Preparation Andapplication Of Super-hydrophobic Aerogel

Surfaces of inorganic materials such as stone and concrete are easily attach orassault by various pollutants, which will cause reduce of gloss, stains, fading of color,poor flatness and surface pulverization, resulting in poor surfaceappearance.Preparing a layer of super-hydrophobic coating of the surface wouldisolate biological contaminants and water pollutants, archives self-cleaning effect,super-hydrophobic aerogel coating will bring great influence to the surfaceself-cleaning of stone and concrete.In this paper, super-hydrophobic aerogels for preparation of super-hydrophobiccoatings is studied,and its preparation process and application performance is alsostudied. Progress of ambient pressure drying of super-hydrophobic aerogels wasstudied, including influences of gelation pH, water-glass dilution, time consuming ofpreparation phases, ion exchange and Na+, aging conditions and dring process;Preparation of super-hydrophobic aerogel powder using microemulsion method isproposed.Microemulsion formulation, influence of surfactants and co-surfactants,drying process are discussed, also discuss advantages of microemulsionmethodcomparing with massive method of preparing aerogels; The hydrophilicity/hydrophobicityof aerogels and super-hydrophobic aerogel coating performance arediscussed. The following conclusions can be obtained:(1), Using water-glass as silicon source, aerogel with bulk density of0.09g/cm3can be prepared by sol-gel method with ambient drying, the best process steps are:wager-glass is diluted with water3times and remove Na+by usingstrong acidic ionexchange resins, gelation pH from6to9, aging more than12h,solvent is graduallyreplaced with ethanol, n-hexane which with smaller surface tension, afterhydrophobic modification,wet gelcan be dried in room temperature,60℃,100℃,150℃and250℃, then lowest bulk density aerogels can be obtained.(2), Minimum apparent density0.04g/cm3, particle size of24.123μmsuper-hydrophobic aerogel powder can be prepared by microemulsion mathod. In this paper, the best process steps are: water glass was diluted with water3times andremove Na+by using strong acidic ion exchange resins, silicic acid solution of pH2~3is obtained, the silicic acid solution and kerosene are mixed at a volume ratio of2:10, hexadecyl trimethyl ammonium bromide (CATB) and n-butanol be added to formmicroemulsion,and then aqueous ammonia solution with pH~12is added for gelgelation. impurity ions and kerosene are washed and removed, after aging, solventreplacement and hydrophobic modification, wet gels can be dried and aerogel powdercan be obtained.(3), Aerogel powder with particle size24.123μm, size distributionfrom7μm to91μm and specific surface area829m2/gcan be prepared using the microemulsion, theaerogel powder have small particle size and narrow distribution, which can beobtained at room temperature in1h and do not have to dried in higher temperature.(4), Contact angle of coating prepared by super-hydrophobic aerogel powder isup to161°an excellent super-hydrophobicity, super-hydrophobic coating can maintain5.67months super-hydrophobicity in precipitation condition of WuHan.