Al_2O_3·nSiO_2-mH_3PO_4磷酸基地质聚合物的制备与结构表征

Preparation and Structural Characterization of Al_2O_3·nSiO_2-mH_3PO_4 Phosphoric Acid-based Geopolymer

通过磷酸激发高纯铝硅酸盐前驱体制备化学成分可控的磷酸基地质聚合物(HPG,Al_2O_3·n SiO_2-m H_3PO_4)。此方法可以精确地模拟以铝硅酸盐为基础的胶凝材料的化学性质,阐明原料中不同Al/P、Al/Si比对HPG结构的影响。利用FT-IR、XRD、FSEM-EDX等测试对其化学键、物相组成及微观形貌进行分析,探究了HPG的结构变化规律。结果表明:随着n(H_3PO_4)/n(Al_2O_3)比例增大,HPG试样抗压强度先增加后降低; n(H_3PO_4)/n(Al_2O_3)=1时,试样达到最大抗压强度,试样结构均匀且致密;随着磷酸用量增加,即n(H_3PO_4)/n(Al_2O_3)> 1,产物由一种均匀凝胶体转变为高硅凝胶和高磷铝凝胶相互填充的多相凝胶体,且两种凝胶相界面之间存在明显间隙;在HPG的溶蚀-聚合反应过程中,粉体中的Al-O是重要的活性基团,Al-O的相对含量的增加有利于提高HPG的抗压强度。

This study demonstrates production of stoichiometrically controlled HPG (Al2O3·n SiO2-mH3PO4) via acid-activation of high-purity aluminosilicate powders. The effects of different Al/P and Al/Si ratios on HPG structures are accurately clarified by this method that can accurately simulate the chemical properties of aluminosilicate-based cementitious materials. The chemical bonds, phase composition and microstructure of phosphoric acid-based geopolymers were characterized using FT-IR, XRD, FSEM-EDX respectively and the structural evolution of phosphoric acid-based geopolymers were investigated. The results show that the compressive strength increased first and then decreased with the molar ratio of n (H3PO4)/ n (Al2O3) increased. When the molar ratio of n (H3PO4)/ n (Al2O3) was 1, the compressive strengths of HPG achieved the maximum value; When the molar ratio of n (H3PO4)/ n (Al2O3) was above 1, the product is transformed from one homogeneous gel to another polyphase gel which included new high phosphorus-aluminum gel and high silica gel were filled with each other and some obvious gaps produced between the two gels; Al-O in powders was an important active group, and the increase of relative content of Al-O was conducive to enhancing the compressive strength in the dissolution-polymerization process of HPG.