1 research outputs found
Hollow Rodlike MgF<sub>2</sub> with an Ultralow Refractive Index for the Preparation of Multifunctional Antireflective Coatings
Antireflective
coatings with superhydrophobic, self-cleaning, and wide-spectrum high-transmittance
properties and good mechanical strength have important practical value.
In this research, hollow nanorod-like MgF<sub>2</sub> sols with different
void volumes were prepared by a template-free solvothermal method
to further obtain hollow nanorod-like MgF<sub>2</sub> crystals with
an ultralow refractive index of 1.14. Besides, a MgF<sub>2</sub> coating
with an adjustable refractive index of 1.10–1.35 was also prepared
by the template-free solvothermal method. Then through the combination
of base/acid two-step-catalyzed TEOS and hydroxyl modification on
the surface of nanosilica spheres, the SiO<sub>2</sub> coating with
good mechanical strength, a flat surface, and a refractive index of
1.30–1.45 was obtained. Double-layer broadband antireflective
coatings with an average transmittance of 99.6% at 400–1400
nm were designed using the relevant optical theory. After the coating
thickness was optimized by the dip-coating method, the double-layer
antireflective coatings, whose parameters were consistent with those
designed by the theory, were obtained. The bottom layer was a SiO<sub>2</sub> coating with a refractive index of 1.34 and a thickness of
155 nm, and the top layer was a hollow rodlike MgF<sub>2</sub> coating
with a refractive index of 1.10 and a thickness of 165 nm. The average
transmittance of the obtained MgF<sub>2</sub>–SiO<sub>2</sub> antireflective coatings was 99.1% at 400–1400 nm, which was
close to the theoretical value. The hydrophobic angle of the coating
surface reached 119° at first, and the angle further reached
152° after conducting surface modification by PFOTES. In addition,
because the porosity of the coating surface was only 10.7%, the pencil
hardness of the coating surface was 5 H and the critical load Lc was
27.05 N. In summary, the obtained antireflective coatings possessed
superhydrophobic, self-cleaning, and wide-spectrum high-transmittance
properties and good mechanical strength