In cold regions, Frost can build up on the surfaces of power cables and cooling equipmentcausing its malfunction. To prevent frost, it is common practice to apply special coatings to equipment surfaces, but with conventional methods that rely solely on surface treatments, the antifreeze effect only lasts a short time. This is because coatings are easily damaged on surfaces with complex structures and durability over a wide range remains an issue.
Therefore, United States researchers have developed a technology frost protection using a hybrid structure that combines a graphene oxide nanomaterial with a macrotexture (a surface with a deviation of 0.5 mm to 50 mm).
“Graphene oxide has a structure that traps water molecules and acts as a container that prevents water vapor from freezing. By combining this with a macrotexture, we can create supersaturation (a state in which the amount of vapor exceeds the limit that a gas can maintain). “But it provides stable frost protection over a long period of time,” explains Kenneth Park, assistant professor of mechanical engineering at Northwestern University.
By controlling the diffusion of water vapor in the air so that it adheres only to the protruding parts of the uneven macrotexture, Park and his team managed to create a surface design that completely prevents frost from forming for more than a week.
Long-term frost protection and excellent durability
Prior to this discovery, in 2020, Park’s research team was inspired by the undulating structure (ripples) of plant leaves and, by applying surface treatments at the millimeter level, they could theoretically prevent frost formation by 80 %.
According to Park, frost usually forms on the ridges of leaves, but rarely in the valleys where the veins meet. From this fact he realized that the spread of frost depends on the shape, not the material. Through simulations, the researchers found that on a surface with an uneven structure, water vapor condensation is amplified on the convex parts and suppressed on the concave parts. The water droplets in the valleys of the leaves evaporate quickly, creating areas where frost does not form.
The researchers now built a 600-micrometer layer of graphene oxide in the flat valleys of a macrotexture with bumps spaced 5 mm apart. This prevents water vapor from freezing on the graphene oxide-coated flat surface and converging at the tip of the mountain, preventing frost from forming.
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