Nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of(Mg_(24)Ni_(10)Cu_2)_(100-x)Nd_x(x=0, 5, 10, 15, 20) were prepared by melt spinning technology and their structures as well as gaseous h...Nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of(Mg_(24)Ni_(10)Cu_2)_(100-x)Nd_x(x=0, 5, 10, 15, 20) were prepared by melt spinning technology and their structures as well as gaseous hydrogen storage characteristics were investigated. The XRD, TEM and SEM linked with EDS detections reveal that the as-spun Nd-free alloy holds an entire nanocrystalline structure but a nanocrystalline and amorphous structure for the as-spun Nd-added alloy, implying that the addition of Nd facilitates the glass forming in the Mg_2Ni-type alloy. Furthermore, the degree of amorphization of the as-spun Nd-added alloy and thermal stability of the amorphous structure clearly increase with the spinning rate rising. The melt spinning ameliorates the hydriding and dehydriding kinetics of the alloys dramatically. Specially, the rising of the spinning rate from 0(the as-cast was defined as the spinning rate of 0 m/s) to 40 m/s brings on the hydrogen absorption saturation ratio(R_5~a)(a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity) increasing from 36.9% to 91.5% and the hydrogen desorption ratio(R_(1 0)~d)(a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity) rising from 16.4% to 47.7% for the(x=10) alloy, respectively.展开更多
The crystallization kinetics of amorphous (Nd3.6Pr5.4Fe83Co3B5) and the preparation of α-Fe/Nd2Fe14B nanocomposite magnets by controlled melt-solidification of (Nd3.6Pr5.4Fe83Co3B5) was investigated by employing DTA,...The crystallization kinetics of amorphous (Nd3.6Pr5.4Fe83Co3B5) and the preparation of α-Fe/Nd2Fe14B nanocomposite magnets by controlled melt-solidification of (Nd3.6Pr5.4Fe83Co3B5) was investigated by employing DTA, XRD, and TEM. The results show that a metastable intermediate phase (Nd8Fe27B24) prior to α-Fe and Nd2Fe14B phases is crystallized as the amorphous Nd3.6Pr5.4Fe83Co3B5 is heated to 1 223 K. The crystallization activation energy of α-Fe and Nd8Fe27B24 phases is larger at the beginning stage of crystallization, and then it decreases with crystallized fraction x for the former and has little change when x is below 70% for the latter, which essentially results in an α-Fe/Nd2Fe14B microstructure with a relatively coarse grain size about 20-60 nm and a non-uniform distribution of grain size in the annealed alloy. The α-Fe/Nd2Fe14B nanocomposite magnets with a small average grain size about 14 nm and a quite uniform grain size distribution were prepared by controlled melt-solidification of (Nd3.6Pr5.4Fe83Co3B5) at a wheel speed of 20 m·s-1 during melt-spinning. The magnets show a high maximum energy product of （BH）max = 194 kJ·m-3, which is nearly twice of that of the nanocomposite magnets made by annealing the amorphous Nd3.6Pr5.4Fe83Co3B5 precursor alloy.展开更多
利用X射线衍射,差热分析及静态磁性测量,研究了退火温度对不同成分的非晶Fe Nb B合金纳米晶化行为和磁性的影响·实验发现:在纳米晶化过程的初期出现磁硬化,矫顽力与最大磁导率均呈现不同程度的恶化·在硼化物(Fe2B和Fe3B)相析...利用X射线衍射,差热分析及静态磁性测量,研究了退火温度对不同成分的非晶Fe Nb B合金纳米晶化行为和磁性的影响·实验发现:在纳米晶化过程的初期出现磁硬化,矫顽力与最大磁导率均呈现不同程度的恶化·在硼化物(Fe2B和Fe3B)相析出前,具有纳米结构的合金由α Fe固溶体和非晶基体相组成,呈现较佳的软磁特性·随纳米晶相体积分数增加而呈现的磁软化现象可解释为由于纳米晶粒间距的减少,交换耦合增强所致·展开更多
基金Projects(51161015,51371094)supported by the National Natural Science Foundation of China
文摘Nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of(Mg_(24)Ni_(10)Cu_2)_(100-x)Nd_x(x=0, 5, 10, 15, 20) were prepared by melt spinning technology and their structures as well as gaseous hydrogen storage characteristics were investigated. The XRD, TEM and SEM linked with EDS detections reveal that the as-spun Nd-free alloy holds an entire nanocrystalline structure but a nanocrystalline and amorphous structure for the as-spun Nd-added alloy, implying that the addition of Nd facilitates the glass forming in the Mg_2Ni-type alloy. Furthermore, the degree of amorphization of the as-spun Nd-added alloy and thermal stability of the amorphous structure clearly increase with the spinning rate rising. The melt spinning ameliorates the hydriding and dehydriding kinetics of the alloys dramatically. Specially, the rising of the spinning rate from 0(the as-cast was defined as the spinning rate of 0 m/s) to 40 m/s brings on the hydrogen absorption saturation ratio(R_5~a)(a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity) increasing from 36.9% to 91.5% and the hydrogen desorption ratio(R_(1 0)~d)(a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity) rising from 16.4% to 47.7% for the(x=10) alloy, respectively.
文摘The crystallization kinetics of amorphous (Nd3.6Pr5.4Fe83Co3B5) and the preparation of α-Fe/Nd2Fe14B nanocomposite magnets by controlled melt-solidification of (Nd3.6Pr5.4Fe83Co3B5) was investigated by employing DTA, XRD, and TEM. The results show that a metastable intermediate phase (Nd8Fe27B24) prior to α-Fe and Nd2Fe14B phases is crystallized as the amorphous Nd3.6Pr5.4Fe83Co3B5 is heated to 1 223 K. The crystallization activation energy of α-Fe and Nd8Fe27B24 phases is larger at the beginning stage of crystallization, and then it decreases with crystallized fraction x for the former and has little change when x is below 70% for the latter, which essentially results in an α-Fe/Nd2Fe14B microstructure with a relatively coarse grain size about 20-60 nm and a non-uniform distribution of grain size in the annealed alloy. The α-Fe/Nd2Fe14B nanocomposite magnets with a small average grain size about 14 nm and a quite uniform grain size distribution were prepared by controlled melt-solidification of (Nd3.6Pr5.4Fe83Co3B5) at a wheel speed of 20 m·s-1 during melt-spinning. The magnets show a high maximum energy product of （BH）max = 194 kJ·m-3, which is nearly twice of that of the nanocomposite magnets made by annealing the amorphous Nd3.6Pr5.4Fe83Co3B5 precursor alloy.
文摘利用X射线衍射,差热分析及静态磁性测量,研究了退火温度对不同成分的非晶Fe Nb B合金纳米晶化行为和磁性的影响·实验发现:在纳米晶化过程的初期出现磁硬化,矫顽力与最大磁导率均呈现不同程度的恶化·在硼化物(Fe2B和Fe3B)相析出前,具有纳米结构的合金由α Fe固溶体和非晶基体相组成,呈现较佳的软磁特性·随纳米晶相体积分数增加而呈现的磁软化现象可解释为由于纳米晶粒间距的减少,交换耦合增强所致·
