Tunca Bensu, Lapauw Thomas, Karakulina Olesia M, Batuk Maria, Cabioc'h Thierry, Hadermann Joke, Delville Rémi, Lambrinou Konstantina, Vleugels Jozef
SCK•CEN , Boeretang 200, B2400 Mol, Belgium.
KU Leuven , Department of Materials Engineering, Kasteelpark Arenberg 44, B-3001 Leuven, Belgium.
Inorg Chem. 2017 Mar 20;56(6):3489-3498. doi: 10.1021/acs.inorgchem.6b03057. Epub 2017 Mar 3.
This study reports on the synthesis and characterization of MAX phases in the (Zr,Ti)AlC system. The MAX phases were synthesized by reactive hot pressing and pressureless sintering in the 1350-1700 °C temperature range. The produced ceramics contained large fractions of 211 and 312 (n = 1, 2) MAX phases, while strong evidence of a 413 (n = 3) stacking was found. Moreover, (Zr,Ti)C, ZrAl, ZrAl, and ZrAl were present as secondary phases. In general, the lattice parameters of the hexagonal 211 and 312 phases followed Vegard's law over the complete Zr-Ti solid solution range, but the 312 phase showed a non-negligible deviation from Vegard's law around the (Zr,Ti)AlC stoichiometry. High-resolution scanning transmission electron microscopy combined with X-ray diffraction demonstrated ordering of the Zr and Ti atoms in the 312 phase, whereby Zr atoms occupied preferentially the central position in the close-packed MX octahedral layers. The same ordering was also observed in 413 stackings present within the 312 phase. The decomposition of the secondary (Zr,Ti)C phase was attributed to the miscibility gap in the ZrC-TiC system.
本研究报道了(Zr,Ti)AlC体系中MAX相的合成与表征。通过反应热压和无压烧结在1350 - 1700°C温度范围内合成了MAX相。所制备的陶瓷含有大量的211和312（n = 1, 2）MAX相，同时发现了413（n = 3）堆积的有力证据。此外，(Zr,Ti)C、ZrAl、ZrAl和ZrAl作为次生相存在。总体而言，六方211和312相的晶格参数在整个Zr - Ti固溶体范围内遵循维加德定律，但312相在(Zr,Ti)AlC化学计量比附近显示出与维加德定律不可忽略的偏差。高分辨率扫描透射电子显微镜与X射线衍射相结合表明，312相中Zr和Ti原子有序排列，其中Zr原子优先占据密排MX八面体层的中心位置。在312相内存在的413堆积中也观察到了相同的有序排列。次生(Zr,Ti)C相的分解归因于ZrC - TiC体系中的混溶间隙。
