4610

4338

كارشناسي ارشد

مواد

اصفهان : دانشگاه صنعتي اصفهان ، دانشكده مواد

1387

ده، 95، [II] ص: مصور ، جدول ، نمودار

ص. ع. به: فارسي وانگليسي

احمد ساعتچي ، كيوان رئيسي

88/5/21

محمد علي گلعذار ، بهزاد رضايي

1396/09/13

كتابنامه

مهندسي مواد

ID4338

به فارسي وانگليسي : قابل رويت در نسخه ديجيتال

The passivation and deposition mechanisms in electrodeposited nano and micro crystalline Ni electrodeposits Mohammadreza Zamanzad Ghavidel m ghavidel@ma iut ac ir March 15 2009 Department of Materials Engineering Isfahan University of Technology 84156 83111 Isfahan IranDegree M Sc Language FarsiDr Ahmad Saatchi Prof Supervisor E mail asaatchi@cc iut ac irDr Keyvan Raeissi Assoc Prof Supervisor E mail k raeissi@cc iut ac irAbstractNickel nanocrystalline coatings were electrodeposited by using direct and pulse current in a Watts type bath The current densities were 2 10 30 50 and 100 mA cm 2 and the substrates were with 111 and 400 texture Scanning electron microscopy SEM and X ray diffraction analysis XRD were employed to study the effectof electrodeposition current density on morphology texture and grain size of deposits The results showed thatthe texture and morphology of deposits were changed at 30 and 50 mA cm 2 on the substrates with 111 and 400 texture components respectively The texture of deposits were changed from 220 to 200 and themorphology was changed from spherical to mixed morphology pyramidal and blocky by increasing the currentthe current density This is attributed to the decrease in hydrogen adsorption at higher current density In pulseelectrodeposition the change of morphology and texture on substrate with 111 texture component waspostponed to higher current density and happened at 100 mA cm 2 The grain size of deposits on substrate with 111 texture component was higher than that on substrate with 400 texture component because of highernucleation rate occurs on substrate with 111 texture component Because the hydrogen adsorption and the Niions concentration are both increased on the substrate during the pulse current electrodeposition the depositswith smaller grain size were obtained Electrochemical impedance spectroscopy EIS showed that the hydrogenadsorption occurred on the substrate surface had a great role on the subsequent change of texture andmorphology Potentiodynamic polarization tests showed that the nanocrystalline deposits had higher corrosion and pittingresistances than microcrystalline deposits in 3 5 NaCl solution Indeed it is concluded that the morphology ismore responsible to obtain more corrosion resistance in nanocrystalline coatings as seen by forming blockylike morphology the pitting resistance is increased These results are in good agreement with results obtainedfrom cycle polarization readings The mott schottky plots showed that the passive layer formed on nano and microcrystalline deposits was an n type semiconductor The results showed that the coatings with less pitting resistance is contained more oxygenvacancies in their passive film structure It was concluded that the break down of passive layer and pittingformation are conformed by point defect model PDM Key WordsNickel nanocrystalline electrodeposition corrosion passive layer mott schottky

احمد ساعتچي ، كيوان رئيسي

محمد علي گلعذار ، بهزاد رضايي