بررسي تشكيل تركيب بين فلزي MoSi2 و كامپوزيت MoSi2-10Vol. % Zro2 طي دو فرايند سنتز احتراقي و آلياژ سازي مكانيكي

چكيده انگليسي :

Investigation of Formation of MoSi2 Intermetallic Compound and MoSi2 ZrO2 Composite by Mechanical Alloying and Combustion Synthesis Processes M Taheri Email address m taheridolatabadi@ma iut ac ir 2012 21 04 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisors name Morteza Shamanian Associate Professor m shamanian@cc iut ac irMasoud Panjepour Assistant Professor panjepour@cc iut ac irAbstractMoSi2 intermetallic compound due to high melting point good electrical and thermal conductivityand high temperature 1000 C oxidation resistance is one of the most important silicideintermetallic compounds However the fracture toughness of MoSi2 is low and to improve it ZrO2particles are used The objective of this study is the investigation of production of MoSi2intermetallic compound and MoSi2 ZrO2 composite by mechanical alloying and combustionsynthesis In order to production of MoSi2 ZrO2 composite the ZrO2 particles were added by ex situ and in situ methods The mechanical alloying under same conditions was performed on thefour powder mixtures including Mo Si Zr MoO3 Mo Si ZrO2 and Mo Si Zr MoO3 Thecombustion synthesis in the mode of SHS and explosive was performed on three compactedpowder mixtures including Zr MoO3 Mo Si ZrO2 and Mo Si Zr MoO3 Phase analysis andmicrostructural investigation were carried out by X ray diffraction XRD scanning electronmicroscopy SEM and energy dispersive spectroscopy EDS Combustion front velocity andtemperature profiles in the combustion synthesized samples in mode of SHS was investigated bythermocouple type S and recording with camera The phase analysis indicated that MoO3 wasreduced by Zr after 6 h with mechanism of SHS The formation of MoSi2 was initiated after about20 h mechanical alloying in the Mo Si and Mo Si ZrO2 powder mixtures and after about 10 hmechanical alloying in the Mo Si Zr MoO3 powder mixture The produced MoSi2 was includingboth and phases In the Mo Si and Mo Si ZrO2 powder mixtures after 60 h mechanicalalloying low amount of Mo existed yet and dominant phase was MoSi2 The formation ofMoSi2 ZrO2 composite in the Mo Si Zr MoO3 powder mixture was completed after about 60 h anddominant phase was MoSi2 On the other hand studies concerning the formation mechanism ofMoSi2 in this process showed that the dominant mechanism is a mechanical collision reaction Thephase and microstructural observations on the products of combustion synthesis process showedthat the dominant phase is MoSi2 The molybdenum and silicon rich phases were also found inthe samples These phases showed that the reaction is not equilibrium and not fully performed Theresults of thermal analysis DTA on mixed Mo Si indicated that the formation mechanism of MoSi2was the Si melting and then formation of MoSi2 by SHS The differential thermal analysis of Zr MoO3 powder mixture illustrated that the reduction of MoO3 was completed until 800 C by Zr So add this mixture to the mixed Mo Si as sample of Mo Si Zr MoO3 not only in the combustionsynthesis process leading to the formation of ZrO2 particles but also the begining temperature ofthis process will reduce The explosive combustion synthesis process on two samples of Mo Si andMo Si Zr MoO3 has been reduced the starting temperature of the reaction from 700 C to 1150 C Thus these results can be deduced that the addition of Zr MoO3 mixed to Mo Si powder mixturecan be affected the mechanism rate of MoSi2 formation during combustion synthesis and themechanical alloying processes Keywords Combustion synthesis Mechanical alloying MoSi2 ZrO2

طاهري، محمد

بررسي تشكيل تركيب بين فلزي MoSi2 و كامپوزيت MoSi2-10Vol. % Zro2 طي دو فرايند سنتز احتراقي و آلياژ سازي مكانيكي

دي سيليسيد موليبدن , زيركونيا