Moiré superlattices formed by twisted stacking in van der Waals materials have emerged as a new platform for exploring the physics of strongly correlated materials and other emergent phenomena^1–5. However, there remains a lack of research on the mechanical properties of twisted-layer van der Waals materials, owing to a lack of suitable strategies for making three-dimensional bulk materials. Here we report the successful synthesis of a polycrystalline boron nitride bulk ceramic with high room-temperature deformability and strength. This ceramic, synthesized from an onion-like boron nitride nanoprecursor with conventional spark plasma sintering and hot-pressing sintering, consists of interlocked laminated nanoplates in which parallel laminae are stacked with varying twist angles. The compressive strain of this bulk ceramic can reach 14% before fracture, about one order of magnitude higher compared with traditional ceramics (less than 1% in general), whereas the compressive strength is about six times that of ordinary hexagonal boron nitride layered ceramics. The exceptional mechanical properties are due to a combination of the elevated intrinsic deformability of the twisted layering in the nanoplates and the three-dimensional interlocked architecture that restricts deformation from propagating across individual nanoplates. The advent of this twisted-layer boron nitride bulk ceramic opens a gate to the fabrication of highly deformable bulk ceramics.

Significance: Diamond is an essential material for industrial and scientific applications due to its exceptional properties. The regulation of diamond performance through microstructural design is a challenging and hot topic. Here, we report the synthesis of diamond with preferentially oriented nanotwin bundles via direct phase transformation of superaligned multiwalled carbon nanotube films under high temperature and pressure. The preferentially oriented nanotwin bundles endow diamond with the highest hardness anisotropy ever recorded and a record hardness value in the direction perpendicular to the oriented nanotwin bundles. Current findings provide valuable insights on the microstructural design and modification of diamond and related materials, contributing to the further tuning of properties in the future.