Chemical partitioning of elements in Ni-base MC-carbide reinforced eutetic superalloys

1983 ◽  
Vol 41 ◽  
pp. 250-251
Author(s):  
E. F. Koch ◽  
E. L. Hall ◽  
S. W. Yang
Keyword(s):  
Alloy Composition ◽  
Volume Fraction ◽  
Lattice Mismatch ◽  
Turbine Blades ◽  
Eutectic Alloys ◽  
Alloy Matrix ◽  
X Ray ◽  
Gas Turbine Blades ◽  
Analytical Electron ◽  
Analytical Electron Microscope

The plane-front solidified eutectic alloys consisting of aligned tantalum monocarbide fibers in a nickel alloy matrix are currently under consideration for future aircraft and gas turbine blades. The MC fibers provide exceptional strength at high temperatures. In these alloys, the Ni matrix is strengthened by the precipitation of the coherent γ' phase (ordered L12 structure, nominally Ni3Al). The mechanical strength of these materials can be sensitively affected by overall alloy composition, and these strength variations can be due to several factors, including changes in solid solution strength of the γ matrix, changes in they γ' size or morphology, changes in the γ-γ' lattice mismatch or interfacial energy, or changes in the MC morphology, volume fraction, thermal stability, and stoichiometry. In order to differentiate between these various mechanisms, it is necessary to determine the partitioning of elemental additions between the γ,γ', and MC phases. This paper describes the results of such a study using energy dispersive X-ray spectroscopy in the analytical electron microscope.

point-Analysis Using the Extrapolation Method in the Analytical Electron microscope

1990 ◽  
Vol 48 (2) ◽  
pp. 430-431
Author(s):  
Zenji Horita ◽  
Ryuzo Nishimachi ◽  
Takeshi Sano ◽  
Minoru Nemoto
Keyword(s):  
Electron Microscope ◽  
Extrapolation Method ◽  
X Ray ◽  
Absorption Correction ◽  
Point Analysis ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Data Points ◽  
Identical Composition ◽  
X Ray Absorption

Absorption correction is often required in quantitative x-ray microanalysis of thin specimens using the analytical electron microscope. For such correction, it is convenient to use the extrapolation method[l] because the thickness, density and mass absorption coefficient are not necessary in the method. The characteristic x-ray intensities measured for the analysis are only requirement for the absorption correction. However, to achieve extrapolation, it is imperative to obtain data points more than two at different thicknesses in the identical composition. Thus, the method encounters difficulty in analyzing a region equivalent to beam size or the specimen with uniform thickness. The purpose of this study is to modify the method so that extrapolation becomes feasible in such limited conditions. Applicability of the new form is examined by using a standard sample and then it is applied to quantification of phases in a Ni-Al-W ternary alloy.The earlier equation for the extrapolation method was formulated based on the facts that the magnitude of x-ray absorption increases with increasing thickness and that the intensity of a characteristic x-ray exhibiting negligible absorption in the specimen is used as a measure of thickness.

Peak-to-background measurements on a 300-kV TEM/STEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1236-1237 ◽  
Author(s):  
S. M. Zemyan ◽  
D. B. Williams
Keyword(s):  
Electron Microscope ◽  
X Ray ◽  
Background Ratio ◽  
Window Method ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Cr Film

As has been reported elsewhere, a thin evaporated Cr film can be used to monitor the x-ray peak to background ratio (P/B) in an analytical electron microscope. Presented here are the results of P/B measurements for the Cr Ka line on a Philips EM430 TEM/STEM, with Link Si(Li) and intrinsic Ge (IG) x-ray detectors. The goal of the study was to determine the best conditions for x-ray microanalysis.We used the Fiori P/B definition, in which P/B is the ratio of the total peak integral to the average background in a 10 eV channel beneath the peak. Peak and background integrals were determined by the window method, using a peak window from 5.0 to 5.7 keV about Cr Kα, and background windows from 4.1 to 4.8 keV and 6.3 to 7.0 keV.

Extended Core Edge Fine Structure in the E.M.

1980 ◽  
Vol 38 ◽  
pp. 120-121
Author(s):  
R.D. Leapman
Keyword(s):  
Fine Structure ◽  
Electron Scattering ◽  
Inelastic Electron ◽  
High Resolution Imaging ◽  
X Ray ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Core Electrons ◽  
Resolution Imaging ◽  
X Ray Absorption

Extended X-ray Absorption Fine Structure (EXAFS) analysis makes use of synchrotron radiaion to measure modulations in the absorption coefficient above core edges and hence to obtain information about local atomic environments. EXAFS arises when ejected core electrons are backscattered by surrounding atoms and interfere with the outgoing waves. Recently, interest has also been shown in using inelastic electron scattering1-4. Some advantages of Extended X-ray-edge Energy Loss Fine Structure (EXELFS) are: a) small probes formed by the analytical electron microscope give spectra from μm to nm sized areas, compared with mm diameter areas for the X-ray technique, b) EXELFS can be combined with other techniques such as electron diffraction or high resolution imaging, and c) EXELFS is sensitive to low Z elements with K edges from ˜200 eV to ˜ 3000 eV (B to Cl).

The Impact of EDS In Materials Science Microanalysis

1998 ◽  
Vol 4 (S2) ◽  
pp. 168-169
Author(s):  
D. B. Williams
Keyword(s):  
Materials Science ◽  
X Ray ◽  
Electron Probe Microanalyzer ◽  
Thin Foils ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Small Collection ◽  
Excellent Energy Resolution ◽  
The Impact

Since its invention in 1968, the EDS has played an essential role in X-ray analysis of materials, at the micrometer level, in the electron probe microanalyzer (EPMA). In the EPMA, the characteristic X-ray intensity from bulk specimens is sufficient that, despite its very small collection angle, the wavelength dispersive spectrometer (WDS) can also be used. Given the excellent energy resolution of the WDS it has often been the spectrometer of choice for bulk quantitative X-ray microanalysis. Therefore, the most important role of the EDS has been in X-ray microanalysis of thin specimens in the analytical electron microscope (AEM) because, in an AEM, the limited confines of the stage mean that EDS is the only viable spectrometer. Since the pioneering work of Cliff and Lorimer in the 1970s, EDS has been the method by which all high spatial resolution X-ray microanalysis of thin foils has been performed.

Optimizing Spatial Resolution for X-ray Microanalysis

2001 ◽  
Vol 7 (S2) ◽  
pp. 694-695
Author(s):  
Eric Lifshin ◽  
Raynald Gauvin ◽  
Di Wu
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Spatial Resolution ◽  
Maximum Diameter ◽  
Thin Sections ◽  
X Ray ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Limiting Value ◽  
Made In

In Castaing’s classic Ph.D. dissertation he described how the limiting value of x-ray spatial resolution for x-ray microanalysis, of about 1 μm, was not imposed by the diameter of the electron beam, but by the size of the region excited inside the specimen. Fifty years later this limit still applies to the majority of measurement made in EMAs and SEMs, even though there is often a need to analyze much finer structures. When high resolution chemical analysis is required, it is generally necessary to prepare thin sections and examine them in an analytical electron microscope where the maximum diameter of the excited volume may be as small as a few nanometers. Since it is not always possible or practical, it is important to determine just what is the best spatial resolution attainable for the examination of polished or “as received” samples with an EMA or SEM and how to achieve it experimentally.

scholarly journals Quantitative evaluation of microtwins and antiphase defects in GaP/Si nanolayers for a III–V photonics platform on silicon using a laboratory X-ray diffraction setup

2015 ◽  
Vol 48 (3) ◽  
pp. 702-710 ◽  
Author(s):  
Yan Ping Wang ◽  
Antoine Letoublon ◽  
Tra Nguyen Thanh ◽  
Mounib Bahri ◽  
Ludovic Largeau ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Lattice Mismatch ◽  
Antiphase Boundary ◽  
Optoelectronic Device ◽  
Absolute Quantification ◽  
Growth Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Transmission ◽  
Antiphase Domains

This study is carried out in the context of III–V semiconductor monolithic integration on silicon for optoelectronic device applications. X-ray diffraction is combined with atomic force microscopy and scanning transmission electron microscopy for structural characterization of GaP nanolayers grown on Si. GaP has been chosen as the interfacial layer, owing to its low lattice mismatch with Si. But, microtwins and antiphase boundaries are still difficult to avoid in this system. Absolute quantification of the microtwin volume fraction is used for optimization of the growth procedure in order to eliminate these defects. Lateral correlation lengths associated with mean antiphase boundary distances are then evaluated. Finally, optimized growth conditions lead to the annihilation of antiphase domains within the first 10 nm.

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