Sol-gel synthesis of Ti2AlC and Ti3AlC2 MAX phases and their sinterability via spark plasma sintering

This study presents a novel sol-gel-based synthesis route for Ti-Al-C MAX phase raw materials in which alkoxidederived gels not only provide homogeneous mixing of elements but also serve as an internal carbon source. Such a molecular-level control over precursor chemistry, together with the application of a controlled heat treatment, represents the first reported sol-gel-based route for Ti3AlC2 formation. Among the various precursor ratios investigated, the mixture with a Ti-/Al-alkoxide/C/Pr4NOH (aq) molar ratio of 3.0:1.0:10:6.0 showed the best results for MAX phase formation. FTIR, XRD and TG analyses confirmed the presence of alkoxide groups, which also act as a carbon source necessary for the synthesis of the MAX phase, and the existence of Ti-O-Al bonds. The sol-gel raw materials were heated under argon atmosphere between 1150 and 1400 degrees C at a rate of 2 degrees C/min, held at these temperatures for 30-60 min, and then cooled in a controlled manner. As the temperature increased, the Ti2AlC phase appeared first and at higher temperatures, especially around 1300-1350 degrees C, the Ti3AlC2 phase formed. At 1400 degrees C, decomposition of the MAX phases was observed. The highest purity of MAX phase (97 %) was obtained at 1300 degrees C with a 90 min dwell time. XRD and EDS results also showed small amounts of aluminum oxide (Al2O3) as secondary phase. Additional analyses using Raman, XPS, SEM, DSC, and TEM confirmed the successful synthesis of layered Ti3AlC2 with typical MAX phase structure.