| HAO Xiao-ru,ZHANG Yu,XIE Jun,SHENG Wei.Surface Wetting Characteristics of Aluminum Oxide Modified by Stearic Acid[J],52(6):400-409 |
| Surface Wetting Characteristics of Aluminum Oxide Modified by Stearic Acid |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.06.037 |
| KeyWord:superhydrophobic molecular dynamics two-step spraying nano alumina stearic acid wetting characteristics |
| Author | Institution |
| HAO Xiao-ru |
School of Mechanical and Power Engineering, Henan Polytechnic University, Henan Jiaozuo , China |
| ZHANG Yu |
School of Mechanical and Power Engineering, Henan Polytechnic University, Henan Jiaozuo , China |
| XIE Jun |
School of Mechanical and Power Engineering, Henan Polytechnic University, Henan Jiaozuo , China |
| SHENG Wei |
School of Mechanical and Power Engineering, Henan Polytechnic University, Henan Jiaozuo , China;Hami Yuxin New Energy Industry Research Institute, Xinjiang Hami , China |
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| Abstract: |
| The work aims to study the wetting behavior of alumina particles modified by stearic acid from the microscopic point of view, in order to explore the wetting principle of polymer self-assembly from the surface modification, and then prepare a superhydrophobic surface with good durability. The method of molecular dynamics simulation and compass force field was used for molecular dynamics simulation and an Al2O3 supercell model system based on non-bonded particles was constructed and optimized by steepest descent method and conjugate gradient method, so as to keep the principle of minimum energy under system equilibrium and solve and analyze the model under periodic boundary conditions. Based on the simulation results, the superhydrophobic surface with cheap stearic acid and nano alumina particles as coating materials was prepared on the glass substrate by two-step spraying method. The contact angle was tested, the surface morphology and surface groups were analyzed, and the correctness of the model was verified from the macro point of view. The micro wetting behavior of water clusters on glass substrate and alumina surface before and after modification by stearic acid was analyzed by simulating conformation, radial distribution function and root mean square displacement. The contact angles of superhydrophobic surface and bare glass surface were 44.7° and 168.8° respectively. The surface morphology, infrared spectrum and group changes were observed. The results showed that the surface of alumina modified by stearic acid changed from hydrophilic surface to hydrophobic surface. Molecular dynamics simulation indicated that when the concentration of stearic acid increased, the surface energy of each stearic acid changed from –110.5 kJ/mol to –80.4 kJ/mol, but the surface energy did not decrease when it increased to a certain concentration. At this time, a layer of molecular film was formed under the action of stearic acid, the hydroxyl group at the head of stearic acid molecule was combined with nano alumina particles by hydrogen bond, and the methyl and methylene in its tail long carbon chain presented the surface hydrophobic characteristics. Thus, the diffusion coefficient of water molecular clusters on the surface of glass and alumina was reduced, and the cluster structure of water molecules on the surface was maintained, which had an important impact on the strength of hydrophobicity. Both alumina particles and glass surface have strong hydrophilicity, and the coordination number of aluminum and silicon particles on alumina surface and glass surface is not enough to fill the system. Therefore, there are some vacancies on the surface. After decomposition of H2O, the free OH– will occupy the vacancy, and the vacancy on aluminum ion surface is excess silicon, which shows that the adsorption capacity of alumina to water molecules is stronger than that of glass. Stearic acid can reduce the surface energy of alumina, and after chemical reaction with nano alumina, alumina is modified from super hydrophilic to superhydrophobic. The superhydrophobic surface remains superhydrophobic after three months, which proves that the superhydrophobic surface prepared in this experiment has stability and durability. By analyzing the surface morphology, it is found that the modified nano alumina particles will agglomerate and grow on the surface of glass carrier, and finally form micro nano rough structure similar to gully. |
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