Approaches To Super-hydrophobic Aluminium Surfaces And Their Conversion To Super-hydrophilic Surfaces By Ultra-fast Laser Processing

A water contact angle of more than 150° and sliding angle of less than 5° surfaces called superhydrophobic surfaces. This property is widely used in the areas of military, construction, mechanical engineering for its special feathers, such as drag reduction, resistance and so on. However, the development of the superhydrophobic surface is restricted for either uncheap equipment or unsimple processes, which makes it difficult and expensive to formation a large numbers of superhydrophobic surface. Al are widely applied in different industrial products for the specially properties, Thus, of great importance to find a easy and cheap way for formation the superhydrophobic surfaces, especially large areas of superhydrophobic surfaces on Al substrates.This thesis is researched under the background of 3551 Optical Valley talent Project-Miracle Plate Technology(MPT). Chemical etching and laser exposure ways put into formation superhydrophobic surface on Al substrate. On the other way. This ways is also put into practice to make the large amount of superhydrophobic successfully. The main content and results of this thesis are show below:(1). Different kinds of acid have been used to etch aluminum substrate and the wetting behaviour of the various aluminum surfaces generated by these processes has been investigated. Further, the feasibility analysis of how to perpare large areas of superhydrophobic surfaces is disscussed in this paper. Experimental results show that HCl and H3PO4 are better than HNO3, but aslo that it is difficult to make the superhydrophobic surface under these acid etching conditions.(2). Investigated into the changes of the sliding angle was done under different p H values and various etching times. Furthermore, the analysis of the wetting behaviour is also mentioned in this paper. The results indicate that all the surface become superhydrophobic, and that a large, but controllable-range of the sliding angles can be generated.(3). Investigation into the changes of contact angle with surfaces roughness has been done under different laser pulse widths, energies and substrates, and the analysis of the subsequent wetting behaviour is also mentioned in the paper. Different parameters were taken into consideration in order to find optimum values for the preparation of superhydrophobic aluminum surfaces. Experimental results show that Rz is reduced linearity with the laser energy increased, but the Rz is increased linearly with laser energy after the acid etching.low Rz surfaces can be obtained under the weak acid etching or high laser energy. Ra is increased lineary as with the laser energy is increased. Controllable production of these parameters be a great advantage to application in the production of printing forms. In addition, both 3D maps and roughness parameter results indicate that the roughness of the sample has no relationship with the time of acid etching, but only to extent of laser exposure. Finally, the surface index, Ra, and the contact angle is increased linearly in proportion to the applied laser energy.