[EN] Nano- and micro-indentation experiments have been used to evaluate the mechanical properties of dense silicon oxycarbide (SiOC) derived materials obtained by spark plasma sintering (SPS). The sintering temperature varied from 1300 to 1700 °C, with a pressure of 40 MPa. The relationship between the mechanical properties and densification, porosity, evolution of the composition, structure and crystallization depending on the SPS sintering temperature has been determined. The SiOC sample obtained at 1400 °C shows the highest values of hardness (12 GPa) and elastic modulus (95 MPa) in both nano- and micro-indentation tests. The SPS treatment produces a neat densification of the material without promoting the phase separation of the Si–O–C matrix. In terms of the elasto-plastic behaviour, hf/hmax >0.5 and Wel/Wtot <0.7, in conjunction with AFM images, highlight the negligible formation of pile-ups. The elastic recovery is quite high, and is probably due to the flexible segregated carbon phase. The Vickers indentation patterns show the Hertzian cones typical of anomalous glasses. Some minor radial cracks can also be seen, and can be attributed to the presence of both stiffer Si–C bonds which reduce the propagation of cracks, and to carbon, which reduces the brittleness of the SiOC derived materials.

This work was supported by project MAT2016–78700-R financed by the Spanish Research Agency and the European Regional Development Fund (AEI/FEDER, EU); and project ENE2012-39385-CO3-01 funded by the Spanish Ministry of Economy, Industry and Competitiveness. We acknowledge support for the publication fee from the Spanish National Research Council (CSIC) Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).

Peer reviewed