Superhydrophobic
metallic materials have drawn broad research interest
because of promising applications in various fields. The mechanical
stability of superhydrophobic surfaces is currently a major concern
limiting their practical applications. Herein, we developed a simple
method to fabricate robust superhydrophobic surfaces on stainless
steel via direct ultrafast laser microprocessing. Of note is that
the fabricated superhydrophobic surfaces can withstand mechanical
abrasion against an 800 grit SiC sandpaper for 2.3 m at an applied
pressure of 5.5 kPa without losing superhydrophobicity. It is proposed
that the robust superhydrophobicity may be attributable to the formation
of unique hierarchical micro-/nanostructures and a nonpolar carbon
layer on the surface. The hierarchical structures are composed of
laser-created micropillars and ablation-induced nanoparticles. The
fabricated surfaces exhibit good thermal stability and still show
superhydrophobicity after thermal treatment at 100 °C for 120
min, which is related to the inorganic nature of metallic materials.
An excellent anti-icing property is achieved on the fabricated surfaces
with the water droplets on it retaining the liquid state for over
500 min at −8.5 ± 0.5 °C, which benefits from the
obtained superhydrophobicity, based on classic nucleation theory and
the heat transfer between the rough solid surface and water droplet.
We envision that the presented method provides a facile and effective
route to fabricate large-area superhydrophobic surfaces with robust
mechanical stability and excellent anti-icing property.
High corrosion rate in physiological environment of the body is the major drawback of magnesium alloys for their successful applications as biodegradable orthopaedic implants. In the present study, corrosion behaviour of AZ91D magnesium alloy after laser surface melting (LSM) was studied in modified-simulated body fluid at 37°C. The improved corrosion resistance of AZ91D alloy using LSM was found to depend on the solidification microstructure in the laser-melted zone. The general and pitting corrosion resistance of laser-treated surface was significantly enhanced due to the refined continuous network of b-Mg 17 Al 12 phases and the increased Al concentration in the laser-melted zone.
Porous structure of reduced graphene oxide (rGO) plays an important role in developing flexible graphene-based devices. In this work, we report a novel methodology for reduction of freestanding graphite oxide (GO) sheet by picosecond pulse laser direct writing in liquid nitrogen. Non-agglomerate and porous structure of rGO is fabricated successfully due to frozen effect during laser processing. Compared with laser-irradiated rGO developed in N2 gas at ambient environment, the frozen rGO developed in liquid N2 shows better ordered structure with less defects, crack-free morphology as well as better electron supercapacitor performance including 50–60 Ω/sq in sheet electrical resistance. Mechanism of cryotemperature photoreduction GO is also discussed.
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