Characterization of Samples

The surface roughness of the samples was measured before etching process using a surface profilometer (Mitutoyo Surftest. 402). The roughness of the samples was measured again after the etching. The roughness parameter measured in the above cases is the average roughness value, Ra, defined as the arithmetic average of the absolute values of the roughness profile ordinates [22].

After that, the contact angles were measured. These measurements were done using the model 250 Rame Hart Goniometer. The measured contact angles showed that none of the surfaces were hydrophobic before etching, though surfaces of the composites had a higher contact angle with water (Table 7.3). This can be attributed to the graphite particles which have an effect on the surface roughness of the composites when compared to the base alloys. Figure 7.18 shows the contact angle profiles of these samples before etching.

Fig. 7.18 Images of water droplet on non-etched samples

Fig. 7.19 Images of water droplet on etched samples

Aluminum base alloy after 20 s etching Aluminum-Graphite after 20 s etching

Fig. 7.20 The schematic of surface before and after etching for a matrix reinforced with particles

Fig. 7.20 The schematic of surface before and after etching for a matrix reinforced with particles

It is observed that all etched samples except Al base alloy became hydrophobic, i.e. have the contact angle greater than 90°. The contact angle profiles for Al- and Cu-samples that were etched for 20 s and 20 h, respectively are as shown in Fig. 7.19.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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