Nitrogen-doped reduced graphene oxide-metal(metal oxides) nanoparticle (N-rGO-M(MO) NPs, M ¼ Fe, MO: M ¼ Co, Mn) composites were prepared through a facile and general method at high temperature (800 C). M(MO) were well-dispersed and tightly anchored on graphene sheets, which were doped with nitrogen simultaneously and further loaded with Pt nanoparticles. Those results showed a more positive onset potential, higher cathodic density, and higher electron transfer number for the ORR in alkaline media. Furthermore, N-rGO-metal(metal oxides)-Pt (N-rGO-M(MO)-Pt) nanoparticles show better durability than the commercial Pt/C catalyst, and can be used as promising potential materials in practical applications.

Compared with conventional permanent magnet synchronous motor, variable flux memory motor (VFMM) possesses the advantage of adjusting the magnetization state online. Because of its wide speed range and large high-efficiency region, it becomes a competitive candidate for the electric drive system. This paper presents a novel parallel hybrid magnets VFMM which is obtained by updating a conventional series hybrid permanent magnets VFMM. The proposed motor adopts a new permanent magnet arrangement and the combination of low coercive force permanent magnet and high coercive force permanent magnet is used. The proposed parallel hybrid permanent magnets VFMM and the series hybrid permanent magnets VFMM are compared. The equivalent magnetic circuit models of the motors are used to explain the principle of the motors. The finite element analysis method is used to study the fundamental properties, such as open circuit radial flux density, unintentional demagnetization with q-axis current, intentional demagnetization with d-axis current, torque capability, and efficiency characteristics. It was shown the efficiency of the parallel hybrid permanent magnets VFMM is higher in the high-speed region and the magnetization state adjustment range of the parallel hybrid permanent magnets VFMM is larger. INDEX TERMS Equivalent magnetic circuit, hybrid permanent magnet, magnetization state, variable flux memory motor.

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