Synchrotron X-ray characterization of materials synthesized under microwave irradiation
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EARLY CAREER SCHOLARS IN MATERIALS SCIENCE 2019: REVIEW Synchrotron X-ray characterization of materials synthesized under microwave irradiation Nathan Nakamura and B. Reeja-Jayana) Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA (Received 6 August 2018; accepted 23 November 2018)
The application of microwave radiation (MWR) during materials synthesis can generate a wide range of interesting phenomena, such as rapid, low-temperature phase transitions and the formation of nonequilibrium phases. However, the underlying mechanisms by which MWR can influence processes like nucleation, crystallization, sintering, and grain growth remain unknown. A critical need for studying these mechanisms is the ability to quantitatively characterize the effects of MWR exposure on atomic structure. In this regard, synchrotron Xray sources provide an opportunity to shed new light on electromagnetic (EM) field–assisted synthesis due to the availability of high-energy X-rays that enable a wide range of experimental characterization techniques. Here, we review the use of synchrotron X-ray sources for both ex situ and in situ studies of MWR-assisted synthesis. While many synchrotron-based tools are available to characterize the structural effects of MWR from the micron down to the atomic scale, work in this field is ongoing, and no clear consensus exists regarding the underlying mechanisms of EM field–mediated phase transitions. We discuss the instrumentation available to study field–matter interaction mechanisms and identify future needs in synchrotron characterization to better understand how EM fields can engineer advanced materials. B. Reeja-Jayan is an assistant professor in Mechanical Engineering at Carnegie Mellon University (CMU), USA. She also holds courtesy appointments in Materials Science and Engineering, Chemical Engineering, and Electrical and Computer Engineering departments at Carnegie Mellon University. Dr. Jayan’s multidisciplinary lab investigates the effect of external fields on materials crystallization and sintering. In particular, by decoupling purely thermal effects from those caused by the field excitation, her lab harnesses EM fields to synthesize materials that can access regions of the free energy/phase space diagram, hitherto unavailable to conventional synthesis routes. These low temperature– processed materials directly grow on flexible, lightweight substrates like fibers, enabling structurally integrated energy harnessing, storage, and sensing. Dr. Jayan is a recipient of the 2018 National Science Foundation (NSF) CAREER Award, 2017 Army Research Office (ARO) Young Investigator Award, 2016 Air Force Office of Scientific Research (AFOSR) Young Investigator Award, the Donald L. and Rhonda Struminger Faculty Fellowship, the Berkman Faculty Development Fund, and Pittsburgh Magazine’s 40 Under 40 Award. B. Reeja-Jayan
I. INTRODUCTION
Application of electromagnetic (EM) fields with frequency between 0.3 and 300 GHz, or microwave radiation (MWR), can generate surprising phen
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