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The crystallization kinetics of Zr60Al15Ni25 amorphous alloy is investigated by differential scanning calorimetry (DSC) under non-isothermal and isothermal conditions. The result of a Kissinger analysis shows that the activation energy for crystallization is 402 kJ/mol, which is much higher than that of Zr&z.sbnd;Ti&z.sbnd;Cu&z.sbnd;Ni&z.sbnd;Be and Zr&z.sbnd;Cu&z.sbnd;Al&z.sbnd;Ni amorphous alloys. The much higher stability against crystallization of Zr60Al15Ni25 amorphous alloy is attributed to the stronger interaction of atoms in the Zr&z.sbnd;Al&z.sbnd;Ni system and the formation of the complicated compounds AlNi4Zr5 and Al2NiZr6 as primary phases. The isothermal crystallization can be modeled by using the Johnson–Mehl–Avrami (JMA) equation. The Avrami exponents suggest that the isothermal crystallization is governed by different mechanism when annealed at different temperatures in the supercooled liquid region. [Copyright &y& Elsevier]

X2–Y2SiO5:A (A=Eu3+, Tb3+, Ce3+) phosphor films and their patterning were fabricated by a sol–gel process combined with a soft lithography. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), scanning electron microscopy (SEM) optical microscopy and photoluminescence (PL) were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 900 °C with X1–Y2SiO5, which transformed completely to X2–Y2SiO5 at 1250 °C. Patterned thin films with different band widths (5 μm spaced by 5 μm and 16 μm spaced by 24 μm) were obtained by a soft lithography technique (micromoulding in capillaries, MIMIC). The SEM and AFM study revealed that the nonpatterned phosphor films were uniform and crack free, and the films mainly consisted of closely packed grains with an average size of 350 nm. The doped rare earth ions (A) showed their characteristic emissions in X2–Y2SiO5 phosphor films, i.e., 5D0–7FJ (J=0,1,2,3,4) for Eu3+, 5D3, 4–7FJ (J=6,5,4,3) for Tb3+ and 5d (2D)–4f (2F2/5, 2/7) for Ce3+, respectively. The optimum doping concentrations for Eu3+, Tb3+ were determined to be 13 and 8 mol% of Y3+ in X2–Y2SiO5 films, respectively. [Copyright &y& Elsevier]

From facile preparation method and available low-cost raw materials, we have synthesized a novel kind of organodisulfide cathode materials based on anthracene for lithium secondary batteries – anthra[1′,9′,8′-b,c,d,e][4′,10′,5′-b′,c′,d′,e′]bis-[1,6,6a(6a-SIV) trithia]pentalene (ABTH) and its homopolymer (PABTH), investigated the application of the organodisulfides to positive active material for lithium secondary batteries. The organodisulfides were characterized by FT-IR, XPS, and elemental analysis. The cyclic voltammetry tests reveal that the redox reaction of the ABTHs was processed in two steps. The experimental results showed that the polymer has the specific capacity of 300 mAh/g at second cycle and 250 mAh/g at the fifth cycle. [Copyright &y& Elsevier]

This letter reports the effect of repeated melting of the ingots on the glass-forming ability (GFA) of Zr60Al15Ni25 and Zr65Al7.5Ni10Cu17.5 alloys. The results indicate that the glass transition temperature Tg and the onset temperature of crystallization Tx of Zr60Al15Ni25 alloy increase as melting times increase. However, the repeated melting of the ingot brings only a little change to Zr65Al7.5Ni10Cu17.5 glassy alloy. Within the framework of structure heredity and thermodynamics, the reason for the improvement of the GFA of alloys is discussed. [Copyright &y& Elsevier]

Previous work suggests that the size factor may be the most crucial one on the glass forming ability (GFA). But the alloys in a system have significant deference for GFA. A criterion λn is defined in the present work to comprehensively evaluate concentration dependence of GFA of alloys in a system. It is found that the values of λn of bulk glass formers with greatest GFA in Zr-, Pd-, Mg-, Nd- and Fe-based systems are nearly constant of 0.18. Based on the mathematical description of regular polytopes and the dense random packing of hard sphere (DRPHS) model, a cluster model is suggested. This model provides the physical meaningful origin of the λn from the view of free volume. The glass structure of bulk glass formers with λn≈0.18 has optimum defect concentration within the framework of the cluster model. In the term of λn criterion, an alloy with λn of about 0.18 will be one of bulk glass former candidates, which is verified by the experimental result of Zr&z.sbnd;Al&z.sbnd;Ni system. [Copyright &y& Elsevier]

This paper reports the formation of compounds during the solidification process of liquid Zr85−xAl15Nix (x=15, 20, 25, 30, 35) alloys studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results indicate that compound AlNi4Zr5 forms when liquid alloys containing 20, 25 and 30 at.% nickel solidify. It is suggested in this work that the large glass forming ability (GFA) of the Zr–Al–Ni system is attributed to the difficulty of formation of compound AlNi4Zr5 as a primary phase during solidification process of liquid alloys. In comparing the phases appearing in the solidification structure of the liquid Zr60Al15Ni25 alloy with the products formed during crystallization process of this amorphous alloy, it is assumed that Al2NiZr6 is a metastable phase, which decomposes into equilibrium phases during the subsequent cooling process. [Copyright &y& Elsevier]

Effects of processing variables using such as the frequency of imposed field (f), imposed magnetic flux density (Be), processing time (t), the diameter of inclusions (dp) and the ratio of pipe radius to skin depth (r1/δ) on the electromagnetic separation (EMS) removal efficiency of inclusions from an aluminum melt were analyzed theoretically. It was found that the removal efficiency (η) reaches a maximum while r1/δ ranges from 1.5 to 2. In addition, wider effective range of r1/δ will be obtained with larger dp or higher f. Experimental results on aluminum melt show that higher frequency and magnetic flux density make for higher removal efficiency, matching well with the theoretical results. In the case of f=15.6 kHz, Be=0.1 T and t=10 s, more than 80% inclusion particles with 6-μm diameter can be removed. [Copyright &y& Elsevier]

The Fe alloy melts containing 7.5, 15, 22.5 and 30 at% Ni were bulk undercooled to investigate the structure evolution. When the undercooling of the four melts is lower than the critical value 110, 125, 175 and 325 K, respectively, only the stable face-centered cubic phase crystallizes. In this case a grain refinement caused by solid superheating is observed in all the alloys, but another grain refinement induced by recrystallization can merely occur in the Fe–30 at%Ni alloy undercooled by 190–325 K. Alternate crystallization of the metastable body-centered cubic phase occurs above the critical undercooling. It is indicated that the subsequent heterogeneous nucleation of the stable phase in the metastable solid and remaining liquid coexisting system is influenced not only by the morphology and surface area of the metastable solid, but also by the effective undercooling of the remaining liquid. On the basis of the experimental results and the theoretical analyses, a structure evolution map for bulk Fe–Ni system is constructed. [ABSTRACT FROM AUTHOR]

Explores the phase evolution relationship during rapid solidification processing (RSP) and the possible design of phase composition in rapidly solidified alloys. Alloy used in the investigation which is the most promising representative of titanium-aluminum-based alloys; Use of a vacuum arc furnace to carry out the process of melting; Transformation of the lamellar structure from primary phase alpha due to the solid transformation in the subsequent cooling process.

Abstract: An analytical treatment of soft impingement has been developed for solid-state precipitation in an isothermal process following the basic assumptions (i.e., a two-stage transformation including a site saturation of nucleation, an isotropic growth and a linear concentration gradient in front of the precipitate/matrix interface). Based on the analytical treatment for soft impingement, a new approach for deducing activation energy for diffusion Q was proposed. The isothermal recipe was mainly determined by two parameters, i.e., the mean size of the second phase r f and the starting time for soft impingement t 1. The method has been successfully applied to deduce Q for isothermal transformations in Al–0.2wt.%Sc alloy and Fe–0.24C–0.93Mo alloy. [Copyright &y& Elsevier]

Abstract: Rapid solidification of undercooled peritectic Fe81.68Co18.32 alloy was investigated using fluxing method. With the increase of initial melt undercooling (ΔT), different microstructures were observed. For low ΔT, a typical peritectic microstructure, if ΔT exceeded a critical value, 177K, metastable phase was observed in the as-solidified microstructure. On this basis, different solidification modes for peritectic Fe81.68Co18.32 alloy were demonstrated. When ΔT <ΔT crit, the melt solidified with peritectic mode, peritectic reaction and peritectic transformation occurred, followed by extension growth of γ at the peritectic layer. When ΔT >ΔT crit, the melt solidified with competitive nucleation mode, competitive nucleation occurred between stable and metastable phase, and metastable phase nucleated primarily from the undercooled melt as a result. [Copyright &y& Elsevier]

Abstract: Applying melt-fluxing, how to predict the maximal recalescence temperature T R upon rapid solidification of bulk undercooled Cu70Ni30 alloy has been investigated. Reproducible experimental results show that T R decreases with the increase of the initial melting undercooling ΔT, and moreover, its value is much lower than that predicted by Level rule and Scheil equation, let alone the equilibrium liquidus temperature. Quantitative thermodynamic calculation, in combination with an analysis of solute distribution, demonstrates that, T R is affected by the difference of Gibbs free energy between the residual liquid and solid after recalescence. Subjected to sufficiently high ΔT, T R should be nearly equal to the thermodynamic T 0 point corresponding to the concentration of the residual melt after recalescence. [Copyright &y& Elsevier]

Abstract: In order to investigate phase selection between stable and metastable phases upon rapid solidification of Fe70Co30 single-phase alloy, different undercooling experiments were performed. The critical undercooling for forming metastable phase upon spontaneous crystallization was observed as ∼203K, whereas, it decreased to ∼169K if artificially triggering was adopted. This can be ascribed to a substantial reduction of the catalytic potency factor f(θ) of bcc phase in the case of triggered nucleation. [Copyright &y& Elsevier]

Abstract: Fe–Co melt was undercooled using fluxing method in this work. With increasing the initial undercooling (ΔT), two kinds of dendrites were obtained in the microstructure of undercooled Fe70Co30 alloy at both low and high undercooling ranges. For ΔT <22K, the as-solidified morphology is similar to the conventional as-cast dendrite, whereas, for 97K<ΔT <173K, a largely developed fine dendritic morphology is observed. BCT model is used to discuss the two different dendritic morphologies, in combination with a stability analysis of dendrite growth based on the morphological instability. [Copyright &y& Elsevier]

Abstract: Adopting cyclic superheating and DSC analysis, solidification behavior of undercooled Cu70Fe30 alloy was investigated. The metastable phase separation is observed if the initial melt undercooling (ΔT) is above 56K. The primary solidification of Fe-rich phase in the phase-separated melt is due to its high nucleation driving force i.e. a high ΔT. The coarsening of Fe-rich droplets is controlled by ΔT and can be ascribed to the Ostwald ripening and coagulation effect in the melt. [Copyright &y& Elsevier]