Neutrons open windows for exploring space glass

Thanks to human ingenuity and weightlessness, we benefit from science in space. Think about smartphones with integrated navigation systems and cameras.

Such transformational technologies seem to integrate into the rhythm of our everyday lives overnight. But they are the result of years of discovery and development of materials that can withstand harsh environments outside our atmosphere. They are the result of decades of fundamental research into understanding how atoms in different materials behave under different conditions.

Building on that past, a global team of researchers has set a new standard for future experiments to make materials in space, rather than for space. The team included members of the Department of Energy’s Oak Ridge and Argonne national laboratories, Materials Development, Inc., NASA, the Japan Aerospace Exploration Agency, or JAXA, the ISIS Neutron and Muon Source, Alfred University, and the University of New Mexico. Together, they discovered that many types of glass, including those that could be developed for next-generation optical devices, have a similar atomic structure and arrangement and can be successfully made in space.

The team’s work will be published in the journal npj microgravity.

“The idea is to explore the mechanisms behind space-based manufacturing that can lead to materials that are not necessarily available on Earth,” said Jörg Neuefeind, who came to ORNL in 2004 to work at the lab’s spallation neutron source To build an instrument called NOMAD (SNS). NOMAD, the world’s fastest neutron diffractometer, helps scientists measure the arrangement of atoms by observing how neutrons bounce off them. NOMAD is one of 20 tools at SNS that help scientists answer big questions and advance countless innovations, such as drugs that treat diseases more effectively, more reliable aircraft and rocket engines, cars that get better gas mileage, and batteries that are safer, charge faster, and last longer .

JAXA employees on Earth made and melted glass remotely using a levitator aboard the International Space Station (ISS). Levitators are used to suspend material samples during experiments to avoid interference from contact with other materials.

When the next ISS mission ended months later and the space glass was brought to Earth, researchers used a combination of techniques, including neutrons, X-rays and powerful microscopes, to compare and contrast glass made and melted in the sky with that on Earth .

“We found that we can produce unconventional glasses in microgravity using containerless techniques such as the levitator,” said JAXA’s Takehiko Ishikawa, pioneer of the electrostatic levitator used to produce the glass beads aboard the ISS.

The researchers relied on NOMAD at SNS to examine the glass samples using neutrons and beamlines at Argonne’s Advanced Photon Source to examine the samples using X-rays. Both SNS and APS are user facilities of the DOE Office of Science.

“There’s only so much material you can fly into space and get back, and that was actually one of the reasons why NOMAD was so well suited for this experiment,” said Stephen Wilke of Materials Development Inc. and a visiting scientist at Argonne . “We only got back individual glass beads about an eighth of an inch in diameter, which are very difficult to measure in terms of atomic structure. Because NOMAD excels at measuring extremely small samples, we were able to easily compare individual beads we made in the lab with those made on the space station.

Secrets of glass

As it turns out, glass isn’t so clear-cut. Unlike crystalline solids such as salt, glass atoms do not have a uniform structure. Its unusual atomic arrangement, while remarkably stable, is best described as a random network of molecules that share coordinated atoms. Glass is neither completely solid nor completely liquid, but also comes in various forms, including polymer, oxide and metal, for things such as eyeglass lenses, fiber optic cables and space mission hardware.

In 2022, Neuefeind, Wilke and Rick Weber, an industry expert in glass, experimented with two oxides of neodymium and titanium and discovered potential for optical applications. The combination of these two elements presents unusual strengths that have not been seen in similar research campaigns. These findings led her to continue her current studies with NASA.

“[The experiment in 2022] “We learned something really remarkable,” said Weber of Materials Development Inc. “One of the glasses has a network that is completely different from the normal four-coordinate network typical of silica. These glasses have a six-coordinate network. They are really out there. From a glass science perspective, it’s exciting. But in practice, it also means more opportunities to do new things with optical materials and novel devices.”

Scientists often use neutrons and X-rays in parallel to collect data that is not possible with other techniques. This allows us to understand the arrangement of atoms of different elements in a sample. Neutrons helped the team detect the lighter elements in space glass, such as oxygen, while X-rays helped them detect the heavier elements such as neodymium and titanium. If there were significant differences between space glass and terrestrial glass, they would likely have appeared in the oxide sublattice or in the arrangement of oxygen atoms, in the distribution of heavy atoms, or in both.

Neutrons are becoming increasingly important tools for unlocking the mysteries of matter as scientists explore new frontiers beyond space.

“We need to understand not only the effects of space on matter, but also its effects on the way things come into being,” Neuefeind said. “Due to their unique properties, neutrons are part of the solution to such puzzles.”