Papers by Author: Yu Zhu Zhang

Abstract: The direct fibrillation of blast furnace slag can solve these problems, such as having not been recycled of sensible heat, the consumption of water resources, environmental pollution and the low additional value of product, which are caused by the traditional water quenching method. The modification is the key problem of fiber forming. The thesis mainly aims at the study of viscosity of slag, the ability of crystallization and mineral phase structure after the modified process of blast furnace slag and confined the relevance of the three to optimize the appropriate texturizer and adding ratio. The results are as following: Iron ore waste rock, fly-ash and compounded texturizer can improve the high temperature viscosity of the slag respectively, while it has different effect on landing gradient of viscosity and temperature (Fly-ash occupies first place, compounded texturizer comes second and iron ore and waste rock comes the minimum). By analyzing the crystallization behavior of the slag in the solidification process, when the proportion of iron ore waste rock is more than 9%, the fly-ash is equal or greater than 8% and the compounded texturizer is more than 9%, the solidification slag will appear amorphous. The mineral composition of the slag transforms gradually from melilite to vitreous body, which will make the air hole of the vitreous body increased and aperture decreased. When the iron ore waste rock is added, the homogeneity of the air hole will deteriorate, while adding the fly-ash and compounded texturizer will strengthen the homogeneity of the air hole and make the mineral structure intensive gradually.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: Boronized layer was prepared on carbon steel substrate by pulse electrodeposition in KCl-NaCl-NaF-Na2B4O7 molten salts. The orthogonal experimental design was used to study the influence of pulse electrodeposition parameters on the thickness of boronized layer. The distribution of boron content of the boronized layer was measured using the glow discharge spectrometry (GDS) and the depth from the surface to the inflection point was taken as the layer thickness. It was found that the order of significant factors for the thickness is electrodeposition temperature > electrodeposition time > current density > borax content > duty cycle. Based on the results of the range analysis, the maximum thickness was found at a current density of 120mA/cm2, a electrodeposition temperature of 900°C, a electrodeposition time of 120 min, a duty cycle of 10%, and a borax content of 0.04 mole ratio.

Abstract: The pore in the sinter is an important character. Because of multiphase and asymmetry in the sinter, the structure of the pore is very complex. To study the character of the pore effectively, the method of mercury intrusion porosimetry is applied to measure the pore in the sinter, and the results are dealt with by the fractal theory. The results prove that the pores in the sinter are actually fractal structure when the size of the pores is more than 204.5 nm because their curves in the log-log plot are linear, and some curves qualified with the linearity obviously possess of the segment linearity character. According to the calculation of the fractal D, the relationship of the strength and fractal D will be established.

Abstract: The sinter ore samples with different content of silica were prepared by the mini-sintering method so as to study the micro-mechanism of sinter. The fractal theory was also applied to analyze quantitatively the grain distribution in the samples’ two-dimensional microstructure. The study found that the grain distribution of the sinter shows the fractal characteristic, its fractal dimension is about 1.95, and the fractal dimension can be used to characterize uniformity of the grain distribution. With the increase of silica content, the fractal dimension of the samples shows a linear decreasing trend and it is the same trend in the comparing sintering-cup experiment when the fractal dimension of particle size distribution reduces, the silica content increases. In addition, the compressive strength of mini-sintering sinter sample was also measured. It shows that the compressive strength is the highest when the silica content is 3.8 wt%, which is correlative with the porosity, the content of calcium ferrite and glassiness in the sinter ore besides the fractal dimension.

Abstract: A gas quenching process to deal with steel slag and its characteristics of the new technology was briefly introduced. The grinding characteristics, mineral phases of gas quenching steel slag and the potential economic benefits of using it as cement mixing material was studied by compared to heat-stew steel slag. The results indicated that the specific surface areas (S) and grinding times (t) of the gas quenching steel slag showed a first order exponential decay relationship. With the extension of time, the specific surface areas of heat-stew steel slag was tending to balance earlier than that of gas quenching steel slag; The energy consumption of gas quenching steel slag was much lower than that of heat-stew steel slag. Gas quenching steel slag was comprised of C₂S, C₃S, a certain amount of (Ca₂(Al, Fe)₂O₅）and RO phase, but the content of RO phase was relatively low, which increased the grindability of the quenching steel slag, so that the grindability of gas quenching steel slag was much better than that of heat-stew steel slag. Gas quenching steel slag prepared for cement addictives would bring great economic benefits.

Abstract: According to a series of experimental studies such as the content of the f-CaO, the relative grindability index of the gas quenching steel slag, the properties of gas quenching steel slag cement and a detailed analysis of the potential economic benefits of steel slag cement. It was found that it has a huge economic benefits in preparing the cement with gas quenching steel slag.The results showed that the content of f-CaO in slag particles less than 2mm were no more than 2.7% and there exists a well proportional relation between it and the grain size; the grindability of gas quenching steel slag is much better than heat-stew steel slag; what's more,because of the high hydration activity of gas quenching steel slag, it can be produced the perfect steel slag cement with excellent hydration, stability and strength.

Abstract: 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.