Precipitation and Growth Behavior of Magnetite Crystal During Continuous Cooling of Molten Nickel Oxide Slag

The efficient extraction of iron from nickel slag has attracted more recent attention in the recycling of nickel slag. In this research, Factsage software was used to predict the formation and preferential precipitation behavior of magnetite crystal in molten nickel oxide slag. The precipitation and growth of magnetite crystal in molten nickel oxide slag during continuous cooling were in-situ observed by high temperature laser confocal microscope (HT-CLSM), and the growth characteristics of magnetite crystal under 5 similar to 50 degrees C/min cooling rate was studied. The morphology, phase and composition of the samples were characterized by SEM-EDS, XRD and ICP. The results show that magnetite crystals are preferentially precipitated from the melt during continuous cooling, and the initial precipitation temperature is between 1430 similar to 1450 degrees C. At low cooling rate (5 similar to 15 degrees C/min), the initial nucleation and precipitation of the crystals are slow, and the grains grow stably at 1200 similar to 1400 degrees C, with an average growth rate of 0.141 gin/s, and the final grain size is more than 100 mu m. High cooling rate (25 similar to 50 degrees C/min) can promote the rapid nucleation and precipitation of magnetite crystal at the initial stage of growth, but the stable growth rate is small, and the final grain size is 20 similar to 30 mu m.