Highly Multifunctional and Thermoconductive Performances of Densely Filled Boron Nitride Nanosheets/Epoxy Resin Bulk Composites

Abstract

In the development of hexagonal boron nitride (h-BN)-based polymeric composites with high thermal conductivity, it is always challenging to achieve a dense filling of h-BN fillers to form a desired high-density thermal transfer network. Here, a series of boron nitride nanosheets (BNNSs)/epoxy resin (EP) bulk composites filled with ultrahigh BNNSs content (65−95 wt %) is successfully constructed through a well-designed mechanical-balling prereaction combined with a general pressure molding method. By means of this method, the highly filled BNNSs fillers are uniformly dispersed and strongly bonded with EP within the composites. As a result, the densely BNNSs-filled composites can exhibit multiple performances. They have excellent mechanical properties, and their maximum compression strength is 30−97 MPa. For a BNNSs/EP composite with filling ultrahigh BNNSs fraction up to 90 wt %, its highly in-plane thermal conductivities (TC) are 6.7 ± 0.1 W m −1 K −1 (at 25 °C) to 8.7 ± 0.2 W m −1 K −1 (200 °C), respectively. In addition, the minimum coefficient of thermal expansion of BNNSs/EP composites is 4.5 ± 1.3 ppm/°C (only ∼4% of that of the neat EP), while their dielectric constants are basically located between 3−4 along with their dielectric loss tangent values exceptionally <0.3 in the ultrahigh frequency range of 12−40 GHz. Additionally, these BNNSs/EP composites exhibit remarkable cycle stability in heat transfer during heating and cooling processes because of their structural robustness. Thus, this type of densely BNNSs-filled BNNSs/ EP composite would have great potential for further practical thermal management fields.

Anchoring modified polystyrene to boron nitride nanosheets as highly thermal conductive composites for heat dissipation

“…The mPS nanoparticles are successfully anchored and immobilized on the BN-OH nanosheets, implying the existence of some interactions including hydrogen bonding interaction πÀπ stacking and van der Waals interactions. [34,40] In particular, when the amount of BN-OH@mPS is 6 wt%, mPS is uniformly distributed on the BN-OH as observed from the SEM image in Figure 3C,D, which is also confirmed by B and C elemental mapping images (Figure 3E,F). It can be found that BN-OH nanosheets are linked to each other, and the BN-OH nanosheets were tightly wrapped by PS nanoparticles forming core-shell structures.…”

“…[32] Compared to the pristine BN, the peak position of the (002) plane of BN-OH has a left shift from 26.90 to 26.64 , which is attributed to the increase of interplanar distance during exfoliation. [34] Besides, the full width at half maxima (FWHM) of the (002) peak of BN-OH is larger than that of BN, revealing that the thickness of the layer becomes thinner. [35] The typical exfoliation and functionalization schematics are displayed in Figure 2G.…”

“…[ 44 ] In contrast, BN‐OH@mPS possesses the characteristic diffraction peaks of BN‐OH and mPS, and their peak positions do not change significantly, thus suggesting that the crystal structures of BN‐OH and mPS are not influenced during the formation of the composite. [ 34 ] Furthermore, the peak intensity of BN‐OH markedly decreased, which could be attributed to the amorphous PS coated on the surface of BN. [ 45 ]…”

A green and facile method to fabricate multifunctional and highly thermally conductive boron nitride‐based polymer composites

“…With the temperature increasing, the thermal conductivities of the composites in both the inplane and out-of-plane directions were reduced, but remained high (in-plane: over 20 W/mK; out-of-plane: over 1.7 W/mK) until 150 C. This shows that the HPF-BNNSs/PVA composites can maintain an excellent heatdissipating function under high temperatures. Compared with other BN-based polymer composites in previous studies (Figure 4f), [37][38][39][40][41][42][43][44][45] our composite exhibited a relatively high thermal conductivity at medium filler loading, and our fabrication method is preferable to those in earlier works, which used complicated procedures and toxic materials.…”

A study on the viscosity reduction mechanism of high-filled silicone potting adhesive by the formation of Al2O3 clusters

“…Thermally conductive but insulating llers such as Al 2 O 3 have low CLTE ($6.6 ppm/ C), 27 which can meet the performance requirements of high thermal conductivity and low CLTE of silicone potting adhesive under the condition of large amount of lling. For example, Fu et al 28 prepared a series of dense boric acid modied BNNSs/EP composites by mechanical ball milling and pressure forming processes; the EP composites with 90 wt% BNNSs achieved the maximum thermal conductivity (6.7 W m À1 k À1 ) and the minimum CLTE (4.5 ppm/ C) at a temperature of 25 C. Unfortunately, high ller loading will inevitably cause a sharp increase in the viscosity of silicone potting adhesive, which makes it impossible to achieve potting under mechanical or articial conditions. 29 In this study, Al 2 O 3 -epoxy and Al 2 O 3 -NH 2 powders were equally lled in vinyl silicone oil to prepare a high Al 2 O 3 loading (89 wt%) precursor of silicone potting adhesive.…”