A new method for manufacturing glass could lead to the production of 'designer glasses' with applications in advanced photonics, whilst also facilitating industrial scale carbon capture and storage. An international team of researchers report in the journal Nature Communications how they have managed to use a relatively new family of sponge-like porous materials to develop new hybrid glasses.
The work revolves around a family of compounds called metal-organic frameworks (MOFs), which are cage-like structures consisting of metal ions linked by organic bonds, making them highly porous. This porous structure has led to proposed applications in carbon capture, hydrogen storage and toxic gas separations, due to their ability to selectively adsorb and store pre-selected target molecules in their pores.
However, since the discovery of MOFs a quarter of a century ago, their potential for large-scale industrial use has been limited. This is mainly due to the difficulty of processing the MOF powders produced by chemical synthesis into linings, thin films, and fibrous or other 'shaped' structures. Such limitations arise from the relatively poor thermal and mechanical properties of MOFs compared to materials such as ceramics or metals, and have in the past resulted in structural collapse during post-processing techniques such as sintering or melt-casting.
“The formation of glasses that contain highly interchangeable metal and organic components is highly unusual, as they are normally either purely organic, for example in solar cell conducting polymers, or entirely inorganic, such as oxide or metallic glasses."Yuanzheng Yue, Aalborg University
Now, a team of researchers from Europe, China and Japan has discovered that careful MOF selection and heating under argon appears to raise the decomposition temperature of the MOFs just enough to allow melting rather than collapse. The resultant liquids have the potential to be shaped, cast and recrystallized, producing solid structures with uses in gas separation and storage.
"Traditional methods used in melt-casting of metals or sintering of ceramics cause the structural collapse of MOFs due to the structures thermally degrading at low temperatures,” explains Thomas Bennett from the Department of Materials Science and Metallurgy at the University of Cambridge. “Through exploring the interface between melting, recrystallization and thermal decomposition, we now should be able to manufacture a variety of shapes and structures that were previously impossible, making applications for MOFs more industrially relevant".
Equally importantly, say the researchers, the glasses that can be produced by cooling the liquids quickly are themselves a new category of materials. Further tailoring of the chemical functionalities may be possible by utilizing the ease with which different elements can be incorporated into MOFs before melting and cooling.
"A second facet to the work is in the glasses themselves, which appear distinct from existing categories,” explains Yuanzheng Yue from Aalborg University. “The formation of glasses that contain highly interchangeable metal and organic components is highly unusual, as they are normally either purely organic, for example in solar cell conducting polymers, or entirely inorganic, such as oxide or metallic glasses. Understanding the mechanism of hybrid glass formation will also greatly contribute to our knowledge of glass formers in general."
Using the advanced capabilities at the UK's Diamond Light Source synchrotron, the team were able to scrutinize the metal organic frameworks in atomic detail. "This work is an exciting example of how work with synchrotron radiation which deepens our fundamental understanding of the properties of glasses also produces tantalizing prospects of practical applications of new materials,” says Trevor Rayment, physical science director at Diamond. “This work could have a lasting impact on both frontiers of knowledge."
The researchers believe the new technique could open up the possibility of producing 'chemically designed' glasses, whereby different metals or organics are swapped into, or out of, the MOFs before melting.
This story is adapted from material from the University of Cambridge, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.