Nb(Si,C,N) composite materials densified by spark plasma sintering

Nb2N/Nb5Si3/Nb ceramic–metal and Nb(C,N)/Nb5Si(3+x)Cx ceramic like composites were densified by spark plasma sintering (SPS). The precursor multiphase powders were synthesized by solid-state reactions of a polysilazane precursor with niobium powder addition. By varying the amount of reactive species of both precursor and niobium the phase composition and structure of the synthesized multiphase powders can be tailored from metal dominated to mainly ceramic like. The results demonstrated that the SPS approach leads to highly dense samples at 1600 °C with an applied uniaxial pressure of 100 MPa. Furthermore, XRD measurements and EBSD analysis proofed that SPS is a feasible method to retain the original phase compositions and grain sizes within the multiphase powders during sintering. The evaluation of the Vickers indents revealed both a dependency of the measured values on phase composition and on residual porosity.