Deformation of hierarchical and anisotropic porous solids by fluid adsorption

提出的研究目标是加强对具有分层孔隙率的单片材料中吸附引起的变形的基本理解。将合成由有序介孔硅柱和微孔壁组成的大孔网络，同时在各个层次上控制孔径、孔体积分数，特别是孔隙各向异性。吸附引起的变形将在介孔系统和宏观水平上进行定量研究。该研究的核心动机是推导纳米尺度吸附诱导变形的物理化学参数与宏观水平上产生的驱动力学行为的分层和各向异性网络结构之间的基本相关性。这些知识构成了在设计可切换组件的分层组织多孔系统的未来应用的基础。本研究的基本目标和创新点如下：开发新的合成方法，以适应具有不同层次孔隙度的单片二氧化硅的各向异性程度，同时控制流体-壁相互作用和微孔隙度。合成是基于外力场（如剪切或单轴压缩）下的溶胶-凝胶路线。碳模型和硅复制品将分别通过硬模板和反应转化从这些硅单体中得到。不同的长度尺度和各向异性将明确考虑在实验研究吸附诱导变形。结构调查使用同步辐射为基础的技术将允许表征结构在所有尺度。流体吸附过程中应用的一种独特的原位技术组合（原位x射线衍射和原位膨胀测量）将用于定量地推导层次对纳米级流体诱导变形的宏观响应的影响。指定的模型流体将是正戊烷和N2，用于推导基本关系，H2O作为更复杂的吸附剂用于应用。将开发和验证吸附诱导变形的分层力学模型。它们基于单个介孔变形的解析和/或数值模型，结合有限元计算来推导宏观应变。该项目结合了奥地利和德国三个研究组的独特和互补的专业知识，并得到了一个致力于吸附诱导变形理论的国际合作伙伴的支持。这一基础研究项目的预期结果被认为对理论家和建模团队都有好处，他们致力于更好地理解吸附引起的变形，同时也对开发传感和驱动装置、能源相关应用和催化装置的应用科学家有好处。

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.