SiO₂‐SiC Mixtures at High Pressures and Temperatures: Implications for Planetary Bodies Containing SiC

Abstract

We present results from high‐pressure and high‐temperature experiments on mixtures of SiC and SiO2 to explore the stability of SiC in the presence of oxygen‐rich silicates at planetary mantle conditions. We observe no evidence of the ambient pressure predicted oxidation products, CO or SiO, resulting from oxidation reactions between SiC and SiO2 at pressures up to ~40 GPa and temperatures up to ~2500 K. We observe the decomposition of SiC through releasing C, resulting in vacancies in the SiC lattice and consequently the contracted SiC ambient volume V0 observed in the heated regions of sample. The decomposition is further supported by the observations of diamond formation and the expanded SiO2 V0 in the heated regions of samples indicating the incorporation of C into SiO2 stishovite. We provide a new interpretation of SiC decomposition on laboratory timescales, in which kinetics prevent the reaction from reaching equilibrium. We consider how the equilibrium decomposition reaction of SiC will influence the differentiation of a SiC‐containing body on planetary timescales and find that the decomposition products may become isolated during early planetary differentiation. The resulting presence of elemental Si and C within a planetary body may have important consequences for the compositions of the mantles and atmospheres of such planets.

Inert structural transition in 4H and 6H SiC at high pressure and temperature: a Raman spectroscopy study

“…While such carbon-rich planets are expected to be rare, SiC may be the main constituent material of the carbon-rich planets. The structure and dynamics of such exotic carbon-rich planets have been largely controlled by the stability and the physical properties of the SiC at high pressure [12,23,24]. However, the stability and bonding character of the polytypes of SiC under high pressure and temperature corresponding to the planetary interior are poorly understood.…”

A Comprehensive Review of High-Pressure Laser-Induced Materials Processing, Part I: Laser-Heated Diamond Anvil Cells

“…When combined with real-time material characterisation techniques, such as X-ray diffraction (XRD), sample compositions and structures can be actively controlled. L-DAC system implementations range from "basic" laser heating and modification of samples [5,[33][34][35][36][37][38][39][40][41][42][43]to laser-driven dynamic compression of materials [44][45][46][47] to laser-induced chemical reactions (e.g., via pyrolysis or photolysis) [25,[48][49][50][51]. This article (Part I) focuses on the first of these implementations, i.e., laser-heated diamond anvil cells (LH-DACs), where a laser is focused onto a sample within a DAC to control its temperature.…”

Experimental Determination of Mantle Solidi and Melt Compositions for Two Likely Rocky Exoplanet Compositions

“…Experimental igneous petrology has been used to study melting on our solar system's planets and moons and has led to insights such as redox conditions, degree of differentiation, melt compositions, location of solidi, magma sources, and planetary cooling rates for these bodies (e.g., Filiberto, 2014;Grove & Krawczynski, 2009;Kiefer et al, 2015Kiefer et al, , 2015Krawczynski & Grove, 2012;Namur et al, 2016;Putirka, 2016;Vander Kaaden et al, 2017;Wadhwa, 2008). Only recently have workers begun to apply concepts from experimental mineralogy and petrology to exoplanets, studies which thus far have focused mostly on Si-C planets and high pressure mineralogy (e.g., Daviau et al, 2019;Duffy & Smith, 2019;Hakim et al, 2018Hakim et al, , 2019Miozzi et al, 2018;Nisr et al, 2017).…”