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

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

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.