Progress in Diamond Cell Experiments: Pressures Above Three Megabars

摘要

Diamond cell experiments at pressures above 2 megabars have many important applications with respect to planetary interiors (e.g., metallization of hydrogen). To make possible acquisition of data at extreme pressures on materials of planetary interest, we have been exploring both numerically and experimentally several aspects of diamond cell design and methodology. We have conducted detailed finite element analyses of the diamond cell to explore how bevelled anvils and material properties of the gasket affect diamond cell performance (1). These calculations include nonlinear equations of state, gasket plasticity, and diamond-gasket interfacial friction. Gasket plasticity has a dramatic effect on the stress field and thus must be included in any physically realistic analysis of the diamond cell; purely elastic calculations, therefore, cannot model adequately the behavior of a diamond cell. Gasket yield strengh is very important in facilitating generation of extreme pressures in a diamond cell. Increasing gasket yield strength allows a higher radial pressure gradient to be supported at a given gasket thickness, which means that failure of an experiment by deformation of the anvils to allow anvil-anvil contact occurs at higher pressures than would occur with a lower yield strength gasket. Furthermore, the finite element analyses indicate that increasing gasket yield strength reduces tensile stresses and stress gradients in the diamond tip. The optimal gasket materials may be metallic glasses which have both high yield strengthsad excellent ductility. (ERA citation 11:024237)