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We developed a simple and effective method to improve the properties of zinc oxide (ZnO) thin films. ZnO thin films were post-treated by ammonia vapor, and the properties such as phase composition, morphology, optical and electrical properties of ZnO thin films were investigated. The results confirmed the addition of nitrogen (N) to the film after the ammonia water vapor treatment, and the oxygen vacancy defects of the ZnO thin films were decreased. The morphological analyses revealed that the grain distribution and grains were well dispersed in the samples after the ammonia water vapor treatment, but the ZnO crystal structure showed a non-significant change. The particle size of ZnO thin films slightly increased, and the light transmittance of ZnO thin films increased from 79.17 to 80.02%. The thin-film resistivity was reduced from 1.43 × 101 to 1.78 × 10–2 Ω cm, which is by 98.7%. This post-treatment process improved the properties of ZnO thin films, which facilitated the application of ZnO films. [ABSTRACT FROM AUTHOR]

Oxidization treatment has been successfully applied on carbon nanotubes grown carbon fiber (CNTs-CF) to improve the surface activity and the interfacial property of CNTs-CF/epoxy resin (CNTs-CF/EP) composite. The surface element, morphology, and mechanical property of CNTs-CF have been systematically studied by X-ray photoelectron spectrum (XPS), scanning electron microscope (SEM), and single fiber tensile strength tester, respectively. The results indicate that the oxygen content on the CNTs-CF surface has been markedly increased from 2.5% to 19.4% after oxidization treatment, while the tensile strength shows no significant decrease. The CNTs layer on the surface protected the carbon fiber from corrosive oxidization agent, at the cost of collapsing and falling off of itself. Contact angle measurement and shear strength test have been introduced to investigate the interfacial property of CNTs-CF/EP composite. The result shows that the contact angle of resin to fiber has been reduced from ~39° to ~35° after oxidization, while the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) has been improved by 14.32% and 12.4% compared with untreated CNTs-CF/EP, respectively. A model is proposed to explain the wave-shaped fracture surface phenomenon of the composite. This work could reveal a novel approach to further improve the surface property of carbon fiber after growing carbon nanotubes. [ABSTRACT FROM AUTHOR]

Hollow structures are an extremely attractive and special feature of nanomaterials, and they have wide application prospects in several fields, such as photocatalysis, biomedicine, energy storage, and photoelectric conversion. The synthesis of hollow nanocrystals is mainly achieved via the fine control of material nucleation, particle growth, and surface connection. According to its growth mechanism, there are typically four strategies, namely, Kirkendall effect, Ostwald ripening, chemical erosion, and template-mediated synthesis. Hollow nanostructures based on iron oxides are environmentally friendly and have high specific capacity; they can address 96% of the volume change caused by the charge-discharge cycles in lithium-ion batteries (LIBs). Thus, they have attractive application prospects as anode materials for LIBs. In this review, advances in the synthesis of hollow nanostructures based on iron oxides are summarised, and their application prospects as anode materials for LIBs, based on the above four strategies, are discussed. [ABSTRACT FROM AUTHOR]

In order to improve the interfacial adhesion of epoxy composites, a hierarchical structure including carbon nanotubes (CNTs) grown on carbon fiber (CF) was prepared by a novel vacuum-assisted chemical vapor deposition (CVD) method at relatively low temperature of 400 °C under a pressure of 0.01 MPa. The short beam method and microbond test were used to measure the interlaminar shear strength (ILSS) and interfacial shear strength (IFSS) of epoxy composites reinforced by different CFs. The results showed that the CNTs-grown CF prepared at the H2 flow rate of 9 L/min had the best reinforcement effect. The ILSS and IFSS of its composites were 19.50% and 62.32% higher than that of the CF/epoxy composites without CNTs grown, respectively. The improvement of interfacial adhesion can be attributed to the fact that CNTs inserted into the matrix enhanced the mechanical interlocking between the fiber and the resin and induced the formation of interphase. Also, two failure modes of CNTs have also been observed, which can absorb extra energy and increased the difficulty of the separation of fiber and resin. The increase in the glass transition temperature (Tg) indicated the movement of the polymer molecular chains at the interphase was restricted by CNTs, which also contributed to the improvement of the interfacial adhesion of composites. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) aerial recovery denotes the technology that UAVs are recovered in the air by the transport aircraft for reuse. During the recovery process, the multiple wind perturbations and fast-changing UAV's engine shutdown will induce oscillations in the cable-drogue-UAV assembly (CDUA) with strong nonlinearities and tight coupling, which affects the safety and speed of the UAV aerial recovery. Aiming at this problem, this paper proposes a non-constraining force direction (NCFD)-based CDUA anti-disturbance trajectory control method for the first time. First, by transforming the CDUA trajectory control to the NCFD control, the coupling and nonlinear effects in the CDUA can be reduced, and the fast-changing disturbances caused by the engine shutdown can be compensated. Then, feed forward control is designed based on the relationship between the NCFD and cable shape, which is established based on the cable dynamics, to improve the response speed. Furthermore, a fixed-time anti-disturbance controller (FTADC) is designed for the flow angle of drogue-UAV assembly (DUA) given by the NCFD controller and compensates for the effects of wind and parameter perturbations. Finally, the stability of the proposed method is analyzed, and the effectiveness is demonstrated by abundant simulations. [ABSTRACT FROM AUTHOR]

Nowadays, the application of supercapacitor in energy storage is more and more extensive, and the selection and preparation of electrode material have become a formidable challenge. Polyaniline (PANI) has turned into one of the most hopeful conductive polymers due to its superior properties. In this article, conductive polyaniline was synthesized by chemical oxidative polymerization to acquire excellent electrochemical properties. Scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry (CV), and galvanostatic charge–discharge (GCD) measurements were adopted to explore the microstructure and energy storage capacity. The PANI is in coralline network morphology with high surface area, which can supply more active sites during charge and discharge process. The PANI shows a high specific capacitance value of 790 F/g, and the highest conductivity is 15.5 S/cm. The consequence shows that PANI synthesized under certain conditions has a promising feasibility for applications in high-performance supercapacitor electrode material. [ABSTRACT FROM AUTHOR]

We theoretically investigate the intra-band transitions in Mobius molecules. Due to the weak magnetic response, the relative permittivity is significantly modified by the presence of the medium while the relative permeability is not. We show that there is hyperbolic dispersion relation induced by the intra-band transitions because one of the eigen-values of permittivity possesses a different sign from the other two, while all three eigen-values of permeability are positive. We further demonstrate that the bandwidth of negative refraction is 0.165 eV for the H-polarized incident light, which is broader than the ones for inter-band transitions by 3 orders of magnitude. Moreover, the frequency domain has been shifted from ultra-violet to visible domain. Although there is negative refraction for the E-polarized incident light, the bandwidth is much narrower and depends on the incident angle. [ABSTRACT FROM AUTHOR]

This paper provides a continuous method for grafting carbon nanotubes (CNTs) on the surface of carbon fibers by chemical vapor deposition (CVD). The control of the morphology of CNTs/CFs can be achieved by adding thiourea to the cobalt nitrate precursor. The sulfur can increase the catalytic activity of the Co catalyst. Scanning electron microscopy reveals that a uniform layer of CNTs is grafted onto the surface of carbon fibers with the presence of thiourea. Through the single-filament tensile strength test, it can be found that the tensile strength of the fiber is increased by up to about 10% compared with the desized carbon fibers after the CVD process. And the reason for the enhancement is explored through X-ray diffraction. Raman spectroscopy reveals that the sample possesses the highest degree of graphitization at a thiourea concentration of 0.02 mol/L. It is found by high-resolution transmission electron microscopy that the growth mechanism of CNTs is tip growth mechanism, and the diameter of the CNTs is about 15 nm. [ABSTRACT FROM AUTHOR]

The purpose of this article is to find a novel way to grow carbon nanotubes (CNTs) on carbon fiber fabrics with improved tensile properties. Using chemical vapor deposition (CVD) method, the CNTs catalyzed by Fe–Co bimetallic catalysts system at a low temperature of 500 °C were demonstrated. TEM and Raman spectra show that the synthesized CNTs perform an obvious tubular hollow structure with high crystallinity. Mechanical test results clearly show that the tensile strength of final single fiber increases by 8.83% and the Weibull modulus improves from 6.85 to 7.78 after the growth of CNTs. The variations of tensile strength and Weibull modulus can be explained by not only the low carbon solubility and high catalytic activity of Fe–Co bimetallic catalysts minimizing support damage at low temperatures, but also the repairment of defects during the CVD process. Such results provided the solid foundation for further development of high-performance multiscale hybrid micro/nanocomposites, broadening their potential applications such as energy-store and electronic flexible device. [ABSTRACT FROM AUTHOR]

Submarine hydrothermal vents are generally considered as the likely habitats for the origin and evolution of early life on Earth. In recent years, a novel hydrothermal system in Archean subseafloor has been proposed. In this model, highly alkaline and high temperature hydrothermal fluids were generated in basalt-hosted hydrothermal vents, where H and CO could be abundantly provided. These extreme conditions could have played an irreplaceable role in the early evolution of life. Nevertheless, sufficient information has not yet been obtained for the abiotic synthesis of amino acids, which are indispensable components of life, at high temperature and alkaline condition. This study aims to propose a new method for the synthesis of glycine in simulated Archean submarine alkaline vent systems. We investigated the formation of glycine from ethanolamine under conditions of high temperature (80-160 °C) and highly alkaline solutions (pH = 9.70). Experiments were performed in an anaerobic environment under mild pressure (0.1-8.0 MPa) at the same time. The results suggested that the formation of glycine from ethanolamine occurred rapidly and efficiently in the presence of metal powders, and was favored by high temperatures and high pressures. The experiment provides a new pathway for prebiotic glycine formation and points out the phenomenal influence of high-temperature alkaline hydrothermal vents in origin of life in the early ocean. [ABSTRACT FROM AUTHOR]

Serious wear-out failure in conical picks leads to low working efficiency when mining protective seams using a coal auger. In this study, to decrease the wear of conical picks in the rotation-drilling cutting process, an interference model of rotation-drilling cutting is established according to coal cutting theory. Then, laboratory rotation-drilling cutting experiments with 28 different cutting angles δ and rotation angles ε are realized on large blocks of test coal wall using one type of conical pick to verify the interference model. The experimental results show that the wear of picks increased gradually with an increase in rotation angle and a decrease in cutting angle. The rotation-drilling cutting experiments verify the correctness of the interference theory model. It is preferable to choose a small rotation angle and large cutting angle when deciding on the installation parameters of conical picks in the theoretical range. [ABSTRACT FROM AUTHOR]

Acrylonitrile-methyl itaconate (AN-MIA) copolymers were successfully prepared by free-radical solution copolymerization, and then were spun into precursors of carbon fibers by one-step wet-spun method in this study. Effect of methyl itaconate(MIA), itaconic acid (IA) and methyl acrylate (MA) on the characteristics of the copolymers and precursors were studied in contrast. The monomer reactivity ratios for AN/MIA system were determined by Kelen-Tudos (K-T) method with r=0.65, r=1.80. The viscosity test shows that using MIA as a co-monomer is an effective way to decrease the viscosity of PAN solution. During the spinning and stretching processes, polyacrylonitrile (PAN) copolymer with MIA as co-monomer can reach the higher total draw-ratio of 12.0 folds, while PAN copolymer with IA as co-monomer can reach only 8.5 folds. The fineness and elongation at-break of the PAN precursors with MIA as co-monomer improve, but the tenacity decreases. DSC test shows MIA is less effective in improving the thermal property than IA. [ABSTRACT FROM AUTHOR]