Effects of processing on mechanical properties of B4C-graphene composites fabricated by hot pressing

Abstract

Abstract Boron carbide (B4C) composites with 4 wt% graphene were fabricated by hot pressing (HP) using two different graphene sources, graphene nanoplatelets (GNPs) and graphene oxide (GO), and two different homogenization methods. B4C–GNPs/GO powder mixtures were homogenized by planetary ball milling and a heterogeneous co-precipitation method using cetyltrimethyl ammonium bromide (CTAB) as the cationic surfactant. The influences of homogenization methods and types of graphene source on the microstructure and mechanical properties of B4C composites were investigated. A maximum flexural strength of 476 MPa was achieved for B4C–GNPs composites homogenized using planetary ball milling with previous ultra-sonication of GNPs in ethanol. Additionally, the fracture toughness of B4C composites was in the range 3.85–5.51 MPa m1/2, which was significantly higher than that of monolithic B4C. Fractography was also performed to evaluate the individual homogenization method. Based on the different processing techniques, the critical flaw sizes of the B4C composites varied from 45 μm to 112 μm. The results reveal that the main fracture origins are processing flaws in the form of structural heterogeneities, graphene agglomerations, and interfacial porosity.