In the frame of the development of new nuclear reactors (Gen-IV project), materials able to withstand very high temperatures are required. Among the components of the cores, the transition metal carbides could be favourably considered as fission products barriers or inert matrix for the fuel. They are highly refractory, have good neutron properties and fission products retention. Unfortunately, first they are brittle and second the elaboration process of bulk materials requires drastical conditions (temperature, pressure). We have then undertaken the comparison of different materials to investigate the potentialities of nano-sized microstructures for the improvement of the mechanical properties and to determine the impact of different elaboration routes to obtain high density articles. The elaboration process of the nano-sized powders is presented elsewhere [M. Dollé et al., this meeting]. Here, we compare different sintering processes (uniaxial hot-pressing, spark plasma sintering) and we present a new process able to produce high density zirconium carbide articles with soft conditions. We show that the sintering of co-ground zirconium and graphite powders lead to high density, homogeneous, low grain-size materials at temperatures as low as 1500°C. At the contrary, the nano-powders appear to be more difficult to densify that classical micro-sized powders.