بررسي خواص مكانيكي نانو كاتاليزورهاي متخلخل با استفاده از شبيه سازي ديناميك مولكولي

چكيده انگليسي :

Study of mechanical properties of nanoporous catalysts by molecular dynamics simulation Maryam Mikelani M mikelani@ma iut ac ir June 15 2016 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language PersianDr Masoud Panjepour Assoc Prof Supervisor Email panjepour@cc iut ac irDr Aboozar Taherizadeh Asist Prof Supervisor Email a taheri@cc iut ac irAbstractFoam catalysts are perfect choice for heat and mass transfer application due to their unique propertiessuch as low density high specific strength and high specific surface Dimensional stability and goodmechanical properties as well as physical and chemical properties of catalysts are important Hence the size distribution and shape of porosity are the most important factors on stability of the chemical physical and mechanical properties that the review of these factors seems to be essential for designingcatalysts According to the matter the effective parameters in mechanical properties such as porosity pore size temperature and strain rate along the loading were investigated For this purpose two typesof geometry for foam with cylindrical geometry and ligament foams were made using X ray microtomography models Then the nanofoams were subjected to uniaxial tensile strain along the 100 axis Also the potential and kinetic energy as well as the stress distribution of nanofoams along theloading were investaigated On the other hand by comparing the potential and kinetic energy curveswith the stress and potential distribution of nanofoams along the loading a standard way to calculatethe yield stress and the ultimate strength was achieved On the other hands the results showed that theYoung s modulus yield strength and ultimate tensile strength were increased by decreasing theporosity and pore size separately Also the effect of temperature and strain rate on tensile loadingwas shown that the Young s modulus yield strength and ultimate tensile strength of foams weredecreased with an increase in temperature But the effect of strain rate was shown that the stressdistributions were changed with increasing strain rate and the Young s modulus yield strength andultimate tensile strength were increased In fact with an increase in strain rate or temperature theradial distribution function RDF curve represented that the crystalline phase had transformed intothe amorphous phase In addition the study of fracture mechanisms of two different geometrics offoams showed that the fracture of nanofoam with cylindrical geometry was done by the stresslocalization nucleation and growth of cracks on the surface of pores But in ligament foams fracturemechanisms is governed by both the ligament size and the joint size due to surface effect of nanofoam in diferent ligament size Finaly the results of simulations were compared with the modifiedGibson Ashby mathematical model and the fracture mechanism of nano foam in different porositywere obtained Keywords Nanoporous Porosity and Pore size Aluminum single crystal Mechanical behavior Molecular dynamics simulation

ميكلاني، مريم

بررسي خواص مكانيكي نانو كاتاليزورهاي متخلخل با استفاده از شبيه سازي ديناميك مولكولي

نانو فوم ها , درصد و اندازه تخلخل , تك كريستال نانو آلومينيوم