Microstructure and physical properties of bismuth–lead–tin ternary eutectic alloy

Using different experimental techniques, microstructure, electrical resistivity, attenuation coefficient, and mechanical and thermal properties of the quenched Bi–Pb–Sn ternary eutectic alloy have been investigated. From the X-ray analysis, Bi₃Pb₇ and Bi–Sn meta-stable phases are detected, in addition to rhombohedral bismuth and Sn body-centered tetragonal phases. This study also compared the physical properties of the Bi–Sn–Pb ternary eutectic alloys with the base binary Bi–Sn and Bi–Pb eutectic alloys.     

Galvanomagnetic properties of thin films of bismuth and bismuth–antimony alloys on substrates with different thermal expansions

Temperature dependences of the galvanomagnetic properties of films of bismuth and Bi_{100 – x}Sb_x (x ≤ 12) on substrates with different temperature expansion coefficients were studied in the temperature range of 77–300 K. The block films were prepared through thermal deposition, and single-crystal Bi_{100 – x}Sb_x were grown by zone recrystallization under a coating. It was found that the temperature expansion coefficient of a substrate substantially influenced the galvanomagnetic properties of Bi and Bi_{100 – x}Sb_x films. Using the experimental data, the change in the charge-carrier concentration in the Bi and Bi_{100 – x}Sb_x films on different substrates at 77 K was estimated.     

Characterization of bismuth–tin–lead and bismuth–tin–lead–cadmium fusible alloys

Microstructure, electrical, mechanical and thermal properties of quenched bismuth–tin eutectic, Rose (Bi₅₀Sn_22.9Pb_27.1) and Wood’s (Bi₅₀Sn_12.5Pb₂₅Cd_12.5) alloys have been investigated using scanning electron microscopy, X-ray diffraction analysis, the double bridge method, the dynamic resonance method, Vickers hardness measurement and thermal analysis. Wood’s alloy (Bi–Pb–Sn–Cd) has low electrical resistivity and melting point but a high elastic modulus and internal friction when compared with the Rose (Bi–Pb–Sn) alloy. The presence of cadmium in Wood’s alloy decreases its melting point and electrical resistivity with an increase in its elastic modulus, which improves the mechanical properties. Wood’s alloy (Bi–Pb–Sn–Cd) has better properties, which make it useful in various applications such as in protection shields for radiotherapy, locking of mechanical devices and welding at low temperature.     

Rapid and sensitive determination of cobalt by adsorptive cathodic stripping voltammetry using tin–bismuth alloy electrode

Tin–bismuth alloy electrode (SnBiE) was used for trace cobalt determination for the first time. Compared to the bismuth bulk electrode, the SnBiE possesses the advantages of higher hydrogen overpotential, easier manufacture, and lower cost. In addition, there is no need for a pretreatment (in terms of modification) of the electrode before measurements. The analysis of Co(II) was made by the adsorptive accumulation of the cobalt–nioxime complex from solution containing 60 μM nioxime and 0.1 M ammonia at pH 9.4 and followed by the reduction of the accumulated complex. The electroanalysis results show that the optimal sensitivity can be obtained by using nitrite as the auxiliary reagent. The calibration plot for Co(II) quantification was linear from 0.2 to 20 nM with a correlation coefficient of 0.998. Meanwhile, a detection limit of 44 pM was obtained in connection with an accumulation time of 60 s, which is more sensitive than that of the mercury, bismuth, lead, and lead–copper electrodes. The practical applications of SnBiE have been performed for the determination of Co(II) in real water samples, and the results are consistent with those results by use of inductively coupled plasma–mass spectrometry (ICP-MS).     

Investigation on the thermal radiation properties of antimony doped tin oxide particles

This paper reports the preparation of antimony doped tin oxide crystalline powders by chemical coprecipitation method. The influence of sintering temperature and the sintering retention time on the thermal infrared emissivity is analysed. The thermal infrared reflectivity is measured and the optimum doping concentration is proposed.     

Effect of electrotransfer and indium additions on contact melting and phase formation in bismuth–tin systems

Contact melting with and without electrotransfer is studied in Sn–Bi systems with small additions of indium to each component. The effect admixtures have on the rate of contact melting is shown to be unclear. The structures of the obtained alloys are highly inhomogenous with multiple inclusions of dendrites. An X-ray analysis of the transformed interlayers is performed. A number of intermetallides are observed, including ones not found on the phase diagrams of binary systems. An attempt is made to explain these findings.     

Preparation and magnetic properties of Fe–Ag granular alloy

An aqueous solution of AgNO₃ in the presence of ammonia and Fe(CO)₅ is sonicated under a H₂/Ar mixture, yielding a nanostructured homogeneous phase of Ag/Fe₂O₃. This composite material is further reduced at 300°C under hydrogen to produce the nanophased Fe/Ag solid mixture. The as-prepared material, as well as the reduced mixture, is analyzed by various conventional methods. Magnetization loops, ESR, Mössbauer, and magnetoresistance measurements are also conducted to determine the magnetic properties of the products.     

Influence of misch metal content on microstructure and magnetic properties of R–Fe–B magnets sintered by dual alloy method

MM_(14)Fe_(79.9)B_(6.1)/Nd_(13.5)Fe_(80.5)B_6 magnets were fabricated by dual alloy method(MM, misch metal). Some magnets have two Curie temperatures. Curie temperatures T_(c1)corresponds to the main phase which contains more La Ce, and T_(c1) decreases from 276.5?C to 256.6?C with the content of MM increasing from 30.3 at.% to 50.6 at.%. The variation of Br with the increase of MM indicates the existence of inter-grain exchange coupling in the magnets. When MM/R ≤ 30.3 at.%,the magnetic properties can reach the level of the intrinsic coercivity Hcj≥ 7.11 kOe and the maximum energy product(BH)max≥ 41 MGOe. Compared with Nd, La and Ce are easier to diffuse to the grain boundaries in the sintering process,and this will cause the decrease of H_(cj) Due to the diffusion between the grains, the atomic ratio of La, Ce, Pr, and Nd in each grain is different and the percentage of Nd in all grains is higher than that in misch metal.     

Optical properties and ultrafast electron dynamics in gold–silver alloy and core–shell nanoparticles

Silver and gold are the two most popular metals used for many nanoparticle applications, such as surface enhanced Raman scattering or surface enhanced fluorescence, in which the local field enhancement associated with the excitation of the localized surface-plasmon–polariton resonance (SPR) is exploited. Therefore, tunability of the SPR over a wide energy range is required. For this purpose we have investigated core–shell nanoparticles composed of gold and silver with different shell thicknesses as well as the impact of alloying on these nanoparticles due to a tempering process. The nanoparticles were prepared by subsequent deposition of Au and Ag atoms or vice versa on quartz substrates followed by diffusion and nucleation. Their linear extinction spectra were measured as a function of shell thickness and annealing temperature. It turned out that different gold shell thicknesses on silver cores allow a tuning of the SPR position from 2.79 to 2.05 eV, but interestingly without a significant change on the extinction amplitude. Heating of core–shell nanoparticles up to only 540 K leads to the formation of alloy nanoparticles, accompanied by a back shift of the SPR to 2.60 eV. Calculations performed in quasi-static approximation describe the experimental results quite well and prove the structural assignments of the samples. In additional experiments, we applied the well-established persistent spectral hole burning technique to the alloy nanoparticles in order to determine the ultrafast dephasing time T ₂. We obtained a dephasing time of T ₂=(8.1±1.6) fs, in good agreement with the dephasing time of T _2,∞=8.9 fs, which is already included in the dielectric function of the bulk.     

Nonlinear optical properties of antimony–germanium–sulfur glasses at 1560 nm

Nonlinear (NL) optical properties of antimony–germanium–sulfur (Sb–Ge–S) glasses were investigated using laser pulses of 65 fs at 1560 nm. Samples having concentration ratio [S]/[Ge]=2.69 with different antimony concentrations were studied. Glasses with different oxidation states of Sb were investigated using the thermally managed Z -scan technique. The influence of the Sb oxidation state on the NL properties was evaluated. NL refraction indices of electronic origin, n ₂≈10⁻¹³ cm²/W, two-orders of magnitude larger than for fused silica and NL absorption coefficients smaller than 0.55 cm/GW were measured. Appropriate figures-of-merit for photonic applications were determined.     

Magnetic properties of Co–Si alloy clusters

We have investigated the electronic structure and the magnetic properties of Co–Si alloy clusters using ab initio spin-polarized density functional calculations. The possible CoSi₂, CoSi, and Co₂Si phase clusters with oblique hexagon prism, icosahedron, and cuboctahedron structures are introduced. The CoSi phase cluster with icosahedron structure has the largest binding energy and amount of charge transfer. We found that HOMO-LUMO gap, magnetic moment, and spin polarization for the Co–Si alloy clusters with icosahedron structure increase with Co concentration. The Si atoms in the CoSi phase with icosahedron structure have negative magnetic moment.     

Density–temperature properties of Ga–Sb alloy melt

In an experiment, the improved Archimedes method was used to test and analyze density–temperature properties of Ga, Sb and Ga–Sb melts. The experimental results indicated that the density of Ga₇Sb₉₃ melt shows a linear trend of decline when its temperature changes within the experimental range, whereas the densities of Ga_36.5Sb_63.5 and Ga₃₀Sb₇₀ melts show a non-continuous change near the melting point, which rises first and then drops abnormally. These results were analyzed from the perspective of a liquid–liquid structure transition according to the property changes of Ga–Sb melt.     

Tensile behavior of post-irradiation annealed Cu–Ni alloy

The present paper investigates the tensile properties of post-irradiation annealed Cu–Ni alloy. The specimens were irradiated with a 15 MeV electron beam at room temperature and the post-irradiation annealing (PIA) of the specimens was carried out under vacuum at 450 °C for 15–120 min. The yield stress (YS), ultimate tensile stress (UTS), percentage elongation, stress relaxation rate and activation volume of both as-irradiated and post-irradiation annealed specimens were examined at room temperature using a universal testing machine. The results show that PIA of the specimen at 450 °C for 15 min decreases its YS and UTS, whereas the percentage elongation is increased. The changes in the tensile parameters become more pronounced with increases in annealing time. Effects of PIA on the stress relaxation rate and activation volume indicate that the relaxation rate of post-irradiation annealed specimens increases, and the activation volume decreases, with an increase in annealing time.     

Electromagnetic wave-absorption properties of rapidly quenched of Nd–Fe–B nanocomposites with low Nd content

The electromagnetic wave-absorption properties of Nd₃Fe_68−xMn_xCo₁₈B₁₁ (x=0, 1, 2) alloys obtained by rapid quenching from the melt was studied. The complex permittivity-frequency and permeability-frequency properties were determined in the microwave frequency regime of 2–18 GHz by vector network analysis. XRD spectra showed that only α-Fe diffraction peak was observed in the as-spun alloys. It is found that the acquired complex permittivity and permeability values match the microwave frequency when the 1 at% Mn content was doped. A minimum reflection loss of −6.9 dB is obtained at 2.7 GHz for composite Nd₃Fe₆₆Mn₂Co₁₈B₁₁ with absorber thickness of 1.5 mm. The exchange interaction was attributed to the microwave absorption properties. The results suggest a new design of microwave absorbers based on electromagnetic wave-absorbing materials.     

Spinodal Decomposition for Multicomponent Cahn–Hilliard Systems

We consider the initial-stage phase separation process in multicomponent Cahn–Hilliard systems through spinodal decomposition. Relying on recent work of Maier-Paape and Wanner, we establish the existence of certain dominating subspaces determining the behavior of most solutions originating near a spatially homogeneous state. It turns out that, depending on the initial concentrations of the alloy components, several distinct phenomena can be observed. For ternary alloys we observe the following two phenomena: If the initial concentrations of the three components are almost equal, the dominating subspace consists of two copies of the finite-dimensional dominating subspace from the binary alloy case. For all other initial concentrations, only one copy of the binary dominating subspace determines the behavior. Thus, in the latter case we observe a strong mutual coupling of the concentrations in the alloy during the initial separation process.     

Correlation study of structural,electrical and mechanical properties of quenched tin–zinc–cadmium solder alloys

It is important, for electronic application, to decrease the melting point of SnZn₉ solder alloy because it is too high as compared with the most popular eutectic Pb–Sn solder alloy. Adding Cd causes structural changes such as phase transformations, dissolution of atoms and formation of Cd crystals in the quenched SnZn₉ alloy, and its physical properties are affected by this change. For example, the melting point is decreased towards the melting point of the Pb–Sn eutectic alloy, or even much less. The structure, electrical and mechanical properties of quenched Sn_{91? x} Zn₉Cd _x (x?=?0 or x?≥?5) alloys have been investigated. Adding Cd to a quenched SnZn₉ alloy increases its electrical resistivity and decreases its elastic modulus and internal friction. The Sn₇₁Zn₉Cd₂₀ alloy has the lowest melting point (162 °C) and electrical and internal frictions as compared with commercial Pb–Sn solder alloys.     

Synthesis,structure stability and magnetic properties of nanocrystalline Ag–Ni alloy

Silver–nickel alloy nanoparticles with an average size of 30–40 nm were synthesized by chemically reducing the mixture of silver and nickel salts using sodium borohydride. The structure and the magnetic properties of the alloy samples with different compositions were investigated. The phase stability of the material was analysed after annealing the sample in vacuum at various temperatures. The material exhibits single fcc phase which is stable up to 400 °C and Ni precipitation sets in when the sample is annealed to 500 °C. The thermal analysis using DSC was carried out to confirm the same. The alloy compositions are found to be in close correlation with the metal salt ratios in the precursors. The synthesized samples exhibit weak paramagnetic to ferromagnetic behaviour. The magnetic measurements reveal that by adjusting the precursor ratio, the Ni content in the material can be altered and hence its magnetic properties tailored to suit specific requirements. The formation of Ag–Ni alloy is confirmed by the observed Curie temperature from the magneto thermogram. Annealing the sample helps to produce significant enhancement in the magnetization of the material.     

ZnO–ZnS heterostructures with enhanced optical and photocatalytic properties

ZnO–ZnS heterostructures were fabricated via using ZnO rods as template in different Na₂S aqueous solutions. These heterostructures are 5–6 μm in length and formed by coating ZnO rod with a layer of porous ZnS shell comprising primary crystals about 10 nm in diameter. Subsequently, intact ZnS polycrystalline tubes were obtained by removing the ZnO cores with 25% (wt) ammonia. The as-prepared products were characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), Fourier transform infrared (FT-IR), and electrochemical impedance spectroscopy (EIS). It was found that the electron transfer between ZnS shell and ZnO core strongly affect the photoluminescence and photocatalytic performances of these heterostructures. The rapid transfer of photo-induced electrons from the ZnS shell to the ZnO core leads to enhanced ultraviolet emission. However, if this correlation was destroyed, then the corresponding heterostructure exhibits improved photocatalytic efficiency due to the reduced volume recombination of the charge carries and the multiple reflection effect. Finally, a model based on band-gap alignment was proposed to elucidate the underlying mechanism of the enhanced UV emission and photocatalytic activity of these unique heterostructures.     

Effect of lead on microstructure and some physical properties of Sn–Zn–Cd alloy

The effect of lead on the structure, electrical resistivity, internal friction, elastic modulus and thermal properties of Sn₈₁Zn₉Cd₁₀ ternary alloys have been investigated using different experimental techniques with their analysis. In addition, properties of this alloy were compared with other Sn–Zn or Sn–Zn–Cd alloys and commercial solder alloys. It has a higher electrical resistivity, internal friction and lower elastic modulus when compared with Sn–Zn or Sn–Zn alloys with other additions such as Cd, Bi or In. The Sn₆₁Zn₉Cd₁₀Pb₂₀ alloy has a lower melting point, electrical resistivity and internal friction when compared with the commercial Pb–Sn solder alloy, but it has a similar elastic modulus.     

Spinodal Decomposition¶for the Cahn–Hilliard–Cook Equation

This paper gives theoretical results on spinodal decomposition for the stochastic Cahn–Hilliard–Cook equation, which is a Cahn–Hilliard equation perturbed by additive stochastic noise. We prove that most realizations of the solution which start at a homogeneous state in the spinodal interval exhibit phase separation, leading to the formation of complex patterns of a characteristic size. In more detail, our results can be summarized as follows. The Cahn–Hilliard–Cook equation depends on a small positive parameter ε which models atomic scale interaction length. We quantify the behavior of solutions as ε→ 0. Specifically, we show that for the solution starting at a homogeneous state the probability of staying near a finite-dimensional subspace ?_ε is high as long as the solution stays within distance r _ε=O(ε ^R ) of the homogeneous state. The subspace ?_ε is an affine space corresponding to the highly unstable directions for the linearized deterministic equation. The exponent R depends on both the strength and the regularity of the noise. Received: 2 May 2000 / Accepted: 8 July 2001