Papers by Keyword: Melt-Spinning

Abstract: Three Heusler alloys, Ni_50-xCo_xMn₃₈Sn₁₂ (x = 1, 2, and 3), were elaborated by rapid solidification. The impact of the Co doping on the structure, magnetic properties, and phase transition in these alloys was studied. The structure of the Ni₄₉Co₁Mn₃₈Sn₁₂ and Ni₄₈Co₂Mn₃₈Sn₁₂ ribbons was martensite 14M monoclinic structure, while the Ni₄₇Co₃Mn₃₈Sn₁₂ sample structure was austenite cubic L2₁. The thermal analysis showed the impact of the substitution Ni by Co. It was noted that the temperatures of martensitic transition moved lower, and a decreases progressively of enthalpy and entropy changed. Likewise, an obvious increase in the temperature of Curie transition for austenite phase (T_A^C) was observed and a jump of magnetization change (ΔM) was detected, with increasing Cobalt content.

Abstract: This article prepared a new type PVA fiber with large diameter by plasticizing melt spinning method, which instead of traditional wet-spinning or gel-spinning method. The mechanical properties and microstructure of fiber were characterized by tensile instrument respectively and SEM. Then, the PVA fiber was used in cementitious composites after surface sizing. The test result shown that: the melt-spinning PVA fiber could achieve stress-strain hardening in ECC system, and appeared multi-cracking phenomenon, the flexural deflection and strength is not worse than the Japan Kurary PVA fiber. Finally, the PVA has an advantage in price.

Abstract: (Pr_0.25Nd_0.75)_10-xDy_xFe₈₂Co₂B₆(x=0~0.3) ribbons were prepared by melt spinning at 25m/s and subsequent annealing. The effect of Dy content on the microstructure and magnetic properties of the ribbons has been investigated by X-ray diffractometer (XRD), scanning electronic microscope (SEM) and vibrating sample magnetometer (VSM). The magnetic properties related to the Dy content were characterized. Intrinsic coercivity of 598kA/m, remanence of 0.58T, and the maximum energy product (BH)_max of 43kJ/m³ were achieved in (Pr_0.25Nd_0.75)_9.8Dy_0.2Fe₈₂Co₂B₆ after annealing at 700°C for 10 minutes.

Abstract: The RE–Mg–Ni-based A₂B₇-type La_0.75−xPr_xMg_0.25Ni_3.2Co_0.2Al_0.1 (x = 0, 0.1, 0.2, 0.3, 0.4) electrode alloys fabricated by melt spinning technology. The impacts of the melt spinning and the replacement of La by Pr on the microstructures and electrochemical performances of the alloys were systematically investigated. The results indicate that the as-cast and spun alloys hold a compound phase structure, containing (La, Mg)₂Ni₇ and LaNi₅ phases as well as a residual phase LaNi₂. A notable grain refinement of the alloys without altering the phase structures of the alloys obtained by melt spinning. The discharge capacity of the alloy (x = 0.2) tend to first augments and then falls with the growing spinning rate. And the as-spun (10 m/s) alloy gains the maximum discharge capacity as Pr content augmenting in the alloys. Furthermore, the measurements of the electrochemical hydrogen storage kinetics reveal that the high rate discharge ability (HRD), the hydrogen diffusion coefficient (D) and the limiting current density (IL_{Subscript text}) of the alloys first increase then decrease with the rising of the spinning rate and the amount of Pr substitution.

Abstract: The Mg2Ni-type alloys with a nanocrystalline and amorphous structure have been confirmed possessing superior electrochemical hydrogen storage kinetics. The melt-spinning technique is used to preparing the nanocrystalline and amorphous Mg2Ni-type alloys with the nominal compositions of Mg20Ni10-xMnx (x = 0, 1, 2, 3, 4). The impacts of the melt spinning and the replacement of Ni by Mn on the structures and the electrochemical performances of the alloys are investigated systematically. The analysis of the structures by XRD and HRTEM reveals that the replacement of Ni by Mn facilitates the glass formation in the Mg2Ni-type alloy, and the amorphization degree of the as-spun alloys increases with the growing of the spinning rate. Furthermore, the replacement renders the formation of secondary phases MnNi and Mg instead of altering the Mg2Ni major phase in the alloys. The measurement of the electrochemical characteristics by an automatic galvanostatic system indicates that the discharge capacity and cycle stability of the alloys dramatically grow with the rising of the spinning rate and the amount of Mn replacement, with which the high rate discharge ability (HRD) of the alloys first augments and then falls.

Abstract: The melt-spinning technique was used to synthesize the Mg₂₀Ni₆M₄ (M=Co, Cu) alloys with nanocrystalline and amorphous structure. The microstructures of the as-spun alloys were characterized by XRD and TEM. The electrochemical hydrogen storage properties of the alloys were measured. The results show that the as-spun (M=Cu) alloys hold an entire nanocrystalline structure, whereas the as-spun (M=Co) alloys display a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg₂Ni-type alloy. The discharge capacity and high rate discharge ability (HRD) of the alloys notably augment with the rising of the spinning rate. The action of the melt spinning on the cycle stability of the alloys is associated with the substitution element. For the (M=Co) alloy, the melt spinning exerts a dramatically positive impact, whereas for the (M=Cu) alloy, its impact is negative.

Abstract: The melt-spinning technique is used to fabricate the Mg20Ni9M1 (M=Cu, Co) alloys with nanocrystalline and amorphous structure. The microstructures of the as-spun alloys were characterized by XRD and TEM. The electrochemical hydrogen storage properties of the alloys were measured. The results show that the as-spun (M=Cu) alloys hold an entire nanocrystalline structure and small amount of amorphous phase is visible on the grain boundaries of the as-spun (M=Co) alloy. The discharge capacity and high rate discharge ability (HRD) of the alloys visibly grow with the rising of the spinning rate. The action of the melt spinning on the cycle stability of the alloys is associated with substitution element. For M=Cu, the capacity retaining rate (SN) evidently falls with the growing of the spinning rate; whereas for M=Co, it first declines and then augments.

Abstract: Nanocomposite (Nd,Dy)₂Fe₁₄B/α-Fe magnets were prepared by directly solidification (DS). The effect of wheel speed on the magnetic properties, microstructure and exchange coupling interaction has been studied. It was found that a uniform R₂Fe₁₄B/α-Fe nanocomposite structure with fine α-Fe grains can be developed at an optimum wheel speed of about 18 m/s. Without any heat treatment, the optimal ribbons (v = 18 m/s) show a strong exchange coupling interaction and good magnetic properties, e.g. _iH_c=1027 kA/m, m_r =0.71, (BH)_max=174 kJ/m³.

Abstract: In order to ameriolate the electrochemical hydrogen storage performances of La–Mg–Ni system A2B7-type electrode alloys, the partial substitution of Zr for La has been performed. The La_0.75−xZrxMg_0.25Ni_3.2Co_0.2Al_0.1 (x = 0, 0.05, 0.1, 0.15, 0.2) electrode alloys were prepared by melt spinning. The influences of substithting La with Zr on the structures and the electrochemical hydrogen storage characteristics of the alloys were investigated. The structure characterized by XRD and TEM displays that the as-spun alloys have a multiphase structure, composing of two main phases (La, Mg)2Ni7 and LaNi5 as well as a residual phase LaNi2. The as-spun Zr-free alloy displays an entire nanocrystalline structure, while an like amorphous structure is detected in the as-spun alloy substituted by Zr, implying that the substitution of Zr for La facilitates the amorphous formation. The substitution of Zr for La markedly enhances the electrochemical cycle stability of the alloys, whereas the impact generated by such substitution on the high rate discharge ability (HRD) of the alloys is different with the variation of the spinning rate. The HRD of the as-spun (5 m/s) alloys yields the largest value with the change of Zr content, but that of the as-spun (20 m/s) alloys always declines with the growing amount of Zr substitution.

Abstract: This work presents the structural comparison of Al₉₀Fe₇Nb₃ alloys obtained by different techniques: (i) partly amorphous powder alloy produced by mechanical milling and their consolidation by hot extrusion (cylindrical bar), (ii) from millimeter portion by casting centrifuged system (square shape), and (iii) from millimeter portion by melt-spinning (ribbon shape). The cylindrical consolidated alloy presented an Al matrix with Al₃Nb and Al₁₃Fe₄ nanophases (intermetallic compounds), the square consolidated alloy resulted in the same structure composed of Al matrix with Al₃Nb and Al₁₃Fe₄ in micro-phase scale. On the other hand, the ribbon alloy exhibits an amorphous matrix with primary Al nanocrystals (fcc-Al phase).