Fabrication Of Super Hydrophobic Surface And Their Anti-icing Properties

The aircraft engine pre-cooler is with extremely strong continuous refrigerating capacity and can reduce the temperature of air flow from 1600℃ to 50℃ in extremely brief period,which makes the engine reach a higher air compression rate and doubles the speed of jet-propelled engine.When the air flow temperature drops below zero,the surface of heat exchanging pipes appears to freeze.Because the thermal conductance effect of ice is rather low,this greatly reduces the thermal conductance effect on engine surface.Therefore it is a must to carry out anti-icing treatment to the surface of heat exchanging pipes of the pre-cooler.The super-hydrophobic material is both anti-icing and ice-thinning as the anti-icing material,with relatively strong application value.This paper,with the base material of common copper of excellent heat-conducting property,used chemical etching to corrode its surface,to obtain fragmentary rough structure and the secondary structure of petal-shaped prominence.By controlling of etching time,the rough surface structures of different roughness were prepared.The copper plate after etching turned from hydrophilic surface to super-hydrophilic surface,in conformity with Wenzel theory.The copper plate surface after etching was modified with super-hydrophobic coating by spraying and the coating completely covered the rough structure after etching.The coating surface was not compact with a lot of porous structure.By analyzing void density on coating surface with 1-bit algorithm,it was found that the more the etching time of original copper plate,the denser the void density was.After etching,the surface of the copper plate turned from super-hydrophilic surface to super-hydrophobic surface,with the maximum contact angle to be 151°.Because the relatively-thick coating with viscous super-hydrophobic materials covered the rough structure of surface after etching,the surface was modified with small molecule fluorosilane as finish.The coating of fluorosilane was relatively dense to basically maintain the fragmentary microscopic structure on the surface of the copper plate.But because of the coating’s cementing action,the fragments connected together,especially that the formerly prominent petal shaped structure had the intervals fully filled.The copper plate after etching modified by fluorosilane turned from super-hydrophilic surface into super-hydrophobic surface,with the maximum contact angle to be 159°.The super-hydrophobic material prepared by chemical etching had disordered surface,impossible to obtain surface roughness factor and other pattern parameters.Therefore,silicon with good micro-nano processability was as the base material and laser etching technology was utilized to control and prepare ordered hexahedron array,and black silicon process technology was used to prepare nano scale columnar structure.By obtaining the actual parameters of the surface micro-structure with micro-structure measurement,substituting Wenzel and Cassie model to calculate theoretical contact angle and compare the actual contact angle,it studied the influence of surface micro-structure on super-hydrophobic performance.It primarily set up testing device for cold surface icing and explored the method to study the influence of contact angle to anti-icing performance.