Abstract:

High performance electromagnetic (EM) absorbing materials are highly desired for aerospace and defense applications such as aircraft engine nozzles and their aerodynamically heated parts. Typical EM absorbing materials consist of high concentrations of iron powders in polymer matrix, however, are heavy and costly. Carbon materials, e.g., carbon nanotubes (CNTs), carbon black, and graphite flakes, can only be used in air for limited temperature applications (<400^oC). For higher temperature and oxidizing environments, such as the airplane nozzle areas, wing tips, and nose cones of fighter jets and missiles, traditional carbon/polymer matrix composites are no longer applicable. Current technologies are lacking a suitable material system with the desired absorbing properties in high temperature and harsh environments. 

In this presentation, we will introduce a new type of high-temperature electromagnetic absorbing ceramic nanocomposite, which has a significantly wide absorption bandwidth covering the entire Ka-band (26.5-40 GHz) and can sustain at high temperature (up to 1800^oC). Such unique ceramic composite is made of polymer derived SiOC ceramic and in-situ partially surface-oxidized ultra-high temperature ceramic (UHTC) ZrB₂ nanoparticles. The strong electromagnetic absorbing property is attributed to the extensive nanointerfaces introduced in the composites and the electronic conduction loss provided by the ZrB₂ nanoparticles. The minimum reflection coefficient (RC) was -29.30 dB at 29.47 GHz for a thickness of 1.26 mm with a normalized weight fraction of ZrB₂ nanoparticles at 32.5%. The DC conductivity of the nanocomposites showed a clear percolation phenomenon as the normalized weight fraction of ZrB₂ nanoparticles increases to 30%. The results provide new insights in designing electromagnetic absorption materials with a wide absorbing frequency range and strong absorbing loss for high-temperature harsh environment applications. The science involved in this research spans a broad range of fundamental physical and material science areas including basic physical/electromagnetic laws/interactions of materials responses at disparate and extreme conditions.

Bio:

Dr. Cheryl Xu received her Ph.D. degree in 2006 in mechanical engineering from Purdue University and the M.S. degree in mechanical manufacturing and automation from Beijing University of Aeronautics and Astronautics. Her research interests are multifunctional ceramic composites, high temperature wireless sensing, and artificial intelligence (AI) for process modeling and real-time control.

She is currently an Associate Professor in the department of Mechanical and Aerospace Engineering at NC State University. Prior to that, she was an Associate Professor at Florida State University (2014-2018), and was an Assistant and Associate Professor at the University of Central Florida (2007-2013).  

Dr. Xu is active in conducting research in the field of advanced manufacturing and artificial intelligence (AI). She has attracted a high level of research funding (~$7.1 M). Her research work has been supported by both government agencies and large defense companies that include Office of Naval Research (ONR), Army Research Office (ARO), Air Force Office of Scientific Research (AFOSR), National Science Foundation (NSF), Department of Energy (DOE), and General Dynamics, etc. She has graduated seven Ph.D. and six M.S. students. Most of her graduated students work in major manufacturing industries, such as SpaceX, GE, Lockheed Martin, Siemens, Honda, Mercedes Bez, etc. 

She has co-authored a textbook (Intelligent Systems: Modeling, Optimization and Control, CRC Press, 2008) and has written seven book chapters. She has published 65 peer-reviewed journal articles and more than 30 refereed conference proceedings. She has 13 US and international patents and patent applications. 

Dr. Xu is a Fellow of the American Society of Mechanical Engineers (ASME). Dr. Xu served on the Fellows Committee in IEEE Education Society since 2014 and chaired NSF 1^st National Wireless Research Collaboration Workshop in 2015. She won the Office of Naval Research (ONR) Young Investigator Award and was awarded the Society of Manufacturing Engineering (SME) Outstanding Young Manufacturing Engineer Award in 2011. She was the only recipient of the IEEE Education Society Teaching Award in 2015. She serves as an Associate Editor of ASME Transactions, Journal of Micro- and Nano- Manufacturing 2015-2019.   

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