The application of ‘extreme’ hydrogen-decrepitation (HD) process using high-pressure disproportionation was extended to Sm-Co5-type-alloy. The alloy with nominal composition of Sm36Co64 was treated under 1.0～2.0 MP...The application of ‘extreme’ hydrogen-decrepitation (HD) process using high-pressure disproportionation was extended to Sm-Co5-type-alloy. The alloy with nominal composition of Sm36Co64 was treated under 1.0～2.0 MPa H2 pressure for several hours at room temperature for decrepitation. After disproportionation were high hydrogen pressures, the bulk alloys were disproportionated into particles with a size of 200. Investigations by powder X-ray diffractometer (XRD) showed, the after HD sample crystallized in the hexagonal CaCu5-type structure. The temperature dependence of pressure analysis (TPA) curve of the SmCo5 alloy showed that the hydrogen absorption temperature was about 150 ℃. Cylindrical sintered magnets of composition Sm36Co64 were prepared using HD ball milled, isostatic pressing, vacuum sintering and subsequent heat treatment. The demagnetization curves showed that the HD processes could improve the magnetic properties and squareness factor of the SmCo5 sintered magnet.展开更多
Magnetic properties and microstructure of SmCo_5 alloys were examined. It is found that the coercivity ofthe alloy is strongly influenced by its microstructure. If more non- 1 : 5 phase precipitated particles wereform...Magnetic properties and microstructure of SmCo_5 alloys were examined. It is found that the coercivity ofthe alloy is strongly influenced by its microstructure. If more non- 1 : 5 phase precipitated particles wereformed, which are properly due to the existing of oxygen in the alloys introduced during the heat treatment process, the magnetic properties of the alloy decrease.展开更多
SmConanoparticles(NPs) have promising applications in high-density magnetic storage and magnetic nanocomposites. In this work, A novel method to yield SmCoparticles with small size and high coercivity was reported. Fi...SmConanoparticles(NPs) have promising applications in high-density magnetic storage and magnetic nanocomposites. In this work, A novel method to yield SmCoparticles with small size and high coercivity was reported. Firstly, SmO-Co NPs with size of 6-15 nm were fabricated by a solvothermal route. Then the agglomerated SmCoparticles were obtained by thermal reduction of the precursor, which show high coercivity of2.0 T at room temperature. At last, the as-synthesized SmCoparticles were further hydrogenated under high hydrogen pressure of 4 MPa at room temperature, where hydrogen absorption process could form small-sized SmCoHparticles due to their lattice expansion and hydrogen desorption process could convert SmCoHNPs into SmCoNPs. The prepared SmCoNPs after hydrogenation, showing well distribution, have a small size of5-20 nm and room temperature coercivity of 1.22 T.展开更多
The relation between the tempering effects of sinterd SmCo^(5)alloy at 750℃and its intrinsic coercivity(i^(Hc))has been studied by the use of photoelectron energy spectrum.X-ray diffraction and high-voltage electron ...The relation between the tempering effects of sinterd SmCo^(5)alloy at 750℃and its intrinsic coercivity(i^(Hc))has been studied by the use of photoelectron energy spectrum.X-ray diffraction and high-voltage electron microscope.The result is that the cause of iHc dropping seriously for sintered SmCo_(5)alloy tempered at 750 t is not the eutectoid decomposition of SmCo_(5)and the increase of oxygen.In fact,iHcdropping is caused by that some defect-rich regions in Sm_(2)Co_(17)decomposed form SmC0_(5)from nucleation centers in reversed magnetization course.展开更多
SmCo_(5)sintered magnets with good thermal stability are mainly used in high-temperature field.In this study,two types of SmCo_(5) powders with different nominal z values were mixed and synthesized into SmCo_(5) magne...SmCo_(5)sintered magnets with good thermal stability are mainly used in high-temperature field.In this study,two types of SmCo_(5) powders with different nominal z values were mixed and synthesized into SmCo_(5) magnets by the traditional powder metallurgy method.The magnetic properties of the SmCo_(5) sintered magnet are maximum energy product of(BH)_(max)=172.29 kJ·m^(-3),remanence of B_(r)=7.47×10^(5)A·m^(-1)and coercivity of H_(ci)=2.42 T.The results show that there are three coexisting phases in the magnet,which are SmCo_(5)phase,Sm_(2)Co_(7)phase and Sm_(2)O_(3)phase.The microstructural observation indicates that the average grain size in the magnet is about 8μm,and the high coercivity of this magnet is attributed to these fine grains.X-ray diffraction(XRD)and electron backscatter diffraction(EBSD)results indicate that the magnet has a well-aligned(00l)orientation texture.展开更多
A new strategy to chemically synthesize exchange-coupled SmCo_(5)/Sm_(2) Co_(17) nanocomposites by in situ decomposition of SmCox(5<x<8.5)is reported in this work.Our synthesis starts with the fabrication of Co/...A new strategy to chemically synthesize exchange-coupled SmCo_(5)/Sm_(2) Co_(17) nanocomposites by in situ decomposition of SmCox(5<x<8.5)is reported in this work.Our synthesis starts with the fabrication of Co/Sm_(2) O_(3)(Sm to Co atomic ratio of Sn/Co=1:4.2),which can be reduced into 40-nm SmCo_(5) single crystal nanoparticles by Ca under the protection of CaO,showing a high coercivity of 2.85 T and saturation magnetization(Ms)of 0.0671 A·m^(2)·g^(-1).By changing the Sm/Co to 1:4.5,1:4.8 and 1:5.2,SmCo_(5)/Sm_(2) Co_(17) nanocomposites with different proportions were acquired using the same process.Owing to the in situ decomposition of SmCo_(x) intermediate,the small size(both of their size less than 10 nm)and uniform phase distribution were achieved in our nanocomposites.Thus,the as-prepared nanocomposites display a strong exchange-coupling interaction.As a consequence,SMCo_(5)/Sm_(2)Co_(17)(Sm/Co=1:5.2)exhibits a coercivity of 1.23 T and enhanced M7 T(magnetization at 7 T)of 0.0812 A·m^(2)·g^(-1),increasing by 21%than pure SmCo_(5).Our synthesis provides a new protocol to prepare exchange-coupled high-performance nanocomposites.展开更多
SmCo_(5)alloy was prepared via direct calciothermic reduction using anhydrous samarium fluoride(SmF_(3))as raw material and cobalt as inducer.Results of the thermodynamic calculation show that the direct reduction of ...SmCo_(5)alloy was prepared via direct calciothermic reduction using anhydrous samarium fluoride(SmF_(3))as raw material and cobalt as inducer.Results of the thermodynamic calculation show that the direct reduction of cobalt-induced SmF_(3)for preparing SmCo_(5)alloy is feasible.An alloy with 33.89 wt%samarium and a yield of 96.45%were achieved under the optimal conditions of 10%and 20%excess of SmF_(3)and calcium over the stoichiometry,respectively,and 1450℃for 4 min.The X-ray diffraction results show that the reduction products are SmCo_(5)alloy and CaF_(2).The scanning electron microscopy micrograph of the SmCo_(5)alloy ingot exhibits a distinct dendritic morphology composed of samarium and cobalt.The X-ray photoelectron spectroscopy shows that the atomic ratio of samarium to cobalt is approximately 1:5 and both elements demonstrate zero valency(Sm^(0),Co^(0)).The magnetic properties measurement of the SmCo_(5)alloy melt-spun ribbon shows the remanent magnetization B_r=0.59 T,intrinsic coercivity H_(Ci)=345.82 kA/m and maximum magnetic energy density(BH)_(max)=42.20 kJ/m^(3).These results may be helpful for the development of novel valence-variable rare-earth alloys.展开更多
基金the National Natural Science Foundation of ChinaBeijing Municipal Science &Technology Commission for financial support for the study
文摘The application of ‘extreme’ hydrogen-decrepitation (HD) process using high-pressure disproportionation was extended to Sm-Co5-type-alloy. The alloy with nominal composition of Sm36Co64 was treated under 1.0～2.0 MPa H2 pressure for several hours at room temperature for decrepitation. After disproportionation were high hydrogen pressures, the bulk alloys were disproportionated into particles with a size of 200. Investigations by powder X-ray diffractometer (XRD) showed, the after HD sample crystallized in the hexagonal CaCu5-type structure. The temperature dependence of pressure analysis (TPA) curve of the SmCo5 alloy showed that the hydrogen absorption temperature was about 150 ℃. Cylindrical sintered magnets of composition Sm36Co64 were prepared using HD ball milled, isostatic pressing, vacuum sintering and subsequent heat treatment. The demagnetization curves showed that the HD processes could improve the magnetic properties and squareness factor of the SmCo5 sintered magnet.
文摘Magnetic properties and microstructure of SmCo_5 alloys were examined. It is found that the coercivity ofthe alloy is strongly influenced by its microstructure. If more non- 1 : 5 phase precipitated particles wereformed, which are properly due to the existing of oxygen in the alloys introduced during the heat treatment process, the magnetic properties of the alloy decrease.
基金financially supported by the National Natural Science Foundations of China (Nos. 51471016 and 51520105002)the Key Natural Science Foundation of Beijing (No. 2151002)
文摘SmConanoparticles(NPs) have promising applications in high-density magnetic storage and magnetic nanocomposites. In this work, A novel method to yield SmCoparticles with small size and high coercivity was reported. Firstly, SmO-Co NPs with size of 6-15 nm were fabricated by a solvothermal route. Then the agglomerated SmCoparticles were obtained by thermal reduction of the precursor, which show high coercivity of2.0 T at room temperature. At last, the as-synthesized SmCoparticles were further hydrogenated under high hydrogen pressure of 4 MPa at room temperature, where hydrogen absorption process could form small-sized SmCoHparticles due to their lattice expansion and hydrogen desorption process could convert SmCoHNPs into SmCoNPs. The prepared SmCoNPs after hydrogenation, showing well distribution, have a small size of5-20 nm and room temperature coercivity of 1.22 T.
文摘The relation between the tempering effects of sinterd SmCo^(5)alloy at 750℃and its intrinsic coercivity(i^(Hc))has been studied by the use of photoelectron energy spectrum.X-ray diffraction and high-voltage electron microscope.The result is that the cause of iHc dropping seriously for sintered SmCo_(5)alloy tempered at 750 t is not the eutectoid decomposition of SmCo_(5)and the increase of oxygen.In fact,iHcdropping is caused by that some defect-rich regions in Sm_(2)Co_(17)decomposed form SmC0_(5)from nucleation centers in reversed magnetization course.
基金the State Key Program of Natural Science Foundation of China(No.51331003)the International S&T Cooperation Program of China(No.2015DFG52020)。
文摘SmCo_(5)sintered magnets with good thermal stability are mainly used in high-temperature field.In this study,two types of SmCo_(5) powders with different nominal z values were mixed and synthesized into SmCo_(5) magnets by the traditional powder metallurgy method.The magnetic properties of the SmCo_(5) sintered magnet are maximum energy product of(BH)_(max)=172.29 kJ·m^(-3),remanence of B_(r)=7.47×10^(5)A·m^(-1)and coercivity of H_(ci)=2.42 T.The results show that there are three coexisting phases in the magnet,which are SmCo_(5)phase,Sm_(2)Co_(7)phase and Sm_(2)O_(3)phase.The microstructural observation indicates that the average grain size in the magnet is about 8μm,and the high coercivity of this magnet is attributed to these fine grains.X-ray diffraction(XRD)and electron backscatter diffraction(EBSD)results indicate that the magnet has a well-aligned(00l)orientation texture.
基金This study was financially supported by the National Natural Science Foundation of China(No.51701109)the Natural Science Foundation of Beijing Municipality,China(No.2192007)+1 种基金the China Postdoctoral Science Foundation(No.2018M641132)Leshan Normal University Research Program,China(No.LZD021).
文摘A new strategy to chemically synthesize exchange-coupled SmCo_(5)/Sm_(2) Co_(17) nanocomposites by in situ decomposition of SmCox(5<x<8.5)is reported in this work.Our synthesis starts with the fabrication of Co/Sm_(2) O_(3)(Sm to Co atomic ratio of Sn/Co=1:4.2),which can be reduced into 40-nm SmCo_(5) single crystal nanoparticles by Ca under the protection of CaO,showing a high coercivity of 2.85 T and saturation magnetization(Ms)of 0.0671 A·m^(2)·g^(-1).By changing the Sm/Co to 1:4.5,1:4.8 and 1:5.2,SmCo_(5)/Sm_(2) Co_(17) nanocomposites with different proportions were acquired using the same process.Owing to the in situ decomposition of SmCo_(x) intermediate,the small size(both of their size less than 10 nm)and uniform phase distribution were achieved in our nanocomposites.Thus,the as-prepared nanocomposites display a strong exchange-coupling interaction.As a consequence,SMCo_(5)/Sm_(2)Co_(17)(Sm/Co=1:5.2)exhibits a coercivity of 1.23 T and enhanced M7 T(magnetization at 7 T)of 0.0812 A·m^(2)·g^(-1),increasing by 21%than pure SmCo_(5).Our synthesis provides a new protocol to prepare exchange-coupled high-performance nanocomposites.
基金Project supported by the National Natural Science Foundation of China(NSFC)(51774155)Jiangxi Provincial Key Research and Development Program(20192BBE50028)the Doctoral Scientific Research Foundation of Jiangxi University of Science and Technology(jxxjbs17077)。
文摘SmCo_(5)alloy was prepared via direct calciothermic reduction using anhydrous samarium fluoride(SmF_(3))as raw material and cobalt as inducer.Results of the thermodynamic calculation show that the direct reduction of cobalt-induced SmF_(3)for preparing SmCo_(5)alloy is feasible.An alloy with 33.89 wt%samarium and a yield of 96.45%were achieved under the optimal conditions of 10%and 20%excess of SmF_(3)and calcium over the stoichiometry,respectively,and 1450℃for 4 min.The X-ray diffraction results show that the reduction products are SmCo_(5)alloy and CaF_(2).The scanning electron microscopy micrograph of the SmCo_(5)alloy ingot exhibits a distinct dendritic morphology composed of samarium and cobalt.The X-ray photoelectron spectroscopy shows that the atomic ratio of samarium to cobalt is approximately 1:5 and both elements demonstrate zero valency(Sm^(0),Co^(0)).The magnetic properties measurement of the SmCo_(5)alloy melt-spun ribbon shows the remanent magnetization B_r=0.59 T,intrinsic coercivity H_(Ci)=345.82 kA/m and maximum magnetic energy density(BH)_(max)=42.20 kJ/m^(3).These results may be helpful for the development of novel valence-variable rare-earth alloys.
