5770

5385

كارشناسي ارشد

شناسايي و انتخاب مواد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1389

[چهارده]،132ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

فتح ا... كريم زاده، محمدحسين عنايتي

29/1/90

محمدحسن عباسي، پرويز كاملي

مهندسي مواد

ID5385

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Synthesis of CoAl Al2O3 nanocomposites and their thermodynamic and kinetic analysis Seyedeh Narjes Hosseini Golenarges63@yahoo com February 22 2011 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi F Karimzadeh Assoc Prof Karimzadeh f@cc iut ac ir M H Enayati Assoc Prof ena78@cc iut ac irAbstractIn this research synthesis of the nanostructured CoAl intermetallic compound and CoAl Al 2O3nanocomposites were investigated by mechanical alloying MA The phase transformations andmicrostructural changes were studied by X ray diffraction XRD scanning electron microscopy SEM transmission electron microscopy TEM and differential thermal analysis DTA The results showed thatMA of the Co50Al50 powder mixture resulted in the direct formation of the nanostructured fully ordered B2 CoAl intermetallic compound by gradual mechanism Thermodynamics analysis using Miedema modelconfirmed that the formed phase had the minimum free energy By incresing MA time disordering of theCoAl compound was occurred with triple defects formation mechanism and long range order LRO parameter reduced to a constant value of 0 82 A general equation was proposed for description of graingrowth kinetics of the nanostructured CoAl compound at temperatures above 0 5 T m During developmentof CoAl Al2O3 nanocomposites it was observed that thermite reaction was occurred abruptly betweenCo3O4 and Al reactants and Al2O3 Co nanocomposite was synthesized Thermal analysis results showedthat the reduction reaction of Co3O4 completed in two steps with formation of the intermediate phase ofCoO Mechanical activation of the initial powder mixture decreased the reduction reaction temperaturefrom 1041 to 869 C The activation energies of reduction reactions calculated using five different model free methods were determined to be about 340 5 and 440 7 kJ mol on a conversion fraction of 0 5 Thereaction mechanism was determined to be one dimensional phase controlled reactions and threedimensional surface reactions The CoAl Al2O3 nanocomposites containing 10 25 and 45 vol Al2O3 werefabricated by MA of different ratios of Co 3O4 Al Co powder mixtures The results showed that thereduction of Co3O4 and CoAl formation reactions occurred simultaneously in a combustion mode Thepresence of the Al2O3 nanoparticles in the nanostructured CoAl matrix decreased the grains growth duringheat treatment Keywords Nanocomposites Intermetallics Mechanical Alloying Kinetic Thermodynamic

فتح ا... كريم زاده، محمدحسين عنايتي

محمدحسن عباسي، پرويز كاملي