4224

3995

كارشناسي ارشد

شناسايي، انتخاب و ساخت مواد

اصفهان : دانشگاه صنعتي اصفهان، دانشكده مواد

1387

ده، [88]، [II] ص. : مصور، جدول، نمودار

ص. ع. به : فارسي و انگليسي

محمد حسين عنايتي، كيوان رئيسي

22/7/1387

احمد ساعتچي، ابراهيم حشمت دهكردي

مهندسي مواد

ID3995

به فارسي و انگليسي : قابل رويت در نسخه ديجيتال

AbstractNanocrystalline Co P coatings prepared by pulse current electrodeposition have currentlyreceived considerable attraction In this work nanocrystalline Co P coating was produced by DCElectrodeposition The effect of current density in range of 150 250 mA cm2 on characteristicsof coating was investigated It was found that by increasing current density the phosphorouscontent of coating reduced from 2wt to 1wt Also the grain size of coating increased from10nm to 16nm as current density increased from 150 to 250 mA cm2 However the morphology texture as well as corrosion behavior in 3 5 NaCl of coating did not affect by currentdensity Moreover the effect of annealing on characteristics of nanocrystalline Co 1 2wt andamorphous Co 9 11Wt was studied The results showed that after annealing the grain size andtexture of nanocrystalline coating remained unchanged whereas the amorphous coatingtransformed to the nanocrystalline structure It was found that the relative intensity basal planefor coating obtained from crystallization of amorphous coating is significantly higher than thatfor nanocrystalline coating Moreover the hardness of both coating increased after annealing asa result of formation of Co2P and CoP precipitates This increase was higher for amorphouscoating due to its high phosphorous content and therefore higher fraction of Co2P and CoPprecipitates Tafel polarization tests of the coatings in 0 1M H2SO4 solution revealed that theamorphous coating has better corrosion resistance compared to nanocrystalline one Corrosionresistance of both coatings in this solution decreased after annealing Neither nanocrystallinenor amorphous coatings did not passivate in 3 5 NaCl or 0 1M H2SO4 solutions but both ofcoatings showed an active passive behavior in 10 NaOH solution Passive current density ofamorphous coating was higher that for than nanocrystalline coating In addition the passivecurrent density of amorphous coating decreased remarkably after annealing but in the case ofnanocrystalline coating this decrease in passive current density was too smaller Also the resultsshowed that the adhesion of the coatings to the substrates prepared by electropolishing is weakbut by substrate activation in 25 HCl adequate adhesion can be achieved Cross section studyof the coatings revealed that there is no crack and porosity in the structure

محمد حسين عنايتي، كيوان رئيسي

احمد ساعتچي، ابراهيم حشمت دهكردي