Hierarchically structured porous ceramics and composites from nanocasting of plant cell walls

成功地将植物组织复制到各向异性二氧化硅和土碱碳酸盐中，使得材料具有层次化和方向性的孔隙率，在几个领域显示出良好的应用潜力。在SPP的上一个资助期内，遵循了功能(第一部分)和结构(第二部分)工程材料的两个最有希望的方向。在第一个项目部分，我们研究了植物组织湿度控制的宏观运动的先决条件，以及使用我们的纳米铸造复制过程将这种功能特性转移到无机材料中的前提条件。首先，我们将研究和模拟当地松果鳞(松树)的驱动，以了解所涉及组织的位移特征。其次，我们将优化松果鳞片的各向异性和层级结构在无机复合材料中的转移和保存。这将使我们能够将复制的无机材料的驱动与自然尺度之一联系起来。因此，我们将能够开发出描述纳米尺度的变形机制的力学模型，以及由此产生的由分级结构介导的宏观驱动。它的主要目的是理解假定的根本不同的分子变形机制如何导致相似的宏观驱动，以及这如何与组织的等级结构相关。为此，我们还计划从各向异性图案的纤维素凝胶中构建一种简化的无机刺激控制驱动装置，其驱动性能可以直接与力学模型进行比较。在第二个项目部分，设想将植物组织复制为非晶态或纳米晶矿物相而不是二氧化硅，以再现纳米级结构，并实现相关建筑材料的各向异性力学性能。一个目的是采用替代方法来获得无定形碱土金属碳酸盐(也不是钙)，以便提高机械稳定性。在这个项目部分的一个重要的进一步发展中，我们将研究复杂的无定形矿物相水合硅酸钙(C-S-H)在植物组织的层次结构中或在二氧化硅复制品中的形成。我们的主要目标是在硅木复制品的纳米孔中生长这样的C-S-H相，这将为在受限的纳米孔几何形状中形成C-S-H相提供基本的见解。利用不同的合成方法，进一步制备C-S-H纤维增强木材和木材复制品，经焙烧后制得透明硅酸钙玻璃。植物材料的半透明硅酸钙复制品在建筑应用中最令人着迷，因为它将透光和隔热/隔音性能结合在一起。

The achieved successful replication of plant tissue into anisotropic silica and earth alkaline carbonates led to materials with a hierarchical and directional porosity which show promising application potentials in several fields. Within the last funding period of the SPP, two of the most promising directions towards functional (part 1) and structural (part 2) engineering materials are followed. In the first project part, we investigate the prerequisites for the humidity controlled macroscopic movement of plant tissues and the transfer of this functional property into an inorganic material using our nanocasting replication process. First, we will study and model the actuation of native pine cone scales (Pinus resinosa) in order to understand the displacement characteristics of the involved tissues. Second, we will optimize the transfer of the anisotropy and preservation of the hierarchical structures of the pine cone scales into the inorganic composite material. This will allow us to correlate the actuation of the replicated inorganic materials with the one of the native scales. As a result, we will be able to develop mechanical models that describe the deformation mechanisms at the nanometre scale and the resulting macroscopic actuation mediated by the hierarchical structure. It is a major aim to understand how the presumed fundamentally different molecular deformation mechanisms lead to similar macroscopic actuation, and how this is related to the hierarchical architecture of the tissue. For this, we also plan to build a simplified inorganic stimuli-controlled actuation device from anisotropically patterned cellulose gels, whose actuation performance can be directly compared with the mechanical models. In the second project part, the replication of plant tissue as amorphous or nano-crystalline mineral phases other than silica is envisioned to reproduce nanoscale structure and to achieve anisotropic mechanical properties of relevant construction materials. One aim is to employ alternative routes to obtain amorphous alkaline earth metal carbonates (also other than Ca) so that the mechanical stability can be improved. In a significant further development within this project part, we will investigate the formation of the complex amorphous mineral phase calcium silicate hydrate (C-S-H) within the hierarchical structure of plant tissues or within silica replicas. Our primary goal here is to grow such C-S-H-phases within the nanopores of a silica wood replica, which will provide fundamental insights into the formation of C-S-H phases in the confined geometry of nanopores. Utilizing different synthesis methods, we further want to prepare C-S-H fibre reinforced wood and wood replicas, which after calcination yield transparent calcium silicate glasses. A translucent calcium silicate replica of a plant material would be most fascinating in construction applications, because it would combine light transmittance and heat/sound insulating properties.