Journal of Organic & Inorganic Chemistry

Short range order, crystal nucleation and crystal growth in liquid colloidal suspensions

2^nd Edition of EuroSciCon Conference on Chemistry
February 19-20, 2019 | Prague, Czech Republic

Dieter M Herlach

Institut fur Materialphysik im Weltraum DLR, Germany Institut fur Experimentalphysik IV, Ruhr-Universitat Bochum, Otto-Schott Institut fur Metallische Werkstoffe, Friedrich-Schiller-Universitat, Germany

Keynote: J Org Inorg Chem

DOI: 10.21767/2472-1123-C1-019

Abstract

Colloidal suspensions are model systems to study phase transformations of first order as crystallization of 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 shortrange 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.

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.

E-mail: dieter.herlach@dlr.de