Jiang Dong, Zhao Zeyu, Mu Shenglong, Phaneuf Vincent, Tong Jianhua
Department of Materials Science and Engineering, Clemson University , Clemson, South Carolina 29634, United States.
Inorg Chem. 2017 Oct 2;56(19):11702-11709. doi: 10.1021/acs.inorgchem.7b01655. Epub 2017 Sep 19.
Mayenite (12CaO·7AlO, C12A7) electride with an anti-zeolite nanoporous structure has attracted intense attention due to its versatile promising application potentials. However, the synthesis difficulty because of extremely harsh conditions (e.g., reduction in sealed calcium or titanium vapor) significantly obstructs its realistic applications. In this work, we employed a simple, efficient, and cost-effective route for synthesizing mayenite electrides (C12A7:e) in both powder and dense ceramic. C12A7:e powders with efficient electron doping (3.5 × 10 cm) were obtained via simple graphite reduction of a novel mixture precursor of CaAlO (CA) and CaAlO (C3A) derived from a modified Pechini method. The structural evolution during the electride formation was investigated, and it was found that reduction below 1300 °C induced the formation of CaAlO (C5A3), while reduction above 1400 °C helped retain the mayenite structure. Fully dense C12A7:e ceramics were also fabricated via graphite reduction of presintered pellets with a relative density of 97.9% starting from the CA+C3A mixture. Careful studies improved the mechanism cognition of graphite treatment that the electrons injection was probably initiated by surface reduction with involatile C species (e.g., C) rather than previously proposed CO, during which the mixed conduction of oxygen ions and electrons played an important role. Furthermore, the stability of C12A7:e in water as well as in the presence of moisture was discussed. These results not only suggest a novel precursor for fabricating high-quality mayenite electrides but also provide in-depth insights into the stability of the mayenite structure toward practical applications.
具有反沸石纳米多孔结构的钙铝石（12CaO·7Al₂O₃，C12A7）电子化物因其具有多种潜在的应用前景而备受关注。然而，由于合成条件极其苛刻（如在密封的钙或钛蒸汽中进行还原），其合成难度显著阻碍了其实际应用。在这项工作中，我们采用了一种简单、高效且经济的方法来合成粉末状和致密陶瓷状的钙铝石电子化物（C12A7:e）。通过对一种由改进的佩琴尼法衍生的新型CaAlO（CA）和CaAlO（C3A）混合前驱体进行简单的石墨还原，获得了具有高效电子掺杂（3.5×10¹⁹ cm⁻³）的C12A7:e粉末。研究了电子化物形成过程中的结构演变，发现1300℃以下的还原诱导了CaAlO（C5A3）的形成，而1400℃以上的还原有助于保留钙铝石结构。还通过对由CA + C3A混合物制成的相对密度为97.9%的预烧结球团进行石墨还原，制备出了完全致密的C12A7:e陶瓷。仔细的研究加深了对石墨处理机制的认识，即电子注入可能是由不挥发的C物种（如C）的表面还原引发的，而不是先前提出的CO，在此过程中氧离子和电子的混合传导起到了重要作用。此外，还讨论了C12A7:e在水以及有水分存在的情况下的稳定性。这些结果不仅为制备高质量的钙铝石电子化物提出了一种新型前驱体，还为钙铝石结构在实际应用中的稳定性提供了深入的见解。
