Browsing by Author "Dahlmann, Rainer"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    On the Mixed Gas Behavior of Organosilica Membranes Fabricated by Plasma-Enhanced Chemical Vapor Deposition (PECVD)
    (Basel : MDPI, 2022-10-13) Rubner, Jens; Skribbe, Soukaina; Roth, Hannah; Kleines, Lara; Dahlmann, Rainer; Wessling, Matthias
    Selective, nanometer-thin organosilica layers created by plasma-enhanced chemical vapor deposition (PECVD) exhibit selective gas permeation behavior. Despite their promising pure gas performance, published data with regard to mixed gas behavior are still severely lacking. This study endeavors to close this gap by investigating the pure and mixed gas behavior depending on temperatures from 0 °C to 60 °C for four gases (helium, methane, carbon dioxide, and nitrogen) and water vapor. For the two permanent gases, helium and methane, the studied organosilica membrane shows a substantial increase in selectivity from αHe/CH4 = 9 at 0 °C to αHe/CH4 = 40 at 60 °C for pure as well as mixed gases with helium permeance of up to 300 GPU. In contrast, a condensable gas such as CO2 leads to a decrease in selectivity and an increase in permeance compared to its pure gas performance. When water vapor is present in the feed gas, the organosilica membrane shows even stronger deviations from pure gas behavior with a permeance loss of about 60 % accompanied by an increase in ideal selectivity αHe/CO2 from 8 to 13. All in all, the studied organosilica membrane shows very promising results for mixed gases. Especially for elevated temperatures, there is a high potential for separation by size exclusion.
  • Thumbnail Image
    Item
    Tuning the Permeation Properties of Poly(1-trimethylsilyl-1-propyne) by Vapor Phase Infiltration Using Trimethylaluminum
    (Weinheim : Wiley-VCH, 2024) Jenderny, Jonathan; Boysen, Nils; Rubner, Jens; Zysk, Frederik; Preischel, Florian; Arcos, Teresa de los; Damerla, Varun Raj; Kostka, Aleksander; Franke, Jonas; Dahlmann, Rainer; Kühne, Thomas D.; Wessling, Matthias; Awakowicz, Peter; Devi, Anjana
    Vapor phase infiltration (VPI) has emerged as a promising tool for fabrication of novel hybrid materials. In the field of polymeric gas separation membranes, a beneficial impact on stability and membrane performance is known for several polymers with differing functional groups. This study for the first time investigates VPI of trimethylaluminum (TMA) into poly(1-trimethylsilyl-1-propyne) (PTMSP), featuring a carbon–carbon double bond as functional group. Saturation of the precursor inside the polymer is already attained after 60 s infiltration time leading to significant densification of the material. Depth profiling proves accumulation of aluminum in the polymer itself, but a significantly increased accumulation is visible in the gradient layer between polymer and SiO2 substrate. A reaction pathway is proposed and supplemented by density-functional theory (DFT) calculations. Infrared spectra derived from both experiments and simulation support the presented reaction pathway. In terms of permeance, a favorable impact on selectivity is observed for infiltration times up to 1 s. Longer infiltration times yield greatly reduced permeance values close or even below the detection limit of the measurement device. The present results of this study set a strong basis for the application of VPI on polymers for gas-barrier and membrane applications in the future.