The facile synthesis of hierarchically porous spherical geopolymer beads via pipetting and low-temperature foaming is reported here. The potassium silica solution and metakaolin-slag-based slurries were modified by amorphous fumed silica in order to regulate the SiO₂–Al₂O₃ ratio and to form a porous structure through chemical foaming technique under alkaline conditions. The addition of fumed silica into 0.01 M KOH resulted in continuous dissolution with bimodal particle size distribution in the range between 158 nm and 3.8 μm. The prepared geopolymer slurries exhibited a shear thinning behavior where the flow properties were intensely affected by the fumed silica concentration. The viscosity of geopolymer slurries was in the range of 0.03–1.6 Pa s at a shear rate of 100 s⁻¹ which strongly influences the formation of the inner porosity and wall thickness. The increased viscosity of the slurries leads to the formation of internally connected struts and spherical-shaped beads with a smoother surface. Silica-based geopolymer matrices exhibited a predominantly amorphous phase of ∼90%. The mechanical strengths of spherical geopolymer beads were evaluated by the means of crushing resistance which reached up to 1.982 N/mm² at internal porosity of 60 vol%. Moreover, X-ray micro-computed tomography (micro-CT) revealed heterogeneous porous architecture in the range of 60–75 vol% with an internal porosity and the presence of combined isolated and interconnected pores between 50 and 500 μm. Thus, this study systematically investigates the influence of viscosity on the porosity, morphology and mechanical strength of silica-based geopolymer beads.

本文报道了通过移液和低温发泡轻松合成分级多孔球形地质聚合物珠粒。用无定形气相二氧化硅对二氧化硅钾溶液和偏高岭土渣浆进行改性，以调节 SiO ₂ –Al ₂ O ₃在碱性条件下通过化学发泡技术形成多孔结构。将气相二氧化硅添加到 0.01 M KOH 中导致连续溶解，双峰粒径分布在 158 nm 和 3.8 μm 之间。制备的地质聚合物浆料表现出剪切稀化行为，其中流动性能受到气相二氧化硅浓度的强烈影响。在 100 s ^-1的剪切速率下，地质聚合物浆的粘度在 0.03-1.6 Pa s 范围内这强烈影响内部孔隙率和壁厚的形成。浆料粘度的增加导致形成内部连接的支柱和具有更光滑表面的球形珠。基于二氧化硅的地质聚合物基质表现出约 90% 的主要非晶相。球状地质聚合物珠粒的机械强度通过抗压强度达到 1.982 N/mm ²来评估内部孔隙率为 60 vol%。此外，X 射线显微计算机断层扫描 (micro-CT) 揭示了 60-75 vol% 范围内的异质多孔结构，具有内部孔隙率和 50 至 500 μm 之间的组合孤立和互连孔的存在。因此，本研究系统地研究了粘度对二氧化硅基地质聚合物珠粒的孔隙率、形态和机械强度的影响。