About

Optimization of the properties and performance of materials is a continual challenge, and necessitates control of microstructural evolution during thermo-mechanical processing. Microstructure controls properties in various industries, such as electrical, defense and even the sports industry (tennis rackets, golf clubs). The properties of these materials are dictated by the distribution and organization of grain boundaries, dislocations and other defects.

To gain a greater understanding of these processing steps, researchers often turn to in situ TEM. This technique provides insight into many aspects of mechanisms that are otherwise unclear in static experiments. Additionally, ultrafast in-situ TEM (the DTEM) can potentially fill in gaps in the current understanding of various structural, chemical, electronic and magnetic properties in a myriad of materials. These capabilities allow for vast improvements of in-situ TEM studies limited by video rate. The results of these time resolved experiments are critical to the fields of grain boundary engineering, catalysts’ role in fuel cells for energy, and electronics, such as blue light emitting diodes.

 

Current Research Areas

Research Header

Materials for Nuclear Energy
The current focus on climate change and domestic dependence of energy is driving a resurgence of research into alternatives to coal and oil. One of the forerunners of this renaissance is nuclear energy: a low cost, zero-carbon, energy-dense resource. The nuclear infrastructure is aging with nearly 50% of the 104 nuclear plants in the United States operating more than 24 years. However, the future is looking bright as up to 30 new plants have been proposed. The success of the aging Generation II nuclear plants, the proposed Generation III reactors, and the future Generation IV reactors outlined by the US Department of Energy are heavily dependent on advancements in the materials employed in their construction. Our research focuses on determining how the microstructure such as grain boundary character can be controlled to mitigate the effects of elevated temperatures and constant radiation on iron-based alloys. This knowledge will be critical to refine current alloys and produce safer, stronger, and more reliable materials for nuclear reactors.Researcher: Greg Vetterick and Christopher Barr Crack in an Irradiated Reactor Steel
Twin Boundary in an Irradiated Reactor Steel
 Dislocation Loops in an Irradiated Reactor Steel
Magnetic Materials for EM Applications
From the motors that drive our household appliances to the transformers that power our computers, electromagnetic materials sustain our modern way of life. Cheaper, more efficient designs are becoming increasingly important as we seek to limit the environmental damage of materials production. Traditional motors and transformers use silicon steel in laminations to reduce electrical losses, but these are expensive to produce, wasteful, and can only conduct magnetic flux in two dimensions. An alternative is to use ferrous metal powders, which can easily be compressed into complex patterns and are capable of conducting flux in three dimensions. Our current research seeks to develop a coating for these powders that will electrically insulate them from one another, improve the magnetic properties of the powder part, and enhance its mechanical stability. More broadly, we seek to understand the interface between iron and various oxides. The interaction of defects, structure, and chemistry interact at these interfaces dictates their magnetic behavior; it is therefore essential to quantify and control these features to achieve desired properties.Researcher: Katie Jo Sunday and Steven Spurgeon SEM - Iron particle
SEM - Agglomerate of iron particles
SEM - Iron particle distribution
Structural Materials
Structural materials hold the world together. From the steel in bridges and buildings to the aluminum in cars and airplanes, these materials provide strong underlying frameworks, much like the human skeleton. The promise of stronger, lighter and lower cost structural materials drives our research to develop novel processing techniques and entirely new alloys. We are investigating steels that contain a complex combination of alloying elements, which provide increased strength and fracture toughness coupled with a decreased production cost, as well as alloys that retain their strength at elevated temperatures. One of the major applications for these alloys is the next generation of nuclear reactors that require new materials because of increased operating temperatures and pressures. The analysis capabilities of our laboratory allow for the direct observation of strengthening mechanisms, such as interactions at grain boundaries and precipitates, which increases our ability to improve macroscopic properties by tailoring microstructures.Researchers: Matthew Hartshorne FIB Lift Out
FIB Lift Out
TEM Dislocations
Multiferroic Materials
The demand for faster, smaller, more energy-efficient, and lower cost computers is the driving force behind the rapid research and development of ever-shrinking silicon-based transistors used in processors, random access memory, and other hardware. Unfortunately, quantum mechanics imposes a fundamental lower limit on the size of silicon-based transistors, so new material systems are being actively researched to find a suitable successor to silicon. New RAM designs that are based on ferroelectric and antiferromagnetic materials hold the promise of producing high density, high throughput, permanent memories which retain stored data without any supplied power. We are currently investigating the structural and electrical properties of bismuth ferrite (BFO), which belongs to a unique class of materials known as multiferroics. Multiferroic materials can possess coupled ferroelectric and ferromagnetic properties, allowing for control of ferroelectric and magnetic domain structures via applied electric fields. Because BFO possesses both ferroelectric and ferromagnetic properties, it constitutes a promising material for incorporation into ferroelectric and magnetoresistive memories, as well as spin valves and magnetic field sensors.Researcher: Michael Jablonski Polarization Vectors
Displacements
Nanoscale Spintronics
In the past decade a new class of materials called spintronics have attracted much attention for use in memory devices where both electron charge and spin are used to convey information. We are currently studying layered piezoelectric and half-metallic ferromagnets with the goal of coupling electronic and magnetic order at interfaces. These heterostructures have opened many new avenues of research, since even minor changes in film thickness, structure, and chemistry can have large effects on magnetoelectric coupling. Understanding and controlling this couple is essential for entirely solid-state spintronic memory devices. Using high resolution transmission electron microscopy (TEM) we are able to visualize atomic scale structure, chemistry, and defects in these materials. We can then correlate this to depth-dependent magnetic information from polarized neutron reflectometry and other magnetic characterization techniques. We are also conducted detailed in situ biasing studies of these devices to understand switching behavior.Researcher: Steven Spurgeon STEM-HAADF of PZT-LSMO
Nuclear Magnetics Structural Multiferroics Nanoscale