Date of Award


Degree Type


Degree Name

Master of Science




Dr. Richard A. Secco


Sulfur is an element with the most complex phase diagram, both in solid and liquid form, of any element. Unique to liquid sulfur is the ^-transition, characterized by a sharp jump in specific heat and almost four orders of magnitude increase in viscosity in the narrow temperature range from 159°C to 187°C at room pressure. As a likely constituent of the Earth’s outer core, the behavior of sulfur under high pressure is important as it can elucidate the potential effect of sulfur on the dynamics and the viscosity of the Earth’s outer core. The viscosity of liquid sulfur was measured at 4.5 GPa and at 726°C and 1100°C, which corresponds to the L and L’ liquid regions of the phase diagram, respectively. The falling sphere and quench and recover method using a 1000 ton cubic anvil press was utilized to evaluate viscosity under indicated pressure and temperatures. The results show that the viscosity of liquid sulfur decreases with temperature and is in line with the results from Terasaki et al. (2004) at lower temperatures. The presence of polymer was established at 4.5 GPa and 726°C and subsequently measured to be 17.8% using CS2 solution method. Evidence from Raman spectroscopy on recovered samples, and experiments at isothermal temperature (800°C) and pressures ranging from 3.5 GPa to 4.5 GPa indicate that polymerization increases with temperature. Additionally, a density driven phase transition was observed at 726°C along with three distinct and time dependent phases coexisting at 1100°C. The existence of the second order liquid-liquid phase transition in liquid sulfur at reported pressure and below 726°C is discussed in the light of recent publications. Moreover, evidence supporting the proposed k-transition, suppressed by the high pressures and shifted significantly upward in the temperature range above the melting curve is presented.



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