Few-Layer Hydroxyl-Functionalized Boron Nitride Nanosheets for Nanoscale Thermal Management

Abstract

Boron nitride nanosheets (BNNSs) are widely used as fillers to increase the thermal conductivity of a substrate. However, the solvent resistance of BNNSs limits their widespread application. In this paper, hydroxyl functionalized boron nitride nanosheets (OH-BNNSs) were prepared through a one-step aqueous shear exfoliation process. The dangling bonds were formed during the exfoliation process and were attacked by water molecules, and thereby hydroxyl functionalization of BNNSs was achieved. The OH-BNNSs were added to poly(vinyl alcohol) (PVA) to prepare a nanocomposite with high thermal conductivity. The highspeed dispersive homogenizer was selected as the shear-exfoliating device, water as solvent, and sodium dodecyl sulfate (SDS) as surfactant. The effects of operating conditions on the concentration of few-layer OH-BNNSs were systematically studied. Under the optimized conditions, 0.88 mg/mL of OH-BNNSs was obtained. The as-obtained OH-BNNSs were filled in PVA to obtain composite film. The in-plane thermal diffusivity of OH-BNNSs-PVA films reached 9.03 mm 2 /s, which was 40-times the in-plane thermal diffusivity of the pure PVA film and 1.6-times the in-plane thermal diffusivity of the PVA composites filled by BNNSs prepared from ultrasonic exfoliation. The reasons were attributed to better dispersibility in PVA aqueous solution for OH-BNNSs. This paper provided a simple, scalable, and environmentally friendly preparation method for OH-BNNSs.

Towards Integration of Two-Dimensional Hexagonal Boron Nitride (2D h-BN) in Energy Conversion and Storage Devices

“…Considering the importance of these surface functional groups and doping level in energy applications, exfoliation or synthesis parameters should be carefully selected. So far, functionalization with the hydroxyl group [-OH] [44], amine group [-NH 2 ] [45], long change molecules [46,47], and doping with carbon [48], fluorine [49], and oxygen [50] have been largely used to modify 2D h-BN. Table 1 provides a summary of 2D h-BN synthesis for energy applications.…”

Aqueous-Phase Exfoliation and Functionalization of Boron Nitride Nanosheets Using Tannic Acid for Thermal Management Applications

“…Although MXenes have recently shown exciting potential in TMMs because of their outstanding thermally conductive performance, their high intrinsic carrier mobility also brings issues associated with high leakage current. , Therefore, thermally conductive but electrical insulation materials are highly desired for fabricating TMMs. To this end, BNNSs, with the analogue structure of graphene, are regarded as the most promising materials by virtue of their ultrahigh λ (∼2000 W m –1 K –1 ), wide band gap (∼5.9 eV), and low dielectric constant (∼3.9). , The fabrication of BNNSs with few-layered thickness is a prerequisite for the further exploration of the unprecedented properties of BNNSs. − …”

“…To this end, BNNSs, with the analogue structure of graphene, are regarded as the most promising materials by virtue of their ultrahigh λ (∼2000 W m −1 K −1 ), wide band gap (∼5.9 eV), and low dielectric constant (∼3.9). 17,18 The fabrication of BNNSs with fewlayered thickness is a prerequisite for the further exploration of the unprecedented properties of BNNSs. 19−21 To date, several strategies have been explored for the preparation of BNNSs, such as the bottom-up chemical vapor deposition (CVD), mechanical cleavage, and liquid-phase exfoliation (LPE).…”

Additive‐free Aqueous Dispersions of Two‐Dimensional Materials with Glial Cell Compatibility and Enzymatic Degradability

“…Additive‐free dispersions have been developed through the use of single solvent and mixed‐solvent strategies based on Hansen solubility parameters [6c, 18, 30] . Often, aqueous dispersibility is enabled by additives such as polymers like polyvinyl pyrrolidone and surfactants like sodium deoxycholate, salts like pyrene butyric acid, photosensitizer molecules like anti‐cancer drugs, and others [7a,d,e] . In the present context, we observe an anomalous dispersibility of these materials in water alone.…”