Fully Ceramic Plasmonic Open Cell Foams for Efficient Solar Photothermal Energy Conversion

• Applicants: Professor Dr.-Ing. Tobias Fieback; Privatdozent Dr. Michael Maas
• Subject Area: Synthesis and Properties of Functional Materials ; Glass, Ceramics and Derived Composites ; Technical Thermodynamics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 572099201

To enhance the performance of solar thermal systems, solar selective absorbing coatings have been designed to absorb as much solar radiation as possible and minimize emissivity in the longer-wavelength IR. However, the established 2d coating methods for flat panels cannot be directly applied to porous 3d materials, which would be favorable for solar thermal systems due to their enhanced surface area increasing light absorption and convective heat transfer. Plasmonic nanoparticles provide a new perspective on solar photothermal energy conversion enabling the promising but challenging combination of ceramic open cell foams with plasmonic solar selective absorber materials. In addition to the excellent heat transfer and flow behavior, these materials can benefit from high mechanical and thermal stability, high longevity and reusability. This allows a highly efficient and sustainable utilization in diverse solar thermal applications including simple domestic water heating, but also industrial applications, solar thermal power plants or specific applications like thermophotovoltaics and photothermal catalysis. In the proposed project, we want to develop and investigate such fully inorganic plasmonic ceramic open cell foams for photothermal conversion of solar energy based on plasmonic heating. The novel materials consist of an inert structural matrix (alumina, aluminum nitride) and surface-deposited or incorporated inorganic plasmonic particles or grains of the transition metal nitrides TiN, ZrN or HfN. While the foams are prepared using regular colloidal processing methods, the transition metal nitrides will be synthesized by magnesiothermic reduction in molten salts from oxidic precursors that are incorporated in the sintered ceramics. Material design, processing as well as chemical and structural characterization including X-ray tomography will be carried out at the University of Bremen. The investigations of the functionality of the new materials will be addressed at the TU Bergakademie Freiberg. First, this comprises a comprehensive analysis of the radiative behavior and the heat generation in the foams, e.g. by spectroscopic transmission and reflection measurements in the UV-Vis-IR allowing to set up an empirical correlation for the prediction of the absorption capacity. The heat dissipation by conduction and convection will be studied numerically and by using a self-designed flow setup enabling a full parametrization of the solar photothermal heating in the plasmonic foams. This leads to the development of an empirical model that can be used to maximize the efficiency of the new materials with regard to a high absorption, adequate heat distribution, high volumetric heat transfer and low radiative heat losses.

• DFG Programme: Research Grants