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Two one-dimensional nanowires, Fe3O4 and MnO2 nanowires, were modified with polyphosphazene-derived carbon (PZSC) using in situ polymerization and high-temperature calcination methods. PZSC coated with MnO2 nanowire (MnO2/PZSCNW) was designed as the positive electrode, while PZSC coated with Fe3O4 nanowire (Fe3O4/PZSCNW) was designed as the negative electrode. Both MnO2/PZSCNW (+) and Fe3O4/PZSCNW (−) exhibit much larger specific capacities than the corresponding MnO2 and Fe3O4 nanowires, reaching 75.5 mAh g−1 and 75.9 mAh g−1, respectively. The maximum specific capacity, power and energy density of MnO2/PZSCNW (+)//Fe3O4/PZSCNW (−) in alkaline electrolyte are up to 63.2 mAh g−1, 429.6 W kg−1 and 53.7 Wh kg−1, respectively. After 10 000 cycles, the cell maintains 100% capacity. The experimental results indicate that the polyphosphazene-derived carbon coating can significantly improve the electrochemical performance, providing a feasible solution for constructing high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Penta-graphene (PG) is a new theoretical two-dimensional metastable carbon allotrope composed entirely of carbon pentagons. In this paper, molecular dynamics simulations are performed to investigate the effects of the hydrogenation on the tensile and shear mechanical properties, together with the failure mechanism of PG with vacancy defects. The results show that hydrogenation can effectively tune the mechanical properties and failure mechanism of PG with vacancy defects. The defective PG (DPG) with low hydrogenation coverages exhibits obvious plastic deformation features under tensile and shear loading, and pentagon-to-polygon structural transformation is observed, while complete hydrogenation can change the failure mechanism of DPG from plastic deformation to brittle fracture. Both the tensile and shear moduli and elastic limit of DPG first decrease dramatically and then increase slowly with the increase of hydrogenation coverage, while tensile and shear strain increases almost monotonically with rising hydrogenation coverage. Complete hydrogenation can result in large enhancement of tensile and shear elastic stress limit and strain. These results may provide an important guideline for effectively tuning the mechanical properties of PG and other two-dimensional nanomaterials. [ABSTRACT FROM AUTHOR]

Penta-graphene is a new two-dimensional metastable carbon allotrope composed entirely of carbon pentagons with unique electronic and mechanical properties. In this work we evaluate the mechanical properties of new classes of defective penta-graphene (DPG) subjected to tensile and shear loading by using molecular dynamics simulations. The types of defects considered here are monovacancy at either 4-coordinated C1 site or 3-coordinated C2 site, and double vacancy (DV). We focus in particular on the effects of the different topologies of defects and their concentrations on the elastic constants and the nonlinear mechanics of this allotropic form of carbon. The results indicate that DPG has a plastic behavior similar to pristine penta-graphene, which is caused by the irreversible pentagon-to-polygon structural transformation occurring during tensile and shear loading. The tensile and shear moduli decrease linearly with the concentration of defects. Monotonic reductions of the tensile yield and shear stresses are also present but less pronounced, while the yield strains are unaffected. Penta-graphene with 4-coordinated and DVs feature a change of the Poisson's ratio from negative to positive when the defect concentration rises to about 3% and 6%. Temperature can trigger structural reconstruction for free-standing DPG. The critical transition temperature increases due to the vacancy defects and the defects can delay the structure transition. These findings are expected to provide important guidelines for the practical applications of penta-graphene based micro/nano electromechanical systems. [ABSTRACT FROM AUTHOR]

Polyphosphazene (PZS) microspheres attached with zinc oxide (ZnO) nanoparticles were successfully synthesized by a simple method. The morphology and structure were characterized by FTIR, SEM and TEM. The characterization results show that the ZnO nanoparticles are attached on the surface of PZS microspheres. The resultant microspheres are about 1.3 μm in diameter and the attached individual ZnO nanoparticles are about 20 nm. The XRD, EDX and XPS analysis demonstrate that the nanoparticles in the resultant microspheres are ZnO nanoparticles. The thermostable properties were investigated by TGA. The data of the photochemical catalysis shows that the product has very good application in photochemical catalysis. The photocatalytic activities of the PZS/ZnO are much higher than that of the pure PZS and ZnO, due to the combination of their merits and the synergistic effects on the enhancement of their photochemical catalytic performance. This is a novel, simple and economic method to preparing hybrid inorganic–organic microspheres using for photochemical catalysis. [ABSTRACT FROM AUTHOR]

The effect of temperature and strain rate on mechanical properties remains an open topic in research of hexagonal boron nitride (h-BN) nanosheets. To examine these fundamental issues we have performed molecular dynamics simulations to record the stress–strain curves in tensile tests and measure Young's modulus, fracture strength and fracture strain in armchair and zigzag directions. Comparing the results obtained at different temperatures and strain rates we have quantified the effects of the two factors on the tensile properties of the h-BN nanosheets. The influence of crystal orientation is also examined in the present study. It is found that the h-BN nanosheets are basically an anisotropic material whose tensile properties vary substantially with temperature and strain rate. In particular, a yielding platform is observed for the h-BN nanomaterial at relatively low temperature. [ABSTRACT FROM AUTHOR]

The tribological behavior of graphene oxide (GO) films deposited on a mica substrate has been investigated by atomic force microscopy, in which different voltages were applied to a tip. It was found that the frictional forces on the GO films remain unchanged in the presence of negative tip voltages, while the frictional forces increase remarkably with an increase of the voltage when positive voltages are given to the tip, and at a certain positive tip voltage the frictional forces reach a stable value with increasing number of repeated cycles. To study the influence of the tip voltage on the frictional forces of the GO films, the adhesive and electrostatic force gradients between the tip and GO films were measured. The results showed that the adhesive and electrostatic forces increased with increase of the positive tip voltages. This phenomenon is due to the polarization of charges in the GO films induced by the applied tip voltages, which causes intensive electrostatic interactions between the tip and GO films and a corresponding rise in the adhesive forces and the frictional forces. [ABSTRACT FROM AUTHOR]