Bing Xiao

Growth of hex-pod-like Cu2O whisker under hydrothermal conditions

Abstract In this paper, hex-pod-like Cu2O whiskers were successfully synthesized from a Cu(CH3COO)2 precursor under hydrothermal conditions, and examined by means of scanning electron microscopy, X-ray microprobe analysis, and X-ray diffraction. The effects of precursor concentration and pH, reaction temperature and time on the evolution of Cu2O synthesis and morphology were investigated. The whiskers were composed of a nucleus and six pods. The pods grow along the 〈0xa00xa01〉 directions, and are bounded to {0xa00xa01} faces. The adjacent pods are perpendicular to each other. The dipolar characteristics of the Cu2O {0xa00xa01} faces are the critical factors in the synthesis of the peculiar Cu2O whiskers. Finally, a possible growth mechanism is proposed.

High-temperature ferromagnetism in (Co, Al)-codoped ZnO powders

Zn0.95−xCo0.05AlxO (x=0,0.01,0.03) powders were prepared from the acetate-derived precursor by the sol-gel route. The structural and magnetic properties of the powders were investigated. X-ray absorption spectroscopy and high-resolution transmission electron microscope analyses indicate that Co2+ substitute for Zn2+ without changing the wurtzite structure. The powder shows paramagnetic behavior at 5K for x=0 sample. For x=0.01 and 0.03, the powders exhibit ferromagnetic behavior at 360K. It was demonstrated experimentally that high-temperature ferromagnetism in Co-doped ZnO powders can be obtained through increasing the carrier concentration which was realized by doping a few percent of Al.

Large-scale fabrication of silicon carbide hollow spheres

The synthesis of SiC hollow spheres is reported. The shell of the spheres is formed through a solid–gas reaction rather than traditional chemical methods. The sphere size can be modulated from the microscale to the nanoscale, and the shell thickness can be finely tuned by adjusting the experimental parameters. This technique presents a new paradigm in the preparation of hollow spheres. Based on this technique, other carbide hollow spheres could also be synthesized.

Magnetic Properties of Mn-Doped ZnO Nanostructures Synthesized by Chemical Vapor Transport

Mn-doped ZnO nanostructures have been fabricated by chemical vapor transport (CVT). Nanobelts, nanorods and nanowires have different growth directions because of their different growth environments. X-ray diffraction, electron paramagnetic resonance and Raman spectrum methods have been used to identify the substitution of a Zn site with Mn ions. Despite their different morphologies, these nanostructures possess the same magnetic properties. Magnetization was paramagnetic and antiferromagnetic. No ferromagnetism was observed even at T=5 K.

Absence of intrinsic ferromagnetism in Zn1−xMnxO alloys

Zn1−xMnxO alloys, with different Mn concentrations, were prepared by the hydrothermal method. X-ray diffraction and electron paramagnetic resonance spectra demonstrate that Zn2+ ions are homogeneously substituted by Mn2+ ions without changing the ZnO wurtzite structure. The x = 0.02 and 0.04 samples are paramagnetic. When the Mn concentrations are increased to x = 0.08 and 0.10, the samples exhibit some ferromagnetism due to a secondary phase, (Zn,Mn)Mn2O4.

Stacking Fault Duplication in 6H-SiC Single Crystal

6H-SiC single crystal was grown by physical vapor transport (PVT). The duplications of several types of stacking fault (SF) such as SF , SF , and SF were observed by high-resolution transmission electron microscopy (HRTEM). First-principle calculations revealed that the formation energies of single SF and SF are very low while that of SF is much higher. Further calculations demonstrated that the continuous SFs possessed larger stress along the c-axis than the separated SFs. This suggests that the stress should be the reason for the SF duplication, and the SF can be duplicated under higher c-axis stress.