120 research outputs found
Strongly Tunable Anisotropic Thermal Transport in MoS2 by Strain and Lithium Intercalation: First--Principles Calculations
The possibility of tuning the vibrational properties and the thermal
conductivity of layered van der Waals materials either chemically or
mechanically paves the way to significant advances in nanoscale heat
management. Using first-principles calculations we investigate the modulation
of heat transport in MoS2 by lithium intercalation and cross-plane strain. We
find that both the in-plane and cross-plane thermal conductivity (kr, kz) of
MoS2 are extremely sensitive to both strain and electrochemical intercalation.
Combining lithium intercalation and strain, the in-plane and cross-plane
thermal conductivity can be tuned over one and two orders of magnitude,
respectively. Furthermore, since kr and kz respond in different ways to
intercalation and strain, the thermal conductivity anisotropy can be modulated
by two orders of magnitude. The underlying mechanisms for such large tunability
of the anisotropic thermal conductivity of \Mos are explored by computing and
analyzing the dispersion relations, group velocities, relaxation times and mean
free paths of phonons. Since both intercalation and strain can be applied
reversibly, their stark effect on thermal conductivity can be exploited to
design novel phononic devices, as well as for thermal management in MoS2-based
electronic and optoelectronic systems
Wind-tunnel investigation at high subsonic speeds of the static longitudinal stability characteristics of a complete model having cropped-delta,swept, and unswept wings and several horizontal-tail heights
Wind-tunnel investigation at high subsonic speeds of the stability characteristics of a complete model having sweptback-,M-,W-,and cranked-wing plan forms and several horizontal-tail locations
The Heat Conduction Renaissance
Some of the most exciting recent advancements in heat conduction physics have
been motivated, enabled, or achieved by the thermal management community that
ITherm serves so effectively. In this paper we highlight the resulting
renaissance in basic heat conduction research, which is linked to cooling
challenges from power transistors to portables. Examples include phonon
transport and scattering in nanotransistors, engineered high-conductivity
composites, modulated conductivity through phase transitions, as well as the
surprising transport properties of low-dimensional (1D and 2D) nanomaterials.
This work benefits strongly from decades of collaboration and leadership from
the semiconductor industry.Comment: Invited perspective presented at the 17th IEEE ITherm conference in
San Diego (30th May 2018) on occasion of the Richard Chu ITherm Award for
Excellence given to Prof. Kenneth Goodso
Measurement of the thermal conductivity and heat capacity of freestanding shape memory thin films using the 3 method,
Thermal conductivity of crystalline AlN and the influence of atomic-scale defects
Aluminum nitride (AlN) plays a key role in modern power electronics and
deep-ultraviolet photonics, where an understanding of its thermal properties is
essential. Here we measure the thermal conductivity of crystalline AlN by the
3 method, finding it ranges from 674 56 W/m/K at 100 K to 186
7 W/m/K at 400 K, with a value of 237 6 W/m/K at room
temperature. We compare these data with analytical models and first principles
calculations, taking into account atomic-scale defects (O, Si, C impurities,
and Al vacancies). We find Al vacancies play the greatest role in reducing
thermal conductivity because of the largest mass-difference scattering.
Modeling also reveals that 10% of heat conduction is contributed by phonons
with long mean free paths, over ~7 m at room temperature, and 50% by
phonons with MFPs over ~0.3 m. Consequently, the effective thermal
conductivity of AlN is strongly reduced in sub-micron thin films or devices due
to phonon-boundary scattering
Integrated microchannel cooling for three-dimensional electronic circuit architectures
The semiconductor community is developing three-dimensiona
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