Nanoscale layer of a minimized defect area of graphene and hexagonal boron nitride on copper for excellent anti-corrosion activity.

In this work, we synthesized a monolayer of graphene and hexagonal boron nitride (hBN) using chemical vapor deposition. The physicochemical and electrochemical properties of the materials were evaluated to determine their morphology. High-purity materials and their atomic-scale coating on copper (Cu) foil were employed to prevent fast degradation rate. The hexagonal two-dimensional (2D) atomic structures of the as-prepared materials were assessed to derive their best anti-corrosion behavior. The material prepared under optimized conditions included edge-defect-free graphene nanosheets (∼0.0034µm2) and hBN (∼0.0038µm2) per unit area of 1µm2. The coating of each material on the Cu surface significantly reduced the corrosion rate, which was âˆ¼2.44 × 10-2/year and 6.57 × 10-3/year for graphene/Cu and hBN/Cu, respectively. Importantly, the corrosion rate of Cu was approximately 3-fold lower after coating with hBN relative to that of graphene/Cu. This approach suggests that the surface coating of Cu using cost-effective, eco-friendly, and the most abundant materials in nature is of interest for developing marine anti-corrosion micro-electronic devices and achieving surface modification of pure metals in industrial applications.

Single- and double-walled boron nitride nanotubes: Controlled synthesis and application for water purification.

Research interest in boron nitride nanotubes (BNNTs) has increased after the recent success of large-scale BNNT syntheses using high-temperature-pressure laser ablation or high-temperature plasma methods. Nonetheless, there are limits to the application and commercialization of these materials because of the difficulties associated with their fine structural control. Herein, the growth kinetics of BNNTs were systemically studied for this purpose. The growth pressure of the nitrogen feed gas was varied while the growth temperature remained constant, which was confirmed by black body radiation measurements and calculations based on a heat loss model. Changing from the diffusion-limited regime to the supply-limited regime of growth kinetics based on the optimized BNNT synthesis condition afforded the control of the number of BNNT walls. The total amount of BNNTs possessing single and double walls was over 70%, and the BNNT surface area increased to 278.2 m2/g corresponding to small wall numbers and diameters. Taking advantage of the large surface area and high-temperature durability of the material, BNNTs utilized as a recyclable adsorbent for water purification. The efficiency of the BNNTs for capturing methylene blue particles in water was approximately 94%, even after three repetition cycles, showing the potential of the material for application in the filter industry.

Dual growth mode of boron nitride nanotubes in high temperature pressure laser ablation.

The morphological analysis of the end of boron nitride nanotubes (BNNTs) using high-resolution transmission electron microscopy (HR-TEM) can provide valuable insight into the growth mechanism in high temperature pressure (HTP) laser ablation where the best quality of BNNT materials can be obtained so far. Two growth modes of BNNT coexisting during the synthesis process have been proposed based on HR-TEM observation and length analysis. One is the root growth mode, in which boron nitride (BN) species formed via the surface interaction between surrounding N2 molecules and boron nanodroplets incorporate into the tubular structure. Another mode called open-end growth mode means the prolongation of tube growth from the exposed BN edge surrounding the surface of boron nanodroplets which is constructed by the heterogeneous nucleation of absorbed BN radicals from the gas plume. The statistical data, the proportions of end structures and the length of BNNTs, could be fitted to two growth modes, and the open-end growth mode is found to be especially effective in producing longer nanotubes with a higher growth rate. The scientific understanding of the growth mechanism is believed to provide the control for optimized production of BNNTs.

QCN-Based Analysis for Predicting the Quality of Resulting Electrospun Nanofiber: Effect of Real-Time Transient Rheological Properties of Precursor Solution on Electrospinning.

There is a large margin between the mechanical properties and morphology of electrospun fibers required in each area. The produced fibers show a large difference depending on the external environment such as temperature, humidity, and season even in optimum concentration and same electrospinning set-up. The properties of polymer solution among the parameters are the largest determinant of the mechanical strength and diameter of electrospun fibers. Herein, the accurate predicting system in advance to electrospinning is required. In this study, we conduct a comparative study on the viscosity (measured by Brookfield rheometer) and the transient mass change and evaporation speed by our lab-made QCN in order to establish a predicting system for the quality of fiber. It was possible to measure the change of mass of the polymer solution in real-time using the lab-made QCN as well as calculating the volatility, the evaporation time of the polymer solution. The volatility of the polymer solution has a significant impact on the quality of the electrospun fiber including the diameter, uniformity, and surface topography. We compare the mass changes, viscosimetric viscosities, and the quality of corresponding fiber, and reveal the potential of QCN as a tool predicting pre-electrospinning fibers.

Boron nitride nanotubes: synthesis and applications.

Boron nitride nanotube (BNNT) has similar tubular nanostructure as carbon nanotube (CNT) in which boron and nitrogen atoms arranged in a hexagonal network. Owing to the unique atomic structure, BNNT has numerous excellent intrinsic properties such as superior mechanical strength , high thermal conductivity, electrically insulating behavior, piezoelectric property, neutron shielding capability, and oxidation resistance. Since BNNT was first synthesized in 1995, developing efficient BNNT production route has been a significant issue due to low yield and poor quality in comparison with CNT, thus limiting its practical uses. However, many great successes in BNNT synthesis have been achieved in recent years, enabling access to this material and paving the way for the development of promising applications. In this article, we discussed current progress in the production of boron nitride nanotube, focusing on the most common and effective methods that have been well established so far. In addition, we presented various applications of BNNT including polymer composite reinforcement, thermal management packages, piezo actuators, and neutron shielding nanomaterial.