Scalable Exfoliation Process for Highly Soluble Boron Nitride Nanoplatelets by Hydroxide-Assisted Ball Milling

Abstract

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.

Simultaneous Production and Functionalization of Boron Nitride Nanosheets by Sugar‐Assisted Mechanochemical Exfoliation

“…Among them, hexagonal boron nitride nanosheets (BNNSs) have excellent thermal conductivity and stability, ultrahigh electrical insulation and breakdown strength, outstanding mechanical strength and stiffness, good impermeability to gases and liquids, high transparency to visible‐light and deep‐UV absorption, as well as good biocompatibility and biodegradability . Those unique properties make BNNSs attractive fillers in composites for a wide range of applications . For example, the uses of BNNS/cellulose nanofiber paper for insulating thermal management, BNNS/polymer films for high‐energy dielectric capacitors operating at high temperature and high voltage, and BNNS/polyethylene films for gas‐barrier packaging, have been demonstrated.…”

“…Those unique properties make BNNSs attractive fillers in composites for a wide range of applications . For example, the uses of BNNS/cellulose nanofiber paper for insulating thermal management, BNNS/polymer films for high‐energy dielectric capacitors operating at high temperature and high voltage, and BNNS/polyethylene films for gas‐barrier packaging, have been demonstrated. However, there is still a long way to go before the possible uses of BNNSs are exhausted.…”

“…For instance, Coleman and co‐workers have produced hydroxyl‐functionalized BNNSs (OH‐BNNSs) by a multistep procedure that involves the exfoliation of BNNSs by ultrasonication, grafting them with alkoxy groups by oxygen‐radical functionalization and subsequent hydrolytic defunctionalization with H 2 O 2 /H 2 SO 4 . Jeon and co‐workers have prepared OH‐BNNSs with a yield of 18% by ball milling for 24 h in 2 m NaOH followed by ultrasonication . Chen and co‐workers have produced amino‐functionalized BNNSs with a yield of up to 85% by urea‐assisted ball milling for 20 h .…”

Covalent Functionalized Boron Nitride Nanosheets as Efficient Lubricant Oil Additives

“…After the hydroxylation of h‐BNNSs, the appearance of the broad absorption peak is at around 3400 cm −1 , which is ascribed to the stretching vibration of O‐H bond. In addition, the peaks at 1235 and 1086 cm −1 are present in the spectrum of OH‐BNNSs, which can be indexed to the B‐OH deformation and the symmetric B‐O stretching band, indicating the presence of hydroxyl groups on the h‐BNNSs surfaces . The hydroxyl functional groups on the as‐exfoliated h‐BNNSs surfaces provide the reaction sites for interaction with silane coupling agent.…”

Mechanical and electromechanical properties of functionalized hexagonal boron nitride nanosheet: A density functional theory study

“…9 Hydroxylation, as a type of chemical functionalization, is defined as the attachment of hydroxyl groups on the surface and edges of h-BN via covalent bonds, mainly to improve their dispersion in water and create more active reaction sites. [9][10][11] Limited studies have concentrated on the hydroxylated hexagonal boron nitride nanosheets (OH-BNNS), and the existing few are more concerned with the functionalization process [12][13][14] and electrical properties 15,16 rather than the mechanical properties of OH-BNNS. Chemical functionalization is usually held responsible for degradation in the engineering properties of graphene oxide (GO); a phenomenon dissected in previous studies 17 and is contributed to the breaking of perfect sp 2 hybridized carbon by hydroxyl groups and forming sp 3 hybridization instead.…”