Deformation of hierarchical and anisotropic porous solids by fluid adsorption

• Applicant: Dr. Gudrun Reichenauer
• Co-Applicants: Professorin Dr. Nicola Hüsing; Professor Dr. Oskar Paris
• Subject Area: Synthesis and Properties of Functional Materials
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 252047785

The goal of the proposed research is to enhance the fundamental understanding of adsorption-induced deformation in monolithic materials with hierarchical porosity. Macroporous networks consisting of struts of ordered mesoporous silica with microporous walls will be synthesized, while controlling pore size, pore volume-fraction, and particularly also pore anisotropy at all hierarchy levels. Adsorption-induced deformation will be investigated quantitatively at the level of the mesopore system as well as on the macroscopic level. The central motivation for the proposed research is to derive basic correlations between the physico-chemical parameters of adsorption-induced deformation at the nanometer scale, and the hierarchical and anisotropic network structure with resulting actuated mechanical behavior at the macroscopic level. This knowledge forms the basis for future applications of hierarchically organized porous systems in designed switchable components. The basic goals and innovative aspects of the proposed research are the following:New synthesis approaches will be developed to tailor the degree of anisotropy in monolithic silica with hierarchical porosity at different levels, while controlling fluid-wall interaction and microporosity. Synthesis is based on sol-gel routes under external force fields such as shear or uniaxial compression. Model carbon and silicon replica will be derived from these silica monoliths by hard templating and reactive conversion, respectively.Different length scales and anisotropy will be explicitly considered experimentally in the investigation of adsorption-induced deformation. Structural investigations using synchrotron radiation based techniques will allow characterizing structure at all scales. A unique combination of in-situ techniques applied during fluid adsorption (in-situ X-ray diffraction and in-situ dilatometry) will be used to quantitatively derive the influence of hierarchy on the macroscopic response to the fluid induced deformation at the nanometer level. Designated Model fluids will be n-Pentane and N2 for derivation of fundamental relationships and H2O as a more complex adsorptive towards applications.Hierarchical mechanical models of adsorption-induced deformation will be developed and validated. They are based on analytical and/or numerical models for single mesopore deformation, coupled with finite element calculations to derive the macroscopic strains. The project combines unique and complementary expertise of three experimental groups in Austria and Germany, supported by an international cooperation partner working on the theory of adsorption- induced deformation. The expected outcomes of this basic research project are believed to fertilize both, theoreticians and modeling groups working on a better understanding of sorption-induced deformation in general, as well as applied scientists developing devices for sensing and actuation, for energy related application, and for catalysis.

• DFG Programme: Research Grants
• International Connection: Austria