Yitai Qian

Controllable Synthesis of Mesoporous Co3O4 Nanostructures with Tunable Morphology for Application in Supercapacitors

Novel and complex mesoporous 2D and 3D architectures of the oxide semiconductor Co(3)O(4), including nanosheets, nearly monodisperse microspheres that are self-assembled from nanosheets, and copper-coin-like nanosheets, have been synthesized through a facile binary-solution route and sequential thermal decomposition at atmospheric pressure. The influence of different reaction conditions on the morphology of the products has been discussed in detail. The results revealed that the volume ratio of H(2)O and ethanolamine (EA) play a crucial role in the morphology of the precursor. The thermal decomposition of the corresponding precursor leads to the formation of the mesoporous structure. The products have been characterized by X-ray diffraction techniques, field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and Raman spectroscopy. The electrochemical properties of the Co(3)O(4) electrodes were investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge measurements. The electrochemical experiments revealed that the specific capacitance of the Co(3)O(4) nanosheets was higher than that of the Co(3)O(4) microspheres in a KOH electrolyte solution (3 m). Furthermore, the Co(3)O(4) nanosheet electrodes exhibited good rate capabilities, and maintained 93% of the initial capacity at a current density of 5 mA cm(-2) in a KOH (3 m) electrolyte solution. The results show that Co(3)O(4) nanosheets might have potential applications as electrode materials for supercapacitors.

A Benzene-Thermal Synthetic Route to Nanocrystalline GaN

A thermal reaction of Li3N and GaCl3 in which benzene was used as the solvent under pressure has been carried out for the preparation of 30-nanometer particles of gallium nitride (GaN) at 280°C. This temperature is much lower than that of traditional methods, and the yield of GaN reached 80%. The x-ray powder diffraction pattern indicated that sample was mainly hexagonal-phase GaN with a small fraction of rocksalt-phase GaN, which has a lattice constant a = 4.100 angstroms. This rocksalt structure, which had been observed previously only under high pressure (at least 37 gigapascals) was observed directly with high-resolution electron microscopy.

A low temperature molten salt process for aluminothermic reduction of silicon oxides to crystalline Si for Li-ion batteries

A low temperature molten salt process is developed to prepare crystalline Si nanoparticles through the reduction of micro-sized high silicon zeolite by metallic Al (or Mg) in molten AlCl3. The reaction can be initiated at 200 °C, and the yield is about 40%. As the reaction temperature increases to 250 °C, the yield can reach about 75%. When the prepared Si was used as an anode for Li-ion batteries, reversible capacities of 2663 mA h g−1 at 0.5 A g−1 after 50 cycles and 870 mA h g−1 at 3 A g−1 after 1000 cycles can be obtained. Similarly, this synthetic strategy is employed to synthesize Si nanoparticles starting from various abundant raw materials including SiO2 powder, kieselguhr, fiberglass, and even the natural mineral of albite.

Synthetic Methodologies for Carbon Nanomaterials

Carbon nanomaterials have advanced rapidly over the last two decades and are among the most promising materials that have already changed and will keep on changing human life. Development of synthetic methodologies for these materials, therefore, has been one of the most important subjects of carbon nanoscience and nanotechnology, and forms the basis for investigating the physicochemical properties and applications of carbon nanomaterials. In this Research News article, several synthetic strategies, including solvothermal reduction, solvothermal pyrolysis, hydrothermal carbonization, and soft-chemical exfoliation are specifically discussed and highlighted, which have been developed for the synthesis of novel carbon nanomaterials over the last decade.

Surface phase decomposition in Bi2Sr2CaCu2Oy single crystals

Phase decomposition in high‐quality Bi2Sr2CaCu2Oy single crystals has been induced by annealing treatments at a temperature over 500 °C. X‐ray diffraction and scanning electron microscope studies show that this change of structure is mainly limited in the surface part of the annealed single crystals and the 2201 phase together with a new phase of cell parameter c=9.6 A segregated from the 2212 phase. The phase decomposition is directly associated with the oxygen content in the annealing atmospheres and evaporation of the Bi is detected and is suggested to be the main factor involving the phase segregation in the annealing process and an important factor for the BiO bilayers in the as‐grown single crystals.