Structure and Function of Materials (IEK-2)

Research Topics

Energetic utilisation of biomass

In thermochemical conversion (combustion, gasification, and pyrolysis) of biomass, mainly the behaviour of the inorganic components (ash) determines the selection of the process and the process parameters. Ash-related problems are e.g. slagging and fouling, bed agglomeration in fluidised beds, (high temperature) corrosion, poisoning of catalysts or environmental pollution. Therefore, basic knowledge of the behaviour and control of inorganic components is essential. Against this background, the release and hot gas chemistry of harmful, volatile trace species is investigated and methods and sorbents to minimise them are developed. In the case of ashes and slags, the main focus is on transformation reactions, sintering, melting behaviour and corrosiveness towards ceramic and metallic materials. For relevant systems and compounds, thermochemical data are experimentally determined and used together with literature data to build up and extend a Calphad-based oxide database. The experimental work is supplemented by thermochemical model calculations. A Calphad-based model was developed for the calculation of slag viscosity.

Salt systems for thermal energy storage

Thermal energy storage systems with high storage capacity are a central element for system integration and flexibilisation of the future energy system. For the high-temperature range in industrial waste heat utilisation as well as in conventional and solar power plant technology, which require temperatures of 100 to >500 °C, salt systems are particularly suitable. Here, the focus is on the experimental determination of thermochemical data of relevant salt systems and compounds, which are used together with literature data to build up and extend the Calphad-based salt database. Model calculations are used for the targeted selection of suitable salt mixtures for defined applications. The long-term stability, corrosiveness and viscosity of the salt mixtures are also researched.

Mixed-conducting membrane systems

In many processes, membrane technology enables an increase in energy efficiency through process intensification and thus offers the potential for cost reduction. Here, the subject of research is mixed-conducting ceramic membranes for use in energy technology, which are e.g. permeable to oxygen, hydrogen or carbon dioxide. The focus of the experimental investigations and model calculations is on the thermochemical stability and compatibility of the materials during manufacture and application, as well as degradation by operationally relevant gaseous trace species and deposits. In addition, thermochemical data of relevant systems are determined experimentally and used together with literature data to extend the Calphad database.

High-temperature fuel cells and electrolysis cells

Due to their state of development, high-temperature fuel cells and electrolysis cells have a high potential for commercial application in a hydrogen-based circular economy. While in the past the focus was primarily on the thermochemical stability of the components under ideal conditions, today the research emphasis more towards application-oriented operating conditions, e.g. the influence of trace substances, and thermochemical aspects of pyrometallic recycling routes.

Electrochemical storage

Interest in batteries has increased significantly in recent years, not least due to increasing electromobility. Solid-state batteries offer the advantage of high energy density with inherent safety. Here, the thermochemical data of relevant systems and compounds are experimentally determined and used together with literature data to extend the Calphad database. The latter enables the optimisation of manufacturing processes, which sometimes require high temperatures.