The Electrical Conductivity Of Iron-carbon Alloys Under High Pressure And The Effect Of Carbon On The Thermal Conductivity Of The Earth's Core

The thermal and electrical conductivity of Earth's core are important geophysical parameters.The thermal conductivity of Earth's core constrains the conductive heat flow out of Earth,s core and therefore impacts the age of Earth's inner core and thermal evolution of Earth,s core and mantle.Based on the abundance of carbon in solar system and in Cl carbonaceous chondrites,stability of iron-carbon phases under high pressure and temperature and sound velocity features,carbon is believed to reside in Earths core.We applied van der Pauw four-probe method to investigate the electrical and thermal conductivity of iron-carbon alloys and compounds at high pressures.The strong alloying effect of carbon was revealed under high pressure which is capable of increasing the electrical resistivity and therefore decreasing thermal conductivity,whereas chemically ordered iron-carbon compounds show anomaly low electrical resistivity.According to high-pressure and high-temperature thermal conductivity model along a geotherm of EarthJs core,at core-mantle boundary condition iron-carbon alloy with 8.4 wt%of carbon has a thermal conductivity of?38 Wm-1K-1,and a consequent conductive heat flow of?6 TW.This results support an older inner core age.At inner core boundary,the components of Earth's core transforms from disordered liquid alloy to ordered solid phase which would results in a jump in thermal conductivity with a factor of?2.3.Therefore the thermal conductivity at uppermost inner core is as high as 198 Wm-1K-1 which makes inner core thermal convection implausible.