High strength metallic wood from nanostructured nickel inverse opal materials

This paper describes a nickel-based cellular material, which has the strength of titanium and the density of water. The material’s strength arises from size-dependent strengthening of load-bearing nickel struts whose diameter is as small as 17 nm and whose 8 GPa yield strength exceeds that of bulk nickel by up to 4X. The mechanical properties of this material can be controlled by varying the nanometer-scale geometry, with strength varying over the range 90–880 MPa, modulus varying over the range 14–116 GPa, and density varying over the range 880–14500 kg/m3. We refer to this material as a “metallic wood,” because it has the high mechanical strength and chemical stability of metal, as well as a density close to that of natural materials such as wood

Probing molten salt flux reactions using time-resolved in situ high-temperature powder X-ray diffraction: A new synthesis route to the mixed-valence NaTi2O4

A new molten salt synthesis route to the mixed-valence sodium titanate NaTi2O4 has been discovered. Reduction of Na 8Ti5O14 by Ti metal powder in a 3:1 molar mixture of NaCl:KCl at 770 °C produced crystals of NaTi2O 4. Use of the molten salt flux lowered the synthesis temperature of this compound by over 400 °C. Time-resolved in situ high-temperature X-ray powder diffraction was used to probe the kinetics and mechanism of the reaction. Energy-dispersive X-ray diffraction (EDXRD) data revealed that the reaction is rapid; the phase begins to form in 30 min at 770 °C, and product formation is essentially complete within 2 h. Crystalline solids are present in the molten salt flux at all times during the course of the reaction, indicating that the mechanism most likely involves reactions occurring at the surfaces of the solid particles, mediated by the molten salt flux. Possible key intermediates identified through EDXRD and quenching studies are Ti 3O, Na2Ti6O13, and Na 0.54TiO2. This new molten salt synthesis route offers a facile way to reproducibly prepare large samples of this mixed-valence compound for further study

Cu/Li4Ti5O12 scaffolds as superior anodes for lithium-ion batteries

Nanostructured active materials with both high-capacity and high-rate capability have attracted considerable attention, but they remain a great challenge to be realized. Herein, we report a new route to fabricate a bicontinuous Cu/Li4Ti5O12 scaffold that consists of Li4Ti5O12 nanoparticles (LTO NPs) with highly exposed (111) facets and nanoporous Cu scaffolds, which enable simultaneous high-capacity and high-rate lithium storage. It is a 'one stone, two birds' strategy. When tested as the anode in lithium-ion batteries LIBs, Cu/LTO showed superior performance, such as a lifespan greater than 2000 cycles and an ultrafast charging time (<45 s). Notably, the ultrahigh capacity slightly larger than the theoretical value was also observed in Cu/LTO at low current density. Density functional theory calculations and detailed characterizations revealed that the highly exposed (111) facets on the edge are the reason for its unique storage mechanism (8a+16c), which is different from the transition between 8a and 16c in bulk LTO