Aug 30, 2018 | By Thomas
Material scientists from the U.S. Army Research Laboratory (ARL) are analyzing metal and ceramic specimens at the atomic level using state-of-the-art 3D imaging atom probe technology. This research aims to understand the interior structure of materials for a next-generation body armor system to keep troops safe.
To get an idea of the size they're working with, imagine the width of a hair. The samples are a thousand times smaller than a human hair.
"The atom probe gives us a 3-D reconstruction at the atomic level," said Dr. Chad Hornbuckle, a materials scientist with the laboratory's Weapons and Materials Research Directorate. "When you see the reconstruction that's made up of millions of dots, the dots are actually individual atoms."
Hornbuckle said the technology sets the standard for accuracy in chemistry. "It's basically the only machine in the world that can do this at the atomic level. There are machines, like transmission electron microscopes, or TEMs, that do chemical analysis, but it is not as accurate as this."
The experiments also require consistency. "You might have one effect one time, but if the chemistry changes, you get a completely different effect the next time," he said. "If you can't control the chemistry, you can't control the properties."
Researchers prepare samples of metal and ceramic for analysis by creating really sharp tips through sandblasting, or milling. Then the chemical element gallium is applied using a dual beam scanning electron microscope. Once the samples are ready, they are inserted into the atom probe.
The interior of the probe is a super cold vacuum. Using a laser, or a voltage pulse, the scientists ionize the atoms on the small tip causing the individual ions to field evaporate from the surface. Then the evaporated ions are analyzed and identified, which results in a 3D model at near-atomic spatial resolution.
"I can give you one specific example of how it's helped our research," said Dr. Denise Yin, a postdoctoral fellow at the lab and graduate of Lehigh University. "We were electrodepositing copper in a magnetic field and we found a chemical phase using the atom probe that didn't otherwise show up in conventional electrodeposition.
Electrodeposition is a process that creates a thin metal coating.
We were having problems identifying this phase using other methods, but the atom probe told us exactly what it was and how it was distributed."
The machine's capability is impressive, she said.
"You can see the atoms show up in real time," Yin said. "Again, it's at the nanometer scale, so it's much finer than all the other characterization techniques. The atom probe told us quite easily that the unknown phase was two different types of a copper hydride phase, and that's not something that we could have detected using those other methods."
The kind of atom probe the Army uses is one of only a handful found in the US.
Images: US Army photos by David McNally
Since there are a limited number of atom probes, universities are also bringing their own samples for analysis.
"One university that we collaborate with is Lehigh University," said Hornbuckle. "At first, this collaboration was more of a mutual exchange of expertise, where I analyzed some of their samples in the atom probe and they used their aberration-corrected transmission electron microscope to analyze some of our copper-tantalum sample. We now have a cooperative agreement with them to continue this collaboration."
The partnership with Lehigh delivered important results. "I actually ran a nickel-tungsten alloy that was electrodeposited for them and identified and quantified the presence of low atomic number elements such as oxygen and sodium," Hornbuckle said. "This resulted in one research journal article with several more in preparation."
Hornbuckle said the Army is also working with the University of Alabama on atomic-level analysis.
"They have a different version of the atom probe," he said. "They have run some our alloys in their version and ours to compare the differences noted in the same material. This material is actually being scaled up through a number of processes that are relevant to the Army."
This collaboration also resulted in numerous research journal articles, Hornbuckle said. "We also have a partnership with them."
Another university collaborating with the Army with is Texas A&M.
"I have analyzed a few nickel-titanium alloys that had been 3D printed," Hornbuckle said. "They noticed some nanoscale precipitates within the 3-D printed materials, but were unable to identify them with their TEM. I am trying to determine the chemistry of the phase using the atom probe, which should help to identify it."
These partnerships give the Army access to university laboratory equipment. The fundamental knowledge gained through this research will be then applied to current Army problems and in the development to future Army relevant materials.
Posted in 3D Printing Application
Source: US Army
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HAHA Just going to say the pictures for this article above really looks like something out of a Jurassic Park or sci-fi movie
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