Regulation mechanism of different additives on the properties of solid waste-based foam glass-ceramics

Abstract

Self-foaming foam glass-ceramics based on copper slag tailings and secondary aluminum dross face a critical bottleneck, high sintering temperatures make it difficult to achieve both low-temperature fabrication and high performance. To resolve this issue, four additives (SrF₂, CaF₂, SrO, and CeO₂) were selected to explore their regulatory effects and underlying mechanisms on foaming behavior, phase structure, and mechanical properties. SrF₂ was selected as the exploratory additive in this research, and a unified sintering benchmark of 1120 °C was established, which is 30 °C lower than that of the basic system. All four additives effectively promote self-foaming. As dosage rises, pore size and porosity increase monotonically, while bulk density and compressive strength decrease simultaneously. However, the regulatory intensity differs notably among the four additives. SrF₂ exhibits the optimal fluxing and foaming effect and can achieve significant lightweighting of the material. CaF₂ realizes balanced adaptation between lightweighting and mechanical properties. SrO can effectively maintain the integrity of the pore wall structure. CeO₂ possesses excellent pore homogenization control and matrix toughening effects. The major crystalline phase of all modified systems is diopside, with no detrimental impurity phases formed. Consistent with the established research consensus on silicate melt structure, anion type is the core factor determining the fluxing effect of the system, and fluorides exhibit significantly superior fluxing efficiency compared to oxides with the same cation. Environmental safety tests show that the leaching concentrations of fluoride ions in all samples are far below the national standard limits. This study provides a scientific basis for the low-temperature sintering and performance customized design of solid waste-based foam glass-ceramics, and opens up a new path for the large-scale and high-value utilization of metallurgical solid wastes.