Fanqing Li

Large-scale synthesis of uniform urchin-like patterns of Bi2S3 nanorods through a rapid polyol process

Abstract A rapid and convenient polyol method has been developed to synthesize uniform urchin-like patterns of Bi2S3 nanorods in ethylene glycol at 197 °C for 30 min. X-ray diffraction pattern indicates that the obtained sample is orthorhombic phase Bi2S3. Scanning electron microscopy images and transmission electron microscopy images reveal that it is produced as uniform urchin-like pattern with spherical symmetry. The individual Bi2S3 nanorods is about 50 nm in diameter. The solvent and the S source material, thiourea, are of great importance on the final urchin-like structures.

Hydrothermal preparation of α-MnS nanorods from elements

A simple and convenient elemental-direction-reaction route has been successfully developed to prepare α-MnS nanorods under hydrothermal conditions using manganese and sulfur powder as starting materials in the temperature range of 240–260°C. It was found that the temperature was a key factor influencing the phase purity of the titled compound. A possible formation mechanism of the α-MnS nanorods was proposed on the basis of our contrast experimental results, which revealed that α-MnS nanorods were formed via an in situ sulfiding Mn(OH)2 nanorods produced by the reaction of manganese and water.

Antimony sulfide tetragonal prismatic tubular crystals

Antimony sulfide tetragonal (rectangular) prismatic tubular crystals with dimenions of 6–10xa0mm in length, 50–60xa0µm in width, and 5–15xa0µm in thickness were successfully synthesized for the first time via a hydrothermal reaction route from antimony trichloride and sodium thiosulfate in the presence of ammonium chloride at 198u2006°C.

Enhanced yellow–green photoluminescence from ZnO–SiO2 composite opal

A remarkably enhanced yellow–green photoluminescence (PL) was observed from ZnO nanocrystals infiltrated into SiO2 opal photonic crystals. It was clearly visible to the naked eye under the excitation of an Xe lamp and had substantially improved thermal stability over pure ZnO nanocrystals. The PL spectrum shape of a ZnO–SiO2 composite opal can be modified by annealing an SiO2 opal or choosing an SiO2 opal with different lattice parameters. The enhancement of PL intensity is interpreted based on the dependence of the PL intensity on the size of SiO2 microspheres as well as the anisotropy of the photoluminescence excitation (PLE) spectra. Our results may be interesting for further application.

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 500u2009°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.

Critical current density of the whiskers

The whiskers with 2212 phase have been grown out by annealing a melt-quenched plate in a stream of gas at for 121 hours. Temperature dependences of the magnetic susceptibility (-T) and the critical current density have been measured. The transition point of the whiskers is 76.2 K, and the value is at 63.4 K, zero magnetic field. near is found, which hints that there may exist some inner grain Josephson junctions in the whisker.

Thermoelectric power properties of graphitic nanotubule bundles

Thermoelectric power (TEP) properties of graphite nanotubule bundles were measured in the range 80–280 K. It was found that the TEP is positive and the magnitude at 280 K reaches about an order of +15 μV/K, far larger than that in highly oriented pyrolytic graphite. Moreover, in the studied range, the TEP can be approximately described by the formula S(μV)=0.167T−(70.2+0.085T)e−302.5/T derived based on a two-band model. The experimental results support such an idea that in the buckybundles both kinds of nanotubes, i.e., metallic tubes with a highly mobile velocity and semiconductive tubes with a narrow energy gap are included. The Fermi energy of the valence band for the metallic tubes is about −0.22 eV, and the average effective energy gap of the semiconductive tubes is estimated at about 52.2 meV. This conclusion is in good agreement with the theoretical predictions.

HIGH Tc SUPERCONDUCTING THIN FILMS BY CHEMICAL SPRAY DEPOSITION

A Chemical spray deposition process with mixed nitrate solution as source was developed to prepare thin films of Ba-Y-Cu oxide on sapphire substrate. By adjusting the source composition and deposition conditions, we have successfully obtained the films in thickness of 2–15μm with essentially orthorhombic Ba2YCu3O7 phase. The films behave super conducting transition with onset above 90K and zero resistance at 68.4K to date. It is believed that the tails in the resistance transition can be improved by searching proper heat treatment and using suitable substrates such as ZrO2 and SrTiO3.

Synthesis of NiS2-xSex solid solution via an ultrasonic solvothermal route

Abstract NiS 2− x Se x solid solution has been successfully prepared via an ultrasonic solvothermal route. The products were characterized by X-ray diffraction, ICP-AES and X-ray photoelectron spectroscopy. It has been found that the lattice parameter a follows a Vegard law with the selenium content x Se . The effects of ultrasonic and solvent on synthesizing NiS 2− x Se x solid solution were discussed. By comparing the Se molar fraction in the reagents to the selenium content in the samples, the formation mechanism of NiS 2− x Se x solid solution was proposed. Scanning electron microscopy images indicate that the products exhibit different morphologies corresponding to different compositions.

Growth of Pb5S2I6 meso-scale tubular crystals

Abstract Pb 5 S 2 I 6 meso-scale tubular crystals were grown from a hydrothermal reaction among PbCl 2 , (NH 2 ) 2 CS and I 2 at 155°C. The tubular crystals were arranged from 5 to 7xa0mm in length and 10–30xa0μm in cross section. A possible growth mechanism for Pb 5 S 2 I 6 tubular crystals is proposed.