Thermal conductivity of Deep Earth's materials studied by combined fast pulsed laser and optical spectroscopy techniques

点击翻译按钮获取中文摘要

Knowledge of thermal conductivity of the Earth's mantle and core materials under extreme conditions is important for understanding the physical and chemical processes and their evolution in the Earth. Sustained heat transport through the mantle is crucial for the existence and stability of the Earth's magnetic field. The Earth's mantle dynamics depends on the rate of heat transfer by convection, conduction, and radiation, and understanding these processes requires knowledge on the conductive and radiative parts of thermal conductivity. The investigators will conduct measurements of the conductive and radiative parts of thermal conductivity at extreme conditions of pressure and temperature that are relevant for the Earth's deep interior. The laser techniques developed in this work will advance other fields, which benefit from knowledge of thermal conductivity under extremes, for example various energy applications. A range of students, including area high school students, undergraduates, graduate students, and postdoctoral associates, will benefit from high-quality scientific training at Carnegie that will be provided by participation in the cutting-edge science that will be developed in the course of this work. The investigators will determine the thermal conductivity of the Earth's key minerals under high pressure and high temperature conditions (up to 150 GPa and 6000 K) by using pump-probe pulsed laser techniques. To determine the lattice thermal conductivity, they will measure the heat flux histories across the sample using time- and spatially- resolved spectroradiometry and/or time-domain thermoreflectance. To infer the radiative thermal conductivity, the team will study the optical spectra of these mantle minerals in the ultraviolet-to-infrared spectral range. They will apply the time-resolved emission and optical broad band spectroscopy tools that they have previously developed including pulsed white laser (supercontinuum) in combination with time-resolved multichannel detectors (streak camera and intensified CCD). The experiments will be performed on Fe and Fe-rich alloys, high-quality geologically relevant samples pre-synthesized at high P-T condition in large-volume devices (e.g. single crystals of bridgmanite), silicate and oxide melts, and planetary ices. These high P-T experimental data will enable a direct estimate of the radiative and conduction parts of the thermal conductivity of the Earth's mantle and core. These measurements will elucidate complex laws which govern thermal conductivity in the deep interior and reach sufficient accuracy to critically improve existing planetary models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.