* BK21/eSSC SEMINAR *

normal>Local structure and phase transformation
of supercooled and supercompressed

normal>liquids using new technologies;
Electrostatic levitation

normal>and Dynamic diamond anvil cell.

≫≫
Speak : 이근우 박사 normal>【Lawrence Livermore National Lab】

≫≫Location
: 물리학과 세미나실 (공학3동 201호)

≫≫Date
& Time : 1월 10일 (수) 오후 15:00 ~ 17:00

Liquids can cool down below their melting
temperature, which is called supercooling. In 1950, Turnbull demonstrated that
most liquid metals undercool about 20 % below their melting temperature. To
explain the undercooling phenomena, Frank hypothesized icosahedral short range
order as the local structure of liquid metals. Over 50 years, this hypothesis
has not been completely resolved. 
Recently, we unambiguously proved this hypothesis by aid of electrostatic
levitation (ESL) technique. In this talk, I will present X-ray diffraction
study for the local order of liquid metals (Ti, Ni, Zr, Si) and alloys
(TiZrNi), and relationship between the the local order and nucleation barrier.
In our study, we also observed that icosahedral short range order can be
distorted depending on electronic properties.

On the other hand, we have developed a new
technology to study kinetics of phase transition under high pressure, called
dynamic diamond anvil cell(d-DAC) which can modulate a given static pressure
with various compression rate and type. This device will complement static
pressure and shock compression studies. I will present the effect of
compression rate on the paths of phase transformation, and crystal growth with water
and ice VI. In particular, dynamic pressure-induced dendritic and shock crystal
growth will be demonstrated, which are observed for the first time.