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The ability to map plastic deformation around high strain gradient microstructural features is central in studying phenomena such as fatigue and stress corrosion cracking. A method for the visualization of plastic deformation in electron back-scattered diffraction (EBSD) data has been developed and is described in this article. This technique is based on mapping the intragrain misorientation in polycrystalline metals. The algorithm maps the scalar misorientation between a local minimum misorientation reference pixel and every other pixel within an individual grain. A map around the corner of a Vickers indentation in 304 stainless steel was used as a test case. Several algorithms for EBSD mapping were then applied to the deformation distributions around air fatigue and stress corrosion cracks in 304 stainless steel. Using this technique, clear visualization of a deformation zone around high strain gradient microstructural features (crack tips, indentations, etc.) is possible with standard EBSD data.
Special Topics: Forensic Science – Solving the Whodunits with Microanalysis
The oxidation state of iron oxide nanoparticles co-generated with soot
during a combustion process was studied using electron energy-loss
spectroscopy (EELS). Spatially resolved EELS spectra in the scanning
transmission electron microscopy mode were collected to detect changes in
the oxidation state between the cores and surfaces of the particles.
Quantification of the intensity ratio of the white lines of the iron
L-ionization edge was used to measure the iron oxidation state.
Quantitative results obtained from Pearson's method, which can be
directly compared with the literature data, indicated that the
L3 /L2-intensity ratio for
these particles changes from 5.5 ± 0.3 in the particles' cores
to 4.4 ± 0.3 at their surfaces. This change can be directly related
to the reduction of the iron oxidation state at the surface of the
particles. Experimental results indicate that the cores of the particles
are composed of γ-Fe2O3, which seems to be
reduced to FeO at their surfaces. These results were also supported by the
fine structure of the oxygen K-edge and by the significant
chemical shift of the iron L-edge.
The M&M 2006 meeting will begin on Sunday, July 30, with a
pre-meeting congress entitled “Materials Research in an
Aberration-Free Environment.” The pre-meeting congress will share
Sunday with a number of topical Short Courses addressing image processing
and analysis, live cell imaging with fluorescence methods, scanning
cathodoluminescence microscopy and spectroscopy, variable pressure and
environmental SEM, and electron tomography. Examples of biological topics
that will be addressed during the week of the meeting include: Cell
Biology; Pathology; Microbiology; Microscopic molecular machines;
Immunolabeling; and Photosynthetic organisms. Topical symposia in the
physical sciences are: Nanoscience and nanotechnology; Catalysis;
Quantitative X-ray microanalysis; Visualizing mechanical behavior; and
Magnetic materials. In joint sessions for biological and materials
scientists, symposia will address TEM automation, cryo-approaches for TEM,
SEM and FIB/SEM, and surface microscopy. We honor the passing of Hans
Ris with a special symposium on Cell Biology and Microscopy, and Art
Chodos with a special symposium on Quantitative X-ray Microanalysis. Of
special interest will be two 50th anniversaries: The first observation of
dislocations, and the first experiments in elemental mapping by X-rays.
Supplementing the topical sessions will be a number of tutorials and
ask-the-experts sessions that will provide the opportunity to learn the
basics behind several popular techniques. As always, the commercial
exhibits will provide a unique opportunity for hands-on learning with the
largest variety of state-of-the-art instrumentation found at any
microscopy meeting worldwide.
The oxide scales of AISI 304 formed in boric acid solutions at
300°C and pH = 4.5 have been studied using X-ray photoelectron
spectroscopy (XPS) depth profiling. The present focus is depth profile
quantification both in depth and chemical composition on a molecular
level. The roughness of the samples is studied by atomic force microscopy
before and after sputtering, and the erosion rate is determined by
measuring the crater depth with a surface profilometer and vertical
scanning interferometry. The resulting roughness (20–30 nm), being
an order of magnitude lower than the crater depth (0.2–0.5 μm),
allows layer-by-layer profiling, although the ion-induced effects result
in an uncertainty of the depth calibration of a factor of 2. The XPS
spectrum deconvolution and data evaluation applying target factor analysis
allows chemical speciation on a molecular level. The elemental
distribution as a function of the sputtering time is obtained, and the
formation of two layers is observed—one hydroxide (mainly
iron–nickel based) on top and a second one deeper, mainly consisting
of iron–chromium oxides.
Following is a list of microscopy-related meetings and courses. The editors would greatly appreciate input to this list via the electronic submission form found in the MSA World-Wide Web page at http://www.msa.microscopy.com. We will gladly add hypertext links to the notice on the web and insert a listing of the meeting in the next issue of the Journal. Send comments and questions to JoAn Hudson, joanh@clemson.edu or Nestor Zaluzec, zaluzec@aaem.amc.anl.gov.
Following is a list of microscopy-related meetings and courses. The
editors would greatly appreciate input to this list via the electronic
submission form found in the MSA World-Wide Web page at http://www.msa.microscopy.com. We will gladly
add hypertext links to the notice on the web and insert a listing of the
meeting in the next issue of the Journal. Send comments and questions to
JoAn Hudson, joanh@clemson.edu or Nestor Zaluzec,
zaluzec@aaem.amc.anl.gov.
Amorphous 1–2-nm-wide intergranular films in ceramics dictate
many of their properties. The detailed investigation of structure and
chemistry of these films pushes the limits of today's transmission
electron microscopy. We report on the reconstruction of the
one-dimensional potential profile across the film from an experimentally
acquired tilt series of energy-filtered electron diffraction patterns.
Along with the potential profile, the specimen thickness, film orientation
with respect to the grain lattice and specimen surface, and the absolute
specimen orientation with respect to the laboratory frame of reference are
retrieved.
Experimental results from the first monochromated and
aberration-corrected scanning transmission electron microscope operated at
200 kV are described. The formation of an electron probe with a diameter
of less than 0.2 nm at an energy width significantly under 0.3 eV and its
planned application to the chemical analysis of nanometer-scale structures
in materials science are described. Both energy and spatial resolution
will benefit from this: The monochromator improves the energy resolution
for studies of energy loss near edge structures. The Cs corrector allows
formation of either a smaller probe for a given beam current or yields, at
fixed probe size, an enhanced beam current density using a larger
condenser aperture. We also point out another advantage of the combination
of both components: Increasing the convergence angle by using larger
condenser apertures in an aberration-corrected instrument will enlarge the
undesirable chromatic focus spread. This in turn influences spatial
resolution. The effect of polychromatic probe tails is proportional to the
product of convergence angle, chromatic aberration constant, and energy
spread. It can thus be compensated for in our new instrument by decreasing
the energy width by the same factor as the beam convergence is increased
to form a more intense probe. An alternative in future developments might
be hardware correction of the chromatic aberration, which could eliminate
the chromatic probe spread completely.
MODERN DEVELOPMENTS AND APPLICATIONS IN MICROBEAM
ANALYSIS
During lab-scale experiments on the reforming of methanol by means of
water at supercritical conditions (T > 374°C, p
> 22.1 MPa), a tubular reactor with a titanium liner was exposed to an
aqueous solvent containing methanol (5 wt%) and KHCO3 (0.3
wt%). At the end of the run, a fibrous precipitate was found at two
positions in the reactor. The material was studied in a field emission
scanning electron microscope equipped with an energy dispersive X-ray
analysis unit (FESEM/EDX). A thin-film support technique using
carbon-filmed TEM grids was applied to perform scanning transmission-type
imaging (STEM-in-SEM operation) and transmission current measurements. The
analysis of the hydrothermally grown fibers resulted in a potassium
titanate species composed of approximately K2TiO3,
which has been confirmed by X-ray diffraction (XRD).
Special Topics: Forensic Science – Solving the Whodunits with Microanalysis
Zinc oxide (ZnO) nanoparticles have been produced using precipitation
methods from ethanolic solution. Rare-earth metal doping was performed,
and the effect of lithium codoping on the luminescence properties of the
rare-earth doped products was assessed. The resulting particles were
characterized using cathodoluminescence and scanning electron microscopy.
It was found that lithium significantly enhanced the cathodoluminescence
signal from the rare-earth ions, which has been attributed to the
increased integration of the rare-earth ions into the ZnO structure. The
nanophase ZnO products were also annealed in argon, hydrogen, and oxygen,
with hydrogen being the most successful for removing the broad defect
emission present in as-grown samples and enhancing the ZnO near band edge
emission.
Scanning electron microscopy (SEM) is widely used in the science of
materials and different parameters were developed to characterize the
surface roughness. In a previous work, we studied the surface topography
with fractal dimension at low scale and two parameters at high scale by
using the variogram, that is, variance vs. step log–log graph, of a
SEM image. Those studies were carried out with the FERImage program,
previously developed by us. To verify the previously accepted hypothesis
by working with only an image, it is indispensable to have reliable
three-dimensional (3D) surface data. In this work, a new program
(EZEImage) to characterize 3D surface topography in SEM has been
developed. It uses fast cross correlation and dynamic programming to
obtain reliable dense height maps in a few seconds which can be displayed
as an image where each gray level represents a height value. This image
can be used for the FERImage program or any other software to obtain
surface topography characteristics. EZEImage also generates anaglyph
images as well as characterizes 3D surface topography by means of a
parameter set to describe amplitude properties and three functional
indices for characterizing bearing and fluid properties.
Following is a list of microscopy-related meetings and courses. The
editors would greatly appreciate input to this list via the electronic
submission form found in the MSA World-Wide Web page at http://www.msa.microscopy.com. We will gladly
add hypertext links to the notice on the web and insert a listing of the
meeting in the next issue of the Journal. Send comments and questions to
Nestor Zaluzec, zaluzec@aaem.amc.anl.gov.
We report on the sub-electron-volt-sub-angstrom microscope (SESAM), a
high-resolution 200-kV FEG-TEM equipped with a monochromator and an
in-column MANDOLINE filter. We report on recent results obtained with this
instrument, demonstrating its performance (e.g., 87-meV energy resolution
at 10-s exposure time, or a transmissivity of the energy filter of
T1 eV = 11,000 nm2). New opportunities to
do unique experiments that may advance the frontiers of microscopy in
areas such as energy-filtered TEM, spectroscopy, energy-filtered electron
diffraction and spectroscopic profiling are also discussed.
X-11: Scanning Cathodoluminescence Microscopy and Spectroscopy, Full
Day: 9:00 AM–5:00 PM, Room 301/303.
X-12: Digital Imaging 101: Scientific Imaging with Photoshop, Full
day: 9:00 AM–5:00 PM, Room 302/304.
X-13: Digital Imaging 102: Image Processing and Analysis, Full Day:
9:00 AM–5:00 PM, Room 306.
X-14: Live Cell Imaging Using Fluorescence Methods, Full Day: 9:00
AM–5:00 PM, Room 305.
X-15: What To Do with a Variable Pressure (VPSEM) or Environmental SEM
(ESEM) And How To Do It (Or At Least How It Ought To Work), Full Day: 9:00
AM–5:00 PM, Room 307.
X-16: 3-Dimensional Electron Microscopy (3DEM) in Life and Material
Science—In-Depth Tutorial about Tomography—Basics and Methods,
Full day: 9:00 AM–5:00 PM, Room 308.
X-17 Failure Analysis and Evidence Preservation by Metallography, Half
day: 9:00 AM–1:00 PM, Room 309/311.
Special events: MSA and MAS presidential happenings, IMS Henry Clifton
Sorby award and lecture, and art exhibit.
Microbes and Materials: Surveillance of the Unknown with Emphasis on Emerging Diseases and Terrorist Events
The carbon contents in carburized steels were investigated by electron
probe microanalysis (EPMA) for a range of carbon levels in the solid
solution less than 1 wt%. This article describes the difficulties
encountered with the classic analytical procedure using the k
ratio of X-ray intensities and the φ(ρz) model. Here, a
suitable calibration curve method is presented with emphasis on the
metallographic study of standard specimens and on the carbon
decontamination of samples.