An ultrathin, highly thermally conductive heat spreader has been fabricated by layer-by-layer stacking of hydroxylated boron nitride nanosheets (HBNNS) for the first time. HBNNS were prepared by a molten hydroxide-assisted liquid exfoliation from hexagonal boron nitride powder. The as-prepared heat spreader of HBNNS exhibits a high thermal conductivity of 51.1 W m(-1) K-1 along the in-plane direction, and can be further enhanced 14% by annealing for de-hydroxylation. This heat spreader with 10-30 mu m in thickness possessed excellent thermal stability with negligible weight loss at wide temperature range up to 700 degrees C, resulting in promising applications for heat dissipation in electronic components operated at high working temperature.

https://iopscience.iop.org/article/10.1088/2053-1583/aa636e/pdf

An ultrathin high-performance heat spreader fabricated with hydroxylated boron nitride nanosheets

Hexagonal boron nitride (h-BN) is also referred to as “white graphite”. Owing to its two-dimensional planar structure, its thermal conductivity along and perpendicular to a basal plane is anisotropic. However, h-BN exhibits properties that are distinct from those of graphite, such as electric insulation, superior antioxidative ability, and purely white appearance. These qualities render h-BN superior as a filler in composites that require thermal conductivity while exhibiting electric insulation. Since the thermal performance of composites is mainly affected by thermal pathways, this article begins with an overall introduction of the preparation of boron nitride nanosheets, followed by a review of the fabrication of h-BN-filled composites. Lastly, the construction of thermally conductive networks is discussed.

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Polymer composites based on hexagonal boron nitride and their application in thermally conductive composites

Bulk Hexagonal Boron Nitride with a Quasi-Isotropic Thermal Conductivity

Due to the strong 'lip–lip' interactions between neighboring nanosheets layers, the scalable exfoliated fabrication of few-layer-thick boron nitride nanosheets (BNNSs) from the bulk hexagonal boron nitride (h-BN) is more challenging than these graphene nanosheets In this work, few-layer (generally less than 10 layers) BNNSs were efficiently synthesized through a simple ball milling technique with the 2-furoic acid (FA) as a modifier The BNNSs as-prepared with a average thickness of about 20 nm and an extremely high production yield (~98%) as well as unprecedentedly high dispersed concentration (~35 mg ml−1) in water The stable aqueous dispersions of BNNSs can be directly used to fabricate ultralight aerogels with a low density of 20 mg cm−3 and thermally conductive film with a highly thermal conductivity of 252 W m−1 K−1 This approach provided us with an environmentally friendly agent with high efficiency for few-layer BNNSs synthesis and demonstrated promising applications for ultralight aerogels and heat dissipation in electronic components

https://iopscience.iop.org/article/10.1088/2053-1583/aad51a/pdf

High-yield synthesis of extremely high concentrated and few-layered boron nitride nanosheet dispersions

Hexagonal boron nitride (hBN) has emerged as a promising two-dimensional (2D) material for photonics device due to its large bandgap and flexibility in nanophotonic circuits. Here, we report bright and localized luminescent centres can be engineered in hBN monolayers and flakes using laser irradiation. The transition from hBN to cBN emerges in laser irradiated hBN large monolayers while is absent in processed hBN flakes. Remarkably, the colour centres in hBN flakes exhibit room temperature cleaner single photon emissions with g 2 (0) ranging from 0.20 to 0.42, a narrower line width of 1.4 nm and higher brightness compared with monolayers. Our results pave the way to engineering deterministic defects in hBN induced by laser pulse and show great prospect for application of defects in hBN used as nano-size light source in photonics.

https://iopscience.iop.org/article/10.1088/2053-1583/aa8e61/pdf

Localized emission from laser-irradiated defects in 2D hexagonal boron nitride

Two-dimensional materials are characterised by a number of unique physical properties which can potentially make them useful to a wide diversity of applications. In particular, the large thermal conductivity of graphene and hexagonal boron nitride (hBN) has already been acknowledged and these materials have been suggested as novel core materials for thermal management in electronics. However, it was not clear if mass produced flakes of hBN would allow one to achieve an industrially-relevant value of thermal conductivity. Here we demonstrate that laminates of hBN exhibit thermal conductivity of up to 20 W/mK, which is significantly larger than that currently used in thermal management. We also show that the thermal conductivity of laminates increases with the increasing volumetric mass density, which creates a way of fine tuning its thermal properties.

https://iopscience.iop.org/article/10.1088/2053-1583/3/1/011004/pdf

High thermal conductivity of hexagonal boron nitride laminates

Two-dimensional materials are characterised by a number of unique physical properties which can potentially make them useful to a wide diversity of applications. In particular, the large thermal conductivity of graphene and hexagonal boron nitride has already been acknowledged and these materials have been suggested as novel core materials for thermal management in electronics. However, it was not clear if mass produced flakes of hexagonal boron nitride would allow one to achieve an industrially-relevant value of thermal conductivity. Here we demonstrate that laminates of hexagonal boron nitride exhibit thermal conductivity of up to 20 W/mK, which is significantly larger than that currently used in thermal management. We also show that the thermal conductivity of laminates increases with the increasing volumetric mass density, which creates a way of fine-tuning its thermal properties.

Tun Wang

Papers

High thermal conductivity of hexagonal boron nitride laminates

High thermal conductivity of hexagonal boron nitride laminates