Durable Candle Soot Icephobic Surfaces With Superwettability:Preparation And Performances

Icing issue is plaguing the entire world by affecting the residential and commercial activities.Ice formation and accretion on surfaces often bring about dramatic economic loss in energy supply and transports.Icing results accidents on road,marine and rail transportation,as well as hinders the operation of the components of aircrafts and telecommunication equipment.In addition,ice accretion and frost formation dramatically affect the performance of refrigerators and heat exchangers.Recent strategies for developing icephobic surfaces are intimately associated with superwettability.Commonly,the superwettability of icephobic materials depends on their surface roughness and chemical composition.The wettability and classical nucleation theories are used to characterize the icephobic surfaces.The superhydrophobic surfaces are used for their short contact time with small radius of water droplet and thermodynamically delay in freezing point of water.Elastomers impart icephobic behavior due to low interfacial toughness and springboard effect.Slippery liquid-infused porous surfaces(SLIPSs)eliminate the possible ice nucleation sites due to its homogeneous interface and delay the freezing time.SLIPSs(aqueous lubricating layer),amphiphilic surfaces,and anti-freezing proteins make non-freezable water due to hydrogen bonding with their respective hydrophilic groups.Organogels show extremely low ice adhesion strength and the stimuli-responsive materials are used for active anti-icing purposes.The present icephobic surfaces still have the problems of complex fabrication methods,high cost,and strong ice adhesion at low temperature.In chapter 2 of this thesis,we describe the fabrication of durable candle soot icephobic coating with RTV-1 as a low modulus binder.The heterogeneous nucleation on 20-40 nm candle soot particles and their fracture mechanism is discussed.The developed coating always shows durable Cassie-Baxter superhydrophobic state with low ice adhesion(18 kPa)and maintain the ?ice about 25 kPa after severe mechanical abrasion,30 liquid nitrogen/water cycles,100 frosting/defrosting cycles,100 icing/deicing cycles,acid/base exposure,under UV and exposure to natural freezing rain in Hangzhou.In addition,the proposed technique is time-efficient,inexpensive and suitable for large-scale applications.However,most of the icephobic surfaces did not show stability after long-term dip under the ice and maintain low ice adhesion strength below-20?.Contrary to superhydrophobic surfaces.the slippery liquid-infused porous surfaces(SLIPSs)are pressure stable,show low ice adhesion strength at subzero temperature and promote homogenous nucleation.To fabricate a pressure stable long-life slippery liquid-infused porous surface suitable porosity,roughness and chemical composition is required.The current methods to fabricate slips are complex and expensive.In chapter 3 of the thesis we demonstrate a simple way to design a non-fluorinated,long-term slippery icephobic surface of candle soot nanoparticles with low a modulus binder RTV-1.The porosity,nanoscale roughness,low energy soot particles,elasticity,strong affinity of substrate with silicone lubricant,and retention of lubricant after curing of binder RTV-1 play an important role in the stability and low ice adhesion strength at sub-zero temperature.The developed surface exhibits extreme slippery property,delay in freezing point along with ultra-low ice adhesion strength(2 kPa)and maintains it even below 7 kPa under harsh environmental conditions;90 frosting/defrosting cycles at-90?;100 liquid nitrogen/water cycles;100 icings/deicing cycles;2 months under the ice layer;2 months at 60?;9 days flow in acidic/basic water and exposure to super-cold water.In addition,the developed technique is cheap,easy to fabricate,environmentally benign and suitable for large-scale applications.Surfaces with both passive anti-icing and active deicing functionalities are very rare.However,their scalability is limited by costs,while heating is generally strongly localized to the incident light beam and the immediate vicinity of the particles.In chapter 4 of the thesis,We report on a "Slippery photothermal trap"which is passively icephobic in nature and can actively deice the surface by converting sun light to heat at the ice-substrate interface.It depends on the properties of the selected three layers:a candle soot layer act as solar radiation absorber,a magnetic nanoparticles layer act as heat spreader for lateral dispersal of sun light,and RTV insulation to reduce the transverse heat loss.Upon illumination,heat confinement at the magnetic nanoparticles layer leads to rapid increase of the surface temperature,ice start to melt and silicone lubricant facilitates the ice removal.Lateral thermal spreading overcomes the unavoidable shadowing of certain areas from direct illumination.The slippery photothermal trap removed the frozen droplet within 40 seconds upon the illumination of sun light and the frozen droplet(10?l)was completely converted into water after 7-minutes illumination of solar light at-20?.The developed slippery photothermal trap also melted the fully covered frost layer within 100 seconds at-20?.The designed slippery photothermal coating showed outstanding active and passive anti-icing performance at subzero temperature.