SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3779-1
Comprehensive mechanical properties, including hardness (H), elastic modulus (E), fracture toughness (KC), and wear resistance, are essential for oxide ceramics used in demanding environments. This work employs nanoindentation to evaluate these properties for RE3TaO7 (RE=La, Sm, Eu, Gd, Dy, Lu) and identifies the optimal calculation method for KC in brittle oxide ceramics. The ratio of indentation crack length to half-diagonal (l/α) is a key parameter: Eq. (3) is suitable when l/α < 1, while Eq. (4) applies when l/α > 1. The indentation energy method is invalid for brittle ceramics due to crack formation at high loads. RE3TaO7 oxides exhibit H of 5.8–14.9 GPa, E of 127.5–247.8 GPa, and KC of 1.0–2.0 MPa·m1/2, surpassing RE2Zr2O7 (KC 1.0–1.5 MPa·m1/2). Wear resistance, indicated by MDP, ranges from 0.55 to 0.67, outperforming RE2Zr2O7. The superior fracture toughness is attributed to weberite structure with crack deflection and tortuous propagation, contrasted with pyrochlore's straight cracks. These findings provide accurate nanoindentation-based methods for assessing mechanical properties of brittle oxide ceramics, facilitating material discovery and optimization for thermal barrier coatings and other high-temperature applications.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3633-5
High-temperature interfacial diffusion in Half-Heusler (HH) thermoelectric devices poses significant challenges for practical applications, particularly the diffusion of Ag from conventional solders, which degrades material performance and device stability. This study reveals anomalous Ag diffusion through a Cr powder barrier layer into Ti0.5Zr0.5NiSn0.98Sb0.02, driven by Sn phase penetration. In contrast, employing a Cr foil barrier layer pre-densified the material, effectively preventing Sn phase penetration and eliminating Ag diffusion pathways, thereby preserving junction integrity. After aging at 973 K for 30 days, the Cr foil junction maintained a clean interface with a low contact resistivity of 0.27 μΩ cm2. Benefiting from this interfacial design, a Hf-free HH module achieved a high conversion efficiency of 10.4% at a hot-side temperature of 976 K, alongside long-term stability. This work addresses critical bottlenecks in developing high-performance, low-cost HH modules, facilitating their commercial application in waste heat recovery.
Journal of Fuel Chemistry and Technology•2026•DOI: 10.3724/2097-213X.2025.JFCT.0029
Pingshuo coal ash, characterized by high silicon-aluminum content (Si+Al >85%) and low Si/Al ratio (<1.5), exhibits ash fusion temperatures (AFTs) exceeding 1550 °C, rendering it unsuitable for entrained-flow gasifiers. This study investigates the effect of calcium-sodium composite flux on ash fusibility and mineral transformation. X-ray diffraction (XRD) and FactSage thermodynamic simulations were employed to analyze mineral evolution, while molecular dynamics (MD) simulations revealed the underlying melting mechanism. Results show that adding 20% composite flux (CaO/Na2O) lowers AFTs more effectively than equivalent additions of CaO or Na2O alone, indicating a synergistic effect. At a CaO/Na2O ratio of 3:7, the flow temperatures (FT) of two Pingshuo coal ashes decreased to 1377 °C and 1279 °C, respectively. The composite flux promotes reactions between quartz and Na2O/CaO, forming low-melting-point minerals such as nepheline, albite, and gehlenite, while inhibiting mullite formation. Additionally, Na+ disrupts the silicate network, inducing Ca2+ to preferentially coordinate with [AlO4]5- tetrahedra, further breaking Si-O-Si bonds. MD simulations show that atomic diffusion, quantified by mean square displacement (MSD), is significantly enhanced below 1600 K with composite flux addition compared to single fluxes. These findings provide a mechanistic basis for optimizing flux formulations to enable efficient gasification of high-AFT coals.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-4016-3
Rare earth-based electromagnetic wave (EMW) absorbing materials are promising due to their strong dielectric and magnetic loss capabilities, yet effective enrichment and utilization of rare earth ions remain challenging. Here, an anionic imidazolium-based metal-organic framework (MOF), MOZ-200, is employed to enrich multiple rare earth ions (La3+, Ce3+, Pr3+, Nd3+, Y3+) via host-guest interactions. The anionic framework uniformly confines these ions, which are converted in situ into highly dispersed high-entropy rare earth alloy nanoparticles during carbonization. The resulting HE@C composites feature a conductive, graphitized carbon matrix with abundant multi-scale polarization centers and heterogeneous interfaces, enhancing dipole polarization, interface polarization, and conductive loss. Consequently, the material achieves excellent EMW absorption in the Ku band, with a minimum reflection loss of -79.20 dB and a maximum effective absorption bandwidth of 5.23 GHz. Integrated into a polyurethane matrix, a multifunctional flexible device is realized, offering EMW absorption, photothermal heating, microwave de-icing, and hydrophobicity. This work provides a feasible strategy for rare earth ion utilization and advances the design of flexible multifunctional EMW absorbing materials.