## 3 Results
### Carbon Deposits Formed in CME/Air and CH\({}_{4}\)/Air Flames  
#### 3.1.1 CME/Air Flame  
In Flame I, the CME/air co-flow flame, the substrate was inserted into the flame volume for a residence time of 5 min at an HAB of 10 mm, 12 mm, 15 mm, and 20 mm. By varying the HAB, carbonaceous deposits display a change in total mass, uniformity, thickness, degree of hydrophobicity, and surface morphology (Figure 3A). Increasing substrate insertion height was followed by changes in uniformity, with the deposits evolving from individual clusters at the very base of the flame (Figure 3A(a1,a2)) to interconnected web-like structures midway in the flame (Figure 3A(b1,b2,c1,c2)), and finally forming a highly uniform layer with few voids at the tip of the flame (Figure 3A(d1,d2)). The changes in C-layer uniformity were generally accompanied by an increase in degree of hydrophobicity (measured by CA), with the only decrease in CA being 1\({}^{\circ}\) as the substrate insertion HAB increased from 15 mm to 20 mm.  
At a substrate insertion height of 10 mm HAB the deposits formed are barely discernable to the naked eye, displayed hydrophilic characteristics, and formed a unique \"granular-like\" microstructure (Figure 3A(a1,a2)). This insertion height of the substrate coincides with the boundary between the pyrolysis zone and the luminous zone of the flame: there is hardly any soot present at this point, and if soot were present, it would be located towards the outer radius of the flame [34; 35; 37]. At 12 mm HAB a thin layer of soot is deposited on the substrate, measuring only 1 mg in mass, and displaying hydrophobic (CA = 144\({}^{\circ}\)) properties. At this point, the first instance of \"spiderweb-like\" soot structures were deposited from the CME/air flame (Figure 3A(b1,b2)). Increasing substrate insertion height to 15 mm HAB produced a noticeably thicker C-layer with a significant increase in mass to 5 mg (Figure 3A(c1,c2)). At this HAB the first superhydrophobic C-layer is formed from the CME/air flame (CA = 157\({}^{\circ}\)). Additionally, the weblike structures appear much more defined than those formed at 12 mm. At the final substrate insertion height into the CME/air flame at 20 mm HAB the mass of the deposited carbon film peaked (9 mg) and the layer remained superhydrophobic (CA = 156\({}^{\circ}\)). These deposition characteristics show a correlation between C-layer properties (mass, thickness, hydrophobicity, and surface morphology) and the substrate's insertion point into the flame height.  
The hydrophobicity of the deposited carbon film depends on the film's unique surface morphology. The non-uniform and \"granular-like\" deposits formed at 10 mm HAB are unable to support and maintain the water droplet's shape. Therefore, the surface of the water droplet breaks and the water spreads across the substrate, indicating that the surface is hydrophilic. When HAB was increased to 12 mm the C-layer began to display a \"spiderweb-like\" structure. This type of branching structure was also present at an HAB of 15 mm; however, the branches appear to be more densely packed together and better defined than those at 12 mm. This webbed structure creates a surface full of nanoscale air pockets that allow the water droplet to rest on the surface without wetting the substrate. The behavior of the water droplet resting on the surface and not breaking its surface tension conforms to the Cassie-Baxter state of hydrophobicity.