The dependence of MAX-phase synthesis on phase composition of the initial mixture and heat treatment terms in the electric furnace was investigated. Using Ti and AlN powders with the molecular ratio 2:1 as an example, the sequence of phase composition changes with increasing exposure temperature was tracked. It was established that the maximum amount of Ti2AlN MAX-phase in the end products is obtained at 1400°C. At this temperature a single phase product (100% wt Ti2AlN) was obtained for the initial mixture Ti:Al:TiN = 1:1:1. The principal possibility of scaling for obtaining a single-phase product of Ti2AlN by vacuum sintering was experimentally shown on the example of the mixture of this composition weighing 500 g at a certain mode of thermal vacuum treatment.

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The synthesis method of aluminium oxynitride (AlON) powders by nitriding of Al/Al2O3 mixture under highpressure nitrogen is proposed. The novelty of this method consists in adding KClO4 or Mg(ClO4)2 and extra Al into the starting mixture (Al+Al2O3) to cause the exothermal aluminium oxidation reaction, which therefore initiates the aluminium nitriding reaction. The microstructure and phase composition of the AlON powders obtained by self-propagating high-temperature synthesis are demonstrated by means of SEM and XRD analysis. Diffuse reflection spectra of AlON powders have been measured and the values of band-gap energy have been calculated. Optical transmission and reflection characteristics of the AlON ceramic samples sintered from AlON powders at 1930°C have been studied. The influence of the technological parameters of ceramics production on their transparency is revealed – the most transparent sample is obtained from the powders synthesized with the Mg(ClO4)2 additive and sintered for 6 h.

The synthesis of MAX phase Ti2AlN from several mixtures of Ti, Al, TiN, and AlN powders by vacuum sintering of greensamples in the form of dense compacts, bulk powder in silica tubes, and plain layer in a closed rectangular molybdenum boat was studied upon variation in charge composition and sintering temperature Ts. The sintering of 2 : 1 Ti–AlN mixture was carried out at 1100, 1200, 1300, 1400, and 1500 °С with exposure time of 60 min. The largest MAX phase content (94 wt.%) was reached at Ts = 1400 °С. The sintering of 1 : 1 TiAl : TiN composition at the same temperature gave 93 wt.% Ti2AlN. The best result (singlephase Ti2AlN in a 100-% yield) was achieved upon the sintering of 1 : 1 : 1 Ti–Al–TiN composition at Ts = 1400 °С. The scalability of our process was checked by the fabrication of a large (0.5 kg) and uniform cake of single-phase Ti2AlN. In experiments we used green samples with shielded lateral surface (bulk powder in silica tubes, plain layer in a closed molybdenum boat) and without shield (dense compacts). It has been shown that shielding of Ti–Al–TiN samples restricts the escape of Al vapor from a sintered mixture, thus providing more favorable conditions for the synthesis of single-phase Ti2AlN. Our process can be readily recommended for practical implementation.

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