A Match Made for the Heavens

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Workers align a mirror segment on the JWST.

Tiny behaviors of huge importance
Telescopes, spaceships, robots and many other devices vital to space exploration can be made to function more efficiently and reliably if engineers understand how their tiny constituent materials behave in the hostile environment of space.

Nanocomposites, nanoribbons and other nanomaterials, for example, should enable engineers to fabricate lighter-weight space vehicles with superior material properties – without sacrificing strength.

But such advantages can only be gained with an improved knowledge of the way these materials behave at the atomic scale.

For this reason, Lehigh's Nanocharacterization Laboratory is critical to the Lehigh-NASA collaboration. Lehigh, with 14 instruments, possesses one of the world's most extensive collections of electron microscopes. Using two aberration-corrected microscopes – a JEOL 2200FS transmission electron microscope (TEM) and a VG HB 603 scanning transmission electron microscope (STEM) – researchers can resolve images to 0.1 nanometer, about half the width of an atom, and can determine the chemical identity of individual atoms in crystalline materials.

Lehigh experts are constantly refining microscopes and developing new analytical techniques. These upgrades make it possible to determine a material's mechanical, chemical and electrical properties, as well as its structure and composition, at the nanoscale.

These analyses can be performed remotely. Lehigh engineers operated the JEOL 2200FS TEM from the Microscopy and Microanalysis 2006 meeting in Chicago, and have teamed with NASA engineers to set up a remote instrument terminal that could enable NASA scientists to operate the instrument anywhere.

"Internet2 and improved software developed by JEOL are making it more viable for people at NASA to do experiments in our labs," says Chris Kiely, director of Lehigh's Nanocharacterization Laboratory. "The only thing you cannot do remotely is to load a specimen. Everything else – setting the apertures, controlling the alignment and acquiring data – can be done remotely."

Workers test the cryogenic (extreme cold) performance of JWST’s backplane

The Lehigh-NASA partnership includes a half-dozen microscopyrelated projects. In one, CAMN research scientist Lolita Rotkina is enhancing the capabilities of the JEOL 2200FS TEM with a novel combined characterization tool – a low-current measurement circuit and scanning probe fabricated by a smaller company called Nanofactory, for Gatan Inc., a leading manufacturer of electron microscopy ancillary equipment. The tool can locate and image an object as small as a single carbon nanotube, and measure its electronic conductivity and simultaneously manipulate it using a piezodriven probe. This tool has potential applications both to the analysis of materials like reinforced nanocomposites and also to molecular electronic devices, which are a focus of current NASA research.

In another collaboration with Gatan, researchers have attached an X-ray ultra microscopy (XuM) system to Lehigh's XL-30 SEM to study volcanic ash, fly ash, biocompatible glass, precipitates in aluminum alloys, clay-reinforced polymer nanocomposites and other materials. The XuM work is being led by CAMN research scientist Carol Kiely.

XuM obtains an image by using a CCD camera to measure the intensity of the X-rays transmitted through a specimen after it has been bombarded by X-rays emitted from a target located within the microscope. Lehigh and the Lawrence Livermore Laboratories are the only two places in the U.S. currently with such an XuM.

The XuM-SEM combination, says Chris Kiely, enables engineers to obtain images from the interior of a relatively thick sample without damaging or destroying it.

"With XuM, you can see through half a millimeter of polymer, and about 100 microns of metal foil, to obtain an image of a material's internal structure," says Kiely. "Using XuM, we have created 3-D reconstructions of precipitates containing heavy atoms sitting within an aluminum matrix.

"XuM is also very effective at visualizing how a crack propagates through a material. In studying polymers reinforced with silica or clay particles, XuM has given us the clearest images yet of crack tip morphology."

Lehigh geologists have used the new XuM to study the shapes of pores within volcanic ash particles, says Kiely. NASA may want to use XuM to study lunar dust morphology to assess its abrasive effect on the mechanical parts of space vehicles.