Al₂O₃–C refractories are important for the continuous casting process. It is essential for safe and effective steel making processes to enhance the strength and oxidation resistance of Al₂O₃–C refractories. A compound MAB phase Cr₂AlB₂ has attracted recent attention due to its high fracture toughness, high damage tolerance and excellent oxidation resistance. In this work, a ternary layered compound Cr₂AlB₂ was introduced into the Al₂O₃–C refractories.The structural evolution of Cr₂AlB₂ in Al₂O₃–C refractories after treated at different temperatures and its effect on the comprehensive properties of Al₂O₃–C refractories were analyzed by X-ray diffraction,scanning electron microscopy and transmission electron microscopy. The results show that a gradual decomposition of Cr₂AlB₂ in Al₂O₃–C refractories generates a core–shell structure of CrB and Al₂O₃ covered with Al₂O₃, and catalyses the formation of carbon nanotubes and carbon fibers on the surface of the core–shell structure after thermal treatment at 800–1200 ℃. Cr₃C₂ covered by BN structure is formed inside the core-shell structure after thermal treatment at 1200–1600 ℃. As a result, the densification of Al₂O₃–C refractories is facilitated, and the cold modulus of rupture and oxidation resistance is enhanced. The cold modulus of rupture after coking at 1400–1600 ℃ is increased by approximately 9%, and the oxide index after treated in air at 1400 ℃ is reduced from 44%to 31%.

Magnesium silicate hydrate (MgO–SiO₂–H₂O M–S–H) is a main bonding phase for microsilica bonded magnesium-castables used for tundish. Its content determines the mechanical properties after demolding. In this paper, M–S–H was synthesized with Na₂SiO₃·9H₂O and MgCl₂·6H₂O as raw materials. The effect of M–S–H at different calcination parameters was investigated by X-ray diffraction, scanning electron microscopy, specific surface area measurement, nuclear magnetic resonance, and thermogravimetry-differential scanning calorimetry. Moreover, the synthesized M–S–H with microsilica powder (1%) was introduced into the magnesia-based castables to evaluate their influences on the properties. The results show that M–S–H has a memory effect when the calcination temperature is below 400℃. Increasing the calcination time can facilitate the insertion of interlayer hydroxyl groups in M–S–H gels and contribute to the formation of a lamellar structure with a higher structure stability. A certain amount of pre-synthesized M–S–H and a small amount of silica powder can assure the castable with a good workability and a sufficient early bonding strength. The reduced silica can suppress the formation of large sized defects due to the volume shrinkage of matrix, in the interface of aggregates and matrix, thus improving the mechanical properties of castables. This work provides a support for the development of magnesia-based castables with a low silica content.

To solve the problems of thermal shock resistance and radiation efficiency attenuation due to the high-temperature oxidation of silicon carbide porous ceramics used in high-temperature combustion of porous media, a silicon carbide billet was prepared by an organic foam impregnation method. Also， porous silicon carbide ceramics containing cordierite infrared radiation coating were fabricated on the surface of silicon carbide skeleton via in-situ reaction sintering. The results show that the vacuum impregnation slurry can coat the skeleton surface and completely fill up the triangular holes of the silicon carbide skeleton. The three-layered porous silicon carbide ceramics with a cordierite coating, the central layer of the silicon carbide skeleton and the cordierite filling layer were prepared by sintering at 1350 ℃ . The mechanical properties, thermal shock resistance and high-temperature wet oxidation resistance of porous silicon carbide ceramics are improved due to the formation of the three-layered structure. The compressive strength of porous silicon carbide ceramics is 1.18 MPa after heat-treatment at 1350 ℃ , and the residual strength retention rate is 67%. According to the results of porous media combustion experiments, the three-layered structure of silicon carbide porous ceramic with a surface reinforcement by cordierite infrared radiation coating can reinforce silicon carbide porous media burner radiation heat transfer process and increase the combustion efficiency, thus increasing the burner surface temperature by 140 ℃ and reducing the emissions of CO and NO_x pollutants in the burner.

Sewage sludge and household garbage are used as an alternative fuel in recent production of cement. However, the alternative fuel causes serious alkali attack and spalling of bauxite-SiC refractories for cement kiln lining, thus having an impact on the operation of the cement kiln. In this paper, the alkali vapor exposure was used to evaluate alkali attack on some raw materials like bauxite, mullite (M60) and molochite, which were used to prepare mullite-SiC composite refractory as a lining of cement kiln. The results show that the alkali attack resistance of these raw materials is closely related to their chemical composition, phase composition and microstructures. Bauxite with corundum and mullite as main phases is attacked by alkali to form a kaliophilite phase and induce cracks and loose structure, further enhancing gaseous alkali penetration and serious damage. Mullite (M60) with mullite as a main phase is attacked by alkali to form leucite and transient liquid phase. The resultant liquid phase prevents from the penetration of alkali, and the attack only occurs on the surface layer, so mullite (M60) exhibits a superior alkali attack resistance. Molochite with mullite and glass (the content of 46%) reacts with alkali vapor to form more liquid phase and leucite. As alkali vapor is dissolved in the glass phase of molochilte, the integrity of molochite is destroyed by alkali attack.