The glass we're most familiar with is made from silicon dioxide, but materials like boron, polymers and metals have also been used. Now, an international team of scientists have developed a brand new class of glass, made from metal-organic compounds. These new materials form glass more readily than other types, and are much more pliable.
The new metal-organic glass is made of zinc and two organic compounds, known as imidazolate and benzimidazolate. The material has the same atomic structure as silica glass, forming a pyramid shape with a zinc atom at the center and four molecules of the organic compounds surrounding it. The researchers called their creation ZIF-62.
One of the defining characteristics of glass is its smooth, non-crystalline structure, and that's the result of a very careful balancing act during production. Whatever source material is used needs to be heated until it melts, then cooled very rapidly so that crystals don't have time to form. How well a material avoids crystallization is known as its glass-forming ability.
Traditionally, silica glass is known to have the best glass-forming ability, but according to the team, ZIF-62 has it beat. In fact, it outperformed 50 existing types of glass, and is far more pliable than silica-based glass. Tweaking the recipe, the researchers found that the more benzimidazolate they added, the better the material's glass-forming ability became.
There are still kinks to be ironed out though. The process for manufacturing silica glass benefits from thousands of years of refinement, and it's hard for ZIF-62 to compete with that at this early stage. To make the new metal-organic glass, the organic compounds first need to be synthesized, then mixed with hydrous zinc nitrate and a solvent. Then, it all needs to be heated to about 800° F (427° C) for long enough to completely melt – but if it hits 980° F (527° C) it will start to vaporize.
Finding ways to scale up production is a key area of future work, as is learning more about the glass itself. So far the researchers have experimented with ZIF-62's optical and mechanical properties, but there's plenty more still to learn, the team says.
"This family of glasses is so new that, while we have determined its glass-forming ability and a few other properties, we have not fully characterized all of its material properties," says John C. Mauro, co-author of a study describing the new material. "There also needs to be research into how to scale-up this process for manufacturing."
This further study will also examine other metallic-organic glass recipes, including a potential cobalt-based glass.
The research was published in the journal Science Advances.
Source: Pennsylvania State University
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