Studies on the High-Temperature Piezoresistivity of Carbon Containing Silicon Oxycarbide Nanocomposites

这个跨学科项目--含碳碳化硅纳米复合材料的高温压阻性研究--专注于聚合物衍生陶瓷，这里是SiOC-纳米复合材料，到目前为止，其压阻性能的探索还处于初级阶段。为了彻底了解这些材料中的压阻效应，需要进行两种类型的补充研究：第一种是结构研究(如X射线衍射、扫描电子显微镜、透射电子显微镜)和光谱分析(如拉曼光谱、傅立叶变换红外光谱)，以揭示材料内部的结构-性能关系(DF)；第二种是面向应用的研究，以鼓励开发在高温和恶劣环境下具有优异性能的新型力/压力传感器(必须)。这些研究的前提是合成具有特定碳含量和碳微结构的SiOC-纳米复合材料。通过使用不同的聚合物前驱体，碳含量将在1%到30%之间变化；相组成/微观结构可以通过无压或热压工艺进行调整。现场拉曼、力和压力相关的电阻率测量提供了压阻效应与碳相的局域和电子结构之间的关系的信息。样品电阻率和压阻效应的温度依赖性将提供关于潜在基本机制的重要信息，并将被用于区分不同的模型(隧道渗流、跳跃传输等)。该项目面向现象学应用的第二部分包括建立专门的设备来精确评估压阻效应，通过测量系数量化压阻效应，并与成熟的传感器布置进行比较。将进行长期稳定性和重复性实验，以确定这些材料是否有可能在特殊条件(高温、恶劣环境)下用作新的压力传感设备。由于这些材料具有优异的性能，例如热稳定性和化学稳定性，以及优异的抗蠕变性能，这些材料将大大扩展压阻式传感器的工作压力和温度范围，超出当前最先进的水平。

The interdisciplinary project -Studies on the High-Temperature Piezoresistivity of Carbon-Containing Silicon Oxycarbide Nanocomposites- focuses on Polymer-Derived Ceramics, here SiOC-nanocomposites, whose piezoresistive properties have been explored only rudimentary so far. Two types of complementary studies are intended to obtain a thorough understanding of the piezoresistive effect in these materials: Firstly, structural (e.g., X-ray diffraction, SEM, TEM) and spectroscopic investigations (Raman, FTIR spectroscopy) to reveal the structure-property relationship within the materials (DF) and, secondly, application-oriented investigations to encourage the development of new force/pressure sensors with superior properties at high temperature and in harsh environments (MuST). Prerequisite for these studies is the synthesis of SiOC-nanocomposites with defined carbon content and carbon microstructure. The carbon content will be varied between 1 and 30 vol % by using different polymeric precursors; the phase composition/microstructure is adjusted by means of pressureless or hot-pressing processing techniques. In-situ Raman and force and pressure-dependent resistivity measurements are carried out to provide information on the correlation of the piezoresistive effect with the local and electronic structure of the carbon phase.The temperature dependence of the sample resistivity and of piezoresistive effect will deliver important information about the underlying basic mechanism and will be used to discriminate between different models (tunneling percolation, hopping transport, etc.).The phenomenological application-oriented second part of the project consists of the build-up of special equipment for precise assessment of the piezoresistive effect, its quantification by the Gauge-Factor and the comparison to well-established sensor arrangements. Experiments on the long term stability and reproducibility will be performed in order to determine whether these materials are potential candidates for new pressure sensing devices at unusual conditions (high temperatures, harsh environments). Due to their outstanding properties, e.g. thermal and chemical stability as well as excellent creep resistance, these materials will allow a substantial extension of the operation pressure and temperature range of piezoresistive sensors, beyond the current state-of-the-art.