probe tomography (APT) has been fast rising in prominence over the past decade as a key tool for nanoscale analytical characterization of a range of materials systems. APT provides three-dimensional mapping of the atom distribution in a small volume of solid material. The technique has evolved, with the incorporation of laser pulsing capabilities, and, combined with progress in specimen preparation, APT is now able to analyse a very range of materials, beyond metals and alloys that used to be its core applications. The present article aims to provide an overview of the technique, providing a brief historical perspective, discussing recent progress leading to the state-of-the-art, some perspectives on its evolution, with targeted examples of applications.
Economic Growth and Institutions: The Influence of External Actors
David Arellano-Gault,Walter Lepore 연세대학교(미래캠퍼스) 빈곤문제국제개발연구원 2008 地域發展硏究 Vol.17 No.2
This paper analyzes the relationship among institutions and economic growth. Based on a review of the current literature on institutional analysis, in particular that related with New Institutional Economics (NIE), we identify and propose a means of integrating additional factors that need to be assessed. In our review, we focus on those studies that emphasize property and contractual rights as being the main explicative variables of economic growth. The principal hypothesis of this current of thought is that liberal (democratic) and market institutions are a prerequisite for encouraging investment, efficiency, innovation, employment, and consequently, economic growth. Latin America developing countries in terms of economic growth. Our results suggest that path dependence variables are as important as the variables traditionally set forth in the literature on NIE. Although our investigation is still in its infancy, in publishing this article we seek to complement NIE’s institutional analysis through introducing variables that are more realistic, complex and useful than the rather simplistic relationships between institutions and economic growth that NIE has heretofore proposed
Peng, Zirong,Choi, Pyuck-Pa,Gault, Baptiste,Raabe, Dierk Cambridge University Press 2017 Microscopy and Microanalysis Vol.23 No.2
<B>Abstract</B><P>Cemented tungsten carbide has been analyzed using laser-pulsed atom probe tomography (APT). The influence of experimental parameters, including laser pulse energy, pulse repetition rate, and specimen base temperature, on the acquired data were evaluated from different aspects, such as mass spectrum, chemical composition, noise-to-signal ratio, and multiple events. Within all the applied analysis conditions, only 1 MHz pulse repetition rate led to a strong detector saturation effect, resulting in a largely biased chemical composition. A comparative study of the laser energy settings showed that an ~12 times higher energy was required for the less focused green laser of the LEAP<SUP>TM</SUP> 3000X HR system to achieve a similar evaporation field as the finer spot ultraviolet laser of the LEAP<SUP>TM</SUP> 5000 XS system.</P>
Atomic diffusion induced degradation in bimetallic layer coated cemented tungsten carbide
Peng, Zirong,Rohwerder, Michael,Choi, Pyuck-Pa,Gault, Baptiste,Meiners, Thorsten,Friedrichs, Marcel,Kreilkamp, Holger,Klocke, Fritz,Raabe, Dierk Elsevier 2017 Corrosion science Vol.120 No.-
<P>We investigated the temporal degradation of glass moulding dies, made of cemented tungsten carbide coated with PtIr on an adhesive Cr or Ni interlayer, by electron microscopy and atom probe tomography. During the exposure treatments at 630 degrees C under an oxygen partial pressure of 1.12 x 10(-23) bar, Cr (Ni) was found to diffuse outwards via grain boundaries in the PtIr, altering the surface morphology. Upon dissolution of the interlayer, the WC substrate also started degrading. Extensive interdiffusion processes involving PtIr, Cr (Ni) and WC took place, leading to the formation of intermetallic phases and voids, deteriorating the adhesion of the coating. (C) 2017 The Authors. Published by Elsevier Ltd.</P>
Elemental partitioning and site-occupancy in γ/γ′ forming Co-Ti-Mo and Co-Ti-Cr alloys
Im, Hye Ji,Makineni, Surendra K.,Gault, Baptiste,Stein, Frank,Raabe, Dierk,Choi, Pyuck-Pa Elsevier 2018 Scripta materialia Vol.154 No.-
<P><B>Abstract</B></P> <P>We report on the sub-nanometer scale characterization of Co-12Ti-4Mo and Co-12Ti-4Cr (at.%) model alloys. Atom probe tomography reveals that Co and Cr partition to γ, whereas Ti and Mo to γ′. Additions of Mo and Cr to the reference Co-12Ti system lead to strong increases in γ′ volume fraction by about 25% and 12%, respectively. Element-specific spatial distribution maps along the [001] direction of the L1<SUB>2</SUB>-ordered γ′ phase reveal that both Mo and Cr preferentially replace Ti on its sublattice. The remaining excess Ti is available for formation of additional γ′, resulting in enhanced γ′ volume fractions.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
On the detection of multiple events in atom probe tomography
Peng, Zirong,Vurpillot, Francois,Choi, Pyuck-Pa,Li, Yujiao,Raabe, Dierk,Gault, Baptiste Elsevier 2018 Ultramicroscopy Vol.189 No.-
<P><B>Abstract</B></P> <P>In atom probe tomography (APT), multiple events can arise as a consequence of e.g. correlated field evaporation and molecular ion dissociation. They represent challenging cases for single-particle detectors and can cause compositional as well as spatial inaccuracies. Here, two state-of-the-art atom probe microscopes (Cameca LEAP 5000 XS and 5000 XR) were used to investigate cemented tungsten carbide, which exhibits high amounts of multiple events. By advanced data analysis methods, the natural character of the multiple events, as well as the performance of the APT detectors, are assessed. Accordingly, possible signal loss mechanisms are discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Delay line detectors in atom probe tomography exhibit dead time and dead zone. </LI> <LI> For both Cameca LEAP 5000 XS and 5000 XR instruments, the dead time is about 3 ns. </LI> <LI> The dead zone evolves with the propagation of signals on the delay lines. </LI> <LI> The dead time and dead zone can cause signal loss during multiple events detection. </LI> <LI> The compositional and spatial accuracies can be strongly deteriorated. </LI> </UL> </P>