Thermoelectric properties of nanoporous three-dimensional graphene networks

Thiyagarajan, Pradheep; Yoon, Jong–Hyun; Jang, Ji‐Hyun

doi:10.1063/1.4883892

Cited by 11 publications

(5 citation statements)

References 28 publications

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“…Here, we investigate a 2D-2D junction, the graphenegraphene junction, which is common in graphene foams that are promising for thermal management and energy storage [53][54][55][56][57] . As indicated in Fig.…”

Section: Phonon Local Non-equilibrium In Graphene-graphene 2d Junctionmentioning

confidence: 99%

Spectral analysis of nonequilibrium molecular dynamics: Spectral phonon temperature and local nonequilibrium in thin films and across interfaces

Feng¹,

Yao²,

Wang³

et al. 2017

Phys. Rev. B

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Although extensive experimental and theoretical works have been conducted to understand the ballistic and diffusive phonon transport in nanomaterials recently, direct observation of temperature and thermal nonequilibrium of different phonon modes has not been realized. Herein, we have developed a method within the framework of molecular dynamics to calculate the temperatures of phonon in both real and phase spaces. Taking silicon thin film and graphene as examples, we directly obtained the spectral phonon temperature (SPT) and observed the local thermal nonequilibrium between the ballistic and diffusive phonons. Such nonequilibrium also generally exists across interfaces and is surprisingly large, and it provides an additional thermal interfacial resistance mechanism. Our SPT results directly show that the vertical thermal transport across the dimensionally mismatched graphene/substrate interface is through the coupling between flexural acoustic phonons of graphene and the longitudinal phonons in the substrate with mode conversion. In the dimensionally matched interfaces, e.g. graphene/graphene junction and graphene/boron nitride planar interfaces, strong coupling occurs between the acoustic phonon modes on both sides, and the coupling decreases with interfacial mixing. The SPT method together with the spectral heat flux can eliminate the size effect of the thermal conductivity prediction induced from ballistic transport. Our work shows that in thin films and across interfaces, phonons are in local thermal nonequilibrium. * λQλ ,whereQ λ (t) is the time derivative of normal mode amplitude, which is given by the Fourier transform of atomic arXiv:1703.10957v1 [cond-mat.mes-hall]

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Section: Phonon Local Non-equilibrium In Graphene-graphene 2d Junctionmentioning

confidence: 99%

Spectral analysis of nonequilibrium molecular dynamics: Spectral phonon temperature and local nonequilibrium in thin films and across interfaces

Feng¹,

Yao²,

Wang³

et al. 2017

Phys. Rev. B

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“…Optimum Zn 0.95 Ni 0.05 O/PPP nanocomposites containing 5 wt % PPP exhibited an increase of electrical conductivity by ∼45% at 650 K and a reduction of thermal conductivity by ∼30% at 1173 K. On the other hand, graphene, a two-dimensional (2D) flat monolayer of sp 2 -bonded carbon atoms, has recently attracted tremendous attention owing to its superior merits of large specific surface area and good electrical conductivity . These favorable characteristics make graphenes potentially excellent TE materials. − Therefore, it can be envisioned that integration of graphene into inorganic TE materials would enhance their TE performance. One such example was recently reported by Dong et al that the in situ chemistry method was used for PbTe–graphene nanocomposites for TE applications .…”

Section: Introductionmentioning

confidence: 99%

One-Step Chemical Synthesis of ZnO/Graphene Oxide Molecular Hybrids for High-Temperature Thermoelectric Applications

Chen

Zhao

Chen

et al. 2015

ACS Appl. Mater. Interfaces

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ZnO as high-temperature thermoelectric material suffers from high lattice thermal conductivity and poor electrical conductivity. Al is often used to n-dope ZnO to form Zn1-xAlxO (AZO). Owing to very limited Al solubility (less than 2 atom %) in AZO, however, electrical conductivity is difficult to improve further. Moreover, such a low concentration of Al dopants can hardly reduce the thermal conductivity. Here, we propose slightly adding chemically reduced graphene oxides (rGOs) to AZO in various contents to modulate the carrier concentration and simultaneously optimize the electrical and thermal conductivities. Such nanocomposites with rGO embedded in AZO matrix are formed on the molecular level by one-step solution chemistry method. No obvious changes are found in crystalline structures of AZO after introducing rGOs. The rGO inclusions are shown to uniformly mix the AZO matrix that consists of compacted nanoparticles. In such AZO/rGO hybrids, Zn2+ is captured by the rGO, releasing extra electrons and thus increasing electron density, as confirmed by Hall measurements. The phonon-boundary scattering at the interface between AZO and rGO remarkably reduces the lattice thermal conductivity. Therefore, a respectable thermoelectric figure of merit of 0.28 at 900 °C is obtained in these nanocomposites at the rGO content of 1.5 wt %, which is 8 times larger than that of pure ZnO and 60% larger than that of alloyed AZO. This work demonstrates a facile wet chemistry route to produce nanostructured thermoelectric composites in which electrical conductivity can be greatly increased while largely lowering thermal conductivity, collectively enhancing the thermoelectric performance.

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“…[ 27 ] Moreover, it also indicates the crystallinity of the samples did not significantly alter. [ 34 ] It is observed that the peak position of D‐band (≈1340 cm −1 ), G‐band (≈ 1580 cm −1 ), and 2D‐band (2685 cm −1 ) did not show an obvious shift, which implies that addition of CNT or CB did not cause the softening or hardening of phonons. [ 35 ] The lower I D / I G ratio of our samples as compared to reported data for FLGs [ 27 ] and the least defects as indicated by very low peak intensity of D‐band demonstrate the high quality of the prepared material and fewer layers of the prepared FLG.…”

Section: Resultsmentioning

confidence: 99%

“…In-plane [40] Suspended single layered graphene (SLG) ≈4840-5300 RT - [41] Suspended graphene ≈3000-5300 RT In-plane [42] Pyrolytic graphite ≈2000 RT In-plane -Pure pitch-bonded graphite ≈200 RT In-plane [43] FLG (n = 2-4) ≈2800-1300 RT In-plane [44] SLG 600 RT - [45] Suspended graphene ≈2600-3100 350 In-plane [43] Porous 3D-graphene networks 0.54-0.90 298-773 - [34] Graphene nanoribbon(n < 5) ≈1000-1400 RT - [46] Oxygen plasma treated defected graphene supported on substrate 36 -- [47] Graphene pellet 0.38-3.02 303-363 Parallel to the pressing direction [48] MWCNT pellet 1.60-2.25 300-923 Parallel to the pressing direction [49] Carbon black pellet ≈0.2-0. pellet which is predictably lower than the graphene sheets.…”

Section: Resultsmentioning

confidence: 99%

Ultralow Thermal Conductivity Achieved by All Carbon Nanocomposites for Thermoelectric Applications

Rafique

Burton

Badieh

et al. 2023

Adv Elect Materials

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Carbon-based materials are becoming a promising candidate for thermoelectricity. Among them, graphene shows limited scope due to its ultra-high thermal conductivity (𝜿). To develop graphene-based thermoelectric devices, reduction of 𝜿 is highly desired while maintaining reasonably high electrical conductivity (𝝈). Herein, multiwalled carbon nanotubes (MWCNTs) and carbon black (CB) fillers are added into few layered graphene (FLG) to produce all-carbon composites yielding ultra-low thermal conductivity (𝜿) desired for thermoelectric applications. The novel preparation method of pristine FLG realizes very low 𝜿 of 6.90 W m −1 K −1 at 1248 K, which further reduces to 0.57, 0.81, and 0.69 W m −1 K −1 at the same temperature for FLG + MWCNTs, FLG + CB, and FLG + MWCNTs + CB, respectively. As-prepared FLG composites also maintain reasonably high 𝝈, whilst the Seebeck coefficient shows over a factor of five improvement after the inclusion of carbon-based fillers. Consequently, the power factor (PF) is significantly improved. The ultralow 𝜿 is attributed to the increased thermal boundary resistance among graphene sheet boundaries. The realization of ultralow 𝜿 with simultaneous improvement in Seebeck coefficients and relatively small drops in 𝝈 with a facile and unique synthesis technique, highlight the potential of these composites.

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Thermoelectric properties of nanoporous three-dimensional graphene networks

Cited by 11 publications

References 28 publications

Spectral analysis of nonequilibrium molecular dynamics: Spectral phonon temperature and local nonequilibrium in thin films and across interfaces

Spectral analysis of nonequilibrium molecular dynamics: Spectral phonon temperature and local nonequilibrium in thin films and across interfaces

One-Step Chemical Synthesis of ZnO/Graphene Oxide Molecular Hybrids for High-Temperature Thermoelectric Applications

Ultralow Thermal Conductivity Achieved by All Carbon Nanocomposites for Thermoelectric Applications

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