Super Hydrophobic Property Of Nano-tube Arrays And The Research Of Ice Phobic Property Based On Silicon Coating

According to the Cassie wetting theory, we can construct that the solid-liquid contact area ratio is the main factor which determines whether the rough surface could be super hydrophobic, and the surface chemistry is the secondary factor. In order to make the theoretical calculation and experimental verification of this inference, in this thesis, we designed polymer nanotube arrays with very low solid-air ratio and single scale by AAO perfusion. Further, nanotube arrays were modified by sol-gel impregnation method. SEM, XPS characterization confirmed that same structure nanotube arrays with the surface energy gradient from low to high have been prepared. The CA (Contact angle) and SA(Slide angle) of the three surface is168°,166°,155°and1°,3.5°,12°, which showed super hydrophobic property. This result verified that we could obtain super hydrophobic state by reduce the solid-liquid contact ratio based on the air cushion in the rough structure of Cassie model which also verified that the wetting state do not depend on surface chemical properties.From the view of thermodynamic, the wetting state of the surface should depend on its chemical properties, but three surfaces show super hydrophobic property, so from the view of dynamic point, the state should be in a metastable phase. Because there is an energy barrier existence on the surface of the arrays, when the external stress is smaller than the barrier, the surface structure played a major role; otherwise it is determined by its chemical properties. Same structure surface with different chemical properties have different energy barrier, low surface energy contribute low energy barrier. In this thesis, we added pressure on three surfaces by impact, mechanical stress and hydraulic method, and verified that the super hydrophobic stability of different chemical properties of the surfaces is different. The stability is directed relate to the surface chemical property, low surface energy materials is more resistance to pressure. If the stress exceeds the barrier, all super hydrophobic properties will lose and can’t restore automatically. Results showed that super hydrophobic property is not stable and in a dynamic metastable phase. Super hydrophobic property can keep for a long time with no external stress, but if the energy barrier is breached, super hydrophobic state will be completely lost and can’t restore automatically.Super hydrophobic surface has lots of potential applications; one of the important applications is used in ice-phobic area. The ideally anti-icing should meet:water cannot ice up on the surface or the ice adhesion force is extremely small. People verified that super hydrophobic surfaces can make super cooled water rebound and roll off which means it has anti-icing effect. But most super hydrophobic surface will lost its super hydrophobic property because of condensation, which make these surfaces can’t be used in the environment with low temperature and high humidity in a long time. In view of the limitation of super hydrophobic surface application in anti-icing area, anti-icing coating has ultra-low ice adhesion can make up the short of super hydrophobic surfaces. This thesis studied the anti-icing characteristics of low surface energy materials like fluorine and silicon based coatings. Then designed a kind of silicone coating which has extremely low adhesion force, and analysis the anting-icing mechanism of the coating. The main achievements and innovations of this thesis are as follows:(1) We designed and prepared polymer Nano tube arrays with different chemical properties. And studied the super hydrophobic property based on this kind of surface. This research achieved super hydrophobic property of hydrophilic material based on Nano tube array structure.(2) The research confirmed that the state of super hydrophobic is not stable; it is a dynamics metastable state. And point out the energy barrier is the restricting factor of stability of super hydrophobic property by adding impact pressure, mechanical stress and hydraulic stress. The external stress will cause partly or completely transformation of Cassie model, this research expanded the study of the stability of super hydrophobic to Nano-scale.(3) We studied the anti-icing effect of the fluorine-containing super hydrophobic and hydrophobic surfaces. Put forward that the chemical property of the surface is the significant correlation of its anti-icing property but not the morphology in the long-term of low temperature and high humidity. The excess of Micro-Nano structure can increase the ice adhesion strength and reduce the performance of ice phobic properties.(4) We Designed and synthesized a silicone based anti-icing coating, enhance the mechanical strength and closed the polar group by adding hydrophobic modified fumed silica. Finally, we obtained a coating which has only3%ice adhesion strength compared with bare Al, which is expected to be used to reduce the damage of icing in overhead power transmission.