Sandia researchers are leaders in nanotechnology, the creation of materials and devices with new or vastly different properties by manipulating individual atoms, molecules, or molecular clusters into structures with dimensions in the 1- to 100-nanometer range. Although nanotechnologies hold great promise for designing materials and devices with extraordinary properties, scientists must first understand the special rules that govern how nanoscale structures behave and interact and then learn how these rules can be harnessed to create materials and devices.
Sandia has pioneered the development of unique force microscopes and other diagnostic tools that allow scientists to observe how atoms and molecules behave. Sandia’s supercomputers, among the world’s most powerful, also play a role in modeling the behavior of nanostructures and designing new nanostructured materials. The new insights, materials, and tools resulting from our nanosciences and nanotechnology R&D are producing direct and spin-off benefits to the Department of Energy’s nuclear weapons stewardship, environmental remediation, efficient energy generation, and national-security work.
We are developing theory and simulation methods to study electronic transport in carbon nanotube devices. Our approach is based on the nonequilibrium Green’s function formalism, which allows us to perform self-consistent quantum transport calculations for real device geometries. We also study optoelectronic applications, developing quantum transport methods to calculate photocurrents in nanotube devices. Our results indicate that nanotube devices can have a broad spectral photoresponse, covering the IR, visible, and UV ranges.
We are conducting fundamental science into numerous aspects of nanoporous behavior. The department plans to synthesize optimized nanoporous materials for use in batteries, supercapacitors, and other energy storage applications. If nanostructured devices have a suboptimal arrangement of pore or channel diameters, their storage capacities are reduced, and their charging rates become very slow. Guided by design principles generated through computational science, we are developing systematic modeling and synthesis methods to allow us to rationally tune the architecture of such materials and thereby permit major performance advances.
Left: Transmission electron microscopy image of nanocrystalline aluminum alloy after spending two hours in a 500°C environment, demonstrating the thermal stability of the fine-grained microstructure. Right: Fracture surface of nanocrystalline aluminum alloy showing ductile fracture, which implies good ductility and relatively high fracture toughness.
Metal alloys with nanocystalline grain size can achieve great strength, but they tend to have low ductility. Recent work has shown that alloys with a bimodal grain structure — that is, large micrometer-scale grains in a matrix of nanocrystalline grains — can offer the best of both worlds: nearly the same ductility as conventional alloys but with significantly greater strength. We are researching the physical and mechanical metallurgy of multiscale and nanocrystalline alloys with an emphasis on weldable aluminum alloys. We aim to design microstructures that combine high strength, high fracture toughness, and thermal stability.
For more information, contact Francois Leonard at (925) 294-3511.