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M A Y / J U N E
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improved the interface of a composite
or weakened it,” he says.
Improving
the ability of composites to withstand
extreme cold and heat, as well as expo-
sure to water, could be a boon to efforts
to build more resilient infrastructure
components such as bridges and wind
turbine blades.
nist.gov.
A FRESH ANGLE ON
3D STRESS DATA
A team of researchers from the
DOE’s Argonne National Laboratory
(ANL), IBM, and Institut Fresnel, France,
developed a new form of imaging to
investigate how planes of atoms in
a material behave under stress. The
method, called single-angle Bragg pty-
chography, marries x-ray diffraction
and Bragg ptychography to reconstruct
3D data in a way that makes fewer
demands on instrument technology
than comparable techniques. In x-ray
diffraction, atoms in a material scat-
ter x-rays into a pattern, producing a
signal that is converted to a series of
waves. While the intensity of the waves
Scientists are using Bragg single-angle ptychography to get a clear picture of how planes of
atoms shi and squeeze under stress. Courtesy of Robert Horn/ANL.
is recorded, their phases are not. How-
ever, both are required to construct 3D
data.
To retrieve the missing phases,
researchers turned to ptychography,
which uses redundant sampling from
the same region of the crystal, shifting
the x-ray beam only slightly between
readings to overlap as much as 60% of
the same real space. “By having a lot of
the same information encoded in neigh-
boring samples, it constrains the possi-
ble configurations of the crystal in real
space,” explains ANL materials scientist
Stephan Hruszkewycz. Knowing the
exact positionof thebeamand theangle
at which the crystal’s atomic planes
would scatter the x-rays allows the sci-
entists to reconstruct the 3D stress data.
anl.gov.