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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Phase evolution of Na2O-Al2O3-SiO2-H2O gels in synthetic aluminosilicate binders
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Phase evolution of Na2O-Al2O3-SiO2-H2O gels in synthetic aluminosilicate binders

机译：合成铝硅酸盐粘合剂中Na2O-Al2O3-SiO2-H2O凝胶的相变

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This study demonstrates the production of stoichiometrically controlled alkali-aluminosilicate gels ('geopolymers') via alkali-activation of high-purity synthetic amorphous aluminosilicate powders. This method provides for the first time a process by which the chemistry of aluminosilicate-based cementitious materials may be accurately simulated by pure synthetic systems, allowing elucidation of physicochemical phenomena controlling alkali-aluminosilicate gel formation which has until now been impeded by the inability to isolate and control key variables. Phase evolution and nanostructural development of these materials are examined using advanced characterisation techniques, including solid state MAS NMR spectroscopy probing Si-29, Al-27 and Na-23 nuclei. Gel stoichiometry and the reaction kinetics which control phase evolution are shown to be strongly dependent on the chemical composition of the reaction mix, while the main reaction product is a Na2O-Al2O3-SiO2-H2O type gel comprised of aluminium and silicon tetrahedra linked via oxygen bridges, with sodium taking on a charge balancing function. The alkali-aluminosilicate gels produced in this study constitute a chemically simplified model system which provides a novel research tool for the study of phase evolution and microstructural development in these systems. Novel insight of physicochemical phenomena governing geopolymer gel formation suggests that intricate control over time-dependent geopolymer physical properties can be attained through a careful precursor mix design. Chemical composition of the main N-A-S-H type gel reaction product as well as the reaction kinetics governing its formation are closely related to the Si/Al ratio of the precursor, with increased Al content leading to an increased rate of reaction and a decreased Si/Al ratio in the N-A-S-H type gel. This has significant implications for geopolymer mix design for industrial applications.
机译：这项研究证明了通过对高纯度合成非晶硅铝酸盐粉末进行碱活化来生产化学计量控制的碱铝硅酸盐凝胶（“地聚合物”）。该方法首次提供了一种过程，通过该过程可以通过纯合成系统准确模拟基于铝硅酸盐的胶凝材料的化学性质，从而阐明了控制碱金属铝硅酸盐凝胶形成的物理化学现象，迄今为止，该现象一直受到无法分离的阻碍。和控制关键变量。使用先进的表征技术，包括探测Si-29，Al-27和Na-23核的固态MAS NMR光谱学，研究了这些材料的相演化和纳米结构发展。凝胶化学计量和控制相演化的反应动力学显示出强烈依赖于反应混合物的化学组成，而主要反应产物是Na2O-Al2O3-SiO2-H2O型凝胶，由通过氧连接的铝和四面硅组成桥，钠承担电荷平衡功能。在这项研究中生产的碱金属铝硅酸盐凝胶构成了一个化学简化的模型系统，该系统为研究这些系统中的相演化和微结构发展提供了一种新颖的研究工具。对控制地质聚合物凝胶形成的物理化学现象的新见解表明，可以通过精心设计的前体混合物来实现对随时间变化的地质聚合物物理特性的复杂控制。主要NASH型凝胶反应产物的化学组成以及控制其形成的反应动力学与前体的Si / Al比密切相关，Al含量增加导致反应速率增加，Si / Al比降低在NASH型凝胶中。这对于工业应用的地质聚合物混合物设计具有重要意义。

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