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[Sandia Lab News]

Vol. 53, No. 2        January 26, 2001
[Sandia National Laboratories]

Albuquerque, New Mexico 87185-0165    ||   Livermore, California 94550-0969
Tonopah, Nevada; Nevada Test Site; Amarillo, Texas

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Materials

The Low Energy Electron Microscope offers Sandia researchers an invaluable tool for learning how certain combinations of atoms spontaneously self-order into stunning structures consisting of nanometer-sized dots, stripes, or polygons. Such nanostructured materials frequently exhibit unique mechanical, optical or electronic properties. Recent experiments provided the elusive proof of a simple theory that explains how interatomic forces compete to produce these structures. Once understood, self-assembly can be exploited to synthesize new classes of materials with tailored properties for multi-functional, miniaturized actuating or sensing systems. (1100, 8700) Neal Shinn, ndshinn@sandia.gov

A new ion beam analysis facility enables researchers to measure -- non-destructively and in depth -- the constituents (including tritium) of neutron tube targets and sources. Further improvements of the process will enable War Reserve certification of our beam-line. This system serves the neutron tube science program, which is closely coordinated with the Labs' neutron tube design and production processes. (1100, 2500, 14400) Wil Gauster, wbgaust@sandia.gov

Sandia researchers, working with an international team of scientists, developed a photochemical technique for producing unique nanostructures (hexagonally-packed tubes or 3-D tetragonal configurations). In the process, silica gels containing photo-activated acids are locally exposed to ultraviolet light, thereby engineering particular nanostructures. This photo-induced densification process has been shown sufficient to modulate the refractive index of the resultant material enough to make a diffraction grating or other optical device. This work was featured in a Science magazine article. (1800, 1100) M.J. Cieslak, mjciesl@sandia.gov

Collapsing tunnels are disastrous in mining and transportation. In an atomic world, however, they can be extremely useful when they trap hazardous materials. Under the Environmental Management Science Program, Sandia scientists discovered a family of tunnel-collapsing materials named Sandia Octahedral Molecular Sieves (SOMS). When SOMS are submerged in waste solutions, specific metals like radioactive strontium stick inside its tiny tunnels. Heating the SOMS collapses the tunnels and traps the hazardous contents so they can be safely disposed. Immobilizing the waste is vital to DOE cleanup efforts. (6200) May Nyman, mdnyman@sandia.gov

Dynamics of Alloying at Surfaces: What are the atomic mechanisms when metals mix to make alloys? Using a unique microscope, Sandians Schmid, Bartelt and Hwang (8700) discovered the surprising way bronze alloy forms when tin is evaporated onto copper. Microscopic tin crystals slowly shrink while "grazing" the copper surface in an entertaining, almost life-like dance. To explain this peculiar motion, the team proposes that a repulsion between tin atoms within the crystals and tin atoms left in their wake pushes the crystals forward, away from the bronze in their tracks(8700) Andreas Schmid, akschmi@sandia.gov

Last modified: January 31, 2001


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