Nav: Home

In-depth insights into glass corrosion

February 28, 2019

Silicate glass has many applications, including the use as a nuclear waste form to immobilize radioactive elements from spent fuel. However, it has one disadvantage - it corrodes when it comes into contact with aqueous solutions. Scientists at the University of Bonn were able to observe in detail which processes take place. The results have now been published in the journal Nature Materials.

The mineralogists and geochemists at the University of Bonn used the so-called confocal Raman spectroscopy for their study, where a laser beam is focused on a sample through a microscope. The light interacts with the molecules in the material, causing them to vibrate. Individually backscattered photons change their color depending on the structure and the chemical properties of the sample. This phenomenon is known as the Raman effect. The originally monochromatic light now also contains other color components. The color spectrum provides detailed insights into the structure and composition of the matter that is excited by the laser beam.

What makes this method even more interesting: The laser can be focused to a specific point in the space with an accuracy of a few thousandths of a millimeter. This facilitates studying the sample point by point, but not only on its surface: If the sample is transparent, the beam can also be focused into internal areas. "And that's exactly what we did," explains Prof. Dr. Thorsten Geisler-Wierwille from the Institute for Geosciences and Meteorology at the University of Bonn.

Opal layer at the glass surface

The researchers used a small piece of silicate glass as a sample that reacted with an aqueous solution in a specially developed heating vessel. It was possible to move the vessel in steps of one thousandth of a millimeter under the Raman microscope - to the right, left, forward, and backward, but also up and down. "We scanned the glass point by point and recorded a Raman spectrum while it reacted with the solution," says Lars Dohmen, who is currently completing his doctorate under the supervision of Geisler-Wierwille. "This allowed us to investigate the reaction almost in real time. This currently works at temperatures of up to 150 degrees, which, for instance, are also expected in a nuclear repository."

The results indicate that silicate glass quickly dissolves when it comes into contact with aqueous solutions - almost like a sugar cube in a cup of coffee. However, while the sugar molecules are quickly distributed evenly in the water by diffusion, this is not the case during glass corrosion: Part of the resulting dissolved silica seems to remain near the surface of the glass. At some point, its concentration becomes so high that it solidifies.

"We then also speak of silica precipitation," explains Prof. Geisler-Wierwille. "Silica molecules in the solution interlink to form aggregates only a few millionths of a millimeter in size, which are deposited at the glass surface and mature into an opal-like state." However, the researchers were able to show that this opal layer does not provide perfect protection against water. Instead, the dissolution-precipitation front continues to eat its way into the glass. As a result, the glass is gradually replaced by opal, although at a decreasing velocity. "For the first time, we have experimentally demonstrated that a boundary solution with dissolved silica forms between the opal layer and the underlying glass," explains Geisler-Wierwille. "As the thickness of the opal layer increases, it increasingly prevents the silica solution from being transported away from the reaction interface. "We suspect that it eventually gels to a viscous mass, which dramatically slows down glass dissolution."

In the study, this was already the case after 25 thousandths of a millimeter. "Even though the reaction became very slow, it cannot be ruled out that this corrosion process will release radioactive elements over long periods of time," emphasizes Geisler-Wierwille. However, glasses used for the vitrification of nuclear waste are by far more stable against water than the investigated glass. "We want to extend our experiments to these glass types in the near future," emphasizes the researcher. Studies with silicate glass in which radioactive elements are already incorporated are also planned. The researchers and their partners want to investigate the influence of self-irradiation damage in the glass on its corrosion resistance. "The current work should mainly prove that our new method can provide far-reaching insights into these processes," says Geisler-Wierwille.

The level of interest shown by industry in this work is also reflected in the financing of the pilot project: One of the sponsors of the study is the renowned glass manufacturer Schott AG.
Publication: Thorsten Geisler, Lars Dohmen, Christoph Lenting and Moritz B. K. Fritzsche: Real-time in situ observations of reaction and transport phenomena during silicate glass corrosion by fluid-cell Raman spectroscopy. Nature Materials,


Prof. Dr. Thorsten Geisler-Wierwille
Institute for Geosciences and Meteorology (formerly Steinmann Institute)
University of Bonn
Tel. +49 (0)228/73 2733

University of Bonn

Related Nuclear Waste Articles:

Taking a bite out of food waste: Scientists repurpose waste bread to feed microbes
Food waste is a serious economic and environmental problem. Researchers have developed a protocol using waste bread as a medium to grow microorganisms for the fermented food industry.
Current model for storing nuclear waste is incomplete
The materials the United States and other countries plan to use to store high level nuclear waste will likely degrade faster than anyone previously knew, because of the way those materials interact, new research shows.
Unused stockpiles of nuclear waste could be more useful than we might think
Chemists have found a new use for the waste product of nuclear power -- transforming an unused stockpile into a versatile compound which could be used to create valuable commodity chemicals as well as new energy sources.
Researchers perfect nanoscience tool for studies of nuclear waste storage
Studying radiation chemistry and electronic structure of materials at scales smaller than nanometres, the University of Guelph team prepared samples of clay in ultra-thin layers.
Deep learning expands study of nuclear waste remediation
A research collaboration between Berkeley Lab, Pacific Northwest National Laboratory, Brown University, and NVIDIA has achieved exaflop performance with a deep learning application used to model subsurface flow in the study of nuclear waste remediation.
Nuclear physics -- probing a nuclear clock transition
Physicists have measured the energy associated with the decay of a metastable state of the thorium-229 nucleus.
Electrospun sodium titanate speeds up the purification of nuclear waste water
Electrospun sodium titanate speeds up the purification of water based on selective ion exchange -- effectively extracts radio-active strontium.
New EU 'urban mining' tools map valuable resources in e-waste, scrap vehicles, mine waste
Expert European organizations have united to create the world's first database of valuable materials available for 'urban mining' from scrap vehicles, spent batteries, waste electronic and electrical equipment, and mining wastes.
Mainz physicists propose a new method for monitoring nuclear waste
New scientific findings suggest neutrino detectors may play an important role in ensuring better monitoring and safer storage of radioactive material in nuclear waste repository sites.
Rutgers-led research could revolutionize nuclear waste reprocessing and save money
Seeking a better way to capture radioactive iodides in spent nuclear reactor fuel, Rutgers-New Brunswick scientists have developed an extremely efficient 'molecular trap' that can be recycled and reused
More Nuclear Waste News and Nuclear Waste Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Clint Smith
The killing of George Floyd by a police officer has sparked massive protests nationwide. This hour, writer and scholar Clint Smith reflects on this moment, through conversation, letters, and poetry.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at