Eu2+ as the structural probe in the phase transformation of CMSA by site-selective occupancy and adjustable multimode white luminescence in Ca2(Mg0.5Al0.5)(Si1.5Al0.5O7) akermanite based on high-aluminum blast furnace slag.

A tunable multimode white emission Ca2(Mg0.5Al0.5)(Si1.5Al0.5O7):Eu2+/Eu3+ phosphor was prepared by doping Eu2O3 in molten high-aluminum blast furnace slag. The structural probe Eu2+ was studied during phase transformation between the glassy state and Ca2(Mg0.5Al0.5)(Si1.5Al0.5O7) crystals based on site-selective Eu2+ occupancy. When the doped Eu2+ ions occupied two different Ca2+ sites in the matrix, blue light (421 nm) and green light (516 nm) emissions were observed corresponding to two types of Eu2+Ca2+, namely Eu2+Ca2+ (Mg2+ → Al3+) and Eu2+Ca2+ (Si4+ → Al3+). The effects of Eu concentration (0.1-2.0 mol%), heat treatment temperature (800-1000 °C), and thermal quenching temperature (30-150 °C) on the structural evolution of the emission unit were studied by differential scanning calorimetry (DSC), photoluminescence spectroscopy (PL) and X-ray diffraction (XRD) analyses. The Eu2+Ca2+ (Mg2+ → Al3+) structure formed by site-selective Eu2+ occupancy possessed better structural stability in the Ca2(Mg0.5Al0.5)(Si1.5Al0.5O7) crystal matrix, in favour of light-emitting diode (LED) illumination and plasma display panels (PDPs).

Growth, Stratification, and Liberation of Phosphorus-Rich C2S in Modified BOF Steel Slag.

Basic oxygen furnace (BOF) slag was modified by adding 3.5% SiO2 and holding at 1673 K for 0, 5, 40, 90, 240, or 360 min. Kilo-scale modification was also carried out. The growth, stratification, and liberation of P-rich C2S in the modified slag were investigated. The optimum holding time was 240 min, and 90% of C2S grains were above 30 µm in size. The phosphorus content increased with holding time, and after modification, the phosphorus content in C2S was nearly three times higher than that in the original slag (2.23%). Obvious stratification of C2S was observed in the kilo-scale modification. Upper C2S particles with a relatively larger size of 20-110 µm was independent of RO (FeO-MgO-MnO solid solution) and spinel, which is favorable for liberation. Lower C2S was less than 3 µm and was embedded in spinel, which is not conducive to liberation. The content of phosphorus in upper C2S (6.60%) was about twice that of the lower (3.80%). After grinding, most of the upper C2S existed as free particles and as locked particles in the lower. The liberation degree of C2S in the upper increased with grinding time, from 86.02% to 95.92% in the range of 30-300 s, and the optimum grinding time was 180 s. For the lower slag grinding for 300 s, the liberation degree of C2S was 40.07%.