9:00 AM - 10:30 AM
[SIT16-P13] Effect of hydrogen on rheology of hcp-Fe
Keywords:inner core, iron hydride, rheology
Among candidates for the light element(s) in the Earth’s core, hydrogen is one of the most important candidates. Although many hypotheses have been proposed for the origin of the inner core seismic anisotropy, there is no general consensus for its origin partly due to lack of accurate information of viscosity in the inner core. In this study, we have studied effect of hydrogen on the rheology of iron based on high-pressure and high-temperature deformation experiments.
A high-pressure deformation apparatus D111-type apparatus was recently installed on a synchrotron beamline BL04B1, SPring-8. We have conducted in-situ high-pressure deformation experiments on iron hydride (FeHx) using this apparatus. Steady-state deformation of double hexagonal close-packed (dhcp)-FeHx with x = 0.74-0.84 was observed at 39 conditions in pressure of 11.7-16.1 GPa and temperature of 573-823 K. Stress values of dhcp-FeHx were only slightly lower than those of hcp-Fe at same conditions. Stress exponent and activation enthalpy at 14 GPa of dhcp-FeHx were determined to be 3.2 and 220 kJ/mol, respectively, at temperatures higher than ~750 K suggesting that power-law dislocation creep is dominant. Several experiments were conducted on hexagonal close-packed (hcp)-FeHx with x = 0.2-0.3. Stress values of hcp-FeHx were also only slightly lower than those of hcp-Fe at same conditions. These results suggests that influence of hydrogen on the inner core viscosity is limited.
A high-pressure deformation apparatus D111-type apparatus was recently installed on a synchrotron beamline BL04B1, SPring-8. We have conducted in-situ high-pressure deformation experiments on iron hydride (FeHx) using this apparatus. Steady-state deformation of double hexagonal close-packed (dhcp)-FeHx with x = 0.74-0.84 was observed at 39 conditions in pressure of 11.7-16.1 GPa and temperature of 573-823 K. Stress values of dhcp-FeHx were only slightly lower than those of hcp-Fe at same conditions. Stress exponent and activation enthalpy at 14 GPa of dhcp-FeHx were determined to be 3.2 and 220 kJ/mol, respectively, at temperatures higher than ~750 K suggesting that power-law dislocation creep is dominant. Several experiments were conducted on hexagonal close-packed (hcp)-FeHx with x = 0.2-0.3. Stress values of hcp-FeHx were also only slightly lower than those of hcp-Fe at same conditions. These results suggests that influence of hydrogen on the inner core viscosity is limited.