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According to research from the University of Michigan, a class of materials once thought it would revolutionize everything from solar panels to frying pans but fell out of favour in 2000 could be poised for commercial revival.
The study was published in Nature Communications. It shows how to produce larger quasicrystals without the same defects as past manufacturers. This led to quasicrystals being dismissed as intellectual curiosity.
Ashwin Shahani (U-M assistant professor in materials science engineering and chemical engineering, and co-author of the paper) stated that industry abandoned quasicrystals because they were full of defects. "But, we hope to bring quasicrystals into the mainstream. This work suggests that it is possible.
Quasicrystals can be made with many attractive properties. They have an ordered structure, but not repeating patterns like ordinary crystals. They can be super-slippery or ultra-hard. They can absorb heat and light in unique ways, and have exotic electrical properties.
The first manufacturers to commercialize the material discovered that there were tiny cracks between crystals. These cracks are called grain boundaries. They invite corrosion and make quasicrystals vulnerable to failure. Since then, commercial development of quasicrystals was mostly abandoned.
Shahani's new research shows that small quasicrystals can collide, meld together and form a single large crystal without the grain boundary imperfections common in smaller crystals. Shahani explained that this phenomenon was discovered during an experiment to observe the formation.
He said that it looked like crystals were healing themselves from collisions, transforming one type defect into another and eventually disappearing altogether. It's amazing, considering that quasicrystals lack periodicity.
The crystals begin as pencil-like solids, measuring just a fraction of millimeter. They are suspended in a molten mixture consisting of aluminum, cobalt, and nickel. This team can then observe the crystals in real-time and in 3D using 3D X-ray tomography. The tiny crystals begin to collide and eventually meld with one another, forming a large quasicrystal which is several times larger than its constituents.
The team recreated the process using computer simulations after observing it at Argonne National Lab. They were able to determine the conditions in which tiny crystals will fuse into larger ones by running simulations under slightly different conditions. For example, they found that the tiny, pencil-shaped crystals must be facing each other within a specific range of alignment to collide and coalesce. Sharon Glotzer, John Werner Cahn University Professor of Engineering and the corresponding author of the paper, performed the simulations.
Glotzer stated that it was exciting to see the same phenomena occurring on the same time and length scales in simulations and experiments. Simulators can see details about crystallization that experiments cannot see and vice versa. This is how simulations help us to understand the process better.
Although commercialization of this technology is unlikely for many years, simulation data could prove to be useful in the development of a process that can efficiently produce large quantities in large production runs. Shahani envisions the use of sintering. This is a well-known industrial process in which materials are melted together by heat and pressure. Although it's still a distant goal, Shahani believes that the new study opens up new research avenues that could eventually lead to this goal.
Shahani and Glotzer have been working together for the moment to learn more about quasicrystal defect formation, movement, and evolution.
"Formation a Single Quasicrystal upon Collision of Multiple Grains" is the title of the paper. Brookhaven National Laboratory is also part of the research team.
Continue exploring Khatyrka meteorite, which has a third quasicrystal
Further information: "Formation a Single Quasicrystal upon Collision of Multiple Grains" Nature Communications (2021). Journal information: Nature Communications, "Formation a Single Quasicrystal upon Collision with Multiple Grains" (2021). DOI: 10.1038/s41467-021-26070-9
