ALBERT

Beschreibung: High gradient magnetic separation (HGMS) achieves effective separation to fine weakly magnetic minerals using numerous small magnetic wires in matrix, and its separation performance is inherently dependent on the capture characteristics of the wires. In this work, the selective capture of magnetic wire to particles in high gradient magnetic field was theoretically described and simulated using COMSOL Multiphysics. It was found that the capture trajectories of a small amount of particles under the ideal condition was significantly different from those of a large amount of particles under the actual condition, and non-magnetic particles would be much more easily entrained into magnetic deposits captured onto the wire surface under the actual condition than those under the ideal condition. These theoretical and simulated results were basically validated with the experimental magnetic capture to an ilmenite ore, and the wires in slow feed mode have achieved much higher capture selectivity than those in the fast feed mode. For instance, at the magnetic induction of 0.8 T, the TiO2 grade of magnetic deposits captured by 3 mm diameter wire in the slow feed model reached 36.78%, which is higher than 28.32% in the fast feed model. The selective capture difference between the fast and slow feed models increased with increase in the magnetic induction and with decrease in the pulsating frequency. This investigation contributes to improve HGMS performance in concentrating fine weakly magnetic ores.

Beschreibung: In harsh environments, the corrosion damage of steel structures and equipment is a serious threat to the operational safety of service. In this paper, a Zn-Al diffusion layer was fabricated on 45 steel by the Mechanical Energy Aided Diffusion Method (MEADM) at 450 °C. The microstructure and composition, the surface topography, and the electrochemical performance of the Zn-Al diffusion layer were analyzed before and after corrosion. The results show that the Zn-Al diffusion layer are composed of Al2O3 and Γ1 phase (Fe11Zn40) and δ1 phase (FeZn6.67, FeZn8.87, and FeZn10.98) Zn-Fe alloy. There is a transition zone with the thickness of about 5 μm at the interface between the Zn-Al diffusion layer and the substrate, and a carbon-rich layer exists in this zone. The full immersion test and electrochemical test show that the compact corrosion products produced by the initial corrosion of the Zn-Al diffusion layer will firmly bond to the Zn-Al diffusion layer surface and fill the crack, which plays a role in preventing corrosion of the corrosive medium and reducing the corrosion rate of the Zn-Al diffusion layer. The salt spray test reveals that the initial corrosion products of the Zn-Al diffusion layer are mainly ZnO and Zn5(OH)8Cl2H2O. New corrosion products such as ZnAl2O4, FeOCl appear at the middle corrosion stage. The corrosion product ZnAl2O4 disappears, and the corrosion products Zn(OH)2 and Al(OH)3 appear at the later corrosion stage.