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1.
The structure and magnetic hysteresis properties of the cast Sm_(1-x)Zr_x(Fe_(0.92)Ti_(0.08))_(10)(x = 0-0.3)alloys and melt-spun ribbons prepared from them were studied.In the cast alloy with x0.2, a considerable amount of the eutectic phase is found in the SEM micrographs.Analysis of the temperature dependences of the magnetic susceptibility and XRD patterns allows amorphous state in the as-spun ribbons with x0.2 to be determined.The specific magnetization measured in a field of 17 kOe and remanence decrease with increasing annealing temperature from 800 to 900 ℃ and weakly depend on Zr concentration.The maximal value of coercivity Hc = 4.7 kOe is obtained on the ribbons with x = 0.2 after annealing at 850℃ for 10 min.After additional hydrogenation of the ribbons,both the coercivity and remanence increase by 54% and 7%,respectively.  相似文献   
2.
ErNi2 ribbons were produced by rapid solidification using the melt spinning technique.Their structural,magnetic and magnetocaloric properties in the as-solidified state were studied by X-ray diffraction,scanning electron microscopy,magnetization and specific heat measurements.Samples are single phase with the MgCu_2-type crystal structure,a Curie temperature T_C of 6.8 K and a saturation magnetization at2 K and 5 T of 124.0 A·m~2/kg.For a magnetic field change μ_0△H of 5 T(2 T) ribbons show a maximum magnetic entropy change |△S_M~(peak)| of 24.1(16.9) J/(kg·K),and an adiabatic temperature change △T_(ad)~(max) of8.1(4.4) K;this is similar to the previously reported literature for bulk alloys that were processed through conventional melting techniques followed by prolonged thermal annealing.In addition,the samples also show slightly wider △S_M(T) curves with respect to bulk alloys leading to a larger refrigerant capacity.  相似文献   
3.
In this work different amorphous melt-spun Fe-alloys (Fe82B18, Fe80Si10B10, Fe60Co20Si10B10) were investigated as cathode materials for the alkaline electrolysis of water. In particular, the influence of cobalt as well as the metalloids boron and silicon on the activity for the hydrogen evolution reaction (HER) was studied in 1 M KOH at 298 K using cyclic voltammetric, galvanostatic and polarization techniques. The electrocatalytic activity was evaluated in the view of the overpotential. It was found that cyclic voltammetric techniques can be used to activate the melt-spun Fe-alloys strongly. Different cyclic voltammetric activation procedures are discussed and the influence of the sweep rate and the potential window on the HER activity was elucidated. The experimental data indicate that the addition of metalloids and, most importantly, of cobalt improves the HER activity of the materials. Thus, the overpotential can be reduced by 200 mV compared to polycrystalline Ni.  相似文献   
4.
The Ni42.7Mn40.8Co5.2Sn11.3 ribbons were prepared by melt spinning. After heat treatment, the martensitic transformation temperature and Curie temperature of austenite of the annealed ribbons increased remarkably. Inverse and direct magnetocaloric properties were investigated in the melt-spun and annealed ribbons. The effective refrigerant capacities for these ribbons were discussed in this paper.  相似文献   
5.
采用熔体快淬法制备不同快淬速度的 La0.8Ce0.2(Fe11.5-xCox)Si1.5 (x=0、0.3、0.5、0.7) 合金条带,经过 1273 K 20 min 热处理,通过 X 射线衍射和磁性测量研究 Co 元素及凝固速度对La-Ce-Fe-Co-Si的相形成和磁性能的影响。结果表明:Co 元素添加和快淬速度提高均有利于 NaZn13 型相的形成;Co 元素添加提高合金居里温度,减小磁滞,但是磁热性能有所降低;快淬速度提高导致合金的磁滞增大,但对磁热性能影响较小。  相似文献   
6.
金慧娟  朱建发 《核技术》1998,21(1):39-42
采用X射线衍射和穆斯堡乐效应等实验方法研究了快淬Nd3.8Fe74.8B21.4合金的磁性和微结构。实验结果表明,经15m/s辊速快淬得到的非晶条带在650℃退火4min后获得的各向同性细晶粉末具有良好的磁性能,分析还表明此时样品主要由Fe3B和Nd2Fe14B两相组成,另可能有极少量的Fe2B相存在,其中软磁相Fe3B为主相,约占90%,均匀分布主相的硬相Nd2Fe14B仅占10%。  相似文献   
7.
The purpose of this paper is to study the influence of Mo addition on the phase morphologies,microstructures and magnetic properties of the designated alloys.It is found out that the coercivity Hcj increases unevenly from 12.2 kOe for (Nd0.8Ce0.2)13Fe82B5 to the maximum value of 13.3 kOe for (Nd0.8Ce0.2)13Fe80B5Mo2.The transmission electron microscopy images demonstrate that the grain size decreases with the addition of Mo,which indicates that Mo has grain refinement effect.The correlative analysis gives rise to the conclusion that the coercivity mechanism of the investigated alloys is dominated by pinning type.All in all,the enhancement of the magnetic properties is mainly attributed to the synergistic impact of grain refinement,pinning effects and the microstructural homogenization.The research may shed light on the potential development and application of rare earth-based counterpart magnets.  相似文献   
8.
This study reports the stabilization of the RFe_(12)-type based compounds where part of R and Fe are substituted with Zr and Co and Si, respectively, in order to examine whether these rare-earth-lean materials are suitable for applications as permanent magnets. Structural and magnetic characterization of the family of alloys with the general formula Nd_(0.4) Zr_(0.6) Fe_(10-x)Co_xS_i2(x = 0 -3) and their melt-spun ribbons were carried out using X-ray diffraction and M€ossbauer spectroscopy. The ThMn_(12)-type structure is obtained for all samples as the majority phase with a minority a-Fe(CoSi) phase(less than 5 wt%) as it was estimated by XRD for x = 1 and 2. The Curie temperature increases linearly with Co substitution from 561 K for x = 0 to 712 K for x = 3. The saturation magnetization decreases slightly from 130.5(x =1)to 129.1 A·m~2/kg(x=3), while the anisotropy field is following the same trend.  相似文献   
9.
In this study,the alloy ingots with nominal compositions of(Nd_(1-x)Ce_x)_(31)Fe_(bal)Co_(0.2)Ga_(0.1)B(x=0, 0.1 wt%,0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%) were prepared and then melt-spun to form nanocrystalline ribbons at the wheel speed of 20 m/s. XRD results show that all melt-spun ribbons exhibit the tetragonal structure(Nd,Ce)_2 Fe_(14)B phase with the space group P42/mmm. The Curie temperature and lattice constant decrease with the increase of Ce content. The Curie temperature decreases gradually from 306 to 247 ℃with the increase of Ce content. Those results indicate that Ce element has been incorporated into Nd_2 Fe_(14)B main crystalline phase and formed(Ce,Nd)-Fe-B hard magnetic phase. It is also found that the remanence ratio(M_r/M_s) decreases from 0.693 to 0.663 and the coercivity(H_c) decreases from 18.7 to14.2 kOe with the increase of Ce content. However, a relatively high coercivity of 18.3 kOe for(Nd_(1-x)Ce_x)_(31)Fe_(bal)Co_(0.2)Ga_(0.1)B(x = 0.2) melt-spun ribbon is achieved. The coercivity is sensitive to microstructure. The AFM patterns show the sample(x = 0.2) has the most uniform and finest microstructure. The magnetization reversal behavior(δM plots) is discussed in detail. The positive δM value is observed in every sample, which confirms the existence of exchange coupling interaction. Evidently, theδM maximum value reaches 0.9 in the sample(x = 0.2). It is indicated that the intergranular exchange coupling effect is the strongest, which is consistent with coercivity enhancing.  相似文献   
10.
Rapidly quenched Zr2Ni amorphous and nanocrystalline ribbons were studied as electrocatalysts for hydrogen evolution in 6 M KOH. Linear polarization, potentiostatic hydrogen charge/discharge and EIS measurements at various potentials were carried out for the Zr alloys with different microstructure with the aim to extract information about the mechanism of hydrogen evolution and absorption and estimate the kinetic parameters of the hydrogen evolution reaction (HER). Though the melt-spun Zr67Ni33 alloys with varying microstructure do not show substantially different catalytic activity for HER, it could be clearly demonstrated that the nanocrystalline material reveals better catalytic performance than the entirely amorphous and nano-/amorphous alloys with the same chemical composition. It was found that all studied Zr–Ni alloys absorb hydrogen under the conditions of the hydrogen evolution experiments, as the amount of the absorbed hydrogen depends to a large degree on the alloys microstructure as well as on the applied potential during the HER experiment. The diffusion coefficient of hydrogen into the amorphous Zr67Ni33 alloy, as well as the thickness of the hydrided layer were found to be noticeably larger than those of the nanocrystalline alloy at the same conditions of hydrogen charging. Therefore the improved electrocatalytic properties of the nanocrystalline alloy could only be explained by its favorable microstructure (e.g. higher density of defects) and weaker hydrogen absorption into the nanostructured material under the conditions of the HER.  相似文献   
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