The transformation of Ni nanoparticles (NPs) of different sizes (average diameters of 9, 26, and 96 nm) during oxidation to hollow (single void) or porous (multiple voids) NiO through the nanoscale Kirkendall effect was observed by transmission electron microscopy. Samples treated for 1-4 h at 200-500 degrees C show that the structures of the completely oxidized NPs do not depend on the temperature, but oxidation proceeds more quickly at elevated temperatures. For the Ni/NiO system, after formation of an initial NiO shell (of thickness approximately 3 nm), single or multiple voids nucleate on the inner surface of the NiO shell, and the voids grow until conversion to NiO is complete. Differences in the void formation and growth processes cause size-dependent nanostructural evolution: For 9 and 26 nm NPs, a single void forms beneath the NiO shell, and the void grows by moving across the NP while conversion to NiO occurs opposite the site where the void initially formed. Because of the differences in the Ni/NiO volume ratios for the 9 and 26 nm NPs when the void first forms, they have distinct nanostructures: The 9 nm NPs form NiO shells that are nearly radially symmetric, while there is a pronounced asymmetry in the NiO shells for 26 nm NPs. By choosing an intermediate oxidation temperature and varying the reaction time, partially oxidized Ni(core)/NiO(shell) NPs can be synthesized with good control. For 96 nm NPs, multiple voids form and grow, which results in porous NiO NPs.

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Ternary bismuth oxyhalide crystalline nanobelts (such as Bi24O31Br10, Bi3O4Br, Bi12O17Br2, BiOCl, and Bi24O31Cl10) and nanotubes (such as Bi24O31Br10) have been synthesized by using convenient hydrothermal methods. The composition and morphologies of the bismuth oxyhalides could be controlled by adjusting some growth parameters, including reaction pH, time, and temperature. All the nanostructures were characterized by using various methods including X-ray diffraction, transmission electron microscopy, high-resolution TEM, electron diffraction, and energy-dispersive X-ray analysis. The possible reaction mechanism and growth of the crystals are discussed based on the experimental results.

Carbonated soybean oil (CSBO) can be used as intermediate for the synthesis of non-isocyanate polyurethanes (NIPUs). In this work, CSBO was prepared by the reaction of epoxidized soybean oil (ESBO) with carbon dioxide (CO 2 ) using a novel composite catalyst comprising SnCl 4 Á 5H 2 O and tetrabutylammonium bromide (TBABr). The evolution of the reaction process and structure of CSBO were studied by means of IR, 1 H-NMR, and GPC techniques. Effects of catalyst formulation and various reaction conditions on the reaction were examined. The results showed that the obvious improvement in ESBO conversion using the present composite catalyst under mild conditions was achieved. Moreover, it was interesting to note that very high purity of CSBO was not a prerequisite for the synthesis of NIPUs with good performance.

Background: Bistability, the capacity to achieve two distinct stable steady states in response to a

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