STUDY OF THE INFLUENCE OF VARIATION OF PHASE COMPOSITION OF COMPOSITE CERAMICS ON RESISTANCE TO RADIATION DAMAGE

The paper presents the results of investigation of the influence of the variation of the phase composition of composite (1−x)Si 3 N 4 – xAl 2 O 3 ceramics on the stability of strength properties in the case of irradiation with heavy ions Xe 23+ (230 MeV) at fluences10 11 –10 14 ions/cm 2 . The variation of the component concentration was chosen taking into account the possibility of obtaining composite ceramics with different phase ratio: Si 3 N 4 , Al 2 O 3 , as well as Al 2 (SiO 4 )O and SiO 2 , the formation of which in the composition of ceramics is associated with the processes of thermal decomposition of Si 3 N 4 during high-temperature annealing in an oxygen-containing atmosphere and phase transformations by the type of solid solution formation. The choice of the type of ions for irradiation is conditioned by the possibilities of simulation of structural damage processes leading to unstrengthening of the damaged layer, comparable to the impact of nuclear fuel fission fragments in ceramics – materials of inert matrices of dispersed nuclear fuel. In the course of the conducted studies, it was established that at irradiation fluences of 10 11 –10 12 ion/cm 2 structural changes associated with the formation of single isolated structurally deformed inclusions do not lead to significant changes in the strength characteristics of ceramics, while small changes observed are associated with deformation distortions, the accumulation of which leads to destabilization of the damaged layer. In the case of higher irradiation fluences (above10 12 ions/cm 2 ), which are characterized by the formation of the effects of overlapping defect regions in the damaged layer, the ceramics of 0,4 Si 3 N 4 – 0,6 Al 2 O 3 , in which, according to X-ray phase analysis data, the dominant phase is Al 2 (SiO 4 )O, the presence of which causes a large number of grain boundaries, which in turn leads to dislocation hardening and restraint of the disordering processes associated with deformation distortions of the damaged layer.