The Research On Processing Asymmetric Wetting Property Mesh By Femtosecond Laser

In recent years,the treatment of oily wastewater has become a global challenge due to the increasing production of industrial oily wastewater and frequent oil spills.At the same time,a large number of harmful chemicals formed during the process of decomposition,they posed a serious threat to marine ecosystems and endangered the health of marine life and humans.Therefore,it is very important to develop new technologies for oil-water separation.In the previous oil-water separation work,researchers usually used a method to manufacture super-hydrophilic/superoleophobic surfaces.However,due to the complicated preparation process,low commercial availability,and inability to adapt to harsh environments,most solutions are not capable of large-scale production and cannot simultaneously be effective for both heavy and light density oils.Aiming at this problem,this paper proposes a method for preparing a mesh with asymmetric wetting properties to realize the separation of light oil-water mixture and heavy oil-water mixture.This paper set up a platform based on femtosecond laser and carried out a series of experimental studies on stainless steel mesh.By combining femtosecond laser ablating technology and printer powder spraying technology together,we achieved asymmetric wetting property and realized the separation of light oil-water mixture and heavy oil-water mixture by one mesh.The detailed description is listed as follows:(1)The characteristics and applications of femtosecond laser surface modification technology are introduced,and the research status of oil-water mixture separation is expounded.A processing platform consisting of a femtosecond laser,a scanning galvanometer,a displacement motion platform,a computer,etc.is set up which can be used to the processing of stainless steel mesh.(2)Design a single pulse ablation threshold experiment of stainless steel,and carry out the experiment by femtosecond laser.The single pulse ablation threshold of the stainless steel material and the beam waist radius of the spot were calculated by straight line fitting.The stainless steel mesh will produce periodic structure when the laser energy density is above the ablation threshold and the mechanism of it was analyzed.(3)Based on the experimental variables controlling principle,the effects of scanning speed,laser power and scanning times on periodic micro-nano stripes were studied.It is found that the micro-nano structure morphology of stainless steel mesh surface will evolve with the change of processing parameters.Finally,the optimal process parameter combination of the femtosecond laser processing stainless steel mesh(scanning pitch 10?m,laser power 5.6W,scanning speed 1m/s,scanning times 1)was obtained,and the mesh surface was processed with obvious and no defects periodic structures.(4)By combining the femtosecond laser scanning technology with the powder coating technology to process two sides of the stainless steel mesh separately,the special wetting property were obtained on both sides of the mesh.Compared to the original grid,one side of the as-prepared mesh is super-hydrophilic and oleophobic under water,and the other side is superolephilic and hydrophobic.(5)The contact angle of the as-prepared mesh to light oil and heavy oil was measured.Separation experiments were carried out on light oil-water mixture and heavy oil-water mixture,and the separation efficiency was all above 96%.At the same time,it was found that the as-prepared mesh has good environmental adaptability and can be workable under acid,alkali,salt and high temperature conditions.The separation mechanism of heavy oil-water mixture,light oil-water mixture was discussed,and the intrusion pressure was found to be a key factor in the separation process.