"Evaluation of kinetics of incongruent vaporization of Mg2Si" 

Jihoon Park, MSE PhD Candidate 

Advisor: Professor Ken Sandhage

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ABSTRACT

Thermal management in electric devices demands effective heat dissipation strategies while maintaining optimal performance and energy conservation. Leveraging water's high specific and latent heat capacities proves pivotal in these applications, particularly in enhancing thermal diffusivity through water vapor absorption into nanopores. This study proposes a method to create nanopores within diatoms to enhance thermal diffusivity. Traditional methods like carbothermal reduction, effective in converting SiO2 into Si, involve temperatures exceeding 2000°C, surpassing the melting point of Si. Electrochemical reduction in molten salts fails to preserve the crucial microscale morphology. Previous attempts to create porous Si frustule replicas through magnesiothermic reactions faced issues due to exothermic reactions causing structural collapse. To circumvent this, an endothermic incongruent vaporization method is proposed to produce a nano-porous silicon layer. Investigating rate-determining steps for the incongruent vaporization of magnesium silicide involved studying systems such as enstatite incongruently evaporating to form forsterite. Three rate-determining steps in incongruent evaporation are identified: a chemical reaction at the Si/Mg2Si interface, Mg diffusion through the bulk gas phase, and transport through the porous Si product layer. This document aims to elucidate the thermodynamics and kinetics of incongruent vaporization of Mg2Si.