AlN-AlON Composites Obtained By Combustion Method
Dariusz Zientara, Jerzy Lis Akademia Górniczo-Hutnicza, Wydział Inżynierii Materiałowej i Ceramiki, Katedra Ceramiki Specjalnej, al. Mickiewicza 30, 30-059 Kraków
Annals 1 No. 1, 2001 pages 93-95
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abstract The pseudobinary system AlN-Al2O3,(AlON) contains materials interesting as structure, functional and refractory ceramics (Fig. 1). In the present investigations, the SHS technique was tested in preparation of sinterable oxynitride powders for their following densification into composite AlON-Al2O3 polycrystals. The starting mixtures of aluminium and alumina powders were blended according to an appropriate final AlN-Al2O3 compositions with AlN content above 50 mole %. The powders were SHS processed according described procedure by combustion in nitrogen (Fig. 2). XRD investigations show that the combustion products were composed of AlON as a major phase with some amount of AlN. The compositions differ from these expected by the phase diagram, what suggests non-equilibrium character of the SHS products. The powders were hot pressed in nitrogen atmosphere under 25 MPa axial pressure. An example of phase composition of materials before and after densification (composition 70% AlN-30% Al2O3) is presented in Fig. 3. It can be generally noticed, that during hot-temperature densification the SHS powders transform creating new compositions with increased AlN content close to those expected according to the phase diagram. The SHS derived powders had high sinterability. SEM investigations confirmed the materials of high densities with fine grains and uniform phase distribution. The mechanical and refractory properties are promising, they look higher than the analogous for composites prepared using reactive sintering.