Anisotropic thermal conductivity tensor of β-Y2Si2O7 for orientational control of heat flow on micrometer scales

Olson, David H.; Avincola, Valentina Angelici; Parker, Cory; Braun, Jeffrey L.; Gaskins, John T.; Tomko, John A.; Opila, Elizabeth J.; Hopkins, Patrick E.

doi:10.1016/j.actamat.2020.02.040

Cited by 14 publications

(6 citation statements)

References 34 publications

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“…The estimated steady-state temperature increase is ∼2 K. The fwhm spatial resolution of this technique is ≈2.2 μm (Figure S5). This technique has been used previously to measure spatially inhomogeneous thermal conductivity in polycrystalline diamond, lithium-intercalated MoS 2 , and other materials. ,,, …”

Section: Methodsmentioning

confidence: 99%

“…This technique has been used previously to measure spatially inhomogeneous thermal conductivity in polycrystalline diamond, 19 lithium-intercalated MoS 2 , 2 and other materials. 14,29,41,42 Molecular Dynamics Simulations. Interatomic interactions are modeled with empirical potentials tested to reproduce the vibrational properties of graphite, MoS 2 , and aluminum.…”

Section: Methodsmentioning

confidence: 99%

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Engineering Thermal Transport across Layered Graphene–MoS₂ Superlattices

et al. 2021

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Layering two-dimensional van der Waals materials provides a high degree of control over atomic placement, which could enable tailoring of vibrational spectra and heat flow at the sub-nanometer scale. Here, using spatially resolved ultrafast thermoreflectance and spectroscopy, we uncover the design rules governing cross-plane heat transport in superlattices assembled from monolayers of graphene (G) and MoS2 (M). Using a combinatorial experimental approach, we probe nine different stacking sequences, G, GG, MG, GGG, GMG, GGMG, GMGG, GMMG, and GMGMG, and identify the effects of vibrational mismatch, interlayer adhesion, and junction asymmetry on thermal transport. Pure G sequences display evidence of quasi-ballistic transport, whereas adding even a single M layer strongly disrupts heat conduction. The experimental data are described well by molecular dynamics simulations, which include thermal expansion, accounting for the effect of finite temperature on the interlayer spacing. The simulations show that an increase of ∼2.4% in the layer separation of GMGMG, relative to its value at 300 K, can lead to a doubling of the thermal resistance. Using these design rules, we experimentally demonstrate a five-layer GMGMG superlattice “thermal metamaterial” with an ultralow effective cross-plane thermal conductivity comparable to that of air.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Engineering Thermal Transport across Layered Graphene–MoS₂ Superlattices

et al. 2021

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“…At the nanoscale, heat flow must navigate length scales intrinsic to material heterogeneities. − This process contributes to the macroscopic thermal properties of a material but is typically aggregated into bulk parameters that can obfuscate microscopic origins. It is well-known that, in the cases of electronic and mass transport, heterogeneity has impacts beyond a simple reduction in diffusivity, leading to fundamentally different transport regimes such as subdiffusive behavior. − Subdiffusion refers to a mean-squared expansion of an initially localized heat distribution evolving as t α , where α < 1, , such that the effective thermal conductivity falls off as a power law with the length scale traversed, tending to zero in the infinite limit .…”

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confidence: 99%

“…The challenge of measuring nanoscale heat transport in heterogeneous media is that it requires a direct indicator of heat flow on the length and time scales of the encounters with nanoscale defects. − ,− Typically, thermal conductivity is measured on length scales orders of magnitude greater than the size of individual defects, yielding an average quantity. Ultrafast optical pump–probe measurements of thin films do not typically image heat spreading, and length-dependent steady-state thermal resistance measurements lack dynamical information and require constraining sample geometries and mechanical properties .…”

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confidence: 99%

“…We suspect that subdiffusive heat transport at the nanoscale may be a common phenomenon in systems with nanoscale heterogeneity. A macroscopic measurement of such a system would average over the impact of the heterogeneities and yield a conductivity smaller than that which could be achieved in the absence of the heterogeneity. ,, By virtue of revealing the relationship between variations in structure to variations in transport, nanoscale thermal conductivity measurements should be valuable to rationalize and improve the bulk thermal properties of materials; the extent to which nanoscale measurements reveal anomalous diffusion and the scales on which it occurs can provide important microscopic information on the origins of suboptimal conduction at larger scales. For example, the distribution of sizes, shapes, and locations of voids could potentially lead to different transport behaviors associated with their characteristic scales that impact macroscopic flow in various ways. , …”

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confidence: 99%

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Nanoscale Disorder Generates Subdiffusive Heat Transport in Self-Assembled Nanocrystal Films

et al. 2021

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Investigating the impact of nanoscale heterogeneity on heat transport requires a spatiotemporal probe of temperature on the length and time scales intrinsic to heat navigating nanoscale defects. Here, we use stroboscopic optical scattering microscopy to visualize nanoscale heat transport in disordered films of gold nanocrystals. We find that heat transport appears subdiffusive at the nanoscale. Finite element simulations show that tortuosity of the heat flow underlies the subdiffusive transport, owing to a distribution of nonconductive voids. Thus, while heat travels diffusively through contiguous regions of the film, the tortuosity causes heat to navigate circuitous pathways that make the observed mean-squared expansion of an initially localized temperature distribution appear subdiffusive on length scales comparable to the voids. Our approach should be broadly applicable to uncover the impact of both designed and unintended heterogeneities in a wide range of materials and devices that can affect more commonly used spatially averaged thermal transport measurements.

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