Engineers Discover New Method to Determine Surface Properties at the Nanoscale

As machines get smaller, knowing characteristics can make huge engineering differences.

Nanoparticle

Known properties of a material can radically change at the nanoscale – a tiny scale about 1/1000 of the diameter of a human hair at which scientists have begun building machines that do work.

Engineering researchers at Texas Tech University have developed a method for characterizing the surface properties of materials at different temperatures at the nanoscale.

Knowing properties of materials at different temperatures is important in engineering, said Gregory McKenna, a professor of chemical engineering and the John R. Bradford Endowed Chair in Engineering. For example, the rubber O-ring that failed during the 1986 space shuttle disaster serves at a tragic case study of what can go wrong when decision-makers don't take this into account.

The problem, he said, is known properties of a material can radically change at the nanoscale – a tiny scale about 1/1000 of the diameter of a human hair at which scientists have begun building machines that do work. McKenna and graduate student Meiyu Zhai looked at several polymers and explosive materials to see how surface properties varied at the nanoscale and how the surface impacts the nanoscale properties.

Their first results on the “multi-curve method” appeared in the peer-reviewed journal, Journal of Polymer Science Part B: Polymer Physics and was highlighted in Advances in Engineering.

“The nanoscale is a funny range of sizes where materials have properties that are not what we expect, even at a step up at the microscale,” he said. “We are developing methods to characterize surface properties and relate them to nanoscale behavior using a nanoindenter and other nano-mechanical measurement methods.”

In nanoindentation, researchers can investigate both the elastic properties (how materials spring back when pushed) or the viscous properties (how the material flows). The group has found several surprising results: For example, in other work, the team found extremely thin polycarbonate films become liquid-like at the nanoscale, while they are glassy at the macroscopic size scale. Nanoindentation can be used to relate surface properties to this observation.

As machines get smaller and smaller, McKenna said, knowing this information can be invaluable to future engineers.

The nanoindentation project was funded by The Office of Naval Research. The researchers also are funded by the National Science Foundation and the American Chemical Society-Petroleum Research Fund.

To see the multi-curve study, click https://advanceseng.com/chemical-engineering/viscoelastic-modeling-nanoindentation-experiments-multicurve-method/.

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Featured Expert

Greg McKenna

Greg McKenna is Horn Professor and John R. Bradford Chair in Engineering in the Department of Chemical Engineering in the Whitacre College of Engineering.


Whitacre College of Engineering

The Edward E. Whitacre Jr. College of Engineering

The Edward E. Whitacre Jr. College of Engineering has educated engineers to meet the technological needs of Texas, the nation and the world since 1925.

Approximately 4,300 undergraduate and 725 graduate students pursue bachelors, masters and doctoral degrees offered through eight academic departments: civil and environmental, chemical, computer science, electrical and computer, engineering technology, industrial, mechanical and petroleum.

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