A competitive advantage for the next generation of materials research.
Over the past few decades, researchers have studied magnetic materials using neutrons produced by research reactors at Oak Ridge and other facilities around the world. The resulting data led to a broad range of commercial innovations, including credit cards, pocket calculators, compact discs, magnetic recording tapes, computer hard disks, magnets for medical imaging devices, and permanent magnets for car seats that adjust automatically. Characterization of material properties by neutron scattering likewise led to improvements in the quality and durability of diverse materials used in airline and military jets, shatter-proof windshields, agricultural pesticides, and hip and knee implants.
Despite these inventions, few people are aware of the extent to which their quality of life is related to discoveries made possible by neutron scattering. With new capabilities in Oak Ridge, the potential for future discoveries is virtually endless.
The accelerator-based Spallation Neutron Source, together with the High Flux Isotope Reactor, will make Oak Ridge National Laboratory the world's foremost center for neutron science. These next-generation user facilities will provide data for computer models that will lead to new physical and biological materials. The resultant quantum leap in the understanding of complex materials will greatly improve the potential for technological breakthroughs in a broad range of consumer products, boosting the competitiveness of American industry.
Natural and Artificial
Every manufacturing sector is looking for materials that are stronger and more durable under challenging conditions and that are easier to shape into products. Some industries are seeking materials that also can produce a higher-strength magnetic field or conduct electricity, heat, or light more efficiently or hold and read more data in a smaller volume.
The research instruments at SNS will make possible neutron-scattering studies of complex materials of interest to industry. These include complex fluids and soft matter, such as proteins and other biological materials, which are of interest to the pharmaceutical industry. Artificially constructed, multilayered, coated, or otherwise complex physical materials are of interest to the energy, electronic, and aerospace industries. These materials include high-temperature superconductors, optical fibers, nanostructured super-lattices, magnetic thin films, polymer–carbon nanotube composites, block copolymers, and materials with correlated electrons, colossal magnetoresistance, or semi-conducting, photovoltaic, ferroelectric, or thermoelectric properties.
Bulk amorphous alloys are a new class of disordered materials of interest to industry. Already this material is being used to make springier golf club heads that help golfers drive the ball farther. The new alloy differs from the typical metal or alloy, which is made of crystalline grains separated by boundaries, like a mosaic. Lacking grain boundaries, bulk amorphous alloys offer high strength, low friction, resistance to wear and corrosion, and the ability to be formed easily into shapes. Because of their combination of elements, these materials can be cast in bulk at a cooling rate slower than normally required to obtain the amorphous state.
During slow solidification, details of the changing positions and motions of the alloy's atoms can be gleaned by neutron scattering. This information on atomic structure and dynamics has been used to construct computer models that guided the development of an aluminum-based, bulk amorphous alloy for making golf club heads with improved elastic properties.
Because its pulses will contain almost 10 times more neutrons than today's best, pulsed spallation sources, the SNS, combined with its instruments, will provide scientists with a comparable increase in the understanding of materials properties. The SNS will enable scientists to trace changes in the positions and motions of atoms and molecules when, for example, a material melts or a metallic alloy switches from magnetic to nonmagnetic or from brittle to ductile. Atomic-level changes can be observed when a geological sample is squeezed at tremendous pressures similar to those near Earth's core.
In another new scientific benefit, the SNS will give researchers the ability to characterize unusually small samples with diameters of less than a tenth of a millimeter. Sometimes only minute specimens are available, such as a newly synthesized, nanostructured material from the Department of Energy user facility located adjacent to the SNS, the Center for Nanophase Materials Sciences.
Small-angle neutron scattering has been used to help explain colossal magnetoresistance—a dramatic change in resistance in a magnetic field, which is present in manganese oxide perovskites. Thin films of these manganites might be useful for making read sensors in smaller computers and magnetic-field sensors. Neutron-scattering studies of oxide superlattice crystals made at ORNL's nanoscience center can help researchers understand and imitate self-organizing behavior that emerges on the nanoscale in chemically complex systems.
By using neutrons to study lubricants and other complex fluids that spread when a force is applied, researchers have discovered which additives improve fluid properties. Modern oils stick to moving metallic engine parts, whereas older oils, when heated during start-up, would spread out and separate from the parts they were supposed to lubricate. The opportunities are exciting. Bridges and other steel structures would need to be painted less frequently. Tiny machines must be lubricated with thin-film coatings, not oil-based fluids. Neutron research on soft matter could lead to time-released, drug delivery systems that target specific body organs.
Neutron-scattering studies of the impact of stress on a variety of materials have led to airplane wings that are more resistant to fracture and oil pipelines that are less likely to corrode and leak. By using neutrons to measure how much distances between planes of atoms have stretched or shrunk, scientists can locate residual stresses in the bulk of materials. These internal stresses, which develop in a component during manufacturing, can predispose the material to cracking, wear, accelerated chemical attack, and even failure brought on by stresses externally imposed on the component during use. Engineers wish to understand when the component is likely to fail and whether use of a different material and manufacturing process, such as heat treatment, would produce a component that will last longer.
Each new generation of commercial and military aircraft and space probes is expected to travel faster and farther using less fuel. To meet these demands, they must be made of lighter materials held together with stronger, lightweight welds rather than heavy rivets. Neutron-scattering results, combined with computer models, will help engineers select or develop materials and welding processes that meet these needs, thereby providing a competitive advantage to American companies.
Like SNS beams, the race to develop exciting new materials to make innovative technology possible is unusually intense. The SNS will help researchers navigate the world of natural and synthetic materials to find the ones that truly matter.
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