The effect of degree of amorphousness on electronic transport behaviors in the Ni–Nb–Zr–H glassy alloys with subnanometer-sized clusters

Material and electronic properties of Ni–Nb–Zr–H glassy alloys were investigated as a function of the rotating wheel speed in the amorphous ribbon-preparation method. Increase in density and amorphous colony size indicates that the degree of amorphousness increases with increase in the rotating speed. Supercooling, which reached by rotating wheel speed of 10,000 rpm (104.7-m/s), of the molten alloy produces a ballistic conductor with electrical conductivity of about 0.1 nΩ cm (× 10^? 9 Ω cm, 0.01% of silver (1.62 μΩ cm)) for (Ni_0.36Nb_0.24Zr_0.40)_94.6 H_5.4 glassy alloy and a room-temperature discrete Coulomb oscillation for (Ni_0.36Nb_0.24Zr_0.40)_91.6H_8.4 glassy alloy. The increase in degree of amorphousness by supercooling induces uniformity of cluster morphology.     

On the decolorization property of Fe–Mo–Si–B alloys with different structures

Decolorization property of Fe–Mo–Si–B ribbons with different structures was investigated, and kinetic analyses elucidated that the decolorization process could be described by a pseudo-first-order kinetic model. Amorphous ribbons were proved to decolorize Acid Orange II solutions much more rapidly than amorphous/nanocrystalline ribbons at the same temperatures. Activation energies of the decolorization process by amorphous ribbons and amorphous/nanocrystalline ribbons were obtained according to Arrhenius equation, and they were proved more or less the same because of the existence of amorphous phase in both ribbons, while the different reactive site amount was considered to lead to the different decolorization rates for the two ribbons with different structures.     

Bulk glassy (Fe0.474Co0.474Nb0.052)100 − x(B0.8Si0.2)x alloys prepared using commercial raw materials

The alloy compositions have been optimized by modifying the B and Si contents in (Fe_0.474Co_0.474Nb_0.052)_100 ? x(B_0.8Si_0.2)_x alloy system with commercial materials. The thermal stability of the supercooled liquid improves with the increased B and Si contents from x = 22 to 28. The composition of the alloy with x = 26 is close to a eutectic point. By copper mold casting, (Fe_0.474Co_0.474Nb_0.052)_100 ? x(B_0.8Si_0.2)_x bulk glassy alloys with diameters up to 5 mm were synthesized for the composition range of x from 22 to 28. In addition to high glass-forming ability (GFA), the (Fe_0.474Co_0.474Nb_0.052)_100 ? x(B_0.8Si_0.2)_x glassy alloys exhibit good soft magnetic properties as well, i.e., rather high saturation magnetization of 0.84–1.07 T, low coercive field of 1.8–3.2 A/m, high initial permeability of 10100–24100 at 1 kHz under a field of 1 A/m and Curie temperature of 620–730 K.     

Effect of germanium on the microstructure and the magnetic properties of Fe–B–Si amorphous alloys

In this work, we present a systematic study on the crystallization kinetics and the magnetic properties of melt-spun Fe₈₀B₁₀Si_10 ? xGe_x (x = 0.0 ? 10.0) amorphous alloys. The activation energy for crystallization, determined by differential scanning calorimetry, displayed a strong dependence on the Ge content, reflecting a deleterious effect on the alloys' thermal stability and their glass forming ability with increasing Ge concentration. On the other hand, the alloys exhibited excellent soft magnetic properties, i.e., high saturation magnetization values (around 1.60 T), alongside Curie temperatures of up to 600 K. Complementary, for increasing Ge substitution, the ferromagnetic resonance spectra showed a microstructural evolution comprising at least two different magnetic phases corresponding to a majority amorphous matrix and to Fe(Si, Ge) nanocrystallites for x ≥ 7.5.     

Effect of Mo–Fe substitution on glass forming ability and thermal stability of Fe–C–B–Mo–Cr–W bulk amorphous alloys

Amorphous Fe_67?xC₁₀B₉Mo_7+xCr₄W₃ (x = 1–7 at.%) plates with 0.64 mm thickness were prepared by copper mold casting. The thermal properties and microstructural development during heat treatments were investigated by a combination of differential scanning calorimetry, differential thermal analysis, and X-ray diffraction. The glass forming ability (GFA) and activation energy for crystallization have a distinct dependence on Mo content. Fe₆₂C₁₀B₉Mo₁₂Cr₄W₃ was the best glass former in this study, demonstrating a supercooled liquid region, ΔT_x = 51 K, and an activation energy for crystallization, Q = 453 kJ/mol. The GFA of alloys in this system was governed by elastic strain optimization resulting directly from the variation in Mo content. Heat treatments were performed to demonstrate resistance to crystallization under typical processing conditions. Alloys in this system exhibited a three phased evolution during crystallization. A second set of heat treatments was performed to identify each phase. An analysis of phase evolution revealed a distinct dependence of phase evolution with stepwise substitution of Mo for Fe in this system.     

Corrosion behavior and in vitro biocompatibility of Zr–Al–Co–Ag bulk metallic glasses: An experimental case study

Ni- and Cu–free Zr–Al–Co–Ag bulk metallic glasses (BMGs) were synthesized by copper mold casting. The effects of Ag addition for partially replacing Co of Zr₅₃Al₁₆Co₃₁ BMG on the corrosion behavior, surface chemistry and in vitro biocompatibility of BMGs were investigated. The Zr–Al–Co–Ag BMGs are spontaneously passivated with low passive current densities in phosphate buffered saline (PBS) solution. Partial substitution of Co by Ag is effective in improving the corrosion resistance of the Zr–Al–Co BMG. X-ray photoelectron spectroscopy (XPS) measurements reveal that the Ag addition increases the concentration of Zr and decreases the concentration of Al in the surface passive film of BMGs, which is responsible for the enhanced corrosion resistance of Zr–Al–Co–Ag BMGs. Mouse MC3T3-E1 pre-osteoblast cell proliferation results and morphology observations show that the Zr–Al–Co–Ag BMGs exhibit comparable cell viability and proliferation activity with those of Ti–6Al–4V alloy, demonstrating their good biocompatibility. The high corrosion resistance in PBS and low in vitro cytotoxicity of Zr–Al–Co–Ag BMGs suggest an initial biocompatibility for biomedical applications.     

Formation and mechanical behavior of (Fe0.5Ni0.5)80−xMoxB20 (x = 0–8) amorphous alloys

Glass forming ability, thermal stability and mechanical behavior of (Fe_0.5Ni_0.5)_80?xMo_xB₂₀ (x = 0, 2, 4, 6, 8) amorphous alloys were studied by XRD, TEM, SEM, DSC, tensile test, microhardness test and tearing test. The effects of Mo addition on glass formation, strength and ductility of (Fe_0.5Ni_0.5)_80?xMo_xB₂₀ amorphous alloys were discussed. The substitution of Mo for Fe and Ni simultaneously causes improvement in glass forming ability and thermal stability, and changes the crystallization process. The tensile fracture strength of amorphous alloy depends on both hardness and ductility; the alloy with high hardness and good ductility simultaneously also has a high tensile fracture strength. The (Fe_0.5Ni_0.5)₇₈Mo₂B₂₀ amorphous alloy exhibits good glass forming ability and the highest tensile fracture strength among (Fe_0.5Ni_0.5)_80?xMo_xB₂₀ alloys. Micro-plastic deformation occurred in ductile and brittle amorphous alloys that both show viscous flow characteristics. The mechanical behavior of (Fe_0.5Ni_0.5)_80?xMo_xB₂₀ amorphous alloys is related to the average outer shell electron concentration of metal atoms.     

Influence of Ta,Y substitutions on the thermal stability,microhardness and magnetic properties of melt spun Fe–B–Si amorphous alloys

In the present research work, thermal stability, magnetic properties and microhardness of Fe₇₂B_19.2Si_4.8M₄ (M = Ta or Y) amorphous ribbons obtained by chill block melt-spinning technique are reported. The crystallization temperatures resulted as high as 1129 K (for M = Ta) and of 1167 K (for M = Y), which indicate a considerable thermal stability for both alloys. On the other hand, the saturation polarization (μ₀M_s) together with the Curie temperature (T_c) also showed excellent combination of values, with 0.95 ± 0.12 T and 586 ± 8 K, respectively (for the Ta-containing alloy) and of 1.55 ± 0.18 T and 698 ± 6 K, respectively (for the Y-containing alloy). Additionally, the Vickers microhardness exhibited values over 1100 kg/mm² for both alloys.     

Thermodynamic prediction of bulk metallic glass forming alloys in ternary Zr–Cu–X (X = Ag,Al, Ti,Ga) systems

Prediction of bulk metallic glass (BMG) forming compositions has always been a challenge due to thermodynamic and kinetic constraints. In the present investigation, a parameter based on the enthalpy of chemical mixing (?H_chem) and the mismatch entropy (?S_σ/k_B) has been used to correlate with glass forming ability in some Zr based BMGs. The new thermodynamic parameter, P_HS = ?H_chem × ?S_σ/k_B, is found to have strong correlation with glass forming ability in the configurational entropy (?S_config/R) range of 0.9–1.0. P_HS has been calculated for compositions in Zr–Cu–Ag, Zr–Cu–Al, Zr–Cu–Ti and Zr–Cu–Ga ternary systems. It is observed that in all the systems studied, the best BMG composition (highest critical diameter (Z_c) of glass formation) is the one that corresponds to the highest negative P_HS value. Present approach using P_HS could be road map to design new BMG forming compositions.     

Correlation between bulk and surface properties in Cd–X (X = Hg,Mg) liquid alloys

A theoretical investigation of the energetics and its effect on the alloying behaviour of Cd–Hg and Cd–Mg liquid alloys have been carried out with the aim of correlating their bulk and surface phenomena. Using the Quasi-chemical approximation for regular solution model, our results indicate that Cd–Hg and Cd–Mg are weakly heterocoordinated both in the bulk and on the surface. We observed that the degree of chemical order in Cd–Mg liquid alloy is more than that of Cd–Hg liquid alloy.     

Crystal structure of tisinalite Na2(Mn,Ca)1 − x (Ti,Zr,Nb,Fe3+)[Si6O8(O,OH)10]

Crystal structure of tisinalite from the Lovozero alkaline massif (the Kola Peninsula) was established by single-crystal X-ray diffraction analysis (SYNTEX $\bar P1$ diffractometer, λMoK_α radiation, 2θ/θ scanning mode). The structure solution (SHELX97 program package, R _hkl = 0.0565, 951 independent reflections, anisotropic refinement of thermal atomic displacements) confirmed that tisinalite belongs to the lovozerite structure type (sp. gr., $\bar P1$ , a = 10.036(5) Å, c = 12.876(9) Å, Z = 3). The difference between the structure of tisinalite and the structures of the minerals of the lovozerite group established earlier consists in the nature of the occupancy of both cation and anion positions.     

The effect of transition M metals on the two-stage enthalpy relaxation behavior of (FeM)83P17 amorphous alloys

The anneal-induced relaxation behavior for (FeM)₈₃P₁₇ (M  Cr, Mo, Mn, Co or Ni) amorphous alloys was examined calorimetrically with the aim to clarify the effect of M substitution on the two-stage relaxation previously found by the present authors. Upon heating the sample annealed at temperatures below T_g, a reversible endothermic reaction (enthalpy relaxation) occurs above T_a. The changes in ΔC_p,endo and with T_a show two distinguishable stages only for The FeMoP alloy which exhibits glass transition; a low-temperature peak at a temperature that is lower by about 180 K than T_g and a high-temperature one just below T_g. However, any indication of the high-temperature peak is not detected for the other alloys which crystallize before T_g. From the data of ΔC_p,endo, ΔH_σ,endo and activation energy for the low-temperature peak which has been thought to generate by relaxation of metal atoms, the first-stage relaxation was concluded to become difficult in the order of Ni < Co < Mn < Cr < V < Mo, i.e., with the decrease in the group number of the periodic table. The change in the first-stage enthalpy relaxation behavior with the substitution of Fe by M is interpreted to originate from the change in the mobility (i.e., relaxation time) of metal atoms through the change in the bonding force among the constituent elements.     

Internal stresses induced by plastic shear deformation of Zr–(Cu,Ag)–Al bulk metallic glasses

Effective internal shear stress σ_i induced by torsional deformation of Zr₄₆(Cu_4/5Ag_1/5)₄₆Al₈ and Zr₄₆Cu₄₆Al₈ bulk metallic glasses different by the glass-forming ability of the maternal melts has been determined by measurements of stress relaxation upon stepwise unloading. It has been found that the ratio σ_i/σ₀ (σ₀ is the initially applied shear stress) decreases upon increasing the temperature from ≈ 0.8 at T = 450K (T ≈ 0.64 × T_g) to ≈ 0.08 at T = 638K (T ≈ 0.91 × T_g) independently of σ₀ and glass composition. The obtained result is in good agreement with earlier data obtained on ribbon metallic glasses. The origin of deformation-induced internal stresses and their connection with deformation mechanisms of metallic glasses has been briefly discussed.     

Magnetic, magnetocaloric, and lattice properties of the La(Fe x Si1 − x )13 ferromagnets

The magnetic and lattice properties of a sample of La(Fe_0.86Si_0.14)₁₃ ferromagnet have been measured. The influence that neutron irradiation has on the physical properties of this ferromagnet is studied. It is shown that the irradiation of this sample by a fluence of 3 × 10¹⁹ n/cm² increases the lattice constant a and the Curie temperature (T _C ) as the volume magnetostriction decreases. A model of ferromagnet is proposed which satisfactorily describes the dependence a(T) of the initial and irradiated samples and their magnetic properties. The temperature dependence of the change in entropy when switching the magnetic field on and off is calculated. It is established that the change in both the magnetic and lattice parts of the total entropy at the magnetic phase transition must be taken into account for La(Fe _x Si_{1 ? x} )₁₃ compounds.     

A3BGa3Si2O14(A=Ca,Sr;B=Nb,Ta)晶体研究进展

介绍了一类性能优异、结构有序的新型材料--A3BGa3Si2O14(A=Ca,Sr;B=Nb,Ta)单晶,总结了其研究进展,并对该类晶体的生长、结构、热学、光学和压电性能进行了描述.     

Synthesis, redox chemistry, and X-ray structure of the mixed-metal cluster Fe2(CO)6(μ3-S)2Ni(dppf)

The reaction between the dianion [Fe₂(CO)₆(₂-S)₂]^2– and NiCl₂(dppf) occurs readily at room temperature to give the mixed-metal cluster Fe₂(CO)₆(₃-S)₂Ni(dppf) in moderate yield. Fe₂(CO)₆(₃-S)₂Ni(dppf) was isolated by preparative chromatography and its solid-state structure established by X-ray diffraction analysis. Fe₂(CO)₆(₃-S)₂Ni(dppf) crystallizes in the monoclinic space group C2/c, a = 20.320(6), b = 13.114(2), c = 15.622(2) Å, = 110.25(2)°, V = 3905.4(11) ų, Z = 4, and d _calc = 1.630 g/cm.³ The X-ray structure of Fe₂(CO)₆(₃-S)₂Ni(dppf) exhibits an Fe₂S₂Ni arachno polyhedral core, with the pendant dppf ligand attached to an essentially square planar Ni center. The redox chemistry of Fe₂(CO)₆(₃-S)₂Ni(dppf) was investigated by cyclic voltammetry which showed a reversible, one-electron oxidation localized on the Fe₂S₂ core along with an irreversible, one-electron reduction that is antibonding with respect to the Fe—Fe and Fe—S bonds. The electrochemical assignments were confirmed by carrying out extended Hückel MO calculations on the model cluster Fe₂(CO)₆(₃-S)₂Ni(H₄-dppf).     

Crystallization behavior of Ce70−xAl10Cu20Cox (x = 0, 1, 3, 5 at.%) amorphous alloys

The effect of Co addition (substituting for Ce) on crystallization behavior of Ce₇₀Al₁₀Cu₂₀ amorphous alloys has been investigated using X-ray diffraction (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM). The Co addition has an obvious effect on topological short-range ordering of Ce–Al–Cu–(Co) amorphous alloys. Moreover, the Co addition can slightly improve the thermal stability of Ce–Al–Cu based amorphous alloys. The 1 and 3 at.% Co additions do not obviously change the crystallization behavior of the Ce–Al–Cu–(Co) amorphous alloys, and the final crystallization products are FCC–CeAlCu(Co)O. However, the 5 at.% Co addition can alter the crystallization behavior of the Ce₇₀Al₁₀Cu₂₀ amorphous alloys. Proper content of Co can effectively suppress the formation of oxide phases during annealing of the Ce–Al–Cu–(Co) amorphous alloys.     

Thermal and electric transport properties of (60−x)V2O5–xAs2O3–20Fe2O3–10CaO–10Li2O unconventional glassy system

This paper presents the results of kinematical studies of glass transition and crystallization in the unconventional glassy system (60?x)V₂O₅–xAs₂O₃–20Fe₂O₃–10CaO–10Li₂O (x = 0, 10, 20, 30, 40 mol%) using differential scanning calorimetry (DSC). The glass transition temperatures (T_g), the onset crystallization temperatures (T_c), and the peak temperatures of crystallization (T_p) were found to be dependent on the compositions and the heating rates. From the dependence on heating rates of (T_g) and (T_p) the activation energy for glass transition (E_g) and the activation energy for crystallization (E_c) are calculated. The thermal stability of (60?x)V₂O₅–xAs₂O₃–20Fe₂O₃–10CaO–10Li₂O was evaluated in term of, criteria ΔT = T_c ? T_g. All the results confirm that the thermal stability increase with increasing As₂O₃ contents. From the electric–dielectric measurements it was found that, σ_dc, σ_ac(ω) and θ_D/2 decrease with increasing As₂O₃ contents. It is also observed that the dielectric constant (ε₁(ω)) and the loss factor (tan δ) decrease with increasing As₂O₃ contents in this glass system.