CAREER: Oxygen Transport in Heterogeneous, Nonoxide Ceramics - Toward Durable New Composite Constituents

非技术描述：基于碳化物、硼化物和氮化物的坚固、坚韧和轻质的陶瓷复合材料可以实现新的高性能和高能效的运输和能量转换技术，包括涡轮机发动机、高超音速飞行器和太阳能-热能系统。然而，与氧化物质如氧气和水蒸气的使用中反应会显著降低这些材料在高温下的耐久性。当由于制造过程中产生的材料结构中的局部变化或缺陷而导致氧化物质以不可预测的方式渗透到材料中时，这种退化尤其成问题。该项目通过开发新的实验和建模方法来解决这一挑战，以系统地了解氧化物质如何在这些异质陶瓷微结构中传输。这些见解用于理解某些最先进材料性能优于其他材料的原因，而并行的努力则利用这种理解来加速新材料和加工途径的发现，以实现更好的性能。作为该计划的一部分培训的本科生和研究生将在支持航空航天和国防技术发展的行业中找到就业机会。该项目结合了实验和建模，以了解单相和多相非氧化物陶瓷中的微观结构异质性如何影响氧化剂传输机制，以及在扩散控制过程和反应控制过程之间的过渡处，内部氧活性的所得空间变化如何影响局部氧化反应。新的实验工具，包括嵌入式化学标记和固态电化学氧泵和传感器正在开发，以支持这些目标。该计划最初侧重于结晶Si，SiC和SiC-C系统和Si-（O）-C聚合物衍生陶瓷（PDC）。关于这些系统行为的见解随后被应用于发现高级PDC、活性填料以及提供上级高温性能的多主元素硼化物和碳化物。这项研究直接影响了解决许多关键社会挑战的努力，当时许多系统的开发受到材料性能和在更高温度和更极端环境下的耐久性的阻碍。鉴于目前工业界对在商业产品中实施陶瓷复合材料的兴趣，这项工作特别及时。这些努力还致力于填补下一代STEM领导者的管道，为高中生开发一个陶瓷科学推广计划，通过与陶瓷艺术的联系建立对陶瓷科学的兴趣，通过书写，在材料科学课程的基础作业，以提高保留的代表性不足的学生与更广泛的兴趣和语言能力。这个奖项反映了NSF的法定使命，通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL DESCRIPTION: Strong, tough, and lightweight ceramic composites based on carbides, borides, and nitrides can enable new high performance and energy efficient transportation and energy conversion technologies including turbine engines, hypersonic vehicles, and solar-thermal energy systems. However, in-service reactions with oxidizing species such as oxygen and water vapor can significantly reduce the durability of these materials at high temperatures. This degradation is particularly problematic when the penetration of the oxidizing species into the material occurs in an unpredictable way due to local variability or defects in the material structure originating during the manufacturing process. This project addresses this challenge by developing new experimental and modeling approaches to systematically understand how oxidizing species are transported within these heterogeneous ceramic microstructures. These insights are used to understand the reasons that some state-of-the art materials perform better than others, while parallel efforts leverage this understanding to accelerate the discovery of new materials and processing pathways to achieve improved performance. The undergraduate and graduate students trained as part of this program will find employment in industries supporting aerospace and defense technology development.TECHNICAL DETAILS: This project combines experiments and modeling to understand how microstructural heterogeneities in single-and multi-phase nonoxide ceramics impact oxidant transport mechanisms, and how the resulting spatial variations in internal oxygen activity impact local oxidation reactions at the transition between diffusion- and reaction-controlled processes. New experimental tools including embedded chemical markers and solid-state electrochemical oxygen pumps and sensors are being developed to support these objectives. The program is initially focusing on crystalline Si, SiC, and SiC-C systems and Si-(O)-C polymer derived ceramics (PDC). Insights about the behavior of these systems is then being applied to discover advanced PDCs, active fillers, and multi-principal element borides and carbides offering superior high temperature performance. This research directly impacts efforts to address many critical societal challenges at a point in time when development of many systems is impeded by inferior material performance and durability at higher temperatures and in more extreme environments. This work is especially timely given the current industrial interest in implementing ceramic composites in commercial products. The efforts is also working to fill the pipeline of next-generation STEM leaders by developing a ceramic science outreach program for high school students that builds interest in the ceramic sciences through connections to the ceramic arts, and by implementing writing-based assignments in the materials science curriculum to improve retention of underrepresented students with broader interests and verbal abilities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.