In this article, our recent progress concerning the effects of atomic substitution, magnetic field, and temperature on the magnetic and magnetocaloric properties of the LaFe13-xAlx compounds are reviewed. With an incr...In this article, our recent progress concerning the effects of atomic substitution, magnetic field, and temperature on the magnetic and magnetocaloric properties of the LaFe13-xAlx compounds are reviewed. With an increase of the aluminum content, the compounds exhibit successively an antiferromagnetic （AFM） state, a ferromagnetic （FM） state, and a mictomagnetic state. Furthermore, the AFM coupling of LaFe13 -xAlx can be converted to an FM one by substituting Si for A1, Co for Fe, and magnetic rare-earth R for La, or introducing interstitial C or H atoms. However, low doping levels lead to FM clusters embedded in an AFM matrix, and the resultant compounds can undergo, under appropriate applied fields, first an AFM-FM and then an FM-AFM phase transition while heated, with significant magnetic relaxation in the vicinity of the transition temperature. The Curie temperature of LaFe13-xAlx can be shifted to room temperature by choosing appropriate contents of Co, C, or H, and a strong magnetocaloric effect can be obtained around the transition temperature. For example, for the LaFel 1.5All.5Co.2Hl.o compound, the maximal entropy change reaches 13.8 J.kg-1.K-1 for a field change of 0-5 T, occurring around room temperature. It is 42% higher than that of Gd, and therefore, this compound is a promising room-temperature magnetic refrigerant.展开更多
Micro-scale Al-Zn-Mg/Fe composite powders (MAF) with high reactivity and good storage properties were prepared by reducing iron onto the surface of Al-Zn-Mg alloy powders. Experimental results show that MAF as advance...Micro-scale Al-Zn-Mg/Fe composite powders (MAF) with high reactivity and good storage properties were prepared by reducing iron onto the surface of Al-Zn-Mg alloy powders. Experimental results show that MAF as advanced zero-valent iron are highly effective for degradation of chlorinated organic compounds. The efficiency of degradation for carbon tetrachloride and perchloroethylene is higher than 99% within a period of 2 h. The efficiency of degradation for trichloroethylene by MAF after storing for one month is equivalent to that by freshly prepared nano-size zero-valent iron particles.展开更多
The compound ingots of Pr0.15TbxDy0.85-xFe2 (x=0 to 0.85) were prepared by arc melting in a water Cu boat using arc furnace under a purified Ar atmosphere. Appropriate annealing (850℃, 100 h) can obtain single Laves ...The compound ingots of Pr0.15TbxDy0.85-xFe2 (x=0 to 0.85) were prepared by arc melting in a water Cu boat using arc furnace under a purified Ar atmosphere. Appropriate annealing (850℃, 100 h) can obtain single Laves phase compound. The magnetostriction for these systems will rise obviously when partially substituted Tb or Dy by Pr.展开更多
The possible geometries of Fe(HCN)n (n = 1~6) compounds were studied by using + DFT/UB3LYP/6-31G(2df) method. The structure and ground state ...The possible geometries of Fe(HCN)n (n = 1~6) compounds were studied by using + DFT/UB3LYP/6-31G(2df) method. The structure and ground state of each fragmental ion are C∞v (4Σ+ or Σ ), D∞h (4Σg ), D3 (4A1 ), C2 or Td or C3v (4A1), and D3 (4A1 ) or C4 ( A1 ) sequentially 6 + + ′ ′ ′ 2 ′ h v h v with n = 1～5. For the compound Fe(HCN)6 , the possible geometry was not obtained. The + sequential incremental interaction energy (–?(?E)), dissociation energy (?D0), enthalpy (–?(?H)) and Gibbs free energy (–?(?G)), and frequencies for HCN-Fe(HCN)n + -1 were also calculated, and the results are all in good agreement with the experiments. The bond length of Fe–N is lengthened with the increase of cluster size, and the strength of Fe+–N coordination bond varies nonmon- tonically as increasing the number of ligands. The Fe+–N bond of Fe(HCN)2 is the strongest in all + compounds.展开更多
The alloy with nominal composition Sm_2(Fe0.94Ti0.06)17 is prepared by arc-melting, hydrogenation and nitrogenation processes. The Sm_2(Fe0.94Ti0.06)17 alloy has a single phase of Sm_3(Fe, Ti)29 with the Nd_3(Fe, Ti)...The alloy with nominal composition Sm_2(Fe0.94Ti0.06)17 is prepared by arc-melting, hydrogenation and nitrogenation processes. The Sm_2(Fe0.94Ti0.06)17 alloy has a single phase of Sm_3(Fe, Ti)29 with the Nd_3(Fe, Ti)29-type structure. The corresponding hydride phase with the same phase structure of the parent alloy was formed after a hydrogen decrepitation (HD) process at 300℃. The hydrogenation at 800℃ mainly shows a HDDR process. The HD and nitrogenation at 500℃ result in increasing the Curie temperature of the alloy by 72℃ and by 158℃ due to lattice expansions, respectively. The anisotropic and isotropic Sm_3(Fe. Ti)29N_y magnets are obtained after HD, HDDR and the consequent nitrogenation, respectively. The optimum magnetic properties of Sm_3(Fe, Ti)29N_y powders achieved in the above two processes are: (i) B_r=0;82 T, _iH_c=4.48 kA/cm. (BH)_max=54.3 kJ/m^3, (ii) B_r=0.68 T, _iH_c=8.14 kA/cm, (BH)max=66.4 kJ/m^3.展开更多
The structural and magnetostrictive properties of (CexTb1-x)0.5Pr0.5Fe_2 were investigated. Ceconcentration must exceed x=0.6 in order to obtain the pure Laves phase. The magnetostriction and anisotropy constant incr...The structural and magnetostrictive properties of (CexTb1-x)0.5Pr0.5Fe_2 were investigated. Ceconcentration must exceed x=0.6 in order to obtain the pure Laves phase. The magnetostriction and anisotropy constant increase with the Tb-content in this system. The anisotropy value of PrFe_2 is lower than that of isostructural DyFe_2. From the X-ray step-scanned data we found that λ_111 of PrFe_2 is 1310x10^-6. A large increase of magnetostriction can be observed under a small prestress of 6 MP_a for Ce_0.5Pr_0.5Fe_2.展开更多
A systematic study of syntheses and magnetic properties of the Nd_3Fe_(29-x)Cr_x (x=4.5, 4.7, 5.0, and 5.5) compounds has been performed. The single-phase compounds of Nd_3Fe_(29-x)Cr_x can be formed in the range 4.5...A systematic study of syntheses and magnetic properties of the Nd_3Fe_(29-x)Cr_x (x=4.5, 4.7, 5.0, and 5.5) compounds has been performed. The single-phase compounds of Nd_3Fe_(29-x)Cr_x can be formed in the range 4.5≤ x ≤ 5.5. The Curie temperature T_C, the saturation magnetization M_s at 4.2 K, the anisotropy field H_A at 4.2 K and room temperature. and the intra-sublattice exchange coupling parameter j_(FeFe) at 4.2 K for the Nd_3Fe_(29-x)Cr_x compounds decrease with increasing Cr composition from x=4.5 to 5.5, respectively. Nitrogenation and carbonation, unlike hydrogenation. result mainly in improvements of the Curie temperature, the saturation magnetization and the anisotropy field at 4.2 K and room temperature for the Nd_3Fe_(29-x)Cr_x compounds compared with their parent compounds.展开更多
The electronic structure of iron-pnictide compound superconductor Ba_2Ti_2Fe_2As_4O, which has metallic intermediate Ti_2O layers, is studied using angle-resolved photoemission spectroscopy. The Ti-related bands show ...The electronic structure of iron-pnictide compound superconductor Ba_2Ti_2Fe_2As_4O, which has metallic intermediate Ti_2O layers, is studied using angle-resolved photoemission spectroscopy. The Ti-related bands show a‘peak-dip-hump＇ line shape with two branches of dispersion associated with the polaronic states at temperatures below around 120 K. This change in the spectra occurs along with the resistivity anomaly that was not clearly understood in a previous study. Moreover, an energy gap induced by the superconducting proximity effect opens in the polaronic bands at temperatures below T_c（~21 K）. Our study provides the spectroscopic evidence that superconductivity coexists with polarons in the same bands near the Fermi level, which provides a suitable platform to study interactions between charge, lattice and spin freedoms in a correlated system.展开更多
The temperature dependent magnetization of the (Ce,Nd) 2(Fe,Si,Mn) 17 intermetallic compounds were measured and analyzed by molecular field theory (MFT). The relationship between T C and the intrasublattic...The temperature dependent magnetization of the (Ce,Nd) 2(Fe,Si,Mn) 17 intermetallic compounds were measured and analyzed by molecular field theory (MFT). The relationship between T C and the intrasublattice coupling interactions was discussed. The two sublattice MFT model can well describe the temperature dependence of the magnetization for all the compounds investigated. Ce ion in (Ce,Nd) 2Fe 17 compounds does not simply dilute the magnetic structure, but is likely present in a mixed valence state. The substitution of Si for Fe strongly raises T C and the mean Fe moment remains unchanged for Ce 2(Si,Fe) 17 compounds, and the 3d exchange coupling constant J FF increases linearly. Mn decreases T C of Nd 2(Mn, Fe) 17 compound by reducing J FF .展开更多
The melting behavior,solid state phase transformation and structure of pseudo-ternary compounds Nd_2(Fe_(1-x)Ni_x)_(14)B and Pr_2(Co_(1-y)Ni_y)_(14)B were studied using differential thermal analysis,optical microscopy...The melting behavior,solid state phase transformation and structure of pseudo-ternary compounds Nd_2(Fe_(1-x)Ni_x)_(14)B and Pr_2(Co_(1-y)Ni_y)_(14)B were studied using differential thermal analysis,optical microscopy X-ray diffraction,and electron probe micro-analysis techniques.At high temperature,eutectoid decomposition R_2(Ni,M)_(17)→R(Ni,M)_5+x-Ni(M) takes place in these two pseudo-ternary compounds,in the composition range x=0.6～1.0 and y=0.3～1.0,respectively.When x(or y)≤0.2,both Nd_2(Fe_(1-x)Ni_x)_(14)B and Pr_2(Co_(1-y)Ni_y)_(14)B are single phase tetragonal.The phase constitutents of these two systems at room tempera- ture are similar in the composition range 0.6≤x(or y)≤1.0.展开更多
The formation of Fe-N compounds by laser nitriding in an atmospheric ambient was reported. By CW-CO2 laser irradiation on pure ferrite iron in the atmospheric ambient, Fe-N compounds (including Fe2N, .Fe3AT and Fe4N) ...The formation of Fe-N compounds by laser nitriding in an atmospheric ambient was reported. By CW-CO2 laser irradiation on pure ferrite iron in the atmospheric ambient, Fe-N compounds (including Fe2N, .Fe3AT and Fe4N) are formed as a result of a laser-enhanced and temperature-enhanced reactions. The samples were analyzed with X-ray diffraction. It is found that the laser power density, scanning speed and nitrogen temperature are the main factors influencing the formation of Fe-N compounds. Nitrogen can be activated by pre-heating at some temperature. Nitrogen activation and sample surface melting by CW-CO2 laser greatly enhance the reaction between the sample surface and nitrogen beam. After annealing at 500℃for 3h, some Fe2N and Fe3N converted into more stable Fe4N.展开更多
基金Project supported by the National Natural Science Foundation of Chinathe Key Research Program of the Chinese Academy of Sciences+1 种基金the National Basic Research Program of Chinathe National High Technology Research and Development Program of China
文摘In this article, our recent progress concerning the effects of atomic substitution, magnetic field, and temperature on the magnetic and magnetocaloric properties of the LaFe13-xAlx compounds are reviewed. With an increase of the aluminum content, the compounds exhibit successively an antiferromagnetic （AFM） state, a ferromagnetic （FM） state, and a mictomagnetic state. Furthermore, the AFM coupling of LaFe13 -xAlx can be converted to an FM one by substituting Si for A1, Co for Fe, and magnetic rare-earth R for La, or introducing interstitial C or H atoms. However, low doping levels lead to FM clusters embedded in an AFM matrix, and the resultant compounds can undergo, under appropriate applied fields, first an AFM-FM and then an FM-AFM phase transition while heated, with significant magnetic relaxation in the vicinity of the transition temperature. The Curie temperature of LaFe13-xAlx can be shifted to room temperature by choosing appropriate contents of Co, C, or H, and a strong magnetocaloric effect can be obtained around the transition temperature. For example, for the LaFel 1.5All.5Co.2Hl.o compound, the maximal entropy change reaches 13.8 J.kg-1.K-1 for a field change of 0-5 T, occurring around room temperature. It is 42% higher than that of Gd, and therefore, this compound is a promising room-temperature magnetic refrigerant.
文摘Micro-scale Al-Zn-Mg/Fe composite powders (MAF) with high reactivity and good storage properties were prepared by reducing iron onto the surface of Al-Zn-Mg alloy powders. Experimental results show that MAF as advanced zero-valent iron are highly effective for degradation of chlorinated organic compounds. The efficiency of degradation for carbon tetrachloride and perchloroethylene is higher than 99% within a period of 2 h. The efficiency of degradation for trichloroethylene by MAF after storing for one month is equivalent to that by freshly prepared nano-size zero-valent iron particles.
基金the Natural Science Foundation of Hebei Province 596028 and the National NaturalScience Foundation of China No.59871062.
文摘The compound ingots of Pr0.15TbxDy0.85-xFe2 (x=0 to 0.85) were prepared by arc melting in a water Cu boat using arc furnace under a purified Ar atmosphere. Appropriate annealing (850℃, 100 h) can obtain single Laves phase compound. The magnetostriction for these systems will rise obviously when partially substituted Tb or Dy by Pr.
基金This research was supported by the National Natural Science Foundation of China (20273013 20303002)+1 种基金 the Key Foundation of Fujian Province (K02012) the Foundation of State Key Laboratory of Structural Chemistry (020051) and of Fuzhou University
文摘The possible geometries of Fe(HCN)n (n = 1~6) compounds were studied by using + DFT/UB3LYP/6-31G(2df) method. The structure and ground state of each fragmental ion are C∞v (4Σ+ or Σ ), D∞h (4Σg ), D3 (4A1 ), C2 or Td or C3v (4A1), and D3 (4A1 ) or C4 ( A1 ) sequentially 6 + + ′ ′ ′ 2 ′ h v h v with n = 1～5. For the compound Fe(HCN)6 , the possible geometry was not obtained. The + sequential incremental interaction energy (–?(?E)), dissociation energy (?D0), enthalpy (–?(?H)) and Gibbs free energy (–?(?G)), and frequencies for HCN-Fe(HCN)n + -1 were also calculated, and the results are all in good agreement with the experiments. The bond length of Fe–N is lengthened with the increase of cluster size, and the strength of Fe+–N coordination bond varies nonmon- tonically as increasing the number of ligands. The Fe+–N bond of Fe(HCN)2 is the strongest in all + compounds.
基金National Natural Science FOundation of China!59571014National Natural Science FOundation of China!59725103National Natur
文摘The alloy with nominal composition Sm_2(Fe0.94Ti0.06)17 is prepared by arc-melting, hydrogenation and nitrogenation processes. The Sm_2(Fe0.94Ti0.06)17 alloy has a single phase of Sm_3(Fe, Ti)29 with the Nd_3(Fe, Ti)29-type structure. The corresponding hydride phase with the same phase structure of the parent alloy was formed after a hydrogen decrepitation (HD) process at 300℃. The hydrogenation at 800℃ mainly shows a HDDR process. The HD and nitrogenation at 500℃ result in increasing the Curie temperature of the alloy by 72℃ and by 158℃ due to lattice expansions, respectively. The anisotropic and isotropic Sm_3(Fe. Ti)29N_y magnets are obtained after HD, HDDR and the consequent nitrogenation, respectively. The optimum magnetic properties of Sm_3(Fe, Ti)29N_y powders achieved in the above two processes are: (i) B_r=0;82 T, _iH_c=4.48 kA/cm. (BH)_max=54.3 kJ/m^3, (ii) B_r=0.68 T, _iH_c=8.14 kA/cm, (BH)max=66.4 kJ/m^3.
基金Natural Science of Hebei Province!(No. 596028)National Natural Science Foundation of China!(No. 59871062).
文摘The structural and magnetostrictive properties of (CexTb1-x)0.5Pr0.5Fe_2 were investigated. Ceconcentration must exceed x=0.6 in order to obtain the pure Laves phase. The magnetostriction and anisotropy constant increase with the Tb-content in this system. The anisotropy value of PrFe_2 is lower than that of isostructural DyFe_2. From the X-ray step-scanned data we found that λ_111 of PrFe_2 is 1310x10^-6. A large increase of magnetostriction can be observed under a small prestress of 6 MP_a for Ce_0.5Pr_0.5Fe_2.
文摘A systematic study of syntheses and magnetic properties of the Nd_3Fe_(29-x)Cr_x (x=4.5, 4.7, 5.0, and 5.5) compounds has been performed. The single-phase compounds of Nd_3Fe_(29-x)Cr_x can be formed in the range 4.5≤ x ≤ 5.5. The Curie temperature T_C, the saturation magnetization M_s at 4.2 K, the anisotropy field H_A at 4.2 K and room temperature. and the intra-sublattice exchange coupling parameter j_(FeFe) at 4.2 K for the Nd_3Fe_(29-x)Cr_x compounds decrease with increasing Cr composition from x=4.5 to 5.5, respectively. Nitrogenation and carbonation, unlike hydrogenation. result mainly in improvements of the Curie temperature, the saturation magnetization and the anisotropy field at 4.2 K and room temperature for the Nd_3Fe_(29-x)Cr_x compounds compared with their parent compounds.
基金Supported by the National Basic Research Program of China under Grant Nos 2013CB921700,2015CB921300 and2015CB921301the National Natural Science Foundation of China under Grant Nos 11234014,11622435,11274362,11674371 and11474340+1 种基金the National Key Research and Development Program of China under Grant Nos 2016YFA0300300,2016YFA0300600,2016YFA0401000 and 2016YFA0400902the Open Large Infrastructure Research of Chinese Academy of Sciences,and the Pioneer Hundred Talents Program(Type C)of Chinese Academy of Sciences
文摘The electronic structure of iron-pnictide compound superconductor Ba_2Ti_2Fe_2As_4O, which has metallic intermediate Ti_2O layers, is studied using angle-resolved photoemission spectroscopy. The Ti-related bands show a‘peak-dip-hump＇ line shape with two branches of dispersion associated with the polaronic states at temperatures below around 120 K. This change in the spectra occurs along with the resistivity anomaly that was not clearly understood in a previous study. Moreover, an energy gap induced by the superconducting proximity effect opens in the polaronic bands at temperatures below T_c（~21 K）. Our study provides the spectroscopic evidence that superconductivity coexists with polarons in the same bands near the Fermi level, which provides a suitable platform to study interactions between charge, lattice and spin freedoms in a correlated system.
文摘The temperature dependent magnetization of the (Ce,Nd) 2(Fe,Si,Mn) 17 intermetallic compounds were measured and analyzed by molecular field theory (MFT). The relationship between T C and the intrasublattice coupling interactions was discussed. The two sublattice MFT model can well describe the temperature dependence of the magnetization for all the compounds investigated. Ce ion in (Ce,Nd) 2Fe 17 compounds does not simply dilute the magnetic structure, but is likely present in a mixed valence state. The substitution of Si for Fe strongly raises T C and the mean Fe moment remains unchanged for Ce 2(Si,Fe) 17 compounds, and the 3d exchange coupling constant J FF increases linearly. Mn decreases T C of Nd 2(Mn, Fe) 17 compound by reducing J FF .
基金the National Natural Science Fundation of China.
文摘The melting behavior,solid state phase transformation and structure of pseudo-ternary compounds Nd_2(Fe_(1-x)Ni_x)_(14)B and Pr_2(Co_(1-y)Ni_y)_(14)B were studied using differential thermal analysis,optical microscopy X-ray diffraction,and electron probe micro-analysis techniques.At high temperature,eutectoid decomposition R_2(Ni,M)_(17)→R(Ni,M)_5+x-Ni(M) takes place in these two pseudo-ternary compounds,in the composition range x=0.6～1.0 and y=0.3～1.0,respectively.When x(or y)≤0.2,both Nd_2(Fe_(1-x)Ni_x)_(14)B and Pr_2(Co_(1-y)Ni_y)_(14)B are single phase tetragonal.The phase constitutents of these two systems at room tempera- ture are similar in the composition range 0.6≤x(or y)≤1.0.
文摘The formation of Fe-N compounds by laser nitriding in an atmospheric ambient was reported. By CW-CO2 laser irradiation on pure ferrite iron in the atmospheric ambient, Fe-N compounds (including Fe2N, .Fe3AT and Fe4N) are formed as a result of a laser-enhanced and temperature-enhanced reactions. The samples were analyzed with X-ray diffraction. It is found that the laser power density, scanning speed and nitrogen temperature are the main factors influencing the formation of Fe-N compounds. Nitrogen can be activated by pre-heating at some temperature. Nitrogen activation and sample surface melting by CW-CO2 laser greatly enhance the reaction between the sample surface and nitrogen beam. After annealing at 500℃for 3h, some Fe2N and Fe3N converted into more stable Fe4N.
