Sustainable energy and thermal
management are among the greatest challenges facing the
society, and heat transfer researchers can
contribute. Solutions to these challenges rely on
extraordinarily fundamental and innovative approaches. In
our lab, we are developing renewable
energy technologies and thermal management solutions for
electronics 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
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
We have labs in both the ME
building and the
Birck Nanotechnology Center. We are also associated with
Energy Center at Purdue.
Most Recent Publications:
 J.J. Shi, J.H. Lee, Y.L.
Dong, A. Roy, T.S. Fisher, and X.L. Ruan, "Dominant phonon
polarization conversion across dimensionally mismatched
interfaces: Carbon-nanotube–graphene junction," Phys. Rev. B
97, 134309 (2018). [PDF]
 J.J. Shi, Y. Zhong, T.S.
Fisher, and X.L. Ruan, "Decomposition of thermal boundary
resistance across carbon nanotube-graphene junctions to
different mechanisms," ACS Appl. Mater. Interfaces 10,
15226-15231 (2018). [PDF]
 Z.Y Ong, B. Qiu, S.L. Xu, X.L.
Ruan, and E. Pop, "Flexural Resonance Mechanism of Thermal
Transport across Graphene-SiO2 Interfaces," J. Appl. Phys.
123, 115107 (2018). [PDF]
 Z. Lu, Y. Wang, and X.L. Ruan,
"The critical particle size for enhancing thermal
conductivity in metal nanoparticle-polymer composites," J.
Appl. Phys. 123, 074302 (2018). [PDF]
B. Xu, T.L.
Feng, M.T. Agne, Q. Tan, Z. Li, K. Imasato, L. Zhou, J.H.
Bahk, X.L. Ruan, G.J. Snyder, and Y. Wu, "Manipulating Band
Structure through Reconstruction of Binary Metal Sulfide
towards High-Performance, Eco-Friendly and Cost-Efficient
Thermoelectrics in Nanostructured Bi13S18I2,"
Angew. Chem. Int.
Ed. 57, 2413-2418
 T.L. Feng and X.L. Ruan,
"Four-phonon scattering reduces intrinsic thermal
conductivity of graphene and the contributions from flexural
phonons," Phys. Rev. B 97, 045202 (2018). [PDF]
list of publications]