Mustafa Erol

Experimental determination of thermal conductivity of solid and liquid phases in Bi−Sn and Zn−Mg binary eutectic alloys

The thermal conductivities of solid phases, Ks, for Bi-43 wt.% Sn and Zn-0.15 wt.%Mg binary alloys at their eutectic temperature are found to be 28.0 τ 1.4 and 137.4–6.9 W/Km, respectively, with a radial heat flow apparatus. The thermal conductivity ratios, R, of liquid phase to solid phase for the same alloys at their eutectic temperature are found to be 0.93 and 0.78, respectively, with a Bridgman type directional solidification apparatus. Thus, the thermal conductivities of the liquid phases, KL, for Bi-43 wt.%Sn and Zn-0.15 wt.%Mg binary alloys at their eutectic temperature are evaluated to be 26.0−1.3 and 107.2−5.4 W/Km, respectively, from the measured values of Ks and R.

Solid-liquid interfacial energy of pyrene

The equilibrated grain boundary groove shapes for commercial purity pyrene (PY) were directly observed by using a temperature gradient stage. From the observed grain boundary groove shapes, the Gibbs-Thomson coefficient and solid-liquid interfacial energy of PY have been determined to be (8.9±0.9)×10−8Km and (21.9±3.3)×10−3Jm−2 with the present numerical model and Gibbs-Thomson equation, respectively. The grain boundary energy of PY phase has been determined to be (42.8±7.3)×10−3Jm−2 from the observed grain boundary groove shapes. Thermal conductivity ratio of liquid phase to solid phase has also been measured to be 0.89.

Photoionization cross section and refractive-index change of hydrogenic impurities in a CdS-SiO2 spherical quantum dot

In this study, we calculate the photoionization cross section and refractive-index change of an on-center hydrogenic impurity in a CdS-SiO2 spherical quantum dot. In numerical calculations, both the finite- and infinite-confinement cases are considered and a variational scheme is adopted to determine the energy eigenvalues for the impurity. The variations of the photoionization cross section with the dot radius, the refractive-index change, and the normalized photon energy are investigated, and the effect of the potential-barrier height on the cross section is discussed. The results obtained show that the photoionization cross section and the refractive-index change in CdS-SiO2 spherical quantum dots are sensitively dependent on the incident optical intensity and on the dot sizes.

DETERMINATION OF ANISOTROPY OF CRYSTAL-MELT INTERFACIAL ENERGY FROM THE OBSERVED GRAIN BOUNDARY GROOVE SHAPES AT MULTIPLE ORIENTATIONS

A specialized high-precision thermal gradient furnace with a rotating stage was developed for in situ observation of the equilibrated grain boundary groove shapes at multiple crystallographic orientations in transparent materials. Anisotropies of solid–liquid interfacial free energy for the distillated succinonitrile (SCN) and pivalic acid (PVA) are determined experimentally through direct observation of the equilibrated grain boundary grooves at the multiple crystallographic orientations stabilized within a controlled thermal gradient. The average anisotropies of solid–liquid interfacial energy for distillated SCN and PVA are found to be 0.42 and 3.12% from observed grain boundary groove shapes at multiple crystallographic orientations. Details related to the experimental apparatus and experimental procedures are given.