Yu Zhu Zhang

Effect of Current Density on Composition and Microstructure of Si Diffusion Layer by Electrodeposition

A Si diffusion layer on grain-oriented low-silicon steel substrates was produced by pulse electrodeposition in KCl-NaCl-NaF-SiO2 molten salt and the effect of current density upon the composition and microstructure of the siliconized layer was investigated. The results showed that by glow discharge spectrometry (GDS), the change of Si content of siliconized layers was similar in the range of 20-60 mA/cm2. Si content in the surface was maximum, and then dropped sharply within the surface layer (< 7 m). The Si content remained nearly constant in the middle part of the siliconized layer. The content of Si near to the substrate decreased relatively slowly. The Si content in the surface and the layer thickness increased with increasing current density. Cross-sectional observations revealed that the Si diffusion layers had a two-layer structure: the top layer composed of columnar grains grown perpendicularly to the substrate surface and a transition layer with equiaxed grains was close to the substrate. In addition, the thickness of the layer was too small when the current density was 20 mA/cm2, while the layer became more porous as the current increased from 40 to 60 mA/cm2 according to SEM observations. The optimum current density for deposition was 30 mA/cm2.

Growth Kinetics and Microstructure of Siliconized Layer by Molten Salt Electrodeposition

The siliconized layers were formed on the surface of hot rolled grain oriented silicon steel using a molten salt pulse electrodeposition method. The process was performed in the temperature range 1023-1123 K and with varying deposition time (60-180 min). The profile distribution of Si in the siliconized layer was measured using the glow discharge spectrometry (GDS) and the depth from the surface to the substrate was taken as the layer thickness. The morphology and structure were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that a longer deposition time tended to produce a larger grain and a looser, rougher layer. The phase structure of the layer was composed of Fe3Si with (110) preferred orientation in the experimental range. The longer deposition time resulted in an increase in thickness layer and the thickness of the layers ranged from 17 to 165m. Kinetic studies showed that the siliconized layer grew with a parabolic rate law, indicating the diffusion controlled growth. The activation energy for growth of siliconized layer was about 242 kJ/mol.

Study of Comprehensive Utilization on Ti-bearing Blast Furnace Slag

With the increase of Ti-bearing blast furnace slag, its harm is growing. It contains high titanium content. How to make good use of Ti-bearing blast furnace slag is currently a hot problem. In this paper, the conditions of comprehensive utilization on Ti-bearing blast furnace slag were described firstly. Then the features, application field and problems of extraction and non-extraction titanium from Ti-bearing blast furnace slag were introduced. The advantages, disadvantages and problems of comprehensive utilization of Ti-bearing blast furnace slag were analyzed. Finally the application prospects were forecasted.

Influence of Duty Cycle on Composition and Microstructure of Siliconized Layer Using Pulse Electrodeposition

The siliconized layer was pulse electrodeposited on grain oriented low-silicon steel sheet substrate in KCl-NaCl-NaF-SiO2 molten salts and the influence of duty cycle on the composition and microstructure of the siliconized layer was investigated. The results showed that when the duty cycle was in the range of 10% to 50% at average current density 30mA/cm2, Si content of siliconized layers was similar and the thickness of the layer was did not change much with different duty cycle. Cross sectional observation revealed that the siliconized layers had a two-layer structure. The top layer composed of columnar grains and a transition layer with equiaxed grains was close to the substrate. The layer was unsmooth when the duty cycle was 10%. While the surface appeared smooth and dense and the grains were fine when the duty cycle were 20% and 30%. The layer became more porous as the duty cycle increased to 40% and 50%.

Study of Comprehensive Utilization on the Steel Slag

At present steel industry is obtained a rapid development in China. More and more steel slag is accumulated. How to deal with steel slag becomes a hot problem. In this paper, the source, composition and characteristics of steel slag are introduced firstly. Then the methods of comprehensive utilization on the steel slag are summarized. Finally the problems are put up and the development trend of steel slag utilization is prospected according to the present situation of comprehensive utilization of steel slag.

Definition of Cohesive Zone in COREX Melter Gasifier Using Image Processing Method

The cohesive zone plays very important role in the operation of COREX melter gasifier, up to now, definition of the cohesive boundary has always been a challenging task. In this paper, a two-dimensional hot model of melter gasifier, in which paraffin and corn are used to simulate DRI, coke and lump coal respectively, has been established to study the cohesive boundary in this paper. While the whole experimental process is recorded by the high-speed camera, the image processing method is put forward to define the cohesive boundary quantificationally.

Growth Characteristics of Pulse Electrodeposition Fe-Si Layer

Fe-Si layer was prepared on silicon steel substrate from KCl-NaCl-NaF-SiO2 molten salts by pulse current at different time. The quantitative Si concentration depth profile, surface morphology and phase structure of the layer were studied by glow discharge optical emission spectroscopy, atomic force microscopy and X-ray diffraction. The layer growing process was analyzed from nucleation process, growth pattern and microstructure. It was observed that the Fe-Si alloy nucleated in the way of three dimensional conical shape and initially grew in the orientation of matrix, then gradually adjusted to the lowest energy state. With deposition time going on, the phase structure of the layer changed in the order of -Fe (Si) →α-Fe (Si) ＋Fe3Si →Fe3Si

Potential of Energy Saving and Technical Measures in Sintering in China

Compared to Japan sintering process, there is a large potential in energy saving in China. In order to reduce the sintering energy consumption, some effective measures such as reducing the solid fuel consumption, the gas consumption and the electricity consumption should be taken, meanwhile new characteristic technology of energy saving should be developed. Recycling the secondary energy is the other way of energy saving for sustainable development. And most especially, waste heat recovery has a great significance for saving energy.

Process Optimization and Structural Characterization of Fe3Si Layer by Pulse Electrodeposition

Fe3Si layer was prepared by pulse eletrodeposition of Si on the surface of non-oriented steel in molten salts. With an orthogonal test the optimal process parameters were determined: the formulation of salts was NaCl:KCl:NaF:SiO2=1:1:3:0.3(mole ratio), current density of 60 mA/ cm2, duty cycle of 30%, pulse period of 1000 s and a deposition time of 50 min, respectively. The compositional depth profile, the structure, the surface morphology and cross sectional micrograph of the layer were studied by glow discharge spectrometry (GDS), X ray diffraction (XRD), scanning electron microscopy (SEM) and optical microscope (OM). The results showed that Si in the layer existed in the form of the gradient distribution. The phase structure of the layer was composed of the single-phase Fe3Si. The layer composed of equiaxed grains. The surface appeared smooth and dense, and with uniform thickness.

Research Progress in Preparation of Carbon Nanotubes

Carbon nanotubes have unique physical and chemical, electrical, mechanical properties. As a new nanomaterial, it has great development potential. In this paper, the structure and properties of carbon nanotubes were briefly described, and the commonly used ways of preparation of carbon nanotubes were also introduced in detail. The importance of the development of new synthetic methods was put forward.