Design And Propeerty Research Of Anti-icing Surface Based On Nanosized POSS And MOF Particles

Icing is a normal phenomenon in nature,and people find much enjoyment of water freezing in sports,food and entertainments.But icing will bring about serious economic losses and even casualties in air transportation,electric power transmission,heat exchanger,ground transportation,etc.After fully understanding the icing mechanism,how to influence or even control the freezing process and thus reduce or eliminate icing hazard is a hot issue and widely generates the public’s interest.In view of the disadvantages of traditional anti-icing and de-icing technologies in energy consumption and environment,developing new effective anti-icing technologies is a hot research topic in academia.Super-hydrophobic surface and slippery liquid infused porous surface（SLIPS）have been considered to be the directions showing the best anti-icing performance and application potential.In this work,we prepared some anti-icing surfaces based on polyhedral oligomeric silsesquioxane（POSS）and metal-organic frameworks（MOF）in nanoscale size towards the both directions of surperhydrophobic surface and SLIPS.We sprayed solutions containing POSS and immersed MOF grafting polypropylene（PP）non-woven fabrics（NWF）with silicone oil,and obtained four kinds of anti-icing surfaces consisted of POSS-polydimethylsiloxane（PDMS）,POSS-epoxy,Poly（vinyl alcohol）（PVA）-POSS and NWF-MOF-silicon oil,respectively.First,we characterized the surface morphology with scanning electron microscope（SEM）,and then we tested the wetting properties,frezzing temperatures of big droplets,the delayed frezzing time and ice adhesion with topography analyzer,optical microscope,cryo console and home-made ice adhesion tester,respectively.Based on above work,we analysed the correlations among processing,structure and properties of anti-icing surfaces,and made the following conclusions:1.During crystallization in solutions,‘open-mouth’hollow spherical partices in micro-nano size were formed through self-assembly of POSS molecules.Spraying octaisobutyl POSS（i8POSS）-PDMS hybrid solution,i8POSS-E51 hybrid solution,or i8POSS single solution on sprayed PVA contings generated micro/nano rough surfaces with superhydrophobicity or close to.2.Changing the solution concentrations or spraying times could induce the variations of total quantities and distances of micro-nano hollow particles,and influence the morphologies of sprayed surfaces.As a result,the wetting and anti-icing properties were consequently changed.Among all sprayed surfaces,i8POSS-PDMS showed the best anti-icing property.When i8POSS concentration was 10%in i8POSS-PDMS solution,we obtained superhyphobic surface with the freezing temperature of-26.3^oC,delayed freezing time of 840s,and ice adhesion of 85.7kPa by spraying once.In comparion,the almost superhydrophobic surface prepared by spraying i8POSS-E51 solution with 5%i8POSS didn’t show very low freezing temperature.But the extremely low sliding angle of water droplet on it and good mechanical properties of E51 resin indicated that i8POSS-E51 based surfaces have certain values both on fundamental research and application in anti-icing field.Highly hydrophobic surface obtaind by spraying 10%i8POSS THF solution twice showed very good anti-icing properties.The freezing temperature and delayed freezing time of water droplet on this surface were-22^oC and 1100s,respectively.3.The chemical structure of POSS had obvious effect on the preparation of superhydrophobic surfaces.It was difficult to obtain superhydrophobic surface by spraying amphipathic trisilanolisobutyl POSS（i7POSS）based hybrid solution,namely i7POSS-PDMS,or single i7POSS solution,which was quite different from hydrophobic i8POSS.Although the freezing temperature and delayed freezing time of water droplets on surface produced by spraying i7POSS-PDMS solution with 2%i7POSS once reached-21^oC and 5219s,the anti-icing performance was more likely as the result of the influences of active hydroxyl on the crystallization of water.Similar situation appeared on PVA surfaces further sparyed with single i7POSS sulutions.4.Curing temperature of PDMS or E51 had obvious influences on the self-assembly process of POSS molecules,the morphologies and anti-icing properties of final surfaces.Curing of sprayed surfaces at high temperature could not form hollow and‘open-mouth’micro-nano particles,but curing at RT could.Variation of curing temperature possiblely influence the progress of POSS molecules through temperature variation induced viscosity changes of resin.Compared with i8POSS-PDMS surfaces cured at RT,the hollow spherical particles on i8POSS-E51surfaces cured in the same condition showed obvious collapse tendency,and the latter surface showed poorer anti-icing properties.This side-fact confirmed that the direct impact of temperature on resin viscosity was the key point to the dependency of morphology on curing temperature.5.Besides the micro-nano structure,the chemical structure of PDMS,E51 and PVA can also influence the anti-icing properties of sprayed surfaces.The freezing temperature of water droplets on i8POSS-E51 and PVA-i8POSS surface was enhanced while these surfaces turned to be almost superhydrophobic,which is totally different from i8POSS-PDMS surfaces.This situation might be resulted from the increase of nucleation sites.6.SLIPS of UiO66-NH₂ grafting NWF further immersed by silicon oil shown extreme anti-icing properties never publicly reported in literatures by far.The freezing temperature of condensed water on this sureface could reach-38.9^oC,close to the homogeneous nucleation temperature of water,and the ice adhesion was only 3.1 kPa.Not only nucleation sites were covered and decreased silimar which was common for traditional SLIPS,the tremendous decrease of freezing temperature was also attributed to potential barrier increase induced by size decrease of the micro-nano particles around condensed water,which was confirmed by theoretical calculation.The optimal addition amounts of silicon oil with the viscosity of 100cst and 1000cst were 0.02g/cm² and 0.05g/cm²,respectively.7.Compared with traditional fabrication methods of anti-icing surfaces,both spraying and immersion with silicon oil used in the work had solid basis in industrial application,for the obvious advantages in procedure convenience,production cost and large-scale manufacturing.