Abstract
Metal oxides, in general, are known to exhibit significant wettability towards water molecules because of the high feasibility of synergetic hydrogen-bonding interactions possible at the solid-water interface. Here we show that the nano sized phosphates of rare earth materials (Rare Earth Phosphates, REPs), LaPO4 in particular, exhibit without any chemical modification, unique combination of intrinsic properties including remarkable hydrophobicity that could be retained even after exposure to extreme temperatures and harsh hydrothermal conditions. Transparent nanocoatings of LaPO4 as well as mixture of other REPs on glass surfaces are shown to display notable hydrophobicity with water contact angle (WCA) value of 120° while sintered and polished monoliths manifested WCA greater than 105°. Significantly, these materials in the form of coatings and monoliths also exhibit complete non-wettability and inertness towards molten metals like Ag, Zn, and Al well above their melting points. These properties, coupled with their excellent chemical and thermal stability, ease of processing, machinability and their versatile photo-physical and emission properties, render LaPO4 and other REP ceramics utility in diverse applications.
Highlights
Metal oxides, in general, are known to exhibit significant wettability towards water molecules because of the high feasibility of synergetic hydrogen-bonding interactions possible at the solid-water interface
XRD and FTIR spectra shown in section S1 show clear match between La2O3 and La(OH)[3] and convincingly prove that the rare earth oxide is susceptible to reaction with humidity in atmosphere leading to the formation of hydroxide
The oxide of lanthanum is unstable and vulnerable to atmospheric moisture exposure we have explored the case of LaPO4 for possible hydrophobic properties
Summary
In general, are known to exhibit significant wettability towards water molecules because of the high feasibility of synergetic hydrogen-bonding interactions possible at the solid-water interface. LaPO4 disc with water droplets kept in freezing condition (Fig. 1e) retained the shape (the droplets appeared as ice hemispheres over its surface) confirming that LaPO4 could manifest its hydrophobicity well under sub-zero temperatures.
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