Synergistic Effects of Boron Nitride (BN) Nanosheets and Silver (Ag) Nanoparticles on Thermal Conductivity and Electrical Properties of Epoxy Nanocomposites

Abstract

Polymer composites, with both high thermal conductivity and high electrical insulation strength, are desirable for power equipment and electronic devices, to sustain increasingly high power density and heat flux. However, conventional methods to synthesize polymer composites with high thermal conductivity often degrade their insulation strength, or cause a significant increase in dielectric properties. In this work, we demonstrate epoxy nanocomposites embedded with silver nanoparticles (AgNPs), and modified boron nitride nanosheets (BNNSs), which have high thermal conductivity, high insulation strength, low permittivity, and low dielectric loss. Compared with neat epoxy, the composite with 25 vol% of binary nanofillers has a significant enhancement (~10x) in thermal conductivity, which is twice of that filled with BNNSs only (~5x), owing to the continuous heat transfer path among BNNSs enabled by AgNPs. An increase in the breakdown voltage is observed, which is attributed to BNNSs-restricted formation of AgNPs conducting channels that result in a lengthening of the breakdown path. Moreover, the effects of nanofillers on dielectric properties, and thermal simulated current of nanocomposites, are discussed.

Thermal Conductivity and Cure Kinetics of Epoxy-Boron Nitride Composites—A Review

“…One of the important parameters with respect to the use of these epoxy-BN composites in insulated metal substrates is the simplicity of the fabrication process, as mentioned in the Introduction, but many of the results discussed above make use of a solvent in the dispersion of the functionalised BN particles in the epoxy resin system, which is generally an undesired industrial practice. The solvents most widely used are acetone [57,74,85,113,131,141,148] and ethanol [68,82,97,155], but others include methyl ethyl ketone and dimethyl formamide [96], and tetrahydrofuran [71]. On the other hand, "dry" or "direct" mixing, which obviates the use of any solvents in this composite fabrication step, was adopted by many researchers [54,88,109,113,123,137,138,144,149,156].…”

Recent Advances and Trends of Nanofilled/Nanostructured Epoxies

“…The total percentage of the nanofiller materials in the composite never exceeded 30 wt.%; it was, therefore, possible to achieve the improved thermal properties without impairing the viscosity of the uncured resin—that is to say, its processability. In the field of electronic applications, the incorporation in an epoxy matrix of BN nanosheets (BNNSs) superficially modified with silver nanoparticles (AgNPs) allows obtaining a binary nanofilled composite (at 25 vol.%) possessing contemporarily high thermal conductivity and electrical insulation values, exploiting the complementary features of BNNSs and AgNPs [ 86 ]. With a properly designed approach to achieve the modification of BNNSs, the electrical insulation properties of epoxy nanocomposites are not reduced by the addition of the nanofiller with high conductivity, i.e., silver nanoparticles, since these are effectively blocked on the surface of electrically insulated BN nanosheets.…”

“…The incorporation of nanoparticles in epoxy resins allows modification of many properties. In comparison to the neat polymer, enhanced mechanical properties [ 6 , 16 , 27 , 32 , 35 , 45 , 57 , 69 , 85 , 101 , 106 , 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 , 119 ], improved corrosion resistance [ 21 , 25 , 59 , 64 , 70 , 92 , 108 , 120 , 121 , 122 , 123 , 124 , 125 , 126 ], increased thermal and electrical conductivity [ 5 , 15 , 16 , 17 , 27 , 45 , 86 , 87 , 101 , 109 , 110 , 117 , 127 , 128 ], high dielectric permittivity and low dielectric loss [ 93 ...…”

“…It has been found that linearly shaped nanoparticles (e.g., CNTs) mainly produce increases in mechanical properties [ 108 ] and 2D nanosheets (such as GNP, graphene oxide, and MoS 2 ) appreciably improve the barrier properties [ 92 , 121 , 124 , 125 ], especially corrosion resistance, while spherically shaped nanofillers (e.g., fullerene), having a low capability to aggregate, yield an overall improvement in nanocomposites’ properties [ 108 , 132 ]. Synergistic effects from using combinations of different nanofillers have been observed [ 86 , 106 , 117 ], even if the benefits are sometimes negligible [ 6 ].…”

“…Contact between the particles of nanofiller is necessary to form thermal conduction pathways; in this condition, the heat flow is promoted and the thermal conductivity increases [ 5 , 16 , 86 , 87 ]. The interfacial interaction is also an important factor since, where weak interactions are developed, the connection between the nanoparticles can be lost and thermal conduction is less efficient [ 45 ].…”