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Journal of Organic & Inorganic Chemistry
ISSN: 2472-1123 Chemistry 2019 Page 14
2nd Edition of EuroSciCon Conference on Chemistry
February 19-20, 2019 | Prague, Czech Republic
Colloidal suspensions are model systems to study phase transformations
of first order as crystallizationof a liquid system.The particles of colloidal
suspensions are in size of several hundred nanometres and the carrier fluid
is transparent in the spectrum of visual light. These characteristic features
make colloidal suspensions easily accessible for optical investigations. The
structural transformations are very sluggish and can be monitored in-situ. In
the present work, light scattering experiments are performed to investigate
homogeneous nucleation in the interior and heterogeneous nucleation
on the container walls of silica colloidal suspensions and to measure the
growth velocity of the crystal. Since nucleation processes require short-
range ordering as precursor of their formation, we conduct ultra-small-angle
scattering of X-rays of synchrotron radiation at DESY Hamburg to determine
the topological short-range order of monodisperse colloidal suspensions in
liquid phase far away from thermodynamic equilibrium. In such a way, the
entire pathway of crystallization from the stable liquid to the metastable
liquid state, the formation of short-range ordering over crystal nucleation and
eventually crystal growth is quantitatively investigated. The experimental
results are analysed within current models of formation of aggregates
of different structure, classical nucleation theory and the Wilson-Frenkel
theory of crystal growth. From measurements of crystal growth and its
analysis within the Wilson-Frenkel theory, the deviation from thermodynamic
equilibrium of a shear melted crystal is inferred as defined by the difference
of chemical potential between the metastable liquid and the stable solid.
The in-situ investigations of homogeneous crystal nucleation are used to
determine the solid-liquid interface which is very difficult to measure by
other methods. The measurement of the growth of a planar liquid-solid
interface allows for detailed information of the particle attachment kinetics
of particles from the liquid to the crystal.
Short range order, crystal
nucleation and crystal growth in
liquid colloidal suspensions
Dieter M Herlach
1 Institut für Materialphysik im Weltraum DLR, Germany
2 Institut für Experimentalphysik IV, Ruhr-Universität Bochum,
3 Otto-Schott Institut für Metallische Werkstoffe,
Friedrich-Schiller-Universität, Germany
Biography
Dieter M Herlach has studied Physics at the
RWTH Aachen University and has received the
Doctoral degree as Doctor rerum naturalium from
the same university. He was Group Leader at the
Institute of Materials Physics in Space and Senior
Scientist of the German Aerospace Center DLR.
He is Full Professor in Physics at Ruhr-Universität
Bochum (RUB). He has authored over 300 scientific
publications in refereed journals and served as
Editor of six books. He educated more than 30 PhD
students. He lead projects of the German Research
Foundation, the German Aerospace Center-Space
Management, European Space Agency and
was Principal Investigator of NASA during three
spacelab missions. He initiated and coordinated
two priority programs of the German Research
Foundation (DFG), He is Honorary Professor of three
universities. He chaired the Division of Metal and
Materials Physics of the German Physical Society
DPG, and was an Elected Member of the council of
DPG, General Review Committee of DFG and Deputy
Chairman of the German Society of Materials
Science and Engineering.
Dieter M Herlach, J Org Inorg Chem 2019, Volume: 5
DOI: 10.21767/2472-1123-C1-019