Research On Laser Preparation Of Aluminum Alloy Surface With Special Wettability And Its Properties

Superhydrophobic surface has many potential applications in industry and agriculture because of its extreme non-wetting properties.At present,the superhydrophobic surface has some prominent problems,such as complicated preparation process,poor surface stability and easy to be polluted by oil.Therefore,it is particularly important to find a simple,convenient and economical method to prepare the superamphiphobic surface(hydrophobic and oleophobic)with high stability,antifouling and wear resistance.In this study,a compact and regular surface texture was constructed on the surface of aluminum alloy by a convenient laser processing method,and then the surface modification method of perfluoro-decyl trichlorosilane was used to fabricate the superamphiphobic surface.The influences of square and equilateral triangle micro-texture and line spacing on wettability were investigated,and the properties and applications of the special wettability surface in tribology,droplet evaporation and droplet transport direction were studied.The main research contents are as follows:1.The special wettability surfaces with different patterns and spacing were prepared on6061 aluminum substrates by laser processing and perfluoro-decyl trichlorosilane modification.The effects of surface texture and line spacing on the wettability of superamphiphobic surfaces were investigated.The results show that the water contact Angle is larger than the oil contact Angle,and the oil rolling Angle is larger than the water rolling Angle for both square and regular triangle textures.In the range of 90?800?m,the contact Angle of the square texture surface is lower than that of the regular triangle,but the rolling Angle of the square texture surface is higher than that of the regular triangle.With the increase of line spacing,the oil rolling Angle of the square texture surface first reaches 90°.But in the range of 10?90?m,the contact Angle of the square texture surface is higher than that of the regular triangle,and the rolling Angle of the square texture surface is lower than that of the regular triangle.2.Three kinds of textured samples with square line spacing of 30?m(f30),90?m(f90)and regular triangle line spacing of 90?m(s90)were selected to test the tribological properties of different samples under the condition of dry friction,water lubrication and oil lubrication(n-cetane)respectively.It is found that the friction coefficient of the pretreated(0)samples is greater than that of the textured samples under three kinds of lubrication conditions,and the surface morphology of the textured samples also greatly affects the tribological properties of the surface.Square textures with line spacing of 30?m formed the whole nanometer granular splashing structure,while square and triangle textures with line spacing of 90?m formed the uneven columnar micro-nano porous structure.The friction coefficient of sample f30 was larger than that of sample f90 under dry friction condition,but smaller than that of sample f90 under water and oil lubrication condition.In addition,it can be found that the surface friction coefficient of sample s90 is smaller than that of sample f90 under three kinds of friction conditions.Moreover,under the three friction experimental conditions,the square texture surface with line spacing of 30?m has the least wear,which is more conducive to improve the surface wear resistance.3.Four samples,namely,square textured sample with line spacing of 90?m,square textured sample with line spacing of 800?m,modified blank surface sample and unmodified blank surface sample,were selected to study the droplet evaporation behavior.It was found that the water droplets evaporated in CCA mode on the surface with 90?m online spacing(f90)and on the surface with 800?m online spacing(f800),and evaporated in Mix mode on the surface with modified blank,and evaporated in CCR mode on the surface with unmodified blank.In general,the evaporation rate of water droplets on the four surfaces decreases gradually over time.The evaporation rates on the surfaces of F90,F800,modified blank and unmodified blank samples increase successively,and the 2/3 power of the evaporation volume of water droplets has a linear relationship with time.4.The samples with linear grooved and trapezoidal patterned superhydrophilic / superhy-drophobic surfaces were prepared by secondary laser etching on sample f90.The results show that the linear grooved superhydrophilic / superhydrophobic patterned surface shows significant anisotropic wetting along the parallel and perpendicular directions of the grooved surface,and the rolling resistance anisotropy increases with the increase of the grooved width,but the groove depth has little effect on the rolling resistance anisotropy.On the trapezoidal groove superhydrophilic / superhydrophobic patterned surface,the droplet movement time in the same distance decreases first and then increases with the decrease of droplet volume/trapezoidal Angle(?).In addition,when exploring the water mist collection experiment,it is found that tree-shaped pattern(compound trapezoidal pattern)can improve the collection and transportation speed of water droplets,thus improving the efficiency of water mist collection.