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日期 2015-06-15 00:00  点击:



讲座题目:Nanoscale Heat Transfer: Thermal Conductivity of Hybrid Organic-Inorganic Materials




讲座摘要:Thermal transport plays an important role in energy and information technologies. There have been significant progresses on the understanding of thermal conductivity and phonon transport mechanisms over the past 2 decades, owing much to the challenging needs in high efficiency energy conversion, high speed electronics, and high power lasers. In concurrence with such technical challenges, significant progresses in computational power makes first-principles prediction of materials possible. Ultrafast lasers can now probe materials both at sub-femtosecond timescale and at atomic or sub-nanometer length scale. In this seminar, I will quickly highlight a few notable accomplishments in the field within the context of establishing multiscale-multiphysics simulation and characterization platforms for the study of phonon transport and thermal conductivity in nanostructured materials.

Atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques with atomic level control enable a new class of hybrid organic–inorganic materials with improved functionality. The cross-plane thermal conductivity and volumetric heat capacity of three types of hybrid organic–inorganic zincone thin films fabricated by molecular layer deposition (MLD) and alternate atomic/molecular layer deposition (ALD/MLD) processes were measured. We revealed the critical role of backbone flexibility in the structural morphology and thermal conductivity of MLD zincone thin films by comparing the thermal conductivity of MLD zincone films with an aliphatic backbone to that with aromatic backbone. This work suggests that dramatic material difference between organic and inorganic materials may provide a route for producing materials with ultralow thermal conductivity.

Coupled with its low thermal conductivity, polymer thermoelectric composites are attractive for energy harvesting and localized cooling where temperature gradients are moderate, surfaces are irregular, toxic or rare elements are avoided, and low-cost processing is preferred. Though great progresses have been made for p-type polymers with a thermoelectric figure of merit (ZT) up to 0.42, there has been a paucity of unipolar n-type composites for this purpose. I will report the measurement and the understanding on the low thermal conductivity of an N-type flexible hybrid TiS2-organic superlattice showing ZT > 0.1, making possible the realization of flexible thermoelectric devices for wearable electronics, with both n- and p-type materials available.

讲座人简介:Dr. Ronggui Yang is the S.P. Chip and Lori Johnson Faculty Fellow in Engineering and an Associate Professor of Mechanical Engineering at the UniversityofColoradoatBoulder. Dr. Yang received his Ph.D degree focusing on Nanoscale Transport Phenomena with Prof. Gang Chen in Mechanical Engineering and Professor Mildred S. Dresselhaus from MIT in February 2006. Prior to MIT, he had a Master’s degree in MEMS from UCLA in 2001, a Master’s degree in Engineering Thermophysics fromTsinghuaUniversityinBeijingin 1999, and a Bachelor’s degree in Thermal Engineering from Xi’an Jiaotong University in 1996. Since January 2006, he started his faculty career as an assistant professor at CU-Boulder and has been promoted to associate professor with early tenure in summer 2011 (two-year ahead of the normal clock at CU-Boulder). His research interests are on the fundamentals of nanoscale transport phenomena and the applications of micro/nanotechnologies for energy conversion, storage and thermal management. Dr. Ronggui Yang has published more than 100 journal papers, delivered ~60 invited seminars and is associated with >160 invited and contributed conference talks and posters. His journal papers are highly cited with a total citation > 3000 times as of May 25, 2015, and an annual citation > 550 times per ISI Web of Science (SCI) since 2013 (an H-Index of 28, a total citation > 4700 times as of May 25, 2015, and an annual citation ~1000 times in 2014, according per Google Scholar). He has won the ITS Young Investigator Award from the International Thermoelectrics Society (ITS) in 2014, JSPS Invitation Fellow (short term) from Japan Society for the Promotion of Science in 2013, the ASME Bergles-Rohsenow Young Investigator Award in Heat Transfer in 2010, an NSF CAREER Award in 2009, the MIT Technology Review’s TR35 Award and the DARPA Young Faculty Award in 2008, and the Goldsmid Award for Research Excellence in Thermoelectrics in 2005 from the International Thermoelectrics Society, and a NASA Tech Brief Award for a Technical Innovation in 2004. He has also won the Provost’s Achievement Award (2012), the Dean’s Performance Award (2010), the Woodward Outstanding Faculty of Mechanical Engineering (2011) and the Outstanding Research Award in Mechanical Engineering (2008 & 2013) from the University of Colorado at Boulder. His advisees have also won numerous Best Paper/Poster/Presentation Awards at ASME, APS, and IEEE conferences and at CU. Dr. Yang is an active member of ASME and has received many Certificate of Appreciation for dedicated services. Dr. Yang is currently the Chair (2014-2016) of Nanoengineering for Energy and Sustainability (NEES) Steering Committee of ASME Nanoengneering Council. He is also the elected Chair (2015-2017) and the founding Vice Chair (2012-2015) of the K-9 Technical Committee on Nanoscale Thermal Transport of ASME Heat Transfer Division. He is currently an editorial board member for Scientific Reports, a journal published by Nature Publishing Group, and a Guest Editor for ASME Journal of Electronic Packaging in charge of Invited Reviews.

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