Fig. 7: Sand spreading tests under CO2 and vacuum atmospheres.
From: Ultra-high entropy rare earth phosphate against environmental corrosion
a, b Melt diffusion processes in sand powder columns under different atmospheres. CO2 and vacuum correspond to the main gaseous environments of Mars and the Moon, respectively53,54,55. Sand dynamic melting under vacuum starts much earlier. c Curves of the contact angle of the powder columns with the spreading process. The yellow curve is a discrete trending of the data due to bubble bursting under vacuum. The gray shadow indicates the temperature range that the sand in a vacuum undergoes from the beginning of melting to the end of heating. The gray shading indicates the temperature range experienced by the sand under vacuum from the onset of melting to the end of heating. The black arrows mark the inflection points of the wetting contact angle in both atmospheres, each followed by rapid spreading. The red dashed line connects these inflection points to highlight the delayed spreading of sand in the CO₂ atmosphere. d Trend of the contact line between molten Sand and MXPOs is used to quantify the rate of spreading.
