The group is primarily focused on various aspects of the highly porous materials: from synthesis and characterization to scale up and process design. The key ingredient of most of the processes under study is the usage of supercritical drying with carbon dioxide.
Context:
First reports on aerogels made by Kistler in 1931 have pointed out the fact that wet gels of both inorganic and organic nature can be dried with minimal loss of the size by bringing the intragel liquid in supercritical state. Resulting materials were found very porous and called aerogels. Kistler’s works, many efforts have been focused on aerogel preparation, characterization and utilization starting from various gels such as silica, other oxides and recently synthetic and biopolymer gels. Nowadays aerogels have firmly established themselves in the material science and technology as a unique class of materials. Holding 15 entries in Guinness book of properties, aerogels are unique materials with a high potential for many challenging problems. A number of scientific groups have investigated applications of aerogels in space engineering, as thermal insulation materials, solar-energy collectors, Cherenkov detector, waste treatment systems, drug delivery and targeting systems and many others. Some of aerogels properties:
- ultra low density: 0.0019 – 0.35 g/cm3
- open pore network with internal surface area of 200 – 3000 m2/g
- thermal conductivity at ambient conditions: 10 – 30 mW/m∙K
- developed pore system with mean pore diameter in the range of 20 – 50 nm
- many aerogels are non-flammable
- can be processed/machined into almost any shape
Main areas of our research:
Continuous aerogel production:
Primary goal: to develop integrated, continuous and cost-effective production processes using pressurized carbon dioxide as gelation facilitator and drying agent. We rely on so called CO2-induced gelation which has been developed in our group first for silica and later for biopolymers such as alginate, pectin, cellulose and chitosan. Within this research area we also study kinetics of the supercritical drying using GC and high-pressure FTIR techniques (in cooperation with Dr. Andreas Bräuer, Friedrich-Alexander-Universität Erlangen-Nürnberg).
Biopolymer aerogels for life science applications:
Biopolymer aerogels (pectin, alginate, proteins, cellulose, chitosan, etc.) exhibit both specific inheritable functions of starting biopolymers and distinctive features of aerogels. This synergy of properties makes biopolymer aerogels promising candidates for a wide gamut of applications such as tissue engineering, regenerative medicine, drug delivery systems and functional foods. We employ supercritical impregnation to load aerogels with active compound (drugs, aromatics, etc.) and post-process them using coating.
Renewable and alternative precursors for aerogel production:
Primary goal: to utilize waste products such as lignin and water-extracted biomasses for the aerogel production. This direction is explored in close cooperation with the Bio-refinery group (group leader Dr. Carsten Zetzl).
Emulsion gelation for aerogel production:
Some applications, in particular food and pharmaceutical ones, require small preferably monodisperse aerogel particles with sizes below 100 µm. We develop approaches toward emulsion gelation of biopolymers with subsequent solvent exchange and supercritical drying putting emphasis on recovery of the continuous phase and on process integration.
Modeling in aerogel science and technology:
We employ a wide range of methods and tools to support aerogel research. Main problems we address are as follows: kinetic modeling of the supercritical drying in idealized (one particle) and real (fixed bed) arrangements; kinetics of the solvent exchange; cellular automata models of the mass transfer in porous media; modeling of solubility in supercritical fluids.
While these studies contribute to our fundamental understanding, our primary interests are in applications, process design and scale up. While these studies contribute to our fundamental understanding, our primary interests are in applications, process design and scale up.
Current public projects:
- NanoHybrids [https://tutech.de/en/nanohybrids/]: New generation of nanoporous organic and hybrid aerogels for industrial applications: from laboratory to pilot scale production; funded by the European Union´s Horizon 2020 research and innovation programme.
- Highly porous protein-based aerogels as carrier matrices for sensitive and sensory unpleasant substances in food products; funded by BMWi via AiF/FEI, in cooperation with Prof. Kulozik (Technische Universität München) and Prof. Heinrich (Hamburg University of Technology) [Abstract English] [Abstract German] Please contact us [irina.smirnova@tuhh.de] for the final report of the project.
- Development of pectin-based aerogels for insulated food packaging; funded by DAAD, in cooperation with Dr. Aleksandra Nesic (Vinca Institute for Nuclear Sciences, Serbia)
- Adsorptive precipitation of polar organic substances in biopolymer aerogels from ternary supercritical fluid mixtures; funded by DFG, in cooperation with Prof. Menshutina (Mendeleev University of Chemical Technology, Russia)
- Stabilization of amorphous drugs in polymer-based formulations: thermodynamic approach; funded by DAAD, in cooperation with Prof. Sadowski (Technical University Dortmund) and Prof. Enders (Karlsruhe Institute of Technology)
Group members:
