Superwetting Coatings Deposited On Copper Mesh For Enhanced Tubular Oil-water Separation Performance

In recent years,oil-water separation materials with special wettability have become one of the hot functional materials in the research fields of environmental ecology,biomedicine and microfluidic technology.Traditional oil-water separation methods have been unable to meet the needs of oil-water separation in practical application scenarios due to their poor applicability and low separation efficiency.Laser cladding and electrostatic spraying are highly valued due to their ease of operation and the ability to deposit the required superwetted coating in one step.In this paper,aluminum foil was cladded to a flexible copper mesh substrate by laser cladding to produce a flexible separation mesh with super hydrophilic surface and super oleophobic underwater.The effect of different parameters on the laser cladding effect was investigated by numerical simulation of the cladding process by transient thermal analysis.The effect of different laser parameters on the performance of the prepared flexible oil-water separation network was analyzed in combination with the results of the numerical simulation.On the other side of the molten substrate,a superhydrophobic fluorinated graphene coating was deposited by electrostatic spraying,so as to prepare Janus separation films with different wetting properties on both sides.Based on the flexible characteristics of the copper mesh,it was curled into the form of a pipe for the separation test of the tubular separation network.The fluid behavior of different application scenarios inside the pipe was simulated by computational fluid dynamics method.Compare the pipe separation test and simulation results of Janus membrane and original membrane to study the influence of hydrophobic outer wall on the fluid inside the micropipe.It is divided into the following parts.(1)One-step deposition of super hydrophilic and super oleophobic oil-water separation films on the surface of copper mesh by laser cladding.By observing the sample appearance of the separation network prepared with different parameters,it was found that the surface nanoparticles became smaller in size and more uniformly distributed with the decrease of the spacing between scanning paths,resulting in a decrease of the surface roughness.With the increase of laser power,the volume change of surface nanoparticles was not obvious and the distribution of nanoparticles did not change significantly.The transient thermal analysis model of ANSYS was used to study the effect of different parameters on the temperature field of the melting process.The simulation results further verified that the reduction of the scan path interval not only caused an overall temperature increase,but also led to an upward shift of the high temperature center in the high temperature region,resulting in a more uniform distribution of the surface nanoparticles.The wettability test shows that the superoleophobic performance of the surface was improved as the scan path spacing was reduced.Similarly,the decrease of the scan path spacing is beneficial to the improvement of the separation performance,while the increase of the laser power had no significant effect on the separation performance.Finally,the corrosion and friction resistance tests verified that the prepared separation network could maintain stable wetting properties after a long period of corrosion and friction,indicating that the prepared separation network is better suited for oil-water separation under harsh environments.(2)Superhydrophobic fluorinated graphene coatings were deposited by electrostatic spraying based on superhydrophilic cladded substrates to prepare Janus membranes with different wettability properties.The quality of the deposited fluorinated graphene coatings was optimized by regulating the applied voltage,spray speed and spraying concentration.The synergistic effect of different fluorinated graphene concentrations and different scan path spacing on the electrostatic spraying was investigated based on the mechanism of the effect of the cladded substrate on the electrostatic spraying.The action of the molten substrate on the deposited graphene fluoride coatings was further investigated by the graphene fluoride coating wetting performance test.Different oil-water separation applications and droplet transfer to the target are proposed by studying the different wettability properties and directional hydrophobic properties of the prepared Janus membrane on both sides.And the effect of hydrophobic graphene fluoride coating on oil bearing properties,water flux,separation efficiency and other oil-water separation properties of hydrophilic alumina coating was investigated by separation performance testing of the prepared Janus membrane.(3)For the tubular transport requirement of oil-water separation,oil-water separation tests and fluid behavior simulation studies were conducted on the flexible separation membrane convoluted formed pipes,and the fluid behavior of different application scenarios were analyzed by computational fluid dynamics method.The separation tests of the tubular separation network showed that the tubular separation network could maintain a stable separation efficiency for different injection flow rates.The reduction of the scanning path spacing is beneficial to the separation efficiency of the tubular separation network.The effect of increasing the laser power on the separation efficiency was not significant.In order to investigate the reasons for the large difference in fluid behavior inside the tubular due to different tube diameter changes,three different fluid behaviors of horizontal tubular flow,horizontal plane flow and vertical free flow were numerically simulated by computational fluid dynamics method,and it was concluded that the horizontal tubular flow behavior was mainly influenced by surface roughness,plane flow was influenced by surface roughness and inlet velocity,respectively,and vertical free flow was mainly influenced by wall wetting condition and roughness.By comparing the Janus micropipes separation results with the original micropipes separation results,the promotion effect of the fluorinated graphene coating on the outer wall surface on the oil-water separation of the alumina coating on the inner wall surface of the pipe was investigated.The different facilitation effects of the outer wall surface with different hydrophobic properties on the internal fluid of the micropipes were further verified by numerical simulation of the Janus micropipes fluid.