Preparation of Optically Transparent Open-Celled Foams and its Morphological Characterization Employing Volume Image Analysis

Authors

  • Ethel C. Bucharsky,

    Corresponding author
    1. Institute for Applied Materials – Ceramics in Mechanical Engineering, Karlsruhe Institute of Technology (KIT) Haid-und-Neu-Str. 7, 76131 Karlsruhe, (Germany)
    • Institute for Applied Materials – Ceramics in Mechanical Engineering, Karlsruhe Institute of Technology (KIT) Haid-und-Neu-Str. 7, 76131 Karlsruhe, (Germany)
    Search for more papers by this author
  • Karl G. Schell,

    1. Institute for Applied Materials – Ceramics in Mechanical Engineering, Karlsruhe Institute of Technology (KIT) Haid-und-Neu-Str. 7, 76131 Karlsruhe, (Germany)
    Search for more papers by this author
  • Peter Habisreuther,

    1. Engler-Bunte-Institute, Division of Combustion Technology, Karlsruhe Institute of Technology (KIT) Engler-Bunte Ring 1, 76128 Karlsruhe, (Germany)
    Search for more papers by this author
  • Rainer Oberacker,

    1. Institute for Applied Materials – Ceramics in Mechanical Engineering, Karlsruhe Institute of Technology (KIT) Haid-und-Neu-Str. 7, 76131 Karlsruhe, (Germany)
    Search for more papers by this author
  • Nikolaos Zarzalis,

    1. Engler-Bunte-Institute, Division of Combustion Technology, Karlsruhe Institute of Technology (KIT) Engler-Bunte Ring 1, 76128 Karlsruhe, (Germany)
    Search for more papers by this author
  • Michael J. Hoffmann

    1. Institute for Applied Materials – Ceramics in Mechanical Engineering, Karlsruhe Institute of Technology (KIT) Haid-und-Neu-Str. 7, 76131 Karlsruhe, (Germany)
    Search for more papers by this author

  • The authors would like to thank the German Research Foundation (DFG) for funding the Research Group FOR 583 “Solid Sponges – Application of monolithic network structures in process engineering.” Special thanks to Dr. Giesela Guthausen, Institute of Mechanical Process Engineering and Mechanics, KIT, and Julia Große, Institute of Thermal Process Engineering, KIT, for the substantial help with the 1H NMR measurements. Also, we would like to thank Mark Fresewinkel for supporting the authors in the experiments.

Abstract

Transparent glass sponges are a new class of materials that can potentially be used for effective light dispersion in photobioreactors. In this work, transparent glass sponges are prepared by the polymer replica technique employing polyurethane sponges with cell sizes of 20 pores per inch as templates and commercially available nanoscaled SiO2 powders. Necessary conditions for obtaining transparent open-celled glass sponges are presented. Topics such as slurry stabilization, temperature for burning-out the polymer and subsequent sintering of the remaining SiO2 structure to transparent cellular bodies are discussed. It was found, that concentrated suspensions at around pH 10 offer suitable properties for both, bringing enough particles onto the polymer template for the formation of a stable and self-supporting SiO2 shell and for successful sintering of the particulate framework to transparent bodies. Therefore, an adjusted burning-out process and an adequate sintering regime is presented. Furthermore, the resulting sponge structure is characterized employing X-Ray diffractometry, light, and scanning electron microscopy. In addition, volume image analysis was performed using magnetic resonance imaging. This method allows the calculation of geometrical parameters like cell-size and specific surface area of the resulting structure, required for application of the new material.

Ancillary