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碱土金属碳酸盐中，导致具有分级和定向孔隙度的材料在几个领域中显示出有希望的应用潜力。在SPP的最后一个资助期内，遵循了功能（第1部分）和结构（第2部分）工程材料的两个最有前途的方向。在第一个项目部分中，我们研究了湿度控制的植物组织的宏观运动的先决条件，并使用我们的纳米铸造复制过程将这种功能性转移到无机材料中。 首先，我们将研究和模拟本地松果鳞片（松）的驱动，以了解所涉及的组织的位移特性。其次，我们将优化转移的各向异性和保存的分级结构的松果鳞片到无机复合材料。这将使我们能够将复制的无机材料的致动与原生尺度之一相关联。因此，我们将能够开发出描述纳米级变形机制的力学模型，以及由此产生的由分层结构介导的宏观驱动。这是一个主要的目标，以了解如何假定的根本不同的分子变形机制导致类似的宏观驱动，以及这是如何与组织的层次结构。为此，我们还计划从各向异性图案化的纤维素凝胶中构建简化的无机刺激控制的致动装置，其致动性能可以直接与机械模型进行比较。在项目的第二部分，设想将植物组织复制为二氧化硅以外的无定形或纳米晶体矿物相，以再现纳米级结构，并实现相关建筑材料的各向异性机械性能。一个目的是采用替代途径来获得无定形碱土金属碳酸盐（也不同于Ca），从而可以改善机械稳定性。在该项目部分的进一步发展中，我们将研究植物组织或二氧化硅复制品的分层结构中复杂的无定形矿物相硅酸钙水合物（C-S-H）的形成。我们的主要目标是在二氧化硅木材复制品的纳米孔内生长这样的C-S-H相，这将为在纳米孔的受限几何形状中形成C-S-H相提供基本的见解。利用不同的合成方法，我们还想制备C-S-H纤维增强木材和木材复制品，其在煅烧后产生透明的硅酸钙玻璃。植物材料的半透明硅酸钙复制品在建筑应用中将是最迷人的，因为它将结合联合收割机的透光性和隔热/隔音性能。

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.