11286

10377

كارشناسي ارشد

شناسايي و انتخاب مواد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مهندسي مواد

1394

پانزده، 107ص.: مصور

رحمت الله عمادي

احمد منشي، مجيد طاووسي

1395/03/25

مهندسي مواد

ID10377

Investigation effect of processing variables on final density and grain size of nano alumina shaped by slip cast method Ali Rahimian Ali Rahimian@ma iut ac ir Date of Submission 2016 03 05 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Rahmatollah Emadi Asso Prof Remadi@cc iut ac irAbstractthe homogeneity of green bodies is of outstanding importance for sintering transparentceramics Because of the birefringence of Al2O3 crystals the grain size of densemicrostructures must be 500 nm to minimize associated scattering losses To this end conventional processes were substituted by advanced shaping approaches that improve theparticle coordination of green bodies and enable a decrease of the sintering temperature by200o 250oC in this research A quantitative assessment of the homogeneity of particlecoordination in green bodies is achieved by addressing pore structures Avoiding a coarser tailof the pore size distribution is important but insufficient for optimum sintering Instead thesteepest slope of the main body of the distribution is responsible for a maximum density atlowest temperature and further progress is enabled by minimizing interparticle spacing theaverage pore size Ranking different technologies with different associated pore sizedistributions the same correlation holds for the impact of homogeneity on i sinteringdensification as ii for the onset of intense grain growth during the final sintering stage Forall of the investigated processing approaches the pore size distributions are observed to remainconstant through the initial and intermediate states of sintering Uniaxial pressing generatesthe widest pore size distribution Because even the largest of these pores 75 200 nm are toosmall to scale with the size of relics of the pressing granules 10 mm the tail of the pore sizedistribution is not associated with a few larger defects but originates from agglomerates ofindividual particles and represents a poor general homogeneity of particle coordination inthese pressed bodies As a consequence locally different shrinkage may give rise to thedevelopment of larger porous defects on subsequent sintering additionally to flaws thatprobably originate from relics of the pressing granules KeyWords Sintering Alumina Agglomerate Defect Homogeneity Green Body Density

رحمت الله عمادي

احمد منشي، مجيد طاووسي