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11 pages, 2404 KiB

Open AccessFeature PaperArticle

A Multiscale Investigation on the Thermal Transport in Polydimethylsiloxane Nanocomposites: Graphene vs. Borophene

by Alessandro Di Pierro, Bohayra Mortazavi, Hamidreza Noori, Timon Rabczuk and Alberto Fina

Nanomaterials 2021, 11(5), 1252; https://doi.org/10.3390/nano11051252 - 11 May 2021

Cited by 8 | Viewed by 3103

Abstract

Graphene and borophene are highly attractive two-dimensional materials with outstanding physical properties. In this study we employed combined atomistic continuum multi-scale modeling to explore the effective thermal conductivity of polymer nanocomposites made of polydimethylsiloxane (PDMS) polymer as the matrix and graphene and borophene [...] Read more.

Graphene and borophene are highly attractive two-dimensional materials with outstanding physical properties. In this study we employed combined atomistic continuum multi-scale modeling to explore the effective thermal conductivity of polymer nanocomposites made of polydimethylsiloxane (PDMS) polymer as the matrix and graphene and borophene as nanofillers. PDMS is a versatile polymer due to its chemical inertia, flexibility and a wide range of properties that can be tuned during synthesis. We first conducted classical Molecular Dynamics (MD) simulations to calculate the thermal conductance at the interfaces between graphene and PDMS and between borophene and PDMS. Acquired results confirm that the interfacial thermal conductance between nanosheets and polymer increases from the single-layer to multilayered nanosheets and finally converges, in the case of graphene, to about 30 MWm⁻² K⁻¹ and, for borophene, up to 33 MWm⁻² K⁻¹. The data provided by the atomistic simulations were then used in the Finite Element Method (FEM) simulations to evaluate the effective thermal conductivity of polymer nanocomposites at the continuum level. We explored the effects of nanofiller type, volume content, geometry aspect ratio and thickness on the nanocomposite effective thermal conductivity. As a very interesting finding, we found that borophene nanosheets, despite having almost two orders of magnitude lower thermal conductivity than graphene, can yield very close enhancement in the effective thermal conductivity in comparison with graphene, particularly for low volume content and small aspect ratios and thicknesses. We conclude that, for the polymer-based nanocomposites, significant improvement in the thermal conductivity can be reached by improving the bonding between the fillers and polymer, or in other words, by enhancing the thermal conductance at the interface. By taking into account the high electrical conductivity of borophene, our results suggest borophene nanosheets as promising nanofillers to simultaneously enhance the polymers’ thermal and electrical conductivity. Full article

(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)

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10 pages, 2235 KiB

Open AccessArticle

Thermally Conductive Film Fabricated Using Perforated Graphite Sheet and UV-Curable Pressure-Sensitive Adhesive

by Hee-Jin Lee, Gayoung Lim, Eunseong Yang, Young-Seok Kim, Min-Gi Kwak and Youngmin Kim

Nanomaterials 2021, 11(1), 93; https://doi.org/10.3390/nano11010093 - 3 Jan 2021

Cited by 12 | Viewed by 3727

Abstract

Thermally conductive films play a crucial role in expanding the lifetime of electronics by dissipating concentrated heat to heatsinks. In this work, a thermally conductive film (g-TC film) was manufactured using a perforated graphite sheet (p-GS) and a UV-curable pressure-sensitive adhesive (PSA) by [...] Read more.

Thermally conductive films play a crucial role in expanding the lifetime of electronics by dissipating concentrated heat to heatsinks. In this work, a thermally conductive film (g-TC film) was manufactured using a perforated graphite sheet (p-GS) and a UV-curable pressure-sensitive adhesive (PSA) by lamination. A novel UV-curable PSA was prepared by incorporating a UV-curable abietic acid ester into a PSA composition. The UV-curable PSA became a tack-free film upon UV irradiation; thus, a flexible g-TC film with a 52-μm thickness was obtained. The defects in the g-TC film caused by air bubbles were removed by treating the p-GS with oxygen plasma. As the UV-cured PSA made a joint through the holes in the p-GS, cleavage of the graphite was not observed after 10,000 U-folding test cycles with a folding radius of 1 mm. The calculated in-plane thermal conductivity of the fabricated g-TC film was 179 W∙m⁻¹K⁻¹, which was stable after the U-folding tests. Full article

(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)

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20 pages, 3816 KiB

Open AccessArticle

Properties of Graphene-Related Materials Controlling the Thermal Conductivity of Their Polymer Nanocomposites

by Samuele Colonna, Daniele Battegazzore, Matteo Eleuteri, Rossella Arrigo and Alberto Fina

Nanomaterials 2020, 10(11), 2167; https://doi.org/10.3390/nano10112167 - 30 Oct 2020

Cited by 23 | Viewed by 3668

Abstract

Different types of graphene-related materials (GRM) are industrially available and have been exploited for thermal conductivity enhancement in polymers. These include materials with very different features, in terms of thickness, lateral size and composition, especially concerning the oxygen to carbon ratio and the [...] Read more.

Different types of graphene-related materials (GRM) are industrially available and have been exploited for thermal conductivity enhancement in polymers. These include materials with very different features, in terms of thickness, lateral size and composition, especially concerning the oxygen to carbon ratio and the possible presence of surface functionalization. Due to the variability of GRM properties, the differences in polymer nanocomposites preparation methods and the microstructures obtained, a large scatter of thermal conductivity performance is found in literature. However, detailed correlations between GRM-based nanocomposites features, including nanoplatelets thickness and size, defectiveness, composition and dispersion, with their thermal conductivity remain mostly undefined. In the present paper, the thermal conductivity of GRM-based polymer nanocomposites, prepared by melt polymerization of cyclic polybutylene terephtalate oligomers and exploiting 13 different GRM grades, was investigated. The selected GRM, covering a wide range of specific surface area, size and defectiveness, secure a sound basis for the understanding of the effect of GRM properties on the thermal conductivity of their relevant polymer nanocomposites. Indeed, the obtained thermal conductivity appeares to depend on the interplay between the above GRM feature. In particular, the combination of low GRM defectiveness and high filler percolation density was found to maximize the thermal conductivity of nanocomposites. Full article

(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)

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12 pages, 5092 KiB

Open AccessArticle

Phonon Bridge Effect in Superlattices of Thermoelectric TiNiSn/HfNiSn With Controlled Interface Intermixing

by Sven Heinz, Emigdio Chavez Angel, Maximilian Trapp, Hans-Joachim Kleebe and Gerhard Jakob

Nanomaterials 2020, 10(6), 1239; https://doi.org/10.3390/nano10061239 - 25 Jun 2020

Cited by 2 | Viewed by 3274

Abstract

The implementation of thermal barriers in thermoelectric materials improves their power conversion rates effectively. For this purpose, material boundaries are utilized and manipulated to affect phonon transmissivity. Specifically, interface intermixing and topography represents a useful but complex parameter for thermal transport modification. This [...] Read more.

The implementation of thermal barriers in thermoelectric materials improves their power conversion rates effectively. For this purpose, material boundaries are utilized and manipulated to affect phonon transmissivity. Specifically, interface intermixing and topography represents a useful but complex parameter for thermal transport modification. This study investigates epitaxial thin film multilayers, so called superlattices (SL), of TiNiSn/HfNiSn, both with pristine and purposefully deteriorated interfaces. High-resolution transmission electron microscopy and X-ray diffractometry are used to characterize their structural properties in detail. A differential 3

ω

-method probes their thermal resistivity. The thermal resistivity reaches a maximum for an intermediate interface quality and decreases again for higher boundary layer intermixing. For boundaries with the lowest interface quality, the interface thermal resistance is reduced by 23% compared to a pristine SL. While an uptake of diffuse scattering likely explains the initial deterioration of thermal transport, we propose a phonon bridge interpretation for the lowered thermal resistivity of the interfaces beyond a critical intermixing. In this picture, the locally reduced acoustic contrast of the less defined boundary acts as a mediator that promotes phonon transition. Full article

(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)

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11 pages, 1580 KiB

Open AccessArticle

Enhancement of Thermal Boundary Conductance of Metal–Polymer System

by Susanne Sandell, Jeremie Maire, Emigdio Chávez-Ángel, Clivia M. Sotomayor Torres, Helge Kristiansen, Zhiliang Zhang and Jianying He

Nanomaterials 2020, 10(4), 670; https://doi.org/10.3390/nano10040670 - 2 Apr 2020

Cited by 24 | Viewed by 5038

Abstract

In organic electronics, thermal management is a challenge, as most organic materials conduct heat poorly. As these devices become smaller, thermal transport is increasingly limited by organic–inorganic interfaces, for example that between a metal and a polymer. However, the mechanisms of heat transport [...] Read more.

In organic electronics, thermal management is a challenge, as most organic materials conduct heat poorly. As these devices become smaller, thermal transport is increasingly limited by organic–inorganic interfaces, for example that between a metal and a polymer. However, the mechanisms of heat transport at these interfaces are not well understood. In this work, we compare three types of metal–polymer interfaces. Polymethyl methacrylate (PMMA) films of different thicknesses (1–15 nm) were spin-coated on silicon substrates and covered with an 80 nm gold film either directly, or over an interface layer of 2 nm of an adhesion promoting metal—either titanium or nickel. We use the frequency-domain thermoreflectance (FDTR) technique to measure the effective thermal conductivity of the polymer film and then extract the metal–polymer thermal boundary conductance (TBC) with a thermal resistance circuit model. We found that the titanium layer increased the TBC by a factor of 2, from 59 × 10⁶ W·m⁻²·K⁻¹ to 115 × 10⁶ W·m⁻²·K⁻¹, while the nickel layer increased TBC to 139 × 10⁶ W·m⁻²·K⁻¹. These results shed light on possible strategies to improve heat transport in organic electronic systems. Full article

(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)

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22 pages, 5968 KiB

Open AccessArticle

Thermal Transport in a 2D Nanophononic Solid: Role of bi-Phasic Materials Properties on Acoustic Attenuation and Thermal Diffusivity

by Haoming Luo, Anthony Gravouil, Valentina Giordano and Anne Tanguy

Nanomaterials 2019, 9(10), 1471; https://doi.org/10.3390/nano9101471 - 16 Oct 2019

Cited by 11 | Viewed by 3056

Abstract

Nanophononic materials have recently arisen as a promising way for controlling heat transport, mirroring the results in macroscopic phononic materials for sound transmission, filtering and attenuation applications. Here we present a Finite Element numerical simulation of the transient propagation of an acoustic Wave-Packet [...] Read more.

Nanophononic materials have recently arisen as a promising way for controlling heat transport, mirroring the results in macroscopic phononic materials for sound transmission, filtering and attenuation applications. Here we present a Finite Element numerical simulation of the transient propagation of an acoustic Wave-Packet in a 2D nanophononic material, which allows to identify the effect of the nanostructuration on the acoustic attenuation length and thus on the transport regime for the vibrational energy. Assuming elastic behavior in the matrix and in the inclusions, we find that the rigidity contrast between them not only tunes the apparent attenuation length of the wave packet along its main trajectory, but gives rise to different behaviours, from weak to strong scattering, and waves pinning. As a consequence, different energy transport regimes can be identified in the three-parameter space of the excitation frequency, inclusions size and rigidity contrast, leading to the identification of a combination of parameters allowing for the shortest attenuation distance. These results could have applications both in the field of acoustic insulation, and for the control of heat transfer. Full article

(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)

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11 pages, 2508 KiB

Open AccessArticle

Thermal Conductivity of Metal-Coated Tri-Walled Carbon Nanotubes in the Presence of Vacancies-Molecular Dynamics Simulations

by Ravindra Sunil Dhumal, Dinesh Bommidi and Iman Salehinia

Nanomaterials 2019, 9(6), 809; https://doi.org/10.3390/nano9060809 - 28 May 2019

Cited by 6 | Viewed by 3241

Abstract

Variation in the thermal conductivity of a metal-coated tri-walled carbon nanotube (3WCNT), in the presence of vacancies, was studied using non-equilibrium molecular dynamics simulations. A Two-Temperature model was used to account for electronic contribution to heat transfer. For 3WCNT with 0.5% and 1% [...] Read more.

Variation in the thermal conductivity of a metal-coated tri-walled carbon nanotube (3WCNT), in the presence of vacancies, was studied using non-equilibrium molecular dynamics simulations. A Two-Temperature model was used to account for electronic contribution to heat transfer. For 3WCNT with 0.5% and 1% random vacancies, there was 76%, and 86% decrease in the thermal conductivity, respectively. In that order, an overall ~66% and ~140% increase in the thermal conductivity was recorded when 3 nm thick coating of metal (nickel) was deposited around the defective models. We have also explored the effects of tube specific and random vacancies on thermal conductivity of the 3WCNT. The changes in thermal conductivity have also been justified by the changes in vibrational density of states of the 3WCNT and the individual tubes. The results obtained can prove to be useful for countering the detrimental effects of vacancies in carbon nanotubes. Full article

(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)

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12 pages, 1908 KiB

Open AccessArticle

Modification of the Raman Spectra in Graphene-Based Nanofluids and Its Correlation with Thermal Properties

by María del Rocío Rodríguez-Laguna, Pedro Gómez-Romero, Clivia M. Sotomayor Torres and Emigdio Chavez-Angel

Nanomaterials 2019, 9(5), 804; https://doi.org/10.3390/nano9050804 - 26 May 2019

Cited by 20 | Viewed by 4927

Abstract

It is well known that by dispersing nanoparticles in a fluid, the thermal conductivity of the resulting nanofluid tends to increase with the concentration of nanoparticles. However, it is not clear what the mechanism behind this phenomenon is. Raman spectroscopy is a characterization [...] Read more.

It is well known that by dispersing nanoparticles in a fluid, the thermal conductivity of the resulting nanofluid tends to increase with the concentration of nanoparticles. However, it is not clear what the mechanism behind this phenomenon is. Raman spectroscopy is a characterization technique connecting the molecular and macroscopic world, and therefore, it can unravel the puzzling effect exerted by the nanomaterial on the fluid. In this work, we report on a comparative study on the thermal conductivity, vibrational spectra and viscosity of graphene nanofluids based on three different amides: N, N-dimethylacetamide (DMAc); N, N-dimethylformamide (DMF); and N-methyl-2-pyrrolidinone (NMP). A set of concentrations of highly stable surfactant-free graphene nanofluids developed in-house was prepared and characterized. A correlation between the modification of the vibrational spectra of the fluids and an increase in their thermal conductivity in the presence of graphene was confirmed. Furthermore, an explanation of the non-modification of the thermal conductivity in graphene-NMP nanofluids is given based on its structure and a peculiar arrangement of the fluid. Full article

(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)

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7 pages, 3053 KiB

Open AccessArticle

Applying Aluminum–Vertically-Aligned Carbon Nanotube Forests Composites for Heat Dissipation

by Yan-Rui Li, Chih-Chung Su and Shuo-Hung Chang

Nanomaterials 2019, 9(5), 758; https://doi.org/10.3390/nano9050758 - 17 May 2019

Cited by 10 | Viewed by 3796

Abstract

Vertically-aligned carbon nanotube forests (VACNTs) with excellent axial heat dissipation properties were formed on aluminum foil to dissipate heat. In addition, the heat dissipation efficiency of aluminum–VACNTs composites in this work was compared with that of commercially available mainstream thermal sheets under the [...] Read more.

Vertically-aligned carbon nanotube forests (VACNTs) with excellent axial heat dissipation properties were formed on aluminum foil to dissipate heat. In addition, the heat dissipation efficiency of aluminum–VACNTs composites in this work was compared with that of commercially available mainstream thermal sheets under the same natural cooling conditions. Chemical vapor deposition (CVD) was employed as a synthesis method using a three-segment high-temperature furnace. Subsequently, the temperature changes in a heating body with the aluminum–VACNTs composites was measured over time subject to natural cooling. In addition, the performance was compared with copper and pyrolytic graphite sheets. The experimental results revealed that the heat dissipation efficiency of the flexible aluminum–VACNTs composites was higher than that of clean aluminum foil, a copper sheet, and a pyrolytic graphite sheet by up to 56%, 40%, and 20%, respectively. Moreover, this work also verified the height of the carbon nanotube (CNT) did not influence the heat dissipation efficiency, indicating that the time cost of synthesis could be reduced. Full article

(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)

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15 pages, 3119 KiB

Open AccessArticle

Short-Chain Modified SiO₂ with High Absorption of Organic PCM for Thermal Protection

by Fuxian Wang, Shiyuan Gao, Jiachuan Pan, Xiaomei Li and Jian Liu

Nanomaterials 2019, 9(4), 657; https://doi.org/10.3390/nano9040657 - 25 Apr 2019

Cited by 12 | Viewed by 4430

Abstract

Organic phase change materials (PCMs) have great potential in thermal protection applications but they suffer from high volumetric change and easy leakage, which require “leak-proof” packaging materials with low thermal conductivity. Herein, we successfully modify SiO₂ through a simple 2-step method consisting [...] Read more.

Organic phase change materials (PCMs) have great potential in thermal protection applications but they suffer from high volumetric change and easy leakage, which require “leak-proof” packaging materials with low thermal conductivity. Herein, we successfully modify SiO₂ through a simple 2-step method consisting of n-hexane activation followed by short-chain alkane silanization. The modified SiO₂ (M-SiO₂) exhibits superior hydrophobic property while maintaining the intrinsic high porosity of SiO₂. The surface modification significantly improves the absorption rate of RT60 in SiO₂ by 38%. The M-SiO₂/RT60 composite shows high latent heat of 180 J·g⁻¹, low thermal conductivity of 0.178 W·m⁻¹·K⁻¹, and great heat capacity behavior in a high-power thermal circuit with low penetrated heating flow. Our results provide a simple approach for preparing hydrophobic SiO₂ with high absorption of organic PCM for thermal protection applications. Full article

(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)

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10 pages, 2004 KiB

Open AccessArticle

Impact of the Regularization Parameter in the Mean Free Path Reconstruction Method: Nanoscale Heat Transport and Beyond

by Miguel-Ángel Sanchez-Martinez, Francesc Alzina, Juan Oyarzo, Clivia M. Sotomayor Torres and Emigdio Chavez-Angel

Nanomaterials 2019, 9(3), 414; https://doi.org/10.3390/nano9030414 - 11 Mar 2019

Cited by 7 | Viewed by 3667

Abstract

The understanding of the mean free path (MFP) distribution of the energy carriers in materials (e.g., electrons, phonons, magnons, etc.) provides a key physical insight into their transport properties. In this context, MFP spectroscopy has become an important tool to describe the contribution [...] Read more.

The understanding of the mean free path (MFP) distribution of the energy carriers in materials (e.g., electrons, phonons, magnons, etc.) provides a key physical insight into their transport properties. In this context, MFP spectroscopy has become an important tool to describe the contribution of carriers with different MFP to the total transport phenomenon. In this work, we revise the MFP reconstruction technique and present a study on the impact of the regularization parameter on the MFP distribution of the energy carriers. By using the L-curve criterion, we calculate the optimal mathematical value of the regularization parameter. The effect of the change from the optimal value in the MFP distribution is analyzed in three case studies of heat transport by phonons. These results demonstrate that the choice of the regularization parameter has a large impact on the physical information obtained from the reconstructed accumulation function, and thus cannot be chosen arbitrarily. The approach can be applied to various transport phenomena at the nanoscale involving carriers of different physical nature and behavior. Full article

(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)

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13 pages, 4895 KiB

Open AccessArticle

Enhancing Thermal Conductivity and Photo-Driven Thermal Energy Charging/Discharging Rate of Annealed CMK-3 Based Phase Change Material

by Yanfeng Chen, Cuiyin Liu, Yue Situ, Jian Liu and Hong Huang

Nanomaterials 2019, 9(3), 364; https://doi.org/10.3390/nano9030364 - 5 Mar 2019

Cited by 10 | Viewed by 3513

Abstract

In this work, the CMK-3 is successfully prepared with SBA-15 as the template and first annealed to 2000 °C to improve thermal conductivity. The annealed CMK-3 has a thermal conductivity of 6.981 W m⁻¹ K⁻¹ higher than un-annealed CMK-3. The annealed [...] Read more.

In this work, the CMK-3 is successfully prepared with SBA-15 as the template and first annealed to 2000 °C to improve thermal conductivity. The annealed CMK-3 has a thermal conductivity of 6.981 W m⁻¹ K⁻¹ higher than un-annealed CMK-3. The annealed CMK-3 is used to encapsulate the RT44HC, and RT44HC/annealed CMK-3 has 10-fold of thermal conductivity and enhanced thermal stability than RT44HC. The RT44HC/annealed CMK-3 has a large melting enthalpy of 177.8 J g⁻¹ and good thermal stability. The RT44HC/annealed CMK-3 has optical absorptive coefficient of visible range of solar spectrum, which identify seven-fold higher than RT44HC. The RT44HC/annealed CMK-3 has great photo-thermal performance, and the photo-driven energy charging and discharging rate of RT44HC/annealed CMK-3 is almost 30-fold larger than the RT44HC. The results show that the annealed CMK-3 is a great mesoporous carbon nanomaterial for phase change materials and the annealed CMK-3 based phase change material has great potential in solar thermal utilizations such as solar water heating system and solar heating building systems. Full article

(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)

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Review

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33 pages, 4915 KiB

Open AccessReview

Heat Transport Control and Thermal Characterization of Low-Dimensional Materials: A Review

by Alexandros El Sachat, Francesc Alzina, Clivia M. Sotomayor Torres and Emigdio Chavez-Angel

Nanomaterials 2021, 11(1), 175; https://doi.org/10.3390/nano11010175 - 13 Jan 2021

Cited by 28 | Viewed by 5589

Abstract

Heat dissipation and thermal management are central challenges in various areas of science and technology and are critical issues for the majority of nanoelectronic devices. In this review, we focus on experimental advances in thermal characterization and phonon engineering that have drastically increased [...] Read more.

Heat dissipation and thermal management are central challenges in various areas of science and technology and are critical issues for the majority of nanoelectronic devices. In this review, we focus on experimental advances in thermal characterization and phonon engineering that have drastically increased the understanding of heat transport and demonstrated efficient ways to control heat propagation in nanomaterials. We summarize the latest device-relevant methodologies of phonon engineering in semiconductor nanostructures and 2D materials, including graphene and transition metal dichalcogenides. Then, we review recent advances in thermal characterization techniques, and discuss their main challenges and limitations. Full article

(This article belongs to the Special Issue Thermal Transport in Nanostructures and Nanomaterials)

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