Due to their exceptional chemical and thermal stabilities as well as electrically insulating property, atomically thin hexagonal boron nitride (h-BN) films have been identified as a promising class of dielectric substrate and encapsulation material for high-performance two-dimensional (2D) heterostructure devices. Herein, we report a facile chemical vapor deposition synthesis of large-area atomically thin h-BN including monolayer single crystals and C-doped h-BN (h-BCN) films utilizing a relatively low-cost, commercially available trimethylamine borane (TMAB) as a single-source precursor. Importantly, pristine 2D h-BN films with a wide band gap of ∼6.1 eV can be achieved by limiting the sublimation temperature of TMAB at 40 °C, while C dopants are introduced to the h-BN films when the sublimation temperature is further increased. The h-BCN thin films displayed band gap narrowing effects as identified by an additional shoulder at 205 nm observed in their absorbance spectra. Presence of N−C bonds in the h-BCN structures with a doping concentration of ∼2 to 5% is confirmed by X-ray photoelectron spectroscopy. The inclusion of low C doping in the h-BN films is expected to result in constructive enhancement to its mechanical properties without significant alteration to its electrically insulating nature. This study provides new insights into the design and fabrication of large-area atomically thin h-BN/h-BCN films toward practical applications and suggests that the range of precursors can be potentially extended to other anime borane complexes as well.

The porous interconnected structure of three-dimensional graphene (3DC) combines the excellent thermal conductivity of graphene with an interconnected architecture, thereby creating a thermal network within composites infused with 3DC. In this study, improvements in thermal conductivity, latent heat of fusion (Hf) and shape-stability of paraffin were compared between paraffin phase change materials (PCM) infused with 3DC and with discrete graphene flakes (GP) at the same filler loading to quantify the advantage of the interconnected structure. Paraffin infused with a 3DC of higher bulk density (3DCH) was also compared to identify the effects of increasing filler density. Thermal conductivity of the PCM composites was measured using the hot-disk method and shape-stabilization was compared through thermal cycling in an environment chamber. We found that the interconnected architecture of 3DC improved the properties of the paraffin matrix in multiple ways. 3DC improved the solidification process for paraffin with heterogeneous nucleation, helped to retain the shape of the PCM composite over thermal cycling, reduced void formation within the PCM and induced a large increase in thermal conductivity at 7.4 times and 5.2 times that of neat paraffin for composites infused with 3DCH and regular 3DC respectively, with only a small trade-off in Hf.

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We demonstrate the potential of a novel hybrid nanostructure three-dimensional graphene (3D-C) coated with boron nitride (BN) as an electromagnetic interference (EMI) shield. BN, deposited by sputtering, encapsulates 3D-C to form a light-weight graphene based EM shield that has an electrically insulating exterior. The BN deposited on 3D-C was homogeneously distributed with even coverage on the struts of 3D-C. EMI shielding results have shown that the hybrid material has a total shielding effectiveness (SET) of 53dB and 58dB in the X band and Ku band respectively.

Controlling the composition and structure of boron carbonitride nanotubes (BCNNTs) is the critical factor for tuning their electrical and optical properties, which in turn allows for the broadening of their applications.However, most of the known methods for synthesizing BCNNTs employ toxic precursors at high temperatures (up to 2000 C) and the achieved BCNNTs usually encounter phase-separation of BN and C.Herein, a facile large-scale synthesis of ternary BCNNTs with controllable composition by a chemical vapor deposition process at a relatively low temperature of 900 C is reported. By simply adjusting the synthetic parameters, BCNNTs with two different atomic ratios of B : C : N can be successfully synthesized. Their morphologies and ternary structure as well as optical properties are further investigated. Notably, the asprepared BNCNTs-50 are stable up to 900 C in air and exhibit an optical band gap of $4.36 eV. The results demonstrated in this study will open new avenues for a variety of potential applications of BCNNTs in electronics, photonics, sensors and high temperature lubricants.