This work presents data on Ni self-diffusion in binary Al-Ni alloys with high precision. For this, we combined two techniques: containerless electromagnetic levitation to position the samples, and neutron time-of-flight spectroscopy to measure the decay of the self-correlation.This combination offers new measurement ranges, especially at low temperatures, several hundreds of Kelvin below the liquidus temperature. Because without container, the primary cristallization seeds for the metallic melt are avoided. But it is also possible to measure reactive samples, and at very high temperatures at and above 2000 K, as problematic reactions with the containing cask won't occur. Furthermore this technique also enables measurements at higher momentum transfer q, as one does not have to limit the q-range of the measurement to avoid Bragg peaks of the solid container material. By this time-of-flight spectroscopy on levitated metallic melts, it is possible to determine the Ni self-diffusion in these alloys directly and on an absolute scale. The dependence of the Ni self-diffusion coefficients on temperature and concentration was studied in pure Ni and binary Al-Ni alloys. In a temperature range of several hundred degrees, we always found Arrhenius-like temperature dependence of the diffusion, irrespective of possible undercooling. In the context of these measurements, we also studied the interdependence between diffusivity in the metallic melt and its quasielastic structure factor. Time-of-flight spectroscopy made it also possible to derive the dynamic partial structure factors of the binary alloy Al$_{80}$Ni$_{20}$. All this to enable a better understanding of the atomic processes in the metallic melt, especially of the undercooled melt, as an alloy is always formed out of the (undercooled) melt of its stoichiometric compounds. For this, material transport and diffusion are immensely important. The final goal would be materials design from the melt, i.e. the prediction of alloy properties in advance by computer simulation. But simulation needs exact data on dynamics and diffusion coefficients in the melt. That is one goal of this work, but also to give an insight into the processes in metallic melts on an atomic scale.     «

This work presents data on Ni self-diffusion in binary Al-Ni alloys with high precision. For this, we combined two techniques: containerless electromagnetic levitation to position the samples, and neutron time-of-flight spectroscopy to measure the decay of the self-correlation.This combination offers new measurement ranges, especially at low temperatures, several hundreds of Kelvin below the liquidus temperature. Because without container, the primary cristallization seeds for the metallic me...     »

Diese Arbeit untersucht die Ni-Selbstdiffusion in binären Al-Ni-Legierungen. Dazu wurden zwei herausragende Techniken kombiniert: die elektromagnetische Levitation als behälterlose Methode zur Probenpositionierung, und die Neutronenflugzeitspektroskopie. Im Kontext dieser detaillierten Untersuchungen ergeben sich aber auch Zusammenhänge von übergeordnetem Interesse, wie z.B. die Relation zwischen effektiver Diffusivität und quasielastischem Strukturfaktor. Die Flugzeitspektroskopie ermöglichte außerdem die Bestimmung der dynamischen partiellen Strukturfaktoren.     «

Diese Arbeit untersucht die Ni-Selbstdiffusion in binären Al-Ni-Legierungen. Dazu wurden zwei herausragende Techniken kombiniert: die elektromagnetische Levitation als behälterlose Methode zur Probenpositionierung, und die Neutronenflugzeitspektroskopie. Im Kontext dieser detaillierten Untersuchungen ergeben sich aber auch Zusammenhänge von übergeordnetem Interesse, wie z.B. die Relation zwischen effektiver Diffusivität und quasielastischem Strukturfaktor. Die Flugzeitspektroskopie ermöglichte a...     »