On 19. November 2024, Asbjørn Torsvik Krüger successfully defended his PhD thesis at the Ruhr-University Bochum, attaining the degree of doctor of natural sciences (Dr. rer. nat.). The defense committee consisted of Prof. Andreas Meyer (Doktorvater), Prof. Daniel Hägele (Zweitprüfer), Prof. Hendrik Hildebrandt (Vorsitzender), Prof. Judith Golda, and Prof. Ilya Eremin. Day-to-day supervision at the Institute was provided by Dr Elke Sondermann.
In his thesis entitled "Thermodiffusion in liquid binary and ternary alloys", he investigated the sensitive effect of thermodiffusion in metallic liquids through experiments conducted at the Institute for Materials Physics in Space.
Thermodiffusion (also called the Soret effect) designates the demixing of a mixture under a temperature gradient, an effect that has implications for solids, liquids, and gases, but in liquid metals especially for crystal growth and solders. Until now, most work has been on organic systems, and only sparse and uncertain results on liquid alloys had been performed, especially due to the high temperatures involved, making direct observation difficult.
His work included the development of a new sample cell, high-temperature experiments with X-ray radiography on several molten aluminium-containing alloys, and comparative calculations with models from the literature attempting to predict the effect in the liquids, showing that no available theoretical model is able to accurately predict the effect even in non-polar systems like liquid alloys.
