Electrochemical hydrogen storage characteristics of nanocrystalline and amorphous Mg_2Ni-type alloys prepared by melt-spinning

The nanocrystalline and amorphous Mg2Ni-type alloys with nominal compositions of Mg2Ni1-xMnx （x=0, 0.1, 0.2, 0.3, 0.4） were synthesized by melt-spinning technique. The spun alloy ribbons with a continuous length, a thickness of about 30 μm and a width of about 25 mm are obtained. The structures of the as-spun alloy ribbons were characterized by XRD and HRTEM. The electrochemical hydrogen storage characteristics of the as-spun alloy ribbons were measured by an automatic galvanostatic system. The electrochemical impedance spectrums （EIS） were plotted by an electrochemical workstation. The hydrogen diffusion coefficients （D） in the alloys were calculated by virtue of potential-step measurement. The results show that all the as-spun （x=0） alloys hold a typical nanocrystalline structure, whereas the as-spun （x=0.4） alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni facilitates the glass formation in the Mg2Ni-type alloy. The substitution of Mn for Ni significantly improves the electrochemical hydrogen storage performances of the alloys, involving the discharge capacity and the electrochemical cycle stability. With an increase in the amount of Mn substitution from 0 to 0.4, the discharge capacity of the as-spun （20 m/s） alloy increases from 96.5 to 265.3 mA·h/g, and its capacity retaining rate （S20） at the 20th cycle increases from 31.3% to 70.2%. Furthermore, the high rate dischargeability （HRD）, electrochemical impedance spectrum and potential-step measurements all indicate that the electrochemical kinetics of the alloy electrodes first increases then decreases with raising the amount of Mn substitution.

Hydriding and dehydriding characteristics of nanocrystalline and amorphous Mg_(20-x)La_xNi_(10)(x=0-6) alloys prepared by melt-spinning

In order to improve the hydrogenation and dehydrogenation performances of the Mg2Ni-type alloys, Mg was partially substituted by La in the alloy, and melt spinning technology was used for the preparation of the Mg20-xLaxNi10 （x=0, 2, 4, 6） hydrogen storage alloys. The structures of the alloys were studied by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and high-resolution transmission electron microscopy （HRTEM）. It was found that no amorphous phase formed in the as-spun La-free alloy, but the as-spun alloys containing La held a major amorphous phase. When La content x≤2, the major phase in the as-cast alloys was Mg2Ni phase, but with further increase of La content, the major phase of the as-cast alloys changed into LaNi5＋LaMg3 phase. Thermal stability of the as-spun alloys was studied by differential scanning calorimetry （DSC）, showing that spinning rate was a negligible factor on the crystallization temperature of the amorphous phase. The hydrogen absorption and desorption kinetics of the as-cast and as-spun alloys were measured using an automatically controlled Sieverts apparatus, confirming that the hydrogen absorption and desorption capacities and kinetics of the as-cast alloys clearly increased with rising La content. For La content x=2, the as-spun alloy displayed optimal hydrogen desorption kinetics at 200 ℃.

INFLUENCE OF POLYMER CHARACTERISTICS AND MELT-SPINNING CONDITIONS ON THE PRODUCTION OF HIGH RANDOMNESS 60PHB/PET THERMOTROPIC LIQUID CRYSTAL COPOLYESTER FIBER

Six samples of linear high randomness 60PHB/ PET thermotropic liquid crystal copolyesters are made by melt copolymerization at 290℃ , whose randomness about 0.955 is measured by the discernible ’H-NMR spectrometer. High tenacity, high module fiber is prepared by melt spinning in liquid crystal phase. The effect of molecular weight, shear rate, temperature as well as spinning drawn ratio on the mechanical behavior of 60PHB / PET copolyester fiber are shown that, lower shear rate (2 10 s-1), higher temperature melting （300℃ ）, lower temperature spinning （280℃ ） and higher molecular weight are favourable to the increase of the fiber mechanical properties. With the variance of drawn ratio, fiber mechanical property has a transition point due to traversion from shear-orientation to drawn-orientation. The copolyester fiber has high crystallinity, high orientation at the crystalline region, high chain orientation and high regular fibrillar structure.

Single phase A2B7-type La-Mg-Ni alloy with improved electrochemical properties prepared by melt-spinning and annealing

La-Mg-Ni alloys were prepared by melt-spinning with different cooling rates and followed by annealing.Elevation of the cooling rate leads to refinement of the grains size and increasing of the abundance of LaNis.Annealing is favorable to formation of the A2 B7-type phase and promotes the discharge capacity,cycling stability and high rate discharge ability of the as-spun alloys.Phase constitution of the annealed alloys is found to be closely related to the microstructure of the as-spun alloys.A single phase A2 B7-type microstructure is obtained in the annealed alloy which is attributed to the lower abundance of the LaNis of the original alloy spun with lower cooling rate.Formation of the single phase A2 B7-type microstructure is also ascribed to the isolated and homogeneous distribution of the morphology of the as-spun alloy.The single phase alloy presents higher discharge capacity and better cycling stability compared with other annealed alloys.

A Novel Nano/Micro-Fibrous Scaffold by Melt-Spinning Method for Bone Tissue Engineering

In order to architecturally and functionally mimic native Extracellular Matrix （ECM）, a novel micro/nano-fibrous scaffold of hydroxyapetite/poly（lactide-co-glycolide） （HA/PLGA） composite was successfully prepared by melt-spinning method. A porous three-dimensional scaffold fabricated by melt-molding particulate-leaching method was used as control. This kind of scaffold comprising both nanofiber and microfiber had an original structure including a nano-network favorable for cell adhe- sion, and a micro-fiber providing a strong skeleton for support. The microfibers and nanofibers were blended homogeneously in scaffold and the compression strength reached to 6.27 MPa, which was close to human trabecular bone. The typical mi- cro/nano-fibrous structure was more benefcial for the proliferation and differentiation of Bone Mesenehymal Stem Cells （BMSCs）. The calcium deposition and Alkaline Phosphatase （ALP） activity were evaluated by the differentiation of BMSCs, and the results indicated that the temporary ECM was very beneficial for the differentiation of BMSCs into maturing osteoblasts. For repairing rabbit radius defects in vivo, micro/nano-fibrous scaffold was used for the purpose of rapid bone remodeling in the defect area. The results showed that a distinct bony callus of bridging was observed at 12 weeks post-surgery and the expression of osteogenesis-related genes （bone-morphogenetic protein-2, Osteonectin, collagen-I） increased because of the ECM-like structure. Based on the results, the novel micro/nano-fibrous scaffold might be a promising candidate for bone tissue engi- neering.

Direct synthesis of Fe-Si-B-C-Cu nanocrystalline alloys with superior soft magnetic properties and ductile by melt-spinning

Structure,magnetic properties and ductile of melt-spun Fe_(83-x)Si_(4)B_(13-y)C_(y)Cu_(x)(x=0-1.7;y=0-8)alloys were investigated.The addition of 1.7 at.%Cu in a Fe_(83)Si_(4)B_(13) amorphous alloy generates abundantα-Fe crystals by providing nucleation sites,and further C doping promotes the growth of the crystals by suitable turning amorphous-forming ability,hence they increase saturation magnetic flux density(B_(s))and slightly worse magnetic softness of the as-spun alloys.The as-spun Fe_(81.3)Si_(4)B_(7)C_(6)Cu_(1.7) alloy possesses a combined structure of a fully amorphous layer in wheel side surface and predominating nanocrystalline structure with gradually enlargedα-Fe crystal,whose average size and volume fraction are determined as about 12 nm and 32%,respectively,therefore superior soft magnetic properties and ductile with a high B_(s)of 1.74 T,coercivity(H_(c))of 32.7 A/m,effective permeability(μ_(e),at 1 kHz)of 3200 and high relatively strain at fracture(ε_(f))of 3.61%can be achieved directly in this alloy by only using melt-spinning.The annealing at 578 K releases internal stress,promotes the growth of theα-Fe crystals and remains the amorphous layer of the Fe_(81.3)Si_(4)B_(7)C_(6)Cu_(1.7) alloy,then improves the soft magnetic properties and maintains the superior ductile with increasing the B_(s)andμ_(e)to 1.80 T and 14,100,respectively,lowering the H_(c)to9.4 A/m and slightly reducing theε_(f)to 2.39%.The combination of superior soft magnetic properties and ductile and simplified synthesis process entitles the Fe-Si-B-C-Cu nanocrystalline alloys great potentials in high performance electromagnetic applications.

Facile synthesis of a melt-spinnable polyborazine from asymmetric alkylaminoborazine

A novel asymmetric alkylaminoborazine monomer,2-propylamino-4,6-bis（methylamino）borazine,was synthesized for the first time,and directly polymerized to give a melt-spinnable polyborazine（PBN）.This asymmetric alkylaminoborazine was synthesized by an aminolysis reaction of 2,4,6-trichloroborazine（TCB） with different amines under mild conditions.This route turns out to be much cheaper and simpler than the conventional routes.The chemical composition,structure,molecular weights and ceramic yield were investigated by EA,FTIR,NMR,GPC and TG analysis.The PBN exhibits suitable rheological property for melt-spinning, which suggests that it is a potential precursor for BN fibers.

Hydrogen storage behaviours of nanocrystalline and amorphous Mg_(20)Ni_(10-x)Co_x(x=0-4) alloys prepared by melt spinning

The Mg2Ni-type alloys with nominal compositions of Mg20Ni10-xCox(x=0,1,2,3,4,%,mass fraction) were prepared by melt-spinning technology.The structures of the alloys were studied by XRD,SEM and HRTEM.The hydrogen absorption/desorption kinetics and the electrochemical performances of the alloys were measured.The results show that no amorphous phase forms in the as-spun Co-free alloy,but the as-spun alloys containing Co show a certain amount of amorphous phase.The hydrogen absorption capacities of the as-cast alloys first increase and then decrease with the incremental change of Co content.The hydrogen desorption capacities of as-cast and spun alloys rise with increasing Co content.The melt spinning significantly improves the hydrogenation and dehydrogenation capacities and kinetics of the alloys.The substitution of Co for Ni clearly enhances the discharge capacities of the alloys and the cycle stability of the as-spun alloys.

Recycle for Sludge Scrap of Nd-Fe-B Sintered Magnet as Isotropic Bonded Magnet

The reduction diffusion method was performed for the sludge scrap of Nd-Fe-B sintered magnets with adding Ca metal to recover the oxidized Nd-Fe-B phase. After washing the resultant powders to remove Ca metal component, the powders obtained were recycled as an isotropic magnetic powder by the melt spinning method. The magnetic properties of powders as recycled were inferior, especially for the coercivity value, due to the deletion of rare earth metals during the washing process. The adjustment of metal composition, i.e., the addition of Nd metal, at the melt spinning process improved the magnetic properties to be B r=～0.75 T, H cj=～0.93 mA·m -1, and (BH) max=～91 kJ·m -3. The magnetic properties of the bonded magnets prepared from the composition-adjusted powders were B r=～0.66 T, H cj=～0.92 mA·m -1, and (BH) max=～70 kJ·m -3, which are approximately comparable to the commercially available MQPB boned one (B r=～0.73 T, H cj=～0.79 mA·m -1, and (BH) max=～86 kJ·m -3).

Influences of melt spinning on electrochemical hydrogen storage performance of nanocrystalline and amorphous Mg_2Ni-type alloys

In order to improve the electrochemical hydrogen storage performance of the Mg2Ni-type electrode alloys, Mg in the alloy was partially substituted by La, and the nanocrystalline and amorphous Mg2Ni-type Mg20-xLaxNi10 （x-=0, 2） alloys were synthesized by melt-spinning technique. The microstructures of the as-spun alloys were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The electrochemical hydrogen storage properties of the experimental alloys were tested. The results show that no amorphous phase is detected in the as-spun Mg20Ni10 alloy, but the as-spun Mg18La2Ni10 alloy holds a major amorphous phase. As La content increases from 0 to 2, the maximum discharge capacity of the as-spun （20 m/s） alloys rises from 96.5 to 387.1 mA.h/g, and the capacity retaining rate （S20） at the 20th cycle grows from 31.3% to 71.7%. Melt-spinning engenders an impactful effect on the electrochemical hydrogen storage performances of the alloys. With the increase in the spinning rate from 0 to 30 m/s, the maximum discharge capacity increases from 30.3 to 135.5 mA.h/g for the Mg20Ni10 alloy, and from 197.2 to 406.5 mA-h/g for the Mg18La2Ni10 alloy. The capacity retaining rate （S20） of the Mg2oNi10 alloy at the 20th cycle slightly falls from 36.7% to 27.1%, but it markedly mounts up from 37.3% to 78.3% for the Mg18La2Ni10 alloy.

Martensitic Transformation and Magnetic-Field-Induced Strain in Magnetic Shape Memory Alloy NiMnGa Melt-Spun Ribbon

A magnetic shape memory alloy with nonstoichiometric Ni50Mn27Ga23 was prepared by using melt-spinning technology. The martensitic transformation and the magnetic-field-induced strain (MFIS) of the polycrystalline melt-spun ribbon were investigated. The experimental results showed that the melt-spun ribbons underwent thermal-elastic martensitic transformation and reverse transformation in cooling and heating process and exhibited typical thermo-elastic shape memory effect. However the start temperature for martensitic transformation decreased from 286 K for as-cast alloy to 254 K for as-quenched ribbon and Curie temperature remains approximately constant. A particular internal stress induced by melt-spinning resulted in the formation of a texture structure in the ribbons, which made the ribbons obtain larger martensitic transformation strain and MFIS. The internal stress was released substantially after annealing, which resulted in a decrease of MFIS of the ribbons.

Nanocrystalline and nanocomposite permanent magnets by melt spinning technique

The melt-spinning technique offers an opportunity for tailoring magnetic properties by controlling the structures and microstructures in both single-phase and composite magnets.This review first broadly discusses the principle of cooling control,amorphization,crystallization,annealing,and consolidation of the melt-spun ribbons.The phase,microstructure,and magnetic properties of popular single-phase nanocrystalline magnets are reviewed,followed by the nanocomposite magnets consisting of magnetically hard and soft phases.The precipitation-hardened magnetic materials prepared by melt spinning are also discussed.Finally,the role of intergrain exchange coupling,thermal fluctuation,and reversible/irreversible magnetization processes are discussed and correlated to the magnetic phenomena in both single-phase and nanocomposite magnets.

Influence of substituting Ni with Co on hydriding and dehydriding kinetics of melt spun nanocrystalline and amorphous Mg_2Ni-type alloys

In order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys,Ni in the alloy is substituted by element Co. The nanocrystalline and amorphous Mg2Ni-type Mg2Ni1-xCox (x=0,0.1,0.2,0.3,0.4) alloys were synthesized by melt-spinning technique. The structures of the as-cast and spun alloys were studied with an X-ray diffractometer (XRD) and a high resolution transmission electronic microscope (HRTEM). An investigation on the thermal stability of the as-spun alloys was carried out with a differential scanning calorimeter (DSC). The hydrogen absorption and desorption kinetics of the alloys were measured with an automatically controlled Sieverts apparatus. The results demonstrate that the substitution of Co for Ni does not alter the major phase of Mg2Ni but results in the formation of secondary phase MgCo2. No amorphous phase is detected in the as-spun Co-free alloy,but a certain amount of amorphous phase is clearly found in the as-spun Co-containing alloys. The substitution of Co for Ni exerts a slight influence on the hydriding kinetics of the as-spun alloy. However,it dramatically enhances the dehydriding kinetics of the as-cast and spun alloys. As Co content (x) increases from 0 to 0.4,the hydrogen desorption capacity increases from 0.19% to 1.39% (mass fraction) in 20 min for the as-cast alloy,and from 0.89% to 2.18% (mass fraction) for the as-spun alloy (30 m/s).

Hydriding and dehydriding kinetics of nanocrystalline and amorphous Mg_2Ni_(1-x)Mn_x(x=0-0.4) alloys prepared by melt spinning

A partial substitution of Ni by Mn was implemented in order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys. The nanocrystalline and amorphous MgzNi-type Mg2Nil-xMnx （x=0, 0. 1, 0.2, 0.3, 0.4） alloys were synthesized by the melt-spinning technique. The structures of the as-cast and spun alloys were studied by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and high resolution transmission electron microscopy （HRTEM）. The hydrogen absorption and desorption kinetics of the alloys were measured with an automatically controlled Sieverts apparatus. The results show that the as-spun Mn-free alloy holds a typical nanocrystalline structure, whereas the as-spun alloys containing Mn display a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni intensifies the glass forming ability of the Mg2Ni-type alloy. The hydrogen absorption and desorption capacities and kinetics of the alloys increase with increasing the spinning rate, for which the nanocrystalline and amorphous structure produced by the melt spinning is mainly responsible. The substitution of Mn for Ni evidently improves the hydrogen desorption performance. The hydrogen desorption capacities of the as-cast and spun alloys rise with the increase in the percentage of Mn substitution.

Ductile Fe-based amorphous alloys with high iron content

Fe-based amorphous alloys with high iron content of 76at%-80at%were synthesized in the Fe-Mo-Si-P-C-B alloy system by the single roller melt-spinning technique.The amorphous ribbons exhibit high Vickers microhardness and good ductility,which can be indented and bent 180°without breaking.A number of shear bands could be observed around the indents and the bending traces.Studies on the magnetic properties of the amorphous alloys show that they possess high saturation magnetizations of 1.34-1.6 T,which increases with the increase of iron content.The core losses of these Fe-based amorphous alloys at various magnetic inductions were tested and found to be significantly dependent on their components.The Fe-Mo-Si-P-C-B amorphous alloys with excellent mechanical properties and soft magnetic properties have promising potential in functional applications.

Structures and electrochemical performances of La_(0.75-x)Zr_xMg_(0.25)Ni_(3.2)Co_(0.2)Al_(0.1) (x=0-0.2) electrode alloys prepared by melt spinning

The La-Mg-Ni system A2B7-type electrode alloys with nominal composition La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1(x=0,0.05, 0.1,0.15,0.2)were prepared by casting and melt-spinning.The influences of melt spinning on the electrochemical performances as well as the structures of the alloys were investigated.The results obtained by XRD,SEM and TEM show that the as-cast and spun alloys have a multiphase structure,consisting of two main phases(La,Mg)Ni3 and LaNi5 as well as a residual phase LaNi2.The melt spinning leads to an obvious increase of the LaNi5 phase and a decrease of the(La,Mg)Ni3 phase in the alloys.The results of the electrochemical measurement indicate that the discharge capacity of the alloys(x≤0.1)first increases and then decreases with the increase of spinning rate,whereas for x>0.1,the discharge capacity of the alloys monotonously falls.The melt spinning slightly impairs the activation capability of the alloys,but it significantly enhances the cycle stability of the alloys.

Study on Two-phase Nanocrystalline Nd_(8.5)Fe_(74)Co_5Cu_1Nb_1Zr_3Cr_1B_(6.5)Permanent Magnet

Nd8.5Fe74Co5Cu1Nb1Zr3Cr1B6.5 bonded magnets were prepared by melt-spun and subsequent heat treatment. Magnetic properties of Br=0.68 T,JHc=716 kA/m, (BH)max=77 kJ/m3 were achieved. The addition of Cr element shows to be significantly advantageous in reducing grain size and increasing the intrinsic coercivity.

Dynamics Model and Simulation of Polyethylene Terephthalate (PET) Hollow Fiber

On the basis of melt-spinning, the dynamics model of polyethylene terephthalate （PET） hollow fiber is established. The effects of spinning conditions on hollow ratio are discussed and verified. Because of the different quenching conditions, there exist differences of the hollow ratio and the vitrification distances between different cycles. The important role of the quenching conditions on the meltspinning of PEr hollow fiber is also mentioned.

Facile Synthesis of Porous SnSb Alloy Anode for Li-Ion Battery

Sn/Sb based alloy anodes have attracted considerable interest as electrodes for next-generation high performance Li-ion batteries (LIBs) owing to their high theoretical capacities. And fabricate porous structure is an effective way to improve materials’ cycling performance. Here, we developed nanoporous SnSb alloy ribbon (NP-SnSb) through a melt-spinning/chemical-etching process and took it as electrode of LIB directly. Being of self-supported and binder free, the NP-SnSb shows a total outperformance over its nonporous counterparts both in cycling performance and kinetic characteristic. Besides, considering the melt-spinning/chemical-etching synthetic process is high-through-put and simple, the ribbon kind of alloy anodes have strong potential application for LIBs research.

Impacts of Melt Spinning and Element Substitution on Electrochemical Characteristics of the La–Mg–Ni-based A₂B₇-Type Alloys

The partial substitution of Zr for La has been performed in order to ameliorate the electrochemical hydrogen storage performances of La–Mg–Ni based A2B7-type electrode alloys. The melt spinning technology was used to prepare the La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1 (x=0, 0.05, 0.1, 0.15, 0.2) electrode alloys. The impacts of the melt spinning and the substituting La with Zr on the structures and the electrochemical hydrogen storage characteristics of the alloys were systemically investigated. The analysis of XRD and TEM reveals that the as-cast and spun alloys have a multiphase structure, composing of two main phases (La, Mg)2Ni7 and LaNi5 as well as a residual phase LaNi2. The electrochemical measurement indicates that both the substitution of Zr for La and the melt spinning ameliorate the electrochemical cycle stability of the alloys dramatically. Furthermore, the high rate discharge ability (HRD) of the as-spun (10 m/s) alloys notably declines with growing the amount of Zr substitution, while it first augments and then falls for the (x=0.1) alloy with rising the spinning rate.