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Name (Title):
Qingsong Mei (ICYS-Sengen researcher)
Affiliation:
International Center for Young Scientists (ICYS-Sengen), NIMS
Address:
1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047 Japan
Email: Mei.Qingsong@nims.go.jp
Homepage: http://www.nims.go.jp/icys/sengen/images/researchers/researcher-mei.html
Presentation Title:
Effect of liquid superheating on liquid supercooling of Al particles
Abstract:
The freezing process of liquids is known to be
prone to the influence of catalysts. Despite the
significance for industry applications, it is still not
clear how various extraneous particles (e.g. grain
refiners or impurities) work to catalyze the freezing
of liquids. 1 The liquid superheating (thermal history)
has been found to have a significant effect on the
supercooling behavior of various metals and alloys,
which is believed to be related to the catalyzing
effect of extraneous particles. 2,3 It is believed that the
key to understand the catalyzing effect of extraneous
particles on freezing of liquids and the ∆T - - ∆T +
relationship lies in the characteristics of the
solid/liquid interfacial structure. 1
In the present study, the effect of melt
superheating (∆T + ) on supercooling (∆T - ) of Al
particles were studied by using differential scanning
calorimeter (DSC). As shown in Fig.1, in which ∆T - is taken as the difference between the onset
temperature of P1 and T0 of Al, and ∆T + is taken as that between the liquid temperature and T0 of
Al, an approximate linear ∆T + dependence of ∆T - was obtained in the ∆T + range of 140-340 °C,
which was found to be related to the catalyzing effect of impurity particles. A core-shell model
was further proposed to interpret the linear ∆T - - ∆T + relationship successfully, with the
supposing that a transitional region (shell) exists between the impurity particle (core) and the host
liquid (Al). The study provided information on the catalyzing mechanism of impurity particles
and characteristics of the solid/liquid interfacial structure. The model also rationalized the
sluggishness of melting process of high-melting particles in liquids.
References:
[1] A. L. Greer, Nat. Mater. 5, 13(2006).
[2] D. Turnbull, J. Chem. Phys. 18, 198 (1950).
[3] W. Luzny, J. Phys.: Condens. Matter 2, 10183 (1990).
124
�T - ( o C)
20
16
12
8
4
�T -
A1/A2
Poster Session PIR-11
0.0
0
0 100 200 300 400 500 600
�T + ( o C)
P2 P1
550 600 650 700
Temperature ( o C)
Heat flow endo up (a.u.)
1.0
0.8
0.6
0.4
0.2
A1/A2
Fig.1 Variation of ∆T - for P1 and relative peak
area (A1/A2) as a function of ∆T + in Al small
particle sample. Insert shows the freezing DSC
curves for different ∆T + as indicated.