Insight into the pyrolysis and gas generation behavior of silicomanganese slag and assessing its foaming abilities in foam glass ceramic

Abstract

This paper proposes a novel route for the utilization of silicomanganese slag in the preparation of high-temperature foam ceramic materials, grounded in the unique characteristics of the slag. The phase evolution and gas generation mechanisms of silicomanganese slag was systematically investigated using thermogravimetric mass spectrometry (TG-MS), thermodynamic simulation, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). Foam glass ceramic with a density of 291 ± 8 kg/m3 and a compressive strength of 2.83 ± 0.07 MPa was prepared using silicomanganese slag as a foaming agent. This research indicated that manganese and sulfur in the silicomanganese slag are critical contributors to gas generation. Manganese in the slag oxidizes to dimanganese trioxide (Mn2O3) before reaching 1000 °C, and at temperatures between 1000 and 1200 °C, trivalent manganese (Mn3+) converts to divalent manganese (Mn2+) and enters the pyroxene crystal, releasing oxygen (O2). Sulfur in the slag, captured by divalent calcium (Ca2+), forms a more stable calcium sulfate (CaSO4) during heating and enriches the slag particle surface. As the temperature exceeds 1000 °C, Ca2+ gradually integrates into the pyroxene, prompting the release of sulfate decomposition products, forming sulfur dioxide (SO2) and O2. A small fraction of unreacted CaSO4 enters the glass phase, forming fibrous crystals that enhance the compressive strength of the foam glass-ceramic through fiber reinforcement. The outcomes of this work offer new insights into the high-value utilization of silicomanganese slag and enrich the understanding of gas generation mechanisms in Mn-based and S-based foaming agents.