Optimalizace přípravy fáze Ti3AlC2 pomocí mechanického zpracování směsi titanu, hliníku a uhlíku

Abstract

MAX phases represent a group of intensively studied materials with potential applications in aerospace, defence, and nuclear industries, and they are also initial materials for the preparation of a novel outstanding group of materials MXenes. The preparation of the MAX phase is usually done in two steps: i) grinding of the mechanical mixture (for example Ti+Al+C) and ii) heat treatment of this mixture at temperatures higher than 1000 °C. The heat treatment is relatively expensive and one of the possibilities to reduce economic costs and simplify the preparation of the MAX phase is the optimisation of the grinding process. For this purpose, a design of experiment approach was adopted. The definition of four factors set at two levels resulted in a series of 16 samples. The selected factors included i) grinding time, ii) rotational speed, iii) number of grinding balls, and iv) amount of grounded material. The X-ray diffraction analysis method was used to determine the phase composition of the mixtures after grinding. It has been shown that, even by simple grinding, the MAX phase Ti3AlC2 can be prepared under specific conditions. The grinding energy for the given grinding conditions of all 16 samples, the amount of internal stress for Ti and Al, and the average crystallite size for Ti and Al were determined. It was shown that both the morphology of the surface of the prepared samples and the values of the internal stress and the average size of the crystallites changed with increasing grinding energy. Selected ground samples under different conditions were thermally processed during their thermogravimetric analysis, and the thus prepared sample was subsequently analysed by X-ray diffraction analysis to determine their phase composition. According to the results of the X-ray diffraction analysis, the first step in the preparation of the MAX phases – i.e. grinding – had a major influence on the resulting shape of the diffraction patterns of the samples after the thermogravimetric analysis.