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102 Chapter 2

afford performances unattainable by any other conventional materials. The spray coating

Figure 2.9.10 a) DC-resistance vs. GNR film thickness, b) Heated RF transparent GNR
layer

technique used to fabricate the thin films is a cost-efficient approach that is amenable to large
scale fabrication. The resulting film is also stable in hostile environments such as those
featuring wind, sand, snow, and wide variation in temperatures.

Figure 2.9.11 demonstrates 50×50mm GNR film produced on flexible polyimide substrate for
test the RF transparency in the anechoic chambers similar to the shown in Figure 2.2.13. It was
found that the net film attenuation does not exceed 0.2dB – 0.4dB in the frequency range
between 2.4 GHz – 4 GHz. The additional high power test demonstrates that such film can
handle the average power density up to 20 kW/m . Meanwhile, GNR layer is so tiny that only
2
10 g of GNR is required for 10 x 10m area. Therefore, with the current price of $10 per gram
we need just $10 to cover such large surface.
Meanwhile, to be conductive is not enough for many deicing applications. For example, the de-
icing layer on car windshield must be transparent
not only to GPS and any other RF
communication signals but should pass through
visible light. Similar requirements are tendered
and demanded the glass building with the deicing
coating. In the case of aircraft deicing, the critical
issues are weight, cost, and stability in hostile
environments such as those featuring wind, sand,
snow, and wide variation in temperatures.

In conclusion, two more notices. As we have
Figure 2.9.11 50x50 mm GNR film mentioned before, graphene has a negative
thermal coefficient of conductivity. It means that
GNR film reduces its resistance as the ambient temperature drops thereby driving more current
from voltage power supply and delivering more heat energy to the deicing surface. Besides,
GNR film might make superhydrophobic meaning that the water on its surface beads into tiny
spherical droplets like drops of water on a lotus leaves or hot pan. This feature is advantageous
because the droplets constantly slide off that significantly increases the efficacy of deicing GNR
film covering the slightly tilted surface.