The study of mixed Al3+/Fe3+ nitrate hydrates is gaining increasing interest with the emergence of new hydraulic binders and Supplementary Cementitious Materials (SCMs) containing significant amounts of iron and aluminum oxides that can be activated by nitrate addition. Layered AFm-NO3 hydrates containing varying proportions of trivalent Al3+ and Fe3+ cations were synthesized and characterized. The AFm-NO3 phase constitutes a continuous solid solution between the two end-members Ca2Al(OH)6·NO3·2H2O and Ca2Fe(OH)6·NO3·2H2O. The obtained Ca2Al1-xFex(OH)6·NO3·yH2O solid solution proves stable for four hydration states, with a significant impact on the interlayer distance: y = 5 (at high relative humidity with an interlayer distance of 10.4 Å), y = 2 (at ambient conditions with an interlayer distance of 8.6 Å), y = 1 (above 60 °C with an interlayer distance of 7.4 Å) and y = 0 (anhydrous above 175 °C with an interlayer distance of 8.0 Å). In fact, thermal variations reveal some differences between the two Al-rich and Fe-rich sides. Finally, AFm-NO3 stability was examined in the presence of other anions, demonstrating the low stability of NO3− with respect to Cl− and CO32− anions.

中文翻译：

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深入研究 AFm-NO3 水合物：Fe 到 Al 的取代、水合水平和阴离子交换能力


随着新的水硬性粘合剂和补充胶凝材料 （SCM） 的出现，对混合 Al3+/Fe3+ 硝酸盐水合物的研究越来越受到关注，这些材料含有大量可通过硝酸盐添加活化的铁和铝氧化物。合成并表征了含有不同比例的三价 Al3+ 和 Fe3+ 阳离子的层状 AFm-NO3 水合物。AFm-NO3 相在两个端元 Ca2Al（OH）6· 之间构成连续固溶体NO3·2H2O 和 Ca2Fe（OH）6·NO3·2H2O.得到的Ca2Al1-xFex（OH）6·NO3·yH2O 固溶体在四种水合状态下均保持稳定，对层间距离有显著影响：y = 5（在高相对湿度下，层间距离为 10.4 Å）、y = 2（在环境条件下，层间距离为 8.6 Å）、y = 1（高于 60 °C，层间距离为 7.4 Å）和 y = 0（无水温度高于 175 °C，层间距离为 8.0 Å）。事实上，热变化揭示了富铝和富铁两面之间的一些差异。最后，在其他阴离子存在下检查 AFm-NO3 的稳定性，证明 NO3− 相对于 Cl− 和 CO32− 阴离子的稳定性较低。