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High‐entropy transition‐metal (IVB–VIB) carbide (HETMC) ceramics consisting of multiple principal components generally correspond to higher configuration entropy, and exhibit better overall performance. However, they also present certain synthesis challenges, for example, in the synthesis of a three‐dimensional six‐principal‐component HETMC aerogel. In the present work, as an example a novel (Ti0.167Cr0.167V0.167Mo0.167Nb0.167Ta0.167)C aerogel was prepared at a relatively low temperature of 1773 K by an in‐situ carbothermal reduction/partial sintering technique following the successful preparation of (Ti0.2V0.2Mo0.2Nb0.2Ta0.2)C and (Ti0.2Cr0.2Mo0.2Nb0.2Ta0.2)C five‐principal‐component HETMC aerogels. The synthesized 6‐HETMC aerogel exhibited a homogeneous microstructure with grain phases and pores of 100–300 nm and 0.2–10 μm, respectively, a density of 0.45 g cm−3, a high porosity and compressive strength of 94.5% and 0.8 MPa, respectively, a low thermal conductivity of 0.128 W (m K)−1 at 298 K, and a good high‐temperature stability at least up to 1673 K in Ar. This research provided a novel strategy for future development of HETMC ceramic aerogels for high‐temperature applications. [ABSTRACT FROM AUTHOR]

Seven microporous MgO–Al2O3 ceramics with an Al2O3 content of 15–90 wt% were prepared using Al(OH)3 and calcined magnesite as raw materials. A wet mixing process was employed during sample preparation to transform the calcined magnesite with a larger particle size to smaller Mg(OH)2 particles. The in situ decomposition synthesis method and the Kirkendall effect were utilized to produce and control the pore structure of the microporous MgO–Al2O3 ceramics. There were two kinds of pores in the microporous MgO–Al2O3 ceramics. The first one resulted from the in situ decomposition of Al(OH)3 and Mg(OH)2 particles, which were small and equally distributed. Another one originated from the position of the Mg(OH)2 particles due to the Kirkendall effect caused by MgO diffusion. They were similar in size to the Mg(OH)2 pseudomorph particles. Simultaneously, the Al2O3 content affected the packing behavior and the spinel formation, which changed the characteristics of the pores and necks among the particles. These mechanisms also affected the strengths of the microporous MgO–Al2O3 ceramics. Thus, when the Al2O3 content was 45–90 wt%, the microporous MgO–Al2O3 ceramics had a high compressive strength (10.0–18.3 MPa) and apparent porosity (52.2%–58.4%). [ABSTRACT FROM AUTHOR]

Refining ladle is generally the last inclusion‐removal vessel before the continuous casting of steel, so, it has a vital effect on the final steel quality. In this work, degradation process of a cement‐free Al2O3‐MgAl2O4 refractory in contact with molten steel/slag in the metal bath area of a Ruhrstahl Heraeus (RH) refining ladle was investigated. A reaction product layer with the formation of ferrospinel (hercynite) and Fe‐rich phases was observed, suggesting that the interactions/reactions between the refractory lining and the molten steel should also be considered to have a better understanding of overall degradation mechanism of the refractory served under the RH refining conditions. The two types of alumina grains in the refractory, sintered and fused alumina, were attacked in an active way and a passive way, respectively. The effect of the crack generation and steel infiltration on degradation of the refractory was also discussed in detail, based on the microstructural characterizations. [ABSTRACT FROM AUTHOR]

Formation of a dense layer on corroded interface to suppress corrosion is always desired, but it is controlled by numerous environmental conditions. In this work, corroded microstructures of MgO/Al2O3‐SiC‐C refractories in metal bath area of ladle furnace were investigated after industrial trails. A liquid‐phase isolation layer in which MgO islands and liquid phases was established on the corroded interface of refractories with 6 wt% coarse/fine SiC‐additive. The formed isolation layer against steel/slag attacks led to an approximate 30% improvement in corrosion resistance than that of refractory with 3 wt% fine SiC‐additive. More importantly, the liquid‐phase isolation layer blocked the direct mass transfer between molten steel and refractories while it decreased exogenous pollution from refractories. SiC‐additive affected the formation process of isolation layer by controlling the generation/migration of Mg(g) on refractory' surface. A further formation mechanism of liquid‐phase isolation layer was discussed in detail and role of SiC was elucidated. [ABSTRACT FROM AUTHOR]

Ladle refining is an efficient process for improvement of quality of steel on secondary metallurgy under harsh conditions. Magnesia refractories with high purity are important raw materials for ladle lining in high‐quality steel production. However, the penetration by CaO–MgO–SiO2 slags damages magnesia refractories, which considerably limits their service life. Abundant grain boundaries in magnesia create channels for slag penetration and lead to the destruction of the structure. The effect of the microstructure on the slag corrosion behavior of magnesia aggregates requires further systematic investigation. In this study, a corrosion model was established to describe the slag penetration process of magnesia aggregates. The effects of the grain‐boundary size and slag CaO/SiO2 mass ratio (C/S ratio) on slag penetration were investigated, and the possibility of the microstructure optimization of magnesia aggregates was discussed. The results indicated that magnesia aggregates exhibited excellent slag resistance for slag with a C/S ratio above 1.5 or even 2.0. When the slag C/S ratio was lower than 1.5, the dissolution rate of magnesia decreased more rapidly with the increase in the slag C/S ratio. In addition, the much smaller grain‐boundary size increased the slag penetration resistance by promoting the formation of a dense isolation layer and inhibiting further penetration processes. The calculation results agreed well with the experimental results, suggesting that the corrosion model is promising for predicting slag corrosion. [ABSTRACT FROM AUTHOR]