Acoustic and thermodynamic properties of the binary liquid system <Emphasis Type="Italic">n</Emphasis>-dodecane+<Emphasis Type="Italic">n</Emphasis>-hexadecane

By the method of direct measurement of the pulse-passage time, the velocity of sound in a binary liquid mixture n-dodecane+n-hexadecane has been investigated in the temperature range 298–433 K and in the pressure range 0.1–100.1 MPa. The maximum measurement error is 0.1%. Experimental data on the velocity of sound for the investigated mixture have been obtained for the first time. On the basis of the data on the velocity of sound, we have determined the density, the isobaric expansion coefficient, the isobaric and isochoric heat capacities, and the isothermal compressibility coefficient of a mixture of three compositions in the 298–433 K temperature range and in the 0.1–100.1 MPa range of pressures. The coefficients of the Tate equations in the above range of parameters have been calculated. A table of thermodynamic properties of the mixture is presented.     

Wear characteristics of spray formed Al-alloys and their composites

In the present investigation, different Al based alloys such as Al–Si–Pb, Al–Si, Al–Si–Fe and 2014Al + SiC composites have been produced by spray forming process. The microstructural features of monolithic alloys and composite materials have been examined and their wear characteristics have been evaluated at different loads and sliding velocities. The microstructural features invariably showed a significant refinement of the primary phases and also modification of secondary phases in Al-alloys. The Pb particles in Al–Si–Pb alloy were observed to be uniformly distributed in the matrix phase besides decorating the grain boundaries. The spray formed composites showed uniform distribution of SiC particles in the matrix. It was observed that wear resistance of Al–Si alloy increases with increase in Pb content; however, there is not much improvement after addition of Pb more than 20%. The coefficient of friction reduced to 0.2 for the alloy containing 20%Pb. A sliding velocity of 1 ms⁻¹ was observed to be optimum for high wear resistance of these materials. Alloying elements such as Fe and Cu in Al–Si alloy lead to improved wear resistance compared to that of the base alloy. The addition of SiC in 2014Al alloy gave rise to considerable improvement in wear resistance but primarily in the low pressure regime. The wear rate seemed to decrease with increase in sliding velocity. The wear response of the materials has been discussed in light of their microstructural features and topographical observation of worn surfaces.     

Effect of strong illumination on current-voltage characteristics of Au/Si, Al/Si and Sn/Si Schottky barriers with native oxide layer

Light induced general degradation in the dark I–V characteristics of Au/Si, Al/Si and Sn/Si junctions at low temperature and at room temperature. Illumination caused changes in the interface and bulk properties of the investigated junctions, all of them prepared under identical conditions. Their barrier heights, φB change with increasing illumination time. The largest rate of degradation in φB upon exposure to light was observed for an Sn/Si junction (lowest φB), whereas the smallest change occurred with an Au/Si junction (highest φB). At low temperature, upon turning off the light, the photogenerated current of the Sn/Si sample exhibited faster recovery in reaching the initial dark current (at till=0) than the Al/Si junction; for the less reactive Au/Si sample, the presence of the oxide layer reduced the leakage current and subsequently delayed recovery of the measured photocurrent. This revised version was published online in August 2006 with corrections to the Cover Date.     

Preparation of Thin Lead Stannate Layers on Single-Crystal Silicon

Thin films containing lead stannates were prepared on single-crystal silicon substrates by annealing Sn/Pb/Si and Pb/Sn/Si structures produced by magnetron sputtering with the use of solid Sn targets and solid or liquid (self-sputtering) Pb targets. The structures were annealed in flowing oxygen for 10 min at temperatures in the range 520–1120 K. The phase composition of the films is found to strongly depend on the Pb deposition procedure, the sequence of layers in the as-grown heterostructure, and thermal oxidation conditions.     

Interfacial reactions between eutectic Sn–Pb solder and Co substrate

This study examined the reaction couples of Co substrate with liquid and solid Sn-37 wt% Pb alloys, respectively. In the liquid/solid Sn–Pb/Co couples, one single-phase CoSn₃ layer was found at the interface at temperatures from 210 to 250 °C. The layer thickness was measured as a function of the reaction time. The layer growth rate increased with increasing temperature. The CoSn₃ layer growth was linear in the early stage and then became parabolic. In addition, the similar CoSn₃ growth behavior results were observed in the solid/solid Sn–Pb/Co couples from 150 to 170 °C. Nevertheless, one Pb-rich phase layer accumulated at the solder/CoSn₃ interface due to Sn consumption. Also, the reaction kinetics of Sn-37 wt% Pb/Co was symmetrically studied at various temperatures. The chemical reaction constants, diffusion constants, and the relevant activation energies were reported.     

Creep and fatigue behaviors of the lead-free Sn–Ag–Cu–Bi and Sn60Pb40 solder interconnections at elevated temperatures

Creep and fatigue behaviors of the interconnections soldered by the lead-free Sn–Ag–Cu–Bi solder were investigated at different elevated temperatures (with the homologue temperature in the range of 0.71– 0.82), with a comparison to that of a traditional Sn60Pb40 solder. The results show that the lead-free Sn–Ag–Cu–Bi solder shows a superior anti-creep performance over the Sn60Pb40 solder, in terms of a much lower creep strain rate and a vastly elongated creep fracture lifetime; in the secondary creep regime, the calculated creep-activation energy for two solders is reasonably close to other published data. In addition, it has also been shown that the joints soldered by the lead-free Sn–Ag–Cu–Bi solder exhibits a superb fatigue property.     

Electrical conductivity, thermoelectric power and viscosity of liquid Sn-based alloys

Shear viscosity of liquid Sn–Ag, Sn–Cu and Sn–Ag–Cu eutectics from melting temperature up to 1100 K and their electrical conductivity and thermoelectric power up to 850 K have been investigated. The electrical properties of liquid Sn with additions of Fe and Ni have also been studied. It is shown that small amounts of metal admixtures affect noticeably the behavior of the physical properties of liquid Sn.     

Shear strength of the Zn–Sn high-temperature lead-free solders

This study examines the shear strength behavior of the high-temperature Zn–20 wt% Sn, Zn–30 wt% Sn, and Zn–40 wt% Sn solders in the temperature range of 298–425 K. The results showed that increasing the Sn content of the alloys decreases both shear yield stress (SYS) and ultimate shear strength (USS) at all test temperatures. This can be attributed to the higher volume fraction of the softer β-Sn matrix and the eutectic α-Zn + β-Sn structure, which replaces the colonies of the harder α-Zn phase in the microstructure. The high shear strength of these high temperature solder alloys makes them suitable for application in harsh environments.     

Thermophysical Properties of Ag and Ag–Cu Liquid Alloys at 1098K to 1573K

The surface tension and density of liquid Ag and Ag–Cu alloys were measured with the sessile drop method. The sessile drop tests were carried out at temperatures from 1098K to 1573 K, on cooling (temperature decreasing stepwise) under a protective atmosphere of high purity Ar (6N). The density of liquid Ag and Ag–Cu alloys decreases linearly with increasing temperature, and an increase in concentration of copper results in a lower density. The surface tension dependence on temperature can be described by linear equations, and the surface tension increases with increasing Cu content. The results of the measurements show good agreement with existing literature data and with thermodynamic calculations made using the Butler equation.     

The microstructure and mechanical properties of unidirectionally solidified Al−Si alloys

Hypereutectic Al−Si alloys with minor additions of Sr were directionally solidified with a temperature gradient of 125°C cm⁻¹ in the liquid. Silicon in the range 14–17 wt%, Sr in the range 0.0–0.5 wt% and specimen traction velocities between 1 and 1500 μm sec⁻¹ were used. The relationship between hardness and traction velocity and spacing in eutectic silicon morphologies is defined and shown to be of the same form as that for yield stress. The possibility of using hardness measurements to be of the same form as that for yield stress. The possibility of using hardness measurements to indicate mechanical properties is discussed. The complex regular silicon structure makes a significant contribution to the hardness of hypereutectic alloys. This makes the relationship between hardness and traction velocity more complex adding difficulties to the use of hardness to measure mechanical properties.     

Superconductivity and Mössbauer effect of Nb3Sn produced by Sn implantation

We have implanted Sn, Ge, and Si into Nb films. The resulting Nb-Sn compounds and their annealing behavior have been analyzed by the Mössbauer effect and compared to samples obtained by diffusion of Sn into Nb foils. Mössbauer spectra show that Nb₃Sn is obtained just by implantation, but with a T _cof only 5 K. The 925°C annealing temperature necessary to form the A15 structure with long-range order of Nb chains and T _cvalues up to 17.8 K is at least 100 °C higher in implanted samples than in samples prepared by diffusion of Sn into Nb. This is explained in terms of implantation-induced lattice defects. The metastable A15 phases of Nb₃Ge and Nb₃Si could not be formed by Ge or Si implantation, regardless of target or annealing temperature. It is suggested that the high-energy ions only form phases stable at high temperatures and with low T _cvalues.On leave from North Dakota State University, Fargo, North Dakota.     

The thermodynamic properties of liquid binary mixtures of <Emphasis Type="Italic">n</Emphasis>-alkanes: <Emphasis Type="Italic">n</Emphasis>-decane + <Emphasis Type="Italic">n</Emphasis>-hexadecane

Data on sound velocity are used for determining the density, the isobaric expansion coefficient, the isobaric and isochoric heat capacity, and the isothermal compressibility of liquid binary mixture of n-decane + n-hexadecane of three compositions in the temperature range of 298–433 K and pressure range of 0.1–100 MPa. The coefficients of Tait equation are calculated in the above-identified range of parameters. The calculation results are compared with experimental data on density. The divergence does not exceed 0.2% for the most reliable data.     

Phase equilibria in pseudoternary systems of IV–VI compounds

Using literature data, experimental data obtained in this study, and a unified thermodynamic model, we have calculated the T-x-y phase diagrams of all the pseudoternary systems formed by the Group 14 chalcogenides: (Ge, Sn, Pb)Te, Pb(S, Se, Te), and Sn(S, Se, Te). The phase diagrams have been constructed using the known interaction parameters of the pseudobinary systems and the ternary interaction parameters derived from experimental data. The systems have small negative ternary interaction parameters, which decrease in the order β-(Ge, Sn, Pb)Te < β-Pb(S, Se, Te) < δ-Sn(S, Se, Te).     

Normal and Superconducting State Properties of Doped CePt3Si

We report on X-ray powder diffraction, magnetic susceptibility, electrical resistivity, and specific heat measurements on samples of Ce_1-xLa_xPt₃Si and CePt₃Si_1+δ in order to better understand this unusual heavy Fermion superconductor’s normal and superconducting state properties. By suppressing the antiferromagnetic transition, T_N = 2.2 K, using La-doping on the Ce-site in CePt₃Si, we find that in Ce_1-xLa_xPt₃Si, x ≥ 0.8, ρ, χ, and C/T show non-Fermi liquid temperature dependences. C/T ~ T^α with α ~ 1 for the temperature range of 0.3–3 K while low-temperature (2–20 K) susceptibility data follow 1/χ−1/χ₀ = aT^η behavior with η = 0.36. In addition, χ and C/T exhibit single-ion behavior in this composition range (x ≥ 0.8), i.e. the measured values expressed per Ce-mole are independent of x. Via doping the Si-site with a small excess—2–4—of Si, we present specific heat data for the bulk superconducting transition at T_c ~ 0.8 K showing that this excess sharpens the transition, obviating the need for annealing. Measurements of the X-ray diffraction patterns, ρ, χ, and C/T of these CePt₃Si_1+δ samples, when compared to similar measurements on annealed CePt₃Si samples, indicate that the microscopic mechanism for the strengthening and sharpening of ΔC(T_c) with Si-excess may be similar to that responsible in the annealed material.     

Ultrasonic properties of fluorosilicate glass-ceramics at cryogenic temperatures

The longitudinal ultrasonic wave velocity and attenuation, and shear wave velocity for machinable fluorosilicate glass-ceramic (MACOR) samples (regular shelf stock, annealed to 900°C, and 1000°C for 10 hrs) were measured as the functions of frequency and temperature with the pulse-echo method. The frequency and temperature range used were 5 MHz to 50 MHz, and 100 K to 300 K respectively. Both velocities for three samples decrease linearly with temperature, and the ultrasonic attenuation increases linearly with the frequency square, and decreases monotonically with increasing temperature. These data were used to calculate the elastic moduli, Lame parameter, and Poisson's ratio for the materials.     

Determination of the thermodynamic properties of liquid <Emphasis Type="Italic">n</Emphasis>-hexadecane from the measurements of the velocity of sound

The density, the isobaric expansion coefficient, the specific heats at constant pressure and constant volume, and the isothermal compressibility coefficient of liquid n-hexadecane have been calculated in the range of temperatures 298–433 K and pressures 0.1–140 MPa from the data on the velocity of sound. The coefficients of the Tate equation in the above parametric range have been determined. The table of the thermodynamic properties of n-hexadecane has been presented. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 150–156, January–February, 2009.     

Investigation of microstructures and tensile properties of a Sn-Cu lead-free solder alloy

In recent years, the pollution of environment from lead (Pb) and Pb-containing compounds in microelectronic devices attracts more and more attentions in academia and industry, the lead-free solder alloys begin to replace the lead-based solders in packaging process of some devices and components. In this work, microstructures and mechanical properties of the lead-free solder alloy Sn99.3Cu0.7(Ni) are investigated. This paper will compare the mechanical properties of the lead-based with lead-free solder alloys (Sn99.3Cu0.7(Ni) and 63Sn37Pb). The tensile tests of lead-based and lead-free solder alloys (Sn99.3Cu0.7(Ni) and Sn63Pb37) were conducted at room and elevated temperature at constant strain rate; the relevant tensile properties of Sn99.3Cu0.7(Ni) and Sn63Pb37 were obtained. Specifically, the tensile strength of this lead-free solder- Sn99.3Cu0.7(Ni) in 25^∘C, 50^∘C, 75^∘C, 100^∘C, 125^∘C was investigated; and it was found that tensile strength of the lead-free solder decreased with the increasing test temperature at constant strain rate, showing strong temperature dependence. The lead-free solder alloy Sn99.3Cu0.7(Ni) was found to have favorable mechanical properties and it may be able to replace the lead-based solder alloy such as Sn63Pb37 in the packaging processes in microelectronic industry.     

Phase Composition and Dielectric Properties of Thin Films Produced by Annealing Sn/Pb/Ti/Si and Pb/Sn/Ti/Si Heterostructures

Sn/Pb/Ti/Si and Pb/Sn/Ti/Si heterostructures were deposited by magnetron sputtering using Ti and Sn solid targets and liquid-phase Pb self-sputtering in the former case and three solid targets in the latter. The heterostructures were then annealed in flowing oxygen at 470–970 K. The major phase in the film produced from the Sn/Pb/Ti/Si heterostructure at 970 K was the Pb(Sn_0.55Ti_0.45)O₃ solid solution with ferroelectric properties. The film prepared from the Pb/Sn/Ti/Si heterostructure consisted of Pb(Sn_0.55Ti_0.45)O₃ and PbTiO₃ and exhibited nonlinear dielectric properties. The coercive field and remanent polarization of the films were determined.     

Mechanism of tin diffusion in ZnTe single crystals

The diffusion coefficient of Sn in single-crystal zinc telluride has been measured. In the temperature range 1070–1270 K, Sn diffusion follows a vacancy mechanism, producing for the most part SnZn substitutional atoms, which act as donors with an ionization energy of ∼0.26 eV.     

Measurement of surface tension and specific heat of Ni-18.8 at.% Si alloy melt by containerless processing

The surface tension and specific heat of superheated and undercooled Ni-18.8 at.% Si alloy melt have been measured by the oscillating drop method and the drop calorimetry technique in combination with electromagnetic levitation, respectively. The surface tension follows a linear relationship with temperature within the range of 1370–2100 K. The surface tension at the melting temperature and the temperature coefficient are determined to be 1.796 N/m and −3.858 × 10⁻⁴ N/m/K, respectively. The specific heat is determined to be 40.80 ± 1.435 J/mol/K over the temperature range 1296–2000 K. The maximum undercooling of 178 K is achieved in the experiments. Based on the measured data of surface tension and specific heat, the viscosity, solute diffusion coefficient, density and thermal diffusivity of liquid Ni-18.8 at.% Si alloy are calculated.