(July 17, 2015) Research
from North Carolina State University shows that lightweight composite metal
foams are effective at blocking X-rays, gamma rays and neutron radiation, and
are capable of absorbing the energy of high impact collisions. The finding
means the metal foams hold promise for use in nuclear safety, space exploration
and medical technology applications.
“This work means there’s an opportunity to use composite
metal foam to develop safer systems for transporting nuclear waste, more
efficient designs for spacecraft and nuclear structures, and new shielding for
use in CT scanners,” says Afsaneh Rabiei, a professor of mechanical and
aerospace engineering at NC State and corresponding author of a paper on the
work.
Rabiei first developed the strong, lightweight metal foam
for use in transportation and military applications. But she wanted to
determine whether the foam could be used for nuclear or space exploration
applications – could it provide structural support, protect against high
impacts and provide shielding against various forms of radiation?
To that end, she and her colleagues conducted multiple tests
to see how effective it was at blocking X-rays, gamma rays and neutron
radiation. She then compared the material’s performance to the performance of
bulk materials that are currently used in shielding applications. The
comparison was made using samples of the same “areal” density – meaning that
each sample had the same weight, but varied in volume.
The most effective composite metal foam against all three
forms of radiation is called “high-Z steel-steel” and was made up largely of
stainless steel, but incorporated a small amount of tungsten. However, the
structure of the high-Z foam was modified so that the composite foam that
included tungsten was not denser than metal foam made entirely of stainless
steel.
The researchers tested shielding performance against several
kinds of gamma ray radiation. Different source materials produce gamma rays
with different energies. For example, cesium and cobalt emit higher-energy
gamma rays, while barium and americium emit lower-energy gamma rays.