guest ::
| Home > Publications database > Structure of complex fluids under shear flows |
| Home > Publications database > Structure of complex fluids under shear flows |
| Book/Dissertation / PhD Thesis | PUBDB-2018-03848 |
;
2018
Verlag Deutsches Elektronen-Synchrotron
Hamburg
This record in other databases:
Please use a persistent id in citations: doi:10.3204/PUBDB-2018-03848
Report No.: DESY-THESIS-2018-028
Abstract: With the recent developments of modern synchrotron and X-ray Free Electron Laser (XFEL) light sources high speed and micrometer sized liquid jets have become one of the most important sample delivery systems. For that reason it is highly important to develop liquid jet devices compatible with micrometer X-ray beams, which are optimized for the investigation of nanostructures and the behavior of complex liquids behavior under flow.This thesis reports a detailed X-ray scattering study of a liquid jet produced by a gas dynamic virtual nozzle (GDVN) system. Due to the very special microjet formation mechanism these injection devices offer a unique possibility to perform rheological studies at very high shear rates.In the framework of this thesis two main topics have been studied:1. The behavior of spindle-shaped hematite particles in a GDVN produced flow by WAXS.2. The impact of microjet and microdroplet geometries on the scattering patterns by SAXS.Therefore, an existing experimental setup was improved in accordance with the demands of the experiments at PETRA III, P10 beamline. The WAXS study shows a pronounced alignment of spindle-shaped particles parallel to the flow direction. The particles’ alignment is found to be depend on the particles’ aspect ratio, the used flow rates and the nozzle diameter. The degree of orientation of the particles was quantified by modeling Debye Scherrer rings describing the behavior of the spindles along and across the microjet and themicrodroplets. Hematite particles show a decrease in alignment downstream the nozzle tip and no orientation was detected in the droplets regime. The degree of alignment was studied with increasing distance from the nozzle tip. The observed loss of alignment is far higher than expected from simple rotational diffusion. The difference between these two values indicates that the particles behavior is dominated by the flow and shear cessation.The second topic of this work is a SAXS study on the impact of microjets and microdroplets geometries on the scattering patterns. A detailed map on the scattering signal was created taken along and across the jet resulting in different diffractions patterns which arise from the different jet geometries. The experimental findings were successfully modeled suggesting that both, micrometerbeam-sizes and micrometer-jet-sizes have to be taken into account in describing the results of the SAXS experiments.
|
The record appears in these collections: |
PDF
PDF (PDFA)