اثر فعالسازي مكانيكي پودر SiO2 در توليد كامپوزيت Al2O3/SiC به روش سنتز خود انتشار دماي بالا ﴿SHS

چكيده انگليسي :

۷۲Effect of Mechanically Activated SiO2 Powder on Fabricated of Al2O3 SiC Composite by Self Propagating High Temperature Synthesis SHS Method Yahya Mohammad Ali Sharifi y m a sharifi@ma iut ac ir 2012 04 23 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiH Edris Professor supervisor h edris@cc iut ac irAbstractThe production costs of refractory materials composites and some intermetallic ternary compounds bytraditional and conventional industrial methods that in which the because of high temperature furnacesrequirements and time consuming methods are very high However the self propagation high temperaturesynthesis SHS as a promising economical and alternative route can be used to produce these kinds ofmaterials The SHS process is a kind of controlled combustion synthesis and in which wide range of uniquematerials can be produced with high exothermic reactions between powder compounds On the other word the SHS process is a self energy consume process In the SHS process the generated heat of raw materials isutilized to progressive of reaction Also mechanical activation can be used to eliminate some parameterssuch as additives to optimize the physical and mechanical properties of products to increase the activity ofraw materials and to improve the SHS process In the mechanical activated SHS process the effectiveparameters of mechanical activation such as the temperature the milling time the weight and the type ofballs and others have great effects on the process Al2O3 SiC composite is on of the ceramic materials thatcan be fabricated by the SHS process Because of some features such as mechanical thermal and tribologicalproperties this composite is an attractive candidate for cutting tools abrasive materials and high temperatureapplications Therefore in this study Al2O3 SiC powder composite has been produced by the self propagation high temperature synthesis SHS using Al SiO2 and C powders as raw materials In this work in order to eliminate the additives such as KNO3 and polyvinyl alcohol the raw powders have beenmechanically activated Because of some problems concerning the mechanical activation of aluminum andcarbon powders only SiO2 powder has been mechanically activated The stoichiometry ratio of SiO2 Al andC powders was selected as 3 4 3 In this study also the effect of the molar ratio of carbon as well asmechanical activation has been investigated The effect of some parameters such as the mechanical activationtime and carbon content on the products of SHS process has been investigated via XRD SEM and thermalanalysis of combustion front temperature The results of XRD showed that by the mechanical activation ofabout 15 30min and in the 5 molar ratio of carbon Al2O3 SiC powder composite can be produced by SHS without any other phases or raw materials However at the low molar ratio of carbon and the short times ofmechanical activation Si as a result of SiO2 decomposition has been detectable in the products On the otherhand with increasing the carbon content up to higher than the stoichiometry level and activation time ofabout 30min Al2OC phase has bee appeared in the products Moreover SEM results of products showed thatwith increasing the activation time of 5 molar ratio carbon samples the difference in the particle sizesdecreased and the elements distribution improved Also the maximum combustion front temperature can becontrolled by activation time and carbon molar ratio This parameter is an important value for the formationof desirable phase in the final product Keywords self propagation high temperature synthesis SHS mechanical activation Al2O3 SiC composite powder planetary ball mill

محمدعلي شريفي، يحيي

اثر فعالسازي مكانيكي پودر SiO2 در توليد كامپوزيت Al2O3/SiC به روش سنتز خود انتشار دماي بالا ﴿SHS

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