Zhang Junping of Lanzhou Institute of Chemicals "AFM": A strong ultra-double thinning coating that can be prepared on a large scale for high-voltage transmission towers to prevent icing

In recent years, superhydrophobic and super-double-thinning coatings have a wide range of application potential

Recently, Zhang Junping, a researcher at the Lanzhou Institute of Chemical Physics of the Chinese Academy of Sciences, developed a general preparation method for mechanically robust superhydrophobic coatings and their practical application

Figure 1.

Preparation of ultra-double thinning coatings

The researchers first synthesized FD-POS@silica nanoparticles

Figure 2.

The SP/FD-POS@silicaNone coating is dense at low magnification and filled with a large number of nanopores at high magnification (Figures 2a-c

Figure 3.

Static and dynamic ultra-double-sparseness

Both SP/FD-POS@silicaNone and SP/FD-POS@silica coatings are superhydrophobic
.
When n-decane with a surface tension of 23.
8 mN–1 and other liquids with higher surface tension are used as probe liquids, SP/FD-POS@silicaNone and SP/FD-POS@silica coatings exhibit the same static superhydrophobicity (Figure 3a-b).

Among them, the SP/FD-POS@silica coating has a static superhydrophobicity
that is significantly better than that of sp/FD-POS@silicaNone coatings.
Dynamic superhydrophobicity differences
between SP/FD-POS@silicaNone and SP/FD-POS@silica coatings were investigated by influencing the highly released water and n-hexadecane droplets (10 μL) on the coating.
Water droplets can bounce on both coatings, but exhibit significantly different impact/bounce behavior
.
On the SP/FD-POS@ silica coating, the droplets have longer bounce times (seven vs four), shorter solid water contact times (9.
75 ms vs 10.
5 ms) and higher bounce heights in the first impact/bounce cycle (2.
48 mm vs 1.
73 mm) (Figure 3c-d).

。 In addition, n-hexadecane droplets can bounce completely on the SP/FD-POS@silica coating, with shorter solid-liquid contact times (20.
00 ms) and higher bounce heights (1.
71 mm) during the first impact/bounce cycle (Figure 3e-f
).
The results show that the SP/FD-POS@silica coating has better dynamic superhydrophobicity
than the SP/FD-POS@silicaNone coating.
SP/FD-POS@silica coatings have better static and dynamic superhydrophobicity, mainly due to their three-layer layered micro/micro/nano structure and lower surface energy
.

Figure 4.
The mechanical robustness of SP/FD-POS@silicaNone and SP/FD-POS@silica coatings

Mechanical robustness

Sp/FD-POS@silica coatings have higher
mechanical strength than SP/FD-POS@silicaNone coatings.
The mechanism is explained below
.
For SP/FD-POS@silicaNone coatings, the top surface is nanoporous, but the interior is very dense (Figures 4a, 2c
).
In addition, the F content gradually decreases from the top surface to the bottom of the coating (Figure 4c), which means that there are more FD-POS@silica nanoparticles on the top and more
SP binder in the coating.
As wear or tape peel cycles increase, the nanoporous top surface is damaged and new dense surfaces with higher surface energy (i.
e.
, more SP binders) are exposed (Figures 4e, f, and i
).
As a result, hyperhydrophobia decreases or even disappears
significantly.
In stark contrast, sp/FD-POS@silica coatings have a self-similar structure with the same F content from top to bottom (Figures 4b, d).

Thus, as wear or tape peel cycles increase, the newly exposed surface of the SP/FD-POS@ silica coating still shows two layers of layered micro/nanostructures (Figure 4g-h) with a surface chemistry very similar to the original surface (Figure 4j).

In addition, the microskeleton of the SP/FD-POS@silica coating can enhance the mechanical strength
of the coating by acting as armor for the FD-POS@silica nanoparticles.
In addition, SP adhesives can enhance the robustness of the coating by joining FD-POS@silica nanoparticles
together.
As a result, SP/FD-POS@silica coatings exhibit superior mechanical strength
through self-similar structures, protective microskeletons and SP adhesives.

Figure 5.
Large-scale preparation of a) FD-POS@silica suspension, b) FD-POS@silica nanoparticles, c-d) SP/FD-POS@silica suspension, e) SP/FD-POS@silica coating
.

Large-scale preparation and practical anti-icing applications

In addition, the researchers also achieved large-scale preparation
of SP/FD-POS@silica suspensions (300 L per day, Figure 5a-d) and SP/FD-POS@ silica superhydrophobic coatings (90 cm × 60 cm, Figure 5e).
The possible application
of SP/FD-POS@silica coatings in passive anti-icing was investigated by recording the water freezing time in the simulated environment (relative humidity = 60%).
The researchers tested the freezing time
of water droplets (60 μL, methylene blue staining) at different temperatures on aluminum alloy plates, SP/FD-POS@silicaNone coated aluminum alloy plates, and SP/FD-POS@silica coated aluminum alloy plates 。 At -5 °C, the water droplets freeze completely after 86.
3 ± 1.
5 s on the aluminium alloy plate, but to 220.
7 ± 10.
7 s on the SP/FD-POS@silicaNone coated aluminum alloy plate and further to 258.
7 ± 5.
9 s on the SP/FD-POS@silica coated aluminum alloy plate (Figure 6a-d).

At -10 °C, the same trend
is observed.

In addition, SP/FD-POS@silica coatings provide better anti-icing properties than SP/FD-POS@silicaNone coatings
.
Compared to coatings with nanoporous sp/FD-POS@silicaNone, SP/FD-POS@silica coatings have three layers of micro/micro/nano structures, so more air can be captured at the solid-water interface (Figure 6e
).
In addition, SP/FD-POS@silica coatings have lower surface energy than SP/FD-POS@silicaNone coatings
.
As a result, heat transfer and icing from water droplets to the substrate are further hampered
.

Figure 6.
Practical ice protection applications for SP/FD-POS@silicaNone and SP/FD-POS@silica

Summary: By spraying a suspension containing FD-POS@silica nanoparticles and binder particles, researchers can prepare mechanically robust ultra-double-thinning coatings
.
The phase separation of the adhesive gives the ultra-double-thinning coating excellent static and dynamic ultra-double-thinning
.
Among them, the ultra-double thinning coating can withstand 100 times of tabor wear and 150 times of tape peel, showing excellent mechanical strength
.
In addition, ultra-double-thinning coatings can be applied to a variety of substrates and prepared on a large scale, and the freezing time
of water is significantly delayed.
Therefore, the ultra-double thinning coating shows good passive anti-icing performance
on the 1000 kV high-voltage transmission tower in the cold winter of Anhui Province.