NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
A Method Based on Radiative Cooling for Detecting Structural Changes in Undercooled Metallic LiquidsWe introduce a structure-sensitive parameter for undercooled melts which can be measured in containerless processing experiments. We have established that the ratio, R(T), of hemispherical total emissivity epsilon(sub T)(T) to constant-pressure specific heat c(sub p)(T) can serve as an indicator which is sensitive to any changes in short range atomic order in undercooled metallic melts. R(T) (triple bonds) epsilon(sub T)(T)/c(sub p)(T) values for nickel, zirconium, and silicon have been obtained using the high temperature electrostatic levitator while the levitated melts were undergoing purely radiative cooling into the deeply undercooled region. R(T) plots for undercooled liquid nickel and zirconium indicate no significant change in short-range structure from their melting temperatures to 15% undercooling. In contrast, liquid silicon shows marked short-range structural changes beginning above its melting temperature and extending throughout the undercooled region. The short-range structure of liquid silicon is related to the highly-directional covalent bonding which characterizes its solid form. The nickel and zirconium data show that epsilon(sub T) varies linearly with T, in support of metal emissivity theories.
Document ID
19990008465
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
Authors
Rulison, Aaron J.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Rhim, Won-Kyu
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1995
Publication Information
Publication: Phys. Chem. Liq.
Publisher: Overseas Publishers Association
Volume: 30
Subject Category
Metallic Materials
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available