Design of Novel Buffer Layers for Excellent Performance UHTCs; Investigation of Diffusion Mechanisms

新型缓冲层设计，实现卓越性能的 UHTC；

• 批准号: 323778385
• 负责人: Professor Dr. Hans-Joachim Kleebe
• 金额: --
• 依托单位: Institut für Angewandte Geowissenschaften (IAG)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/323778385?language=en
• 关键词: Design; Novel; Buffer; Layers; Excellent

ZrB2 is an ultra-high temperature ceramic (UHTC) possessing a melting point exceeding 3000°C and interesting engineering and physical properties. As such, ZrB2 ceramics are considered potential candidates for space and hypersonic components. The main drawbacks that restrict the employment of ZrB2 ceramics for a wider spectrum of applications are mainly related to its low damage tolerance, poor oxidation resistance and relatively high density. However, the introduction of discontinuous SiC fibers can both increase the toughness of ZrB2 above 6 MPa·m½ and parallel a notably decrease in density. Moreover, the addition of secondary phases such as MoSi2 can further improve the high-temperature strength and, most importantly, the oxidation performance of the boride matrix. The ultimate scope of the project is to obtain a functionally graded (FG) composite made up of a ZrB2-MoSi2 outer scale to provide oxidation and ablation resistance and a progressively SiC fiber-enriched body from top to bottom to guarantee a higher failure tolerance and a lower density of the entire structure. The major obstacle to overcome is the detrimental chemical reaction between Mo-compounds and SiC fibers occurring during sintering, which leads to the microstructural degradation of the fibers and, hence, to the loss of their toughening function.To reach the above mentioned aim, the focus of the project is on the development of a novel ZrB2-based buffer scale able to prevent chemical reactions between SiC fibers and Mo-compounds and on the study of interdiffusion processes across the interface, both during sintering and upon oxidation. It is envisioned to utilize mixtures of ZrB2 and Si3N4, SiCN and HfSiN for the diffusion barrier. The understanding of the chemical reactions across the various layers will be fundamental for the design of a novel UHTC for applications under extreme environments.The work plan foresees the development of various baseline ceramic joints with different composition of the buffer layer and a thorough microstructural characterization of the as-sintered and oxidized specimens by transmission electron microscopy. These analyses, coupled to thermodynamic predictions, will be essential in revealing local diffusion processes and will lead to the definition of an optimized buffer layer composition for the design of a functional UHTC. Thermo-mechanical characterization and arc-jet tests of the optimized composite will be carried out to assess the performance of the novel material.

ZRB2是一种超高温度陶瓷（UHTC），具有超过3000°C的熔点以及有趣的工程和物理性能。因此，ZRB2陶瓷被认为是空间和高超音速组件的潜在候选者。限制ZRB2陶瓷用于更广泛应用的主要缺点主要与其低损伤耐受性，抗氧化耐药性差和相对较高的密度有关。但是，不连续的SIC纤维的引入既可以将Zrb2的韧性提高到6 MPa·M½以上，又可以使密度显着降低。此外，添加辅助相（例如MOSI2）可以进一步提高高温强度，最重要的是，硼化物基质的氧化性能。该项目的最终范围是获得由ZRB2-MOSI2外部尺度组成的功能分级（FG）复合材料，以提供氧化和消融能力，以达到上述目标，该项目的重点是开发新型ZRB2基于ZRB2的缓冲量表，能够在基于SIC纤维和Mo-Compiffer和Mo-Compunds之间的化学反应上进行互为相互作用，并相互交织。氧化。它设想将Zrb2和Si3n4，SICN和HFSIN的混合物用于扩散屏障。对各个层的化学反应的理解将是针对极端环境下应用的新型UHTC的设计。这些分析与热力学预测相结合，对于揭示局部差异过程至关重要，并将导致对功能性UHTC设计的优化缓冲层组成的定义。将进行优化复合材料的热机械表征和电弧喷射测试，以评估新型材料的性能。