Microstructure and Electrochemical Characteristics of Melt-Spinning Alloy Ml(NiCoMnAl)_5

The microstructure and electrochemical characteristics of Ml(NiCoMnAl) 5 alloys prepared by both the melt spinning method and the conventional induction melting were investigated and compared. SEM and XRD studies show that the microstructure of melt spinning alloys is columnar structure. With increasing melt spinning rate, the crystal grains become finer and preferentially grow along (111)[111] direction. The melt spinning and cast alloys belong to CaCu 5 type hexagonal crystal structure. The electrochemical measurements show that the initial capacities of melt spinning alloy electrodes are all above 210 mAh·g -1 with good activation behavior, reaching their maximum capacities after two charge discharge cycles. The maximum capacity (294 mAh·g -1 ) of melt spinning (10 m·s -1 ) alloy electrodes is as the same as that of as cast alloy electrode, and stability of charge discharge cycles of all melt spinning alloy electrodes is better than that of the as cast alloy electrodes. When charged at 600 mA·g -1 , the capacity of melt spinning (10 m·s -1 ) alloy electrode could reach 65% of its maximum capacity about 45 min with high rate discharge capability; but with the cycle number increasing, the stability of its capacity is less than that electrodes of melt spinning rate.

Effects of melt spinning process parameters and wheel surface quality on production of 6060 aluminum alloy powders and ribbons

The aim of this study is to investigate the surface quality of the melt spinning wheel, which was changed from smooth type to textured structure, to atomize liquid metal to form powders. The effects of melt spinning process parameters like wheel speed, gas ejection pressure, molten metal temperature, nozzle–wheel gap and wheel surface quality on the morphological and microstructural features of 6060 aluminum alloy powders and ribbons were investigated. It was observed that ribbon type material was obtained with the smooth wheel and the powder was produced with textured type. The sizes of produced ribbons with smooth surface wheel varied in the range of 30-170 μm in thickness, 4-8 mm in width, and 0.5-1 m in length. The average powder size of the powders manufactured using the textured wheel was in the range of 161-274 μm, depending on the process parameters.Increasing the wheel speed, melt temperature and decreasing gas ejection pressure, nozzle-wheel gap resulted in the decrease of both ribbon thickness and powder size. The microstructures of the powders and ribbons were the equiaxed cellular type, and the average grain sizes diminished with decreasing the ribbon thickness and powder size. The maximum cooling rates were 2.00×10^5 and 1.26×10^4 K/s for the ribbon with thickness of 30 μm and for the powder with size of 87 μm, respectively.

ANALYSIS OF MECHANICS IN BALL SPINNING OF THIN-WALLED TUBE

Ball spinning is applied to manufacturing thin-walled tube with high precision and high mechanical properties. On the basis of plastic mechanics, by simplifying ball spinning of thin-walled tube as plane strain problem, slab method is used for the purpose of calculating the contact deformation pressure. The spinning force components, the torsional moment, the deformation power and the deformation work are calculated further as well. The influence of the two important process parameters such as the feed ratio and the ball diameter on the spinning force components is analyzed in order to further control the spinning force components by regulating the two process variables during the ball spinning process. The stress and strain state in deformable zone as well as mechanics boundary conditions in ball spinning are obtained. The effect of the three spinning force components on the formability of the spun part is analyzed and validated through the ball spinning experiments. The theoretical and experimental results show that the radial spinning component plays a significant role in ball spinning of thin-walled tube, and the mechanics situation in backward ball spinning contributes to enhancing the plasticity of the metal material, but that in forward ball spinning contributes to advancing the axial flow of the metal material.

Light curve inversion of asteroid(585)Bilkis with Lommel-Seeliger ellipsoid method

The basic physical parameters of asteroids, such as spin parameters, shape and scattering parameters, can provide us with information on the formation and evolution of both the asteroids themselves and the entire solar system. In a majority of asteroids, the disk-integrated photometry measurement constitutes the primary source of the above knowledge. In the present paper, newly observed photometric data and existing data on（585） Bilkis are analyzed based on a Lommel-Seeliger ellipsoid model. With a Markov chain Monte Carlo（MCMC） method, we have determined the spin parameters（period, pole orientation）and shape（b/a, c/a） of（585） Bilkis and their uncertainties. As a result, we obtained a rotational period of 8.5738209 h with an uncertainty of 9×10^-7h, and derived a pole of（136.46°, 29.0°） in the ecliptic frame of J2000.0 with uncertainties of 0.67°and 1.1°in longitude and latitude respectively. We also derived triaxial ratios b/a and c/a of（585） Bilkis as 0.736 and 0.70 with uncertainties of 0.003 and 0.03 respectively.

Mg-based inorganic nanofibers constructing fast and multi-dimensional ion conductive pathways for all-solid-state lithium metal batteries

Solid-state electrolytes(SSEs),which replace flammable and toxic liquid electrolytes,have attracted widely attention.However,there exist still some challenges in actual application such as poor interfacial compatibility and slow ionic migration.In this study,Mg O nanofibers and MgF;nanofibers were prepared via the electro-blow spinning and high-temperature calcination methods,and were applied to all-solid-state lithium metal batteries for the first time.The organic-inorganic composite SSEs exhibited continuous conduction paths based on the virtue of the nanofibers with high length-to-diameter ratio,which were designed and prepared by mixing prepared fillers into the poly(ethylene oxide)(PEO)/lithium bis(trifluoromethane)sulfonilimide(Li TFSI)system.The effect of filler with different morphologies,doping ratios and component on ionic conductivity,electrochemical stability and cycle performance were explored under two kinds of[EO]/[Li^(+)]ratios and ambient temperatures.The ionic conductivities of electrolytes containing Mg O and MgF;nanofibers can reach up to 1.19×10^(-4) and 1.39×10^(-4) S cm^(-1) at 30℃,respectively.They were attributed to specific ionic conductive enhancement at the organicinorganic interface,reduced crystallinity and Lewis acid interaction,which can effectively promote the dissociation of the lithium salts.Especially MgF_(2) nanofiber,combining low electronic conductance,excellent electrochemical stability and outstanding inhibition for lithium dendrites of fluorides,endowed the battery with an initial specific capacity of 140.6 m Ah g^(-1) and capacity decay rate per cycle of 0.055%after500 cycles at 50℃.The work can provide an idea to design SSE with fast and multi-dimensional Li conductive paths and excellent interfacial compatibility.

Investigation on the Tensile Properties and Fracture Characteristics of Amorphous Ribbons Fe81.50B1.40Si7.95Nb7.37Cu1.73P0.05

A number of Fe-Si-B amorphous ribbons are made by using melt spinning method. The microstructure, mechanical and other relevant properties of thin amorphous ribbons of Fe81.50B1.40Si7.95Nb7.37Cu1.73P0.05 alloy at room temperature were studied with several equipment including Differential scanning calorimetry (DSC), X-ray diffraction (XRD),Scanning electron microscope (SEM), and tensile machine. Significantly different microstructures exist between the free and wheel face of the thin amorphous ribbons. The free face is smooth while the wheel face is coarse with a great number of micro voids on the surface. Experimental results show that the tensile strength and elastic modulus of thethin amorphous ribbons at room temperature are 1951 MPa and 70 GPa. In addition, the amorphous ribbons possess reasonable tensile elongation (2.46%). The fracture appearance of amorphous ribbons of Fe81.50B1.40Si7.95Nb7.37Cu1.73P0.05 alloyis a mixed mode of ductile and brittle fracture which includes dimples and partial cleavage fracture similar to the crystalline materials. The dimple feature proves that it still has plastic characteristics on the micro scale.

Tuning field emission properties of boron nanocones with catalyst concentration

Single crystalline boron nanocones are prepared by using a simple spin spread method in which Fe3O4 nanoparticles are pre-manipulated on Si（lll） to form catalyst patterns of different densities. The density of boron nanocones can be tuned by changing the concentration of catalyst nanoparticles. High-resolution transmission electron microscopy analysis shows that the boron nanocone has a β-tetragonal structure with good crystallization. The field emission behaviour is optimal when the spacing distance is close to the nanocone length, which indicates that this simple spin spread method has great potential applications in electron emission nanodevices.

Spin and pseudospin symmetries of the Dirac equation with shifted Hulthe′n potential using supersymmetric quantum mechanics

In this paper, we obtain approximate analytical solutions of the Dirac equation for the shifted Hulthén potential within the framework of spin and pseudospin symmetry limits for arbitrary spin–orbit quantum number κ using the supersymmetry quantum mechanics. The energy eigenvalues and the corresponding Dirac wave functions are obtained in closed forms.

A key factor to the spin parameter of uniformly rotating compact stars: crust structure

We study the dimensionless spin parameter j ≡ cJ/（GM2） of different kinds of uniformly rotating compact stars, including traditional neutron stars, hyperonic neutron stars and hybrid stars, based on relativistic mean field theory and the MIT bag model. It is found that j ~ 0.7, which had been suggested in traditional neutron stars, is sustained for hyperonic neutron stars and hybrid stars with M 〉 0.5 MG. Not the interior but rather the crust structure of the stars is a key factor to determine jmax for three kinds of selected compact stars. Furthermore, a universal formula j = 0.63（f/fK） -- 0.42（f/fK）2 ＋ 0.48（f/fK）z is suggested to determine the spin parameter at any rotational frequency f smaller than the Keplerian frequency fK.

Laser-induced topology optimized amorphous nanostructure and corrosion electrochemistry of supersonically deposited Ni_(30)Cr_(25)Al_(15)Co_(15)Mo_(5)Ti_(5)Y_(5) HEA coating based on AIMD

A novel Ni_(30)Cr_(25)Al_(15)Co_(15)Mo_(5)Ti_(5)Y_(5) high-entropy alloy(HEA)coating was irradiated to optimize its internal structure via laser after supersonic particle deposition(SPD).Owing to the high energy density of the laser and large temperature gradient,the crystallization process of the molecules and atoms in the coating was restrained and supercooling occurred.Experimental results showed that a considerable number of nano-crystal grains precipitated and amorphous structures were formed because of the random orientation of the crystals.The baseline of differential scanning calorimetry scans obtained for the coating started to shift at the Tg of 939.37℃ and a step was observed.Multiple dispersion peaks and lattice fringes indicated that the nucleation of the irradiated laser-induced topology optimized(LTO)coating was incomplete.The laser-induced topology optimizing treatment led to quasi-isotropy in the SPD coating.Furthermore,the LTO coating exhibited a residual stress of 18.4 MPa,stress-strain response,and fatigue limit of 265 MPa.Hence,the LTO coating exhibited higher performance than the unirradiated SPD coating.The Nyquist and Bode electrochemical impedance spectra of the LTO coating,including two relaxation processes,indicated that the corrosion process steadily recovered to the equilibrium state.This implies that the uniform oxidation passivation layer on the surface of the LTO coating insulated the material from the corrosive medium,protecting the substrate from further corrosion,thus enhancing the structural security of the material for use in super-intense laser facility applications.