Vol. 54, Special Issue        February 2002

Materials, physics, and chemistry

Conjugated polymers have long been competitive materials for light-emitting diodes. Unfortunately, the polymer chains are inherently disordered and are not robust. Thus, before they find widespread use in opto-electronics, they must be prepared in ways that organize and stabilize the chains. We have solved that technical challenge by self-assembling the organic monomers in a highly-ordered silica matrix and polymerizing them in place. In fact, the polymers within this protective, hard scaffold exhibit unique optical properties not observed in the bulk material. (1100, 1800). Alan Burns, aburns@sandia.gov

We have improved the power output of our near-ultraviolet light-emitting diodes (LEDs) by a factor of 15. This dramatic improvement was accomplished in two different ways: first, by developments in the growth of the GaN nucleation layer that greatly reduced defect density; second, using a Sandia-invented low dislocation substrate technique ‹ Cantilever Epitaxy. This is a significant step toward our goal of improving the efficiency and cost of LEDs enough that they can replace existing lighting. (1100, 6200) Robert Biefeld, rmbiefe@sandia.gov

Understanding how water molecules interact with solid surfaces will answer many questions in environmental chemistry, biology, corrosion, and flow physics. Recent theoretical work (published in Science) has shown that the first layer of water molecules on the metal ruthenium surface does not form the believed ³ice-like² structure. Instead, some water molecules dissociate to spontaneously create an intricate layer consisting of molecules and fragments. This surprisingly complex structure is the template that determines how subsequent water layers are arranged and consequently controls the interfacial chemistry. (1100) Neal Shinn, ndshinn@sandia.gov

The Z accelerator was used to obtain the first isentropic compression equation-of-state (EOS) data to 2 Mbar on stockpile materials. This novel capability enables critical validation of ASCI code simulations of weapon performance and allows magnetic launching of precision flyer plates to velocities three times faster than conventional techniques. This technique has been used to obtain the first highly accurate EOS data on liquid deuterium to 700 kbar for evaluating quantum mechanical theories of hydrogen. (1600) Marcus Knudson, mdknuds@sandia.gov

Lightweight and high-strength alloys have great importance in the automotive and aerospace industries due to their strength both at low and high temperatures. A breakthrough in the scientific understanding of technologically vital alloys has been achieved. This new understanding of this important alloy could have great impact in the heat treatment of aluminum engine blocks and the optimization of the processing of half a billion pounds of aluminum each year. (8700) Bob Hwang, rqhwang@sandia.gov

Development work demonstrated the viability of the active braze alloy ³Nicoro+2%Ti² (62wt.%Cu-35Au-1Ni-2Ti) for use in a major subassembly of the MC4300 neutron tube. The alloy exhibits good wetting of alumina ceramic surfaces and the ability to make strong, hermetic metal/ ceramic braze joints. An evaluation build this year will use the alloy as baseline in the tube¹s header subsassembly. The Nicoro+2%Ti alloy was developed during FY98 as part of a Research Foundation (RF) brazing project, in cooperation with WESGO Metals, Inc. (1800, 14100, 14400, 2500) John Stephens, jjsteph@sandia.gov

The Aircraft Composite Inspection and Reference Standards Team produced an optimum set of composite reference standards to allow for accurate damage assessment and post-repair inspection of all composite aircraft structures. The team¹s work will simplify the process of evaluating the severity of damage to composite aircraft structures and more accurately determine the necessary repairs. The results of this effort were formally documented in industry-recognized Aerospace Recommended Practices and are being adopted into Boeing and Airbus maintenance manuals. Sandia¹s Airworthiness Assurance Center participated in this effort by leading an Inspection Task Group within the international Commercial Aircraft Composite Repair Committee. (6200) Dennis Roach, dproach@sandia.gov

Last modified: February 28 , 2002

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