Defect fluorite high-entropy ceramics were designed by tailoring the A-site rare-earth composition and partially substituting Hf with Zr at the B-site. All specimens formed single-phase structures without detectable secondary phases. The HEO ceramics exhibited substantially lower thermal conductivity (1.46–0.95 W·m –1 ·K –1 ) than YSZ (3.06–2.56 W·m –1 ·K –1 ). HEO5 showed the lowest value (1.13–0.95 W·m –1 ·K –1 ), owing to enhanced phonon scattering caused by atomic-mass fluctuations, ionic-radius mismatch, Hf/Zr-induced lattice distortion, and cation and oxygen-vacancy disorder. The CTEs were comparable to or slightly higher than that of YSZ; HEO5 reached 10.15 × 10 –6 K –1 at 1273 K, compared with 10.09 × 10 –6 K –1 for YSZ. Its relatively high CTE was attributed to reduced lattice stiffness and enhanced lattice anharmonicity arising from Hf/Zr substitution and structural disorder. Although fracture toughness was lower, hardness and elastic modulus remained comparable to those of YSZ, demonstrating their potential for advanced TBC applications.
Predicting hydration kinetics, mechanical performance, and durability of cement-based materials remains challenging due to the complex interactions between hydration, pore structure evolution, and transport properties. This study proposes a numerical framework coupling cement hydration and carbonation models to predict hydration products, compressive strength development, and carbonation depth of concrete. The hydration model uses the Parrot–Killoh approach to determine the degree of hydration based on cement composition, Blaine surface area, water-to-cement ratio, and curing temperature. Unlike conventional empirical approaches, the model directly predicts the evolution of CH, C-S-H, and porosity from hydration kinetics and hydrate stoichiometry, while Powers’ gel-space theory is applied for strength prediction. The model predictions show good agreement with experimental results. The coupled carbonation model successfully captures the effects of water-to-cement ratio, CO2 concentration, and exposure time on carbonation behavior. This framework provides a physically meaningful and computationally efficient approach for predicting cement performance and durability.
Defect fluorite high-entropy ceramics were designed by tailoring the A-site rare-earth composition and partially substituting Hf with Zr at the B-site. All specimens formed single-phase structures without detectable secondary phases. The HEO ceramics exhibited substantially lower thermal conductivity (1.46–0.95 W·m–1·K–1) than YSZ (3.06–2.56 W·m–1·K–1). HEO5 showed the lowest value (1.13–0.95 W·m–1·K–1), owing to enhanced phonon scattering caused by atomic-mass fluctuations, ionic-radius mismatch, Hf/Zr-induced lattice distortion, and cation and oxygen-vacancy disorder. The CTEs were comparable to or slightly higher than that of YSZ; HEO5 reached 10.15 × 10–6 K–1 at 1273 K, compared with 10.09 × 10–6 K–1 for YSZ. Its relatively high CTE was attributed to reduced lattice stiffness and enhanced lattice anharmonicity arising from Hf/Zr substitution and structural disorder. Although fracture toughness was lower, hardness and elastic modulus remained comparable to those of YSZ, demonstrating their potential for advanced TBC applications.
