Papers by Keyword: Hot Modulus of Rupture

Abstract: The effects of addition of silicon powder (1 wt. %) and Na₂CO₃ (converting to additional 0.5%, 1% Na₂O) on the hot modulus of rupture (HMOR) of MgO-Al-C bricks were investigated. MgO-Al-C refractories were prepared by using fused magnesia and graphite flake as main starting materials, and Si, Na₂CO₃ or both as additives. Its phase composition and microstructure were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and EDS. The results showed that the HMOR of MgO-Al-C bricks increased slightly with addition of Si powder. However, the HMOR decreased when adding Na₂CO₃ and Si powder together. Moreover, the HMOR deduced with the increase of Na₂CO₃ content. The mechanism is that Al powder reacted to form fibrous Al₄C₃ and AlN, which could improve the HMOR. When silicon was added, β-SiC and M₂S were formed, which could fill the passages and pores. So the densification and strength were improved. The addition of Na₂CO₃ could promote the oxidation of Al powder to form Al₂O₃, and inhibit the formation of Al₄C₃ and AlN. Hence the strength of MgO-Al-C deduced.

Abstract: Based on the Al-O-N phase stable diagram and adopting inverse reaction sintering process, corundum-silicon nitride composite refractories were prepared using corundum, silicon nitride, clay and aluminium powder as the main starting materials. The specimens were sintered at 1600 for 3 hours under air atmosphere with different oxygen partial pressure obtained by addition of different amount of aluminium powder. The effects of aluminium powder additions(0, 4wt.%, 8 wt.% and 12 wt.% respectively) on the hot modulus of rupture were investigated .The phase composition and microstructure were tested by means of XRD, SEM and EDAS.The results showed that aluminium would be oxidized, nitrided and displaced as aluminium powder increased during sintering, which reduced the oxygen partial pressure in the specimen. The hot modulus of rupture (HMOR) increased considerably due to large amounts of fibrous sialon formed.