Analytical electron microscopy of planar faults in SrO-doped CaTiO3

1997 ◽  
Vol 12 (9) ◽  
pp. 2438-2446 ◽  
Author(s):  
M. Čeh ◽  
H. Gu ◽  
H. Müllejans ◽  
A. Rečnik
Keyword(s):  
Electron Microscopy ◽  
Perovskite Phase ◽  
Analytical Electron Microscopy ◽  
Scanning Transmission Electron Microscope ◽  
Extended Defects ◽  
Spatially Resolved ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Scanning Transmission ◽  
Ca Ions

Oxide-rich planar faults within a perovskite matrix are the prevailing type of extended defects in polycrystalline SrO-doped CaTiO3. These defects form, depending on the temperature of sintering, random networks, or ordered structures. The chemistry of the polytypoid, the isolated planar faults, and the perovskite phase have been studied by spatially resolved electron energy-loss and energy-dispersive x-ray spectroscopies using a dedicated scanning transmission electron microscope. We have found that Sr ions from SrO additions preferably substitute Ca in the CaTiO3 lattice, thus forming a solid solution (Ca1–xSrx)TiO3. The surplus of Ca ions forms single and ordered CaO-rich planar faults in the host (Ca1–xSrx)TiO3 phase. Whereas the excess Ca segregates in a form of single planar faults at lower temperatures, it forms a stable polytypoidic phase at higher temperatures. For materials having up to 25 mol% of SrO additions, this phase has (Ca1–xSrx)4Ti3O10 composition, comprising a sequence of CaO faults followed by three (Ca1–xSrx)TiO3 perovskite layers. Analytical electron microscopy revealed that the composition of the single planar faults, formed at lower temperatures, is identical to that of polytypoids, which are stable at higher sintering temperatures.

The effect of small additions of Cu on precipitation in Al-Mg-Si alloys

1990 ◽  
Vol 48 (2) ◽  
pp. 442-443
Author(s):  
M. Tamizifar ◽  
G. Cliff ◽  
R.W. Devenish ◽  
G.W. Lorimer
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Scanning Transmission Electron Microscope ◽  
Argon Atmosphere ◽  
Age Hardening ◽  
X Ray ◽  
Transmission Electron ◽  
Heat Treated ◽  
Analytical Electron ◽  
Scanning Transmission

Small additions of copper, <1 wt%, have a pronounced effect on the ageing response of Al-Mg-Si alloys. The object of the present investigation was to study the effect of additions of copper up to 0.5 wt% on the ageing response of a series of Al-Mg-Si alloys and to use high resolution analytical electron microscopy to determine the composition of the age hardening precipitates.The composition of the alloys investigated is given in Table 1. The alloys were heat treated in an argon atmosphere for 30m, water quenched and immediately aged either at 180°C for 15 h or given a duplex treatment of 180°C for 15 h followed by 350°C for 2 h2. The double-ageing treatment was similar to that carried out by Dumolt et al. Analyses of the precipitation were carried out with a HB 501 Scanning Transmission Electron Microscope. X-ray peak integrals were converted into weight fractions using the ratio technique of Cliff and Lorimer.

Analytical electron microscopy of fresh and vehicle-aged catalysts

1988 ◽  
Vol 46 ◽  
pp. 714-715
Author(s):  
Sooho Kim
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Analytical Electron Microscopy ◽  
Scanning Transmission Electron Microscope ◽  
Automotive Catalysts ◽  
Area Reduction ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Scanning Transmission

Automotive catalysts have a general loss of activity during aging, basically due to two principal deactivation mechanisms. One of them is thermally induced “sintering,” which results in catalytic surface area reduction. The other is chemically induced “poisoning,” which in part causes blockage of active metal sites. The conventional bulk techniques have indicated that various catalyst functions were affected differently by poisons and thermal damage; however, they generally did not provide detailed descriptions of the mechanisms of deactivation. Only analytical electron microscopy (AEM) can provide microchemical and microstructural information to gain a more thorough and fundamental understanding of catalytic deactivation.Fresh and vehicle-aged commercial automotive catalysts containing Pt, Pd, and Rh on alumina supports were prepared for AEM by a microtomy technique, which retains the spatial integrity of the catalyst pellet with uniform thickness. Then these AEM specimens were characterized in a transmission electron microscope (TEM) and in a dedicated scanning transmission electron microscope (STEM).

Application of analytical electron microscopy to studies of equilibrium and non-equilibrium segregation in materials

1992 ◽  
Vol 50 (2) ◽  
pp. 1214-1215
Author(s):  
Edward A Kenik
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Extended Defects ◽  
Probe Diameter ◽  
Specimen Holder ◽  
Analytical Electron ◽  
Scanning Transmission ◽  
Solute Atoms ◽  
Equilibrium Segregation ◽  
Non Equilibrium

Segregation of solute atoms to grain boundaries, dislocations, and other extended defects can occur under thermal equilibrium or non-equilibrium conditions, such as quenching, irradiation, or precipitation. Generally, equilibrium segregation is narrow (near monolayer coverage at planar defects), whereas non-equilibrium segregation exhibits profiles of larger spatial extent, associated with diffusion of point defects or solute atoms. Analytical electron microscopy provides tools both to measure the segregation and to characterize the defect at which the segregation occurs. This is especially true of instruments that can achieve fine (<2 nm width), high current probes and as such, provide high spatial resolution analysis and characterization capability. Analysis was performed in a Philips EM400T/FEG operated in the scanning transmission mode with a probe diameter of <2 nm (FWTM). The instrument is equipped with EDAX 9100/70 energy dispersive X-ray spectrometry (EDXS) and Gatan 666 parallel detection electron energy loss spectrometry (PEELS) systems. A double-tilt, liquid-nitrogen-cooled specimen holder was employed for microanalysis in order to minimize contamination under the focussed spot.

Considerations of the Current Potential and Limits of Analytical Electron Microscopy

1980 ◽  
Vol 38 ◽  
pp. 82-85
Author(s):  
D. B. Williams
Keyword(s):  
Imaging Techniques ◽  
Analytical Electron Microscopy ◽  
Thin Foil ◽  
Scanning Transmission Electron Microscope ◽  
Analytical Instrument ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Scanning Transmission ◽  
Physical Limitations ◽  
Current Potential

With the development of the scanning transmission electron microscope (STEM) the TEM was transformed into an analytical instrument capable of high resolution microanalysis and diffraction, as well as offering a broad range of imaging techniques. The combination of a < 10 nm electron probe and thin foil specimens permits analytical information to be gained from regions < 50 nm in diameter since beam spreading in thin specimens is of this order. This article will use specific examples to illustrate the possible applications of STEM in the study of materials, as well as the physical limitations of the analysis procedure which are only now being defined.

High Spatial Resolution X-ray Microanalysis of Radiation-Induced Segregation in Proton-Irradiated Stainless Steels

1999 ◽  
Vol 589 ◽  
Author(s):  
E.A. Kenik ◽  
J.T. Busby ◽  
G.S. Was
Keyword(s):  
Grain Boundaries ◽  
Analytical Electron Microscopy ◽  
Scanning Transmission Electron Microscope ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Scanning Transmission ◽  
Spatial Redistribution ◽  
Radiation Induced ◽  
Composition Profiles ◽  
Compositional Changes

AbstractThe spatial redistribution of alloying elements and impurities near grain boundaries in several stainless steel alloys arising from non-equilibrium processes have been measured by analytical electron microscopy (AEM) in a field emission scanning transmission electron microscope. Radiation-induced segregation (RIS) has been shown to result in significant compositional changes at point defects sinks, such as grain boundaries. The influence of irradiation dose and temperature, alloy composition, prior heat treatment, and post-irradiation annealing on the grain boundary composition profiles have been investigated. Understanding the importance of these microchemical changes relative to the radiation-induced microstructural change in irradiation-assisted stress corrosion cracking (IASCC) of the irradiated materials is the primary goal of this study.

X-ray Energy-Dispersive Spectrometry During In Situ Liquid Cell Studies Using an Analytical Electron Microscope

2014 ◽  
Vol 20 (2) ◽  
pp. 323-329 ◽  
Author(s):  
Nestor J. Zaluzec ◽  
M. Grace Burke ◽  
Sarah J. Haigh ◽  
Matthew A. Kulzick
Keyword(s):  
Electron Microscope ◽  
Analytical Electron Microscopy ◽  
Scanning Transmission Electron Microscope ◽  
Energy Dispersive ◽  
X Ray ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Scanning Transmission ◽  
Liquid Cell

AbstractThe use of analytical spectroscopies during scanning/transmission electron microscope (S/TEM) investigations of micro- and nano-scale structures has become a routine technique in the arsenal of tools available to today’s materials researchers. Essential to implementation and successful application of spectroscopy to characterization is the integration of numerous technologies, which include electron optics, specimen holders, and associated detectors. While this combination has been achieved in many instrument configurations, the integration of X-ray energy-dispersive spectroscopy and in situ liquid environmental cells in the S/TEM has to date been elusive. In this work we present the successful incorporation/modifications to a system that achieves this functionality for analytical electron microscopy.

Elemental analysis in a V-Ti-C alloy using electron energy loss spectroscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 552-553
Author(s):  
Hamish L. Fraser
Keyword(s):  
Binary Systems ◽  
Analytical Electron Microscopy ◽  
Scanning Transmission Electron Microscope ◽  
High Temperature Materials ◽  
Transmission Electron ◽  
Interstitial Component ◽  
Analytical Electron ◽  
Scanning Transmission ◽  
Electron Energy Loss

There has been considerable interest in the recent past concerning the application of refractory metal-interstitial systems as high temperature materials. it is important to understand the behavior of the interstitial component, and thus the determination of precipitation processes has been an area of study. in addition to making observations in simple binary systems, there is a need to characterize the changes that occur when other substitutional alloying elements are added. recently, bruemmer has studied the precipitation of carbides in a v-8Ti-c alloy over a range of temperatures. it is particularly interesting to characterize the carbides that precipitate at temperatures when the ti can diffuse rapidly (e.g. 1000°c), and determine not only the structure of the carbide but also perform microchemistry on as fine a scale as possible using analytical electron microscopy. bruemmer used a scanning transmission electron microscope (stem) (jeol jsem 200) coupled with an ortec energy dispersive x-ray analyzer to make measurements of the v:ti ratio in the carbide.

Development of 200 kV Scanning-Transmission Electron Microscope

1974 ◽  
Vol 32 ◽  
pp. 410-411
Author(s):  
H. Koike ◽  
S. Sakurai ◽  
K. Ueno ◽  
M. Watanabe
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Scanning Transmission Electron Microscope ◽  
The Other ◽  
Morphological Observation ◽  
Magnetic Domains ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Backscattered Electron ◽  
Increasing Demand

In recent years, there has been increasing demand for higher voltage SEMs, in the field of surface observation, especially that of magnetic domains, dislocations, and electron channeling patterns by backscattered electron microscopy. On the other hand, the resolution of the CTEM has now reached 1 ∼ 2Å, and several reports have recently been made on the observation of atom images, indicating that the ultimate goal of morphological observation has beem nearly achieved.

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.

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