Edge‐Grafted Molecular Junctions between Graphene Nanoplatelets: Applied Chemistry to Enhance Heat Transfer in Nanomaterials

Bernal, M. Mar; Pierro, Alessandro Di; Novara, Chiara; Giorgis, Fabrizio; Mortazavi, Bohayra; Saracco, Guido; Fina, Alberto

doi:10.1002/adfm.201706954

Cited by 40 publications

(36 citation statements)

References 69 publications

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“…Diphenoxyalcane junctions have been recently demonstrated experimentally viable by Bernal et al [53] for the edge functionalization of graphene nanoplatelets. Therefore, in this section, the conductance and phonon transfer on this type of molecules was studied in detail.…”

Section: Aromatic/aliphatic Molecular Junctionsmentioning

confidence: 99%

Thermal bridging of graphene nanosheets via covalent molecular junctions: A non-equilibrium Green’s functions–density functional tight-binding study

et al. 2019

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Despite the uniquely high thermal conductivity of graphene is well known, the exploitation of graphene into thermally conductive nanomaterials and devices is limited by the inefficiency of thermal contacts between the individual nanosheets. A fascinating yet experimentally challenging route to enhance thermal conductance at contacts between graphene nanosheets is through molecular junctions, allowing covalently connecting nanosheets otherwise interacting only via weak Van der Waals forces. Beside the bare existence of covalent connections, the choice of molecular structures to be used as thermal junctions should be guided by their vibrational properties, in terms of phonon transfer through the molecular junction. In this paper, density functional tight-binding combined with Green's functions formalism was applied for the calculation of thermal conductance and phonon spectra of several different aliphatic and aromatic molecular junctions between graphene nanosheets. Effect of molecular junction length, conformation, and aromaticity were studied in detail and correlated with phonon tunnelling spectra. The theoretical insight provided by this work can guide future experimental studies to select suitable molecular junctions in order to enhance the thermal transport by suppressing the interfacial thermal resistances, particularly attractive for various systems, including graphene nanopapers and graphene polymer nanocomposites, as well as related devices. In a broader view, the possibility to design molecular junctions to control phonon transport currently appears as an efficient way to produce phononic devices and controlling heat management in nanostructures.

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Section: Aromatic/aliphatic Molecular Junctionsmentioning

confidence: 99%

Thermal bridging of graphene nanosheets via covalent molecular junctions: A non-equilibrium Green’s functions–density functional tight-binding study

et al. 2019

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“…To form covalent bonds to the surface of various materials, as shown in Figure 1B, diazotization is a simple, flexible, and promising attachment on metal, diamond, and carbon, such as carbon black, carbon nanotubes, graphene sheets, and graphite to enhance interfacial interaction of these materials with a polymer matrix. Aryl diazonium salt chemistry can produce stable organic layers on the surface via carbide bond formation . Melamine (MEL) is often used as a precursor for diazonium salt formation because of the presence of three amine functionalities in the triazine ring, which makes molecules efficient for diazonium grafting .…”

Section: Introductionmentioning

confidence: 99%

Direct diazotization of graphite nanoplatelets with melamine and their favorable application in epoxy resins

Qin

Zhang

2020

Polymers for Advanced Techs

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The ease of undesirable agglomeration and a low efficiency are two problems that restrict the application of graphite nanoplatelets (GNPs) in epoxy resins (EP). Herein, a new strategy with melamine (MEL) as the precursor to functionalize GNPs chemically, which form a bonding layer that is compatible with epoxy matrix, is reported.The MEL fragments with secondary amine groups were grafted uniformly on the GNPs surface by covalent junctions to exploit the diazonium chemistry. This behavior led to a better dispersion and a stronger interaction with the epoxy matrix and resulted in an enhanced glass transition temperature and bending strength, compared with the pure EP. When only 1 wt% functionalized GNPs (f-GNPs) was used, the Tg of the modified EP raised of about 15 C compared with pure EP, and the bending strength increased by approximately 39%. The dielectric constant of the EP with f-GNPs was impacted slightly, and the dielectric loss decreased. At 10 5 Hz, the dielectric loss of the EP with 1 wt% f-GNPs decreased by approximately 11% compared with pure EP. Therefore, diazotization modification of the GNPs is a useful approach to improve the compatibility in nanoparticle networks. K E Y W O R D S compatibility, epoxy resins, graphite nanoplatelets

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“…As a two-dimensional carbon material, graphene has been widely used in the fields of heat conduction, [6] medicine, [7] sensing, [8] catalysis, [9] adsorption, [10] and protection [11] due to its specific structure and properties. As a carbon-forming additive and tortuous path, [12] graphene is also used as a flame retardant to provide flame retardancy of the polymer matrix.…”

Section: Introductionmentioning

confidence: 99%

Superior thermal stability and smoke suppression of epoxy resin composites with graphene/LDHphosphorus‐rich hybrids

Zhou

Kang

Huang³

et al. 2020

J of Applied Polymer Sci

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In this article, graphene/LDH phosphorus‐rich triple hybrid was prepared by a mild method and used to effectively improve the thermal stability and smoke suppression of epoxy resin (EP). The graphene was firstly reacted with hexamethylenediamine (HA) and followed by the treatment with the layered double hydroxide (LDH) and NaH2PO4 solutions. Compared to the unmodified graphene, the initial decomposition temperature of the triple hybrids increases significantly from 168.6 to 292.5°C. The residual carbon content is greatly improved and the residual mass is up to 84.1%. Elemental analysis reveals the content of phosphorus in EP composites is as high as 10 wt%. In flame retardancy tests, the peak heat release rate of the EP composite with 5 wt% graphene/LDH phosphorus‐rich hybrids decreases to 786.15 KW/m2, 41.19% drastic reduction compared to that of EP. These results indicate that the triple functionalization process effectively expands the interval distribution of heat release and makes the heat release process more gradual and spread flames smaller. The smoke production rate and total smoke production rate of EP composite with 5 wt% graphene/LDH phosphorus‐rich hybrids are 0.32 m2/s and 40.91 m2, which are significantly reduced by 65.22 and 57.83%, respectively. This gentle and efficient process provides a new approach to multi‐functional design to improve the thermal stability and smoke suppression of resin‐based composites.

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Edge‐Grafted Molecular Junctions between Graphene Nanoplatelets: Applied Chemistry to Enhance Heat Transfer in Nanomaterials

Cited by 40 publications

References 69 publications

Thermal bridging of graphene nanosheets via covalent molecular junctions: A non-equilibrium Green’s functions–density functional tight-binding study

Thermal bridging of graphene nanosheets via covalent molecular junctions: A non-equilibrium Green’s functions–density functional tight-binding study

Direct diazotization of graphite nanoplatelets with melamine and their favorable application in epoxy resins

Superior thermal stability and smoke suppression of epoxy resin composites with graphene/LDHphosphorus‐rich hybrids

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