The variation of surface free energy of Al during superhydrophobicity processing

- Surface free energy variation after superhydrophobicity creation of Al surface is examined.
- Molecular dynamics simulation is employed for surface free energy calculation of bare Al.
- For superhydrophobic Al, critical surface tension approach was used to measure surface free energy.
- Both experimental and theoretical approaches verify surface free energy reduction after superhydrophobicity creation.

Surface free energy (SFE) of solids is a main property. This parameter can be affected by various phenomena such as superhydrophobicity creation. Two circumstances are necessary to achieve superhydrophobicity characteristics. These requirements are roughness improvement as well as surface energy reduction. The ZnO nanoparticle deposition is a suitable method for obtaining desirable roughness and consequently decreased SFE with stearic acid (STA) ethanol solution. The SFE of bare Al at room temperature was investigated using molecular dynamics (MD) simulation. After fabrication of superhydrophobicity property on Al surface, its SFE was calculated by applying equation of state and critical surface tension methods. The comparison between results based on two considered methods led to the fact that SFE significantly reduces after superhydrophobicity processing and reaches to STA, applied as a modifier, surface tension value. In addition to the theoretical results, water contact angle (CA) measurements confirm the SFE reduction due to superhydrophobic processing. Furthermore, the presence of STA on the superhydrophobic surface can be verified experimentally with Fourier transform infrared in conjunction with attenuated total reflection (FTIR-ATR) analysis. Therefore, both computational and experimental results approve the existence of STA on superhydrophobic Al surface and its grafting may lead to SFE reduction.

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