Jiemin Wang

Super-compatible functional boron nitride nanosheets/polymer films with excellent mechanical properties and ultra-high thermal conductivity for thermal management

High heat-dissipation polymers are currently in great demand especially with the rapid development of electronic devices. However, traditional polymer composites usually suffer from both low thermal conductivity due to poor dispersibility and low concentration of fillers in the polymer matrix. To address this issue, it is necessary to improve the compatibility between the thermal conductive fillers and polymer matrix. Here, we designed a highly water-soluble functionalized boron nitride (FBN) nanosheet. Unlike most functional BN nanosheets that are only dispersible in water with polymer matrix at low concentrations, our FBN nanosheets can be mutually dispersed with aqueous polymers such as polyvinyl alcohol (PVA) in arbitrary weight ratios. The super compatibility between FBN and PVA is further interpreted by the Pickering emulsion formed from water and n-hexane. Moreover, after facile vacuum filtration, the robust FBN/polymer freestanding films with layer-by-layer laminate nanostructures are well fabricated. The nanocomposite films exhibit superior in-plane thermal conductivity (120 W m−1 K−1 for 90 wt% FBN loading in FBN/PVA film), which is nearly 100 times larger than that of the pristine PVA film. The FBN/polymer films provide good fire-retardant ability, thus effectively retarding flammability. In addition, the nanocomposite film with high concentration of FBN up to 70 wt% still possessed excellent flexibility and toughness even after being rolled and folded 100 times. Interestingly, the rolled film hollow cylinder supported 25 000 times its own weight without cracking, highlighting the extra strong interaction between the FBN and PVA. These properties make the nanosheet an excellent candidate for thermal management in electronics.

Hydrophilic PAN based carbon nanofibres with improved graphitic structure and enhanced mechanical performance using ethylenediamine functionalized graphene

Polyacrylonitrile (PAN) reinforced with nano-carbons such as graphene (Gr) and carbon nanotubes (CNTs) provides great opportunity for the development of low-cost and high-performance carbon materials. However, the poor dispersion and weak interaction between the carbon nanofillers and the surrounding PAN matrix prevent the final carbonized materials from reaching their full potential. Herein, we demonstrate a chemical approach using ethylenediamine (EDA) acting as a linker between graphene nanoplatelets and PAN for improved mechanical performance. The as-prepared CNFs exhibit a higher carbon yield and tensile modulus as well as improved graphitic structure compared to pristine PAN and PAN/Gr nanofibres. Furthermore, EDA can act as a N source for N-doping during the carbonization, enabling CNFs with hydrophilicity performance.

Functionalized boron nitride membranes with ultrafast solvent transport performance for molecular separation

Pressure-driven, superfast organic solvent filtration membranes have significant practical applications. An excellent filtration membrane should exhibit high selectivity and permeation in aqueous and organic solvents to meet increasing industrial demand. Here, we report an amino functionalized boron nitride (FBN) based filtration membrane with a nanochannel network for molecular separation and permeation. This membrane is highly stable in water and in several organic solvents and shows high transport performance for solvents depending on the membranes’ thickness. In addition, the FBN membrane is applicable for solute screening in water as well as in organic solvents. More importantly, the FBN membranes are very stable in acidic, alkaline and oxidative media for up to one month. The fast-flow rate and good separation performance of the FBN membranes can be attributed to their stable networks of nanochannels and thin laminar structure, which provide the membranes with beneficial properties for practical separation and purification processes.2D materials show promise for membrane filtration technologies, but their permeance to organic solvents is typically poor. Here, the authors prepare functionalized boron nitride membranes with high flux and high molecular separation performances in both aqueous solutions and organic solvents.

B/N co-doped carbon nanosphere frameworks as high-performance electrodes for supercapacitors

Energy storage devices capable of high power outputs currently attract much research interest. An example is supercapacitors, which show both high capacitance and sustained cycling ability. However, their electrodes, especially those based on carbon materials, often suffer from either low capacitance at high current density or poor durability after many cycles. Here we report a novel boron/nitrogen co-doped carbon nanosphere (B/N–CNS) framework that is simply prepared by annealing boron oxide, ammonium chloride, and glucose. The resulting B/N–CNS framework exhibits an ultra-high specific capacitance of 423 F g−1 at 0.2 A g−1 and excellent rate capability of up to 125 F g−1 at 50 A g−1. The improved performance is ascribed to its interconnected framework of nanospheres and B/N co-doping. In addition, unlike most carbon materials, this framework displays exceptional stability, showing no capacitance fading at 10 A g−1 after 30 000 cycles. Furthermore, an all-solid sandwich-structured symmetric supercapacitor with B/N–CNS framework electrodes can power a light emitting diode, demonstrating its practicability as a fully integrated energy storage device. The facile synthesis strategy and impressive capacitive performances of B/N–CNS framework make this material significantly promising in the fabrication of novel electrode materials for energy storage applications.

Boron Nitride Nanosheets/PNIPAM Hydrogels with Improved Thermo-Responsive Performance

Thermo-responsive hydrogel is an important smart material. However, its slow thermal response rate limits the scope of its applications. Boron nitride nanosheet-reinforced thermos-responsive hydrogels, which can be controlled by heating, were fabricated by in situ polymerization of N-isopropylacrylamide in the presence of boron nitride nanosheets. The hydrogels exhibit excellent thermo-responsiveness and much enhanced thermal response rate than that of pure poly(N-isopropylacrylamide) hydrogels. Interestingly, the hydrogels can be driven to move in aqueous solution by heating. Importantly, the composite hydrogel is hydrophilic at a temperature below lower critical solution temperature (LCST), while it is hydrophobic at a temperature above LCST. Therefore, it can be used for quick absorption and release of dyes and oils from water. All these properties demonstrate the potential of hydrogel composites for water purification and treatment.