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Electroless Ni-P coating containing ZrO2particles was successfully co-deposited on low carbon steel substrate. The surface and cross-sectional micrographs of the composite coatings were observed with scanning electron microscopy (SEM). And the chemical composition of the coating was analyzed with energy dispersive spectroscopy (EDS). The oxidation resistance was evaluated by weight gains during high temperature oxidation test. The results showed that the embedded ZrO2particles with irregular shape uniformly distributed in the entire Ni-P matrix, and the coating showed a good adhesion to the substrate. The weight gain curves of Ni-P-ZrO2composite coatings and Ni-P coating at 923K oxidation experiments were in accordance with . The ZrO2particles in Ni-P matrix could significantly enhance the high temperature oxidation resistance of the carbon steel substrate as compared to pure Ni-P coating.

This article proposes an idea for the development of a novel frequency-tunable electromagnetic energy harvester, which mainly consists of a frequency-tuning system component and an electromagnetic energy-harvesting component. A magneto-rheological elastomer, a kind of smart material, was utilized in the design of the frequency-tuning part using its unique rheological characteristic that its shear modulus can be altered by changing the strength of an external magnetic field. When external excitation is provided to the system, the tip magnet oscillates relative to the coil to produce electricity. The stiffness of the system's equivalent torsional spring composed of magneto-rheological elastomer blocks can be altered by changing the gap distance between two tuning magnets, which results in a shift in the primary natural frequency of the system and significant improvement of energy-harvesting efficiency. This article presents the detailed process for the design, simulation, experiment, and fabrication of the proposed energy harvester. Experiments and numerical simulations were also conducted under band-limited random excitation to support the validity of the present system.

This study focuses on the design, simulation, and load power optimization for the development of a novel frequency-tunable electromagnetic vibrational energy harvester. The unique characteristic of a magnetorheological elastomer (MRE) is utilized, that the shear modulus can be varied by changing the strength of an applied magnetic field. The electromagnetic energy harvester is fabricated, the external electric circuit is connected, and the performance is evaluated through a series of experiments. The resonant frequencies and the parasitic damping constant are measured experimentally for different tuning magnet gap distances, which validate the application of the MRE to the development of a frequency-tunable energy harvesting system. The harvested energy of the system is measured by the voltage across the load resistor. The maximum load power is attained by optimizing the external circuit connected to the coil system. The analysis results are presented for harvesting the maximum load power in terms of the coil parameters and external circuit resistance. The optimality of the load resistance is validated by comparing the analytical results with experimental results. The optimal load resistances under various resonance frequencies are also found for the design and composition of the optimal energy harvesting circuit of the energy harvester system.

Short carbon fibre (C f ) reinforced TiCN-based cermets (C f /TiCN composites) were produced by powder metallurgy method with pressureless sintering technology. The phase evolution, microstructure and fracture morphology of C f /TiCN composites were investigated. The results showed that TiC, TiN, WC, Cr 3 C 2 and Mo phases disappeared gradually and diffused into core and rim phases by dissolution-reprecipitation process, finally formed new hard TiCN core phases and complex compound (Cr, W, Mo, Ti)(CN) rim phases, with the sintering temperature increasing. The added C f did not change the 'core-rim' microstructure but improved the mechanical properties of TiCN-based cermets. The C f /TiCN composite containing 3 wt-% C f achieved the best comprehensive mechanical properties, with fracture toughness and bending strength increasing by about 14.4% and 30.8%, respectively, when compared with the composite without C f . Toughening and strengthening mechanisms of C f /TiCN composite were concluded as crack deflection and branch, as well as the pull-out, fracture and bridging of carbon fibres.

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