On the Viscosity of Liquid Selenium

Abstract

Abstract The viscosities of liquid selenium and partially-chlorinated liquid selenium were measured in the temperature range from 235°C to 305°C using an Ubbelohde-type tilting viscometer. The “intrinsic” viscosities, η0, were estimated by extrapolating the values of the viscosities, ηθ, of various rates of shear to a zero rate of shear. The “intrinsic” viscosities of the liquid selenium were estimated to be 20.18, 13.46, 9.11, 6.32, 3.67 and 2.30 poise at 235, 245, 255, 265, 285, and 305°C respectively. The viscosities of the chlorinated liquid selenium decreased with an increase in the chlorine content, but they varied discontinuously at a chlorine content of 0.0125% and then decreased linearly. The apparent activation energy for the viscous flow of the liquid selenium was estimated to be 17.9 kcal/mol. The apparent activation energies for the viscous flow of the chlorinated selenium varied discontinuously at a chlorine content of about 0.0125%, as in the case of the viscosity. The average-chain length of the selenium molecules was considered not to be changed, but the radicals at both ends of the linear chain vanish in forming the bonds with chlorine atoms with an increase in the chlorination below a chlorine content of 0.0125%. Therefore, it is concluded that the presence of radicals at the molecular ends would have an influence upon the viscosity and the apparent activation energy for the viscous flow of selenium. The notable large value of the apparent activation energy of such a non-branched polymer as selenium was attributed to the large amount of energy needed to transport the segments into the holes.