Colloids as model systems for undercooled metallic melts

Abstract

We present investigations of short-range order (SRO) of charged colloidal suspension by applying Ultra-Small-Angle X-ray Scattering using synchrotron radiation at DESY Hamburg. The colloidal system is shear melted, subsequently, it is in a liquid state far from equilibrium. The development of the structure factor is measured as a function of time after shear melting. The deviation from equilibrium is determined by the difference of the chemical potential between solid and liquid state. The structure factors as measured are analysed within a cluster model. The results reveal the preference of icosahedral SRO in the metastable liquid colloidal system. With decreasing deviation from equilibrium the icosahedral SRO is reduced and eventually vanishes at equilibrium. The SRO of the stable liquid state is determined to be fcc like. The results obtained from the colloidal suspensions are compared with previous investigations of SRO in undercooled melts of pure metals studied by elastic neutron diffraction.