The effect of temperature, pressure, and sulfur content on viscosity of the Fe–FeS melt

Thermal Evolution and Magnetic Field Generation in Terrestrial Planets and Satellites

“…Assuming a super-isentropic heat flow at the core-mantle boundary (CMB) of, say, δQ = 4πr 2 c kδT /δz ≈ 1 TW (r c being the radius of the core), one can obtain a typical thickness for the boundary layer of δz ∼ 0.8 m. This shows that the boundary layers that must exist in the core are very thin with very small total super-isentropic temperature differences. The reason is the very low viscosity of liquid iron (Poirier 1988;Terasaki et al 2001) which likely applies to other planetary cores as well. Note that the boundary layers in the mantle are many orders of magnitude thicker as will be addressed further below.…”

Toward comprehensive studies of liquids at high pressures and high temperatures: Combined structure, elastic wave velocity, and viscosity measurements in the Paris–Edinburgh cell

“…Structure and physical properties of liquids have been much less studied than those of crystalline materials due to experimental difficulties. Some efforts have been made to investigate structure of liquids [e.g., Tsuji et al, 1989;Mezouar et al, 2002;Shen et al, 2004;Yamada et al, 2011], physical properties such as density [e.g., Katayama et al, 1998;Shen et al, 2002;Ohtani et al, 2005], viscosity [e.g., Kushiro et al, 1976;Kanzaki et al, 1987;Dobson et al, 2000;Terasaki et al, 2001;Perrillat et al, 2010], and elastic wave velocity [e.g., Krisch et al, 2002;Decremps et al, 2009;Nishida et al, 2013]. However, these results were often based on individual techniques, and the discussions were made by comparisons with results obtained by other researchers using in different apparatus using different techniques.…”

Anomaly in the viscosity of liquid KCl at high pressures

“…However, the effect of pressure on the viscosity of liquids remains poorly understood partly due to the lack of experimental data. High-pressure falling-sphere viscometry was first developed in an effort to measure viscosities of molten earth materials [15][16][17][18][19][20][21][22]. These measurements were confined to highly viscous materials due to the limited imaging rate (typically 30-60 frames/second and up to 125 frames/second) in common x-ray radiography apparatus.…”

“…As a consequence, it was difficult to investigate low viscosity liquids such as metals [23] and salts [24] whose viscosities are around 1 mPa s or less at ambient pressure. Some studies report viscosities in the 4-20 mPa s range for iron alloys [18,19] using falling sphere velocities determined based on only 2 -4 images. This limited imaging rate makes it difficult to ensure that the falling sphere has reached terminal velocity and results in large uncertainties in the calculated viscosity.…”