The scalable preparation of two-dimensional hexagonal boron nitride (h-BN) is essential for practical applications. Despite intense research in this area, high-yield production of two-dimensional h-BN with large-size and high solubility remains a key challenge. In the present work, we propose a scalable exfoliation process for hydroxyl-functionalized BN nanoplatelets (OH-BNNPs) by a simple ball milling of BN powders in the presence of sodium hydroxide via the synergetic effect of chemical peeling and mechanical shear forces. The hydroxide-assisted ball milling process results in relatively large flakes with an average size of 1.5 μm with little damage to the in-plane structure of the OH-BNNP and high yields of 18%. The resultant OH-BNNP samples can be redispersed in various solvents and form stable dispersions that can be used for multiple purposes. The incorporation of the BNNPs into the polyethylene matrix effectively enhanced the barrier properties of the polyethylene due to increased tortuosity of the diffusion path of the gas molecules. Hydroxide-assisted ball milling process can thus provide simple and efficient approaches to scalable preparation of large-size and highly soluble BNNPs. Moreover, this exfoliation process is not only easily scalable but also applicable to other layered materials.

Scalable exfoliation process for highly soluble boron nitride nanoplatelets by hydroxide-assisted ball milling

Thermally conductive ceramic/plastic composite materials are needed in various industries for thermal management. The present work aimed at creating composite films of hexagonal boron nitride (h-BN) particles and polyimide. A thermal conductivity of 7 W m−1 K−1 was achieved at solids loading of 60 vol% with flexibility maintained.

Thermally conductive composite films of hexagonal boron nitride and polyimide with affinity-enhanced interfaces

Electrochemical stability of organic electrolytes in supercapacitors: Spectroscopy and gas analysis of decomposition products

Engineering of the optical, electronic, and magnetic properties of hexagonal boron nitride (h-BN) nanomaterials via oxygen doping and functionalization has been envisaged in theory However, it is still unclear as to what extent these properties can be altered using such methodology because of the lack of significant experimental progress and systematic theoretical investigations Therefore, here, comprehensive theoretical predictions verified by solid experimental confirmations are provided, which unambiguously answer this long-standing question Narrowing of the optical bandgap in h-BN nanosheets (from ≈55 eV down to 21 eV) and the appearance of paramagnetism and photoluminescence (of both Stokes and anti-Stokes types) in them after oxygen doping and functionalization are discussed These results are highly valuable for further advances in semiconducting nanoscale electronics, optoelectronics, and spintronics

Tuning of the Optical, Electronic, and Magnetic Properties of Boron Nitride Nanosheets with Oxygen Doping and Functionalization.

Adding functional fillers is a simple but efficient way to improve the dielectric properties of polymer materials. However, the improvement of dielectric constant is usually accompanied by a decrease of breakdown strength (BDS), and vice versa, which results in only a limited increase of the energy storage density of polymer composites. In this work, boron nitride nanosheets (BNNSs), an insulator with high theoretical BDS (800 kV mm−1), were used to improve the dielectric properties of poly(vinylidene fluoride) (PVDF). To improve the dispersion of BNNSs and the interfacial interaction with the PVDF matrix, the grafting of hydroxyl groups onto the surface of BNNSs was first carried out to obtain surface modified BNNSs (OH-BNNSs). Interestingly, the surface hydroxylation of BNNSs could realize simultaneous enhancement both in BDS and dielectric constant. Therefore, a high energy storage density of 13.1 J cm−3 has been achieved for PVDF/OH-BNNS nanocomposites with only 6 wt% filler content, which represents an impressive enhancement compared with neat PVDF (440%) or PVDF/BNNS (166%) nanocomposites. Moreover, decreased dielectric loss tangent, and improved thermal and mechanical properties of PVDF have also been achieved by adding OH-BNNSs. This research provides a new dimension of the surface modification of BNNSs and broadens their practical applications in the field of dielectric energy storage.

O.-M. Moon

Papers

Temperature effect on structural properties of boron oxide thin films deposited by MOCVD method

A comparative study on SiC thin films grown on both uncatalyzed and Ni catalyzed Si(100) substrates by thermal MOCVD using single molecular precursors