Education

Research Description

Dr. Liu leads an energy conversion, storage, and management research group focusing on developing computational and experimental tools for understanding nanoscale thermal transport, probing new transport phenomena in micro/nano-scale structures, and applying the results to design thermal management and energy conversion/storage systems with nano-engineered functional materials. He is currently working on (1) developing ultrafast laser-based pump-probe system for characterizing thermal and elastic properties of materials (e.g. TDTR, TRMOKE, Raman); (2) developing numerical simulation tools for understanding energy transport mechanisms in soft matters and hybrid materials (e.g. moledular dynamics, density functional theory, lattice dynamics); (3) establishing novel functional thermal materials, especially soft materials and hybrid materials. Those materials serve as elementary building blocks for thermal management and energy conversion/storage devices and systems with enhanced performance.

Honors and Awards

• NSF CAREER Award, 2020
• Outstanding Dissertation Award, 2013

Publications

A Ubiquitous Thermal Conductivity Formula for Liquids, Polymer Glass, and Amorphous Solids (vol 37, 104401, 2020)

Xi, Q., Zhong, J., He, J., Xu, X., Nakayama, T., Wang, Y., … Li, B. (2021, March), CHINESE PHYSICS LETTERS, Vol. 38. https://doi.org/10.1088/0256-307X/38/3/039901

Evaluating the roles of temperature-dependent eigenvectors in predicting phonon transport properties of anharmonic crystals using normal mode analysis methods

He, J., & Liu, J. (2021), JOURNAL OF APPLIED PHYSICS, 6. https://doi.org/10.1063/5.0053287

Molecular dynamics simulation of thermal transport in semicrystalline polyethylene: Roles of strain and the crystalline-amorphous interphase region

He, J., & Liu, J. (2021), Journal of Applied Physics. https://doi.org/10.1063/5.0067999

Parallel Frameworks for Robust Optimization of Medium-Frequency Transformers

Booth, K., Subramanyan, H., Liu, J., & Lukic, S. M. (2021), IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS, 9(4), 5097–5112. https://doi.org/10.1109/jestpe.2020.3042527

Thermal boundary conductance across solid-solid interfaces at high temperatures: A microscopic approach

Zhong, J., Xi, Q., Wang, Z., Nakayama, T., Li, X., Liu, J., & Zhou, J. (2021), JOURNAL OF APPLIED PHYSICS, 5. https://doi.org/10.1063/5.0047396

Thermal percolation and electrical insulation in composite materials with partially metallic coated fillers

Zhong, J., Xi, Q., He, J., Liu, J., & Zhou, J. (2021), APPLIED PHYSICS LETTERS, 11. https://doi.org/10.1063/5.0067875

A skin layer made of cured polysilazane and yttria stabilized zirconia for enhanced thermal protection of carbon fiber reinforced polymers (CFRPs)

Jia, Y., Ajayi, T. D., Ramakrishnan, K. R., Negi, A., Liu, J., Ekkad, S., & Xu, C. (2020), Surface and Coatings Technology, 404, 126481. https://doi.org/10.1016/j.surfcoat.2020.126481

Efficiency improvement of liquid piston compressor using metal wire mesh for near-isothermal compressed air energy storage application

, (2020). Journal of Energy Storage. https://doi.org/10.1016/j.est.2020.101226

In-Plane Thermoelectric Properties of Flexible and Room-Temperature-Doped Carbon Nanotube Films

, (2020). ACS Applied Energy Materials. https://doi.org/10.1021/acsaem.0c00995

Size Effects in the Thermal Conductivity of Amorphous Polymers

, (2020). Physical Review Applied. https://doi.org/https://doi.org/10.1103/PhysRevApplied.14.044023

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Grants

Domain-Engineering Enabled Thermal Switching in Ferroelectric Materials

National Science Foundation (NSF)(7/01/20 - 6/30/24)

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Domain-Engineering Enabled Thermal Switching in Ferroelectric Materials

Sponsor: National Science Foundation (NSF)

Start Date: 7/01/20

End Date: 6/30/24

Abstract

The research goal is to understand how thermal conductivity of ferroelectric materials can be switched with external electric fields and how this switching behavior can be engineered through the reconfigurable ferroelectric domains. This is motivated by the possible new paradigm of energy regulation for harvesting, saving, and management if dynamic control of thermal energy transport can be achieved. Seeking solutions for thermal control in materials are limited by the traditional toolkit of linear, static, and passive thermal components, such as thermal resistors and thermal capacitors. This paucity of thermal options pales in comparison to the rich selection of highly nonlinear, switchable, and active components in the electrical domain. Since switchable and nonlinear thermal components are not nearly as mature as their electrical counterparts, the pursuit of these thermal components remains a motivating interdisciplinary challenge to researchers for years. In this project, we will measure the thermal conductivity- domain structure correlation to reveal the effects of domain walls and domain engineering. The studies on the manipulation of domain walls using domain engineering has translational implications for a range of applications, such as infrared imaging, solid-state cooling, and waste-heat energy conversion due to pyroelectric and electrocaloric effects, and sensors based piezoelectric effects.

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Travel Support for Student Participation at the 2019 ASME International Mechanical Engineering Congress and Exposition (ASME-IMECE) Society-wide Micro and Nano Technology Forum

National Science Foundation (NSF)(11/01/19 - 6/30/20)

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Travel Support for Student Participation at the 2019 ASME International Mechanical Engineering Congress and Exposition (ASME-IMECE) Society-wide Micro and Nano Technology Forum

Sponsor: National Science Foundation (NSF)

Start Date: 11/01/19

End Date: 6/30/20

Abstract

Part of the mission of the NSF, and in particular the Engineering Directorate, is to attract young talented researchers and to mentor them for a career in science and engineering. In the spirit of this mission, this proposal seeks NSF travel funding for 43 students and postdocs to attend the 2019 ASME International Mechanical Engineering Congress and Exposition (IMECE) in Salt Lake City, UT so they can present their research at the society-wide micro-nano poster forum. The ASME Society-Wide Micro and Nano Technology Forum (Topic 17-15) focuses on new developments in the field of micro and nanoengineering and sciences. As co-chairs of this productive gathering, we value the chance to support these upcoming researchers as they showcase their scientific accomplishments, interact with their peers and extend their network within the broader academic community. This support will create future career opportunities for students and postdoctoral researchers such as faculty and researcher appointments and positions within industry. Priority will be given to student participants who are women or who come from underrepresented groups, and to undergraduate students, so as to promote diverse participation at the ASME conference, in the short term, and in STEM fields, more long term.

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CAREER: Pushing the Lower Limit of Thermal Conductivity in Layered Materials

National Science Foundation (NSF)(3/01/20 - 2/28/25)

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CAREER: Pushing the Lower Limit of Thermal Conductivity in Layered Materials

Sponsor: National Science Foundation (NSF)

Start Date: 3/01/20

End Date: 2/28/25

Abstract

The research goal is to understand the microscopic mechanisms of the vibrational energy transport and push the lower limit of thermal conductivity in layered materials. As a general scientific interest, a large and ongoing effort has been set forth to expand the limits of heat conduction. On one end of the spectrum, materials with low thermal conductivity have many applications such as thermal insulation and thermoelectric. Even though the amorphous phases of materials usually exhibit low thermal conductivity, the record-low thermal conductivity in fully dense solid, ~0.05 W m-1 K-1, has been found in two crystalline materials: disordered layered WSe2 crystals and fullerene derivative. Can we further push the lower limit to achieve exceptionally-low thermal conductivity? We will focus on layered materials, such as MoS2, to specifically test two hypotheses : (1) Expanding the interlayer spacing would further decrease the thermal conductivity due to the weakened interlayer coupling and enhanced bonding anisotropy; (2) inhomogeneous variation of interlayer spacing can create a much larger reduction in thermal conductivity than the homogenous one. If successful, the proposed strategy combining bonding anisotropy and inhomogeneous layer expansion to achieve record-low thermal conductivity could be potentially applied for thermal insulation or thermoelectrics. Moreover, they also provide transformative opportunities to develop thermal functional materials with thermal conductivities widely tuned by external stimuli, due to the reversibility of electrochemistry process.

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Fundamental Studies on the Thermal Spin-Transfer-Torque: Towards the Next Generation Nonvolatile Memory for Space Exploration

NCSU NC Space Grant Consortium(7/01/18 - 5/31/19)

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Fundamental Studies on the Thermal Spin-Transfer-Torque: Towards the Next Generation Nonvolatile Memory for Space Exploration

Sponsor: NCSU NC Space Grant Consortium

Start Date: 7/01/18

End Date: 5/31/19

Abstract

The space exploration capability, especially for imaging missions, greatly depends on the performance of onboard memory system. The next-generation memory chip for space missions requires larger data capacity and higher data density with lower power consumption and shorter access time. One promising candidate is the spin-transfer-torque (STT) based spintronic memory device. The objective of this program is to: (1) experimentally study the mechanism of the novel thermal-induced STT and demonstrate the ability to locally manipulate a memory bit; (2) train undergraduate and graduate students with the fundamental knowledge and technical skills in this area; and (3) collect preliminary experimental data for NASA fellowship and grants.

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