State-of-Art Interferometry

Scientists at The National Corrosion Center  have unveiled a one-of-a-kind microscope  that lets them zoom in for the closest look anyone has ever gotten of corrosion in action.

	TOMMY LAVERGNE
	Dr. Rolf Arvidson, left, and Dr. Andreas Lüttge demonstrate the new ZeMapper interferometer.

“There is no other instrument like this in the world,” said NCC director Andreas Lüttge at the Oct. 14 Rice University open house for the center’s new interferometry laboratory. “With this interferometer we can measure corrosion quantitatively before most techniques can even see it,” said Lüttge, professor of Earth science and of chemistry.

The most costly and common form of corrosion is rust. Every bridge, dam or building that contains iron or steel is potentially subject to damage from corrosion. And corrosion starts when atoms of iron react with oxygen atoms to form iron oxide.

“Corrosion is governed at the molecular and atomic level,” said NCC geochemist Rolf Arvidson, senior research scientist in Earth science. Arvidson said scientists need to track reaction rates and follow the progress of reactions at the nanometer-scale if they are to fully understand how corrosion begins and spreads.

The lab’s newest addition is a ZeMapper interferometer built and customized for Rice researchers by Zemetrics Inc.

“It helps to bring those small details into focus by utilizing super-resolution techniques in combination with interferometry,” said University of Göttingen scientist Cornelius Fischer, an adjunct assistant professor of Earth science at Rice. He helped develop techniques used with the new microscope during a Humbolt Foundation fellowship at Rice in 2006-2008.

Interferometers work by probing samples with light in a way that allows them to resolve small features in high resolution. Thanks to a patented technique developed by Lüttge’s group and by Rice Earth science professor Dale Sawyer over the past five years, Rice’s interferometer has even greater resolution. The technique involves shifting the sample in minute, subpixel increments. A new dataset is acquired after each shift, and software developed at Rice combines the data to resolve details at a lateral scale on the order of tens of nanometers and at a vertical resolution of less than an angstrom. By viewing the images in sequence, the machine can even create videos that show and measure corrosion occurring at the nanometer scale.

The patented interferometer technology may eventually be used in biomedical, environmental and material science applications, but the NCC team’s immediate plan is to answer fundamental questions about how corrosion works at the molecular scale. Ulitmately, the team hopes to set the stage for the discovery of new corrosion prevention and mitigation technologies.

“It’s exciting to measure things at the atomic scale and to create pretty movies, but ultimately society and policymakers want to know, What do we design for? What do we need to plan for?” said Rice’s Emil Pena, executive director of both the NCC and the Energy & Environmental Systems Institute. “Translating what we learn at the small scale to the larger world is an important part of this process.”

The NCC’s new interferometer was purchased with funds from the Air Force Office of Scientific Research and CORPRO Systems.

Pictured, Rice’s Dr. Enrique Barrera and Emil Peña,
with Jesus Soto (El Paso Corp.), attend the reception
unveiling the interferometer.