Nd（DBM）3Phen-doped （DBM is dibenzoylmethane and Phen is phenanthroline） polymethyl methacrylate （PMMA） is prepared. Optical absorption, excitation and emission spectra were analyzed for Nd^3＋ in Nd（DBM）3Phen-...Nd（DBM）3Phen-doped （DBM is dibenzoylmethane and Phen is phenanthroline） polymethyl methacrylate （PMMA） is prepared. Optical absorption, excitation and emission spectra were analyzed for Nd^3＋ in Nd（DBM）3Phen-doped PMMA. Using the Judd-Ofelt theory, the absorption spectrum was analyzed. The Judd-Ofelt（J-O） intensity parameters of Nd（DBM）3Phen-doped polymethyl methacrylate were calculated to be Ω2 = 20.97 × 10^-20 cm^2, Ω4= 3.42 × 10^-20 cm^2, Ω6 = 2.90 × 10^-20 cm^2. The radiative lifetime （631 μs） of the excited 4F3/2 level is given. The stimulated emission cross-sections and the fluorescence branch ratios for the ^4F3/2 →^4Ij′ transitions are also evaluated. Analysis reveals that Nd（DBM）3Phen-doped PMMA is promising for application in polymer optical fibers and planar waveguides.展开更多
The magnetic performance and mechanical properties including hardness, brittleness, fracture toughness and strength characteristics of the as-sintered and the optimal aged Nd-Fe-B magnets were examined in this work. A...The magnetic performance and mechanical properties including hardness, brittleness, fracture toughness and strength characteristics of the as-sintered and the optimal aged Nd-Fe-B magnets were examined in this work. A new method of Vickers hardness indentation combined with acoustic emission was used to test the brittleness of the magnets.The results show that the magnetic properties of the magnets could be improved through aging treatment, especially the intrinsic coercive force. But it is accompanied by a decrease of strength and fracture toughness. Theoretical calculation confirms that acoustic emission energy accumulated count value could be used to characterize the material brittleness. The bending fracture morphologies of the as-sintered and the optimal aged Nd Fe B magnets were investigated with the emphasis on the relationship between mechanical properties and microstructure using a field emission scanning electron microscopy(FE-SEM). The research results indicate that the intergranular fracture is the primary fracture mechanism for both as-sintered and optimal aged Nd Fe B magnets. Aging treatment changes the morphology and distribution of the Nd-rich phases, reducing the sliding resistance between Nd_2Fe_(14)B main crystal grains and lowers the grain boundary strength, which is the main reason for the strength and fracture toughness decrease of the aged Nd-Fe-B magnets.展开更多
基金ACKN0WLEDGMENT This work was supported by the National Natural Science Foundation of China （No.90201013）, the Natural Science Foundation of Fujian Province of China （No.A0510014）, and the Science Foundation of the Educational Department of Fujian Province of China （No JB03151 and JB04246）.
文摘Nd（DBM）3Phen-doped （DBM is dibenzoylmethane and Phen is phenanthroline） polymethyl methacrylate （PMMA） is prepared. Optical absorption, excitation and emission spectra were analyzed for Nd^3＋ in Nd（DBM）3Phen-doped PMMA. Using the Judd-Ofelt theory, the absorption spectrum was analyzed. The Judd-Ofelt（J-O） intensity parameters of Nd（DBM）3Phen-doped polymethyl methacrylate were calculated to be Ω2 = 20.97 × 10^-20 cm^2, Ω4= 3.42 × 10^-20 cm^2, Ω6 = 2.90 × 10^-20 cm^2. The radiative lifetime （631 μs） of the excited 4F3/2 level is given. The stimulated emission cross-sections and the fluorescence branch ratios for the ^4F3/2 →^4Ij′ transitions are also evaluated. Analysis reveals that Nd（DBM）3Phen-doped PMMA is promising for application in polymer optical fibers and planar waveguides.
基金Project((2012)1743)supported by the China National Major Special Program for the Rare Earth and Rare Metallic Materials
文摘The magnetic performance and mechanical properties including hardness, brittleness, fracture toughness and strength characteristics of the as-sintered and the optimal aged Nd-Fe-B magnets were examined in this work. A new method of Vickers hardness indentation combined with acoustic emission was used to test the brittleness of the magnets.The results show that the magnetic properties of the magnets could be improved through aging treatment, especially the intrinsic coercive force. But it is accompanied by a decrease of strength and fracture toughness. Theoretical calculation confirms that acoustic emission energy accumulated count value could be used to characterize the material brittleness. The bending fracture morphologies of the as-sintered and the optimal aged Nd Fe B magnets were investigated with the emphasis on the relationship between mechanical properties and microstructure using a field emission scanning electron microscopy(FE-SEM). The research results indicate that the intergranular fracture is the primary fracture mechanism for both as-sintered and optimal aged Nd Fe B magnets. Aging treatment changes the morphology and distribution of the Nd-rich phases, reducing the sliding resistance between Nd_2Fe_(14)B main crystal grains and lowers the grain boundary strength, which is the main reason for the strength and fracture toughness decrease of the aged Nd-Fe-B magnets.
