Avaliação microestrutural e cristalográfica da ocorrência de Fe em polímeros inorgânicos do sistema Al-Si-O-Na-H

Abstract

The scientific community has been searching for other binding materials, which are resistant, with high technological efficiency and with little environmental impact. There is a material that can perfectly be an alternative to Portland cement for some applications and that has material characteristics equal or superior to CP. This type of binder comprises alkali activation in materials rich in alumina and silica. This binder is called geopolymer, which in turn has efficient thermomechanical properties, high initial strength, and ecological advantages, since it can be produced at low temperatures without apparent release of CO2 into the atmosphere. The objective of this work is to evaluate the crystallographic and microstructural characteristics of the occurrence of iron cations in crystalline phases in alkaline activated materials. Residual clay samples with different Fe/Al contents were alkaline activated with sodium hydroxyl at 55ºC. The chemical composition of the phases of the activated samples was evaluated by point dispersive energy through phase separation by backscattered electron contrast and electron microscopy. The crystalline phases were studied from the data provided in the IUCr databases. The results show a clear interaction between Fe and the Al and Si cations of the polymer chain. This relationship occurs consistently in the activated systems and in the crystalline phases. The occurrence of Fe occurs with a predominance of tetrahedral sites, but also in octahedrons with oxidation state III. The data show lower chances of formation of Fe-containing phases in oxidation state II and in octahedral and bi pyramidal sites. For the first time, a systematic study categorizes the occurrence and limits of Fe in structures of the Na-Fe-Al-Si-O-H system, indicating that there is a potential for phases with engineering applications, mainly for environmental remediation given the predominance of zeolite-like phases.