عنوان :
بررسي ترموديناميكي رشد دانه در ساختار نانو كريستالي فلزات به همراه شبيه سازي هاي اتمي
مقطع تحصيلي :
كارشناسي ارشد
گرايش تحصيلي :
شناسايي و انتخاب و روش ساخت مواد
محل تحصيل :
اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد
صفحه شمار :
ده،132ص.: مصور،جدول،نمودار
يادداشت :
ص.ع.به فارسي و انگليسي
استاد راهنما :
مسعود پنجه پور، غلامرضا آريانپور
توصيفگر ها :
مدل معادله حالت , مدل تقريب شبيه هارمونيك دباي , مدل سانگ , شبيه سازي مونت كارلو , شبيه سازي ديناميك مولكولي
تاريخ نمايه سازي :
29/5/90
استاد داور :
محمد حسن عباسي، مهدي احمديان
چكيده فارسي :
به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي
چكيده انگليسي :
Thermodynamic Study of Grain Growth in Nanocrystalline Structure of Metals with Atomistic Simulations Sayyed Ali Sabeti Email Address sa sabetivarzane@ma iut ac ir Date of Submission April 30 2011 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Languge FarsiSupervisor s Name and Email Address M Panjepour panjepour@cc iut ac irG Aryanpour aryanpour@cc iut ac irAbstractIn recent years the importance of nanocrystals has attracted the attention of many researchers The reason is the uniqueproperties of nanocrystals compared with conventional materials The main origin of their excellent properties is thehigh fraction of grain boundaries and consequently high energy content On the other hand these materials have noproper stability even at room temperatureand reduce their energy through grain growth Therefore thermodynamicstudy of the grain growth and research about how we can stop this process and stabilize the nanocrystals to keep theirunique properties are very important In this research for the study of grain growth process in nanocrystalline metals the dilated crystal model was used to obtain grain boundary s thermodynamic parameters Then the free energy ofgrain boundary was calculated versusexcess volume for nanocrystalline Palladium using Equation of State EOS Quasi harmonic Debye Approximation QDA and Song s models Plotting of thermodynamic diagrams based on EOSand Song s models showed that by reducing the grain size of Palladiumtoa critical value the nanocrystal becomesmetastable and the grain growth stops But based on QDA model the stoppage of grain growth was impossible Toevaluate these results Monte Carlo and molecular dynamics simulation methods were used Results of both methods confirmed the predictions of EOS and Song s models and rejected the results of QDA model Also the study oftemperature effect on the mentioned diagrams showed that by the increase of the temperature the critical grain size isincreased and the stoppage of grain growthis facilitated Subsequent simulation results confirmed this procedure andshowed that EOS model has more accurate predictions compared with Song s model Then the critical temperatures ofnanocrystalline Palladium for the stoppage of grain growth in each grain size was calculated using simulation Also comparing these results with the EOS results a modified equation was proposed for the correlation of the criticalexcess volume and the critical grain size To ensure the results obtained from the performed simulations poly crystalsimulations also was carried out via two different methods and the results showed that Voronoi tessellation method forthe generation of poly crystals has no proper outcome suitable for grain growth simulations but the results of meltgrowth method matches the previous results Finally the grain growth in poly crystalline iron was simulated Theresults showed that the Palladium s obtained results are true for iron too Key Words Nanocrystalline metals Thermodynamic of grain growth Equation of state model Quasi harmonicDebye approximation model Song s model Monte Carlo simulation Molecular dynamicsimulation
استاد راهنما :
مسعود پنجه پور، غلامرضا آريانپور
استاد داور :
محمد حسن عباسي، مهدي احمديان
