Polycrystalline Pr2Fe17-xMnx（x = 0, 1, and 2）alloys were studied by X-ray diffraction（XRD）, heat capacity, ac susceptibility, and isothermal magnetization measurements. All the alloys adopt the rhombohedral Th2Zn1...Polycrystalline Pr2Fe17-xMnx（x = 0, 1, and 2）alloys were studied by X-ray diffraction（XRD）, heat capacity, ac susceptibility, and isothermal magnetization measurements. All the alloys adopt the rhombohedral Th2Zn17-type structure. The Curie temperature increases from 283 K at x = 0 to 294 K at x = 1, and then decreases to 285 K at x = 2. The magnetic phase transition at the Curie temperature is a typical second-order paramagnetic–ferromagnetic transition. For an applied field change from0 to 5 T, the maximum-△SM for Pr2Fe17-xMnxalloys with x = 0, 1, and 2 are 5.66, 5.07, and 4.31 J·kg^-1·K^-1,respectively. The refrigerant capacity（RC） values range from 458 to 364 J·kg^-1, which is about 70 %–89 % that of Gd. The large, near room temperature △SM and RC values,chemical stability, and a high performance-to-cost ratio make Pr2Fe17-xMnxalloys be selectable materials for room temperature magnetic refrigeration applications.展开更多
Sm2Fe17 alloy was the precursor of Sm2Fe17Nx magnetic materials.Reduction-diffusion(R/D) method was a new preparation process for the Sm2Fe17 alloy,and had been widely employed as a new preparation method for rare ear...Sm2Fe17 alloy was the precursor of Sm2Fe17Nx magnetic materials.Reduction-diffusion(R/D) method was a new preparation process for the Sm2Fe17 alloy,and had been widely employed as a new preparation method for rare earth-transition metal intermetallic compounds.In this text,thermodynamics and kinetics for the synthesis of the Sm2Fe17 alloy by reduction-diffusion(R/D) method in the Ca-Sm2O3-Fe system were analyzed.The related synthesis mechanism of this reaction was investigated in detail by means of scanning electron microscope(SEM).The results showed that the thickness of the Sm2Fe17 alloy layer versus the reaction time could be fit by the parabola law,and its growth model was determined to be:(L0-L)2=43.848 t,the diffusion of Sm into Fe proceeded with the formation of the Sm2Fe17 phase from the very beginning of the reaction,and rich samarium phases,such as SmFe2 and SmFe3,were not formed,and the rate-determining step of the R/D reaction was found to be the peritectic reaction between liquid samarium and solid iron.展开更多
Sinee Coey et al. prepared the R<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> compounds by means of doping the nitrogenin gas-phase reaction, the magnetic properties of R<sub>2<...Sinee Coey et al. prepared the R<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> compounds by means of doping the nitrogenin gas-phase reaction, the magnetic properties of R<sub>2</sub>Fe<sub>17</sub> intermetallic compounds havebeen significantly improved. This aroused wide interest of relevant scientists. Recent re-search results show that Sm<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> has excellent intrinsic magnetic properties, but the nitridesR<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> consisting of other rare-earth elements except Sm, have an easy-plane anisotropy.In addition, Sm is very expensive. This kind of permanent magnetic materials is展开更多
基金financially supported by the U.S. Department of Energy by Iowa State University (No. DE-AC0207CH11358)the Guangdong Provincial Science & Technology Program (No. 2010B050300008)+2 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (No. x2clB7120290)the Guangzhou Municipal Science and Technology Program (No. 12F582080022)the Fundamental Research Funds for the Central Universities (Nos. 2012ZZ0013 and 2011ZM0014)
文摘Polycrystalline Pr2Fe17-xMnx（x = 0, 1, and 2）alloys were studied by X-ray diffraction（XRD）, heat capacity, ac susceptibility, and isothermal magnetization measurements. All the alloys adopt the rhombohedral Th2Zn17-type structure. The Curie temperature increases from 283 K at x = 0 to 294 K at x = 1, and then decreases to 285 K at x = 2. The magnetic phase transition at the Curie temperature is a typical second-order paramagnetic–ferromagnetic transition. For an applied field change from0 to 5 T, the maximum-△SM for Pr2Fe17-xMnxalloys with x = 0, 1, and 2 are 5.66, 5.07, and 4.31 J·kg^-1·K^-1,respectively. The refrigerant capacity（RC） values range from 458 to 364 J·kg^-1, which is about 70 %–89 % that of Gd. The large, near room temperature △SM and RC values,chemical stability, and a high performance-to-cost ratio make Pr2Fe17-xMnxalloys be selectable materials for room temperature magnetic refrigeration applications.
文摘Sm2Fe17 alloy was the precursor of Sm2Fe17Nx magnetic materials.Reduction-diffusion(R/D) method was a new preparation process for the Sm2Fe17 alloy,and had been widely employed as a new preparation method for rare earth-transition metal intermetallic compounds.In this text,thermodynamics and kinetics for the synthesis of the Sm2Fe17 alloy by reduction-diffusion(R/D) method in the Ca-Sm2O3-Fe system were analyzed.The related synthesis mechanism of this reaction was investigated in detail by means of scanning electron microscope(SEM).The results showed that the thickness of the Sm2Fe17 alloy layer versus the reaction time could be fit by the parabola law,and its growth model was determined to be:(L0-L)2=43.848 t,the diffusion of Sm into Fe proceeded with the formation of the Sm2Fe17 phase from the very beginning of the reaction,and rich samarium phases,such as SmFe2 and SmFe3,were not formed,and the rate-determining step of the R/D reaction was found to be the peritectic reaction between liquid samarium and solid iron.
文摘Sinee Coey et al. prepared the R<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> compounds by means of doping the nitrogenin gas-phase reaction, the magnetic properties of R<sub>2</sub>Fe<sub>17</sub> intermetallic compounds havebeen significantly improved. This aroused wide interest of relevant scientists. Recent re-search results show that Sm<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> has excellent intrinsic magnetic properties, but the nitridesR<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> consisting of other rare-earth elements except Sm, have an easy-plane anisotropy.In addition, Sm is very expensive. This kind of permanent magnetic materials is
