Neutron imaging for calculating hydrogen diffusivity in polycrystalline forsterite aggregates
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Date
2018-12-13
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American Geophysical Union
Abstract
An understanding of hydrogen diffusion in nominally anhydrous minerals is essential for the correct interpretation of conductivity dissimilarity in the Earth mantle. The mechanism of hydrogen diffusion in dominant mantle minerals was described by Demouchy (2010) using a defect model in crystalline materials. The effects of in-grain and grain boundary diffusion are separated using the bricklayer model and other derivatives of it (Tuller 2000). Separation of the two components of proton conductivity in olivine will substantially improve the current proton conduction model. It will help to interpret magnetotelluric data and will give prospects to find new mineral sources and explain other phenomena such as volcanism and plate tectonics.
A recent insight is that the high conductivities determined from proton conduction measurements at low temperatures are mainly due to conduction along grain boundaries (Demouchy 2010). We have repeated Demouchy (2010) experiment using neutron imaging to image time and temperature dependent hydrogen diffusion profiles as neutrons are highly sensitive to hydrogen. We carried out a series of experiments where we diffused H2O through a forsterite polycrystalline matrix at high-pressure and temperature. The recovered samples were imaged using the DINGO neutron tomography facility at the Australian Centre for Neutron Scattering. The results indicate hydrogen transport inside the forsterite aggregates as changing neutron attenuation along the diffusion direction of the polycrystalline mineral block. It correlates with the temperature dependent hydrogen diffusion in this mineral. This study revealed the ability of neutron imaging technique to find the hydrogen diffusion coefficient of forsterite. We are sharing these results in this conference.
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The citation shows F. Salvemini incorrectly as F. F. Salvemin.
Keywords
Hydrogen, Diffusion, Minerals, Earth mantle, Materials, Volcanism, Plate tectonics, ANSTO, Tomography, Grain boundaries
Citation
Patabendigedara, S. K., Clark, S., M., & Salvemin, F. F. (sic). (2018). Neutron imaging for calculating hydrogen diffusivity in polycrystalline forsterite aggregates. Paper presented at the AGU Fall Meeting, Washington, D. C., 10 to 14 December 2018. Retrieved from: https://agu.confex.com/agu/fm18/meetingapp.cgi/Paper/372315