Modern materials, developed for use at extreme conditions, such as variety of high-temperature aerospace applications, including hypersonic aircraft thermal structure and advanced rocket propulsion thrust chambers or application in fusion reactor, should have high thermal conductivity, low gas permeability, suitable mechanical properties at elevated temperatures, radiation stability at high fluxes of neutrons and high oxidation resistance. Among few ceramic materials, approaching required properties, are silicon carbide based materials. Particularly promising is composite material based on SiC continuous-fibers embedded in SiC based matrix with nanometer-sized particles.

SiCf/SiC materials were prepared by various methods, such as chemical vapor infiltration (CVI), infiltration with nanoparticle suspensions and electrophoretic deposition (EPD). The main problems we tried to solve were high sintering temperature of SiC, high neutron activation of commonly used sintering additives and poor adhesion of matrix phase to continuos fibers. Coating of the surfaces of particles and fibers with nanosized layers of various substances was used. Coatings enabled the modification of powder properties in the desired direction, and consequently enabled the tailoring of the properties of the final product. Nano-coatings enabled more uniform distribution of phases inside materials, the homogeneous distribution of suitable sintering aids and better processing.

Microstructure of differently prepared materials was studied with analytical electron microscopy using dedicated FEG TEM/STEM. Methods, such as high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy (EDXS), electron energy-loss spectroscopy (EELS), high-angle annular dark-field detector imaging (Z-contrast) and electron nano-diffraction were used for characterization of fiber-matrix interfaces, chemical composition of phases present and crystal defects. The influence of the preparation technique and processing parameters on microstructural features are discussed.