scholarly journals Solute segregation and deviation from bulk thermodynamics at nanoscale crystalline defects

2016 ◽  
Vol 2 (12) ◽  
pp. e1601796 ◽  
Author(s):  
Michael S. Titus ◽  
Robert K. Rhein ◽  
Peter B. Wells ◽  
Philip C. Dodge ◽  
Gopal Babu Viswanathan ◽  
...  
Keyword(s):  
First Principles ◽  
Atomic Layer ◽  
Atom Probe ◽  
Solute Segregation ◽  
Chemical Mapping ◽  
Free Energies ◽  
Crystalline Defects ◽  
Transmission Electron ◽  
Bulk Thermodynamics ◽  
Scanning Transmission

It has long been known that solute segregation at crystalline defects can have profound effects on material properties. Nevertheless, quantifying the extent of solute segregation at nanoscale defects has proven challenging due to experimental limitations. A combined experimental and first-principles approach has been used to study solute segregation at extended intermetallic phases ranging from 4 to 35 atomic layers in thickness. Chemical mapping by both atom probe tomography and high-resolution scanning transmission electron microscopy demonstrates a markedly different composition for the 4–atomic-layer–thick phase, where segregation has occurred, compared to the approximately 35–atomic-layer–thick bulk phase of the same crystal structure. First-principles predictions of bulk free energies in conjunction with direct atomistic simulations of the intermetallic structure and chemistry demonstrate the breakdown of bulk thermodynamics at nanometer dimensions and highlight the importance of symmetry breaking due to the proximity of interfaces in determining equilibrium properties.

scholarly journals Characterization of Precipitation in Al-Li Alloy AA2195 by means of Atom Probe Tomography and Transmission Electron Microscopy

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Muna Khushaim ◽  
Torben Boll ◽  
Judith Seibert ◽  
Ferdinand Haider ◽  
Talaat Al-Kassab
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atom Probe Tomography ◽  
Stoichiometric Composition ◽  
Equilibrium Composition ◽  
Atom Probe ◽  
Chemical Mapping ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Matrix

The microstructure of the commercial alloy AA2195 was investigated on the nanoscale after conducting T8 tempering. This particular thermomechanical treatment of the specimen resulted in the formation of platelet-shapedT1Al2CuLi/θ′Al2Cuprecipitates within the Al matrix. The electrochemically prepared samples were analyzed by scanning transmission electron microscopy and atom probe tomography for chemical mapping. Theθ′platelets, which are less than 2 nm thick, have the stoichiometric composition consistent with the expected Al2Cu equilibrium composition. Additionally, the Li distribution inside theθ′platelets was found to equal the same value as in the matrix. The equally thinT1platelet deviates from the formula (Al2CuLi) in its stoichiometry and shows Mg enrichment inside the platelet without any indication of a higher segregation level at the precipitate/matrix interface. The deviation from the (Al2CuLi) stoichiometry cannot be simply interpreted as a consequence of artifacts when measuring the Cu and Li concentrations inside theT1platelet. The results show rather a strong hint for a true lower Li and Cu contents, hence supporting reasonably the hypothesis that the real chemical composition for the thinT1platelet in the T8 tempering condition differs from the equilibrium composition of the thermodynamic stable bulk phase.

scholarly journals Coupling Atom Probe Tomography with Aberration-Corrected Scanning Transmission Electron Microscopy and First-Principles Computations to Investigate Omega Precipitation in Titanium Alloys

2013 ◽  
Vol 19 (S2) ◽  
pp. 946-947
Author(s):  
S. Nag ◽  
A. Devaraj ◽  
N. Gupta ◽  
R. Williams ◽  
S. Srivilliputhur ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Titanium Alloys ◽  
First Principles ◽  
Atom Probe Tomography ◽  
Scanning Transmission Electron Microscopy ◽  
Atom Probe ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Aberration Corrected

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

High-resolution x-ray imaging of small copper-rich precipitates in steels

1988 ◽  
Vol 46 ◽  
pp. 528-529
Author(s):  
J. R. Michael ◽  
K. A. Taylor
Keyword(s):  
Electron Microscopy ◽  
Thermomechanical Processing ◽  
Atom Probe ◽  
Ferrite Matrix ◽  
Scanning Transmission Electron Microscope ◽  
Probe Field ◽  
X Ray ◽  
Subsequent Transformation ◽  
Transmission Electron ◽  
Scanning Transmission

Although copper is considered an incidental or trace element in many commercial steels, some grades contain up to 1-2 wt.% Cu for precipitation strengthening. Previous electron microscopy and atom-probe/field-ion microscopy (AP/FIM) studies indicate that the precipitation of copper from ferrite proceeds with the formation of Cu-rich bcc zones and the subsequent transformation of these zones to fcc copper particles. However, the similarity between the atomic scattering amplitudes for iron and copper and the small misfit between between Cu-rich particles and the ferrite matrix preclude the detection of small (<5 nm) Cu-rich particles by conventional transmission electron microscopy; such particles have been imaged directly only by FIM. Here results are presented whereby the Cu Kα x-ray signal was used in a dedicated scanning transmission electron microscope (STEM) to image small Cu-rich particles in a steel. The capability to detect these small particles is expected to be helpful in understanding the behavior of copper in steels during thermomechanical processing and heat treatment.

scholarly journals Revisiting the Bøggild Intergrowth in Iridescent Labradorite Feldspars: Ordering, Kinetics, and Phase Equilibria

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 727
Author(s):  
Shiyun Jin ◽  
Huifang Xu ◽  
Seungyeol Lee
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atom Probe ◽  
Phase Region ◽  
Two Phase ◽  
Subsolidus Phase ◽  
Plagioclase Feldspar ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission

The enigmatic Bøggild intergrowth in iridescent labradorite crystals was revisited in light of recent work on the incommensurately modulated structures in the intermediated plagioclase. Five igneous samples and one metamorphic labradorite sample with various compositions and lamellar thicknesses were studied in this paper. The lamellar textures were characterized with conventional transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The compositions of individual lamellae were analyzed with high-resolution energy-dispersive X-ray spectroscopy (EDS) mapping and atom probe tomography (APT). The average structure states of the studied samples were also compared with single-crystal X-ray diffraction data (SC-XRD). The Na-rich lamellae have a composition of An44–48, and the Ca-rich lamellae range from An56 to An63. Significant differences between the lamellar compositions of different samples were observed. The compositions of the Bøggild intergrowth do not only depend on the bulk compositions, but also on the thermal history of the host rock. The implications on the subsolidus phase relationships of the plagioclase feldspar solid solution are discussed. The results cannot be explained by a regular symmetrical solvus such as the Bøggild gap, but they support an inclined two-phase region that closes at low temperature.

scholarly journals Comparison of the Growth and Thermal Properties of Nonwoven Polymers after Atomic Layer Deposition and Vapor Phase Infiltration

Coatings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1028
Author(s):  
Laura Keskiväli ◽  
Pirjo Heikkilä ◽  
Eija Kenttä ◽  
Tommi Virtanen ◽  
Hille Rautkoski ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Electron Microscope ◽  
Atomic Layer Deposition ◽  
Atomic Layer ◽  
Scanning Transmission Electron Microscope ◽  
Scanning Calorimetry ◽  
Polymeric Surfaces ◽  
Transmission Electron ◽  
Layer Deposition ◽  
Scanning Transmission

The growth mechanism of Atomic Layer Deposition (ALD) on polymeric surfaces differs from growth on inorganic solid substrates, such as silicon wafer or glass. In this paper, we report the growth experiments of Al2O3 and ZnO on nonwoven poly-L-lactic acid (PLLA), polyethersulphone (PES) and cellulose acetate (CA) fibres. Material growth in both ALD and infiltration mode was studied. The structures were examined with a scanning electron microscope (SEM), scanning transmission electron microscope (STEM), attenuated total reflectance-fourier-transform infrared spectroscopy (ATR-FTIR) and 27Al nuclear magnetic resonance (NMR). Furthermore, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis were used to explore the effect of ALD deposition on the thermal properties of the CA polymer. According to the SEM, STEM and ATR-FTIR analysis, the growth of Al2O3 was more uniform than ZnO on each of the polymers studied. In addition, according to ATR-FTIR spectroscopy, the infiltration resulted in interactions between the polymers and the ALD precursors. Thermal analysis (TGA/DSC) revealed a slower depolymerization process and better thermal resistance upon heating both in ALD-coated and infiltrated fibres, more pronounced on the latter type of structures, as seen from smaller endothermic peaks on TA.

Understanding the Growth Mechanisms of Tin Oxide Nanowires by Chemical Vapor Deposition

2021 ◽  
Vol 21 (4) ◽  
pp. 2538-2544
Author(s):  
Nguyen Minh Hieu ◽  
Nguyen Hoang Hai ◽  
Mai Anh Tuan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Chemical Mapping ◽  
X Ray Diffraction ◽  
Lattice Constants ◽  
Transmission Electron ◽  
Scanning Transmission

Tin oxides nanowires were prepared by chemical vapor deposition using shadow mask. X-ray diffraction indicated that the products were tetragonal having crystalline structure with lattice constants a = 0.474 nm and c = 0.318 nm. The high-resolution transmission electron microscopy revealed that inter planar spacing is 0.25 nm. The results chemical mapping in scanning transmission electron microscopy so that the two elements of Oxygen and Tin are distributed very homogeneously in nanowires and exhibit no apparent elements separation. A bottom-up mechanism for SnO2 growth process has been proposed to explain the morphology of SnO2 nanowires.

scholarly journals A Thermodynamic Investigation of Ni on Thin-Film Titanates (ATiO3)

Inorganics ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 69
Author(s):  
Chao Lin ◽  
Alexandre C. Foucher ◽  
Eric A. Stach ◽  
Raymond J. Gorte
Keyword(s):  
Atomic Layer Deposition ◽  
Coulometric Titration ◽  
Equilibrium Constants ◽  
Atomic Layer ◽  
Co2 Reforming ◽  
Co2 Reforming Of Ch4 ◽  
Transmission Electron ◽  
Layer Deposition ◽  
Ni Oxidation ◽  
Scanning Transmission

Thin, ~1-nm films of CaTiO3, SrTiO3, and BaTiO3 were deposited onto MgAl2O4 by Atomic Layer Deposition (ALD) and then studied as catalyst supports for ~5 wt % of Ni that was added to the perovskite thin films by Atomic Layer Deposition. Scanning Transmission Electron Microscopy demonstrated that both the Ni and the perovskites uniformly covered the surface of the support following oxidation at 1073 K, even after redox cycling, but large Ni particles formed following a reduction at 1073 K. When compared to Ni/MgAl2O4, the perovskite-containing catalysts required significantly higher temperatures for Ni reduction. Equilibrium constants for Ni oxidation, as determined from Coulometric Titration, indicated that the oxidation of Ni shifted to lower PO2 on the perovskite-containing materials. Based on Ni equilibrium constants, Ni interactions are strongest with CaTiO3, followed by SrTiO3 and BaTiO3. The shift in the equilibrium constant was shown to cause reversible deactivation of the Ni/CaTiO3/MgAl2O4 catalyst for CO2 reforming of CH4 at high CO2 pressures, due to the oxidation of the Ni.

scholarly journals Growth and characterization of CNT–TiO2 heterostructures

2014 ◽  
Vol 5 ◽  
pp. 946-955 ◽  
Author(s):  
Yucheng Zhang ◽  
Ivo Utke ◽  
Johann Michler ◽  
Gabriele Ilari ◽  
Marta D Rossell ◽  
...  
Keyword(s):  
Good Control ◽  
Atomic Layer ◽  
Oxide Material ◽  
Electronic Information ◽  
Transmission Electron ◽  
Layer Deposition ◽  
Metal Metal ◽  
Scanning Transmission ◽  
Electron Energy Loss

A thriving field in nanotechnology is to develop synergetic functions of nanomaterials by taking full advantages of unique properties of each component. In this context, combining TiO2 nanocrystals and carbon nanotubes (CNTs) offers enhanced photosensitivity and improved photocatalytic efficiency, which is key to achieving sustainable energy and preventing environmental pollution. Hence, it has aroused a tremendous research interest. This report surveys recent research on the topic of synthesis and characterization of the CNT–TiO2 interface. In particular, atomic layer deposition (ALD) offers a good control of the size, crystallinity and morphology of TiO2 on CNTs. Analytical transmission electron microscopy (TEM) techniques such as electron energy loss spectroscopy (EELS) in scanning transmission mode provides structural, chemical and electronic information with an unprecedented spatial resolution and increasingly superior energy resolution, and hence is a necessary tool to characterize the CNT–TiO2 interface, as well as other technologically relevant CNT–metal/metal oxide material systems.

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