Effect of impurity on microstructure and properties on hot-pressed boron carbide ceramics

It is very important to understand the influence of impurity elements on the quality of boron carbide and control impurity elements. In the present work, boron carbide powders with different impurity levels were sintered by hot pressing under the same conditions, in which a set of aggregation pores and secondary phases can be detected. The reaction and distribution of impurities in the sintering process were analyzed. The mechanism of impurities on densification and pore generation is discussed. It can be found that the Fe2O3 and SiO2 will react with boron carbide to form FeB, FeB4 and Si5C3, and the impurities cause significant aggregation pores and promote the abnormal grain growth, which have an unapparent influence on hardness and strength but sharply decline the toughness of sintered B4C samples from (1.97 +/- 0.03) MPa center dot m(1/2 )to (0.33 +/- 0.04) MPa center dot m(1/2).