An Analysis of the Structure of Irradiation induced Cu-enriched Clusters in Low and High Nickel Welds

2000 ◽  
Vol 650 ◽  
Author(s):  
Jonathan M. Hyde ◽  
Colin A. English
Keyword(s):  
Atom Probe ◽  
Radius Of Gyration ◽  
Number Density ◽  
Transmission Electron ◽  
Fe Content ◽  
High Nickel ◽  
Scanning Transmission ◽  
The Mean ◽  
Data Representative ◽  
Very High

ABSTRACTTwo high copper irradiated welds, one containing very low Ni and the other containing very high Ni, have been examined using 3-D atom probe (3DAP) microscopy, small angle neutron scattering (SANS) and field emission gun-scanning transmission electron microscopy (FEG- STEM).Irradiation induced clusters were observed in both welds. They were found to be significantly smaller and exist at a higher number density in the high Ni weld. A new algorithm was developed to precisely identify the shape, composition and size of clusters observed in the atom probe data. Representative irradiation induced clusters from each weld were then examined in greater detail. They were shown to be ramified and have a significant Fe content (∼60at.%). Cu was found to be more strongly associated with the core of the clusters than Mn or Ni. In the low Ni weld, there was evidence for P at the interfaces between the clusters and matrix. Cluster composition estimates from FEG-STEM analyses were consistent with those observed by 3DAP microanalysis. For each weld, the mean radius of gyration of the clusters was found to be almost identical to the radius of gyration determined directly from SANS analyses of these materials. Finally, the number density of features was estimated from the SANS data by using the compositional information from the 3DAP observations. Consistency with the number density calculated directly from the 3DAP data was obtained provided that it is assumed that the clusters exhibit some magnetic properties.

Reduction of Specimen Contamination in Electron-Beam Instruments

1976 ◽  
Vol 34 ◽  
pp. 576-577
Author(s):  
G. Lehmpfuhl ◽  
P. J. Smith
Keyword(s):  
Electron Beam ◽  
Cold Trap ◽  
Beam Diameter ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Hydrocarbon Molecules ◽  
Electron Microscopes ◽  
Combination Of Methods ◽  
Convergent Beam ◽  
Very High

Specimens being observed with electron-beam instruments are subject to contamination, which is due to polymerization of hydrocarbon molecules by the beam. This effect becomes more important as the size of the beam is reduced. In convergent-beam studies with a beam diameter of 100 Å, contamination was observed to grow on samples at very high rates. Within a few seconds needles began forming under the beam on both the top and the underside of the sample, at growth rates of 400-500 Å/s, severely limiting the time available for observation. Such contamination could cause serious difficulty in examining a sample with the new scanning transmission electron microscopes, in which the beam is focused to a few angstroms.We have been able to reduce the rate of contamination buildup by a combination of methods: placing an anticontamination cold trap in the sample region, preheating the sample before observation, and irradiating the sample with a large beam before observing it with a small beam.

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.

Phase Transformation of Powdered Material by Using Metal Jet

2012 ◽  
Vol 706-709 ◽  
pp. 741-744 ◽  
Author(s):  
Akio Kira ◽  
Ryuichi Tomoshige ◽  
Kazuyuki Hokamoto ◽  
Masahiro Fujita
Keyword(s):  
Phase Transformation ◽  
Powdered Material ◽  
Scanning Transmission Electron Microscope ◽  
Ultrahigh Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Metal Jet ◽  
Very High

The various techniques of phase transformation of the material have been proposed by many researchers. We have developed several devices to generate the ultrahigh pressure by using high explosive. One of them uses metal jets. It is expected that the ultrahigh pressure occurs by the head-on collision between metal jets, because the velocity of the metal jet is very high. By mixing a powdered material with metal jets, the pressure of the material becomes high. The purpose of this study is to transform the phase of the powdered material by using this high pressure. The powders of the graphite and hBN were applied. The synthesis to the diamond and cBN was confirmed by X-ray diffraction (XRD). In this paper, the mechanism of the generation of the ultrahigh pressure is explained and the results of the observation of the powder by using scanning transmission electron microscope (STEM) are reported.

Techniques for Investigating Structure and Composition with High Spatial Resolution

1981 ◽  
Vol 8 ◽  
Author(s):  
John B. Vander Sande
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Spatial Resolution ◽  
Scanning Transmission Electron Microscopy ◽  
High Spatial Resolution ◽  
Compositional Analysis ◽  
Atom Probe ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

ABSTRACTThe techniques of scanning transmission electron microscopy and field iron microscopy/atom probe are briefly described. The advantages of these techniques for high spatial resolution compositional analysis are discussed and examples cited.

scholarly journals Effects of Te- and Fe-doping on the superconducting properties in FeySe1-xTex thin films

2021 ◽  
Author(s):  
Yalin Zhang ◽  
Tong Wang ◽  
Zhihe Wang ◽  
Zhongwen Xing
Keyword(s):  
Thin Films ◽  
Chemical Composition ◽  
Interfacial Structure ◽  
Epitaxial Thin Films ◽  
Superconducting Transition ◽  
Transmission Electron ◽  
Fe Content ◽  
Scanning Transmission ◽  
Microscopy Images ◽  
Deposition Technology

Abstract High quality FeySe1−xTex epitaxial thin films have been fabricated on TiO2-buffered SrTiO3 substrates by pulsed laser deposition technology. There is a significant composition deviation between the nominal target and the thin film. Te doping can affect the Se/Te ratio and Fe content in chemical composition. The superconducting transition temperature Tc is closely related to the chemical composition. Fe vacancies are beneficial for the FeySe1−xTex films to exhibit the higher Tc. A 3D phase diagram is given that the optimize range is x = 0.13 − 0.15 and y = 0.73 − 0.78 for FeySe1−xTex films. The anisotropic, effective pining energy and critical current density for the Fe0.72Se0.94Te0.06, Fe0.76Se0.87Te0.13 and Fe0.91Se0.77Te0.23 samples were studied in detail. The scanning transmission electron microscopy images display a regular pattern without obviously scale defects at the interfacial structure.

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