Jin Gang Qi

Study on Preparation and Optical Absorption of Ge Doped TiO2 Composite Thin Films by Sol-Gel Method

By using the sol-gel method, TiO2 thin films and Ge doped TiO2 composite thin films were fabricated onto quartz substrates. XRD, XPS and UV-vis were used to characterize the phase structure, the atomic chemical states and optical absorption of these composite TiO2 thin films. XRD results indicate that diffraction peak of anatase is observed in samples. XPS result reveals that there is Ge crystal in Ge doped films which were prepared by sol-gel method, and Ge exists as elemental Ge and GeO2 in the films. The composite TiO2 thin films by sol-gel method exhibits the absorption shift to visible region due to Ge doped TiO2 thin films.

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.

Influence of Electrical Pulse on Shape Memory Effects and Phase Transition of FeMnSiCrNi Shape Memory Alloy

This paper studies the electric-pulse applied in the solidification process of the FeMnSiCrNi shape memory alloy, by applying different pulse frequency and polarity on the FeMnSiCrNi shape memory alloy to improve the shape memory effects. The results show : electric-pulse was conducive to FeMnSiCrNi alloys grain refinement, the alloy can improve the shape memory effect of Compression deformation, the absolute shape recovery rate is improved from 2% to 3.2% which is not treated by the electric-pulse ; when the liquid metal was connected with the anode of the pulse, it is easy to get the columnar grain structure and the column spacing is smaller; when the liquid metal was connected with the cathode of the pulse, the column spacing is larger; Columnar grain is conducive to FeMnSiCrNi alloy specimens compressed shape recovery, it has the smaller column spacing, yet the shape recovery rate is higher; equiaxed is favor in bending back, columnar crystals impede the bending response.

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.

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.

Influences of Melt Temperature on Casting Structure of Al-Cu-Mn Alloy Treated by Electric Pulse Modification

It was investigated that the effect of electric pulse modification (EPM) on the hot tearing of Al-5%Cu-0.8%Mn alloy. The results indicate that hot tearing tendency of all samples can be reduced treated by electric pulse with different parameters, moreover, hot tearing stress of alloy with EPM was enhanced 3 times or so than that of samples without treatment. Decreasing the quantity of eutectic in grain boundaries, decreasing the end-solidifying temperature of the alloys, and refining the grains are main causations for increasing hot tearing resistance of Al-5%Cu-0.8%Mn alloy by electric pulse modification.

Effects of Electric Pulse Modification on the Hot Tearing of Al-5%Cu-0.8%Mn Alloy

It was investigated that the effect of electric pulse modification (EPM) on the hot tearing of Al-5%Cu-0.8%Mn alloy. The results indicate that hot tearing tendency of all samples can be reduced treated by electric pulse with different parameters, moreover, hot tearing stress of alloy with EPM was enhanced 3 times or so than that of samples without treatment. Decreasing the quantity of eutectic in grain boundaries, decreasing the end-solidifying temperature of the alloys, and refining the grains are main causations for increasing hot tearing resistance of Al-5%Cu-0.8%Mn alloy by electric pulse modification.

Morphology Control of Cobalt Oxalate Particles under the Action of Pulsed Electromagnetic Field

It is very important for spheroidic metal cobalt powders production to control the morphology of cobalt oxalate powders precursor. The spheroidic cobalt oxalate powders were prepared by conventional precipitation when a pulsed electromagnetic field (PEMF) was introduced. Scanning electron microscopy (SEM) images and X-ray powder diffraction (XRD) were used to characterize morphologies and phase structures of the cobalt oxalate powders. The research results show that a pulsed electromagnetic field (PEMF) play a key role in the process of preparation of spheroidic cobalt oxalate powders. In addition, a possible morphology control mechanism was preliminarily discussed based on the effects of PEMF on the process of growth of cobalt oxalate particles.

The Effect of Mixture Parameter on the Properties of SCC

It is not difficult to prepare self-compacting concrete (SCC) in laboratory now. The problem researchers faced is how SCC can be popularized in civil engineering. A modified densification mixture design algorithm (DMDA) is used in this study to prepare the control mixture. And on the basis of the system analysis for exist studies, 6 factors are chosen as experimental factor and 25 experiments are designed by orthogonal design experiment method. The results analysis indicates that only 3 factors are significant on SCC and their recommend value is obtained respectively. It may shed light on the application of SCC.