Pseudomorphic Conversion of Cellulose-based Paper to Functionalized Ceramic Papers

在应用项目中，纤维素基纸材料的孔隙空间用于原位生产具有分级孔隙率和形态的功能陶瓷纸。主要目标之一是通过利用合适的基于聚合物的单源前体（SSP）将纸浆基纸的形态和拓扑特征假晶转化为陶瓷系统。此外，纤维素纸的形态应该配备有原位生长的1D纳米结构，其影响陶瓷纸的性质，例如孔结构、高温稳定性或柔性。为了生产陶瓷纸，首先通过与含金属的陶瓷前体聚合物的缩合反应对纸浆纸进行表面改性，并在进一步的热步骤中转化为具有分级多尺度孔隙率和形态的陶瓷纸（perimorphoses）。在这种情况下，优选生产金属改性的SiOC、Si（C）N基陶瓷纸，其在700-900 °C的转化温度下提供分级的宏观/介观孔隙率。用合适的含金属聚合物进行改性导致金属或金属硅化物纳米颗粒在聚合物基质内局部沉淀。在较高温度下的陶瓷化（即，在1100-1500° C之间）的热处理导致原位形成含有功能性金属或金属硅化物尖端（如Fe、Ni、Ti、Fe 3Si）的SiC或Si 3 N4基1D纳米结构。在这里，有关的纸浆纸的表面功能化和分层的纸张孔隙空间上的陶瓷化行为的SSP的影响的问题是非常重要的。除了陶瓷纸的制备，在孔隙空间中产生的一维纳米结构的特征在于详细的电子光学方法。这里的中心问题是如何获得的微观结构，相结构和拓扑结构的陶瓷纸和功能的一维纳米纤维后，成功的赝晶转变。因此，从微米（SEM）到纳米尺度（TEM）进行详细的材料表征。总体目标是获得跨尺度的纸张形态的理解，以及关于所得到的内在纳米结构，以生成定制的属性配置文件。另一个重要方面是单个纸纤维的固有结构被保持到何种程度的问题（周晶），或者在原始纤维长丝内转化时存在何种类型的孔隙率和相组合。此外，应考虑所生产的陶瓷纸的机械柔性可达到何种程度的问题。

Within the applied project, the pore space of cellulose-based paper materials is used for in-situ production of functional ceramic papers with hierarchical porosity and morphology. One of the main objectives is the pseudomorphic conversion of morphological and topological features of pulp-based paper to ceramic systems by utilization of suitable polymer-based single-source precursors (SSPs). In addition, the morphology of the cellulose paper should be equipped with in-situ grown 1D nanostructures affecting the properties of the ceramic paper such as pore structure, high temperature stability, or flexibility. For the production of ceramic papers, pulp papers are first surface-modified via condensation reactions with metal-containing preceramic polymers and, in a further thermal step, are converted into ceramic papers (perimorphoses), having a hierarchical multiscale porosity and morphology. In this case, preferentially metal-modified SiOC, Si(C)N-based ceramic papers are produced, which provide hierarchical macro/meso porosities at conversion temperatures of 700–900 °C. The modification with suitable metal-containing polymers leads to local precipitation of metal or metal silicide nanoparticles within the polymer matrix. Ceramization at higher temperatures (i.e., between 1100–1500° C) results in the in-situ formation of SiC or Si3N4-based 1D nanostructures containing functional metal or metal silicide tips (such as Fe, Ni, Ti, Fe3Si). Here, questions concerning the surface functionalization of pulp paper and the effects of the hierarchical paper pore space on the ceramization behavior of the SSPs are of great importance.In addition to the preparation of the ceramic papers, the 1D nanostructures produced in the pore space are characterized in detail by electron-optical methods. The central question here is how the microstructure, the phase structure and the topology of the ceramic papers and the functional 1D nanofibers are obtained after successful pseudomorphic transformation. Therefore, detailed material characterization is performed from the micrometer (SEM) to the nanometer scale (TEM). The overall goal is to obtain an understanding of the paper morphology across scales as well as about the resulting intrinsic nanostructures in order to generate tailored property profiles. Another important aspect is the question to what extent the intrinsic structure of the individual paper fiber is maintained (perimorphose), or what type of porosity and phase assemblage is present upon conversion within the original fiber filament. Furthermore, the question should be considered to what extent a mechanical flexibility of the produced ceramic papers can be achieved.