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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.