High-yield boron nitride nanosheets from 'chemical blowing': towards practical applications in polymer composites

Boron nitride materials as emerging catalysts for oxidative dehydrogenation of light alkanes

Light olefins (C₂-C₄) play a crucial role as basic ingredients in chemical industry, and oxidative dehydrogenation (ODH) of light alkanes to olefins has been one of the popular routes since the shale gas revolution. ODH of light alkanes has advantages on energy-and-cost saving as compared with traditional direct dehydrogenation, but it is restricted by its overoxidation which results in the relatively low olefin selectivity. Boron nitride (BN), an interesting nanomaterial with an analogous structure to graphene, springs out and manifests the superior performance as advanced catalysts in ODH, greatly improving the olefin selectivity under high alkane conversion. In this review, we introduce BN nanomaterials in four dimensions together with typical methods of syntheses. Traditional catalysts for ODH are also referred as comparison on several indicators-olefin yields and preparation techniques, including the metal-based catalysts and the non-metal-based catalysts. We also surveyed the BN catalysts for ODH reaction in recent five years, focusing on the different dimensions of BN together with the synthetic routes accounting for the active sites and the catalytic ability. Finally, an outlook of the potential promotion on the design of BN-based catalysts and the possible routes for the exploration of BN-related catalytic mechanisms are proposed.

Characterization of 2D boron nitride nanosheets with hysteresis effect in the Schottky junctions

Carbon doped two-dimensional (2D) hexagonal boron nitride nanosheets (BNNSs) are obtained through a CO2—pulsed laser deposition (CO2—PLD) technique on silicon dioxide (SiO2) or molybdenum (Mo) substrates, showing - stable hysteresis characteristics over a wide range of temperatures, which makes them a promising candidate for materials based on non-volatile memory devices. This innovative material with electronic properties of n-type characterized in the form of back-to-back Schottky diodes appears to have special features that can enhance the device performance and data retention due to its functional properties, thermal-mechanical stability, and its relation with resistive switching phenomena. It can also be used to eliminate sneak current in resistive random-access memory devices in a crossbar array. In this sense constitutes a good alternative to design two series of resistance-switching Schottky barrier models in the gold/BNNS/gold and gold/BNNS/molybdenum structures; thus, symmetrical and non-symmetrical characteristics are shown at low and high bias voltages as indicated by the electrical current-voltage (I–V) curves. On the one hand, the charge recombination caused by thermionic emission does not significantly change the rectification characteristics of the diode, only its hysteresis properties change due to the increase in external voltage in the Schottky junctions. The addition of carbon to BNNSs creates boron vacancies that exhibit partially ionic character, which also helps to enhance its electrical properties at the metal-BNNS-metal interface.

A space network structure constructed by tetraneedlelike ZnO whiskers supporting boron nitride nanosheets to enhance comprehensive properties of poly(L-lacti acid) scaffolds

In this study, the mechanical strength and modulus of poly(L-lacti acid) (PLLA) scaffolds were enhanced with the mechanical properties of boron nitride nanosheets (BNNSs) and tetraneedlelike ZnO whiskers (T-ZnOw). The adhesion and proliferation of cells were improved as well as osteogenic differentiation of stem cells was increased. Their dispersion statues in PLLA matrix were improved through a space network structure constructed by three-dimensional T-ZnOw supporting two-dimensional BNNSs. The results showed that the compressive strength, modulus and Vickers hardness of the scaffolds with incorporation of 1 wt% BNNSs and 7 wt% T-ZnOw together were about 96.15%, 32.86% and 357.19% higher than that of the PLLA scaffolds, respectively. This might be due to the effect of the pull out and bridging of BNNSs and T-ZnOw as well as the crack deflection, facilitating the formation of effective stress transfer between the reinforcement phases and the matrix. Furthermore, incorporation of BNNSs and T-ZnOw together into PLLA scaffolds was beneficial for attachment and viability of MG-63 cells. More importantly, the scaffolds significantly increased proliferation and promoted osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs). The enhanced mechanical and biological properties provide the potentials of PLLA/BNNSs/T-ZnOw scaffolds for the application into bone tissue engineering.

Large-surface-area BN nanosheets and their utilization in polymeric composites with improved thermal and dielectric properties

High-throughput few-layered BN nanosheets have been synthesized through a facile chemical blowing route. They possess large lateral dimensions and high surface area, which are beneficial to fabricate effectively reinforced polymeric composites. The demonstrated composites made of polymethyl methacrylate and BN nanosheets revealed excellent thermal stability, 2.5-fold improved dielectric constant, and 17-fold enhanced thermal conductivity. The results indicate multifunctional practical applications of such polymeric composites in many specific fields, such as thermoconductive insulating long-lifetime packaging for electrical circuits.