Long Room (EUA)

Solid or liquid? Researcher proposes a new definition of glass

Publicado em 20 outubro 2017

Is glass a solid or a liquid? This question, which has been vigorously debated by specialists in the field for some decades, has just been answered anew: "Glass is a non-equilibrium, non-crystalline state of matter that appears solid on a short timescale but continuously relaxes toward the liquid state."

A more elaborate alternative definition is this: "Glass is a non-equilibrium, non-crystalline condensed state of matter that exhibits a glass transition. The structure of glasses is similar to that of their parent supercooled liquids (SCL), and they spontaneously relax toward the SCL state. Their ultimate fate, in the limit of infinite time, is to crystallize."

Definitions - Glass - Errors - Edgar - Dutra

"There are several definitions of glass, but most of them contain serious errors," said Edgar Dutra Zanotto, one of the authors of the new definition. "Many definitions say a glass is a solid, and others say it's an isotropic material [whose properties are the same in all directions], but many glasses are not."

Jointly with John C. Mauro, Professor of Materials Science & Engineering at Penn State University in the U.S., Zanotto published an article in which he argues "[glass] structure is very different from that of solids. Glass relaxes continuously and crystallizes." The article was published in the Journal of Non-Crystalline Solids.

Researcher - Points - Dozens - Articles - Glass

The researcher points that dozens of articles have already placed glass outside the category of solids due to three characteristics. One of them is that the structure of glass is very similar to that of the liquids from which it is formed. Another is that glass flows (deforms) spontaneously over time in response to minimal pressure, which can be less than the action of gravity. Crystalline solids deform only in response to external pressure that is inversely proportional to temperature. The lower the temperature, the greater the pressure that must be applied to a crystalline solid to...

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