Non - destructive inspection of SiCf / SiC composites structure

Fiber reinforced ceramic matrix composite is an attractive candidate as a structural material for future fusion power plants because of their light weight, high temperature capability, high strength and toughness. Ceramic matrix composite made of silicon carbide matrix and fibers (SiCf/SiC) is promising for nuclear and fusion technology due to its excellent radiation resistance, especially exposure to high-energy particles such as neutron, proton, and alpha. However, porosity, which is mainly due to manufacturing process of the SiCf/SiC composites, is a critical issue in its application in fusion technology. Internal pores mitigate most of the outstanding properties of the SiCf/SiC composites such as thermal conductivity, high strength and radiation stability. The pores in composites are unavoidable and significantly reduce the life time and performance of the composites under harsh environments. The aim of the study is to examine the pore structure and alignment between the matrix/fiber bundles and hightemperature induced changes within the SiCf/SiC composite. By means of non-destructive cold neutron tomography (at Helmholtz Zentrum Berlin) and small angle neutron scattering (at Paul Scherrer Institute, PSIVilligen) techniques inner microstructure of the composites have been investigated. The cold neutron tomography and small angle neutron scattering techniques have been applied in order to gain complementary information on the microstructure of the SiCf/SiC composites. After heat treatment of the composites at 1300 °C, 1400 oC and 1500 oC for 5 hours small angle neutron scattering (SANS) measurements have been carried out to understand the structural changes under high-temperature: pore size changes induced by high temperature. Scattering curves have revealed the changes in pore size at elevated temperatures.