Effects ofSiCandSiC-GNP additions on the mechanical properties and oxidation behavior of NbB2

Abstract

Monolithic NbB₂, NbB₂-<i>SiC</i>, and NbB₂-<i>SiC</i>-GNP samples were produced by spark plasma sintering (SPS), and the effects of additives on the mechanical and thermal properties, microstructures, and oxidation behavior of the samples were investigated. The addition of <i>SiC</i> up to 30 vol% decreased the Vickers hardness of the binary composites due to microcrack formation. The fracture toughness and oxidation resistance of NbB₂ were improved with the incorporation of <i>SiC</i>. Fracture toughness was higher for all the composites in comparison to monolithic NbB₂, moreover the highest value of ~5.2 MPa·m^1/2 exhibited by 3 vol% GNP-containing composite. A strong interface and homogeneous distribution of GNPs enhanced the thermal transfer properties and improved the oxidation resistance of selected NbB₂-<i>SiC</i> ceramics in oxidation studies at 1200°C. A combination of high mechanical properties, high thermal conductivity, and low mass gain was achieved for the NbB₂-<i>SiC</i>-GNP samples with 1 and 3 vol% GNPs.