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Physics major Thomas Nunnally’07 (Pennsburg, Pa.) recently spent a great deal of time tending to the growth of a fragile object, but it’s not something found thriving in the great outdoors.
Nunnally grew microscopic, snowflake-like crystals. When the crystals formed, he used their growth patterns to predict the properties of metal alloys.
Nunnally worked under the guidance of Andrew Dougherty, associate professor of physics, through Lafayette’s distinctive EXCEL Scholars program, in which students conduct research with faculty while earning a stipend. The program has helped to make Lafayette a national leader in undergraduate research. Many of the more than 160 students who participate each year share their work through articles in academic journals and/or conference presentations.
“People are interested in knowing what properties metals have,” says Nunnally, a member of Physics Club. “The way crystals grow indicates metals’ properties when the crystals get bigger.”
When the crystals grow, they form dendrites, which look like the arms of a snowflake, Dougherty says. Many hundreds of these dendrites woven together comprise the strong metal alloy. In fact, if one were to take apart a metal alloy and look at it under a microscope, dendrites would be seen.
“It’s actually a convenient model of a system for metal alloys,” Dougherty says. “The patterns we see here are very similar to what you see in metals, but they’re at a temperature that’s convenient and they’re transparent so we can see them.
“We looked at determining the particular sizes, what controls size, how fast they grow, what controls the speed — those are the things required to know how many you would need to grow to make an alloy.”
Once the growth patterns of crystals are understood, the information can be applied to the growth of metals, he adds.
Nunnally watched the initial growth of the crystal, a time-consuming process as it can take a week to set up an experiment and hours for the crystal to grow. He measured the size and shape of the dendrites as they formed and then entered that data into a computer program. He compared that data with theoretical simulations of the growth, Dougherty says.
Nunnally was amazed by the scale of the project. He chose Lafayette specifically for its undergraduate research opportunities, he says.
“I never thought a temperature change of .1 Kelvin would make a difference, but it’s a totally different world,” Nunnally says. “It’s crazy how something that small can have such a definite way it can form, but also do such weird things.”
The “behavior” of crystals mirrors the world around us, Dougherty says.
“I always come back to watch them grow. They’re very beautiful; they’re not perfectly symmetrical, but they come close,” he says. “They live in the delicate balance between order and disorder that makes so many things in life interesting.”
Dougherty asked Nunnally to be his research aide because of his interest in molecular physics. He also wanted him to learn skills that would stick with him throughout his life.
“I think working on a long-term project requires or develops skill for record keeping, note taking, persistence, and depth of analysis that you don’t get in classrooms,” Dougherty says. “Because all of the (research) projects, out of necessity, are smaller and more contained…they get a different exposure here than they would in a classroom setting. And the opportunity to really direct — to help determine — what comes next is unique to a research project.”
Nunnally is a graduate of Quakertown High School.
As a national leader in undergraduate research, Lafayette sends one of the largest contingents to the National Conference on Undergraduate Research each year. Forty-two students were accepted to present their work at the last annual conference in April.