Materials

Liquid glass discovered as new state of matter

Liquid glass discovered as new...
Researchers have discovered a new state of matter called liquid glass
Researchers have discovered a new state of matter called liquid glass
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Researchers have discovered a new state of matter called liquid glass
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Researchers have discovered a new state of matter called liquid glass
A diagram showing the positions and orientation of the team's elliptical particles in the liquid glass state
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A diagram showing the positions and orientation of the team's elliptical particles in the liquid glass state

Mundane as it may seem, glass is a surprisingly mysterious material. Now scientists at the University of Konstanz have identified a new state of matter called liquid glass, which has some unusual properties.

It’s a persistent fallacy that glass already is a liquid, spread by misinformed high school teachers and tour guides. But that’s not technically true – glass is an amorphous solid. Normally when a substance transitions from a liquid to a solid, the formerly free-flowing atoms line up into a rigid crystal formation. That’s not the case with glass though: its atoms “freeze” in their disordered state.

Or at least, that’s how it usually goes. In the new study, the researchers discovered a form of glass where the atoms exhibit a complex behavior that’s never been seen in bulk glass before. Essentially, the atoms can move but aren’t able to rotate.

The team made this discovery in a model system of colloidal suspensions. These mixtures are made up of large solid particles suspended in a fluid, making it easier for scientists to observe the physical behavior of atoms or molecules. Normally these particles are spheres, but for this experiment the team used elliptical ones so they could tell which direction they were pointing.

A diagram showing the positions and orientation of the team's elliptical particles in the liquid glass state
A diagram showing the positions and orientation of the team's elliptical particles in the liquid glass state

The researchers tested different concentrations of particles in the fluid, tracking how well they could move and rotate. Eventually they found that at higher concentrations, the particles blocked each other from rotating, but they could still move, forming a liquid glass state.

“At certain particle densities orientational motion froze whereas translational motion persisted, resulting in glassy states where the particles clustered to form local structures with similar orientation,” says Andreas Zumbusch, lead author of the study.

The team says that the observed behavior comes from two competing glass transitions interacting with each other. Liquid glass has been predicted for decades, and the new observation suggests that similar processes could be at work in other glass-forming systems.

“This is incredibly interesting from a theoretical vantage point,” says Matthias Fuchs, senior author of the study. “Our experiments provide the kind of evidence for the interplay between critical fluctuations and glassy arrest that the scientific community has been after for quite some time.”

The research was published in the journal Proceedings of the National Academy of Sciences.

Source: University of Konstanz

19 comments
19 comments
Catweazle
I disagree that it is a fallacy that glass is a supercooled fluid.

At school in the physics laboratory we had a large measuring cylinder ~18" long that had been lying undisturbed on its side in a cupboard for well over 100 years, it had sagged in the centre by approximately half an inch; it had been maintained like this as an example of the behaviour of supercooled fluids.

Further, I can point out locally a number of panes of glass in windows up to 350 years old that have become noticeably thinner at the top and thicker at the bottom;, I have often seen the same phenomenon in ancient buildings all over the British Isles.
Kpar
I concur with Catweazle, my own education included much of the same information. Glass flows slowly over time.
Username
Catweazle - It comes down to the definition of liquid. A lot of solids will sag over a period of time.
WB1200
If you put glass into a high speed centrifuge will it sag?
Douglas Bennett Rogers
Cathedral panes were made wedge shaped to be picked up with tongs. Telescope mirrors and lenses retain their shape to parts per million over decades. There are glass beads that are billions of years old that are still bead shaped. There may be glasses that are much more flowable than these examples.
Pete Davis
Normal glass is an amorphous solid, just like wax, some plastics, gel, etc. End of story. It's not a fluid, super-cooled or otherwise.
Lamar Havard
So, is it sticky?
Expanded Viewpoint
In a science book I used to have many moons ago, it said that if you took a glass rod or a tube about 4' long and .25" diameter, and supported it at both ends, then hung a weight in the center that was near the breaking point of the glass, after about a month or so, the glass will have taken a curved set to it.
Gravity never shuts off, so with the constant pulling down on all molecules in an object, they should eventually succumb to it and find their lowest level.

Randy
mr.sugg
Sorry Catweazle and Kpar. The reason why old building glass is heavier at the bottom is because of the old method of manufacture prior to sheet glass on molten tin. The glass was spun into a circle - getting thinner at the circumference due to centrifugal force and after cooling was cut into small panes - hence natural distortion and the use of leadlight.
JasonStanton
It's an obvious phenomenon no matter what the nature of it.
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