High Spatial Resolution Microanalysis of Catalyst Particles

1985 ◽  
Vol 62 ◽  
Author(s):  
C. E. Lyman
Keyword(s):  
Image Feature ◽  
Single Element ◽  
X Rays ◽  
Qualitative And Quantitative Analysis ◽  
Thin Sections ◽  
X Ray ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
High Concentrations ◽  
Electron Energy Loss

ABSTRACTQualitative and quantitative analysis of small catalyst particles is possible in the analytical electron microscope down to analysis areas on the order of 10 nm in diameter. The location of elements in the image field can be determined either by placing the electron probe on a particu-lar image feature or by forming a digital x-ray image showing the distribu-tion of various elements. In either case analysis of specimens of well defined thickness such as microtomed thin sections preserves spatial relationships in catalyst particles and simplifies interpretation of single element x-ray images. Electron energy loss spectroscopy can be combined with x-ray spectroscopy to reduce the ambiguity in x-ray spectra caused by spurious x-rays generated by electrons scattered from the analy-sis area to regions of high concentrations of elements removed from the analysis area.

scholarly journals More Than One Ever Wanted To Know About X-ray Detectors Part V: Wavelength - The "Other" Spectroscopy

1995 ◽  
Vol 3 (4) ◽  
pp. 8-9
Author(s):  
Mark W. Lund
Keyword(s):  
X Rays ◽  
X Ray ◽  
Modern Times ◽  
Semiconductor Crystals ◽  
Wavelength Dispersive Spectrometry ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Electron Microscopes ◽  
Electron Energy Loss ◽  
Visible Light Spectroscopy

The use of x-ray spectrometry in electron microscopy has been a powerful market driver not only for electron microscopes but also for x-ray spectrometers. More x-ray spectrometers are sold with electron microscopes than in any other configuration. A general name for the combination is AEM, or analytical electron microscope, though in modern times AEM can include other instrumentation such as electron energy loss spectroscopy and visible light spectroscopy. In previous articies I have discussed energy dispersive spectrometers (EDS). These use semiconductor crystals to detect the x-rays and measure the energy deposited in the crystal. A second type of x-ray spectrometer measures the wavelength of the x-rays, and so is called "wavelength dispersive spectrometry" (WDS).

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.

X-ray detection performance of a 300KV field-emission Analytical Electron Microscope

1993 ◽  
Vol 51 ◽  
pp. 250-251
Author(s):  
C. E. Lyman ◽  
J. I. Goldstein ◽  
D.B. Williams ◽  
D.W. Ackland ◽  
S. von Harrach ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Field Emission ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Detection Performance ◽  
Electron Gun ◽  
X Rays ◽  
X Ray ◽  
Analytical Electron ◽  
Analytical Electron Microscope

A major goal of analytical electron micrsocopy (AEM) is to detect small amounts of an element in a given matrix at high spatial resolution. While there is a tradeoff between low detection limit and high spatial resolution, a field emission electron gun allows detection of small amounts of an element at sub-lOnm spatial resolution. The minimum mass fraction of one element measured in another is proportional to [(P/B)·P]-1/2 where the peak-to-background ratio P/B and the peak intensity P both must be high to detect the smallest amount of an element. Thus, the x-ray detection performance of an analytical electron microscope may be characterized in terms of standardized measurements of peak-to-background, x-ray intensity, the level of spurious x-rays (hole count), and x-ray detector performance in terms of energy resolution and peak shape.This paper provides measurements of these parameters from Lehigh’s VG Microscopes HB-603 field emission AEM. This AEM was designed to provide the best x-ray detection possible.

An EM Study of silicone hydrophobicity in commercial gypsum wallboard

1990 ◽  
Vol 48 (4) ◽  
pp. 886-887
Author(s):  
H. A. Freeman ◽  
Y. A. Peters
Keyword(s):  
Electron Microscope ◽  
Water Resistance ◽  
X Rays ◽  
X Ray ◽  
Low Viscosity ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Scanning Transmission ◽  
Improved Performance ◽  
Strength Improvement

Considerably improved performance is provided by gypsum construction wallboard which has been formulated to enhance durability and water resistance in applications that are susceptible to high humidity and moisture. One ingredient that is economically added in small amounts for this purpose is a low viscosity methyl hydrogen silicone fluid. The silicone was found to provide the necessary hydrophobic character and strength improvement when it was incorporated with the gypsum slurry in early stages of wallboard manufacture. However, it remained unknown where the silicone became localized to achieve this effect. Microanalyses were therefore performed in the analytical electron microscope to define the distribution of silicone in commercial gypsum wallboard samples.Gypsum samples were obtained which included those containing silicone and others to which no silicone had been added during manufacture. Analyses were performed in a JEM 2000FX analytical electron microscope operated at 200 keV and equipped with Tracor Northern Micro-ZHV and Microtrace energy dispersive x-ray spectrometers. Scanning (SEM), transmission (TEM), and scanning transmission (STEM) images were correlated with the mapped distributions of as many as six different elements acquired simultaneously. Low Z substrates and tilting specimen holders effectively minimized incorporation of spurious x rays in the final spectra.

Combined elemental and structural imaging in a computer contrlled analytical electron microscope

1983 ◽  
Vol 41 ◽  
pp. 10-13
Author(s):  
R. D. Leapman ◽  
C. E. Fiori ◽  
K. E. Gorlen ◽  
C. C. Gibson ◽  
C. R. Swyt
Keyword(s):  
Electron Microscope ◽  
Computer Hardware ◽  
X Ray ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Scanning Transmission ◽  
Northern Side ◽  
Electron Energy Loss ◽  
Modern Analytical ◽  
Digital Equipment

The modern analytical electron microscope incorporates a scanning transmission (STEM) capability together with a variety of detectors for signals resulting from the interaction of the electron probe with the sample. Information about both the elemental composition and morphology of the sample is available. The images derived from STEM signals can be readily digitized, thus allowing precise numerical processing of the data. Since several signals may be recorded concurrently one pixel at at time, the corresponding images are in registration and may be overlaid for comparison or combined for example to give the ratio of two elements. Such composite images can be expected to provide more information than each separately.The large amount of data which has to be processed in the acquisition of a digitized image requires a considerable amount of computer hardware and software. The system developed at NIH for application in biology has been described by Gorlen et al. and Fiori et al. and is outlined in Fig. 1. A Digital Equipment Corporation PDP 11/60 computer with an LSI 11/23 satellite computer is interfaced to a Hitachi H700H TEM-STEM with a magnetic sector electron energy loss spectrometer (EELS), one Kevex top-looking energy dispersive x-ray detector and one Tracor Northern side-looking detector; these provide the analytical signals with digital output.

Elemental Mapping by Core Level Excitations in the Analytical Electron Microscope

1987 ◽  
Vol 45 ◽  
pp. 192-195
Author(s):  
R.D. Leapman
Keyword(s):  
Electron Microscope ◽  
Fluorescence Yield ◽  
Core Level ◽  
Limiting Factor ◽  
X Ray ◽  
Probe Diameter ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Counting Statistics ◽  
Electron Energy Loss

Elemental distributions can be obtained in the analytical electron microscope by detecting core level excitations resulting from interaction of the scanned electron beam with atoms in the sample. This core level signal is recorded either through inelastic scattering measured by electron energy loss spectroscopy (EELS) or through x-ray emission measured by energy dispersive x-ray spectroscopy (EDXS). EELS is well suited to analysis of light elements for which the fluorescence yield is low whereas EDXS is sensitive to heavier elements; for several elements the two methods are competitive. The spatial resolution can approach the probe diameter, typically 1 to 50 nm, provided (i) the sample is thin enough to limit beam spreading effects, (ii) the counting statistics are adequate to detect a particular element, (iii) radiation damage is not a limiting factor, and (iv) delocalization of the scattering events is smaller than the probe diameter (in the case of high resolution studies).

A comparison of sensitivities between parallel-EELS and EDXS in biological microanalysis

1989 ◽  
Vol 47 ◽  
pp. 400-401
Author(s):  
R.D. Leapman
Keyword(s):  
Experimental Data ◽  
Electron Microscope ◽  
Energy Loss ◽  
X Ray ◽  
Fitting Procedure ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Photodiode Array ◽  
Electron Energy Loss ◽  
Difference Mode

With recent improvements in electron energy loss spectroscopy (EELS) and energy-dispersive x-ray spectroscopy (EDXS) it is useful to compare detection limits for the two techniques, a question originally addressed by Isaacson and Johnson. We have derived theoretical estimates of relative sensitivities for some elements encountered in biological microanalysis. These results are then compared with experimental data obtained using a Hitachi H700H analytical electron microscope equipped with a Gatan (model 666) parallel EELS and with a Tracor Northern Microtrace EDXS detector. These spectra were collected simultaneously using a Tracor TN5500 computer system to control acquisition and to process the EDXS data. Most of the EELS data were collected in the second difference mode to remove channel-to-channel gain variations in the photodiode array and were further processed on another computer using standard reference spectra and a multiple least squares fitting procedure.

Comparison of Performance of an Analytical Electron Microscope at 300 and 100 kV

1984 ◽  
Vol 41 ◽  
Author(s):  
J. Bentley ◽  
E. A. Kenik ◽  
P. Angelini ◽  
A. T. Fisher ◽  
P. S. Sklad ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Materials Science ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
X Ray ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Convergent Beam ◽  
Electron Energy Loss

AbstractPreliminary results on the performance of an analytical electron microscope (AEM) operating at 300 kV have been obtained and compared with the performance at 100 kV. Some features of the anticipated improvements for transmission electron microscopy (TEM) imaging, convergent beam electron diffraction (CBED), energy dispersive X-ray spectroscopy (EDS), and electron energy loss spectroscopy (EELS) have been studied from the aspect of materials science applications. The electron microscope used was a Philips EM430T operated with a LaB6 cathode and equipped with EDAX 9100/70 EDS and Gatan 607 EELS systems.

NiO Test Specimens for Analytical Electron Microscopy: Round-Robin Results

1995 ◽  
Vol 1 (4) ◽  
pp. 143-149 ◽  
Author(s):  
J.C. Bennett ◽  
R.F. Egerton
Keyword(s):  
Thin Film ◽  
Electron Microscopy ◽  
Test Specimen ◽  
Analytical Electron Microscopy ◽  
X Rays ◽  
Elemental Ratios ◽  
X Ray ◽  
Analytical Electron ◽  
Electron Energy Loss ◽  
Nio Films

Improvements in instrumentation for energy-dispersive X-ray microanalysis (EDX) and electron energy-loss spectroscopy (EELS) have underlined the need for suitable standards for measuring performance. We report the results from several laboratories that were supplied with a test specimen consisting of a thin film of nickel oxide supported on a molybdenum grid. The Ni-Kα/Mo-Kα count ratio was used as an indication of number of stray electrons and/or X-rays in the TEM column; the Ni-Kα peak/background ratio provided a measure of the total background in the EDX spectrum, including bremsstrahlung contributions and the effect of detector electronics. By providing values typical of current instrumentation, the results illustrate how the test specimen can be used to evaluate TEM/EDX systems prior to purchase, during installation, and (periodically) during operation. The NiO films were also used to test EELS acquisition and quantification procedures: measured Ni/O elemental ratios were all within 10% of stoichiometry.

scholarly journals Calcium Transport Mechanism in Molting Crayfish Revealed by Microanalysis

1983 ◽  
Vol 31 (1A_suppl) ◽  
pp. 214-218 ◽  
Author(s):  
Vinci Mizuhira ◽  
Masaki Ueno
Keyword(s):  
Calcium Transport ◽  
Transport Mechanism ◽  
X Rays ◽  
Thin Sections ◽  
X Ray ◽  
Fresh Freeze ◽  
Ca Ions ◽  
Electron Microanalysis ◽  
Electron Energy Loss ◽  
Ca Oxalate

Crayfish provide a good model in which to study the transport mechanism of Ca ions. During the molting stage, decalcified Ca ions are transferred into the blood and accumulate in the gastrolith epithelium, after which a gastrolith is formed on the surface of the epithelium. The gastrolith is dissolved in the stomach after molting, and the Ca is reabsorbed and redistributed throughout the newly formed exoskeleton. We studied the mechanism of Ca transport by cytochemical precipitation of Ca ions and by electron microanalysis, including X-ray microanalysis (EDX) and electron energy-loss spectroscopy (EELS), with a computer. In EDX analysis, the fine precipitates of K-antimonate in the gastrolith mitochondria clearly defined Ca with antimony; we also observed a large amount of Ca-oxalate in the mitochondria, and Ca-K X-ray pulses were clearly defined. Ca-K X-rays were also detected from fresh freeze-substituted mitochondria. Finally, we succeeded in taking a Ca-L EELS image from the mitochondria of fresh freeze-substituted thin sections. Only a very small amount of Ca was detected from the cell membrane and other organelles. Ca-adenosine triphosphatase (ATPase) and Mg-ATPase activity was also very clearly demonstrated in the mitochondria. These enzymes may play an important role in Ca metabolism.

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