Enhanced through-plane thermal conductivity of boron nitride/epoxy composites
TL;DR: In this paper, a facile strategy was reported to fabricate vertically oriented and densely packed hexagonal boron nitride (h-BN)/epoxy (EP) composites via vacuum filtration followed by slicing up.
Abstract: A facile strategy was reported to fabricate vertically oriented and densely packed hexagonal boron nitride (h-BN)/epoxy (EP) composites via vacuum filtration followed by slicing up. This route is simple and high-efficient without special treatment and/or chemical modification. A high through-plane thermal conductivity of 9 W/m K was obtained at a h-BN loading of 44 vol% in the composites. Laser flash thermal analyzer (LFA) and thermogravimetric analysis (TGA) results indicated that the through-plane thermal conductivity of the composites increased with the fraction of the fillers. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) tests indicated that h-BN microplatelets were mainly vertically oriented in the composites. In addition, as-made composites showed good mechanical strength. Therefore, it has great potential as thermal interface materials, which is very important in the thermal management of electronics, especially in electronic packages where electrical insulation is required.
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TL;DR: In this article, a hexagonal boron nitride platelet and aluminum nitride (AlN) particles are used as hybrid fillers to improve the thermal conductivity of polytetrafluoroethylene (PTFE).
Abstract: Due to the strong horizontal orientation tendency of hexagonal boron nitride (hBN) platelets, hBN/polymer composites generally exhibit high in-plane thermal conductivity while low through-plane thermal conductivity. In this work, hBN platelets and aluminum nitride (AlN) particles are used as hybrid fillers to improve the thermal conductivity of polytetrafluoroethylene (PTFE). AlN particles effectively disrupt the alignment of hBN platelets along the lateral direction during the compression processing, which can be proved by the results of SEM and XRD. At 30 vol% filler loading, a high through-plane thermal conductivity as 1.04 W/mK is achieved, which is 3.8 times that of neat PTFE. The significantly increased thermal conductivity is related not only to the synergetic effect of hybrid fillers, but also the reduced in-plane orientation degree of hBN. Hashin-Shtrikman model is also used to quantify the filler connectivity within polymer matrix. The result suggests that filler morphology and orientation influence the filler connectivity and both control the effective thermal conductivity of composites.
180 citations
TL;DR: In this paper, a fabrication of epoxy resin/oriented BN composites via a facile hot-pressing strategy is reported, which renders the prepared composites an elevated thermal conductivity up to 6.09
170 citations
TL;DR: In this paper, vertically aligned and interconnected SiC nanowire (SiCNW) networks are used as efficient fillers for polymer composites, achieving significantly enhanced thermal conductivity, compared to the pure matrix.
Abstract: Efficient heat removal via thermal management materials has become one of the most critical challenges in the development of modern microelectronic devices. However, previously reported polymer composites exhibit limited enhancement of thermal conductivity, even when highly loaded with thermally conductive fillers, because of the lack of efficient heat transfer pathways. Herein, we report vertically aligned and interconnected SiC nanowire (SiCNW) networks as efficient fillers for polymer composites, achieving significantly enhanced thermal conductivity. The SiCNW networks are produced by freeze-casting nanowire aqueous suspensions followed by thermal sintering to consolidate the nanowire junctions, exhibiting a hierarchical architecture in which honeycomb-like SiCNW layers are aligned. The composite obtained by infiltrating SiCNW networks with epoxy resin, at a relatively low SiCNW loading of 2.17 vol %, represents a high through-plane thermal conductivity (1.67 W m–1 K–1) compared to the pure matrix, whi...
170 citations
Journal Article•
TL;DR: In this article, Boron nitride nanotubes (BNNT)/polyvinyl alcohol (PVA) composite fibers were fabricated via electrospinning so that all BNNTs became aligned in the fiber casting direction.
Abstract: Boron nitride nanotube (BNNT)/polyvinyl alcohol (PVA) composite fibers (<5 vol % BNNTs) were fabricated via electrospinning so that all BNNTs became aligned in the fiber casting direction. A several-fibers-thick ensemble of parallel-arranged contacting fibers made a single polymer sheet. Numerous sheets were then stacked in different ways with respect to the BNNT orientation (all fibers in adjacent sheets were either parallel or alternately rotated 90°) to make multilayer films that were finally hot-pressed. Various BNNT textures were reflected by the corresponding differences in the measured thermal conductivities of the resultant films due to anisotropy of thermal transport in the nanotubes. The highest values (0.54 W/mK) were obtained along the long axes of aligned BNNTs. Somewhat lower values (0.38 W/mK) were documented in films with alternately stacked fibers/tubes. The theoretical thermal conductivity values were estimated using the Nielsen’s model. These show good match with the experimental data. ...
162 citations
TL;DR: In this article, three-dimensional (3D) boron nitride nanosheets (BNNSss) wrapped melamine foams were first fabricated by repeated layer-by-layer (L-B-L) assembly using melamine skeleton as substrate and BNNss as building blocks.
157 citations
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TL;DR: This review gives an introduction to the rich BN nanotube/nanosheet field, including the latest achievements in the synthesis, structural analyses, and property evaluations, and presents the purpose and significance of this direction in the light of the general nanotubes/ nanosheet developments.
Abstract: Hexagonal boron nitride (h-BN) is a layered material with a graphite-like structure in which planar networks of BN hexagons are regularly stacked. As the structural analogue of a carbon nanotube (CNT), a BN nanotube (BNNT) was first predicted in 1994; since then, it has become one of the most intriguing non-carbon nanotubes. Compared with metallic or semiconducting CNTs, a BNNT is an electrical insulator with a band gap of ca. 5 eV, basically independent of tube geometry. In addition, BNNTs possess a high chemical stability, excellent mechanical properties, and high thermal conductivity. The same advantages are likely applicable to a graphene analogue-a monatomic layer of a hexagonal BN. Such unique properties make BN nanotubes and nanosheets a promising nanomaterial in a variety of potential fields such as optoelectronic nanodevices, functional composites, hydrogen accumulators, electrically insulating substrates perfectly matching the CNT, and graphene lattices. This review gives an introduction to the rich BN nanotube/nanosheet field, including the latest achievements in the synthesis, structural analyses, and property evaluations, and presents the purpose and significance of this direction in the light of the general nanotube/nanosheet developments.
1,990 citations
TL;DR: In this paper, a number of cubic crystals, two-dimensional layered materials, nanostructure networks and composites, molecular layers and surface functionalization, and aligned polymer structures are examined for potential applications as heat spreading layers and substrates, thermal interface materials, and underfill materials in future-generation electronics.
1,269 citations
TL;DR: In this article, the effective thermal conductivity, elastic modulus, and coefficient of thermal expansion of epoxy resins filled with ceramic fillers like silica, alumina, and aluminum nitride were determined.
Abstract: The effective thermal conductivity, elastic modulus, and coefficient of thermal expansion of epoxy resins filled with ceramic fillers like silica, alumina, and aluminum nitride were determined. The data obtained was compared with theoretical and semitheoretical equations in the literature that are used to predict the properties of two phase mixtures. It was found that Agari's model provided a good estimate of the composite thermal conductivity. The Hashin-Shtrikman lower bound for composite modulus fits the modulus data fairly well at low concentrations of the filler. Also, it was found that the coefficients of thermal expansion of the filled composites lie in between Schapery's upper and lower bounds. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3396–3403, 1999
646 citations
TL;DR: It is shown that micrometer-sized reinforcing particles coated with minimal concentrations of superparamagnetic nanoparticles can be controlled by using ultralow magnetic fields to produce synthetic composites with tuned three-dimensional orientation and distribution of reinforcements.
Abstract: The orientation and distribution of reinforcing particles in artificial composites are key to enable effective reinforcement of the material in mechanically loaded directions, but remain poor if compared to the distinctive architectures present in natural structural composites such as teeth, bone, and seashells. We show that micrometer-sized reinforcing particles coated with minimal concentrations of superparamagnetic nanoparticles (0.01 to 1 volume percent) can be controlled by using ultralow magnetic fields (1 to 10 milliteslas) to produce synthetic composites with tuned three-dimensional orientation and distribution of reinforcements. A variety of structures can be achieved with this simple method, leading to composites with tailored local reinforcement, wear resistance, and shape memory effects.
567 citations
TL;DR: In this article, an ideal dielectric thermally conductive epoxy nanocomposite is successfully fabricated using polyhedral oligosilsesquioxane (POSS) functionalized boron nitride nanotubes (BNNTs) as fillers.
Abstract: Dielectric polymer composites with high thermal conductivity are very promising for microelectronic packaging and thermal management application in new energy systems such as solar cells and light emitting diodes (LEDs). However, a well-known paradox is that conventional composites with high thermal conductivity usually suffer from the high dielectric constant and high dielectric loss, while on the other hand, composite materials with excellent dielectric properties usually possess low thermal conductivity. In this work, an ideal dielectric thermally conductive epoxy nanocomposite is successfully fabricated using polyhedral oligosilsesquioxane (POSS) functionalized boron nitride nanotubes (BNNTs) as fillers. The nanocomposites with 30 wt% fraction of POSS modified BNNTs exhibit much lower dielectric constant, dielectric loss tangent, and coefficient of thermal expansion in comparison with the pure epoxy resin. As an example, below 100 Hz, the dielectric loss of the nanocomposites with 20 and 30 wt% BNNTs is reduced by one order of magnitude in comparison with the pure epoxy resin. Moreover, the nanocomposites show a dramatic thermal conductivity enhancement of 1360% in comparison with the pristine epoxy resin at a BNNT loading fraction of 30 wt%. The merits of the designed composites are suggested to originate from the excellent intrinsic properties of embedded BNNTs, effective surface modification by POSS molecules, and carefully developed composite preparation methods.
519 citations