The Heart of Matter
Designing Materials at the Atomic Level
4-H became a big part of Beth Dickey's life when she was a teenager in the Lexington area. "I was in sewing for a while, but I was really bad," she says. "I also took public speaking, and I did a lot of leadership activities." In high school Dickey was the president of the Kentucky 4-H and helped create the fall leadership conference, which the organization still holds. "My favorite 4-H activity was showing horses," Dickey says. Since her father was a horse trainer and her mother a nurse, everyone assumed Beth was predestined to be a veterinarian.
"But I wanted to do something different," Dickey says. Not quite sure what that was, Dickey got involved as a Woodford County High School student in UK's Engineering Ahead program and got her first glimpse into the world of materials engineering. "I liked school, and I was good at math and physics, but I didn't have a clear picture of what I wanted to do until I started working in this UK College of Engineering program," Dickey says. "Materials engineering intrigued me because it bridged physics, chemistry and engineering. So I thought I'd give it a try, and if I didn't like it I could always switch to something else."
Hooked on materials
Dickey became sold on materials engineering during her summer internship at Oak Ridge National Laboratories after her freshman year at UK. Oak Ridge is the largest of the U.S. Department of Energy's five multi-program laboratories. Near Knoxville, Tennessee, Oak Ridge employs 5,000 staff and hosts more than 4,000 visiting researchers.
That summer Dickey began work in the ceramic processing group and made professional contacts with scientists she still collaborates with today. "I was hooked after that internship," Dickey says.
After her junior year, she went to the nation's capital for the Washington Internship for Students of Engineering. She worked with the Society of Automotive Engineers on a project to analyze the consequences of moving away from metal to plastic car components. "There was already a great system set up for handling scrap metal, but the question now was, when you put plastic and other materials in cars, what happens when they're scrapped? Do you just throw them in a landfill?" Dickey says the public-policy angle of this internship brought to life the applications and problems associated with designing materials.
Next February UK will install a $1.8 million atomic resolution transmission electron microscope thanks to a grant from NSF through the Experimental Program to Stimulate Competitive Research (EPSCoR) and matching state funds.
Dickey graduated with her bachelor's degree in materials engineering from UK in 1992 and enrolled in Northwestern University in Illinois, which has one of the best materials science programs in the nation. At Northwestern she was a National Science Foundation Graduate Research Fellow and a research assistant. Her training culminated in a Ph.D. in 1997. Dickey returned to UK in the spring of 1997 as an assistant professor of materials engineering.
"In 10 words or less, what I do is design materials at the atomic level to get certain properties," she says. The properties she's most interested in are mechanical, electrical and thermal. "I try to design the chemistry, the structure and the micro-structure of a material to optimize its properties."
Every property of a material is related to how its atoms are locked together. "A lot of what I do is look at the interfaces between two materialswhat happens when you bring two dissimilar materials together," she says.
The microscopic behavior and the macroscopic behavior of a material are intimately related, Dickey says. "When we look at things at the atomic level, we ask, 'If we change how things are bonded, how atoms are arranged, how does that affect the macroscopic properties?'" All materials applications deal with the macroscopic. "For example," she says, "you want to know what's going to happen when you heat up the material or what happens when you pull on it.
"A lot of what I do is very basic science. I'm trying to understand the fundamental structure-property relationships, so I can start to predict what would happen if I alter the chemistry of a material," Dickey says.
There are three basic classes of materials: metals, polymers and ceramics. Ceramics are Dickey's bread and butter.
Her work on high-temperature ceramics won her national recognition last February. Dickey received the Presidential Early Career Award for Scientists and Engineers (PECASE), the U.S. government's highest honor for young engineers. The presidential award will fund Dickey's work with a five-year, $500,000 research grant. She was one of only 60 recipients and is the first faculty member at UK to receive this prestigious award. The PECASE was established by President Clinton in 1996 to recognize the nation's best scientists and engineers who show potential for scientific leadership in the next century.
PECASE nominations come from eight federal agencies, including NSF, NASA, and the Department of Defense. "Winning this award was surprising and extremely exciting," Dickey says. Alex Pechenik, acting director of the Air Force Aerospace and Materials Sciences Directorate, nominated her for the award. "I met Alex at a few scientific meetings and knew he was interested in the work I was doing with some people at NASA. He took it upon himself to nominate me, which was wonderful."
Pechenik's comments on her abilities are a resounding vote of confidence. "Professor Dickey has developed a number of techniques for characterizing interfaces in materials, particularly high-temperature ceramic materials. Her command of electron microscopy, X-ray diffraction, and neutron diffraction has brought some important insights into the structure of interfaces," he says.
"She has the potential of becoming one of the leading researchers in the field of high-temperature materials in the near future. Her collaboration with many researchers at the Air Force Research Laboratory, working on designing new, improved high-temperature materials for turbine and rocket engines, makes her work very valuable for the Air Force," Pechenik says.
Coffee cups and jet engines
These are not your grandma's ceramics. Ceramics have moved far beyond pottery, dinnerware, glass, and tile to a whole new world. Light bulbs, scissors, and watches; engine components, electronic sensors, catalytic converters and spark plugs; joint implants, bone and eye substitutes, and dental work are just a few new ceramic applications.
Ceramics are hard but lightweight, with good heat, wear and corrosion resistance. But there are a few problems. "If you drop your coffee cup on the floor you get an object lesson on the main drawback of ceramics: they're brittle," Dickey says.
Beth Dickey's work on high-temperature ceramics was recognized earlier this year by as Presidential Early Career Award for Scientists and Engineersa five-year, $500,000 grant.
Alumina, a widely used ceramic, stays strong at temperatures that can melt steel. On its own, alumina will fracture under stress, but reinforced with microscopic fibers of silicon carbide, alumina is strong enough to cut steel.
"The work I'm doing for the Air Force, funded by the presidential award, is focusing on how to make ceramics less brittle for applications in jet engines," she says. "If something flies into your engine, you don't want a catastrophic failure." Dickey is designing the micro-structure of the interface of the two materials to absorb energy. "If a crack forms it won't propagate throughout the material, and you'll have some prior notice that the component is going to fail.
"Today's jet engines are made from super alloys, metallic materials that have wonderful properties but at 1200 degrees Celsius they start to change chemically and even melt. What I'm looking at for the Air Force is using oxide ceramic composites to try to increase the temperature to 1400 degrees Celsius," says Dickey, "Even though this may seem like a small change in operating temperature, it has a huge impact on overall engine efficiency."
Dickey says developing high-temperature materials could have a wide range of applications. "In ground-based planes, there are applications in turbine engines. In space there is a whole range of applications because of the extreme heat during reentry," she says. The tiles that cover the current space shuttle are ceramic-based. While these ceramics differ from the ones she's working on, Dickey says the results of her work will be applicable to a variety of extreme-temperature and extreme-corrosion uses.
A lot of the materials developed in the aerospace industry end up in our homes and on our sidewalks. "What is at first an exotic material for specific applications eventually filters down into common household materials," Dickey points out. Many of today's household materials were born in NASA labs. "In the past 10 or 15 years, one material a lot of people are aware of is carbon fiber-reinforced composites, which started in aerospace and have been worked into the sports market," Dickey says. "When they were first developed, they were very expensive, but as they've become cheaper to produce they've been worked into bikes and tennis rackets."
Dickey uses a variety of tools to design the atomic makeup of materials, and the most vital and versatile is the electron microscope. She manages the Electron Microscopy Facility, housed in the Advanced Science and Technology Commercialization Center (ASTeCC) on campus, which makes available a variety of modern analytical equipment to researchers engaged in materials science and engineering at UK and in industry. UK currently has 13 electron microscopes across campus.
Dickey uses two kinds of electron microscopes. The first, a scanning electron microscope (SEM), utilizes a focused probe of electrons that scans across the material. Electrons are collected and measured by a detector that sits next to the microscope. An SEM gives information about the surface of a material. "UK's scanning electron microscope provides micron (millionth of a meter) information," Dickey says. "A hair looks pretty big under an SEM. One hair is about 100 microns in diameter."
The second microscope, a transmission electron microscope, analyzes a very thin slice of material. "The electrons penetrate all the way through, and it measures the electrons scattered by the sample," Dickey says. "Electrons scatter inside the material, and based on how they scatter you see contrast. You can see almost down to the atomic level inside the material.
"I've been doing all of my atomic-scale work at Oak Ridge because we haven't had the instruments to see atomic-level information," she says. "After I began work at the university, I realized there is quite a large demand on campus for this type of data, and I decided it was in our best interest to get our own instrument." Next February UK will install a $1.8 million atomic resolution transmission electron microscope thanks to a grant from NSF through the Experimental Program to Stimulate Competitive Research (EPSCoR) and matching state funds. "This microscope will be a resource for the whole state," Dickey says.
"A really nice feature of this microscope is the field emission gun, which gives you a much higher intensity beam and allows you to get chemical information at the atomic level," she says. "You can get structural information from the images and then focus the probe to sit on a column of atoms and get chemical information. You can correlate structure and chemistry. "With the addition of this microscope, UK will have one of the best electron microscopy facilities in the country," Dickey says.
Beth Dickey used electron microscopes at UK and Oak Ridge National Laboratories to capture these images. A) is an SEM image of nickel; B) is a TEM image of colleague Robert Haddon's carbon nanotubes; and C) is a TEM image of a zirconium oxide (ZrO2) grain boundary, a sample of the work on which Dickey is collaborating with Susan Sinnott to discover how atoms move along grain boundaries.
This electron microscope will contribute to an innovative new project funded by NSF. Dickey co-wrote the grant for this project with Susan Sinnott, also an assistant professor in materials science engineering. Their work will focus on parallel atomic-scale experimental and theoretical studies.
"I can get only so much information experimentally about where atoms are in an interface," Dickey says. "But Susan can take my data, create a model and further refine the structure to identify things like the energy and strength of the interface, things that are difficult to measure experimentally."
The subject of their joint project is interface segregation, which specifically focuses on two mechanical properties of materials: fracture toughness and creep.
"Interface segregation means you've got foreign atoms (atoms which aren't inherent to the basic crystal structure of the material) that are moving to defects in the material," Dickey says. "Many materials are crystalline, but few are perfect single crystals. Most materials have clusters of crystallites, and where these crystallites come together is called the grain boundary. Grain boundaries are defects in the material and foreign atoms tend to go there.
"In a lot of ceramic materials, if you break the material the fracture won't go straight through. It will split around the different grain boundaries," she says. "So if you change the strength of the grain boundaries, you can change the mechanical behavior of the material."
Fracture toughness deals with the amount of energy a material can absorb as it fails, and is the primary mechanical property of interest to Dickey and Sinnott.
Another property is called creep. "Creep doesn't involve cracks. It involves pulling on the material at high temperatures, which makes it deformit flows like plastic," Dickey explains. "What is happening is the grain boundaries are sliding, moving past each other under the weight of the load. This is related to diffusion (the intermingling of molecules) at the grain boundaries." By preventing diffusion at the grain boundaries, Dickey says researchers could prevent things from moving around and keep the material from deforming.
"Nobody really understands this process, which is why Susan and I are doing these fundamental studies to get experimental data and theoretical calculations to find out what these atoms are doing, and how they are affecting diffusion at the atomic level. Having complementary experiment and theory is a very powerful approach to understanding materials," Dickey says.
Dickey teaches three materials classes at the University of Kentucky: a one-hour freshman introductory class, a four-hour ceramic engineering class and a four-hour materials characterization class. Ceramic engineering, a required course for undergraduates in the materials program, has weekly labs where students measure ceramic properties and participate in industrial tours to places like the Corning plant in Harrodsburg, Kentucky, where glass flat-panel displays are manufactured. "The quality of the undergraduate program is very high and students get good experience," says Dickey, who also serves as faculty advisor for Alpha Sigma Mu, the materials honor society. "In my ceramics engineering class this spring, every single person was doing an internship in industry, at a national lab or at UK."
The materials characterization class, which focuses on X-ray diffraction and electron microscopy techniques, is taking on a new dimension this fall. "We've cross-listed this class with the University of Louisville," she says. "We'll teach it over videoconferencing. Students will do some of the lab components in Louisville and others at UK." Graduate students, upper-level undergrads, Lexmark employees and other industrial workers take this class.
The College of Engineering recognized Dickey's teaching skills with the outstanding teacher award in materials engineering for 1999. "I enjoy teaching, but it's extremely time-consuming to do a good job," says Dickey. "I think my teaching ends up benefiting my research, and the students benefit by seeing current examples. You can give it relevance by being able to tell them what you're doing in the lab."
How do engineers spend their free time? "Painting, mowing and picking cherries right now," Dickey says. She and husband Craig Grimes, a professor of electrical engineering at UK, were married in May 1998 and live on a 13-acre farm outside Lexington. "Craig's a triathlete, so we bike and run together as much as we can," she says. "He's a very well-rounded person, and I'd like to think I'll be one too someday." Dickey and Grimes often travel together to conferences. One will participate in a conference and the other will travel as the spouse and speak at a nearby university. "We went to Japan together last fall. We were both invited to give short courses at Aoyama Gakuin University in Tokyo," Dickey says.
"We do end up talking about work at home. We're both very into it and we care about what's going on," she says. "I'm not sure that I could do what I do without him being a professor too. If we need to come back to campus at night or on the weekends, it's not so lonely. We drive to work together and eat lunch together every day. Maybe it's because we're newlyweds and we're not tired of being together yet," she laughs, "but I don't think things will change. It makes it easier to be so involved at work because your best friend is coming with you."
Juggling a personal life, teaching and research is challenging, Dickey says, but she looks forward to getting more involved in the community. "Since I've been back in Kentucky, I've been so busy with this job that I haven't had time for much else," she says. "I'd like to see what things I can get involved in outside the university.? One thing she'd like to do is become more involved in the 4-H program. "They're giving me the Outstanding Young Kentuckian Award this year and I'm very flattered. Being involved with 4-H was a wonderful thing for me, and I'm glad 4-H is still helping kids realize their potential."