7148

469 دكتري

دكتري

مواد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1391

پانزده،129ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

احمد منشي، محمدحسن عباسي

3/8/91

علي نعمتي،محمدرضا رحيمي پور، علي سعيدي

مهندسي مواد

ID469 دكتري

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Preparation and characterization of B 4C SiC nanocomposite by microwave and SPS and creep behavior study Bibi Malmal Moshtaghioun Mali moshtagh@gmail co m 2012 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran1 th Supervisor Ahmad Monshi a monshi@cc iut ac ir2 nd Supervisor Mohammad Hasan Abbasi abbasi32@cc iut ac irAdvisor Fath Karimzadeh kari mzadeh f@cc iut ac irDepartment Graduate coordinator Kei van Raeissi AbstractThis study aimed at preparation of B 4 C SiC nano composites and also characterization andcomparing with pure one In first step sinterability of boron carbide and mechanical properties of itwere studied and also the influence of adding silicon carbide nanoparticles that were synthesized inthis study as well as graphite to B4 C matrix was investigated In this regard spark plasma sintering SPS was used The results showed fullu dense boron carbide sintered at 1700 C for 3 min asoptimal conditions However with the highest hardness resulting from lower values of the averagegrain size fracture toughness did not improve considerabley The fracture toughness is greatlyimproved in composites compare to the pure boron carbide specimens and the improvement ismore notable in composite without graphite Improvement in the fracture toughness of compositescan be attributed to activating of toughening mechanisms from the influence of SiC nanoparticlesdistributed in B4 C matrix on the crack path The addition of SiC particles as a second phase to B 4 Cmatrix also has strong influence in fracture surface For fully dense pure boron carbide almost all ofthe grains fractured transgranularly However in nanocomposites that sintered at same conditionthe B4 C matrix fractured transgranularly whereas intergranular fracture occurred at the interfacesbetween SiC grains and B4 C grains Silicon carbide nanoparticles as a reinforcement synthesizedby carbothermic reduction of silica in furnace and later in microwave Results showed SiCnanoparticles were produced in furnace at 1450 C for 60min and in microwave at 1200 C for 5min Finally for the first time high temperature deformation of boron carbide and B 4 C SiCnanocomposite were presented Plastic deformation is admitted to be produced by dislocationactivity and grain boundary sliding The presence of solute atoms seems to play a crucial role onthe main creep characteristics in this material On the other hand the presence of an increasingcavitation is consistent with limited grain boundary sliding Keywords SiC B4 C Microwave processing Spark plasma sintering Mechanical properties Professor Depart ment of Materials Engineering Isfahan University of Technology Isfahan Iran Associate Professor Department of Materials Engineering Isfahan University of Technology Isfahan Iran

احمد منشي، محمدحسن عباسي

علي نعمتي،محمدرضا رحيمي پور، علي سعيدي