The ultra-high sintering temperatures required for high-entropy borides (HEB) pose a significant challenge to their processing and practical application. This study introduces an efficient low-temperature fabrication route for dense HEB-based ceramics using reactive ZrSi₂-assisted heavy direct current sintering, with a maximum heating rate exceeding 3700 °C/min. A porosity of 1.60 ± 0.61% can be achieved at a sintering temperature of 1000 °C, which is reduced by 600-1000 °C compared to state-of-the-art spark plasma sintering/field-assisted sintering techniques processing of HEBs. Microstructural analysis revealed interdiffusion between HEB and ZrSi₂, leading to a core-shell HEB architecture and layered high-entropy silicides. Meanwhile, dislocations and non-uniform stress fields were observed within the HEB grains. These microstructural features synergistically inhibit crack propagation and promote crack deflection and branching. Consequently, both flexural strength and fracture toughness are significantly enhanced. A flexural strength of 963 MPa was attained at 1400 °C, and a fracture toughness of 7.4 MPa·m^1/2 was achieved at 1500 °C, surpassing most reported HEB-based ceramics. These results demonstrate that reactive ZrSi₂-assisted heavy direct current sintering is a profoundly effective approach for low-temperature manufacturing of high-performance HEB-based ceramics.

The preparation of dense ZrB₂-based ceramics typically requires high temperatures and long sintering time, which often result in significant grain coarsening and thus deterioration of mechanical properties. Ultrafast sintering techniques offer a solution to inhibit grain coarsening by reducing the processing time. However, the ultrafast preparation of dense ZrB₂-based ceramics remains a challenge. In this work, we successfully fabricated dense ZrB₂-based ceramics in just a few minutes using heavy continuous direct current (DC) Joule heating and pressing. Notably, the densification rate peaked at 1218 °C, and the densification process was nearly complete at a relatively low temperature of 1500 °C. The application of heavy continuous direct current not only promotes the densification of the ceramics but also enhances the texturization of ZrB₂. This results in optimally aligned ZrB₂ grains that form a three-dimensional bonded skeletal network. These unique microstructures can effectively induce multi-stage fracture surfaces during failure, which helps synergistic strengthening and toughening of the ceramics. The ceramics exhibit remarkable comprehensive mechanical properties, with flexural strength and fracture toughness values reaching 773±114 MPa and 5.88±0.08 MPa·m^1/2, respectively, surpassing those of conventional hot pressed samples. This technique is expected to be applied to other ultra-high temperature ceramics, providing a promising approach for the development of thermal protection materials.

The difficulty of reducing the diameter of lutetium oxide (Lu₂O₃) continuous fibers below 50 μm not only limits the flexibility of the sample but also seriously affects their application and development in high-energy lasers. In this work, a Lu-containing precursor with high ceramic yield was used as raw material, fiberized into precursor fibers by dry spinning. The pressure-assisted water vapor pretreatment (PAWVT) method was creatively proposed, and the effect of pretreatment temperature on the ceramization behavior of the precursor fibers was studied. By regulating the decomposition behavior of organic components in the precursor, the problem of fiber pulverization during heat treatment was effectively solved, and the Lu₂O₃ continuous fibers with a diameter of 40 μm were obtained. Compared with the current reported results, the diameter was reduced by about 50%, successfully breaking through the diameter limitation of Lu₂O₃ continuous fibers. In addition, the tensile strength, elastic modulus, flexibility, and temperature resistance of Lu₂O₃ continuous fibers were researched for the first time. The tensile strength and elastic modulus of Lu₂O₃ continuous fibers were 373.23 MPa and 31.55 GPa, respectively. The as-obtained flexible Lu₂O₃ continuous fibers with a limit radius of curvature of 3.5–4.5 mm had a temperature resistance of not lower than 1300 ℃, which established a solid foundation for the expansion of their application form in the field of high-energy lasers.

Yttria-stabilized zirconia (YSZ) fiber composites are highly efficient thermal insulating materials; however, the poor thermal shock resistance limits their versatile applications. In the present study, YSZ fiber was mixed directly with Al₂TiO₅ fiber, which had an extremely low thermal expansion coefficient, to prepare YSZ-Al₂TiO₅ (ZAT) fiber composites by compression molding and heat treatment. The minimum thermal expansion coefficient of the prepared ZAT fiber composites was measured to be 7.74×10^-6 K^-1, which was 26% lower than that of the YSZ fiber composites (10.42×10^-6 K^-1). It was shown that the prepared ZAT fiber composites maintain the integrity after undergoing 51 thermal shock cycles between 1100 ℃ and room temperature. Whereas, YSZ fiber composites burst immediately after only one thermal shock cycle under the same condition. In addition, the ZAT fiber composites also exhibit considerable mechanical and thermal insulating performance.