Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 39 for “"atom probe tomography"”.
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Atom probe tomography study of wide bandgap semiconductor materials
This dissertation focuses on developing atom probe tomography (APT) for semiconductors. APT is quickly gaining interest in the field of material characterization because of its unique ability to provide 3D nanoscale studies. APT has been widely used in metals and conductive materials but design …
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Nitride semiconductors studied by atom probe tomography and correlative techniques
… transmission electron microscopy (TEM), and atomic force microscopy (AFM). This thesis describes the study of nitride semiconductor materials using these traditional methods, as well as atom probe tomography (APT), a technique more usually applied to metals that provides three-dimensional …
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Self-organization of Cu-based immiscible alloys under irradiation: an atom-probe tomography study
… impart energy into the material, thereby causing atomic displacements to occur. These displacements result in the creation of point defects and the random ballistic mixing of the atoms. Consequently, the material is driven away from its equilibrium structure. The supersaturation of defects can …
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Characterization and Mechanical Properties of Nanoscale Precipitates in Modified Al-Si-Cu Alloys Using Transmission Electron Microscopy and 3D Atom Probe Tomography.
… electron microscopy and three dimensional atom probe tomography. The Mn and Mg effects on the microstructure and mechanical properties are discussed with crystallographic study on the iron intermetallic phases. The microstructural evolution and nucleation study on the precipitates in the …
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Amorphization and De-vitrification in Immiscible Copper-Niobium Alloy Thin Films
… in immiscible Cu-Nb alloy thin films using 3D atom probe tomography has been presented. This evidence clearly indicates that the nanoscale phase separation is responsible for the stabilization of the amorphous phase in such immiscible systems since it substantially reduces the free energy of …
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Effect of microalloying on pearlite transformation of high carbon wire steels
… apparent based on a Taleff regression analysis. Atom probe tomography of an industrially processed wire rod with vanadium additions revealed vanadium enrichment of cementite, and vanadium supersaturation in ferrite. Enhanced nucleation of V(C,N) on prior austenite grain boundaries was …
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Phase stability in ti/bcc multilayered thin films
… have been employed to determine the phase with atom probe tomography used to characterize the chemical compositions within the materials and across the interfaces. This work will delineate how intrinsic film stress drives compositional intermixing across such interfaces which can …
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Stability of nanostructured : amorphous aluminum-manganese alloys
… alloys were studied via three dimensional atom probe tomography and aberration-corrected scanning electron microscopy. The segregation energies were calculated based on the experimental results and compared with the values calculated from a thermodynamic-based segregation model. Upon …
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Advanced characterization of the early-stage evolution of microstructures and mechanical properties in neutron-irradiated commercial steels
… transmission electron microscopy (TEM), atom probe tomography (APT) and energy dispersive X-ray spectroscopy (EDS), the nucleation, growth and stability of dislocation loops, G phase, α’ phase, and other precipitates were quantitatively analyzed. The irradiation hardening in these two …
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Probing complex ionic dynamics on the nanoscale via energy discovery platforms
… in-situ techniques, i.e. time-resolved Kelvin probe force microscopy and electrochemical impedance spectroscopy, were performed on the same sample to cover a full range of ionic response. Structural and compositional analysis were performed via a variety of techniques including atomic force …
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Role of alloy additions on strengthening in 17-4 PH stainless steel
… (Cu) precipitation in steels was studied using atom probe tomography. A narrower precipitate size distribution was observed in the steels with Co addition. The concentration profile across the matrix / precipitate interface indicated rejection of Co atoms from the copper precipitates. This …
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Effects of copper on wear and rolling-sliding contact fatigue of rail steels
… copper content within the hypereutectoid steels. Atom probe tomography was used to investigate the location of the copper within the hypereutectoid rail steels, and clusters of higher copper concentration within the ferrite at the ferrite/cementite interface were observed.
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Shear induced mixing and self-organization in immiscible alloys during severe plastic deformation
… transmission electron microscopy (TEM), and atom probe tomography (APT). The experimental results support the prediction of a ‘superdiffusive’ model for shear induced mixing in Cu-Ag system, where the dissolution rate of particles is controlled by the rate of dislocation glide across …
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Microstructural alterations in bearing steels under rolling contact fatigue
… transmission electron microscopy (TEM) and atom probe tomography (APT), with the observation validating the postulated formation mechanisms. It is demonstrated that DERs, WEBs and WEAs follow the same principle during formation – strain induced carbon redistribution. This is the first time …
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Hard and tough electrodeposited aluminum-manganese alloys with tailored nanostructures
… in these alloys are investigated using atom probe tomography. Implanted Ga ions are used as chemical markers for the amorphous phase; this method permits more robust phase identification and measurement of their compositions. Whereas uniform Mn distributions are observed in the single …
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Mechanisms of microstructural damage during rolling contact fatigue of bearing steels
… area were studied both on a macroscale and on an atomic-scale. The degree of stress concentration near a microcrack was calculated employing a nite element method. The microstructure, as well as the segregation behaviour of alloying elements in the white-etching area, were investigated by …
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Microstructural evolution of silicate immiscible liquids in solidifying ferrobasalts
… (Iceland). High-resolution imaging, electron probe microanalysis, and atom probe tomography are combined to examine the role played by compositional boundary layers in promoting unmixing around growing crystals at melt-crystal interfaces. The effects of cooling rate on silicate liquid …
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Enhancing stability of powder-route nanocrystalline tungsten-titanium via alloy thermodynamics
… Nanocrystalline tungsten alloys with 0-20 atomic percent titanium content are produced by high-energy ball milling and tested at the expected sintering temperature of 1100°C. With an addition of 20 atomic percent titanium, nanocrystalline tungsten shows retention of nanoscale grain size …
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Weibull mixture model for grouped data and pattern identification in spatial and spatial-temporal data.
… tools for charactering materials at the atomic level with a multivariate three-dimensional atom probe tomography dataset as an example. We use Moran's I statistic to study the global spatial structure of each atomic feature and apply the local indicator of spatial association (LISA) to …
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STUDY OF WURTZITE AND ZINCBLENDE GAN BASED GREEN LED HETEROSTRUCTURE
… and was further confirmed by the measurements in atom probe tomography (APT). Indium was found segregating next to the SFs whereas aluminium was found segregating to the SFs. Protruding surface features were produced by the growth of QWs and were suggested to correlate with SF bunches. …
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