In 1915, Sir William Henry Bragg and his son, William, received the first Nobel Prize ever given for materials characterization. Using x-rays, the Braggs revealed the crystal structure of rock salt, the first crystal structure ever characterized. Their success launched a century of exploration into the field of materials characterization or the practice of peering into a material’s internal structure to learn its secrets—namely, its microstructure and chemistry.
Transmission electron microscopes and scanning electron microscopes are now the tools of choice for materials research. These are multi-million dollar pieces of complex equipment that require significant training to use. At Carnegie Mellon’s Materials Characterization Facility (MCF), students and faculty have access to the full gamut of today’s most advanced materials characterization technology.
“The microstructure is what gives a material its properties and performance,” says Marc De Graef. “If we can understand the microstructure, we can begin to think about how we might change it to affect the behavior of the material—make it stronger, more conductive, more resistant to corrosion, anything you’d like.”
De Graef is a professor of Materials Science and Engineering and co-director of the MCF. Under his supervision, graduate students at the MCF are taking materials characterization in novel directions.
Take Isha Kashyap, for example. As a second year Ph.D. candidate in Materials Science and Engineering, Kashyap studies the structure of ferromagnetic shape memory alloys. Using Lorentz Transmission Electron Microscopy (LTEM), one of only a handful of university-based LTEMs in the United States, Kashyap investigates defects and qualities of these alloys, which are used in magnetically induced mechanical actuators, a kind of motor that transforms energy into motion.
“The performance of the actuators depends on the properties of the alloys, which in turn depend on atomic level interactions. These interactions can only be observed using powerful instruments with nanometer level resolution,” explains Kashyap.
“My work is concerned with the experimental side,” she says, “but Dr. De Graef’s students are doing a lot of cool computational work to analyze the images we acquire.”
One of those students is Saransh Singh, who has spent the past three years developing software to simulate the images and diffraction patterns observed in scanning electron microscopes. Singh’s custom software, which he has made available for free online, can predict the outcome of materials characterization experiments without having to run the materials through high-powered, high-cost microscopes.
“Unless you have a theoretical understanding of what’s going on in an experiment, you will have no clue how to interpret the results of that experiment,” Singh says. “The software provides the theoretical framework to help people understand what’s going on. We’ve taken the theory and turned it into a user-friendly computational platform.”
One of the main applications of Singh’s software so far is in industry. Often, manufacturers will develop a material they want to use, but they need to ensure that it does what it is designed to do. Not only that, but they need assurance it will continue to behave predictably throughout its entire lifespan. The instruments in the MCF, used in tandem with Singh’s software, can gather the information necessary to predict how these materials will respond in the future.
“The instruments in the MCF are really essential for my work,” says Singh. “I can immediately go check my theory to see if it is correct. You can come up with any theory you want, but unless you have some experimental validation of what you’re doing, it’s of no use to anyone.”
Over the period of 2011 – 2014, the Materials Characterization Facility has enabled the publication of more than 320 research papers in peer-reviewed journals.