SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4394-x
Spiral graphene, characterized by Bernal-stacked layers and unique electronic properties, holds promise for advanced quantum and optoelectronic devices. However, its controlled synthesis remains challenging. Here, we report the self-assembly growth of single-crystal spiral graphene on a liquid heterogeneous substrate via chemical vapor deposition (CVD). A 50-μm-thick Cu foil was placed on a Ni support and heated to 1083 °C, the melting point of pure Cu, ensuring a fully molten Cu layer on solid Ni. Growth proceeded for 30 minutes under optimized conditions. The resulting spiral graphene exhibits a uniform Bernal stacking configuration, as confirmed by transmission electron microscopy and selected-area electron diffraction. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling and isotope-labeling experiments reveal that carbon incorporation occurs predominantly at the spiral step edges, following a self-assembly mechanism driven by the liquid substrate's dynamic surface. Control experiments on solid Cu-Ni alloys yield no spiral morphology, underscoring the critical role of the liquid phase. The liquid heterogeneous substrate facilitates rapid carbon diffusion and step-edge attachment, enabling the growth of high-quality single-crystal spirals with controlled layer number. This work provides a scalable route to synthesize spiral graphene with tailored stacking, advancing its application in twistronics and high-performance electronics.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-4028-5
The escalating thermal management demands of modern electronics necessitate materials with superior thermal conductivity and matched thermal expansion. Cu/Diamond composites are promising, yet their fabrication typically requires extreme conditions (high temperature/pressure) or complex coating processes. This work introduces a one-step, heat-source-free cold manufacturing method using ultrasonic vibration to consolidate Cu/Diamond composites at room temperature and a low pressure of ~16 MPa within seconds. The applied pressure is reduced by 200–500 times, and the required temperature is only 20% of that used in conventional high-temperature high-pressure sintering. Direct metallurgical bonding at Cu-Cu interfaces and solid embedding of diamond particles in the Cu matrix are achieved, yielding a composite with a high yield strength of 150 MPa. The method enables a maximum diamond proportion of ~60%, resulting in a thermal conductivity exceeding 1043 W/(m·K) and a coefficient of thermal expansion below 10×10⁻⁶ K⁻¹. Complex shapes are readily fabricated, and heat dissipation tests demonstrate superior performance compared to commercial Al₂O₃ and AlN substrates. The loose preparation conditions and rapid processing confer significant industrial production potential.
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.