The Au nanoparticles decorated graphene (AuNPs@Gr)/nickel foam (Gr/NiF) nanocomposite (AuNPs@Gr/NiF) was prepared by chemical vapor deposition followed by electrophoretic deposition of AuNPs on Gr/NiF. The morphology, microstructure and sensing performance of the as-prepared AuNPs@Gr/NiF nanocomposite were characterized and measured, respectively by scanning electron microscope, transmission electron microscope, ultraviolet visible spectroscopy and chemical workstation. The as-prepared AuNPs@Gr/NiF nanocomposite was used as the electrode to construct a chemical sensor for the detection of hydrogen peroxide (H2O2). The results showed that the AuNPs distributed homogenously and stably on the surface of Gr/NiF. The chemical sensor exhibits a sensitive and selective performance to the detection of H2O2.

•Nonstoichiometric of mesoporous LaMn1±xO3 perovskite can be easily synthesized by sol-gel.•Oxygen vacancies and Mn4+ ions concentrations can be modulated by Mn/La ratio.•A high specific capacity of 202.1 mAhg−1 (727.6 Cg−1) is obtained for LaMn1.1O3-δ.A series of LaMn1±xO3 perovskite (x = 0, 0.05, 0.1) has been synthesized via a facile sol–gel method and applied as supercapacitor electrodes. The morphology, phase structure, composition, chemical states of constituents and electrochemical properties are investigated. As a result, all the LaMn1±xO3 samples revealed a single mesoporous phase of perovskite with typical pore sizes from 2 to 5 nm. The nonstoichiometric LaMn1.1O3 sample showed much higher specific capacity (202.1 mAhg−1/727.6 Cg−1 at 1 Ag−1) than stoichiometric LaMnO3 perovskite (114.4 mAhg−1/411.8 Cg−1 at 1 Ag−1). Detailed chemical analysis demonstrated that the presence of point defects such as oxygen and cation vacancies, and a high Mn4+/Mn3+ ratio contributed to the excellent electrochemical performance. Furthermore, the cycle stability analyses of the LaMn1±xO3 perovskite revealed that LaMn1.1O3 manifested an exceptionally high rate capability. These results prove that nonstoichiometric LaMn1.1O3 can be a promising material for supercapacitor electrodes.Download high-res image (226KB)Download full-size image

•A synthetic method of Si@porous-C was developed using nano-MgO as the pore-former.•Si nanoparticles were homogeneously embedded in porous-C with spherical space.•Si@porous-C possesses enhanced cyclic stability and high-rate capability.•The template method employed in the present work is industrially scalable.In the present work, the sample of Si nanoparticles embedded in porous C (denoted as Si@porous-C) has been successfully synthesized by using nano-MgO as the pore-former. Observations by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) on Si@porous-C sample reveal that Si nanoparticles homogeneously disperse in porous carbon scaffold. As anode of lithium ion battery (LIB), Si@porous-C preserves a charge-discharge capacity of 1172 mAh g−1 after 40 cycles, possessing enhanced cyclic deterioration of only 0.35% per cycle in comparison with Si nanoparticles and Si nanoparticles embedded in ordinary carbon (denoted as Si@C). It delivers reversible capacities of about 947 mAh g−1, 670 mAh g−1, and 394 mAh g−1 in current densities of 1000 mA g−1, 2000 mA g−1, and 4000 mA g−1, respectively, all of which are higher than those of commercial nano-silicon and Si@C. The improved high-rate capability of Si@porous-C could be attributed to a decreased resistance and enhanced infiltration of electrolytic solution around nano-silicon particles. The merits of scalable synthetic process and improved electrochemical properties recommend Si@porous-C as a promising anode material for high performance Li-ion batteries.

Graphene-based hierarchically porous materials have exhibited enormous potentials in high-performance lithium-ion batteries. However, the electrochemical performance of these materials is hampered due to the detachment of active materials from graphene upon long-term cycling. Therefore, the interfacial design between active materials and graphene is crucial for their high performance in lithium-ion storage. In this study, a hierarchically porous architecture of spatially confining carbon-coated SnO2 nanospheres (C-SnO2 NSs) within graphene foam has been designed and fabricated by employing the H-bonding effect of sodium carboxymethyl cellulose to bridge the C-SnO2 NSs and graphene sheets in a complete encapsulation arrangement. The as-fabricated architecture not only prevents the detachment of C-SnO2 from graphene and direct exposure of them in electrolyte, but also suppresses the electrode's pulverization caused by the large volume change of SnO2 during charge/discharge processes, thus achieving SnO2 interfacial and structural stability. Moreover, benefiting from the hierarchical porosity and interconnected graphene network, electrode reaction kinetics is greatly enhanced. As a result of these merits, the as-built electrode shows extraordinary rate capability (611.1 mA h g−1 at 4.0 A g−1; 427.9 mA h g−1 at 8.0 A g−1) and robust cycling stability (1458.8 mA h g−1 remaining after 700 cycles at 1.0 A g−1).Download high-res image (429KB)Download full-size image

The dynamic indentation response of several ductile metallic materials [Al(111), polycrystalline copper, Fe, and Ti6Al4V] has been investigated using a pendulum-based nano-impact test. The impact process involves repetitive contact cycles until finally coming to rest in the material. Each cycle includes four phases: acceleration, indentation, rebound, and deceleration. The dynamic indentation resistance of the metallic materials scales with their hardness determined under quasi-static conditions. However, through a one-dimensional analytical model, it has been shown that the relationship between the dynamic resistance and the depth during indentation cannot be adequately described using the quadratic relationship commonly found under quasi-static conditions. A power law relationship with a reduced index was proposed and it is found the index is around 1 when the quasi-static and dynamic compliance are similar. A linear relationship between impact resistance and depth has been found during rebound, where the released elastic energy is much higher than that produced by quasi-static nanoindentation.

•Both mechanical properties and microstructural factors affect impact resistance.•Coating design for high H3/E2 is generally beneficial.•Substrate stiffness influences failure behaviour at high load.•Coating plasticity index influences the damage tolerance on continuing impacts.A key step in optimisation of coating behaviour is to understand the relationship between a range of parameters that can easily be obtained in the repetitive nano-impact test and ultimate coating performance in demanding applications. In this study we have performed a statistical analysis of multiple repetitive impact tests on advanced nitride coating systems and have identified the key parameters that can be used to assess durability and wear resistance. At lower load the coating mechanical properties and microstructure are beneficial in providing improved impact resistance. At higher load the initial impact resistance is also enhanced in non-columnar coatings with higher resistance to plastic deformation but their limited ductility can affect their damage tolerance under continued impact.

Nanoindentation tests with loading rates spanning three orders of magnitude were carried out on annealed polycrystalline copper. In addition to the hardness increasing with loading rate, the formation and development of pile-up around the indentation sites were also found to be strongly rate-dependent. The development of pile-up with increased time at peak load was found to be sensitive to the prior loading rate, being much larger for tests at 50 mN/s than at 0.05 mN/s. The underlying mechanisms were investigated in terms of the kinetic aspects of the nucleation and interactions of dislocations, and can be well explained by the activation volume and the strain gradient plasticity theory.

A graphene film was synthesized using chemical vapor deposition and then transferred to a flexible poly(ethylene terephthalate) (PET) substrate. The nanomechanical properties of the graphene/PET (G/PET) system were investigated by nanoindentation. The hardness (H) and reduced modulus (Er) of PET and G/PET were calculated using the Oliver–Pharr method with corrections for creep and material pile-up around the contact. The H and Er of the G/PET were 97% and 16% higher respectively than on the PET substrate. The increase in Er can be attributed to the high in-plane elastic modulus of graphene, the smaller increase in Er than H merely reflecting the far-field nature of the elastic stress field compared to the plastic stress field. The creep behavior of the PET is strongly hindered by the presence of the graphene overlayer. A simple volume contribution model was adopted to calculate the elastic modulus of the graphene overlayer and the computed values were of the right magnitude for graphene film.