Relationships between the coercivity of hydrogenation disproportionation desorption recombination （HDDR） Nd12.5Fe81.5-xfo6Bx bonded magnets and boron content were investigated. Nd2Fe17 phase with planar magnetic ani...Relationships between the coercivity of hydrogenation disproportionation desorption recombination （HDDR） Nd12.5Fe81.5-xfo6Bx bonded magnets and boron content were investigated. Nd2Fe17 phase with planar magnetic anisotropy is present in the microstructure when x= 4at%-5.88at%, which does not reduce the coercivity of the bonded magnets. High-resolution transmission electron microscopy （TEM） images show that Nd2Fe17 phase exists in the form of nanocrystals in the Nd2Fe14B matrix. There is an exchange-coupling interaction between the two phases so that the coercivity of HDDR Nd12.5Fe81.5-xCo6Bx bonded magnets is hardly reduced with a decrease in boron content.展开更多
The catalytic effects of ZrC powder on the dehydrogenation properties of LiAlH4 prepared by designed mixing processes were systematically investigated.The onset dehydrogenation temperatures for the 10 mol% ZrC-doped s...The catalytic effects of ZrC powder on the dehydrogenation properties of LiAlH4 prepared by designed mixing processes were systematically investigated.The onset dehydrogenation temperatures for the 10 mol% ZrC-doped sample are 85.3 and 148.4℃for the first two dehydrogenation stages,decreasing by 90.7 and 57.8℃,respectively,compared with those of the as-received LiAIH4.The isothermal volumetric measurement indicates that adding ZrC powder could significantly enhance the desorption kinetics of LiAlH4.The reaction constant and Avrami index show that the first dehydrogenation stage is controlled by diffusion mechanism with nucleation rate gradually decreasing and the second stage is a freedom nucleation and subsequent growth process.The microstructures and phase transformation characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared spectroscopy(FTIR) reveal that the improved desorption behavior of LiAlH4 is primarily due to the high density of surface defects and embedded catalyst particles on the surface of LiAlH4 particles during the high-energy mixing process.展开更多
基金financially supported by the National High-Tech Research and Development Program of China (No.2011AA03A403)
文摘Relationships between the coercivity of hydrogenation disproportionation desorption recombination （HDDR） Nd12.5Fe81.5-xfo6Bx bonded magnets and boron content were investigated. Nd2Fe17 phase with planar magnetic anisotropy is present in the microstructure when x= 4at%-5.88at%, which does not reduce the coercivity of the bonded magnets. High-resolution transmission electron microscopy （TEM） images show that Nd2Fe17 phase exists in the form of nanocrystals in the Nd2Fe14B matrix. There is an exchange-coupling interaction between the two phases so that the coercivity of HDDR Nd12.5Fe81.5-xCo6Bx bonded magnets is hardly reduced with a decrease in boron content.
基金financially supported by the National High Technology Research and Development Program of China (No.2006AA05Z132)the National Natural Science Foundation of China (No.51471054)
文摘The catalytic effects of ZrC powder on the dehydrogenation properties of LiAlH4 prepared by designed mixing processes were systematically investigated.The onset dehydrogenation temperatures for the 10 mol% ZrC-doped sample are 85.3 and 148.4℃for the first two dehydrogenation stages,decreasing by 90.7 and 57.8℃,respectively,compared with those of the as-received LiAIH4.The isothermal volumetric measurement indicates that adding ZrC powder could significantly enhance the desorption kinetics of LiAlH4.The reaction constant and Avrami index show that the first dehydrogenation stage is controlled by diffusion mechanism with nucleation rate gradually decreasing and the second stage is a freedom nucleation and subsequent growth process.The microstructures and phase transformation characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared spectroscopy(FTIR) reveal that the improved desorption behavior of LiAlH4 is primarily due to the high density of surface defects and embedded catalyst particles on the surface of LiAlH4 particles during the high-energy mixing process.
