Morphology control of nickel nanoparticles prepared in situ within silica aerogels produced by novel ambient pressure drying.

Silica aerogels are low density solids with high surface area and high porosity which are ideal supports for catalyst materials. The main challenge in aerogel production is the drying process, which must remove liquid from the pores of the wet gel while maintaining the solid network. In this work, the synthesis of silica aerogels and nickel-doped silica aerogels by a low energy budget process is demonstrated. Silica aerogels are produced by ambient drying using ammonium bicarbonate, rather than a conventional low surface tension solvent. Heating dissociates the ammonium bicarbonate, so generating CO2 and NH3 within the pores of the wet gel which prevents pore collapse during drying. Nickel-doped aerogels were produced by reducing nickel ions within pre-synthesised silica aerogels. The morphology of the resulting nickel particles-spheres, wires and chains-could be controlled through an appropriate choice of synthesis conditions. Materials were characterized using nitrogen adsorption/desorption isotherms, scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis and X-ray diffraction. The surface area of undoped aerogel is found to increase with the concentration of ammonium bicarbonate salts from 360 to 530 m2 g-1, and that of nickel-doped silica aerogel varies from 240 to 310 m2 g-1 with nickel doping conditions.

Bioinspired Synthesis of Monolithic and Layered Aerogels.

Aerogels are the least dense and most porous materials known to man, with potential applications from lightweight superinsulators to smart energy materials. To date their use has been seriously hampered by their synthesis methods, which are laborious and expensive. Taking inspiration from the life cycle of the damselfly, a novel ambient pressure-drying approach is demonstrated in which instead of employing low-surface-tension organic solvents to prevent pore collapse during drying, sodium bicarbonate solution is used to generate pore-supporting carbon dioxide in situ, significantly reducing energy, time, and cost in aerogel production. The generic applicability of this readily scalable new approach is demonstrated through the production of granules, monoliths, and layered solids with a number of precursor materials.

Synthesis and Characterisation of Reduced Graphene Oxide/Bismuth Composite for Electrodes in Electrochemical Energy Storage Devices.

A reduced graphene oxide/bismuth (rGO/Bi) composite was synthesized for the first time using a polyol process at a low reaction temperature and with a short reaction time (60 °C and 3 hours, respectively). The as-prepared sample is structured with 20-50 nm diameter bismuth particles distributed on the rGO sheets. The rGO/Bi composite displays a combination of capacitive and battery-like charge storage, achieving a specific capacity value of 773 C g-1 at a current density of 0.2 A g-1 when charged to 1 V. The material not only has good power density but also shows moderate stability in cycling tests with current densities as high as 5 A g-1 . The relatively high abundance and low price of bismuth make this rGO/Bi material a promising candidate for use in electrode materials in future energy storage devices.

Extraordinarily long-ranged structural relaxation in defective achiral carbon nanotubes.

We present a systematic ab initio density functional theory-based study which demonstrates that even one of the simplest defects in single-wall carbon nanotubes, the reconstructed monovacancy (a pentagonal ring and a single dangling bond known as a 5-1db defect), leads to extraordinarily long-ranged structural distortions. We show that relaxation due to reconstruction can only be modeled accurately through a careful selection of boundary conditions and an appropriately long nanotube fragment.