Mar 20, 2013
Nano-embossing reveals properties of metallic supercooled liquids
When fabricating nanoscale devices by surface embossing techniques, it can be difficult to control pattern uniformity and make durable master moulds. Now, researchers at Texas Tech and Yale University in the US have demonstrated that nano-embossing with amorphous metals (metallic glasses) not only overcomes these hurdles, but also provides a wealth of information about the properties of metallic glasses in the supercooled liquid state.
Our study focused on mechanisms that control pattern non-uniformity observed in nano-embossing of metallic glasses (see figure). We have developed a quantitative model that describes how the nanoimprinted pattern forms and predicts how interfacial forces (such as the capillary pressure) affect pattern non-uniformity profiles.
The theory is an important step towards developing a controllable nanoimprinting technique, and it also provides a new way to evaluate the surface tension of metallic glasses by comparing the observed surface pattern with the theory model. The surface tension of metallic glasses is difficult to measure using standard techniques because of high material viscosity under thermoplastic forming conditions.
Our team has also shown that for oxidation-prone metallic liquids, an additional surface force, associated with the rigidity of the surface oxide layer, hinders nanopattern formation. The model can be used to determine the degree of oxidation and the strength of the oxide layer at the entrance of mould nanocavities, and the theory has been validated by experiments conducted on oxidation-resistant and oxidation-prone metallic glasses.
Understanding the properties of amorphous metals in the supercooled liquid state is critical for fundamental science as well as for a wide range of applications that involve thermoplastic processing of metallic glasses. This work will provide new ways of measuring the properties of thermoplastics and hopefully lead to nanoscale applications for metallic glasses.
More details of the study can be found in the journal Nanotechnology.
About the author
Dr Golden Kumar is an assistant professor in the Department of Mechanical Engineering at Texas Tech University. His research focus is on surface engineering, nanomechanics, size effects and metallic glasses. Dr Jerzy Blawzdziewicz is a professor in the Department of Mechanical Engineering at Texas Tech University. His research involves theoretical and numerical descriptions of complex materials and biological matter. Dr Jan Schroers is a professor in the Department of Mechanical Engineering and Materials Science at Yale University. His research activities include metallic glasses, thermoplastic processing, artificial microstructures, materials for energy conversion, and combinatorial characterization methods.