Neutrons open window to explore space glass

Thanks to human ingenuity and gravity, we can reap important benefits from space science. Think of smartphones with built-in navigation systems and cameras.

Such transformational technologies seem to merge into the rhythm of our daily lives overnight. But they emerged from years of discoveries and developments in materials that can withstand harsh conditions outside our atmosphere. They emerged from decades of laying foundations in fundamental science to understand how atoms in different materials behave under different conditions.

Building on this past, a global team of researchers has set a new benchmark for future experiments that create materials in space rather than for space. The team included members from the Department of Energy’s Oak Ridge and Argonne National Laboratories, Materials Development, Inc., NASA, the Japan Aerospace Exploration Agency, or JAXA, ISIS Neutron and Muon Source, Alfred University, and the University of New Mexico . Together they discovered that many types of glass, including ones that could be developed for next-generation optical devices, have similar atomic structures and arrangements and could be successfully created in space.

The team’s article is published in the journal npj Microgravity.

“The idea is to figure out the mechanisms behind space-based manufacturing, which could lead to materials that aren’t necessarily available on Earth,” says Jörg Neuefeind, who joined ORNL in 2004 to build an instrument called NOMAD at the Spallation Laboratory Neutron Source. (SNS). NOMAD, the fastest neutron diffractometer in the world, helps scientists measure the arrangement of atoms by seeing how neutrons bounce off them. NOMAD is one of 20 tools at SNS that are helping scientists answer big questions and spurring countless innovations, such as drugs that treat diseases more effectively, more reliable airplanes and rocket engines, cars that get better gas mileage, and batteries that are safer, charge faster, and last longer go along. .

JAXA operators on Earth made and melted glass aboard the International Space Station (ISS), via remote control using a levitator. Levitators are used to suspend material samples during experiments to prevent interference from contact with other materials.

When the next ISS mission ended months later and the space glass was brought back to Earth, researchers used a combination of techniques, including neutrons, X-rays and high-powered microscopes, to measure and compare glass made and melted from celestial and terrestrial.

“We discovered that with containerless techniques, such as the levitator, we can create unconventional glasses in microgravity,” says Takehiko Ishikawa of JAXA, pioneer of the electrostatic levitator used to make the glass beads on board the ISS.

The researchers relied on NOMAD at SNS to study the glass samples with neutrons and beamlines at Argonne’s Advanced Photon Source to study the samples with 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 recovered only a few glass beads about a centimeter in diameter, which are very difficult to measure in terms of atomic structure. Because NOMAD excels at measuring extremely small samples, we could easily compare the individual beads we made in the laboratory with those made on the space station.”

Mysteries of glass

Glass turns out not to be so clear. Unlike crystalline solids, such as salt, glass atoms do not have a uniform structure. The unusual atomic arrangement, while remarkably stable, is perhaps best described as a random network of molecules sharing coordinated atoms. Glass is neither completely solid nor completely liquid, but also exists in various forms, including polymer, oxide and metal, such as for eyeglass lenses, fiber optic threads and space mission hardware.

In 2022, Neuefeind, Wilke and Rick Weber, an expert in the field of glass, experimented with two oxides of neodymium and titanium and discovered a potential for optical applications. The combination of these two elements exhibits unusual strengths not seen in comparable research campaigns. These findings led them to continue their current studies at NASA.

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

Scientists often use neutrons and X-rays in parallel to collect data that no other technique can produce, allowing us to understand the arrangement of atoms of different elements within a sample. Neutrons helped the team see the lighter elements in the space glass, such as oxygen, while X-rays helped them see the heavier elements, such as neodymium and titanium. If significant differences existed between the space glass and the terrestrial glass, they would likely have been reflected in the oxide sublattice, or the arrangement of the oxygen atoms, in the distribution of the heavy atoms, or both.

Neutrons will become increasingly important tools for unlocking the mysteries of matter as scientists explore new frontiers despite space.

“We need to understand not only the effects of space on matter, but also its effects on how things form,” Neuefeind said. “Because of their unique properties, neutrons are part of solving these types of puzzles.”