Papa Elettra, Landi Elena, Miccio Francesco, Medri Valentina
National Research Council of Italy, Institute of Science and Technology for Ceramics (CNR-ISTEC), Via Granarolo 64, 48018 Faenza, Italy.
Materials (Basel). 2022 Jan 27;15(3):1008. doi: 10.3390/ma15031008.
In this paper, four near-net shaped foams were produced via direct foaming, starting from a benchmark metakaolin-based geopolymer formulation. Hydrogen peroxide and metallic silicon were used in different amounts as blowing agents to change the porosity from meso- to ultra-macro-porosity. Foams were characterized by bulk densities ranging from 0.34 to 0.66 g cm, total porosity from 70% to 84%, accessible porosity from 41% to 52% and specific surface area from 47 to 94 m g. Gas permeability tests were performed, showing a correlation between the pore features and the processing methods applied. The permeability coefficients k (Darcian) and k (non-Darcian), calculated applying Forchheimer's equation, were higher by a few orders of magnitude for the foams made using HO than those made with metallic silicon, highlighting the differing flow resistance according to the interconnected porosity. The gas permeability data indicated that the different geopolymer foams, obtained via direct foaming, performed similarly to other porous materials such as granular beds, fibrous filters and gel-cast foams, indicating the possibility of their use in a broad spectrum of applications.
在本文中，从一种基准偏高岭土基地质聚合物配方出发，通过直接发泡制备了四种近净形泡沫材料。使用不同用量的过氧化氢和金属硅作为发泡剂，将孔隙率从中孔改变为超大孔。泡沫材料的特征在于，堆积密度为0.34至0.66 g/cm，总孔隙率为70%至84%，可及孔隙率为41%至52%，比表面积为47至94 m²/g。进行了气体渗透性测试，结果表明孔隙特征与所应用的加工方法之间存在相关性。应用福希海默方程计算得到的渗透系数k（达西）和k（非达西），使用过氧化氢制备的泡沫比使用金属硅制备的泡沫高几个数量级，这突出了根据连通孔隙率不同而产生的不同流动阻力。气体渗透性数据表明，通过直接发泡获得的不同地质聚合物泡沫，其性能与其他多孔材料（如粒料床、纤维过滤器和凝胶浇铸泡沫）相似，这表明它们有可能用于广泛的应用领域。
