Highly Efficient Growth of Boron Nitride Nanotubes and the Thermal Conductivity of Their Polymer Composites

We developed a novel strategy for the gram-scale fabrication of boron nitride nanotubes (BNNTs). Li₃N was used as the promoter: it not only catalyzes the BNNTs growth but also serves as the nitrogen source. BNNT/thermoplastic polyurethane (TPU) are flexible, transparent, and thermally conductive composite films that were also fabricated with an in-plane thermal conductivity of 14.5 W m^–1 K^–1 at 1.0 wt % BNNTs. This is an improvement of more than 400% over neat TPU. This study will enable BNNTs to be used in heat dissipation materials, high temperature components, and thermal protection systems

Highly Efficient Mass Production of Boron Nitride Nanosheets via a Borate Nitridation Method

Boron nitride nanosheets (BNNSs) have attracted intensive attention because of their fantastic properties, including excellent electrical insulating ability, splendid thermal conductivity, and outstanding oxidation resistance. However, facing the rising demand for versatile applications, the cost-effective mass production of BNNSs, similar to graphene, remains a huge challenge. Here, we provide a highly effective strategy for BNNS synthesis via a borate nitridation method utilizing solid borate precursors, producing gram-scale yields with efficiencies up to 88%. Combined with density functional theory (DFT) calculations, a vapor–solid–solid (VSS) mechanism was proposed in which ammonia vapor reacts with the solid borates, producing solid BNNSs at the vapor–solid interfaces. The strategy proposed herein, together with the diversity of borate compounds, allows numerous choices for the facile mass production of BNNSs at low cost. In addition, the remarkably enhanced thermal conductivity in composite materials demonstrated good quality and huge potential for these BNNSs in thermal management. This work reveals a cost-efficient method for the large-scale production of BNNSs, which should promote practical applications in various fields

Wrapping Aligned Carbon Nanotube Composite Sheets around Vanadium Nitride Nanowire Arrays for Asymmetric Coaxial Fiber-Shaped Supercapacitors with Ultrahigh Energy Density

The emergence of fiber-shaped supercapacitors (FSSs) has led to a revolution in portable and wearable electronic devices. However, obtaining high energy density FSSs for practical applications is still a key challenge. This article exhibits a facile and effective approach to directly grow well-aligned three-dimensional vanadium nitride (VN) nanowire arrays (NWAs) on carbon nanotube (CNT) fiber with an ultrahigh specific capacitance of 715 mF/cm² in a three-electrode system. Benefiting from their intriguing structural features, we successfully fabricated a prototype asymmetric coaxial FSS (ACFSS) with a maximum operating voltage of 1.8 V. From core to shell, this ACFSS consists of a CNT fiber core coated with VN@C NWAs as the negative electrode, Na₂SO₄ poly­(vinyl alcohol) (PVA) as the solid electrolyte, and MnO₂/conducting polymer/CNT sheets as the positive electrode. The novel coaxial architecture not only fully enables utilization of the effective surface area and decreases the contact resistance between the two electrodes but also, more importantly, provides a short pathway for the ultrafast transport of axial electrons and ions. The electrochemical results show that the optimized ACFSS exhibits a remarkable specific capacitance of 213.5 mF/cm² and an exceptional energy density of 96.07 μWh/cm², the highest areal capacitance and areal energy density yet reported in FSSs. Furthermore, the device possesses excellent flexibility in that its capacitance retention reaches 96.8% after bending 5000 times, which further allows it to be woven into flexible electronic clothes with conventional weaving techniques. Therefore, the asymmetric coaxial architectural design allows new opportunities to fabricate high-performance flexible FSSs for future portable and wearable electronic devices