SMART - Surface tension of metals above vaporization temperature

Surface tension effects have widely been researched. However, the effects on the surface tension above evaporation temperature is less observed. Physical theories predict that surface tension is very low at vaporization temperature. However, in practice, surface tension is observable.

Therefore, the purpose of the project is to explain the physical effects that influence the surface tension of evaporating surfaces. A combination of theoretical modeling and experiments is proposed. The theoretical model will calculate the material evaporation rate based on the surface temperature and the acting forces that determine the surface tension considering the forces between the atomic layers. It will be investigated how the surface reacts on the loss of evaporated particles and how this affects the surface tension.

A measuring method based on laser irradiation of falling metal drops including temperature and high-speed imaging is proposed to determine metal material surface tension at surface temperatures above vaporization temperature to be compared to theoretical models considering metal ion loss.

Within four years project time, the theoretical and experimental tests will be conducted and combined in a theory. These methods promise new insight in the behavior and properties of metal materials at superheated surfaces. The results are valuable for many high temperature material testing and processes using lasers, e.g. during welding, drilling, cutting or surface structuring.