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.

A theoretical calculation combined with experiment was used to study highentropy (Hf 0.2 Ti 0.2 Mo 0.2 Ta 0.2 Nb 0.2 )B 2 (HEB-HfTiMoTaNb). The theoretical calculation suggested HEB-HfTiMoTaNb could be stable over a wide temperature range. Then, a novel solvothermal/molten salt-assisted borothermal reduction method was proposed to efficiently pre-disperse transitional metal atoms in a precursor and synthesize (Hf 0.2 Ti 0.2 Mo 0.2 Ta 0.2 Nb 0.2 )B 2 nanoscale powders at 1573 K for 6 h, which is nearly 300 K lower than previous reports. The characterization results indicated that the as-synthesized nanoscale HEB-HfTiMoTaNb powder was hexagonal single-phase with homogeneous elements distribution and uniform size, and the oxygen content of the particles is 0.97 wt%. Simultaneously, the mechanical properties, anisotropic nature, and thermal properties of HEB-HfTiMoTaNb were investigated by density functional theory (DFT) calculations. The Cannikin's law was adopted to explain the improvement of comprehensive mechanical properties. In addition, a significant reduction of thermal conductivity was observed for HEB-HfTiMoTaNb and it only was 1/15 of the value of HfB 2 . This work suggests a reliable technique for synthesis of nanosized HEB powders and discovery of high-entropy materials under the guidance of first-principle theory.

The precise control of molten steel temperature in tundish is a key factor to ensure the quality of the cast billets, so it is important to develop permanent lining castables for tundish with low thermal conductivity and bulk density. In this work, the hydrophobic modification of pearlescent sand was carried out with hydrogen silicone oil, and 3% of modified pearlescent sand was added to mullitebauxite castable to realize its low thermal conductivity and light weight. It is found that modified pearlescent sand still has good hydrophobicity at 350 • C, the addition of modified pearlescent sand effectively increases the apparent porosity and reduces the bulk density of the castable. At 1500 • C, the bulk density of modified pearlescent sand-castable is 25.54% less than that of conventional castable.Compared with conventional castable, the mechanical properties and thermal shock resistance of modified pearlescent sand castable are worse, but they are sufficient to meet the use conditions of tundish permanent lining castable. At 600-1000 • C, the thermal conductivity of the modified pearlescent sand castable is about 30% lower than that of the conventional castable, which proves that the addition of modified pearlescent sand can significantly improve the thermal insulation performance of mullite-bauxite castable.