| Biomimetical fabrication of superhydrophobic wood can effectively decrease the interaction between wood and moisture,thus avoiding a series of problems such as deformation,cracking,decay,mildew,discoloration,and degradation caused by water absorption.Meanwhile,it can endow superhydrophbic wood with conductive,flame retardant,antibacterial,magnetic,self-cleaning,and other functions,which important for the high value-added application and functional extension of wood.However,the simple and effective method as well high physical and chemical stability are key factors for the practical application of superhydrophobic wood.Based on bionic principal,superhydrophobic wood were fabricated by vapor-assisted migration method.From physical and chemical perspectives,porous-buffer structure and alkaline liquid driven approach were demonstrated to improve mechanical robustness of superhydrophobic coating and the bonding strength between superhydrophobic coating and wood.Meanwhile,the versatility of vapor-assisted migration method towards nanoparticles,modifiers,and substrates was studied.The fabrication mechanism of superhydrophobic surface based on vapor-assisted migration method was revealed.The enhancement mechanism of mechanical stability was also analyzed.Moreover,superhydrophobic wood surface with self-healing,photo-degradation,fireproof was prepared.The mechanism of photocatalytic property enhanced by superhydrophobicity and self-healable behavior with assistance of wood fiber movement were studied.The main conclusions are as follows:(1)Superhydrophobic wood surface with a contact angle of?153° and sliding angle of 1.80 was achieved by vapor-assisted migration method reported in this work.The growth,modification,and assemble of nanoparticles in 3 dimensional space can be controlled by vapor-assisted migration,which contributed to the successful fabrication of micro/nano hierarchical structure and low surface energy layer to support superhydrophobic surface..Superhydrophobic wood also demonstrated high resistance towards coffee,milk,red wine,soy sauce,and cola.Meanwhile,for the different type of nanoparticle(such as SiO2 and BiOCl),modifier(e.g.organosiloxane and fluorine-containing modifier)and substrate materials(e.g.glass and bamboo),it has versatile applicability.(2)Based on vapor-assisted migration method,porous-buffer structure with epoxy as skeleton was prepared via heat-driven manner.Such structure integrated superhdyrophobic structure and enhancement structure in one system.It had a contact angle of?156° and sliding angle of less than 10°,and was also able to enhance the mechanical stability of superhydrophobic wood.After a 300 cm abrasion length at the pressure of 2 kPa,160 cm abrasion length at the pressure of 5 kPa,and 110 cm abrasion length at the pressure of 10 kPa,respectively and withstanding sequential destruction including wearing,such as pressing,brushing,knife cutting,sandpaper polishing,etc.,as well as a person with 60 kg stepping on its surface for 1 hour,the superhydrophobic woods based on porous-buffer structure were not lost superhydrophobicity,as indicated by a contact angle of more than 150° and sliding angle of less than 10? on their surface,showing excellent abrasion resistance and mechanical strength.Superhydrophobic porous-buffer structure can simultaneously improve the strength of superhydrophobic coating and its bonding strength with wood,as well effectively disperse the impact force,which contributed to the impressive mechnical stability.(3)Based on vapor-assisted migration method,mechanical stability of superhydrophobic wood was improved by control of surface active site and micro/nano structure with assisatnce of alkaline.The results show that superhydrophobic surface could stand 270 cm sandpaper abrasion length when prepared by solution with 24 mL 0.1 mol/L sodium hydroxide.However,in the same condition,the superhydrophobic surface could stand 60 cm sandpaper abrasion length when prepared by solution with 6 mL 0.1 mol/L sodium hydroxide solution.Fourier infrared spectrometer(FTIR)and scanning electron microscope(SEM)analysis show that sodium hydroxide can control the amount of hydroxyl from wood surface and reaction system,and then promote the growth and modifictaion of silica as well the fabrication of superhydrophobic structure composed by high density hydrophobic silica.Such structure with high density hydrophobic silica is favor of mechanical stability via regeneration mechanism.(4)Multifunctional superhydrophobic wood with self-healing,photo-degradation,fireproof was prepared via controll of function components in reaction system.The as-prepared superhydrophobic wood can repair various damages based on "thermal response characteristics" of wood fiber and self-healing agents,including but not limit to the degradation of low surface energy material,structural wear,and large cuts.Additionally,it can degrade rhodamine B(Rh B)with high efficiency and stability.The results show that the photocatalitic degradation efficiency was more than 97%at 14th degradation cycle.More importantly,it was found superhydrophobicity can improve the photocatalytic efficiency by>10%.Photocatalytic property can improve superhydrophobic stability towards organic pollutants.Moreover,superhydrophobic wood with excellent fire resistant performance was demonstrated.Compared with that of untreated wood,its second peak heat release rate and the total heat release was reduced by 49.3%and 34.5%,respectively.(5)The superhydrophobic treatment had significant effect on dimension stability,mechanical property,thermal stability,and etc.of wood.Superhydrophobic treatment can improve the dimension stability of wood,demonstrated by that the mass change ratio and volume change ratio of superhydrophobic wood were reduced by 72.38%and 29.33%,respectively compared with that of untreated wood.Besides,the time to the maximum change in dimension was increased about 20 days.Superhydrophobic treatment significantly influences the mechanical properties of wood.After superhydrophobic treatment,the bending strength,modulus of elasticity in static bending,compressive modulus of elasticity parallel to grain and compression strength perpendicular to grain of the superhydrophobic wood were reduced by 16.05%,4.18%,39.93%and 27.11%,respectively.However,the compressive strength parallel to grain and modulus of elasticity in compression perpendicular to grain are improved by 21.94%and 11.11%.Superhydrophobic treatment significantly improves the thermal stability of wood,which indicated by that the initial pyrolysis temperature was increased by 100?,the temperature of the maximum weight loss rate was increased by 30?,and the residual amount of material was increased by 6.45%.Superhydrophobic treatment can enhance the UV durability of wood.After superhydrophobic treatment,the composite chromatic index change of wood was reduced by 72.5%after long time UV irradiation. |
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