Effect of ZrB2 on the ablation properties of carbon composites

Zirconium diboride reinforced carbon (ZrB2/C) composites were prepared from petroleum coke, coal tar pitch and ZrB2 powder by hot-pressing. Their ablation resistance was tested in an oxyacetylene flame with high velocity gas. The effects of the ZrB2 additives on the ablation properties were studied. Results showed that the values of mass and linear ablation rates were lower in the composites than those measured for pure carbon, decreasing with increasing ZrB2 content. A dense and uniform ZrO2 layer could be formed on the substrate surface when the ZrB2 content was higher than 10 wt.% in raw materials. This layer acted as an effective oxygen barrier and greatly reduced the ablation rates of the composites. The ablation resistance mechanism of the composites was also discussed according to SEM and XRD analysis.