پديد آورنده :
كثيري عسگراني، مسعود
عنوان :
اثر فعال سازي مكانيكي برفرايند كربوكلراسيون دي اكسيد زير كونيوم
محل تحصيل :
اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد
صفحه شمار :
چهارده،124ص.:مصور،جدول،نمودار
يادداشت :
ص.ع.به فارسي و انگليسي
استاد مشاور :
محمدحسن عباسي
توصيفگر ها :
زيركونيا , آسيابكاري , كلراسيون
تاريخ نمايه سازي :
22/9/88
استاد داور :
اسكند كشاورز علمداري، جليل وحدتي خاكي،مسعود پنجه ور
كد ايرانداك :
ID267 دكتري
چكيده فارسي :
ب فارسي و انگليسي: قابل رويت در نتسخه ديجيتالي
چكيده انگليسي :
Effect of Mechanical Activation on Carbochlorination of Zirconium Oxide Masoud Kasiri Asgarani kasiri@ma iut ac ir 3 October 2009 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Ali Saidi Prof Mohammad Hasan Abbasi Prof AbstractChlorination and carbochlorination of zirconium oxide under isothermal and non isothermalconditions along with the effects of mechanical activation on these issues were studied Evaluation ofthe samples were carried out using XRD TEM SEM TG and BET techniques The effect ofmechanochemical treatment on phase transformations of monoclinic zirconia via high energyplanetary ball mill at different milling times was studied By using quantitative phase analysis throughx ray diffraction and internal standard of LiF the most proper conditions of milling were specified atball to powder weight ratio of 20 and milling speed of 600 rmp for balls with 20mm diameters Mechanical treatment during the milling resulted in fine grains increase of lattice strain phasetransformation to unstable tetragonal t and cubic c TEM and XRD studies revealed the existence ofprominent amounts of amorphous phase which had been produced during milling The decrease ofspecific surface estimated by BET at long milling durations reveal agglomeration of zirconia with thehelp of the amorphous phase as binder Mechanical treatment extremely increased reactivity ofzirconia with chlorine gas chlorination Also annealing of milled zirconia in Chlorine atmosphereresulted in formation of anionic vacancies crystallization of amorphous phase and its transformationinto cubic and tetragonal phases and the increase of stability temperature of such phases to 800 C and1000 C respectively Under these conditions the low border energy of the grains and the existence ofoxygen vacancies play an important role in the stability of tetragonal and cubic phases By usingthermogravimeter which was designed and manufactured for the corrosive chlorine atmosphere TGexperiments were carried out for carbochlorination of zirconia in a non isothermal way with thespeed of 12 degrees per minute and chlorine flow of 60ml min The kinetic of carbochlorination wasstudied by Coats Redfern method and it was revealed that carbochlorination of unmilled zirconium isa chemical control reaction with an activation energy of 64kcal mol and 9 26 108 min 1pre exponential factor Through mechanical activation of zirconium for 30 60 and 80 hours the startingtemperature of carbochlorination decreases from 912 C to 881 C 720 C and 620 C respectively themechanism remaining a chemical control reaction Because of activation process both the activationenergy and 1pre exponential factor will decrease The obtained results showed that such decreases aredue to phase transformations caused by mechanical activation In other words reactivity of tetragonaland cubic phases which have been formed by mechanochemical process is more than that ofmonoclinic phase Key Words Zirconia Mechanochemical Chlorination Carbochlorination Thermogravimetery
استاد مشاور :
محمدحسن عباسي
استاد داور :
اسكند كشاورز علمداري، جليل وحدتي خاكي،مسعود پنجه ور
