Unique structure and surface-related elastic modulus of alumina nanobelts

Single-crystalline α-AlO nanobelts were synthesized by high-temperature chemical vapor deposition in a high-purity H atmosphere. The crystalline planes for the upper and side surfaces of the nanobelts were and and the orientations along height, length and width directions were and respectively. The formation of such a unique structure was dependent on the strong reducing atmosphere used in the growth process, and the deactivation of the plane by hydrogen could be the primary cause. The elastic modulus of the nanobelts was measured using a thermal resonance method. The moduli for the nanobelts were about 320 GPa for thicknesses above 40 nm, and slightly increased to 356 GPa as the thickness decreased to 31 nm. The slightly low modulus values compared to the theoretical value of 371 GPa is attributed to oxygen vacancies within the nanobelts, while the increase in modulus with decreased thickness comes from the stiffening effect caused by surface relaxation

Hollow carbon nanospheres with extremely small size as anode material in lithium-ion batteries with outstanding cycling stability

Hollow carbon nanospheres (HCNSs) were fabricated by annealing the Cu-C core-shell nanoparticles at 1250 degrees C in vacuum. The as-obtained HCNSs have ultrathin shell of 1-3 nm in thickness, small size of about 20 nm in diameter, high surface area of 300 m(2) g(-1), and ultrasmall pores below 5 nin within the C shells. The HCNSs exhibit excellent electrochemical performance as anode materials for lithium-ion batteries. A reversible capacity of 400 mAh g(-1) and capacity retention of nearly 100% are achieved at the current density of 186 mA g(-1) after 100 charging-discharging cycles. The high reversible capacity, improved high-rate capability, and outstanding cycling stability could be attributed to their unique structural characteristics including the extremely small diameter, the high surface area and the hollow structure with porous, ultrathin shell

Synthesis and magnetic properties of Fe3C-C core-shell nanoparticles

FeC-C core-shell nanoparticles were fabricated on a large scale by metal-organic chemical vapor deposition at 700 °C with ferric acetylacetonate as the precursor. Analysis results of x-ray diffraction, transmission electron microscope and Raman spectroscope showed that the FeC cores with an average diameter of ∼35 nm were capsulated by the graphite-like C layers with the thickness of 2-5 nm. The comparative experiments revealed that considerable FeO-FeC core-shell nanoparticles and C nanotubes were generated simultaneously at 600 and 800 °C, respectively. A formation mechanism was proposed for the as-synthesized core-shell nanostructures, based on the temperature-dependent catalytic activity of FeC nanoclusters and the coalescence process of FeC-C nanoclusters. The FeC-C core-shell nanoparticles exhibited a saturation magnetization of 23.6 emu g and a coercivity of 550 Oe at room temperature