Sintering and proporties of NbC_1-x-NbO₂ composites

Justyna Mucha, Agnieszka Gubernat, Ludosław Stobierski

Quarterly No. 3, 2013 pages 185-192

DOI:

keywords: composites NbC_1-x-NbO₂, single-phase niobium carbide, mechanical, thermal and chemical properties

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abstract The paper presents results of research on sintering, polycrystals manufacture and determination of the characteristics of the obtained NbC_1-x - NbO₂ composites. For the manufacturing of composites powders synthesized from the elements in the solid phase reaction method in the laboratory of Department of Ceramics and Refractories WIMiC, AGH were used. As a result of grinding and drying, carbide powders have undergone a surface oxide passivation. In order to improve the granulation and moulding capacity of powders and to partially deoxidize them, a small amounts of Nowolak MR resin were introduced into powders, as a carbon precursor. The prepared granulates were used to manufacture composites with the pressureless sintering and hot pressing. Mechanical properties, thermal and chemical properties were investigated and compared with the results obtained for the single-phase niobium carbide polycrystals. It was found that the composites are characterized by: high hardness (HV~16 GPa; HK 12÷14 GPa), higher than the polycrystals bending strength (~500 MPa) and fracture toughness (5 MPa∙m0.5) and good thermal conductivity (12÷15 W/m∙deg). Oxidation resistance of the composites is the same as the single-phase materials.