Catalytic combustion synthesis of MgO@C nanochains composite powders and the influences on the conductivity of carbon/ceramic composites

Abstract

MgO@C nanochains composite powders were prepared by the catalytic combustion synthesis method, employing C₄H₄O₄ and Mg powders as the primary raw materials, Ni (NO₃)₂·6H₂O as the catalyst. The carbon/ceramic composites were prepared by carbon-bed sintering with MgO@C nanochains composite powders as a conductive filler. The effects of the catalyst content on the phase composition and microstructure of the MgO@C nanochains composite powders, and on the degree of graphitization of the carbon in the composite powders were investigated. Furthermore, the phase composition, microstructure, apparent porosity, bulk density, and electrical resistivity of carbon/ceramic composites were also investigated. The results indicated that the yield of the composite powders is about 44 wt.%. The X-ray diffraction showed that the MgO@C nanochains composite powders consisted of C and MgO phases. Moreover, MgO@C nanochains composite powders prepared with 0.2 wt.% Ni (NO₃)₂·6H₂O addition had a higher degree of graphitization. The TEM images revealed the nanochains in the composite powders. For the carbon/ceramic composites with MgO@C nanochains composite powders, the resistivity of the carbon/ceramic composites decreased significantly as the content of composite powder increased, indicating that the MgO@C nanochains composite powders formed a conductive network in the carbon/ceramic composites, which contributed to the decrease in the resistivity of the samples. When composite powders are added at 9 wt.%, the properties of the sample are optimal. The apparent porosity was 27.17%, and the electrical resistivity of the sample was 590 Ω·cm.