تاثير مشخصات ساختاري سطح آلومينيوم خالص بر زاويه تماس آن با آب

چكيده انگليسي :

79Effects of structural features of pure aluminum on its contact angle with water Simin Nosouhian s nosouhian@ma iut ac ir 2017 06 17 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor B Niroumand Prof behzn@cc iut ac irAbstractControl of wetting angle between solid surfaces and water is a significant task undertaken indifferent industries to improve surface properties of materials exposed to humidity water and ice Hydrophobic surfaces have attracted a lot of attention in recent years due to their effects oncorrosion wear and icing reduction of solid surfaces This is primarily done using proprietaryhydrophobic coatings The main challenge for such coatings is their wearing off with time Thiscan be overcome if the hydrophobicity can be induced by the stable microstructural features of thesubstrate In order to investigate the effects of such microstructural features as grainscrystallographic orientation and morphology and also the effects of environment and surfacepreparation method on the wetting angle of water on the surface of commercially pure aluminum adirectionally solidified sample was cast and large samples were cut from it in longitudinal transverse and 45 degree directions The preferred orientation of both longitudinal and transversecross sections were determined to be 200 and that of 45 cross section was 111 Each sectionwas separately etched and wetting angle and roughness measurements were carried out on givenpositions of the surfaces immediately and 1 7 and 15 days after chemical etching The surfacepositions examined included inside a large grain on a single boundary on a grain boundary triplepoint and on an area with large number of grain boundaries Morphologies of the defined pointswere also studied by scanning electron microscopy SEM 1 7 and 15 days after etching In orderto study the effects of surface preparation method all mentioned steps were carried out on thepolished and etched longitudinal cross section with 200 texture as well The results showed thatcorrosion caused by etching in a strong Cl ion bearing solution created deep multi layered andangular tunnels on the planes with 200 texture whereas on the planes with 111 texture wideshallow cubes and surface with lower roughness were observed It was concluded that the preferredtexture of the surfaces having identically composition could affect their morphology and roughnessinduced by etching In all of the positions studied on the etched surfaces the surface behaviorchanged from hydrophilic to hydrophobic after one or two days of air exposure For example theinside the grain wetting angle on the longitudinal section increased from 18 to 100 This seems tobe due to absorption of organic compounds on the surfaces with time The ascending rate of thecontact angle was gradually decreased by saturation of the surfaces with organic compounds sothat in the 15th day of air exposure the contact angle of all surfaces became steady Considering thesharper rate of increase in the contact angle of surfaces with 200 orientation it seemed that therate and amount of absorption of organic compounds by the oxide layer on the 200 texture wasmore than that of the surfaces with 111 texture Based on the results it seems that wettingbehavior of all the selected areas on the three cross sections follow Cassie Baxter model It wasconcluded that grains crystallographic orientation and morphology amorphousor crystalline state of the surface aluminum oxide layer atmosphere exposure and SiO2 particlesattachment on the surface affect wetting angle of pure aluminum surfaces with water Keywords Metal matrix composite Aluminum Titanium aluminide Accumulative roll bonding Annealing

نصوحيان، سيمين

تاثير مشخصات ساختاري سطح آلومينيوم خالص بر زاويه تماس آن با آب

زاويه ترشوندگي , آب گريزي , آلومينيوم خالص , زبري سطح , بافت , ريزساختار سطحي , تاثيرات محيطي