Fabrication And Performance Of Black Super-wicking Aluminum Sheet By Femtosecond Laser

Under the background of increasingly tense fresh water resources in human society,various cutting-edge water purification technologies emerge in an endless stream,and green,efficient,and low-cost technologies are the first choice for future development.Femtosecond laser has great advantages in the field of material processing,such as high power,fast scanning speed and small heat affected zone.Aluminum has large reserves,light weight and good stability,and is widely used in the production and life of human society.The use of femtosecond laser to prepare the surface of black aluminum plate with super-wicking function can not only absorb solar energy efficiently,but also absorb water efficiently,realize interface evaporation on the same surface,greatly improve the utilization rate of energy,and meet the above requirements for water purification technology development requirements.In this thesis,the effect of femtosecond laser processing parameters on the surface morphology of the aluminum plate is studied,the ablation threshold of the surface is calculated,and the grain size change inside the aluminum plate before and after laser processing is observed through an optical microscope.Then a large-area black super-wicking aluminum plate surface was prepared,characterized by scanning electron microscopy and white light profiler,and the rising rate of the liquid level inside the microgroove was fitted.Finally,the evaporation rate of the surface of the black super-wicking aluminum plate was measured under different conditions,and the transformation mechanism of its surface wettability in the atmospheric environment was analyzed.The results show that the ablation threshold of the aluminum plate surface is 0.94J/cm~2.The amount of defocus has the greatest effect on the ablation line width.The repetition rate is the main factor affecting the depth of the ablation line.A lower scanning speed will make the internal structure of the microgroove more uniform.Appropriate scanning line spacing not only reduces the reflectivity of the surface of the aluminum plate,but also maintains the integrity of the micro-groove structure.The internal grain size of the processed aluminum plate has almost no change,which corresponds to the"cold processing"of the femtosecond laser.The microgrooves on the surface of the prepared black super-wicking aluminum plate have a width of“ridge”of about 17.5μm,a width of“valley”of about 22.5μm,and a depth range of 60-70μm.In the absence of light indoors,the evaporation rate on the surface of the black super-wicking aluminum plate is about 1.31 kg/m~2/h.Through XPS analysis,it was found that the wettability change of the aluminum plate surface after laser processing was due to the adsorption of organic matter in the atmospheric environment,which resulted in the increase of C-C bonds with hydrophobic effect on the surface.