| The vigorous rise of bionics has led to the rapid development of material surface functionalization.Among them,the artificial superhydrophobic and slippery surfaces inspired by the special wettability of the lotus leaf and the pitcher plant have shown broad application prospects in the fields of anti-fouling,anti-corrosion,droplet manipulation,anti-icing,drag reduction and cell engineering,and have attracted widespread attention from researchers.At present,all kinds of artificial bionic superhydrophobic and slippery surfaces exhibit excellent wetting properties,but there are common problems that the preparation processes are complicated,and the process conditions are too harsh to achieve mass production.Meanwhile,the fragility and poor durability of the prepared functional films greatly limit the practical applications.In response to the above problems,TC4(Ti6Al4V)titanium alloy,which is widely used in aerospace,marine engineering,and biomedical fields,is taken as the research object in this study,and high-efficiency laser direct writing technology is adopted for micro-structure design.Oxide layer with pore array pattern on the titanium alloy surface is constructed to enhance the mechanical stability of the film.In addition,combined with a simple chemical method,nano-structure grows in-situ with the intrinsic properties of the titanium alloy substrate,and a micro-nano composite structure film is prepared.Then,through the modification of low surface energy organics and the injection of lubricant with suitable viscosity,the superhydrophobic and slippery surfaces with excellent wettability and long-term durability are finally obtained,which promotes the functional surfaces with special wettability from the experimental research stage to industrialization.First,micron-scale pore structure with pore array pattern is constructed on the surface of TC4 titanium alloy by nanosecond laser equipment.Based on the systematic analysis of the influence of pore array arrangement,pore spacing and pore depth on wetting properties(contact angle and sliding angle),a superhydrophobic surface(modified with myristic acid)with a contact angle of 160.6°and a sliding angle of 1.2°is obtained through laser process adjustment and optimization.Then,by building a thermodynamic analysis model,the influence of intrinsic contact angle(?Y),pore spacing(b)and pore depth(H)on the wetting state and wetting properties are theoretically analyzed,and calculation of critical conditions of pore array laser-induced surface for transition between different wetting states(Cassie/Wenzel)and prediction of wetting properties are realized.The verification of the model shows that the prediction results of this model are very close to the experimental ones,indicating that the model in this study is much credible and can be used to guide the design and process optimization of the pore array laser-induced superhydrophobic surface.Based on the pore array laser-induced microstructure surface,anatase Ti O2 nanowire structure grows in-situ on the surface of the micron-scale pore structure through the"hydrothermal-acidification-calcination"process.The optimized hydrothermal reaction temperature(250?),reaction time(15 h)and alkali concentration(1 M)are determined by the orthogonal test method.With the uniformly coated nano-structure on micron-scale pore structure,the micro-nano composite structure surface is obtained.After the modification of organosilane,the contact angle of the surface is up to 165.2°,and the sliding angle is less than1°.Compared with the laser-induced surface,which has a single micron-scale structure,the superhydrophobicity of the micro-nano composite structure surface shows better durability.After being impacted by 13.24 m/s high-speed water flow for 5 min,immersed in the 3.5 wt.%Na Cl solution for 146 h or 5 cycles of friction,the micro-nano composite structure surface still maintains superhydrophobicity.Furthermore,the stability of different organic for surface modification is compared.The results show that polydimethylsiloxane(PDMS)has better thermal stability and resistance to photocatalytic degradation than hexadecyltrimethoxysiloxane(HDTMS),which can withstand high temperature at 450?for30 min without decomposition and 8 h ultraviolet light(250 W,365 nm)without degradation.Based on the micro-nano composite structure surface mentioned above,dimethyl silicone oil is chosen as the injection lubricant to construct the slippery liquid infused porous surface(SLIPS)in this study.The injection volume of lubricants with different viscosities(20,50,100,350,500 m Pa·s)and the surface morphology after injection are analyzed.The results show that low-viscosity lubricants are more likely to be lost when the surface is tilted,and the surface micro-structure fails to be completely covered,so the roughness is relatively high.While the surfaces injected with the high-viscosity lubricant are relatively flat with low roughness.The test results of water agitation and scouring show that the slippery surface(20-SLIPS)injected with low-viscosity lubricant(20 m Pa·s)has a faster water droplet rolling speed,but as the scouring time increases,the rolling speed decreases the most.As for the slippery surfaces(350-SLIPS,500-SLIPS)injected with the high-viscosity lubricant(350,500m Pa·s),the rolling speed of water droplets is slow,while after long-term(4 days)of water flow agitation and scouring,the performance remains basically unchanged.In the self-healing test,both the 350-SLIPS and 500-SLIPS samples showed self-healing to the scratches of the blade,while the other samples showed"anti-self-healing".This abnormal phenomenon can be contributed to the capillary force of nano-structure and the injection volume of lubricant,and the mechanism analysis has been carried out in this study.In terms of lyophobic properties,slippery surfaces show more extensive lyophobicity than superhydrophobic surfaces,especially for organic solvents,which have broad application prospects. |
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