查看更多>>摘要：To solve the problem of poor high-temperature service performance caused by low carbonization of MgO-C refractories,low-carbon MgO-C refractories with excellent thermal shock,oxidation and corrosion resistances were successfully designed by using SiC whiskers as reinforcing phases and introducing micro-Al2O3 powders as additives.The results indicated that the addition of micro-Al2O3 powders optimized the internal structure of the material,like the columnar β-Si3N4 with a stepped distribution and the mosaic structure formed between granular and flaky Mg2SiO4,which syner-gistically strengthened and toughened the material and gave the material excellent mechanical properties and thermal shock resistance.Specifically,the cold modulus of rupture and cold crushing strength after thermal shock were increased by 4.1 and 20.3 MPa,respectively.Moreover,the addition of micro-Al2O3 powders promoted the formation of fine particles of Mg2SiO4,MgAl2O4 and MgO,as well as a dense protective layer of Mg2SiO4 in the material under high-temperature environment.Furthermore,spinel and high-temperature solid solution were formed in the corrosion envi-ronment.The oxidation and corrosion resistances were greatly improved by 41％and 15％,respectively.
查看更多>>摘要：Reticulated ceramic foam filters provide an effective way to purify molten steel by removing non-metallic inclusions.We proposed a novel strategy to improve the purification performance of Al2O3-based ceramic filters by using microporous corundum-spinel raw materials to replace dense raw materials.Three kinds of Al2O3-based ceramic filters fabricated from dense α-Al2O3 micro-powder or microporous corundum-spinel powder were selected to carry out the immersion tests with molten steel.On the one hand,the higher surface roughness of the filter skeleton prepared from microporous raw materials increased the adsorption capacity of skeleton surface on inclusions in molten steel.On the other hand,the higher apparent porosity and larger pore size of the filter skeleton were more beneficial to the penetration of molten steel in the micropores of skeleton.The reaction process at the solid-liquid interface also improved the wettability of the interface between skeleton and molten steel,resulting in a larger penetration depth and a better adsorption effect on the inclusions.In summary,the novel Al2O3-based ceramic filter prepared with microporous corundum-spinel powder and addition of 5 wt.％nano-Al2O3 powder reduced the total oxygen content of the steel from 40.2 × 10-4 to 12.7 × 10-4 wt.％by 68.4％and the Al content from 0.46 to 0.18 wt.％by 60.9％after immersion test,presenting the most excellent purification performance on molten steel.
查看更多>>摘要：MgO-CaO(40 wt.％CaO)refractory aggregates were prepared using the calcined dolomite and light-burned magnesia fine powder as raw materials and TiO2 as additive.The effect of TiO2 on their phase composition,microstructures and properties was investigated by X-ray diffraction and scanning electron microscopy.The properties such as bulk density,apparent porosity,relative aggregate tube strength and hydration resistance were also investigated.The results showed that the CaTiO3 generated by the reaction between CaO and TiO2 was distributed around the CaO grain boundaries and intermittently distributed with MgO,which formed an isolation layer around CaO and greatly improved the hydration resistance.Meanwhile,the introduction of TiO2 promoted sintering and increased the grain size,further improving the strengths and hydration resistance of the materials.In addition,the most significant enhancement in the hydration resistance and strengths of the samples was achieved when 1.0-2.0 wt.％TiO2 was added.In this case,the relative strength of aggregate increased from 33.3％to 37.3％-43.1％,and the mass gain after the hydration test decreased from 3.13％to 1.26％-1.45％.
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