Craig A. Zuhlke
Date of this Version
Schulz, J. H. Directional Emissivity via Femtosecond Laser Surface Processing. MS thesis, 2023. University of Nebraska-Lincoln
Recently, much research has been carried out on developing femtosecond laser surface processing (FLSP) techniques to enhance surface properties. Specifically, it has been shown that FLSP can be used to enhance the emissivity of materials. This thesis explores using FLSP techniques to create angled quasi-periodic microstructures with nanoscale features on stainless steel to create surfaces with directional broadband emissivity.
The FLSP methods developed for creating surfaces with uniform and controlled angled structures are discussed in this thesis. Additionally, the implication that processing materials at an angle has on FLSP parameters is discussed. A set of laser processing parameters that result in angled structures were found and used to process stainless steel 304 samples. Data was collected for each sample on the emissivity as a function of angle, measured using a thermal imaging camera. The micro- and nano-scale features on the samples were also analyzed using scanning electron microscopy.
An analysis of the results was performed to show how each of the FLSP parameters affected both the emissivity and the shapes of the structures. The shapes of the structures were also linked to the directional emissivity performance. Understanding into how to optimize directional emissivity is also discussed in detail.
Advisor: Craig A. Zuhlke