Interaction of water
on heterogeneous nonwetting interfaces has
fascinated researchers’ attention for wider applications. Herein,
we report the evolution of hierarchical micro-/nanostructures on superhydrophobic
pseudoboehmite surfaces created from amorphous Al2O3 films and unraveled their temperature-driven wettability
and surface energy properties. The influence of hot water immersion
temperature on the dissolution–reprecipitation mechanism and
the surface geometry of the Al2O3 film have
been extensively analyzed, which helped in attaining the optimal Cassie–Baxter
state. The evolution of pseudoboehmite films has been structurally
characterized using grazing incidence X-ray diffraction, field-emission scanning electron microscopy,
high-resolution transmission electron microscopy, X-ray photoelectron
spectroscopy and atomic force microscopy. Interfacial surface energy
components on the structured superhydrophobic surface exhibited a
very low surface energy of ∼4.6 mN/m at room temperature and
ultrahigh water contact angle >175°. The interaction between
water droplets on the nonwetting surface was comprehended and correlated
to the temperature-dependent surface energy properties. The surface
energy and wettability of the structured pseudoboehmite superhydrophobic
surface exhibited an inverse behavior as a function of temperature.
Interestingly, the superhydrophobic surface exhibited “Leidenfrost
effect” below the boiling point of water (67 °C), which
is further correlated with the intermolecular forces, interfacial
water molecules and surface-terminated groups. These high-temperature
wetting transition studies could be potentially valuable for solid–liquid
systems working at nonambient temperatures, and also this approach
can pave new pathways for better understanding of the solid/liquid
interfacial interactions on nanoengineered superhydrophobic surfaces.
The paper reports on plant megafossils found in the lower part of the Pariwar (Parihar) Formation exposod in the Jaisalmer Basin, Rajasthan. The plant fossils belong to the groups Filicales, Cycadales, Bennettitales and Coniferales. The identifiable species are: ?Gleichenites sp., Phlebopteris sp., Frond type I, Taeniopteris vitlata, T. densinervis, T. spatulata, Pterophyllum sp., Otozamites imbricatus, Ptilophyllum acutifolium, Elatocladus conferta, ?Elatocladus sp. and Pagiophyllum sp. In general composition the fossil assemblage is more akin to that known from the Kutch Basin of Gujarat, and is probably Upper Jurassic in age.
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