scholarly journals Electrical and Thermal Conductivity of Epoxy-Carbon Filler Composites Processed by Calendaring

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1522 ◽  
Author(s):  
Andrea Caradonna ◽  
Claudio Badini ◽  
Elisa Padovano ◽  
Mario Pietroluongo
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Hybrid Composites ◽  
Synergetic Effect ◽  
Multiwall Carbon Nanotubes ◽  
Carbon Filler ◽  
Aspect Ratios ◽  
Roll Mill ◽  
Mill Equipment ◽  
Noticeable Improvement

Electrical and thermal conductivity of composites which contain carbon-based fillers in an epoxy matrix were investigated. The fillers were dispersed in the liquid matrix by using three roll mill equipment. The filler/matrix mixture was cast in a mold and then cured, thus obtaining composite specimens. Multiwall carbon nanotubes, graphene-like nanoplatelets, and graphite were used as fillers and their effect on conductivity was investigated. Electrical and thermal conductivity were measured at different filler loads. It was found that the formation of percolation paths greatly enhanced electrical conductivity, although they were not so effective in improving thermal conductivity. The behavior of composites containing each single filler was compared with that of hybrid composites containing combinations of two different fillers. Results show that fillers with different aspect ratios displayed a synergetic effect resulting in a noticeable improvement of electrical conductivity. However, only a small effect on thermal conductivity was observed.

Improving Electrical Conductivity and Thermal Properties of Polymers by the Addition of Carbon Nanotubes as Fillers

MRS Bulletin ◽  
2007 ◽  
Vol 32 (4) ◽  
pp. 348-353 ◽  
Author(s):  
Karen I. Winey ◽  
Takashi Kashiwagi ◽  
Minfang Mu
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Polymer Composites ◽  
Structure Property ◽  
Structure Property Relationships ◽  
Aspect Ratios ◽  
Polymer Properties ◽  
The Matrix ◽  
Conductivity Of Nanotubes

AbstractThe remarkable electrical and thermal conductivities of isolated carbon nanotubes have spurred worldwide interest in using nanotubes to enhance polymer properties. Electrical conductivity in nanotube/polymer composites is well described by percolation, where the presence of an interconnected nanotube network corresponds to a dramatic increase in electrical conductivity ranging from 10−5 S/cm to 1 S/cm. Given the high aspect ratios and small diameters of carbon nanotubes, percolation thresholds are often reported below 1 wt% although nanotube dispersion and alignment strongly influence this value. Increases in thermal conductivity are modest (∼3 times) because the inter facial thermal re sis tance between nanotubes is considerable and the thermal conductivity of nanotubes is only 104 greater than the polymer, which forces the matrix to contribute more toward the composite thermal conductivity, as compared to the contrast in electrical conductivity, >1014. The nanotube network is also valuable for improving flame-retardant efficiency by producing a protective nanotube residue. In this ar ticle, we highlight published research results that elucidate fundamental structure–property relationships pertaining to electrical, thermal, and/or flammability properties in numerous nanotube-containing polymer composites, so that specific applications can be targeted for future commercial success.

scholarly journals Direction Dependent Electrical Conductivity of Polymer/Carbon Filler Composites

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 591 ◽  
Author(s):  
Karina Kunz ◽  
Beate Krause ◽  
Bernd Kretzschmar ◽  
Levente Juhasz ◽  
Oliver Kobsch ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Multiwalled Carbon Nanotubes ◽  
Vinylidene Fluoride ◽  
Extrusion Direction ◽  
Filler Concentration ◽  
Multiwalled Carbon ◽  
Carbon Filler ◽  
Aspect Ratios ◽  
Extruded Films

The method of measuring electrical volume resistivity in different directions was applied to characterize the filler orientation in melt mixed polymer composites containing different carbon fillers. For this purpose, various kinds of fillers with different geometries and aspect ratios were selected, namely carbon black (CB), graphite (G) and expanded graphite (EG), branched multiwalled carbon nanotubes (b-MWCNTs), non-branched multiwalled carbon nanotubes (MWCNTs), and single-walled carbon nanotubes (SWCNTs). As it is well known that the shaping process also plays an important role in the achieved electrical properties, this study compares results for compression molded plates with random filler orientations in the plane as well as extruded films, which have, moreover, conductivity differences between extrusion direction and perpendicular to the plane. Additionally, the polymer matrix type (poly (vinylidene fluoride) (PVDF), acrylonitrile butadiene styrene (ABS), polyamide 6 (PA6)) and filler concentration were varied. For the electrical measurements, a device able to measure the electrical conductivity in two directions was developed and constructed. The filler orientation was analyzed using the ratio σin/th calculated as in-plane conductivity σin-plane (σin) divided by through-plane conductivity σthrough-plane (σth). The ratio σin/th is expected to increase with more pronounced filler orientation in the processing direction. In the extruded films, alignment within the plane was assigned by dividing the in-plane conductivity in the extrusion direction (x) by the in-plane conductivity perpendicular to the extrusion direction (y). The conductivity ratios depend on filler type and concentration and are higher the higher the filler aspect ratio and the closer the filler content is to the percolation concentration.

scholarly journals PLA/Graphene/MWCNT Composites with Improved Electrical and Thermal Properties Suitable for FDM 3D Printing Applications

2019 ◽  
Vol 9 (6) ◽  
pp. 1209 ◽  
Author(s):  
Evgeni Ivanov ◽  
Rumiana Kotsilkova ◽  
Hesheng Xia ◽  
Yinghong Chen ◽  
Ricardo Donato ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electrical Conductivity ◽  
Thermal Properties ◽  
3D Printing ◽  
Filler Content ◽  
Hybrid Composites ◽  
Filler Concentration ◽  
Fused Deposition ◽  
Aspect Ratios ◽  
Uniform Dispersion

In this study, the structure, electrical and thermal properties of ten polymer compositions based on polylactic acid (PLA), low-cost industrial graphene nanoplates (GNP) and multi-walled carbon nanotubes (MWCNT) in mono-filler PLA/MWCNT and PLA/GNP systems with 0–6 wt.% filler content were investigated. Filler dispersion was further improved by combining these two carbon nanofillers with different geometric shapes and aspect ratios in hybrid bi-filler nanocomposites. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy exhibited uniform dispersion of nanoparticles in a polymer matrix. The obtained results have shown that for the mono-filler systems with MWCNT or GNP, the electrical conductivity increased with decades. Moreover, a small synergistic effect was observed in the GNP/MWCNT/PLA bi-filler hybrid composites when combining GNP and CNT at a ratio of 3% GNP/3% CNT and 1.5% GNP:4.5% CNT, showing higher electrical conductivity with respect to the systems incorporating individual CNTs and GNPs at the same overall filler concentration. This improvement was attributed to the interaction between CNTs and GNPs limiting GNP aggregation and bridging adjacent graphene platelets thus, forming a more efficient network. Thermal conductivity increases with higher filler content; this effect was more pronounced for the mono-filler composites based on PLA and GNP due to the ability of graphene to better transfer the heat. Morphological analysis carried out by electron microscopy (SEM, TEM) and Raman indicated that the nanocomposites present smaller and more homogeneous filler aggregates. The well-dispersed nanofillers also lead to a microstructure which is able to better enhance the electron and heat transfer and maximize the electrical and thermal properties. The obtained composites are suitable for the production of a multifunctional filament with improved electrical and thermal properties for different fused deposition modelling (FDM) 3D printing applications and also present a low production cost, which could potentially increase the competitiveness of this promising market niche.

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

2021 ◽  
Author(s):  
Alessandro Di Pierro ◽  
Bohayra Mortazavi ◽  
Hamidreza Noori ◽  
Timon Rabczuk ◽  
Alberto Fina
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Effective Thermal Conductivity ◽  
Volume Content ◽  
Thermal Conductance ◽  
Single Layer ◽  
Interfacial Thermal Conductance ◽  
Aspect Ratios ◽  
The Matrix ◽  
Dynamics Simulations

Graphene and borophene are highly attractive two-dimensional materials with outstanding physical properties. In this study we employed a combined atomistic continuum multiscale modeling to explore the effective thermal conductivity of polymers nanocomposites made of PDMS polymer as the matrix and graphene and borophene as nanofillers. We first conduct classical molecular dynamics simulations to investigate the interfacial thermal conductance between graphene/PDMS and borophene/PDMS interfaces. Acquired results confirm that the interfacial thermal conductance between nanosheets and polymer increases from the single-layer to multilayered nanosheets and finally converges. The data provided by the atomistic simulations were then used in the finite element method simulations to evaluate the effective thermal conductivity of polymer nanocomposites at continuum level. We explore the effects of nanofillers type, their volume content, geometry aspect ratio and thickness on the nanocomposites effective thermal conductivity. As a very interesting finding, we show that borophene nanosheets, despite 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 another word 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.

scholarly journals N-Type Thermoelectric Textile Fabrics Based on Vapor Grown Carbon Nanofibers

2020 ◽  
Vol 2 (1) ◽  
pp. 10
Author(s):  
S. Machado ◽  
E. M. F. Vieira ◽  
A. M. Rocha ◽  
A. J. Paleo
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Carbon Nanofibers ◽  
Room Temperature ◽  
Thermoelectric Module ◽  
Multiwall Carbon Nanotubes ◽  
Chemical Vapor ◽  
Textile Fabrics ◽  
Wide Range ◽  
P Type

Thermoelectric (TE) devices that convert a heat gradient directly into electricity are considered as a clean technology for energy harvesting. Both hole-transporting (p-type) and electron-transporting (n-type) materials are required in order to fabricate a thermoelectric module. Carbon nanotube (CNT)-based textile fabrics are relevant in this context for the production of wearable TE modules due to the combination of the high electrical conductivity and thermopower (Seebeck coefficient) from the CNT and the low thermal conductivity and flexibility provided by the textile fabric [1]. Nevertheless, most as-produced CNTs are p-type materials due to their inherent oxygen doping, and therefore the production of air- and thermally stable n-type CNT-based textile fabrics remains a challenge nowadays [2]. On the other hand, vapor-grown carbon nanofibers (VGCNF), produced by chemical vapor deposition (CVD), have similar structures to multiwall carbon nanotubes (MWCNT), which make them valuable for electronic applications. For instance, by adjusting process variables during their CVD and post-growth heat treatment, VGCNF can be tailored to have a wide range of thermal conductivity and electrical conductivity at room temperature. In particular, the unexpected n-type character at room temperature that they supply to dip-coated cotton fabrics will be the issue of this presentation [3].

scholarly journals Dielectric Relaxation in the Hybrid Epoxy/MWCNT/MnFe2O4 Composites

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 697 ◽  
Author(s):  
Darya Meisak ◽  
Jan Macutkevic ◽  
Artyom Plyushch ◽  
Polina Kuzhir ◽  
Algirdas Selskis ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Percolation Threshold ◽  
Dielectric Relaxation ◽  
Electrical Transport ◽  
Hybrid Composites ◽  
Relaxation Times ◽  
Synergetic Effect ◽  
Dielectric Relaxation Spectroscopy ◽  
Low Frequencies

The electrical properties of epoxy/MWCNT (multi-walled carbon nanotubes)/MnFe2O4 hybrid composites loaded with MWCNTs (below, 0.09 vol.%, and above, 0.58 vol.%, percolation threshold) and varying concentrations of MnFe2O4 up to 10 vol.% were studied in a wide frequency range (20 Hz–40 GHz) at different temperatures (20 K–500 K). At low frequencies, the dielectric permittivity and the electrical conductivity of composites with fixed amounts of MWCNT are strongly dependent on MnFe2O4 content. For MWCNT concentrations above the percolation threshold (i.e., 0.58 vol.%), the electrical conductivity highly decreases with the increase of the MnFe2O4 fraction. In contrast, for the epoxy/MWCNT just below the onset of electrical conductivity (0.09 vol.% of MWCNTs), there exists an optimal concentration of MnFe2O4 inclusions (i.e., 0.025 vol.%), leading to a dramatic increase of the electrical conductivity by three orders of magnitude. The electrical transport in composites is mainly governed by electron tunneling at lower temperatures (below 200 K), and it is highly impacted by the matrix conductivity at higher temperatures (above 400 K). The electrical properties were discussed in terms of the Maxwell–Wagner relaxation and distributions of relaxation times. A non-invasive platform based on dielectric relaxation spectroscopy was proposed for enhancing the synergetic effect coursed by using multiple nanoinclusions in polymer composites just below the percolation threshold.

Enhancement of electrical conductivity of epoxy using graphene and determination of their thermo-mechanical properties

2017 ◽  
Vol 37 (2) ◽  
pp. 118-133 ◽  
Author(s):  
Kazi A Imran ◽  
Kunigal N Shivakumar
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Average Diameter ◽  
Processing Technique ◽  
Epoxy System ◽  
Mechanical Mixing ◽  
Weight Percentage ◽  
Roll Mill

A three-roll mill processing technique was used to disperse graphene nanoplatelets into epon 828 epoxy system. As a first step of this research, processing of graphene/epoxy nanocomposites was explored with different weight percentages of graphene. After establishing an optimal and repeatable process to achieve good electrical properties, the materials were tested for thermal conductivity and mechanical properties. The xGnP-25 graphene nanoplatelet supplied by XG Science Inc. was used; the graphene average diameter was 25 μm and thickness was 6–10 nm. Mechanical mixing, sonication and three-roll mill dispersion techniques were investigated to disperse graphene in epon 828 epoxy. The study showed that the three-roll dispersion is effective, repeatable and potentially scalable to disperse graphene into epoxy to increase the electrical conductivity. The weight percentage of graphene used ranged from 0.5 to 5.0. Percolation threshold of graphene was found to be 1.0 wt%. Through-the-thickness or volume electrical conductivity increased by nine log cycles, thermal conductivity doubled and fracture toughness increased by one-third for 1.0 wt% addition of graphene to epon 828. However, the mechanical properties remained almost unchanged.

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

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1252
Author(s):  
Alessandro Di Pierro ◽  
Bohayra Mortazavi ◽  
Hamidreza Noori ◽  
Timon Rabczuk ◽  
Alberto Fina
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Effective Thermal Conductivity ◽  
Polymer Nanocomposites ◽  
Volume Content ◽  
Thermal Conductance ◽  
Single Layer ◽  
Md Simulations ◽  
Aspect Ratios ◽  
Wide Range

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.

COPPER ALLOY No. 815

Alloy Digest ◽  
1977 ◽  
Vol 26 (5) ◽  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Corrosion Resistance ◽  
Physical Properties ◽  
Copper Alloy ◽  
Heat Treating ◽  
Chromium Alloy ◽  
High Electrical Conductivity ◽  
Medium Hardness ◽  
Hardened Condition

Abstract Copper Alloy No. 815 is an age-hardenable cast copper-chromium alloy. It is characterized by high electrical and thermal conductivities combined with medium hardness and strength in the age-hardened condition. It is used for components requiring high electrical conductivity or high thermal conductivity. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as casting, heat treating, machining, and joining. Filing Code: Cu-332. Producer or source: Copper alloy foundries.

Influence of filler hybridization on thermomechanical properties of hemp/silver epoxy composite

2020 ◽  
pp. 096739112097811
Author(s):  
Munjula Siva Kumar ◽  
Santosh Kumar ◽  
Krushna Gouda ◽  
Sumit Bhowmik
Keyword(s):  
Thermal Conductivity ◽  
Silver Nanoparticles ◽  
Epoxy Polymer ◽  
Hybrid Composites ◽  
Conductive Filler ◽  
Weight Fraction ◽  
Mechanical Analysis ◽  
Thermomechanical Properties ◽  
Material Behavior ◽  
Good Crystallinity

The polymer composite material’s thermomechanical properties with fiber as reinforcement material have been widely studied in the last few decades. However, these fiber-based polymer composites exhibit problems such as fiber orientation, delamination, fiber defect along the length and bonding are the matter of serious concern in order to improve the thermomechanical properties and obtain isotropic material behavior. In the present investigation filler-based composite material is developed using natural hemp and high thermal conductive silver nanoparticles (SNP) and combination of dual fillers in neat epoxy polymer to investigate the synergetic influence. Among various organic natural fillers hemp filler depicts good crystallinity characteristics, so selected as a biocompatible filler along with SNP conductive filler. For enhancing their thermal conductivity and mechanical properties, hybridization of hemp filler along with silver nanoparticles are conducted. The composites samples are prepared with three different combinations such as sole SNP, sole hemp and hybrid (SNP and hemp) are prepared to understand their solo and hybrid combination. From results it is examined that, chemical treated hemp filler has to maximized its relative properties and showed, 40% weight % of silver nanoparticles composites have highest thermal conductivity 1.00 W/mK followed with hemp filler 0.55 W/mK and hybrid 0.76 W/mK composites at 7.5% of weight fraction and 47.5% of weight fraction respectively. The highest tensile strength is obtained for SNP composite 32.03 MPa and highest young’s modulus is obtained for hybrid composites. Dynamic mechanical analysis is conducted to find their respective storage modulus and glass transition temperature and that, the recorded maximum for SNP composites with 3.23 GPa and 90°C respectively. Scanning electron microscopy examinations clearly illustrated that formation of thermal conductivity chain is significant with nano and micro fillers incorporation.

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