Buket Saatçi

Thermal and electrical conductivities of Cd-Zn alloys

The composition and temperature dependences of the thermal and electrical conductivities of three different Cd-Zn alloys have been investigated in the temperature range of 300-650 K. Thermal conductivities of the Cd-Zn alloys have been determined by using the radial heat flow method. It has been found that the thermal conductivity decreases slightly with increasing temperature and the data of thermal conductivity are shifting together to the higher values with increasing Cd composition. In addition, the electrical measurements were determined by using a standard DC four-point probe technique. The resistivity increases linearly and the electrical conductivity decreases exponentially with increasing temperature. The resistivity and electrical conductivity are independent of composition of Cd and Zn. Also, the temperature coefficient of Cd-Zn alloys has been determined, which is independent of composition of Cd and Zn. Finally, Lorenz number has been calculated using the thermal and electrical conductivity values at 373 and 533 K. The results satisfy the Wiedemann-Franz (WF) relation at T 373 K), the WF relation could not hold and the phonon component contribution of thermal conductivity dominates the thermal conduction.

The interfacial free energy of solid Sn on the boundary interface with liquid Cd–Sn eutectic solution

Equilibrated grain boundary groove shapes for solid Sn in equilibrium with Cd?Sn liquid were directly observed after annealing a sample at the eutectic temperature for about 8 days. The thermal conductivities of the solid phase, KS, and the liquid phase, KL, for the groove shapes were measured. From the observed groove shapes, the Gibbs?Thomson coefficients were obtained with a numerical method, using the measured G, KS and KL values. The solid?liquid interfacial energy of solid Sn in equilibrium with Cd?Sn liquid was determined from the Gibbs?Thomson equation. The grain boundary energy for solid Sn was also calculated from the observed groove shapes.

Determination of thermal conductivities of solid and liquid phases for rich-Sn compositions of Sn-Mg alloy

The variations of thermal conductivities of solid phases versus temperature for pure Sn and Sn-1 wt% Mg, Sn-2 wt% Mg, and Sn-6 wt% Mg binary alloys were measured with a radial heat flow apparatus. Thermal conductivity variations versus temperature for pure Sn and Sn-1 wt% Mg, Sn-2 wt% Mg, and Sn-6 wt% Mg binary alloys were found to be 60.60 ± 3.63, 61.99 ± 3.71, 68.29 ± 4.09, and 82.04 ± 4.92 W/Km, respectively. The thermal conductivity ratios of liquid phase to solid phase for pure Sn and eutectic Sn-2 wt% Mg alloy at their melting temperature were found to be 1.11 and 1.08, respectively, with a Bridgman type directional solidification apparatus. Thus the thermal conductivities of liquid phases for pure Sn and eutectic Sn-2 wt% Mg binary alloy at their melting temperature were evaluated to be 67.26 ± 4.03 and 73.75 ± 4.42 W/Km, respectively, by using the values of solid phase thermal conductivities and the thermal conductivity ratios of the liquid phase to the solid phase.

Experimental determination of interfacial energy for solid Zn solution in the Sn-Zn eutectic system

The grain boundary groove shapes for Zn solid solution in equilibrium with Sn-Zn eutectic liquid were observed with a radial heat flow apparatus. From the observed grain boundary groove shapes, the Gibbs-Thomson coefficient, the solid-liquid and the grain boundary energy for the Zn solid solution in equilibrium with Sn-Zn eutectic liquid were determined to be (2.32 ± 0.13)×10−8 Km, (120.87 ± 13.29)×10−3 J.m−2 and (194.76 ± 23.37)×10−3 J.m−2, respectively. The termal conductivity of the eutectic Sn-9 wt% Zn solid solution, κS, was obtained as 74.74 W/Km by using a radial heat flow apparatus. The thermal conductivity ratio of the eutectic liquid to the eutectic solid, R = κL/κS was found to be 0.58 with a Bridgman-type directional growth apparatus. Thus, the value of the thermal conductivity of eutectic Sn-9 wt% Zn liquid solution, κL, was obtained as 43.82 W/Km.

Thermal Conductivity of Solid and Liquid Phases for Pb-Cd Alloys

Thermal conductivities of solid phases for pure Pb and Pb-x weight% Cd (5, 12, 17.4, 50, and 95) binary alloys were measured with a radial heat flow apparatus. Thermal conductivity depending on temperature and composition for pure Pb and Pb-x weight% Cd (5, 12, 17.4, 50, and 95) binary alloys were obtained to be 32.4±2.2, 33.4±2.2, 41.2±2.8, 37.2±4.8, 49.2±3.3, and 84.6±5.7  W/Km. The thermal conductivity ratio of liquid phase to solid phase for the eutectic Pb-17.4 weight% Cd alloy at its melting temperature is found to be 1.31 with a Bridgman-type directional solidification apparatus. Thus, the thermal conductivity of the liquid phase for the eutectic alloy at its melting temperature was found to be 48.7±3.3  W/Km by using the values of solid phase thermal conductivity and the thermal conductivity ratio of liquid phase to solid phase.

STRUCTURAL, SURFACE AND TRANSPORT PROPERTIES OF Sn–Ag ALLOYS

The structural, surface and transport properties of Sn–Ag alloys were investigated by X-ray diffraction (XRD), radial heat flow, energy-dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM) and four-point probe techniques. We observed that the samples had tetragonal crystal symmetry except for the pure Ag sample which had cubic crystal symmetry, and with the addition of Ag the cell parameters increased slightly. Smooth surfaces with a clear grain boundary for the samples were shown on the SEM micrographs. The grain sizes of pure Ag, β-Sn and the formed Ag3Sn intermetallic compound phase for Sn–x wt.% Ag [x=1.5, 3.5] binary alloys were determined to be 316nm, between 92nm and 80nm and between 36nm and 34nm, respectively. The values of electrical resistivity for pure Sn, pure Ag and Sn–x wt.% Ag [x=1.5, 3.5] were obtained to be 22.60×10−8, 62.36×10−8, 23.54×10−8, 24.62×10−8Ω⋅m at the temperature range of 300–450K, respectively. Thermal conductivity values of pure Sn and Sn–x wt.% Ag [x=1.5, 3.5] binary alloys were found to be 60.60±3.75, 69.00±4.27 and 84.60±5.24W/Km. These values slightly decreased with increasing temperature and increase with increasing of the Ag composition. Additionally, the temperature coefficients of thermal conductivity and electrical resistivity and the Lorenz numbers were calculated.