تشكيل و بررسي رفتار خوردگي و تريبولوژيكي پوشش الكترولس كامپوزيتي نيكل-فسفر-نانو لوله كربني

چكيده انگليسي :

Formation and Investigation of Corrosion and Tribological Behavior of Electroless Ni P CNT Composite Coating Mostafa Alishahi alishahi@ma iut ac ir Date of Submission 2009 07 29 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Seyyed Mahmud Moonir vaghefi vagh mah@cc iut ac irAbstract Carbon nanotubes CNTs have super strong mechanical characteristics and unique hollow nanotubestructure and are believed as very ideal materials for fabricating the excellent composites In this study Ni P CNT composite coatings with different contents of carbon nanotube 0 5 2 5 wt on the surface ofcopper was proposed by electroless plating The Scanning Electron Microscopy SEM was used to characterizethe coatings The SEM results showed that the thickness of the coatings was about 30 m and the depositedcoatings had nodular features with a typical cauliflower like structure and uniformly dispersed CNT in thenickel matrix The effects of CNT concentration in the bath on the microstructure of the composite coatings CNT content in the composite coatings and the hardness of composite coatings were studied It was found thatwith increasing CNT concentration both the CNT content in the composite coatings and the hardness ofcomposite coatings increased at first and then decreased The microstructural characterization was done bymeans of x ray diffraction It was found that the heat treatment induces structural changes As depositedcoatings exhibit broadened x ray reflections which indicates a semi amorphous structure Heat treatmentdecreased the amorphous phase In addition the final equilibrium phases were Ni3P and Ni crystals with ananocrystalline size The maximum hardness was achieved in the specimens heat treated 400 C for 1 5 hours The reason could be the formation of stable intermetallic Ni3P phase at this temperature which acts as aprecipitation hardener The corrosion behavior of the composite coatings was evaluated by polarization curvesand electrochemical impedance spectroscopy in 3 5wt NaCl solutions at room temperature It was found thatthe corrosion resistance of Ni P CNT composite coatings is excellent in comparison with that of Ni P coatings According to the results with increasing the CNT concentration corrosion rate decreases at first and thenincreases The results showed that the incorporation of CNT in Ni P coatings is advantageous for formation ofbetter passive films The corrosion resistance of the coatings indicates that increasing the temperature to 400 Cleads to an increase in corrosion resistance followed by a decrease in higher temperatures Heat treatment at thetemperatures less than 400 C leads to the crystallization of the amorphous phase This phenomenon results inthe increase in the number of grain boundaries which is suitable for nucleation of passive film Therefore theheat treatment of electroless Ni P CNT composite coatings at the temperatures less than 400 C forms denserpassive films and significantly increases their corrosion resistance The wear behavior of the coatings wereinvestigated using a pin on disk test rig and wear rate along with the friction coefficient were reported Frictionand wear tests were conducted at a sliding speed of 0 014 m s 1 and at an applied load of 15 N Theexperimental results indicated that increasing the CNT content in the coatings displays better tribologicalperformance due to self lubrication and unique topological structure of CNT Within the range of weightpercentage of CNT from 0 to 11 the wear rate and the friction coefficient of the composite coatings showed asteadily decreasing trend with increasing weight percentage of CNT KeywordsCarbon nanotube Electroless plating Composite Corrosion Wear Friction coefficient

عليشاهي، مصطفي

تشكيل و بررسي رفتار خوردگي و تريبولوژيكي پوشش الكترولس كامپوزيتي نيكل-فسفر-نانو لوله كربني

سايش , غلظت CNT