College of Engineering Mechanical Engineering Birck Nanotechnology Center Energy Center
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About the PI:

Professor Ruan received his B.S. and M.S. in Engineering Thermophysics from Tsinghua University in 2000 and 2002, respectively. He received an M.S. in Electrical Engineering and Ph.D. in Mechanical Engineering from the University of Michigan at Ann Arbor, in 2006 and 2007 respectively. He then joined Purdue as an assistant professor. He was promoted to associate professor with tenure in 2013. Dr. Ruan received the NSF CAREER Award in 2012. He was an Air Force Summer Faculty Fellow at the Wright Patterson Air Force Base at Dayton, Ohio in 2010, 2011, and 2013. He currently serves as an Editorial Board Member for Scientific Reports, a journal published by the Nature Publishing Group. [CV]


Office: ME 2153 and BNC 1270     Phone: 765-494-5721 (ME), 765-494-6603 (BNC), Fax: 765-494-0539    

e-mail: ruan@purdue.edu

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Positions open: We may have positions for postdoc fellows, graduate students, and undergraduate students. Please check here.


04/2015: M.S. thesis defense. Chris Robinson has successfully defended his MS thesis. Congratulations, Chris! 


04/2015: Invited Talk. Dr. Ruan gave an invited talk at the 2015 MRS Spring Meeting.


03/2015: Student Award. Yan Wang received the College of Engineering Outstanding Graduate Student Research Award. Congratulations, Yan!


03/2015: M.S. thesis defense. Eshaan Mathew has successfully defended his MS thesis. Congratulations, Eshaan! 


10/2014: Invited Seminars. Dr. Ruan was invited to visit Taiwan and give seminars at National Cheng Kung University, National Taiwan University, and National Tsing Hua University.


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Mission Statement:


Sustainable energy and energy efficiency are among the greatest challenges facing the society, and heat transfer scientists and engineers can contribute. Solutions to these challenges rely on extraordinarily fundamental and innovative approaches. In our lab, we are developing efficient energy and renewable energy technologies using the emerging nanotechnology.


The behavior of all energy systems can be related to atomic-scale description. With an atomic-level knowledge of the thermal energy carriers (photon, electron, phonon, and fluid particle), one is able to design nano- and micro-structures with the desired size effects, or to synthesize new materials with the desired functionalities. Our lab is building and expanding the understanding of the fundamentals of atomic-level carrier transport and interactions, and is applying this knowledge to important applications for energy efficiency and electronics thermal management technologies.


Current projects fall in two main themes: nanoscale heat conduction, and nano-photonics (including nanoscale thermal radiation). Projects in the nanoscale heat conduction (or nano-phononics) category include: (1) high-performance nanostructured thermoelectric materials for power generation and thermoelectric refrigeration; (2) thermal transport and thermal rectification in carbon nanotube and graphene for electronic thermal management applications; (3) thermal interface resistance across CNT (or graphene)-metal interfaces for electronic thermal management applications. Projects in the nano-photonics category include: (4) Suppression of electron-phonon coupling in quantum dot solar cell materials for enhanced efficiency; (5) Enhanced optical absorption in silicon nanowire arrays for potentially enhanced solar cell efficiency; (6) Multiscale control of thermal radiation in ordered array of carbon nanotubes; (7) enhanced laser cooling of semiconductors and ion-doped solids.


These projects involve theoretical, computational, and experimental components. Currently our lab devotes 2/3 efforts to theoretical and simulation studies, and 1/3 effort to experimental work. Theoretical tools include heat transfer, materials science, quantum mechanics, solid state physics, optics, and electromagnetic theory. Computational tools involve multiscale simulation techniques of nanoscale energy transport, including molecular dynamics simulations, first principles calculations, Monte-Carlo simulations, and Boltzmann transport theory. Experiments include fabrication of nanomaterials and devices, and characterizations of these materials and devices using advanced imaging and spectroscopy techniques. Detailed information of our research can be found here.


We have labs in both the ME building and the Birck Nanotechnology Center. We are also associated with the Energy Center at Purdue.

Most Recent Publications:


[57] B. Qiu, Z.T. Tian, A. Vallabhaneni, B.L. Liao, J.M. Mendoza, O.D. Restrepo, X.L. Ruan, and G. Chen, “First-principles simulation of electron mean-free-path spectra and thermoelectric properties in silicon”, EPL 109, 57006, (2015). [PDF]


[56] Y. Wang, C.J. Gu, and X.L. Ruan, “Optimization of the random multilayer structure to break the random-alloy limit of thermal conductivity”, Appl. Phys. Lett. 106, 073104 (2015). [PDF]


[55] Z.Y. Wang, T.L. Feng, and X.L. Ruan, “Thermal conductivity and spectral phonon properties of freestanding and supported silicone”, J. Appl. Phys. 117, 084317 (2015). [PDF]


[54] H. Bao, A. Kumar, Y. Cai, Y. Ji, T.S. Fisher, and X.L. Ruan, Optical Properties of Thin Graphitic Nanopetal Arrays, Journal of Quantitative Spectroscopy and Radiative Transfer 158, 84–90 (2015). [PDF]


[53] Y. Wang, H.X. Huang, and X.L. Ruan, "Decomposition of coherent and incoherent phonon conduction in superlattices and random multilayers," Phys. Rev. B 90, 165406 (2014). [PDF]


[52] B.T. Spann, S.V. Bhat, Q. Nian, K.M. Rickey, G.J. Cheng, X.L. Ruan, and X.F. Xu, “Enhancing Photo-induced Ultrafast Charge Transfer across Heterojunctions of CdS and Laser-Sintered TiO2 Nanocrystals,” Phys. Chem. Chem. Phys. 16, 10669-10678 (2014). [PDF]


[complete list of publications]

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