The effect of (nano, mesoporous) alumina and their composite with MWCNT additives on microstructure, physical and mechanical properties of alumina-C refractories
Subject Areas :
Amirabbas
Nourbakhsh
1
(no.112,negin abshar building,rezvan alley ,abshar)
Keywords: MWCNT, Refractories, Al2O3-C, Al2O3 Mesoporous,
Abstract :
Alumina-C refractories have been widely used as slide gate submerged entry nozzles and mono block stoppers in steelmaking due to their unique physical and mechanical properties.In this research,the effect of different source of alumina having unlike surface areas(nano and mesoporous)and MWCNT additives on physical and mechanical properties of Al2O3-C refractories was investigated.In this regard mesoporous alumina was synthesized by sol-gel method.Then the mesoporous and nano alumina precursors were added to the functionalized MWCNT.In order to better distribution of 0.5-1.5 wt% nano additives the additives were firstly added to the matrix and then mixed with coarse particles of Al2O3-C refractories. Following in order to physical and mechanical properties investigation, all samples pressed under 150Mpa pressure by uniaxial then pressed and tempered at 200 ℃ for 6h, and afterward fired under coke atmosphere at 1450℃ for 2 h.The bulk density apparent porosity and cold crushing strength were determined according to their respective standard. Moreover their microstructure and phase analysis was investigated by XRD and SEM.The results confirmed that the sample containing1wt% nano Al2O3-MWCNT composite showed the highest CCS of about 137 Mpa,and sample with1.5 wt% mesoporous Al2O3 showed the lowest CCS (94 Mpa).The improvement of mechanical properties could be related to the higher SiC formation in the presence of nano Al2O3- MWCNT by vapor- solid mechanism. The main reason for decreasing mechanical properties in the presence of mesoporous additives could be attributed to limiting of gas-solid reaction due to trap of gases and therefore lower formation of SiC whiskers through the matrix.
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