Chemo-hydrodynamics at particle-forming reaction fronts
Contact person: Dr.-Ing. Karin Schwarzenberger
Project staff: Dipl.-Ing. Patrick Schlereth
Funding: German Aerospace Center (DLR) with funds provided by the Federal Ministry for Economic Affairs and Energy (BMWi) due to an enactment of the German Bundestag (Grant No. 50WM2443, project ChemFront)
Motivation
Reaction-Diffusion-Advection (RDA) fronts are phenomena present in a wide variety of disciplines, creating a fascinating interplay of chemical and physical mechanisms. While being relevant to applications like nanotechnologies, CO2 sequestration and art restoration, the dynamics of such systems are yet to be fully understood. In order to shed light on the effects of buoyancy, microscale experiments are conducted under standard gravity conditions (on ground) as well as on various experimental micro-gravity platforms, e.g. on board of a parabolic flight.
Precipitation pattern of an RDA front in a Hele-Shaw cell in a laboratory experiment
Goals
- Investigation of flow patterns and instabilities in reaction-diffusion-advection fronts
- Compare results with existing theory and propose new models
- Transfer knowledge to industrial applications (CO2 sequestration, art restoration, re-calcification)
Methods
- Experiments in custom-made experimental microscale devices (such as Hele-Shaw cells and ultra-thin capillaries)
- Flow visualization techniques (i.e. μ-PIV, stereo-PIV)
- Utilization of micro-gravity platforms (sounding rocket mission, parabolic flight)
RDA reaction front in a thin square capillary in side view and top-down view
Results
Experiments are conducted in specialized setups, allowing optical access to extract various information about the ongoing RDA reaction. Hele-Shaw cell reactors offer insight into radial front propagation and pattern formation of a precipitation reaction. Ultra-thin capillaries grant the observation of buoyancy effects like the stratification of reactants and the resulting front deformation in both top-down and side view.
As RDA systems are influenced by the complex interplay of flow properties and product formation, a characterization of the precipitation reaction of
Na2CO3+CaCl2 → 2NaCl+CaCO3↓
into advection, agglomeration and gelation regimes has been realized.
Initial results from experiments onboard of a parabolic flight are suggesting a strong dependence of RDA front dynamics on buoyant effects.
Publications
Stergiou, Y., Escala, D. M., Papp, P., Horváth, D., Hauser, M. J., Brau, F., ... & Schwarzenberger, K. (2024). Unraveling dispersion and buoyancy dynamics around radial A+ B→ C reaction fronts: microgravity experiments and numerical simulations. npj Microgravity, 10(1), 53.
Stergiou, Y., Perrakis, A., De Wit, A., & Schwarzenberger, K. (2025). Flow-driven pattern formation during coacervation of xanthan gum with a cationic surfactant. Physical Chemistry Chemical Physics.