Jian Zhong Wang

Synthesis and Characterization of Nanocrystalline ZnO Powders by a Novel Combustion Synthesis Method

Nanocrystalline ZnO powders have been synthesized by a novel combustion synthesis method using glycine and urea as mixed fuels and zinc nitrates as oxidant. The as-synthesized ZnO powders are characterized by DSC, XRD and SEM. Results show that the as-synthesized ZnO powders show well crystalline with hexagonal crystal structure and purity without any other impurities and the particle sizes are about 50~70nm calculated by the Scherrer formula.

Effect of Solution Concentration on Growth and Photoluminescence of ZnO Nanorod Arrays

Well-aligned ZnO nanorod arrays had been successfully prepared by using hydrothermal methods. XRD and SEM analysis showed ZnO nanorod arrays had well orientation along the [0 0 1] direction of ZnO nanorods. The length to diameter is biggest among these samples and is about 25 when solution concentration is 0.8mol/l. The UV emission caused mainly by exciton combination. Furthermore the formation mechanism of ZnO nanorob arrays was studied in detail.

Effects of Electric Pulse Treatment during Solidification on the Solidification Structure of Al-5%Cu Alloy

In this paper, the effects of electric pulse on solidified structure and graining process of near eutectic Al-5%Cu alloy have been investigated during solidified process. It was treated with different pulse voltages at 740°C in this experiment, and established the cooling curve. The results show that the improvement of alloy casting macro-segregation and solidification structure refinement by electric pulse discharging; The change of the solidified casting structure has a preferable coincidence relation with the change of the cooling curve, and analysis of the cooling curve shows that the best granular effect has a maximal supercooling on the curve.

Effects of pulsed electromagnetic field on morphology and size of cobalt oxalate particles

Abstract It is of much significance to control the morphology and size of cobalt oxalate precursor for the preparation of cobalt powders. The cobalt oxalate powders were prepared by conventional precipitation at different initial cobalt chloride concentrations in the presence of pulsed electromagnetic field. Scanning electron microscopy images and size analysis indicate that spherical and fine cobalt oxalate particles with uniform size are obtained. Conductivity analysis demonstrates that pulsed electromagnetic field plays an important role in the preparation of monodisperse cobalt oxalate particles owing to the inhibition of the secondary nucleation. X-ray powder diffraction results show the formation of β-CoC2O4·2H2O with a micro-size change of cobalt oxalate grain when the extra pulsed electromagnetic field is present. Fourier transform infrared spectroscopy results indicate that the transition of bond way in CoC2O4·2H2O favours to develop stable crystal nucleus. Besides, a possible mechanism for the interaction between pulsed electromagnetic field and cobalt oxalate reaction system was preliminarily discussed.

Al doping effects on ZnO nanostructure and growth mechanism

Abstract High-energy and large surface Al-doped ZnO nanostructure arrays were fabricated using hydrothermal methods under the action of pulsed electromagnetic field. The morphology, structure and component features were analysed by field emission scanning electron microscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy. Results showed that the hexagonal sheet like Al-doped ZnO regularly interlaced with each other and vertically grew on the FTO substrate. The surfaces of the ZnO nanosheets were larger than those of the undoped ZnO nanorods. In addition, the formation mechanism of Al-doped ZnO nanostructure was explained.

Effect of Post-Annealing Ambient on Electrical Structural Properties and Optical Properties of ZnO:Al Transparent Films

Transparent ZnO:Al films deposited by RF/DC magnetron sputtering in room temperature are annealed under gaseous ammonia ambient and air ambient, respectively. The characteristics of ZnO films are examined by XRD, SEM, Hall measurement and optical transmission spectra. The XRD and SEM analysis shows that both films are crystallized in the wurzite phase with a preferential orientation along the c-axis and have a smooth dense surface. Hall measurement results indicate ZnO:Al films annealed under ammonia ambient convert to p-type conduction with the high carrier concentration of 8.3×1018 cm-3. Optical transmission spectra show a high transmittance (~85%) in the visible region.

Effects of Different Melt Modification Techniques on the Structure and Properties of Silicon Brass

The melt of nonleaded free-cutting brass is modified by the electric pulse and the effects on the solidification structure and properties of Silicon Brass are studied with different Bi contents and under different pulse parameters. The results show that the varieties of Bi contents and pulse parameters have a greater impact on grain size and microstructure uniformity of the brass. After silicon brass with 0.5% Bi is modified by electric pulse, the Bi grain size is reduced to 5μm from 30μm, and its shape is changed into being granular from worm-like or long-strip-like, distributed more evenly in α phase and α phase boundary, and a few of which goes into the β phase matrix.

Methods of Improving Shape Memory Effect of FeMnSiCr Alloy Pipe Joint

The influence of different broaching rate, the training of thermo-mechanical cycle and Electro-pulse Modification (EPM) on the shape memory effect of the FeMnSiCr alloy was investigated. The recovery pulling force can be realized as high as 22850N after EPM treatment. The Fe-based shape memory alloy (SMA) pipe joint can meet the requirement of engineering application.

Effects of Pulse Electric Field on the Clusters of Pb-Sn Molten Alloy

The authors investigate the effect of electric pulse field (EPF) on the grain size of Pb-Sn alloy and conclude the optimization parameter of EPF through the specialized experiment. Applying the electric dipole theory, the electro-migration theory and combining with the electrostatic force analysis, the author explain that the EPF can modify the liquid structure, can make the smaller cluster reorganized and growing up and at the same time can make the bigger cluster fission, then induce the cluster scale to the same and therefore improve the solidification structure from the theory point of view.

Study on the Influence of Different Pulse Temperatures on Al-22%Si Alloy Solidification Structure

Taking the hypereutectic Al-Si alloy as the research object, the fading characteristics of Al-22% Si alloy at different pulse temperatures are investigated in this paper in order to analyze the mechanism of electrical pulse modification to the alloy. We can get the conclusion by observing the microstructure of the sample, measuring the microhardness and calculating the volume fraction and the average size of primary silicon: at different pulse temperatures, the effect of electric pulse modification is fading with static duration prolonging; meanwhile, with the temperature upward, the modification effect and fading trends to be weak, which indicates the best pulse temperature is one of the important factors to influence the modification effect.