Improving the thermal stability of oxide ceramic composites: Study of fiber-matrix interactions by combining experiments and phase-field modeling

提高氧化物陶瓷复合材料的热稳定性：结合实验和相场建模研究纤维-基体相互作用

• 批准号: 516465404
• 负责人: Dr. Julia Kundin
• 金额: --
• 依托单位: Fachgebiet Keramische Werkstoffe und Bauteile
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/516465404?language=en
• 关键词: Improving; thermal; stability; oxide; ceramic

Conceptualized to increase the damage tolerance of ceramics, current oxide ceramic matrix composites (Ox-CMC) are still far from reaching their full potential. The main limitation of Ox-CMCs is related to the thermal stability of polycrystalline oxide fibers. At around 1000°C, commercial oxide fibers show strength loss caused by microstructural changes such as grain growth, grooving of defects and crystal phase transformations. Furthermore, the surrounding matrix can also influence the thermal stability of the fibers due to fiber-matrix element diffusion. This is a very concerning issue since temperatures above 1000°C are expected during the processing and possible target applications of Ox-CMCs. Hence, it can be expected that the properties of the fibers in the composites are different than their as-received state. Thus, the main objective of this project is to understand the microstructural changes and interactions in different oxide fiber-matrix systems at high temperatures and their relation to the macroscopic properties of the resultant composites. This goal shall be achieved by combining experimental study with phase-field modeling. For that, several alumina- and mullite-based fibers will be investigated in oxide matrices with different compositions before and after thermal exposures. The experimental part will cover the evolution of grain size distribution and morphology, crystal phase transformations and element diffusion between fiber and matrix. Furthermore, the result of such microstructural changes will be related to the macroscopic mechanical properties of fibers and composites. In parallel, a phase-field model for the 3D anisotropic grain growth of different fiber-matrix systems will be developed. The model will consider the combined effects of anisotropy, constituents' chemical composition, crystal phases, segregation and the presence of defects on the grain growth mechanisms of oxide fibers. Key model parameters will be determined by comparison with the experimental observations. Having a better understanding of the thermal stability of oxide fibers in different oxide matrix systems, the second objective of this work is to be able to successively predict these microstructural changes to develop Ox-CMCs with tailored properties regarding strength and thermal stability. In other words, the results of modeling will be used to adjust matrix composition in accordance to the used oxide fiber and its target application. This can widen the area of application of Ox-CMCs and improve their reliability. In addition, the results of this project can also potentially help on the development of new oxide fibers.

概念化以提高陶瓷的损伤耐受性，当前的氧化陶瓷基质组成（OX-CMC）仍然远未达到其全部潜力。 OX-CMC的主要局限性与多晶氧化物纤维的热稳定性有关。在大约1000°C的情况下，商业氧化物纤维显示出由微结构变化（例如晶粒生长，缺陷的槽和晶体相变的）引起的强度损失。此外，周围的基质还可以影响纤维 - 矩阵元素差异引起的纤维的热稳定性。这是一个非常令人担忧的问题，因为预计在加工过程中预期了1000°C以上的温度以及OX-CMC的可能应用。因此，可以预期组成中纤维的性质不同于其所接受的状态。这是该项目的主要目的是了解高温下不同氧化物纤维 - 矩阵系统中的微观结构变化和相互作用，以及它们与所得组合物的宏观特性的关系。该目标应通过将实验研究与相位场建模相结合来实现。为此，将在热暴露之前和之后的氧化物材料中研究几种氧化铝和mullite纤维。实验部分将涵盖晶粒尺寸分布和形态，晶体相变的演变以及纤维和基质之间的元素差异。此外，这种微观结构变化的结果将与纤维和成分的宏观机械性能有关。同时，将开发出一个不同纤维矩阵系统的3D各向异性晶粒生长的相位模型。该模型将考虑各向异性，成分的化学成分，晶体相，隔离以及氧化物纤维晶粒生长机理的缺陷的综合作用。关键模型参数将通过与实验观测值进行比较来确定。这项工作的第二个目标是更好地了解不同氧化物基质系统中氧化物纤维的热稳定性，以便能够成功预测这些微观结构变化，以开发具有有关强度和热稳定性的量身定制特性的OX-CMC。换句话说，建模的结果将用于根据用过的氧化物纤维及其目标应用来调整基质组成。这可以扩大OX-CMC的应用领域并提高其可靠性。此外，该项目的结果还可以有助于开发新的氧化纤维。