Properties and microstructure of graphitised ZrC/C or SiC/C composites

Doped graphites were prepared from calcined coke, coal-tar pitch and dopants (Zr, Si and Si-Zr) by hot-pressing in order to investigate the effects of the composition and amount of dopants on their thermal conductivity, electrical resistivity, bending strength and microstructure. Experimental results showed that the single element (Zr or Si) and bi-element (Si-Zr) graphitised doped-carbons exhibited highly improved conductivity, but the bending strength is lower in the case of Si-doped graphite. Microstructure analyses showed that the d₀₀₂ spacing decreased with the increasing dopant concentration for the single element (Zr or Si) doped graphite. From this result, it is inferred that the degree of graphitization increased. The thermal conductivity of a (9% Zr, 2% Si) graphitised doped-carbons is 380 W m⁻¹ K⁻¹. Correlations between the composition and content of dopants and the microstructure of doped graphite are tentatively discussed.