[S-CG44] Rheology, fracture and friction in Earth and planetary sciences

[SCG44-P04] Electric field assisted sintering and deformation: its application to Earth's mantle

*Miki Tasaka¹, Namu Fujii¹, Koki Maeda¹, Kohta Nambu^2,3, Hidehiro Yoshida⁴ (1.Shizuoka University, 2.Kyushu University, 3.National Institute for Material Science, 4.Univ. of Tokyo)

Keywords:mantle, sintering, deformation, diffusion, electrical field, grain growth

A new technique called “electric field assisted sintering” has recently been proposed in the field of materials science. When oxide powders are sintered in an electrical field, densification accelerates at a certain temperature, and the sintering is completed in a shorter time and at a lower temperature as compared with conventional sintering experiments. In addition, tensile deformation experiments conducted on a dense oxide polycrystalline aggregate in an electrical field have shown that plastic deformation can be enhanced at lower temperatures with lower stresses, as compared with conventional deformation experiments. Fluctuations in the magnetic and electrical fields derived from outside Earth, such as solar activity, induce a weak electrical field inside Earth. Although electrical fields inside Earth may affect the deformation behavior of rocks, no experimental studies have been conducted on geological materials to assess this effect. Therefore, based on these recent findings in materials science, we conducted sintering and deformation experiments to examine the effects of an electrical field on high-temperature mass transport. We used forsterite + diopside crystal aggregates, which are analogs for Earth’s mantle. The sintering experiments demonstrated that the relative density increases with an increasing electrical field at a constant temperature. In the deformation experiment, the samples in an electrical field of 1000 V/cm were deformed by 10 × higher strain rate than for samples not in an electrical field. These features suggest that diffusional mass transport is enhanced in an electrical field. We propose that the presence of an electrical field within Earth may accelerate the deformation of mantle materials.