A new glass material, developed by Tampere University researcher Erkka Frankberg and colleagues, appears to possess metal-like ductility at room temperature.
Thin films of glassy alumina (Al2O3) subjected to mechanical stress. Image credit: Tampere University.
“Conventional glass is brittle and easily shatters under pressure,” Dr. Frankberg said.
“We discovered a way to manufacture glass that exhibits ductile behavior. In other words, our glass is tougher than conventional glass.”
Dr. Frankberg and co-authors from Finland, France, Italy, Austria, Norway, and the United States used a challenging technique called pulsed laser deposition to convert alumina (Al2O3) into a glass-like state.
“It is exceedingly difficult to convert aluminum oxide into a glassy substance,” he said.
“The traditional glass manufacturing processes cannot be applied to aluminum oxide because it easily transforms into the crystalline form. The solution is to cool the material down extremely fast from a high temperature to prevent crystallization.”
The fabrication of a glass that exhibits plasticity is extremely challenging. The process must be further refined and developed before the new type of glass can be manufactured on a larger scale.
“Both aluminum and oxygen are abundant on Earth, but we require an unconventional manufacturing process to achieve the desired properties,” Dr. Frankberg explained.
“The produced glass also needs to be sufficiently pure and flawless which presents a further challenge.”
A high quality glass material is mandatory for the ductility. The presence of any imperfections in the glass, such as cracks, bubbles or impurities, may result in fracture.
“In our glass, the atoms are able to move from one location to another before the glass reaches the stress needed for fracture, whereas in conventional glass the fracture stress is achieved before the atoms begin to move, which is why the glass breaks easily,” Dr. Frankberg said.
The team prepared thin films of their glass and subjected them to mechanical stress. Although the material exhibits metal-like properties, it is still glass.
“We stretched and compressed samples of our material,” he said.
“By carrying out combined compression and shear tests, we were able to demonstrate that the material is also capable of adjusting to a shear force.”
“Demonstrating the ductility is only the beginning. Next we will investigate which other glasses have the same ability and why some glasses remain brittle,” Dr. Frankberg said.
The team’s work was published in the November 15, 2019 issue of the journal Science.
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Erkka J. Frankberg et al. 2019. Highly ductile amorphous oxide at room temperature and high strain rate. Science 366 (6467): 864-869; doi: 10.1126/science.aav1254
