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Thursday, March 21

Getting the Hot Structures - Determining Order in Supercooled Metallic Liquids from X-ray and Neutron Electrostatic Levitation Studies

Kenneth F. Kelton, Washington University in St. Louis, St. Louis
Neutron Sciences Directorate Seminar
1:00 PM — 2:00 PM, Central Laboratory and Office Building (SNS),
Building 8600, Room C-156
Contact: Roy Cutler (fww@sns.gov), 865.382.0252

Abstract

Experimental and theoretical studies show that metallic liquids develop significant short- and medium-range topological order with increased supercooling; icosahedral short-range ordering (ISRO) is typically dominant. The structural order can have a significant influence on the crystal nucleation barrier and has been identified to play an important role in the glass transition. Our studies of supercooled Cu-Zr liquids have shown that it can also correlate with chemical ordering. Experimental synchrotron scattering data obtained at the APS for equilibrium and supercooled liquids in a containerless, high-vacuum, environment are presented. The order inferred from these scattering studies and its influence on phase transitions and properties are discussed. The synchrotron data were obtained using the technique of electrostatic levitation (ESL). We have designed and constructed a NESL (neutron ESL) for use at the SNS; it recently passed the first commissioning step on the VULCAN beamline.